1,721,836 research outputs found
Resonant-mass detectors: status and perspectives
No full textWe review the main features and the perspectives of the resonant-mass gravitational wave detectors. Bar detectors have been taking data for the last few years with burst sensitivity h sime 4 × 10−19 at SNR = 1, or, in spectral units, 3 × 10−22 Hz −1/2 over a bandwidth of about 1 Hz, with a duty cycle mainly limited by cryogenic operations. In addition to the systematic search for impulsive events, the data collected are being used to detect periodic waves over long time periods, to give new upper limits for the stochastic background of cosmological origin, and to study possible correlation with gamma ray bursts. The recent developments of readout electronics have allowed us to increase the detection bandwidth to a few tens of Hz, and even larger bandwidths are expected in the near future. Resonant-mass detectors of spherical shape have been investigated and many different solutions have been proposed. Two small (about 60 cm in diameter) spheres are under construction in Holland and Brazil. Recently, a new scheme has been proposed, the 'dual' detector, which can provide a wideband performance. We briefly describe the status of traditional resonant-mass detectors and the main features and the state of the art of the advanced acoustic detectors
Multimessenger search for astrophysical bursts with Gravitational Waves and Low Energy Neutrinos
No full textThe next galactic Core Collapse Supernova (CCSN) may represent one of the
most important events in modern astrophysics. The electromagnetic (EM)
emission of the explosion is well understood, but we have no information
about the inner mechanisms that cause it. Neutrinos (\nu) and gravitational
waves (GWs) are the only messengers able to carry information about the inner
working mechanisms of a CCSN. Neutrinos from supernova carry thermodynamic
informations about the collapse, and GWs may reveal the dynamics
involved in the collapse. Via coincident detection and joint analysis
of \nu and GWs from the next nearby core collapse event, we will increase
the knowledge of the astrophysics, neutrino physics, and nuclear physics involved
in these sources.
In this thesis work, we studied the detection efficiency and the misidentification
of networks of \nu detectors to the same burst event, simulating the
detectors background and injecting signals produced using for the emission
a general description of an astrophysical burst of low-energy neutrinos with
a characteristic temporal structure and quasi-thermal spectral shape. We provide
a challenging method to better discriminate under threshold signals
from experimental background. With respect to previous search strategies
this method, without decreasing the detection efficiency, allows to knockingdown
the misidentification probability by a factor of 7, in the worse case,
within a distance of D \sim 20 kpc and, in the better case, this improvement
can reach a factor \sim 20 till an horizon of \si 75 kpc. After the definition of
the methodology to be used to construct the \nu network, we searched for coincident
events between GW data (archival data from LIGO and Virgo taken
before the upgrade to advanced detectors) and the correponding archival
data. We analyzed the obtained results, giving confidence intervals for the
observe coincident event
SFERA: The new spherical gravitational wave detector
No full textThis paper describes the main properties of gravitational wave detectors of spherical shape, the experimental achievements obtained up to now towards the development of this kind of detectors and the expected sensitivity of SFERA, a 2 meters diameter spherical antenna proposed as the next step in the development of resonant gravitational wave detectors
Developments in resonant-mass detectors
No full textAbstract After a brief summary of the state of the art of resonant-mass detectors, we will describe the planned developments of bar antennas and the near-term perspectives related to the development of SFERA, a new, 33 ton, spherical detector
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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