Top quark pair production in the exclusive processes at the LHC

Abstract

We analyze the LHC prospects for measurements of the tt pair produced exclusively in photon-photon or semiexclusively in photon-Pomeron and Pomeron-Pomeron processes using protons tagged in forward proton detectors on both sides of the interaction point. These processes are interesting from the point of view of a possible measurement of the top quark mass and constraining models used in beyond the Standard Model physics. Focusing on the semileptonic channel, tt → jjblν lb , making use of the exclusive nature of the final state, together with the use of timing information provided by forward proton detectors, relevant exclusive and inclusive backgrounds are studied in detail for different luminosity (or pileup) scenarios and found to be important for further consideration. While good prospects are found for observing the signal, the top quark mass measurement turns out not to be competitive with measurements in inclusive channels.

ATLAS Forward Proton Detectors – Special 2017 Low Pile-up Runs

“…The predictions of forward proton scattering arise in a diverse range of physics, including the hard [1,2] and nonperturbative QCD [3], interactions at electroweak scale [4][5][6][7], and searches for physics beyond Standard Model [8][9][10][11][12][13]. Such events, usually called diffractive, involve an exchange of a colourless object between interacting protons, one or both of which may remain intact.…”

Challenging exclusive top quark pair production at low and high luminosity LHC

“…An alternative, recently proposed in Ref. [1] (see also Ref. [10]), is the study of top quark production in pp collisions characterized by intact protons in the final state.…”

“…In our previous article [1], we have performed the first comprehensive study of the elastic top quark for all luminosity scenarios considered, although a good separation between the two is observed for rather low amounts of pile-up, typically lower than 50. In particular in Ref.…”

“…Rev. D102, 074014 (2020) [1] which has demonstrated that the sum of two semi-exclusive t t production modes, namely in photon-Pomeron (γP) and Pomeron-Pomeron (PP) interactions, can be experimentally measured when the t t system decays semi-leptonically, t t → jjblν l b, both forward protons are tagged and a low amount of pile-up is present. In this study we focus on separating individual channels and a special attention is paid to the situation at high-luminosity LHC environment.…”

Central exclusive production of W boson pairs in pp collisions at the LHC in hadronic and semi-leptonic final states

“…Previous phenomenology studies based on the use of the proton tagging technique to study two-photon fusion interactions can be found in refs. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Other interesting studies that aim also to describe photon fluxes in processes with proton dissociation, treated in the k T factorization framework, are presented in refs.…”