The N N -> NN pi+ Reaction near Threshold in a Chiral Power Counting Approach

Power-counting arguments are used to organize the interactions contributing to the N N -> d pi, p n pi reactions near threshold. We estimate the contributions from the three formally leading mechanisms: the Weinberg-Tomozawa (WT) term, the impulse term, and the $\Delta$-excitation mechanism. Sub-leading but potentially large mechanisms, including $S$-wave pion-rescattering, the Galilean correction to the WT term, and short-ranged contributions are also examined. The WT term is shown to be numerically the largest, and the other contributions are found to approximately cancel. Similarly to the reaction p p -> p p pi0, the computed cross sections are considerably smaller than the data. We discuss possible origins of this discrepancy.Comment: 31 pages, 17 figure

Nucleon-nucleon charge symmetry breaking and the dd -> alpha pi0 reaction

We show that using parameters consistent with the charge symmetry violating difference between the strong nn and pp scattering lengths provides significant constraints on the amplitude for the dd -> alpha pi0 reaction.Comment: 4 pages, 1 figur

Medium Modification of the Jet Properties

In the case that a dense medium is created in a heavy ions collision, high-E_t jets are expected to be broadened by medium-modified gluon emission. This broadening is directly related, through geometry, to the energy loss measured in inclusive high-p_t particle suppression. We present here the modifications of jet observables due to the presence of a medium for the case of azimuthal jet energy distributions and k_t-differential multiplicities inside the jets.Comment: 4 pages, 3 postscript figures. Proceedings for Quark Matter 200

Observation of the Charge Symmetry Breaking d + d -> 4He + pi0 Reaction Near Threshold

We report the first observation of the charge symmetry breaking d + d -> 4He + pi0 reaction near threshold at the Indiana University Cyclotron Facility. Kinematic reconstruction permitted the separation of 4He + pi0 events from double radiative capture 4He + gamma + gamma events. We measured total cross sections for neutron pion production of 12.7 +- 2.2 pb at 228.5 MeV and 15.1 +- 3.1 pb at 231.8 MeV. The uncertainty is dominated by statistical errors.Comment: 7 pages, 2 figures, plain Te

Charge-Symmetry-Breaking Three-Nucleon Forces

Leading-order three-nucleon forces that violate isospin symmetry are calculated in Chiral Perturbation Theory. The effect of the charge-symmetry-breaking three-nucleon force is investigated in the trinucleon systems using Faddeev calculations. We find that the contribution of this force to the 3He - 3H binding-energy difference is approximately 5 keV.Comment: 14 pages, 3 figure