Symmetry factor

It looks like things at LHC are progressing quite fast. Last week, at DPF-2009, we heard a talk from  Lyn Evans that LHC will start in November with energies “as close as possible to, but not above 5TeV” per beam.  Now, Interactions.org reported that the start-up energy would be 3.5 TeV per beam.  I’m curious how many physics projections will need to be updated for this first lower-energy scenario. And when LHC will ramp up to full 7 TeV x 7 TeV design energy…

The DPF-2009 conference started yesterday at Wayne State University in Detroit. This particular conference is close to my heart because I’m a chair of the Organizing Committee. And because of that I will not be able to report on my impressions of that conference — for one, I’m very much biased. Oh, and I’m also a bit busy with making sure that it runs smoothly.

So, we have a very nice program with a variety of talks — it started with the LHC machine status talk by Lyn Evans from CERN and will end on Friday with a talk by the Fermilab Director Pier Oddone. Please check our DPF-2009 website for the program of plenary and parallel sessions and other things (note that all of the talks are there thanks to the Indico system)! And for those readers, who are present at this conference — please do write about your impressions.

I am at the CHARM-2009 conference in Leiman (a suburb of Heidelberg, Germany). This is the third charm conference that I’m participating in since the rebirth of the series in 2006. That year the conference was in Beijing and it finally made it to Germany by the way of Cornell University. All of those places have rich connections to charm (BESII/III experiment in Beijing, CLEO-c at Cornell and the upcoming PANDA at GSI just a short drive from Leimen). The conference is winding down, so I wanted to update you on what happened. Please see the talks posted on the website next week.

The program of talks has three days of plenary presentations. The first day is mainly devoted to hidden charm states, both conventianl and exotic. So everything you wanted to know about states from J/psi to X, Y, and Z was discussed. The second day is all about open charm states, with strong and electroweak studies of all of those with a main concentration on mixing of DDbar mesons and CP-violation. The topic continued today (during the third day), gradually moving to “future hardware” — i.e. how upcoming data from current BESIII and upcoming PANDA, LHCb, and SuperFlavor factories will change the world.

The first day had a lot of discussions on QCD studies with charmonia. The main reason one wants to study QCD with heavy quarkonium states is the fact that this is one of the simplest QCD systems, kina like positronium in QED. But unlike QED, QCD is much more complicated, so one can study quite non-trivial systems such as molecules built of heavy mesons that behave just like hidden charm states. The cool thing is that those things are actually experimentally observed!!! In fact, most of discoveries (not “anomalies” as in cosmic ray physics) done in the past seven years were done in charm systems.Pierre Artoisenet, Antonio Vairo, Gunnar Bali, Steve Olsen, Helmut Vogel,Kay Yi, Daniel Gamermann,Ruslan Chistov, and Claudia Patrigiani talked about various experimental and theoretical issues in quarkonium states. I wanted to mention that, according to Pierre Artoisenet, there problem of chamonium polarization in ppbar collisions has been solved. The problem is (was) that in non-relativistic QCD (NRQCD), at the leading order, one predicts that a J/psi state that is transvesely polarized. This comes from the fact that the dominant mechanism is gluon fragmentation to charm-anticharm pair — so J/psi retains polarization of a gluon, which is transverse (as gluon is a massless particle). Now the problem was that experiment (CDF) saw J/psi’s being quite an opposite condition – longitudinally polarized. So he claimed that at higher orders in QCD one gets new channels (new machainisms for J/psi production) that for some reason (?) makes J/psi polarized longtudinally.  Steve Olsen reported a (yet another) new charmonium state, X(3915). It’s amazing that some years ago people talked about the fact that experimentally we see too few charmonium states. Now I think we have too many. Helmut Vogel pointed out an intersting problem in radiative decays of J/psi and psi(2s) into eta and eta’ mesons. In addition, charmonia production in heavy ion collisions was discussed by Carlos Lourenco, Hermine Woehri, and Peter Petreczky.

The second day was mainly about DDbar mixing. It is the last meson-antimeson mixing observed experimentally (in total agreement with theoretical predictions ). Tina Cartaro, Marko Staric, Paras Naik, Angelo di Canto gave talks on DDbar measurments from different experiments, AlanS chwartz gave an HFAG (Heavy Flavor Averaging Group) take on that — and provided us with most recent averages of  mixing and CP-violating parametres. Ikaros Bigi and I gave theoretical reviews on mixing and CP-violation. Then it was an area of Dalitz plot analyses… It’s interesting that there are not so many people who know how to “work” Dalitz plots…

And today we talked about open charm exotic states. An interesting discussion came after Christoph Hanhart’s claims about mlecular nature of some states and Fulvia de Fazio’s statements about their “conventioal” nature. Leptonic and semileptonic decays of charm were also discussed, with the recent controvercy about f_Ds, the observation vs. lattice computation of leptonic decay constants… And then there are “machine” talks. BESIII was just over. What I also learned from Yifang Wang’s talk, besides the current status of BESSIII (they are slowly getting to their design lumnocity of 10^33 cm^-2 s^-1, now getting a third of it), is ajoke  that they wanted to buy a beampipe in the US, but they wouldn’t sell it to them. I wonder why…

I thought I’d put this blog “to work for me”. Well, I have a postdoctoral position open this year — of course, subject to “budgetary approval.” In other words, if US Department of Energy approves continuation of my grant… Well, here is the ad anyway…

The high energy theory group at Wayne State University (http://www.physics.wayne.edu/~apetrov/particle_nuclear/) anticipates making one postdoctoral research appointment to start September 1, 2009, subject to budgetary approval. The initial appointment will be for one year, and may be extended for one or more years depending on the performance and availability of funding

Research interests of the group include particle phenomenology, physics beyond the Standard Model, particle astrophysics, Dark Matter phenomenology, effective field theories, heavy quark physics, and CP violation. Applications including CV, list of publications, a brief statement of research interests and three letters of recommendation should be sent to:

Prof. Alexey A. Petrov

Department of Physics and Astronomy

Wayne State University

Detroit, Michigan, 48201

or electronically to apetrov@wayne.edu. The deadline for application is January 15, 2009. Later applications will be considered until the position is filled. Informal inquiries are welcome. The WSU Department of Physics and Astronomy offers a unique opportunity of close interaction with experimental high energy particle and nuclear physics groups.

Wayne State University is an affirmative action/equal opportunity employer. Women and members of minority groups are encouraged to apply

… was given today to Yoichiro Nambu of the University of Chicago “for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics” and to Makoto Kobayashi and Toshihide Maskawa “for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature.” A Nobel Prize in particle physics.

Nambu is well-known for his work on the origins of spontaneous breaking of symmetries in quantum field theories (in particular related to strong interactions, where he addressed spontaneous breaking of chiral symmetry – which nowdays is a base of the standard language for description of low-energy pion interactions) and has many things associated with his name (Nambu-Goldstone bosons, Nambu-Jona-Lasinio model, Han-Nambu quarks (which happen to have incorrect color charge assignment), etc.).

Kobayashi and Maskawa are given the prize essentially for the CKM (Cabibbo-Kobayashi-Maskawa) matrix. CKM matrix is a generalization of the Cabibbo’s idea that quarks actually mix – he used it to explain strange results in the physics of weak decays of strange quark, where properties of weak transitions of strange quark from non-leptonic hyperon decay rates differ from the ones in semileptonic kaon decays. Since, in particle phsyics, up-, down-, and strange-quarks belong to the first two generations of quarks, this mixing is described by a two-by-two matrix. Anyhow, Kobayashi and Maskawa generalized this idea to the case of three generations (3×3 matrix). It so happens that this “generalization” predicts a new phenomenon in weak decays of elementary particles: CP-violation orginating from the CKM matrix! In other words, it describes a difference between matter and anti-matter interactions in the Standard Model, which is needed for generating baryon asymmetry of the Universe (Ok, this now sounds like my “Introduction to particle physics” lecture for beginning graduate students)… Unfortunately, there is “not enough CP-violation” in the CKM matrix to claim explanation of the baryon asymmetry of the Universe from the Standard Model, BUT: this source of CP-violation was experimentally confirmed! And now studies of the CKM matrix serve as a base for indirect studies of New Physics in low-energy transitions — which, if discovered, will be used as additional information needed to classify possible New Physics possibly observed at the LHC, once they fix it… And that’s why Nobel Prize was given to Kobayashi and Maskawa.

Still, I can’t believe they didn’t give it to Cabibbo as well..

P.S. There is an intersting local story that was told to me once I got to WSU. Nambu is also considered one of the fathers of string theory (look for Nambu-Goto action). So the story is that in the 60s there was a quark-model conference at WSU hosted by Suraj Gupta, during which Nambu came up with his idea to describe hadrons in terms of strings. How about that?