1,070 research outputs found
Opportunities With Decay-At-Rest Neutrinos From Decay-In-Flight Neutrino Beams
Neutrino beam facilities, like spallation neutron facilities, produce copious
quantities of neutrinos from the decay at rest of mesons and muons. The
viability of decay-in-flight neutrino beams as sites for decay-at-rest neutrino
studies has been investigated by calculating expected low-energy neutrino
fluxes from the existing Fermilab NuMI beam facility. Decay-at-rest neutrino
production in NuMI is found to be roughly equivalent per megawatt to that of
spallation facilities, and is concentrated in the facility's target hall and
beam stop regions. Interaction rates in 5 and 60 ton liquid argon detectors at
a variety of existing and hypothetical locations along the beamline are found
to be comparable to the largest existing decay-at-rest datasets for some
channels. The physics implications and experimental challenges of such a
measurement are discussed, along with prospects for measurements at targeted
facilities along a future Fermilab long-baseline neutrino beam.Comment: 6 pages, 3 figure
Adiabatic motion of a neutral spinning particle in an inhomogeneous magnetic field
The motion of a neutral particle with a magnetic moment in an inhomogeneous magnetic field is considered. This situation, occurring, for example, in a Stern-Gerlach experiment, is investigated from classical and semiclassical points of view. It is assumed that the magnetic field is strong or slowly varying in space, i.e., that adiabatic conditions hold. To the classical model, a systematic Lie-transform perturbation technique is applied up to second order in the adiabatic-expansion parameter. The averaged classical Hamiltonian contains not only terms representing fictitious electric and magnetic fields but also an additional velocity-dependent potential. The Hamiltonian of the quantum-mechanical system is diagonalized by means of a systematic WKB analysis for coupled wave equations up to second order in the adiabaticity parameter, which is coupled to Planck’s constant. An exact term-by-term correspondence with the averaged classical Hamiltonian is established, thus confirming the relevance of the additional velocity-dependent second-order contribution
Long-Term Testing and Properties of Acrylic for the Daya Bay Antineutrino Detectors
The Daya Bay reactor antineutrino experiment has recently measured the
neutrino mixing parameter sin22{\theta}13 by observing electron antineutrino
disappearance over kilometer-scale baselines using six antineutrino detectors
at near and far distances from reactor cores at the Daya Bay nuclear power
complex. Liquid scintillator contained in transparent target vessels is used to
detect electron antineutrinos via the inverse beta-decay reaction. The Daya Bay
experiment will operate for about five years yielding a precision measurement
of sin22{\theta}13. We report on long-term studies of poly(methyl methacrylate)
known as acrylic, which is the primary material used in the fabrication of the
target vessels for the experiment's antineutrino detectors. In these studies,
acrylic samples are subjected to gaseous and liquid environmental conditions
similar to those experienced during construction, transport, and operation of
the Daya Bay acrylic target vessels and detectors. Mechanical and optical
stability of the acrylic as well as its interaction with detector liquids is
reported.Comment: 17 pages, 13 figures Submitted to JINS
Quantum Charged Spinning Particles in a Strong Magnetic Field (a Quantal Guiding Center Theory)
A quantal guiding center theory allowing to systematically study the
separation of the different time scale behaviours of a quantum charged spinning
particle moving in an external inhomogeneous magnetic filed is presented. A
suitable set of operators adapting to the canonical structure of the problem
and generalizing the kinematical momenta and guiding center operators of a
particle coupled to a homogenous magnetic filed is constructed. The Pauli
Hamiltonian rewrites in this way as a power series in the magnetic length making the problem amenable to a perturbative analysis. The
first two terms of the series are explicitly constructed. The effective
adiabatic dynamics turns to be in coupling with a gauge filed and a scalar
potential. The mechanism producing such magnetic-induced geometric-magnetism is
investigated in some detail.Comment: LaTeX (epsfig macros), 27 pages, 2 figures include
Ray helicity: a geometric invariant for multi-dimensional resonant wave conversion
For a multicomponent wave field propagating into a multidimensional
conversion region, the rays are shown to be helical, in general. For a
ray-based quantity to have a fundamental physical meaning it must be invariant
under two groups of transformations: congruence transformations (which shuffle
components of the multi-component wave field) and canonical transformations
(which act on the ray phase space). It is shown that for conversion between two
waves there is a new invariant not previously discussed: the intrinsic helicity
of the ray
Reactor Fuel Fraction Information on the Antineutrino Anomaly
We analyzed the evolution data of the Daya Bay reactor neutrino experiment in
terms of short-baseline active-sterile neutrino oscillations taking into
account the theoretical uncertainties of the reactor antineutrino fluxes. We
found that oscillations are disfavored at with respect to a
suppression of the reactor antineutrino flux and at
with respect to variations of the and
fluxes. On the other hand, the analysis of the rates of the
short-baseline reactor neutrino experiments favor active-sterile neutrino
oscillations and disfavor the suppression of the flux at
and variations of the and fluxes
at . We also found that both the Daya Bay evolution data and the
global rate data are well-fitted with composite hypotheses including variations
of the or fluxes in addition to
active-sterile neutrino oscillations. A combined analysis of the Daya Bay
evolution data and the global rate data shows a slight preference for
oscillations with respect to variations of the and
fluxes. However, the best fits of the combined data are given
by the composite models, with a preference for the model with an enhancement of
the flux and relatively large oscillations.Comment: 9 page
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