1,043 research outputs found
Using Electron Scattering Superscaling to predict Charge-changing Neutrino Cross Sections in Nuclei
Superscaling analyses of few-GeV inclusive electron scattering from nuclei
are extended to include not only quasielastic processes, but now also into the
region where -excitation dominates. It is shown that, with reasonable
assumptions about the basic nuclear scaling function extracted from data and
information from other studies of the relative roles played by correlation and
MEC effects, the residual strength in the resonance region can be accounted for
through an extended scaling analysis. One observes scaling upon assuming that
the elementary cross section by which one divides the residual to obtain a new
scaling function is dominated by the transition and employing a
new scaling variable which is suited to the resonance region. This yields a
good representation of the electromagnetic response in both the quasielastic
and regions. The scaling approach is then inverted and predictions are
made for charge-changing neutrino reactions at energies of a few GeV, with
focus placed on nuclei which are relevant for neutrino oscillation
measurements. For this a relativistic treatment of the required weak
interaction vector and axial-vector currents for both quasielastic and
-excitation processes is presented.Comment: 42 pages, 9 figures, accepted for publication in Physical Review
Relativistic effects in two-particle emission for electron and neutrino reactions
Two-particle two-hole contributions to electroweak response functions are
computed in a fully relativistic Fermi gas, assuming that the electroweak
current matrix elements are independent of the kinematics. We analyze the
genuine kinematical and relativistic effects before including a realistic
meson-exchange current (MEC) operator. This allows one to study the
mathematical properties of the non-trivial seven-dimensional integrals
appearing in the calculation and to design an optimal numerical procedure to
reduce the computation time. This is required for practical applications to CC
neutrino scattering experiments, where an additional integral over the neutrino
flux is performed. Finally we examine the viability of this model to compute
the electroweak 2p-2h response functions.Comment: Major revision (shortened). 22 pages, 18 figure
2p-2h excitations in neutrino scattering: angular distribution and frozen approximation
We study the phase-space dependence of 2p-2h excitations in neutrino
scattering using the relativistic Fermi gas model. We follow a similar approach
to other authors, but focusing in the phase-space properties, comparing with
the non-relativistic model. A careful mathematical analysis of the angular
distribution function for the outgoing nucleons is performed. Our goals are to
optimize the CPU time of the 7D integral to compute the hadron tensor in
neutrino scattering, and to conciliate the different relativistic and non
relativistic models by describing general properties independently of the
two-body current. For some emission angles the angular distribution becomes
infinite in the Lab system, and we derive a method to integrate analytically
around the divergence. Our results show that the frozen approximation, obtained
by neglecting the momenta of the two initial nucleons inside the integral of
the hadron tensor, reproduces fairly the exact response functions for constant
current matrix elements.Comment: 8 pages, 4 figures. Contribution to 16th International Workshop on
Neutrino Factories and Future Neutrino Beam Facilities, 25-30 August, 2014.
Held at University of Glasgow, United Kingdo
The frozen nucleon approximation in two-particle two-hole response functions
We present a fast and efficient method to compute the inclusive two-particle
two-hole (2p-2h) electroweak responses in the neutrino and electron
quasielastic inclusive cross sections. The method is based on two
approximations. The first neglects the motion of the two initial nucleons below
the Fermi momentum, which are considered to be at rest. This approximation,
which is reasonable for high values of the momentum transfer, turns out also to
be quite good for moderate values of the momentum transfer . The
second approximation involves using in the "frozen" meson-exchange currents
(MEC) an effective -propagator averaged over the Fermi sea. Within the
resulting "frozen nucleon approximation", the inclusive 2p-2h responses are
accurately calculated with only a one-dimensional integral over the emission
angle of one of the final nucleons, thus drastically simplifying the
calculation and reducing the computational time. The latter makes this method
especially well-suited for implementation in Monte Carlo neutrino event
generators.Comment: 8 pages, 5 figures and 1 tabl
Two-nucleon emission in neutrino and electron scattering from nuclei: the modified convolution approximation
The theoretical formalism of inclusive lepton-nucleus scattering in the
two-nucleon emission channel is discussed in the context of a simplified
approach, the modified convolution approximation. This allows one to write the
2p2h responses of the relativistic Fermi gas as a folding integral of two 1p1h
responses with the energies and momenta transferred to each nucleon. The idea
behind this method is to introduce different average momenta for the two
initial nucleons in the matrix elements of the two-body current, with the
innovation that they depend on the transferred energies and momenta. This
method treats exactly the two-body phase space kinematics, and reduces the
formulae of the response functions from seven-dimensional integrals over
momenta to much simpler three-dimensional ones. The applicability of the method
is checked by comparing with the full results within a model of electroweak
meson-exchange currents. The predictions are accurate enough, especially in the
low-energy threshold region where the average momentum approximation works the
best.Comment: 35 pages, 13 figure
Nuclear dependence of the 2p2h electroweak response in the Relativistic Fermi Gas model
We present the results of a recent study of meson-exchange two-body currents
in lepton-nucleus inclusive scattering at various kinematics and for different
nuclei within the Relativistic Fermi Gas model. We show that the associated
nuclear response functions at their peaks scale as , for Fermi
momentum going from 200 to 300 MeV/c and momentum transfer from
to 2 GeV/c. This behavior is different from what is found for the
quasielastic response, which scales as . This result can be valuable in
the analyses of long-baseline neutrino oscillation experiments, which need to
implement these nuclear effects in Monte Carlo simulations for different
kinematics and nuclear targets.Comment: 11 pages, 6 figures, Proccedings of the Workshop "Advanced Aspects in
Nuclear Structure and Reactions at Different Energy Scales", 25-28 April
2017, Arbanasi, Bulgari
Emission of neutron-proton and proton-proton pairs in electron scattering induced by meson-exchange currents
We use a relativistic model of meson-exchange currents to compute the
proton-neutron and proton-proton yields in scattering from C in
the 2p-2h channel. We compute the response functions and cross section with the
relativistic Fermi gas model for a range of kinematics from intermediate to
high momentum transfers. We find a large contribution of neutron-proton
configurations in the initial state, as compared to proton-proton pairs. The
different emission probabilities of distinct species of nucleon pairs are
produced in our model only by meson-exchange currents, mainly by the
isobar current. We also analyze the effect of the exchange contribution and
show that the direct/exchange interference strongly affects the determination
of the np/pp ratio.Comment: 5 pages, 6 figure
Development and validation of the facilitative interpersonal skills scale for clients
Objective: Psychotherapy studies have revealed that therapist characteristics are responsible for 5% to 9% of outcome variance. The therapist-facilitative interpersonal skills (FIS) have been shown to predict both alliance and outcomes, indicating that higher FIS therapists are more effective than lower FIS therapists. The current study focused on the development and validation of the FIS-client version (FIS-C) instrument, aimed at collecting the clients' perspectives on relevant therapist characteristics. Method: The clinical outcomes in routine evaluation—outcome measures, the session rating scale, and the FIS questionnaire—client version were filled out by psychotherapy clients. Exploratory, confirmatory factor, and test–retest analysis were conducted. Results: Results indicate robust psychometric characteristics, in terms of validity (factorial, convergent, discriminant, and nomological), reliability, and sensitivity. Conclusion: The validation of the FIS-C represents an important contribution to clinical research and practice, namely to the field of client feedback and therapist expertise.info:eu-repo/semantics/publishedVersio
Density dependence of 2p-2h meson-exchange currents
We analyze the density dependence of the contribution of meson-exchange
currents to the lepton-nucleus inclusive cross section in the two-particle
two-hole channel. The model is based on the Relativistic Fermi Gas, where each
nucleus is characterized by its Fermi momentum . We find that the 2p-2h
nuclear response functions at their peaks scale as for Fermi momentum
going from 200 to 300 MeV/c and momentum transfer from to 2 GeV/c.
This behavior is different from what is found for the quasielastic response,
which scales as . Additionally, the deep scaling region is also
discussed and there the usual scaling behavior is found to be preferable.Comment: 9 pages, 8 figure
Effects of Short-Range Correlations in (e,e'p) reactions and nuclear overlap functions
A study of the effects of short-range correlations over the (e,e'p) reaction
for low missing energy in closed shell nuclei is presented. We use correlated,
quasi-hole overlap functions extracted from the asymptotic behavior of the
one-body density matrix, containing central correlations of Jastrow type, up to
first-order in a cluster expansion, and computed in the very high asymptotic
region, up to 100 fm. The method to extract the overlap functions is checked in
a simple shell model, where the exact results are known. We find that the
single-particle wave functions of the valence shells are shifted to the right
due to the short-range repulsion by the nuclear core. The corresponding
spectroscopic factors are reduced only a few percent with respect to the shell
model. However, the (e,e'p) response functions and cross sections are enhanced
in the region of the maximum of the missing momentum distribution due to
short-range correlations.Comment: 45 pages, 15 figure
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