188 research outputs found
Search for Slowly Moving Magnetic Monopoles with the MACRO Detector
A search for slowly moving magnetic monopoles in the cosmic radiation was conducted from October 1989 to November 1991 using the large liquid scintillator detector subsystem of the first supermodule of the MACRO detector at the Gran Sasso underground laboratory. The absence of candidates established an upper limit on the monopole flux of 5.6 × 10^(−15) cm^(−2) sr^(−1) s^(−1) at 90% confidence level in the velocity range of 10^(−4)≲β<4×10^(−3). This result places a new constraint on the abundance of monopoles trapped in our solar system
Limits on dark matter WIMPs using upward-going muons in the MACRO detector
We perform an indirect search for Weakly Interacting Massive Particles
(WIMPs) using the MACRO detector to look for neutrino-induced upward-going
muons resulting from the annihilation of WIMPs trapped in the Sun and Earth.
The search is conducted in various angular cones centered on the Sun and Earth
to accommodate a range of WIMP masses. No significant excess over the
background from atmospheric neutrinos is seen and limits are placed on the
upward-going muon fluxes from Sun and Earth. These limits are used to constrain
neutralino particle parameters from supersymmetric theory, including those
suggested by recent results from DAMA/NaI.Comment: 14 pages, 7 figures, submitted to Phys. Rev.
The primary cosmic ray composition between 10**15 and 10**16 eV from Extensive Air Showers electromagnetic and TeV muon data
The cosmic ray primary composition in the energy range between 10**15 and
10**16 eV, i.e., around the "knee" of the primary spectrum, has been studied
through the combined measurements of the EAS-TOP air shower array (2005 m
a.s.l., 10**5 m**2 collecting area) and the MACRO underground detector (963 m
a.s.l., 3100 m w.e. of minimum rock overburden, 920 m**2 effective area) at the
National Gran Sasso Laboratories. The used observables are the air shower size
(Ne) measured by EAS-TOP and the muon number (Nmu) recorded by MACRO. The two
detectors are separated on average by 1200 m of rock, and located at a
respective zenith angle of about 30 degrees. The energy threshold at the
surface for muons reaching the MACRO depth is approximately 1.3 TeV. Such muons
are produced in the early stages of the shower development and in a kinematic
region quite different from the one relevant for the usual Nmu-Ne studies. The
measurement leads to a primary composition becoming heavier at the knee of the
primary spectrum, the knee itself resulting from the steepening of the spectrum
of a primary light component (p, He). The result confirms the ones reported
from the observation of the low energy muons at the surface (typically in the
GeV energy range), showing that the conclusions do not depend on the production
region kinematics. Thus, the hadronic interaction model used (CORSIKA/QGSJET)
provides consistent composition results from data related to secondaries
produced in a rapidity region exceeding the central one. Such an evolution of
the composition in the knee region supports the "standard" galactic
acceleration/propagation models that imply rigidity dependent breaks of the
different components, and therefore breaks occurring at lower energies in the
spectra of the light nuclei.Comment: Submitted to Astroparticle Physic
Measurement of the residual energy of muons in the Gran Sasso underground Laboratories
The MACRO detector was located in the Hall B of the Gran Sasso underground
Laboratories under an average rock overburden of 3700 hg/cm^2. A transition
radiation detector composed of three identical modules, covering a total
horizontal area of 36 m^2, was installed inside the empty upper part of the
detector in order to measure the residual energy of muons. This paper presents
the measurement of the residual energy of single and double muons crossing the
apparatus. Our data show that double muons are more energetic than single ones.
This measurement is performed over a standard rock depth range from 3000 to
6500 hg/cm^2.Comment: 28 pages, 9 figure
Muon Energy Estimate Through Multiple Scattering with the Macro Detector
Muon energy measurement represents an important issue for any experiment
addressing neutrino induced upgoing muon studies. Since the neutrino
oscillation probability depends on the neutrino energy, a measurement of the
muon energy adds an important piece of information concerning the neutrino
system. We show in this paper how the MACRO limited streamer tube system can be
operated in drift mode by using the TDC's included in the QTPs, an electronics
designed for magnetic monopole search. An improvement of the space resolution
is obtained, through an analysis of the multiple scattering of muon tracks as
they pass through our detector. This information can be used further to obtain
an estimate of the energy of muons crossing the detector. Here we present the
results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines,
to provide a full check of the electronics and to exploit the feasibility of
such a multiple scattering analysis. We show that by using a neural network
approach, we are able to reconstruct the muon energy for 40 GeV. The
test beam data provide an absolute energy calibration, which allows us to apply
this method to MACRO data.Comment: 25 pages, 11 figures, Submitted to Nucl. Instr. & Meth.
Search for diffuse neutrino flux from astrophysical sources with MACRO
Many galactic and extragalactic astrophysical sources are currently
considered promising candidates as high energy neutrino emitters. Astrophysical
neutrinos can be detected as upward-going muons produced in charged-current
interactions with the medium surrounding the detector. The expected neutrino
fluxes from various models start to dominate on the atmospheric neutrino
background at neutrino energies above some tens of TeV. We present the results
of a search for an excess of high energy upward-going muons among the sample of
data collected by MACRO during ~5.8 years of effective running time. No
significant evidence for this signal was found. As a consequence, an upper
limit on the flux of upward-going muons from high-energy neutrinos was set at
the level of 1.7 10^(-14) cm^(-2) s^(-1) sr^(-1).
The corresponding upper limit for the diffuse neutrino flux was evaluated
assuming a neutrino power law spectrum. Our result was compared with
theoretical predictions and upper limits from other experiments.Comment: 19 pages, 8 figures, 2 table
The frequency of metal enrichment of cool helium-atmosphere white dwarfs using the DESI early data release
There is an overwhelming evidence that white dwarfs host planetary systems; revealed by the presence, disruption, and accretion of planetary bodies. A lower limit on the frequency of white dwarfs that host planetary material has been estimated to be ≃ 25–50 per cent; inferred from the ongoing or recent accretion of metals on to both hydrogen-atmosphere and warm helium-atmosphere white dwarfs. Now with the unbiased sample of white dwarfs observed by the Dark Energy Spectroscopic Instrument (DESI) survey in their Early Data Release (EDR), we have determined the frequency of metal enrichment around cool-helium atmosphere white dwarfs as 21 ± 3 per cent using a sample of 234 systems. This value is in good agreement with values determined from previous studies. With the current samples we cannot distinguish whether the frequency of planetary accretion varies with system age or host-star mass, but the DESI data release 1 will contain roughly an order of magnitude more white dwarfs than DESI EDR and will allow these parameters to be investigated
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