arXiv subjects

Murat M. Kaskulov

Publications and source records attributed to Murat M. Kaskulov.

12 recordsLinked to original sources

arXiv2013

Momentum dependent mean-field dynamics of compressed nuclear matter and neutron stars

Nuclear matter and compact neutron stars are studied in the framework of the non-linear derivative (NLD) model which accounts for the momentum dependence of relativistic mean-fields. The generalized form of the energy-momentum tensor is derived which allows to consider different forms of the regulator functions in the NLD Lagrangian. The thermodynamic consistency of the NLD model is demonstrated for arbitrary choice of the regulator functions. The NLD approach describes the bulk properties of the nuclear matter and compares well with microscopic calculations and Dirac phenomenology. We further study the high density domain of the nuclear equation of state (EoS) relevant for the matter in $β$-equilibrium inside neutron stars. It is shown that the low density constraints imposed on the nuclear EoS and by the momentum dependence of the Schrödinger-equivalent optical potential lead to a maximum mass of the neutron stars around $M \simeq 2 M_{\odot}$ which accommodates the observed mass of the J1614-2230 millisecond radio pulsar.

nucl-th↗

arXiv2011

Primakoff production of $π^0$, $η$ and $η'$ in the Coulomb field of a nucleus

Photoproduction of neutral pseudoscalar mesons $π^0,η(547)$ and $η'(958)$ in the Coulomb field of an atomic nucleus is studied using a model which describes the Primakoff and nuclear parts of the production amplitude. At high energies the nuclear background is dominated by the exchange of $C$-parity odd Regge trajectories. In the coherent production the isospin filtering makes the $ω(782)$ a dominant trajectory. The calculations are in agreement with $π^0$ data from JLAB provided the photon shadowing and final state interactions of mesons are taken into account. The kinematic conditions which allow to study the Primakoff effect in $η$ and $η'$ photoproduction off nuclei are further discussed. We also give predictions for the higher energies available at the JLAB upgrade.

nucl-th↗

arXiv2011

Neutral pion electroproduction in $p(e,e'π^0)p$ above $\sqrt{s}>2$ GeV

Electroproduction of neutral pions in exclusive reaction $p(e,e'π^0)p$ is studied above the resonance region, $\sqrt{s}>2$ GeV. The reaction amplitude is described by exchanges of vector $ω(782)$, $ρ(770)$ and axial-vector $h_1(1170)$ and $b_1(1235)$ Regge trajectories. The residual effect of $s$- and $u$-channel nucleon resonances is taken into account using a dual connection between the exclusive form factors and inclusive deep inelastic structure functions. In photoproduction at forward angles the exchange of Regge trajectories dominates and the dip region is filled by the resonances. In electroproduction the excitation of nucleon resonances explains the high $Q^2$ data from JLAB. The results for the beam spin azimuthal asymmetry measured at CLAS/JLAB are presented. Model calculations in the deep inelastic region at HERMES/DESY are given.

nucl-th↗

arXiv2011

Exclusive pion electroproduction off nucleons and nuclei

We present our results for the exclusive electroproduction of pions off nucleons and nuclei at high values of $Q^2$. In electroproduction of nuclei $A(e,e'π)$ we consider the Color Transparency (CT) effect recently observed at JLAB. It is shown that the description of $π$ production off nucleons is mandatory for the proof of the CT signal at JLAB. We further develop the models for exclusive production of $π$ off nucleons at JLAB and HERMES. At first we describe a model based on exclusive-inclusive connection. In the second approach we combine a Regge pole approach with the residual effect of nucleon resonances. The nucleon resonances are described using a dual connection between the exclusive form factors and inclusive deep inelastic structure functions. We present the results for the beam spin azimuthal asymmetries measured at JLAB in exclusive electroproduction of charged and neutral pions.

nucl-th↗

arXiv2011

Beam spin asymmetry in deeply virtual $π$ production

An interpretation of the beam spin azimuthal asymmetries measured at JLAB in deep exclusive electroproduction of charged and neutral pions is presented. The model combines a Regge pole approach with the effect of nucleon resonances. The $s$- and $u$-channel contributions are described using a dual Bloom-Gilman connection between the exclusive form factors and inclusive deep inelastic structure functions. The results are in agreement with data provided the excitations of nucleon resonances are taken into account.

hep-ph↗

arXiv2010

Deep exclusive charged $π$ electroproduction above the resonance region

A description of exclusive charged pion electroproduction $(e,e'π^{\pm})$ off nucleons at high energies is proposed. The model combines a Regge pole approach with residual effect of nucleon resonances. The exchanges of $π$(140), vector $ρ(770)$ and axial-vector $a_1(1260)$ and $b_1(1235)$ Regge trajectories are considered. The contribution of nucleon resonances is described using a dual connection between the exclusive hadronic form factors and inclusive deep inelastic structure functions. The model describes the measured longitudinal, transverse and interference cross sections at JLAB and DESY. The scaling behavior of the cross sections is in agreement with JLAB and deeply virtual HERMES data. The results for a polarized beam-spin azimuthal asymmetry in $(\vec{e},e'π^{\pm})$ are presented. Model predictions for JLAB at 12 GeV are given.

hep-ph↗

arXiv2009

Deep exclusive electroproduction of $π^+$ at HERMES

Deeply virtual electroproduction of pion in exclusive reaction $p(e,e'π^+)n$ is studied using a two-component model which includes soft hadronic and hard partonic reaction mechanisms. The results are compared with the experimental data measured at HERMES in the deep inelastic region for values of $Q^2>1$ GeV$^2$ and $W^2 > 10$ GeV$^2$. At forward angles the $π^+$ cross section is longitudinal and is dominated by exchange of Regge poles, with $π$ the dominant trajectory. The off-forward region with $-t>1$ GeV$^2$ is transverse and shows the dominance of partonic subprocesses. An implication of present results for the future JLAB facilities are briefly discussed.

hep-ph↗

arXiv2009

Pionic transparency in semi-exclusive electroproduction off nuclei

We investigate the early onset of pionic color transparency ($π$CT) observed at Jefferson Laboratory (JLAB) in semi--exclusive pion electroproduction reaction $A(e,e'π^+)$ off nuclei. In the present description the primary $γ^*p \to π^+ n$ interaction is described very well both for the longitudinal and the transverse polarizations. For the final state interactions a coupled--channel treatment of the interactions of transmitted hadrons allows to go beyond the Glauber approximation. We show that a proper distinction between the soft hadronic and hard partonic components of the electroproduction amplitude is essential for a quantitative description of the measured nuclear transparency. The data are well reproduced if one assumes that point--like configurations are produced in the regime of hard deep--inelastic scattering (DIS) off partons and dominate the transverse channel.

nucl-th↗

arXiv2009

Deeply inelastic pions in the exclusive reaction $p(e,e'π^+)n$ above the resonance region

A model for the $p(e,e'π^+)n$ reaction which combines an improved treatment of gauge invariant meson--exchange currents and hard deep--inelastic scattering (DIS) of virtual photons off nucleons is proposed. It is shown that DIS dominates and explains the transverse response at moderate and high photon virtualities $Q^2$ whereas the longitudinal response is dominated by hadronic degrees of freedom and the pion electromagnetic form factor. This leads to a combined description of the longitudinal and transverse components of the cross section in a wide range of photon virtuality $Q^2$ and momentum transfer to the target $t$ and solves the longstanding problem of the observed large transverse cross sections. The latter are shown to be sensitive to the intrinsic transverse momentum distribution of partons.

hep-ph↗

arXiv2006

Two pion mediated scalar isoscalar NN interaction in the nuclear medium

We study the modification of the nucleon nucleon interaction in a nuclear medium in the scalar isoscalar channel, mediated by the exchange of two correlated ($σ$ channel) or uncorrelated pions. For this purpose we use a standard approach for the renormalization of pions in nuclei. The corrections obtained for the $NN$ interaction in the medium in this channel are of the order of 20% of the free one in average, and the consideration of short range correlations plays an important role in providing these moderate changes. Yet, the corrections are sizable enough to suggest further studies of the stability and properties of nuclear matter.

nucl-th↗

arXiv2004

Correlated two-pion exchange and large-N(C) behavior of nuclear forces

The effect of correlated scalar-isoscalar two-pion exchange (CrTPE) modes is considered in connection with central and spin-orbit parts of the NN force. The two-pion correlation function is coupled directly to the scalar form factor of the nucleon which we calculate in the large-N(C) limit where the nucleon can be described as a soliton of an effective chiral theory. The results for the central NN force show a strong repulsive core at short internucleon distances supplemented by a moderate attraction beyond 1 fm. The long-range tail of the central NN potential is driven by the the pion-nucleon sigma term and consistent with the effective $σ$ meson exchange. The spin-orbit part of the NN potential is repulsive. The large-N(C) scaling behavior of the scalar-isoscalar NN interaction is addressed. We show that the spin-orbit part is O(1/N^2(C)) in strength relative to the central force resulting in the ratio $\simeq 1/9$ suggested by the 1/N(C) expansion for N(C)=3. The latter is in agreement with our numerical analysis and with the Kaplan-Manohar large-N(C) power counting. Unitarization of the $ππ$ scattering amplitude plays here an important role and improves the tree level results. Analytical representations of the CrTPE NN potential in terms of elementary functions are derived and their chiral content is discussed.

nucl-th↗

arXiv2004

The electric form factor of the neutron and its chiral content

Considering the nucleon as a system of confined valence quarks surrounded by pions we derive a Galster-like parameterization of the neutron electric form factor $G_E^n$. Furthermore, we show that the proposed parameterization can be linked to properties of the pion cloud. By this, the high quality data for the pion form factor can be used in predictions of $G_E^n$ in the low $Q^2$ region, where the direct double polarization measurements are not available.

nucl-th↗