Search results for "Elastic scattering"
showing 10 items of 735 documents
Compton scattering by a pion and off-shell effects
1994
We consider Compton scattering by a pion in the framework of chiral perturbation theory. We investigate off--shell effects in the s-- and u--channel pole diagrams. For that purpose we perform a field transformation which, in comparison with the standard Gasser and Leutwyler Lagrangian, generates additional terms at order $p^4$ proportional to the lowest--order equation of motion. As a result of the equivalence theorem the two Lagrangians predict the same Compton scattering S--matrix even though they generate different off--shell form factors. We conclude that off--shell effects are not only model--dependent but also representation--dependent.
Doubling of α-cluster statesin22Ne
2001
Excitation functions for ${}^{18}\mathrm{O}+\ensuremath{\alpha}$ elastic scattering were measured by a method using inverse kinematics and a thick gas target. An analysis of the data corresponding to the excitation energy regions of 11.8--13.7 MeV and 19.0--22.0 MeV in ${}^{22}\mathrm{Ne}$ was carried out. A surprising splitting of ${1}^{\ensuremath{-}},$ ${3}^{\ensuremath{-}},$ ${7}^{\ensuremath{-}},$ and ${9}^{\ensuremath{-}}$ $\ensuremath{\alpha}$-cluster levels into doublets was found in ${}^{22}\mathrm{Ne}.$
Study of Cluster Structures in Nuclei through the Ratio Method. A Tribute to Mahir Hussein
2020
For one-neutron halo nuclei, the cross sections for elastic scattering and breakup at intermediate energy exhibit similar angular dependences. The Recoil Excitation and Breakup (REB) model of reactions elegantly explains this feature. It also leads to the idea of a new reaction observable to study the structure of loosely-bound nuclear systems: the Ratio. This observable consists of the ratio of angular distributions for different reaction channels, viz. elastic scattering and breakup, which cancels most of the dependence on the reaction mechanism; in particular it is insensitive to the choice of optical potentials that simulate the projectile-target interaction. This new observable is very…
Virtual Compton Scattering and Neutral Pion Electroproduction in the Resonance Region up to the Deep Inelastic Region at Backward Angles
2009
We have made the first measurements of the virtual Compton scattering (VCS) process via the H$(e,e'p)\gamma$ exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the $W$-dependence at fixed $Q^2=1$ GeV$^2$, and for the $Q^2$-dependence at fixed $W$ near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed $Q^2$-dependence is smooth. The measured ratio of H$(e,e'p)\gamma$ to H$(e,e'p)\pi^0$ cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to Real Compton Scattering (RCS) at high energy and large angles, our VCS data…
Combined description of N-barN scattering and annihilation with a hadronic model.
1995
A model for the nucleon-antinucleon interaction is presented which is based on meson-baryon dynamics. The elastic part is the {ital G}-parity transform of the Bonn {ital NN} potential. Annihilation into two mesons is described in terms of microscopic baryon-exchange processes including all possible combinations of {pi},{eta},{rho},{omega},{ital a}{sub 0},{ital f}{sub 0},{ital a}{sub 1},{ital f}{sub 1},{ital a}{sub 2},{ital f}{sub 2},{ital K},{ital K}{sup *}. The remaining annihilation part is taken into account by a phenomenological energy- and state-independent optical potential of Gaussian form. The model enables a simultaneous description of nucleon-antinucleon scattering and annihilatio…
πNscattering in relativistic baryon chiral perturbation theory reexamined
2011
We have analyzed pion-nucleon scattering using the manifestly relativistic covariant framework of infrared regularization up to $\mathcal{O}({q}^{3})$ in the chiral expansion, where $q$ is a generic small momentum. We describe the low-energy phase shifts with a similar quality as previously achieved with heavy baryon chiral perturbation theory, $\sqrt{s}\ensuremath{\lesssim}1.14$ GeV. New values are provided for the $\mathcal{O}({q}^{2})$ and $\mathcal{O}({q}^{3})$ low-energy constants, which are compared with previous determinations. This is also the case for the scattering lengths and volumes. Finally, we have unitarized the previous amplitudes and as a result the energy range where data …
Neutral-current atmospheric neutrino flux measurement using neutrino-proton elastic scattering in Super-Kamiokande
2003
Recent results show that atmospheric $\nu_\mu$ oscillate with $\delta m^2 \simeq 3 \times 10^{-3}$ eV$^2$ and $\sin^2{2\theta_{atm}} \simeq 1$, and that conversion into $\nu_e$ is strongly disfavored. The Super-Kamiokande (SK) collaboration, using a combination of three techniques, reports that their data favor $\nu_\mu \to \nu_\tau$ over $\nu_\mu \to \nu_{sterile}$. This distinction is extremely important for both four-neutrino models and cosmology. We propose that neutrino-proton elastic scattering ($\nu + p \to \nu + p$) in water \v{C}erenkov detectors can also distinguish between active and sterile oscillations. This was not previously recognized as a useful channel since only about 2% …
Elastic pion scattering on the deuteron in a multiple scattering model
1996
Pion elastic scattering on deuterium is studied in the KMT multiple scattering approach developed in momentum space. Using a Paris wave function and the same methods and approximations as commonly used in pion scattering on heavier nuclei excellent agreement with differential cross section data is obtained for a wide range of pion energies. Only for $T_{\pi}>250$ MeV and very backward angles, discrepancies appear that are reminiscent of disagreements in pion scattering on $^3$He, $^3$H, and $^4$He. At low energies the second order corrections have been included. Polarization observables are studied in detail. While tensor analyzing powers are well reproduced, vector analyzing powers exhibit…
An Appearance-Like Reactor Experiment To Measure Ue3
2004
Conventional reactor neutrino experiments are dissapearance experiments, and thus have less sensitivity to small mixing angles than appearance experiments do. It has been recently shown that future reactor neutrino experiments consisiting of a near and far detector are competitive with first-generation superbeams in order to determine sin^2{2 theta_{13}} down to 10^{-2}. We show that by using the antineutrino-electron elastic scattering at the near detector around the configuration where dsigma^{bar{\nu}_e}/dT presents a dynamical zero, an appearance-like experiment can be simulated, with a sensitivity comparable to the one achieved with the inverse beta-decay reaction in the far detector. …
Backward spin polarizabilityγπof the proton
2002
Using the Mainz $48\mathrm{cm}\ensuremath{\emptyset}\ifmmode\times\else\texttimes\fi{}64\mathrm{cm}$ NaI(Tl) detector and the segmented G\"ottingen recoil detector SENECA in coincidence, Compton scattering by the proton at ${\ensuremath{\theta}}_{\ensuremath{\gamma}}^{\mathrm{lab}}=136\ifmmode^\circ\else\textdegree\fi{}$ has been measured at MAMI (Mainz) in the energy range from 200 to 470 MeV. The new data confirm the previous observation that there is a systematic discrepancy between MAMI and LEGS (Brookhaven) data leading to different spin polarizabilities ${\ensuremath{\gamma}}_{\ensuremath{\pi}}=\ensuremath{-}38.7\ifmmode\pm\else\textpm\fi{}1.8$ and $\ensuremath{-}27.2\ifmmode\pm\else\…