Search

We investigate the production of antideuterons from decaying dark matter, using gravitinos in supersymmetric models with trilinear R-parity violating (RPV) operators as an example. The model used for antideuteron formation is shown to induce large uncertainties in the predicted flux, comparable to uncertainties from cosmic-ray propagation models. We improve on the formation model by tuning hadronization and coalesence parameters in Monte Carlo simulations to better reproduce the hadron spectra relevant for antideuteron production. In light of current bounds on fluxes and future prospects from the AMS-II and GAPS experiments we set limits on RPV couplings as a function of the gravitino mass., Updated; corresponds to version published in Phys. Rev. D. 14 pages, 9 figures

Supersymmetric models with a small neutralino-chargino mass difference, and as a result metastable charginos, have been a popular topic of investigation in collider phenomenology, e.g. in anomaly-mediated models of supersymmetry breaking. Recently, the absence of any supersymmetric signal at the 8 TeV LHC data has led to significant interest in the so-called Natural SUSY models with light higgsinos. These models also have a naturally small neutralino-chargino mass difference. However, we show here that when relevant indirect constraints from results at the LHC and elsewhere are applied, this possibility is heavily constrained within the Minimal Supersymmetric Standard Model (MSSM): massive metastable higgsinos are not a signature of Natural SUSY., Comment: Extended discussion, updated references, matches version to appear in JHEP

Supersymmetric models with R-parity violation (RPV) have become more popular following the lack of any excess of missing energy events at the 8 TeV LHC. To identify such models, the suggested searches generally rely on the decay products of the (effectively) lightest supersymmetric particle (LSP), with signals that depend on the identity of the LSP and the relevant RPV operators. Here we look at the prospects for detecting RPV chargino decays at the LHC and find substantial patches of parameter space in the Minimal Supersymmetric Standard Model with possibly spectacular signatures, such as three charged-lepton resonances., Comment: Version published in JHEP

This chapter of the 'Flavor in the era of LHC' workshop report discusses flavor-related issues in the production and decays of heavy states at the LHC at high momentum transfer Q, both from the experimental and the theoretical perspective. We review top quark physics, and discuss the flavor aspects of several extensions of the standard model, such as supersymmetry, little Higgs models or models with extra dimensions. This includes discovery aspects, as well as the measurement of several properties of these heavy states. We also present publicly available computational tools related to this topic. © Springer-Verlag / Società Italiana di Fisica 2008., 0, SCOPUS: ar.j, info:eu-repo/semantics/published

Presented at: European Physical Society Europhysics Conference on High Energy Physics. Krakow, Poland, July 16-22, 2009 We study the charged cosmic rays arising from the slow decay of gravitino dark matter within supersymmetric scenarios with trilinear R-parity violation. It is shown that operators of the LLE type can very well account for the recent anomalies in cosmic ray electron and positron data reported by PAMELA, ATIC and Fermi LAT, without violating any other bounds. This scenario will soon be tested by the Fermi LAT data on diffuse gamma ray emission. publishedVersion

Recently there has been much interest in the use of single-jet mass and jet substructure to identify boosted particles decaying hadronically at the LHC. We develop these ideas to address the challenging case of a neutralino decaying to three quarks in models with baryonic violation of R-parity. These decays have previously been found to be swamped by QCD backgrounds. We demonstrate for the first time that such a decay might be observed directly at the LHC with high significance, by exploiting characteristics of the scales at which its composite jet breaks up into subjets., 5 pages, 3 figures; updated to reflect content of published paper

Decay-frame Kinematics (DK) has previously been introduced as a technique to reconstruct neutralino masses from their three-body decays to leptons. This work is an extension to the case of two-body decays through on-shell sleptons, with Monte Carlo simulation of LHC collisions demonstrating reconstruction of neutralino masses for the SPS1a benchmark point., 17 pages, 5 figures

We study the charged cosmic rays arising from the slow decay of gravitino dark matter within supersymmetric scenarios with trilinear R-parity violation. It is shown that operators of the LLE type can very well account for the recent anomalies in cosmic ray electron and positron data reported by PAMELA, ATIC and Fermi LAT, without violating any other bounds. This scenario will soon be tested by the Fermi LAT data on diffuse gamma ray emission., Comment: To appear in the proceedings of EPS-HEP 2009, Krakow, Poland

We study photonic, neutrino and charged particle signatures from slow decays of gravitino dark matter in supersymmetric theories where R-parity is explicitly broken by trilinear operators. Photons and (anti-)fermions from loop and tree-level processes give rise to spectra with distinct features, which, if observed, can give crucial input on the possible mass of the gravitino and the magnitude and flavour structure of R-violating operators. Within this framework, we make detailed comparisons of the theoretical predictions to the recent experimental data from PAMELA, ATIC and Fermi LAT., Comment: Version published in Phys. Lett. B

This chapter of the 'Flavor in the era of LHC' workshop report discusses flavor-related issues in the production and decays of heavy states at the LHC at high momentum transfer Q, both from the experimental and the theoretical perspective. We review top quark physics, and discuss the flavor aspects of several extensions of the standard model, such as supersymmetry, little Higgs models or models with extra dimensions. This includes discovery aspects, as well as the measurement of several properties of these heavy states. We also present publicly available computational tools related to this topic. © Springer-Verlag / Società Italiana di Fisica 2008.

We review the use of invariant mass distributions in cascade decays to measure the masses of New Physics (NP) particles in scenarios where the final NP cascade particle is invisible. We extend earlier work by exploring further the problem of multiple solutions for the masses.

We study radiative gravitino decay within the framework of R-violating supersymmetry. For trilinear R-violating couplings that involve the third generation of fermions, or for light gravitinos, we find that the radiative loop-decay $\tilde{G} \to \gamma \nu$ dominates over the tree-level ones for a wide set of parameters. We calculate the gravitino decay width and study its implications for cosmology and collider physics. Slow-decaying gravitinos are good dark matter candidates, for a range of parameters that would also predict observable R-violating signatures in colliders. In general the branching ratios are very dependent on the relative hierarchies of R-violating operators, and may provide relevant information on the flavour structure of the underlying fundamental theory., Comment: 17 pages, 5 figures

Most sparticle decay cascades envisaged at the Large Hadron Collider (LHC) involve hadronic decays of intermediate particles. We use state-of-the art techniques based on the \kt jet algorithm to reconstruct the resulting hadronic final states for simulated LHC events in a number of benchmark supersymmetric scenarios. In particular, we show that a general method of selecting preferentially boosted massive particles such as W, Z or Higgs bosons decaying to jets, using sub-jets found by the \kt algorithm, suppresses QCD backgrounds and thereby enhances the observability of signals that would otherwise be indistinct. Consequently, measurements of the supersymmetric mass spectrum at the per-cent level can be obtained from cascades including the hadronic decays of such massive intermediate bosons., 1+29 pages, 12 figures

We present our work on reconstructing sparticle masses in purely hadronic decay chains, using the $k_T$ jet-algorithm on Monte Carlo simulated events at LHC energies., Comment: 3 pages, 1 figure, contributed to the proceedings of the EPS HEP 2007 Conference, Manchester (UK)

We investigate the measurement of massive metastable charged particles in ATLAS, using timing information from the resistive plate chambers (RPCs). As representative particle candidates we use staus, the partners of $ au$ leptons in supersymmetric models with gravitino dark matter (GDM), which may well be stable on the scale of the detector. The generic signatures of massive metastable charged particles are a long Time-of-Flight (ToF) and high energy-loss ($dE/dx$). The RPC timing information allows us to measure the ToF of a particle which, taken in conjunction with the measurement of the particle's momentum from its track, allows one to determine its mass. We pioneer the study of the RPCs' potential for this measurement. We also consider triggering effects on the event selection, and discuss quantitatively the ATLAS potential for measuring the stau mass in three specific GDM benchmark scenarios.

In SUSY scenarios with invisible LSP, sparticle masses can be determined from fits to the endpoints of invariant mass distributions. Here we discuss possible improvements by using the shapes of the distributions. Positive results are found for multiple-minima situations and for mass regions where the endpoints do not contain sufficient information to obtain the masses., to appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 2006

We present a new method to search for a light scalar top (stop), decaying dominantly into $c\tilde\chi^0_1$, at the LHC. The principal idea is to exploit the Majorana nature of the gluino, leading to same-sign top quarks in events of gluino pair production followed by gluino decays into top and stop. We demonstrate the reach of our method in terms of the gluino mass and the stop-neutralino mass difference., Comment: 4 pages, 1 figure, to appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 2006

Report of the Landscape session of the Tev4LHC workshop - Synthèse d'une série de 4 Rencontres : TeV4LHC Workshop, tenues à Fermilab, Brookhaven et CERN (2004 - 2005); This is the "TeV4LHC" report of the "Physics Landscapes" Working Group, focused on facilitating the start-up of physics explorations at the LHC by using the experience gained at the Tevatron. We present experimental and theoretical results that can be employed to probe various scenarios for physics beyond the Standard Model.

We present a new method to search for a light scalar top with $m_{\tilde{t}_1}\lsim m_t$, decaying dominantly into a c-jet and the lightest neutralino, at the LHC. The principal idea is to exploit the Majorana nature of the gluino, leading to same-sign top quarks in events of gluino-pair production followed by gluino decays into top and stop. The resulting signature is 2 b-jets plus 2 same-sign leptons plus additional jets and missing energy. We perform a Monte Carlo simulation for a benchmark scenario, which is in agreement with the recent WMAP bound on the relic density of dark matter, and demonstrate that for $m_{\tilde{g}}\lsim 900$ GeV and $m_{\tilde{q}}>m_{\tilde{g}}$ the signal can be extracted from the background. Moreover, we discuss the determination of the stop and gluino masses from the shape of invariant-mass distributions. The derivation of the shape formulae is also given., 20 pages, 6 figures, minor changes; version to appear in PRD

We investigate the measurement of supersymmetric particle masses at the LHC in gravitino dark matter (GDM) scenarios where the next-to-lightest supersymmetric partner (NLSP) is the lighter scalar tau, or stau, and is stable on the scale of a detector. Such a massive metastable charged sparticle would have distinctive Time-of-Flight (ToF) and energy-loss ($dE/dx$) signatures. We summarise the documented accuracies expected to be achievable with the ATLAS detector in measurements of the stau mass and its momentum at the LHC. We then use a fast simulation of an LHC detector to demonstrate techniques for reconstructing the cascade decays of supersymmetric particles in GDM scenarios, using a parameterisation of the detector response to staus, taus and jets based on full simulation results. Supersymmetric pair-production events are selected with high redundancy and efficiency, and many valuable measurements can be made starting from stau tracks in the detector. We recalibrate the momenta of taus using transverse-momentum balance, and use kinematic cuts to select combinations of staus, taus, jets and leptons that exhibit peaks in invariant masses that correspond to various heavier sparticle species, with errors often comparable with the jet energy scale uncertainty., Comment: 23 pages, 10 figures, updated to version published in JHEP

We derive analytical expressions for the shape of the invariant mass distributions of massless Standard Model endproducts in cascade decays involving massive New Physics (NP) particles, D -> Cc -> Bbc -> Aabc, where the final NP particle A in the cascade is unobserved and where two of the particles a, b, c may be indistinguishable. Knowledge of these expressions can improve the determination of NP parameters at the LHC. The shape formulas are composite, but contain nothing more complicated than logarithms of simple expressions. We study the effects of cuts, final state radiation and detector effects on the distributions through Monte Carlo simulations, using a supersymmetric model as an example. We also consider how one can deal with the width of NP particles and with combinatorics from the misidentification of final state particles. The possible mismeasurements of NP masses through `feet' in the distributions are discussed. Finally, we demonstrate how the effects of different spin configurations can be included in the distributions., 39 pages, 14 figures (colour), JHEP class

We study gravitino dark matter and slow gravitino decays within the framework of R-violating supersymmetry, with particular emphasis on the flavour dependence of the branching ratios and the allowed R-violating couplings. The dominant decay modes and final state products turn out to be very sensitive to the R-violating hierarchies. Mixing effects can be crucial in correctly deriving the relative magnitude of the various contributions, particularly for heavy flavours with phase space suppression. The study of the strength of different decay rates for the gravitino is also correlated to collider signatures expected from decays of the Next-to-Lightest Supersymmetric Particle (NLSP) and to single superparticle production., Comment: 20 pages, 7 figures; v2 also includes photons from three-body decays in coupling limits, one additional author, matches version to appear in PLB