Little Higgs Dark Matter and Its Implications at the LHC Chuan-Ren Chen (NTNU) XS 2014, 5/6/2014 In collaboration with H-C Tsai, M-C Lee, [hep-ph]

Outline CRC (NTNU) 2 LHT BSM EXP, OBS predictions explanations constraints evidences

Higgs boson CRC (NTNU) 3 July 4 CERN Higgs boson is discovered, a significant step for understanding of EWSB!

Naturalness “Problem” CRC (NTNU) 4 Higgs is naturally ~ 200 GeV

CRC (NTNU) 5 e.g. Supersymmetry

Little Higgs Model CRC (NTNU) 6 100, Kaplan…

Littlest Higgs Model CRC (NTNU) 7

8 gauge symmetries are embedded in global SU(5) Littlest Higgs Model kinetic term top sector

Cancellation CRC (NTNU) 9

Little Higgs Model CRC (NTNU) 10

Little Higgs Model w/ T-parity CRC (NTNU) 11

Yukawa Sector CRC (NTNU) 12

Top Sector CRC (NTNU) 13

particle spectrum CRC (NTNU) 14 SM T-parity EvenT-parity Odd * parameters: f, k q, k l, λ 1, m h * The lightest T-odd particle is stable dark matter candidate

EW constraints CRC (NTNU) 15

Unitarity CRC (NTNU) 16 constraining λ ’s Belyaev, CRC, Tobe, Yuan, hep-ph/

T-odd Fermions CRC (NTNU) 17 Cao, CRC,

Higgs Pheno. CRC (NTNU) 18 m h (GeV) gg -> h production is always suppressed CRC, Tobe, Yuan, hep-ph/ t, T +, q -

Higgs Pheno. CRC (NTNU) 19 gg -> h -> γ γ is suppressed CRC, Tobe, Yuan, hep-ph/ Han, Wang, Yang, Zhu,

Dark Matter CRC (NTNU) 20 Some evidences A nonbaryonic, “dark”, charge-neutral object which interacts weakly with normal matters

Dark Matter at LHT CRC (NTNU) 21 two possible candidates: heavy photon, T-odd neutrinos dark matter: T-odd partner of photon T-odd partner of neutrino

Dark Matter & LHT CRC (NTNU) 22 Ωh2Ωh2 can fit relic density data well. XENON100 HOWEVER Direct search of DM excludes >> Planck+WMAP

Dark Matter & LHT CRC (NTNU) 23 two possible candidates: heavy photon, T-odd neutrinos dark matter: T-odd partner of photon T-odd partner of neutrino dark matter:

Dark Matter & LHT CRC (NTNU) 24 M h = 125 GeV solution? Yes, M AH ≳ M h /2 For heavier A H, co-annihilations with T-odd fermions are needed!

co-annihilation w/ T-odd leptons (T-odd quarks are heavy!) CRC (NTNU) 25

w/ light T-odd leptons CRC (NTNU) 26 M h = 125 GeV are so light! LHC should be able to produce lots of them. Planck WMAP-9yrs

light T-odd leptons at LHC 8 TeV CRC (NTNU) 27 f (GeV) dilepton + met lepton + met large production cross section 1 ~ 10 pb met only 100%

arbitrary P t (e) (GeV) CRC (NTNU) 28 dilepton + met dilepton + MET search at LHC: slepton pair or chargino pair in SUSY NO Constraint

MT2 (GeV) arbitrary CRC (NTNU) 29 dilepton + met dilepton + MET search at LHC: NO Constraint slepton pair or chargino pair in SUSY kill all signals

CRC (NTNU) 30 one lepton + MET search at LHC: f (GeV) lepton + met search for W’ one high pt lepton + large MT M T (GeV) M T > 1 TeV kill signal NO constraint from current data

light T-odd leptons at LHC 8 TeV CRC (NTNU) 31 arbitrary P t (e) (GeV) f (GeV) dilepton + met lepton + met met only charged lepton is soft! can contribute mono-jet + met signal at LHC soft direct search is very challenging!

w/ light T-odd leptons CRC (NTNU) 32 M h = 125 GeV Direct search:

co-annihilation w/ T-odd quarks (T-odd leptons are heavy!) CRC (NTNU) 33

CRC (NTNU) 34 w/ light T-odd quarks 3 down-type: 3 up-type: degenerate case inconsistent with stable heavy quark search at colliders However, ∵ ( M t_ - M AH ) < M W < M top top partner ONLY has 4-body decay channel, decay life time is too long!

CRC (NTNU) 35 w/ non-degenerate T-odd quarks projective LUX 2014 can explore M AH up to ~190 GeV, future expts can explore whole parameter space.

CRC (NTNU) 36 arbitrary P t (j) (GeV) HUGE production cross section, jet p T is very soft! light T-odd quarks at the LHC dijet + MET search is very challenging!

CRC (NTNU) 37 light T-odd quarks at the LHC contributes to mono-jet BSM search at LHC. soft

CRC (NTNU) 38 95% C.L. exclusion 2.8 pb 0.16 pb 0.05 pb 0.02 pb f < ~1.4 TeV (M AH < ~ 220 GeV) is DISFAVORED. light T-odd quarks at the LHC allow one other jet > 35 GeV

CRC (NTNU) 39 Summary  With M h = 125 GeV, co-annihilation is needed for heavier (not ~ M h /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 M AH < 220 GeV.  Future DM direct search exps can explore whole parameter space.

CRC (NTNU) 40 Back UP

Little Hierarchy Problem CRC (NTNU) 41 Effective SM Schmaltz et al, hep-ph/ and references therein New Physics should be larger than 5 TeV tension between 1 TeV and 5 TeV!!

CRC (NTNU) 42

CRC (NTNU) 43

EW constraints CRC (NTNU) 44

CRC (NTNU) 45 “heavy neutrino” can NOT be a dark matter KK neutrino in UED model relic density elastic scattering w/ nuclei ~ 2x10 -3 pb >> pb (current limit) same as SM coupling Servant, Tait, hep-ph/ Servant, Tait, hep-ph/

mono-jet +MET at LHC CRC (NTNU) 46 95% C.L. exclusion 2.8 pb 0.16 pb 0.05 pb 0.02 pb SR3: jet P t > 350 GeV NO constraint from current data

CRC (NTNU) 47 “Solution”

New Particles CRC (NTNU) 48 + SM particles T-parity Even T-parity Odd * parameters: f, k q, k l, λ 1, m h * The lightest T-odd particle is stable dark matter candidate