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B. Pire

Publications and source records attributed to B. Pire.

At least 55 records · Page 3Linked to original sources
arXiv2018

Probing axial quark generalized parton distributions through exclusive photoproduction of a $γ\,π^\pm$ pair with a large invariant mass

Exclusive photoproduction of a $γ\,π^\pm$ pair in the kinematics where the pair has a large invariant mass and the final nucleon has a small transverse momentum is described in the collinear factorization framework. The scattering amplitude is calculated at leading order in $α_s$ and the differential cross sections for the process are estimated in the kinematics of the JLab~12-GeV experiments. The order of magnitude of the predicted cross-sections seems sufficient for a dedicated experiment to be performed. The process turns out to be very sensitive to the axial generalized parton distribution combination $\tilde{H}_u - \tilde{H}_d$.

hep-ph↗
arXiv2018

Exclusive photoproduction of a $γ\,ρ$ pair with a large invariant mass

Exclusive photoproduction of a $γ\,ρ$ pair in the kinematics where the pair has a large invariant mass and the final nucleon has a small transverse momentum is described in the collinear factorization framework. The scattering amplitude is calculated at leading order in $α_s$ and the differential cross sections for the process where the $ρ-$meson is either longitudinally or transversely polarized are estimated in the kinematics of the JLab 12-GeV experiments.

hep-ph↗
arXiv2017

Hard exclusive pion electroproduction at backward angles with CLAS

We report on the first measurement of cross sections for exclusive deeply virtual pion electroproduction off the proton, $e p \to e^\prime n π^+$, above the resonance region at backward pion center-of-mass angles. The $φ^*_π$-dependent cross sections were measured, from which we extracted three combinations of structure functions of the proton. Our results are compatible with calculations based on nucleon-to-pion transition distribution amplitudes (TDAs) and shed new light on nucleon structure.

nucl-ex↗
arXiv2017

Exclusive neutrino-production of a charmed vector meson and transversity gluon GPDs

We calculate at the leading order in $α_s$ the QCD amplitude for exclusive neutrino production of a $D^*$ or $D_s^*$ charmed vector meson on a nucleon. We work in the framework of the collinear QCD approach where generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions. We include $O(m_c)$ terms in the coefficient functions and $O(m_D)$ term in the definition of heavy meson distribution amplitudes. The show that the analysis of the angular distribution of the decay $D_{(s)}^*\to D_{(s)} π$ allows to access the transversity gluon GPDs.

hep-ph↗
arXiv2017

Exploring GPDs through the photoproduction of a $γρ$ pair

We describe the process $γN \to γ\,ρN'$ in the generalized Bjorken regime where the $γ\,ρ$ pair has a large invariant mass. In the collinear QCD factorization framework, the amplitude gives access to both chiral-even and chiral-odd quark generalized parton distributions (GPDs), and is insensitive to gluon GPDs. The separation of longitudinally and transversely polarized $ρ$ meson production allows to distinguish chiral-even and chiral-odd contributions. Production rates are estimated in the kinematics of the near-future JLab~12-GeV experiments.

hep-ph↗
arXiv2017

On neutrino production of a charmed meson

We calculate in the framework of the collinear QCD approach the amplitude for exclusive neutrino-production of a pseudoscalar charmed $D$ meson. This process allows to access gluon and both chiral-odd and chiral-even quark generalized parton distributions (GPDs), which contribute in specific ways to the amplitude for different polarization states of the $W$ boson. The energy dependence of the cross section allows to separate different contributions and the measurement of the azimuthal dependence helps to single out the transversity chiral-odd GPDs contributions. The flavor dependence, and in particular the difference between $D^+$ and $D^0$ production rates, allows to test the importance of gluonic contributions. The behaviour of the proton and neutron target cross sections enables to separate the $u$ and $d$ quark contributions. Planned medium and high energy neutrino facilities will thus allow some important progress in the realm of hadronic physics.

hep-ph↗
arXiv2017

Hard exclusive neutrino production of a light meson

We update the leading order in $α_s$ QCD amplitude for deep exclusive neutrino and antineutrino production of a light meson on an unpolarized nucleon. The factorization theorems of the collinear QCD approach allow us to write the amplitude as the convolution of generalized parton distributions (GPDs) and perturbatively calculable coefficient functions. We study both the pseudoscalar meson and longitudinally polarized vector meson cases. It turns out that, contrarily to the electroproduction case, the leading twist scattering amplitudes for $π$ and $ρ_L$ productions are proportional to one another, which may serve as an interesting new test of the leading twist dominance of exclusive processes at medium scale. The dominance of the gluonic contribution to most cross sections is stressed.

hep-ph↗
arXiv2017

Exclusive neutrino-production of a charmed meson

We calculate the leading order in $α_s$ QCD amplitude for exclusive neutrino and antineutrino production of a $D$ pseudoscalar charmed meson on an unpolarized nucleon. We work in the framework of the collinear QCD approach where generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions. We include both $O(m_c)$ terms in the coefficient functions and $O(M_D)$ mass term contributions in the heavy meson distribution amplitudes. We emphasize the sensitivity of specific observables on the transversity quark GPDs.

hep-ph↗
arXiv2017

Backward charmonium production in $πN$ collisions

The QCD collinear factorization framework allows to describe exclusive backward production of a $J/ψ$ meson in pion-nucleon collisions in terms of pion-to-nucleon transition distribution amplitudes. We calculate the scattering amplitude at the leading order in the strong coupling constant and estimate the cross section of this reaction in the backward kinematical region for a medium energy pion beam available at the J-Parc experimental facility.

hep-ph↗
arXiv2016

QCD description of charmonium plus light meson production in antiproton-nucleon annihilation

The associated production of a $J/ψ$ and a $π$-meson in antiproton-nucleon annihilation is studied in the framework of QCD collinear factorization. In this approach, a hard subprocess responsible for the production of the heavy quark-antiquark pair factorizes from soft hadronic matrix elements, such as the antiproton (nucleon) distribution amplitude and the nucleon-to-pion (antiproton-to-pion) transition distribution amplitude. This reaction mechanism should dominate the forward and backward kinematical regions, where the cross sections are expected to be measurable in the set-up of the PANDA experiment at the GSI-Fair facility.

hep-ph↗
arXiv2016

Baryon-to-meson transition distribution amplitudes: formalism and models

In specific kinematics, hard exclusive amplitudes may be factorized into a short distance dominated part computable in a perturbative way on the one hand, and universal, confinement related hadronic matrix elements on the other hand. The extension of this description to processes such as backward meson electroproduction and forward meson production in antiproton-nucleon scattering leads to define new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes, which shed a new light on the nucleon structure.

hep-ph↗
arXiv2016

Photoproduction of a large invariant mass $γρ$ pair at small momentum transfer

The collinear factorization framework allows to describe the exclusive photoproduction of a $γ\,ρ$ pair in the generalized Bjorken regime in terms of a perturbatively calculable coefficient function and universal generalized parton distributions. The kinematics are defined by a large invariant mass of the $γρ$ pair and a small transverse momentum of the final nucleon. We calculate the scattering amplitude at leading order in $α_s$ and the differential cross sections for the process where the $ρ-$meson is either longitudinally or transversely polarized, in the kinematics of the near future Jlab experiments. Our estimate of the cross section demonstrates that this process is measurable at JLab 12-GeV.

hep-ph↗
arXiv2016

Revealing transversity GPDs through the photoproduction of a photon and a $ρ$ meson

Photoproduction of a pair of particles with large invariant mass is a natural extension of collinear QCD factorization theorems which have been much studied for deeply virtual Compton scattering and deeply virtual meson production. We discuss the production of a photon and a meson, where the wide angle Compton scattering on a meson subprocess factorizes from generalized parton distribution. We calculate at dominant twist and leading order in $α_s$, the production cross-section of a transversely polarized $ρ$ meson which is sensitive to chiral-odd GPDs, and show that it may be measurable in near future JLab experiments.

hep-ph↗
arXiv2016

Probing the transversity spin structure of a nucleon in neutrino-production of a charmed meson

Including O(m_c) terms in the coefficient functions and/or O(m_D) twist 3 contributions in the heavy meson distribution amplitudes leads to a non-zero transverse amplitude for exclusive neutrino production of a D pseudoscalar charmed meson on an unpolarized target. We work in the framework of the collinear QCD approach where chiral-odd transversity generalized parton distributions (GPDs) factorize from perturbatively calculable coefficient functions.

hep-ph↗
arXiv2016

GPDs in heavy meson production and Compton scattering

Exclusive processes of heavy meson production and spacelike and timelike deeply virtual Compton scattering allow us to investigate the hadron structure in terms of Generalized Parton Distributions (GPDs). We review recent developments in the NLO description of such processes.

hep-ph↗
arXiv2015

On $γN \to γρN'$ at large $γρ$ invariant mass

Photoproduction of a pair of particles with large invariant mass is a natural extension of collinear QCD factorization theorems which have been much studied for deeply virtual Compton scattering and deeply virtual meson production. We consider the case where the wide angle Compton scattering subprocess $γ(q\bar q) \to γρ$ factorizes from generalized parton distribution. At dominant twist, separating the transverse (respectively longitudinal) polarization of the $ρ$ meson allows one to get access to chiral-odd (respectively chiral-even) GPDs. This opens a new way to the extraction of these elusive transversity GPDs.

hep-ph↗
arXiv2015

Probing GPDs in photoproduction processes at hadron colliders

Generalized parton distributions (GPDs) enter QCD factorization theorems for hard exclusive reactions. They encode rich information about hadron partonic structure. We explore a possibility to constrain GPDs in experiments at LHC considering two different exclusive processes: the timelike Compton scattering and the photoproduction of heavy vector mesons.

hep-ph↗