Gravitino Dark Matter in the CMSSM With Improved Constraints from BBN

In the framework of the Constrained MSSM we re--examine the gravitino as the lightest superpartner and a candidate for cold dark matter in the Universe. Unlike in other recent studies, we include both a thermal contribution to its relic population from scatterings in the plasma and a non--thermal one from neutralino or stau decays after freeze--out. Relative to a previous analysis [1] we update, extend and considerably improve our treatment of constraints from observed light element abundances on additional energy released during BBN in association with late gravitino production. Assuming the gravitino mass in the GeV to TeV range, and for natural ranges of other supersymmetric parameters, the neutralino region is excluded, while for smaller values of the gravitino mass it becomes allowed again. The gravitino relic abundance is consistent with observational constraints on cold dark matter from BBN and CMB in some well defined domains of the stau region but, in most cases, only due to a dominant contribution of the thermal population. This implies, depending on the gravitino mass, a large enough reheating temperature. If \mgravitino>1 GeV then $T_R>10^7$ GeV, if allowed by BBN and other constraints but, for light gravitinos, if \mgravitino>100 keV then $T_R>3\times 10^3$ GeV. On the other hand, constraints mostly from BBN imply an upper bound T_R \lsim {a few}x 10^8\times10^9 GeV which appears inconsistent with thermal leptogenesis. Finally, most of the preferred stau region corresponds to the physical vacuum being a false vacuum. The scenario can be partially probed at the LHC.Comment: Version with Erratum. Numerical bug fixed. An upper bound on the reheating temperature strengthened by about an order of magnitud

Highlights of the DNA cutters:a short history of the restriction enzymes

In the early 1950’s, ‘host-controlled variation in bacterial viruses’ was reported as a non-hereditary phenomenon: one cycle of viral growth on certain bacterial hosts affected the ability of progeny virus to grow on other hosts by either restricting or enlarging their host range. Unlike mutation, this change was reversible, and one cycle of growth in the previous host returned the virus to its original form. These simple observations heralded the discovery of the endonuclease and methyltransferase activities of what are now termed Type I, II, III and IV DNA restriction-modification systems. The Type II restriction enzymes (e.g. EcoRI) gave rise to recombinant DNA technology that has transformed molecular biology and medicine. This review traces the discovery of restriction enzymes and their continuing impact on molecular biology and medicine

Low-mass right-handed sneutrino dark matter: SuperCDMS and LUX constraints and the Galactic Centre gamma-ray excess

Recent results from direct and indirect searches for dark matter (DM) have motivated the study of particle physics models that can provide weakly interacting massive particles (WIMPs) in the mass range 1–50 GeV. Viable candidates for light WIMP DM must fulfil stringent constraints. On the one hand, the observation at the LHC of a Higgs boson with Standard Model properties set an upper bound on the coupling of light DM particles to the Higgs, thereby making it difficult to reproduce the correct relic abundance. On the other hand, the recent results from direct searches in the CDMSlite, SuperCDMS and LUX experiments have set upper constraints on the DM scattering cross section. In this paper, we investigate the viability of light right-handed sneutrino DM in the Next-to-Minimal Supersymmetric Model (NMSSM) in the light of these constraints. To this aim, we have carried out a scan in the NMSSM parameter space, imposing experimental bounds on the Higgs sector and low-energy observables, such as the muon anomalous magnetic moment and branching ratios of rare decays. We demonstrate that the enlarged Higgs sector of the NMSSM, together with the flexibility provided by the RH sneutrino parameters, make it possible to obtain viable RH sneutrino DM with a mass as light as 2 GeV. We have also considered the upper bounds on the annihilation cross section from Fermi LAT data on dwarf spheroidal galaxies, and extracted specific examples with mass in the range 8–50 GeV that could account for the apparent low-energy excess in the gamma-ray emission at the Galactic Centre. Then, we have computed the theoretical predictions for the elastic scattering cross-section of RH sneutrinos. Finally, after imposing the recent bounds from SuperCDMS and LUX, we have found a wide area of the parameter space that could be probed by future low-threshold direct detectio

Unstable Gravitino Dark Matter and Neutrino Flux.

The gravitino is a promising supersymmetric dark matter candidate which does not require exact R-parity conservation. In fact, even with some small R-parity breaking, gravitinos are sufficiently long-lived to constitute the dark matter of the Universe, while yielding a cosmological scenario consistent with primordial nucleosynthesis and the high reheating temperature required for thermal leptogenesis. In this paper, we compute the neutrino flux from direct gravitino decay and gauge boson fragmentation in a simple scenario with bilinear R-parity breaking. Our choice of parameters is motivated by a proposed interpretation of anomalies in the extragalactic gamma-ray spectrum and the positron fraction in terms of gravitino dark matter decay. We find that the generated neutrino flux is compatible with present measurements. We also discuss the possibility of detecting these neutrinos in present and future experiments and conclude that it is a challenging task. However, if detected, this distinctive signal might bring significant support to the scenario of gravitinos as decaying dark matter.Comment: 24 pages, 8 figures; references added and typos corrected, agrees with published versio

Towards the next generation of simplified Dark Matter models

This White Paper is an input to the ongoing discussion about the extension and refinement of simplified Dark Matter (DM) models. It is not intended as a comprehensive review of the discussed subjects, but instead summarises ideas and concepts arising from a brainstorming workshop that can be useful when defining the next generation of simplified DM models (SDMM). In this spirit, based on two concrete examples, we show how existing SDMM can be extended to provide a more accurate and comprehensive framework to interpret and characterise collider searches. In the first example we extend the canonical SDMM with a scalar mediator to include mixing with the Higgs boson. We show that this approach not only provides a better description of the underlying kinematic properties that a complete model would possess, but also offers the option of using this more realistic class of scalar mixing models to compare and combine consistently searches based on different experimental signatures. The second example outlines how a new physics signal observed in a visible channel can be connected to DM by extending a simplified model including effective couplings. In the next part of the White Paper we outline other interesting options for SDMM that could be studied in more detail in the future. Finally, we review important aspects of supersymmetric models for DM and use them to propose how to develop more complete SDMMs. This White Paper is a summary of the brainstorming meeting “Next generation of simplified Dark Matter models” that took place at Imperial College, London on May 6, 2016, and corresponding follow-up studies on selected subjects