Search

In view of a possible upgrade of the RHIC-Spin program at BNL, concerning both the machine and the detectors, we give some predictions concerning the potentialities of New Physics detection with polarized proton beams. We focus on parity-violating asymmetries in one-jet production due to contact terms or to a new leptophobic neutral gauge boson. We comment on the main uncertainties and we compare with unpolarized searches at Tevatron., Comment: Latex file, 9 pages and 1 ps fig included with psfig.sty

The absence of deviations from the Standard Model for the differential cross section ${d\sigma}/{dQ^2}$ at HERA is used to set limits on electron quark compositeness scale and on new vector bosons, especially the hadrophilic one recently introduced as a possible explanation for LEP/SLC and CDF anomalies., Comment: Latex file, 7 pages and 1 ps fig, few comments on others experiments are added, results are unchanged. To appear in Phys. Let. B

We test the robustness and flexibility of the Chevallier-Polarski-Linder (CPL) parametrization of the dark energy equation of state w(z)=w{sub 0}+w{sub a}(z/1+z) in recovering a four-parameter steplike fiducial model. We constrain the parameter space region of the underlying fiducial model where the CPL parametrization offers a reliable reconstruction. It turns out that non-negligible biases leak into the results for recent (z

Supernovae searches have shown that a simple matter-dominated and decelerating universe should be ruled out. However a determination of the present deceleration parameter $q_0$ through a simple kinematical description is not exempt of possible drawbacks. We show that, with a time dependent equation of state for the dark energy, a bias is present for $q_0$ : models which are very far from the so-called Concordance Model can be accommodated by the data and a simple kinematical analysis can lead to wrong conclusions. We present a quantitative treatment of this bias and we present our conclusions when a possible dynamical dark energy is taken into account., 4 pages, 3 figures, submitted

Observation of thousands of type Ia supernovae should offer the most direct approach to probe the dark energy content of the universe. This will be undertaken by future large ground-based surveys followed by a space mission (SNAP/JDEM). We address the problem of extracting the cosmological parameters from the future data in a model independent approach, with minimal assumptions on the prior knowledge of some parameters. We concentrate on the comparison between a fiducial model and the fitting function and adress in particular the effect of neglecting (or not) the time evolution of the equation of state. We present a quantitative analysis of the bias which can be introduced by the fitting procedure. Such bias cannot be ignored as soon as the statistical errors from present data are drastically improved., Comment: 22 pages, 10 figures, submitted to Phys. Rev. D

We present a revised interpretation of recent analysis of supernovae data. We evaluate the effect of the priors on the extraction of the dark energy equation of state. We find that the conclusions depend strongly on the $\Omega_M$ prior value and on its uncertainty, and show that a biased fitting procedure applied on non concordant simulated data can converge to the "concordance model". Relaxing the prior on $\Omega_M$ points to other sets of solutions, which are not excluded by observational data., Comment: 1+4 pages, 6 figures, submitted to Phys. Rev

Concerning new physics beyond the Standard Model we explore the discovery and analysis potentials of polarized (hadronic) experiments and we compare with the unpolarized case. For discovery, beam polarization is helpful in the case of purely hadronic new interactions. In any case, beam polarization provides us a unique piece of information on the chiral and flavour structures., Comment: Latex file, 7 pages and 3 ps fig included with psfig.sty. To appear in the proceedings of the ECT* workshop ``The Spin Structure of the Proton and Polarized Collider Physics'', July 2001, Trento, Italy

We investigate the potential of the CERN LHC to probe the R parity violating couplings involving the third generation by considering single top quark production. This study is based on particle level event generation for both signal and background, interfaced to a simplified simulation of the ATLAS detector.

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., 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 1999

The discovery potential of the HERA collider, with and without polarized beams, for electron-quark contact interactions in neutral current scattering is reviewed. The measurement of spin asymmetries in the polarized case could give crucial information on the chiral structure of new interactions., LaTeX, 4 pages, 1 figure, uses iopart style files, contribution to the 3rd UK Workshop on HERA Physics, Durham, Sept. 1998

Theoretical and phenomenological arguments are in favor of an elusive new neutral vector boson Z' with a relatively low mass, chiral couplings to ordinary quarks and whose couplings to ordinary leptons are suppressed (leptophobia). We point out that this new particle could induce some parity violating spin asymmetries which could be measured soon at the Brookhaven Relativistic Heavy Ion Collider (RHIC), running part of the time as a polarized hadronic collider., Comment: Latex file, 13 pages and 3 ps fig. included in tex file with psfig.sty

In the context of general $SU(2)_L\otimes SU(2)_R\otimes U(1)$ models a relatively light W' is still allowed in some scenarios with a heavy right-handed neutrino and a quark mixing matrix $U^R$ close to unity. We explore the consequences of the presence of this new charged current on the parity violating spin asymmetries which could be induced in one-jet inclusive production in polarized proton-proton or proton-neutron collisions. Such measurements could be performed within a few years at the Brookhaven Relativistic Heavy Ion Collider (RHIC) running part of the time as a polarized hadronic collider., Latex file, 10 pages and 2 ps fig

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., 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)

We show that the measurement of some parity violating asymmetry in the production of a large ET jet could reveal the presence of a new hadrophilic Z' such as the one recently introduced to interpret possible departures from the Standard Model predictions both at LEP and at CDF. Such a measurement could be perform within a few years by the RHIC Spin Collaboration (RSC) using the Relativistic Heavy Ion Collider (RHIC) as a polarized proton-proton collider., 10 pages, latex file and 2 ps figures

A new handed interaction between subconstituents of quarks could be at the origin of some small parity violating effects in one-jet inclusive production. Within a few years, the Relativistic Heavy Ion Collider (RHIC) will be used as a polarized proton-proton collider. In this context, we analyse the possibilities of disentangling some new parity violating effects from the standard spin asymmetries which are expected due to the Standard Model QCD-Weak interference. We also explore the possibilities of placing some more stringent limits on the quark compositeness scale $\Lambda$ thanks to measurements of such spin asymmetries., Comment: 10 pages, Latex, 4 figures to be appended