Vanamali Shastry

Scattering off unstable states

Francesco Giacosa, Vanamali Shastry

Unstable states that live long enough may appear as in(out)going particles in scattering experiments. Yet, the standard QFT approach strictly applies only to fully stable asymptotic states. This is evident when scattering involving unstable particles develops a t -channel singularity at specific …

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Scattering off unstable states

Francesco Giacosa, Vanamali Shastry

Unstable states that live long enough may appear as in(out)going particles in scattering experiments. Yet, the standard QFT approach strictly applies only to fully stable asymptotic states. This is evident when scattering involving unstable particles develops a $t$-channel singularity at specific angles. …

Nonperturbative aspects of the electromagnetic pion form factor at high energies

K. Quirion, César Fernández Ramírez, V. Mathieu, Glòria Montaña et autres

The structure of hadronic form factors at high energies and their deviations from perturbative quantum chromodynamics provide insight on nonperturbative dynamics. Using an approach that is consistent with dispersion relations, we construct a model that simultaneously accounts for the pion wave function, …

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Studying π + π − photoproduction beyond Pomeron exchange

Łukasz Bibrzycki, N. Hammoud, V. Mathieu, Robert J. Perry et autres

Forward photoproduction of π + π − pairs with invariant mass of the order of m ρ ∼ 770 MeV is traditionally attributed to Pomeron exchange. Based on a detailed analysis of the CEBAF Large Acceptance Spectrometer photoproduction data collected at photon …

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Revisiting gauge invariance and Reggeization of pion exchange

Glòria Montaña, D. Winney, Łukasz Bibrzycki, César Fernández Ramírez et autres

The Reggeized pion is expected to provide the main contribution to the forward cross section in light meson photoproduction reactions with charge exchange at high energies. We discuss the Reggeization of pion exchange in charged pion photoproduction with an emphasis on consistency …

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Unitary coupled-channel three-body amplitude with pions and kaons

F. Gil-Domínguez, M. Döring, R. Molina, Maxim Mai et autres

Three-body dynamics above threshold is required for the reliable extraction of many amplitudes and resonances from experiment and lattice QCD. The S-matrix principle of unitarity can be used to construct dynamical coupled-channel approaches in which three particles scatter off each other, rearranging …

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Revisiting gauge invariance and Reggeization of pion exchange

Glòria Montaña, D. Winney, Łukasz Bibrzycki, César Fernández Ramírez et autres

The Reggeized pion is expected to provide the main contribution to the forward cross section in light meson photoproduction reactions with charge exchange at high energies. We discuss the Reggeization of pion exchange in charged pion photoproduction with an emphasis on consistency …

A unitary coupled-channel three-body amplitude with pions and kaons

Yuchuan Feng, M. Döring, R. Molina, Maxim Mai et autres

Three-body dynamics above threshold is required for the reliable extraction of many amplitudes and resonances from experiment and lattice QCD. The S-matrix principle of unitarity can be used to construct dynamical coupled-channel approaches in which three particles scatter off each other, re-arranging …

X Y Z spectroscopy at electron-hadron facilities. III. Semi-inclusive processes with vector exchange

D. Winney, A. Pilloni, R. J. Perry, C. Fernandez-Ramirez et autres

Inclusive production processes will be important for the first observations of X Y Z states at new generation electron-hadron colliders, as they generally benefit from larger cross sections than their exclusive counterparts. We make predictions of semi-inclusive photoproduction of the χ c …

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Studying $π^+π^-$ photoproduction beyond Pomeron exchange

Łukasz Bibrzycki, Nadine Hammoud, V. Mathieu, Robert J. Perry et autres

Forward photoproduction of $π^+π^-$ pairs with invariant mass of the order of $m_ρ\sim 770$ MeV is traditionally understood to be produced via Pomeron exchange. Based on a detailed analysis of the CLAS photoproduction data, it is shown that the dynamics of two-pion …

Off-shellness in generalized parton distributions and form factors of the pion

Vanamali Shastry, Wojciech Broniówski, E. Ruiz Arriola

We study the effects of off-shellness in the generalized parton distributions of the pion. On general grounds, these distributions exhibit a richer structure than in the on-shell case due to absence of the crossing symmetry. In particular, their moments involve additional terms …

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Sill distribution: genesis and salient features

Francesco Giacosa, Vanamali Shastry

We present the so-called Sill distribution, both in the nonrelativistic and relativistic cases, as a natural and simple way to include the effect of threshold(s) on the energy line shapes of resonances. The Sill is correctly normalized (even for broad states), is …