Using b-tagging to enhance the SUSY reach of the CERN Large Hadron Collider

Assuming that supersymmetry is realized with parameters in the hyperbolic branch/focus point (HB/FP) region of the minimal supergravity (mSUGRA) model, we show that by searching for multijet + missing E_T events with tagged b jets the reach of experiments at the LHC may be extended by as much as 20% from current projections. The reason for this is that gluino decays to third generation quarks are enhanced because the lightest neutralino has substantial higgsino components. Although we were motivated to perform this analysis because the HB/FP region is compatible with the recent determination of the relic density of cold dark matter, our considerations may well have a wider applicability since decays of gluinos to third generation quarks are favoured in a wide variety of models.Comment: 16 pages, 1 figur

Bounds on Scalar Leptoquarks from Z Physics

We analyse the constraints on scalar leptoquarks coming from radiative corrections to $Z$ physics. We perform a global fitting to the LEP data including the contributions of the most general effective Lagrangian for scalar leptoquarks, which exhibits the $SU(2)_L \times U(1)_Y$ gauge invariance. We show that the bounds on leptoquarks that couple to the top quark are much stronger than the ones obtained from low energy experiments.Comment: RevTeX 3.0, 26 pages, 4 postscript figures included as uufil

Signals for New Spin-1 Resonances in Electroweak Gauge Boson Pair Production at the LHC

The mechanism of electroweak symmetry breaking (EWSB) will be directly scrutinized soon at the CERN Large Hadron Collider (LHC). We analyze the LHC potential to look for new vector bosons associated with the EWSB sector. We present a possible model independent approach to search for these new spin--1 resonances. We show that the analyses of the processes pp --> l^+ l^- Emiss_T, l^\pm j j Emiss_T, l^\pm l^+ l^- Emiss_T, and l^+ l^- j j (with l=e or \mu and j=jet) have a large reach at the LHC and can lead to the discovery or exclusion of many EWSB scenarios such as Higgsless models.Comment: 10 pages, 11 figure

Supersymmetric Higgs pair discovery prospects at hadron colliders

We study the potential of hadron colliders in the search for the pair production of neutral Higgs bosons in the framework of the Minimal Supersymmetric Standard Model. Using analytical expressions for the relevant amplitudes, we perform a detailed signal and background analysis, working out efficient kinematical cuts for the extraction of the signal. The important role of squark loop contributions to the signal is emphasised. If the signal is sufficiently enhanced by these contributions, it could even be observable at the next run of the upgraded Tevatron collider in the near future. At the LHC the pair production of light and heavy Higgs bosons might be detectable simultaneously.Comment: 5 pages, hep99, 6 figures; Presented at the International Europhysics Conference on High Energy Physics, Tampere, Finland, 15-21 July 199

p p -> j j e+/- mu+/- nu nu and j j e+/- mu-/+ nu nu at O(\alpha_{em}^6) and O(\alpha_{em}^4 \alpha_s^2) for the Study of the Quartic Electroweak Gauge Boson Vertex at LHC

We analyze the potential of the CERN Large Hadron Collider (LHC) to study the structure of quartic vector-boson interactions through the pair production of electroweak gauge bosons via weak boson fusion q q -> q q W W. In order to study these couplings we have performed a partonic level calculation of all processes p p -> j j e+/- mu+/- nu nu and pp -> j j e+/- mu-/+ nu nu at the LHC using the exact matrix elements at O(\alpha_{em}^6) and O(\alpha_{em}^4 \alpha_s^2) as well as a full simulation of the t tbar plus 0 to 2 jets backgrounds. A complete calculation of the scattering amplitudes is necessary not only for a correct description of the process but also to preserve all correlations between the final state particles which can be used to enhance the signal. Our analyses indicate that the LHC can improve by more than one order of magnitude the bounds arising at present from indirect measurements.Comment: 26 pages, 8 figures, revised version with some typos corrected, and some comments and references adde

Heavy Quarkonia Production in p+p Collisions from the PHENIX Experiment

Quarkonia provide a sensitive probe of the properties of the hot dense medium created in high energy heavy ion collisions. Hard scattering processes result in the production of heavy quark pairs that interact with the collision medium during hadronization. These in-medium interactions convey information about the fundamental properties of the medium itself and can be used to examine the modification of the QCD confining potential in the collision environment. Baseline measurements from p+p and d+Au collision systems are used to distinguish cold nuclear matter effects while measurements from heavy ion collision systems are used to quantify in-medium effects. The PHENIX experiment has the capability of detecting heavy quarkonia at $1.2<|\eta|<2.2$ via the $\mu^+\mu^-$ decay channel and at $|\eta|<0.35$ via the $e^+e^-$ decay channel. Recent runs have resulted in the collection of high statistics p+p data sets that provide an essential baseline reference for heavy ion measurements and allow for further critical evaluation of heavy quarkonia production mechanisms. The latest PHENIX results for the production of the $J/\psi$ in p+p collisions are presented and future prospects for $\psi'$, $\chi_{c}$ and $\Upsilon$ measurements are discussed.Comment: 4 pages, 2 figures, Proceedings for Quark Matter 200