401 research outputs found
Interrupted versus uninterrupted NOAC peri-implantation of cardiac device: A single-centre randomised prospective pilot trial
BACKGROUND: Many patients requiring cardiac implantable electronic device (CIED) implantation are on long-term oral anticoagulant therapy. While continuation of warfarin has been shown to be safe and reduce bleeding complications compared to interruption of warfarin therapy and heparin bridging, it is not known which novel oral anticoagulants (NOAC) regimen (interrupted vs. uninterrupted) is better in this setting. METHODS: One-hundred and one patients were randomized to receive CIED implantation with either interrupted or uninterrupted/continuous NOAC therapy before surgery. No heparin was used in either treatment arm. The primary end-point was the presence of a clinically significant pocket haematoma after CIED implantation. The secondary end-point was a composite of other major bleeding events, device-related infection, thrombotic events and device-related admission length post device implantation. RESULTS: Both treatment groups were equally balanced for baseline variables and concomitant medications. One clinically significant pocket haematoma occurred in the uninterrupted NOAC group and none in the interrupted group (p = 0.320). There was no difference in other bleeding complications. No thrombotic events were observed in either of the two groups. CONCLUSIONS: Despite the paucity of bleeding events, data from this pilot study suggest that uninterrupted NOAC therapy for CIED implantation appears to be as safe as NOAC interruption and does not increase bleeding complications
Test of candidate light distributors for the muon (g2) laser calibration system
The new muon (g-2) experiment E989 at Fermilab will be equipped with a laser
calibration system for all the 1296 channels of the calorimeters. An
integrating sphere and an alternative system based on an engineered diffuser
have been considered as possible light distributors for the experiment. We
present here a detailed comparison of the two based on temporal response,
spatial uniformity, transmittance and time stability.Comment: accepted to Nucl.Instrum.Meth.
Proton-air cross section measurement with the ARGO-YBJ cosmic ray experiment
The proton-air cross section in the energy range 1-100 TeV has been measured
by the ARGO-YBJ cosmic ray experiment. The analysis is based on the flux
attenuation for different atmospheric depths (i.e. zenith angles) and exploits
the detector capabilities of selecting the shower development stage by means of
hit multiplicity, density and lateral profile measurements at ground. The
effects of shower fluctuations, the contribution of heavier primaries and the
uncertainties of the hadronic interaction models, have been taken into account.
The results have been used to estimate the total proton-proton cross section at
center of mass energies between 70 and 500 GeV, where no accelerator data are
currently available.Comment: 14 pages, 9 figure
Search for Gamma Ray Bursts with the Argo-YBJ Detector in Scaler Mode
We report on the search for Gamma Ray Bursts (GRBs) in the energy range 1-100
GeV in coincidence with the prompt emission detected by satellites using the
Astrophysical Radiation with Ground-based Observatory at YangBaJing (ARGO-YBJ)
air shower detector. Thanks to its mountain location (Yangbajing, Tibet, P.R.
China, 4300 m a.s.l.), active surface (about 6700 m**2 of Resistive Plate
Chambers), and large field of view (about 2 sr, limited only by the atmospheric
absorption), the ARGO-YBJ air shower detector is particularly suitable for the
detection of unpredictable and short duration events such as GRBs. The search
is carried out using the "single particle technique", i.e. counting all the
particles hitting the detector without measurement of the energy and arrival
direction of the primary gamma rays.
Between 2004 December 17 and 2009 April 7, 81 GRBs detected by satellites
occurred within the field of view of ARGO-YBJ (zenith angle < 45 deg). It was
possible to examine 62 of these for >1 GeV counterpart in the ARGO-YBJ data
finding no statistically significant emission. With a lack of detected spectra
in this energy range fluence upper limits are profitable, especially when the
redshift is known and the correction for the extragalactic absorption can be
considered. The obtained fluence upper limits reach values as low as 10**{-5}
erg cm**{-2} in the 1-100 GeV energy region.
Besides this individual search for a higher energy counterpart, a statistical
study of the stack of all the GRBs both in time and in phase was made, looking
for a common feature in the GRB high energy emission. No significant signal has
been detected.Comment: accepted for publication in Ap
Study of the diffuse gamma-ray emission from the Galactic plane with ARGO-YBJ
The events recorded by ARGO-YBJ in more than five years of data collection
have been analyzed to determine the diffuse gamma-ray emission in the Galactic
plane at Galactic longitudes 25{\deg} < l < 100{\deg} and Galactic latitudes .
The energy range covered by this analysis, from ~350 GeV to ~2 TeV, allows the
connection of the region explored by Fermi with the multi-TeV measurements
carried out by Milagro. Our analysis has been focused on two selected regions
of the Galactic plane, i.e., 40{\deg} < l < 100{\deg} and 65{\deg} < l <
85{\deg} (the Cygnus region), where Milagro observed an excess with respect to
the predictions of current models. Great care has been taken in order to mask
the most intense gamma-ray sources, including the TeV counterpart of the Cygnus
cocoon recently identified by ARGO-YBJ, and to remove residual contributions.
The ARGO-YBJ results do not show any excess at sub-TeV energies corresponding
to the excess found by Milagro, and are consistent with the predictions of the
Fermi model for the diffuse Galactic emission. From the measured energy
distribution we derive spectral indices and the differential flux at 1 TeV of
the diffuse gamma-ray emission in the sky regions investigated.Comment: 11 pages, 6 figures, published in AP
Measurement of the cosmic ray antiproton/proton flux ratio at TeV energies with the ARGO-YBJ detector
Cosmic ray antiprotons provide an important probe to study the cosmic ray
propagation in the interstellar space and to investigate the existence of dark
matter. Acting the Earth-Moon system as a magnetic spectrometer, paths of
primary antiprotons are deflected in the opposite sense with respect to those
of the protons in their way to the Earth. This effect allows, in principle, the
search for antiparticles in the direction opposite to the observed deficit of
cosmic rays due to the Moon (the so-called `Moon shadow').
The ARGO-YBJ experiment, located at the Yangbajing Cosmic Ray Laboratory
(Tibet, P.R. China, 4300 m a.s.l., 606 g/cm), is particularly effective in
measuring the cosmic ray antimatter content via the observation of the cosmic
rays shadowing effect due to: (1) good angular resolution, pointing accuracy
and long-term stability; (2) low energy threshold; (3) real sensitivity to the
geomagnetic field.
Based on all the data recorded during the period from July 2006 through
November 2009 and on a full Monte Carlo simulation, we searched for the
existence of the shadow cast by antiprotons in the TeV energy region. No
evidence of the existence of antiprotons is found in this energy region. Upper
limits to the flux ratio are set to 5 % at a median energy of 1.4
TeV and 6 % at 5 TeV with a confidence level of 90%. In the TeV energy range
these limits are the lowest available.Comment: Contact authors: G. Di Sciascio ([email protected]) and R.
Iuppa ([email protected]), INFN Sezione di Roma Tor Vergata, Roma, Ital
4.5 years multi-wavelength observations of Mrk 421 during the ARGO-YBJ and Fermi common operation time
We report on the extensive multi-wavelength observations of the blazar
Markarian 421 (Mrk 421) covering radio to gamma-rays, during the 4.5 year
period of ARGO-YBJ and Fermi common operation time, from August 2008 to
February 2013. In particular, thanks to the ARGO-YBJ and Fermi data, the whole
energy range from 100 MeV to 10 TeV is covered without any gap. In the
observation period, Mrk 421 showed both low and high activity states at all
wavebands. The correlations among flux variations in different wavebands were
analyzed. Seven large flares, including five X-ray flares and two GeV gamma-ray
flares with variable durations (3-58 days), and one X-ray outburst phase were
identified and used to investigate the variation of the spectral energy
distribution with respect to a relative quiescent phase. During the outburst
phase and the seven flaring episodes, the peak energy in X-rays is observed to
increase from sub-keV to few keV. The TeV gamma-ray flux increases up to
0.9-7.2 times the flux of the Crab Nebula. The behavior of GeV gamma-rays is
found to vary depending on the flare, a feature that leads us to classify
flares into three groups according to the GeV flux variation. Finally, the
one-zone synchrotron self-Compton model was adopted to describe the emission
spectra. Two out of three groups can be satisfactorily described using injected
electrons with a power-law spectral index around 2.2, as expected from
relativistic diffuse shock acceleration, whereas the remaining group requires a
harder injected spectrum. The underlying physical mechanisms responsible for
different groups may be related to the acceleration process or to the
environment properties.Comment: 17 pages, 9 figures, 5 tables, Accepted for publication in ApJ
The ASIMOV Prize for scientific publishing - HEP researchers trigger young people toward science
This work presents the ASIMOV Prize for scientific publishing, which was launched in Italy in 2016. The prize aims to bring the young generations closer to scientific culture, through the critical reading of popular science books. The books are selected by a committee that includes scientists, professors, Ph.D. and Ph.D. students, writers, journalists and friends of culture, and most importantly, over 800 school teachers. Students are actively involved in the prize, according to the best practices of public engagement: they read, review the books and vote for them, choosing the winner. The experience is quite successful: 12,000 students from 270 schools all over Italy participated in the last edition.
The possibility of replicating this experience in other countries is indicated, as was done in Brazil in 2020 with more than encouraging results
The cosmic ray proton plus helium energy spectrum measured by the ARGO-YBJ experiment in the energy range 3-300 TeV
The ARGO-YBJ experiment is a full-coverage air shower detector located at the
Yangbajing Cosmic Ray Observatory (Tibet, People's Republic of China, 4300 m
a.s.l.). The high altitude, combined with the full-coverage technique, allows
the detection of extensive air showers in a wide energy range and offer the
possibility of measuring the cosmic ray proton plus helium spectrum down to the
TeV region, where direct balloon/space-borne measurements are available. The
detector has been in stable data taking in its full configuration from November
2007 to February 2013. In this paper the measurement of the cosmic ray proton
plus helium energy spectrum is presented in the region 3-300 TeV by analyzing
the full collected data sample. The resulting spectral index is . These results demonstrate the possibility of performing an accurate
measurement of the spectrum of light elements with a ground based air shower
detector.Comment: 18 pages, 8 figures, preprint submitted to Phys. Rev.
EAS age determination from the study of the lateral distribution of charged particles near the shower axis with the ARGO-YBJ experiment
The ARGO-YBJ experiment, a full coverage extensive air shower (EAS) detector
located at high altitude (4300 m a.s.l.) in Tibet, China, has smoothly taken
data, with very high stability, since November 2007 to the beginning of 2013.
The array consisted of a carpet of about 7000 m Resistive Plate Chambers
(RPCs) operated in streamer mode and equipped with both digital and analog
readout, providing the measurement of particle densities up to few particles
per cm. The unique detector features (full coverage, readout granularity,
wide dynamic range, etc) and location (very high altitude) allowed a detailed
study of the lateral density profile of charged particles at ground very close
to the shower axis and its description by a proper lateral distribution
function (LDF). In particular, the information collected in the first 10 m from
the shower axis have been shown to provide a very effective tool for the
determination of the shower development stage ("age") in the energy range 50
TeV - 10 PeV. The sensitivity of the age parameter to the mass composition of
primary Cosmic Rays is also discussed
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