Speaker
Prof.
Elena Botta
(Universita' di Torino and INFN Sezione di Torino)
Description
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{ \bf Charge Symmetry Breaking in $s-$ and $p-$shell \LL-hypernuclei: \\ an updated review}
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E.~Botta$^{a,b}$
$^{a}$Dipartimento di Fisica, Universit\`a di Torino, via P. Giuria 1, \\ 10125 Torino, Italy
$^{b}$INFN Sezione di Torino, via P. Giuria 1, 10125 Torino, Italy
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As is well known, the Charge Symmetry of the strong interaction requires that $nn$ and $pp$ interaction strengths are equal. As a consequence, the energy levels of nuclear isospin multiplets are expected to be identical, after correcting for the Coulomb energy difference. The breaking of this symmetry manifests itself in experiments at a level of $\sim$0.07 MeV for the $NN$ interaction in normal, not strange, nuclei.
In $\Lambda$ hypernuclei, where the $\Lambda N$ interaction acts, the breaking is predicted to be $\sim$0.05 MeV by theoretical models which do not consider the effects of $\Lambda N - \Sigma N$ coupling and of the three-body $\Lambda N N$ forces. However, from the experimental side, a large value of binding energy difference has been found for the $A$=4 isospin doublet, $^{4}_{\Lambda}$H - $^{4}_{\Lambda}$He, in experiments based on emulsion techniques in the seventies. The same experiments gave also indications about the binding energy difference in A=7, 8, 10, 12 isomultiplets which did not show a substantial breaking effect.
In the last few years, several magnetic spectrometers provided high precision results in the field of Hypernuclear Physics.
In particular, the accurate determination of the \LL-binding energy for A=7, 10, 12, 16 systems contributed to stimulate considerably the discussion about the Charge Symmetry Breaking effect in \LL-hypernuclei isomultiplets.
Also for the $A$=4 isospin doublet, very precise measurements of $^{4}_{\Lambda}$H ground state binding energy and of $^{4}_{\Lambda}$He first excited state energy have been obtained.
My contribution aims at making an overview, focusing on recent experimental results and analyses, to introduce the discussion on the involved experimental aspects and on the recent theoretical calculations on Charge Symmetry Breaking in $s-$ and $p-$shell \LL-hypernuclei.
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Primary author
Prof.
Elena Botta
(Universita' di Torino and INFN Sezione di Torino)
