Monday, 23 May 2016

Planck 2016 Liveblog: Day One Session Three

Unlike some Plancks I've been to, here we're into the parallel sessions from day one.  First off, I've chosen to attend the Higgs I session.

Also, mostly unrelated but lunch today was the best conference food I've ever had.

3:00 pm: Higgs Physics, Elisabetta Gallo

Run 1 and 2 results from both CMS and ATLAS.  Over 600 different production/decay channels combined.  Result of it all is a global fit on signal strength μ = 1.09 with 10% errors.  All combined production modes agree with SM at 1σ, except ttH; all decay modes except ZZ.  Combined searches for ττ observed at 5σ.  Differential cross sections in WW also in excellent agreement (high statistics, MET).

At run 2, only 2.7 ifb of data used due to problem with solenoid cold box (now fixed).  Pile-up of 13.  Signals in golden channel (4l) a bit low at ATLAS/CMS so far.  Similar with γγ.  Both channels have better S/B at run 2, due to improved analysis.

ttH production enhanced by factor of 4.  Use MEM to remove ttbb background.  Trilepton channel at CMS persists!

Double Higgs production a target: classic sign of NP in form of new resonances or enhanced self-coupling.  Possible observation of SM process so can exclude some models.

Bounds on non-resonant diHiggs?  DNK
Ratio of BRs?  All look good except bb/ZZ, but that is probably not meaningful.
Excess in ttH? Run 2 has net deficit if sum all channels.

3:20 pm: Singlets in Composite Higgs Models in light of the LHC di-boson searches, Thomas Flacke

Minimal UV models of composite Higgs involve additional states: coloured light states and additional scalars producing diboson signals.  Specifically, demanding no new elementary scalars, a simple hyper-colour group, a Higgs and top-partners excludes minimal symmetry breaking group SO(5)/SO(4).  Smallest are SU(4)/Sp(4), SU(5)/SO(5) and SU(4)xSU(4)/SU(4).  All models contain coloured pNGBs; and two spontaneously broken U(1) symmetries leading to SM singlets.  One is anomalous and associated states heavy, while the other only couples to SM through WZW term.

Coloured Goldstones lead to searches in four tops.  Easy to apply limits.

Existence of (potentially light) singlet attractive for 750 GeV study.  List of models that can explain this notably truncated; all in reach of near-future searches.

What effect does giving mass to singlets have?  Interesting question, direct are of work.
Can SM couplings be used?  No, because singlet.  But might depend on top Yukawas, depending. 

3:40 pm: New physics and signal-background interference in associated HZ production at LHC, Alberto Tonero

pp → ZZ or HZ good channels to constrain Higgs sector, especially at high momentum transfer.  Constrain dimension-6 effective operator.

4:00 pm: Higgs mass from (super)-split supersymmetry, Jae-hyeon Park

First post-title slide: nothing but equations.

When SUSY scale is large, must resum logarithms.  Match quartic at MSUSY and run down.  This was done in 2014, found upper limit of 1012 GeV (high-scale) or 108 (split).  Equivalent to instability in SM potential near that scale vs positive definite nature of quartic in MSSM.

Clever idea exploiting non-decoupling nature of a bounce solution that I didn't quite follow.

4:20 pm: Opening the Higgs portal window, Javier Quilis Sancho

Standard scalar singlet Higgs portal model has many nice properties.  This includes that it can be ruled out.  LZ can do this except for tiny region right on the resonance.

However, we can add one extra unstable Higgs portal scalar.  Removes lower bound on portal coupling for large masses, leading to essentially no constraints.  Doesn't work at low masses, because H2S1S2 portal coupling leads to invisible decays.

Was Sommerfeld enhancement included?  No. 

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