Commissioning status of the Virgo interferometer

An Erratum for this article has been published in 2010 Class. Quantum Grav. 27 149801 (The full author list for this article was omitted in error).International audienceThe Virgo interferometer is one of the big observatories aimed at detecting gravitational waves. This paper will describe the Virgo + upgrades and the commissioning work performed between the first Virgo science run (VSR1) and the second Virgo science run (VSR2). Some first results of VSR2 will be discussed, which was recently started with a good duty cycle and an inspiral range for the detection of binary neutron-star inspirals of 10 Mpc. To conclude, an outlook will be given on some future upgrades of the detector

Joint searches for gravitational waves and high-energy neutrinos

Many of the astrophysical sources and violent phenomena observed in our Universe are potential joint emitters of gravitational waves and high-energy cosmic radiation, in the form of photons, hadrons, and also neutrinos. This has triggered a collaborative analysis project between gravitational wave detectors and high-energy neutrino telescopes. In this article, we review some of the motivations for having pursuing science jointly and present the effort’s status

Open questions in astrophysically triggered gravitational wave searches

Sources of gravitational waves are often expected to also be observable through several other messengers, such as gamma rays, X-rays, optical, radio, and/or neutrino emission. Some of these channels are already being used in searches for gravitational waves with the LIGO-GEO600-Virgo interferometer network, and others are currently being incorporated into new searches. Astrophysical targets include gamma-ray bursts, soft-gamma repeaters, supernovae, and glitching pulsars. The simultaneous observation of electromagnetic or neutrino emission could be a crucial aspect for the first direct detection of gravitational waves. Information on the progenitor, such as trigger time, direction and expected frequency range, can enhance our ability to identify gravitational wave signatures with amplitudes close to the noise floor of the detector. Furthermore, combining gravitational waves with electromagnetic and neutrino observations will enable the extraction of scientific insight that was hidden from us before. The paper discusses the status of transient multimessenger detection efforts as well as intriguing questions that might be resolved in the future by advanced and third generation gravitational wave detector

Measurement of jet multiplicity distributions in t(t)over-bar production in pp collisions at root s=7TeV

The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7(Formula presented.) at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton+jets decay channels using data corresponding to an integrated luminosity of 5.0(Formula presented.). Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the (Formula presented.) production is determined as a function of the additional jet multiplicity in the lepton+jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed

Search for gravitational waves from compact binary coalescence in LIGO and Virgo data from S5 and VSR1

We report the results of the first search for gravitational waves from compact binary coalescence using data from the LIGO and Virgo detectors. Five months of data were collected during the concurrent S5 (LIGO) and VSR1 (Virgo) science runs. The search focused on signals from binary mergers with a total mass between 2 and 35 Msun. No gravitational waves are identified. The cumulative 90%-confidence upper limits on the rate of compact binary coalescence are calculated for non-spinning binary neutron stars, black hole-neutron star systems, and binary black holes to be 8.7x10^-3, 2.2x10^-3 and 4.4x10^-4 yr^-1 L_10^-1 respectively, where L_10 is 10^10 times the blue solar luminosity. These upper limits are compared with astrophysical expectations