[en] Deeply virtual Compton scattering (DVCS) is the simplest hard exclusive process to access generalized parton distributions (GPDs). In the case of a neutron this process is mostly sensitive to E, the least constrained GPD, which enters Ji's sum rule linking GPDs to the total quark angular momentum. We present the first dedicated DVCS experiment on the neutron which took place in the Hall A of Jefferson Lab in fall 2004. Experimental setup and preliminary results are discussed

[en] Here, we report the first longitudinal/transverse separation of the deeply virtual exclusive π"0 electroproduction cross section off the neutron and coherent deuteron. Furthemore, the corresponding four structure functions dσ_L/dt, dσ_T/dt, dσ_L_T/dt and dσ_T_T/dt are extracted as a function of the momentum transfer to the recoil system at Q"2=1.75 GeV"2 and x_B=0.36. The ed→edπ"0 cross sections are found compatible with the small values expected from theoretical models. The en→enπ"0 cross sections show a dominance from the response to transversely polarized photons, and are in good agreement with calculations based on the transversity GPDs of the nucleon. By combining our results with previous measurements of π"0 electroproduction off the proton, we present a flavor decomposition of the u and d quark contributions to the cross section.

[en] The gamma flux rate generated by the Tunisian National Nuclear Sciences Center ⁶⁰Co gamma irradiator is shown to be equivalent, within less than one percent discrepancy, to that of a unique pencil of equal height and equal activity placed along the source symmetry axis. - Highlights: → We calculate the gamma flux rate, generated by a ⁶⁰Co gamma irradiator. → This irradiator is placed along the source symmetry axis. → This flux rate is equivalent to that generated by a unique pencil. → discrepancy between the two calculations is less than 1%.

[en] The spatial resolution of laterally segmented electromagnetic calorimeters, built of lead fluoride material, is studied on the basis of Monte-Carlo simulations. Parametrization of the relative resolution on the shower position is proposed and optimized in terms of the energy of incoming particles and the elementary size of the calorimeter blocks. A new fit algorithm method is proposed that improves spatial resolution at high energies (> 5 GeV), and provides guidance for the design optimization of electromagnetic calorimeters.

[en] This paper gives the preliminary results of the experimental cross section for deeply virtual Compton scattering (DVCS) on the neutron (en → enγ). The E08-025 experiment was performed at Jefferson Lab Hall A. We measured the (D(e, eX - H(e, e,e'γ)X) unpolarized cross section and we extracted, for the first time, a non-zero contribution of (neutron-DVCS + coherent-deuteron-DVCS) at Q"2 = 1.75 GeV"2 and x_B = 0.36. (authors)

[en] Virtual Compton Scattering (VCS) and Deeply Virtual Compton Scattering (DVCS) on the nucleon are two processes accessed via the photon electroproduction reaction (eN → eγN). In the first part of this paper we are interested by the DVCS on the neutron. We measured the (D(e, eγ)X-H(e, e'γ)X) unpolarized cross section and we extracted, for the first time, a non-zero contribution of (neutron-DVCS + coherent- deuteron-DVCS) at Q² = 1.75 GeV² and x_B = 36 from Jefferson Lab experiment E08-025. VCS on the proton has been studied at Mainz Microtron MAMI at the four-momentum transfer squared Q² = 0.5 GeV², below the pion production threshold. In the second part of this paper we present our preliminary results of the structure functions (P_LL − (P_TT/ε)) and P_LT, and the electric and magnetic generalized polarizabilities α_E(Q²) and β_M(Q²) extracted from this experiment.

[en] A set of measurements have been carried out in order to determine the activity-levels in some powdered milks available in Tunisia. The study has shown that the average activity is about 160 ± 19 and 2.26 ± 0.5 Bq/kg respectively for ⁴⁰K and ¹³⁷Cs, whereas it is below the detection limit for ²²⁶Ra and ²³²Th. The mean annual ingestion dose is about 102 and 225 μSv/y for respectively ≤ 1 year and 1–2 years old infants. The calculation of the radiological risk show that no significant threat on the infant's health due to consumption of these milks. (author)

[en] Double Deeply Virtual Compton Scattering (DDVCS) is the only experimental channel for the determination of the dependence of the Generalized Parton Distributions (GPDs) on both the average and the transferred momentum independently. The physics observables of the electron induced di-muon production reaction ${\stackrel{\to <!--\; ???\; -->}{e}}^{\pm <!--\; ??\; -->}$p → $e^{\pm <!--\; ??\; -->}$pµ${}^{+}$µ${}^{-<!--\; ???\; -->}$ off unpolarized hydrogen are discussed. Their measurement with the high luminosity and large acceptance SoLID spectrometer at the Thomas Jefferson National Accelerator Facility, using polarized and unpolarized positron and electron beams at 11 GeV is investigated. This experimental configuration is shown to provide unprecedented access to the GPDs with the determination of the real and imaginary parts of the Compton Form Factor H in an unexplored phase space, and to enable an exploratory investigation of higher twist effects.

[en] We present the first measurements of the e(vector sign)p→epγ cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q² dependence (from 1.5 to 2.3 GeV²) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q². The helicity-independent cross section is also measured at Q²=2.3 GeV². We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation

[en] The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e-vector,e^'γ)X cross section measured at Q²=1.9 GeV² and x_B=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_q, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced