Studying the MSSM Higgs sector by forward proton tagging at the LHC

TL;DR

This study evaluates how central exclusive diffractive Higgs production with forward proton tagging at the LHC can probe the MSSM Higgs sector. By modeling $pp\to p\oplus h/H\oplus p$ and decays to $b\bar b$, $\tau^+\tau^-$, and $WW^{(*)}$ under MSSM benchmark scenarios, the authors quantify discovery potentials across the $M_A$–$\tan\beta$ plane for both light and heavy CP-even Higgs bosons, incorporating higher-order corrections, detector acceptances, and background estimates. They show that, especially at high integrated luminosity and with pile-up control, the CED channel can access the bottom Yukawa coupling and CP properties, and can cover most of the MSSM parameter space in favorable scenarios, including the wedge region for heavy Higgs bosons. The work also discusses the more challenging prospects for CP-odd $A$ production in diffractive channels and outlines experimental considerations, including FP420/220 m detectors, trigger strategies, and mass-resolution optimization, necessary to realize these physics goals.

Abstract

We show that the use of forward proton detectors at the LHC installed at 220 m and 420 m distance around ATLAS and / or CMS can provide important information on the Higgs sector of the MSSM. We analyse central exclusive production of the neutral CP-even Higgs bosons h and H and their decays into bottom quarks, tau leptons and W bosons in different MSSM benchmark scenarios. Using plausible estimates for the achievable experimental efficiencies and the relevant background processes, we find that the prospective sensitivity of the diffractive Higgs production will allow to probe interesting regions of the M_A--tan_beta parameter plane of the MSSM. Central exclusive production of the CP-even Higgs bosons of the MSSM may provide a unique opportunity to access the bottom Yukawa couplings of the Higgs bosons up to masses of M_H \lsim 250 GeV. We also discuss the prospects for identifying the CP-odd Higgs boson, A, in diffractive processes at the LHC.

Figures (14)

• Figure 1: Schematic diagram for central exclusive diffractive (CED) Higgs production at the LHC, $pp \to p \oplus H \oplus p$.
• Figure 2: Contours for the ratio of signal events in the MSSM to those in the SM in the $h \to b \bar{b}$ channel in CED production in the $M_A$--$\tan \beta$ plane. The ratio is shown in the $M_h^{\rm max}$ benchmark scenario (with $\mu = +200 \,\, \mathrm{GeV}$, upper plot) and in the no-mixing scenario (with $\mu = +200 \,\, \mathrm{GeV}$, lower plot). The values of the mass of the light ${\cal CP}$-even Higgs boson, $M_h$, are indicated by dashed contour lines. The dark shaded (blue) region corresponds to the parameter region that is excluded by the LEP Higgs searches in the channel $e^+e^- \to Z^* \to Z h, H$LEPHiggsSMLEPHiggsMSSM.
• Figure 3: $5 \sigma$ discovery contours (upper plot) and contours of $3 \sigma$ statistical significance (lower plot) for the $h \to b \bar{b}$ channel in CED production in the $M_A$--$\tan \beta$ plane of the MSSM within the $M_h^{\rm max}$ benchmark scenario. The results are shown for assumed effective luminosities (see text, combining ATLAS and CMS) of 60 $\hbox{fb}^{-1}$, 60 $\hbox{fb}^{-1}$ eff$\times2$, 600 $\hbox{fb}^{-1}$ and 600 $\hbox{fb}^{-1}$ eff$\times2$. The values of the mass of the light ${\cal CP}$-even Higgs boson, $M_h$, are indicated by contour lines. The dark shaded (blue) region corresponds to the parameter region that is excluded by the LEP Higgs searches in the channel $e^+e^- \to Z^* \to Z h, H$LEPHiggsSMLEPHiggsMSSM.
• Figure 4: $5 \sigma$ discovery contours (upper plot) and contours of $3 \sigma$ statistical significance (lower plot) for the $h \to b \bar{b}$ channel in CED production in the $M_A$--$\tan \beta$ plane of the MSSM within the no-mixing benchmark scenario. The results are shown for assumed effective luminosities (see text, combining ATLAS and CMS) of 60 $\hbox{fb}^{-1}$, 60 $\hbox{fb}^{-1}$ eff$\times2$, 600 $\hbox{fb}^{-1}$ and 600 $\hbox{fb}^{-1}$ eff$\times2$. The values of the mass of the light ${\cal CP}$-even Higgs boson, $M_h$, are indicated by contour lines. The dark shaded (blue) region corresponds to the parameter region that is excluded by the LEP Higgs searches in the channel $e^+e^- \to Z^* \to Z h, H$LEPHiggsSMLEPHiggsMSSM.
• Figure 5: $5 \sigma$ discovery contours (upper plot) and contours of $3 \sigma$ statistical significance (lower plot) for the $h \to \tau^+\tau^-$ channel in CED production in the $M_A$--$\tan \beta$ plane of the MSSM within the $M_h^{\rm max}$ benchmark scenario. The results are shown for assumed effective luminosities (see text, combining ATLAS and CMS) of 60 $\hbox{fb}^{-1}$, 60 $\hbox{fb}^{-1}$ eff$\times2$, 600 $\hbox{fb}^{-1}$ and 600 $\hbox{fb}^{-1}$ eff$\times2$. The values of the mass of the light ${\cal CP}$-even Higgs boson, $M_h$, are indicated by contour lines. The dark shaded (blue) region corresponds to the parameter region that is excluded by the LEP Higgs searches in the channel $e^+e^- \to Z^* \to Z h, H$LEPHiggsSMLEPHiggsMSSM.