invisible higgs @ lhckimcs.yonsei.ac.kr/.../2011a_schedule/cskim_invhiggs.pdf · 2015-11-17 · 1...
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Invisible Higgs @ LHC(from B K + missing)
C S Kim (Yonsei)
C.S. Kim, S. Park, K. Wang, G. Zhu
arXiv:0910.4291 [hep-ph] Phys.Rev.D81:054004,2010
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Contents
• 1 Higgs Search at LHC• 2 Hidden sector Scalar and its
Cosmological Bound • 3 and missing • 4 Invisible Higgs (at LHC,…)• 5 Conclusions
B K νν→ + B K→ +
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1 Higgs searCH at tHe LHC
The Higgs boson is the last particle in the standard model that hasn’t been observed directly!
The History:Legacy of LEP --precision electroweak measurements
LEPEWWG as of July 2006:
Minimal chi-square atHiggs mass = 85 GeVwith an uncertainty of+39 GeV and -28 GeV
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Precision Tests of the StandardModelLepton couplings Pulls in global fit
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Very recently Fermilab announced exclusion of a SM Higgs in the mass range 160 - 170 GeV from an inclusive search at CDF and D0:
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The State of the Higgs: May 2009
• Direct search limit from LEP:mH > 114.4 GeV
• Electroweak fit sensitive to mt
(Now mt = 173.1 ± 1.3 GeV)• Best-fit value for Higgs mass:
mH = 84+34–26 GeV
• 95% confidence-level upper limit: mH < 154 GeV, or 185 GeV including direct limit
• Tevatron exclusion:mH < 160 GeV or > 170 GeV
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The focus has now shifted to Tevatron and the LHC:Main production mechanisms of the Higgs at hadron
colliders:
Ref: A. Djouadi,hep-ph/0503172
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Among them gluon fusion is the dominant mechanism!
Ref: A. Djouadi, hep-ph/0503172
At Tevatron:
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At LHC:
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Decay channels depend on the Higgs mass:
Ref: A. Djouadi, hep-ph/0503172
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2 Hidden seCtor sCaLar, and its CosmoLogiCaL Bound
Assuming renormalizability, Lagrangian of hidden sector scalar,
2Z symmetry ensures S is stable S = dark matter candidate,
Now considering WMAP data ( )
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We can easily avoid this cosmological constraint if the singlet S decays intolight particles, by breaking symmetry from QG effects, eg.
scalar particle may decays to a pair of photons or gluons through dim=5 operators,
2Z
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Preliminary(work in progress)
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3 and missing
We consider as -
And for
cf.
B K νν→ + B K→ +
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Motivation for BK(K* )νν (bs with 2 neutrinos)
SM: BF(BK* νν) ~1.3 x 10-5
BSM: New particles in the loop
c.f. SM: BF(BK- νν) ~4 x 10-6
[Belle preliminary (275 x 106 B Bbar) : BF(BK- νν) <3.6 x 10-5]
Other weakly coupled particles: light dark matter
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2011-03-10 Leptonic B decay & Leptophobic Z'
18
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Search for BK*νν (532 x 106 B Bbar pairs)
0 *0 4( ) 3.4 10B B K νν −→ < × (at 90% C.L)
Extra Calorimeter Energy (GeV)
3.12.64.7Yield +
−=
(1.7σ stat. significance)Sideband = 19
MC expectation = 18.7±3.3
BELLE-CONF-0627
Result from a blind analysis.
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BK(*)νν are particularly interesting and challenging modes (Bτν is even a small background)
The experimental signature is BK + Nothing
The “nothing” can also be light dark matter
(mass of order (1 GeV))
DAMA NaI 3σ Region
Direct dark-matter searches cannot see M<10 GeV region
C. Bird et al PRL 93 201803
.(T. Adams et al. PRL 87 041801;A. Dedes et al., PRD 65 015001)
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Expectation value within the SM is
Recent BELLE result is
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2011-03-10
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2011-03-10
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2011-03-10
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2011-03-10
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2011-03-10
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We assume a singlet scalar particle, GeV,in addition to ALL SM, only interact with Higgs
2Sm ≤
*
52( ) (1 )tb tseff s
H
V VH b sSS C s bSSm
λ γ→ = +
Then, the effective Hamiltonian for b s SS becomes
4 invisiBLe Higgs (at LHC,…)
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After summing all 9 Feynman diagrams, we obtain
And after QCD running effects,
And for form factors, we use
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with
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5 ConCLusionsAssuming renormalizability, we minimally extend the SM with
Then, the effective Hamiltonian for b s SS becomes
*
52( ) (1 )tb tseff s
H
V VH b sSS C s bSSm
λ γ→ = +
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