我们考虑B3 mSUGRA模型，其中我们有一个轻子数违反LQD算子在大统一尺度。这可以改变超对称质谱，导致超中微子成为参数空间中最轻的超对称粒子。我们考虑了中微子质量、μ子反常磁矩、b -> s γ和其他精密测量的限制。我们进一步调查现有的限制，直接搜索在LEP，Tevatron和欧洲核子研究中心p \bar p对撞机。然后，我们给出的LHC的特征签名的例子。
英文摘要：
We consider B3 mSUGRA models where we have one lepton number violating LQD operator at the GUT scale. This can alter the supersymmetric mass spectrum leading to a sneutrino as the lightest supersymmetric particle in a large region of parameter space. We take into account the restrictions from neutrino masses, the muon anomalous magnetic moment, b -> s gamma and other precision measurements. We furthermore investigate existing restrictions from direct searches at LEP, the Tevatron and the CERN p\bar p collider. We then give examples for characteristic signatures at the LHC.
Contrary to common expectation, a left-sneutrinos can occasionally be the lightest supersymmet- ric particle. This has important implications in both collider and dark matter studies. We show that same-sign tri-lepton (SS3L) events at the Large Hadron Collider, with any lepton having opposite sign vetoed, distinguish such scenarios, up to gluino masses exceeding 2 TeV. The jets + M ET signal rate is somewhat suppressed in this case, thus enhancing the scope of leptonic signals.
The minimal supersymmetric (SUSY) standard model (MSSM) augmented by right chiral sneutrinos may lead to one such sneutrino serving as the lightest supersymmetric particle and a non-thermal dark matter candidate, especially if neutrinos have Dirac masses only. In such cases, if the lightest MSSM particle is a stau, the signal of SUSY at the LHC consists in stable charged tracks which are distinguishable from backgrounds through their time delay between the inner tracker and the muon chamber. We show how to determine in such scenarios the mass hierarchy between the lightest neutralino and right…
We study a supersymmetric neutrinophilic Higgs model with large neutrino Yukawa couplings where neutrinos are Dirac particles and the lightest right-handed (RH) sneutrino is the lightest supersymmetric particle (LSP) as a dark matter candidate. Neutrinophilic Higgs bosons need to be rather heavy by the precise determination of the muon decay width and dark radiation constraints for large Yukawa couplings. From the Large Hadron Collider constraints, neutrinophilic Higgsino mass need to be heavier than several hundred GeV or close to the RH sneutrino LSP mass. The latter case is interesting beca…
We show that the $B-L$ Supersymmetric Standard Model with Inverse Seesaw (BLSSMIS) provides new Dark Matter (DM) candidates (lightest right-handed sneutrino and lightest $B-L$ neutralino) with mass of order few hundreds GeV, while most of other SUSY spectrum can be quite heavy, consistently with the current Large Hadron Collider (LHC) constraints. We emphasize that the thermal relic abundance and direct detection experiments via relic neutralino scattering with nuclei impose stringent constraints on the $B-L$ neutralinos. These constraints can be satisfied by few points in the parameter space …
Scenarios where left- and right-handed sneutrinos mix and the lightest mixed one act as a thermal dark matter candidate can solve the dark matter, neutrino mass, and hierarchy problems simultaneously. We focus on the dark matter mass region of the order of 1 GeV, where dark matter direct detections are insensitive. We calculate the decay rate of a false vacuum induced by a large sneutrino trilinear coupling as well as other observables constrained by experiments. As a result, we show that there is an allowed region where the mass of the lightest neutralino is around 1 GeV. The allowed region c…
We consider MSSM with right-chiral neutrino superfields with Majorana masses, where the lightest right-handed sneutrino dominated scalars constitutes non-thermal dark matter (DM). The $Δ\,L=2$ masses are subject to severe constraints coming from freeze-in relic density of such DM candidates as well as from sterile neutrino $\textit{freeze-in}$. In addition, big-bang Nucleosynthesis and $\textit{freeze-out}$ of the next-to-lightest superparticle shrink the viable parameter space of such a scenario. We examine various $Δ\,L=2$ mass terms for families other than that $Δ\,L=2$ masses are difficult…
Right-handed sneutrinos are natural components of left-right symmetric supersymmetric models where the gauge sector is extended to include right-handed weak interactions. Unlike in other models where right-handed sneutrinos are gauge singlets, here the right sneutrino is part of a doublet and could be a dark matter candidate whose annihilation proceeds via gauge interactions. We investigate this possibility, and find that relic density, low-energy observable and direct supersymmetry search constraints can be satisfied when the lightest supersymmetric particle is a right-handed sneutrino. We in…
In supersymmetric models with Dirac neutrinos, the lightest sneutrino can be an excellent thermal dark matter candidate when the soft sneutrino trilinear parameter is large. We focus on scenarios where the mass of the mixed sneutrino is of the order of GeV and sensitivity of dark matter direct detection is weak. We investigate phenomenological constraints on the model parameter space including the vacuum stability bound. We show that the allowed regions can be explored by measuring Higgs boson properties at future collider experiments.
We investigate the collider signatures of neutral and charged Long-Lived Particles (LLPs), predicted by the Supersymmetric $B-L$ extension of the Standard Model (BLSSM), at the Large Hadron Collider (LHC). The BLSSM is a natural extension of the Minimal Supersymmetric Standard Model (MSSM) that can account for non-vanishing neutrino masses. We show that the lightest right-handed sneutrino can be the Lightest Supersymmetric Particle (LSP), while the Next-to-the LSP (NLSP) is either the lightest left-handed sneutrino or the left-handed stau, which are natural candidates for the LLPs. We analyze …
Stop searches in supersymmetric frameworks with $R$-parity conservation usually assume the lightest neutralino to be the lightest supersymmetric particle. In this paper we consider an alternative scenario in which the left-handed tau sneutrino is lighter than neutralinos and stable at collider scales, but possibly unstable at cosmological scales. Moreover the (mostly right-handed) stop $\widetilde t$ is lighter than all electroweakinos, and heavier than the scalars of the third generation doublet, whose charged component, $\widetildeτ$, is heavier than the neutral one, $\widetildeν$. The remai…
We perform a detailed analysis of dark matter signals of supersymmetric models containing an extra $U(1)^\prime$ gauge group. We investigate scenarios in which either the right sneutrino or the lightest neutralino are phenomenologically acceptable dark matter candidates and we explore the parameter spaces of different supersymmetric realisations featuring an extra $U(1)^\prime$. We impose consistency with low energy observables, with known mass limits for the superpartners and $Z^\prime$ bosons, as well as with Higgs boson signal strengths, and we moreover verify that predictions for the anoma…
A mostly right-handed sneutrino as the lightest supersymmetric particle (LSP) is an interesting dark matter candidate, leading to LHC signatures which can be quite distinct from those of the conventional neutralino LSP. Using SModelSv1.0.1 for testing the model against the limits published by ATLAS and CMS in the context of so-called Simplified Model Spectra (SMS), we investigate to what extent the supersymmetry searches at Run 1 of the LHC constrain the sneutrino-LSP scenario. Moreover, we discuss the most relevant topologies for which no SMS results are provided by the experimental collabora…
We study an extension of the minimal supersymmetric standard model (MSSM) with additional right-handed singlet neutrino superfields. While such an extension incorporates a mechanism for the neutrino mass, it also opens up the possibility of having the right-sneutrinos ($\widetildeν$) as the lightest supersymmetric particle (LSP). In this work, we focus on the the viability of rather small ($\lesssim 500$ GeV) higgsino mass parameter ($μ$), an important ingredient for "naturalness", in the presence of such a LSP. For simplicity, we assume that the bino and wino mass parameters are much heavier,…
Non-zero trilinear parameter in the mSUGRA model - dark matter and collider signals at Tevatron and LHC
在具有小$m_0$和小$m_{1/2}$的最小超引力（mSUGRA）模型中，参数空间的现象学上可行和有趣的区域与WMAP关于暗物质遗迹密度的数据和LEP 2中最轻的希格斯标量$ m_h>$ 114 GeV的质量上的束缚一致，如果相当特别的假设$A_0$ =0，则打开，其中$A_0$是常见的三线性软破裂参数，在大多数现有的分析中使用的是放松的。由于该区域对应于相对较轻的方子和胶子，它们可能在LHC实验的早期阶段被广泛探测，因此详细研究了$A_0$的中等或大负值的后果。我们发现，在该区域，最轻超对称粒子对湮灭、超对称粒子对与较轻的τ-slepton（${\tilde τ}_1$）共湮灭和超对称粒子对与较轻的顶夸克（${\tilde t}_1$）共湮灭等过程对观测到的暗物质遗迹密度都有贡献. % \sout{The possibility that a relic density producing ${\tilde t}_1$ can be %observed at the current experiments at the Tevatron is wide open.}一个${\tilde t}_1$，可以参与共湮灭与最轻的中性伴子，以满足WMAP约束的遗迹密度，同时被观察到在目前的实验在Tevatron的可能性是很大的开放。在大型强子对撞机上，大量的夸克-胶子事件导致了一个非常独…
Within the framework of the $μν$SSM, a displaced dilepton signal is expected at the LHC from the decay of a tau left sneutrino as the lightest supersymmetric particle (LSP) with a mass in the range $45 - 100$ GeV. We compare the predictions of this scenario with the ATLAS search for long-lived particles using displaced lepton pairs in $pp$ collisions, considering an optimization of the trigger requirements by means of a high level trigger that exploits tracker information. The analysis is carried out in the general case of three families of right-handed neutrino superfields, where all the neut…
