Study of Higgs boson production and its b-bbar decay in gamma-gamma processes in proton-nucleus collisions at the LHC

Abstract

We explore for the first time the possibilities to measure an intermediate-mass (m H = 115 -140 GeV/c 2 ) Standard-Model Higgs boson in electromagnetic proton-lead (p Pb) interactions at the CERN Large Hadron Collider (LHC) via its b b decay. Using equivalent Weizsäcker-Williams photon fluxes and Higgs effective field theory for the coupling γ γ → H, we obtain a leading-order cross section of the order of 0.3 pb for exclusive Higgs production in elastic (p Pb γ γ − − → p H Pb) and semielastic (p Pb γ γ − − → X H Pb) processes at √ s NN = 8.8TeV. After applying various kinematics cuts to remove the main backgrounds (γ γ → b b and misidentified γ γ → q q events), we find that a Higgs boson with m H = 120 GeV/c 2 could be observed in the b b channel with a 3σ-significance integrating 300 pb −1 with an upgraded p A luminosity of 10 31 cm −2 s −1 . We also provide for the first time semielastic Higgs cross sections, along with elastic tt cross sections, for electromagnetic pp, p A and AA collisions at the LHC .

Proton–nucleus collisions at the LHC: scientific opportunities and requirements

“…These W + W − pairs, characterised by small pair p T , are sensitive to the quartic gauge boson couplings. Lastly, even Higgs boson production would be measurable if the p+A luminosity were increased by a factor of 60 [100].…”

Constraints for the nuclear parton distributions from Z and W production at the LHC

“…2 ahead) to around 4000 events in the mid-rapidity y R = 0 unit bin and still around 1000 events at |y R | = 3 unit bin. Moreover, knowing that larger luminosities could be possible [22], the heavy boson study in proton-nucleus collisions at the LHC looks feasible. For PbPb-collisions the corresponding numbers are similar as the smaller luminosity is compensated by a additional factor of 208.…”

Observing light-by-light scattering at the Large Hadron Collider

“…A final LbyL/CEP ratio of order one is reachable applying the aforementioned p γ γ T and ∆φ γ γ cuts. Yet, given the low p-Pb event rates expected (Table I) a potential observation of LbyL scattering would require an increment of the integrated luminosity (which can be achieved increasing the p-beam intensity from its conservative default value [47]) and a careful control of the CEP background.…”

“…Additional (e.g. acollinearity) cuts [47] could be applied to remove any remaining QED di-fermion continuum (notably γ γ → q q → π 0 π 0 ) with very small signal loss. Figure 2 (right) shows the dominant QED and CEP backgrounds, expected after cuts in one Pb-Pb run, compared to the LbyL signal as a function of the diphoton mass.…”