Saturday, 31 August 2013

SUSY 2013 Live Blog: Day Six

The final day of SUSY 2013 is, like most conferences, only a half-day.  The two sessions cleanly split into a pre-coffee flavour session, followed by a post-coffee wrap-up.  I'll be honest, the latter is more attractive to me (plus talks from John Ellis and Nima (again)).  But I won't dismiss this first session yet.

Between this being the last day of the conference—so people are starting to leave—and the conference banquet last night, the auditorium is strikingly empty this morning.  Still, unlike some conferences *cough*Pheno 2013*cough* SUSY at least got it right in putting the banquet after all the parallel sessions had finished.

9:00am: Mitesh Patel, "LHCb results relevant to SUSY and BSM physics"

Indirect measurements from virtual fluctuations have often given us the first clue to new physics, e.g. the first evidence for the charm and for the top being heavy.

LHCb can probe the CKM picture through discovery and precision measurements of a number of rare processes.  Sadly, everything so far looks consistent with the CKM.

Neat trick: compare the measurement of the unitary triangle angle γ in tree- and loop-processes, and compare.  Former/latter should be insensitive/sensitive to new physics.  Combined tree-level process measurement has accuracy of 12 degrees (about 20% relative accuracy).

Mixing-induced CPV in Bs system is another depressing story, where the slight discrepancy in the Tevatron results has disappeared in the more-precise LHCb measurements.  Similarly, probing the mixing with semileptonic asymmetries tells the same story.

More hopeful story in B to Dτν versus B to Dlν.  The combined BABAR and BELLE data is over four sigma from the SM, and hasn't been measured at LHCb yet, so it's still alive as an anomaly!

B to μμ, another channel expected to have high sensitivity to new physics.  Recent updates from all LHC experiments, combined data leads to discovery in one channel.  Tragically, in agreement with SM.  Get the standard plot of model space with ideas cut down in their prime by inconvenient truths.

Interesting stuff in kaon decays to muons.  Data to be updated soon, keep an eye out for it.

Another interesting anomaly in D to Κμμ, where one observable has as 3.7 sigma deviation.  Including look-elsewhere effect, end up with 0.5% probability that due to random chance.  Another thing to look at in more detail.  Recent theory reference; but tricky to fit to standard BSM (SUSY, Composite Higgs etc.)

Question: can we really do the B to Dτν measurement at LHCb?  B-factories distinguish one- versus three-neutrino decays (!), obviously impossible at LHCb.  So would have to do with hadronic τ decays; really possible?  Answer: maybe, still being worked on by the experimentalists.

9:35am: Luca Silvestrini, "Flavour overview"

Luca wants to convince us that flavour is still very relevant to BSM.

Worth distinguishing between indirect evidence (e.g. flavour, EW fits that gave us the expected Higgs and top masses) and arguments (that only suggest the existence of new physics, but are vague on the scale; e.g. the bottom quark).  This is where flavour comes into its own, thanks to e.g. the absence of tree-level FCNC and the GIM suppression of loop processes makes it very sensitive to new physics.  This sensitivity can offer indirect evidence as to the scale of new physics.

Status of the SM: Unitarity triangle fit.  Oh look, it works.  Data updated using results of summer conferences; new lattice results, and new experimental measurements including the B to μμ decays of note.

Notable tensions: inclusive versus exclusive measurements of Vub; sin 2β; BK; and the dimuon asymmetries.

Going BSM, the obvious starting point is MFV.  Can define generalised Unitary triangle; the fit to this is comparable to the SM.  Limits on MFV: one Higgs, or 2HDM with low tanβ; then corrections due to modifications of top Yukawa/loops leads to lower bounds on NP scales around 6-9 TeV.  If tanβ is large, bottom Yukawa can become important.  However, this is basically ruled out now; large tanβ requires heavy Higgs masses.

Going beyond MFV, various model-independent approaches; essentially look for new room in FCNC processes either at amplitude or EFT level.  Various notes, nothing here striking me.  The EFT approach gives us a bound on new physics.  In complete anarchy, bound is over 105 TeV; with some structure (but not MFV) can only bring this down to 102 TeV.

No comments:

Post a Comment