PHYSICAL REVIEW D 98, 035043 (2018)
Probing a light sterile neutrino through heavy charged Higgs boson decays at the LHC
Yi-Lei Tang* School of Physics, KIAS, 85 Hoegiro, Seoul 02455, Republic of Korea
(Received 23 April 2018; published 29 August 2018)
We present a 13 TeV proton-proton collider simulation in a ν-two-Higgs-doublet model. The heavy charged Higgs bosons are produced in pairs through the electroweak processes and decay to the light sterile neutrinos (lighter than the W=Z boson masses). The light sterile neutrino further decays into a jet-like object with a muon in it. This helps us discriminate the signal from the backgrounds composed of the standard model jets.
DOI: 10.1103/PhysRevD.98.035043
I. INTRODUCTION well [40,41]. However, as known, there is a gap in the interesting parameter space where m ≪ m and The seesaw mechanisms [1–5] introduce some right- N H m ≲ m . In this area, each of the largely boosted sterile handed or sterile neutrinos with extremely heavy Majorana N Z=W masses (∼109–1012 GeV) to create the light neutrino neutrinos decays into a single jet-like collimated object, masses (≲0.1 eV according to the oscillation data). and thus the usual method of analyzing separated objects However, this sort of model is far beyond the reach of a loses its effectiveness. (For some works on neutrino jets, m
† † λ5 † 2 † 2 Published by the American Physical Society under the terms of þ λ4ðΦ1Φ2ÞðΦ2Φ1Þþ ½ðΦ1Φ2Þ þðΦ2Φ1Þ ; ð1Þ the Creative Commons Attribution 4.0 International license. 2 Further distribution of this work must maintain attribution to Φ the author(s) and the published article’s title, journal citation, where 1;2 are the two-Higgs doublets with hypercharge 3 ¼ 1 λ 2 and DOI. Funded by SCOAP . Y 2, 1−5 are the coupling constants, and m1;2;12 are the
2470-0010=2018=98(3)=035043(7) 035043-1 Published by the American Physical Society YI-LEI TANG PHYS. REV. D 98, 035043 (2018) mass parameters. The ν-THDM is based on the type-I Therefore, we do not consider the possibility of the THDM in which all the SM particles QL, uR, dR, LL, and secondary vertex cases. eR couple with the Φ2 field, III. SIMULATION DETAILS AND RESULTS SM ¯ ˜ ¯ L ¼ −Y Q Φ2u − Y Q Φ2d Yukawa uij Li Rj dij Li Rj In this paper, we concentrate on the decay pp → Z = − ¯ Φ þ ð Þ þ − ∓ YlijLLi 2lRj H:c: 2 γ → H H , with the H → μ N, N → μ W → μ qq¯ decay chains as shown in Fig. 1. We have chosen the The sterile neutrino together with the left-handed lepton Φ hadronic decay channel of the sterile neutrino because it doublets couple with the 1 field. In this paper, without has the largest branching ratio and it is more convenient loss of generality, we consider only one sterile neutrino N. for reconstructing the H masses. The muon appearing in Therefore, the corresponding Lagrangian is given by the decay products (clustered inside a jet together with the ν ¯ ¯ ˜ other elements) can help us tag the jets decayed from the L ¼ −m NN − ðY L Φ1N þ H:c:Þ; ð3Þ Yukawa N i Li sterile neutrinos. where mN is the mass of the sterile neutrino and Yi, i ¼ 1, The muons appearing in the decay products can also be 2, 3 are the Yukawa coupling constants corresponding to replaced by electrons or taus. Here we have chosen the the e, μ, and τ lepton doublets. muon channels for the collider’s distinctive ability to In the following discussions, we do not need to care identify a muon, especially a muon inside of a jet. about the details of the electroweak symmetry breaking, nor As for the electron cases, we can estimate the correspond- do we need to discuss the neutral Higgs bosons. After the ing SM background from the result in this paper due to the electroweak symmetry breaking, we acquire the coupling lepton universality in the SM. However, one should be aware of the greater difficulties in identifying an electron þ¯ inside a jet than a muon when attempting to apply our result L ⊃−Yi sin βH liPRN þ H:c:; ð4Þ to the other lepton cases. v2 where tan β ¼ is the ratio of the Φ1 2 vacuum expectation The missing energy is predicted to be small in our v1 ; expected signal. The reducible backgrounds with neutrinos values, and H is the charged Higgs with the mass mH . In the large tan β ≫ 1 case, Eq. (4) becomes the most should be eliminated by applying the transverse missing significant coupling for H decay, and therefore H → energy (MET) cuts. However, the pileup effects at the l N will become the dominant decay channel when future high-luminosity colliders might seriously smear the MET distributions in both the signal and background mN