In recent years, cooling technology for liquid xenon(LXe) detectors has advanced driven by the development of dark matter(DM) detectors with target mass in the 100–1000 kg range. The next generation of DM detectors b...In recent years, cooling technology for liquid xenon(LXe) detectors has advanced driven by the development of dark matter(DM) detectors with target mass in the 100–1000 kg range. The next generation of DM detectors based on LXe will be in the 50,000 kg(50 t)range requiring more than 1 k W of cooling power. Most of the prior cooling methods become impractical at this level.For cooling a 50 t scale LXe detector, a method is proposed in which liquid nitrogen(LN2) in a small local reservoir cools the xenon gas via a cold finger. The cold finger incorporates a heating unit to provide temperature regulation. The proposed cooling method is simple, reliable, and suitable for the required long-term operation for a rare event search. The device can be easily integrated into present cooling systems, for example the ‘‘Cooling Bus’ ’employed for the Panda X I and II experiments. It is still possible to cool indirectly with no part of the cooling or temperature control system getting in direct contact with the clean xenon in the detector. Also, the cooling device can be mounted at a large distance, i.e., the detector is cooled remotely from a distance of 5–10 m. The method was tested in a laboratory setup at Columbia University to carry out different measurements with a small LXe detector and behaved exactly as predicted.展开更多
A nonzero-mass hypothesis for the photon can produce a frequency-dependent dispersion of light, which results in arrival-time differences of photons with different frequencies originating from a given transient source...A nonzero-mass hypothesis for the photon can produce a frequency-dependent dispersion of light, which results in arrival-time differences of photons with different frequencies originating from a given transient source. Extragalactic fast radio bursts(FRBs), with their low frequency emissions, short time durations, and long propagation distances, are excellent astrophysical probes to constrain the rest mass of the photon mγ. However, the derivation of a limit on mγis complicated by the similar frequency dependences of dispersion expected from the plasma and nonzero photon mass effects. If a handful measurements of redshift for FRBs are available, then the different redshift dependences of the plasma and photon mass contributions to the dispersion measure(DM) might be able to break dispersion degeneracy in testing the photon mass. For now, nine FRBs with redshift measurements have been reported, which can turn this idea into reality. Taking into account the DM contributions from both the plasma and a possible photon mass,we use the data on the nine FRBs to derive a combined limit of mγ≤ 7.1 × 10^-51 kg, or equivalently mγ≤ 4.0 × 10^-15 e V/c2 at 68% confidence level, which is essentially as good as or represents a factor of 7 improvement over previous limits obtained by the single FRBs. Additionally, a reasonable estimation for the DM contribution from the host galaxy, DMhost, can be simultaneously achieved in our analysis. The rapid progress in localizing FRBs will further tighten the constraints on both mγ and DMhost.展开更多
A conservative constraint on the rest mass of the photon can be estimated under the assump- tion that the frequency dependence of dispersion from astronomical sources is mainly contributed by the nonzero photon mass e...A conservative constraint on the rest mass of the photon can be estimated under the assump- tion that the frequency dependence of dispersion from astronomical sources is mainly contributed by the nonzero photon mass effect. Photon mass limits have been set earlier through the optical emissions of the Crab Nebula pulsar, but we demonstrate that these limits can be significantly improved with the dispersion measure （DM） measurements of radio pulsars in the Large and Small Magellanic Clouds. The combination of DM measurements of pulsars and distances of the Magellanic Clouds provides a strict upper limit on the photon mass as low as mγ≤2.0 ～ 10-45 g, which is at least four orders of magnitude smaller than the constraint from the Crab Nebula pulsar. Although our limit is not as tight as the current best result （～ 10-47 g） from a fast radio burst （FRB 150418） at a cosmological distance, the cosmological origin of FRB 150418 remains under debate; and our limit can reach the same high precision of FRB 150418 when it has an extragalactic origin （ ～10-45 g）.展开更多
We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured pr...We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections,allowing us to assess how these collisions affect the spectra of CR boron and carbon.We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species.In a specific example with a coupling strength of b_(χ)=0.1 and a DM mass of m_(χ)=0.1 GeV,considering a simplified scenario where DM interacts exclusively with oxygen,a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed.Particularly,the peak within the spectrum,spanning from 0.1 to 10 GeV,experiences an enhancement of approximately 1.5 times.However,in a more realistic scenario where DM particles interact with all CRs,this peak can be amplified to twice its original value.Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio,we estimate a 95%upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass.Our findings reveal that at m_(χ)?2 MeV,the effective inelastic cross-section between DM and protons must be less than O(10^(-32))cm^(2).展开更多
The largest and most detailed map of the distribution of dark matter in the Universe has been recently created by the Dark Energy Survey(DES)team.The distribution was found to be slightly(by a few percent)smoother and...The largest and most detailed map of the distribution of dark matter in the Universe has been recently created by the Dark Energy Survey(DES)team.The distribution was found to be slightly(by a few percent)smoother and less clumpy than predicted by general relativity.This result was considered as a hint of some new physical laws.In the present paper we offer a relatively simple model that could explain the above result without resorting to any new physical laws.The model deals with the dynamics of a system consisting of a large number of gravitating neutral particles,whose mass is equal to the mass of hydrogen atoms.The central point of the model is a partial inhibition of the gravitation for a relatively small subsystem of the entire system.It would be sufficient for this subsystem to constitute just about a few percent of the total ensemble of particles for explaining the few percent more smooth distribution of dark matter(observed by the DES team)compared to the prediction of general relativity.The most viable candidate for the dark matter particles in this model is the second flavor of hydrogen atoms(SFHA)that has only S-states and therefore does not couple to the electric dipole radiation or even to higher multipole radiation,so that the SFHA is practically dark.The SFHA has experimental confirmation from atomic experiments,it does not go beyond the Standard Model,it is based on standard quantum mechanics and it explains puzzling astrophysical observations of the redshifted line 21 cm from the early Universe.Thus,our model explaining the DES result of a little too smooth distribution of dark matter without resorting to any new physical laws seems to be self-consistent.展开更多
With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence...With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.展开更多
Exact solutions to the Einstein field equations for class I spacetime symmetry in relativistic stars are generated.The symmetry provides a relation between the gravitational potentials that lead to generalized solutio...Exact solutions to the Einstein field equations for class I spacetime symmetry in relativistic stars are generated.The symmetry provides a relation between the gravitational potentials that lead to generalized solutions of the Einstein field equations.We choose one of the gravitational potentials on a physical basis,which allows us to obtain the other gravitational potential via an embedding approach.It is therefore possible to generate a model with astrophysical significance.The model generated satisfies physical properties like stability,causality,regularity,equilibrium and energy conditions.展开更多
The Dark Matter Particle Explorer(DAMPE)has been undergoing a stable on-orbit operation for more than 6 yr and acquired observations of over 11 billion events.A better understanding of the overall radiation environmen...The Dark Matter Particle Explorer(DAMPE)has been undergoing a stable on-orbit operation for more than 6 yr and acquired observations of over 11 billion events.A better understanding of the overall radiation environment of the DAMPE orbit is crucial for both simulation data production and fiight data analysis.In this work,we study the radiation environment at low Earth orbit and develop a simulation software package using the framework of ATMNC3,in which state-of-the-art full 3D models of the Earth’s atmospheric and magnetic-field configurations are integrated.We consider in our Monte Carlo procedure event-by-event propagation of cosmic rays in the geomagnetic field and their interaction with the Earth’s atmosphere,focusing on the particles above Ge V that are able to trigger the DAMPE data acquisition system.We compare the simulation results with the cosmic-ray electron and positron(CRE)fiux measurements made by DAMPE.The overall agreement on both the spectral and angular distribution of the CRE fiux demonstrates that our simulation is well established.Our software package could be of more general usage for simulation of the radiation environment of low Earth orbit at various altitudes.展开更多
The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is propose...The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is proposed as the early stage of the GRAND project,consisting of a hybrid array of radio antennas and scintillator detectors.The latter,as a mature and traditional detector,is used to cross-check the nature of the candidate events selected from radio observations.In this study,we developed a simulation software called G4GRANDProto300,based on the Geant4 software package,to optimize the spacing of the scintillator detector array and to investigate its effective area.The analysis was conducted at various zenith angles under different detector spacings,including 300,500,600,700,and 900 m.Our results indicate that,for large zenith angles used to search for cosmic-ray in the GRAND project,the optimized effective area is with a detector spacing of 500 m.The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.展开更多
Precise measurements of energy spectra of different cosmic ray(CR) species have been obtained in recent years, by particularly the AMS-02 experiment on the International Space Station. It has been shown that apparent ...Precise measurements of energy spectra of different cosmic ray(CR) species have been obtained in recent years, by particularly the AMS-02 experiment on the International Space Station. It has been shown that apparent differences exist in different groups of the primary CRs. However, it is not straightforward to conclude that the source spectra of different particle groups are different since they will experience different propagation processes(e.g., energy losses and fragmentations) either. In this work, we study the injection spectra of different nuclear species using the measurements from Voyager-1 outside the solar system, and ACR-CRIS and AMS-02 on the top of atmosphere, in a physical framework of CR transportation. Two types of injection spectra are assumed, the broken power-law(BPL) form and the non-parametric spline interpolation form. The non-parametric form fits the data better than the BPL form, implying that potential structures beyond the constrained spectral shape of BPL may exist. For different nuclei the injection spectra are overall similar in shape but do show some differences among each other. For the non-parametric spectral form, the helium injection spectrum is the softest at low energies and the hardest at high energies. For both spectral shapes, the low-energy injection spectrum of neon is the hardest among all these species, and the carbon and oxygen spectra have more prominent bumps in 1–10 GV in the R2 d N dRpresentation.Such differences suggest the existence of differences in the sources or acceleration processes of various nuclei of CRs.展开更多
DArk Matter Particle Explorer(DAMPE) is a general purpose high energy cosmic ray and gamma ray observatory, aiming to detect high energy electrons and gammas in the energy range 5 Ge V to 10 Te V and hundreds of Te V ...DArk Matter Particle Explorer(DAMPE) is a general purpose high energy cosmic ray and gamma ray observatory, aiming to detect high energy electrons and gammas in the energy range 5 Ge V to 10 Te V and hundreds of Te V for nuclei. This paper provides a method using machine learning to identify electrons and separate them from gammas, protons, helium and heavy nuclei with the DAMPE data acquired from 2016 January 1 to 2017 June 30, in the energy range from 10 to 100 Ge V.展开更多
The burst of radio emission by an extensive air shower provides a promising alternative for detecting ultra-high energy cosmic rays. We have developed an inde- pendent numerical program to simulate these radio signals...The burst of radio emission by an extensive air shower provides a promising alternative for detecting ultra-high energy cosmic rays. We have developed an inde- pendent numerical program to simulate these radio signals. Our code is based on a microscopic treatment, with both the geosynchrotron radiation and charge included. Here we give the first presentation of our basic program and its results. When the time-domain signals for different polarizations are computed, we find that the pulses take on a bipolar pattern and the spectrum is suppressed towards the lower frequencies. We investigate how showers at different heights in the atmosphere contribute to the total signal, and examine the signal strength and distribution at sites with different elevations. We also study the signal from showers with different inclination angles and azimuth directions. In all these cases we find the charge excess effect is important.展开更多
A universe consisting of protons, neutrons, and electrons with electrical neutrality is consistent with an equal number of c and preons, assuming the rishon preon theory of Shupe and Harari. Similarly, a universe cons...A universe consisting of protons, neutrons, and electrons with electrical neutrality is consistent with an equal number of c and preons, assuming the rishon preon theory of Shupe and Harari. Similarly, a universe consisting of antiprotons, antineutrons, and positrons with electrical neutrality is consistent with an equal number of c and preons. Hence, any combination of such matter-antimatter compositions is also consistent with an equal number of c and preons and overall electrical neutrality. It is proposed that the difference observed in baryon-antibaryon number density relative to photon number density, ~5 × 10<sup>-10</sup>, is due to allocation of preons between matter and antimatter during preon condensation into normal matter. Three approaches of increasing rigor and complexity are considered: 1) an allocation at times corresponding to the Planck temperature due to fluctuations, 2) an allocation at times corresponding to quark formation due to preon bonding, and 3) an allocation at times corresponding to the electroweak scale. All approaches can give the correct order of magnitude of the asymmetry assuming out-of-equili-brium freeze-out and a slight and allowed charge (C) asymmetry in preon condensation in a self-consistent quantum field theory. Sakharov’s baryon non-conservation condition is evidently circumvented with these approaches, because they assume another level of matter (preons) which is present before quark formation. Thus, preons can provide an elementary explanation of primordial matter-antimatter asymmetry. A relationship between Higgs boson states and preons is proposed.展开更多
The elastic resonance scattering of ^17F＋p is studied in inverse kinematics via a thick-target method. The excitation function for ^17F＋p elastic scattering is obtained within the energy interval of Ec.m ≈ 0.4-1.7 ...The elastic resonance scattering of ^17F＋p is studied in inverse kinematics via a thick-target method. The excitation function for ^17F＋p elastic scattering is obtained within the energy interval of Ec.m ≈ 0.4-1.7 MeV. The experimental excitation function is analyzed with a multilevel R-matrix code MULTI7, and the proton widths are deduced. The α decay from 6.15 MeV 1- state in 18Ne is observed, which is critical to the 14O（α, p）17F reaction as the main breakout route from CNO cycle to rp-process in supernovae and x-ray bursts.展开更多
Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-ha...Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63mHz. The wave vector in the GSE coordinates is estimated to be k = （-4.29, 2.28, 1.21）×10^-4 km^-1, In the solar wind frame, the frequency of waves becomes - 9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.展开更多
We report the results of timing and spectral analysis of the x-ray pulsar EXO2030＋375. The observations were made using the Rossi x-ray timing explorer space satellite. The spectral analysis is carried out for the fl...We report the results of timing and spectral analysis of the x-ray pulsar EXO2030＋375. The observations were made using the Rossi x-ray timing explorer space satellite. The spectral analysis is carried out for the flux of x-ray energy range 3-30 keV. The x-ray continuum spectra of proportional counter array could be represented by a two-component model, a power law with an exponential cutoff at higher energies and a blackbody. An iron line at about 6.4-6.6 keV was also detected.展开更多
Specific activity of primordial radionuclides and associated radiation hazards due to 40K, 226Ra, and 232Th have been measured in backed red brick samples, collected from five highly populated areas of the North West ...Specific activity of primordial radionuclides and associated radiation hazards due to 40K, 226Ra, and 232Th have been measured in backed red brick samples, collected from five highly populated areas of the North West Frontier Province of Pakistan. For the detection, analysis and data acquisition, a high purity germanium detector was used. Associated external doses were calculated using a Monte Carlo neutron photon transport code. A theoretical model to determine the gamma dose rate at 1 m height from the floor, made of bricks, was employed for the calculation of mass attenuation coefficient and self-absorption in the floor for the gamma energies of these radionuclides and their progeny. Monte Carlo simulation shows that in this study the floor, having more than an effective thickness of 15 cm, contributes very little to the external gamma dose rate. The values of the external dose rate and annual effective dose are found to be much lower than the world average as well as from other countries of the world.展开更多
In the first part of this Chapter the present state of knowledge from the observations of cosmic rays between 10^(13) and 10^(20) eV is summarized.This is not intended to be a complete review,but rather a broad overvi...In the first part of this Chapter the present state of knowledge from the observations of cosmic rays between 10^(13) and 10^(20) eV is summarized.This is not intended to be a complete review,but rather a broad overview of the relevant processes involving cosmic rays,including the astrophysical environments in which they take place.This overview mainly concerns experimental results and phenomenological aspects of their interpretation,therefore experiments’description is not given but references to the vast bibliography are provided in the text.Some attempt is made to address the most popular explanations offered by theoretical models.The second part is devoted to the description of the LHAASO performance and of its capability to provide a response to several open questions,still unanswered,concerning cosmic rays above 10^(13) eV,highlighting which major steps forward in this field could be taken from LHAASO observations.展开更多
Explosive astrophysical transients at cosmological distances can be used to place precision tests of the basic assumptions of relativity theory,such as Lorentz invariance,the photon zero-mass hypothesis,and the weak e...Explosive astrophysical transients at cosmological distances can be used to place precision tests of the basic assumptions of relativity theory,such as Lorentz invariance,the photon zero-mass hypothesis,and the weak equivalence principle(WEP).Signatures of Lorentz invariance violations(LIV)include vacuum dispersion and vacuum birefringence.Sensitive searches for LIV using astrophysical sources such as gamma-ray bursts,active galactic nuclei,and pulsars are discussed.The most direct consequence of a nonzero photon rest mass is a frequency dependence in the velocity of light propagating in vacuum.A detailed representation of how to obtain a combined severe limit on the photon mass using fast radio bursts at different redshifts through the dispersion method is presented.The accuracy of the WEP has been well tested based on the Shapiro time delay of astrophysical messengers traveling through a gravitational field.Some caveats of Shapiro delay tests are discussed.In this article,we review and update the status of astrophysical tests of fundamental physics.展开更多
基金the Ministry of Science and Technology of China(No.2016YFA0400301)the grants for the XENON Dark Matter Project。
文摘In recent years, cooling technology for liquid xenon(LXe) detectors has advanced driven by the development of dark matter(DM) detectors with target mass in the 100–1000 kg range. The next generation of DM detectors based on LXe will be in the 50,000 kg(50 t)range requiring more than 1 k W of cooling power. Most of the prior cooling methods become impractical at this level.For cooling a 50 t scale LXe detector, a method is proposed in which liquid nitrogen(LN2) in a small local reservoir cools the xenon gas via a cold finger. The cold finger incorporates a heating unit to provide temperature regulation. The proposed cooling method is simple, reliable, and suitable for the required long-term operation for a rare event search. The device can be easily integrated into present cooling systems, for example the ‘‘Cooling Bus’ ’employed for the Panda X I and II experiments. It is still possible to cool indirectly with no part of the cooling or temperature control system getting in direct contact with the clean xenon in the detector. Also, the cooling device can be mounted at a large distance, i.e., the detector is cooled remotely from a distance of 5–10 m. The method was tested in a laboratory setup at Columbia University to carry out different measurements with a small LXe detector and behaved exactly as predicted.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.11673068,11725314 and U1831122)the Youth Innovation Promotion Association(2017366)+1 种基金the Key Research Program of Frontier Sciences(Grant Nos.QYZDB-SSW-SYS005 and ZDBS-LY-7014)the Strategic Priority Research Program“Multi-waveband gravitational wave universe”(Grant No.XDB23000000)of Chinese Academy of Sciences。
文摘A nonzero-mass hypothesis for the photon can produce a frequency-dependent dispersion of light, which results in arrival-time differences of photons with different frequencies originating from a given transient source. Extragalactic fast radio bursts(FRBs), with their low frequency emissions, short time durations, and long propagation distances, are excellent astrophysical probes to constrain the rest mass of the photon mγ. However, the derivation of a limit on mγis complicated by the similar frequency dependences of dispersion expected from the plasma and nonzero photon mass effects. If a handful measurements of redshift for FRBs are available, then the different redshift dependences of the plasma and photon mass contributions to the dispersion measure(DM) might be able to break dispersion degeneracy in testing the photon mass. For now, nine FRBs with redshift measurements have been reported, which can turn this idea into reality. Taking into account the DM contributions from both the plasma and a possible photon mass,we use the data on the nine FRBs to derive a combined limit of mγ≤ 7.1 × 10^-51 kg, or equivalently mγ≤ 4.0 × 10^-15 e V/c2 at 68% confidence level, which is essentially as good as or represents a factor of 7 improvement over previous limits obtained by the single FRBs. Additionally, a reasonable estimation for the DM contribution from the host galaxy, DMhost, can be simultaneously achieved in our analysis. The rapid progress in localizing FRBs will further tighten the constraints on both mγ and DMhost.
基金partially supported by the National Basic Research Program of China(973 Program,Grant Nos.2014CB845800 and 2013CB834900)the National Natural Science Foundation of China(Grant Nos.11322328,11433009,11673068 and 11603076)+4 种基金the Youth Innovation Promotion Association(2011231)the Key Research Program of Frontier Sciences(QYZDBSSW-SYS005)the Strategic Priority Research Program“The Emergence of Cosmological Structures”(Grant No.XDB09000000)of the Chinese Academy of Sciencesthe Natural Science Foundation of Jiangsu Province(Grant No.BK20161096)the Guangxi Key Laboratory for Relativistic Astrophysics
文摘A conservative constraint on the rest mass of the photon can be estimated under the assump- tion that the frequency dependence of dispersion from astronomical sources is mainly contributed by the nonzero photon mass effect. Photon mass limits have been set earlier through the optical emissions of the Crab Nebula pulsar, but we demonstrate that these limits can be significantly improved with the dispersion measure （DM） measurements of radio pulsars in the Large and Small Magellanic Clouds. The combination of DM measurements of pulsars and distances of the Magellanic Clouds provides a strict upper limit on the photon mass as low as mγ≤2.0 ～ 10-45 g, which is at least four orders of magnitude smaller than the constraint from the Crab Nebula pulsar. Although our limit is not as tight as the current best result （～ 10-47 g） from a fast radio burst （FRB 150418） at a cosmological distance, the cosmological origin of FRB 150418 remains under debate; and our limit can reach the same high precision of FRB 150418 when it has an extragalactic origin （ ～10-45 g）.
基金supported by the National Key Research and Development Program of China(2022YFF0503304,2020YFC2201600,2018YFA0404504 and 2018YFA0404601)the Ministry of Science and Technology of China(2020SKA0110402,2020SKA0110401 and 2020SKA0110100)+4 种基金the National Natural Science Foundation of China(11890691,12205388 and 12220101003)the CAS Project for Young Scientists in Basic Research(YSBR-061,YSBR-092)the China Manned Space Project with No.CMS-CSST-2021(A02,A03 and B01)the Major Key Project of PCLthe 111 project(B20019)。
文摘We investigate the impact of inelastic collisions between dark matter(DM)and heavy cosmic ray(CR)nuclei on CR propagation.We approximate the fragmentation cross-sections for DM-CR collisions using collider-measured proton-nuclei scattering cross-sections,allowing us to assess how these collisions affect the spectra of CR boron and carbon.We derive new CR spectra from DM-CR collisions by incorporating their cross-sections into the source terms and solving the diffusion equation for the complete network of reactions involved in generating secondary species.In a specific example with a coupling strength of b_(χ)=0.1 and a DM mass of m_(χ)=0.1 GeV,considering a simplified scenario where DM interacts exclusively with oxygen,a notable modification in the boron-to-carbon spectrum due to the DM-CR interaction is observed.Particularly,the peak within the spectrum,spanning from 0.1 to 10 GeV,experiences an enhancement of approximately 1.5 times.However,in a more realistic scenario where DM particles interact with all CRs,this peak can be amplified to twice its original value.Utilizing the latest data from AMS-02 and DAMPE on the boron-to-carbon ratio,we estimate a 95%upper limit for the effective inelastic cross-section of DM-proton as a function of DM mass.Our findings reveal that at m_(χ)?2 MeV,the effective inelastic cross-section between DM and protons must be less than O(10^(-32))cm^(2).
文摘The largest and most detailed map of the distribution of dark matter in the Universe has been recently created by the Dark Energy Survey(DES)team.The distribution was found to be slightly(by a few percent)smoother and less clumpy than predicted by general relativity.This result was considered as a hint of some new physical laws.In the present paper we offer a relatively simple model that could explain the above result without resorting to any new physical laws.The model deals with the dynamics of a system consisting of a large number of gravitating neutral particles,whose mass is equal to the mass of hydrogen atoms.The central point of the model is a partial inhibition of the gravitation for a relatively small subsystem of the entire system.It would be sufficient for this subsystem to constitute just about a few percent of the total ensemble of particles for explaining the few percent more smooth distribution of dark matter(observed by the DES team)compared to the prediction of general relativity.The most viable candidate for the dark matter particles in this model is the second flavor of hydrogen atoms(SFHA)that has only S-states and therefore does not couple to the electric dipole radiation or even to higher multipole radiation,so that the SFHA is practically dark.The SFHA has experimental confirmation from atomic experiments,it does not go beyond the Standard Model,it is based on standard quantum mechanics and it explains puzzling astrophysical observations of the redshifted line 21 cm from the early Universe.Thus,our model explaining the DES result of a little too smooth distribution of dark matter without resorting to any new physical laws seems to be self-consistent.
基金supported by the National Natural Science Foundation of China under grant Nos.12393854,12022502 and 12263007by the High-level Talent Support program of Yunnan Province。
文摘With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.
基金the University of Dodoma in Tanzania for the continuous support and encouragement to complete this research workthe Ministry of Education,Science and Technology of Tanzania for sponsorshipthe South African Research Chair Initiative of the Department of Science and Technology and the National Research Foundation that facilitate the research funding。
文摘Exact solutions to the Einstein field equations for class I spacetime symmetry in relativistic stars are generated.The symmetry provides a relation between the gravitational potentials that lead to generalized solutions of the Einstein field equations.We choose one of the gravitational potentials on a physical basis,which allows us to obtain the other gravitational potential via an embedding approach.It is therefore possible to generate a model with astrophysical significance.The model generated satisfies physical properties like stability,causality,regularity,equilibrium and energy conditions.
基金supported in part by the National Key R&D Program of China(2021YFA0718404)the National Natural Science Foundation of China(Grant Nos.11773085,U1738207,and 12173098)the Youth Innovation Promotion Association CAS and the Scientific Instrument Developing Project of the Chinese Academy of Sciences,Grant No.GJJSTD20210009。
文摘The Dark Matter Particle Explorer(DAMPE)has been undergoing a stable on-orbit operation for more than 6 yr and acquired observations of over 11 billion events.A better understanding of the overall radiation environment of the DAMPE orbit is crucial for both simulation data production and fiight data analysis.In this work,we study the radiation environment at low Earth orbit and develop a simulation software package using the framework of ATMNC3,in which state-of-the-art full 3D models of the Earth’s atmospheric and magnetic-field configurations are integrated.We consider in our Monte Carlo procedure event-by-event propagation of cosmic rays in the geomagnetic field and their interaction with the Earth’s atmosphere,focusing on the particles above Ge V that are able to trigger the DAMPE data acquisition system.We compare the simulation results with the cosmic-ray electron and positron(CRE)fiux measurements made by DAMPE.The overall agreement on both the spectral and angular distribution of the CRE fiux demonstrates that our simulation is well established.Our software package could be of more general usage for simulation of the radiation environment of low Earth orbit at various altitudes.
基金supported by the National Natural Science Foundation of China(Nos.12322302,12275279 and U1931201)the National Key R&D Program of China(No.2023YFE0102300)+2 种基金the Project for Young Scientists in Basic Research of Chinese Academy of Sciences(No.YSBR-061)the Chinese Academy of Sciencesthe Entrepreneurship and Innovation Program of Jiangsu Province。
文摘The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is proposed as the early stage of the GRAND project,consisting of a hybrid array of radio antennas and scintillator detectors.The latter,as a mature and traditional detector,is used to cross-check the nature of the candidate events selected from radio observations.In this study,we developed a simulation software called G4GRANDProto300,based on the Geant4 software package,to optimize the spacing of the scintillator detector array and to investigate its effective area.The analysis was conducted at various zenith angles under different detector spacings,including 300,500,600,700,and 900 m.Our results indicate that,for large zenith angles used to search for cosmic-ray in the GRAND project,the optimized effective area is with a detector spacing of 500 m.The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.
基金supported by the National Key Research and Development Program of China(No. 2021YFA0718404)the National Natural Science Foundation of China (No. 12220101003)the Project for Young Scientists in Basic Research of Chinese Academy of Sciences(No. YSBR-061)。
文摘Precise measurements of energy spectra of different cosmic ray(CR) species have been obtained in recent years, by particularly the AMS-02 experiment on the International Space Station. It has been shown that apparent differences exist in different groups of the primary CRs. However, it is not straightforward to conclude that the source spectra of different particle groups are different since they will experience different propagation processes(e.g., energy losses and fragmentations) either. In this work, we study the injection spectra of different nuclear species using the measurements from Voyager-1 outside the solar system, and ACR-CRIS and AMS-02 on the top of atmosphere, in a physical framework of CR transportation. Two types of injection spectra are assumed, the broken power-law(BPL) form and the non-parametric spline interpolation form. The non-parametric form fits the data better than the BPL form, implying that potential structures beyond the constrained spectral shape of BPL may exist. For different nuclei the injection spectra are overall similar in shape but do show some differences among each other. For the non-parametric spectral form, the helium injection spectrum is the softest at low energies and the hardest at high energies. For both spectral shapes, the low-energy injection spectrum of neon is the hardest among all these species, and the carbon and oxygen spectra have more prominent bumps in 1–10 GV in the R2 d N dRpresentation.Such differences suggest the existence of differences in the sources or acceleration processes of various nuclei of CRs.
基金supported by the State Key Project of Research and Development Plan (2016YFA0400204)the National Natural Science Foundation of China (U1738133)+3 种基金Strategic Pioneer Research Program in Space Science of the Chinese Academy of Science (CAS)Youth Innovation Promotion Association of CASMinistry of Science and Technology of Jiangsu Province (17KJD510001)Changzhou Institute of Technology (YN1611)
文摘DArk Matter Particle Explorer(DAMPE) is a general purpose high energy cosmic ray and gamma ray observatory, aiming to detect high energy electrons and gammas in the energy range 5 Ge V to 10 Te V and hundreds of Te V for nuclei. This paper provides a method using machine learning to identify electrons and separate them from gammas, protons, helium and heavy nuclei with the DAMPE data acquired from 2016 January 1 to 2017 June 30, in the energy range from 10 to 100 Ge V.
基金Supported by the National Natural Science Foundation of China
文摘The burst of radio emission by an extensive air shower provides a promising alternative for detecting ultra-high energy cosmic rays. We have developed an inde- pendent numerical program to simulate these radio signals. Our code is based on a microscopic treatment, with both the geosynchrotron radiation and charge included. Here we give the first presentation of our basic program and its results. When the time-domain signals for different polarizations are computed, we find that the pulses take on a bipolar pattern and the spectrum is suppressed towards the lower frequencies. We investigate how showers at different heights in the atmosphere contribute to the total signal, and examine the signal strength and distribution at sites with different elevations. We also study the signal from showers with different inclination angles and azimuth directions. In all these cases we find the charge excess effect is important.
文摘A universe consisting of protons, neutrons, and electrons with electrical neutrality is consistent with an equal number of c and preons, assuming the rishon preon theory of Shupe and Harari. Similarly, a universe consisting of antiprotons, antineutrons, and positrons with electrical neutrality is consistent with an equal number of c and preons. Hence, any combination of such matter-antimatter compositions is also consistent with an equal number of c and preons and overall electrical neutrality. It is proposed that the difference observed in baryon-antibaryon number density relative to photon number density, ~5 × 10<sup>-10</sup>, is due to allocation of preons between matter and antimatter during preon condensation into normal matter. Three approaches of increasing rigor and complexity are considered: 1) an allocation at times corresponding to the Planck temperature due to fluctuations, 2) an allocation at times corresponding to quark formation due to preon bonding, and 3) an allocation at times corresponding to the electroweak scale. All approaches can give the correct order of magnitude of the asymmetry assuming out-of-equili-brium freeze-out and a slight and allowed charge (C) asymmetry in preon condensation in a self-consistent quantum field theory. Sakharov’s baryon non-conservation condition is evidently circumvented with these approaches, because they assume another level of matter (preons) which is present before quark formation. Thus, preons can provide an elementary explanation of primordial matter-antimatter asymmetry. A relationship between Higgs boson states and preons is proposed.
基金Supported by the National Basic Research Program of China under Grant No 2007CB815003, and the National Natural Science Foundation of China under Grant Nos 10875173, 10575136 and 10735100.
文摘The elastic resonance scattering of ^17F＋p is studied in inverse kinematics via a thick-target method. The excitation function for ^17F＋p elastic scattering is obtained within the energy interval of Ec.m ≈ 0.4-1.7 MeV. The experimental excitation function is analyzed with a multilevel R-matrix code MULTI7, and the proton widths are deduced. The α decay from 6.15 MeV 1- state in 18Ne is observed, which is critical to the 14O（α, p）17F reaction as the main breakout route from CNO cycle to rp-process in supernovae and x-ray bursts.
基金Supported by the National Natural Science Foundation of China under Grant Nos 40931054 and 40523006, the National Basic Research Program of China under Grant No 2006CB806305, the National High-Tech Research and Development Program of China under Grant No 2008AA12A216, and the Specialized Research Fund for State Key Laboratories.
文摘Characteristics of ULF waves associated with the solar wind deceleration in the Earth＇s foreshock on 6-7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63mHz. The wave vector in the GSE coordinates is estimated to be k = （-4.29, 2.28, 1.21）×10^-4 km^-1, In the solar wind frame, the frequency of waves becomes - 9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.
文摘We report the results of timing and spectral analysis of the x-ray pulsar EXO2030＋375. The observations were made using the Rossi x-ray timing explorer space satellite. The spectral analysis is carried out for the flux of x-ray energy range 3-30 keV. The x-ray continuum spectra of proportional counter array could be represented by a two-component model, a power law with an exponential cutoff at higher energies and a blackbody. An iron line at about 6.4-6.6 keV was also detected.
文摘Specific activity of primordial radionuclides and associated radiation hazards due to 40K, 226Ra, and 232Th have been measured in backed red brick samples, collected from five highly populated areas of the North West Frontier Province of Pakistan. For the detection, analysis and data acquisition, a high purity germanium detector was used. Associated external doses were calculated using a Monte Carlo neutron photon transport code. A theoretical model to determine the gamma dose rate at 1 m height from the floor, made of bricks, was employed for the calculation of mass attenuation coefficient and self-absorption in the floor for the gamma energies of these radionuclides and their progeny. Monte Carlo simulation shows that in this study the floor, having more than an effective thickness of 15 cm, contributes very little to the external gamma dose rate. The values of the external dose rate and annual effective dose are found to be much lower than the world average as well as from other countries of the world.
基金Supported by the National Key R&D Program of China(2018YFA0404203)the International Scholarship Program of the MOST of China(G2021166002L)+1 种基金National Natural Science Foundation of China(NSFC)(12147208,U2031103,U1931204)the Science and Technology Department of Sichuan Province(2021YFSY0031)。
文摘In the first part of this Chapter the present state of knowledge from the observations of cosmic rays between 10^(13) and 10^(20) eV is summarized.This is not intended to be a complete review,but rather a broad overview of the relevant processes involving cosmic rays,including the astrophysical environments in which they take place.This overview mainly concerns experimental results and phenomenological aspects of their interpretation,therefore experiments’description is not given but references to the vast bibliography are provided in the text.Some attempt is made to address the most popular explanations offered by theoretical models.The second part is devoted to the description of the LHAASO performance and of its capability to provide a response to several open questions,still unanswered,concerning cosmic rays above 10^(13) eV,highlighting which major steps forward in this field could be taken from LHAASO observations.
基金the National Natural Science Foundation of China(Grant Nos.11673068,11725314,U1831122,and 12041306)the Youth Innovation Promotion Association(2017366),the Key Research Program of Frontier Sciences(Grant Nos.QYZDB-SSW-SYS005 and ZDBS-LY-7014)the Strategic Priority Research Program“Multi-waveband gravitational wave universe”(Grant No.XDB23000000)of Chinese Academy of Sciences.
文摘Explosive astrophysical transients at cosmological distances can be used to place precision tests of the basic assumptions of relativity theory,such as Lorentz invariance,the photon zero-mass hypothesis,and the weak equivalence principle(WEP).Signatures of Lorentz invariance violations(LIV)include vacuum dispersion and vacuum birefringence.Sensitive searches for LIV using astrophysical sources such as gamma-ray bursts,active galactic nuclei,and pulsars are discussed.The most direct consequence of a nonzero photon rest mass is a frequency dependence in the velocity of light propagating in vacuum.A detailed representation of how to obtain a combined severe limit on the photon mass using fast radio bursts at different redshifts through the dispersion method is presented.The accuracy of the WEP has been well tested based on the Shapiro time delay of astrophysical messengers traveling through a gravitational field.Some caveats of Shapiro delay tests are discussed.In this article,we review and update the status of astrophysical tests of fundamental physics.
