Diphoton Background to Higgs Boson Production at the LHC with Soft Gluon Effects

TL;DR

The paper tackles the challenge of accurately predicting the diphoton background to Higgs production in proton-proton collisions at the LHC. It extends soft-gluon resummation (CSS) to diphoton production, incorporating the exact one-loop gg → γγ g amplitude and matching to fixed-order results within the ResBos framework. The authors quantify resummation effects on both the diphoton invariant mass and transverse momentum distributions, showing significant enhancements over fixed-order predictions in the low-to-mid Q_T region and providing guidance for Higgs searches using inclusive γγ with a Q_T cut. Their findings support a jet-free diphoton Higgs search strategy with improved theoretical reliability and reduced scale dependence. Overall, the work enhances background modeling for H → γγ analyses at the LHC and clarifies the role of gg-initiated contributions across kinematic regimes.

Abstract

The detection and the measurement of the production cross section of a light Higgs boson at the CERN Large Hadron Collider demand the accurate prediction of the background distributions of photon pairs. To improve this theoretical prediction, we present the soft-gluon resummed calculation of the $p p \to γγX$ cross section, including the exact one loop $g g \to γγg$ contribution. By incorporating the known fixed order results and the leading terms in the higher order corrections, the resummed cross section provides a reliable prediction for the inclusive diphoton invariant mass and transverse momentum distributions. Given our results, we propose the search for the Higgs boson in the inclusive diphoton mode with a cut on the transverse momentum of the photon pair, without the requirement of an additional tagged jet.

Figures (4)

• Figure 1: The resummed part of invariant mass and transverse momentum distributions of photon pairs at the LHC, calculated for the $q{\bar{q}} + q g \to \gamma \gamma X$ subprocess using ResBos. The solid curves are calculated using the exact Wilson coefficient $C^{(1)}$. For the dashed curves, $C^{(1)}$ is set identical to that of the Drell-Yan process. For the dotted curves, $C^{(1)}$ is set to zero.
• Figure 2: Invariant mass distributions of photon pairs at the LHC, calculated using ResBos. The total curve (upper solid) is the sum of the ${\cal O}(\alpha_S)$$q{\bar{q}} + q g \to \gamma \gamma X$ (dashed) and the ${\cal O}(\alpha_S^3)$$g g + q g \to \gamma \gamma X$ (dotted) contributions. The leading order curves for the contributions from ${\cal O}(\alpha_S^0)$$q {\bar{q}} \to \gamma \gamma$ (dash-dotted) and ${\cal O}(\alpha_S^2)$$g g \to \gamma \gamma$ (lower solid) are also shown for comparison.
• Figure 3: Transverse momentum distributions of photon pairs at the LHC. The total resummed curve (upper solid) is the sum of the resummed $q{\bar{q}} + q g \to \gamma \gamma X$ (dashed), and the resummed $g g + q g \to \gamma \gamma X$ (dotted) contributions. The fixed-order curves for the contributions from ${\cal O}(\alpha_S)$$q{\bar{q}} + q g \to \gamma \gamma X$ (dash-dotted) and ${\cal O}(\alpha_S^3)$$g g + q g \to \gamma \gamma X$ (middle solid) are also shown for comparison. The approximation for the latter used in BalazsBergerMrennaYuan is also shown (lower solid).
• Figure 4: Invariant mass distributions of photon pairs at the LHC, with the cut $Q_T>30$ GeV. The total resummed curve (upper solid) is the sum of the resummed $q{\bar{q}} + q g \to \gamma \gamma X$ (dashed), and the resummed $g g + q g \to \gamma \gamma X$ (dotted) contributions. The fixed-order curves for the contributions from ${\cal O}(\alpha_S)$$q{\bar{q}} + q g \to \gamma \gamma X$ (dash-dotted) and ${\cal O}(\alpha_S^3)$$g g + q g \to \gamma \gamma X$ (lower solid) are also shown for comparison.