Observations of Forbush Decreases of Cosmic-Ray Electrons and Positrons with the Dark Matter Particle Explorer

The Forbush decrease (FD) represents the rapid decrease of the intensities of charged particles accompanied with the coronal mass ejections or high-speed streams from coronal holes. It has been mainly explored with the ground-based neutron monitor network, which indirectly measures the integrated intensities of all species of cosmic rays by counting secondary neutrons produced from interaction between atmospheric atoms and cosmic rays. The space-based experiments can resolve the species of particles but the energy ranges are limited by the relatively small acceptances except for the most abundant particles like protons and helium. Therefore, the FD of cosmic-ray electrons and positrons have just been investigated by the PAMELA experiment in the low-energy range (<5 GeV) with limited statistics. In this paper, we study the FD event that occurred in 2017 September with the electron and positron data recorded by the Dark Matter Particle Explorer. The evolution of the FDs from 2 GeV to 20 GeV with a time resolution of 6 hr are given. We observe two solar energetic particle events in the time profile of the intensity of cosmic rays, the earlier, and weaker, one has not been shown in the neutron monitor data. Furthermore, both the amplitude and recovery time of fluxes of electrons and positrons show clear energy dependence, which is important in probing the disturbances of the interplanetary environment by the coronal mass ejections

Measurement of the light component (p+He) energy spectrum with the DAMPE space mission

The DArk Matter Particle Explorer (DAMPE) is a space-based particle detector launched in a Sun- synchronous orbit on December 17th, 2015 from the Jiuquan Satellite Launch Center, in China. It has been taking data very smoothly for more than 5 years. Science goals of the DAMPE mission include the study of the electron-positron energy spectrum, the study of galactic cosmic-rays, gamma-ray astronomy, and indirect dark matter search. Performing precise measurements of light elements in space, the most abundant components of cosmic radiation, is necessary to address major problems in galactic cosmic ray acceleration and propagation mechanisms. Selecting a combined proton and helium sample (instead of proton or helium alone) allows larger efficiency and purity, also minimizing systematic effects in the reconstruction of the energy spectrum, due to possible cross-contaminations. The use of looser analysis cuts allows collecting larger statistics thus extending the covered energy range and providing a link between direct and indirect cosmic- ray measurements. The measurement of the p+He energy spectrum up to ∼ 150 TeV will be presented, along with a discussion on the features of the spectrum and a comparison with other experimental results

Machine learning methods for helium flux analysis with DAMPE experiment

DAMPE is a space-borne experiment for the measurement of the cosmic-ray fluxes at energies up to around 100 TeV per nucleon. At energies above several tens of TeV, the electronics of DAMPE calorimeter would saturate, leaving certain bars with no energy recorded. It is also observed that at high energies the tracker and the scintillator detector that serve for the charge identification become heavily populated with back-splash tracks. Both effects interfere in precise measurements of the helium flux at highest energies. In the present contribution we discuss the application of machine learning techniques for the treatment of DAMPE data, to compensate the calorimeter energy lost by saturation and to identify helium events

Performance of the DAMPE silicon-tungsten tracker-converter during the first 5 years of in-orbit operations

Since its launch, in December 2015, the satellite-based DAMPE (DArk Matter Particle Explorer) particle detector is taking data smoothly. The Silicon-Tungsten tracKer-converter (STK) of DAMPE consists of six tracking planes (6x, 6y) of single-sided silicon micro-strip detectors mounted on seven support trays. The STK is able to measure the charge and precisely reconstruct the track of traversing charged particles. Tungsten plates (1 mm thick) are integrated in the second, third and fourth tray from the top to serve as γ → e+e- converters. Commissioned rapidly after the launch, the STK is running extremely well since then. The STK in-orbit calibration and performance during its first more than 5 years of operation, including the noise behaviour and the thermal and mechanical stability, are presented in this contribution

Direct Measurement of the Cosmic-Ray Iron Spectrum with the Dark Matter Particle Explorer

Dark Matter Particle Explorer(DAMPE) is a calorimetric-type, satellite-borne detector for observations of high energy electrons, gamma-rays, and cosmic-ray nuclei. Using five years data collected with DAMPE from January 1, 2016 to December 31, 2020, we analyzed the spectrum of iron. Detailed studies of the fragmentation of iron in the detector have been performed using Monte Carlo simulations

Search for gamma-ray lines in the Galaxy with DAMPE

DArk Matter Particle Explorer (DAMPE) has a great potential in the search of monochromatic and sharp gamma-ray structures in GeV-TeV range thanks to its good energy resolution. In this work, we search for gamma-ray line structures using 5.0 years of DAMPE data. To improve the sensitivity, we develop two types of data sets and adopt the signal-to-noise ratio optimized regions of interest (ROIs) for different DM density profiles. No line signals or candidates, including those located at 133 GeV and 43 GeV, are found between 10 GeV and 300 GeV in the Galaxy. Therefore we calculate the 95% confidence level constraints on the velocity-averaged cross section for χχ → γγ and the decay lifetime for χ → γν with systematic uncertainties included. Our constraints on DM parameters are mostly comparable to the Fermi-LAT 5.8-yr results. The lower limit for DM decay lifetime below 100 GeV are better than that of Fermi-LAT

Charge measurement of cosmic rays by Plastic Scintillator Detector of DAMPE

Plastic Scintillator Detector (PSD) of DArk Matter Particle Explorer (DAMPE) is designed to measure the charge of cosmic-rays and it servers as a veto for gamma-rays. In this work, we present some updated correction methods to further improve the quality of PSD charge measurement, especially for heavy nuclei. DAMPE has collected nearly 10 billions events by middle of 2021, it has substantial potential to measure the spectra of cosmic ray nuclei up to hundreds of TeV energies. These measurements could largely benefit from the correction of the PSD signal

Simulation of the DAMPE detector

Extensive Monte Carlo (MC) simulations are essential in understanding the detector’s response for high energy particle detection experiments. We present the infrastructure and status of MC simulations of the DArk Matter Particle Explorer (DAMPE), a satellite project for the direct detection of high-energy cosmic rays and gamma rays. The DAMPE simulation tool employs two widely used softwares, GEANT4 and FLUKA, which implement various physics lists to simulate the interactions of particles in the detector. The framework of the simulation tool, the production farms, the data-MC comparison, and the performance of MC simulations on the analysis are summarized

On-orbit performance of the DAMPE BGO calorimeter

The DArk Matter Particle Explorer (DAMPE) is the first Chinese cosmic-ray direct detection experiment. It has been operating smoothly on-orbit since its successful launch at the end of 2015. Currently, its sub-detectors and the satellite are in good working order. The DAMPE payload employs a BGO Calorimeter for energy measurements, trigger and e/p identification. The calorimeter is constructed of 308 BGO crystals, and PMTs are coupled to the crystals with optical filters to readout scintillation light. In this work, we present the status and performance of the calorimeter, including status of detector units, energy measurement, especially in TeV range, detector endurance, and long term performance in a duration of 65 months