Revisiting the Electroweakino Sector of the Baryon Number Violating MSSM at the HL-LHC with Deep Neural Networks

TL;DR

The study probes HL-LHC prospects for electroweakinos in a baryon-number violating MSSM with RPV couplings $oldsymbol{
}^{112}_{}$ and $oldsymbol{
}^{113}_{}$, focusing on a simplified spectrum with a wino-like NLSP and a bino-like LSP. Direct production $pp o ilde{
}^{} ilde{
}^0$ proceeds via cascades producing $W$, $Z$, or $h$, while the LSP decays to three quarks through the UDD operators, yielding high-multiplicity final states. The authors deploy multiple benchmark-specific Multilayer Perceptrons (MLPs) trained on four-momenta plus a handful of high-level observables to separate signal from dominant SM backgrounds across five channels corresponding to different RPV couplings and Higgs decay modes. Across all channels, HL-LHC projections yield 2σ exclusion reaches up to ~$ ext{900 GeV}$ for certain channels with $m_{ ilde{
}^0} o 50$ GeV, and ~700–850 GeV for others, illustrating how ML-based signal-region classifiers can significantly extend the accessible RPV parameter space for electroweakinos at the HL-LHC.

Abstract

We study the projected sensitivity of direct electroweakino production $pp \to \tildeχ_1^{\pm} \tildeχ_2^0$ at the HL-LHC in a simplified framework with wino-like, mass degenerate $\tildeχ_1^{\pm}$ and $\tildeχ_2^0$, and a bino-like lightest neutralino $\tildeχ_1^0$, assuming R-parity violating~(RPV) through the baryon number violating $λ^{\prime \prime}_{112}u^c d^c d^c$ and $λ^{\prime \prime}_{113}u^c d^c b^c$ operators. We consider three channels with the $λ^{\prime \prime}_{112}u^c d^c d^c$ RPV operator: $Wh$ mediated $1\,\ell + 2\,b + \rm E{\!\!\!/}_T$, $Wh$ mediated $1\,\ell + (\geq 2\,j) + 2\, γ+ \rm E{\!\!\!/}_T$, and $WZ$ mediated $3\ell + (\geq 2 j) + \rm E{\!\!\!/}_T$. In each channel, we train benchmark-specific multi-layer perceptrons (MLPs), analogous to signal-region classifiers, on the four-momenta of the final state particles along with a small set of higher-level observables to distinguish the signal from the dominant SM backgrounds. We find that the HL-LHC will be able to probe winos up to $\sim 900~$GeV, $\sim 780~$GeV, and $\sim 880~$GeV in the $Wh$ mediated $1\,\ell + 2\,b + \rm E{\!\!\!/}_T$, $Wh$ mediated $1\,\ell + (\geq 2\,j) + 2\, γ+ \rm E{\!\!\!/}_T$, and $WZ$ mediated $3\ell + (\geq 2 j) + \rm E{\!\!\!/}_T$ channels, respectively, for $m_{\tildeχ_1^0} \sim 50~$GeV, in the presence of $λ^{\prime \prime}_{112}u^c d^c d^c$ couplings, at $2σ$ sensitivity. In case the $λ^{\prime \prime}_{113}u^c d^c b^c$ operator is solely switched on, the projected sensitivity for winos reach up to $\sim 700~$GeV for $Wh$ mediated $1\,\ell + (\geq 1\,b)\, + (\geq 1j)\, + 2\, γ+ \rm E{\!\!\!/}_T$ and $\sim 850~$GeV for the $WZ$ mediated $3\ell + (\geq 1 b) + \rm E{\!\!\!/}_T$ channel.

Figures (11)

• Figure 1: Representative Feynman diagrams for Process (a) Process $\mathcal{P}_1$, (b) Process $\mathcal{P}_2$, (c) Process $\mathcal{P}_3$, (d) Process $\mathcal{P}_4$, and (e) Process $\mathcal{P}_5$
• Figure 2: Differential distributions for the missing transverse energy ($\rm E{\!\!\!/}_T$), the contransverse mass ($M_{CT}$), $\Delta \phi$ between the lepton and missing transverse energy ($\Delta\phi_{\ell\rm E{\!\!\!/}_T}$), and $\Delta R$ between the two $b$-tagged jets associated with the Higgs boson ($\Delta R_{b_1b_2}$), are shown for signal benchmark points BP1A$~= \{m_{\tilde{\chi}_1^{\pm}} = 350~\rm{GeV},\, m_{\tilde{\chi}_1^0} = 165~\rm{GeV}\}$ (blue) and BP1B$~= \{m_{\tilde{\chi}_1^{\pm}} = 425~\rm{GeV},\, m_{\tilde{\chi}_1^0} = 75~\rm{GeV}\}$ (red), along with the major SM background, $t\bar{t}+\rm{jets}$ (green), at the $\sqrt{s}=14~$TeV LHC.
• Figure 3: Projected exclusion reach in the $m_{\tilde{\chi}_1^{\pm}/\tilde{\chi}_2^0}$-$m_{\tilde{\chi}_1^0}$ plane of the R-parity violating MSSM scenario with $\lambda^{\prime\prime}_{112}$ coupling via searches in the $1\ell+2b + \rm E{\!\!\!/}_T$ channel at the HL-LHC is shown as a blue dashed line. The black dotted line represents the Higgs mass line where the mass difference between the NLSP and LSP is equal to the Higgs mass $m_h = 125~$GeV.
• Figure 4: Normalized distributions of number of bottom jets ($N_b$), missing transverse energy ($\rm E{\!\!\!/}_T$), transverse momentum of di-photon system ($p_T^{\gamma\gamma}$), and scalar $p_T$ sum of light jets ($H_T^j$) are shown for two signal benchmark points, BP2A (300,150) and BP2E (700,50) and the SM backgrounds, $t\bar{t}h+\text{jets}$, $Wh+\text{jets}$, and $Zh+\text{jets}$. The signal benchmark points, BP2A and BP2E, are denoted with blue and red solid lines, respectively. The brown, magenta, and green solid lines stand for $t\bar{t}h+\text{jets}$, $Wh+\text{jets}$, and $Zh+\text{jets}$, respectively.
• Figure 5: Projected exclusion reach in the $m_{\tilde{\chi}_1^{\pm}/\tilde{\chi}_2^0}$-$m_{\tilde{\chi}_1^0}$ plane of the $\lambda^{\prime\prime}_{112}$-type R-parity violating MSSM scenario for $1\ell+(\geq2j)+2\gamma + \rm E{\!\!\!/}_T$ channel at the HL-LHC is marked with the blue dashed line. The black dashed line corresponds to $(m_{\tilde{\chi}_1^{\pm}/\tilde{\chi}_2^0} - m_{\tilde{\chi}_1^0}) = m_h$.