Abstract
We study the exotic decay of the 125 GeV Higgs boson (h) into a pair of light spin-0 particles (phi ) which subsequently decay and result in a 4b final state. This channel is well motivated in models with an extended Higgs sector. Instead of searching at the Large Hadron Collider (LHC) and the high luminosity LHC (HL-LHC) which are beset by large standard model (SM) backgrounds, we investigate this decay channel at the much cleaner Large Hadron Electron Collider (LHeC). With some simple selection cuts this channel becomes nearly free of background at this ep machine, in sharp contrast to the situation at the (HL-)LHC. With a parton level analysis we show that for the phi mass range [20,60]~{text{ GeV }}, with 100~{text{ fb }^{-1}} luminosity the LHeC is generally capable of constraining C_{4b}^2equiv kappa _{V}^2times {mathrm {Br}}(hrightarrow phi phi )times {mathrm {Br}}^2(phi rightarrow bbar{b}) (kappa _{V} denotes the hVV(V=W,Z) coupling strength relative to the SM value) to a few percent level (95% CLs). With 1~{text{ ab }^{-1}} luminosity C_{4b}^2 at a few per mille level can be probed. These sensitivities are much better than the HL-LHC performance and demonstrate the important role expected to be played by the LHeC in probing exotic Higgs decay processes, in addition to the already proposed invisible Higgs decay channel.
Highlights
Because the total charged current (CC) backgrounds are at 10−3 fb to a few times 10−4 fb level depending on mφ, the PHP backgrounds would become negligible if the E/ T > E0 cut and perhaps missing energy isolation cuts could bring down the PHP cross section by another two or three orders of magnitude, which could be achieved for E0 ∼ 40 − 60 GeV by our current rough estimation, given the situation that the
In this paper we studied the Large Hadron Electron Collider (LHeC) sensitivity to the exotic Higgs decay process h → φφ → 4b in which φ denotes a spin-0 particle lighter than half of 125 GeV
Using the Higgs singlet extension of the standard model (SM) as an illustration, we showed that the LHeC direct search of h → φφ → 4b is the most sensitive probe of much of the parameter space of the model in the future, if no lepton colliders are available
Summary
It is worth noticing that with such high collision energy and luminosity, the LHeC becomes a Higgs boson factory [14]. With Higgs boson production cross section of about 200 fb−1, the LHeC will provide amazing opportunities for precision Higgs physics, due to the fact that major QCD backgrounds will be much smaller than LHC and the complication due to pile-up will be greatly reduced. Previous studies on Higgs physics at the LHeC include measuring bottom Yukawa coupling [13,15,16], anomalous gauge–Higgs coupling [17,18,19], invisible Higgs decay [20] and MSSM Higgs production [21]. To quantitatively estimate the sensitivity of the LHeC to the exotic Higgs decay h → φφ → 4b, we perform a parton level study for the signal and background . In the last section we present our discussion and conclusion
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