How light a higgsino or a wino dark matter can become in a compressed scenario of MSSM

Higgsinos and Wino have strong motivations for being Dark Matter (DM) candidates in supersymmetry, but their annihilation cross sections are quite large. For thermal generation and a single component DM setup the higgsinos or wino may have masses of around 1 or 2-3 TeV respectively. For such DM candidates, a small amount of slepton coannihilation may decrease the effective DM annihilation cross section. This, in turn reduces the lower limit of the relic density satisfied DM mass by more than 50%. Almost a similar degree of reduction of the same limit is also seen for squark coannihilations. However, on the contrary, for near degeneracy of squarks and higgsino DM, near its generic upper limit, the associated coannihilations may decrease the relic density, thus extending the upper limit towards higher DM masses. We also compute the direct and indirect detection signals. Here, because of the quasi-mass degeneracy of the squarks and the LSP, we come across a situation where squark exchange diagrams may contribute significantly or more strongly than the Higgs exchange contributions in the spin-independent direct detection cross section of DM. For the higgsino-DM scenario, we observe that a DM mass of 600 GeV to be consistent with WMAP/PLANCK and LUX data for sfermion coannihilations. The LUX data itself excludes the region of 450 to 600 GeV, by a half order of magnitude of the cross-section, well below the associated uncertainty. The similar combined lower limit for a wino DM is about 1.1 TeV. There is hardly any collider bound from the LHC for squarks and sleptons in such a compressed scenario where sfermion masses are close to the mass of a higgsino/wino LSP.Comment: Modified version with added explanations, with no essential change in results or conclusion. 39 pages, 12 figures, 1 tabl

Implication of Higgs at 125 GeV within Stochastic Superspace Framework

We revisit the issue of considering stochasticity of Grassmannian coordinates in N=1 superspace, which was analyzed previously by Kobakhidze {\it et al}. In this stochastic supersymmetry(SUSY) framework, the soft SUSY breaking terms of the minimal supersymmetric Standard Model(MSSM) such as the bilinear Higgs mixing, trilinear coupling as well as the gaugino mass parameters are all proportional to a single mass parameter \xi, a measure of supersymmetry breaking arising out of stochasticity. While a nonvanishing trilinear coupling at the high scale is a natural outcome of the framework, a favorable signature for obtaining the lighter Higgs boson mass $m_h$ at 125 GeV, the model produces tachyonic sleptons or staus turning to be too light. The previous analyses took $\Lambda$, the scale at which input parameters are given, to be larger than the gauge coupling unification scale $M_G$ in order to generate acceptable scalar masses radiatively at the electroweak scale. Still this was inadequate for obtaining $m_h$ at 125 GeV. We find that Higgs at 125 GeV is highly achievable provided we are ready to accommodate a nonvanishing scalar mass soft SUSY breaking term similar to what is done in minimal anomaly mediated SUSY breaking (AMSB) in contrast to a pure AMSB setup. Thus, the model can easily accommodate Higgs data, LHC limits of squark masses, WMAP data for dark matter relic density, flavor physics constraints and XENON100 data. In contrast to the previous analyses we consider $\Lambda=M_G$, thus avoiding any ambiguities of a post-grand unified theory physics. The idea of stochastic superspace can easily be generalized to various scenarios beyond the MSSM . PACS Nos: 12.60.Jv, 04.65.+e, 95.30.Cq, 95.35.+dComment: LaTex, 35 pages, 7 figures. Minor changes in text. B-physics constraints updated with no change in conclusion. Version to be published in PR

Higgsino Dark Matter in Nonuniversal Gaugino Mass Models

We study two simple and well motivated nonuniversal gaugino mass models, which predict higgsino dark matter. One can account for the observed dark matter relic density along with the observed Higgs boson mass of ~ 125 GeV over a large region of the parameter space of each model, corresponding to higgsino mass of ~ 1 TeV. In each case this parameter region covers the gluino mass range of 2-3 TeV, parts of which can be probed by the 14 TeV LHC experiments. We study these model predictions for LHC in brief and for dark matter detection experiments in greater detail.Comment: 35 pages, 11 figures, pdflatex, new references and a few relevant decay branching ratios added in two tables. Version to appear in Phys Rev

The Electroweak Sector of the pMSSM in the Light of LHC - 8 TeV and Other Data

Using the chargino-neutralino and slepton search results from the LHC in conjunction with the WMAP/PLANCK and $(g-2)_{\mu}$ data, we constrain several generic pMSSM models with decoupled strongly interacting sparticles, heavier Higgs bosons and characterized by different hierarchies among the EW sparticles. We find that some of them are already under pressure and this number increases if bounds from direct detection experiments like LUX are taken into account, keeping in mind the associated uncertainties. The XENON1T experiment is likely to scrutinize the remaining models closely. Analysing models with heavy squarks, a light gluino along with widely different EW sectors, we show that the limits on gluino mass are not likely to be below 1.1 TeV, if a multichannel analysis of the LHC data is performed. Using this light gluino scenario we further illustrate that in future LHC experiments the models with different EW sectors can be distinguished from each other by the relative sizes of the $n$-leptons + $m$-jets + {\mbox{{E\!\!\!\!/_T}}} signals for different choices of $n$.Comment: 52 pages, 14 figures; few references added; published in JHE

Reduced LHC constraints for higgsino-like heavier electroweakinos

As a sequel to our earlier work on wino-dominated $\tilde \chi_1^{\pm}$ and $\tilde \chi_2^{0}$ (wino models), we focus on the pMSSM models where $\tilde \chi_1^{\pm}$ and $\tilde \chi_{2,3}^{0}$ are either higgsino dominated (higgsino models) or admixtures of significant amount of higgsino and wino components (mixed models), with or without light sleptons. The LHC constraints in the trilepton channel are significantly weaker even in the presence of light sleptons, especially in the higgsino models, compared to those mostly studied by the LHC collaborations with wino-dominated $\tilde \chi_1^{\pm}$ and $\tilde \chi_2^{0}$. The modes $\tilde \chi_{2,3}^{0}\rightarrow h~\tilde\chi_1^{0}$ with large branching ratios (BRs) are more common in the higgsino models and may produce spectacular signal in the LHC Run-II. In a variety of higgsino and mixed models we have delineated the allowed parameter space due to the LHC constraints, the observed Dark Matter (DM) relic density of the universe, which gets contributions from many novel DM producing mechanisms i.e., the annihilation/coannihilation processes that lead to the correct range of relic density, and the precise measurement of the anomalous magnetic moment of the muon. In the higgsino models many new DM producing mechanisms, which are not allowed in the wino models, open up. We have also explored the prospects of direct and indirect detection of DM in the context of the LUX and IceCube experiments respectively. In an extended model having only light gluinos in addition to the electroweak sparticles, the gluinos decay into final states with multiple taggable b-jets with very large BRs. As a consequence, the existing ATLAS data in the $0l$ + jets (3b) + $E\!\!\!\!/_T$ channel provide the best limit on $m_{\tilde g}$ ($\approx$ 1.3 TeV). Several novel signatures of higgsino models for LHC Run-II and ILC have been identified.Comment: 55 pages, 13 figures, 10 tables. Version published in JHE

Improved (g−2)μ(g-2)_\mu Measurements and Supersymmetry

The electroweak (EW) sector of the Minimal Supersymmetric Standard Model (MSSM) can account for a variety of experimental data. The lighest supersymmetric particle (LSP), which we take as the lightest neutralino, $\tilde \chi_1^0$, can account for the observed Dark Matter (DM) content of the universe via coannihilation with the next-to-LSP (NLSP), while being in agreement with negative results from Direct Detection (DD) experiments. Owing to relatively small production cross-sections a comparably light EW sector of the MSSM is also in agreement with the unsuccessful searches at the LHC. Most importantly, the EW sector of the MSSM can account for the persistent $3-4\,\sigma$ discrepancy between the experimental result for the anomalous magnetic moment of the muon, $(g-2)_\mu$, and its Standard Model (SM) prediction. Under the assumption that the $\tilde \chi_1^0$ provides the full DM relic abundance we first analyze which mass ranges of neutralinos, charginos and scalar leptons are in agreement with all experimental data, including relevant LHC searches. We find an upper limit of $\sim 600$ GeV for the LSP and NLSP masses. In a second step we assume that the new result of the Run 1 of the ``MUON G-2'' collaboration at Fermilab yields a precision comparable to the existing experimental result with the same central value. We analyze the potential impact of the combination of the Run 1 data with the existing $(g-2)_\mu$ data on the allowed MSSM parameter space. We find that in this case the upper limits on the LSP and NLSP masses are substantially reduced by roughly $100$ GeV. This would yield improved upper limits on these masses of $\sim 500$ GeV. In this way, a clear target could be set for future LHC EW searches, as well as for future high-energy $e^+e^-$ colliders, such as the ILC or CLIC.Comment: Typos corrected, matches published EPJC versio

(g−2)μ(g-2)_\mu and SUSY Dark Matter: Direct Detection and Collider Search Complementarity

The electroweak (EW) sector of the Minimal Supersymmetric Standard Model (MSSM) can account for variety of experimental data. The EW particles with masses of a few hundred GeV evade the LHC searches owing to their small production cross sections. Such a light EW sector can in particular explain the reinforced $4.2\,\sigma$ discrepancy between the experimental result for the anomalous magnetic moment of the muon, \gmin2, and its Standard Model (SM) prediction. The lightest supersymmetric particle (LSP), assumed to be the lightest neutralino, $\tilde{\chi}_1^0$, as a Dark Matter (DM) candidate is furthermore in agreement with the observed limits on the DM content of the universe. Here the Next-to LSP (NLSP) serves as a coannihilation partner and is naturally close in mass to the LSP. Such scenarios are also to a large extent in agreement with negative results from Direct Detection (DD) experiments. The DM relic density can fully be explained by a nearly pure bino or a mixed bino/wino LSP. Relatively light wino and higgsino DM, on the other hand, remains easily below the DM relic density upper bound. Using the improved limits on $(g-2)_\mu$, we explore the mass ranges of the LSP and the NLSP in their correlation with the DM relic density for bino, bino/wino, wino and higgsino DM. In particular analyze the sensitivity of future DM DD experiments to these DM scenarios. We find that higgsino, wino and one type of bino scenario can be covered by future DD experiments. Mixed bino/wino and another type of bino DM can reach DD cross sections below the neutrino floor. In these cases we analyze the complementarity with the (HL-)LHC and future $e^+e^-$ linear colliders. We find that while the prospects for the HL-LHC are interesting, but not conclusive, an $e^+e^-$ collider with $\sqrt{s} \le 1$ TeV can cover effectively all points of the MSSM that may be missed by DD experiments.Comment: 32 pages, 9 figures. arXiv admin note: text overlap with arXiv:2103.1340

New physics implications of VBF searches exemplified through the Georgi-Machacek model

LHC searches for nonstandard scalars in vector boson fusion (VBF) production processes can be particularly efficient in probing scalars belonging to triplet or higher multiplet representations of the Standard Model $SU(2)_L$ gauge group. They can be especially relevant for models where the additional scalars do not have any tree-level couplings to the Standard Model fermions, rendering VBF as their primary production mode at the LHC. In this work, we employ the latest LHC data from VBF resonance searches to constrain the properties of nonstandard scalars, taking the Georgi-Machacek model as a prototypical example. We take into account the theoretical constraints on the potential from unitarity and boundedness-from-below as well as indirect constraints coming from the signal strength measurements of the 125 GeV Higgs boson at the LHC. To facilitate the phenomenological analysis we advocate a convenient reparametrization of the trilinear couplings in the scalar potential. We derive simple correlations among the model parameters corresponding to the decoupling limit of the model. We explicitly demonstrate how a combination of theoretical and phenomenological constraints can push the GM model towards the decoupling limit. Our analysis suggests that the VBF searches can provide key insights into the composition of the electroweak vacuum expectation value.Comment: 17 pages, 7 figure