Search results for "Inelastic Scattering"

Total decay and transition rates from LQCD

2018

We present a new technique for extracting total transition rates into final states with any number of hadrons from lattice QCD. The method involves constructing a finite-volume Euclidean four-point function whose corresponding infinite-volume spectral function gives access to the decay and transition rates into all allowed final states. The inverse problem of calculating the spectral function is solved via the Backus-Gilbert method, which automatically includes a smoothing procedure. This smoothing is in fact required so that an infinite-volume limit of the spectral function exists. Using a numerical toy example we find that reasonable precision can be achieved with realistic lattice data. …

The EPPS16 nuclear PDFs

2017

We report on EPPS16 - the first analysis of NLO nuclear PDFs where LHC p-Pb data (Z, W, dijets) have been directly used as a constraint. In comparison to our previous fit EPS09, also data from neutrino-nucleus deeply-inelastic scattering and pion-nucleus Drell-Yan process are now included. Much of the theory framework has also been updated from EPS09, including a consistent treatment of heavy quarks in deeply-inelastic scattering. However, the most notable change is that we no longer assume flavour-blind nuclear modifications for valence and sea quarks. This significantly reduces the theoretical bias. All the analysed data are well reproduced and the analysis thereby supports the validity o…

Nucleon Structure Functions in a Constituent Quark Scenario

1999

Using a simple picture of the constituent quark as a composite system of point-like partons, we construct the polarized part on distributions by a convolution between constituent quark momentum distributions and constituent quark structure functions. We achieve good agreement with experiments in the unpolarized as well as in the polarized case, though a good description of the recent polarized neutron data requires the introduction of one more paramater. When our results are compared with similar calculations using non-composite constituent quarks, the accord with the experiments of the present scheme is impressive. We conclude that DIS data are consistent with a low energy scenario dominat…

Final COMPASS results on the deuteron spin-dependent structure functiong1dand the Bjorken sum rule

2017

Final results are presented from the inclusive measurement of deep-inelastic polarised-muon scattering on longitudinally polarised deuterons using a 6 LiD target. The data were taken at 160 GeV beam energy and the results are shown for the kinematic range 1(GeV/c)2 4GeV/c2 in the mass of the hadronic final state. The deuteron double-spin asymmetry A1d and the deuteron longitudinal-spin structure function g1d are presented in bins of x and Q2 . Towards lowest accessible values of x , g1d decreases and becomes consistent with zero within uncertainties. The presented final g1d values together with the recently published final g1p values of COMPASS are used to again evaluate the Bjorken sum rul…

Two-photon exchange correction to2S−2Psplitting in muonicHe3ions

2017

We calculate the two-photon exchange correction to the Lamb shift in muonic $^{3}\mathrm{He}$ ions within the dispersion relations framework. Part of the effort entailed making analytic fits to the electron-$^{3}\mathrm{He}$ quasielastic scattering data set, for purposes of doing the dispersion integrals. Our result is that the energy of the $2S$ state is shifted downwards by two-photon exchange effects by 15.14(49) meV, in good accord with the result obtained from a potential model and effective field theory calculation.

Quantum Coherence Effects in One-Dimensional Chains with Inelastic Scattering

1991

To describe the ballistic transport in a 1 D chain Landauer [1] has calculated the resistance R of a series of elastic scatterers from their transmission coefficient T $$R = \frac{h}{{{e^2}}}\frac{{1 - T}}{T}$$ (1) This relation implies complete quantum coherence between incident and all backscattered waves. Dephasing due to irreversible processes has been introduced into this model by Buttiker [2] who added inelastic scatterers coupled to an external heat bath to the chain. In this way it is possible to describe also certain dissipative aspects of electron transport. However, his approach does not allow to study the gradual transition from coherent to incoherent transport with increasing s…

Inelastic neutron scattering by coupled rotational and translational modes in KCN

1980

The TA [100] phonon branch of the molecular crystal KCN was studied by inelastic neutron scattering in the cubic phase. In addition the distribution of the quasielastic scattered neutrons was investigated. The results are analysed by assuming a coupling of the phonon modes to the rotational degrees of freedom of the CN-dumb-bells which are regarded as a system of interacting quadrupoles. A good description of the present results and also of the existing ultrasonic and Brillouin data is achieved by a simple model which uses a single collective rotational mode of finite excitation energy and line width.

Two-photon exchange correction in elastic unpolarized electron-proton scattering at small momentum transfer

2015

We evaluate the two-photon exchange (TPE) correction to the unpolarized elastic electron-proton scattering at small momentum transfer $ Q^2 $. We account for the inelastic intermediate states approximating the double virtual Compton scattering by the unpolarized forward virtual Compton scattering. The unpolarized proton structure functions are used as input for the numerical evaluation of the inelastic contribution. Our calculation reproduces the leading terms in the $ Q^2 $ expansion of the TPE correction and goes beyond this approximation by keeping the full $ Q^2 $ dependence of the proton structure functions. In the range of small momentum transfer, our result is in good agreement with …

Low Energy Behaviour of the Phase Shifts for Velocity-Dependent Potentials

1973

Measurements of Absolute Cross Sections for (e,H2) Collision Processes. Formation and Decay ofH2−Resonances

1970

Energy and angular dependences of the elastic and inelastic scattering of electrons from ${\mathrm{H}}_{2}$ have been measured in the energy range 10 to 16 eV and for scattering angles ranging from 10\ifmmode^\circ\else\textdegree\fi{} to 120\ifmmode^\circ\else\textdegree\fi{}. Three resonance series have been investigated starting at 11.30, 11.50, and 13.63 eV, respectively. The last two series decay preferentially into one single electronic channel, while the first resonance (resonance I) decays into all energetically possible exit channels, i.e., $X^{1}\ensuremath{\Sigma}_{g}^{+}$, $b^{3}\ensuremath{\Sigma}_{u}^{+}$, $B^{1}\ensuremath{\Sigma}_{u}^{+}$. Throughout, stress is laid on the i…