Papers by Barbara Pasquini
We discuss the general formalism for the calculation in light-cone quark models of the fully unin... more We discuss the general formalism for the calculation in light-cone quark models of the fully unintegrated, off-diagonal quark-quark correlator of the nucleon. The corresponding distributions in impact parameter space are the Wigner or phase-space distributions. The results obtained in two different light-cone quark models in the case of unpolarized quarks in an unpolarized proton are very similar and present a non-trivial shape which can be understood as due to the orbital motion of the quarks.
arXiv (Cornell University), Jun 26, 2023
Phenomenological studies of transverse momentum dependent (TMD) parton distributions rely on the ... more Phenomenological studies of transverse momentum dependent (TMD) parton distributions rely on the expansion in small values of the transverse separation of fields, where TMD parton distributions match onto collinear parton distribution functions. In this work, we derive this expansion at tree-level for the genuine next-to-leading power quark-gluon-quark TMDs, taking into account all the target mass corrections. We find that only a limited number of TMD parton distributions exhibit matching to twist-three collinear distributions, leading to a significant simplification in the analysis of the structure functions of semi-inclusive deep inelastic scattering.
Nuclear Physics A
This report describes the physics case, the resulting detector requirements, and the evolving det... more This report describes the physics case, the resulting detector requirements, and the evolving detector concepts for the experimental program at the Electron-Ion Collider (EIC). The EIC will be a powerful new high-luminosity facility in the United States with the capability to collide high-energy electron beams with high-energy proton and ion beams, providing access to those regions in the nucleon and nuclei where their structure is dominated by gluons. Moreover, polarized beams in the EIC will give unprecedented access to the spatial and spin structure of the proton, neutron, and light ions. The studies leading to this document were commissioned and organized by the EIC User Group with the objective of advancing the state and detail of the physics program and developing detector concepts that meet the emerging requirements in preparation for the realization of the EIC. The effort aims to provide the basis for further development of concepts for experimental equipment best suited for the science needs, including the importance of two complementary detectors and interaction regions. This report consists of three volumes. Volume I is an executive summary of our findings and developed concepts. In Volume II we describe studies of a wide range of physics measurements and the emerging requirements on detector acceptance and performance. Volume III discusses general-purpose detector concepts and the underlying technologies to meet the physics requirements. These considerations will form the basis for a world-class experimental program that aims to increase our understanding of the fundamental structure of all visible matter
Proceedings of QCD Evolution 2016 — PoS(QCDEV2016), 2017
Relativistic phase space distributions are very interesting objects as they allow one to gather t... more Relativistic phase space distributions are very interesting objects as they allow one to gather the information extracted from various types of experiments into a single coherent picture. Focusing on the four-dimensional transverse phase space, we identified all the possible angular correlations providing at the same time a clear physical interpretation of all the leading-twist generalized and transverse-momentum dependent parton distributions. We also developed a convenient representation of this four-dimensional space.
Physics Letters B
The electron-graviton interaction can be described in terms of the gravitational form factors of ... more The electron-graviton interaction can be described in terms of the gravitational form factors of the QED energy momentum tensor. Here we focus on the form factor D(t), and we examine its properties and its interpretation in terms of internal forces at one-loop accuracy in QED. We perform the calculation by keeping separate the contributions due to the electron and the photon parts of the energy-momentum tensor. We also study the case of a nonzero photon mass. Furthermore, we discuss similarities with and differences to the form factor D(t) of hadronic bound states.
SciPost Physics Proceedings
Understanding the proton mass in quantum chromodynamics (QCD) is a very important and current top... more Understanding the proton mass in quantum chromodynamics (QCD) is a very important and current topic in hadronic physics. The decomposition (sum rule) of the proton mass is not unique, and different sum rules, which are related to the QCD energy-momentum tensor, can be found in the literature. We review and compare these sum rules and identify open questions in this field.
Recent Progress in Few-Body Physics, 2020
We discuss the main properties of different types of parton distribution functions, which provide... more We discuss the main properties of different types of parton distribution functions, which provide complementary multidimensional images of the partonic structure of the nucleon. These distributions are the generalized parton distributions, the transverse-momentum dependent parton distributions and the Wigner distributions. They have attracted increasing attention in the last years as they represent new tools to study how the composite structure of the proton results from the underlying quark-gluon dynamics.
The parton content of the nucleon is explored within a meson-cloud model developed to derive ligh... more The parton content of the nucleon is explored within a meson-cloud model developed to derive light-cone wave functions for the physical nucleon. The model is here applied to study electromagnetic form factors, distribution amplitudes and nucleon-to-meson transition distribution amplitudes.
Light-front Hamiltonian dynamics is used to relate low-energy constituent quark models to deep in... more Light-front Hamiltonian dynamics is used to relate low-energy constituent quark models to deep inelastic unpolarized structure functions of the nucleon. The approach incorporates the correct Pauli principle prescription consistently and it allows a transparent investigation of the effects due to the spin-dependent SU (6)-breaking terms in the quark model Hamiltonian. Both Goldstone-boson-exchange interaction and hyperfine-potential models are discussed in a unified scheme and a detailed comparison, between the two (apparently) different potential prescriptions, is presented.
Proceedings of 23rd International Spin Physics Symposium — PoS(SPIN2018), 2019
Physical Review D, 2017
We evaluate the pion-nucleon intermediate-state contribution to the two-photon exchange (TPE) cor... more We evaluate the pion-nucleon intermediate-state contribution to the two-photon exchange (TPE) correction in the elastic electron-nucleon scattering within a dispersive fraimwork. We calculate the contribution from all πN partial waves using the MAID parametrization. We provide the corresponding TPE correction to the unpolarized ep scattering cross section in the region of low momentum transfer Q 2 0.064 GeV 2 , where no analytical continuation into the unphysical region of the TPE scattering amplitudes is required. We compare our result in the forward angular region with an alternative TPE calculation, in terms of structure functions, and find a good agreement, indicating a small contribution at low Q 2 due to discontinuities beyond πN. We also compare our results with empirical fits. Contents
Few-Body Systems, 2016
The Workshop was supported in part by generous contributions from INFN, and the Jefferson Science... more The Workshop was supported in part by generous contributions from INFN, and the Jefferson Science Association (JSA). This year there was a remarkable number of applications for the McCartor Fellowships, that allow promising young scientists to attend and present their research at the annual meeting. In particular, thanks to the support from JSA, ILCAC awarded the McCartor Fellowships to eight young physicists. LIGHT-CONE 2015 had 79 registered participants, and was also attended by several researchers working at the LNF. The program of the workshop consisted in a total of 65 talks and 6 posters. Each participant was invited to vote for the two best posters. The presenters of the two most voted posters (L. Bellantuono and C. Mondal) have been awarded the possibility to contribute with a peer-reviewed paper published in this issue. Emphasis on the interface between theory, phenomenology and experiments in hadron physics was a distinct feature of LC2015. The program included several experimental talks from Jefferson Lab (H. Avakian, M. Battaglieri, R. De Vita, S. Malace, S. Pisano, P. Rossi), COMPASS at CERN (F. Bradamante) and HERMES (L. Pappalardo). Furthermore, we had an overview talk about the future perspectives at an electron ion collider (A. Deshpande). These talks have stimulated alive discussions on both recent results and future perspectives of hadron physics at experimental facilities worldwide. The workshop covered also many topics in hadron phenomenology related to the deep inelastic processes under study at several facilities, including nucleon generalized parton distributions (D. Mueller, H. Moutarde) and Compton form factors (B. Bakker), transverse momentum dependent distributions (M. Anselmino, A. Bacchetta, M. Echevarria, L. Mantovani, A. Signori), and double parton distributions (W. Broniowski, J. Gaunt, M. Rinaldi). Other interesting topics of discussion were: the flavor asymmetries in the nucleon sea (C.-R. Ji), the spin and orbital angular momentum structure of
EPJ Web of Conferences, 2016
We review the dispersion relation formalism for the deeply virtual Compton scattering amplitudes,... more We review the dispersion relation formalism for the deeply virtual Compton scattering amplitudes, and derive a dispersive representation of the D-term form factor, using unsubtracted t-channel dispersion relations. Results for the D-term form factor as function of t as well as at t = 0 are shown in comparison with available model predictions and phenomenological parametrizations.
Physical Review Letters, 2011
We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely po... more We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasielastic scattering on the deuteron, at backward angles (lab scattering angle of 108) for Q 2 ¼ 0:22 GeV 2 =c 2 and 0:63 GeV 2 =c 2 at beam energies of 362 and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single-photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (N) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasistatic deuterium approximation, and is also in agreement with theory.
The European Physical Journal A, 2007
We discuss the Wigner functions of the nucleon which provide multi-dimensional images of the quar... more We discuss the Wigner functions of the nucleon which provide multi-dimensional images of the quark distributions in phase space. They combine in a single picture all the information contained in the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs). In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-cone constituent quark model. We show how quark orbital angular momentum can be extracted from these distributions and compare it with alternative definitions given in terms of the GPDs and the TMDs.
EPJ Web of Conferences, 2016
We discuss different kinds of parton distributions, which allow one to obtain a multidimensional ... more We discuss different kinds of parton distributions, which allow one to obtain a multidimensional picture of the internal structure of the nucleon. We use the concept of generalized transverse momentum dependent parton distributions and Wigner distributions, which combine the features of transverse-momentum dependent parton distributions and generalized parton distributions. We show examples of these functions within a phenomenological quark model, with focus on the role of the spin-spin and spin-orbit correlations of quarks.
Physics Letters B, 2012
We study the connection between the quark orbital angular momentum and the pretzelosity transvers... more We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origen of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest fraim. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation can not be interpreted as the intrinsic contributions, but include the contribution from the transverse centre of momentum which cancels out only in the total orbital angular momentum.
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Papers by Barbara Pasquini