Central exclusive diffractive production as a spin--parity analyser: from hadrons to Higgs

TL;DR

This work establishes a Regge-theory framework for central exclusive diffractive production as a spin-parity analyser, deriving how the double-Reggeon amplitude, helicity structure, and small-$t$ behavior depend on the central state’s $J^P$. It shows that absorptive (gap-survival) corrections strongly affect cross sections and angular correlations in a state-dependent way, with $0^+$ and $0^−$ Higgs production exhibiting distinct patterns. Applying the framework to Higgs physics, the authors compare Standard Model-like $0^+$ production with MSSM $0^-$ (and nearby $0^+$) states, highlighting sizable MSSM enhancements and the potential to distinguish Higgs states via the azimuthal correlations of forward protons and high-precision missing-mass measurements. The results advocate proton-tagging at the LHC as a powerful tool to resolve Higgs-sector questions, including separating $h$, $H$, and $A$ and probing widths, particularly in scenarios with large $\tan\beta$ where inclusive channels may be challenging.

Abstract

We present the general rules for double-Reggeon production of objects with different spins and parities. The existing experimental information on resonance production in these central exclusive diffractive processes is discussed. The absorptive corrections are calculated and found to depend strongly on the quantum numbers of the produced states. The central exclusive diffractive production of 0^+ and 0^- Higgs bosons is studied as an illustrative topical example of the use of the general rules. The signal for diffractive 0^+ and 0^- Higgs production at the LHC is evaluated using, as an example, the minimal supersymmetric model, with large tan(beta).

Figures (7)

• Figure 1: (a) The central production of a state $h$ by double-Reggeon exchange. (b) The double-Pomeron exchange contribution to $pp\to p + h + p$, which dominates at high energies, where the $+$ signs are used to indicate the presence of Pomeron-induced rapidity gaps.
• Figure 2: Unitarity or rescattering corrections to the exclusive diffractive process $pp\to p + h + p$.
• Figure 3: (a) The QCD diagram for double-diffractive exclusive production of a Higgs boson $h$, $pp\to p + h + p$, where the gluons of the hard subprocess $gg\to h$ are colour screened by the second $t$-channel gluon. (b) The rescattering or absorptive corrections to $pp\to p + h + p$, where the shaded region represents the multi-Pomeron exchanges of Fig. \ref{['fig:2']}.
• Figure 4: The $\phi$ dependences of diffractive exclusive $h(0^+)$ and $A(0^-)\equiv h(0^-)$ production, $pp\to p + h + p$, at the LHC, with $m_h = 120~\rm GeV$. $\phi$ is the angle in the transverse plane between the outgoing protons. The curves are for central rapidity and do not include absorptive corrections. They correspond to the effective luminosities for the $gg\to h(0^\pm)$ subprocesses integrated over the outgoing proton momenta $\vec{p}_{i\perp}$, assuming an $\exp(-b p_{i\perp}^2)$ behaviour of the unintegrated gluon densities $f_g$, with slope $b = 2~\rm GeV^{-2}$.
• Figure 5: The suppression factors $S^2$ of $h(0^+)$ and $A(0^-)\equiv h(0^-)$ Higgs production via the process $pp\to p + h + p$ at the LHC, arising from rescattering effects. The outgoing protons are integrated over (i) all $p_{i\perp}$ and (ii) $p_{i\perp} < 0.35~\rm GeV$ (dotted curves). For illustration, the continuous curve for $h(0^-)\equiv A(0^-)$ production includes the general $\sin\phi$ behaviour of the bare amplitude.