X. Q. Li

Evidence for Octupole Correlations in Multiple Chiral Doublet Bands

Two pairs of positive-and negative-parity doublet bands together with eight strong electric dipole transitions linking their yrast positive- and negative-parity bands have been identified in ^{78}Br. They are interpreted as multiple chiral doublet bands with octupole correlations, which is supported by the microscopic multidimensionally-constrained covariant density functional theory and triaxial particle rotor model calculations. This observation reports the first example of chiral geometry in octupole soft nuclei.

Properties of strangelets at finite temperature in the liquid drop model

A comprehensive study of the properties of strangelets at zero and finite temperature is presented within the framework of liquid drop model, including the essential finite size effects. Strong parameter dependences of the properties are found and discussed. {copyright} {ital 1996 The American Physical Society.}

Cold strangelets formation with finite size effects in high energy heavy-ion collisions.

We have studied the phase diagram and evolution of a strangelet in equilibrium with a finite hadronic gas. Significant finite size modifications of the phase diagram are found and their parameter dependences are studied. With the inclusion of finite size effects we have also been able to obtain the detailed properties of the cold strangelet emerging in the final stage of the isentropic expansion of a finite strange fireball in high energy heavy-ion collisions. {copyright} {ital 1996 The American Physical Society.}

Efficiency calibration of a large-area neutron detector by using Am/Be neutron source

Neutron detection efficiency for a long wedge-shaped plastic scintillation detector was measured by using the Am/Be neutron source. The overall efficiency attains 23% at around 2 MeV and decreases to 15% at about 5 MeV. The experimental results are in agreement with the Monte Carlo simulation calculations.

Knockout reaction induced by 6He at 82.3 MeV/u

A knockout reaction experiment was carried out using a 6He beam at 82.3 MeV/u impinged on carbon and hydrogen targets. The recoil protons were detected in coincidence with the forward moving charged fragments and neutrons. It is demonstrated that through the correlation between the recoil protons and forward moving charged fragments, the core fragment knockout and valence nucleon knockout reaction mechanisms can be discriminated at energies around 100 MeV/u. The 5He ground-state resonance was reconstructed based on the selection of the valence nucleon knockout mechanism. The resonance parameters were obtained for both carbon and hydrogen targets, which are consistent with those previously reported in the literature. The importance of selecting appropriate reaction mechanisms is discussed based on reconstructions using events with larger transverse momentum transfer.

8He cluster structure studied by recoil proton tagged knockout reaction

Knockout reaction experiment for 8He at 82.3 MeV/u on Hydrogen target was carried out at the RIPS beam line in RIKEN. Recoil protons were detected in coincidence with the forward moving core fragments and neutrons. The quasi-free knockout mechanism is identified through the polar angle correlation and checked by various kinematics conditions. The absolute differential cross sections for 6He core cluster are obtained and compared with the simple Glauber model calculations. The extracted spectroscopic factor is close to unity and a shrinking of the cluster size is evidenced.

Evolution of the X(5) critical-point symmetry in rotating \mathrm{\mathbf {^{176}Os}}

Lifetimes of excited states above 10+ in the yrast band in 176Os have been measured using the Doppler shift attenuation method, via the fusion evaporation reaction . Lifetimes of states over 12+ were measured for the first time. The deduced transitional quadruple moments (Qt), together with the previous data using a recoil distance method, are compared with theoretical calculations based on the X(5) model and the interaction boson model. For the states below spin 10+, the data of previous work support an X(5)-like structure, but for the states above 10+, the value of Qt remains almost constant, being the characteristic of a symmetric rotor. The present result suggests that the shape of the nucleus 176Os changes from X(5) critical-point symmetry to an axially deformed rotor with increasing spin.

Magnetic rotation in {sup 112}In

The high spin states of {sup 112}In have been investigated with in-beam {gamma}-ray spectroscopic methods using the {sup 110}Pd({sup 7}Li,5n){sup 112}In reaction at a beam energy of 50 MeV. A level scheme with three band structures has been established and their configurations are discussed. The positive-parity dipole band has been assigned as a magnetic rotation band. Particle-rotor model calculations have also been performed to interpret the rotational structures in {sup 112}In.

Recoiled Proton Tagged Knockout Reaction for 8He

Recently recoiled proton tagged knockout reaction experiments were carried‐out for 8He at 82 MeV/nucleon. The purpose of the experiment are: (1) Through the core knocked out technique, to study the correlation of the valence neutrons in the ground state of 8He. This should provide new experimental information to the neutron coupling and neutron matter, including the BCS pairing and BEC pairing. (2) Through the valence neutron knocked out technique, to study the resonant states 7He and the related single particle states. This will be complementary to the previous similar measurement but with better selection of the reaction mechanism.Some new recoiled proton telescopes and the forward neutron spectrometer was applied in the experiment. Performance of the detection system and very preliminary experimental results are shown here.

A Vector Dominance Model of the Radiative Decay Σ+ → pγ*

In this work, we propose a new mechanism for the ΔS = 1 radiative decay Σ+ → pγ, where the reaction occurs via a decay to a proton and a virtual vector meson, which converts later into a real photon by virtue of the vector dominance mechanism. The numerical result shows that this mechanism may be the dominant one, or at least, very important compared to the others. An implied direct CP violation is also discussed, its order is found to be 10-4 ~ 10-5