Search for binary black hole mergers in the third observing run of Advanced LIGO-Virgo using coherent WaveBurst enhanced with machine learning

In this work, we use the coherent WaveBurst (cWB) pipeline enhanced with machine learning (ML) to search for binary black hole (BBH) mergers in the Advanced LIGO-Virgo strain data from the third observing run. We detect, with equivalent or higher significance, all gravitational-wave (GW) events previously reported by the standard cWB search for BBH mergers in the third GW Transient Catalog. The ML-enhanced cWB search identifies five additional GW candidate events from the catalog that were previously missed by the standard cWB search. Moreover, we identify three marginal candidate events not listed in third GW Transient Catalog. For simulated events distributed uniformly in a fiducial volume, we improve the sensitive hypervolume with respect to the standard cWB search by approximately 28% and 34% for the stellar-mass and intermediate mass black hole binary mergers respectively, detected with a false-alarm rate less than 1/100 yr-1. We show the robustness of the ML-enhanced search for detection of generic BBH signals by reporting increased sensitivity to the spin-precessing and eccentric BBH events as compared to the standard cWB search. Furthermore, we compare the improvement of the ML-enhanced cWB search for different detector networks

Networks of gravitational wave detectors and three figures of merit

This paper develops a general framework for studying the effectiveness of networks of interferometric gravitational wave detectors and then uses it to show that enlarging the existing LIGO-VIRGO network with one or more planned or proposed detectors in Japan (LCGT), Australia, and India brings major benefits, including much larger detection rate increases than previously thought... I show that there is a universal probability distribution function (pdf) for detected SNR values, which implies that the most likely SNR value of the first detected event will be 1.26 times the search threshold. For binary systems, I also derive the universal pdf for detected values of the orbital inclination, taking into account the Malmquist bias; this implies that the number of gamma-ray bursts associated with detected binary coalescences should be 3.4 times larger than expected from just the beaming fraction of the gamma burst. Using network antenna patterns, I propose three figures of merit that characterize the relative performance of different networks... Adding {\em any} new site to the planned LIGO-VIRGO network can dramatically increase, by factors of 2 to 4, the detected event rate by allowing coherent data analysis to reduce the spurious instrumental coincident background. Moving one of the LIGO detectors to Australia additionally improves direction-finding by a factor of 4 or more. Adding LCGT to the original LIGO-VIRGO network not only improves direction-finding but will further increase the detection rate over the extra-site gain by factors of almost 2, partly by improving the network duty cycle... Enlarged advanced networks could look forward to detecting three to four hundred neutron star binary coalescences per year.Comment: 38 pages, 7 figures, 2 tables. Accepted for publication in Classical and Quantum Gravit

Quantum-secured time transfer between precise timing facilities: a field trial with simulated satellite links

Global Navigation Satellite Systems (GNSSs), such as GPS and Galileo, provide precise time and space coordinates globally and constitute part of the critical infrastructure of modern society. To reliably operate GNSS, a highly accurate and stable system time is required, such as the one provided by several independent clocks hosted in Precise Timing Facilities (PTFs) around the world. The relative clock offset between PTFs is periodically measured to have a fallback system to synchronize the GNSS satellite clocks. The security and integrity of the communication between PTFs is of paramount importance: if compromised, it could lead to disruptions to the GNSS service. Therefore, securing the communication between PTFs is a compelling use-case for protection via Quantum Key Distribution (QKD), since this technology provides information-theoretic security. We have performed a field trial demonstration of such a use-case by sharing encrypted time synchronization information between two PTFs, one located in Oberpfaffenhofen (Germany) and one in Matera (Italy)—more than 900 km apart. To bridge this large distance, a satellite-QKD system is required, plus a “last-mile” terrestrial link to connect the optical ground station (OGS) to the actual location of the PTF. In our demonstration, we have deployed two full QKD systems to protect the last-mile connection at both locations and have shown via simulation that upcoming QKD satellites will be able to distribute keys between Oberpfaffenhofen and Matera, exploiting already existing OGSs

Correlation between Gamma-Ray bursts and Gravitational Waves

The cosmological origin of $\gamma$-ray bursts (GRBs) is now commonly accepted and, according to several models for the central engine, GRB sources should also emit at the same time gravitational waves bursts (GWBs). We have performed two correlation searches between the data of the resonant gravitational wave detector AURIGA and GRB arrival times collected in the BATSE 4B catalog. No correlation was found and an upper limit \bbox{$h_{\text{RMS}} \leq 1.5 \times 10^{-18}$} on the averaged amplitude of gravitational waves associated with $\gamma$-ray bursts has been set for the first time.Comment: 7 pages, 3 figures, submitted to Phys. Rev.

Measurements of the reaction pˉp→ϕη\bar{p}p \to \phi \eta of antiproton annihilation at rest at three hydrogen target densities

The proton-antiproton annihilation at rest into the $\phi\eta$ final state was measured for three different target densities: liquid hydrogen, gaseous hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in the liquid hydrogen target is smaller than in the low-pressure gas target. The branching ratios of the $\phi\eta$ channel were calculated on the basis of simultaneous analysis of the three data samples. The branching ratio for annihilation into $\phi\eta$ from the $^3S_1$ protonium state turns out to be about ten times smaller as compared to the one from the $^1P_1$ state.Comment: 10 pages, 3 Postscript figures. Accepted by Physics Letters

Saúde mental e violência entre estudantes da sexta série de um município paulista

OBJECTIVE: To analyze risk and protective factors for mental health problems among adolescents. METHODS: Cross-sectional study with a random sample (N=327; attrition rate=6.9%) of sixth grade students from all public and private schools in the city of Barretos, Southeastern Brazil, conducted in 2004. The factors studied were: exposure to intrafamilial and urban violence, family socioeconomic level, sex, motherless household, participation in social activities (protective factor). All the independent risk and protective factors were included in the initial logistic regression model. Only the variable with a significance level of pOBJETIVO: Analisar fatores de proteção e de risco para problemas de saúde mental entre adolescentes. MÉTODOS: Estudo transversal realizado com amostra aleatória (N=327; perda=6,9%) de estudantes da sexta série de todas as escolas públicas e privadas de Barretos, SP, em 2004. Os fatores examinados foram: exposição à violência doméstica e urbana, nível socioeconômico familiar, sexo, morar sem a mãe, participar de atividades sociais (fator de proteção). As associações entre esses fatores e problemas de saúde mental foram analisadas por meio de modelos de regressão logística. Todos os fatores de risco e proteção independentes foram incluídos no modelo inicial de regressão logística, permanecendo no modelo final apenas a variável com nível de significância inferior a 0,05. RESULTADOS: Verificou-se que apenas exposição à violência permaneceu no modelo final como fator associado a problemas de saúde mental (p=0,02; IC 95%: 1,12;4,22). Crianças expostas à violência doméstica tinham três vezes mais chances de apresentarem estes problemas do que aquelas expostas à violência urbana (p=0,04; IC 95%: 1,03;7,55). CONCLUSÕES: A violência doméstica associou-se a problemas de saúde mental nos adolescentes do estudo, podendo ser mais importante que a violência urbana em cidades de médio porte

Reconstruction of the gravitational wave signal h(t)h(t) during the Virgo science runs and independent validation with a photon calibrator

The Virgo detector is a kilometer-scale interferometer for gravitational wave detection located near Pisa (Italy). About 13 months of data were accumulated during four science runs (VSR1, VSR2, VSR3 and VSR4) between May 2007 and September 2011, with increasing sensitivity. In this paper, the method used to reconstruct, in the range 10 Hz-10 kHz, the gravitational wave strain time series $h(t)$ from the detector signals is described. The standard consistency checks of the reconstruction are discussed and used to estimate the systematic uncertainties of the $h(t)$ signal as a function of frequency. Finally, an independent setup, the photon calibrator, is described and used to validate the reconstructed $h(t)$ signal and the associated uncertainties. The uncertainties of the $h(t)$ time series are estimated to be 8% in amplitude. The uncertainty of the phase of $h(t)$ is 50 mrad at 10 Hz with a frequency dependence following a delay of 8 $\mu$s at high frequency. A bias lower than $4\,\mathrm{\mu s}$ and depending on the sky direction of the GW is also present.Comment: 35 pages, 16 figures. Accepted by CQ

Virgo calibration and reconstruction of the gravitational wave strain during VSR1

Virgo is a kilometer-length interferometer for gravitational waves detection located near Pisa. Its first science run, VSR1, occured from May to October 2007. The aims of the calibration are to measure the detector sensitivity and to reconstruct the time series of the gravitational wave strain h(t). The absolute length calibration is based on an original non-linear reconstruction of the differential arm length variations in free swinging Michelson configurations. It uses the laser wavelength as length standard. This method is used to calibrate the frequency dependent response of the Virgo mirror actuators and derive the detector in-loop response and sensitivity within ~5%. The principle of the strain reconstruction is highlighted and the h(t) systematic errors are estimated. A photon calibrator is used to check the sign of h(t). The reconstructed h(t) during VSR1 is valid from 10 Hz up to 10 kHz with systematic errors estimated to 6% in amplitude. The phase error is estimated to be 70 mrad below 1.9 kHz and 6 micro-seconds above.Comment: 8 pages, 8 figures, proceedings of Amaldi 8 conference, to be published in Journal of Physics Conference Series (JPCS). Second release: correct typo

Calibration and sensitivity of the Virgo detector during its second science run

The Virgo detector is a kilometer-length interferometer for gravitational wave detection located near Pisa (Italy). During its second science run (VSR2) in 2009, six months of data were accumulated with a sensitivity close to its design. In this paper, the methods used to determine the parameters for sensitivity estimation and gravitational wave reconstruction are described. The main quantities to be calibrated are the frequency response of the mirror actuation and the sensing of the output power. Focus is also put on their absolute timing. The monitoring of the calibration data as well as the parameter estimation with independent techniques are discussed to provide an estimation of the calibration uncertainties. Finally, the estimation of the Virgo sensitivity in the frequency-domain is described and typical sensitivities measured during VSR2 are shown.Comment: 30 pages, 23 figures, 1 table. Published in Classical and Quantum Gravity (CQG), Corrigendum include