Coherent Meson Production Research Articles

A radial time projection chamber for [formula omitted] detection in CLAS at JLab

A new Radial Time Projection Chamber (RTPC) was developed at the Jefferson Laboratory to track low-energy nuclear recoils to measure exclusive nuclear reactions, such as coherent deeply virtual Compton scattering and coherent meson production off 4He. In 2009, we carried out these measurements using the CEBAF Large Acceptance Spectrometer (CLAS) supplemented by the RTPC positioned directly around a gaseous 4He target, allowing a detection threshold as low as 12 MeV for 4He. This article discusses the design, principle of operation, calibration methods and performances of this RTPC.

Coherent meson production in antinucleon annihilation on nuclei

A phenomenological optical potential for antinucleon-nucleon (NN) interaction in an energy range of 1 to 15 GeV is presented in an eikonal model. In addition to the discussion of the strength and energy dependence, the potential is used to describe initial state interactions for coherent meson production on nuclei. To describe nuclear matter effects, Hartree-Fock Bogoliobuv (HFB) densities are used. As a first step we calculate the production of two mesons, namely pions. To cover the large energy range, the final state pion-nucleus ( πA) interaction is improved by adding resonances beyond the Δ resonance to a Kisslinger-type ansatz. Results for NN and πA cross sections are presented.

Meson Production in Coherent Antiproton-Nucleus Annihilation

The study of a fully quantum mechanical description of coherent meson production in antinucleon annihilation on nuclei is presented. Two different reaction mechanisms are presented including initial and final state interactions, which are both derived from a folding approach. The underlying fundamental antinucleon-nucleon N̄N and pion-nucleon πN interactions enter into the optical potentials, which are folded with Hartree-Fock-Bogoliubov nuclear densities. Existing approaches to pion nucleus interactions have been extended to higher energies beyond the Δ-resonance. Cross sections are shown.

Delta excitation in nuclei and coherent meson production

We report on inclusive cross sections for reactions of the type ( 3He,t), (p,n), (p,p′) on nuclei around the Δ excitation region. Particular emphasis is made on the coherent process which leaves the nucleus in the ground state and produce pions. Coherent pion production leads to an excitation function with a Δ peak shifted towards lower excitation energies and is an important ingredient in the explanation of the shift of the total inclusive cross section. Coherent eta production is also studied and it is shown to be an excellent tool to determine the coupling g ηNN , so far unknown experimentally.

Coherent meson production relativistic heavy-ion collision: Dipak Ghosh et al, Can J Phys, 66, 1988, 26–28

Coherent meson production relativistic heavy-ion collision: Dipak Ghosh et al, Can J Phys, 66, 1988, 26–28

Neutrino reactions in the low-y region.

The physics of nonscaling components in the region of low energy transfer (low-y region) is described. The following neutrino-induced processes were considered: resonance production, quasielastic scattering, and coherent meson production off nuclei or nuclear fragments. It is shown that the total exclusive cross section in a certain kinematical domain is energy independent at high energies (above 20 GeV). This fact can, in principle, be used for relative normalization of the neutrino flux.

Neutrino interactions

A review is given of the experimental status of some topics in neutrino interactions. Results are presented on measurements of total cross-sections, like-sign dimuon production, tests of universality, limits on ν T-production, coherent meson production, a test of PCAC, and measurements of weak neutral-current parameters.

Coherent meson production relativistic heavy-ion collision

This paper presents a study on the coherent meson production in 12C–emulsion interactions at 4.5 Gev∙c−1∙nucleon−1 incident momentum. The search for coherence was done through noting the shape of the multiplicity distribution in different narrow rapidity bins and observing whether or not the distribution was according to Poisson; when the fields are completely coherent the multiplicity should have a Poisson distribution. It was observed that the multiplicity distribution was Poisson in nature in two bins of higher rapidity, and consequently the field was coherent in those rapidity bins. The percentage of coherent meson production was estimated to be 48%.

Three-body mechanisms in coherent meson production by pd capture

Meson double scattering is shown to be the good candidate for accounting for the discrepancies left out by the conventional analysis of pd mesonic capture in terms of one-and two-body mechanisms.

COSY - A Cooler Synchrotron and Storage Ring

The storage ring COSY with phase space cooling and RF acceleration is designed to accept protons and light ions injected from the existing cyclotron JULIC or protons from the LINAC of the proposed neutron spallation source (SNQ). The lay-out of COSY was developed in cooperation with the Universities in Nordrhein-Westfalen and meets the experimental requirements of variable and high quality beams which are necessary for future nuclear research under discussion. The motivation for the cooler-synchrotron COSY emerged from discussions of nuclear physicists in Nordrhein-Westfalen on future research activities. The Workshop on Electron Coolinq in 1982 came to the conclusion that a cooler-synchrotron I is an excellent tool for advanced nuclear research experiments. It should be built at the KFA in cooperation with the surrounding Universities. The three essential properties of the storage ring will be: - high luminosities and very efficient use of the beam in the storage ring by thin internal targets - energy variability in the range of 20 MeV to 1.5 GeV by RF acceleration - very high beam quality through phase space cooling. Two classes of experiments will be feasible in the first step of construction. At proton energies up to about 200 MeV it will be possible to excite selectively fundamental nuclear spin isospin modes and to resolve the corresponding nuclear levels with the existing high resolution spectrometer BIG KARL'. At higher energies single nucleons in the nucleus can be excited internally and coherent meson production can be studied, processes which reflect details of the subnuclear structure.

Coherent meson production as a test for neutral weak currents of exotic space-time structure

Usually the weak neutral current is assumed to be a vector-axial vector current, but exotic space-time structures such as scalar, pseudoscalar and tensor currents are not excluded by experiment. In this paper we discuss the coherent production of the π 0 and the ϱ 0 in neutrino scattering, as a possibility of distinguishing between VA and SPT. We have calculated the pion production cross sections numerically using the optical model approximation. Pion production is strongly suppressed in the forward direction for SPT but not for VA. In ϱ production the VA cross section is suppressed if CVC holds. Tensor currents can be distinguished from CVC violation. Assuming VA, the absolute pion production rate can be used as a model-independent test for the signs of the chiral coupling constants of the weak neutral quark currents.

Coherent meson production as a test for neutral weak currents of exotic space-time structure

Coherent meson production as a test for neutral weak currents of exotic space-time structure