Sneutrino DM in the NMSSM with inverse seesaw mechanism

In supersymmetric theories like the Next-to-Minimal Supersymmetric Standard Model (NMSSM), the lightest neutralino with bino or singlino as its dominant component is customarily taken as dark matter (DM) candidate. Since light Higgsinos favored by naturalness can strength the couplings of the DM and thus enhance the DM-nucleon scattering rate, the tension between naturalness and DM direct detection results becomes more and more acute with the improved experimental sensitivity. In this work, we extend the NMSSM by inverse seesaw mechanism to generate neutrino mass, and show that in certain parameter space the lightest sneutrino may act as a viable DM candidate, i.e. it can annihilate by multi-channels to get correct relic density and meanwhile satisfy all experimental constraints. The most striking feature of the extension is that the DM-nucleon scattering rate can be naturally below its current experimental bounds regardless of the higgsino mass, and hence it alleviates the tension between naturalness and DM experiments. Other interesting features include that the Higgs phenomenology becomes much richer than that of the original NMSSM due to the relaxed constraints from DM physics and also due to the presence of extra neutrinos, and that the signatures of sparticles at colliders are quite different from those with neutralino as DM candidate.Comment: 33 page

A Possible Signal for QGP Formation from the Minimum-Bias Data of Relativistic Large Heavy Ion Collisions

It is argued that the experimentally observed strong upward-bending of the logarithm of factorial moments versus that of phase space partition number in the higher-dimensional phase space of nucleus-nucleus collisions is due to the superposition of elementary collision processes in these collisions. A direct implication of this observation is that, at high enough energy and/or density, when the produced particles from individual elementary processes are melted into a unique system the above-mentioned superposition effect will disappear and the factorial moments will not be strongly upward-bending any more. So, the disappearance of strong upward-bending of higher-dimensional factorial moments in heavy ion collision may be taken as a signal for the formation of a unique system, or QGP, in this collision.Comment: 5 pages 3 Postscript figures, Late

Impact of recent measurement of (g−2)μ(g-2)_\mu, LHC search for supersymmetry, and LZ experiment on Minimal Supersymmetric Standard Model

Motivated by the recent measurement of muon anomalous magnetic moment at Fermilab, the rapid progress of the LHC search for supersymmetry, and the significantly improved sensitivities of dark matter direct detection experiments, we studied their impacts on the Minimal Supersymmetric Standard Model (MSSM). We conclude that higgsino mass should be larger than about $500~{\rm GeV}$ for $M_1 100~{\rm GeV}$, where $M_1$ denotes the bino mass. These improved bounds imply a tuning of ${\cal{O}}(1\%)$ to predict the $Z$-boson mass and simultaneously worsen the naturalness of the $Z$- and $h$-mediated resonant annihilations to achieve the measured dark matter density. We also conclude that the LHC restrictions have set lower bounds on the sparticle mass spectra: $m_{\tilde{\chi}_1^0} \gtrsim 210~{\rm GeV}$, $m_{\tilde{\chi}_2^0}, m_{\tilde{\chi}_1^\pm} \gtrsim 235~{\rm GeV}$, $m_{\tilde{\chi}_3^0} \gtrsim 515~{\rm GeV}$, $m_{\tilde{\chi}_4^0} \gtrsim 525~{\rm GeV}$, $m_{\tilde{\chi}_2^\pm} \gtrsim 530~{\rm GeV}$, $m_{\tilde{\nu}_\mu} \gtrsim 235~{\rm GeV}$, $m_{\tilde{\mu}_1} \gtrsim 215~{\rm GeV}$, and $m_{\tilde{\mu}_2} \gtrsim 250~{\rm GeV}$, where $\tilde{\chi}_{2}^0$ and $\tilde{\chi}_1^\pm$ are wino-dominated when they are lighter than about $500~{\rm GeV}$. These bounds are far beyond the reach of the LEP experiments in searching for supersymmetry and have not been acquired before. In addition, we illuminate how some parameter spaces of the MSSM have been tested at the LHC and provide five scenarios in which the theory coincides with the LHC restrictions. Once the muon g-2 anomaly is confirmed to originate from supersymmetry, this research may serve as a guide to explore the characteristics of the MSSM in future experiments.Comment: 41 pages, 7 figures, 10 table

Singlino-dominated dark matter in general NMSSM

The general Next-to-Minimal Supersymmetric Standard Model (NMSSM) describes the singlino-dominated dark-matter (DM) property by four independent parameters: singlet-doublet Higgs coupling coefficient $\lambda$, Higgsino mass $\mu_{tot}$, DM mass $m_{\tilde{\chi}_1^0}$, and singlet Higgs self-coupling coefficient $\kappa$. The first three parameters strongly influence the DM-nucleon scattering rate, while $\kappa$ usually affects the scattering only slightly. This characteristic implies that singlet-dominated particles may form a secluded DM sector. Under such a theoretical structure, the DM achieves the correct abundance by annihilating into a pair of singlet-dominated Higgs bosons by adjusting $\kappa$'s value. Its scattering with nucleons is suppressed when $\lambda v/\mu_{tot}$ is small. This speculation is verified by sophisticated scanning of the theory's parameter space with various experiment constraints considered. In addition, the Bayesian evidence of the general NMSSM and that of $Z_3$-NMSSM is computed. It is found that, at the cost of introducing one additional parameter, the former is approximately $3.3 \times 10^3$ times the latter. This result corresponds to Jeffrey's scale of 8.05 and implies that the considered experiments strongly prefer the general NMSSM to the $Z_3$-NMSSM.Comment: 29 pages, 9 figure

Status of the singlino-dominated dark matter in general Next-to-Minimal Supersymmetric Standard Model

With the rapid progress of dark matter direct detection experiments, the attractiveness of the popular bino-dominated dark matter in economical supersymmetric theories is fading. As an alternative, the singlino-dominated dark matter in general Next-to-Minimal Supersymmetric Standard Model (NMSSM) is paying due attention. This scenario has the following distinct characteristics: free from the tadpole problem and the domain-wall problem of the NMSSM with a $Z_3$-symmetry, predicting more stable vacuum states than the $Z_3$-NMSSM, capable of forming an economical secluded dark matter sector to yield the dark matter experimental results naturally, and readily weaken the restrictions from the LHC search for SUSY. Consequently, it can explain the muon g-2 anomaly in broad parameter space that agrees with various experimental results while simultaneously breaking the electroweak symmetry naturally. In this study, we show in detail how the scenario coincides with the experiments, such as the SUSY search at the LHC, the dark matter search by the LZ experiment, and the improved measurement of the muon g-2. We provide a simple and clear picture of the physics inherent in the general NMSSM