Date: May 23, from 16:00
Place: RIBF Building, 2F large meeting room
Leturer: Atsushi Tamii (RCNP)
Title: Tensor Correlation in the Ground States of N=Z Nuclei
Abstract:
The nucleon-nucleon (NN) interaction contains a strong tensor interaction due to pion exchange.
The strong attraction of the tensor interaction contributes significantly to the binding energy of nuclei.
Therefore it is natural to treat the tensor interaction explicitly in nuclear structure calculations.
Such calculations are, however, limited in few-nucleon systems due to mainly technical difficulty.
Thus the role of the tensor interaction, or tensor correlation, in nuclear structure has not been
explicitly taken into account in conventional shell-model and mean-field calculations, and has been hidden.
Experimental trial for probing the effects of tensor correlation is one of hot topics.
We have recently observed bulk contribution of the tensor correlation in the ground states of
self-conjugate (N=Z) even-even nuclei. The experiment was performed at the Research Center for Nuclear Physics (RCNP),
employing a high-resolution proton beam at 295 MeV and the Grand Raiden spectromter. Spin-M1 transition strengths
from the ground states of 12C, 16O, 20Ne, 24Mg, 28Si, 32S, 36Ar, and 40Ca nuclei have been determined for each of
isoscalar and isovector transitions up to 16 MeV. The observed transition strengths are converted, by using a sum-rule,
to an expected value of the ground state wave-function <S_p . S_n>, where S_p(n) is the vector-sum of
all the proton (neutron) spin-operators. The value is quite sensitive to the tensor correlation between protons and neutrons.
The extracted number is ~0.1 and is more or less flat in sd-shell region. The number is consistent with predictions
for the 4He nucleus using realistic NN interactions. I will report on the experiment and discuss the results.