Monday, 5 May 2014

Pheno 2014 Liveblog: Day One Session 1

It's conference time, and that means live blogs!  I'm planning to do a slightly different format to last year, with less during-talk blogging and more of a summary post for each talk.  This will minimise the amount of typing I have to do during the talks, which might annoy people sat near me!

It's the first plenary session, so that means a review of experimental (collider) results.  This is fairly straightforward, as the LHC has been shut down for a while and this isn't the place any new discoveries would be announced anyway.

8:45 am: Standard Model physics results from ATLAS and CMS, Jacob Searcy

Covers everything that is SM but not Higgs.  So precision tests/measurements of non-perturbative physics.

The short summary: the SM works pretty well.

Jet physics: a lot of work going on here.  Useful both to improve event generators/pdfs, also useful for jet substructure searches.

Top Asymmetry: this is definitely an interesting question with the long-standing Tevatron anomaly, and the fact the LHC cannot directly measure the same quantity.  See the SM, though the error bars are still quite large.  Systematically limited already, which does raise the question of how much better we can do.  Apparently, since exciting physics lives in the tails of the distributions, there is still hope for improvement.

First talk, first technical difficulty!

Single top: LHC program still in its early days.  Number of different channels.

Gauge boson quartic interactions: first measurements being made.  A direct observation of gauge invariance in non-Abelian theories, and also a probe for lots of different new physics.  A similar probe of vector-boson scattering, which is sensitive to the Higgs couplings/heavy Higgses.

In summary, while there's a lot of new processes being studied, which is interesting, the SM is looking good.  Also, many results still only at 7 TeV; precision measurements take time, so it is important to keep an eye out for upcoming 8 TeV papers.

9:20 am: Recent BSM results from ATLAS and CMS, Yuri Gershtein

Quote: "Don't have inflated expectations."

DM searches based on mono-X are among the most model-independent searches that exist, but even there sizeable theoretical uncertainty can exist from interference.

Also looking for DM coupling to 3rd generation, because of Dan Hooper and his gamma ray excess from the galactic centre.

Interesting limits on hidden valley-type signals from Higgs decays (h to XX to SM).  Limits for X lifetime of ~1 cm now down to a few fb.  This is equivalent to branching fractions of 0.01%.

A number of exotic limits (W', black holes, vector-like quarks) but these all look qualitatively similar to stuff I've seen before.

SUSY gets to come last, which says something by itself, even if Yuri is in the "Higgs discovery makes SUSY more likely" camp.  Most interesting thing here is the experimentalists talking about recasting experiments, so they are thinking about putting their data/analysis in forms more useful for us theorists.  That's a good thing, obviously.

Constrained models "dead"; might be interesting were John Ellis here, to see what he would say on that.

We end with the realisation that we have covered a lot of search topologies, but seen nothing.  Yuri still seems optimistic that there is a lot of space to cover, based on natural SUSY it seems.

Question about mono-Higgs DM searches.  Seems still well short of probing realistic parameter space.

9:55 am: Higgs boson production and coupling measurements at the LHC, Garabed Halladjian

We've seen a lot of these results in the last few years.  Sadly, we still don't have 5 σ in any fermion channel alone, though that does correspond to saying that we have more freedom in the Higgs Yukawa couplings.  Actually, maybe ττ would pass that if you combined the data of ATLAS and CMS, it's not clear.

The signal strength analysis is unchanged; both experiments roughly comparable with each other and the SM.  ATLAS is slightly high based on their long-standing γγ excess.

Summary: familiar, and I haven't slept enough.

10:15 am: Measurements of the Higgs boson mass, width, and spin at the LHC, Daniela Bortoletto

Higgs mass: from ZZ particularly, nothing really new here.

JPC measurements assuming that pure CP even/odd, etc; definite preference for even scalar.  But what of mixed CP eigenstates?  Beginning to consider this in the ZZ to 4l channel.

Higgs width points to non-standard Higgs decays, but hard to measure directly at LHC due to energy resolution and inability to scan over resonance.  Using interference between gluon fusion/VBF to get new handle on this.

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