We investigate the properties of the hidden-charm pentaquark-like resonances first observed by the LHCb Collaboration in 2015, by measuring the polarization transfer KLL between the incident photon ...and the outgoing proton in the exclusive photoproduction of J/ψ near threshold. We present a first estimate of the sensitivity of this observable to the pentaquark photocouplings and hadronic branching ratios, and extend our predictions to the case of the initial-state helicity correlation ALL, using a polarized target. These results serve as a benchmark for the SBS experiment at Jefferson Lab, which proposes to measure for the first time the helicity correlations ALL and KLL in J/ψ exclusive photoproduction, in order to determine the pentaquark photocouplings and branching ratios.
AI-supported algorithms, particularly generative models, have been successfully used in a variety of different contexts. This work employs a generative modeling approach to unfold detector effects ...specifically tailored for exclusive reactions that involve multiparticle final states. Our study demonstrates the preservation of correlations between kinematic variables in a multidimensional phase space. We perform a full closure test on two-pion photoproduction pseudodata generated with a realistic model in the kinematics of the Jefferson Lab CLAS g11 experiment. The overlap of different reaction mechanisms leading to the same final state associated with the CLAS detector’s nontrivial effects represents an ideal test case for AI-supported analysis. Uncertainty quantification performed via bootstrap provides an estimate of the systematic uncertainty associated with the procedure. The test demonstrates that GANs can reproduce highly correlated multidifferential cross sections even in the presence of detector-induced distortions in the training datasets, and provides a solid basis for applying the framework to real experimental data.
The first CLAS12 experiments will provide high-precision data on inclusive electron scattering observables at a photon virtuality Q2 ranging from 0.05 to 12GeV2 and center-of-mass energies W up to 4 ...GeV. In view of this endeavor, we present the modeling of the resonant contributions to the inclusive electron scattering observables. As input, we use the existing CLAS electrocoupling results obtained from exclusive meson electroproduction data off protons, and evaluate for the first time the resonant contributions based on the experimental results on the nucleon resonance electroexcitation. The uncertainties are given by the data and duly propagated through a Monte Carlo approach. In this way, we obtain estimates for the resonant contributions, important for insight into the nucleon parton distributions in the resonance region and for the studies of quark-hadron duality.
In view of the precise data available on inclusive polarized electron scattering off polarized proton targets in the nucleon resonance excitation region, we compare these results with the coherent ...sum of resonant contributions to the polarized structure function
g
1
and virtual photon asymmetry
A
1
. To this goal, we employ the nucleon resonance electroexcitation amplitudes determined for photon virtualities
Q
2
< 5.0 GeV
2
from analyses of the CLAS data on exclusive electroproduction off protons in the resonance region. Most of the well established resonances of four star PDG status in the mass range up to 1.75 GeV are included. We find that the resonance-like structures observed in the inclusive
g
1
data are related to the resonant contributions in the entire range of photon virtuality
Q
2
where the data on
g
1
are available. In the range of invariant mass of the final hadron system
W
> 1.5 GeV, the data on the asymmetry
A
1
are well reproduced even when accounting for resonant contributions only, especially for the larger values of
Q
2
and energies analysed. This observation offers an interesting hint to quark-hadron duality seen in polarized inclusive electron scattering observables.
Nucleon resonance contributions to the polarized proton g1 and g2 structure functions are computed from resonance electroexcitation amplitudes extracted from CLAS exclusive meson electroproduction ...data. Including resonances in the mass range up to 1.75~GeV, and taking into account the interference between excited states, we compare the resonant contributions with the polarized proton structure function and polarization asymmetry data from Jefferson Lab 6 GeV measurements. All resonance-like structure observed in the polarized structure functions and asymmetries can be attributed to the resonant contributions, suggesting their essential role in the behavior of g1 and g2 at large parton momentum fraction x in the resonant region over the entire range Q2 < 7.5 GeV2 covered by the measurements. Comparing the resonance contributions with the g1 and g2 structure functions computed from parton distribution functions extrapolated from the deep-inelastic region, we also quantify the degree to which quark-hadron duality holds for g1 and g2 and their moments.
•Two different types of piezoelectric actuators were developed for ITER diagnostics to operate in vacuum under high thermal and neutron fluxes.•Results of irradiation test of the piezoelectric ...actuators are analyzed.•Four types of the most common piezoelectric ceramic materials were tested.•Effects of radiation on piezoelectric ceramics are discussed as a challenge for piezoelectric actuators at ITER.•It is shown that depolarization of the piezoelectric ceramics related to irradiation and multiple baking in ITER can be reversed remotely.
As a part of ITER diagnostics design and development, ultrasonic and stick-slip piezoelectric motors and several types of piezoelectric ceramics were tested under severe neutron and gamma ray irradiation (∼ 1019 per cm2 at E > 0.1 MeV) in a pool-type fission reactor. The fission neutron and gamma ray spectra were corrected to comply with conditions expected under ITER divertor cassettes. Taking into account possible neutron-induced amorphization of crystal structure, four types of piezoelectric ceramics were pre-selected. To restore the electronic structure of piezoelectric ceramic damaged by gamma rays, recovery polarization (i.e. heating while applying reverse bias) was suggested. The motors and piezoceramic samples were assessed for performance before and after irradiation as well as after recovery polarization. Recovery polarization was performed at 330 °C as it is expected close to the divertor cassettes during baking. Two most promising types of piezoelectric ceramics survived multiple cycles of depolarization/polarization at both 330 °C and 200 °C as appropriate for baking ITER divertor and vacuum vessel, respectively. All the experiments and procedures are described in detail.
In this study, a resonance-like structure, the Pc(4450), has recently been observed in the J/ψ p spectrum by the LHCb collaboration. We discuss the feasibility of detecting this structure in J/ψ ...photoproduction in the CLAS12 experiment at JLab. We present a first estimate of the upper limit for the branching ratio of the Pc(4450) to J/ψ p. Our estimates, which take into account the experimental resolution effects, lead to a sizable cross section close to the J/ψ production threshold, which makes future experiments covering this region very promising.
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