Computing gravitational waves from slightly nonspherical stellar collapse to black hole: Odd-parity perturbation

Nonspherical stellar collapse to a black hole is one of the most promising gravitational wave sources for gravitational wave detectors. We numerically study gravitational waves from a slightly nonspherical stellar collapse to a black hole in linearized Einstein theory. We adopt a spherically collapsing star as the zeroth-order solution and gravitational waves are computed using perturbation theory on the spherical background. In this paper we focus on the perturbation of odd-parity modes. Using the polytropic equations of state with polytropic indices $n_p=1$ and 3, we qualitatively study gravitational waves emitted during the collapse of neutron stars and supermassive stars to black holes from a marginally stable equilibrium configuration. Since the matter perturbation profiles can be chosen arbitrarily, we provide a few types for them. For $n_p=1$, the gravitational waveforms are mainly characterized by a black hole quasinormal mode ringing, irrespective of perturbation profiles given initially. However, for $n_p=3$, the waveforms depend strongly on the initial perturbation profiles. In other words, the gravitational waveforms strongly depend on the stellar configuration and, in turn, on the ad hoc choice of the functional form of the perturbation in the case of supermassive stars.Comment: 31 pages, accepted for publication in Phys. Rev. D, typos and minor errors correcte

The rotational modes of relativistic stars: Numerical results

We study the inertial modes of slowly rotating, fully relativistic compact stars. The equations that govern perturbations of both barotropic and non-barotropic models are discussed, but we present numerical results only for the barotropic case. For barotropic stars all inertial modes are a hybrid mixture of axial and polar perturbations. We use a spectral method to solve for such modes of various polytropic models. Our main attention is on modes that can be driven unstable by the emission of gravitational waves. Hence, we calculate the gravitational-wave growth timescale for these unstable modes and compare the results to previous estimates obtained in Newtonian gravity (i.e. using post-Newtonian radiation formulas). We find that the inertial modes are slightly stabilized by relativistic effects, but that previous conclusions concerning eg. the unstable r-modes remain essentially unaltered when the problem is studied in full general relativity.Comment: RevTeX, 29 pages, 31 eps figure

Restricting quark matter models by gravitational wave observation

We consider the possibilities for obtaining information about the equation of state for quark matter by using future direct observational data on gravitational waves. We study the nonradial oscillations of both fluid and spacetime modes of pure quark stars. If we observe the $f$ and the lowest $w_{\rm II}$ modes from quark stars, by using the simultaneously obtained radiation radius we can constrain the bag constant $B$ with reasonable accuracy, independently of the $s$ quark mass.Comment: To appear in Phys. Rev.

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review

Search for supersymmetry in final states with jets, missing transverse momentum and one isolated lepton in sqrt{s} = 7 TeV pp collisions using 1 fb-1 of ATLAS data

We present an update of a search for supersymmetry in final states containing jets, missing transverse momentum, and one isolated electron or muon, using 1.04 fb^-1 of proton-proton collision data at sqrt{s} = 7 TeV recorded by the ATLAS experiment at the LHC in the first half of 2011. The analysis is carried out in four distinct signal regions with either three or four jets and variations on the (missing) transverse momentum cuts, resulting in optimized limits for various supersymmetry models. No excess above the standard model background expectation is observed. Limits are set on the visible cross-section of new physics within the kinematic requirements of the search. The results are interpreted as limits on the parameters of the minimal supergravity framework, limits on cross-sections of simplified models with specific squark and gluino decay modes, and limits on parameters of a model with bilinear R-parity violation.Comment: 18 pages plus author list (30 pages total), 9 figures, 4 tables, final version to appear in Physical Review

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary

This paper constructs the reduction of heterotic $M$-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and for the boundary conditions on the bulk fields. Some general features of dualisation on a manifold with boundary are used to explain the origin of some topological terms in the action. The effect of gaugino condensation on the fermion boundary conditions leads to a `twist' in the chirality of the gravitino which can provide an uplifting mechanism in the vacuum energy to cancel the cosmological constant after moduli stabilisation.Comment: 16 pages, RevTe

Measurement of tau polarization in W->taunu decays with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV

In this paper, a measurement of tau polarization in W->taunu decays is presented. It is measured from the energies of the decay products in hadronic tau decays with a single final state charged particle. The data, corresponding to an integrated luminosity of 24 pb^-1, were collected by the ATLAS experiment at the Large Hadron Collider in 2010. The measured value of the tau polarization is Ptau = -1.06 +/- 0.04 (stat) + 0.05 (syst) - 0.07 (syst), in agreement with the Standard Model prediction, and is consistent with a physically allowed 95% CL interval [-1,-0.91]. Measurements of tau polarization have not previously been made at hadron colliders.Comment: 10 pages plus author list (25 pages total), 4 figures, 4 tables, revised author list, matches published EPJC versio

Readiness of the ATLAS liquid argon calorimeter for LHC collisions

The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an overview of the liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events. Results on the detector operation, timing performance, electronics noise, and gain stability are presented. High energy deposits from radiative cosmic muons and beam splash events allow to check the intrinsic constant term of the energy resolution. The uniformity of the electromagnetic barrel calorimeter response along eta (averaged over phi) is measured at the percent level using minimum ionizing cosmic muons. Finally, studies of electromagnetic showers from radiative muons have been used to cross-check the Monte Carlo simulation. The performance results obtained using the ATLAS readout, data acquisition, and reconstruction software indicate that the liquid argon calorimeter is well-prepared for collisions at the dawn of the LHC era.ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1140/epjc/s10052-010-1354-y</p