Proposal for a Supersymmetric Standard Model

The fact that neutrinos are massive suggests that the minimal supersymmetric standard model (MSSM) might be extended in order to include three gauge-singlet neutrino superfields with Yukawa couplings of the type $H_2 L \nu^c$. We propose to use these superfields to solve the $\mu$ problem of the MSSM without having to introduce an extra singlet superfield as in the case of the next-to-MSSM (NMSSM). In particular, terms of the type $\nu^c H_1 H_2$ in the superpotential may carry out this task spontaneously through sneutrino vacuum expectation values. In addition, terms of the type $(\nu^c)^3$ avoid the presence of axions and generate effective Majorana masses for neutrinos at the electroweak scale. On the other hand, these terms break lepton number and R-parity explicitly implying that the phenomenology of this model is very different from the one of the MSSM or NMSSM. For example, the usual neutralinos are now mixed with the neutrinos. For Dirac masses of the latter of order $10^{-4}$ GeV, eigenvalues reproducing the correct scale of neutrino masses are obtained.Comment: 9 pages, latex, title modified. Final version published in PR

On a reinterpretation of the Higgs field in supersymmetry and a proposal for new quarks

In the framework of supersymmetry, when R-parity is violated the Higgs doublet superfield Hd can be interpreted as another doublet of leptons, since all of them have the same quantum numbers. Thus Higgs scalars are sleptons and Higgsinos are leptons. We argue that this interpretation can be extended to the second Higgs doublet superfield Hu, when right-handed neutrinos are assumed to exist. As a consequence, we advocate that this is the minimal construction where the two Higgs doublets can be interpreted in a natural way as a fourth family of lepton superfields, and that this is more satisfactory than the usual situation in supersymmetry where the Higgses are ‘disconnected’ from the rest of the matter and do not have a three-fold replication. On the other hand, in analogy with the first three families where for each lepton representation there is a quark counterpart, we propose a possible extension of this minimal model including a vector-like quark doublet representation as part of the fourth family. We also discuss the phenomenology of the associated new quarksThe work of D.E. López-Fogliani was supported by the Argentinian CONICET. He acknowledges the hospitality of the IFT during whose stay this work was started. The work of C. Muñoz was supported in part by the Programme SEV-2012-0249 ‘Centro de Excelencia Severo Ochoa’. We also acknowledge the support of the Spanish grant FPA2015-65929-P (MINECO/FEDER, UE), and MINECO’s Consolider-Ingenio 2010 Programme under grant MultiDark CSD2009-0006

The Higgs sector of the munuSSM and collider physics

The $\mu\nu$SSM is a supersymmetric standard model that accounts for light neutrino masses and solves the $\mu$ problem of the MSSM by simply using right-handed neutrino superfields. Since this mechanism breaks R-parity, a peculiar structure for the mass matrices is generated. The neutral Higgses are mixed with the right- and left-handed sneutrinos producing 8$\times$8 neutral scalar mass matrices. We analyse the Higgs sector of the $\mu\nu$SSM in detail, with special emphasis in possible signals at colliders. After studying in general the decays of the Higges, we focus on those processes that are genuine of the $\mu\nu$SSM, and could serve to distinguish it from other supersymmetric models. In particular, we present viable benchmark points for LHC searches. For example, we find decays of a MSSM-like Higgs into two lightest neutralinos, with the latter decaying inside the detector leading to displaced vertices, and producing final states with 4 and 8 $b$-jets plus missing energy. Final states with leptons and missing energy are also found.Comment: Final version to appear in JHEP. The discussion on signals at colliders, expanded. 33 pages, 8 figures and 9 table

WIMP Dark Matter in the Uμν\mu \nuSSM

The U$\mu\nu$SSM is a $U(1)'$ extension of the $\mu\nu$SSM supersymmetric model, where baryon-number-violating operators as well as explicit mass terms are forbidden, and the potential domain wall problem is avoided. The gauge anomaly-cancellation conditions impose the presence of exotic quark superfields in the spectrum of U$\mu\nu$SSM models, and allow the presence of several singlet superfields under the standard model gauge group, in addition to the right-handed neutrino superfields. The gauge structure implies an additional discrete $Z_2$ symmetry in the superpotential, ensuring the stability of a singlet which behaves as WIMP dark matter without invoking $R$-parity. We analyze this novel possibility in detail, using the fermionic component of the singlet as the dark matter candidate. In particular, we compute its amount of relic density via $Z'$, Higgs-right sneutrino and dark matter mediated annihilations, and its potential signals in dark matter direct detection experiments. The constraints on the parameter space due to $Z'$ direct searches at the LHC are imposed in the analysis, as well as those from the hadronization inside the detector of the exotic quarks. Large regions of the parameter space turn out to be in the reach of the upcoming Darwin experiment

WIMP Dark Matter in the Uμν\mu \nuSSM

The U$\mu \nu$SSM is a U(1)' extension of the U$\mu \nu$SSM supersymmetric model, where baryon-number-violating operators as well as explicit mass terms are forbidden, and the potential domain wall problem is avoided. The gauge anomaly-cancellation conditions impose the presence of exotic quark superfields in the spectrum of U$\mu \nu$SSM models, and allow the presence of several singlet superfields under the standard model gauge group, in addition to the right-handed neutrino superfields. The gauge structure implies an additional discrete Z $_{2}$ symmetry in the superpotential, ensuring the stability of a singlet which behaves as WIMP dark matter without invoking R-parity. We analyze this novel possibility in detail, using the fermionic component of the singlet as the dark matter candidate. In particular, we compute its amount of relic density via Z', Higgs-right sneutrino and dark matter mediated annihilations, and its potential signals in dark matter direct detection experiments. The constraints on the parameter space due to Z'; direct searches at the LHC are imposed in the analysis, as well as those from the hadronization inside the detector of the exotic quarks. Large regions of the parameter space turn out to be in the reach of the upcoming Darwin experiment

Exotic diboson Z ' decays in the U mu nu SSM

We thank Javier Aguilar-Saavedra for the use of computing resources. The research of JAAS was supported by the Spanish Agencia Estatal de Investigacion (AEI) through project PID2019-110058GB-C21. The work of IL was funded by the Norwegian Financial Mechanism 2014-2021, grant DEC-2019/34/H/ST2/00707. The work of DL was supported by the Argentinian CONICET, and also acknowledges the support through PIP 11220170100154CO. The research of CM was supported by the Spanish AEI through the grants PGC2018-095161-B-I00 and IFT Centro de Excelencia Severo Ochoa SEV-2016-0597. The authors acknowledge the support of the Spanish Red Consolider MultiDark FPA2017-90566-REDC.Searches for new leptophobic resonances at high energy colliders usually target their decay modes into pairs of light quarks, top quarks, or standard model bosons. Additional decay modes may also be present, producing signatures to which current searches are not sensitive. We investigate the performance of generic searches that look for resonances decaying into two large-radius jets. As benchmark for our analysis we use a supersymmetric U(1) extension of the Standard Model, the so-called UμνSSM, where all the SM decay modes of the Z boson take place, plus additional (cascade) decays into new scalars. The generic searches use a generic multi-pronged jet tagger and take advantage of the presence of b quarks in the large-radius jets, and are sensitive to all these Z decay modes (except into light quarks) at once. For couplings that are well below current experimental constraints, these generic searches are sensitive at the 3σ − 4σ level with Run 2 LHC data.Spanish Agencia Estatal de Investigacion (AEI) PID2019-110058GB-C21Norwegian Financial Mechanism 2014-2021 DEC-2019/34/H/ST2/00707Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET)IFT Centro de Excelencia Severo Ochoa SEV-2016-0597Spanish Red Consolider MultiDark FPA2017-90566-REDCSpanish AEI PGC2018-095161-B-I00 PIP 11220170100154C