arXiv subjects

M. El Beiyad

Publications and source records attributed to M. El Beiyad.

9 recordsLinked to original sources

arXiv2010

On chiral-odd Generalized Parton Distributions

While the chiral-even content of the nucleon is better and better studied, the chiral-odd transversity generalized parton distributions (GPDs) remain almost unknown. These GPDs can be accessed experimentally through the exclusive photoproduction process gamma + N -> pi + rho + N', in the kinematics where the meson pair has a large invariant mass and the final nucleon has a small transverse momentum, provided the vector meson is produced in a transversally polarized state. We calculate perturbatively the scattering amplitude at leading order in alpha_s. We build a simple model for the dominant transversity GPD H_T(x,xi,t) based on the concept of double distribution. We estimate the unpolarized differential cross section for this process in the kinematics of the Jlab and COMPASS experiments. Counting rates show that the experiment looks feasible with the real and quasi real photon beam characteristics expected at JLab@12 GeV, and with the quasi real photon beam in the COMPASS experiment.

hep-ph↗

arXiv2010

New ways to access the transverse spin content of the nucleon

We first describe a new way to access the chiral odd transversity parton distribution in the proton through the photoproduction of lepton pairs. The basic ingredient is the interference of the usual Bethe-Heitler or Drell-Yan amplitudes with the amplitude of a process, where the photon couples to quarks through its chiral-odd distribution amplitude, which is normalized to the magnetic susceptibility of the QCD vacuum. We also show how the chiral-odd transversity generalized parton distributions (GPDs) of the nucleon can be accessed experimentally through the exclusive electro - or photoproduction process of a meson pair with a large invariant mass and when the final nucleon has a small transverse momentum. We calculate perturbatively the scattering amplitude at leading order, both in the high energy domain which may be accessed in electron-ion colliders and in the medium energy range. Estimated rates are encouraging.

hep-ph↗

arXiv2010

Photoproduction of a πρPair and Transversity GPDs

We demonstrate that the chiral-odd transversity generalized parton distributions (GPDs) of the nucleon can be accessed through the exclusive photoproduction process gamma + N -> pi + rho + N', in the kinematics where the meson pair has a large invariant mass and the final nucleon has a small transverse momentum, provided the vector meson is produced in a transversely polarized state. We calculate perturbatively the scattering amplitude at leading order in alpha_s: We build a simple model for the dominant transversity GPD HT (x; chi; t) based on the concept of double distribution. Counting rates estimates show that the experiment looks feasible with the real photon beam characteristics expected at JLab@12 GeV, in low Q2 leptoproduction at Jlab@12 GeV and in the COMPASS experiment.

hep-ph↗

arXiv2010

Chiral-odd transversity GPDs from a leading twist hard amplitude

The chiral-odd transversity generalized parton distributions (GPDs) of the nucleon can be accessed experimentally through the exclusive photoproduction process gamma + N -> pi + rho + N', in the kinematics where the meson pair has a large invariant mass and the final nucleon has a small transverse momentum, provided the vector meson is produced in a transversally polarized state. We calculate perturbatively the scattering amplitude at leading order in alpha_s. We build a simple model for the dominant transversity GPD H_T(x,xi,t) based on the concept of double distribution. We estimate the unpolarized differential cross section for this process in the kinematics of the Jlab and COMPASS experiments. Counting rates show that the experiment looks feasible with the real photon beam characteristics expected at JLab@12 GeV, and with the quasi real photon beam in the COMPASS experiment.

hep-ph↗

arXiv2010

Photoproduction of a pi rhoT pair with a large invariant mass and transversity generalized parton distribution

The chiral-odd transversity generalized parton distributions (GPDs) of the nucleon can be accessed experimentally through the exclusive photoproduction process gamma + N -> pi + rho + N', in the kinematics where the meson pair has a large invariant mass and the final nucleon has a small transverse momentum, provided the vector meson is produced in a transversally polarized state. We calculate perturbatively the scattering amplitude at leading order in alpha_s. We build a simple model for the dominant transversity GPD H_T(x,xi, t) based on the concept of double distribution. We estimate the unpolarized differential cross section for this process in the kinematics of the Jlab and COMPASS experiments. Counting rates show that the experiment looks feasible with the real photon beam characteristics expected at JLab@12 GeV, and with the quasi real photon beam in the COMPASS experiment.

hep-ph↗

arXiv2009

Transversity Generalized Parton Distributions from gamma N -> pi rhot N' with a Large pi rhot Invariant Mass

The chiral-odd transversity generalized parton distributions of the nucleon can be accessed experimentally through the exclusive photoproduction process gamma N -> pi rhoT N', with or without beam and target polarization, provided the vector meson is produced in a transversely polarized state. The kinematical domain of factorization is defined through a large invariant mass of the meson pair and a small transverse momentum of the final nucleon. We calculate perturbatively the scattering amplitude at leading order in alpha_s and build a simple model for the dominant transversity GPD H_T(x, xi, t) based on the concept of double distribution. Counting rate estimates are in progress.

hep-ph↗

arXiv2009

Probing photon structure in DVCS on a photon target

The factorization of the amplitude for the deeply virtual Compton scattering (DVCS) process gamma*(Q) gamma -> gamma gamma at high Q2 is demonstrated in two distinct kinematical domains, allowing to define the photon generalized parton distributions and the diphoton generalized distribution amplitudes. Both these quantities exhibit an anomalous scaling behaviour and obey new inhomogeneous QCD evolution equations.

hep-ph↗

arXiv2008

Two Photon Distribution Amplitudes

The factorization of the amplitude of the process gamma* gamma -> gamma gamma in the low energy and high photon virtuality region is demonstrated at the Born order and in the leading logarithmic approximation. The leading order two photon (generalized) distribution amplitudes exhibit a characteristic ln Q2 behaviour and obey new inhomogeneous evolution equations.

hep-ph↗

arXiv2008

Diphoton Generalized Distribution Amplitudes

We calculate the leading order diphoton generalized distribution amplitude by calculating the amplitude of the process gamma* gamma -> gamma gamma in the low energy and high photon virtuality region at the Born order and in the leading logarithmic approximation. As in the case of the anomalous photon structure functions, the gamma gamma generalized distribution amplitude exhibits a characteristic \ln Q^2 behaviour and obeys inhomogeneous evolution equations.

hep-ph↗