Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThree--Dimensional parton structure of light nuclei
105
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
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 nucleus. The 3D structure in coordinate space can be accessed through deep exclusive processes, whose non-perturbative part is encoded in generalized parton distributions (GPDs). In this way, the distribution of partons in the transverse plane can be obtained. As an example, coherent deeply virtual Compton scattering (DVCS) off $^3$He nuclei, important to access the neutron GPDs, will be discussed. In Impulse Approximation (IA), the sum of two 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 GPD $tilde H$ of $^3$He is also found to be largely dominated, at low momentum transfer, by the neutron contribution. 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.
rate research
Read More
The measurement of nuclear Generalized Parton Distributions (GPDs) represents a valuable tool to understand the structure of bound nucleons and the phenomenology of hard scattering off nuclei. By using a realistic, non-relativistic microscopic approach for the evaluation of GPDs of 3He, it will be shown that conventional nuclear effects, such as isospin and binding ones, or the uncertainty related to the use of a given nucleon-nucleon potential, are bigger than in the forward case so that, if great attention is not paid, conventional nuclear effects can be easily mistaken for exotic ones. It is stressed that 3He, for which the best realistic calculations are possible, represents a unique target to discriminate between conventional and exotic effects. The complementary information which could be obtained by using a 3H target, the possible extraction of the neutron information, as well as the relevance of a relativistic treatment, will be also addressed.
We review recent studies of the cluster structure of light nuclei within the framework of the algebraic cluster model (ACM) for nuclei composed of k alpha-particles and within the framework of the cluster shell model (CSM) for nuclei composed of k alpha-particles plus x additional nucleons. The calculations, based on symmetry considerations and thus for the most part given in analytic form, are compared with experiments in light cluster nuclei. The comparison shows evidence for Z_2, D_{3h} and T_d symmetry in the even-even nuclei 8Be (k=2), 12C (k=3) and 16O (k=4), respectively, and for the associated double groups Z_2 and D_{3h} in the odd nuclei 9Be, 9B (k=2, x=1) and 13C (k=3, x=1), respectively.
The present understanding of nuclear electromagnetic properties including electromagnetic moments, form factors and transitions in nuclei with A $le$ 10 is reviewed. Emphasis is on calculations based on nuclear Hamiltonians that include two- and three-nucleon realistic potentials, along with one- and two-body electromagnetic currents derived from a chiral effective field theory with pions and nucleons.
We present an update of the event generator based on the three-fluid dynamics (3FD), complemented by Ultra-relativistic Quantum Molecular Dynamics (UrQMD) for the late stage of the nuclear collision~-- the three-fluid Hydrodynamics-based Event Simulator Extended by UrQMD final State interactions (THESEUS). Two modifications are introduced. The THESEUS table of hadronic resonances is made consistent with that of the underlying 3FD model. The main modification is that the generator is extended to simulate the light-nuclei production in relativistic heavy-ion collisions, on the equal basis with hadrons. These modifications are illustrated by applications to the description of available experimental data. The first run of the updated generator revealed a good reproduction of the NA49 data on the light nuclei. The reproduction is achieved without any extra parameters, while the coalescence approach in 3FD requires special tuning of the coalescence coefficients for each light nucleus separately.
The generalized parton distribution H and E of the 3He nucleus, which could be measured in hard exclusive processes, such as coherent deeply virtual Compton scattering, are thoroughly analyzed in impulse approximation, within the Av18 interaction. It is found that their sum is dominated to a large extent by the neutron contribution: The peculiar spin structure of 3He makes this target unique for the extraction of the neutron information. This observation could allow to access for the first time, in dedicated experiments, the orbital angular momentum of the partons in the neutron.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
