Little Higgs Dark Matter and Its Implications at the LHC

Chuan-Ren Chen(NTNU)

HEP Seminar @ AS, 5/30/2014

In collaboration with H-C Tsai, M-C Lee, 1402.6815[hep-ph]

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Outline

LHT

BSM EXP, OBS

predictionsexplanations

constraintsevidences

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Higgs boson July 4 2012 @ CERN

Higgs boson is discovered, a significant step for understanding of EWSB!

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Naturalness “Problem”

Higgs is naturally ~ 200 GeV

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e.g. Supersymmetry

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Little Higgs Model

100

, Kaplan…

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Littlest Higgs Model

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gauge symmetries are embedded in global SU(5)

Littlest Higgs Model

kinetic term

top sector

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Cancellation

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Little Higgs Model

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Little Higgs Model w/ T-parity

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Yukawa Sector

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Top Sector

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particle spectrum

SM

T-parity Even T-parity Odd

* parameters: f, kq, kl, λ1, mh

* The lightest T-odd particle is stabledark matter candidate

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EW constraints

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Unitarity constraining λ’s Belyaev, CRC, Tobe, Yuan, hep-ph/0609179

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T-odd Fermions

Cao, CRC, 0707.0877

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Higgs Pheno.

mh (GeV)gg -> h production is always suppressed

CRC, Tobe, Yuan, hep-ph/0602211

t, T+, q-

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Higgs Pheno.

gg -> h -> γ γ is suppressed

CRC, Tobe, Yuan, hep-ph/0602211

Han, Wang, Yang, Zhu, 1301.0090

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Dark MatterSome evidences

A nonbaryonic, “dark”, charge-neutral object which interacts weakly with normal matters

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Dark Matter at LHTtwo possible candidates: heavy photon, T-odd neutrinos

dark matter:

T-odd partner of photon

T-odd partner of neutrino

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Dark Matter & LHTΩh

2

can fit relic density data well.

XENON100

HOWEVER

Direct search of DM excludes

>>Planck+WMAP

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Dark Matter & LHTtwo possible candidates: heavy photon, T-odd neutrinos

dark matter:

T-odd partner of photon

T-odd partner of neutrino

dark matter:

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Dark Matter & LHT

Mh = 125 GeVsolution?Yes, MAH ≳ Mh/2

For heavier AH, co-annihilations with T-odd fermions are needed!

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co-annihilation w/ T-odd leptons (T-odd quarks are heavy!)

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w/ light T-odd leptonsMh = 125 GeV

are so light! LHC should be able to produce lots of them.

Planck2013 + WMAP-9yrs

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light T-odd leptons at LHC 8 TeV

f (GeV)

dilepton + met

lepton + met

large production cross section 1 ~ 10 pb

met only

100%

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arbi

trary

Pt(e) (GeV)

dilepton + met

dilepton + MET search at LHC:slepton pair or chargino pair in SUSY NO Constraint

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MT2 (GeV)

arbi

trary

dilepton + met

dilepton + MET search at LHC:

NO Constraint

slepton pair or chargino pair in SUSY

kill all signals

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one lepton + MET search at LHC:

f (GeV)

lepton + met

search for W’

one high pt lepton + large MT

MT (GeV)

MT > 1 TeV

kill signal

NO constraint from current data

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light T-odd leptons at LHC 8 TeV

arbi

trary

Pt(e) (GeV)

f (GeV)

dilepton + met

lepton + met

met only

charged lepton is soft!

can contribute mono-jet + met signal at LHC

soft

soft

direct search is very challenging!

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w/ light T-odd leptonsMh = 125 GeV

Direct search:

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co-annihilation w/ T-odd quarks (T-odd leptons are heavy!)

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w/ light T-odd quarks

3 down-type:

3 up-type:

degenerate case

inconsistent with stable heavy quark search at colliders

However, ∵ ( Mt_ - MAH ) < MW < Mtop

top partner ONLY has 4-body decay channel, decay life time is too long!

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w/ non-degenerate T-odd quarks

projective LUX 2014 can explore MAH up to ~190 GeV, future expts

can explore whole parameter space.

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arbi

trary

Pt(j) (GeV)

HUGE production cross section, jet pT is very soft!

light T-odd quarks at the LHC

dijet + MET search is very challenging!

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light T-odd quarks at the LHCcontributes to mono-jet BSM search at LHC.

soft

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95% C.L. exclusion

2.8 pb

0.16 pb

0.05 pb

0.02 pb

f < ~1.4 TeV (MAH < ~ 220 GeV) is DISFAVORED.

light T-odd quarks at the LHC

allow one other jet > 35 GeV

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Summary With Mh = 125 GeV, co-annihilation is needed for heavier (not

~ Mh/2) dark matter in LHT model to explain current universe.

In co-annihilation region, T-odd new heavy fermions should be very light, large production cross section at the LHC.

The small mass difference between dark matter and T-odd leptons makes collider search very difficult.

light T-odd top quark partner decays “too late” -> not allowed by collider searches.

mono-jet + MET from light T-odd quarks + 1jet production at the LHC exceed current limit if MAH < 220 GeV.

Future DM direct search exps can explore whole parameter space.

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Back UP

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Little Hierarchy ProblemEffective SM Schmaltz et al, hep-ph/0502182 and references therein

New Physics should be larger than 5 TeV

tension between 1 TeV and 5 TeV!!

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EW constraints

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“heavy neutrino” can NOT be a dark matter

KK neutrino in UED model

relic density

elastic scattering w/ nuclei

~ 2x10-3 pb >> 10-9 pb (current limit)

same as SM coupling

Servant, Tait, hep-ph/0206071 Servant, Tait, hep-ph/0209262

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mono-jet +MET at LHC 95% C.L. exclusion

2.8 pb

0.16 pb

0.05 pb

0.02 pb SR3: jet Pt > 350 GeV

NO constraint from current data

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“Solution”