Quantum Diaries http://www.quantumdiaries.org Thoughts on work and life from particle physicists from around the world. Wed, 29 Jul 2015 13:37:41 +0000 en-US hourly 1 http://wordpress.org/?v=4.2.4 Trois mots pour résumer une conférence http://www.quantumdiaries.org/2015/07/29/trois-mots-pour-resumer-une-conference/ http://www.quantumdiaries.org/2015/07/29/trois-mots-pour-resumer-une-conference/#comments Wed, 29 Jul 2015 13:18:32 +0000 http://www.quantumdiaries.org/?p=36067 Impressionnant, excitant et plein de nouvelles perspectives. Cela résume mon impression alors que se termine aujourd’hui la conférence de physique des particules de la Société européenne de physique (EPS) à Vienne.

Nous avons été exposés à une quantité impressionnante de nouvelles données. Non seulement les expériences du Grand collisionneur de hadrons (LHC) du CERN ont finalisé la plupart de leurs analyses sur l’ensemble des données recueillies avant l’arrêt début 2013, mais elles ont aussi déjà commencé à analyser les nouvelles données. Ceci confirme que tout, des détecteurs aux logiciels de reconstruction, fonctionne parfaitement après le vaste programme d’améliorations et de réparations.

conference-dinner

Souper de clôture de la conférence au magnifique palais Schönbrunn à Vienne (Photo: Gertrud Konrad)

Tous les outils nécessaires aux analyses de physique – simulations, systèmes d’acquisition de données, trigger, calibrations et algorithmes d’analyse – produisent déjà des résultats de haute qualité avec les données des collisions à une énergie de 13 TeV. Les expériences sont clairement en mesure de reprendre les analyses là où elles les avaient laissées avec les données collectées à 8 TeV. Bien sûr, il n’y a encore aucuns signes de nouveaux phénomènes mais les expériences LHCb, CMS et ATLAS ont toutes de petites anomalies qui devraient être élucidées avec les nouvelles données du LHC.

Durant cette conférence, on a pu apprécié aussi la variété des expériences en place et les nouveaux résultats qui commencent déjà à arriver sur la matière sombre et l’énergie sombre. De nouvelles avenues sont aussi explorées pour élargir les recherches dans l’espoir de découvrir les 95 % du contenu de l’Univers qui manquent toujours à l’appel. Les expériences ont fait des pas de géants et on s’attend à des percées majeures d’ici à peine quelques années. On peut aussi espérer des développements dans le secteur des neutrinos, un domaine de recherche prolifique mais aussi un des plus déconcertants et embrouillants depuis de nombreuses années.

Comme l’a souligné Pierre Binetruy, un théoricien travaillant en cosmologie : « Les découvertes simultanées du boson de Higgs et la confirmation de quelques unes des caractéristiques de l’inflation (la période marquée par une expansion fulgurante juste après le Big Bang) a ouvert une nouvelle ère dans la compréhension commune de la cosmologie et de la physique des particules ». Nous sommes clairement à la veille de percées majeures et de nouvelles découvertes dans plusieurs domaines. La prochaine conférence sera sans aucun doute un événement à ne pas manquer.

Pauline Gagnon

Pour recevoir un avis lors de la parution de nouveaux blogs, suivez-moi sur Twitter: @GagnonPauline ou par e-mail en ajoutant votre nom à cette liste de distribution ou consultez mon site web.

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Three words to summarize a conference http://www.quantumdiaries.org/2015/07/29/three-words-to-summarize-a-conference/ http://www.quantumdiaries.org/2015/07/29/three-words-to-summarize-a-conference/#comments Wed, 29 Jul 2015 13:12:31 +0000 http://www.quantumdiaries.org/?p=36064 Impressive, exciting and eye-opening. This is how I would summarize the European Physics Society (EPS) particle physics conference that is ending today in Vienna.

The participants were treated to an impressive amount of new data. Not only had the Large Hadron Collider (LHC) experiments at CERN finalised most of their analyses on the entire set of data collected prior to the long shutdown of the last two years, but they had also already started analysing the new data. This confirms that everything, from hardware to software, is up and running after extensive upgrades, repairs and improvements.

All the tools for physics analysis – simulations, data acquisition systems, trigger menus, calibration and analysis algorithms – are already performing beautifully at the new collision energy of 13 TeV. The experiments are clearly in a position to take up the analyses where they had left them with the 8 TeV data. True, there are no signs for new physics anywhere yet but LHCb, CMS and ATLAS all have little hints that will soon be elucidated with the new data.

conference-dinner

Conference dinner in the beautiful Schönbrunn castle in Vienna (Credit: Gertrud Konrad)

A wealth of new experiments and results were also presented at the conference on dark matter and dark energy. New avenues are also explored to broaden the searches in the hope of accounting for the 95% of the content of the Universe that is still completely unknown. Giant steps have already been taken and major breakthroughs are expected in the very near future. Developments are also expected in the neutrino sector, a prolific research domain that has been most puzzling and confusing for many years.

As stated by Pierre Binetruy, a theorist working on cosmology: “The simultaneous discovery of the Higgs and confirmation of some of the basic features of inflation (the rapid expansion that followed the Big Bang) has opened a new era in the common understanding of cosmology and particle physics“. It is clear that we are on the eve of major advances and discoveries. The next conference is sure to be an event not to be missed.

Pauline Gagnon

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La route cahoteuse menant aux découvertes http://www.quantumdiaries.org/2015/07/28/la-route-cahoteuse-menant-aux-decouvertes/ http://www.quantumdiaries.org/2015/07/28/la-route-cahoteuse-menant-aux-decouvertes/#comments Tue, 28 Jul 2015 13:32:16 +0000 http://www.quantumdiaries.org/?p=36050 La conférence de physique des particules de la Société de Physique Européenne (EPS) se poursuit à Vienne, les sessions parallèles ayant cédé la place aux sessions plénières. Les présentateurs et présentatrices ont maintenant la dure tâche de récapituler les centaines de résultats présentés jusqu’ici à la conférence et d’en tirer une vue d’ensemble.

Durant les deux dernières années, le Grand Collisionneur de Hadrons (LHC) a subi des améliorations majeures. Les expérimentalistes en ont profité pour examiner sous toutes les coutures (et même plus!) l’ensemble des données accumulées avant l’arrêt. Avec les calibrations finales et des algorithmes améliorés, presque toutes les analyses incluent maintenant la totalité des données récoltées à une énergie de 8 TeV. Dans la plupart des cas, ces mois de travail acharné effectué par des centaines de personnes n’auront produit qu’une légère amélioration dans la précision des résultats. Ces récents résultats, bien que solides comme le roc, n’ont malheureusement rien révélé de nouveau.

C’est la mauvaise nouvelle. La bonne nouvelle : on s’attend à quatre fois plus de données dans l’année qui vient et à plus haute énergie, ce qui rendra de nouveaux phénomènes accessibles.

En voici un exemple. Les expériences CMS et ATLAS cherchent, entre autres, des particules lourdes mais encore hypothétiques qui se désintègreraient en deux bosons connus, à savoir des photons, ou des bosons Z, W ou de Higgs. Les trois derniers bosons peuvent à leur tour se désintégrer en jets de particules légères faites de quarks.

La désintégration d’une particule s’apparente à faire la monnaie pour une grosse pièce de monnaie : la pièce de monnaie initiale ne contient pas de petites pièces, mais peut être échangée pour des pièces de valeur égale, comme sur le diagramme ci-dessous. Les quatre pièces de 50 centimes pourraient provenir d’une pièce de deux euros ou de deux pièces de un euro. De même, dans nos détecteurs, quand nous trouvons quatre jets de particules, ils peuvent provenir de deux bosons produits indépendamment (dans l’exemple ci-dessus, deux bosons Z), ou venir de quatre quarks produits directement. Tout ceci constitue le bruit de fond, tandis que le signal correspond dans ce cas au nouveau boson, celui qui s’est désintégré en deux bosons.

pieces de monnaie

La désintégration d’une particule s’apparente à faire la monnaie pour une pièce.

Une pièce de monnaie n’a qu’une valeur mais une particule possède à la fois masse et énergie. Quand on échange une grosse pièce pour de la monnaie, la valeur initiale est conservée. Avec des particules, nous devons prendre en compte la masse et l’énergie de tous les produits de désintégration pour calculer la masse combinée de la particule originale. Dernier détail : si la particule qui se désintègre est beaucoup plus lourde que les deux bosons qu’elle produit, les jets venant de ces bosons seront à peine séparés. Ils se déplaceront côte à côte. On n’observera alors non pas quatre jets, mais seulement deux jets plus évasés.

Si ces deux larges jets proviennent de deux Z bosons produits indépendamment, la valeur totale de leur masse combinée sera aléatoire, comme si nous additionnions la valeur de la monnaie au fond de nos poches. Si des milliers de personnes notaient sur un graphe la valeur de leur petite monnaie, nous obtiendrions une distribution comme celle de la ligne bleue ci-dessous. La majorité des gens ne traîne qu’un peu de monnaie, mais certaines personnes trimbalent une petite fortune en pièces de monnaie.

ATLAS-bump

Un excès d’évènement trouvés ayant une masse de 2 TeV trouvés par ATLAS

L’axe horizontal donne la valeur de la masse combinée des deux jets pour chaque événement récolté par la Collaboration d’ATLAS qui en contenait deux. L’axe vertical montre combien d’événements ont été trouvés avec une valeur de masse particulière. La ligne bleue montre les contributions du bruit de fond et les autres lignes colorées correspondent à diverses hypothèses théoriques. Les points noirs représentent les données réelles et devraient être distribués de façon similaire à la ligne bleu en l’absence de nouvelles particules.

Une petite bosse est visible autour d’une valeur de masse de 2 TeV : il y a plus d’événements dans les données que ce à quoi on s’attend venant de sources connues. Mais il y a toujours un certain flou dans toute mesure à cause des erreurs expérimentales. Si on répétait la même mesure mille fois, au moins une de ces mesures aurait un écart semblable. Il est donc beaucoup trop tôt pour dire qu’il pourrait s’agir des premiers signes de la présence d’une nouvelle particule, comme un boson W’ hypothétique par exemple. Mais ce sera à suivre dans les nouvelles données.

CMS-dijet-8TeV-13TeV

Des évènements intrigants trouvés par CMS dans les nouvelles (à gauche) et les anciennes données (à droite)

La Collaboration CMS a aussi quelques événements intrigants, comme celui ci-dessus à gauche trouvé parmi les toutes nouvelles données recueillies depuis la reprise du LHC à 13 TeV. Les deux jets ont une masse combinée d’environ 5,0 TeV. Un évènement semblable ayant une masse combinée de 5,15 TeV (droite) a aussi été trouvé dans les données accumulées à 8 TeV. Il y a 500 fois moins de données à 13 TeV qu’à 8 TeV, mais les expériences peuvent déjà poursuivre les analyses effectuées à 8 TeV.

Il est beaucoup trop tôt pour dire quoi que ce soit. Un peu comme si nous regardions à distance, par un jour brumeux et à la tombée de la nuit, essayant de voir si le train s’en vient. La forme floue aperçue au loin est-elle réelle ou juste une illusion ? Personne ne le sait, il faut attendre que le train se rapproche. Mais pas pour longtemps puisque le LHC est déjà en marche. Les expériences CMS et ATLAS devraient bientôt avoir suffisamment de nouvelles données pour pouvoir trancher. Et là, attachez bien vos tuques, ça va devenir excitant!

Pauline Gagnon

Pour recevoir un avis lors de la parution de nouveaux blogs, suivez-moi sur Twitter: @GagnonPauline ou par e-mail en ajoutant votre nom à cette liste de distribution ou consultez mon site web.

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The bumpy road to discoveries http://www.quantumdiaries.org/2015/07/28/the-bumpy-road-to-discoveries/ http://www.quantumdiaries.org/2015/07/28/the-bumpy-road-to-discoveries/#comments Tue, 28 Jul 2015 13:21:33 +0000 http://www.quantumdiaries.org/?p=36045 Yesterday, at the European Physics Society (EPS) Particle Physics conference in Vienna, we moved from parallel sessions to plenary sessions. The tasks of the speakers is now to summarize the hundreds of results presented so far at the conference, and draw the big picture.

For the past two years, the Large Hadron Collider underwent major upgrade work. Experimentalists have used this downtime to look at all collected data from all possible angles (and a few more!). With final calibrations and improved algorithms everywhere, nearly all analyses now included all data collected at 8 TeV. In most cases, months of hard work for hundreds of people only slightly improved the resolution. But these rock solid results have unfortunately not revealed new discoveries.

That’s the bad news. The good news is that four times more data is expected in the coming year at higher energy, making new phenomena accessible.

Here is one example. Both the CMS and ATLAS experiments are looking for heavy hypothetical particles that would decay into two of the known bosons, namely photons, Z, W or Higgs bosons. In turns, the last three bosons could decay into jets of light particles made of quarks.

A particle decay is very similar to making change for a large coin: the initial coin does not contain the smaller coins but can be exchanged for smaller coins of equal value, like on the diagram below. The four pieces of 50 centimes could come either from a two euro coin or from two coins of one euro. Likewise in our detectors, when we find four jets of particles, they can come from two independently produced Z, W or H bosons, or simply from four quarks produced directly. All this is called the background while the signal in this case would be a new boson that first decayed into two bosons.

decay-coins

A particle decay is like making small change for a large coin.

A coin only has one value but a particle carries both mass and energy. When one breaks a large coin, its total value is conserved. With particles, we must take into account the mass and the energy of all the decay products to calculate the combined mass of the original particle. One last detail: when the initial decaying particle is much heavier than the two bosons it produces, the jets coming from these bosons will hardly be separated. They will fly along side each other. In the end, we will not see four jets but rather two broader jets.

If the two broad jets come from two unrelated Z bosons, their total combined mass will be random, just as if we were to sum up the values of the small coins we carry in our pocket. If thousands of people told us the value of their small change, we would get a distribution like the one shown below by the blue line. Most people have only a little change, but some carry a small fortune in coins.

ATLAS-bumpThe horizontal axis gives the combined mass value of each event containing two broad jets found by the ATLAS Collaboration. The vertical axis shows (on a logarithmic scale) how many events were found with a particular value. The blue line shows what is expected from various backgrounds and the other colourful lines correspond to a few hypotheses. The black dots represent the real data and would look similar to the blue line if nothing new were there.

A small bump shows up around a mass value of 2 TeV, that is, more events are seen in data than what is predicted. The excess is 3.4 σ. Since there is always a spread in measured values due to the experimental errors, such a difference would occur at least once if we were to measure this quantity 1000 times. Hence, it is to early to say this could be the first sign of something new like a hypothetical boson denoted W’.

CMS-dijet-8TeV-13TeV

Intriguing events found by CMS with a mass around 5 TeV in the new (left) and old (right) data.

The CMS Collaboration also showed a few intriguing events. One is found in the newest data collected at 13 TeV after the restart of the LHC. The two jets combined mass is 5 TeV (left figure). The second event comes from the data collected earlier at 8 TeV and has a mass of 5.15 TeV. With 500 times less data at 13 TeV than 8 TeV, the experiments are already extending the analyses started with the 8 TeV data.

At this stage, it is way too early to tell. This is similar to looking in the distance on a foggy day, at dusk, trying to see if the train is coming. A faint shape is visible but is this real or just a mirage? No one knows, we must wait for the train to come closer. But not for long since the LHC is on track. Both experiments should soon have enough new data to be more definitive. And then, hold on to your hat, it’s going to get really exciting.

Pauline Gagnon

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Trop passionnant pour ne pas partager http://www.quantumdiaries.org/2015/07/27/trop-passionnant-pour-ne-pas-partager/ http://www.quantumdiaries.org/2015/07/27/trop-passionnant-pour-ne-pas-partager/#comments Mon, 27 Jul 2015 12:11:39 +0000 http://www.quantumdiaries.org/?p=36042 La plupart des physiciens et physiciennes sont d’accord: la physique est bien trop passionnante pour la réserver seulement aux scientifiques. Et pour la première fois, la Société Européenne de Physique (EPS) y a consacré une session entière samedi lors de sa conférence de physique des particules en cours à Vienne. Plusieurs y ont rapporté des initiatives variées visant à partager le meilleur de la physique des particules avec le grand public.

La plupart des activités décrites visaient des étudiants et étudiantes de tous âges, venant de pays développés ou en développement. Kate Shaw, chercheure au Centre International de Physique Théorique (ICTP) de Trieste en Italie, a souligné comment la science peut aider à résoudre divers problèmes d’environnement et de développement. Le monde a besoin de plus de scientifiques, a déclaré Kate. Investir dans l’éducation, ainsi que dans les institutions technologiques et culturelles jouent un rôle-clé dans le développement d’une économie basée sur la connaissance. La recherche fondamentale stimule les sciences appliquées par l’innovation, la technologie et l’ingénierie. Elle a aussi souligné l’importance d’inclure toutes les minorités et les jeunes issus de familles à faible revenu.

Kate a fondé le programme “Physique sans Frontières” au ICTP et organisé des “Masterclasses” (voir ci-dessous) et autres activités en Palestine, en Égypte, au Népal, au Liban, au Viêt-Nam et en Algérie. Non seulement elle inspire les jeunes à entreprendre des études en science, mais elle les assiste aussi, les aidant à accéder à des programmes de maîtrise et de doctorat. Kate a reçu aujourd’hui le Outreach Award de l’EPS « pour son travail de dissémination de la physique des particules dans des pays qui n’ont pas de programmes bien établis ».

Palestine

Etudiantes participant à une Masterclasse en Palestine dans le cadre du programme “Physique sans Frontières”

Une Masterclasse consiste en une journée entière d’activités interactives conçues pour des élèves. Des scientifiques décrivent d’abord la physique des particules et l’expérience à laquelle ils ou elles participent. Un repas pris en commun facilite les échanges avant de se lancer dans de vraies analyses avec de vraies données. Chaque année, une masterclasse internationale réunit environ 10 000 élèves de 42 pays. Ils et elles rejoignent des scientifiques de 200 universités ou laboratoires voisins, pour effectuer de véritables mesures de physique en collaboration internationale avec les autres élèves. Pourquoi ne pas participer à une Masterclasse?

Ces élèves ainsi que d’autres groupes peuvent aussi prendre part à une visite virtuelle d’une expérience de physique. Un ou une scientifique sur place au laboratoire interagit avec le groupe, avant de leur faire visiter les installations à l’aide d’une connexion vidéo en direct.

Vous cherchez une activité inspirante qui soit simple, bon marché et accessible pour un événement spécial, une conférence ou un groupe? Invitez-les à une visite virtuelle au CERN (ATLAS ou CMS). Ainsi en janvier, 500 élèves de Mumbai ont profité de leur “visite” de l’expérience IceCube située à 12 000 km au pôle sud, pour bombarder les scientifiques avec leurs questions.

Le Teacher Programme du CERN a déjà accueilli un millier de personnes. Les enseignants et enseignantes du niveau secondaire venus de partout dans le monde s’en font mettre plein la vue pendant plusieurs semaines afin de s’assurer qu’ils partageront leur enthousiasme avec leurs élèves à leur retour.

Les présentations publiques et les livres de vulgarisation scientifique visent un public plus général. Beaucoup de scientifiques, moi y compris, se feront un plaisir de venir donner une conférence près de chez vous. Il suffit de demander.

Pauline Gagnon

Pour recevoir un avis lors de la parution de nouveaux blogs, suivez-moi sur Twitter: @GagnonPauline ou par e-mail en ajoutant votre nom à cette liste de distribution ou consultez mon site web.

 

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Too exciting to leave it only to physicists http://www.quantumdiaries.org/2015/07/27/too-exciting-to-leave-it-only-to-physicists/ http://www.quantumdiaries.org/2015/07/27/too-exciting-to-leave-it-only-to-physicists/#comments Mon, 27 Jul 2015 12:04:18 +0000 http://www.quantumdiaries.org/?p=36038 Most physicists agree: physics is too interesting to leave it only to physicists. For the first time, the European Physics Society (EPS) dedicated a whole session to Outreach this year at its ongoing Particle Physics conference in Vienna. The participants reported on a wealth of creative initiatives undertaken by individuals or institutions to share the best of particle physics with the general public.

Most activities described aimed at students of all ages, in developed and developing countries. Kate Shaw, a researcher from the International Centre for Theoretical Physics (ICTP) in Trieste, Italy, stressed how science can help solve various environmental and developmental problems. The world needs more scientists, Kate stated, and investing in education, technology and cultural institutions plays a key-role in developing a knowledge-based economy. Fundamental research stimulates applied sciences through innovation, technology and engineering. She also mentioned the importance of reaching out to all minorities and low-income students everywhere.

Kate initiated the Program “Physics without Frontiers” at ICTP and conducted “Masterclasses” (see below) in the Palestinian Territories, Egypt, Lebanon, Nepal, Vietnam and Algeria. Not only does she inspire students to study in science, but she also mentors them to help them access Masters and PhD programs. Kate received today the EPS Outreach Prize “for bringing particle physics to countries with no strong tradition in particle physics”.

Palestine

Students taking part in a Masterclass in Palestine sponsored by “Physics without Frontiers”

Masterclasses refer to a full-day of interactive activities designed for high-school and undergraduate students. Physicists first describe their fields and their experiment. Then the students can interact with them over lunch before launching into real analysis with real data. Every year, an international Masterclass brings together some 10000 students from 42 countries. They join scientists at 200 nearby universities or research centres, measuring meaningful quantities in collaboration with the other international students. You too could participate in a Masterclass.

Masterclasses participants and other groups are also often treated to a virtual visit of a top-notch experiment. A scientist located at the laboratory interacts with the group, then “walks” them through the facilities using a live video connection.

Are you looking for an inspiring activity that is simple, cheap and accessible to all for a special event, conference or group? Treat them to a virtual visit to CERN (ATLAS or CMS). In January, 500 students from Mumbai “visited” the IceCube. experiment at the South Pole 12,000 km away, flooding the scientists with questions.

The CERN’s Teacher Programme is also thriving, with one thousand participants so far. High-school teachers from all over the world are treated to unforgettable experiences to make sure they will share their enthusiasm and excitement with their students when they return home.

Public lectures and popular science books aim at more general audiences. Many scientists worldwide, including myself, will be happy to come give a public lecture in your area upon request. Just ask.

Pauline Gagnon

To be alerted of new postings, follow me on Twitter: @GagnonPauline  or sign-up on this mailing list to receive an e-mail notification. You can also visit my website

 

 

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Matière sombre et énergie sombre n’ont qu’à bien se tenir http://www.quantumdiaries.org/2015/07/24/matiere-sombre-et-energie-sombre-nont-qua-bien-se-tenir/ http://www.quantumdiaries.org/2015/07/24/matiere-sombre-et-energie-sombre-nont-qua-bien-se-tenir/#comments Fri, 24 Jul 2015 15:19:23 +0000 http://www.quantumdiaries.org/?p=36036 La matière sombre et l’énergie sombre sont bien en évidence à la conférence de physique des particules de la Société de Physique Européenne à Vienne. Bien que les physiciens et physiciennes comprennent maintenant assez bien les constituants de base de la matière, tout ce que l’on voit sur la Terre, dans les étoiles et les galaxies, cette énorme quantité de matière ne représente que 5 % du contenu total de l’Univers. Pas étonnant alors qu’autant d’efforts soient déployés pour élucider le mystère de la matière sombre (27 % de l’Univers) et de l’énergie sombre (68 %).

Depuis le Big Bang, non seulement l’Univers s’étend mais cette expansion va en accélérant. Quelle énergie alimente cette accélération ? Nous l’appelons énergie sombre. Cela demeure absolument inconnu mais l’équipe du Dark Energy Survey cherche à obtenir des éléments de réponse. Ces scientifiques vont examiner un quart du ciel de l’hémisphère sud, cataloguant l’emplacement, la forme et la distribution d’objets astronomiques tels que des amas galactiques (regroupements de galaxies) et de supernovæ (étoiles en explosion). Leur but est de recueillir de l’information sur 300 millions de galaxies et 2500 supernovæ.

Les galaxies se sont formées grâce à l’effet attractif de la gravité, qui a permis à la matière de se regrouper, malgré l’effet dispersif de l’énergie sombre, qui disperse la matière avec l’expansion de l’Univers. Les scientifiques de DES étudient essentiellement comment les grandes structures telles que les amas galactiques se sont développées dans le temps en observant des objets situés à différentes distances et dont la lumière provient de différentes époques dans le temps. Avec plus de données, ces scientifiques espèrent mieux comprendre la dynamique de l’expansion.

La matière sombre est tout aussi inconnue. Jusqu’ici, elle ne s’est manifestée qu’à travers ses effets gravitationnels. Nous pouvons “sentir” sa présence mais pas la voir, puisqu’elle n’émet aucune lumière, contrairement à la matière ordinaire contenue dans les étoiles et supernovæ. Comme si l’Univers entier était rempli de fantômes.

Une douzaine de détecteurs, utilisant des techniques différentes, essaient d’attraper ces particules fantômes. Pas facile de les traquer quand on ne sait ni comment, ni même si ces particules interagissent avec la matière. Elles doivent cependant interagir très rarement car autrement, elles auraient déjà été décelées. On utilise donc des détecteurs massifs dans l’espoir qu’une de ces particules de matière sombre frappe un noyau d’un des atomes du détecteur, induisant une petite vibration décelable. Les différentes équipes de scientifiques tentent de sonder toute la gamme de possibilités. Celles-ci dépendent de la masse possible des particules de matière sombre et leur affinité à interagir avec la matière.

Le graphe ci-dessous illustre la possibilité qu’une particule de matière sombre interagisse avec un noyau (axe vertical) en fonction de leur masse (axe horizontal). Cela couvre une vaste région de possibilités qu’il faut tester. Chaque courbe sur le graphe représente les résultats d’une expérience différente. Les régions au-dessus de ces courbes représentent les possibilités qui sont exclues. La partie gauche du graphe est la plus difficile à explorer car plus les particules de matière noire sont légères, plus la vibration induite est petite.

CRESST-limit

La Collaboration CRESST utilise de petits cristaux opérant à très basse température. Ils peuvent déceler la hausse de température minime que provoquerait une particule de matière sombre en frappant un noyau atomique. Cela leur a permis de réussir là où des dizaines d’expériences précédentes avaient échoué : la recherche de particules très légères. C’est ce que l’on peut voir sur le graphe. Toutes les possibilités au-dessus du trait continu rouge dans le coin supérieur gauche sont désormais exclues. Jusqu’ici, cette zone n’était accessible qu’aux expériences du Grand Collisionneur de Hadron (LHC) du CERN (non incluses dans ce graphe), mais au prix de plusieurs suppositions. CRESST vient d’ouvrir tout un monde de possibilités. Les particules de matière sombre légères n’ont qu’à bien se tenir.

Pauline Gagnon

Pour recevoir un avis lors de la parution de nouveaux blogs, suivez-moi sur Twitter: @GagnonPauline ou par e-mail en ajoutant votre nom à cette liste de distribution ou consultez mon site web

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Dark matter and dark energy better watch out http://www.quantumdiaries.org/2015/07/24/dark-matter-and-dark-energy-better-watch-out/ http://www.quantumdiaries.org/2015/07/24/dark-matter-and-dark-energy-better-watch-out/#comments Fri, 24 Jul 2015 15:10:30 +0000 http://www.quantumdiaries.org/?p=36033 Dark matter and dark energy feature prominently at the European Physics Society conference on particle physics in Vienna. Although physicists now understand pretty well the basic constituents of matter, all what one sees on Earth, in stars and galaxies, this huge amount of matter only accounts for 5% of the whole content of the Universe. Not surprising then that much efforts are deployed to elucidate the nature of dark matter (27% of the Universe), and dark energy (68%).

Since the Big Bang, the Universe is not only expanding, but this expansion is also accelerating. So which energy fuels this acceleration? We call it dark energy. This is still something absolutely unknown but the Dark Energy Survey (DES) team is determined to get some answers. To do so, they are searching a quarter of the southern sky, mapping the location, shape and distribution of various astronomical objects such as galactic clusters (large groups of galaxies) and supernovae (exploding stars). Their goal is to record information on 300 million galaxies and 2500 supernovae.

Galaxies formed thanks to gravity that allowed matter to cluster. But this happened against the dispersive effect of dark energy, since the expansion of the Universe scattered matter away. The DES scientists essentially study how large structures such as galactic clusters evolved in time by looking at objects at various distances, and whose light comes from different times in the past. With more data, they hope to better understand the dynamic of expansion.

Dark matter is just as unknown. So far, it has only manifested itself through gravitational effects. We can “feel” its presence but we cannot see it, since it emits no light, unlike regular matter found in stars and supernovae. As if the whole Universe was full of ghosts. A dozen detectors, using different techniques, are trying to find dark matter particles.

Not easy to catch such elusive particles when no one knows how and if these particles interact with matter. Moreover, these particles must interact very rarely with regular matter (otherwise, they would already have been found), the name of the game is to use massive detectors, in the hope one nucleus from one of the detector atoms will recoil when hit by a dark matter particle, inducing a small but detectable vibration in the detector. The experiments search for a range of possibilities, depending on the mass of the dark matter particles and how often they can interact with matter.

The plot below shows how often dark matter particles could interact with a nucleus (vertical axis) as a function of their mass (horizontal axis). This spans a wide region of possibilities one must test. The various curves indicate what has been achieved so far by different experiments. All possibilites above the curves are excluded. The left part of the plot is harder to probe since the lighter the dark matter particles is, the smaller the vibration induced.

CRESST-limitThe CRESST Collaboration uses small crystals operating at extremely low temperature. They are sensitive to the temperature rise that would occur if a dark matter particle deposited the smallest amount of energy. This allowed them to succeed where tens of previous experiments had failed: looking for very light particles. This is shown on the plot by the solid red curve in the upper left corner. All possibilities above are now excluded. So far, this area was only accessible to the Large Hadron Collider (LHC) experiments (results not shown here) but only when making various theoretical hypotheses. CRESST has just opened a new world of possibilities and they will sweep nearly the entire area in the coming years. Light dark matter particles better watch out.

Pauline Gagnon

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Fermilab magnet team helps bring brighter beams to APS Upgrade Project at Argonne http://www.quantumdiaries.org/2015/07/24/fermilab-magnet-team-helps-bring-brighter-beams-to-aps-upgrade-project-at-argonne/ http://www.quantumdiaries.org/2015/07/24/fermilab-magnet-team-helps-bring-brighter-beams-to-aps-upgrade-project-at-argonne/#comments Fri, 24 Jul 2015 14:46:39 +0000 http://www.quantumdiaries.org/?p=36030 This article appeared in Fermilab Today on July 24, 2015.

Argonne National Laboratory was attracted to the expertise of this Fermilab magnet team. The team recently developed a pre-prototype magnet for Argonne's APS Upgrade Project. Photo: Doug Howard, Fermilab

Argonne National Laboratory was attracted to the expertise of this Fermilab magnet team. The team recently developed a pre-prototype magnet for Argonne’s APS Upgrade Project. Photo: Doug Howard, Fermilab

A magnet two meters long sits in the Experiment Assembly Area of the Advanced Photon Source at Argonne National Laboratory. The magnet, built by Fermilab’s Technical Division, is fire engine red and has on its back a copper coil that doesn’t quite reach from one end to the other. An opening on one end of the magnet’s steel casing gives it the appearance of a rectangular alligator with its mouth slightly ajar.

“It’s a very pretty magnet,” said Argonne’s Glenn Decker, associate project manager for the accelerator. “It’s simple and it’s easy to understand conceptually. It’s been a very big first step in the APS Upgrade.”

The APS is a synchrotron light source that accelerates electrons nearly to the speed of light and then uses magnets to steer them around a circular storage ring the size of a major-league baseball stadium. As the electrons bend, they release energy in the form of synchrotron radiation — light that spans the energy range from visible to x-rays. This radiation can be used for a number of applications, such as microscopy and spectroscopy.

In 2013, the federal Basic Energy Sciences Advisory Committee, which advises the Director of the Department of Energy’s Office of Science, recommended a more ambitious approach to upgrades of U.S. light sources. The APS Upgrade will create a world-leading facility by using new state-of-the-art magnets to tighten the focus of the APS electron beam and dramatically increase the brightness of its X-rays, expanding its experimental capabilities by orders of magnitude.

Instead of the APS’ present magnet configuration, which uses two bending magnets in each of 40 identical sectors, the upgraded ring will deploy seven bending magnets per sector to produce a brighter, highly focused beam.

Because the APS Upgrade requires hundreds of magnets — many of them quite unusual — Argonne called on experts at Fermilab and Brookhaven National Laboratory for assistance in magnet design and development.

Fermilab took on the task of designing, building and testing a pre-prototype for a groundbreaking M1 magnet — the first in the string of bending magnets that makes up the new APS arrangement.

“At Fermilab we have the whole cycle,” said Fermilab’s Vladimir Kashikhin, who is in charge of magnet designs and simulations. “Because of our experience in magnet technology and the people who can simulate and fabricate magnets and make magnetic measurements, we are capable of making any type of accelerator magnet.”

The M1’s magnetic field is strong at one end and tapers off at the other end, reducing the impact of processes that increase the beam size, producing a brighter beam. Because of this change in field, this magnet is different from anything Fermilab had ever built. But by May, Fermilab’s team had completed and tested the magnet and shipped it to Argonne, where it charged triumphantly through a series of tests.

“The magnetic field shape they were asking for was a little bit challenging,” said Dave Harding, the principal investigator leading the project at Fermilab. “Getting the shape of the steel to produce that distribution and magnetic field required some tinkering. But we did it.”

Although this pre-prototype magnet is unlikely to be installed in the complete storage ring, scientists working in this collaboration view the M1 development as an opportunity to learn about technical difficulties, validate their designs and strengthen their skills.

“Getting our hands on some real hardware injected a dose of reality into our process,” Decker said. “We’re going to take the lessons we learned from this M1 magnet and fold them into the next iteration of the magnet. We’re looking forward to a continuing collaboration with Fermilab’s Technical Division on magnetic measurements and refinement of our magnet designs, working toward the next world-leading hard X-ray synchrotron light source.”

Ali Sundermier

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Antineutrinos et pentaquarks : ça chauffe à Vienne! http://www.quantumdiaries.org/2015/07/23/antineutrinos-et-pentaquarks-ca-chauffe-a-vienne/ http://www.quantumdiaries.org/2015/07/23/antineutrinos-et-pentaquarks-ca-chauffe-a-vienne/#comments Thu, 23 Jul 2015 15:26:57 +0000 http://www.quantumdiaries.org/?p=36021 Hauptgebäude1

“Nous posons des questions depuis 1365″. Cette déclaration inspirante accrochée près de son imposant portail d’entrée, marque le 650ième anniversaire de l’Université de Vienne. Cette bannière accueillait ce matin les 730 physiciens et physiciennes venu assister à la principale conférence de physique des particules de l’année organisée par la Société Européenne de Physique. Pendant une semaine, les participants et participantes devront choisir parmi des centaines de présentations où on fera le tour des connaissances actuelles en physique des particules et des nouvelles avenues avancées. Première énorme surprise : le thermomètre affichait 39˚C hier, la plus haute température jamais enregistrée à Vienne.

Déjà, la première journée comportait son lot de résultats récents et excitants. Tel qu’annoncé la semaine dernière, la collaboration LHCb du CERN a découvert les tous premiers pentaquarks, des particules composées de cinq quarks. Les quarks sont quelques uns des grains de matière fondamentaux. Les physiciens et physiciennes observent déjà depuis des décennies des dizaines de particules faites de deux ou trois quarks. Par exemple, plusieurs particules sont faites d’une paire de quark et d’antiquark. D’autres particules, comme les protons et les neutrons, contiennent trois quarks. Tout récemment, quelques groupes expérimentaux avaient aussi rapporté la découverte de tétraquarks, des objets composés de quatre quarks. Et finalement, la semaine dernière, grâce à l’énorme quantité de données rendues disponibles par le Grand Collisionneur de Hadrons, ou LHC, les scientifiques de l’expérience LHCb ont fièrement annoncé la découverte de pentaquarks. Ils et elles ont ainsi pu réaliser ce que beaucoup d’autres groupes avaient en vain essayé de faire pendant des décennies. On s’attendait à leur existence, mais ils n’avaient jamais été observés auparavant. Ce qui prouve bien qu’il nous reste encore beaucoup à découvrir et à comprendre.

Autre belle nouvelle: l’expérience de neutrinos T2K, qui se déroule au Japon, a peut-être détecté les premiers signes d’oscillations d’antineutrinos. On connaît à ce jour trois types de neutrinos, chacun accompagnant sa propre particule, soit l’électron, le muon ou le tau. Le processus d’oscillation décrit comment des neutrinos d’un type particulier peuvent se changer en un autre type de neutrinos.  Ce phénomène a déjà été observé pour les neutrinos, mais ce serait une première avec les antineutrinos. Mais tout est loin d’être clair, au contraire. D’abord, l’équipe de T2K n’a que trois petits évènements à se mettre sous la dent et il n’y a encore aucune certitude qu’on ait bel et bien affaire à des antineutrinos et non pas des neutrinos. Il faudra encore attendre une année ou deux avant que suffisamment d’évènements soient accumulés pour qu’on puisse en avoir le cœur net. Mais si c’était le cas, cela nous en apprendrait davantage sur les similitudes ou différences entre matière et antimatière.

Plusieurs expériences essaient aussi d’établir s’il n’existerait pas un autre type de neutrinos, appelés neutrinos stériles, dont le spin serait l’inverse des autres neutrinos, c’est-à-dire qu’ils tourneraient sur eux-mêmes dans le sens inverse des neutrinos habituels. Bien sûr, toute découverte de nouvelles particule est à suivre. Mais la confirmation de l’existence de neutrinos stériles tout particulièrement. Cela enverrait une onde de choc en physique des particules car ce serait une observation directe d’une physique nouvelle bien plus vaste que le Modèle Standard actuel. Il faudrait alors tout revoir. Et qui sait? Les physiciens et physiciennes pourraient bien avoir de quoi continuer à se poser des questions pendant les 650 années à venir…

Pauline Gagnon

Pour recevoir un avis lors de la parution de nouveaux blogs, suivez-moi sur Twitter: @GagnonPauline ou par e-mail en ajoutant votre nom à cette liste de distribution ou consultez mon site web

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Antineutrinos and pentaquarks: it’s hot in Vienna! http://www.quantumdiaries.org/2015/07/23/antineutrinos-and-pentaquarks-its-hot-in-vienna/ http://www.quantumdiaries.org/2015/07/23/antineutrinos-and-pentaquarks-its-hot-in-vienna/#comments Thu, 23 Jul 2015 15:15:37 +0000 http://www.quantumdiaries.org/?p=36018 Hauptgebäude1« We have been asking questions since 1365 ». This inspiring statement marking the 650th anniversary of the University of Vienna, is hanging near the imposing entrance of its main building. This sign welcomed this morning the 730 physicists who came to Vienna to participate to the main particle physics conference this year organised by the European Physics Society. For a week, the participants will have to choose among hundreds of presentations where the current status of knowledge in particle physics will be presented along with the newest avenues. and we are already making history: Vienna recorded yesterday its highest ever temperature with 39 ˚C.

And this first day brought recent and exciting results. As announced last week, the LHCb collaboration at CERN has discovered the first pentaquarks, composite objects made of five quarks. Quarks are some of the building blocks of matter. Physicists have observed for decades dozens of different particles made of two or three quarks. For example, many particles are made of a pairs of quark and antiquark, while others, like protons and neutrons, contain three quarks. However, in recent years, a few experimental groups also reported the discovery of tetraquarks, objects composed of four quarks. Finally, last week, thanks to the huge dataset made available by the Large Hadron Collider, scientists from the LHCb experiment achieved what many other groups had tried to do for decades without success, and proudly announced the discovery of pentaquarks. Such composite objects were expected but never observed before. It goes to show how much we still have to discover and understand.

Another nice piece of news: the T2K neutrino experiment, which takes place in Japan, may have detected the first signs for oscillations of antineutrinos. To this day, there are three known types of neutrinos, each one accompanying its own particle, namely the electron, the muon and the tau. The oscillation process describes how one type of neutrinos can change into another type. This phenomenon has already been observed for neutrinos, but it would be the first observation for antineutrinos. However, all is far from being set in concrete yet, quite the contrary. With only three events at hands, the T2K team still needs to verify if these events really involve antineutrinos and not just neutrinos. They therefore need to collect more date for another year or two before this issue can be settled. If it turns out to be indeed antineutrinos, we would learn more on the similarities or the differences between matter and antimatter.

Several experiments are also trying to establish if there could also be another type of neutrinos, called sterile neutrinos. Their spin would be the opposite of known neutrinos, meaning they would be spinning on themselves in the opposite direction. Clearly, any new type of particle is something worth watching for. The confirmation of the existence of sterile neutrinos would send a shock wave in particle physics since it would constitute an indisputable proof for the existence of a theory more encompassing than the current theoretical model, called the Standard Model. Everything would then have to be rethought. And who knows? Physicists could very well have enough to keep asking difficult questions for another 650 years…

Pauline Gagnon

To be alerted of new postings, follow me on Twitter: @GagnonPauline, sign-up on this mailing list to receive an e-mail notification or consult my website.

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Nerds and Names http://www.quantumdiaries.org/2015/07/16/nerds-and-names/ http://www.quantumdiaries.org/2015/07/16/nerds-and-names/#comments Thu, 16 Jul 2015 14:07:45 +0000 http://www.quantumdiaries.org/?p=36000 If there’s one thing that makes me jealous about planetary scientists, it’s how many things they get to name. They also seem to have an awful lot of fun with it. Consider these typical naming processes:

  • Experimental particle physicists: “Jeff Weiss did an ‘availability search” of the Greek alphabet and found that the Greek letter Upsilon was not yet used”. [1]
  • Planetary scientists: “Woooooooo, another mountain range! Let me get my copy of the Silmarillion!” [2]

They also seem to have snuck in a Marvel Cinematic Universe tie-in while naming one of Pluto’s newer moons.

Hydra_Revealed_Tweet

But wait, you may ask, doesn’t particle physics have whimsical names?  A few, sure. But it was the theoretical physicists who named things like “quarks”; by the time we discover them, we already know what they’re supposed to be and don’t get to make up new names.  New particles with 5 quarks?  We’ll just be literal and call them “pentaquarks”; the specific states can be Pc(4450)+ and Pc(4380)+[3], names which give useful information about charge and mass but aren’t really any fun.  Really, the most fun we ever get to have is with tortured acronyms [4].  It’s just not fair at all.

But seriously, congratulations to everyone working on New Horizons.  Enjoy your fun — you’ve earned it. And maybe the next particle we discover, we’ll take a page from your playbook.

[1] J. Yoh (1998). “The Discovery of the b Quark at Fermilab in 1977: The Experiment Coordinator’s Story“. AIP Conference Proceedings 424: 29–42.

[2] Not an actual quote (as far as I know). But since yesterday, Pluto has a “Cthulhu” and a “Balrog” and Charon has a “Mordor”.

[3] See Adrian Davis’s Quantum Diaries post from yesterday.

[4] ATLAS Collaboration (2008). “The ATLAS experiment at the Large Hadron Collider.” JINST 3 S08003. See the acronym list appendix.

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Finding a five-leafed clover http://www.quantumdiaries.org/2015/07/15/finding-a-five-leafed-clover/ http://www.quantumdiaries.org/2015/07/15/finding-a-five-leafed-clover/#comments Wed, 15 Jul 2015 07:30:17 +0000 http://www.quantumdiaries.org/?p=35951 Photo Credit: Cathy Händel, Published on http://www.suttonelms.org.uk/olla12.html

Photo Credit: Cathy Händel, Published on http://www.suttonelms.org.uk/olla12.html

Sometimes when you’re looking for something else, you happen across an even more exciting result. That’s what’s happened at LHCb, illustrated in the paper “Observation of \(J/\psi p\) resonances consistent with pentaquark states in \(\Lambda_b^0\to J/\psi K^-p\) decays”, released on the arXiv on the 14th of July.

I say this is lucky because the analysts found these states while they were busy looking at another channel; they were measuring the branching fraction of \(B^0\to J/\psi K^+ K^-\). As one of the analysts, Sheldon Stone, recalled to me, during the review of the \(B^0\) analysis, one reviewer asked if there could be a background from the decay \(\Lambda_b^0\to J/\psi K^- p\), where the proton was misidentified as a kaon. As this was a viable option, they looked at the PDG to see if the mode had been measured, and found that it had not. Without a certain knowledge of how large this contribution would be, the analysts looked. To their surprise, they found a rather large rate of the decay, allowing for a measurement of the lifetime of the \(\Lambda_b^0\). At the same time, they noticed a peak in the \(J/\psi p\) spectrum. After completing the above mentioned analysis of the \(B^0\), they returned to the channel.

It’s nice to put yourself in the analysts shoes and see the result for yourself. Let’s start by looking at the decay \(\Lambda_b^0\to J/\psi p K^-\). As this is a three body decay, we can look at the Dalitz Plots.

Dalitz plots from the decay Lambda_b^0\to J/\psi K p. Compiled from http://arxiv.org/abs/1507.03414

Dalitz plots from the decay \(\Lambda_b^0\to J/\psi K^- p\). Compiled from http://arxiv.org/abs/1507.03414

The above Dalitz plots show all combinations of possible axes to test. In the one on the left, around \(m^2=2.3\) GeV\(^2\), running vertically, we see the \(\Lambda(1520)\) resonance, which decays into a proton and a kaon. Running horizontally is a band which does not seem to correspond to a known resonance, but which would decay into a \(J/\psi\) and a proton. If this is a strong decay, then the only option is to have a hadron whose minimum quark content is \(uud\bar{c}c\). The same band is seen on the middle plot as a vertical band, and on the far right as the sloping diagonal band. To know for sure, one must perform a complete amplitude analysis of the system.

You might be saying to yourself “Who ordered that?” and think that something with five quarks hadn’t been postulated. This is not the case. Hadrons with quark content beyond the minimum were already thought about by Gell-Mann and Zweig in 1964 and quantitatively modeled by Jaffe in 1977  to 4 quarks and 5 quarks by Strottman in 1979. I urge you to go look at the articles if you haven’t before.

It appears as though a resonance has been found, and in order to be sure, a full amplitude analysis of the decay was performed. The distribution is first modeled without any such state, shown in the figures below.

Projections of the fits of the Lambda_b^0\to J/\psi K^- p spectrum without any additional components. From http://arxiv.org/abs/1507.03414

Projections of the fits of the\( \Lambda_b^0\to J/\psi K^- p\) spectrum without any additional components. Black is the data, and red is the fit. From http://arxiv.org/abs/1507.03414

Try as you might, the models are unable to explain the invariant mass distribution of the \(J/\psi p\). Without going into too much jargon, they wrote down from a theoretical standpoint what type of effect a five quark particle would have on the Dalitz plot, then put this into their model. As it turns out, they were unable to successfully model the distribution without the addition of two such pentaquark states. By adding these states, the fits look much better, as shown below.

Mass projection onto the J/\psi p axis of the total fit to the Dalitz plot. Again, Black is data, red is the fit. The inset image is for the kinematic range...  From http://arxiv.org/abs/1507.03414

Mass projection onto the \(J/\psi p\) axis of the total fit to the Dalitz plot. Again, Black is data, red is the fit. The inset image is for the kinematic range \(m(K p)>2 GeV\).
From http://arxiv.org/abs/1507.03414

The states  are called the \(P_c\) states. Now, as this is a full amplitude analysis, the fit also covers all angular information. This allows for determination of the total angular momentum and parity of the states. These are defined by the quantity \(J^P\), with \(J\) being the total angular momentum and \(P\) being the parity. All values for both resonances are tried from 1/2 to 7/2, and the best fit values are found to be with one resonance having \(J=3/2\) and the other with \(J=5/2\), with each having the opposite parity as the other. No concrete distinction can be made between which state has which value.

Finally, the significance of the signal is described by under the assumption \(J^P=3/2^-,5/2^+\) for the lower and higher mass states; the significances are 9 and 12 standard deviations, respectively.

The masses and widths turn out to be

\(m(P_c^+(4380))=4380\pm 8\pm 29 MeV\)

\(m(P_c^+(4450))=4449.8\pm 1.7\pm 2.5 MeV\)

With corresponding widths

Width\((P_c^+(4380))=205\pm 18\pm 86 MeV\)

Width\((P_c^+(4450))=39\pm 5\pm 19 MeV\)

Finally, we’ll look at the Argand Diagrams for the two resonances.

Argand diagrams for the two P_c states. From http://arxiv.org/abs/1507.03414

Argand diagrams for the two \(P_c\) states.
From http://arxiv.org/abs/1507.03414

 

Now you may be saying “hold your horses, that Argand diagram on the right doesn’t look so great”, and you’re right. I’m not going to defend the plot, but only point out that the phase motion is in the correct direction, indicated by the arrows.

As pointed out on the LHCb public page, one of the next steps will be to try to understand whether the states shown are tightly bound 5 quark objects or rather loosely bound meson baryon molecule. Even before that, though, we’ll see if any of the other experiments have something to say about these states.

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Fermilab’s flagship accelerator sets world record http://www.quantumdiaries.org/2015/07/09/fermilabs-flagship-accelerator-sets-world-record/ http://www.quantumdiaries.org/2015/07/09/fermilabs-flagship-accelerator-sets-world-record/#comments Thu, 09 Jul 2015 20:35:56 +0000 http://www.quantumdiaries.org/?p=35946 This Fermilab press release came out on July 8, 2015.

Fermilab's Main Injector accelerator, one of the most powerful particle accelerators in the world, has just achieved a world record for high-energy beams for neutrino experiments. Photo: Fermilab

Fermilab’s Main Injector accelerator, one of the most powerful particle accelerators in the world, has just achieved a world record for high-energy beams for neutrino experiments. Photo: Fermilab

A key element in a particle-accelerator-based neutrino experiment is the power of the beam that gives birth to neutrinos: The more particles you can pack into that beam, the better your chance to see neutrinos interact in your detector. Today scientists announced that Fermilab has set a world record for the most powerful high-energy particle beam for neutrino experiments.

Scientists, engineers and technicians at the U.S. Department of Energy’s Fermi National Accelerator Laboratory have achieved for high-energy neutrino experiments a world record: a sustained 521-kilowatt beam generated by the Main Injector particle accelerator. More than 1,000 physicists from around the world will use this high-intensity beam to more closely study neutrinos and fleeting particles called muons, both fundamental building blocks of our universe.

The record beam power surpasses that of the 400-plus-kilowatt beam sent to neutrino experiments from particle accelerators at CERN.

Setting this world record is an initial step for the Fermilab accelerator complex as it will gradually increase beam power over the coming years. The next goal for the laboratory’s two-mile-around Main Injector accelerator — the final and most powerful in Fermilab’s accelerator chain — is to deliver 700-kilowatt beams to the laboratory’s various experiments. Ultimately, Fermilab plans to make additional upgrades to its accelerator complex over the next decade, achieving beam power in excess of 1,000 kilowatts, also referred to as 1 megawatt.

“We have the world’s highest-power beam for neutrinos, and we’re only going up from here,” said Ioanis Kourbanis, head of the Main Injector Department at Fermilab.

Laboratory-made neutrino experiments start by accelerating a beam of particles, typically protons, and then smashing them into a target to create neutrinos. Scientists then use particle detectors to “catch” as many of those neutrinos as possible and record their interactions. Neutrinos rarely engage with matter: Only one out of every trillion emerging from the proton beam will interact in an experiment’s detector. The more particles in that beam, the more opportunities researchers will have to study these rare interactions.

The amped-up particle beam provided by the Main Injector enriches the lab’s neutrino supply, positioning Fermilab to become the primary laboratory for accelerator-based neutrino research. Neutrinos are also made in stars and in the Earth’s core, and they pass through everything — people and planets alike.

“The idea is that if you build a more intense beam, neutrino scientists from around the world will beat a path to your door,” said Fermilab Deputy Director Joe Lykken. “This is exactly what’s happening.”

Fermilab currently operates four neutrino experiments: MicroBooNE, MINERvA, MINOS+ and the laboratory’s largest-to-date neutrino experiment, NOvA, which sends particles from Fermilab’s suburban Chicago location to a far detector 500 miles away in Ash River, Minnesota. The laboratory is working with scientists from around the world on expanding its short-baseline neutrino program and would also serve as host to the proposed flagship Long-Baseline Neutrino Facility and Deep Underground Neutrino Experiment, or DUNE. Scientists aim to address basic questions about the mass and properties of each kind of neutrino as well as the role neutrinos played in the evolution of the universe.

“Reaching this milestone is a fantastic achievement for Fermilab; beam power is everything in our field,” said DUNE co-spokesperson Mark Thomson of the University of Cambridge. “The ability for Fermilab to deliver, yet again, gives the international neutrino community huge confidence in the future U.S.-hosted neutrino program.”

Fermilab is also preparing to operate two experiments for studying muons, short-lived particles that could reveal secrets about the earliest moments of the universe. The increased beam power will also benefit the Fermilab Test Beam Facility, one of the few facilities in the world that provides muons, pions and other particles that researchers can use to test their particle detectors.

Since 2011, Fermilab has made significant upgrades to its accelerators and reconfigured the complex to provide the best possible particle beams for neutrino and muon experiments. With the dedicated work of the Fermilab Accelerator Division, the Main Injector is on track to nearly double its Tevatron-era beam power by 2016.

“Fermilab’s beamline has been a tremendous driver of neutrino science for many years, and the continued improvements to the intensity mean that it will remain a driver for many years to come,” said Indiana University’s Mark Messier, co-spokesperson for the NOvA experiment.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC. Visit Fermilab’s website at www.fnal.gov, and follow us on Twitter at @Fermilab.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

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Getting teachers back on TRAC http://www.quantumdiaries.org/2015/07/08/getting-teachers-back-on-trac/ http://www.quantumdiaries.org/2015/07/08/getting-teachers-back-on-trac/#comments Wed, 08 Jul 2015 14:53:26 +0000 http://www.quantumdiaries.org/?p=35941 This article appeared in Fermilab Today on July 8, 2015.

Kerbie Reader, a high school math teacher, works at the Muon g-2 ring as part of Fermilab's TRAC program. Photo: Ali Sundermier

Kerbie Reader, a high school math teacher, works at the Muon g-2 ring as part of Fermilab’s TRAC program. Photo: Ali Sundermier

Bonnie Weiberg sits down in front of a small monitor in the Proton Assembly Building at Fermilab. Her job is to test the signal strength of the liquid-argon purification monitors for the proposed DUNE experiment. But Weiberg isn’t your average particle physicist. In fact she isn’t a physicist at all: She’s a physics and chemistry teacher at Niles North High School in Skokie, Illinois.

Weiberg is here this summer as part of the Fermilab TRAC program, which is funded by the Particle Physics Division. Harry Cheung, an associate head for the CMS Department who has been head of the TRAC program since 2010, said that this year, seven teachers were selected from a pool of 33 applicants to be matched with a mentor and work on cutting-edge physics.

The TRAC program gives middle school and high school teachers of science, math, computer science and engineering an opportunity to come to Fermilab, work with a scientist or an engineer for eight weeks, and experience what Fermilab research is like.

This summer the teachers, most of whom are from Illinois, are working on projects such as building and testing photodetectors, reconstructing the Muon g-2 ring and controlling high-voltage supplies for the MINERvA neutrino experiment.

“Many of us haven’t done any research since college,” Weiberg said. “It’s nice to come back and be in a research environment to see what’s happening on the cutting edge.”

Kerbie Reader, a high school math teacher at Forest Ridge School of the Sacred Heart in Bellevue, Washington, said that TRAC is the only program she could find in the country that enables teachers to participate in this sort of research. She appreciates the opportunity to remember what it’s like to be a student and to gain experience that will help her relate to her own students.

“We’re seeing the same material year after year. We forget what it’s like to be the person who’s learning,” Reader said. “Instead of saying it’s been 10 or 20 years since I felt that way, I can say, ‘I felt that way last summer. I get that it’s hard, and this is how we’re going to work through it.'”

Weiberg and Reader agreed that the most valuable aspect of this program is being able to gain real-life experiences that they can bring back to their schools and share with their students. Weiberg is even working on a unit about particle physics to incorporate into her curriculum.

“It’ll help us engage our students more,” Weiberg said. “The more real-world things you can bring into your classroom, the better.”

Reader added that the TRAC program gives her a chance to participate in difficult research: to be challenged and learn the value of getting things wrong.

“I want to teach my students not to give up on something because they think it’s hard, to be able to tell them: making a mistake is not the problem,” Reader said. “Everybody that works on all these fantastic things have been making mistakes their entire lives. The day you figure out what your mistakes are, that’s the day you celebrate.”

Ali Sundermier

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