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Extensions of the minimal supersymmetric standard model (MSSM) gauge group abound in the literature. Several of these include an additional $U(1)_X$ gauge group. Chiral fermions charge assignments under $U(1)_X$ are constrained to cancel local anomalies in the extension and they determine the structure and phenomenology of it. We provide all anomaly-free charge assignments up to a maximum absolute charge of $Q_text{max}=10$, assuming that the chiral superfield content of the model is that of the MSSM plus up to three Standard Model (SM) singlet superfields. The fermionic components of these SM singlets may play the r^{o}le of right-handed neutrinos, whereas one of the scalar components may play the r^{o}le of the flavon, spontaneously breaking $U(1)_X$. Easily scanned lists of the charge assignments are made publicly available on Zenodo. For the case where no restriction is placed upon $Q_text{max}$, we also provide an analytic parameterisation of the general solution using simple techniques from algebraic geometry.
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Spontaneously broken, flavour-dependent, gauged $U(1)$ extensions of the Standard Model (SM) have many phenomenological uses. We chart the space of solutions to the gauge anomaly cancellation equations in such extensions, for both the SM chiral fermion content and the SM plus (up to) three right-handed neutrinos (SM$ u_R$). Methods from Diophantine analysis allow us to efficiently index the solutions arithmetically, and produce the complete solution space in particular cases. In order to solve the general case, we build a computer program which cycles through possible $U(1)$ charge assignments, providing all solutions for charges up to some pre-defined maximum absolute charge. Lists of anomaly-free $U(1)$ charge assignments result, which corroborate the results of our Diophantine analysis. We make these lists, which may be queried for further desirable properties, publicly available. This previously uncharted space of anomaly-free charge assignments has been little explored until now, paving the way for future model building and phenomenological studies.
We perform a study of the stability of R-parity-conserving vacua of a constrained version of the minimal supersymmetric model with a gauged U(1)_{B-L} which can conserve R-parity, using homotopy continuation to find all the extrema of the tree-level potential, for which we also calculated the one-loop corrections. While we find that a majority of the points in the parameter space preserve R-parity, we find that a significant portion of points which naively have phenomenologically acceptable vacua which conserve R-parity actually have deeper vacua which break R-parity through sneutrino VEVs. We investigate under what conditions the deeper R-parity-violating vacua appear. We find that while previous exploratory work was broadly correct in some of its qualitative conclusions, we disagree in detail.
The Fermilab Muon $g-2$ collaboration recently announced the first result of measurement of the muon anomalous magnetic moment ($g-2$), which confirmed the previous result at the Brookhaven National Laboratory and thus the discrepancy with its Standard Model prediction. We revisit low-scale supersymmetric models that are naturally capable to solve the muon $g-2$ anomaly, focusing on two distinct scenarios: chargino-contribution dominated and pure-bino-contribution dominated scenarios. It is shown that the slepton pair-production searches have excluded broad parameter spaces for both two scenarios, but they are not closed yet. For the chargino-dominated scenario, the models with $m_{tilde{mu}_{rm L}}gtrsim m_{tilde{chi}^{pm}_1}$ are still widely allowed. For the bino-dominated scenario, we find that, although slightly non-trivial, the region with low $tan beta$ with heavy higgsinos is preferred. In the case of universal slepton masses, the low mass regions with $m_{tilde{mu}}lesssim 230$ GeV can explain the $g-2$ anomaly while satisfying the LHC constraints. Furthermore, we checked that the stau-bino coannihilation works properly to realize the bino thermal relic dark matter. We also investigate heavy staus case for the bino-dominated scenario, where the parameter region that can explain the muon $g-2$ anomaly is stretched to $m_{tilde{mu}}lesssim 1.3$ TeV.
Recent LHC data significantly extend the exclusion limits for supersymmetric particles, particularly in the jets plus missing transverse momentum channels. The most recent such data have so far been interpreted by the experiment in only two different supersymmetry breaking models: the constrained minimal supersymmetric standard model (CMSSM) and a simplified model with only squarks and gluinos and massless neutralinos. We compare kinematical distributions of supersymmetric signal events predicted by the CMSSM and anomaly mediated supersymmetry breaking (mAMSB) before calculating exclusion limits in mAMSB. We obtain a lower limit of 900 GeV on squark and gluino masses at the 95% confidence level for the equal mass limit, tan(beta)=10 and mu>0.
Local supersymmetry (SUSY) provides an attractive framework for the incorporation of gravity and unification of gauge interactions within Grand Unified Theories (GUTs). Its breakdown can lead to a variety of models with softly broken SUSY at low energies. In this review article we focus on the SUSY extension of the Standard Model (SM) with an extra U(1)_{N} gauge symmetry originating from a string-inspired E_6 grand unified gauge group. Only in this U(1) extension of the minimal supersymmetric standard model (MSSM) inspired by E_6 GUTs the right-handed neutrinos can be superheavy providing a mechanism for the generation of the lepton and baryon asymmetry of the Universe. The particle content of this exceptional supersymmetric standard model (E_6SSM) includes three 27 representations of the E_6 group, to ensure anomaly cancellation, plus a pair of SU(2)_W doublets as required for gauge coupling unification. Thus E_6SSM involves extra exotic matter beyond the MSSM. We consider symmetries that permit to suppress non-diagonal flavour transitions and rapid proton decay, as well as gauge coupling unification, the breakdown of the gauge symmetry and the spectrum of Higgs bosons in this model. The possible Large Hadron Collider (LHC) signatures caused by the presence of exotic states are also discussed.
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