118 research outputs found
Enhanced time response of 1-in. LaBr3(Ce) crystals by leading edge and constant fraction techniques
We have characterized in depth the time response of three detectors equipped
with cylindrical LaBr (Ce) crystals with dimensions of 1-in. in height
and 1-in. in diameter, and having nominal Ce doping concentration of 5%, 8% and
10%. Measurements were performed at Co and Na {\gamma}-ray
energies against a fast BaF reference detector. The time resolution was
optimized by the choice of the photomultiplier bias voltage and the fine tuning
of the parameters of the constant fraction discriminator, namely the
zero-crossing and the external delay. We report here on the optimal time
resolution of the three crystals. It is observed that timing properties are
influenced by the amount of Ce doping and the crystal homogeneity. For the
crystal with 8% of Ce doping the use of the ORTEC 935 CFD at very shorts delays
in addition to the Hamamatsu R9779 PMT has made it possible to improve the
LaBr(Ce) time resolution from the best literature value at 60Co photon
energies to below 100 ps.Comment: Article submitted to Nuclear Instruments and Methods in Physics
Research Section A: Accelerators, Spectrometers, Detectors and Associated
Equipmen
Final state interaction effects in neutrino-nucleus quasielastic scattering
We consider the charged-current quasielastic scattering of muon neutrinos on
an Oxygen 16 target, described within a relativistic shell model and, for
comparison, the relativistic Fermi gas. Final state interactions are described
in the distorted wave impulse approximation, using both a relativistic mean
field potential and a relativistic optical potential, with and without
imaginary part. We present results for inclusive cross sections at fixed
neutrino energies in the range 200 MeV - 1 GeV, showing that final
state interaction effects can remain sizable even at large energies.Comment: 4 pages, 4 figures; poster session of the Third International
Workshop on Neutrino-Nucleus Interactions in the Few GeV Region (NuInt04),
Gran Sasso (Italy), March 17-21, 2004; to appear in the proceeding
New Analysis of Threshold Photoproduction Data from MAMI
In this talk I will review the recently published results by the A2 and
CB-TAPS Collaborations at MAMI on neutral pion photoproduction in the
near-threshold region. The combined measurement of the differential cross
section and the photon beam asymmetry with low statistical errors allowed for a
precise determination of the energy dependence of the real parts of the S- and
P-wave amplitudes for the first time, providing the most stringent test to date
of the predictions of Chiral Perturbation Theory and its energy region of
agreement with experiment.Comment: 4 pages. Contribution to the 13th International Conference on
Meson-Nucleon Physics and the Structure of the Nucleon (MENU 2013), Rome,
September-October 201
The Relativistic Green's Function Model for Quasielastic Neutrino-Nucleus Scattering
A model based on the relativistic impulse approximation for quasielastic
lepton-nucleus scattering is presented. The effects of the final-state
interactions (FSI) between the emitted nucleon and the residual nucleus are
described by the relativistic Green's function model where FSI are treated
consistently with the exclusive scattering and using the same complex optical
potential. The results of the model are compared with the results of different
descriptions of FSI and with available data for neutrino-nucleus scattering.Comment: 10 pages, 4 figures, contribution to IWNT-32, 23-29 June 2013, Rila
Mountains (Bulgaria
Upper Energy Limit of Heavy Baryon Chiral Perturbation Theory in Neutral Pion Photoproduction
With the availability of the new neutral pion photoproduction from the proton
data from the A2 and CB-TAPS Collaborations at Mainz it is mandatory to revisit
Heavy Baryon Chiral Perturbation Theory (HBChPT) and address the extraction of
the partial waves as well as other issues such as the value of the low-energy
constants, the energy range where the calculation provides a good agreement
with the data and the impact of unitarity. We find that, within the current
experimental status, HBChPT with the fitted LECs gives a good agreement with
the existing neutral pion photoproduction data up to 170 MeV and that
imposing unitarity does not improve this picture. Above this energy the data
call for further improvement in the theory such as the explicit inclusion of
the \Delta (1232). We also find that data and multipoles can be well described
up to 185 MeV with Taylor expansions in the partial waves up to first
order in pion energy.Comment: 6 pages, 5 figures, version to be published in Physics Letters
Global relativistic folding optical potential and the relativistic Green's function model
Optical potentials provide critical input for calculations on a wide variety of nuclear reactions, in particular, for neutrino-nucleus reactions, which are of great interest in the light of the new neutrino oscillation experiments. We present the global relativistic folding optical potential (GRFOP) fits to elastic proton scattering data from C-12 nucleus at energies between 20 and 1040 MeV. We estimate observables, such as the differential cross section, the analyzing power, and the spin rotation parameter, in elastic proton scattering within the relativistic impulse approximation. The new GRFOP potential is employed within the relativistic Green's function model for inclusive quasielastic electron scattering and for (anti) neutrino-nucleus scattering at MiniBooNE kinematics
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