Low-scale Scenarios Research Articles

TeV scale leptogenesis with dark matter in non-standard cosmology

We study the consequence of a non-standard cosmological epoch in the early universe on the generation of baryon asymmetry through leptogenesis as well as dark matter abundance. We consider two different non-standard epochs: one where a scalar field behaving like pressure-less matter dominates the early universe, known as early matter domination (EMD) scenario while in the second scenario, the energy density of the universe is dominated by a component whose energy density red-shifts faster than radiation, known as fast expanding universe (FEU) scenario. While a radiation dominated universe is reproduced by the big bang nucleosynthesis (BBN) epoch in both the scenario, the high scale phenomena like generation of baryon asymmetry and dark matter relic get significantly affected. Adopting a minimal particle physics framework known as the scotogenic model which generates light neutrino masses at one-loop level, we find that in one specific realisation of EMD scenario, the scale of leptogenesis can be lower than that in a standard cosmological scenario. The other non-standard cosmological scenarios, on the other hand, can be constrained from the requirement of successful low scale leptogenesis and generating correct dark matter abundance simultaneously. Such a low scale scenario not only gives a unified picture of baryon asymmetry, dark matter and origin of neutrino mass but also opens up interesting possibilities for experimental detection.

GMSB with light stops

Gauge mediated supersymmetry breaking (GMSB) is an elegant mechanism to transmit supersymmetry breaking from the hidden to the MSSM observable sector, which solves the supersymmetric avor problem. However the smallness of the generated stop mixing requires superheavy stops to reproduce the experimental value of the Higgs mass. A possible way out is to extend the MSSM Higgs sector with singlets and/or triplets providing extra tree-level corrections to the Higgs mass. Singlets will not get any soft mass from GMSB and triplets will contribute to the parameter which could be an issue. In this paper we explore the second possibility by introducing extra supersymmetric triplets with hypercharges Y = (0; 1), with a tree-level custodial SU(2)L SU(2)R global symmetry in the Higgs sector protecting the parameter: a supersymmetric generalization of the Georgi-Machacek model, dubbed as supersymmetric custodial triplet model (SCTM). The renormalization group running from the messenger to the electroweak scale mildly breaks the custodial symmetry. We will present realistic low-scale scenarios (with the NLSP being a Bino-like neutralino or the right-handed stau) based on general (non-minimal) gauge mediation and consistent with all present experimental data. Their main features are: i) Light ( 1 TeV) stops; ii) Exotic couplings (H W Z and H W W ) absent in the MSSM and proportional to the triplets VEV, v ; and, iii) A possible (measurable) universality breaking of the Higgs couplings WZ = rWW=rZZ6 1.

SLAM, a Mathematica interface for SUSY spectrum generators

We present and publish a Mathematica package, which can be used to automatically obtain any numerical MSSM input parameter from SUSY spectrum generators, which follow the SLHA standard, like SPheno, SOFTSUSY, SuSeFLAV or Suspect. The package enables a very comfortable way of numerical evaluations within the MSSM using Mathematica. It implements easy to use predefined high scale and low scale scenarios like mSUGRA or mhmax and if needed enables the user to directly specify the input required by the spectrum generators. In addition it supports an automatic saving and loading of SUSY spectra to and from a SQL data base, avoiding the rerun of a spectrum generator for a known spectrum. Program summaryProgram title: SLAMCatalogue identifier: AERX_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AERX_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 4387No. of bytes in distributed program, including test data, etc.: 37748Distribution format: tar.gzProgramming language: Mathematica.Computer: Any computer where Mathematica version 6 or higher is running providing bash and sed.Operating system: Linux.Classification: 11.1.External routines: A SUSY spectrum generator such as SPheno, SOFTSUSY, SuSeFLAV or SUSPECTNature of problem:Interfacing published spectrum generators for automated creation, saving and loading of SUSY particle spectra.Solution method:SLAM automatically writes/reads SLHA spectrum generator input/output and is able to save/load generated data in/from a data base.Restrictions:No general restrictions, specific restrictions are given in the manuscript.Running time:A single spectrum calculation takes much less than one second on a modern PC.