Higgsino Mass Research Articles

NMSSM explanation for excesses in the search for neutralinos and charginos and a 95 GeV Higgs boson

The observed excesses in the search for neutralinos and charginos by ATLAS and CMS can be fitted simultaneously in the minimal supersymmetric standard model (MSSM) assuming a light higgsino mass, of magnitude less than about 250 GeV, and a compressed higgsino dominated neutralino and chargino spectrum, with 5–10% mass splittings. However, light higgsinos as dark matter would have far too large direct detection cross sections. We consider the Next-to-MSSM (NMSSM) with an additional singlino-like lightest supersymmetric particle (LSP) a few GeV below the next-to-lightest supersymmetric particle (NLSP). Sparticles prefer to decay first into the NLSP and remnants from the final decay into the LSP are too soft to contribute to the observed signals. Co-annihilation in the higgsino-sector can generate a relic density in the WMAP/Planck window. The singlino-like LSP has automatically a direct detection cross section below present and future sensitivities: a direct detection signal in the near future would exclude this scenario. The singlet-like Higgs scalar of the NMSSM can have a mass around 95 GeV and signal cross sections in the bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$b\\bar{b}$$\\end{document} channel at LEP and in the γγ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\gamma \\gamma $$\\end{document} channel at the LHC compatible with the respective observations.

Radiative corrections to aid the direct detection of the Higgsino-like neutralino dark matter: Spin-independent interactions

The lightest neutralino (χ˜10) is a good dark matter (DM) candidate in the R-parity conserving minimal supersymmetric Standard Model. In this work, we consider the light Higgsino-like neutralino as the lightest stable particle, thanks to a rather small Higgsino mass parameter μ. We then estimate the prominent radiative corrections to the neutralino-neutralino-Higgs boson vertices. We show that for Higgsino-like χ˜10, these corrections can significantly influence the spin-independent direct detection cross section, even contributing close to 100% in certain regions of the parameter space. These corrections, therefore, play an important role in deducing constraints on the mass of the Higgsino-like lightest neutralino DM, and thus the μ parameter. Published by the American Physical Society 2024

Confronting electroweak MSSM through one-loop renormalized neutralino-Higgs interactions for dark matter direct detection and the muon g−2

We compute the next-to-leading order (NLO) corrections to the vertices where a pair of the lightest neutralino couples to CP-even (light or heavy) Higgs scalars. In particular, the lightest neutralino is assumed to be a dominantly binolike mixed state, composed of bino and Higgsino or bino, wino, and Higgsino. After computing all the three-point functions in the electroweak minimal supersymmetric Standard Model (MSSM), we detail the contributions from the counterterms that arise in renormalizing these vertices in one-loop order. The amendment of the renormalized vertices impacts the spin-independent direct detection cross sections of the scattering of nucleons with dark matter. We perform a comprehensive numerical scan over the parameter space where all the points satisfy the present B-physics constraints and accommodate the muon’s anomalous magnetic moment. Finally, we exemplify a few benchmark points, which indulge the present searches of supersymmetric particles. After including the renormalized one-loop vertices, the spin-independent DM-nucleon cross sections may be enhanced up to 20% compared to its tree-level results. Finally, with the NLO cross section, we use the recent LUX-ZEPLIN (LZ) results on the neutralino-nucleon scattering to display the relative rise in the lowest allowed band of the Higgsino mass parameter in the M1−μ plane of the electroweak MSSM. Published by the American Physical Society 2024

Search for pair production of higgsinos in events with two Higgs bosons and missing transverse momentum in s=13 TeV pp collisions at the ATLAS experiment

This paper presents a search for pair production of higgsinos, the supersymmetric partners of the Higgs bosons, in scenarios with gauge-mediated supersymmetry breaking. Each higgsino is assumed to decay into a Higgs boson and a nearly massless gravitino. The search targets events where each Higgs boson decays into bb¯, leading to a reconstructed final state with at least three energetic b-jets and missing transverse momentum. Two complementary analysis channels are used, with each channel specifically targeting either low or high values of the higgsino mass. The low-mass (high-mass) channel exploits 126 (139) fb−1 of s=13 TeV data collected by the ATLAS detector during Run 2 of the Large Hadron Collider. No significant excess above the Standard Model prediction is found. At 95% confidence level, masses between 130 GeV and 940 GeV are excluded for higgsinos decaying exclusively into Higgs bosons and gravitinos. Exclusion limits as a function of the higgsino decay branching ratio to a Higgs boson are also reported. © 2024 CERN, for the ATLAS Collaboration 2024 CERN

Search for Nearly Mass-Degenerate Higgsinos Using Low-Momentum Mildly Displaced Tracks in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector.

Higgsinos with masses near the electroweak scale can solve the hierarchy problem and provide a dark matter candidate, while detecting them at the LHC remains challenging if their mass splitting is O(1 GeV). This Letter presents a novel search for nearly mass-degenerate Higgsinos in events with an energetic jet, missing transverse momentum, and a low-momentum track with a significant transverse impact parameter using 140 fb^{-1} of proton-proton collision data at sqrt[s]=13 TeV collected by the ATLAS experiment. For the first time since LEP, a range of mass splittings between the lightest charged and neutral Higgsinos from 0.3 to 0.9GeV is excluded at 95% confidence level, with a maximum reach of approximately 170GeV in the Higgsino mass.

Implications of purity constraints on light Higgsinos

The lightest supersymmetric particles could be Higgsinos that have a small mixing with gauginos. If the lightest Higgsino-like state makes up some or all of the dark matter with a thermal freeze-out density, then its mass must be between about 100 GeV and 1150 GeV, and dark matter searches put bounds on the amount of gaugino contamination that it can have. Motivated by the generally good agreement of flavor- and CP-violating observables with Standard Model predictions, I consider models in which the scalar particles of minimal supersymmetry are heavy enough to be essentially decoupled, except for the 125 GeV Higgs boson. I survey the resulting purity constraints as lower bounds on the gaugino masses and upper bounds on the Higgsino mass splittings. I also discuss the mild excesses in recent soft lepton searches for charginos and neutralinos at the LHC, and show that they can be accommodated in these models if tanβ is small and μ is negative. Published by the American Physical Society 2024

Soft supersymmetry breaking as the sole origin of neutrino masses and lepton number violation

We discuss a scenario in which the supergravity induced soft terms, conventionally used for breaking supersymmetry, also lead to non-zero Majorana neutrino masses. The soft terms lead to the spontaneous violation of the lepton number at the gravitino mass scale m3/2 which in turn leads to (i) the Majorana masses of O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(m3/2) for the right-handed neutrinos and (ii) the R-parity breaking at the same scale. The former contributes to light neutrino masses through the type I seesaw mechanism, while the latter adds to it through neutrino-neutralino mixing. Both contributions can scale inversely with respect to m3/2 given that gaugino and Higgsino masses are also of order m3/2. Together, these two contributions adequately explain observed neutrino masses and mixing. One realization of the scenario also naturally leads to a μ parameter of O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(m3/2). Despite the lepton number symmetry breaking close to the weak scale, the Majoron in the model exhibits very weak coupling to leptons, satisfying existing constraints on Majoron-lepton interactions. The right-handed neutrinos in the model have a large coupling to Higgsinos. This coupling and the relatively large heavy-light neutrino mixing induced through the seesaw mechanism may lead to the observable signals at colliders in terms of displaced vertices.

Search for direct production of winos and higgsinos in events with two same-charge leptons or three leptons in pp collision data at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV with the ATLAS detector

A search for supersymmetry targeting the direct production of winos and higgsinos is conducted in final states with either two leptons (e or μ) with the same electric charge, or three leptons. The analysis uses 139 fb−1 of pp collision data at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV collected with the ATLAS detector during Run 2 of the Large Hadron Collider. No significant excess over the Standard Model expectation is observed. Simplified and complete models with and without R-parity conservation are considered. In topologies with intermediate states including either Wh or WZ pairs, wino masses up to 525 GeV and 250 GeV are excluded, respectively, for a bino of vanishing mass. Higgsino masses smaller than 440 GeV are excluded in a natural R-parity-violating model with bilinear terms. Upper limits on the production cross section of generic events beyond the Standard Model as low as 40 ab are obtained in signal regions optimised for these models and also for an R-parity-violating scenario with baryon-number-violating higgsino decays into top quarks and jets. The analysis significantly improves sensitivity to supersymmetric models and other processes beyond the Standard Model that may contribute to the considered final states.

Lighting up the LHC with Dark Matter

We show that simultaneously explaining dark matter and the observed value of the muon’s magnetic dipole moment may lead to yet unexplored photon signals at the LHC. We consider the Minimal Supersymmetric Standard Model with electroweakino masses in the few-to-several hundred GeV range, and opposite sign of the Bino mass parameter with respect to both the Higgsino and Wino mass parameters. In such region of parameter space, the spin-independent elastic scattering cross section of a Bino-like dark matter candidate in direct detection experiment is suppressed by cancellations between different amplitudes, and the observed dark matter relic density can be realized via Bino-Wino co-annihilation. Moreover, the observed value of the muon’s magnetic dipole moment can be explained by Bino and Wino loop contributions. Interestingly, “radiative” decays of Wino-like neutralinos into the lightest neutralino and a photon are enhanced, whereas decays into leptons are suppressed. While these decay patterns weaken the reach of multi-lepton searches at the LHC, the radiative decay opens a new window for probing dark matter at the LHC through the exploration of parameter space regions beyond those currently accessible. To complement the current electroweakino searches, we propose searching for a single (soft) photon plus missing transverse energy, accompanied by a hard initial state radiation jet.

Is Light Neutralino Thermal Dark Matter in the Phenomenological Minimal Supersymmetric Standard Model Ruled Out?

We explore the parameter space of the phenomenological minimal supersymmetric standard model with a light neutralino thermal dark matter (m_{χ[over ˜]_{1}^{0}}≤m_{h}/2) that is consistent with current collider and astrophysical constraints. We consider both positive and negative values of the higgsino mass parameter (μ). Our investigation shows that the recent experimental results from the LHC as well as from direct detection searches for dark matter by the LUX-ZEPLIN Collaboration rule out the Z-funnel region for the μ>0 scenario. The same results severely restrict the h-funnel region for positive μ; however, the allowed points can be probed easily with few more days of data from the LUX-ZEPLIN experiment. In the μ<0 scenario, we find that very light higgsinos in both the Z and h funnels might survive the present constraints from the electroweakino searches at the LHC, and dedicated efforts from experimental collaborations are necessary to make conclusive statements about their present status.

Higgsino Dark Matter Confronts 14Years of Fermi γ-Ray Data.

Thermal Higgsino dark matter (DM), with mass around 1TeV, is a well-motivated, minimal DM scenario that arises in supersymmetric extensions of the standard model. Higgsinos may naturally be the lightest superpartners in split-supersymmetry models that decouple the scalar superpartners while keeping Higgsinos and gauginos close to the TeV scale. Higgsino DM may annihilate today to give continuum γ-ray emission at energies less than a TeV in addition to a linelike signature at energies equal to the mass. Previous searches for Higgsino DM, for example with the H.E.S.S. γ-ray telescope, have not reached the necessary sensitivity to probe the Higgsino annihilation cross section. In this work we make use of 14years of data from the Fermi Large Area Telescope at energies above ∼10 GeV to search for the continuum emission near the Galactic Center from Higgsino annihilation. We interpret our results using DM profiles from MilkyWay analog galaxies in the FIRE-2 hydrodynamic cosmological simulations. We set the strongest constraints to date on Higgsino-like DM. Our results show a mild, ∼2σ preference for Higgsino DM with a mass near the thermal Higgsino mass and, depending on the DM density profile, the expected cross section.

Light Higgsino scenario confronted with the 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 $\mu$ 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 $2\sigma$, 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.

Dynamically induced topological inflation

We propose an inflation model in which the inflationary era is driven by the strong dynamics of $Sp(2)$ gauge theory. The quark condensation in the confined phase of $Sp(2)$ gauge theory generates the inflaton potential comparable to the energy of the thermal bath at the time of phase transition. Afterwards, with a super-Planckian field value at the global minimum, the inflation commences at a false vacuum region lying between true vacuum regions and hence the name ``topological inflation.'' Featured by the huge separation between the scale of the false vacuum ($V(0{)}^{1/4}\ensuremath{\sim}{10}^{15}\text{ }\text{ }\mathrm{GeV}$) and the field value at the global minimum (${\ensuremath{\phi}}_{\mathrm{min}}\ensuremath{\sim}{M}_{P}$), the model can be consistent with cosmic microwave background (CMB) observables without suffering from the initial condition problems. Crucially, this is achieved only with some mild tuning of parameters in $V(\ensuremath{\phi})$. In addition to $Sp(2)$, this model is based on an anomaly free ${Z}_{6R}$ discrete $R$ symmetry. Remarkably, while all parameters are fixed by CMB observations, the model predicts a hierarchy of energy scales including the inflation scale, supersymmetry-breaking scale, R-symmetry breaking scale, Higgsino mass and the right-handed neutrino mass given in terms of the dynamical scale of $Sp(2)$.

Twin Supersymmetric Dark Matter in Light of the First LZ Results

We review the status of dark matter (DM) candidates in supersymmetric Twin Higgs models in light of the first results of the LUX-ZEPLIN (LZ) experiment. We found that, for twin bino-dominated DM, the new results strengthened the lower bound on the higgsino mass. However, a large part of the parameter space consistent with natural electroweak symmetry breaking is still allowed. In the case of twin-stau DM, the new results imply that, if the thermal abundance of the twin-stau LSP fits the observed density of DM, the twin stau cannot have a large left-handed component anymore.

Muon and electron (g-2) anomalies with non-holomorphic interactions in MSSM

The recent Fermilab muon g-2 result and the same for electron due to fine-structure constant measurement through {}^{133}textrm{Cs} matter-wave interferometry are probed in relation to MSSM with non-holomorphic (NH) trilinear soft SUSY breaking terms, referred to as NHSSM. Supersymmetric contributions to charged lepton (g-2)_l can be enhanced via the new trilinear terms involving a wrong Higgs coupling with left and right-handed scalars. Bino-slepton loop is used to enhance the SUSY contribution to g-2 where wino mass stays at 1.5 TeV and the left and right slepton mass parameters for the first two generations are considered to be the same. Unlike many MSSM-based analyses completed before, the model does not require a light electroweakino, or light sleptons, or unequal left and right slepton masses, or a very large higgsino mass parameter. In absence of popular UV complete models, we treat the NH terms at par with MSSM soft terms, in a model independent framework of Minimal Effective Supersymmetry. The first part of the analysis involves the study of (g-2)_mu constraint along with the limits from Higgs mass, B-physics, collider data, direct detection of dark matter (DM), while focusing on a higgsino DM which is underabundant in nature. We then impose the constraint from electron g-2 where a large Yukawa threshold correction (an outcome of NHSSM) and opposite signs of trilinear NH coefficients associated with mu and e fields are used to satisfy the dual limits of Delta {a_mu } and Delta {a_e} (where the latter comes with negative sign). Varying Yukawa threshold corrections further provide the necessary flavor-dependent enhancement of Delta {a_e}/m_e^2 compared to that of Delta {a_mu }/m_mu ^2. A larger Yukawa threshold correction through A^prime _e for y_e also takes away the direct proportionality of a_e with respect to tan beta . With a finite intercept, a_e becomes only an increasing function of tan beta . We identified the available parameter space in the two cases while also satisfying the ATLAS data from slepton pair production searches in the plane of slepton mass parameter and the mass of the lightest neutralino.

Higgs information in Split-SUSY at the LHC

Information theory turns out to be an interesting tool for studying the consequences of Higgs observations to various new physics candidate theories by means of the information measure as the entropy of Higgs-Boson through its various detection modes at the Large Hadron Collider. The present article investigates the parameter space of a supersymmetric scenario where sfermions and one of the Higgs superfields are decoupled, while the gauginos, Higgsinos, and the remaining Higgs doublet are still allowed to be lighter. Our analysis reveals that this is quite a viable choice in the light of LHC discovery of a Higgs which resembles the SM Higgs-Boson and nothing else so far. While the supersymmetry breaking scale MS could be as high as 1011 GeV or so, the most preferred values of the MS and tan⁡β are found to be around 3.6×107 GeV and 41 respectively, which is also consistent with the relic abundance of the neutralino dark matter. The corresponding value of neutralino (mχ˜10) LSP is estimated to be around 1.01 TeV. The preferred values of other parameters, namely, the Higgsino mass (μ) and gaugino mass parameters (M1 and M2) are found to be about 1.05 TeV, 1.74 TeV, and 2.57 TeV, respectively.

Deep learning jet images as a probe of light Higgsino dark matter at the LHC

A Higgsino in supersymmetric standard models can play the role of a dark matter particle. In conjunction with the naturalness criterion, the Higgsino mass parameter is expected to be around the electroweak scale. In this work, we explore the potential of probing the nearly degenerate light Higgsinos with machine learning at the LHC. By analyzing jet images and other jet substructure information, we use the convolutional neural network to enhance the signal significance. We find that our deep learning jet image method can improve the previous result based on the conventional cut flow by about a factor of 2 at the High-Luminosity LHC.

Upper bound on the smuon mass from vacuum stability in the light of muon g − 2 anomaly

We derive an upper bound on the smuon mass assuming that the muon g−2 anomaly is explained by the supersymmetric (SUSY) contribution. In the minimal SUSY standard model, the SUSY contribution to the muon g−2 is enhanced when the Higgsino mass parameter is large. Then, the smuon-smuon-Higgs trilinear coupling is enhanced, which may destabilize the electroweak vacuum. We calculate precisely the decay rate of the electroweak vacuum in such a case. We include one-loop effects which are crucial to determine the overall normalization of the decay rate. Requiring that the theoretical prediction of the muon anomalous magnetic moment is consistent with the observed value at the 1 and 2σ levels (equal to the central value of the observed value), we found that the lightest smuon mass should be smaller than 1.38 and 1.68TeV (1.20TeV) for tan⁡β=10 (with tan⁡β being the ratio of the vacuum expectation values of the two Higgs bosons), respectively, and the bound is insensitive to the value of tan⁡β.

New angular and other cuts to improve the Higgsino signal at the LHC

Motivated by the fact that naturalness arguments strongly suggest that the SUSY-preserving higgsino mass parameter mu cannot be too far above the weak scale, we re-examine higgsino pair production in association with a hard QCD jet at the HL-LHC. We focus on \ell^+\ell^-+\eslt+j events from the production and subsequent decay, \tchi_2^0\to\tchi_1^0\ell^+\ell^-, of the heavier neutral higgsino. The novel feature of our analysis is that we suggest angular cuts to reduce the important background from Z(\to \tau\tau)+j events more efficiently than the m_{\tau\tau}^2<0 cut that has been used by the ATLAS and CMS collaborations. Other cuts, needed to reduce backgrounds from t\bar{t}, WWj and W/Z+\ell\bar{\ell} production, are also delineated. We plot out the reach of LHC14 for 300 and 3000~fb^{-1} and also show distributions that serve to characterize the higgsino signal, noting that higgsinos may well be the only superpartners accessible at LHC14 in a well-motivated class of natural SUSY models.

Search for supersymmetry in final states with two or three soft leptons and missing transverse momentum in proton-proton collisions at sqrt{s} = 13 TeV

A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at sqrt{s} = 13 TeV collected in the three-year period 2016–2018 by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to 137 fb−1. The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at 95% confidence level are set on {overset{sim }{upchi}}_2^0/{overset{sim }{upchi}}_1^{pm } masses up to 275 GeV for a mass difference of 10 GeV in the wino-bino case, and up to 205(150) GeV for a mass difference of 7.5 (3) GeV in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter μ up to 180 GeV with the bino mass parameter M1 at 800 GeV. In the top squark interpretation, exclusion limits are set at top squark masses up to 540 GeV for four-body top squark decays and up to 480 GeV for chargino-mediated decays with a mass difference of 30 GeV.