Speaker
Dr
Tomokazu Suzuki
(Department of Physics, Osaka univ.)
Description
A spontaneous symmetry breaking is a common keyword in modern physics.
Chiral symmetry breaking in nuclear structure has recently been debated.
This phenomenon is related to time reversal
and arises from mutually perpendicular angular momenta of the
valence proton, valence neutron, and core rotation in the body fixed frame.
The nuclear chirality results in a nearly degenerate pair of
$\Delta I = 1$ rotational bands, called chiral doublets.
First experimental step is to identify such a twin rotational bands,
which are observed several odd-odd and
a few odd-$A$ nuclei in the $A\sim$130 and $A\sim$100 regions.
However, in the case of $^{134}$Pr,
$B(M1)$ and $B(E2)$ values are clearly different between both bands,
that is, their electromagnetic properties are very different.
Hence, lifetime measurement for chiral candidates were one of the
major requirements for establishing nuclear chirality.
Indeed, a few candidates are measured,
and the $B(E2)$ and $B(M1)$ values between both twin bands
in $^{135}$Nd are very similar.
A similar measurement in the other mass region of $A\sim$100 has been
much anticipated.
Chiral candidates for $^{103,104}$Rh,
are considered one of the best cases to study by lifetime measurements
via the recoil distance Doppler shift (RDDS) method.
The high spin states of $^{103,104}$Rh were populated in the
$^{11}$B($^{96}$Zr,4(3)n)$^{103(104)}$Rh reactions at the beam energy
of 330-MeV provided by the Argonne Tandem Linear Accelerator System (ATLAS).
The Cologne plunger device and GAMMASPHERE array were used.
The data were collected for 7 distances between the target and the degrader;
8, 15, 23, 35, 50, 75, 100~$\mu$m.
On average, a total of approximately $4 \times 10^8$ unfolded events were
sorted into $\gamma - \gamma$ matrices for each distance.
The germanium detectors are grouped in 17 rings by the same polar angles.
However,
only 7 rings having forward or backward angles
with respect to the beam axis were analyzed.
About 80 matrices were analyzed,
and three and four lifetimes of the levels suspected for chiral nature
are measured in $^{103}$Rh and $^{104}$Rh, respectively.
The results of analysis will be presented and discussed.
Primary author
Dr
Tomokazu Suzuki
(Department of Physics, Osaka univ.)
Co-authors
Dr
Alfred Deward
(Institute f\"ur Kernphysik der Universit\"at zu K\"oln)
Mr
Alin Costin
(Department of Physics and Astronomy, SUNY, Stonybrook)
Dr
Christpher J Lister
(Physics Div. Argonne National Laboratory)
Dr
Constantin Vamman
(NSCL, Michigan State Univ.)
Dr
Georgi Rainovski
(St.~Kliment Oridski University of Sofia, Bulgaria)
Dr
Janos Tim\'ar
(Institute of Nuclear Research (ATOMKI))
Dr
Mike Carpenter
(Physics Div. Argonne National Laboratory)
Dr
Milaslov Danchev
(Department of Physics, University of Tennessee)
Dr
Norbert Pietralla
(Institute f\"ur Kernphysik der Technische Universit\"at Darmstadt)
Dr
Oliver M\"oler
(Institute f\"ur Kernphysik der Universit\"at zu K\"oln)
Dr
Robert V Janssence
(Physics Div. Argonne National Laboratory)
Dr
Robert Wadsworth
(Department of Physics, University of York)
Dr
Shaofei Zhu
(Physics Div. Argonne National Laboratory)
Dr
Takeshi Koike
(Department of Physics, Tohoku univ.)
Dr
Tan Ahn
(Department of Physics and Astronomy, SUNY, Stonybrook)
Dr
Tsutomu Shinozuka
(Cyclotron and RI center, Tohoku univ.)
