## Archive for July, 2011

### Ubuntu One!

Saturday, July 30th, 2011

So as I might have mentioned in the past I have made a full transition to every computer in my house to Linux (with the exception of my wife’s Mac, which she loves). The platform I have chosen after sampling many different releases is Ubuntu 11.04.

After a few hiccups getting important applications installed on my desktop and laptop that I use for particle physics work (Kerberos, ROOT, etc…all of which have now been resolved by either Ubuntu or the respective software release) I have been very impressed by the look and running of this OS. The installation on both my laptop and my desktop with dual screen was the easiest thing I’ve ever done in Linux. Gone is the day of having to hack away at your video card and wireless card to trick you computer into accepting Linux and letting you move on with your day.

Now Ubuntu has taken the next step and offers cloud storage FOR FREE! They call their service Ubuntu One and as of this last month you get 5 GB of free storage. Additionally they already offer streaming music to you Android mobile device along with the sync of your contacts. They are also developing the platform on the iPhone as well with that expected to come soon.

This feature alone has improved my work life 5 fold. Between going to meetings, traveling to and from the lab, and working from home I was always trying to remember which file on what computer was the most recent version of my thesis paper, analysis nTuple, or even event reduction table. Now I don’t have to worry about it, I just end my work session with allowing Ubuntu One to sync anything I chose to drop into the shared folder and then download it when I get home or to my laptop. Also the looming fear of a computer crashing and losing all my work is greatly diminished, a horror story I’ve heard from too many particle physics people.

The feature is expandable and for a low price they are offering up to 20 GB of cloud and streaming, however I expect that number to rise. If you have been looking to make the jump into Linux world and the world of free software and open source code, this distribution is for you.

Oh yeah, did I mention that they are allowing Ubuntu One to be open source development … so you know the world of users are only going to make this feature even better.

### Just when you think you know something…

Friday, July 29th, 2011

– By Byron Jennings, (Ex) Theorist (or is it: once a theorist, always a theorist…) and Project Coordinator

Thomas Kuhn (1922 – 1996) began his career as a physicist but then, as a post-doc, went over to the dark side and became a philosopher. It is for his work on the dark side that he became famous. Normally one assumes that when a scientist starts doing philosophy it is a sign of senility, but in his case it was too early in his career and his insights were actually useful (Yes, philosophy can be useful). His main contribution, in my opinion, was his introduction of the idea of the paradigm. A paradigm is the set of interlocking assumptions and methodologies that define a field of study. It provides the foundation for all work in the field and a common language for discourse. It is the fundamental model for the field and in historical studies is sometimes referred to as the controlling narrative.

If you’ve ever heard the phrase ‘paradigm change,’ you would think that all paradigms do is change. But the idea of the paradigm is actually subversive – it helped undermine the “received view” of what science is and still undermines experimentalist’s attempts to eliminate theory (Which can’t be done, by the way!). Full disclosure: I am, or rather was, a theorist. Administration is even farther to the dark side than philosophy.

The concept of paradigm was introduced in contradistinction to the ideas of positivism that defined the “received view”. The positivists tried to work directly with observations and eliminate all metaphysics or model dependence. Kuhn, on the other hand, claimed the observations themselves are theory laden or model dependent.  You cannot, as a matter of principle, eliminate the metaphysics because the observation, or at least their interpretation, depends on the theory, model, or paradigm.  The paradigm sets the frameworks that gives meaning to the observations and frames the very questions that are considered worthy of addressing.  Examples of paradigms would be Aristotelian physics, classical physics, the standard model of particle physics, or the modern synthesis of evolution.

While paradigms do more than change but they do indeed change and when they do all—oops I cannot say that!—all heck breaks loose. Things one thought one knew and could rely on suddenly go poof. This going ‘poof’ was what the positivists tried and failed to get around by eliminating the models and working directly with the observations.

As Einstein (I like name dropping) pointed out, when paradigms change, it tends to be the most central parts of the previous paradigm that are eliminated. In Aristotelian physics, it was the fixed earth and the perfect heavens that Galileo destroyed with his telescope. Classical mechanics is built on Euclidean three-dimensional space and well-defined trajectories. Special and general relativity eliminated Euclidean geometry, and string theory, if correct, means space is not three-dimensional. Quantum mechanics eliminated the well-defined trajectories. This still causes some people sleepless nights but does not bother me since most of the time I do not know where I am or where I am going anyway. Evolution wrecked havoc with the concept of species. Before continental drift was accepted, a central concept of geology was the fixed continents. The examples are endless.

A side effect of this is that one cannot depend on the contents of the present theories or models to have any direct connection with reality.  The ether (electromagnetism), caloric (heat), phlogiston (fire), and mal air (medicine) that at one time were essential parts of the understanding of how the universe works were eliminated by new improved models. There is no guarantee that the contents of the current models will not be similarly eliminated.  Maybe we will find quarks disappearing or more likely, time, since it is apparently more fundamental.

So what is science and what is it good for if the basic concepts keep changing?  Well now, that is a good question.

– to be continued –

### Don’t Stop Me Now…

Friday, July 29th, 2011

Today I’m going to describe the last, but definitely not least LHCb subdetector, the muon subsystem, which unsurprisingly from the name, is designed to detect muons. Just in case you’ve all forgotten what the LHCb detector looks like, I’ve included a schematic below. The muon subsystem is the rightmost one, with alternating layers of light and dark green.

So why is a completely separate subsystem required to detect muons on top of the previously described vertex location, tracking, particle identification and calorimeter subsystems?

It all comes down to how muons interact with matter. In my last post, I said that the goal of the LHCb calorimeter subsystem is to stop particles in the detector and measure how much energy is produced through interactions with the detector material. However, I left out the important fact that different particles interact differently with detector material. In particular, muons pass through the calorimeters almost without any energy loss. Flip has a very nice explanation about why in this post, where he compares electron interactions to muon interactions… which he hopefully won’t mind if I borrow…

Electrons are light, so let’s imagine that they’re ping pong balls. On the other hand, muons are heavy, so let’s imagine them as bowling balls. As you probably know, the LHC detectors are big and full of stuff… by that I mean atoms, which in turn are made up of a nucleus and a cloud of electrons. We can thus imagine a sea of ping pong balls (kind of like an IKEA ball pit). When electrons hit this ball pit, they end up distributing all of their energy into the other balls. Muons on the other hand, are so massive that they just barrel straight through the ball pit to reach the other side.

Why go to all this effort just to detect muons?

Apart from muons being the only particle you can make farm jokes about, the fact that muons are the only known particles which the calorimeters don’t stop is quite useful. It means that if any signals are seen in a detector that is located behind the calorimeters, they must originate from a muon. This makes searching for decays involving muons much simpler than searching for decays involving other particles, such as electrons. An example of such a decay is the rare $$B_s \rightarrow\mu\mu$$ decay which may reveal new physics, as discussed previous by both Ken and Flip.

So how does LHCb detect muons?

The muon subsystem comprises five rectangular ‘stations’, gradually increasing in size and covering a combined area of 435 square metres. Each station contains chambers filled with a combination of three gases – carbon dioxide, argon, and tetrafluoromethane. The passing muons react with this mixture, and wire electrodes detect the results. In total, the muon subsystem contains around 1,400 chambers and some 2.5 million wires.

Here is a nice photo taken between two of the stations…

So now you know all about the LHCb detector, you should be able to understand the following event display of a $$B_s \rightarrow\mu\mu$$ event. If not, don’t fear, because there’s a very good explanation here.

And that ends my series of posts describing the LHCb detector… I hope you all enjoyed reading them as much as I enjoyed writing them.

### Fermilab helps PHENIX give wings to quark gluon plasma study

Friday, July 29th, 2011
This story appeared in Fermilab Today July 29.
PHENIX, one of two major experiments located at the Relativistic Heavy Ion Collider (RHIC) based at Brookhaven National Laboratory, is upgrading again with help from Fermilab’s Slicon Detector Facility (SiDet). Fermilab technicians finished assembling hundreds of forward silicon vertex tracker (FVTX) detector components in early July.

One of the hundreds of forward silicon vertex tracker (FVTX) components assembled at Fermilab's Silicon Detector Facility. Photo: Vassili Papavassiliou, New Mexico State University

The wedge-shaped components will be installed in PHENIX to help scientists study the properties of quark gluon plasma (QGP), which theorists believe made up the universe moments after the Big Bang.

Eric Mannel, a physicist from Columbia University and one of about 450 PHENIX contributors, worked as an electronics project engineer overseeing the final stages of assembly at Fermilab.

“We want to understand how the universe evolved the way it did from the very beginning,” Mannel said. “The FVTX detector will provide a higher resolution for tracking of particles which will allow us to study the properties of QGP.”

QGP is a near-perfect liquid composed of disassociated quarks and gluons suspended in plasma. It is said to be nearly perfect because it contains almost no internal friction—if you were to stir the plasma, it would continue to swirl forever. Physicists create QGP by smashing heavy ions and protons together. SiDet personnel provided a technical capabilities unique to Fermilab, to construct detectors that will allow physicists to study those collisions in more detail than ever before.

“We anticipate that we’ll be able to reconstruct secondary vertices from the decay of charm and beauty quarks with a resolution of 70 microns. The typical decay lengths for those particles are several hundred microns in heavy-ion collisions at RHIC,” Mannel said. The average human hair is about 100 microns thick.

The SiDet team completed the microassembly of FVTX components in mid-July. From left to right: Tammy Hawke, Michelle Jonas, Nina Ronzhina, Bert Gonzalez and Mike Herron. Also part of the group is Hogan Nguyen, not pictured. The FVTX group of PHENIX collaborators are also not pictured: Eric Mannel, Vassili Papavassiliou, Elaine Tennant, AAron Veicht and Dave Winter. Photo: Reidar Hahn.

AAron Veicht, a Ph.D. student at Columbia University, spent nearly 10 months working with the technicians at SiDet and will be part of the team installing the detector in PHENIX this fall.

“I’ll get to see the project from the very early stages all the way through to analyzing the data, so it’s very exciting,” Veicht said. “I gained a lot of experience while working with the technicians at Fermilab. It was a vital part of my education.”

Bert Gonzalez was the Fermilab technical supervisor on the design project. “The process went quite well, as this was the first endeavor where we worked with program collaborators,” Gonzalez said. Gonzalez and his Fermilab team spoke with PHENIX collaborators via conference calls for most of the design and development of the components.

“It was a good run,” Gonzalez said. “The project will be missed at SiDet, because it was a concrete job; you could dig your hands into it.”

Veicht felt that the people at SiDet were helpful and knowledgeable.

“It was my first time at Fermilab, and it was absolutely fantastic,” Veicht said.

PHENIX detector. Photo: Brookhaven National Laboratory

PHENIX collaborators plan to commission the detector in October and begin data collection this January.

– Ashley WennersHerron

Related information:

*PHENIX website

*RHIClets: A collection of Java applet games about the RHIC collider and RHIC physics.

*PHENIX cartoons

### Weighing Antimatter

Thursday, July 28th, 2011

How much does antimatter weigh?

It is a great question and to be honest physicists don’t know. In fact, it is a great question precisely because we don’t know. To clarify: I am talking about “weight,” not “mass.” I wrote a few words at the bottom of this post about the difference between the two. For now I will just say that mass is what makes pushing or pulling something in a new direction harder; weight is that pull, by a planet’s gravity, on things that have mass. In the Universe, there are some kinds of matter that do not have mass, like photons (packets of light), and thus are also weightless. Other kinds of matter, like protons & electrons, do have mass and consequentially weigh something.

Figure 1: CERN’s Atomic Spectroscopy And Collisions Using Slow Antiprotons (ASACUSA) Experiment. (Photo: CERN)

Okay, so here is where things get interesting. Back in the 1920’s a guy named Paul Dirac discovered the theory of antimatter.  The theory not only predicted that each piece of matter has an “antimatter partner” but also that the two partners have the same mass. This morning, the ASACUSA Experiment (Fig. 1) at CERN announced that the anti-proton has the same mass as its partner, the proton. Well, at least up to experiment’s capabilities of resolving the two. Anyone keeping track of CERN’s anti-matter physics program, or has watched the first 15 minutes of “Demons & Angles,” might know that the lab has been making significant progress trapping and collecting anti-hydrogen. While the amount being produced at CERN may not be enough to make a small city-state disappear, it is close to the amount needed to determine the weight of anti-hydrogen. This is good news for physicists at Fermilab who are working on the Antimatter Gravity Experiment (AGE), the goal of which is to measure anti-hydrogen’s weight. Interesting, no?

Figure 2: A hydrogen atom consists of an electron and a proton orbiting around one another, and are kept together because of their mutual electric attraction. Similarly, an anti-hydrogen atom consists of a positron (anti-electron) and an anti-proton. (Image: Wikipedia)

Now for the exciting part. Our theories, e.g. the time-tested Standard Model of Physics, only say that matter-antimatter partners should have the same mass. There is NO reason whatsoever, other than helping one sleep at night, that the partners should have the same weight. Since weight is innately related to gravity, any measurement of an individual anti-particle’s weight is inherently a measurement of gravity at the quantum scale. Additionally, any description of the behavior of antimatter acting under gravity is at the very least a stepping stone to Quantum Gravity. Quantum Gravity, by the way, is the theory of gravity at the microscopic scale; it does not really exist, yet; and is preventing physicists from constructing a full description (theory) of our universe. Determining that the proton and anti-proton have the same mass makes it easier to spot any differences in their weight. On top of that, if there is a difference in the weight of hydrogen & anti-hydrogen, then it might also explain why there is so much more matter in the universe than antimatter.

If you are not excited by now, I give up. 🙂 Note: A big thanks to @symmetrymag for bringing this news to my attention.

### A Few Words on Mass vs. Weight

Physically, “inertia” is the natural resistance to a change in movement; a measurement of inertia is called “mass.” One way to think about mass is if you & I were running down a football pitch, side-by-side, and you tried pushing me over. Mass is that bit of resistance you feel when you try pushing me over. If I were twice as tall, it would be harder to push me over. If I were half as tall, it would be easier to push me over. Next time you are playing football, like right after you read this Quantum Diaries post, try it out. “Weight” is that specific, attractive pull (force) a planet has on an object. The big difference is that mass is universal property of an object whereas weight can vary. A single electron will always have the same mass but a human will weigh less and less the further away he/she is from the Earth. Since this rock I like to call home is approximately a sphere, the gravitational pull it has at its surface is approximately constant. Consequentially, the difference between 1 lb (a unit of force) and 1 kg (a unit of mass) is a numerical constant. I hope this helped.

Happy Colliding.

– richard (@bravelittlemuon)

### Quest for Understanding the Perfect Liquid Continues

Thursday, July 28th, 2011

This story first appeared on Brookhaven Lab’s homepage.

Over the past few years, scientists have seen an exciting convergence of three distinct lines of research on different kinds of extreme quantum matter. Two of these involve quantum fluids that can be studied in the laboratory: ultracold quantum gases and the quark-gluon plasma produced at Brookhaven’s Relativistic Heavy Ion Collider (RHIC). Even though these two quantum fluids exist at vastly different energy scales — from near absolute zero to four trillion degrees — their physical properties are remarkably similar. The third line of research is based on the discovery of a new theoretical tool, derived from string theory, for investigating the properties of extreme quantum matter — namely holographic dualities, a mathematical relationship between quantum mechanical systems in our world and black holes that theoretically exist in a higher dimensional space. (more…)

### Too early to despair! New physics is bound to show up.

Thursday, July 28th, 2011

That’s the main message that came out of the first large physics conference of the summer. After attending for several days all sessions of the European Physics Society meeting, hearing one report after another from the LHC and Tevatron experiments that the limits for the observation of all new and exciting phenomena besides the Higgs have been pushed yet even further can easily get to the hardiest physicist. But Professor Guido Altarelli, one of CERN’s leading theorist remains optimistic: “It’s too early to despair!” he said.

Asides from CMS and ATLAS reporting on small anomalies that could be interpreted as the first signs of the Higgs boson, it’s been low in the excitement department. No supersymmetric particles, no Hidden Valley or dark matter candidate, not even a new boson to munch on. Instead, impressive limits were set in so many new areas.

So eagerness is starting to affect many particle physicists. Never before have we had such a powerful accelerator delivering so much data, and detectors allowing the most precise and diversified measurements. With less than a year of data in, the LHC is already overtaking the Tevatron results in nearly all areas. After two decades in the making, it’s hard not to be chomping at the bit. But patience is really what we need. As Professor David Gross, a Nobel Prize winner and well-known theorist, reminded us: “We have one inverse femtobarn of data in, and 2999 more to go!” Much more data are coming and so will the new phenomena in due time.

Some theorists like Professor Altarelli excel at putting things in perspective and he too reminded us that we are just at the start of exploring the LHC capabilities. Looking at the way things are going, we will have the final word on the Higgs by the end of 2012. By then, we will have enough data to know for sure if the Higgs exists or if we should exclude it for good. We should also be able to explore every possible corner where supersymmetric particles could be hiding with the actual search strategy or even new ones.

This summer, I had the opportunity to spend a week at a theory workshop. Being the only experimentalist there, I spent plenty of time discussing what was going on in their camp. Clearly, they are not sitting idle while we are frantically searching our recently collected data for signs of new physics or the Higgs boson. On the contrary, many of them were already hard at work trying to find excuses for supersymmetry and reasons why it has not shown up yet as anticipated. Are we looking for it in the wrong way? Could our general approach be wrong? Many theorists I met already had new alternatives we could test.

It’s hard to be patient after waiting for all these great possible discoveries for so long. But as Prof. Altarelli reminded us, something is bound to happen: all the current theoretical knowledge indicates that we will either find a light Higgs boson (and we could already be on its heels), or we won’t. In either case, it will have to come with some new physics to explain dark matter or the hierarchy problem for example (why electrons are so much lighter that the top quarks). “New physics is guaranteed”, he said.
Dr Rolf Heuer, CERN Director General, even went further: “Finding or not finding the Higgs will be a discovery”, he reminded the audience. Excluding any of the theoretical models currently under test and setting new limits will enable us to progress in the right direction.

Theorists have their own worries. As Professor John Illiopoulos commented, at the rate the LHC is progressing, they only have a few months left to propose new ideas. “The time for speculations is over. The LHC is working!”

On the Higgs boson search front, Dr Bill Murray summarized the current knowledge following last week report of the possible first signs of a Higgs boson sighting. At this point, the situation could not be more ambiguous. We need more data, and to see the combined results. Both require a bit more time. But there is already enough hints to keep staring in that direction. I think we are seeing the caravan appearing in the far horizon. In just a few months, we will see it clearly or discover we all had sand in our eyes…

But given the amount of data analyzed so far, if the Higgs boson mass is really somewhere around 144 GeV, the small excess of events reported last week would be exactly what we would observe. A clearer picture will be given in late August at the Lepton-Photon conference in Mumbai.

Pauline Gagnon

### Trop tôt pour désespérer; les découvertes seront au rendez-vous

Thursday, July 28th, 2011

C’est du moins le message qui se dégage de la première grande conférence de physique de l’été qui s’est terminé hier à Grenoble en France. Malgré un rapport après l’autre venant des différentes grandes expériences en cours repoussant encore plus loin l’échéancier pour l’observation de nouveaux et excitants phénomènes de physique, il y a de quoi commencer à s’inquiéter. Mais le professeur Guido Altarelli, un des théoriciens les plus en vue du CERN demeure des plus optimistes: “Il est beaucoup trop tôt pour désespérer!” a t-il affirmé sans hésiter.

A part les anomalies rapportées par ATLAS et CMS la semaine dernière qui seront peut-être les premiers signes du boson de Higgs, aucune autre découverte spectaculaire n’était au rendez-vous. Pas une seule particule supersymmétrique ou de matière noire à se mettre sous la dent! Au contraire, la première moisson de résultats du LHC limite encore plus la marge de manoeuvre pour tout phénomène de nouvelle physique.

Cette annonce d’une attente prolongée use peu à peu les nerfs des physiciens et physiciennes des particules. Pas facile de faire preuve de patience surtout lorsqu’on a en main les plus puissants outils (accélérateur et détecteurs) jamais construits, et qu’on espérait beaucoup de ce premier coup d’oeil sur les récentes données. Malgré la quantité phénoménale de données disponible, lorsqu’on cherche des phénomènes qui se produisent une fois par trillions d’évènements, et même plus, ce n’est pas si surprenant. Mais comme nous l’a rappelé le professeur David Gross, prix Nobel de physique et théoricien réputé: “Nous n’avons vu qu’un seul femtobarn inverse de données, 2999 autres restent à venir!”

Déjà, ces premières données ont permis un débroussaillage impressionnant. En à peine un an d’opération, le LHC surpasse déjà la plupart des résultats obtenus avec le Tevatron.

Certaines personnes comme le professeur Altarelli ont le don de tout remettre dans le bon contexte et lui aussi à rappelé à son audience que nous n’en étions encore qu’au tout début. Et si la tendance se maintient, d’ici fin 2012, on aura le dernier mot sur le boson de Higgs: ou on l’aura trouvé, ou rayé de la carte définitivement. Scénario semblable pour la supersymmétrie. D’ci là, on aura amplement le temps d’explorer tous les coins et racoins où elle pourrait encore se dissimuler.

J’ai eu la chance cet été de participer à un atelier de travail composé entièrement de théoriciennes et théoriciens. Étant la seule expérimentatrice, j’ai pu constater ce qui les occupe ces jours-ci. Personne ne se tournait les pouces en attendant nos résultats! Au contraire, plusieurs d’entres eux avaient déjà de nouveaux modèles prêts à être testé pour expliquer pourquoi la supersymmétrie n’avait pas encore été découverte comme plusieurs l’avaient prévu.

Pas facile d’être patiente surtout quand on attend ces découvertes depuis si longtemps. Le Directeur Général du CERN, le Prof. Rolf Heuer quant à lui est formel: que l’on trouve le Higgs ou pas, ce sera une grande découverte car cela nous mettra sur la bonne voie.

Le professeur Altarelli est confiant: quelque chose va se produire. Toutes nos connaissances théoriques actuelles indiquent qu’on doit soit trouver le Higgs bientôt (et il semble déjà pointer le bout du nez!), soit pas, peu importe. Des phénomènes associés à une nouvelle physique, une physique qui dépasse notre cadre théorique actuel, vont se manifester d’ici peu. C’est essentiel car plusieurs phénomènes comme l’existence de la matière noire ne peuvent être expliqués autrement.

Les gens de la théorie ont leurs propres soucis. Comme le professeur John Illiopoulos l’a exprimé: au rythme où vont les choses avec le LHC, il nous reste à peine quelques mois pour postuler de nouvelles théories!

Et en ce qui concerne la traque pour le boson de Higgs, le Dr Bill Murray n’a pas pu en dire beaucoup plus sur les premiers signes du Higgs boson. Sans plus de données et sans la combinaison complète des résultats actuels, la situation demeure ambigüe. Dans les deux cas, il faut patienter encore un peu, même si les signes précurseurs sont encourageants. A mon avis, on vient d’apercevoir une petite tache tout au bout de l’horizon. D’ici peu, on saura si c’est une caravane qui progresse dans notre direction ou si nous avons tous du sable dans les yeux…

Pour l’instant, si on a bel et bien affaire à un Higgs dans les 144 GeV, il se comporte exactement comme prévu. Espérons qu’on en apprendra plus à la prochaine conférence qui se tiendra fin aout à Bombay en Inde.

Pauline Gagnon

Pour être averti-e lors de la parution de nouveaux blogs, suivez-moi sur Twitter: @GagnonPauline

### EPS: Close, but far….

Wednesday, July 27th, 2011

The EPS conference is now over, and, for the benefit of our readers, here is an attempt at a roundup of what LHC physics was presented there. Before we get started, please note that I didn’t attend the conference myself! I didn’t hear the talks, or actually talk to anyone who attended; I just read the slides that were posted online and the comments of others. (In fact, those of you who know me personally can attest that I’m actually on vacation this week. I will be attending the DPF conference in two weeks, and will try to let you know what develops there.) I welcome comments from others who were on the scene and would like to give a different take on things.

Higgs searches: This is of course one of the headline measurements from the LHC, and also the Tevatron which is still going strong. Here are some plots summarizing the results of the searches from the Tevatron (combined D0 and CDF), CMS, and ATLAS:

The bottom line for reading these plots is that if the solid black line falls below 1 on the vertical axis, it means that a Higgs of the mass given on the horizontal axis is excluded at 95% confidence level. (The dashed line indicates how well the experiments would expect to do if there is no Higgs boson at that mass.) All of the experiments exclude a fairly wide range around 165 GeV, and the LHC experiments are able to exclude a Higgs at much higher masses, a range that the Tevatron cannot access. These are the strongest direct limits on the Higgs masses to date. It seems to indicate that if there is actually a Higgs boson, it must be relatively light, with a mass between about 115 and 150 GeV. As it happens, this is one of the most challenging mass ranges for an observation at the LHC, although you can be sure that all the experiments will pull out all the stops to explore that region, while the Tevatron experiments will make the most of the data that will be recorded before the accelerator shuts down in a mere two months.

However, all of the experiments independently see that the limits are weaker than expected in that lower mass range, as indicated by the fact that the solid lines are higher than the dashed lines. This might (might!) indicate that in fact there is something to be observed there. But there is a lot more to learn yet; in particular, ATLAS and CMS will work on a combination of their results to try to make a joint statement soon, and of course recording and analyzing more data will help clarify things. Excesses like this have come and gone in the past, but of course we have to remain hopeful.

Searches for physics beyond the standard model: For all the hype about the Higgs, it’s “merely” a standard-model particle, in that it is a critical element of the theory that has served as an excellent model of particle physics for decades now. What would be truly exciting is if we were to find something that’s not predicted by that model. (On top of that, we know that the standard model is inherently problematic, and we believe some new physics must come into play to remedy that.) All of the LHC experiments are looking for a wide variety of new phenomena. And, so far, no one has found anything; instead, increasingly stringent limits have been set on the properties of hypothetical new particles, suggesting that if they exist, they must have very large masses. It’s a disappointment; certainly we might have hoped that we’d see something very new soon after turning on the LHC. Instead, while perhaps we are close to finding the last particle of the standard model, it looks like we might be some distance away from observing something that will give us clues about a new model for particle interactions. That won’t keep us from trying, and the data that the LHC will record during this rest of this year will make a difference in these searches.

Bs: In a previous post we discussed the CDF search for the decay of the Bs meson to a pair of muons, and their modest excess of signal over background. At EPS, both CMS and LHCb presented their own searches. So far, the CDF excess is not confirmed, and neither experiment observes the decay. The two experiments have already combined their results to show that their limit on the branching fraction is a factor of 3.4 times the expected value from the standard model, and about a factor of two below the implied CDF branching fraction. All three experiments will need to record more data to try to resolve this discrepancy.

At this conference, all of the experiments laid their best cards on the table. Over the next few weeks, everyone will be trying to interpret these results, and we can expect a thorough consideration of them, including new syntheses, at the upcoming DPF and Lepton-Photon conferences. And, more importantly, we have seen what the LHC experiments can do with what is still relatively little data. We’ll perhaps double the LHC dataset by the end of the year (or so I hope); the experimental conditions will be increasingly challenging, but the detectors appear to be ready to handle them, and we know that the scientists can turn the data around quickly. We’ll have an even better understanding of what’s going on at this energy scale over the next few months. Stay tuned!

### Gabriel’s Notebook: Fixing an ion source

Wednesday, July 27th, 2011

– By Gabriel Stewart, visiting PIMS student

Day 1

Today I saw a model of the cyclotron and got a brief science lesson from the supervisor, Keerthi Jayamanna.

Day 2

When I arrived the second day, Keerthi and Kasia Tokarska explained to me how the power source works because I was working with OLIS (Off Line Ion Source). It is the one and only supplier of the stable atomic elements into the experiments — without them, DRAGON and TIGRESS wouldn’t really work, so this is where DRAGON and OLIS and TIGRESS coincide. The other thing I did was look at the beam line and try to understand it.

Gabriel (left) and Kasia in the ISAC-I Control room.

Day 3

This was my last day with OLIS. Today was interesting—there was something wrong with the wave emitter so they were fixing it when I got there. I got to help fix a wave emitter. I also saw Jennifer Fallis, the person I worked with from DRAGON. And at the very end of the day I got to meet the person I will be working with from TIGRESS next week. He showed me the gamma radiation detector. He explained that it’s the thing from Hulk the movie made in 2000, but in that movie it was a gamma emitter that turned the character into the hulk. That was pretty much my week. I still say it beats staying at home…

Kasia (left), Gabriel near OLIS as Keerthi works on fixing the equipment.