124682883
A geometric factor calculation method based on the isotropic flux assumption
One of the instruments onboard the China Seismic Electromagnetic Satellite (CSES) is the Low Energy Particle Detector (LEPD). The primary objective of LEPD is to provide measurements of the fluxes, energy spectra and pitch angles of 100 keV to 10 MeV electrons and protons from 2 to 50 MeV in the Earth's magnetosphere. The geometric factor is one of the principle parameters of a detector, which converts the physical quantity count rate to the particle quantity-flux. In this paper, we calculated the geometric factor of LEPD via computer modeling of an isotropic radiation environment. It was first demonstrated that the radiation intensity related should obey a cosine-law, then a general sampling method of generating this distribution via CPS of GEANT4 was explained. Furthermore, combined with flux normalization, a comparison of the geometric factor calculation of a set of 2-layer detectors with different shapes (cylinder, truncated cone and rectangle) was performed. Results show a generally good agreement between simulation and analytical calculations for the cylinder and truncated cone detectors, and the result of the rectangular one, for which there is no accurate analytical formula, is consistent with the previous simulated results by others. As a practical instance of the 2-layer rectangle detector, the geometric factor of LEPD is 10.336 +/- 0.036 cm(2).sr for 10 MeV proton and 8.211 +/- 0.032 cm(2).sr for 8 MeV electron.
123742975
Design and performance study of the LEPD silicon tracker onboard the CSES satellite
The low energy particle detector (LEPD) is one of the main payloads onboard the China seismic electromagnetic satellite (CSES). The detector is designed to ascertain space electrons (0.1–10 MeV) and protons (2–50 MeV). It has the capability of identifying the electrons and protons, to measure the energy spectrum and the incident angle of the particles. The LEPD is made up of a silicon tracker system, a CsI (Tl) mini-calorimeter, an anti-coincidence system made by plastic scintillator, as well as electronics and a data acquisition system (DAQ). The tracker is also a kind of ΔE-E telescope; it consists of two layers of double-sided silicon strip detectors (DSSD). The signals emerging from the silicon tracker can be read out by two pieces of application specific integrated circuit (ASIC), which also can generate an event trigger for the LEPD. The functions of the DSSD system in the LEPD for charged particles were tested by 241Am @5.486 MeV α particles. The results show that the DSSD system works well, and has high performance to detect charged particles and measure the position of incident particles.
118497313
Inflation in de Sitter spacetime and CMB large scale anomaly
The influence of cosmological constant-type dark energy in the early universe is investigated. This is accommodated by a new dispersion relation in de Sitter spacetime. We perform a global fit to explore the cosmological parameter space by using the CosmoMC package with the recently released Planck TT and WMAP polarization datasets. Using the results from the global fit, we compute a new CMB temperature temperature (TT) spectrum. The obtained TT spectrum has lower power compared with that based on the ACDM model at large scales.
123863059
Design and simulations for the detector based on DSSSD
The present paper describes the design and simulation results of a position-sensitive charged particle detector based on the Double Sided Silicon Strip Detector (DSSSD). Also, the characteristics of the DSSSD and its testing result were are discussed. With the application of the DSSSD, the position-sensitive charged particle detector can not only give particle flux and energy spectra information and identify different types of charged particles, but also measure the location and angle of incident particles. As the detector can make multiparameter measurements of charged particles, it is widely used in space detection and exploration missions, such as charged particle detection related to earthquakes, space environment monitoring and solar activity inspection.
73685393
First moments of nucleon generalized parton distributions
We extrapolate the first moments of the generalized parton distributions using heavy baryon chiral perturbation theory. The calculation is based on the one loop level with the finite range regularization. The description of the lattice data is satisfactory, and the extrapolated moments at physical pion mass are consistent with the results obtained with dimensional regularization, although the extrapolation in the momentum transfer to t = 0 does show sensitivity to form factor effects, which lie outside the realm of chiral perturbation theory. We discuss the significance of the results in the light of modern experiments as well as QCD inspired models.
119108965
Coulomb gauge model for hidden charm tetraquarks
Abstract The spectrum of tetraquark states with hidden charm is studied within an effective Coulomb gauge Hamiltonian approach. Of the four independent color schemes, two are investigated, the ( q c ¯ ) 1 ( c q ¯ ) 1 singlet–singlet (molecule) and the ( q c ) 3 ( q ¯ c ¯ ) 3 triplet–triplet (diquark), for selected J PC states using a variational method. The predicted masses of triplet–triplet tetraquarks are roughly a GeV heavier than the singlet–singlet states. There is also an interesting flavor dependence with ( q q ¯ ) 1 ( c c ¯ 1 ) states about half a GeV lighter than ( q c ¯ ) 1 ( q ¯ c ) 1 . The lightest 1 + + and 1 − − predictions are in agreement with the observed X ( 3872 ) and Y ( 4008 ) masses suggesting they are molecules with ω J / ψ and η h c , rather than D ⁎ D ¯ ⁎ and D D ¯ , type structure, respectively. Similarly, the lightest isovector 1 + + molecule, having a ρ J / ψ flavor composition, has mass near the recently observed charged Z c ( 3900 ) value. These flavor configurations are consistent with observed X , Y and Z c decays to π π J / ψ .
122752259
Insights Into the High-Energy Gamma-ray Emission of Markarian 501 from Extensive Multifrequency Observations in the Fermi Era
We report on the gamma-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average LAT gamma-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 +/- 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of 2), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 +/- 0.14, and the softest one is 2.51 +/- 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3GeV. In this paper, we also present the first results from the 4.5-month-long multifrequency campaign (2009 March 15 - August 1) on Mrk 501, which included the VLBA, Swift, RXTE, MAGIC and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton model. In the framework of this model, we find that the dominant emission region is characterized by a size <~ 0.1 pc (comparable within a factor of few to the size of the partially-resolved VLBA core at 15-43 GHz), and that the total jet power (~10^{44} erg s^{-1}) constitutes only a small fraction (~10^{-3}) of the Eddington luminosity. The energy distribution of the freshly-accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3GeV-10TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks.
62821553
High-statistics study of K0S pair production in two-photon collisions
We report a high-statistics measurement of the differential cross section of the process gamma gamma -> (KSKS0)-K-0 in the range 1.05 GeV (KSKS0)-K-0 is reported. The detailed behavior of the cross section is updated and compared with QCD-based calculations.
53311398
Chiral extrapolation of nucleon magnetic form factors
The extrapolation of nucleon magnetic form factors calculated within lattice QCD is investigated within a framework based upon heavy baryon chiral effective-field theory. All one-loop graphs are considered at arbitrary momentum transfer and all octet and decuplet baryons are included in the intermediate states. Finite range regularization is applied to improve the convergence in the quark-mass expansion. At each value of the momentum transfer (${Q}^{2}$), a separate extrapolation to the physical pion mass is carried out as a function of ${m}_{\ensuremath{\pi}}$ alone. Because of the large values of ${Q}^{2}$ involved, the role of the pion form factor in the standard pion-loop integrals is also investigated. The resulting values of the form factors at the physical pion mass are compared with experimental data as a function of ${Q}^{2}$ and demonstrate the utility and accuracy of the chiral extrapolation methods presented herein.