Scattering of 3MEV neutrons from heavy nuclei

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A helium gas scintillator active target for photoreaction measurements

A multi-cell He gas scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 g/cm3 at an operating pressure of 2 MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of N2 to the He, to shift the scintillation emission from UV to visible, is discussed. First results of measurements at the MAX IV Laboratory tagged-photon facility show that the target has a timing resolution of around 1 ns and can cope well with a high-flux photon beam. The determination of reaction cross sections from target yields relies on a Monte Carlo simulation, which considers scintillation light transport, photodisintegration processes in 4He, background photon interactions in target windows and interactions of the reaction-product particles in the gas and target container. The predictions of this simulation are compared to the measured target response

Measurement of analysing powers for neutron scattering on CH2, CH, C and Cu target for momenta from 3.0 to 4.2 GeV/c

During two beam runs in the years 2016 and 2017, the analyzing powers (Ay) for protons and neutrons scattering on CH2, CH, C and Cu targets were measured at the nucleon momentum from 3.0 to 4.2 GeV/c with the ALPOM2 setup at the Nuclotron accelerator. The data for polarized neutron beam are obtained for the first time, thanks to the unique polarized deuteron beam that is presently available up to 13 GeV/c. Earlier, analyzing powers for polarized neutrons had been measured only for thin hydrogen targets. Cross sections and analyzing powers for np, for both elastic scattering and charge exchange are known up to 29 GeV/c. No data existed for thick analyzers. The measurement of the angular dependence of Ay for the neutron is essential to the continuation of the neutron form factor measurements to the highest possible transferred momentum-Q2 at the Jefferson Laboratory. The reaction p+Cu(W), with the detection of a neutron in the forward direction by a hadron calorimeter, can be used for the measurement of the proton polarization at the future NICA collider

Neutron polarisation transfer, Cx′, in π+ photoproduction off the proton, d(γ⊙,n→π+)nspec

We report a first measurement of the double-polarisation observable, Cx′, in π+ photoproduction off the proton. The double-polarisation observable represents the transfer of polarisation from a circularly polarised photon beam to the recoiling neutron. The MAMI circularly polarised photon beam impinged on a liquid deuterium target cell, with reaction products detected in the Crystal Ball calorimeter. Ancillary apparatus surrounding the target provided tracking, particle identification and determination of recoil nucleon polarisation. The Cx′ observable is determined for photon energies 800-1400 MeV, providing new constraints on models aiming to elucidate the spectrum and properties of nucleon resonances. This is the first determination of any polarisation observable from the beam-recoil group of observables for this reaction. Inclusion of the new data in the database of the SAID partial wave analysis shifted the solution to a new global minima which, not only gives better agreement with the current data, but also improves the description of a range of other single and double polarisation observables for charged pion photoproduction