What Kind of Higgs Boson Do We Have?
In July 2012, physicists at CERN announced discovering a new boson. By March of 2013, physicists on the ATLAS and CMS experiments were increasingly convinced that their particle was the long-sought Higgs boson, but it wasn’t clear which larger theoretical model of particles this boson might fit. For example, depending on its characteristics this Higgs boson might support a model for new physics such as supersymmetry. Now the LHC experiments have presented even more evidence that in fact this new particle is a perfect fit to the Standard Model of particle physics.
Both the ATLAS and CMS collaborations at CERN have now shown solid evidence that the new particle discovered in July 2012 behaves even more like the Higgs boson, by establishing that it also decays into particles known as tau leptons, a very heavy version of electrons.
Since 4th July 2012, the physicists at CERN have had a new boson to play with. This new boson was first seen in the searches that were optimised to find the world famous Higgs boson, and the experiments went as far as to call it a “Higgs-like” boson. Since then there has been an intense program to study its spin, width, decay modes and couplings and so far it’s passed every test of Higgs-ness. Whether or not the new boson is the Standard Model Higgs boson is one of the most pressing questions facing us today, as there is still room for anomalous couplings. Whatever the answer is, a lot of physicists will be pleased.
Since the Higgs boson’s discovery a little over a year ago at CERN I have been getting a lot of questions from my friends to explain to them “what this Higgs thing does.” So I often tried to use the crowd analogythat is ascribed to Prof. David Miller, to describe the Higgs (or Englert-Brout-Higgs-Guralnik-Hagen-Kibble) mechanism. Interestingly enough, it did not work well for most of my old school friends, majority of whom happen to pursue careers in engineering. So I thought that perhaps another analogy would be more appropriate. Here it is, please let me know what you think!
Paradigm and paradigm shift are so over used and misused that the world would benefit if they were simply banned. Originally Thomas Kuhn (1922–1996) in his 1962 book, The Structure of Scientific Revolutions, used the word paradigm to refer to the set of practices that define a scientific discipline at any particular period of time. A paradigm shift is when the entire structure of a field changes, not when someone simply uses a different mathematical formulation. Perhaps it is just grandiosity, everyone thinking their latest idea is earth shaking (or paradigm shifting), but the idea has been so debased that almost any change is called a paradigm shift, down to level of changing the color of ones socks.
The archetypal example, and I would suggest the only real example in the natural and physical sciences, is the paradigm shift from Aristotelian to Newtonian physics. This was not just a change in physics from the perfect motion is circular to an object either is at rest or moves at a constant velocity, unless acted upon by an external force but a change in how knowledge is defined and acquired. There is more here than a different description of motion; the very concept of what is important has changed. In Newtonian physics there is no place for perfect motion but only rules to describe how objects actually behave. Newtonian physics was driven by observation. Newton, himself, went further and claimed his results were derived from observation. While Aristotelian physics is broadly consistent with observation it is driven more by abstract concepts like perfection. Aristotle (384 BCE – 322 BCE) would most likely have considered Galileo Galilei’s (1564 – 1642) careful experiments beneath him. Socrates (c. 469 BC – 399 BC) certainly would have. Their epistemology was not based on careful observation.
While there have been major changes in the physical sciences since Newton, they do not reach the threshold needed to call them a paradigm shifts since they are all within the paradigm defined by the scientific method. I would suggest Kuhn was misled by the Aristotle-Newton example where, indeed, the two approaches are incommensurate: What constitutes a reasonable explanation is simply different for the two men. But would the same be true with Michael Faraday (1791 – 1867) and Niels Bohr (1885–1962) who were chronologically on opposite sides of the quantum mechanics cataclysm? One could easily imagine Faraday, transported in time, having a fruitful discussion with Bohr. While the quantum revolution was indeed cataclysmic, changing mankind’s basic understanding of how the universe worked, it was based on the same concept of knowledge as Newtonian physics. You make models based on observations and validate them through testable predictions. The pre-cataclysmic scientists understood the need for change due to failed predictions, even if, like Albert Einstein (1879 – 1955) or Erwin Schrödinger (1887 – 1961), they found quantum mechanics repugnant. The phenomenology was too powerful to ignore.
Sir Karl Popper (1902 – 1994) provided another ingredients missed by Kuhn, the idea that science advances by the bold new hypothesis, not by deducing models from observation. The Bohr model of the atom was a bold hypothesis not a paradigm shift, a bold hypothesis refined by other scientists and tested in the crucible of careful observation. I would also suggest that Kuhn did not understand the role of simplicity in making scientific models unique. It is true that one can always make an old model agree with past observations by making it more complex. This process frequently has the side effect of reducing the old models ability to make predictions. It is to remedy these problems that a bold new hypothesis is needed. But to be successful, the bold new hypothesis should be simpler than the modified version of the original model and more crucially must make testable predictions that are confirmed by observation. But even then, it is not a paradigm shift; just a verified bold new hypothesis.
Despite the nay-saying, Kuhn’s ideas did advance the understanding of the scientific method. In particular, it was a good antidote to the logical positivists who wanted to eliminate the role of the model or what Kuhn called the paradigm altogether. Kuhn made the point that is the framework that gives meaning to observations. Combined with Popper’s insights, Kuhn’s ideas paved the way for a fairly comprehensive understanding of the scientific method.
But back to the overused word paradigm, it would be nice if we could turn back the clock and restrict the term paradigm shift to those changes where the before and after are truly incommensurate; where there is no common ground to decide which is better. Or if you like, the demarcation criteria for a paradigm shift is that the before and after are incommensurate. That would rule out the change of sock color from being a paradigm shift. However, we cannot turn back the clock so I will go back to my first suggestion that the word be banned.
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 This is known as the Duhem-Quine thesis.
 There are probably paradigm shifts, even in the restricted meaning of the word, if we go outside science. The French revolution could be considered a paradigm shift in the relation between the populace and the state.
Both the ATLAS and CMS collaborations at CERN have now shown solid evidence that the new particle discovered in July 2012 behaves even more like the Higgs boson, by establishing that it also decays into particles known as tau leptons, a very heavy version of electrons.
Why is this so important? CMS and ATLAS had already established that the new boson was indeed one type of a Higgs boson. In that case, theory predicted it should decay into several types of particles. So far, decays into W and Z bosons as well as photons were well established. Now, for the first time, both experiments have evidence that it also decays into tau leptons.
The decay of a particle is very much like making change for a coin. If the Higgs boson were a one euro coin, there would be several ways to break it up into smaller coins, but, so far, the change machine seemed to only make change in some particular ways. Now, additional evidence for one more way has been shown.
There are two classes of fundamental particles, called fermions and bosons depending on their spin, their value of angular momentum. Particles of matter (like taus, electrons and quarks) belong to the fermion family. On the other hand, the particles associated with the various forces acting upon these fermions are bosons (like the photons and the W and Z bosons.).
The CMS experiment had already shown evidence for Higgs boson decays into fermions last summer with a signal of 3.4 sigma when combining the tau and b quark channels. A sigma corresponds to one standard deviation, the size of potential statistical fluctuations. Three sigma is needed to claim evidence while five sigma is usually required for a discovery.
For the first time, there is now solid evidence from a single channel – and two experiments have independently produced it. ATLAS collaboration showed evidence for the tau channel alone with a signal of 4.1 sigma, while CMS obtained 3.4 sigma, both bringing strong evidence that this particular type of decays occurs.
Combining their most recent results for taus and b quarks, CMS now has evidence for decays into fermions at the 4.0 sigma level.
The data collected by the ATLAS experiment (black dots) are consistent with coming from the sum of all backgrounds (colour histograms) plus contributions from a Higgs boson going into a pair of tau leptons (red curve). Below, the background is subtracted from the data to reveal the most likely mass of the Higgs boson, namely 125 GeV (red curve).
CMS is also starting to see decays into pairs of b quarks at the 2.0 sigma-level. While this is still not very significant, it is the first indication for this decay so far at the LHC. The Tevatron experiments have reported seeing it at the 2.8 sigma-level. Although the Higgs boson decays into b quarks about 60% of the time, it comes with so much background that it makes it extremely difficult to measure this particular decay at the LHC.
Not only did the experiments report evidence that the Higgs boson decays into tau leptons, but they also measured how often this occurs. The Standard Model, the theory that describes just about everything observed so far in particle physics, states that a Higgs boson should decay into a pair of tau leptons about 8% of the time. CMS measured a value corresponding to 0.87 ± 0.29 times this rate, i.e. a value compatible with 1.0 as expected for the Standard Model Higgs boson. ATLAS obtained 1.4 +0.5 -0.4, which is also consistent within errors with the predicted value of 1.0.
One of the events collected by the CMS collaboration having the characteristics expected from the decay of the Standard Model Higgs boson to a pair of tau leptons. One of the taus decays to a muon (red line) and neutrinos (not visible in the detector), while the other tau decays into a charged hadron (blue towers) and a neutrino. There are also two forward-going particle jets (green towers).
With these new results, the experiments established one more property that was expected for the Standard Model Higgs boson. What remains to be clarified is the exact type of Higgs boson we are dealing with. Is this indeed the simplest one associated with the Standard Model? Or have we uncovered another type of Higgs boson, the lightest one of the five types of Higgs bosons predicted by another theory called supersymmetry.
It is still too early to dismiss the second hypothesis. While the Higgs boson is behaving so far exactly like what is expected for the Standard Model Higgs boson, the measurements lack the precision needed to rule out that it cannot be a supersymmetric type of Higgs boson. Getting a definite answer on this will require more data. This will happen once the Large Hadron Collider (LHC) resumes operation at nearly twice the current energy in 2015 after the current shutdown needed for maintenance and upgrade.
Meanwhile, these new results will be refined and finalised. But already they represent one small step for the experiments, a giant leap for the Higgs boson.
For all the details, see:
Presentation given by the ATLAS Collaboration on 28 November 2013
Presentation given by the CMS Collaboration on 3 December 2013
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Les collaborations ATLAS et CMS du CERN ont maintenant l’évidence que la nouvelle particule découverte en juillet 2012 se comporte de plus en plus comme le boson de Higgs. Les deux expériences viennent en fait de démontrer que le boson de Higgs se désintègre aussi en particules tau, des particules semblables aux électrons mais beaucoup plus lourdes.
Pourquoi est-ce si important? CMS et l’ATLAS avaient déjà établi que ce nouveau boson était bien un type de boson de Higgs. Si tel est le cas, la théorie prévoit qu’il doit se désintégrer en plusieurs types de particules. Jusqu’ici, seules les désintégrations en bosons W et Z de même qu’en photons étaient confirmées. Pour la première fois, les deux expériences ont maintenant la preuve qu’il se désintègre aussi en particules tau.
La désintégration d’une particule s’apparente beaucoup à faire de la monnaie pour une pièce. Si le boson de Higgs était une pièce d’un euro, il pourrait se briser en différentes pièces de monnaie plus petites. Jusqu’à présent, le distributeur de monnaie semblait seulement donner la monnaie en quelques façons particulières. On a maintenant démontré qu‘il existe une façon supplémentaire.
Il y a deux classes de particules fondamentales, appelées fermions et bosons selon la valeur de quantité de mouvement angulaire. Les particules de matière comme les taus, les électrons et les quarks appartiennent tous à la famille des fermions. Par contre, les particules associées aux diverses forces qui agissent sur ces fermions sont des bosons, comme les photons et les bosons W et Z.
L”été dernier, l’expérience CMS avait déjà apporté la preuve avec un signal de 3.4 sigma que le boson de Higgs se désintégrait en fermions en combinant leurs résultats pour deux types de fermions, les taus et les quarks b. Un sigma correspond à un écart-type, la taille des fluctuations statistiques potentielles. Trois sigma sont nécessaires pour revendiquer une évidence tandis que cinq sigma sont nécessaires pour clamer une découverte.
Pour la première fois, il y a maintenant évidence pour un nouveau canal de désintégration (les taus) – et deux expériences l’ont produit indépendamment. La collaboration ATLAS a montré la preuve pour le canal des taus avec un signal de 4.1 sigma, tandis que CMS a obtenu 3.4 sigma, deux résultats forts prouvant que ce type de désintégrations se produit effectivement.
Les données rassemblées par l’expérience ATLAS (les points noirs) sont en accord avec la somme de tous les évènements venant du bruit de fond (histogrammes en couleur) en plus des contributions venant d’un boson de Higgs se désintégrant en une paire de taus (la ligne rouge). En dessous, le bruit de fond est soustrait des données pour révéler la masse la plus probable du boson de Higgs, à savoir 125 GeV (la courbe rouge).
CMS commence aussi à voir des désintégrations en paires de quarks b avec un signal de 2.0 sigma. Bien que ceci ne soit toujours pas très significatif, c’est la première indication pour cette désintégration jusqu’ici au Grand collisionneur de hadrons (LHC). Les expériences du Tevatron avaient rapporté l’observation de telles désintégrations à 2.8 sigma. Bien que le boson de Higgs se désintègre en quarks b environ 60 % du temps, il y a tant de bruit de fond qu’il est extrêmement difficile de mesurer ces désintégrations au LHC.
Non seulement les expériences ont la preuve que le boson de Higgs se désintègre en paires de taus, mais elles mesurent aussi combien de fois ceci arrive. Le Modèle Standard, la théorie qui décrit à peu près tout ce qui a été observé jusqu’à maintenant en physique des particules, stipule qu’un boson de Higgs devrait se désintégrer en une paire de taus environ 8 % du temps. CMS a mesuré une valeur correspondant à 0.87 ± 0.29 fois ce taux, c’est-à-dire une valeur compatible avec 1.0 comme prévu pour le boson de Higgs du Modèle Standard. ATLAS obtient 1.4 +0.5-0.4, ce qui est aussi consistent avec la valeur de 1.0 à l‘intérieur des marges d’erreur.
Un des événements captés par la collaboration CMS ayant les caractéristiques attendues pour les désintégrations du boson de Higgs du Modèle Standard en une paire de taus. Un des taus se désintègre en un muon (ligne rouge) et en neutrinos (non visibles dans le détecteur), tandis que l’autre tau se désintègre en hadrons (particules composées de quarks) (tours bleues) et un neutrino. Il y a aussi deux jets de particules vers l’avant (tours vertes).
Avec ces nouveaux résultats, les expériences ont établi une propriété de plus prédite pour le boson de Higgs du Modèle Standard. Reste encore à clarifier le type exact de boson de Higgs que nous avons. Est-ce bien le plus simple des bosons, celui associé au Modèle Standard? Ou avons nous découvert un autre type de boson de Higgs, le plus léger des cinq bosons de Higgs prévus par une autre théorie appelée la supersymétrie.
Il est encore trop tôt pour écarter cette deuxième hypothèse. Tandis que le boson de Higgs se comporte jusqu’ici exactement comme ce à quoi on s’attend pour le boson de Higgs du Modèle Standard, les mesures manquent encore de précision pour exclure qu’il soit de type supersymétrique. Une réponse définitive exige plus de données. Ceci arrivera une fois que le LHC reprendra du service à presque deux fois l’énergie actuelle en 2015 après l’arrêt actuel pour maintenance et consolidation.
En attendant, ces nouveaux résultats seront affinés et finalisés. Déjà ils représentent un petit pas pour les expériences et un bond de géant pour le boson de Higgs.
Pour tous les détails (en anglais seulement)
Présentation donnée par la collaboration ATLAS le 28 novembre 2013
Présentation donnée par la collaboration CMS le 3 décembre 2013
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Since 4th July 2012, the physicists at CERN have had a new boson to play with. This new boson was first seen in the searches that were optimised to find the world famous Higgs boson, and the experiments went as far as to call it a “Higgs-like” boson. Since then there has been an intense program to study its spin, width, decay modes and couplings and so far it’s passed every test of Higgs-ness. Whether or not the new boson is the Standard Model Higgs boson is one of the most pressing questions facing us today, as there is still room for anomalous couplings. Whatever the answer is, a lot of physicists will be pleased. If we find that the properties match those of a Standard Model Higgs boson exactly then we will hail it as a triumph of science and a fitting end to the quest for the Standard Model which has taken the work of thousands of physicists over many decades. If we find some anomaly in the couplings this would be a hint to new physics hiding “just around the corner” and tease is with what we may see at higher energies when the LHC turns on again in 2015.
For those who have read my blog for a long time, you may remember that I wrote a post saying how I was skeptical that we would find the Standard Model Higgs boson. In fact I even bet a friend $20 that we wouldn’t find the Standard Model Higgs boson by 2020, and until today I’ve been holding on to my money. This week I found that ATLAS announced the results of their search for the Higgs boson decaying to two tau leptons, and the results agree with predictions. When we take this result alongside the decays to bosons, and the spin measurements it’s seems obvious that this is the Higgs boson that we were looking for. It’s not fermiophobic, and now we have direct evidence of this. We have see the ratio of the direct ferimonic couplings to direct bosonic couplings, and they agree very well. We’d had indirect evidence of fermionic couplings from the gluon fusion production, but it’s always reassuring to see the direct decays as well. (As a side note I’d like to point out that the study of the Higgs boson decaying to two tau leptons has been the result of a huge amount of very hard work. This is one of the most difficult channels to study, requiring a huge amount of knowledge and a wide variety of final states.)
Now the reason for my skepticism was not because I thought the Standard Model was wrong. In fact the Standard Model is annoyingly accurate in its predictions, making unexpected discoveries very difficult. What I objected to was the hyperbole that people were throwing around despite the sheer lack of evidence. If we’re going to be scientists we need to rely on the data to tell us what is real about the universe and not what some particular model says. If we consider an argument of naturalness (by which I mean how few new free terms we need to add to the existing edifice of data) then the Higgs boson is the best candidate for a new discovery. However that’s only an argument about plausibility and does not count as evidence in favour of the Higgs boson. Some people would say things like “We need a Higgs boson because we need a Brout-Englert-Higgs mechanism to break the electroweak symmetry.” It’s true that this symmetry needs to be broken, but if there’s no Higgs boson then this is not a problem with nature, it’s a problem with our models!
The fact that we’ve seen the Higgs boson actually makes me sad to a certain extent. The most natural and likely prediction has been fulfilled, and this has been a wonderful accomplishment, but it is possible that this will be the LHC’s only new discovery. As we move into LHC Run II will we see something new? Nobody knows, of course, but I would not be surprised if we just see more of the Standard Model. At least this time we’ll probably be more cautious about what we say in the absence of evidence. If someone says “Of course we’ll see strong evidence of supersymmetry in the LHC Run II dataset.” then I’ll bet them $20 we won’t, and this time I’ll probably collect some winnings!
This summer, The New York Times’ Opinionator blog posted a photo of an ordinary, fluorescent-lit hallway, indistinct apart from one feature: a placard proclaiming “Dungeon” in tall capital letters. As part of the blog’s “summer game” series, readers were asked to guess the context of the photo. Many correctly guessed “conference room,” but none deduced the precise location: Fermi National Accelerator Laboratory, a Department of Energy-funded high-energy physics lab in the suburbs of Chicago.
As it turns out, Fermilab plays host to a trove of whimsical, bizarrely named conference rooms.
While the Dungeon is found in the lab’s Cross Gallery, a building dedicated to accelerator operations, most of the conference rooms are housed in the lab’s main office building, Wilson Hall. John Kent, the building manager for Wilson Hall, said that rooms are often named by those who would most often use them. The building, modeled after a Gothic cathedral in Beauvais, France, has one of the world’s largest atriums, and, at 16 stories, it towers over the rest of the lab grounds. Much of the work conducted there translates into high-tech particle accelerator experiments and contributions to scientific discoveries such as the Higgs field.
Let’s explore, from the ground up.
1. Names of meeting rooms start out simple and ordinary on the first floor: One North, One East, One West and The Small Dining Room.
2. The second floor, though, is where things start to get weird. For starters, both the Black Hole and the Snake Pit flank the north end of the building. Then, the Comitium is just a short jog away, its name stemming from the Latin word for “assembly.” Fermilab’s first director and Wilson Hall’s namesake, Robert Wilson, chose that one personally as a hat tip to the so-named outdoor public meeting spaces of ancient Rome — Wilson had spent some time studying art in Italy prior to his directorship days.
Wilson also named Curia II, another second-floor conference room (preceded by the Curia in the Fermilab Village), this time after a Latin word thought to derive from the word “coviria,” meaning a “gathering of men.” No word on how Fermilab’s female employees feel about this.
As one climbs higher in the Brutalist concrete tower that is Wilson Hall (there’s a reason it’s also called the high-rise), the conference rooms get fewer and farther between.
3. The third floor only has two of them, and while they sometimes go by “Theory Conference Rooms 3-Northeast and 3-Northwest,” the names Conjectiorium and Theory lend more individuality.
4. The fourth floor, though equally scant in its conference room offerings, has a bit more flair. The Req Room’s name conjures up visions of Hogwarts’ Room of Requirement, while the Abacus was christened in an employee naming-contest.
5. The ConFESSional, on the fifth floor, plays with the acronym for Fermilab’s Facilities Engineering Services Section and, together with the Baptismal and Tabernacle, creates some kind of holy trinity of religion-themed conference room names.
6 and 7. Up a floor, the Dark Side channels George Lucas. Then, on seven, there’s the Racetrack (perhaps paying homage to the particles that some accelerators hurtle around a circular tunnel at high speeds). Other sports-themed conference rooms include the Bullpen, also on the seventh floor, the 19th Hole, on 14, and elsewhere on the Fermilab grounds, the Outfield, in MW-9 near the Meson Assembly Building.
8. Wilson Hall’s eighth floor’s claim to fame is the Hornet’s Nest, marked by an actual hornet’s nest on display. A plaque by the nest jokingly says “a piece of the DZero Muon Chamber.” The detector from the DZero experiment was one of two that were positioned along the now shut-down Tevatron accelerator ring; muon chambers made up the outermost layer of DZero’s detector. Colorful signs posted on either side of the conference room state the words or phrases for “hornet’s nest” in many languages: “zes muv,” “avispero,” “nido del calabrone,” “Hornissennest.”
In its day, the buildings housing the DZero experiment had a few quirky room titles of their own, among them: Hurricane Deck, Doghouse, Salles Des Heros (“room of heroes” in French) and the Far Side. The latter might be a nod to the popular cartoonist Gary Larson, who often draws tongue-in-cheek portrayals of scientists in his comics. Too bad for DZero, though; Larson already has a species of lice named after him — Strigiphilus garylarsoni — and is unlikely to be wooed by a conference room namesake.
9. It seems most likely that Wilson Hall ninth floor’s Libra is yet another reference to a Latin term rather than a zeal for the astrological. But you never know.
11. Users may watch the sun rise from the Sunrise conference room, located on the northeast corner of the 11th floor, or enjoy a view of the setting sun from the southwest corner of 11, in the Sunset conference room.
12. The 12th floor houses the Nu’s Room, which has nothing to do with the HBO drama series and everything to do with the Greek letter v. In particle physics, v, or nu, represents subatomic particles called neutrinos.
15. The highest conference room in Wilson Hall is the Aquarium. One can only imagine how often mix-ups occur with the Quarium, a room located on floor 8.
About 2,500 researchers from 34 countries collaborate on Fermilab experiments, some of them full-time employees and more of them visiting experimenters from other institutions. If one thing is clear from this list, it’s that researchers from all different backgrounds can be brought together by puns, inside jokes, dead languages, offbeat pop culture references and passed-down traditions.
Si vous n’avez pas eu la chance de visiter le CERN à Genève, vous pouvez maintenant le faire à Londres. En effet, le Musée de la science de Londres vient tout juste d’ouvrir une nouvelle exposition intitulée : Collider. J’ai pu la visiter et peux confirmer que cette exposition transmet réellement l’impression d’être au CERN.
L’exposition, ouverte jusqu’en mai 2014, explore les personnes, la science et l’ingénierie derrière la plus grande expérience scientifique jamais construite, le Grand collisionneur de hadrons (LHC) du CERN.
L’exposition commence dans un petit amphithéâtre où les visiteurs ont le sentiment d’assister à la réunion tenue dans celui du CERN le 4 juillet 2012. C’était le jour où l’on a annoncé la découverte d’une nouvelle particule, qui s’avéra bien être un boson de Higgs. Quelques physicien-ne-s y partagent leurs impressions sur la physique des particules et leur participation aux travaux ayant mené à cette découverte.
Comme la conservatrice Alison Boyle nous a expliqué à mes collègues et à moi, leur idée était de décrire en essence les diverses personnes qu’ils et elle avaient rencontrées au CERN au cours des deux années requises pour préparer cette exposition. Bien que quelques personnages nous aient semblé légèrement étranges, d’autres étaient drôlement familiers.
Les professeurs Peter Higgs et Stephen Hawking durant leur visite de l’exposition Collider (© Science Museum)
L’exposition est stupéfiante dans son utilisation intelligente de différents effets visuels. Les visiteurs traversent des pièces aux murs couverts d’images grandeur nature représentants des endroits clés du CERN, donnant l’impression d’y être. Des notes griffonnées sur des tableaux ou des bouts de papiers collés aux murs, comme on en voit tant partout au CERN, renforcent la similitude tout en fournissant les explications nécessaires. De vrais objets rehaussent les images pour créer une ambiance bien spéciale. Une super animation vidéo donne aussi une idée de ce que les particules rencontrent lors de leur passage à travers les détecteurs.
Mais pour les gens du CERN, l’élément le plus surprenant est la reproduction d’un couloir dans toute sa splendeur d’architecture des années 1950. Les murs vieillots sont couverts d’affiches annonçant toute une série de conférences passées ou futures ainsi que des activités locales, aussi bien celles du choeur du CERN que du groupe LGBT. J’ai eu l’impression d’être au travail tout en me trouvant à des milliers de kilomètres de distance.
Si vous ne pouvez pas venir visiter l’original, voici donc un excellent succédané qui vous plongera dans l’ambiance du CERN. L’exposition partira éventuellement en tournée à travers le monde, donnant ainsi la chance à plus de monde de voir un peu comment ça se passe au plus grand laboratoire de physique du monde.
Vous pouvez suivre le blog de l’exposition ici.
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If you have not had a chance to visit CERN in Geneva, you can now do it in London. The London Science Museum just opened a new exhibition called: Collider. I had the opportunity to visit it and can confirm that this exhibition conveys the impression of being at CERN.
The exhibition, open until May 2014, explores the people, science and engineering behind the largest scientific experiment ever constructed, the Large Hadron Collider at CERN.
The exhibition starts in a small amphitheatre where visitors get the feeling of sitting in CERN main auditorium on 4 July 2012. That was the day the discovery of a new particle, which was later confirmed to be a Higgs boson, was announced. There, a few physicists share their thoughts about particle physics and their participation in that search.
As the curator Alison Boyle explained to my colleagues and I, they tried to portray the essence of various people they had met at CERN over the two years it took them to prepare this exhibition. Although some characters seemed slightly odd, others were strangely familiar.
The exhibit is stunning in its clever use of visual effects. Visitors wander at their own leisure through rooms where the walls are covered with life-size pictures of various places at CERN, giving them a sense of being there. Notes scribbled on boards or pieces of papers taped to the wall as one often finds all over the place at CERN add to the likeliness and provide the necessary explanations. Real objects enhance the pictures to create a very special ambiance. A great video animation also gives a feel for what particles go through as they zip through the detectors.
But for CERN people, the most surprising piece is the reproduction of one corridor in its 1950s architecture glory. The walls are pasted with posters announcing a plethora of past and future conferences as well as local events, from the CERN choir down to the LGBT group. It felt like being at work thousands of kilometres away from work.
So if you cannot come see the real thing, this is an excellent substitute to get immersed in CERN ambiance. The exhibition is due to go on tour across the world, giving even more people a chance to experience what it feels like at the world’s largest physics laboratory.
You can follow the exhibition blog here.
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As many of you may know (and some of you may not) the next phase in the long term planning for the future of High Energy Physics (HEP) over the next 10 – 20 years in kicking into gear.
The centre piece of this phase is a panel of scientists who have been appointed to develop a strategy based on the various important pieces of physics, planned experiments, and various budget scenarios HEP faces. This panel is (terribly) named the Particle Physics Project Prioritization Panel, or more commonly referred to as P5. (www.interactions.org/p5)
This panel is meeting immediately following the summer study known as Snowmass to seize on the opportunities for interesting physics that were brought forward during this 8 month long study.
I was personally involved in one aspect of the Snowmass study by trying to get young (untenured) scientists to participate in the Snowmass study and to help ensure that their positions and opinions were heard. The group that I helped lead was known as Snowmass Young (http://snowmassyoung.hep.net) and through an online survey as well as attending countless meetings we attempted to capture these opinions in a paper which you can now find on the arxiv! (Snowmass 2013 Young Physicists Science and Career Survey Report)
However, our work hasn’t stopped there. With the P5 holding open town halls last month as well as December Snowmass Young has been trying to ensure that all voices are heard during this important process. The great news is we have been met with open and encouraging arms. The chair of the P5 process, Prof Steve Ritz, has met with Snowmass Young to hear from us and encourage all young scientists to come to the P5 town hall meetings and have their voices heard. Prof Ritz has written a letter to the young community which can be found in full here and I quote below:
The purpose of this note is to reaffirm that engagement by everyone in our community, including Snowmass Young Physicists, is needed.
Each of the upcoming meetings (our first face-to-face meeting on 2-4 November at Fermilab, then 2-4 December at SLAC, and 15-18 December at Brookhaven) has a Town Hall, and all sessions except the executive sessions are completely open. I encourage you to attend and participate. The Town Halls are deliberately unstructured: most of the time will be devoted to open-mike statements and discussions. If there is something you want to say, just come up to one of the microphone stations in the aisles.
Don’t be subtle! Let us hear from you about your concerns, advice, and input.
With these words in mind Snowmass Young is working to make sure that as many opinions are heard at the upcoming P5 meetings. The Fermilab meeting has already passed with only limited attendance from young people, so we want to work hard to change that for the upcoming meetings.
All scientists (especially young scientists) have received encouragement to attend the upcoming P5 meeting at SLAC from Kelen Tuttle (Editor in Chief at Symmetry Magazine) in the below letter where more details can be found
SLAC will host the next Particle Physics Project Prioritization Panel (P5) meeting on Dec. 2-4, and you’re invited!The meeting, which will focus on the Cosmic Frontier, is open to all and will take place in SLAC’s Kavli Auditorium with overflow in Redwood C&D. In addition, the meeting will be live-streamed online (details on how to access the feed will be posted to the meeting website soon: https://indico.bnl.gov/conferenceDisplay.py?confId=688). Although there won’t be a way for online viewers to comment or ask questions in real time, the P5 committee welcomes feedback via its online form: http://www.usparticlephysics.org/p5/formP5 held the first town hall at Fermilab in early November, and will follow the SLAC meeting with another at Brookhaven National Laboratory Dec. 15-18.In addition to the three town hall meetings, P5 is receiving input from the US Department of Energy, the National Science Foundation, and the full community via the Snowmass process. The end goal is a new strategic plan for US high-energy physics investments over the next 10 to 20 years. The plan will offer a coherent path forward, building a strong position from which the US high-energy physics community, working with the international community, can answer grand scientific questions and improve our understanding of nature.More information can be found at: http://www.usparticlephysics.org/p5
For the upcoming Brookhaven meeting Elizabeth Worcester (a Snowmass Young convener and brilliant research scientist) is organizing a dedicated session during the meeting as a way to help entice more people to attend. You can find her letter below with more details
Dear colleagues,As you may know, a P5 Workshop on the Future of High Energy Physics is being held at Brookhaven National Lab, December 15-18, 2013 (http://www.bnl.gov/p5workshop2013/). The P5 committee has strongly encouraged early-career physicists to attend the workshops, participate in the Town Halls, and provide input to the P5 process. To further facilitate input from early-career physicists, a Young Physicists Forum is being held at the BNL meeting, during the lunch hour on Monday, December 16. The chair of P5, Steve Ritz, has agreed to speak briefly at the forum and answer questions from the young community. We encourage pre-tenure scientists who wish to learn about the P5 process and/or share their perspectives to attend the workshop and this forum.Please help us spread the word by encouraging any young scientists who may not be on this list to attend. For planning purposes, please contact Elizabeth Worcester (firstname.lastname@example.org) if you plan to attend the Young Physicists Forum.Best,Elizabeth, for the Snowmass Young conveners
Too many of the attempts to sell science are like the proverbial minister preaching to the choir: they convince nobody but the already converted. This is unfortunate because we, as scientists, have a duty and a responsibility to sell science to a wider audience. There are four motivations for this:
- There are important technical questions that can only be answered by the scientific method. These include, for example, what is causing global warming? Or why are the returning salmon runs in British Columbia so erratic? We must make the case that science and only science can address these types of questions and that the answers science provides should be listened to.
- To provide answers to questions like those above, science must have ongoing support since the answers can only come from a scientific infrastructure that is maintained for the long haul. In addition to answering practical questions, science also has the important cultural role of satisfying human curiosity. To satisfy either the practical or cultural goals, science needs support from the public purse. This means science must be sold to politicians and the general public who elect them and support science through their taxes.
- We need to excite the next generation’s best and brightest to consider science as a career. This is the only way that we can ensure science’s future.
- Selling science is rewarding and can even be fun. You should have seen the fun both TRIUMF staff and visitors had at the last TRIUMF Open House. There is also something contagious about explaining a topic you are passionate about.
The allusions to religion in the opening sentence are appropriate as many attempts to sell science come across as a claim that science is the one true religion and anyone who disagrees is a fool. While that may, indeed, be true, hollering it from the hill tops is a strategy doomed to failure. A frontal attack on a major component of a person’s world view will only arouse hostility. Hence, to sell science, we have to start with a common ground with the audience. To achieve maximum impact, you have to know your audience and tailor what you say to its interests.
However, there are three things that should be part of any attempt to sell science:
- A definition of what science is. This may seem self-evident but I have seen seminars on selling science that carefully avoided any attempt to define what science actually is. I have this real nice pig in the poke to sell you. Even worse are attempts to define science that are wrong and/or annoy people. A major impediment to selling science is that there is no commonly accepted definition of what science is. However, allow me to offer a fairly safe definition: using observation as a basis for modeling how the universe works. This definition is simple, understandable and reasonably accurate. Alternatively, one can talk about the ability to make testable predictions as the hallmark of the scientific method. Use the word theory sparingly as that word has multiple meanings and invariably leads to confusion. Using words like objective reality, truth, or fact is a real turn off to many audiences. Besides, every Christian will tell you that Jesus is the truth and the more fundamentalist Christians that the bible is fact. You cannot win with those words, avoid them.
- Examples of scientific successes. This is the greatest strength in selling science. We have a plethora of examples to choose from, but it is probably not a good idea to start with the nuclear bomb. Again, it is important to understand the audience. To a person talking non-stop on his cell phone, the cell phone would be a good example (if you can get his attention) but to other people the cell phone is an anathema. The same is true of almost any example you can choose. After all, curing disease (and motherhood) leads to world overpopulation. On TV or radio, the role of science in enabling TV and radio is a good bet. On YouTube, the internet would be a good example. Despite the comment above, curing disease usually gets brownie points for science. But claiming the Higgs boson cures cancer is a bit of a stretch.
- Your personal experience of the thrill of science; whether it is for the good of humanity or just learning more about how the universe works. It is here that the emotional aspect of science can come to the fore. To some of us, the hunting of the Higgs boson is more thrilling than hunting grizzly bears and probably more environmentally friendly. Using personal experience may seem as going against our training as scientist; but here we can learn from the professionals, those who sell religion or political parties: Do not talk about theology but your personal experience. Do not talk about the platform but your own experience. In the end, this may be a telling argument and it is important to counter the stereotype of the mad scientist in his (almost always male) laboratory plotting world domination or ignoring the obvious flaws in his theory and its disastrous side effects. Drs. Faustus and Frankenstein are never far from people’s conception of the scientist.
You would think that selling science would be easy. We have a well-defined technique, four hundred years of successes to prove its usefulness and the thrill of the hunt. But we are up against two formidable foes: competing world views and vested interests. If someone believes they will be raptured to Heaven in the near future, learning about the world below is not a high priority. Similarly if they subscribe to the old hymn, I Don’t Want to Get Adjusted to This World Below, finding a crack in which to start a conversation is difficult.
In the same vein, if you have spent your life building a tobacco empire the last thing you want is some scientist claiming tobacco causes cancer. Or if you have made selling tar-sands oil a key political plank, you do not want scientists claiming it is destroying the earth. In these cases, science, itself, tends to become the target of the counterattack. With the world’s best public-relations machines powered by religion, politics and vested interests in opposition it is not at all clear that the efforts to sell science will be successful. But we must try. The motivations are so compelling, we must try.
Acknowledgement: I would like to thank T. Meyer and members of the TRIUMF Communications Group for comments on various drafts of this post.
To receive a notice of future posts follow me on Twitter: @musquod.
 Or not, as the case may be.
 My Quantum Diary blogs support this definition of science.
 Unless you are in Los Alamos.
 A well-known mega church pastor.
 Obama campaign worker.
This article appeared in symmetry on Nov. 12, 2013.
Scientists interested in protons and the sea of particles that compose them are in good spirits this week. Researchers from 15 different institutions that participate in the SeaQuest experiment are watching beam flow into their experiment and data flow out.
The SeaQuest experiment, based at Fermilab and managed by a group of scientists from Argonne laboratory, studies the structure of protons and the behavior of the particles of which they’re made.
Protons contain a constantly simmering sea of particles bound together by the aptly named strong force, which is the strongest of the four fundamental interactions of nature—above the weak force, electromagnetism and gravity.
In the experiment, a particle accelerator sends a beam of protons at very high speeds into a target made of either liquid hydrogen or deuterium or solid carbon, iron or tungsten. These bursts of beam come once a minute and each last about 5 seconds.
This causes protons to essentially break apart and release the quarks and antiquarks within. (Antiquarks are the antiparticle of quarks, meaning they have the same mass but opposite charge.)
SeaQuest physicists will then study in great detail the particles that are released during these interactions. Their aim is to resolve questions about the particles that make up the visible mass in our universe.
Initially, experimenters hope to shed light on the internal structure of protons, specifically, the ratio of anti-up quarks to anti-down quarks—two types of antiquarks with different properties.
Results from SeaQuest’s predecessor, NuSea, and DESY’s Hermes experiment, both reported in 1998, found a surprise in measuring the ratio of anti-down quarks to anti-up quarks in the proton; it trended toward a value of less than one. This shook up current assumptions about symmetry between these particles and might hint that we have an incomplete understanding of the strong force.
SeaQuest is re-examining this notion, using beam with about one-eighth of the energy and 50 times the luminosity of that of NuSea.
“We think in several months we will have enough data to confirm what NuSea saw,” says Argonne physicist Paul Reimer, spokesperson for SeaQuest. “Then we of course want to do better, which will take a year or more after that.”
The experiment is also intended to study how exactly the strong force binds these subnuclear particles together and how those effects are modified when the proton is inside an atom’s nucleus rather than isolated and separated from it. Quarks’ angular momentum, also called their “spin,” is known to be distributed differently depending on if the proton is “free” or if it is bound inside a nucleus at the time.
Yet another goal of the experiment is to measure how much energy quarks lose as they pass through cold nuclear matter. Both of these pursuits will be explored simultaneously.
The last time SeaQuest saw beam, during a commissioning run, it lasted about six weeks, from March 8 to the end of April 2012. The data from that run, Reimer says, was useful for debugging the detector and hammering out the algorithms they need to take data this time around.
Over the past year and a half, while beam was shut down for scheduled upgrades, SeaQuest researchers and technicians used that downtime to make technical improvements to the experiment’s spectrometer (pictured above) to enable higher beam quality and smoother delivery of protons, which should result in greater accuracy.
University of Michigan postdoc Josh Rubin says the detector and experiment are ready to take on the mysteries of the proton.
“We are all excited at the chance to study the sea of quarks,” he says.