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Posts Tagged ‘Higgs’

Getting to the Bottom of the Higgs

Thursday, January 30th, 2014

Updated Friday, January 31, 2014: Candidate event of Higgs boson decaying to bottom quarks has been added at the bottom.

CMS has announced direct evidence of the Higgs coupling to bottom quarks. This is special.

Last week, the Compact Muon Solenoid Experiment, one of the two general purpose experiments at the CERN Large Hadron Collider (LHC), submitted two papers to the arXiv. The first claims the first evidence for the Higgs boson decaying directly to tau lepton pairs and the second summarizes the evidence for the Higgs boson decaying directly to bottom quarks and tau leptons. (As an aside: The summary paper is targeted for Nature Physics, so it is shorter and more broadly accessible than other ATLAS and CMS publications.) These results are special, and why they are important is the topic of today’s post. For more information about the evidence was obtained, CERN posted a nice QD post last month.

Event display of a candidate Higgs boson decaying into a tau lepton and anti-tau lepton in the CMS detector.

Fig 1. Event display of a candidate Higgs boson decaying into a tau lepton and anti-tau lepton in the ATLAS detector.

There is a litany of results from ATLAS and CMS regarding the measured properties of the Higgs boson. However, these previous observations rely on the Higgs decaying to photons, Z bosons, or W bosons, as well as the Higgs being produced from annihilating gluons or being radiated off a W or Z. Though the top quark does contribute to the Higgs-photon and Higgs-gluon interactions, none of these previous measurements directly probe how fermions (i.e., quarks and leptons) interact with the Higgs boson. Until now, suggestions that the Higgs boson couples to fermions (i) proportionally to their masses and (ii) that the couplings possess no other scaling factor were untested hypotheses. In fact, this second hypothesis remains untested.

CMS-Htautau1

Fig. 2: Event display of a candidate Higgs boson decaying into a tau lepton and anti-tau lepton in the CMS detector.

As it stands, CMS claims “strong evidence for the direct coupling of the 125 GeV Higgs boson” to bottom quarks and tau leptons. ATLAS has comparable evidence but only for tau leptons. The CMS experiment’s statistical significance of the signal versus the “no Higgs-to-fermion couplings” hypothesis is 3.8 standard deviations, so no rigorous discovery yet (5 standard deviations is required). For ATLAS, it is 4.1 standard deviations. The collaborations still need to collect more data to satisfactorily validate such an incredible claim. However, this should not detract from that fact that we are witnessing phenomena never before seen in nature. This is new physics as far as I am concerned, and both ATLAS and CMS should be congratulated on discovering it.

Event display of a candidate Higgs boson decaying into a tau lepton and anti-tau lepton in the CMS detector.

Fig. 3: Event display of a candidate Higgs boson decaying into a bottom quark and anti-bottom quark in the ATLAS detector. HT to Jon Butterworth for the link.

The Next Step

Once enough data has been collected to firmly and undoubtedly demonstrate that quarks and leptons directly interact with the Higgs, the real tests of the Standard Model of particle physics start up. In the Standard Model, the strength at which a fermion interacts with the Higgs is proportional to the fermion mass and inversely proportional to the ground state energy of the Higgs field. There is no other factor involved. This is definitively not the case for a plethora of new physics models, including scenarios with multiple Higgs bosons, like supersymmetry, as well as scenarios with new, heavy fermions (heavy bottom quark and tau lepton partners). This is definitely a case of using newly discovered physics to find more new physics.

Happy Colliding.

- Richard (@bravelittlemuon)

PS I was unable to find an event display of a Higgs boson candidate decaying into a pair of bottom quarks. If anyone knows where I can find one, I would be very grateful.

PSS Much gratitude toward Jon Butterworth for providing a link to Higgs-bbar candidate events.

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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.

En combinant leurs résultats les plus récents pour les taus et les quarks b, CMS a maintenant une évidence pour des désintégrations en fermions avec 4.0 sigma.
ATLAS-H-tautau

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.

CMS-Htautau1

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

Pauline Gagnon

Pour être averti-e 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.

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Higgs Convert

Friday, November 29th, 2013

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.

A candidate for a Higgs boson decaying to two tau leptons (ATLAS)

A candidate for a Higgs boson decaying to two tau leptons (ATLAS)

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!

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Today the 2013 Nobel Prize in Physics was awarded to François Englert (Université Libre de Bruxelles, Belgium) and Peter W. Higgs (University of Edinburgh, UK). The official citation is “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider.” What did they do almost 50 years ago that warranted their Nobel Prize today? Let’s see (for the simple analogy see my previous post from yesterday).

The overriding principle of building a theory of elementary particle interactions is symmetry. A theory must be invariant under a set of space-time symmetries (such as rotations, boosts), as well as under a set of “internal” symmetries, the ones that are specified by the model builder. This set of symmetries restrict how particles interact and also puts constraints on the properties of those particles. In particular, the symmetries of the Standard Model of particle physics require that W and Z bosons (particles that mediate weak interactions) must be massless. Since we know they must be massive, a new mechanism that generates those masses (i.e. breaks the symmetry) must be put in place. Note that a theory with massive W’s and Z that are “put in theory by hand” is not consistent (renormalizable).

The appropriate mechanism was known in the beginning of the 1960′s. It goes under the name of spontaneous symmetry breaking. In one variant it involves a spin-zero field whose self-interactions are governed by a “Mexican hat”-shaped potential

MexicanHat

It is postulated that the theory ends up in vacuum state that “breaks” the original symmetries of the model (like the valley in the picture above). One problem with this idea was that a theorem by G. Goldstone required a presence of a massless spin-zero particle, which was not experimentally observed. It was Robert Brout, François Englert, Peter Higgs, and somewhat later (but independently), by Gerry Guralnik, C. R. Hagen, Tom Kibble who showed a loophole in a version of Goldstone theorem when it is applied to relativistic gauge theories. In the proposed mechanism massless spin-zero particle does not show up, but gets “eaten” by the massless vector bosons giving them a mass. Precisely as needed for the electroweak bosons W and Z to get their masses!  A massive particle, the Higgs boson, is a consequence of this (BEH or Englert-Brout-Higgs-Guralnik-Hagen-Kibble) mechanism and represents excitation of the Higgs field about its new vacuum state.

It took about 50 years to experimentally confirm the idea by finding the Higgs boson! Tracking the historic timeline, the first paper by Englert and Brout, was sent to Physical Review Letter on 26 June 1964 and published in the issue dated 31 August 1964. Higgs’ paper, received by Physical Review Letters on 31 August 1964 (on the same day Englert and Brout’s paper was published)  and published in the issue dated 19 October 1964. What is interesting is that the original version of the paper by Higgs, submitted to the journal Physics Letters, was rejected (on the grounds that it did not warrant rapid publication). Higgs revised the paper and resubmitted it to Physical Review Letters, where it was published after another revision in which he actually pointed out the possibility of the spin-zero particle — the one that now carries his name. CERN’s announcement of Higgs boson discovery came 4 July 2012.

Is this the last Nobel Prize for particle physics? I think not. There are still many unanswered questions — and the answers would warrant Nobel Prizes. Theory of strong interactions (which ARE responsible for masses of all luminous matter in the Universe) is not yet solved analytically, the nature of dark matter is not known, the picture of how the Universe came to have baryon asymmetry is not cleared. Is there new physics beyond what we already know? And if yes, what is it? These are very interesting questions that need answers.

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A Nobel Prize most appreciated at CERN

Tuesday, October 8th, 2013

The whole of CERN was elated today to learn that the Nobel Prize for Physics had been awarded this year to Professors François Englert and Peter Higgs for their theoretical work on what is now known as the Brout-Englert-Higgs mechanism. This mechanism explains how all elementary particles get their masses.

higgs-and-englert

CERN had good reason to celebrate, since last year on 4 July, scientists working on LHC experiments proudly announced the discovery of a new particle, which was later confirmed to be a Higgs boson. This particle proves that the theory Robert Brout, François Englert and Peter Higgs developed, along with others, in 1964 was indeed correct.

The Higgs boson discovery was essential to establish their theory so we are all happy to see their work (and to some extent, our work) acknowledged with this prestigious award.

It took another decade before Steve Weinberg, co-recipient of the Nobel Prize in 1979, saw the full implication of their work while unifying two fundamental forces, the electromagnetic and weak forces, as Peter Higgs explained in July at the European Physical Society meeting of the Particle Physics division, where he gave a highly appreciated presentation. There he detailed the work of all those who preceded him, including Englert and Brout, in bringing key elements that enabled him to conceive his own work.

Peter Higgs recalled how it all began with pioneering work on “spontaneous symmetry breaking” done by Yoichiro Nambu in 1960 (for which he shared the Nobel Prize in 2008). Nambu himself was inspired by Robert Schrieffer, a condensed matter physicist who had developed similar concepts for the theory of superconductivity with John Bardeen and Leon Cooper (1972 Nobel Prize).

Spontaneous symmetry breaking is central in the Brout-Englert-Higgs mechanism rewarded today by the Swedish Academy of Science.

Jeffrey Goldstone then introduced a scalar field model often referred to as the “Mexican hat” potential while another condensed matter theorist, Philip Anderson (Nobel Prize in 1977) showed how to circumvent some problems pointed out by Goldstone.

Then, Englert and Brout published their paper, where the mechanism was finally laid out. Peter Higgs, who was working entirely independently from Brout and Englert, had his own paper out a month later with a specific mention of an associated boson. Tom Kibble, Gerald Guralnik and Carl Hagen soon after contributed additional key elements to complete this theory.

“I had to mention this boson specifically because my paper was first rejected for lack of concrete predictions”, Peter Higgs explained good-heartedly in his address last summer. This explicit mention of a boson is partly why his name got associated with the now famous boson.

The history of the Brout-Englert-Higgs mechanism just goes to show how in theory just like in experimental physics, it takes lots of people contributing good ideas, a bit of luck but mostly great collaboration to make ground-breaking discoveries.

The thousands of physicists, engineers and technicians who made the discovery of the Higgs boson possible at the LHC are also all celebrating today.

Pauline Gagnon

To find out more about the Higgs boson, here is a 25-minute recorded lecture I gave at CERN on Open Days

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

 

 

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Nobel Dreams

Friday, October 4th, 2013

The liveblog

Greeting from Brussels! This is my liveblog of the Nobel Prize Announcement Ceremony, bringing you the facts and the retweets as they happen.

14:14: Press Conference ongoing. “This is a great day for young people.”

13:56: A moving statement from Kibble (source):

I am glad to see that the Swedish Academy has recognized the importance of the mass-generating mechanism for gauge theories and the prediction of the Higgs boson, recently verified at CERN. My two collaborators, Gerald Guralnik and Carl Richard Hagen, and I contributed to that discovery, but our paper was unquestionably the last of the three to be published in Physical Review Letters in 1964 (though we naturally regard our treatment as the most thorough and complete) and it is therefore no surprise that the Swedish Academy felt unable to include us, constrained as they are by a self-imposed rule that the Prize cannot be shared by more than three people. My sincere congratulations go to the two Prize winners, François Englert and Peter Higgs. A sad omission from the list was Englert’s collaborator Robert Brout, now deceased.

13:37: CERN are holding a press conference at 14:00 (CET) link

13:22: Commentary continues at the Nobel Prize page. Currently discussing why the boson was so hard to find. “This particle has been looked for at every accelerator that has existed.”

13:20: As expected, so many news sites have been created: CMS, ATLAS, ULB, Edinburgh

13:14: I think my twitter account has exploded with tweets. Also, some Belgian news pages are down, probably due to high traffic. Wow!

13:11: Wow, what a great announcement. Too short though!

13:08: Find out more about the physics at Brussels, where the Brout-Englert-Higgs mechanism was born! The IIHE and the Nobel Prize

13:01: Englert is on the phone. Good to hear from him :)

12:59: Animation of the boson appearing, cool!

12:57: We just opened the champagne here at ULB!

12:52: Text for the announcement:

“For the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider”

12:48: The award goes to Englert and Higgs!

12:44: One minute to go!

12:39: We all know what the Brout-Englert-Higgs mechanism is and what the boson discovery means, so let’s instead take a look at the other likely awards. The prize could go to the discovery of extra solar planets. 51 Pegasi b was an extra solar planet discovered in 1995, orbiting a sun-like star. This discovery could have far reaching implications. What would happen if we saw spectral lines suggesting the presence amino acids coming from the planet? (I’m not sure such a phenomenon is even possible, but if it is it would be a very strong indicator of RNA-like life from another planet.) That discovery took place 18 years ago, and the Brout-Englert-Higgs boson was discovered only one year ago. Either discovery would certainly be worthy of the prize.

12:33: A quantum approach to the delay problem:

Someone go observe the academy and make them leave this terrible superposition. (@lievenscheire)

12:32: Another possible reason for the delay:

There’ll be a new hunt for the #Higgs. He’s gone to the Highlands to avoid the fuss if he wins #nobelprize. Maybe reason for delay. (@BBCPallab)

12:31: The Nobel Prize committee are stalling by suggesting we look at previous awards. At least they are trying to keep up amused while we wait :)

12:29: Around the world people are patiently waiting. People from the US have been awake since 5:00am. In Marakech the ATLAS Collaboration looks on. Here are ULB/IIHE the cafeteria seem deserted. (I’m glad there’s a coffee machine on the desk next time mine.) I’m starting to think this is a plot to get some more media attention for what is bound to be a controversial year for physics. There are many good choices of topic this year, and even some of the topics have controversial choices of Laureates.

12:21: Some humourous speculation about the delay:

The Academy only has 3 #sigma evidence of more votes for than against, waiting for more data (@SethZenz)

They can’t get Comic Sans installed on the Academy’s computer (@orzelc)

The committee were mobbed trying to get across a cocktail party. (@AstroKatie)

12:07: The announcement is delayed until 12:45 CET. People are complaining about the background music!

11:58: The announcement is delayed until 12:30 CET.

11:44: According to the Guardian (source) there will be a delay of 30 minutes.

11:42: Just over two minutes to go. This could be a very exciting year for Belgium.

11:33: See the livecast.

Other info

On Tuesday October 8th the recipient(s) of the 2013 Nobel Prize in Physics will be announced. There has already been a lot of speculation about who might be the Nobel Laureates this year, and there is a lot of interest in the likely contenders! Each year Thomson Reuters publishes predictions of who might receive the Nobel Prizes, and this year they have narrowed the scope down to three likely awards in physics:

  • ‣ Francois Englert and Peter Higgs, for their prediction of the Brout-Englert-Higgs mechanism. (Brout is deceased and the Nobel Prize is not awarded posthumously.)
  • ‣ Hideo Hosono, for his discovery of iron-based superconductors.
  • ‣ Geoffrey Marcy, Michel Mayor, and Didier Queloz, for their discoveries of extrasolar planets.
The 2012 Nobel Prize Award Ceremony (Copyright © Nobel Media AB 2012 Photo: Alexander Mahmoud)

The 2012 Nobel Prize Award Ceremony (Copyright © Nobel Media AB 2012 Photo: Alexander Mahmoud)

There has also been speculation that either Anderson or Nambu may receive a second Nobel Prize for their work related to spontaneous symmetry breaking.

With so many different predictions and so many opinions it can be hard to keep up with all the latest news and blogs! I know that a lot of people plan to share their views and experiences of the day, so I’ll be keep a list of bloggers and tweeters that you can follow.

Seth Zenz:

See Seth’s excellent post about the Nobel Prize, Englert and Higgs, and CERN. You can also follow his twitter account: @SethZenz

James Doherty:

See James’s great post about the Nobel Prize, He’s on twitter too: @JimmyDocco

Guardian liveblog

Other twitter accounts to follow:

@CERN

@aidanatcern

@kylecranmer

@kenbloomunl

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A Higgs Nobel? And to Whom?

Tuesday, October 1st, 2013

The smart money for this year’s Nobel Prize, it seems, is on Peter Higgs and François Englert to win for developing the theory of the boson that bears one of their names. Awarding the prize to the two of them would, of course, be a great oversimplification of assigning credit for that theory. Robert Brout, who worked with Englert, died in 2011 and so is ineligible for the prize. Gerald Guralnik, C. R. Hagen, and Tom Kibble published independent work on the same problems at the same time. All six shared the 2010 Sakurai Prize “for elucidation of the properties of spontaneous symmetry breaking in four-dimensional relativistic gauge theory and of the mechanism for the consistent generation of vector boson masses,” but the Nobel rules are more restrictive.

If the Nobel Prize goes to only two of six theorists, it is certainly in the tradition of the prize, whose structure implicitly assumes that great scientific breakthroughs are made by great people through well-defined leaps of genius. More often, though, theoretical work is incremental. Ideas are exchanged, developed partially by one person before being expanded upon by the next. The positive way to look at it is that the prize would be symbolic, awarded to two people who represent a broader effort.

Of course, the main reason the Higgs boson is of interest right now is the experimental work done in finding it! Could there be a Nobel Prize for that? Well, I can’t see any way to award an individual for the efforts of thousands of people over decades. An untold number of “little” problems have been solved by those people in building a bigger and better accelerator, and bigger and better detectors, than have ever been built before. So what I would like to see is the Nobel Committee changing its traditions and awarding the physics prize to CERN along with the theorists.

A prize to CERN would again be symbolic. Not everyone who made important contributions to finding the Higgs works at CERN. Thousands of the contributors worked at United States labs and universities from the very beginning, for example. But as the center of the LHC effort, it does represent all that work. Not a sudden flash of genius, but lots of hardworking people tackling tough scientific and technical problems. In other words, the way great science is usually done.

Flip Tanedo, Katie Yurkewicz, and the Higgs boson

Katie Yurkewicz, Flip Tanedo, and the Higgs boson. (Originally for this contest in Symmetry.)

For a more humorous take on all this, please see this Scientific American article on the early awarding of the prize to the boson itself. My favorite bit is this: “A member of CERN’s PR division also wore a large, squishy Higgs costume, doing his best to mimic the behavior of the fleeting particle as he whizzed from one end of the room to another, hid and emerged from behind a curtain and breathlessly answered questions about gauge symmetry and vacuum fluctuations.” As you can see at right, this is frighteningly close to what some USLHC communicators have actually been involved in.

The real Nobel Prize in Physics will be announced next Tuesday, October 8. So stay tuned!

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Higgs Hunting in Progress

Wednesday, August 28th, 2013

ParishiggshuntingLast month I was at the annual Higgs Hunting workshop, in Orsay and  Paris, France.  Starting less than a week after EPS, it didn’t have much in the way of new results.  What it did give us is an opportunity to talk through where we are and where we’re going.  What do we know about the Higgs so far?  What do we still need to find out, and how do we go about it?  Why aren’t the coffees stronger, or at least larger?

It’s true, the last question isn’t about the Higgs, but it does reflect that a lot of the learning and discussion went on during the coffee breaks.  (I should stress in case the organizing committee reads this that the drinks and snacks at the coffee breaks were, on the whole, quite excellent.)  But of course we had talks too, and you can see both the slides and videos here.  I should warn you, though, that the talks are very technical — even more technical than might be usual for a Higgs conference, because it was generally assumed that participants already know the strategy for hunting the Higgs.

My talk was about the CMS search for Higgs decays to bottom quark pairs.  It covered four analyses, which are different from each other not because of what the Higgs decays into but because of what it’s produced in association with.  Without extra particles, we can’t see the Higgs in this decay channel because of all the bottom quark pairs from QCD.  But this direction of looking at different production mechanisms is also where Higgs searches as a whole are going, because ultimately Higgs production tells us as much about what the Higgs interacts with as Higgs decay.  And what we really hope to find is some difference from the Standard Model in those interactions.

From what we’ve seen so far, it looks like we’re hunting precisely the Standard Model Higgs.  But we are far from an exact answer; we haven’t even officially established evidence for the Higgs to bottom quark pair decay at all, yet.  So we’ll keep hunting, and hope the Higgs Beast turns out to be subtly different from the one we’re expecting.

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The ILC site has been chosen. What does this mean for Japan?

Credit: linearcollider.org

The two ILC candidate sites: Sefuri in the South and Kitakami in the North. Credit: linearcollider.org

Hi Folks,

It is official [Japanese1,Japanese2]: the Linear Collider Collaboration and the Japanese physics community have selected the Kitakami mountain range in northern Japan as the site for the proposed International Linear Collider. Kitakami is a located in the Iwate Prefecture and is just north of the Miyagi prefecture, the epicenter of the 2011 Tohoku Earthquake. Having visited the site in June, I cannot aptly express how gorgeous the area is, but more importantly, how well-prepared Iwate City is for this responsibility.

Science is cumulative: new discoveries are used to make more discoveries about how nature works, and physics is no different. The discovery of the Higgs boson at the Large Hadron Collider was a momentous event. With its discovery, physicists proved how some particles have mass and why others have no mass at all. The Higgs boson plays a special role in this process, and after finally finding it, we are determined to learn more about the Higgs. The International Linear Collider (ILC) is a proposed Higgs boson factory that would allow us to intimately understand the Higgs. Spanning 19 miles (31 km) [310 football pitches/soccer fields], if constructed, the ILC will smash together electrons and their antimatter partners, positrons, to produce a Higgs boson (along with a Z boson). In such a clean environment (compared to proton colliders), ultra-precise measurements of the Higgs boson’s properties can be made, and thereby elucidate the nature of this shiny new particle.

credit: li

The general overview schematic of the International Linear Collider. Credit: linearcollider.org

However, the ILC is more than just a experiment. Designing, constructing, and operating the machine for 20 years will be a huge undertaking with lasting effects. For staters, the collider’s Technical Design Report (TDR), which contains every imaginable detail minus the actual blueprints, estimates the cost of the new accelerator to be 7.8 billion USD (2012 dollars). This is not a bad thing. Supposing 50% of the support came from Asia, 25% from the Americas, and 25% from Europe, that would be nearly 2 billion USD invested in new radio frequency technology in England, Germany, and Italy. In the US, it would be nearly 2 billion USD invested in coastal and Midwestern laboratories developing new cryogenic and superconducting technology. In Asia, this would be nearly 4 billion USD invested in these technologies as well as pure labor and construction. Just as the LHC was a boon on the European economy, a Japanese-based ILC will be a boon for an economy temporarily devastated  by an historic earthquake and tsunami. These are just hypothetical numbers; the real economic impact will be  larger.

I had the opportunity to visit Kitakami this past June as a part of a Higgs workshop hosted by Tohoku University. Many things are worth noting. The first is just how gorgeous the site is. Despite its lush appearance, the site offers several geological advantages, including stability against earthquakes of any size. Despite its proximity to the 2011 earthquake and the subsequent tsunami, this area was naturally protected by the mountains. Below is a photo of the Kitakami mountains that I took while visiting the site. Interestingly, I took the photo from the UNESCO World Heritage site Hiraizumi. The ILC is designed to sit between the two mountains in the picture.

ilcSite_Kitakami

The Kitamaki Mountain Range as seen from the UNESCO World Heritage Site in Hiraizumi, Japan. Credit: Mine

What I want to point out in the picture below is the futuristic-looking set of tracks running across the photo. That is the rail line for the JR East bullet train, aka the Tohoku Shinkansen. In other words, the ILC site neighbours a very major transportation line connecting the Japanese capital Tokyo to the northern coast. It takes the train just over 2 hours to traverse the 250 miles (406.3 km) from Tokyo station to the Ichinoseki station in Iwate. The nearest major city is Sendai, capital of Miyagi, home to the renown Tohoku University, and is only a 10 minute shinkansen ride from Ichinoseki station.

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The Kitamaki Mountain Range as seen from the UNESCO World Heritage Site in Hiraizumi, Japan. Credit: Mine

What surprised me is how excited the local community is about the collider. After exiting the Ichinoseki station I discovered this subtle sign of support:

There is much community support for the ILC: The Ichinoseki Shinkansen Station in Iwate Prefecture, Japan. Credit: Mine

The residents of Iwate and Miyagi, independent of any official lobbying organization, have formed their own “ILC Support Committee.” They even have their own facebook page. Over the past year, the residents have invited local university physicists to give public lectures on what the ILC is; they have requested that more English, Chinese, Korean, and Tagalog language classes be offered at local community centers; that more Japanese language classes for foreigners are offered in these same facilities; and have even discussed with city officials how to prepare Iwate for the prospect of a rapid increase in population over the next 20 years.

Despite all this, the real surprises were the pamphlets. Iwate has seriously thought this through.

asdsad

Pamphlets showcasing the Kitakami Mountain Range in Iwate, Japan. Credit: Mine

The level of detail in the pamphlets is impressive. My favourite pamphlet has the phrase, “Ray of Hope: Tohoku Is Ready to Welcome the ILC” on the front cover. Inside is a list of ways to reach the ILC site and the time it takes. For example: it takes 12 hours 50 minutes to reach Tokyo from Rome and 9 hours 40 minutes from Sydney. The brochure elaborates that the Kitakami mountains maintain roughly the same temperature as Switzerland (except in August-September) but collects much more precipitation through the year. Considering that CERN is located in Geneva, Switzerland, and that many LHC experimentalists will likely become ILC experimentalists, the comparison is very helpful. The at-a-glance annual festival schedule is just icing on the cake.

asdd

“Ray of Hope” pamphlet describing how to each different ILC campuses by train.  Credit: Mine

Now that the ILC site has been selected, surveys of the land can be conducted so that blue prints and a finalized cost estimate can be established. From my discussions with people involved in the site selection process, the decision was very difficult. I have not visited the Fukuoka site, though I am told it is a comparably impressive location. It will be a while still before any decision to break ground is made. And until that happens, there is plenty of work to do.

Happy Colliding

- Richard (@bravelittlemuon)

 

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À l’occasion de l’ouverture de l’appel à candidature 2013 de “Sciences à l’Ecole” pour l’accueil d’enseignants français au CERN durant une semaine, nous publions ces jours-ci le journal quotidien plein d’humour de Jocelyn Etienne qui a suivi ce programme l’année dernière, au mois de novembre dernier.

 

La visite s’accélère !
Jeudi 08 novembre 2012

Un élément d’un accélérateur (je ne sais plus lequel).

Un élément d’un accélérateur (je ne sais plus lequel).

La journée commence par une citation de notre collègue Joseph : « si tu veux pas entendre parler de protons, va à Conforama ! » Notre guide ce matin s’appelle François. Il est belge et ingénieur en informatique. Il nous présente le site LINAC-LEIR où l’on trouve tous ce qu’il faut pour préparer les noyaux que l’on va injecter ensuite dans les différents accélérateurs. Il porte un détecteur de radioactivité pour mesurer les doses qu’il reçoit dans une journée. D’ailleurs, il y a des détecteurs de radioactivité à l’entrée et à la sortie du CERN, et gare à celui qui a subi une injection de radio-isotopes pour une analyse médicale, il va sonner aux portiques pendant une semaine (c’est déjà arrivé). Sinon, en cas de problème, faire le 74444 (les pompiers).

Mario Campanelli est un physicien italien qui travaille sur le projet ATLAS (après le Tevatron aux USA, Gran Sasso en Italie…), ce n’est pas une tablette tactile même géante qui va lui faire peur !

Mario Campanelli et sa  tablette tactile géante.

Mario Campanelli est un physicien italien qui travaille sur le projet ATLAS (après le Tevatron aux USA, Gran Sasso en Italie…), ce n’est pas une tablette tactile même géante qui va lui faire peur.

DSC04253Il nous montre une représentation quasiment en temps réel des informations qui circulent  sur le réseau de calcul du CERN à travers le monde. Il s’agit du GRID, sorte de WEB des logiciels, un partage réseau mondial dont on voit un bout à droite, nécessaire pour traiter les milliards de données qu’engendrent les collisions de particules dans le LHC (sous linux toujours).

On appelle ce lieu le CCC : le Centre de Contrôle du CERN. On voit les personnels à travers une vitre mais la plupart ne contrôle rien à l’instant car un apéro est organisé pour fêter les objectifs de puissance atteints. Tout est prétexte pour ne plus mettre un coup de rame hein ?!

On appelle ce lieu le CCC : le Centre de Contrôle du CERN. On voit les personnels à travers une vitre mais la plupart ne contrôle rien à l’instant car un apéro est organisé pour fêter les objectifs de puissance atteints. Tout est prétexte pour faire la fête hein ?!

A 11h, petite pause conférence (Solène Chevalier-Théry de Sciences à l’école puis Morgan Piezel professeur, pour l’exploitation de ce stage dans nos lycées) dans la salle où a été annoncée la découverte du Higgs, ou en tout cas, quelque chose qui s’en rapproche. Les physiciens que nous rencontrons espèrent d’ailleurs que ce n’est pas exactement le boson prévu par le Modèle Standard, car alors… ça serait trop simple.

DSC04278
La soirée se termine avec une partie de quarks poker, un jeu inventé par le physicien retraité Patrick Roudeau. En comprendre les règles fut un des exercices les plus difficiles de la semaine.

À suivre…

Jocelyn Etienne est enseignant au lycée Feuillade de la ville de Lunel.

Pour soumettre sa candidature pour la prochaine session du stage au CERN, c’est par ici.


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