Search for Scalar Leptoquarks with polarized protons (and neutrons) at HERA and future ep(n)ep(n) Machines

The effects of Scalar Leptoquarks in various channels have been analysed for the HERA collider and also for an eventual new $ep$ machine running at higher energies. We emphasize the relevance of polarized beams.Comment: Latex file, 3 pages and 3 ps fig. Need style files : twoside,fleqn,espcrc2,epsfig. To appear in the proceedings of the DIS99 Workshop, DESY-Zeuthen, Germany, April 199

Search and identification of Scalar and Vector Leptoquarks at HERA with polarization

We analyze the effects of Scalar and Vector Leptoquarks on various observables in electron (positron) - proton deep inelastic scattering. In view of the future program of the HERA collider, with a high luminosity and also with polarization, we present the constraints that can be reached using this facility for several Leptoquark scenarios. We address the question of the identification of the nature of a discovered Leptoquark. We emphasize the relevance of having polarized lepton and proton beams in order to disentangle completely the various Leptoquark models. This study is also relevant in the context of the TESLA$\times$HERA project.Comment: Version to appear in Eur.Phys.J.C. 3 typos have been correcte

Discovery limits for a new contact interaction at future hadronic colliders with polarized beams

The production of high-transverse energy jets in hadron-hadroncollisions is sensitive to the presence of new contact interactions between quarks. If proton polarization were available, the measurement of some parity violating spin asymmetries in one-jet production at large transverse energy would complement the usual search for deviations from the expected QCD cross section. In the same time, a unique information on the chirality structure of the new interaction could be obtained. In this context, we compare the potentialities of various $pp$ and $p\bar p$ colliders that are planned or have been proposed, with the additional requirement of beam polarization.Comment: Latex file, 9 pages and 1 ps fig, definition of the subprocess variables and one example of the effect of new contact terms on the parity violating spin asymmetry are added. Eq. 8 (now eq. 9) and the following equation are changed, giving better bounds in the polarized pp case (new figure

Short Gamma Ray Bursts as possible electromagnetic counterpart of coalescing binary systems

Coalescing binary systems, consisting of two collapsed objects, are among the most promising sources of high frequency gravitational waves signals detectable, in principle, by ground-based interferometers. Binary systems of Neutron Star or Black Hole/Neutron Star mergers should also give rise to short Gamma Ray Bursts, a subclass of Gamma Ray Bursts. Short-hard-Gamma Ray Bursts might thus provide a powerful way to infer the merger rate of two-collapsed object binaries. Under the hypothesis that most short Gamma Ray Bursts originate from binaries of Neutron Star or Black Hole/Neutron Star mergers, we outline here the possibility to associate short Gamma Ray Bursts as electromagnetic counterpart of coalescing binary systems.Comment: 4 pages, 1 figur

Summary of the SUSY Working Group of the 1999 Les Houches Workshop

The results obtained by the Working Group on Supersymmetry at the 1999 Les Houches Workshop on Collider Physics are summarized. Separate chapters treat "general" supersymmetry, R-parity violation, gauge mediated supersymmetry breaking, and anomaly mediated supersymmetry breaking.Comment: LaTeX, 110 pages with numerous .ps and .eps files. proc.tex is main tex fil

Single top production at the LHC as a probe of R parity violation

We investigate the potential of the LHC to probe the R parity violating couplings involving the third generation by considering single top production. This study is based on particle level event generation for both signal and background, interfaced to a simplified simulation of the ATLAS detector.Comment: 11 pages, 5 figures, 5 tables (LaTeX, style revtex), few references adde

Cosmological models with interacting components and mass-varying neutrinos

A model for a homogeneous and isotropic spatially flat Universe, composed of baryons, radiation, neutrinos, dark matter and dark energy is analyzed. We infer that dark energy (considered to behave as a scalar field) interacts with dark matter (either by the Wetterich model, or by the Anderson and Carroll model) and with neutrinos by a model proposed by Brookfield et al.. The latter is understood to have a mass-varying behavior. We show that for a very-softly varying field, both interacting models for dark matter give the same results. The models reproduce the expected red-shift performances of the present behavior of the Universe.Comment: 8 pages, 5 figures, to be published in Gravitation and Cosmolog

Dynamical Dark Energy or Simply Cosmic Curvature?

We show that the assumption of a flat universe induces critically large errors in reconstructing the dark energy equation of state at z>~0.9 even if the true cosmic curvature is very small, O(1%) or less. The spuriously reconstructed w(z) shows a range of unusual behaviour, including crossing of the phantom divide and mimicking of standard tracking quintessence models. For 1% curvature and LCDM, the error in w grows rapidly above z~0.9 reaching (50%,100%) by redshifts of (2.5,2.9) respectively, due to the long cosmological lever arm. Interestingly, the w(z) reconstructed from distance data and Hubble rate measurements have opposite trends due to the asymmetric influence of the curved geodesics. These results show that including curvature as a free parameter is imperative in any future analyses attempting to pin down the dynamics of dark energy, especially at moderate or high redshifts.Comment: 5 pages, 2 figures. To appear in JCA