arXiv subjects

Pengxuan Zhu

Publications and source records attributed to Pengxuan Zhu.

At least 19 recordsLinked to original sources

arXiv2026

What has the LHC told us about the electroweakino sector of the Minimal Supersymmetric Standard Model?

We perform global fits of the electroweak sector of the Minimal Supersymmetric Standard Model (MSSM) using a comprehensive set of LEP searches, 34 Run 2 LHC searches, and 63 Run 2 LHC measurements. Scanning the bino, wino and Higgsino mass parameters, and the ratio of the Higgs vacuum expectation values, we find that for a light, bino $\tildeχ_{1}^0$, the mass of the next-to-lightest neutralino must be $m_{\tildeχ_{2}^0} \gtrsim 760$ GeV. While MSSM electroweakinos can explain individual excesses observed by ATLAS and CMS in searches targeting compressed spectra, we find no scenarios that fit these excesses simultaneously. When we add a light gravitino, neutralinos are further excluded up to about 1 TeV, though this depends on their composition; Higgsino-dominated $\tildeχ_{1}^0$ requires only $m_{\tildeχ_{1}^0} \approx m_{\tildeχ_{2}^0} \gtrsim 650$ GeV. Lastly, the newer LHC searches and measurements exclude a low-mass region that was preferred in a previous study. This is the most complete summary of collider constraints on the electroweakino sector of the MSSM performed to date.

hep-ph↗

arXiv2026

Endothermic dark matter with a light dark photon and the LUX--ZEPLIN high-energy nuclear-recoil candidate

The LUX-ZEPLIN (LZ) experiment has reported a single nuclear-recoil candidate at $E_{\rm nr}=248\pm23_{\rm stat}\pm23_{\rm sys}\,{\rm keV}$. We investigate whether this event can be explained by endothermic inelastic dark matter coupled to a kinetically mixed dark photon, while reproducing the observed dark-matter relic abundance. Performing a global scan of the five model parameters, combining an energy-only recast of the LZ high-energy likelihood with a relic-density likelihood, we find a preferred region with TeV-scale dark matter masses, mass splittings of a few hundred keV, and a GeV-scale dark photon. The high recoil energy requires the splitting to lie close to the kinematic threshold, so that the signal is supplied by the high-velocity tail of the halo, while the secluded annihilation mechanism fixes the dark gauge coupling, largely independently of the kinetic mixing. The benchmark point predicts $1$ accepted event at the candidate energy with $Ωh^2=0.120$. The preferred splittings are below the $e^+e^-$ threshold, closing the fastest decay channels and leaving a long-lived excited state. Its surviving population is subject to stringent cosmological constraints from energy injection and can also produce an additional exothermic scattering signal, making the late-time abundance an important consistency condition for the minimal model. A dimension-five transition dipole provides a simple way to efficiently deplete $χ_2$ without modifying either the relic abundance or the endothermic LZ signal. The corresponding light-dark-photon scenario remains testable in accelerator searches, including future LHCb, Belle II, and SHiP experiments.

hep-ph↗

arXiv2026

Interpreting the 95 GeV di-photon and di-tau Excesses in the Georgi-Machacek Model

We revisit the 95~GeV $γγ$ and $ττ$ excesses in the Georgi--Machacek model using a combined fit to a single light $CP$-even custodial singlet $H$. Using the one-loop renormalization group-improved effective potential and positive-definiteness conditions for vacuum stability, together with perturbative unitarity, electroweak precision tests, $B$-physics, and Higgs data, we identify a narrow but viable parameter region. In the allowed region $μ_{γγ}$ approaches the experimental central value, while $μ_{ττ}$ reaches only $\sim0.5$ (about $1.4σ$ below the CMS central value) and remains within the $2σ$ interval - a good description of the di-photon excess but only a partial accommodation of the di-tau excess. The scenario predicts characteristic patterns in the singlet mixing and triplet vacuum expectation values and is highly testable at the HL-LHC and future lepton colliders via precision $κ_V$ measurements and direct exotic searches.

hep-ph↗

arXiv2026

Extracting a Toponium Signal at the LHC with Spin and Quantum Information Tools

We investigate near-threshold top-antitop production at the LHC, focusing on the impact of toponium formation on spin correlations and quantum information properties of the final state. Considering the top-antitop system as a mixed two-qubit state, we reconstruct spin density matrices via quantum tomography and evaluate several observables including some inspired by quantum information. We then compare their sensitivity in discriminating toponium effects from top-antitop production without these effects. Our results demonstrate that combining these variables is expected to significantly enhance sensitivity to toponium effects, bringing new ways to explore these subtle features.

hep-ph↗

arXiv2026

Jarvis-HEP: A lightweight Python framework for workflow composition and parameter scans in high-energy physics

High-energy physics phenomenology often requires linking multiple computational tools to evaluate observables, likelihoods, and experimental constraints across nontrivial parameter spaces. In this work, we introduce Jarvis-HEP, a lightweight Python framework for workflow composition and parameter scans in high-energy physics. The framework provides YAML-based workflow specification, dependency-aware execution, modular calculator integration, and asynchronous task scheduling for multi-step computational studies. It supports both external software packages and internally implemented components within a unified workflow, and the current implementation includes several built-in sampling backends for exploratory scans. This paper describes the design and user interface of Jarvis-HEP and illustrates its use with representative synthetic and phenomenological examples.

hep-ph↗

arXiv2026

Exploring vector-like $B$-quark pair production at CLIC in fully hadronic final states

We investigate the discovery potential of the $3~{\rm TeV}$ Compact Linear Collider (CLIC) for a singlet vector-like bottom partner $B$ decaying via $B \to tW$. Focusing on the fully hadronic final state $B\bar{B} \to tW\,tW$, we reconstruct boosted top and $W$ candidates using large-$R$ Valencia jets, supplemented by a merging strategy for partially resolved decays. A systematic scan of the jet-radius parameter identifies $R=0.8$ as the optimal choice, balancing boosted-jet containment with jet multiplicity. Using a cut-based analysis optimized for the $(2t+2W)$ topology and an integrated luminosity of $5~{\rm ab}^{-1}$, CLIC can achieve sensitivity to $m_B \lesssim 1.5\,\mathrm{TeV}$. These results highlight CLIC's excellent capability to probe heavy vector-like quarks in high jet multiplicity environments, extending well beyond the reach of current hadron collider searches.

hep-ph↗

arXiv2025

Probing compressed Higgsinos at the FASER experiment

In the Minimal Supersymmetric Standard Model (MSSM), compressed Higgsinos spectrum ($Δm^0 \lesssim 1$ GeV) occurs when $|μ| \ll |M_1|, |M_2|$ and ${\rm sign}(M_1\cdot M_2)<0$, which leads to a long-lived next-to-lightest neutralino. Such a long-lived neutralino could be copiously produced at the LHC, however escape the detection at the LHC main detectors. We examine the discovery potential at the FASER experiment and find that the FASER 2 could cover the neutral Higgsino mass up to about 130 GeV with mass splitting between 4 to 30 MeV. It is complementary to both the LHC Higgsino search in the $Δm^{0,\pm} \gtrsim 1$ GeV region, and displaced vertex and disappearing track searches of charginos with $Δm^\pm \lesssim 1$ GeV.

hep-ph↗

arXiv2025

Revisiting CMSSM with Non-Universal Gaugino Masses under Current Constraints

To address the longstanding tension between the Constrained Minimal Supersymmetric Standard Model (CMSSM) and recent experimental data, we investigate non-universal gaugino masses within an SU(5) Grand Unified Theory (GUT) framework, focusing on the $\tilde{g}$-SUGRA scenario where $\lvert M_{3} \rvert \gg \lvert M_{1} \rvert, \lvert M_{2} \rvert$. This hierarchy enables a heavier gluino, thereby evading current experimental bounds on supersymmetric particles. Our analysis reveals that precise Higgs measurements place stringent constraints on the model, requiring $\tanβ\gtrsim 5$ and $ M_{0} \gtrsim 20 \, \tanβ\,\text{GeV}$. Although the $\tilde{g}$-SUGRA scenario can help reconcile the persistent $(g-2)_μ$ anomaly, the Higgs constraints significantly restrict its parameter space, making a large contribution to $(g-2)_μ$ challenging. We also assess the discovery prospects in upcoming dark matter direct detection experiments, including PandaX-xT (200 t.y.), LZ (projected), and XENONnT (20 t.y.), which may not fully cover the viable parameter space. In contrast, future collider experiments$-$such as the High-Luminosity LHC at $3\,\mathrm{ab}^{-1}$ and $\mathrm{CLIC}_{1500}$ at $2.5\,\mathrm{ab}^{-1}$$-$can comprehensively probe the remaining regions. These findings highlight $\tilde{g}$-SUGRA as a promising solution to the CMSSM tension and offer clear, testable predictions for upcoming collider searches.

hep-ph↗

arXiv2024

HL-LHC sensitivity to higgsinos from natural SUSY with gravitino LSP

In the realm of natural supersymmetric models, higgsinos are typically the lightest electroweakinos. In gauge-mediated supersymmetry breaking models, the lightest higgsino-dominated particles decay into a $Z$-boson or a Higgs boson ($h$), along with an ultra-light gravitino ($\tilde{G}$) serving as the lightest supersymmetric particle (LSP). This scenario suggests a significant non-resonant $hh$ production. Basing on the recent global fitting results of the $\tilde{G}$-EWMSSM (MSSM with light electroweakinos and an eV-scale gravitino as the LSP) performed by the \textsf{GAMBIT} collaboration, which support a higgsino dominated electroweakino as light as 140 GeV, we develop two simplified models to evaluate their detection potential at the high-luminosity LHC (HL-LHC) with $\sqrt{s} = 14~{\rm TeV}$ and an integrated luminosity of $3000~{\rm fb}^{-1}$. The first model examines the processes where heavier higgsino-dominated states decay into soft $W/Z$ bosons, while the second focuses on direct decays of all three higgsino-dominated electroweakinos into $W/Z/h$ plus a $\tilde{G}$. Our study, incorporating both models and their distinct decay channels, utilizes detailed Monte Carlo simulations for signals and standard model backgrounds. We find that the HL-LHC can probe higgsinos up to 575 GeV, potentially discovering or excluding the natural SUSY scenario in the context of a gravitino LSP. Further, we reinterpret this discovery potential using the GAMBIT global fit samples, and find that the entire parameter space of $|μ| \leq 500~{\rm GeV}$ with an electroweak fine-tuning measure ($Δ_{\rm EW}$) under 100 in $\tilde{G}$-EWMSSM is accessible at the HL-LHC.

hep-ph↗

arXiv2023

Reconstructing masses for semi-invisibly decaying particles pair-produced at lepton colliders

We present a set of Lorentz invariant kinematic variables for reconstructing mass of semi-invisible decaying particles pair-produced at lepton colliders, $m_{\rm RC}^{\rm min}$, $m_{\rm RC}^{\rm max}$ and $m_{\rm LSP}^{\rm max}$, with analytical formulas. They give the minimal and maximum bounds of the decaying particle mass and upper bound of the invisible particle mass. In the search of new physics, these variables can greatly enhance the statistical significance of signal. For the process of smuon pair production at $\sqrt{s}=240~{\rm GeV}$ lepton collider of 5 ab$^{-1}$, the cross section detection limit is pushed by one order, and the expected exclusion and discovery limits are set above $\sqrt{s}\big/2$ and go into the off-shell region. Moreover, these variables can also be used to improve the precision of $W$-boson mass measurement in full leptonic decayed channel. At future lepton collider, the precision can reach to $2\sim 3$ MeV level.

hep-ph↗

arXiv2023

A concise review on some Higgs-related new physics models in light of current experiments

Higgs boson may serve as a portal to new physics beyond the standard model (BSM) which is implied by theoretical naturalness or experimental anomalies. In this note we briefly survey some Higgs-related BSM physics models, including the low energy SUSY (focusing on the minimal SUSY model), the little Higgs models, the two-Higgs-doublet models and the simplest singlet extensions of the Higgs sector. For each illustrated BSM model, we emphatically elucidate its phenomenological power in explaining current measurements of the muon g-2, the W-boson mass and the dark matter. For the singlet extensions like the xSM and 2HDM+S, we discuss the induced cosmic phase transition and the dark matter relic density as well as the vacuum stability. Finally, we give an outlook.

hep-ph↗

arXiv2023

Light higgsino scenario confronted with muon g-2

Light higgsinos below several hundred GeV are favored or required by the naturalness of low energy supersymmetry. If only higgsinos are light while other sparticles are sufficiently heavy, we have the so-called light higgsino scenario. Confronted with the muon $g-2$ data, this scenario is examined in this work. Since in this scenario the LSP (lightest sparticle) is higgsino-like, we need to also consider the dark matter constraints. Assuming a light higgsino mass parameter $μ$ in the range of 100-400 GeV while gaugino mass parameters above TeV, we explore the parameter space under the muon $g-2$ data and the dark matter constraints. We find that, to explain the muon $g-2$ anomaly at $2σ$, the winos and sleptons are respectively upper bounded by 3 TeV and 800 GeV. In this case, we find that the light higgsino-like dark matter can sizably scatter with nucleon and thus the allowed parameter space can be covered almost fully by the future LZ dark matter detection project. We also perform a Monte Carlo simulation to figure out the potential of HL-LHC to detect the light sleptons in this scenario. It turns out that compared with the current LHC limits, the HL-LHC can further cover a part of the parameter space.

hep-ph↗

arXiv2022

A brief survey of low energy supersymmetry under current experiments

This is a brief overview on the low energy supersymmetry in light of current experiments including the LHC searches, the dark matter (DM) detections, the muon g-2 and the CDF II measurement of the W-boson mass. We focus on the minimal framework of supersymmetry, namely the minimal supersymmetric model (MSSM), and obtain the following conclusions: (i) The MSSM can survive all current experiments, albeit suffering from the little hierarchy problem due to the heavy stops pushed up by the LHC searches; (ii) The DM relic density can be readily achieved by the thermal freeze-out of the lightest neutralino and the null results of DM direct detections are typically driving the parameter space to the bino-like lightest neutralino region; (iii) The muon g-2 anomaly reported by FNAL and BNL can be explained at 2-sigma level, which indicates light sleptons and electroweakinos possibly accessible at the HL-LHC; (iv) The CDF II measurement of the W-boson mass can be marginally explained, but requires light stops near TeV which may soon be covered by the LHC searches.

hep-ph↗

arXiv2021

Improved $(g-2)_μ$ measurement and singlino dark matter in $μ$-term extended $\mathbb{Z}_3$-NMSSM

Very recently, a Fermilab report of muon $g-2$ showed a $4.2σ$ discrepancy between it and the standard model (SM) prediction. Motivated by this inspiring result and the increasing tension in supersymmetric interpretation of the anomalous magnetic moment, it is argued that in the general next-to-minimal supersymmetric standard model (GNMSSM), a singlino-dominated neutralino can act as a feasible dark matter (DM) candidate in explaining the discrepancy naturally. In this case, the singlino-dominated DM and singlet-dominated Higgs bosons can form a secluded DM sector with $\tildeχ_1^0\tildeχ_1^0 \to h_s A_s$ responsible for the measured DM relic abundance. when $m_{\tildeχ_1^0} \gtrsim 150~{\rm GeV}$ and the Yukawa coupling $κ$ is around $0.2$. This sector communicates with the SM sector by weak singlet-doublet Higgs mixing, so the scatterings of the singlino-dominated DM with nucleons are suppressed. Furthermore, due to the singlet nature of the DM and the complex mass hierarchy, sparticle decay chains in the GNMSSM are lengthened in comparison with the prediction of the minimal supersymmetric standard model. These characteristics lead to sparticle detection at the Large Hadron Collider (LHC) being rather tricky. This study surveys a specific scenario of the GNMSSM, which extends the $\mathbb{Z}_3$-NMSSM by adding an explicit $μ$-term, to reveal the features. It indicates that the theory can readily explain the discrepancy of the muon anomalous magnetic moment without conflicting with the experimental results in DM and Higgs physics, and the LHC searches for sparticles.

hep-ph↗

arXiv2021

Electron and Muon Anomalous Magnetic Moments in the Inverse Seesaw Extended NMSSM

The recently improved observation of the fine structure constant has led to a negative $2.4σ$ anomaly of electron $g-2$. Combined with the long-existing positive $4.2σ$ discrepancy of the muon anomalous magnetic moment, it is interesting and difficult to explain these two anomalies with a consistent model without introducing flavor violations. We show that they can be simultaneously explained in the inverse seesaw extended next-to-minimal supersymmetric standard model (ISS-NMSSM) by the Higgsino--sneutrino contributions to $(g-2)_e$ and $(g-2)_μ$. The spectrum features prefer light $μ$, which can predict $m_Z$ naturally, and it is not difficult to obtain a $τ$-type sneutrino dark matter candidate that is compatible with the observed dark matter relic density and the bounds from dark matter direct detection experiments. Due to the compressed spectra and the undetectable decay mode of selectrons, they can evade the current Large Hadron Collider (LHC) constraints.

hep-ph↗

arXiv2020

Impact of leptonic unitarity and dark matter direct detection experiments on the NMSSM with inverse seesaw mechanism

In the Next-to-Minimal Supersymmetric Standard Model with the inverse seesaw mechanism to generate neutrino masses, the lightest sneutrino may act as a feasible dark matter candidate in vast parameter space. In this case, the smallness of the leptonic unitarity violation and the recent XENON-1T experiment can limit the dark matter physics. In particular, they set upper bounds of the neutrino Yukawa couplings $λ_ν$ and $Y_ν$. We study such effects by encoding the constraints in a likelihood function and carrying out elaborated scans over the parameter space of the theory with the Nested Sampling algorithm. We show that these constraints are complementary to each other in limiting the theory, and in some cases, they are very strict. We also study the impact of the future LZ experiment on the theory.

hep-ph↗

arXiv2020

Anomalous Muon Magnetic Moment in the Inverse Seesaw Extended Next-to-Minimal Supersymmetric Standard Model

The present work investigates the possibility that both dark matter and the anomalous magnetic moment of the muon may be explained within the context of the inverse seesaw extended Next-to-Minimal Supersymmetric Standard Model (ISS-NMSSM). In ISS-NMSSM, the newly introduced Higgs-neutrino Yukawa coupling $Y_ν$ provides additional Higgsino-sneutrino loop contribution to $(g-2)_μ$. If the deviation between the experimental observations and the Standard Model predictions of the anomalous muon magnetic moment is confirmed by the further experimental and theoretical studies, it can be explained naturally within the ISS-NMSSM framework without conflicting with the current stringent limits on the direct detection of dark matter and Large Hadron Collider searches.

hep-ph↗

arXiv2020

Suppressing the Scattering of WIMP DM with Nucleons in Supersymmetric Theories

The continuously improving sensitivity of dark matter direct detection experiments has limited the interaction between dark matter and nucleons being increasingly feeble, while the dark matter relic density favors it to take part in weak interactions. After taking into account the constraints from the Large Hadron Collider (LHC) search for Higgs bosons and sparticles, it is becoming difficult for the neutralino dark matter in the Minimal Supersymmetric Standard Model and the Next-to-Minimal Supersymmetric Standard Model to possess these two seemingly paradoxical features in their most natural parameter space for electroweak symmetry breaking due to the limited theoretical structure. In contrast, the seesaw extension of the Next-to-Minimal Supersymmetric Standard Model, which was initially proposed to solve the neutrino mass problem, enables the lightest sneutrino to act as a viable dark matter candidate, readily has these features, and thus, it easily satisfies the constraints from dark matter and LHC experiments. Compared with the Type-I seesaw extension, the dark matter physics in the inverse seesaw extension is more flexible, allowing it to be consistent with the experimental results in broader parameter space. We conclude that weakly interacting massive particles (such as the sneutrino in this study) work well in supersymmetric theories as dark matter candidates.

hep-ph↗