Search results for "PARTICLE PHYSICS"
showing 10 items of 6826 documents
Unveiling the strong interaction among hadrons at the LHC
2020
One of the key challenges for nuclear physics today is to understand from first principles the effective interaction between hadrons with different quark content. First successes have been achieved using techniques that solve the dynamics of quarks and gluons on discrete space-time lattices1,2. Experimentally, the dynamics of the strong interaction have been studied by scattering hadrons off each other. Such scattering experiments are difficult or impossible for unstable hadrons3–6 and so high-quality measurements exist only for hadrons containing up and down quarks7. Here we demonstrate that measuring correlations in the momentum space between hadron pairs8–12 produced in ultrarelativistic…
Inclusive pion-nucleus double charge exchange.
1989
Inclusive double charge exchange reaction is studied by using a model which combines a microscopic many-body calculation of reaction probabilities with a Monte Carlo simulation procedure. Comparison with present experimental results requires that the (\ensuremath{\pi},2\ensuremath{\pi}) reaction be included and a proper evaluation of this latter reaction is also done. The combined results compare favorably with experiment, giving extra support to this model of the pion-nucleus interaction which was previously shown to provide a good description of all other inclusive reactions and elastic scattering.
Observation of Meson-Exchange Effects in Deuteron Electrodisintegration
1976
Electrodisintegration of the deuteron has been measured for an incident energy of 300 MeV at 30\ifmmode^\circ\else\textdegree\fi{} and 90\ifmmode^\circ\else\textdegree\fi{} scattering angles. The maximum energy transfer was 116 MeV. Very good agreement with theory was achieved when the pionic-exchange currents were included. Near the threshold and for momentum transfer $\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}}_{\mathrm{c}.\mathrm{m}.}^{}{}_{}{}^{2}=3.9$ ${\mathrm{fm}}^{\ensuremath{-}2}$, the meson-exchange currents contribute about 40% to the total cross section.
On the annual modulation signal in dark matter direct detection
2012
We derive constraints on the annual modulation signal in Dark Matter (DM) direct detection experiments in terms of the unmodulated event rate. A general bound independent of the details of DM distribution follows from the assumption that the motion of the earth around the sun is the only source of time variation. The bound is valid for a very general class of particle physics models and also holds in the presence of an unknown unmodulated background. More stringent bounds are obtained, if modest assumptions on symmetry properties of the DM halo are adopted. We illustrate the bounds by applying them to the annual modulation signals reported by the DAMA and CoGeNT experiments in the framework…
Pygmy dipole resonance in 124Sn populated by inelastic scattering of 17O
2014
L. Pellegri et al. ; 5 pags. ; 6 figs. ; open access article under the CC BY license. Funded by SCOAP3
Estimating the two-particle $K$-matrix for multiple partial waves and decay channels from finite-volume energies
2017
An implementation of estimating the two-to-two $K$-matrix from finite-volume energies based on the L\"uscher formalism and involving a Hermitian matrix known as the "box matrix" is described. The method includes higher partial waves and multiple decay channels. Two fitting procedures for estimating the $K$-matrix parameters, which properly incorporate all statistical covariances, are discussed. Formulas and software for handling total spins up to $S=2$ and orbital angular momenta up to $L=6$ are obtained for total momenta in several directions. First tests involving $\rho$-meson decay to two pions include the $L=3$ and $L=5$ partial waves, and the contributions from these higher waves are f…
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% …