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

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˜ t 1

5 CHALLENGES TO MSSM

-problem

MSSM superpotential -term

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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

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W = μ ˆ H u ⋅ ˆ H d

with

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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.

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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

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{ ˜ 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

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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

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(Z → χ 10χ 1

0,AiH j )

• Scan over all relevant parameters• Require

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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

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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

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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

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M H1~ 100 GeV

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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

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Often lightest χ 10 is singlino dominated

with χ 20,...,χ 5

0 MSSM - like

lower MSSM bound

Dark matter

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Relic density in n/sMSSM from

χ 10χ 1

0 → Z annihilation

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Mχ 1

0 < 30 GeV ruled out

Constraints from CDM complementary: CDM excludes very light Higgs mass in n/sMSSM

WMAPallowed

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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

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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

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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!