[Paper Review] Central exclusive diffractive Higgs boson production in hadron-nucleus and nucleus-nucleus collisions at the LHC

E. Levin, J. Miller|ArXiv.org|Jan 23, 2008

High-Energy Particle Collisions Research10 references4 citations

TL;DR

This paper demonstrates that central exclusive diffractive Higgs boson production in hadron-nucleus and nucleus-nucleus collisions at the LHC is dominated by photon-photon fusion rather than gluon-gluon fusion due to significantly higher survival probabilities. The cross section reaches 0.64 pb in proton-gold and 3.9 nb in gold-gold collisions, making photon fusion a viable and theoretically calculable pathway for Higgs boson detection with minimal background.

ABSTRACT

In this paper, it is shown that in hadron-nucleus and nucleus-nucleus collisions, the main source for central exclusive diffractive Higgs production is photon-photon fusion. At the LHC energy, the total cross section for this process is about 0.6 pb (for proton-gold scattering), and 3.9 nb (for gold-gold collision) while the gluon-gluon fusion leads to the value of the cross section for CED Higgs production which is about 0.1 nb and 3.9 pb respectively.

Motivation & Objective

• To evaluate the feasibility of central exclusive diffractive Higgs boson production in hadron-nucleus and nucleus-nucleus collisions at LHC energies.
• To compare the cross sections for Higgs production via gluon-gluon fusion versus photon-photon fusion in nuclear collisions.
• To quantify the role of survival probability in suppressing background processes and enhancing signal visibility.
• To assess the theoretical robustness of photon-photon fusion as a dominant mechanism due to calculable survival probabilities.
• To establish that nuclear collisions offer a superior environment for detecting the Higgs boson via exclusive diffractive processes compared to proton-proton collisions.

Proposed method

• Employing the Glauber multiple scattering approach to calculate the survival probability for central exclusive diffractive processes in nuclear collisions.
• Using the impact parameter-dependent opacity model with nuclear density profiles (Wood-Saxon parametrization) to compute the exponential damping factor exp(−Ω(b)) for proton-nucleus and nucleus-nucleus systems.
• Calculating the hard amplitude A_H(b) for both γγ → Higgs and gg → Higgs processes, showing that γγ fusion has a flatter b-dependence than gg fusion.
• Applying the survival probability formula ⟨|S²|⟩ = ∫ d²b A_H(b) exp(−Ω(b)) / ∫ d²b A_H(b) to compute the effective cross section suppression.
• Using the total proton-proton cross section (110 mb) and nuclear thickness functions to compute Ω(s,b) = σ_tot × T_A(b) for gold nuclei.
• Scaling the pp cross sections by A² for gluon fusion and Q_A² × ⟨|S²|⟩ for photon fusion, where Q_A is the number of protons in the nucleus.

Experimental results

Research questions

• RQ1 Why is central exclusive Higgs production in proton-nucleus and nucleus-nucleus collisions dominated by photon-photon fusion rather than gluon-gluon fusion?
• RQ2 What is the role of survival probability in suppressing non-exclusive processes and enhancing the signal for Higgs production in nuclear collisions?
• RQ3 How do the different b-dependences of the hard amplitudes for γγ and gg fusion affect the survival probability in nuclear environments?
• RQ4 Can the cross section for central exclusive Higgs production in nuclear collisions reach experimentally measurable levels?
• RQ5 To what extent can theoretical uncertainties be reduced in Higgs production via photon fusion in nuclear collisions compared to proton-proton collisions?

Key findings

• The survival probability for γγ → Higgs fusion in proton-gold collisions is approximately 0.8, while for gg → Higgs fusion it is negligible (~10⁻⁶), due to the flatter b-dependence of the γγ hard amplitude.
• The cross section for central exclusive Higgs production via γγ fusion in proton-gold collisions at the LHC is estimated at 0.64 pb, significantly higher than the 0.1 nb from gluon-gluon fusion.
• In gold-gold collisions, the γγ fusion cross section reaches 3.9 nb, while the gg fusion cross section is only 3.9 pb, due to the extreme suppression of survival probability in the latter.
• The enhancement factor for γγ fusion in gold-gold collisions is ~3.9×10⁷ due to Q_A⁴ scaling, making it the dominant mechanism.
• The theoretical cross section for γγ fusion is calculable without model dependence, making it a robust and promising channel for Higgs boson detection at the LHC.
• Nuclear collisions provide a favorable environment for detecting the Higgs boson via central exclusive diffractive processes due to high survival probabilities and measurable cross sections.