Singlet Extensions of the MSSM Vernon Barger at SUSY 06 June 15, 2006.
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Transcript of Singlet Extensions of the MSSM Vernon Barger at SUSY 06 June 15, 2006.
Singlet Extensions of the MSSM
Vernon Barger
at
SUSY 06
June 15, 2006
softly broken Minimal Supersymmetric Standard Model (MSSM)
I. Solves the gauge hierarchy problemII. Unifies gauge couplingsIII. Automatic EWSB from RGE evolutionIV. Precision electroweak agreementV. Dark matter candidate - the lightest neutralino
5 PILLARS:
same SU(3)SU(2)U(1) gauge symmetry as SM, 2 Higgs doublet fields, plus R-parity
I. Light Higgs not yet found:LEP excludes low tan
II. EWSB: large fine-tuning cancellations to get MZ sufficiently light
III. Electroweak baryogenesisneeds and light Higgs; not yet found
IV. Neutralino relic density reproduces DM ~ 0.25 only in limited regions of CMSSM space
V. The -problem€
m ˜ t 1≤ mt
€
˜ t 1
5 CHALLENGES TO MSSM
-problem
MSSM superpotential -term
€
W = μ ˆ H u ⋅ ˆ H d
: only dimensionful MSSM parameter
unrelated to EWSB and SUSY-breaking scales
But all mass parameters should be O(TeV)rather than MGUT or Mplanck
A very important unsolved problem in the MSSM
Singlet Higgs to the rescue!Well motivated: SM singlet very common in string constructions
Replace SSM superpotential
€
W = μ ˆ H u ⋅ ˆ H d
with
€
eff = hs S
With all VEVs of order MSUSY, -problem is solved
S-field gives additional neutral Higgs state (and associated Neutralinos)
Higgs singlet-doublet mixing relaxes the constraints thatare difficult for the MSSM.
€
W = hsˆ S ˆ H u ⋅ ˆ H d
Then effective -term generated by VEV of S-field
Many contributors to singlet extended models
CP studies and Non-Standard Higgs Physics - comprehensive report in preparation
Perspective in my talk based on recent work with Paul Langacker, Hye-Sung Lee, and Gabe Shaughnessy
AbelBaggerBalazs
Basetro-GilBatra
BirkedalCarenaChoi
CveticDedes
DelgadoDemir
DermisekDobrescu
DreesEllis
EllwangerErler
EspinosaEverettFayet
GodboleGunion
HaberHan
HooperHugonie
KaoKaplanKing
Landsberg Li
MatchevMcElrath
MegevandMenonMiller
MorettiMorrisseyNevzorov
PanagiotakopoulosPerelsteinPilaftsisPoppitzQuiros
RandallRosner
D. P. RoySarkar
SopczakTait
TamvakisVempatiWagnerWhiteZerwasZhang
My apologies to those whose names may have been missed
4 Models with Dynamical An underlying new symmetry defines each model.
Features of modelsNMSSM (Next-to-Minimal): domain walls from discrete
symmetry may be problematic
nMSSM (nearly Minimal) a.k.a. MNSSN (Minimal Non-minimal): light H1, A possible
U(1)´ models: tension related to MZ´
UMSSM: exotics to cancel chiral anomalies
sMSSM: secluded U(1)´ model avoids tension connecting MZ´ and Z-Z´ mixing
sMSSM nMSSM at large si All models MSSM in large s limit
Black = MSSM (with hs<S>)Orange = extensionsBlue = NMSSM (g1´ = 0, F = 0, S = 0)Purple = UMSSM (F = 0, S = 0, = 0, A = 0)Red = n/sMSSM (g1´ = 0, = 0, A = 0)
For a particular model irrelevant parameters turned off.
Tree-level potential
Leading top-stop loop corrections to Higgs masses are common (same as MSSM)since singlet does not couple to MSSM particles other than the Higgs doublets
So all differences in predictions from tree-level
Diagonalize 33 mass-squared matrices in the {Hd, Hu, S}basis, including leading loop corrections, to find physical Higgs states
Neutralinos
Supersymmetry companions of S and Z´ change neutralino sector
Mass matrix (M) in basis
€
{ ˜ B , ˜ W 3, ˜ H d0, ˜ H u
0, ˜ S , ˜ Z '}
Same model parameters + gaugino mass: new probe
M1 = 0.5 M2 = M1´ unification assumed
Explore model predictions by
Impose experimental constraints from LEP
ZZh coupling (from e+e- Zh)ZAh search
€
Mχ ± >104 GeV
Z-Z´ mixing constraint on U(1)´ model: ZZ´ < O(10-3)
New physics contributions to invisible Z-width < 1.8 MeV
€
(Z → χ 10χ 1
0,AiH j )
• Scan over all relevant parameters• Require
€
M H i
2 > 0, MA i
2 > 0, m ˜ t 2 > 0,
(avoid solutions with unstable saddle points of the potential)
Unified analysis of Higgs and Neutralino Sectors
SM bound from LEP on light Higgsrelaxed by singlet-doublet mixing
Reduced ZZHi couplingLEP SM
€
ZZH i= gZZH i
gZZh
SM( )
2
Sopczak (2005)
Light Higgs with reduced ZZh couplings couldhave been missed at LEP!
Lightest CP-even Higgs mass range
• H1 mass range expanded inN and n/s models - can be very light or heavier than MSSM
• Z-Z´ mixing disfavors light H1 in U(1)´ model
• CP-Odd mass can also be very light in N and n/s models• MA vanishes in Peccei-Quinn limit (or U(1)R limit)
Lightest CP-odd Higgs mass range
Sample eigenstate composition
(A) light Higgs illustration
Comments:
Very light Higgs states are mostly singlet, so are nearly decoupled from SM particles(suppressing their production)
A very light H1 in the N or n/s models is generically accompanied by a MSSM-like H2 with a mass in the 115-135 GeV range
Non-SM decays can be dominantwhen kinematically accessible
invisible decays (n/s model)
Total Higgs width can be up to 105 times the SM value
€
H1,2 → χ 10χ 1
0H1,2 A1 A1
(N and n/s models)
Invisible Higgs can only be inferred indirectly
CDM
Finding an invisible Higgs
At the LHC, invisible Higgs can be probed via Z-Higgstrahlung and weak boson fusion
At the ILC, invisible Higgs can be discovered via Z-recoil spectrum in Z+Hinv production
mH = 120 GeV 5 discovery in Z+Hinv with 10 fb-1
mH ~ 15 GeV with 100 fb-1 with ZH and WBFDavoudiasl, Han, Logan
A corner of NMSSM parameter space
Dermisek, Gunion, Hooper, McElrath
H1A1 A1 decays with
escapes LEP constraints if
€
M H1~ 100 GeV
€
MA1< 2Mb
Neutralino spectra illustration(A) Corresponds to light Higgs case
Note that extended models are unlikely to have an LSP with the typical dominant Bino composition of the MSSM
Neutralino cascade decay chains depend on the model
€
Often lightest χ 10 is singlino dominated
with χ 20,...,χ 5
0 MSSM - like
lower MSSM bound
Dark matter
€
Relic density in n/sMSSM from
χ 10χ 1
0 → Z annihilation
€
Mχ 1
0 < 30 GeV ruled out
Constraints from CDM complementary: CDM excludes very light Higgs mass in n/sMSSM
WMAPallowed
€
n/s model allows only Mχ 1
0 <100 GeV
Z annihilation is most relevant channel
VB-Kao-Langacker-Lee
Easing the LEP tension
UMSSM similar to MSSM since Z-Z´ mixing constraint requires large s
BEFORE(MSSM)
AFTER(N and n/s Models)
Can the Higgs bosons of the singlet-extendedmodels be discovered?
FOR BETTER OR WORSE…
•The signals could be larger or smaller than SM or MSSM
BFs larger than SM dueto smaller
€
Γ(H → bb )
Higgs Decays
Higgs signals (SM curves)
ggH , LHC ggH WW*, Tevatron
Even Higgs detection in MSSM troublesome compared to SM due to sharing of couplings:
MSSM: g(H1WW)2+ g(H2WW)2 = g(HSMWW)2
Large Higgs singlet component usually spells trouble for detection
CP-violation in nMSSM
Naturally obtain strong first order electroweak phasetransition needed to preserve baryon asymmetry producedby Electroweak Baryogenesis
Induced through phase of gaugino masses
Inference from baryogenesis and relic DM density
Menon, Morrissey, Wagner
with invisible H1 11
€
mχ 1~ 30 − 40 GeV
Conclusions
• Introduction of a Higgs singlet solves the important -problem and lessens potential confilicts of the MSSM with data
• Several ways to extend the MSSM with different underlying symmetries
• More new physics at TeV scale than in MSSM(extra Higgs, neutralinos, Z´): How many of these can be discovered?
•With the addition of the singlet, the properties of the Higgsbosons and neutralinos can be substantially different from the MSSM
•Features of models
Lighter or heavier CP-even Higgs than MSSM
Low tan values allowed, unlike MSSM
Low Higgs mass associated with large singlet component
Approach MSSM limit for large singlet vev s
Collider signals:
Light Higgs could have been missed at LEP(reduced ZZh coupling or invisible decays)
Partial widths suppressed by large singlet composition
BFs can be larger due to H bb suppression
Enhanced signal at LHC possible for H
Neutralino decay cascades may be very different from MSSM
Higgs sector and neutralino sector provide complementary probes
Cold Dark Matter indirectly constrains the light Higgs mass
Dynamical term points to very rich new Higgs/neutralino physics at LHC!