Dear Michael and Chip,

Please find below some draft discovery stories from the Higgs group.

-Heather



Higgs discovery stories (draft 2013/06/20)
(* = Need to sharpen these numbers)
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(1) Higgs coupling deviations from SM for natural SUSY or compositeness

LHC uncovers deviations of the Higgs couplings from the SM prediction
at the 10% level, by combining channels in a constrained
parameterization (compositeness scenario: all couplings shifted by the
same factor; SUSY scenario: hgg and h gamma gamma shifted due to light
stops and charginos in the loops).

SUSY: Light stops are discovered with 300 fb-1 and hints of light
Higgsinos are uncovered at HL-LHC.  An e+e- collider measures light
SUSY particle spectrum and properties with high precision.  It
confirms consistency with the loop-induced Higgs couplings to within
uncertainties (h -> gg and h -> gamma gamma are limited by b/c/g
separation and statistics, respectively).  The hbb and h tau tau
couplings are about 5% higher than the SM prediction (5 sigma for hbb)
indicating heavy SUSY Higgses around a TeV*.  SAPPHIRE is approved to
nail the h gamma gamma effective coupling to 1%* to clearly see the
stop and chargino loop contributions and probe their couplings to the
Higgs, providing a test of the hierarchy problem solution.

Compositeness: A first RS resonance is seen at a few TeV at the LHC.
HL-LHC solidifies the discovery (Z'/W' = compositeness techni-rho?)
and shows hints of a second resonance*.  The double-Higgs production
rate is found to deviate significantly* (how much?) from the SM
expectation.  Belle-II observes* non-CKM flavor violation (thinking of
Soni's RS-for-flavor).  Meanwhile, e+e- collider measurements of Higgs
couplings confirm the pattern of shifts; high-energy ILC/CLIC running
shows hints of s-channel Z' exchange in the Zh cross section, allowing
the Z' Z h coupling to be roughly constrained.  Ultimately, the RS
spectrum is explored in detail with a 100 TeV p-p collider.


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(2) Higgs CP violation for electroweak baryogenesis

CP violation is detected in tth and gg -> h + 2 jets* azimuthal
distributions at the LHC.  Simultaneously, various Higgs couplings are
seen to be off the SM predictions in a pattern consistent with a
Type-II 2HDM with CP violation and tan beta ~ 0.8. [thinking of
1304.0773 for baryogenesis.]  Hints* of heavy Higgses h2, h3 are seen
at LHC around 500 GeV (in WW/ZZ? check this).  HL-LHC studies these
states in detail* and tan beta is measured.  Heavy Higgs rates are
consistent with "the rest of" the CP mixing.

The triple-Higgs coupling is measured to be consistent with the SM
within the LHC's order-100% uncertainty.  HL-LHC sees a hint of a
deviation but is inconclusive within uncertainties.  ILC/CLIC sees a
modification of the triple-Higgs coupling from SM expectations at the
level of 3 sigma or so*.

New electron (or neutron?) EDM measurements come up positive,
consistent with the new 2HDM source of CP violation.

(How do we prove that the model yields successful EW baryogenesis?)


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(3) No deviation from the SM Higgs overthrows naturalness paradigm

LHC measures Higgs couplings and finds no deviation from the SM,
setting 95% CL limits on sigma x BRs order 10%*.  No BSM particles are
found either.

e+e- collider measurements drive down the upper bounds on Higgs
sigma x BR deviations down below the 2% level; no other discrepancies
from the SM are found.  Improved measurements of the top and Higgs
mass point to the SM vacuum being on the boundary between stability
and metastability at the Planck scale.

At some point we are driven to a paradigm shift: the universe does not
care about naturalness!  (When do we become convinced of this?*)

Resonant microwave cavity searches discover axion dark matter.


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(4) Heavy Higgs discovery

LHC discovers a heavy Higgs decaying to tau-tau with mass around 800
GeV and rate corresponding to tan(beta) ~ 30* (check sensitivity
numbers).  This is consistent with MSSM H/A production.  (No SUSY
particles are seen yet.)

HL-LHC resolves two states in the mu-mu final state*, measuring their
masses with good precision.  (Is this possible?  Do we need a muon
collider to resolve them?)  Hints emerge of electroweak gauginos at a
few hundred GeV.  A high-energy e+e- collider studies the properties
of the electroweak gauginos in detail and measures the properties of
the H/A states (need cm energy of at least 1600 GeV) and discovers the
associated charged Higgs.  A muon collider studies resonant production
of H and A, resolving well their masses and lineshapes and determining
couplings that way.




----------------------------------------------------------
Heather E. Logan     http://www.physics.carleton.ca/~logan
Department of Physics, Carleton University, Ottawa, Canada

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