Lecturer: Prof. Avraham Gal
Affiliation: Racah Institute of Physics,
The Hebrew University of Jerusalem
Abstract:
Charge symmetry breaking (CSB) in the light
hadronic spectrum,e.g. the neutron-proton
mass difference, has been recently explained by
LQCD-LQED calculations in terms of the u-d
quark mass difference plus electromagnetic
interactions among the u,d,s quarks. A similar
level of understanding CSB is lacking for two-
baryon configurations (e.g. pp, pn and nn, and
more so for Lambda-p and Lambda-n). In nuclei,
the CSB contribution of about 70 keV to the
Coulomb-dominated 764 keV 3He-3H mass
difference is accounted for by hadronic
contributions. Given this background, the CSB
implied by the Lambda separation energy
difference 350+/-60 keV in the A = 4 mirror
hypernuclei ground states, obtained by
attaching a Lambda hyperon to the (3H, 3He)
mirror nuclei, is LARGE. It has defied theoretical
attempts to reproduce it in terms of CSB in
hyperon masses and in hyperon-nucleon
interactions, including one pion exchange
arising from (Lambda < --> Sigma0) mixing. In
this talk I will review new calculations of CSB in
the A = 4 Lambda hypernuclei, plus extensions
to heavier mirror Lambda hypernuclei, using
several strong-interaction (Lambda N < -->
Sigma N) coupling potential models, including a
chiral EFT model in leading order. These
calculations demonstrate for the first time that
the observed CSB splitting of mirror levels in
Lambda hypernuclei can be reproduced using
realistic theoretical interaction models.
References: (i) A. Gal, PLB 744 (2015) 352; (ii) D.
Gazda and A. Gal, arXiv:1512.01049.
Additional details of the upcoming Israeli
Joint Nuclear Physics' Seminars can be
found on the following link.