arXiv subjects

Yapeng Zhang

Publications and source records attributed to Yapeng Zhang.

59 records · Page 4Linked to original sources

arXiv2018

Charge Measurement of Cosmic Ray Nuclei with the Plastic Scintillator Detector of DAMPE

One of the main purposes of the DArk Matter Particle Explorer (DAMPE) is to measure the cosmic ray nuclei up to several tens of TeV or beyond, whose origin and propagation remains a hot topic in astrophysics. The Plastic Scintillator Detector (PSD) on top of DAMPE is designed to measure the charges of cosmic ray nuclei from H to Fe and serves as a veto detector for discriminating gamma-rays from charged particles. We propose in this paper a charge reconstruction procedure to optimize the PSD performance in charge measurement. Essentials of our approach, including track finding, alignment of PSD, light attenuation correction, quenching and equalization correction are described detailedly in this paper after a brief description of the structure and operational principle of the PSD. Our results show that the PSD works very well and almost all the elements in cosmic rays from H to Fe are clearly identified in the charge spectrum.

astro-ph.IM↗

arXiv2018

Calibration of the DAMPE Plastic Scintillator Detector and its on-orbit performance

DArk Matter Particle Explorer (DAMPE) is a space-borne apparatus for detecting the high-energy cosmic-rays like electrons, $γ$-rays, protons and heavy-ions. Plastic Scintillator Detector (PSD) is the top-most sub-detector of the DAMPE. The PSD is designed to measure the charge of incident high-energy particles and it also serves as a veto detector for discriminating $γ$-rays from charged particles. In this paper, PSD on-orbit calibration procedure is described, which includes five steps of pedestal, dynode correlation, response to minimum-ionizing particles (MIPs), light attenuation function and energy reconstruction. A method for reconstructing the charge of incident high energy cosmic-ray particles is introduced. The detection efficiency of each PSD strip is verified to be above 99.5%, the total efficiency of the PSD for charged particles is above 99.99%.

astro-ph.IM↗

arXiv2018

Planet Formation in Highly Inclined Binary Systems. II. Orbital Alignment or Anti-alignment and Planet Growth Boost in Intermediate Separation Binaries

Stars are commonly formed in binary systems, which provide a natural laboratory for studying planet formation in extreme conditions. In our first paper (Paper I) of a series Xie et al. (2011), we have shown that the intermediate stage - from planetesimals to planetary embryos/cores - of planet formation can proceed even in highly inclined binaries. Following Paper I, here we numerically study the late stage of terrestrial planet formation, i.e., from embryos to full planets, in binary systems of various orbital configurations. We identify an orbital alignment or anti-alignment effect; namely, although an inclined binary generally misaligns the planetary orbits with respect to the spin axis of the primary host star (i.e., causing large obliquity), it could align or anti-align the planetary orbits with respect to the binary orbit. Such an orbital (anti-)alignment effect is caused by the combination of orbital differential precession and self-damping, and it is mostly significant in cases of intermediate binary separations, i.e., a_B~40-200 AU for terrestrial planet formation around 1 AU from the primary stars. In such intermediate separation binaries, somewhat contrary to intuition, the binary companion can aid planet growth by having increased the rate of collisions, forming significantly more massive but fewer planets. In the other two ends, the companion is ether too close thus plays a violently disruptive role or too wide to have significant effect on planet formation. Future observations, which can discover more planet-bearing binary star systems and constrain their masses and 3-D orbital motions will test our numerical findings.

astro-ph.EP↗

arXiv2018

A Generalized Model for Light Transport in Scintillators

Transported light in the medium usually shows as an exponential decay tendency. In the DAMPE strip scintillators, however, the phenomenon of light attenuation as the hit position approaches the end of the scintillator can not be described by the simple exponential decay model. The spread angle of PMT relative to hit position is distance-dependent, so the larger the angle, the larger the proportion $η$ of emitted light to becomes the effective input light. We consider the contribution of the spread angle, and propose a generalized model: $f(x)=I_0η_{a}(x)e^{-x/λ}+I_0η_{b}(x)e^{-(2L-x)/λ}$. The model well describes the light attenuation in the scintillator, reducing the maximum deviation of the sample from the fit function from 29\% to below 2\%. Moreover, our model contains most of the traditional models, so the experimental data that traditional models can fit and our models fit well.

physics.ins-det↗

arXiv2017

The Link between Magnetic-field Orientations and Star Formation Rates

Understanding star formation rates (SFR) is a central goal of modern star-formation models, which mainly involve gravity, turbulence and, in some cases, magnetic fields (B-fields). However, a connection between B-fields and SFR has never been observed. Here, a comparison between the surveys of SFR and a study of cloud-field alignment - which revealed a bimodal (parallel or perpendicular) alignment - shows consistently lower SFR per solar mass for clouds almost perpendicular to the B-fields. This is evidence of B-fields being a primary regulator of SFR. The perpendicular alignment possesses a significantly higher magnetic flux than the parallel alignment and thus a stronger support of the gas against self-gravity. This results in overall lower masses of the fragmented components, which are in agreement with the lower SFR.

astro-ph.GA↗