289 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
Behaviour in Magnetic Fields of Fast Conventional and Fine-Mesh Photomultipliers
The performance of both conventional and fine-mesh Hamamatsu photomultipliers
has been measured inside moderate magnetic fields. This has allowed the test of
effective shielding solutions for photomultipliers, to be used in
time-of-flight detectors based on scintillation counters. Both signal amplitude
reduction or deterioration of the timing properties inside magnetic fields have
been investigated
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
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
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
Neutron-Antineutron Oscillations in Nuclei Revisited
An upper limit on oscillations can be obtained from the stability
of matter. This relation has been worked out theoretically and together with
data yields . A recent publication
claims a different relation and finds a nuclear suppression of the
oscillations which is two orders of magnitude weaker than the previous
evaluations. Using the same approach we find, nevertheless, that the earlier
estimates are correct and conclude that future experiments with free neutrons
from reactors are capable to put a stronger limit on the
oscillation time than experiments with large amount of neutrons bound in
nuclei.Comment: To be published in proc. of the Workshop on Future Directions in
Quark Nuclear Physics, Adelaide, March 9 - 20, 199
CPT violation and particle-antiparticle asymmetry in cosmology
General features of generation of the cosmological charge asymmetry in CPT
non-invariant world are discussed. If the effects of CPT violation manifest
themselves only in mass differences of particles and antiparticles, the baryon
asymmetry of the universe hardly can be explained solely by breaking of CPT
invariance. However, CPT non-invariant theories may lead to a new effect of
distorting the usual equilibrium distributions. If this takes place, CPT
violation may explain the baryon asymmetry of the universe.Comment: 7 pages, no figures. Submitted to a special issue of Yadernaya Fizika
(Physics of Atomic Nuclei) dedicated to 80th birthday of L.B. Okun. Three
references are adde
A local trigger system for the large LAr-TPC detector
A special dedicated double-rebinning algorithm has been successfully developed in order to extract the physical hit signal from the TPC wires. This solution has been implemented on digital boards, allowing to realize a local trigger able to identify even localized low-energy small events
Measurement of a large electron lifetime in a liquid argon TPC
An unprecedentedly high value of electron lifetime in a liquid argon TPC, about 21ms, has been measured in a test facility at INFN-LNL. This results opens the way to the future development of TPCs with very long drift distances
Critical Examination of the "Field-Theoretical Approach" to the Neutron-Antineutron Oscillations in Nuclei
We demonstrate that so called "infrared divergences" which have been
discussed in some publications during several years, do not appear within the
correct treatment of analytical properties of the transition amplitudes, in
particular, of the second order pole structure of the amplitudes describing the
transition in nuclei. Explicit calculation with the help of the
Feynman diagram technique shows that the neutron-antineutron oscillations are
strongly suppressed in the deuteron, as well as in heavier nuclei, in
comparison with the oscillations in vacuum. General advantages and some
difficulties of the field theoretical methods applied in nuclear theory are
reminded for the particular example of the parity violating
capture amplitude.Comment: 15 pages, 4 figures; prepared for Eur.Phys.J.
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