1,019 research outputs found
Search for Gravitational Waves from Binary Black Hole Inspiral, Merger and Ringdown
We present the first modeled search for gravitational waves using the complete binary black hole gravitational waveform from inspiral through the merger and ringdown for binaries with negligible component spin. We searched approximately 2 years of LIGO data taken between November 2005 and September 2007 for systems with component masses of 1-99 solar masses and total masses of 25-100 solar masses. We did not detect any plausible gravitational-wave signals but we do place upper limits on the merger rate of binary black holes as a function of the component masses in this range. We constrain the rate of mergers for binary black hole systems with component masses between 19 and 28 solar masses and negligible spin to be no more than 2.0 per Mpc^3 per Myr at 90% confidence
Beating the Spin-Down Limit on Gravitational Wave Emission from the Vela Pulsar
We present direct upper limits on continuous gravitational wave emission from the Vela pulsar using data from the Virgo detector\u27s second science run. These upper limits have been obtained using three independent methods that assume the gravitational wave emission follows the radio timing. Two of the methods produce frequentist upper limits for an assumed known orientation of the star\u27s spin axis and value of the wave polarization angle of, respectively, 1.9\ee{-24} and 2.2\ee{-24}, with 95% confidence. The third method, under the same hypothesis, produces a Bayesian upper limit of 2.1\ee{-24}, with 95% degree of belief. These limits are below the indirect {\it spin-down limit} of 3.3\ee{-24} for the Vela pulsar, defined by the energy loss rate inferred from observed decrease in Vela\u27s spin frequency, and correspond to a limit on the star ellipticity of . Slightly less stringent results, but still well below the spin-down limit, are obtained assuming the star\u27s spin axis inclination and the wave polarization angles are unknown
Accurate calibration of test mass displacement in the LIGO interferometers
We describe three fundamentally different methods we have applied to
calibrate the test mass displacement actuators to search for systematic errors
in the calibration of the LIGO gravitational-wave detectors. The actuation
frequencies tested range from 90 Hz to 1 kHz and the actuation amplitudes range
from 1e-6 m to 1e-18 m. For each of the four test mass actuators measured, the
weighted mean coefficient over all frequencies for each technique deviates from
the average actuation coefficient for all three techniques by less than 4%.
This result indicates that systematic errors in the calibration of the
responses of the LIGO detectors to differential length variations are within
the stated uncertainties.Comment: 10 pages, 6 figures, submitted on 31 October 2009 to Classical and
Quantum Gravity for the proceedings of 8th Edoardo Amaldi Conference on
Gravitational Wave
Radiation damage in the LHCb vertex locator
The LHCb Vertex Locator (VELO) is a silicon strip detector designed to reconstruct charged particle trajectories and vertices produced at the LHCb interaction region. During the first two years of data collection, the 84 VELO sensors have been exposed to a range of fluences up to a maximum value of approximately 45 Ă 1012 1 MeV neutron equivalent (1 MeV neq). At the operational sensor temperature of approximately â7 °C, the average rate of sensor current increase is 18 ÎŒA per fbâ1, in excellent agreement with predictions. The silicon effective bandgap has been determined using current versus temperature scan data after irradiation, with an average value of Eg = 1.16±0.03±0.04 eV obtained. The first observation of n+-on-n sensor type inversion at the LHC has been made, occurring at a fluence of around 15 Ă 1012 of 1 MeV neq. The only n+-on-p sensors in use at the LHC have also been studied. With an initial fluence of approximately 3 Ă 1012 1 MeV neq, a decrease in the Effective Depletion Voltage (EDV) of around 25 V is observed. Following this initial decrease, the EDV increases at a comparable rate to the type inverted n+-on-n type sensors, with rates of (1.43±0.16) Ă 10â12 V/ 1 MeV neq and (1.35±0.25) Ă 10â12 V/ 1 MeV neq measured for n+-on-p and n+-on-n type sensors, respectively. A reduction in the charge collection efficiency due to an unexpected effect involving the second metal layer readout lines is observed
Performance of the LHCb vertex locator
The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment. The performance of the detector during the first years of its physics operation is reviewed. The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7 mm from the LHC beam for physics data taking. The performance and stability of these characteristic features of the detector are described, and details of the material budget are given. The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described. The system performance is fully characterised. The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 ÎŒm is achieved at the optimal track angle. The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 0.5%, and the detector has less than 1% of faulty strips. The proximity of the detector to the beam means that the inner regions of the n+-on-n sensors have undergone space-charge sign inversion due to radiation damage. The VELO performance parameters that drive the experiment's physics sensitivity are also given. The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 ÎŒm for translations in the plane transverse to the beam. A primary vertex resolution of 13 ÎŒm in the transverse plane and 71 ÎŒm along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 ÎŒm is achieved for particles with transverse momentum greater than 1 GeV/c
Precision luminosity measurements at LHCb
Measuring cross-sections at the LHC requires the luminosity to be determined accurately at each centre-of-mass energy âs. In this paper results are reported from the luminosity calibrations carried out at the LHC interaction point 8 with the LHCb detector for âs = 2.76, 7 and 8 TeV (proton-proton collisions) and for âsNN = 5 TeV (proton-lead collisions). Both the "van der Meer scan" and "beam-gas imaging" luminosity calibration methods were employed. It is observed that the beam density profile cannot always be described by a function that is factorizable in the two transverse coordinates. The introduction of a two-dimensional description of the beams improves significantly the consistency of the results. For proton-proton interactions at âs = 8 TeV a relative precision of the luminosity calibration of 1.47% is obtained using van der Meer scans and 1.43% using beam-gas imaging, resulting in a combined precision of 1.12%. Applying the calibration to the full data set determines the luminosity with a precision of 1.16%. This represents the most precise luminosity measurement achieved so far at a bunched-beam hadron collider
Triangulation of gravitational wave sources with a network of detectors
There is significant benefit to be gained by pursuing multi-messenger
astronomy with gravitational wave and electromagnetic observations. In order to
undertake electromagnetic follow-ups of gravitational wave signals, it will be
necessary to accurately localize them in the sky. Since gravitational wave
detectors are not inherently pointing instruments, localization will occur
primarily through triangulation with a network of detectors. We investigate the
expected timing accuracy for observed signals and the consequences for
localization. In addition, we discuss the effect of systematic uncertainties in
the waveform and calibration of the instruments on the localization of sources.
We provide illustrative results of timing and localization accuracy as well as
systematic effects for coalescing binary waveforms.Comment: 20 pages, 5 figure
Search for gravitational-wave bursts in LIGO data from the fourth science run
The fourth science run of the LIGO and GEO 600 gravitational-wave detectors,
carried out in early 2005, collected data with significantly lower noise than
previous science runs. We report on a search for short-duration
gravitational-wave bursts with arbitrary waveform in the 64-1600 Hz frequency
range appearing in all three LIGO interferometers. Signal consistency tests,
data quality cuts, and auxiliary-channel vetoes are applied to reduce the rate
of spurious triggers. No gravitational-wave signals are detected in 15.5 days
of live observation time; we set a frequentist upper limit of 0.15 per day (at
90% confidence level) on the rate of bursts with large enough amplitudes to be
detected reliably. The amplitude sensitivity of the search, characterized using
Monte Carlo simulations, is several times better than that of previous
searches. We also provide rough estimates of the distances at which
representative supernova and binary black hole merger signals could be detected
with 50% efficiency by this analysis.Comment: Corrected amplitude sensitivities (7% change on average); 30 pages,
submitted to Classical and Quantum Gravit
First joint search for gravitational-wave bursts in LIGO and GEO600 data
We present the results of the first joint search for gravitational-wave
bursts by the LIGO and GEO600 detectors. We search for bursts with
characteristic central frequencies in the band 768 to 2048 Hz in the data
acquired between the 22nd of February and the 23rd of March, 2005 (fourth LSC
Science Run - S4). We discuss the inclusion of the GEO600 data in the
Waveburst-CorrPower pipeline that first searches for coincident excess power
events without taking into account differences in the antenna responses or
strain sensitivities of the various detectors. We compare the performance of
this pipeline to that of the coherent Waveburst pipeline based on the maximum
likelihood statistic. This likelihood statistic is derived from a coherent sum
of the detector data streams that takes into account the antenna patterns and
sensitivities of the different detectors in the network. We find that the
coherentWaveburst pipeline is sensitive to signals of amplitude 30 - 50%
smaller than the Waveburst-CorrPower pipeline. We perform a search for
gravitational-wave bursts using both pipelines and find no detection candidates
in the S4 data set when all four instruments were operating stably.Comment: 30 pages, 8 figure
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