Light-front spin-dependent spectral function and nucleon momentum distributions for a three-body system

A new generation of experiments is expected to shed light on the elusive parton structure of the bound proton. One of the most promising directions is incoherent deeply virtual Compton scattering, which can provide a tomographic view of the bound proton. The first measurement has been recently performed, using 4 He targets at Jefferson Lab. In the work presented here, a rigorous Impulse Approximation analysis of this process is proposed. As ingredients, state-of-theart models of the nuclear spectral function and of the parton structure of the struck proton, together with novel scattering amplitudes expressions for a bound moving nucleon, have been used. A good overall agreement with the data is obtained, in particular at high values of the photon virtuality. The observed big difference between results for the bound proton and those for the free one turns out to be due in small part to modifications of the parton structure, and rather it should be related to kinematical nuclear effects. The analysis demonstrates that the comparison of the results of this approach, based on a conventional description, with future precise data, has the potential to expose exotic quark and gluon effects in nuclei.

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“…Such a problem could be solved with a Light Front approach, as proposed in Ref. [19] for a 3−body system. The BSA assumes the schematic form…”

mentioning

confidence: 99%

Catching a glimpse of the parton structure of the bound proton

2020

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“…[37], [38]). To this aim, in the last few years, we have developed a relativistic description of 3 He using a Poincaré covariant spectral function built up within the light-front Hamiltonian dynamics (LFHD) [39].…”

Section: Discussionmentioning

confidence: 99%

Three–Dimensional parton structure of light nuclei

Scopetta

Dotto

Kaptari³

et al. 2018

J. Phys.: Conf. Ser.

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Two promising directions beyond inclusive deep inelastic scattering experiments, aimed at unveiling the three dimensional structure of the bound nucleon, are reviewed, considering in particular the 3 He nuclear target. The 3D structure in coordinate space can be accessed through deep exclusive processes, whose non-perturbative part is encoded in generalized parton distributions. In this way, the distribution of partons in the transverse plane can be obtained. As an example of a deep exclusive process, coherent deeply virtual Compton scattering (DVCS) off 3 He nuclei, important to access the neutron generalized parton distributions (GPDs), will be discussed. In Impulse Approximation (IA), the sum of the two leading twist, quark helicity conserving GPDs of 3 He, H and E, at low momentum transfer, turns out to be dominated by the neutron contribution. Besides, a technique, able to take into account the nuclear effects included in the Impulse Approximation analysis, has been developed. The spin dependent GPDH of 3 He is also found to be largely dominated, at low momentum transfer, by the neutron contribution. The knowledge of the GPDs H, E andH of 3 He is relevant for the planning of coherent DVCS off 3 He measurements. Semi-inclusive deep inelastic scattering processes access the momentum space 3D structure parameterized through transverse momentum dependent parton distributions. A distorted spin-dependent spectral function has been recently introduced for 3 He, in a non-relativistic framework, to take care of the final state interaction between the observed pion and the remnant in semi-inclusive deep inelastic electron scattering off transversely polarized 3 He. The calculation of the Sivers and Collins single spin asymmetries for 3 He, and a straightforward procedure to effectively take into account nuclear dynamics and final state interactions, will be reviewed. The Light-front dynamics generalization of the analysis is also addressed.

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“…Integration of the LF spectral function on the intrinsic energy ǫ of the (A − 1) system, gives the LF spin-dependent momentum distribution [5] n…”

Section: Spin-dependent Momentum Distributionmentioning

confidence: 99%