Search results for "Cross Section"
showing 10 items of 3111 documents
Measurement of cross section for e+e−→Ξ0Ξ¯0 near threshold
2021
Abstract Using e + e − collision data at ten center-of-mass energies between 2.644 and 3.080 GeV collected with the BESIII detector at BEPCII and corresponding to an integrated luminosity of about 500 pb−1, we measure the cross sections and effective form factors for the process e + e − → Ξ 0 Ξ ¯ 0 utilizing a single-tag method. A fit to the cross section of e + e − → Ξ 0 Ξ ¯ 0 with a pQCD-driven power function is performed, from which no significant resonance or threshold enhancement is observed. In addition, the ratio of cross sections for the processes e + e − → Ξ − Ξ ¯ + and Ξ 0 Ξ ¯ 0 is calculated using recent BESIII measurement and is found to be compatible with expectation from isosp…
Anomalous electromagnetic moments of τ lepton in γγ → τ+τ− reaction in Pb+Pb collisions at the LHC
2020
We discuss the sensitivity of the γγ→τ+τ− process in ultraperipheral Pb+Pb collisions on the anomalous magnetic (aτ) and electric (dτ) moments of τ lepton at LHC energies. We derive the corresponding cross sections by folding the elementary cross section with the heavy-ion photon fluxes and considering semi-leptonic decays of both τ leptons in the fiducial volume of ATLAS and CMS detectors. We present predictions for total and differential cross sections, and for the ratios to γγ→e+e−(μ+μ−) process. These ratios allow to cancel theoretical and experimental uncertainties when performing precision measurements at the LHC. The expected limits on aτ with existing Pb+Pb dataset are found to be b…
Measuring the phi meson width in the medium from p induced phi production in nuclei
2004
We study the $A$ dependence of the $\phi$ meson production cross section in proton nucleus reactios at energies just above threshold, which are accessible in an experimental facility like COSY. This $A$ dependence has two sources: the distortion of the incident proton and the absorption of the $\phi$ in its way out of the nucleus. This second process reduces the cross section in about a factor two in heavy nuclei. Thus we show that the $A$ dependence of the cross section contains valuable information on the $\phi$ width in the nuclear medium.
Theoretical study of incoherent phi photoproduction on a deuteron target
2012
We study the photoproduction of phi mesons in deuteron, paying attention to the modification of the cross section from bound protons to the free ones with the aim of comparing with recent results at LEPS. For this purpose we take into account Fermi motion in single scattering and rescattering of the phi to account for phi absorption on a second nucleon as well as the rescattering of the proton. We find that the contribution of the double scattering is much smaller than the typical cross section of gamma p to phi p in free space, which implies a very small screening of the phi production in deuteron. The contribution from the proton rescattering, on the other hand, is found to be not negligi…
Structure functions from the NMC
1992
The New Muon Collaboration has measured deep inelastic muon scattering on hydrogen and deuterium at incident energies of 90 and 280 GeV. From the measured cross section ratios σd/σp the difference of R, the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, was obtained. Covering a range in x from 0.01 to 0.3 at a typical Q2 of 9 GeV2 the results are compatible with zero. The structure functions F2p and F2d were extracted in a wide kinematic range: 0.006 1 GeV2. Extrapolation to small χ of recent parton distributions are shown to disagree with the NMC results.
The neutron long counter NERO for studies of neutron emission in the r-process
2010
Abstract The neutron long counter NERO was built at the National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, for measuring β -delayed neutron-emission probabilities. The detector was designed to work in conjunction with a β -delay implantation station, so that β decays and β -delayed neutrons emitted from implanted nuclei can be measured simultaneously. The high efficiency of about 40%, for the range of energies of interest, along with the small background, are crucial for measuring β -delayed neutron emission branchings for neutron-rich r-process nuclei produced as low intensity fragmentation beams in in-flight separator facilities.
Dilepton photoproduction on a deuteron target
2019
We investigate the sensitivity of the cross section for lepton pair production off a deuteron target, $\gamma d \to l^+ l^- d$, to the deuteron charge radius. We show that for small momentum transfers the Bethe-Heitler process dominates, and that it is sensitive to the charge radius such that a cross section ratio measurement of about $0.1 \%$ relative accuracy could give a deuteron charge radius more accurate that the current electron scattering value and sufficiently accurate to distinguish between the electronic and muonic atomic values.
Double pion photoproduction in nuclei
1995
The inclusive A(gamma,pi+ pi-)X reaction is studied theoretically. A sizeable enhancement of the cross section is found, in comparison with the scaling of the deuteron cross section (sigma_deuteron * A/2). This enhancement is due to the modifications in the nuclear medium of the gamma N ----> pi pi N amplitude and the pion dispersion relation. The enhancement is found to be bigger than the one already observed in the (pi,pi pi) reaction in nuclei.
The imaginary part of the nucleon self-energy in hot nuclear matter
1996
A semiphenomenological approach to the nucleon self-energy in nuclear matter at finite temperatures is followed. It combines elements of Thermo Field Dynamics for the treatment of finite temperature with a model for the self-energy, which evaluates the second order diagrams taking the needed dynamics of the NN interaction from experiment. The approach proved to be accurate at zero temperature to reproduce Im(Sigma) and other properties of nucleons in matter. In the present case we apply it to determine Im(Sigma) at finite temperatures. An effective NN cross section is deduced which can be easily used in analyses of heavy ion reactions.
Inclusive pion double charge exchange on 16O at 0.6-1.1 GeV
2003
The inclusive pion double charge exchange (DCX) on oxygen nuclei has been measured in the region where additional pion production is kinematically forbidden. The experiment was performed at ITEP PS at incident pi- kinetic energies T_0= 0.59, 0.75 and 1.1 GeV. The integrated forward differential cross section was found to decrease with energy slowly. At 1.1 GeV it exceeds the theoretical prediction within the conventional sequential single charge exchange mechanism with a neutral pion in the intermediate state (Glauber elastic rescattering) by about half an order of magnitude. The sequential mechanism with two pions in the intermediate state (Glauber inelastic rescatterings), which was propo…