We have analyzed the beam spin asymmetry and the longitudinally polarized target spin asymmetry of the Deep Virtual Compton Scattering process, recently measured by the Jefferson Lab CLAS ...collaboration. Our aim is to extract information about the Generalized Parton Distributions of the proton. By fitting these data, in a largely model-independent procedure, we are able to extract numerical values for the two Compton Form Factors HIm and H˜Im with uncertainties, in average, of the order of 30%.
We have analyzed the longitudinally polarized proton target asymmetry data of the Deep Virtual Compton process recently published by the HERMES Collaboration in terms of Generalized Parton ...Distributions. We have fitted these new data in a largely model-independent fashion and the procedure results in numerical constraints on the H˜Im Compton Form Factor. We present its t- and ξ-dependencies. We also find improvement on the determination of two other Compton Form Factors, HRe and HIm.
Tomographic image of the proton Dupré, R.; Guidal, M.; Vanderhaeghen, M.
Physical review. D,
01/2017, Volume:
95, Issue:
1
Journal Article
Peer reviewed
Open access
We have carried out a phenomenological analysis of the latest deep virtual Compton scattering experimental data based on the generalized parton distribution formalism. This allows us to extract the ...dependence of the spatial size of the proton on the quark’s longitudinal momentum. This results in the first continuous two-dimensional momentum-space image and tomography of the proton based on experimental data.
We describe the architecture and functionalities of a C++ software framework, coined PARTONS, dedicated to the phenomenology of Generalized Parton Distributions. These distributions describe the ...three-dimensional structure of hadrons in terms of quarks and gluons, and can be accessed in deeply exclusive lepto- or photo-production of mesons or photons. PARTONS provides a necessary bridge between models of Generalized Parton Distributions and experimental data collected in various exclusive production channels. We outline the specification of the PARTONS framework in terms of practical needs, physical content and numerical capacity. This framework will be useful for physicists - theorists or experimentalists - not only to develop new models, but also to interpret existing measurements and even design new experiments.
.
The CLAS and Hall A Collaborations at Jefferson Laboratory have recently released new results for the
e
p
→
e
p
γ
reaction. We analyze these new data within the Generalized Parton Distribution ...formalism. Employing a fitter algorithm introduced and used in earlier works, we are able to extract from these data new constraints on the kinematical dependence of three Compton Form Factors. Based on experimental data, we subsequently extract the dependence of the proton charge radius on the quarks’ longitudinal momentum fraction.
The HERMES Collaboration has recently published a set of (correlated) beam charge, beam spin and target spin asymmetries for the Deeply Virtual Compton Scattering (DVCS) process. This reaction allows ...in principle to access the Generalized Parton Distributions (GPDs) of the nucleon. We have fitted, in the QCD leading-order and leading-twist handbag approximation, but in a model-independent way, this set of data and we report our results for the extracted Compton form factors. In particular, we are able to extract constrains on the
H
GPD.
A model for high energy pion and kaon photoproduction (
E
γ
≳ 4 GeV) is presented which interpolates between the low and higher momentum transfer regions. At low momentum transfer (which is described ...in terms of Regge trajectory exchanges), the model is able to give an economical description of unpolarized and polarized data for both the charged and neutral pion photoproduction reactions as well as for
K
+
Λ and
K
+
Σ photoproduction data, available at high energy. At higher momentum transfer, an extrapolation based on saturating Regge trajectories, and which satisfies scaling laws at asymptotically large transfers, is found able to describe the few existing
γp →
nπ
+ data. The model can be used as a guidance to interpret forthcoming data at larger momentum transfers.
In the following, the subject of Deep Virtual Compton Scattering on the nucleon and its relation to the recently introduced concept of Generalized Parton Distributions are briefly reviewed. The ...general theoretical framework and the links between theory and experiment will be outlined and the recently published data which look promising for the development of this field will be discussed. Finally, the experimental prospectives of the domain will be presented.
We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a Q2 of 0.230 (GeV/c)(2) and a scattering angle of theta ...(e) = 30 degrees - 40 degrees. Using a large acceptance fast PbF2 calorimeter with a solid angle of delta omega = 0.62 sr, the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). The standard model expectation assuming no strangeness contributions to the vector form factors is A(0) = (-6.30+/-0.43) x 10(-6). The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G(s)(E) + 0.225G(s)(M) = 0.039+/-0.034 or F(s)(1) + 0.130F(s)(2) = 0.032+/-0.028.
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