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Charm associated production of the pseudoscalar Higgs boson $h''$ in the MCPM' at the LHC

Rafał Maciuła, Markos Maniatis, Otto Nachtmann, Antoni Szczurek

TL;DR

This work investigates the MCPM' scenario with a pseudoscalar $h''$ of mass $m_{h''}=95.4$ GeV, motivated by CMS CMS:2023yay observations in the $\gamma\gamma$ channel. The authors compute charm-associated production processes $pp\to h''\,c\bar c$ and the dominant $h''\to c\bar c$ decay, along with backgrounds from SPS and DPS, and study $pp\to c\bar c c\bar c+X$, including $h''gg$-induced contributions. They show sizeable resonance-like enhancements in the $c\bar c$ invariant-mass spectra near $m_{h''}$, and demonstrate that optimized kinematic cuts—especially selecting leading charm jets with specific $p_T$, $\Delta R$, and $\Delta\eta$—substantially improve the signal-to-background ratio. The results suggest that charm-tagged final states at the LHC (and potentially ALICE-3) could test or constrain the MCPM' explanation for the CMS excess and probe the model’s distinctive Yukawa structure, particularly its strong coupling of $h''$ to charm quarks. Overall, the paper provides a concrete phenomenological path to explore MCPM'-predicted resonances in multi-charm final states at current and future collider experiments.

Abstract

We discuss charm associated production of the pseudoscalar Higgs boson $h''$ in the MCPM'. In our analysis we assume $m_{h''}$ = 95.4 GeV, which corresponds to an enhancement observed by the CMS collaboration in the $γγ$ channel. As discussed recently, the MCPM' is consistent with the CMS enhancement. In this model the $h''$ Higgs boson of this mass decays dominantly into $c \bar c$ jets. The cross section for the associated $h''$ production in $p p \to h'' c \bar c$ is found to be almost as big as that for the Drell-Yan (DY) $c \bar c \to h''$ production, much larger than that for two-gluon fusion $g g \to h''$. Since in the MCPM' the dominant $h''$ decay is into the $c \bar c$ channel we have to deal with the $p p \to c \bar c c \bar c$ process with $c$ and $\bar c$ jets. In addition to the signal processes, we have sizeable single parton scattering (SPS) and double parton scattering (DPS) nonresonant background. In our analysis we include diagrams of gluon-gluon fusion $g g \to h''$ which lead to the $c \bar c c \bar c$ final state. We discuss also the possible role of the reaction $p p \to h'' h''$. Assuming 100\% c and $\bar c$ jet tagging we discuss in detail how to improve the signal-to-background ratio. Our analysis shows promising resonance-like enhancements and relatively large cross sections in the $c \bar c c \bar c$ channel within the MCPM'. The ALICE-3 project would be ideal in the future to perform the experimental studies corresponding to the theoretical studies discussed here.

Charm associated production of the pseudoscalar Higgs boson $h''$ in the MCPM' at the LHC

TL;DR

This work investigates the MCPM' scenario with a pseudoscalar of mass GeV, motivated by CMS CMS:2023yay observations in the channel. The authors compute charm-associated production processes and the dominant decay, along with backgrounds from SPS and DPS, and study , including -induced contributions. They show sizeable resonance-like enhancements in the invariant-mass spectra near , and demonstrate that optimized kinematic cuts—especially selecting leading charm jets with specific , , and —substantially improve the signal-to-background ratio. The results suggest that charm-tagged final states at the LHC (and potentially ALICE-3) could test or constrain the MCPM' explanation for the CMS excess and probe the model’s distinctive Yukawa structure, particularly its strong coupling of to charm quarks. Overall, the paper provides a concrete phenomenological path to explore MCPM'-predicted resonances in multi-charm final states at current and future collider experiments.

Abstract

We discuss charm associated production of the pseudoscalar Higgs boson in the MCPM'. In our analysis we assume = 95.4 GeV, which corresponds to an enhancement observed by the CMS collaboration in the channel. As discussed recently, the MCPM' is consistent with the CMS enhancement. In this model the Higgs boson of this mass decays dominantly into jets. The cross section for the associated production in is found to be almost as big as that for the Drell-Yan (DY) production, much larger than that for two-gluon fusion . Since in the MCPM' the dominant decay is into the channel we have to deal with the process with and jets. In addition to the signal processes, we have sizeable single parton scattering (SPS) and double parton scattering (DPS) nonresonant background. In our analysis we include diagrams of gluon-gluon fusion which lead to the final state. We discuss also the possible role of the reaction . Assuming 100\% c and jet tagging we discuss in detail how to improve the signal-to-background ratio. Our analysis shows promising resonance-like enhancements and relatively large cross sections in the channel within the MCPM'. The ALICE-3 project would be ideal in the future to perform the experimental studies corresponding to the theoretical studies discussed here.

Paper Structure

This paper contains 12 sections, 59 equations, 22 figures.

Table of Contents

  1. Introduction
  2. Results: generalities and integrated cross sections
  3. Distributions
  4. Cuts
  5. Cross sections for $p + p \to h" + c + \bar{c} + X$ with $h" \to c + \bar{c}$
  6. Cross sections for $p + p \to c + \bar{c}+ c + \bar{c}+X$
  7. Two dimensional correlations
  8. Optimizing cuts
  9. Conclusions
  10. Partial decay width of $h"$ into a gluon pair and the effective $h"$-gluon-gluon interaction
  11. Digression on total cross sections
  12. Double $h"$ production

Figures (22)

  • Figure 1: (a): Example of a diagram for charm-associated production of the $h"$ boson which decays into a $c \bar{c}$ pair. (b): Example of a SM diagram contributing to the background.
  • Figure 2: Examples of diagrams for $p p \to h" c \bar{c} X$ where the boson $h"$ couples to gluons via a fermionic loop. This is described by the effective $h"GG$ coupling derived in Appendix \ref{['appA']}.
  • Figure 3: Example of diagram for $p p \to h" c \bar{c} X$ where the $c\bar{c}$ pair comes from the fragmentation of one proton remnant.
  • Figure 4: Distribution of the transverse momentum of $c$ quark (or $\bar{c}$ antiquark) in the reaction \ref{['eq:h2cc']}. (a): The contributions from charm quarks originating from the decay of the $h"$ boson (long dashed) and those associated with the accompanying charm quarks (dashed). (b): The distributions without distinguishing the origin of the charm quarks. The solid histogram corresponds to the case where the $c$ quarks and $\bar{c}$ antiquarks are not sorted by their transverse momentum, while the long dashed histogram represents the distribution of the leading $p_{T}$ charm quark (or anti-charm quark).
  • Figure 5: $\Delta R$ distribution of the $c\bar{c}$ pair in the reaction \ref{['eq:h2cc']}. (a): The contributions corresponding to $c\bar{c}$ pairs formed by quarks and antiquarks originating from the decay of the $h"$ (long dashed), by associated charm quarks (dashed), or by combinations where one quark comes from the decay and the other is an associated quark (long dash-dotted). (b): The distributions without distinguishing the origin of the charm quarks. The solid histogram corresponds to the case where the $c\bar{c}$ pair is formed by quarks and antiquarks not sorted by their transverse momentum, while the long dashed histogram represents the distribution of the leading $c\bar{c}$ pair.
  • ...and 17 more figures