Less Minimal Supersymmetric Standard Model

Most of the phenomenological studies of supersymmetry have been carried out using the so-called minimal supergravity scenario, where one assumes a universal scalar mass, gaugino mass, and trilinear coupling at MGUT . Even though this is a useful simplifying assumption for phenomenological analyses, it is rather too restrictive to accommodate a large variety of phenomenological possibilities. It predicts, among other things, that the lightest supersymmetric particle (LSP) is an almost pure B-ino, and that the μ-parameter is larger than the masses of the SU(2)L and U(1)Y gauginos. We extend the minimal supergravity framework by introducing one extra parameter: the Fayet–Iliopoulos D-term for the hypercharge U(1), DY . Allowing for this extra parameter, we find a much more diverse phenomenology, where the LSP is ν̃τ , τ̃ or a neutralino with a large higgsino content. We discuss the relevance of the different possibilities to collider signatures. The same type of extension can be done to models with the gauge mediation of supersymmetry breaking. We argue that it is not wise to impose cosmological constraints on the parameter space. ∗This work was supported in part by the U.S. Department of Energy under Contracts DE-AC03-76SF00098, in part by the National Science Foundation under grant PHY-9514797. AdG was also supported by CNPq (Brazil). HM was also supported by the Alfred P. Sloan Foundation. Supersymmetry (SUSY) is regarded as one of the most promising extensions of the Standard Model. A supersymmetric version of the Standard Model will be the subject of exhaustive searches in this and the next generation of collider experiments. The Lagrangian of the minimal supersymmetric extension of the Standard Model, the so-called “Minimal Supersymmetric Standard Model” (MSSM), consists of a SUSY-preserving piece and a SUSY-breaking piece[1]. The SUSY-preserving piece contains all of the Standard Model parameters plus the so-called μ-term, once R-parity is imposed to prevent baryon/lepton number violation. In this letter, we assume an exact or approximate Rparity, which implies that the lightest supersymmetric particle (LSP) does not decay inside detectors. The SUSY-breaking Lagrangian will, ultimately, be determined by the physics of supersymmetry breaking and flavor but at the moment the best approach is to simply parameterize it with a general set of explicitly SUSYbreaking parameters. A general explicit soft SUSY-breaking Lagrangian LSUSY = −m 2 Hd |Hd| 2 −m2Hu|Hu| 2 + (BμHuHd +H.c.)