Contact PersonsStefania Gori, Jessie Shelton, and Tao Liu More details on this mode may be found in Section 15 of Survey of Exotic Higgs Decays (arXiv:1312.4992).
Theoretical Motivationh→ 2l+ MET exotic decays can arise in many classes of theories where an initial decay h→ X1 X2 is followed by the decay X2→ ll + MET while X1 (which may or may not be the same species as X2) is either invisible (for example, if X1 is stable or if X1 → neutrinos ) or its decay products are too soft to pass the kinematic cuts (for example, X1 → 2j + MET where the jets are soft). A list of theoretical models satisfying these decay topologies is briefly discussed in h → 4 ℓ (isolated) + MET. The role of X1/X2 is played by the neutralinos in the N(MSSM), hidden sector mesons in the hidden sector models or heavy neutrinos in models with extra singlet fermions.
Existing Experimental ConstraintsA detailed collider study for the decay channel h→χ2χ1→ 2lχ1χ1 (where χ1 is stable and appears as MET) using existing LHC searches for SM Higgs in the decay channel h → W W* → 2 l + MET can be found in Section 15.2 of arXiv:1312.4992, however the main results are summarized as follows. The benchmark considered is similar to the "optimistic" scenario described in Section 4 l+ MET, where mχ1=20 GeV and mχ2 = 55 GeV. The limits on the benchmark model are obtained by recasting the h → W W* searches by ATLAS  and CMS . In particular, the CMS search employs a multivariate discriminant in states with same-flavor leptons. Approximating the efficiency of this multivariate discriminant at the SM Higgs-like value, and combining the effect of this multivariate cut with the rest of the analysis selection, one can estimate the limit Br(h→ 2l+MET) <~0.1 for the reference benchmark point.
Related Decay ModesExotic Higgs decays of the kind h → X1 X2 can lead to a plethora of experimental signatures depending on the decay of X2 and/or X1 : h → 4 ℓ (isolated) + MET , h → 1 lepton-jet + X, h → 2 lepton-jets + X and h → 4 ℓ.
Additional RemarksAs also noticed in , existing SM Higgs searches start to constrain BSM leptons + invisible Higgs decays, though the tailoring of SM Higgs searches to SM decay kinematics reduces their reach. The bounds presented in this section are only approximate due to the lack of information about the multivariate discriminants employed in the searches, this is an obvious avenue for improvement. Further, better sensitivity could be obtained by considering different-flavor and same-flavor final states separately.
Here we list new experimental results pertinent to this exotic higgs decay channel.
- CMS collaboration, Measurement of Higgs boson production and properties in the WW decay channel with leptonic final states, JHEP 1401 (2014) 096 (CMS-HIG-13-023, arXiv:1312.1129).
- ATLAS Collaboration, Measurements of the properties of the Higgs-like boson in the W W* → l ν l ν decay channel with the ATLAS detector using 25 fb-1 of proton-proton collision data, 2013. ATLAS Public Note ATLAS-CONF-2013-030.
- Evidence for a particle decaying to w+w- in the fully leptonic final state in a standard model higgs boson search in pp collisions at the lhc, Tech. Rep. CMS-PAS-HIG-13-003, CERN, Geneva, 2013.
- S. Chang and T. Gregoire, Discovering a Nonstandard Higgs in a Standard Way, [arXiv:0903.0403].
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