Longitudinal response function of 4He with a realistic force

The longitudinal response function of 4He is calculated with the Argonne V18 potential. The comparison with experiment suggests the need of a three-body force. When adding the Urbana IX three-body potential in the calculation of the lower longitudinal multipoles, the total strength is suppressed in the quasi-elastic peak, towards the trend of the experimental data.Comment: 3 pages, 3 figures, proceedings of the 20th European Conference on Few-Body Problems in Physics (EFB20

Omega Production in pp Collisions

A model-independent irreducible tensor formalism which has been developed earlier to analyze measurements of $\vec{p}\vec{p}\to pp \pi^\circ$, is extended to present a theoretical discussion of $\vec{p}\vec{p}\to pp \omega$ and the polarization of $\omega$ in $pp\to pp \vec{\omega}$. The recent measurement of unpolarized differential cross section for $pp\to pp \omega$ is analyzed using this theoretical formalism.Comment: 5 pages (double column), no figures, uses revtex

Cross sections for nu(mu) and (nu)over-bar(mu) induced pion production on hydrocarbon in the few-GeV region using MINERvA

Separate samples of charged-current pion production events representing two semi-inclusive channels nu(mu)-CC(pi(+)) and (nu) over bar (mu) -CC(pi(0)) have been obtained using neutrino and antineutrino exposures of the MINERvA detector. Distributions in kinematic variables based upon mu(+/-)-track reconstructions are analyzed and compared for the two samples. The differential cross sections for muon production angle, muon momentum, and four-momentum transfer Q(2) are reported, and cross sections versus neutrino energy are obtained. Comparisons with predictions of current neutrino event generators are used to clarify the role of the Delta(1232) and higher-mass baryon resonances in CC pion production and to show the importance of pion final-state interactions. For the nu(mu)-CC(pi(+)) [(nu) over bar (mu)-(pi(0))] sample, the absolute data rate is observed to lie below (above) the predictions of some of the event generators by amounts that are typically 1-to- 2 sigma. However the generators are able to reproduce the shapes of the differential cross sections for all kinematic variables of either data set

Covariant calculation of mesonic baryon decays

We present covariant predictions for pi and eta decay modes of N and Delta resonances from relativistic constituent-quark models based on one-gluon-exchange and Goldstone-boson-exchange dynamics. The results are calculated within the point-form approach to Poincare-invariant relativistic quantum mechanics applying a spectator-model decay operator. The direct predictions of the constituent-quark models for covariant pi and eta decay widths show a behaviour completely different from previous ones calculated in nonrelativistic or so-called semirelativistic approaches. It is found that the present theoretical results agree with experiment only in a few cases but otherwise always remain smaller than the experimental data (as compiled by the Particle Data Group). Possible reasons for this behaviour are discussed with regard to the quality of both the quark-model wave functions and the mesonic decay operator.Comment: 10 pages, 2 figures, accepted for publication in Phys. Rev.

Pseudoscalar meson photoproduction: from known to undiscovered resonances

The role of dynamics in spin observables for pseudoscalar meson photoproduction is investigated using a density matrix approach in a multipole truncated framework. Extraction of novel rules for $\gamma p \rightarrow \pi^+ n,~ K^+ \Lambda$ and $\eta p$ reactions based on resonance dominance, and on other broad and reasonable dynamical assumptions, are discussed. Observables that are particularly sensitive to missing nucleonic resonances predicted by quark-based approaches, are singled out.Comment: 22 pages, latex, 3 figure

Unquenching the Quark Model and Screened Potentials

The low-lying spectrum of the quark model is shown to be robust under the effects of `unquenching'. In contrast, the use of screened potentials is shown to be of limited use in models of hadrons. Applications to unquenching the lattice Wilson loop potential and to glueball mixing in the adiabatic hybrid spectrum are also presented.Comment: 6 pages, 3 ps figures, revtex. Version to appear in J. Phys.

Charged pion production in nu(mu) interactions on hydrocarbon at \u3c E-nu \u3e=4.0 GeV

Charged pion production via charged-current nu(mu) interactions on plastic scintillator (CH) is studied using the MINERvA detector exposed to the NuMI wideband neutrino beam at Fermilab. Events with hadronic invariant massW \u3c 1.4 GeV and W \u3c 1.8 GeV are selected in separate analyses: the lower W cut isolates single pion production, which is expected to occur primarily through the Delta(1232) resonance, while results from the higher cut include the effects of higher resonances. Cross sections as functions of pion angle and kinetic energy are compared to predictions from theoretical calculations and generator-based models for neutrinos ranging in energy from 1.5-10 GeV. The data are best described by calculations which include significant contributions from pion intranuclear rescattering. These measurements constrain the primary interaction rate and the role of final state interactions in pion production, both of which need to be well understood by neutrino oscillation experiments