Reflectance spectra of Fe(2+)-Mg(2+) disordered pyroxenes: Implications to remote-sensed spectra of planetary surfaces

The reflectance spectra of Fe(2+)-Mg(2+) disordered orthopyroxenes are relevant to surfaces of terrestrial planets onto which basaltic magma has been extruded. If cooling rates of basalt lava flows were fast, equilibrium iron intersite partitioning may not have been achieved so that abnormal enrichments of Fe(2+) ions in M1 sites would occur. The two intense pyroxene Fe(2+) site CF bands in the 1 micron and 2 micron regions would continue to dominate the the reflectance spectra so that the pyroxene composition and structure type would be readily identified in telescopic spectral profiles. However, abnormal intensification of the Fe(2+)/M1 site CF band at 1.20 microns could lead to the false identification of olivine in remote sensed spectra because in pyroxene-olivine mixtures the inflection around 1.20 microns is the only spectral feature for detecting the presence of olivine. The identification of iron-bearing plagioclase feldspars, too, would be obscured by the pyroxene Fe(2+)/M1 site CF band at 1.20 microns. Such interference would be a major problem if in situ reflectance spectra could be measured on the surface of Venus where ambient temperatures are as high as 475 C. Disordering of Fe(2+) and Mg(2+) ions comparable to that in the orthopyroxenes used in this spectral chemical study might be expected in low Ca pyroxenes occurring on the Venusian surface. Researchers conclude that Fe(2+)/M1 site spectral features need to be carefully assessed in remote-sensed spectra before deductions are made about the presence of olivine on planetary surfaces

Scalar Kaluza-Klein modes in a multiply warped braneworld

The Kaluza-Klein (KK) modes of a massive scalar field on a 3-brane embedded in six dimensional multiply warped spacetime are determined. Due to the presence of warping along both the extra dimensions the KK mass spectrum splits into two closely spaced branches which is a distinct feature of this model compared to the five dimensional Randall-Sundrum model. This new cluster of the KK mode spectrum is expected to have interesting phenomenological implications for the upcoming collider experiments. Such a scenario may also be extended for even larger number of orbifolded extra dimensions.Comment: 10 pages, Revte

Report of the GDR working group on the R-parity violation

This report summarizes the work of the "R-parity violation group" of the French Research Network (GDR) in Supersymmetry, concerning the physics of supersymmetric models without conservation of R-parity at HERA, LEP, Tevatron and LHC and limits on R-parity violating couplings from various processes. The report includes a discussion of the recent searches at the HERA experiment, prospects for new experiments, a review of the existing limits, and also theoretically motivated alternatives to R-parity and a brief discussion on the implications of R-parity violation on the neutrino masses.Comment: 60 pages, LaTeX, 22 figures, 2 table

Matter-gravity interaction in a multiply warped braneworld,

The role of a bulk graviton in predicting the signature of extra dimensions through collider-based experiments is explored in the context of a multiply warped spacetime. In particular it is shown that in a doubly warped braneworld model, the presence of the sixth dimension, results in enhanced concentration of graviton Kaluza Klein (KK) modes compared to that obtained in the usual 5-dimensional Randall-Sundrum model. Also, the couplings of these massive graviton KK modes with the matter fields on the visible brane turn out to be appreciably larger than that in the corresponding 5- dimensional model. The significance of these results are discussed in the context of KK graviton search at the Large Hadron Collider (LHC).Comment: 13 pages, 2 table

Search for associated Higgs boson production using like charge dilepton events in p(p)over-bar collisions at root s=1.96 TeV

We present a search for associated Higgs boson production in the process p (p) over bar -> W/ZH -> l(+/-)l'(+/-) + X in ee, e mu, and mu mu final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at root s = 1.96 TeV corresponding to 5.3 fb(-1) of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C. L. observed (expected) upper limits on ratio of the production cross section to the standard model prediction of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass of 115 GeV

Study of Inclusive J/psi Production in Two-Photon Collisions at LEP II with the DELPHI Detector

Inclusive J/psi production in photon-photon collisions has been observed at LEP II beam energies. A clear signal from the reaction gamma gamma -> J/psi+X is seen. The number of observed N(J/psi -> mu+mu-) events is 36 +/- 7 for an integrated luminosity of 617 pb^{-1}, yielding a cross-section of sigma(J/psi+X) = 45 +/- 9 (stat) +/- 17 (syst) pb. Based on a study of the event shapes of different types of gamma gamma processes in the PYTHIA program, we conclude that (74 +/- 22)% of the observed J/psi events are due to `resolved' photons, the dominant contribution of which is most probably due to the gluon content of the photon.Comment: 13 pages, 8 figures, Accepted by Phys. Lett.

Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance

This paper presents DELPHI measurements and interpretations of cross-sections, forward-backward asymmetries, and angular distributions, for the e+e- -> ffbar process for centre-of-mass energies above the Z resonance, from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are consistent with the predictions of the Standard Model and are used to study a variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering and several models which include physics beyond the Standard Model: the exchange of Z' bosons, contact interactions between fermions, the exchange of gravitons in large extra dimensions and the exchange of sneutrino in R-parity violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.

A Determination of the Centre-of-Mass Energy at LEP2 using Radiative 2-fermion Events

Using e+e- -> mu+mu-(gamma) and e+e- -> qqbar(gamma) events radiative to the Z pole, DELPHI has determined the centre-of-mass energy, sqrt{s}, using energy and momentum constraint methods. The results are expressed as deviations from the nominal LEP centre-of-mass energy, measured using other techniques. The results are found to be compatible with the LEP Energy Working Group estimates for a combination of the 1997 to 2000 data sets.Comment: 20 pages, 6 figures, Accepted by Eur. Phys. J.

Evidence for an Excess of Soft Photons in Hadronic Decays of Z^0

Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qqbar disintegrations of the Z^0 were studied in the kinematic range 0.2 < E_gamma < 1 GeV and transverse momentum with respect to the closest jet direction p_T < 80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/- 0.27) x 10^{-3} gamma/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340 +/- 0.001 +/- 0.038) x 10^{-3} gamma/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.Comment: 37 pages, 9 figures, Accepted by Eur. Phys. J.