Prospects for New Physics observations in diffractive processes at the LHC and Tevatron

TL;DR

Khoze, Martin, and Ryskin develop a unified framework for predicting double-diffractive processes at the LHC and Tevatron, detailing exclusive and inclusive mechanisms, Pomeron–Pomeron fusion, and γγ/WW fusion. They compute gap-survival effects and gluon-luminosity factors to predict hard-subprocess cross sections for Higgs, dijets, tt̄, and SUSY signatures, providing concrete rates (e.g., ~3 fb for exclusive Higgs at the LHC) and background assessments. The work demonstrates the potential of exclusive diffractive Higgs searches, outlines a gluon-rich luminosity monitor via exclusive dijets, and discusses soft-dQCD phenomena and multi-gap diffraction as avenues to probe beyond-Standard-Model physics and the strong interaction. Overall, it offers a practical toolkit for estimating and interpreting diffractive signals and backgrounds in high-energy hadron colliders.

Abstract

We study the double-diffractive production of various heavy systems (e.g. Higgs, dijet, t tbar and SUSY particles) at LHC and Tevatron collider energies. In each case we compute the probability that the rapidity gaps, which occur on either side of the produced system, survive the effects of soft rescattering and QCD bremsstrahlung effects. We calculate both the luminosity for different production mechanisms, and a wide variety of subprocess cross sections. The results allow numerical predictions to be readily made for the cross sections of all these processes at the LHC and the Tevatron collider. For example, we predict that the cross section for the exclusive double-diffractive production of a 120 GeV Higgs boson at the LHC is about 3 fb, and that the QCD background in the b bbar decay mode is about 4 times smaller than the Higgs signal if the experimental missing-mass resolution is 1 GeV. For completeness we also discuss production via gamma gamma or WW fusion.

Figures (7)

• Figure 1: Different mechanisms for the double-diffractive production of a system of mass $M$ in high energy proton-proton collisions.
• Figure 2: The luminosity $M^2 \partial {\cal L}/\partial y \partial M^2$ versus $M$, for the double-diffractive production of a heavy system of mass $M$ with rapidity $y = 0$. The three plots are for $pp$ (or $p\bar{p}$) collider energies of $\sqrt{s} = 2, 8$ and 14 TeV. Various production mechanisms are studied: the curves marked excl., incl., C-inel and soft${I\!\!P}{I\!\!P}$ correspond, respectively, to production by the exclusive process $pp \rightarrow p + M + p$ of Section 2.1, to production by the inclusive process $pp \rightarrow X + M + Y$ of Section 2.2, and to production by the processes shown in Figs. 6(a) and 6(b) as described in Section 2.3. The $\gamma\gamma$ luminosity is obtained as described in Section 2.4.
• Figure 3: The luminosity $M^2 \partial {\cal L}/\partial y \partial M^2$ versus $y$ for the double-diffractive production by various mechanisms of a heavy system of mass $M = 120$ GeV at $\sqrt{s} = 2, 8$ and 14 TeV. The notation for the curves is as in Figs. 2 and 6. The upper curve in each plot shows the inelastic luminosity $(\Delta \eta = 0)$ assuming that the fusing $gg$ pair are in a colour singlet state.
• Figure 4: As for Figure 3, but for the production of a system of mass $M = 500$ GeV at $pp$ collider energies of $\sqrt{s} = 8$ and 14 TeV.
• Figure 5: The amplitude of Fig. 1(b) multiplied by its complex conjugate, which gives the cross section for the inclusive double-diffractive production of a system $M$. The effective parton densities, $G (x_i)$ of (\ref{['eq:a10']}), are to be evaluated at scales $k_{it}^2$.