Conferences - Seminars

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The 20th International Conference on General Relativity and Gravitation (GR20) and the 10th Amaldi Conference on Gravitational Waves (Amaldi10)
Warsaw, Poland, July 2013

Searching for cosmic strings with the LIGO-Virgo gravitational-wave experiments
Cosmic strings are linear topological defects which are expected to form during symmetry-breaking phase transitions in the early universe. In addition, some inflation models based on string theory predict that fundamental strings and D-strings could grow to cosmic scales and constitute a network of cosmic superstrings. When forming loops, cosmic strings radiate energy through bursts of gravitational waves in the presence of cuspy features. This mechanism represents one of the most promising observational signatures to detect the existence of cosmic strings. The sensitivity of ground-based gravitational-wave detectors LIGO and Virgo allows us to explore an unconstrained region of the cosmic string parameter space. After reviewing the cosmic string models and the targeted gravitational-wave signals, we present the search for cosmic string burst signals which has been conducted over 5 years of joint LIGO-Virgo data. We discuss the astrophysical impact of this search and the future prospects for the advanced detectors era.
Rencontres de Moriond - Gravitation Session
La Thuile, Italy, March 2011

Searches for gravitational wave transients in the LIGO and Virgo data
Slides Proceedings
In 2011, the Virgo gravitational wave (GW) detector will definitively end its science program following the shut-down of the LIGO detectors last year. The years to come will be devoted to the development and installation of second generation detectors. It is the opportune time to review what has been learned from the GW searches in the kilometric interferometers data.
Since 2007 data have been collected by the LIGO detectors (S5 and S6 runs) and the Virgo detector (VSR1, VSR2 and VSR3 runs). Analyses have been developed and performed jointly by the two collaborations. Though no detection has been made so far, meaningful upper limits have been set on the astrophysics of the sources and on the rate of GW events.
This talk will focus on the transient GW searches performed over the last 3 years. This includes the searches of GW produced by compact binary systems, supernovae core collapse, pulsar glitches or cosmic string cusps. The analyses which have been specifically developed for that purpose will be presented along with the most recent results. The great efforts which have been made to perform low-latency transient searches will also be explained. To conclude, the plans for the future advanced detectors as well as the physics which can be expected will be shown.
Gravity, Lorentz Symmetry and Quantum Gravity
Paris, France, June 2010

Gravitational wave bursts produced by cosmic strings cusps
Virgo presentation and status - Cosmic string cusps analysis
Gravitational Wave Data Analysis Workshop 14 (GWDAW-14)
Rome, Italy, January 2010

Data quality in gravitational wave burst and inspiral searches in the second Virgo science run
Slides Proceedings
In July 2009 Virgo started its second science run (VSR2), jointly with the LIGO detectors (S6). Large efforts have been made to understand the new sources of noise disturbance in Virgo data due to the detector or its environment. This understanding is crucial in order to reject noise events that could mimic a genuine gravitational wave (GW). It also helps at enhancing the significance of such an event by rejecting very noisy periods around. Finally, it provides the commissioning team with interesting hints to fix problems and to improve the sensitivity of the detector.
Moreover, VSR2 has been the beginning of online analyses for burst and inspiral GW searches. Therefore, one of the main challenges was to be able to monitor the data quality with a very low latency. Indeed, online analyses need the veto information to provide serious GW event candidates to be eventually followed-up by external collaborations.
First we will review the sources of noise which have been identified. Then we will explain the tools which have been put in place to produce low latency vetoes, to store them and to provide them to online analyses. Finally, we will present the effect of data quality vetoes on individual Virgo triggers.
Semaine de l'Astrophysique Française - Journées de la SF2A 2009
Besancon, France, July 2009

Recent Virgo results and future prospects
Two years after its first scientific run, Virgo is about to start a new data taking campaign, jointly with the LIGO detectors. For this year's run, upgrades of the detector and intense commissioning efforts have been made to further increase the performances of the detectors. This presentation aims at reviewing the recent results and their astrophysical consequences. We also discuss the expected improvements in sensitivity, with the upcoming run and with the future Advanced Virgo detector, and their impact on the detection of gravitational waves.
XVI International Workshop on Deep-Inelastic Scattering and Related Subjects - DIS
London, England, April 2008

ΔG/G from Open Charm Events at COMPASS
Slides Proceedings
One of the main goals of the COMPASS experiment at CERN is to measure the gluon polarization, ΔG/G in the nucleon, which can be accessed through spin asymmetries of polarized photon-gluon fusion processes (PGF). A very clean way to tag PGF events is to look for charmed mesons, such as D* or D0, in the final state. All COMPASS data taken with a deuteron target (2002-2006) are analysed. Since this channel is statistically limited, a weighted method was developed to minimize the statistical error. In the new analysis presented here, the weight is improved and contains more information on the probability for an event for being a PGF process. The new weighting has been applied on already released 2002-2004 data but also on data taken in 2006, resulting in a statistical error reduced by a factor 1.7.
Journées de Rencontre Jeunes Chercheurs
Dinard, France, December 2007

Mesure de la contribution du spin des gluons au spin du nucleon
Slides (french) Proceedings (french)
L'un des objectifs principaux de l'experience COMPASS au CERN est de mesurer la polarisation des gluons dans le nucleon. Celle-ci peut etre obtenue en mesurant des asymetries de spin pour des diffusions de muons polarises sur une cible de lithium deutere (LiD) polarise. Les evenements de fusion photon-gluon, necessaires a cette mesure, sont signes par la production de mesons charmes, ce qui permet d'extraire un signal tres propre. Un premier resultat pour des donnees prises en 2002-03-04 est presente mais nous verrons que la statistique, encore limitee, est sur le point d'etre amelioree.
The 2007 European School of High-Energy Physics
Trest, Czech Republic, August 2007

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