1,308 research outputs found
Showering Cosmogenic Muons in A Large Liquid Scintillator
We present the results of FLUKA simulations of the propagation of cosmogenic
muons in a 20 kton spherical liquid scintillator detector underneath 700 to 900
meters of rock. A showering muon is one which deposits at least 3 GeV in the
detector in addition to ionization energy. We find that 20 percent of muons are
showering and a further 10 percent of muon events are muon bundles of which
more than one muon enters the detector. In this range the showering and bundle
fractions are robust against changes in the depth and topography, thus the
total shower and bundle rate for a given experiment can be obtained by
combining our results with an estimate for the total muon flux. One consequence
is that a straightforward adaptation of the full detector showering muon cuts
used by KamLAND to JUNO or RENO 50 would yield a nearly vanishing detector
efficiency.Comment: 24 pages, 18 figures, v4: Improved precision of bundle rate
Secondary Beam Monitors for the NuMI Facility at FNAL
The Neutrinos at the Main Injector (NuMI) facility is a conventional neutrino
beam which produces muon neutrinos by focusing a beam of mesons into a long
evacuated decay volume. We have built four arrays of ionization chambers to
monitor the position and intensity of the hadron and muon beams associated with
neutrino production at locations downstream of the decay volume. This article
describes the chambers' construction, calibration, and commissioning in the
beam.Comment: Accepted for publication in Nucl. Instr. Meth.
Neutron production by cosmic-ray muons at shallow depth
The yield of neutrons produced by cosmic ray muons at a shallow depth of 32
meters of water equivalent has been measured. The Palo Verde neutrino detector,
containing 11.3 tons of Gd loaded liquid scintillator and 3.5 tons of acrylic
served as a target. The rate of one and two neutron captures was determined.
Modeling the neutron capture efficiency allowed us to deduce the total yield of
neutrons neutrons per muon
and g/cm. This yield is consistent with previous measurements at similar
depths.Comment: 12 pages, 3 figure
High-energy neutrinos from reverse shocks in choked and successful relativistic jets
Highly relativistic jets are a key element of current gamma-ray burst models,
where the jet kinetic energy is converted to radiation energy at optically thin
shocks. High-energy neutrinos are also expected, from interactions of protons
accelerated in the same shocks. Here we revisit the early evolution of a
relativistic jet, while the jet is still inside the star, and investigate its
neutrino emission. In particular we study propagation of mildly relativistic
and ultrarelativistic jets through a type Ib progenitor, and follow reverse
shocks as the jets cross the star. We show that protons can be accelerated to
10^4-10^5 GeV at reverse shocks, and efficiently produce mesons. The mesons
experience significant cooling, suppressing subsequent neutrino emission. We
show, however, that the neutrino yield from the reverse shock is still
reasonably large, especially for low-luminosity and long-duration jets, where
meson cooling is less severe. We discuss implications of our results in the
context of neutrinos from choked jets, which are completely shock heated and do
not break out of the star. From a choked jet with isotropic equivalent energy
of 10^{53} erg at 10 Mpc, we expect ~20 neutrino events at IceCube.Comment: 11 pages, 7 figures, 2 tables; accepted for publication in Physical
Review
Non-Critical Liouville String Escapes Constraints on Generic Models of Quantum Gravity
It has recently been pointed out that generic models of quantum gravity must
contend with severe phenomenological constraints imposed by gravitational
Cerenkov radiation, neutrino oscillations and the cosmic microwave background
radiation. We show how the non-critical Liouville-string model of quantum
gravity we have proposed escapes these constraints. It gives energetic
particles subluminal velocities, obviating the danger of gravitational Cerenkov
radiation. The effect on neutrino propagation is naturally flavour-independent,
obviating any impact on oscillation phenomenology. Deviations from the expected
black-body spectrum and the effects of time delays and stochastic fluctuations
in the propagation of cosmic microwave background photons are negligible, as
are their effects on observable spectral lines from high-redshift astrophysical
objects.Comment: 15 pages LaTeX, 2 eps figures include
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