MinimalU(1)′extension of the minimal supersymmetric standard model

Abstract

Motivated by the apparent need for extending the MSSM and perhaps mitigating naturalness problems associated with the µ parameter and fine-tuning of the soft masses, we augment the MSSM spectrum by a SM gauge singlet chiral superfield, and enlarge the gauge structure by an additional U(1) ′ invariance, so that the gauge and Higgs sectors are relatively secluded. One crucial aspect of U(1) ′ models is the existence of anomalies, cancellation of which may require the inclusion of exotic matter which in turn disrupts the unification of the gauge couplings. In this work we pursue the question of canceling the anomalies with a minimal matter spectrum and no exotics. This can indeed be realized provided that U(1) ′ charges are family-dependent and the soft-breaking sector includes non-holomorphic operators for generating the fermion masses. We provide the most general solutions for U(1) ′ charges by taking into account all constraints from gauge invariance and anomaly cancellation. We analyze various laboratory and astrophysical bounds ranging from fermion masses to relic density, for an illustrative set of parameters. The U(1) ′ charges admit patterns of values for which family nonuniversality resides solely in the lepton sector, though this does not generate leptonic FCNCs due to the U(1) ′ gauge invariance. *

Search for gauge extensions of the MSSM at the LHC

“…The left side of the table lists the particle spectrum of the G SM Uð1Þ 0 model whereas on the right side, the chiral fieldsN,D u andD d form a sector necessary for canceling the anomalies [19], yet too heavy to leave any significant impact on the LHC experiments [9]. Clearly, Uð1Þ c is a viable model for solving the problem of the MSSM but Uð1Þ is not.…”

“…The gluinos, unlike the SUð2Þ L Uð1Þ Y Uð1Þ 0 gauginos, can be pair-produced via the gluon exchange in the s-channel at the LHC energies via pp !gg;qq;gq; (19) through gluon-gluon, gluon-quark and quark-quark scattering [17]. Following their production, gluinos and squarks decay further.…”

“…This observation is consistent with the region of the parameter space considered here, since for instance, scalar neutrinos heavier than~0 2 and scalar leptons would make it competitive with the others. Table V [19][20][21]. We discuss these plots in terms of their ability to discriminative between the MSSM and Uð1Þ 0 models.…”

“…Indeed, the lightest Higgs boson h in the Uð1Þ 0 model weighs well above M Z already at tree level [3], and thus, large radiative corrections (and hence large top-stop mass splitting) are not warranted to satisfy the LEP lower bound on m h [12][13][14]. This property can prove useful in moderating the little hierarchy problem (especially when a set of the MSSM singlet chiral fields are included to form a secluded sector [19]). …”

Tension between gauge coupling unification, the Higgs boson mass, and a gauge-breaking origin of the supersymmetricμ-term

“…The simplest choice for such a symmetry, and the one we shall consider in the present work, is a U (1) X gauge symmetry in addition to the G SM = SU (3) × SU (2) × U (1) Y gauge symmetry of the MSSM [10,11,12,13]. The choice of a U (1) X is also attractive because its lone gauge boson will be massive after symmetry breaking.…”