arXiv subjects

Yi-Qing Guo

Publications and source records attributed to Yi-Qing Guo.

At least 55 records · Page 3Linked to original sources

arXiv2021

Constraining the cosmic ray propagation halo thickness using Fermi-LAT observations of high-latitude clouds

As a basic characteristic of cosmic ray (CR) propagation, the diffusive halo can advance our understanding of many CR-related studies and indirect dark matter. The method to derive the halo size usually has degeneracy problems thus affected by large uncertainties. The diffusion gamma ray from high-latitude clouds might shed light on the halo size independently. Since the spatially dependent propagation (SDP) model has a better agreement with the observed CRs, compared with conventional propagation model, in this work, we investigate the halo thickness based on SDP model with Fermi-LAT $\rmγ$-ray observation on the high- and intermediate-velocity clouds. As a result, in order not to exceed the relative $γ$-ray emissivity in the high-latitude clouds, halo thickness should be in the range of $\rm ~3.3\sim9~ kpc$. Moreover, the spatial morphology of $\rmγ$-rays estimated based on SDP model under different values of halo thickness are distinctive, which provides us a tool to determine the halo size. We hope that our model could be tested and tuned by multi-wavelength observations in the future.

astro-ph.HE↗

arXiv2020

Nearby source interpretation of differences among light and medium composition spectra in cosmic rays

Recently the AMS-02 reported the precise measurements of the energy spectra of medium-mass compositions (Neon, Magnesium, Silicon) of primary cosmic rays, which reveal different properties from those of light compositions (Helium, Carbon, Oxygen). Here we propose a nearby source scenario, together with the background source contribution, to explain the newly measured spectra of cosmic ray Ne, Mg, Si, and particularly their differences from that of He, C, O. Their differences at high energies can be naturally accounted for by the element abundance of the nearby source. Specifically, the abundance ratio of the nearby source to the background of the Ne, Mg, Si elements is lower by a factor of $\sim1.7$ than that of the He, C, O elements. Such a difference could be due to the abundance difference of the stellar evolution of the progenitor star or the acceleration process/environment, of the nearby source. This scenario can simultaneously explain the high-energy spectral softening features of cosmic ray spectra revealed recently by CREAM/NUCLEON/DAMPE, as well as the energy-dependent behaviors of the large-scale anisotropies. It is predicted that the dipole anisotropy amplitudes below PeV energies of the Ne, Mg, Si group are smaller than that of the He, C, O group, which can be tested with future measurements.

astro-ph.HE↗

arXiv2019

Anisotropies of different mass compositions of cosmic rays

The spectral hardenings of cosmic ray nuclei above $\sim 200$ GV followed by softenings around 10 TV, the knee of the all-particle spectrum around PeV energies, as well as the pattern change of the amplitude and phase of the large-scale anisotropies around 100 TeV indicate the complexities of the origin and transportation of Galactic cosmic rays. It has been shown that nearby source(s) are most likely to be the cause of such spectral features of both the spectra and the anisotropies. In this work, we study the anisotropy features of different mass composition (or mass groups) of cosmic rays in this nearby source model. We show that even if the spectral features from the nearby source component is less distinctive compared with the background component from e.g., the population of distant sources, the anisotropy features are more remarkable to be identified. Measurements of the anisotropies of each mass composition (group) of cosmic rays by the space experiments such as DAMPE and HERD and the ground-based experiments such as LHAASO in the near future are expected to be able to critically test this scenario.

astro-ph.HE↗

arXiv2019

Indication of nearby source signatures of cosmic rays from energy spectra and anisotropies

The origin of Galactic cosmic rays (GCRs) remains a mystery after more than one century of their discovery. The diffusive propagation of charged particles in the turbulent Galactic magnetic field makes us unable to trace back to their acceleration sites. Nevertheless, nearby GCR source(s) may leave imprints on the locally measured energy spectra and the anisotropies of the arrival direction. In this work we propose a simple but natural description of the GCR production and propagation, within a two-zone disk-halo diffusion scenario together with a nearby source, to understand the up-to-date precise measurements of the energy spectra and anisotropies of GCRs. We find that a common energy scale of $\sim100$ TeV appears in both energy spectra of protons and Helium nuclei measured recently by CREAM and large-scale anisotropies detected by various experiments. These results indicate that one or more local sources are very likely important contributors to GCRs below $100$ TeV. This study provides a probe to identify source(s) of GCRs by means of joint efforts of spectral and anisotropy measurements.

astro-ph.HE↗

arXiv2019

Electron and positron spectra in the three dimensional spatial-dependent propagation model

The spatial-dependent propagation model has been successfully used to explain diverse observational phenomena, including the spectral hardening of cosmic-ray nuclei above $200$ GV, the large-scale dipole anisotropy and the diffusive gamma distribution. In this work, we further apply the spatial-dependent propagation model to both electrons and positrons. To account for the excess of positrons above $10$ GeV, an additional local source is introduced. And we also consider a more realistic spiral distribution of background sources. We find that due to the gradual hardening above $10$ GeV, the hardening of electron spectrum above tens of GeV can be explained in the SDP model and both positron and electron spectra less than TeV energies could be naturally described. The spatial-dependent propagation with spiral-distributed sources could conforms with the total electron spectrum in the whole energy. Meanwhile compared with the conventional model, the spatial-dependent propagation with spiral-distributed sources could produce larger background positron flux, so that the multiplier of background positron flux is $1.42$, which is much smaller than the required value by the conventional model. Thus the shortage of background positron flux could be solved. Furthermore we compute the anisotropy of electron under spatial-dependent propagation model, which is well below the observational limit of Fermi-LAT experiment.

astro-ph.HE↗

arXiv2018

On the knee of Galactic cosmic rays in light of sub-TeV spectral hardenings

More than fifty years after the discovery of the knee in the cosmic ray spectra, its physical origin remains a mystery. This is partly due to the ambiguity of the energy spectrum of individual composition. Recently, direct measurements from several balloon/satellite-borne detectors found significant spectral hardenings of cosmic ray nuclei at a few hundred GV rigidities. A joint modeling of the direct and indirect measurements of the cosmic ray spectra may help to understand the experimental systematics and probably the physics of the knee. In this work, we update the phenomenological "poly-gonato" model of the knee to include the spectral hardenings, with a changing spectral index of $γ+ β\cdot \log E$ with respect to energy. We find that there is some tension between the direct and indirect measurements. Specifically, the hard spectra of CREAM suggest a relatively low energy cutoff of the individual cosmic ray spectrum around the knee, which is inconsistent with the light component spectra of the air shower measurements. Furthermore, the light component data from AS$γ$/ARGO-YBJ/WFCTA/KASCADE are consistent with the all-particle spectra. We expect that more precise measurements of the cosmic ray spectrum of individual composition at TeV energies and beyond by the operating space detectors such as CALET and DAMPE, and the ground based experiments such as LHAASO, will eventually solve these discrepancies. Finally, as an illustration, we show that a spatial-dependent diffusion under two-halo model is able to reproduce the results of this "modified poly-gonato" model.

astro-ph.HE↗

arXiv2018

On the PeV knee of cosmic rays spectrum and TeV cutoff of electron spectrum

Spectra of Cosmic Rays (CRs), particularly their features, may hold essential information about astroparticle and fundamental physics. Realizing that both $4$ PeV CR knee and electron's TeV break have nearly identical Lorentz factor, i.e. $γ\sim 10^6$, we propose that both CR nuclei and electron experience a threshold interaction with unknown light particle $\rm X$, widespread in the diffusive halo. The interaction occurs only when the Lorentz factor of CRs is larger than $10^6$. Via this process, the energy spectrum of each component has deformation above the threshold Lorentz factor, so both knee and spectral break of electrons can be naturally reproduced. Given the large uncertainties of the available measurements and simplified assumption, our model accommodates a wide mass range of the particle X, which is allowable from ultralight value to $\sim 1$ eV.

astro-ph.HE↗

arXiv2018

Understanding the spectral hardenings and radial distribution of Galactic cosmic rays and Fermi diffuse gamma-rays with spatially-dependent propagation

Recent direct measurements of Galactic cosmic ray spectra by balloon/space-borne detectors reveal spectral hardenings of all major nucleus species at rigidities of a few hundred GV. The all-sky diffuse gamma-ray emissions measured by the Fermi Large Area Telescope also show spatial variations of the intensities and spectral indices of cosmic rays. These new observations challenge the traditional simple acceleration and/or propagation scenario of Galactic cosmic rays. In this work we propose a spatially-dependent diffusion scenario to explain all these phenomena. The diffusion coefficient is assumed to be anti-correlated with the source distribution, which is a natural expectation from the charged particle transportation in turbulent magnetic field. The spatially-dependent diffusion model also gives a lower level of anisotropies of cosmic rays, which are consistent with observations by underground muons and air shower experiments. The spectral variations of cosmic rays across the Galaxy can be properly reproduced by this model.

astro-ph.HE↗

arXiv2018

Revisiting Spatial-Dependent Propagation Model with Latest Observations of Cosmic Ray Nuclei

Recently AMS-02 collaboration publish their measurements of light cosmic-ray nuclei, including lithium, beryllium, boron, carbon and oxygen. All of them reveal a prominent excess above $\sim$ 200 GV, coinciding with proton and helium. Particularly, the secondary cosmic rays even harden than the primary components above that break. One of the viable interpretations for above anomalies is the spatial-dependent diffusion process. Such model has been successfully applied to multiple observational phenomena, for example primary cosmic ray nuclei, diffuse gamma ray and anisotropy. In this work, we investigate the spatial-dependent propagation model in light of the new observational data. We find that such model is able to explain the upturn of secondary spectrum as well as the primary's. All the spectra can be well reproduced and the calculated ratios are also in good agreement with the observations.

astro-ph.HE↗

arXiv2017

Interpretations of the DAMPE electron data

The DArk Matter Particle Explorer (DAMPE), a high energy cosmic ray and $γ$-ray detector in space, has recently reported the new measurement of the total electron plus positron flux between 25 GeV and 4.6 TeV. A spectral softening at $\sim0.9$ TeV and a tentative peak at $\sim1.4$ TeV have been reported. We study the physical implications of the DAMPE data in this work. The presence of the spectral break significantly tightens the constraints on the model parameters to explain the electron/positron excesses. The spectral softening can either be explained by the maximum acceleration limits of electrons by astrophysical sources, or a breakdown of the common assumption of continuous distribution of electron sources at TeV energies in space and time. The tentive peak at $\sim1.4$ TeV implies local sources of electrons/positrons with quasi-monochromatic injection spectrum. We find that the cold, ultra-relativistic $e^+e^-$ winds from pulsars may give rise to such a structure. The pulsar is requird to be middle-aged, relatively slowly-rotated, mildly magnetized, and isolated in a density cavity. The annihilation of DM particles ($m_χ\sim1.5$ TeV) into $e^+e^-$ pairs in a nearby clump or an over-density region may also explain the data. In the DM scenario, the inferred clump mass (or density enhancement) is about $10^7-10^8$ M$_\odot$ (or $17-35$ times of the canonical local density) assuming a thermal production cross section, which is relatively extreme compared with the expectation from numerical simulations. A moderate enhancement of the annihilation cross section via, e.g., the Sommerfeld mechanism or non-thermal production, is thus needed.

astro-ph.HE↗

arXiv2017

The Galactic Center: A PeV Cosmic Ray Acceleration Factory

The multi-TeV $γ$-rays from the Galactic Center (GC) have a cutoff at tens of TeV, whereas the diffuse emission has no such cutoff, which is regarded as an indication of PeV proton acceleration by the HESS experiment. It is important to understand the inconsistency and study the possibility that PeV cosmic-ray acceleration could account for the apparently contradictory point and diffuse $γ$-ray spectra. In this work, we propose that the cosmic rays are accelerated up to $>$PeV in GC. The interaction between cosmic rays and molecular clouds is responsible for the multi-TeV $γ$-ray emissions from both the point source and diffuse sources today. Enhanced by the small volume filling factor (VFF) of the clumpy structure, the absorption of the $γ$-rays leads to a sharp cutoff spectrum at tens of TeV produced in the GC. Away from galactic center, the VFF grows and the absorption enhancement becomes negligible. As a result, the spectra of $γ$-ray emissions for both point source and diffuse sources can be successfully reproduced under such self-consistent picture. In addition, a "surviving-tail" at $\sim$100 TeV is expected from the point source, which can be observed by future projects CTA and LHAASO. Neutrinos are simultaneously produced during proton-proton (PP) collision. With 5-10 years observations, the KM3Net experiment will be able to detect the PeV source according to our calculation.

astro-ph.HE↗

arXiv2015

Spatial-Dependent Diffusion of Cosmic Rays and the Ratio of pbar/p, B/C

Recent precise measurements of cosmic ray spectral revealed an anomalous hardening at ~200 GV for nuclei from PAMELA, CREAM, ATIC, AMS02 experiments and at tens of GeV for primary electron derived from AMS02 experiment. Particularly, the latest observation of pbar/p ratio by AMS02 demonstrated a flat distribution, which further validated the spectrum anomalies of secondary particles. All those new phenomena indicated that the conventional propagation model of cosmic rays meet challenge. In this work, the spatial-dependent propagation coefficient D(r,z,ρ) is employed by tracing the source distribution under the physical picture of two-halo model in DRAGON package. Under such scenario, the model calculation will result in a two-component spectral for primary nuclei and electron. Simultaneously, due to the smaller rigidity dependence of D(r,z,ρ) in galactic disk, the ratio of secondary-to-primary will be inevitablly flatter than the calculation in the conventional propagation model. As a result, we can reproduce the spectral hardening of proton, electron and the flat ratio of pbar/p and B/C by only adopting the spatial-dependent propagation coefficient D(r,z,ρ) in galactic disk.

astro-ph.HE↗

arXiv2014

Hybrid model of GeV-TeV gamma ray emission from Galactic Center

The observations of high energy $γ$-ray emission from the Galactic center (GC) by HESS, and recently by Fermi, suggest the cosmic ray acceleration in the GC and possibly around the supermassive black hole. In this work we propose a lepton-hadron hybrid model to explain simultaneously the GeV-TeV $γ$-ray emission. Both electrons and hadronic cosmic rays were accelerated during the past activity of the GC. Then these particles would diffuse outwards and interact with the interstellar gas and background radiation field. The collisions between hadronic cosmic rays with gas is responsible to the TeV $γ$-ray emission detected by HESS. With fast cooling in the strong radiation field, the electrons would cool down and radiate GeV photons through inverse Compton scattering off the soft background photons. This scenario provides a natural explanation of the observed GeV-TeV spectral shape of $γ$-rays.

astro-ph.HE↗

arXiv2014

Implications of the AMS-02 positron fraction in cosmic rays

The AMS-02 collaboration has just released its first result of the cosmic positron fraction $e^+/(e^-+e^+)$ with high precision up to $\sim 350$ GeV. The AMS-02 result shows the same trend with the previous PAMELA result, which requires extra electron/positron sources on top of the conventional cosmic ray background, either from astrophysical sources or from dark matter annihilation/decay. In this paper we try to figure out the nature of the extra sources by fitting to the AMS-02 $e^+/(e^-+e^+)$ data, as well as the electron and proton spectra by PAMELA and the $(e^-+e^+)$ spectrum by Fermi and HESS. We adopt the GALPROP package to calculate the propagation of the Galactic cosmic rays and the Markov Chain Monte Carlo sampler to do the fit. We find that the AMS-02 data have implied essential difference from the PAMELA data. There is {\rm tension} between the AMS-02 $e^+/(e^-+e^+)$ data and the Fermi/HESS $(e^-+e^+)$ spectrum, that the AMS-02 data requires less contribution from the extra sources than Fermi/HESS. Then we redo the fit without including the Fermi/HESS data. In this case both the pulsars and dark matter annihilation/decay can explain the AMS-02 data. The pulsar scenario has a soft inject spectrum with the power-law index $\sim 2$, while the dark matter scenario needs $τ^+τ^-$ final state with mass $\sim 600$ GeV and a boost factor $\sim 200$.

astro-ph.HE↗

arXiv2012

Quantum wave equation of non-conservative system

It is well known that Schrödinger's equation is only suitable for the particle in conservative force field. In atomic and molecular field, a particle can suffer the action of non-conservative force. In this paper, a new quantum wave equation is proposed, which can describe the particle in non-conservative force field. We think the new quantum wave equation can be used in many fields.

quant-ph↗

arXiv2011

Non-factorization contributions in $D\rightarrow πK, KK$ decay

We have analyzed the $D\rightarrow πK, KK$ decay with the naive factorization (NF), QCD factorization (QCDF)and QCD factorization including soft-gluon exchanges (QCDF+SGE). In these decay channels, the soft-gluon effects are firstly calculated with light cone QCD sum rules. Comparing the three kind approaches, we can find the calculation results have made much more improved QCD factorization (QCDF) than the naive factorization (NF), and the calculation results have also made improved QCD factorization including soft-gluon exchanges (QCDF+SGE) than the QCD factorization (QCDF) in the color-suppressed decay channels. In addition, we find the soft-gluon effects are larger than the leading order contributions, and the calculation results are close to the experimental data for the color-suppressed decay channels. In color-allowed decay channel $D^{0}\rightarrow π^{+} K^{-}$, the soft-gluon effects are small and we should consider other power terms, such as final state interaction and annihilation effects.

hep-ph↗

arXiv2011

Quantum theory of light diffraction

At present, the theory of light diffraction only has the simple wave-optical approach. In this paper, we study light diffraction with the approach of relativistic quantum theory. We find that the slit length, slit width, slit thickness and wave-length of light have affected to the diffraction intensity and form of diffraction pattern. However, the effect of slit thickness on the diffraction pattern can not be explained by wave-optical approach, and it can be explained in quantum theory. We compare the theoretical results with single and multiple slits experiment data, and find the theoretical results are accordance with the experiment data. Otherwise, we give some theory prediction. We think all the new prediction will be tested by the light diffraction experiment.

quant-ph↗

arXiv2007

Classical and quantum theory for Superluminal particle

As we all know, when the relative velocity of two inertial reference frames $\sum$ and $\sum^{'}$ is less than the speed of light, the relations of $x_μ$ with $x_μ^{'}$, a particle mass $m$ with its velocity $\upsilon$, and a particle mass with its energy are all given by Einstein's special relativity. In this paper, we will give new relation of $x_μ$ and $x_μ^{'}$ when the relative velocity of $\sum$ and $\sum^{'}$ frame is larger than the speed of light, and also we give the relation of a particle mass $m$ with its velocity $\upsilon$, and a particle mass $m$ with its energy $E$ when the particle velocity $v$ is larger than the speed of light.

quant-ph↗