Narrow Results

Presymmetry, the hidden symmetry underlying the charge and generational patterns of quarks and leptons, is utilized for repairing the left–right asymmetry of the standard model with Dirac neutrinos. It is shown that the restoration of parity is consequent with an indispensable left–right symmetric residual presymmetry. Thus, presymmetry substantiates left–right symmetry and the experimental search for the latter is the test of the former, with the nature of neutrinos as a crucial feature that can distinguish the left–right symmetry alone and its combination with presymmetry. This phenomenological implication is in accordance with the fact that Majorana neutrinos are usually demanded in the first case, but forbidden in the second.

One of the key experiments of the physics program of WASA-at-COSY is the determination of the p- wave contributions to the Charge Symmetry breaking amplitude in the reaction dd → ⁴Heπ⁰ at 1.2 GeV/c beam momentum. As a first step towards realisation of this goal the Charge Symmetry conserving reaction dd → ³Henπ⁰ was measured. For an overall theoretical analysis of CSB reactions in terms of Chiral Perturbation Theory this reaction channel will be used to gain information on the deuteron-deuteron initial state interaction for s- and p- wave pion production.

The measurment of the charge symmetry conserving reactions dd → ³He p π^- and dd → ³He n π⁰ is the first step of the charge symmetry breaking physics program with WASA-at-COSY. The analysis of these channels helps to understand the experimental conditions and provides additional parameters for theoretical studies. The data have been collected in November 2007.

Recent work unambiguously resolves the level of charge symmetry violation in moments of parton distributions using (2 + 1)-flavor lattice QCD. We introduce the methods used for that analysis by applying them to determine the strong contribution to the proton–neutron mass difference. We also summarize related work which reveals that the fraction of baryon spin which is carried by the quarks is in fact structure-dependent rather than universal across the baryon octet.

Recent work unambiguously resolves the level of charge symmetry violation in moments of parton distributions using (2+1)-flavor lattice QCD. We introduce the methods used for that analysis by applying them to determine the strong contribution to the proton–neutron mass difference. We also summarize related work which reveals that the fraction of baryon spin which is carried by the quarks is in fact structure-dependent rather than universal across the baryon octet.