Pluto: A Monte Carlo Simulation Tool for Hadronic Physics

Pluto is a Monte-Carlo event generator designed for hadronic interactions from Pion production threshold to intermediate energies of a few GeV per nucleon, as well as for studies of heavy ion reactions. This report gives an overview of the design of the package, the included models and the user interface.Comment: XI International Workshop on Advanced Computing and Analysis Techniques in Physics Research, April 23-27 2007, Amsterdam, the Netherland

Measurements of scattering observables for the pdpd break-up reaction

High-precision measurements of the scattering observables such as cross sections and analyzing powers for the proton-deuteron elastic and break-up reactions have been performed at KVI in the last two decades and elsewhere to investigate various aspects of the three-nucleon force (3NF) effects simultaneously. In 2006 an experiment was performed to study these effects in $\vec{p}+d$ break-up reaction at 135 MeV with the detection system, Big Instrument for Nuclear polarization Analysis, BINA. BINA covers almost the entire kinematical phase space of the break-up reaction. The results are interpreted with the help of state-of-the-art Faddeev calculations and are partly presented in this contribution.Comment: Proceedings of 19th International IUPAP Conference on Few-Body Problems in Physics, Bonn University, 31.08 - 05.09.2009, Bonn, GERMAN

The reaction γp→π∘γ′p\gamma p \to \pi^\circ \gamma^\prime p and the magnetic dipole moment of the Δ+(1232)\Delta^+(1232) resonance

The reaction $\gamma p \to \pi^\circ \gamma^\prime p$ has been measured with the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI for energies between $\sqrt{s}$ = 1221--1331 MeV. Cross sections differential in angle and energy have been determined for all particles in the final state in three bins of the excitation energy. This reaction channel provides access to the magnetic dipole moment of the $\Delta^{+}(1232)$ resonance and, for the first time, a value of $\mu_{\Delta^+} = (2.7_{-1.3}^{+1.0}(stat.) \pm 1.5 (syst.) \pm 3(theo.)) \mu_N$ has been extracted

Signatures of three-nucleon interactions in few-nucleon systems

Recent experimental results in three-body systems have unambiguously shown that calculations based only on nucleon-nucleon forces fail to accurately describe many experimental observables and one needs to include effects which are beyond the realm of the two-body potentials. This conclusion owes its significance to the fact that experiments and calculations can both be performed with a high accuracy. In this review, both theoretical and experimental achievements of the past decade will be underlined. Selected results will be presented. The discussion on the effects of the three-nucleon forces is, however, limited to the hadronic sector. It will be shown that despite the major successes in describing these seemingly simple systems, there are still clear discrepancies between data and the state-of-the-art calculations.Comment: accepted for publication in Rep. Prog. Phy

Photoproduction of eta-mesic 3He

The photoproduction of eta-mesic 3He has been investigated using the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI. The total inclusive cross section for the reaction gamma+3He->eta+X has been measured for photon energies from threshold to 820 MeV. The total and angular differential coherent eta cross sections have been extracted up to energies of 745 MeV. A resonance-like structure just above the eta production threshold with an isotropic angular distribution suggests the existence of a resonant quasi-bound state. This is supported by studies of a competing decay channel of such a quasi-bound eta-mesic nucleus into pi^0+p+X. A binding energy of (-4.4+-4.2) MeV and a width of (25.6+-6.1) MeV is deduced for the quasi-bound eta-mesic state in 3He.Comment: v1: 4 pages, 4 figures, submitted to PRL; v2: minor revisions and corrections, new figure added, 4 pages, 5 figs; v3: minor change

Chiral Symmetry and light resonances in hot and dense matter

We present a study of the $\pi\pi$ scattering amplitude in the $\sigma$ and $\rho$ channels at finite temperature and nuclear density within a chiral unitary framework. Meson resonances are dynamically generated in our approach, which allows us to analyze the behavior of their associated scattering poles when the system is driven towards chiral symmetry restoration. Medium effects are incorporated in three ways: (a) by thermal corrections of the unitarized scattering amplitudes, (b) by finite nuclear density effects associated to a renormalization of the pion decay constant, and complementarily (c) by extending our calculation of the scalar-isoscalar channel to account for finite nuclear density and temperature effects in a microscopic many-body implementation of pion dynamics. Our results are discussed in connection with several phenomenological aspects relevant for nuclear matter and Heavy-Ion Collision experiments, such as $\rho$ mass scaling vs broadening from dilepton spectra and chiral restoration signals in the $\sigma$ channel. We also elaborate on the molecular nature of $\pi\pi$ resonances.Comment: 14 pages, 14 figures. Contribution to Hard Probes 2008, Illa de A Toxa, Spain, June 8th-14th 200

In-medium modifications of the ππ\pi\pi interaction in photon-induced reactions

Differential cross sections of the reactions $(\gamma,\pi^\circ\pi^\circ)$ and $(\gamma,\pi^\circ\pi^++\pi^\circ\pi^-)$ have been measured for several nuclei ($^1$H,$^{12}$C, and $^{\rm nat}$Pb) at an incident-photon energy of $E_{\gamma}$=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the $\pi\pi$ invariant-mass distribution is found in the $\pi^\circ\pi^\circ$ channel. This dependence is not observed in the $\pi^\circ\pi^{+/-}$ channel and is consistent with an in-medium modification of the $\pi\pi$ interaction in the $I$=$J$=0 channel. The data are compared to $\pi$-induced measurements and to calculations within a chiral-unitary approach

Hard photon and neutral pion production in cold nuclear matter

The production of hard photons and neutral pions in 190 MeV proton induced reactions on C, Ca, Ni, and W targets has been for the first time concurrently studied. Angular distributions and energy spectra up to the kinematical limit are discussed and the production cross-sections are presented. From the target mass dependence of the cross-sections the propagation of pions through nuclear matter is analyzed and the production mechanisms of hard photons and primordial pions are derived. It is found that the production of subthreshold particles proceeds mainly through first chance nucleon-nucleon collisions. For the most energetic particles the mass scaling evidences the effect of multiple collisions.Comment: submitted to Phys. Lett.