408 research outputs found
Neutron-antineutron Oscillations in the Trapping Box
We have reexamined the problem of oscillations for ultra-cold
neutrons (UCN) confined within a trap. We have shown that the growth of the
component with time is to a decent accuracy given by where is the mixing parameter,
sec in the neutron propagation time between subsequent collisions
with the trap walls. Possible corrections to this law and open questions are
discussed.Comment: 11 pages, LaTeX2
Multidimensional news quality: A comparison of crowdsourcing and nichesourcing
In the age of fake news and of filter bubbles, assessing the quality of information is a compelling issue: it is important for users to understand the quality of the information they consume online. We report on our experiment aimed at understanding if workers from the crowd can be a suitable alternative to
The Rise Times of High and Low Redshift Type Ia Supernovae are Consistent
We present a self-consistent comparison of the rise times for low- and
high-redshift Type Ia supernovae. Following previous studies, the early light
curve is modeled using a t-squared law, which is then mated with a modified
Leibundgut template light curve. The best-fit t-squared law is determined for
ensemble samples of low- and high-redshift supernovae by fitting simultaneously
for all light curve parameters for all supernovae in each sample. Our method
fully accounts for the non-negligible covariance amongst the light curve
fitting parameters, which previous analyses have neglected. Contrary to Riess
et al. (1999), we find fair to good agreement between the rise times of the
low- and high-redshift Type Ia supernovae. The uncertainty in the rise time of
the high-redshift Type Ia supernovae is presently quite large (roughly +/- 1.2
days statistical), making any search for evidence of evolution based on a
comparison of rise times premature. Furthermore, systematic effects on rise
time determinations from the high-redshift observations, due to the form of the
late-time light curve and the manner in which the light curves of these
supernovae were sampled, can bias the high-redshift rise time determinations by
up to +3.6/-1.9 days under extreme situations. The peak brightnesses - used for
cosmology - do not suffer any significant bias, nor any significant increase in
uncertainty.Comment: 18 pages, 4 figures, Accepted for publication in the Astronomical
Journal. Also available at http://www.lbl.gov/~nugent/papers.html Typos were
corrected and a few sentences were added for improved clarit
Free electron lifetime achievements in Liquid Argon Imaging TPC
A key feature for the success of the liquid Argon imaging TPC (LAr-TPC)
technology is the industrial purification against electro-negative impurities,
especially Oxygen and Nitrogen remnants, which have to be continuously kept at
an exceptionally low level by filtering and recirculating liquid Argon.
Improved purification techniques have been applied to a 120 liters LAr-TPC test
facility in the INFN-LNL laboratory. Through-going muon tracks have been used
to determine the free electron lifetime in liquid Argon against
electro-negative impurities. The short path length here observed (30 cm) is
compensated by the high accuracy in the observation of the specific ionization
of cosmic ray muons at sea level as a function of the drift distance. A free
electron lifetime of (21.4+7.3-4.3) ms, namely > 15.8 ms at 90 % C.L. has been
observed over several weeks under stable conditions, corresponding to a
residual Oxygen equivalent of about 15 ppt (part per trillion). At 500 V/cm,
the free electron speed is 1.5 m/ms. In a LAr-TPC a free electron lifetime in
excess of 15 ms corresponds for instance to an attenuation of less than 15 %
after a drift path of 5 m, opening the way to the operation of the LAr-TPC with
exceptionally long drift distances.Comment: 15 pages, 10 figures; Accepted for publication in JINS
Neutron-Mirror-Neutron Oscillations in a Trap
We calculate the rate of neutron-mirror-neutron oscillations for ultracold
neutrons trapped in a storage vessel. Recent experimental bounds on the
oscillation time are discussed.Comment: v4: typos correcte
Some Implications of Neutron Mirror Neutron Oscillation
We comment on a recently discussed possibility of oscillations between
neutrons and degenerate mirror neutrons in the context of mirror models for
particles and forces. It has been noted by Bento and Berezhiani that if these
oscillations occurred at a rate of , it would
help explain putative super GKZ cosmic ray events provided the temperature of
the mirror radiation is times that of familiar cosmic microwave
background radiation. We discuss how such oscillation time scales can be
realized in mirror models and find that the simplest nonsupersymmetric model
for this idea requires the existence of a low mass (30-3000 GeV) color triplet
scalar or vector boson. A supersymmetric model, where this constraint can be
avoided is severely constrained by the requirement of maintaining a cooler
mirror sector. We also find that the reheat temperature after inflation in
generic models that give fast oscillation be less than about 300 GeV in
order to maintain the required relative coolness of the mirror sector.Comment: 12 pages, 2 figures; minor changes in the text; accepted for
publication in Phys. Lett.
The design and commissioning of the MICE upstream time-of-flight system
In the MICE experiment at RAL the upstream time-of-flight detectors are used
for particle identification in the incoming muon beam, for the experiment
trigger and for a precise timing (sigma_t ~ 50 ps) with respect to the
accelerating RF cavities working at 201 MHz. The construction of the upstream
section of the MICE time-of-flight system and the tests done to characterize
its individual components are shown. Detector timing resolutions ~50-60 ps were
achieved. Test beam performance and preliminary results obtained with beam at
RAL are reported.Comment: accepted on Nuclear Instruments and Methods
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