Tuesday, 5 May 2015

Pheno 2015 Liveblog Day 1 Session 3

First parallel session, I'll be moving around a bit.  I'll start in Higgs I.

2:00 pm: Physics Under the Higgs Lightpost, Ian Lewis

Now have complete prediction for SM.  Everything so far lining up pretty much exactly with SM.  Measurements of WW, ZZ couplings are probes of EWSB.  LHC prospects for measurements at 5% in best channels.  This will thoroughly test this sector.

What do Higgs rates tell us about NP?  How do we get it?

TeV physics leads to 1% Higgs coupling shift.  LHC won't get there.  Two origins: mixing & vertex corrections.

Mixing constraints: scalar singlet, 2HDM.  For former, bounds on mixing angle sin2 < 0.12 with current data, based purely on rates.  2HDM obviously depend on fermion couplings, e.g. Type I ve Type II.  Pushed towards decoupling limit, and can really get there just with LHC.  Generally superior with couplings vs direct searches for heavy Higgses.

Loops: gg, γγ.  Need another measurement to break degeneracy between new loop, shifted top Yukawa.  One possibility is add a high-pT jet.  Can still use EFT for top partners thanks to direct search limits.  Test EFT with dimension-7 operators; few percent corrections.

What of flavour-non-diagonal Higgs couplings?  Must consider diHiggs production.

More general models looking for enhanced Higgs rates: vector-like fourth generation.  Doesn't work because of constraints (e.g. EWPO), correlations in EFT.  Enhancements need to be very exotic.

Finish on a positive note: scalar singlet decaying to diHiggs, can enhance signal up to ~ 16 this way.  Not ruled out yet.  Can be probed by LHC.

2:30 pm: Minimal Non-Supersymmetric Unified SO(10) Model, Saka Khan

I've bounced over to BSM I for the next few talks.  By non-SUSY, means ordinary field theory, not a composite Higgs.

First question is what the Higgs session that breaks SO(10).  Problem is to avoid breaking through SU(5) channel, due to proton constraints.  Use a real 54 to break to a Pati-Salaam-type group, then a 126 to break further.  Expected scalar masses based on scale of VEVs (i.e. fine tuning exactly as much as needed).

Unification works via the intermediate PT scale of breaking.  This leads to rough upper bound on proton lifetime, so can be ruled out by next-generation proton decay experiments.  Challenge due to non-trivial relations among Higgs masses.  Found some points that work.

Fermion mass problem reduces to something solved in the literature.

What is D-Parity? A LR parity.

2:45 pm: SM hypercharge: From Superconnection to Noncommutative Geometry, Chen Sun

Superconnection formalism: unrelated to SUSY.  Extend the gauge connection without extending the gauge symmetry.  RH/LH fermions live on different sheets, with the Higgs the interpolation.  The VEV is the (inverse) separation.

New terms in connection look like Higgs but problems: VEV, mixing of 1- and 0-forms.

3:00 pm: Mass Reach Scaling for Constructing Lagrangians, Thomas Rizzo

Should we have a specific luminosity goal in mind for a 100 TeV collider?  (Primary focus on new heavy resonances.)  Default scaling by energy squared, so a factor of 50 from LHC.

Suggestion: want to maintain ratio between scales probed vs collider energy.  What would that mean for luminosity?  What would that mean for cost?

Simple analysis based just on counting.  Cross section goes down for fixed scale due to running of QCD coupling and from parton densities.  Look at a number of NP channels and find a range of additional suppressions, typically by 2 to 3 over the naive scaling expectation.  Better for EW-dominated processes, worse for QCD-dominated.

If you don't get so much luminosity, what does that mean as far as searches go?  Don't suffer as much as expected.  A factor of 3 in luminosity is typically only a 10% shift in reach.  Even a factor of 10 is only 20 to 30% in reach.

What of backgrounds?  Might be better or worse.

3:15 pm: Clues for Simplified Models from SUGRA Sparticle Hierarchies and LHC Data, Sujeet Akula

Lots of possible spectral orderings in SUSY models.  31 new particles, so 31! possible orderings.  What do we expect based on SUGRA GUTs?  Much fewer--bottom of spectrum has only tens of possibilities.

Sorry, I prefer the bottom-up simplified models to the top-down GUTs.

3:30 pm: LHC Constraints on Mini-Split Anomaly and Gauge Mediation and Prospects for a Future 100 TeV pp Collider, Hugues Beauchesne

Integrating out the heavy scalars in mini-split models deviates the gaugino masses from the usual anomaly or gauge mediation expectations ('deflected').  Corrections can be order 1!!  But still easily calculable.

Gluino limits at 1.3 TeV from LHC, up to 12 TeV at 100 TeV machine.

3:45 pm: The 2015+ Phenomenology of Deflected Mirage Mediation, Todd Garon

DMM is a scenario with vector-like messengers at an intermediate scale.  We have gravity, guage and anomaly mediation contributions, with the scalar masses appearing to unify at a "mirage" low scale.  High-scale model so small parameter set: 9 parameters.  Corrections push scalars up and gauginos down.

Parameter scan of 3 million points.  8% pass necessary experimental cuts.  NLSP mostly Higgsino, with small fraction of Bino or Wino NLSPs not seen in conventional mirage mediation.

Can we discover anything?  Claimes yes, most of scan, but I don't fully believe that.

No comments:

Post a Comment