Axions are hypothetical particles proposed to solve the strong CP problem in QCD and may constitute a significant fraction of the dark matter in the universe. Axions are expected to be produced in superfluid neutron s...Axions are hypothetical particles proposed to solve the strong CP problem in QCD and may constitute a significant fraction of the dark matter in the universe. Axions are expected to be produced in superfluid neutron stars and subsequently decay, producing gamma-rays detectable by the Fermi Large Area Telescope (Fermi-LAT). Considering that light QCD axions, as opposed to axions > 1 eV, may travel a long range before they decay into gamma rays, neutron stars may appear as a spatially extended source of gamma rays. We extend our previous search for gamma rays from axions, based on a point source model, to consider the neutron star as an extended source of gamma rays. The extended consideration of neutron stars leads to higher sensitivity to searches for axions, as it will be shown. We investigate the spatial emission of gamma rays using phenomenological models of neutron star axion emission. We present models including the fundamental astrophysics and relativistic, extended gamma-ray emission from axions around neutron stars. A Monte Carlo simulation of the LAT gives us an expectation for the extended angular profile and spectrum. For a source of ≃100 pc, we predict a mean angular spread of ≃2˚ with gamma-ray energies in the range 10 - 200 MeV, due to the cutoff of the spin-structure function Sσ(ω). We demonstrate the feasibility of setting more stringent limits for axions in this mass range, excluding a range not probed by observations before. We consider projected sensitivities for mass limits on axions from RX J1856-3754, a neutron star at a distance of 130 pc. The limit based on 7.9 years of Fermi-LAT data is 3.9 meV for an inner temperature of the neutron star of 20 MeV.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
1.Aims and scope Chinese Physics C (CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, ...1.Aims and scope Chinese Physics C (CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, and cosmology.展开更多
The Voyager spacecrafts have been measuring since 2012 the rates of electron and nuclei of the cosmic radiation beyond the solar cavity at a distance of more than 1013 meters from the Earth.A record of unique and nota...The Voyager spacecrafts have been measuring since 2012 the rates of electron and nuclei of the cosmic radiation beyond the solar cavity at a distance of more than 1013 meters from the Earth.A record of unique and notable findings has been reported and among them,the electron-to-proton flux ratio of 50 to 100 below energies of 50 MeV.This ratio is thoroughly opposite to that of 0.01 measured at higher energies in the range 10 GeV to 10 TeV.The difference amounts to four orders of magnitude.Arguments and calculations to show how this surprising and fundamental ratio lends support to the empirical evidence of the ubiquitous electrostatic field in the Milky Way Galaxy are presented.In other respects,this paper examines and calculates,for the first time,the electric charge balance in the solar system delimited by the termination shock of the solar wind.展开更多
1. Aims and scope Chinese Physics C(CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, ...1. Aims and scope Chinese Physics C(CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, and cosmology.2. Submission Manuscripts must be submitted through the online submission system at http://cpc.ihep.ac.cn. Submissions by email will not be accepted. By submitting a paper for publication in CPC, the authors imply that the material has not been published previously nor has been submitted for publication elsewhere.展开更多
1.Aims and scope Chinese Physics C (CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, ...1.Aims and scope Chinese Physics C (CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, and cosmology.2. Submission Manuscripts must be submitted through the online submission system at http://cpc.ihep.ac.cn. Submissions by email will not be accepted. By submitting a paper for publication in CPC, the authors imply that the material has not been published previously nor has been submitted for publication elsewhere.展开更多
1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cos...1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.2.Submission Manuscripts must be submitted through the online submission system at http://cpc.ihep.ac.cn.展开更多
1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cos...1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.展开更多
1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cos...1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.展开更多
1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cos...1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.展开更多
The Fermi Gamma-ray Space Telescope, formerly called GLAST, measures the cosmic gamma-ray flux in the energy range 8 keV to 〉 300 GeV. In addition to breakthrough capabilities in energy coverage and localization, the...The Fermi Gamma-ray Space Telescope, formerly called GLAST, measures the cosmic gamma-ray flux in the energy range 8 keV to 〉 300 GeV. In addition to breakthrough capabilities in energy coverage and localization, the very large field of view enables observations of 20~ of the sky at any instant, and the entire sky on a timescale of a few hours. With its launch in 2008, Fermi opens a new and important window on a wide variety of phenomena, including pulsars, black holes and active galactic nuclei, gamma-ray bursts, supernova remnants and the origins of cosmic rays, and searches for hypothetical new phenomena such as particle dark matter annihilations. A brief overview and selected science highlights from the first four years are provided.展开更多
1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cos...1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.2.Submission Manuscripts must be submitted through the online submission system at http://cpc.ihep.ac.cn.Submissions by email will not be accepted.By submitting a paper for publication in CPC,the authors imply that the material has not been published previously nor has been submitted for publication elsewhere.3.Preparation of manuscripts 3.1.Manuscript:The manuscript should be formatted in LaTeX if possible.Otherwise,Microsoft Word format may be used.展开更多
文摘Axions are hypothetical particles proposed to solve the strong CP problem in QCD and may constitute a significant fraction of the dark matter in the universe. Axions are expected to be produced in superfluid neutron stars and subsequently decay, producing gamma-rays detectable by the Fermi Large Area Telescope (Fermi-LAT). Considering that light QCD axions, as opposed to axions > 1 eV, may travel a long range before they decay into gamma rays, neutron stars may appear as a spatially extended source of gamma rays. We extend our previous search for gamma rays from axions, based on a point source model, to consider the neutron star as an extended source of gamma rays. The extended consideration of neutron stars leads to higher sensitivity to searches for axions, as it will be shown. We investigate the spatial emission of gamma rays using phenomenological models of neutron star axion emission. We present models including the fundamental astrophysics and relativistic, extended gamma-ray emission from axions around neutron stars. A Monte Carlo simulation of the LAT gives us an expectation for the extended angular profile and spectrum. For a source of ≃100 pc, we predict a mean angular spread of ≃2˚ with gamma-ray energies in the range 10 - 200 MeV, due to the cutoff of the spin-structure function Sσ(ω). We demonstrate the feasibility of setting more stringent limits for axions in this mass range, excluding a range not probed by observations before. We consider projected sensitivities for mass limits on axions from RX J1856-3754, a neutron star at a distance of 130 pc. The limit based on 7.9 years of Fermi-LAT data is 3.9 meV for an inner temperature of the neutron star of 20 MeV.
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.
文摘1.Aims and scope Chinese Physics C (CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, and cosmology.
文摘The Voyager spacecrafts have been measuring since 2012 the rates of electron and nuclei of the cosmic radiation beyond the solar cavity at a distance of more than 1013 meters from the Earth.A record of unique and notable findings has been reported and among them,the electron-to-proton flux ratio of 50 to 100 below energies of 50 MeV.This ratio is thoroughly opposite to that of 0.01 measured at higher energies in the range 10 GeV to 10 TeV.The difference amounts to four orders of magnitude.Arguments and calculations to show how this surprising and fundamental ratio lends support to the empirical evidence of the ubiquitous electrostatic field in the Milky Way Galaxy are presented.In other respects,this paper examines and calculates,for the first time,the electric charge balance in the solar system delimited by the termination shock of the solar wind.
文摘1. Aims and scope Chinese Physics C(CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, and cosmology.2. Submission Manuscripts must be submitted through the online submission system at http://cpc.ihep.ac.cn. Submissions by email will not be accepted. By submitting a paper for publication in CPC, the authors imply that the material has not been published previously nor has been submitted for publication elsewhere.
文摘1.Aims and scope Chinese Physics C (CPC) publishes original research papers, letters and reviews, covering theory and experiments in the fields of particle physics, nuclear physics, particle and nuclear astrophysics, and cosmology.2. Submission Manuscripts must be submitted through the online submission system at http://cpc.ihep.ac.cn. Submissions by email will not be accepted. By submitting a paper for publication in CPC, the authors imply that the material has not been published previously nor has been submitted for publication elsewhere.
文摘1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.2.Submission Manuscripts must be submitted through the online submission system at http://cpc.ihep.ac.cn.
文摘1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.
文摘1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.
文摘1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.
文摘The Fermi Gamma-ray Space Telescope, formerly called GLAST, measures the cosmic gamma-ray flux in the energy range 8 keV to 〉 300 GeV. In addition to breakthrough capabilities in energy coverage and localization, the very large field of view enables observations of 20~ of the sky at any instant, and the entire sky on a timescale of a few hours. With its launch in 2008, Fermi opens a new and important window on a wide variety of phenomena, including pulsars, black holes and active galactic nuclei, gamma-ray bursts, supernova remnants and the origins of cosmic rays, and searches for hypothetical new phenomena such as particle dark matter annihilations. A brief overview and selected science highlights from the first four years are provided.
文摘1.Aims and scope Chinese Physics C(CPC)publishes original research papers,letters and reviews,covering theory and experiments in the fields of particle physics,nuclear physics,particle and nuclear astrophysics,and cosmology.2.Submission Manuscripts must be submitted through the online submission system at http://cpc.ihep.ac.cn.Submissions by email will not be accepted.By submitting a paper for publication in CPC,the authors imply that the material has not been published previously nor has been submitted for publication elsewhere.3.Preparation of manuscripts 3.1.Manuscript:The manuscript should be formatted in LaTeX if possible.Otherwise,Microsoft Word format may be used.
