Speaker
Dr
Patrick Achenbach
(Mainz University)
Description
Charge symmetry of the strong interaction predicts that the Λp and Λn interaction and consequently their contribution to the binding energies of mirror hypernuclei are identical. In the system of A=4 hypernuclei, however, emulsion measurements found an exceptionally large difference of 0.35 ± 0.05 MeV for the ground state binding energies. Very recently gamma-ray measurements in Λ-He4 at J-PARC indicate that the breaking of the symmetry is large in the 0+ ground state but is nearly vanishing in the 1+ excited state, demonstrating that the symmetry breaking part in the ΛN interaction has a strong spin dependence.
The effect resists a consistent reproduction by theory until today and makes a confirmation of all binding energies in the A=4 system with independent experimental techniques desirable, especially since there is no exact knowledge about the systematic uncertainty for the emulsion data.
The first observation of Λ-H4 by means of decay-pion spectroscopy with a high resolution magnetic spectrometer was performed 2012 at the Mainz Microtron MAMI. Demonstrating an almost one order of magnitude higher precision, it showed to be consistent with the emulsion result, while being limited by systematic uncertainties. In 2014, an extended measurement campaign was performed with improved control over systematic effects, increasing the yield of observed hypernuclei and confirming the measurement with two spectrometers at the same time.
All values for the Λ-H4 binding energy measured at MAMI are consistent with a large charge symmetry breaking effect that leads to a 0.24 MeV binding energy difference in the A = 4 system when combined with emulsion data.
Summary
This talk will discuss the measurements of Λ-H4 binding energy at MAMI and its implications on the Charge Symmetry Breaking in Hypernuclei.
Primary author
Dr
Patrick Achenbach
(Mainz University)
