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Omar Benhar

Publications and source records attributed to Omar Benhar.

88 records · Page 5Linked to original sources
arXiv2007

Total neutrino and antineutrino nuclear cross sections around 1 GeV

We investigate neutrino-nucleus interactions at energies around 1 GeV. In this regime, the main contributions to the cross sections come from quasi-elastic and $Δ$ production processes. Our formalism, based on the Impulse Approximation is well suited to describe both types of interactions. We focus on a series of important nuclear effects in the interaction of electron neutrinos with $^{16}O$, also relevant to future $β$-Beams. Our results show that the Fermi gas model, widely used in data analysis of neutrino experiments, overestimates the total cross sections by as much as 20 %.

hep-ph↗
arXiv2006

Estimates of the uncertainties associated with models of the nucleon structure functions in the $Δ$ production region

Theoretical studies of the inclusive electron-nucleus cross section at beam energies up to few GeV show that, while the region of the quasi-elastic peak is understood at quantitative level, the data in the $Δ$ production region are sizably underestimated. We analize the uncertainty associated with the description of the nucleon structure functions $W_1$ and $W_2$ and its impact on the nuclear cross section. The results of our study suggest that the failure to reproduce the data is to be mostly ascribed to the poor knowledge of the neutron structure functions at low $Q^2$.

hep-ph↗
arXiv2006

Final state interactions in the electroweak nuclear response

I review the description of the electroweak nuclear response at large momentum transfer within nonrelativistic many-body theory. Special consideration is given to the effects of final state interactions, which are known to be large in both inclusive and semi-inclusive processes. The results of theoretical calculations of electron-nucleus scattering observables are compared to the data, and the generalization to charged current neutrino-nucleus interactions is discussed.

hep-ph↗
arXiv2005

Perturbative approach to the structure of rapidly rotating neutron stars

We construct models of rotating stars using the perturbative approach introduced by J. Hartle in 1967, and a set of equations of state proposed to model hadronic interactions in the inner core of neutron stars. We integrate the equations of stellar structure to third order in the angular velocity and show, comparing our results to those obtained with fully non linear codes, to what extent third order corrections are needed to accurately reproduce the moment of inertia of a star which rotates at rates comparable to that of the fastest isolated pulsars.

gr-qc↗
arXiv2005

Neutron star matter equation of state and gravitational wave emission

The EOS of strongly interacting matter at densities ten to fifteen orders of magnitude larger than the typical density of terrestrial macroscopic objects determines a number of neutron star properties, including the pattern of gravitational waves emitted following the excitation of nonradial oscillation modes. This paper reviews some of the approaches employed to model neutron star matter, as well as the prospects for obtaining new insights from the experimental study of gravitational waves emitted by neutron stars.

astro-ph↗
arXiv2005

Electron- and neutrino-nucleus scattering in the impulse approximation regime

A quantitative understanding of the weak nuclear response is a prerequisite for the analyses of neutrino experiments such as K2K and MiniBOONE, which measure energy and angle of the muons produced in neutrino-nucleus interactions in the energy range $0.5-3$ GeV and reconstruct the incident neutrino energy to determine neutrino oscillations. In this paper we discuss theoretical calculations of electron- and neutrino-nucleus scattering, carried out within the impulse approximation scheme using realistic nuclear spectral functions.Comparison between electron scattering data and the calculated inclusive cross section off oxygen, at beam energies ranging between 700 and 1200 MeV, show that the Fermi gas model, widely used in the analysis of neutrino oscillation experiments,fails to provide a satisfactory description of the measured cross sections,and inclusion of nuclear dynamics is needed.

hep-ph↗
arXiv2004

Stability of the mixed phase in hybrid stars

The transition from hadronic matter to quark matter in the core of neutron stars is likely to be associated with the appearance of a mixed phase, leading to a smooth variation of the star density profile. We discuss the results of a systematic study of the properties of the mixed pase upon Coulomb and surface effects. A state of the art nonrelativistic equation of state of nuclear matter has been used for the low density phase, while quark matter has been described within the MIT bag model, including the effect of perturbative one-gluon exchange interactions. The implications for neutron star structure are discussed.

astro-ph↗
arXiv2004

Electron- and neutrino-nucleus scattering

I review the main features of the nuclear response extracted from electron scattering data. The emerging picture clearly shows that the shell model does not provide a fully quantitative description of nuclear dynamics. On the other hand, many body approaches in which correlation effetcs are explicitely taken into account lead to a satisfactory account of electron scattering observables. The possibility of exploiting the knowledge acquired from electron scattering to reduce the systematic uncertainty of neutrino oscillation experiments is outlined.

nucl-th↗
arXiv2004

Neutrino-nucleus cross section in the impulse approximation regime

In the impulse approximation regime the nuclear response to a weakly interacting probe can be written in terms of the measured nucleon structure fuctions and the target spectral function, yielding the energy and momentum distribution of the constituent nucleons. We discuss a calculation of charged current neutrino-oxygen interactions in the quasielastic channel, carried out within nuclear many body theory. The proposed approach, extensively and successfully employed in the analysys of electron-nucleus scattering data, allows for a parameter free prediction of the neutrino-nucleus cross section, whose quantitative understanding will be critical to the analysis of the next genaration of high precision neutrino oscillation experiments.

nucl-th↗
arXiv2003

Nuclear response beyond the Fermi gas model

The Fermi gas model, while providing a reasonable qualitative description of the continuum nuclear response, does not include the effects of dynamical nucleon-nucleon correlations in the initial and final states, that have long been recognized to play a critical role in specific kinematical regions. We review a many-body approach in which these effects are consistently taken into account and discuss the results of a calculation of the quasielastic neutrino-oxygen cross section as an illustrative example.

nucl-th↗
arXiv2002

Scaling in many-body systems and proton response

The observation of scaling in processes in which a weakly interacting probe delivers large momentum ${\bf q}$ to a many-body system reflects the dominance of incoherent scattering off target constituents. While a suitably defined scaling function can provide rich information on the internal dynamics of the target, in general its extraction from the measured cross section requires careful consideration of the nature of the interaction driving the scattering process. The analysis of deep inelastic electron-proton scattering in the target rest frame within standard many-body theory naturally leads to the emergence of a scaling function that, unlike the commonly used structure functions $F_1$ and $F_2$, can be identified with the intrinsic proton response. The implications for the theoretical analysis of deep inelastic scattering and the interpretation of the data are discussed.

nucl-th↗
arXiv2001

Scaling in many-body systems and proton structure function

The observation of scaling in processes in which a weakly interacting probe delivers large momentum ${\bf q}$ to a many-body system simply reflects the dominance of incoherent scattering off target constituents. While a suitably defined scaling function may provide rich information on the internal dynamics of the target, in general its extraction from the measured cross section requires careful consideration of the nature of the interaction driving the scattering process. The analysis of deep inelastic electron-proton scattering in the target rest frame within standard many-body theory naturally leads to the emergence of a scaling function that, unlike the commonly used structure functions $F_1$ and $F_2$, can be directly identified with the intrinsic proton response.

nucl-th↗
arXiv2000

A different view of deep inelastic electron-proton scattering

Deep inelastic electron-proton scattering is analyzed in the target rest frame using a theoretical approach suitable to describe many-body systems of {\em bound} constituents subject to {\em interactions}. At large three-momentum transfer $\magq$, this approach predicts the onset of scaling in the variable $\yt=ν$-$\magq$, where $ν$ denotes the energy transfer. The present analysis shows that the data, plotted at constant $\magq$, exhibit a remarkable scaling behavior in $\yt$ and manifestly display the presence of sizable interaction effects.

nucl-th↗
arXiv1999

Two-Nucleon Spectral Function in Infinite Nuclear Matter

The two-nucleon spectral function in nuclear matter is studied using Correlated Basis Function perturbation theory, including central and tensor correlations produceded by a realistic hamiltonian. The factorization property of the two-nucleon momentum distribution into the product of the two single nucleon distributions shows up in an analogous property of the spectral function. The correlated model yields a two-hole contribution quenched whith respect to Fermi gas model, while the peaks acquire a quasiparticle width that vanishes as the two momenta approach $k_F$. In addition, three-hole one-particle and more complicated intermediate states give rise to a background, spread out in energy and absent in the uncorrelated models. The possible connections with one- and two-nucleon emission processes are briefly discussed.

nucl-th↗
arXiv1999

Interpretation of y-scaling of the nuclear response

The behavior of the nuclear matter response in the region of large momentum transfer, in which plane wave impulse approximation predicts the onset of y-scaling, is discussed. The theoretical analysis shows that scaling violations produced by final state interactions are driven by the momentum dependence of the nucleon-nucleon scattering cross section. Their study may provide valuable information on possible modifications of nucleon-nucleon scattering in the nuclear medium.

nucl-th↗