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SUMMARY:np spin-correlation in the ground state studied by the sum-rules
of the spin-M1 transition matrix elements and implications to the IS
np pairing correlation
DTSTART:20170328T043000Z
DTEND:20170328T060000Z
DTSTAMP:20240302T105400Z
UID:indico-event-2470@indico2.riken.jp
DESCRIPTION:=Date and Place=\nMar.28th(Tue.)\, 13:30~ at RIBF Hall(room 20
1)\n\n= Lecturer=\nProf.Atsushi Tamii\n(Research Center for Nuclear Physi
cs\, Osaka University)\n\n=Title=\n np spin-correlation in the ground sta
te studied by the sum-rules of the spin-M1 transition matrix elements and
implications to the IS np pairing correlation\n\n=Abstract=\n How are nuc
leons correlated in the ground state of atomic nuclei? It is one of fundam
ental questions to understand the strongly correlated nuclear system. Amon
gst many correlations\, the correlation between a neutron and a proton\, m
ore specifically the isoscalar (IS) np pairing correlation\, is thought to
play a minor role in mean-field models while the isovector (IV) paring co
rrelations are well descried by the quasi-particle description. However\,
the IS np paring is obviously stronger in the ground state of light nuclei
\, e.g. a deuteron or 6Li. How does the IS paring correlation manifest its
elf in heavier nuclei? We have obtained an evidence of np spin-correlati
on\, that naturally emerges from the np pairing correlation\, in sd-shel
l nuclei. The np spin-correlation function (npSCF) is proportional to the
difference of the non energy-weighted sum-rule values of the IS and IV spi
n-M1 squared transition matrix elements. The npSCP takes a value of +1/4(-
3/4) for the full spin-alignment (anti-alignment) that emerges from the IS
(IV) np pairing in s-wave. The observed npSCFs showed a positive value of
+0.1 for all the measured even-even self-conjugated nuclei in the sd-shel
l [1]. The result shows stronger IS np-pairing than the IV np-pairing.\n
How can one understand the result with theoretical models? The shell-model
with the USD interaction does not reproduce the positive npSCFs. Similar
result was obtained for a large-scale shell model calculation [2]. However
the non-core shell-model predictions hint the positive npSCFs [1] that im
plies the importance of the core-polarization effect. The positive npSCFs
are also predicted for 4He by ab initio calculations employing modern NN i
nteractions [1\,3]. Recent phenomenological study using shell-model wave f
unctions could reproduce the positive npSCFs by introducing an enhanced IS
spin-triplet pairing interaction and the Delta-hole coupling effect [4].\
n In this seminar\, I will discuss in detail the experimental finding and
its interpretations as well as possible future extensions to other excite
d states.\n\n[1] H. Matsubara et al.\, Phys. Rev. Lett. [2] N. Shimizu\, Y
. Utsuno\, and N. Tsunoda\, private communication [3] W. Horiuchi et al.\,
Phys. Rev. C 87\, 034001 (2013).[4] H. Sagawa et al.\, Phys. Rev. C 94\,
041303(R).\n\nhttps://indico2.riken.jp/event/2470/
LOCATION:201 (RIBF Hall)
URL:https://indico2.riken.jp/event/2470/
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