Another Milestone for the SM!

The standard model (SM) of particle physics has crossed another milestone as reported by LHCb collaboration at the recent hadron collider physics symposium held in Kyoto. They have done an incredible measurement of B meson decaying into muon anti-muon pairs. However, people started using this SM milestone as a bullet in SUSY's chest. BBC reported LHCb UK spokesperson saying, "SUSY might not be dead yet, but these results have certainly put her into hospital". And this statement was enough to spark off a debate in the blogosphere followed by couple of arXiv pre-prints. Well, its true that no sign of new physics in this measurement is disappointing, but it amazes me that SUSY has suffered the most whereas there are plenty of other beyond standard model frameworks in the market. I could see three different types of reactions : SUSY is dead or in hospital, SUSY is less natural than thought and SUSY is still alive or in good health. The first reaction is of course a bit harsh and extreme but probably was good for many others who have come up with pre-prints showing available parameter space (natural parameter space probably, I am confused though what to call natural nowadays) which exactly fit these observations. Even if we collect as much data as we want, they will probably never justify the first reaction and at the worst case will leave us with a situation which is a linear combination of the second two reactions.

SUSY..hope you are still there!

Couple of weeks back there were lots of hue and cry among young researchers who might have heard about SUSY but have not worked on it in great details. It's because of the ATLAS and CMS experiment at Large Hadron Collider (LHC), CERN (Geneva) publishing two independent results related to supersymmetry (SUSY) searches in the 7 TeV run of LHC. One of them looked for missing energy+ jet signatures whereas the other looked for lepton+jet signatures, but their conclusion was more or less similar. They ruled out significant amount of parameter space of Constrained Minimal Supersymmetric Standard Model (CMSSM). This is a rather constrained version of MSSM where the number of free parameters are just 5 compared to 124 or so parameters in the MSSM. So obviously the CMSSM has far more predictability and hence getting almost ruled out. Although its really heartbreaking to see such predictable models losing their fight, yet this does not really mean SUSY is not there. We still need more data and scan of other available models to rule out TeV scale SUSY. And even if LHC rule out TeV scale SUSY, it can not say anything about existence of SUSY at even higher energies. But many of the theoretical advantages of SUSY would be lost if we keep pushing SUSY towards higher and higher scales and will be as good as having no SUSY at all. Anyway, hope LHC will soon confirm its presence around the TeV corner. But nevertheless, the ATLAS/CMS result created lots of hype among both experts as well as others. One of our over-curious mate in the department got pumped up so much (may be after reading about it in some newspapers and not in the arxiv papers) that he asked one of our senior prof, what's the point of doing SUSY as LHC has already ruled it out? I don't know what was the professor's reaction at that moment, but I can imagine how shocking such a news (if true) to a person working in particle physics for a long time. Blame it on popular news sites or news papers which put the title of such news in such a way that young kids easily get misled. Anyway, hope many such news (positive I mean) about SUSY would be coming soon from the heart of LHC :)

Wish I were a collider physicist...........

Tevatron at Fermilab although gonna be shut down soon, producing lots of excitement among the high energy physics community. Although LHC has lot claimed any new physics so far, recent Tevatron data are showing deviations from the Standard Model predictions at 2.5-3 sigma confidence level. Although these can not be taken as a discovery of new physics and we need to wait till more data come out and analyzed, they give physicists lots of opportunities to publish papers with high citations. Initially it was about like sign dimuon charge asymmetry, then it was about top quark forward backward asymmetry and now its about dijet excess of events in the range 120-160 GeV all of which do not agree with the Standard Model predictions. It would be really sad to see Tevatron dying amidst such excitements. But anyway, LHC will take this charge from Tevatron very soon and will continue this excitement. For PhD students like me, I think it would be the smartest step to switch to collider physics as long as these colliders are alive and publish as many papers as possible ;)

Competition vs Collaboration

There was a recent discussion in the high energy physics community whether to run Tevatron at Fermi National Accelerator Laboratory, Batavia, Illinois. It is said that many top scientists including Nobel Laurette are suggesting an extension of another three years after the proposed shutdown in 2011. People are saying that Tevatron is not dead yet and it still has a great potential to search the Higgs boson. I agree upto this point. But I found some comments like this also : "Fermilab researchers have a chance to see the Higgs boson first because the more powerful Large Hadron Collider (LHC) at the European particle physics laboratory, CERN, near Geneva, Switzerland, is running years behind schedule and is going to be shut for around 15 months in 2012 for some repair work". I do not understand the meaning of competing with the CERN. After all, LHC is an international collaboration and the US is also contributing to it. Running Tevatron for another three years is a good thing provided it has a potential to discover some new physics beyond the standard model, like it has recently seen some dimuon asymmetry which is 3.2 sigma away from standard model predictions. But the motive to run the Tevatron should not be just to compete with CERN. We should compete with Nature to unfold her secrets, (no matter how hard She tries to hide them) rather than spending billion dollars just to compete amongst ourselves specially during a time when there is a crisis in the global economy. We should also save some money to build the proposed ILC (International Linear Collider) which is supposed to confirm whatever LHC finds :)

LHC & the end of the world....

After all the unnecessary panic regarding the end of world stuffs after the protons start colliding at LHC, I have read a brief essay by Michael Peskin (SLAC) where he talks about how this dire possibility can be ruled out both theoretically as well as experimentally. He talks about the paper Physical Review D 78, 035009 where Steven Giddings(UCSB) and Michelangelo Mangano(CERN) have argued with explicit calculations that if LHC can produce such a black hole which can swallow the earth these kind of events would have astrophysical consequences in the past Universe. But we dont see any well known astrophysical objects swallowed by such dangerous black holes.
Peskin also points out the fact that although we keep on saying that any micro blackholes if produced in CERN would evaporate almost instantaneously by Hawking Radiation, there is no experimental evidence of Hawking Radiation so far. But the theoretical arguments behind Hawking radiation is so strong that we can't rule it out. Although there is a model by Unruh where black holes do not radiate, it is also constrained by the fact that it happens only at the cost of violating Lorentz invariance which can happen only at the Planck scale. Thus LHC which operates in TeV scale( 16 orders of magnitude below the Planck scale) is safe enough from these dangerous circumstances.
Peskin says,"If we ignore these strong theoretical arguments we could pursue another path. Huge numbers of high-energy cosmic rays have hit the earth over its lifetime. Thus we an argue, nature has already carried out the LHC experiments many times. If we are still here, the LHC must be safe."
He also talks about some scenerios where these arguments are insufficient. There are some "slippery" black holes which arise in the extra dimensional models which may creat a genunie problem. But in the paper mentioned above the authors have addressed this problem as well. You can at least see the Peskin's review article which doesnt need any subscription from Physical Review. The link is
http://physics.aps.org/articles/v1/14

LHC delay..

Its a pretty old news that LHC(Large Hadron Collider) has been delayed by approximately 6-8 months which is now scheduled to restart next year (probably in May or June). Its due to some superconducting magnet failure whose details CERN has already released here : http://press.web.cern.ch/press/PressReleases/Releases2008/PR14.08E.html
One of our department Prof (in IIT Bombay) who specializes in experimental condensed matter physics( specially magnetism) was chatting with one of my friend here regarding this incident. He said that those magnets were sent by India to the CERN and it was the faulty welding between two such magnets which caused the incident.Well whatever it is what happened was really unfortunate.
Just like there were lots of rumours(e.g. Big-Bang,Black Hole etc etc) just before the start-up of LHC on 10th Sep 2008, similar is the case after it has stopped. One of my friend (non-HEP PhD student ;)) told me she heard somewhere that the whole system of the LHC was hacked by someone who were opposing such too costly as well as fatal(?) experiments.I have seen such incidents in many crappy hollywood movies where the whole US govt netwrok is hacked by some and bla bla...Anyway although sucn comments,views are irritating most of the times...they sound funny to me sometimes. I remember one incident when the whole media were shouting the possible collapse of the whole earth after the LHC gets turned on etc etc...one person from my village...(well its a village where people hardly know anything about particle physics, LHC, Black-Hole, Big-Bang etc)..called me up to say "Good-Bye"..because he was pretty confident that the very next day everything would be over..somehow which he did not bother about.I was laughing like hell at it..it was so funny..at the same time I wanted to kick the ass of those media who has put these stupid things, fears in the minds of common people.Then I assured him that nothing of this kind gonna happen..so theres no need to worry about. :P
Anyway hope LHC would start working soon and let us zoom closer and closer into the nature to reveal her secrets....