Search results for "Scattering length"

Determination of the ηHe3 threshold structure from the low energy pd→ηHe3 reaction

2017

We analyze the data on cross sections and asymmetries for the $pd\ensuremath{\rightarrow}\ensuremath{\eta}\phantom{\rule{0.16em}{0ex}}^{3}\mathrm{He}$ reaction close to threshold and look for bound states of the $\ensuremath{\eta}\phantom{\rule{0.16em}{0ex}}^{3}\mathrm{He}$ system. Rather than parameterizing the scattering matrix, as is usually done, we develop a framework in which the $\ensuremath{\eta}{\phantom{\rule{0.16em}{0ex}}}^{3}\mathrm{He}$ optical potential is the key ingredient, and its strength, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe…

Chiral dynamics in systems with strangeness

2002

In this talk a brief review of several problems involving systems with strangeness is made. In the first place one shows how the $\Lambda (1405)$, $\Lambda(1670)$ and $\Sigma(1620)$ states, for $S = -1$, and the $\Xi(1620)$ for $S= -2$ are generated dynamically in the context of unitarized chiral perturbation theory. The results for the $\bar{K}N$ interaction are then used to evaluate the $K^- d$ scattering length. Results obtained for the kaon selfenergy in a nuclear medium within this approach, with application to $K^-$ atoms, are also mentioned. Finally a few words are said about recent developments in the weak decay of $\Lambda$ hypernuclei and the puzzle of the $\Gamma_n/\Gamma_p$ rati…

The End Point Tagger physics program at A2@MAMI

2017

The A2-Collaboration uses a beam of real photons from the tagged photon facility at the electron accelerator MAMI in Mainz, Germany, to study photo-produced mesons. A new tagging device allows access to the higher photon beam energy range of 1.4 to 1.6 GeV. A large dataset containing more than 6 million η ′ and roughly 29 million ω decays has been obtained. Analyses are ongoing, including a study of the cusp effect and Dalitz plot in η ′ → ηπ 0 π 0 , giving insight to the π π scattering length and the structure of the ηππ system, as well as the measurement of the electromagnetic transition form factor in η ′ → e + e − γ , a cross section measurement of γ p → 3 π 0 , and branching ratio anal…

ϒ photoproduction on the proton at the Electron-Ion Collider

2020

We present a dispersive analysis with the aim to extract the $\mathrm{\ensuremath{\Upsilon}}\text{\ensuremath{-}}p$ scattering length from $\ensuremath{\gamma}p\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}p$ experiments. In this framework, the imaginary part of the $\mathrm{\ensuremath{\Upsilon}}\text{\ensuremath{-}}p$ forward scattering amplitude is obtained from $\ensuremath{\gamma}p\ensuremath{\rightarrow}\mathrm{\ensuremath{\Upsilon}}p$ cross section measurements and is constrained at high energies from existing HERA and LHC data. Its real part is calculated through a once-subtracted dispersion relation, and the subtraction constant is proportional to the $\mathrm{\ensuremath{\…

Role of excitons in double Raman resonances in GaAs quantum wells

1996

Raman scattering by longitudinal-optical phonons has been measured in GaAs-AlAs multiple quantum wells at high magnetic fields. Doubly resonant scattering processes are observed at photon energies corresponding to magneto-excitons with different principal quantum numbers for the incoming and outgoing channels. The existence of these initially forbidden scattering processes, their resonance energies, and their relative intensities are correctly reproduced by our theoretical description. The model takes into account the excitonic nature of the intermediate states, as well as scattering processes involving a nonzero in-plane phonon wave vector, which is required to allow inter-Landau level sca…

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

1973

Relativistic scattering theory of charged spinless particles

1986

In the context of a relativistic quantum mechanics we discuss the scattering of two and three charged spinless particles. The corresponding transition operators are shown to satisfy four-dimensional Lippmann-Schwinger and eight-dimensional Faddeev-type equations, respectively. A simplified model of two particles with Coulomb interaction can be solved exactly. We calculate: (i) The partial waveS-matrix from which we extract the bound state spectrum. The latter agrees with a fourth-order result of Schwinger, (ii) The full scattering amplitude which in the weakfield limit coincides with the expression derived by Fried et al. from eikonalized QED.

Scattering amplitudes for two charged fragments

2008

Neutron scattering and molecular correlations in a supercooled liquid

1999

We show that the intermediate scattering function $S_n(q,t)$ for neutron scattering (ns) can be expanded naturely with respect to a set of molecular correlation functions that give a complete description of the translational and orientational two-point correlations in the liquid. The general properties of this expansion are discussed with special focus on the $q$-dependence and hints for a (partial) determination of the molecular correlation functions from neutron scattering results are given. The resulting representation of the static structure factor $S_n(q)$ is studied in detail for a model system using data from a molecular dynamics simulation of a supercooled liquid of rigid diatomic m…

Measurement of the Coherent Neutron Scattering Length of (3) He.

2005

By means of neutron interferometry the s-wave neutron scattering length of the (3)He nucleus was re-measured at the Institut Laue-Langevin (ILL). Using a skew symmetrical perfect crystal Si-interferometer and a linear twin chamber cell, false phase shifts due to sample misalignment were reduced to a negligible level. Simulation calculations suggest an asymmetrically alternating measuring sequence in order to compensate for systematic errors caused by thermal phase drifts. There is evidence in the experiment's data that this procedure is indeed effective. The neutron refractive index in terms of Sears' exact expression for the scattering amplitude has been analyzed in order to evaluate the m…