Symmetry factor

I arrived to CERN last Monday for a two-week stay. It’s a great place to be this year, as both theoretical and experimental part of the lab (not to say about accelerator people, technicians, etc.) are preparing for the start of the machine, which, according to a recent talk, should happen in July. Last week was one of the “focus weeks” of the very interesting “Flavour as a Window to New Physics at the LHC” workshop. With the recent P5 report to HEPAP, it might just be that flavor physics, once again, comes back to the US (at least in the form of participation in “overseas flavor factory”)…

P.S. Where in the world is that laundry room in Bldg. 41 and where do I buy the detergent? Yeah, questions like that are normally not amongst the greatest mysteries of the Universe…

Today, at the conference NO-VE (IV International Workshop on neutrino oscillations) in Venice, collaboration DAMA/LIBRA claimed to see Dark Matter (DM) interactions in their detector. The effect is at the 8.2 sigma level (which means that the chance that it is a background that mimics their signal is WAY smaller than 1%). See their talk here. Here is their website.

Their search technique is based on DM interacting with their detector material (which happens to be well-known NaI), so they can trigger on detector’s “matter recoil” when DM particle hits the detector. In principle, it is a hard way to search for DM, as many non-DM backgrounds can also interact with NaI! For example, neutrons… Well, the deal with DAMA is that they look for the modulations in their signal that can appear due to Earth’s motion around the Sun (see Drukier, Freese and Spergel’s paper in Phys Rev D48). So one looks for a cosine-type signal over some years of data collecting. This cosine-type signal is very difficult to emulate by any (known) background. Nevertheless, (known) background studies are very important — and about half of the above talk is about them

This result is interesting, but still controversial… See, that XENON experiment has something to say about it — they used liquid xenon as their detecting media, which is very similar in properties to iodine in NaI that DAMA used. The thing is, they didn’t see anything…

I finally got around to update my blog. There are many things to talk about. But first, I have to finish blogging about that conference that happened more than a month ago. So here it is.

In the days 2-5 of the conference there were many interesting talks, so I can not talk about them all. One nice feature was that they introduced two special sessions for young scientists — each talk in a session was only 5 min long! You might be surprised how much info one can put into 5 min talk… Anyway, Lisa Randall gave a nice talk about warped geometries at the LHC,  where she indicated some potentially new ways of looking for extra dimensions.  Kellogg Stelle (who, among other five languages, speaks absolutely fluent Russian)  gave an excellent (but maybe a bit misplaced) talk about finite supergravity. Adam Falkowski gave a talk about Kaluza-Klein parity in Randall-Sundrum models (ways of creating stable Dark Matter candidates). Gustavo Burdman gave a talk about model building with extra dimensions… Thomas Humbye gave a nice talk about implications of see-saw mechanism in neutrinos. On experimental side, I want to emphasize final result from KTeV: Re e’/e=(19.2 +- 2.1)*10^(-4), which is a bit larger than corresponding NA48 result… but the error bars touch… Jean-Francois Glicenstein from HESS collaboration gave a talk about their Dark Matter (DM) search from dwarf galaxies with gamma-rays. They claim to put a strong exclusion bound on higgsino-type DM (one of the SUSY candidates), pretty much excluding masses of the order 80-200 GeV! This depends, of course, on the model of DM distribution, but it is a pretty strong claim! I tried to understand their result going to the original paper, but it’s not very clear. In particular, they claim exclusions of that mass range with technical gamma-ray threshold for their search of about 120 GeV (what also confuses me is that they talk about gamma rays with E > 250 GeV in their paper)… Of course, if gamma rays are produced in DM annihilations, their energies cannot exceed masses of those DM particles. That is to say, you cannot exclude 80 GeV DM particle by looking for gamma rays with energies greater than 120 GeV… N. Parua gave an experimental update on heavy meson and baryon lifetimes from FNAL without referencing any recent theoretical papers on this subject, including this seminal paper. I also learned about a cool experiment called COUPP — they managed to eat up part of available parameter space for DM. Their experiment is located in one of the FNAL neutrino tunnels – I wonder if high-energy neutrinos pose an irreducible background for them..

If you want to see the complete schedule of talks, you can find it here.

So now that I finally twisted my knee and removed from skiing, I can report on that Moriond meeting. Most of the talks from the conference can be found here, and thus I’ll only briefly comment on the talks. The morning session was about Higgs searches and in general about electroweak symmetry breaking. Curiously enough, it was callled “LHC and Brout-Englert-Higgs Mechanism” (emphasis is mine — I wonder what happened to the names of G. Guralnik, C. R. Hagen, T. Kibble, P. Anderson and E. Stückelberg who also could lay claim on that mechanism…).

The first talk was, as usual, a welcome by the conference founder Jean Tran Thanh Van – although he told me later that he wants to retire form this post and this would be his last conference. This conference is, and alwys has been, organized impeccably, so I hope this tradition will be kept. The first two talks dealt with Higgs boson searches at the Tevatron in the low mass (< 140 GeV) and high mass regions (> 140 GeV), and also non-SM Higgs (Yorita, Zivovic and Haas). This curious separation is due to the fact that search techniques are very different for those mass ranges, which has to do with WW threshold. As you could guess, no discovery yet… but it was emphasized that Fermilab’s HighRise looks like an “H” which might stand for Higgs, so maybe they’d beat LHC to it… One nice thing about the analyses was that the results were presented as plots of Higgs mass vs Higgs production cross-section. This is nice, as if it is discovered, we’d know if its couplings are given by the Standard Model or not… Michel Tytgat gave a nice talk about a very cute model of Dark Matter which is jsut a neutral Higgs of some limit of two-Higgs model (”Inert Higgs”), which is a nice way to connect the two. Gustavo Burdman gave a review of holographic way of electroweak symmetry breaking. Lyn Evans gave a talk about LHC commissioning schedule (Jester wrote about that in his blog, so I’m not going to go into that) and D. Aguila talked about how LHC can help with tests of see-saw mechanism of neutrino mass generation.

The conference continued after the ski break with talks about SM physics at the Tevatron, HERA, and (in the future) LHC — talks by Han, Han, de Boer, Christiansen, Plamodon) and searches for new physics with photons and jets by Jaffre. A nice talk about Higgs as an inflaton was given by Fedor Bezrukov, which is a nice attempt to unify Higgs and the inflaton (field that drives inflation on the early Universe) by introducing non-minimal gravitational couplings for that scalar. The model that he described requires some careful choice of couplings to make sure early Universe develops properly, which almost drives him in the strong coupling limit. Also, higher-dimensional operators can be problematic… but the model is indeed cute! The session ended with a pedagogical talk from S. Kraml about SUSY Dark Matter.

I ‘ll try to update regularly from now on, but the Internet here is only available at the bar and you can gues how much work can be done at the bar….

Starting tody, I’m in La Thuille, a small skiing resort in Italian Alps and the place of annual Rencontres de Moriond conference series. This year I’m attending the section on Electroweak interactions and Unified theories. I’ll try to blog about that more or less regularily… the Internet connection here is only available in the same romm as a bar… hmm….