Precision spectroscopy of pionic 1s states of Sn nuclei and evidence for partial restoration of chiral symmetry in the nuclear medium.
Deeply bound 1s states of pi(-) in (115,119,123)Sn were preferentially observed using the Sn(d,3He) pion-transfer reaction under the recoil-free condition. The 1s binding energies and widths were precisely determined and were used to deduce the isovector parameter of the s-wave pion-nucleus potential to be b1=-(0.115+/-0.007)m(-1)(pi). The observed enhancement of |b(1)| over the free piN value (b(free)1/b1=0.78+/-0.05) indicates a reduction of the chiral order parameter, f*pi(rho)2/f2pi approximately 0.64, at the normal nuclear density, rho=rho(0).
Suzuki
K
K
Department of Physics, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Fujita
M
M
Geissel
H
H
Gilg
H
H
Gillitzer
A
A
Hayano
R S
RS
Hirenzaki
S
S
Itahashi
K
K
Iwasaki
M
M
Kienle
P
P
Matos
M
M
Münzenberg
G
G
Ohtsubo
T
T
Sato
M
M
Shindo
M
M
Suzuki
T
T
Weick
H
H
Winkler
M
M
Yamazaki
T
T
Yoneyama
T
T