Search results for "Nucleon"
showing 10 items of 1041 documents
Experiments on polarised lepton scattering off polarised nucleons
1992
Abstract The current experimental status of the spin dependent structure functions as measured in polarised deep inelastic scattering of charged leptons from nucleons is reviewed. The proposals for new experiments at SLAC and HERA are discussed. Special emphasis is put on the experiment of the Spin Muon Collaboration at CERN which has started taking data in 1991.
Neutrino production of opposite sign dimuons in the NOMAD experiment
2000
The NOMAD Collaboration presents a study of opposite sign dimuon events in the framework of Leading Order QCD. A total of 2714 neutrino- and 115 antineutrino-induced opposite sign dimuon events with $E_{\mu 1}, E_{\mu 2} > 4.5$ GeV, $15 1\;(\mbox{GeV}/\mbox{c})^{2}$ are observed %in the data from the 1995 and 1996 runs. in the Front-Calorimeter of NOMAD during the 1995 and 1996 runs. The analysis yields a value for the charm quark mass of $m_{c} = 1.3^{+0.3\;+0.3}_{-0.3\;-0.3}\;\mbox{GeV}/\m box{c}^{2}$ and for the average semileptonic branching ratio of $B_{c} = 0.095^{+0.007\;+0.014}_{-0.007\;-0.013}$. The ratio of the strange to non-strange sea in the nucleon is measured to be $\kappa = …
Weak pion production off the nucleon
2007
We develop a model for the weak pion production off the nucleon, which besides the Delta pole mechanism (weak excitation of the $\Delta(1232)$ resonance and its subsequent decay into $N\pi$), includes also some background terms required by chiral symmetry. We re-fit the $C_5^A(q^2)$ form factor to the flux averaged $\nu_\mu p \to \mu^-p\pi^+$ ANL $q^2-$differential cross section data, finding a substantially smaller contribution of the Delta pole mechanism than traditionally assumed in the literature. Within this scheme, we calculate several differential and integrated cross sections, including pion angular distributions, induced by neutrinos and antineutrinos and driven both by charged and…
Effects of Strong and Electromagnetic Correlations on Neutrino Interactions in Dense Matter
1998
An extensive study of the effects of correlations on both charged and neutral current weak interaction rates in dense matter is performed. Both strong and electromagnetic correlations are considered.The propagation of particle-hole interactions in the medium plays an important role in determining the neutrino mean free paths. The effects due to Pauli-Blocking and density, spin, and isospin correlations in the medium significantly reduce the neutrino cross sections. Due to the lack of experimental information at high density, these correlations are necessarily model dependent. For example, spin correlations in nonrelativistic models are found to lead to larger suppressions of neutrino cross …
Antikaon-nucleon interaction and Lambda(1405) in chiral SU(3) dynamics
2016
The properties of the Lambda(1405) resonance are key ingredients for determining the antikaon-nucleon interaction in strangeness nuclear physics, and the novel internal structure of the Lambda(1405) is of great interest in hadron physics, as a prototype case of a baryon that does not fit into the simple three-quark picture. We show that a quantitative description of the antikaon-nucleon interaction with the Lambda(1405) is achieved in the framework of chiral SU(3) dynamics, with the help of recent experimental progress. Further constraints on the Kbar N subthreshold interaction are provided by analyzing pi Sigma spectra in various processes, such as the K-d -> pi Sigma n reaction and the…
Unified framework for generalized and transverse-momentum dependent parton distributions within a 3Q light-cone picture of the nucleon
2011
We present a systematic study of generalized transverse-momentum dependent parton distributions (GTMDs). By taking specific limits or projections, these GTMDs yield various transverse-momentum dependent and generalized parton distributions, thus providing a unified framework to simultaneously model different observables. We present such simultaneous modeling by considering a light-cone wave function overlap representation of the GTMDs. We construct the different quark-quark correlation functions from the 3-quark Fock components within both the light-front constituent quark model as well as within the chiral quark-soliton model. We provide a comparison with available data and make prediction…
Renormalization of the weak hadronic current in the nuclear medium
2000
The renormalization of the weak charge-changing hadronic current as a function of the reaction energy release is studied at the nucleonic level. We have calculated the average quenching factors for each type of current (vector, axial vector and induced pseudoscalar). The obtained quenching in the axial vector part is, at zero momentum transfer, 19% for the sd shell and 23% in the fp shell. We have extended the calculations also to heavier systems such as $^{56}$Ni and $^{100}$Sn, where we obtain stronger quenchings, 44% and 59%, respectively. Gamow--Teller type transitions are discussed, along with the higher order matrix elements. The quenching factors are constant up to roughly 60 MeV mom…
Dispersion relation formalism for virtual Compton scattering and the generalized polarizabilities of the nucleon
2000
A dispersion relation formalism for the virtual Compton scattering (VCS) reaction on the proton is presented, which for the first time allows a dispersive evaluation of 4 generalized polarizabilities at a four-momentum transfer $Q^2 \leq$ 0.5 GeV$^2$. The dispersive integrals are calculated using a state-of-the-art pion photo- and electroproduction analysis. The dispersion formalism provides a new tool to analyze VCS experiments above pion threshold, thus increasing the sensitivity to the generalized polarizabilities of the nucleon.
Comparing non-perturbative models of the breakup of neutron-halo nuclei
2012
Breakup reactions of loosely-bound nuclei are often used to extract structure and/or astrophysical information. Here we compare three non-perturbative reaction theories often used when analyzing breakup experiments, namely the continuum discretized coupled channel model, the time-dependent approach relying on a semiclassical approximation, and the dynamical eikonal approximation. Our test case consists of the breakup of 15C on Pb at 68 MeV/nucleon and 20 MeV/nucleon.
Nucleon polarization in exclusive deuteron electrodisintegration with polarized electrons and a polarized target
1995
Nucleon polarization in exclusive electrodisintegration of the deuteron using a polarized beam and an oriented target is systematically investigated in a nonrelativistic framework but with lowest order relativistic contributions to the one-body current including the kinematic part of the wave function boost. The structure functions and the asymmetries corresponding to the various nucleon polarization components are studied with respect to their sensitivity to the potential model, to subnuclear degrees of freedom, and to relativistic effects in different kinematical regions. Furthermore, a few new observables are found which are very sensitive to the neutron electric form factor ${\mathit{G}…