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Secondary cosmic ray fluxes are important probes of the propagation and interaction of high-energy particles in the Galaxy. Recent measurements of primary and secondary cosmic ray nuclei have revealed unexpected spectral features that demand a deeper understanding. In this work we report the direct measurement of the cosmic ray boron spectrum from $10\mathrm{GeV}/\mathrm{n}$ to $8\mathrm{TeV}/\mathrm{n}$ with eight years of data collected by the Dark Matter Particle Explorer (DAMPE) mission. The measured spectrum shows a hardening at $182\pm 24\mathrm{GeV}/\mathrm{n}$ with a spectral index of ${\gamma }_1=3.02\pm 0.01$ before the break and an index change of $\mathrm{\Delta }\gamma =0.31\pm 0.05$ after the break. A simple power law model is disfavored at a confidence level of $8\sigma$. Compared with the hardenings measured in the DAMPE proton and helium spectra, the secondary boron spectrum hardens roughly twice as much as these primaries, which is consistent with a propagation related mechanism to interpret the spectral hardenings of cosmic rays observed at hundreds of $\mathrm{GeV}/\mathrm{n}$.

Nickel, one of the most tightly bound nuclei alongside iron, is the most abundant heavy element beyond iron in cosmic rays. With DAMPE’s excellent charge resolution and broad energy range, a high-precision energy spectrum provides valuable insights into the acceleration sources of heavy nuclei and their propagation through the interstellar medium. In this analysis, we report the direct measurement of cosmic-ray nickel spectrum from 10 GeV/n to 2 TeV/n with nine years of flight data. The nickel spectrum is consistent with a single power law with spectral index $-2.60\pm 0.03$ from 40 GeV/n to 1 TeV/n. This Letter provides an accurate measurement of differential flux of nickel with kinetic energy extending to TeV/n for the first time.

We have precisely measured reaction cross sections (${\sigma }_R$) for ${}^8\mathrm{Li}$ using ${}^9\mathrm{Be}$, ${}^{12}\mathrm{C}$, ${}^{27}\mathrm{Al}$, and proton targets at intermediate energies by the transmission method. From the energy dependence of the ${\sigma }_R$ including the high energy data, the density distribution of ${}^8\mathrm{Li}$ was deduced through a modified Glauber model. It is shown that ${}^8\mathrm{Li}$ has a shorter tail structure in the density as compared with that of ${}^8\mathrm{B}$ and the matter radius of ${}^8\mathrm{Li}$ is similar to those of the other nonhalo Li isotopes. The result is consistent with the previous experiments that there is a tendency for ${}^8\mathrm{Li}$ to be a skin nucleus.

Precise direct cosmic-ray (CR) measurements provide an important probe to study the energetic particle sources in our Galaxy, and the interstellar environment through which these particles propagate. Uncertainties on hadronic models, ion-nucleon cross sections in particular, are currently the limiting factor toward obtaining more accurate CR ion flux measurements with calorimetric space-based experiments. We present an energy-dependent measurement of the inelastic cross section of protons and helium-4 nuclei (alpha particles) on a ${\mathrm{Bi}}_4$${\text{Ge}}_3{\mathrm{O}}_{12}$ target, using 88 months of data collected by the DAMPE space mission. The kinetic energy range per nucleon of the measurement points ranges from 18 GeV to 9 TeV for protons, and from $5\mathrm{GeV}/\mathrm{n}$ to $3\mathrm{TeV}/\mathrm{n}$ for helium-4 nuclei. Our results lead to a significant improvement of the CR flux normalization. In the case of helium-4, these results correspond to the first cross section measurements on a heavy target material at energies above $10\mathrm{GeV}/\mathrm{n}$.

The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, for a calorimetric experiment like DAMPE, uncertainties in hadronic models persist as a major barrier in achieving more accurate measurements of fluxes of cosmic ray nuclei. This study centers on the measurement of the inelastic hadronic cross sections of carbon and oxygen nuclei interacting BGO crystals target over an extensive energy range, spanning from 200 GeV to 10 TeV. For carbon nuclei interacting with the BGO target. The measurements of the cross sections have achieved a total relative uncertainty of less than 10% below 8 TeV for carbon, and below 3 TeV for oxygen. For oxygen nuclei, the same level of precision was attained below 3 TeV. Additionally, we compare the experimental results with geant4 and fluka simulations to validate the accuracy and consistency of these simulation tools. Through comprehensive analysis of the inelastic hadronic interaction cross sections, this research provides validation for the hadronic interaction models used in DAMPE’s cosmic-ray flux measurements.

Recent observations of the light component of the cosmic-ray spectrum have revealed unexpected features that motivate further and more precise measurements up to the highest energies. The Dark Matter Particle Explorer is a satellite-based cosmic-ray experiment that has been operational since December 2015, continuously collecting data on high-energy cosmic particles with very good statistics, energy resolution, and particle identification capabilities. In this work, the latest measurements of the energy spectrum of $\mathrm{proton}+\mathrm{helium}$ in the energy range from 46 GeV to 464 TeV are presented. Among the most distinctive features of the spectrum, a spectral hardening at 600 GeV has been observed, along with a softening at 29 TeV measured with a $6.6\sigma$ significance. Moreover, the detector features and the analysis approach allowed for the extension of the spectral measurement up to the sub-PeV region. Even if with small statistical significance due to the low number of events, data suggest a new spectral hardening at about 150 TeV.

The Forbush decrease of cosmic rays is an important probe of the interplanetary environment disturbed by solar activities. In this Letter, we study the properties of eight Forbush decreases’ electrons (including positrons) between 2 and 20 GeV from January 2016 to March 2024 with the Dark Matter Particle Explorer. The maximum decrease amplitudes of these events are about 30%–15%, and the amplitudes reduce with energy. The recovery time of these events shows diverse behaviors of their energy dependence. Some of them show strong energy dependence, while some have a nearly constant recovery time. It has been shown that such diverse behaviors could be related to the geometry of the regions of the interplanetary space disturbed by coronal mass ejections, which can be characterized by the combined effect of the coronal mass ejection velocity, angular spread, and ejection direction.

More than a century after the performance of the oil drop experiment, the possible existence of fractionally charged particles (FCPs) still remains unsettled. The search for FCPs is crucial for some extensions of the Standard Model in particle physics. Most of the previously conducted searches for FCPs in cosmic rays were based on experiments underground or at high altitudes. However, there have been few searches for FCPs in cosmic rays carried out in orbit other than AMS-01 flown by a space shuttle and BESS by a balloon at the top of the atmosphere. In this study, we conduct an FCP search in space based on on-orbit data obtained using the Dark Matter Particle Explorer (DAMPE) satellite over a period of five years. Unlike underground experiments, which require an FCP energy of the order of hundreds of GeV, our FCP search starts at only a few GeV. An upper limit of $6.2\times {10}^{-10}{\mathrm{cm}}^{-2}{\mathrm{sr}}^{-1}{\mathrm{s}}^{-1}$ is obtained for the flux. Our results demonstrate that DAMPE exhibits higher sensitivity than experiments of similar types by three orders of magnitude that more stringently restricts the conditions for the existence of FCP in primary cosmic rays.

The measurement of the energy spectrum of cosmic ray helium nuclei from 70 GeV to 80 TeV using 4.5 years of data recorded by the Dark Matter Particle Explorer (DAMPE) is reported in this work. A hardening of the spectrum is observed at an energy of about 1.3 TeV, similar to previous observations. In addition, a spectral softening at about 34 TeV is revealed for the first time with large statistics and well controlled systematic uncertainties, with an overall significance of $4.3\sigma$. The DAMPE spectral measurements of both cosmic protons and helium nuclei suggest a particle charge dependent softening energy, although with current uncertainties a dependence on the number of nucleons cannot be ruled out.