Long-lived staus from strong production in a simplified model approach

We study the phenomenology of a supersymmetric scenario where the next-to-lightest superparticle is the lighter stau and long-lived due to a very weakly coupled lightest superparticle, such as the gravitino. We investigate the LHC sensitivity and its dependence on the superparticle spectrum with an emphasis on strong production and decay. We do not assume any high-scale model for SUSY breaking but work along the lines of simplified models. Devising cuts that yield a large detection efficiency in the whole parameter space, we determine the LHC's discovery and exclusion potential. This allows us to derive robust limits on m_stau, m_gluino, a common m_squark, and m_stop1. We briefly discuss the prospects for observing stopped staus.Comment: 25 pages + references, 27 eps figures; v3: Matches journal version, typo in table 1 correcte

Leptogenesis, Gravitino Dark Matter and Entropy Production

Many extensions of the Standard Model predict super-weakly interacting particles, which typically have to decay before Big Bang Nucleosynthesis (BBN). The entropy produced in the decays may help to reconcile thermal leptogenesis and BBN in scenarios with gravitino dark matter, which is usually difficult due to late decays of the next-to-lightest supersymmetric particle (NLSP) spoiling the predictions of BBN. We study this possibility for a general neutralino NLSP. We elaborate general properties of the scenario and strong constraints on the entropy-producing particle. As an example, we consider the saxion from the axion multiplet and show that, while enabling a solution of the strong CP problem, it can also produce a suitable amount of entropy.Comment: 28 pages, 3 figures; v2: references updated, changes in presentation including some generalization, results and conclusions unchanged; v3: 1 reference added, matches published versio

Small-Scale Crisis in Cosmology – Sterile Neutrinos to the Rescue?

The ΛCDM standard model of cosmology is in excellent agreement with data on large scales but has difficulty explaining all observations on small scales. I discuss a simple particle physics model involving a new MeV-scale gauge boson that mediates dark matter self-interactions and dark matter interactions with a new light fermion. This allows to solve all small-scale problems of ΛCDM cosmology. It would be very attractive to identify the new light particle with a sterile neutrino, but it appears that this option is disfavored.publishedVersio

Trilinear-Augmented Gaugino Mediation

We consider a gaugino-mediated supersymmetry breaking scenario where in addition to the gauginos the Higgs fields couple directly to the field that breaks supersymmetry. This yields non-vanishing trilinear scalar couplings in general, which can lead to large mixing in the stop sector providing a sufficiently large Higgs mass. Using the most recent release of FeynHiggs, we show the implications on the parameter space. Assuming a gravitino LSP, we find allowed points with a neutralino, sneutrino or stau NLSP. We test these points against the results of Run 1 of the LHC, considering in particular searches for heavy stable charged particles.Comment: 13 pages + references, 4 figures, v4: corrected plot labels in figs. 1-

A survey for low stau yields in the MSSM

We study the implications of LHC results for the abundance of long-lived staus after freeze-out from thermal equilibrium in a super-WIMP dark matter scenario. We classify regions in the MSSM parameter space according to the stau yield, considering all possible co-annihilation effects as well as the effects of resonances and large Higgs-sfermion couplings. Afterwards, we examine the viability of these regions after imposing experimental and theoretical constraints, in particular a Higgs mass around 125 GeV and null-searches for heavy stable charged particles (HSCP) at the LHC. We work in a pMSSM framework and perform a Monte Carlo scan over the parameter space. To interpret the HSCP searches in our scenario, we consider all potentially important superparticle production processes, developing a fast estimator for NLO cross sections for electroweak and strong production at the LHC. After applying all constraints, we find that stau yields below 10^-14 occur only for resonant annihilation via a heavy Higgs in combination with either co-annihilation or large left-right stau mixing. We encounter allowed points with yields as low as 2x10^-16, thus satisfying limits from big bang nucleosynthesis even for large stau lifetimes.Comment: 60 pages + refereces, 60 eps figures, v2: references added, presentation improved, figure 9 changed, results and conclusions unchanged, matches journal versio

Renormalization Group Analysis of Neutrino Mass Parameters

Tools for calculating the Renormalization Group Equations for renormalizable and non-renormalizable operators in various theories are reviewed, which are essential for comparing experimental results with predictions from models beyond the Standard Model. Numerical examples for the running of the lepton mixing angles in models with non-degenerate see-saw scales are shown, in which the best-fit values of the experimentally favored LMA solution are produced from maximal or from vanishing solar neutrino mixing at the GUT scale.Comment: 6 pages, 17 figures; to appear in the proceedings of the 10th International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY02), June 17 - 23, DESY Hambur

Neutrino Mass Operator Renormalization Revisited

We re-derive the renormalization group equation for the effective coupling of the dimension five operator which corresponds to a Majorana mass matrix for the Standard Model neutrinos. We find a result which differs somewhat from earlier calculations, leading to modifications in the evolution of leptonic mixing angles and CP phases. We also present a general method for calculating beta-functions from counterterms in MS-like renormalization schemes, which works for tensorial quantities.Comment: 9 pages, 2 figures, references update

Supersymmetric Musings on the Predictivity of Family Symmetries

We discuss the predictivity of family symmetries for the soft supersymmetry breaking parameters in the framework of supergravity. We show that unknown details of the messenger sector and the supersymmetry breaking hidden sector enter into the soft parameters, making it difficult to obtain robust predictions. We find that there are specific choices of messenger fields which can improve the predictivity for the soft parameters.Comment: 20 pages, 5 figure

Neutrino Mass Matrix Running for Non-Degenerate See-Saw Scales

We consider the running of the neutrino mass matrix in the Standard Model and the Minimal Supersymmetric Standard Model, extended by heavy singlet Majorana neutrinos. Unlike previous studies, we do not assume that all of the heavy mass eigenvalues are degenerate. This leads to various effective theories when the heavy degrees of freedom are integrated out successively. We calculate the Renormalization Group Equations that govern the evolution of the neutrino mass matrix in these effective theories. We show that an appropriate treatment of the singlet mass scales can yield a substantially different result compared to integrating out the singlets at a common intermediate scale.Comment: 12 pages, 9 figure