arXiv subjects

Xunxiu Zhou

Publications and source records attributed to Xunxiu Zhou.

5 recordsLinked to original sources

arXiv2026

Constraining Cosmic-Ray Acceleration and Escape in Middle-Aged Supernova Remnants with GeV-TeV Gamma-Ray Observations

In this work, we perform a systematic, time-dependent study of the gamma-ray emission from four representative middle-aged SNRs (W51C, IC~443, W44, W28), incorporating both CRs within the remnant shells and escaped CRs interacting with surrounding molecular clouds. We compare our results with GeV--TeV gamma-ray observations from Fermi-LAT, H.E.S.S., MAGIC, and LHAASO, including a dedicated analysis of the Fermi-LAT data for regions A and B associated with W28. We find that the observed spectra favor steeper CR injection spectra with indices of $α\sim4.2$--$4.3$, maximum proton energies of $\sim$ $100$--$300$ TeV, diffusion coefficients below the Galactic average, and CR acceleration efficiencies from a few to tens of percent. In particular, the VHE emission detected by LHAASO from W51C is more naturally explained by escaped CRs interacting with a nearby molecular cloud. We also investigate the contribution of escaped CRs to the VHE emission from IC~443, W44, and W28. We further demonstrate that escaped CRs can substantially enhance the TeV neutrino flux from middle-aged SNRs, improving their prospects as potential neutrino sources. These results provide new constraints on CR acceleration and escape in middle-aged SNRs and highlight the important role of escaped CRs in shaping their high-energy gamma-ray and neutrino emission.

astro-ph.HE↗

arXiv2024

Effect of near-earth thunderstorm electric field on the flux of cosmic ray air showers in LHAASO-KM2A

The Large High Altitude Air Shower Observatory (LHAASO) is located at Haizi Mountain, Daocheng, Sichuan province, China. Due to its high-altitude location with frequent thunderstorm activities, the LHAASO is suited for studying the effects of near-earth thunderstorm electric fields on cosmic ray air showers. In this paper, Monte Carlo simulations are performed with CORSIKA and G4KM2A to analyze the flux variations of cosmic ray air showers detected by the kilometer-square array of LHAASO (LHAASO-KM2A) during thunderstorms. The strength, polarity, and layer thickness of atmospheric electric field (AEF) during thunderstorm are found to be associated with the shower rate variations. The flux of shower events satisfying trigger conditions of the KM2A increases with field intensity, particularly within negative fields, and the enhanced amplitude is more than 5% in -600 V/cm and 12% in -1000 V/cm, whereas it increases by only 1% and 7% in equivalent positive fields, respectively. While in positive fields ranging from 0 to 400 V/cm, the shower rate decreases with smaller amplitudes. Furthermore, the shower rate increases dramatically with the AEF layer thickness until a certain value, above which the variation trend slows down. The dependence of the trigger rate variation on the primary zenith angle has also been revealed, increasing in lower zenith angle ranges and showing opposite behaviors in higher ones. Additionally, we study that the relationship between the trigger rate variations and the primary energies, and find the enhanced amplitude of the shower rate decreases with increasing primary energy. Simultaneously, the shower events with lower primary energy show a significant increase, whereas events with higher primary energy are hardly affected during thunderstorms. Our simulations offer insights into the variation of the trigger rate detected by LHAASO-KM2A during thunderstorms.

astro-ph.HE↗

arXiv2022

The Large High Altitude Air Shower Observatory (LHAASO) Science Book (2021 Edition)

Since the science white paper of the Large High Altitude Air Shower Observatory (LHAASO) published on arXiv in 2019 [e-Print: 1905.02773 (astro-ph.HE)], LHAASO has completed the transition from a project to an operational gamma-ray astronomical observatory LHAASO is a new generation multi-component facility located in Daocheng, Sichuan province of China, at an altitude of 4410 meters. It aims at measuring with unprecedented sensitivity the spectrum, composition, and anisotropy of cosmic rays in the energy range between 10$^{12}$ and 10$^{18}$~eV, and acting simultaneously as a wide aperture (one stereoradiant) continuously operating gamma-ray telescope in the energy range between 10$^{11}$ and $10^{15}$~eV with the designed sensitivity of 1.3\% of the Crab Unit (CU) above 100 TeV. LHAASO's capability of measuring simultaneously different shower components (electrons, muons, and Cherenkov/fluorescence light), will allow it to investigate the origin, acceleration, and propagation of CR through measurement of the energy spectrum, elemental composition, and anisotropy with unprecedented resolution. The remarkable sensitivity of LHAASO will play a key role in CR physics and gamma-ray astronomy for a general and comprehensive exploration of the high energy universe and will allow important studies of fundamental physics (such as indirect dark matter search, Lorentz invariance violation, quantum gravity) and solar and heliospheric physics. The LHAASO Collaboration organized an editorial working group and finished all editorial work of this science book, to summarize the instrumental features and outline the prospects of scientific researches with the LHAASO experiment.

astro-ph.HE↗

arXiv2016

Sensitivity study of (10,100) GeV gamma-ray bursts with double shower front events from ARGO-YBJ

ARGO-YBJ, located at the YangBaJing Cosmic Ray Observatory (4300 m a.s.l., Tibet, China), is a full coverage air shower array, with an energy threshold of 300 GeV for gamma-ray astronomy. Most of the recorded events are single front showers, satisfying the trigger requirement of at least 20 particles detected in a given time window. However, in 13% of the events, two randomly arriving showers may be recorded in the same time window, and the second one, in generally smaller, does not need to satisfy the trigger condition. These events are called double front shower events. By using these small showers, well under the trigger threshold, the detector primary energy threshold can be lowered to a few tens of GeV. In this paper, the angular resolution that can be achieved with these events is evaluated by a full Monte Carlo simulation. The ARGO-YBJ sensitivity in detecting gamma-ray bursts (GRBs) by using double front shower events is also studied for various cutoff energies, time durations, and zenith angles of GRBs in the field view of ARGO.

astro-ph.HE↗

arXiv2015

Development of Yangbajing Air shower Core detector array for a new EAS hybrid Experiment

Aiming at the observation of cosmic-ray chemical composition at the "knee" energy region, we have been developinga new type air-shower core detector (YAC, Yangbajing Air shower Core detector array) to be set up at Yangbajing (90.522$^\circ$ E, 30.102$^\circ$ N, 4300 m above sea level, atmospheric depth: 606 g/m$^2$) in Tibet, China. YAC works together with the Tibet air-shower array (Tibet-III) and an underground water cherenkov muon detector array (MD) as a hybrid experiment. Each YAC detector unit consists of lead plates of 3.5 cm thick and a scintillation counter which detects the burst size induced by high energy particles in the air-shower cores. The burst size can be measured from 1 MIP (Minimum Ionization Particle) to $10^{6}$ MIPs. The first phase of this experiment, named "YAC-I", consists of 16 YAC detectors each having the size 40 cm $\times$ 50 cm and distributing in a grid with an effective area of 10 m$^{2}$. YAC-I is used to check hadronic interaction models. The second phase of the experiment, called "YAC-II", consists of 124 YAC detectors with coverage about 500 m$^2$. The inner 100 detectors of 80 cm $\times $ 50 cm each are deployed in a 10 $\times$ 10 matrix from with a 1.9 m separation and the outer 24 detectors of 100 cm $\times$ 50 cm each are distributed around them to reject non-core events whose shower cores are far from the YAC-II array. YAC-II is used to study the primary cosmic-ray composition, in particular, to obtain the energy spectra of proton, helium and iron nuclei between 5$\times$$10^{13}$ eV and $10^{16}$ eV covering the "knee" and also being connected with direct observations at energies around 100 TeV. We present the design and performance of YAC-II in this paper.

physics.ins-det↗