little higgs dark matter and its implications at the lhc
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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”
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