Effects of the high-momentum tail of nucleon momentum distribution on the isospin-sensitive observables

Based on the Isospin-dependent transport model Boltzmann-Uehling-Uhlenbeck (IBUU), effects of the high momentum tail (HMT) of nucleon momentum distribution in colliding nuclei on some isospin-sensitive observables are studied in the semi-central $^{197}\rm {Au}+^{197}\rm {Au}$ reactions at incident beam energy of 400 MeV/nucleon. It is found that the nucleon transverse flow, the difference of neutron and proton transverse flows, the nucleon elliptic flow and free neutron to proton ratio are all less sensitive to the HMT, while the isospin-sensitive nucleon elliptic flow difference is clearly affected by the HMT. Except at very high kinetic energies, the kinetic energy distributions of $\pi^{-}$, $\pi^{+}$ and charged pion ratio $\pi^{-}/\pi^{+}$ are all sensitive to the HMT.Comment: 6 pages, 6 figures, to appear in Eur. Phys. J.

Design of a large dynamic range readout unit for the PSD detector of DAMPE

A large dynamic range is required by the Plastic Scintillator Detector (PSD) of DArk Matter Paricle Explorer (DAMPE), and a double-dynode readout has been developed. To verify this design, a prototype detector module has been constructed and tested with cosmic rays and heavy ion beams. The results match with the estimation and the readout unit could easily cover the required dynamic range

Chemical Abundances of Planetary Nebulae in the Substructures of M31

We present deep spectroscopy of planetary nebulae (PNe) that are associated with the substructures of the Andromeda Galaxy (M31). The spectra were obtained with the OSIRIS spectrograph on the 10.4 m GTC. Seven targets were selected for the observations, three in the Northern Spur and four associated with the Giant Stream. The most distant target in our sample, with a rectified galactocentric distance >100 kpc, was the first PN discovered in the outer streams of M31. The [O III] 4363 auroral line was well detected in the spectra of all targets, enabling electron temperature determination. Ionic abundances are derived based on the [O III] temperatures, and elemental abundances of helium, nitrogen, oxygen, neon, sulfur, and argon are estimated. The relatively low N/O and He/H ratios as well as abundance ratios of alpha-elements indicate that our target PNe might belong to populations as old as ~2 Gyr. Our PN sample, including the current seven and the previous three observed by Fang et al., have rather homogeneous oxygen abundances. The study of abundances and the spatial and kinematical properties of our sample leads to the tempting conclusion that their progenitors might belong to the same stellar population, which hints at a possibility that the Northern Spur and the Giant Stream have the same origin. This may be explained by the stellar orbit proposed by Merrett et al. Judging from the position and kinematics, we emphasize that M32 might be responsible for the two substructures. Deep spectroscopy of PNe in M32 will help to assess this hypothesis.Comment: Accepted for publication in the ApJ. 23 pages, including 13 figures and 7 table