48. Planck 2008: day 3

The third day of the conference started with the talk by Daniel Froideveaux (CERN) about experimental side of the LHC. Some facts which were not of great importance for me, but still somehow I’ve managed to remember them from the talk:

• 2008-09 are not going to be devoted to the Higgs physics, the peak luminocity () will only be achieved in 2010.
• CMS is not ready yet, pixels are to be installed soon this year, while end-cap. crystals – next year. What an extremely long project! David said he worked on LHC almost 20 years, if I recall it correctly, one can imagine how many young people came to science during this time and have focused their entire career on the physics of LHC. David said that the community of people who writes about LHC now is about 2000 people – it became industry.
• detectors will hopefully survive for 10 or so years of operation

David also listed some physics which one may expect to be found during years of LHC operation:

• excited quarks, TeV
• leptoquarks, TeV
• monopoles (from ),up to TeV
• compositeness, up to TeV

etc. etc. Higgs boson’s selfcoupling is probably beyond LHC.

James Wells (CERN & MCTP) continued to discuss the possible expectations and was focused more on the theoretical side. According to him what we might see during LHC first year are dilepton resonances (Z’ and KK), light gravitino SUSY and modified Higgs boson signals. He discussed a lot hidden sectors; what are the possible impications if we will not find Higgs at LHC (basically, he said, Higgs mixing is the way out).

Matt Strassler continued the discussion of hidden sectors with particular focus on hidden valley scenario. Hidden valley scenario is the scenario when confining gauge interaction in the hidden sector leads to the existence of bound states with relatively low mass (smaller than 1 TeV, although coupling to the hidden sector proceeds through the operators suppressed at 1 TeV). As he said, hidden valley events are mostly characterized by multiplicity of jets and leptons in the final state, and events
are typically more spherical than those from the SM background processes. He also mentioned that unparticle models (see below) with mass gaps are in fact examples of hidden valley scenarios.

Next, Markus Luty (UCLA Davis) discussed quirks. The idea is the following. Suppose the hidden sector is QCD like (say, it represents the gauge theory with group and fermions ) with confinement scale TeV. On the other hand, the particles in the hidden sector have the masses of the order of 1 TeV. If so, it is hard to break the hidden-QCD string, and the latter instead can get stretched to the macroscopic scales. Suppose that quirks also carry usual QCD colors. If the hidden-QCD string is oscillating, the usual QCD staff gets also excited. As a result, we should see some effects of quirk physics in QCD processes above 1 TeV scale – for example, distribution of hardrons into jets may have a surprosing form.

Next after Markus, Mikhail Shifman discussed his two papers about flux tubes in SQCD (although he was clearly planning to discuss something less – unfortunately, he ddi not have enough time), and that talk was a revelation for me. In a few words, the thing is the following. There exists an extremely old idea (by ‘t Hooft and Mandelstam) that confinement in non-abelian gauge theories is nothing but the dual Meissner effect: similarly to the way how magnetic monopoles get connected by the flux tube (string) in QED, quarks (electric degrees of freedom) get connected by the tube of electric QCD flux. As we know, this idea turned out to be precisely correct for N=2 SQCD (Seiberg-Witten), but for N=1 SQCD (as well as confining non-SUSY QCD) the situation looked more complicated. Shifman says that they were able to construct correct dual degrees of freedom for N=1 SQCD and the corresponding theory on the world sheet (flux tube is the string) turns out to be sigma model. I don’t quite understand the physics of this and want to learn more, so I will definitely write more about N=1 SQCD strings in the future.