Search for a Lorentz invariance violation contribution in atmospheric neutrino oscillations using MACRO data

Neutrino-induced upward-going muons in MACRO have been analysed in terms of relativity principles violating effects, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of nu_mu -> nu_tau transitions. The data disfavor these exotic possibilities even at a sub-dominant level, and stringent 90% C.L. limits are placed on the Lorentz invariance violation parameter |Delta v| < 6 * 10^(-24) at sin2theta_v = 0 and |Delta v| < 2.5--5 * 10^(-26) at sin2theta_v = +/-1. These limits can also be re-interpreted as upper bounds on the parameters describing violation of the Equivalence Principle.Comment: 8 pages, 2 figures, submitted to Physics Letters

New limits on dark--matter WIMPs from the Heidelberg--Moscow experiment

New results after 0.69 kg yr of measurement with an enriched 76Ge detector of the Heidelberg--Moscow experiment with an active mass of 2.758 kg are presented. An energy threshold of 9 keV and a background level of 0.042 counts/(kg d keV) in the energy region between 15 keV and 40 keV was reached.The derived limits on the WIMP--nucleon cross section are the most stringent limits on spin--independent interactions obtained to date by using essentially raw data without background subtraction.Comment: 8 pages (latex) including 5 postscript figures and 2 tables. To appear in Phys. Rev. D, 15. December 199

Ribbons on the CBR Sky: A Powerful Test of a Baryon Symmetric Universe

If the Universe consists of domains of matter and antimatter, annihilations at domain interfaces leave a distinctive imprint on the Cosmic Background Radiation (CBR) sky. The signature is anisotropies in the form of long, thin ribbons of width $\theta_W\sim 0.1^\circ$, separated by angle $\theta_L\simeq 1^\circ(L/100h^{-1}{Mpc})$ where L is the characteristic domain size, and y-distortion parameter $y \approx 10^{-6}$. Such a pattern could potentially be detected by the high-resolution CBR anisotropy experiments planned for the next decade, and such experiments may finally settle the question of whether or not our Hubble volume is baryon symmetric.Comment: LaTeX, 10 pages, 4 figures in epsf. Revised version corrects a couple of relevant mistake

Antideuterons as a Signature of Supersymmetric Dark Matter

Once the energy spectrum of the secondary component is well understood, measurements of the antiproton cosmic-ray flux at the Earth will be a powerful way to indirectly probe for the existence of supersymmetric relics in the galactic halo. Unfortunately, it is still spoilt by considerable theoretical uncertainties. As shown in this work, searches for low-energy antideuterons appear in the mean time as a plausible alternative, worth being explored. Above a few GeV/n, a dozen spallation antideuterons should be collected by the future AMS experiment on board ISSA. For energies less than about 3 GeV/n, the antideuteron spallation component becomes negligible and may be supplanted by a potential supersymmetric signal. If a few low-energy antideuterons are discovered, this should be seriously taken as a clue for the existence of massive neutralinos in the Milky Way.Comment: 16 pages, 9 figure

Search for nuclearites with the SLIM detector

We discuss the properties of cosmic ray nuclearites, from the point of view of their search with large nuclear track detector arrays exposed at different altitudes, in particular with the SLIM experiment at the Chacaltaya high altitude lab (5290 m a.s.l.). We present calculations concerning their propagation in the Earth atmosphere and discuss their possible detection with CR39 and Makrofol nuclear track detectors.Comment: 11 pages, 6 figure

Charge amplification concepts for direction-sensitive dark matter detectors

Direction measurement of weakly interacting massive particles in time-projection chambers can provide definite evidence of their existence and help to determine their properties. This article demonstrates several concepts for charge amplification in time-projection chambers that can be used in direction-sensitive dark matter search experiments. We demonstrate reconstruction of the 'head-tail' effect for nuclear recoils above 100keV, and discuss the detector performance in the context of dark matter detection and scaling to large detector volumes.Comment: 15 pages, 9 figure

Search for Magnetic Monopoles Trapped in Matter

There have been many searches for magnetic monopoles in flight, but few for monopoles in matter. We have searched for magnetic monopoles in meteorites, schists, ferromanganese nodules, iron ores and other materials. The detector was a superconducting induction coil connected to a SQUID (Superconducting Quantum Interference Device) with a room temperature bore 15 cm in diameter. We tested a total of more than 331 kg of material including 112 kg of meteorites. We found no monopole and conclude the overall monopole/nucleon ratio in the samples is $<1.2 \times 10^{-29}$ with a 90\% confidence level.Comment: 6 pages, rev tex, no figure

Gaugino Anomaly Mediated SUSY Breaking: phenomenology and prospects for the LHC

We examine the supersymmetry phenomenology of a novel scenario of supersymmetry (SUSY) breaking which we call Gaugino Anomaly Mediation, or inoAMSB. This is suggested by recent work on the phenomenology of flux compactified type IIB string theory. The essential features of this scenario are that the gaugino masses are of the anomaly-mediated SUSY breaking (AMSB) form, while scalar and trilinear soft SUSY breaking terms are highly suppressed. Renormalization group effects yield an allowable sparticle mass spectrum, while at the same time avoiding charged LSPs; the latter are common in models with negligible soft scalar masses, such as no-scale or gaugino mediation models. Since scalar and trilinear soft terms are highly suppressed, the SUSY induced flavor and CP-violating processes are also suppressed. The lightest SUSY particle is the neutral wino, while the heaviest is the gluino. In this model, there should be a strong multi-jet +etmiss signal from squark pair production at the LHC. We find a 100 fb^{-1} reach of LHC out to m_{3/2}\sim 118 TeV, corresponding to a gluino mass of \sim 2.6 TeV. A double mass edge from the opposite-sign/same flavor dilepton invariant mass distribution should be visible at LHC; this, along with the presence of short-- but visible-- highly ionizing tracks from quasi-stable charginos, should provide a smoking gun signature for inoAMSB.Comment: 30 pages including 14 .eps figure

Quantum-Gravitational Diffusion and Stochastic Fluctuations in the Velocity of Light

We argue that quantum-gravitational fluctuations in the space-time background give the vacuum non-trivial optical properties that include diffusion and consequent uncertainties in the arrival times of photons, causing stochastic fluctuations in the velocity of light ``in vacuo''. Our proposal is motivated within a Liouville string formulation of quantum gravity that also suggests a frequency-dependent refractive index of the particle vacuum. We construct an explicit realization by treating photon propagation through quantum excitations of $D$-brane fluctuations in the space-time foam. These are described by higher-genus string effects, that lead to stochastic fluctuations in couplings, and hence in the velocity of light. We discuss the possibilities of constraining or measuring photon diffusion ``in vacuo'' via $\gamma$-ray observations of distant astrophysical sources.Comment: 17 pages LATEX, uses axodraw style fil