Precision inclusive Higgs physics at e+e− colliders with tracking detectors and without calorimetry

Abstract

A primary goal of a future e+e− collider program will be the precision measurement of Higgs boson properties. For practical reasons it is of interest to determine the minimal set of detector specifications required to reach this and other scientific goals. Here we investigate the precision obtainable for the e+e−Zhμ+μ−X inclusive cross section and the Higgs boson mass using the di-muon recoil method, considering a detector that has only an inner tracking system within a solenoidal magnetic field, surrounded by many nuclear interaction lengths of absorbing material, and an outer muon identification system. We find that the sensitivity achievable in these measurements with such a tracking detector is only marginally reduced compared to that expected for a general purpose detector with additional electromagnetic and hadronic calorimeter systems. The difference results mainly from multi-photon backgrounds that are not as easily rejected with tracking detectors. We also comment on the prospects for an analogous measurement of the e+e−→Zh→e+e−X inclusive cross section. Finally, we study searches for light scalars utilizing the di-muon recoil method, estimating the projected reach with a tracking or general purpose detector.

Testing the seesaw mechanisms via displaced right-handed neutrinos from a light scalar at the HL-LHC

“…Although the production cross section σ(pp → s) drops for heavier s, it is compensated by the growing branching ratio, results in almost constant σ(pp → s → N N ) ≈ 70 fb for m s 20 GeV. The proposed Higgs factories such as the ILC, CEPC and FCC-ee will have potential to determine the Higgs couplings about one magnitude more precisely [58], leading to stringent limits on the Higgs mixings sin α 0.01 [59]. Nevertheless, potential observation is still available even for sin α ∼ 10 −3 .…”

Shedding light on the electroweak phase transition from exotic Higgs boson decays at the lifetime frontiers

“…Therefore, from the figure, in most of the parameter space, we have θ O(10 −1 ), especially for M h 1 < M h 1 /2 ≈ 62.5 GeV where the exotic decays of the Higgs h 2 → h 1 h 1 can happen. The HL-LHC with much larger integrated luminosity, and the proposed Higgs factories, can further constrain the mixings down to O(10 −2 ) [79].…”

Exotic Higgs Decays and the Electroweak Phase Transition

“…Currently, | cos θ| 0.07 is allowed for all masses between 10 GeV ≤ m 1 ≤ 120 GeV [30], with larger mixing angles allowed at large masses. Although the precise limits vary by mass, ongoing precision Higgs analyses at the LHC and, potentially, at future colliders will continue to probe smaller and smaller values of | cos θ|, likely down to the O(0.01) level [31]. We will focus here on the experimentally challenging regime with | cos θ| 0.01, where we will see that exotic Higgs decays provide a powerful and complementary probe.…”