The 111-Years-Old Cosmic Ray Puzzle Has Been Solved?

We show that recently multi-messenger astronomy has provided compelling evidence that the bulk of high energy cosmic rays (CRs) are produced by highly relativistic narrow jets of plasmoids launched in core collapse of stripped-envelope massive stars to neutron stars and stellar mass black holes. Such events produce also a visible GRB if the jet happens to point in our direction. This has been long advocated by the cannon ball (CB) model of high energy CRs and GRBs, but the evidence has been provided only recently by what were widely believed to be unrelated discoveries. They include the very recent discovery of a knee around TeV in the energy spectrum of high energy CR electrons, the peak photon energy in the “brightest of all time” GRB221009A, and the failure of IceCube to detect high energy neutrinos from GRBs, including GRB221009A. They were all predicted by the cannonball (CB) model of high energy CRs and GRBs long before they were discovered in observations, despite a negligible probability to occur by chance.

Galactic cosmic ray propagation: sub-PeV diffuse gamma-ray and neutrino emission

The Tibet ASγexperiment just reported their measurement of sub-PeV diffuse gamma-ray emission from the Galactic disk,with the highest energy up to 957 TeV.These diffuse gamma rays are most likely the hadronic origin by cosmic ray(CR)interaction with interstellar gas in the galaxy.This measurement provides direct evidence to the hypothesis that the Galactic Cosmic Rays(GCRs)can be accelerated beyond PeV energies.In this work,we try to explain the sub-PeV diffuse gamma-ray spectrum with different CR propagation models.We find that there is a tension between the sub-PeV diffuse gamma-ray and the local CR spectrum.To describe the sub-PeV diffuse gamma-ray flux,it generally requires larger local CR flux than measurement in the knee region.We further calculate the PeV neutrino flux from the CR propagation model.Even all of these sub-PeV diffuse gamma rays originate from the propagation,the Galactic Neutrinos(GNs)only account for less than~15%of observed flux,most of which are still from extragalactic sources.

Galactic cosmic ray propagation: sub-PeV diffuse gamma-ray and neutrino emission

The Tibet ASγexperiment just reported their measurement of sub-PeV diffuse gamma-ray emission from the Galactic disk,with the highest energy up to 957 TeV.These diffuse gamma rays are most likely the hadronic origin by cosmic ray(CR)interaction with interstellar gas in the galaxy.This measurement provides direct evidence to the hypothesis that the Galactic Cosmic Rays(GCRs)can be accelerated beyond PeV energies.In this work,we try to explain the sub-PeV diffuse gamma-ray spectrum with different CR propagation models.We find that there is a tension between the sub-PeV diffuse gamma-ray and the local CR spectrum.To describe the sub-PeV diffuse gamma-ray flux,it generally requires larger local CR flux than measurement in the knee region.We further calculate the PeV neutrino flux from the CR propagation model.Even all of these sub-PeV diffuse gamma rays originate from the propagation,the Galactic Neutrinos(GNs)only account for less than∼15%of observed flux,most of which are still from extragalactic sources.

The Giant Radio Array for Neutrino Detection(GRAND):Science and design

The Giant Radio Array for Neutrino Detection(GRAND)is a planned large-scale observatory of ultra-high-energy(UHE)cosmic particles,with energies exceeding 10~8 Ge V.Its goal is to solve the long-standing mystery of the origin of UHE cosmic rays.To do this,GRAND will detect an unprecedented number of UHE cosmic rays and search for the undiscovered UHE neutrinos and gamma rays associated to them with unmatched sensitivity.GRAND will use large arrays of antennas to detect the radio emission coming from extensive air showers initiated by UHE particles in the atmosphere.Its design is modular:20 separate,independent sub-arrays,each of 10000 radio antennas deployed over 10000 km^2.A staged construction plan will validate key detection techniques while achieving important science goals early.Here we present the science goals,detection strategy,preliminary design,performance goals,and construction plans for GRAND.

Neutrino astronomy： An update

Detecting neutrinos associated with the still enigmatic sources of cosmic rays has reached a new watershed with the completion of IceCube, the first detector with sensitivity to the anticipated fluxes. In this review, we will briefly revisit the rationale for constructing kilometer-scale neutrino detectors and summarize the status of the field.

Prospects for detecting ultra-high-energy particles with FAST

The origin of the highest-energy particles in nature, ultra-high-energy(UHE) cosmic rays, is still unknown. In order to resolve this mystery, very large detectors are required to probe the low flux of these particles — or to detect the as-yet unobserved flux of UHE neutrinos predicted from their interactions. The‘lunar Askaryan technique' is a method to do both. When energetic particles interact in a dense medium,the Askaryan effect produces intense coherent pulses of radiation in the MHz–GHz range. By using radio telescopes to observe the Moon and look for nanosecond pulses, the entire visible lunar surface(20 million km^2) can be used as a UHE particle detector. A large effective area over a broad bandwidth is the primary telescope requirement for lunar observations, which makes large single-aperture instruments such as the Five-hundred-meter Aperture Spherical radio Telescope(FAST) well-suited to the technique. In this contribution, we describe the lunar Askaryan technique and its unique observational requirements. Estimates of the sensitivity of FAST to both the UHE cosmic ray and neutrino flux are given, and we describe the methods by which lunar observations with FAST, particularly if equipped with a broadband phased-array feed, could detect the flux of UHE cosmic rays.

Constraints on cosmic-ray boosted dark matter in CDEX-10

Dark matter(DM)direct detection experiments have been setting strong limits on the DM-nucleon scattering cross section at the DM mass above a few GeV,but leave large parameter spaces unexplored in the low mass region.DM is likely to be scattered and boosted by relativistic cosmic rays in the expanding universe if it can generate nuclear recoils in direct detection experiments to offer observable signals.Since low energy threshold detectors using Germanium have provided good constraints on ordinary halo GeV-scale DM,it is necessary to re-analyze102.8 kgxday data in the CDEX-10 experiment assuming that DM is boosted by cosmic rays.For the DM mass range 1 keV<m_(χ)<1 MeV and the effective distance within 1 kpc,we reach an almost flat floor limit at8.32×10^(-30) cm^(2) for the spin-independent DM-nucleon scattering cross section,at a 90%confidence level.The CDEX-10 result is able to close the gap unambiguously in the parameter space between the MiniBooNE and XENON IT constraints,which were partially hindered by the Earth attenuation effect.We also quantitatively calculate the expected neutrino floor on searching for CRBDM in future direct detection experiments using Germanium.

Implication from GRB 221009A:Can TeV emission come from the GRB prompt phase?

Recently,the B.O.A.T.(“brightest of all time”)gamma-ray burst,dubbed GRB 221009A,was detected by various instruments.Unprecedentedly,the GRB presented very-high-energy(VHE,energy above 0.1 Te V)gamma-ray emission with energy extending above 10 Te V,as reported by the Large High Altitude Air Shower Observatory(LHAASO).We here demonstrate that the VHE and especially>10 Te V emission may originate from the internal hadronic dissipation of the GRB,without the need of invoking any exotic processes as suggested by some previous studies.The possible prompt origin of LHAASO photons may imply the first detection of the GRB prompt phase in the VHE regime.We also discuss the constraints on the properties of the GRB ejecta from multiwavelength and multi-messenger observations,which favors a magnetically dominated GRB ejecta.The suggested Poynting-flux-dominated GRB ejecta in this work supports the Blandford&Znajek(BZ)mechanism as the possible central engine model of GRB,as well as the possible strong magnetic dissipation and acceleration.

Chapter 6 Multimessenger Physics

Combining observations of multi-messengers help in boosting the sensitivity of astrophysical source searches,and probe various aspects of the source physics.In this chapter we discuss how LHAASO observations of very high energy(VHE)gamma rays in combination with telescopes for the other messengers can help in solving the origins of VHE neutrinos and galactic and extragalactic cosmic rays.

On the contribution of a hard galactic plane component to the excesses of secondary particles

The standard model of cosmic ray propagation has been very successful in explaining all kinds of galactic cosmic ray spectra. However, high precision measurement have recently revealed an appreciable discrepancy between data and model expectations, from spectrum observations of γ-rays, e＋/e- and probably the B/C ratio starting from -10 GeV energy. In this work, we propose that a hard galactic plane component, supplied by the fresh cosmic ray sources and detained by local magnetic fields, can contribute additional secondary particles interacting with local materials. By properly choosing the intensity and spectral index of the harder component up to multi-TeV energy, a two-component T-ray spectrum is obtained and agrees very well with the observation. Simultaneously, the expected neutrino numbers from the galactic plane could contribute - 60% of IceCube observed neutrino number below a few hundreds of TeV under our model. In addition to these studies, we find that the same pp-collision process responsible for the excess gamma ray emission could account for a significant amount of the positron excess, but a more detailed mechanism is needed for a full agreement. It is expected that the excesses in the p/p and B/C ratio will show up when energy is above ,-10 GeV. We look forward this model being tested in the near future by new observations from AMS02, IceCube, AS% HAWC and future experiments such as LHASSO, HiSCORE and CTA.

高能中微子天文观测进展

高能宇宙线在宇宙加速器中的产生和在宇宙空间的传播通常会伴随高能中微子的产生.高能中微子天文学是了解高能天体物理现象的独特的窗口.最近,位于南极的立方公里级的中微子探测器IceCube探测到了一批高能(>Te V)事例,在5.7σ的置信度之上排除了大气背景的起源.这是人类第一次探测到的来自地外的高能中微子事例,开启了人类探索宇宙的一个新的窗口,标志着高能中微子天文学的诞生.本文简要介绍了高能中微子的探测历史,高能中微子探测器(特别是IceCube)的探测原理及现状,IceCube中微子探测结果,中微子起源的理论探讨以及高能中微子天文的未来展望.