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Energy calibration of Calorimetric Electron Telescope (CALET) in space
Abstract
The Calorimetric Electron Telescope (CALET) is a space experiment, currently under development by Japan in collaboration with Italy and the United States. CALET will measure the flux of cosmic ray electrons (including positrons) up to 20 TeV, gamma-rays up to 10 TeV and nuclei from Z = 1 up to 40 up to 1000 TeV during a two-year mission on the International Space Station (ISS), extendable to five years. The unique feature of CALET is its thick, fully active calorimeter that allows measurements well into the TeV energy region with excellent energy resolution ( ), coupled with a fine imaging upper calorimeter to accurately identify the starting point of electromagnetic showers. For continuous high performance of the detector, it is required to calibrate each detector component on orbit. We use the measured response to minimum ionizing particles for the energy calibration, taking data in a dedicated trigger mode and selecting useful events in off-line analysis. In this paper, we present on-orbit and off-line data handling methods for the energy calibration developed through beam tests at CERN-SPS and Monte Carlo simulations.
... Employing dual shaping amplifiers with two different gains for each APD (PMT) and PD, increases the dynamical range to 10 6 (10 4 ). As a consequence, the TASC can measure the energy of the incident electrons and gamma rays with a resolution < 2% above 100 GeV [11] . Another important role of the TASC is to efficiently identify high-energy electrons among the overwhelming background of cosmic-ray protons. ...
... Their energy spectrum depends on the cutoff rigidity, and hence the geomagnetic latitude. As a result, the position of the MIP peaks will shift by several percent as a function of the geomagnetic latitude [11] . To account for this effect, the incident particle energy distributions are assessed by simulating the energy spectra of incoming primary particles [11] using ATMNC3 [13] , in which AMS-01 proton and helium spectra [14] were used as input, since these data were taken at various geomagnetic latitudes, as well as them being in good agreement with BESS [15] and re- cent experiments. ...
... As a result, the position of the MIP peaks will shift by several percent as a function of the geomagnetic latitude [11] . To account for this effect, the incident particle energy distributions are assessed by simulating the energy spectra of incoming primary particles [11] using ATMNC3 [13] , in which AMS-01 proton and helium spectra [14] were used as input, since these data were taken at various geomagnetic latitudes, as well as them being in good agreement with BESS [15] and re- cent experiments. As well, contamination by interacting particles and/or scattered and stopped particles can cause a systematic shift in the determined position of MIP peaks. ...
In August 2015, the CALorimetric Electron Telescope (CALET), designed for long exposure observations of high energy cosmic rays, docked with the International Space Station (ISS) and shortly thereafter began to collect data. CALET will measure the cosmic ray electron spectrum over the energy range of 1 GeV to 20 TeV with a very high resolution of 2% above 100 GeV, based on a dedicated instrument incorporating an exceptionally thick 30 radiation-length calorimeter with both total absorption and imaging (TASC and IMC) units. Each TASC readout channel must be carefully calibrated over the extremely wide dynamic range of CALET that spans six orders of magnitude in order to obtain a degree of calibration accuracy matching the resolution of energy measurements. These calibrations consist of calculating the conversion factors between ADC units and energy deposits, ensuring linearity over each gain range, and providing a seamless transition between neighboring gain ranges. This paper describes these calibration methods in detail, along with the resulting data and associated accuracies. The results presented in this paper show that a sufficient accuracy was achieved for the calibrations of each channel in order to obtain a suitable resolution over the entire dynamic range of the electron spectrum measurement.
... The on-orbit commissioning phase was successfully completed in the first days of October 2015. Calibration and test of the instrument took place at the CERN-SPS during five campaigns between 2010 and 2015 with beams of electrons, protons, and relativistic ions [40][41][42]. ...
... A dedicated trigger mode [42,43] allows the selection of penetrating protons and He particles for the individual onorbit calibration of all channels. First, raw data are corrected for gain differences among the channels, light output nonuniformity, and any residual dependence on time and temperature. ...
The Calorimetric Electron Telescope (CALET), in operation on the International Space Station since 2015, collected a large sample of cosmic-ray iron over a wide energy interval. In this Letter a measurement of the iron spectrum is presented in the range of kinetic energy per nucleon from 10 GeV/n to 2.0 TeV/n allowing the inclusion of iron in the list of elements studied with unprecedented precision by space-borne instruments. The measurement is based on observations carried out from January 2016 to May 2020. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number Z=40). The energy is measured by a homogeneous calorimeter with a total equivalent thickness of 1.2 proton interaction lengths preceded by a thin (3 radiation lengths) imaging section providing tracking and energy sampling. The analysis of the data and the detailed assessment of systematic uncertainties are described and results are compared with the findings of previous experiments. The observed differential spectrum is consistent within the errors with previous experiments. In the region from 50 GeV/n to 2 TeV/n our present data are compatible with a single power law with spectral index −2.60±0.03.
... In order to assess the relatively large uncertainties in the hadronic interactions, a series of beam tests were carried out at CERN-SPS using the CALET beam test model [43][44][45]. Trigger efficiency and energy response derived from MC simulations were tuned using the beam test results obtained in 2012 [43,44,46] with proton beams of 30, 100, and 400 GeV. The correction for the trigger efficiency obtained by the EPICS simulation was determined to be 7.7% for the LE trigger and 11.2% for the HE trigger, irrespective of proton energies. ...
... In order to assess the relatively large uncertainties in the hadronic interactions, a series of beam tests were carried out at CERN-SPS using the CALET beam test model [43][44][45]. Trigger efficiency and energy response derived from MC simulations were tuned using the beam test results obtained in 2012 [43,44,46] with proton beams of 30, 100, and 400 GeV. The correction for the trigger efficiency obtained by the EPICS simulation was determined to be 7.7% for the LE trigger and 11.2% for the HE trigger, irrespective of proton energies. ...
In this paper, we present the analysis and results of a direct measurement of the cosmic-ray proton spectrum with the CALET instrument onboard the International Space Station, including the detailed assessment of systematic uncertainties. The observation period used in this analysis is from October 13, 2015 to August 31, 2018 (1054 days). We have achieved the very wide energy range necessary to carry out measurements of the spectrum from 50 GeV to 10 TeV covering, for the first time in space, with a single instrument the whole energy interval previously investigated in most cases in separate subranges by magnetic spectrometers (BESS-TeV, PAMELA, and AMS-02) and calorimetric instruments (ATIC, CREAM, and NUCLEON). The observed spectrum is consistent with AMS-02 but extends to nearly an order of magnitude higher energy, showing a very smooth transition of the power-law spectral index from −2.81±0.03 (50–500 GeV) neglecting solar modulation effects (or −2.87±0.06 including solar modulation effects in the lower energy region) to −2.56±0.04 (1–10 TeV), thereby confirming the existence of spectral hardening and providing evidence of a deviation from a single power law by more than 3σ.
... The total thickness of the TASC is about 27 X 0 at normal incidence. In order to identify individual chemical elements in the cosmic-ray flux, a Charge Detector (CHD) is positioned at the top of the CALET instrument to provide a measurement of the electric charge [1,2,3]. Calibration and test of the instrument took place at CERN SPS during five campaigns in 2010, 2011, 2012, 2013 and 2015 with beams of electrons, protons and relativistic ions. ...
... Using the dedicated CHarge Detector (CHD) on top of the instrument, a charge resolution of 0.15 -0.3 charge units has been demonstrated [2,3]. Nevertheless, a redundant measurement of the charge of the incident particle is of great importance. ...
... The calibration of each channel of CHD, IMC and TASC is performed using penetrating protons and He particles, selected in-flight with a dedicated trigger mode (Asaoka et al., 2017;Niita et al., 2015). Raw data are corrected for gain differences among the channels, light output nonuniformity, and any residual dependence on time and temperature. ...
... Detailed Monte Carlo (MC) simulations have been performed, based on the EPICS simulation package [46,47]. In order to assess the relatively large uncertainties in the modeling of hadronic interactions, a series of beam tests were carried out at the CERN-SPS using the CALET beam test model [48][49][50]. Trigger efficiency and energy response derived from MC simulations were tuned using the beam test results obtained in 2015 with ion beams of 13, 19, and 150 GeV=n. For helium nuclei a shower energy correction of 10.4% (8%) at 13ð19Þ GeV=n was applied, while a 3.2% energy independent correction was applied at 150 GeV=n and above. ...
We present the results of a direct measurement of the cosmic-ray helium spectrum with the CALET instrument in operation on the International Space Station since 2015. The observation period covered by this analysis spans from October 13, 2015, to April 30, 2022 (2392 days). The very wide dynamic range of CALET allowed for the collection of helium data over a large energy interval, from ∼40 GeV to ∼250 TeV, for the first time with a single instrument in low Earth orbit. The measured spectrum shows evidence of a deviation of the flux from a single power law by more than 8σ with a progressive spectral hardening from a few hundred GeV to a few tens of TeV. This result is consistent with the data reported by space instruments including PAMELA, AMS-02, and DAMPE and balloon instruments including CREAM. At higher energy we report the onset of a softening of the helium spectrum around 30 TeV (total kinetic energy). Though affected by large uncertainties in the highest energy bins, the observation of a flux reduction turns out to be consistent with the most recent results of DAMPE. A double broken power law is found to fit simultaneously both spectral features: the hardening (at lower energy) and the softening (at higher energy). A measurement of the proton to helium flux ratio in the energy range from 60 GeV/n to about 60 TeV/n is also presented, using the CALET proton flux recently updated with higher statistics.
... Many space-borne experiments, such as AMS-02 [1], PAMELA [2], CALET [3], Fermi-LAT [4], measured galactic CR fluxes which are important in understanding their origin and propagation mechanisms. DAMPE is a satellite-based general-purpose high energy particle detector. ...
... Raw data are corrected for nonuniformity in light output, time and temperature dependence, and gain differences among the channels. The latter are individually calibrated on orbit by using penetrating proton and He particles, selected by a dedicated trigger mode [34,35]. After calibrations, each CR particle track is reconstructed and a charge and an energy are assigned for each event. ...
In this paper, we present the measurement of the energy spectra of carbon and oxygen in cosmic rays based on observations with the Calorimetric Electron Telescope on the International Space Station from October 2015 to October 2019. Analysis, including the detailed assessment of systematic uncertainties, and results are reported. The energy spectra are measured in kinetic energy per nucleon from 10 GeV/n to 2.2 TeV/n with an all-calorimetric instrument with a total thickness corresponding to 1.3 nuclear interaction length. The observed carbon and oxygen fluxes show a spectral index change of ∼0.15 around 200 GeV/n established with a significance >3σ. They have the same energy dependence with a constant C/O flux ratio 0.911±0.006 above 25 GeV/n. The spectral hardening is consistent with that measured by AMS-02, but the absolute normalization of the flux is about 27% lower, though in agreement with observations from previous experiments including the PAMELA spectrometer and the calorimetric balloon-borne experiment CREAM.
... HERE are some space-borne experiments (AMS [1], Fermi-LAT [2], PAMELA [3], CALET [4]) to search for evidence of dark matter by measuring the spectra of photons, electrons and positrons. Exciting results from the successful operation of these experiments have been published [5][6][7][8]. ...
The DArk Matter Particle Explorer (DAMPE) developed in China was designed to search for evidence of dark matter particles by observing primary cosmic rays and gamma rays in the energy range from 5 GeV to 10 TeV. Since its launch in December 2015, a large quantity of data has been recorded. With the data set acquired during more than a year of operation in space, a precise time-dependent calibration for the energy measured by the BGO ECAL has been developed. In this report, the instrumentation and development of the BGO Electromagnetic Calorimeter (BGO ECAL) are briefly described. The calibration on orbit, including that of the pedestal, attenuation length, minimum ionizing particle peak, and dynode ratio, is discussed, and additional details about the calibration methods and performance in space are presented.
... The reduced accuracy with which the energy deposit can be determined below 10 GeV is due to pedestal noise. As reported in detail in Ref. [4], the requirements for the calibration error of each TASC log can be relaxed by a factor of ∼3 compared to that for the energy resolution, as long as these individual errors of in total ∼6% are randomly distributed. This is due to the fact that, on average, ∼10 TASC logs contribute significantly to an event's energy measurement. ...
... Yosui Akaike event rate. Details are described in the reference [12], so we present here just an outline. ...
... Combining these components as well as the trigger system, data acquisition system and support sensors described in the following sections, the CALET detector features (1) a proton rejection factor of more than 10 5 , (2) a 2% energy resolution above 30 GeV, (3) an angular resolution of 0.1 to 0.5 • , and (4) a large geometrical factor on the order of 0.1 m 2 sr. The basic features of detector performance were investigated using Monte Carlo (MC) simulations [7], and verified by the beam tests at CERN-SPS [8][9][10]. The sufficiently high rejection capability of protons enables the suppression of systematic errors in the electron spectrum due to uncertainties in proton rejection factor calculation due to pos-sible interaction model dependence. ...
The CALorimetric Electron Telescope (CALET), launched for installation on the International Space Station (ISS) in August, 2015, has been accumulating scientific data since October, 2015. CALET is intended to perform long-duration observations of high-energy cosmic rays onboard the ISS. CALET directly measures the cosmic-ray electron spectrum in the energy range of 1 GeV to 20 TeV with a 2% energy resolution above 30 GeV. In addition, the instrument can measure the spectrum of gamma rays well into the TeV range, and the spectra of protons and nuclei up to a PeV.
In order to operate the CALET onboard ISS, JAXA Ground Support Equipment (JAXA-GSE) and the Waseda CALET Operations Center (WCOC) have been established at JAXA and Waseda University, respectively. Scientific operations using CALET are planned at WCOC, taking into account orbital variations of geomagnetic rigidity cutoff. Scheduled command sequences are used to control the CALET observation modes on orbit. Calibration data acquisition by, for example, recording pedestal and penetrating particle events, a low-energy electron trigger mode operating at high geomagnetic latitude, a low-energy gamma-ray trigger mode operating at low geomagnetic latitude, and an ultra heavy trigger mode, are scheduled around the ISS orbit while maintaining maximum exposure to high-energy electrons and other high-energy shower events by always having the high-energy trigger mode active. The WCOC also prepares and distributes CALET flight data to collaborators in Italy and the United States.
As of August 31, 2017, the total observation time is 689 days with a live time fraction of the total time of ∼ 84%. Nearly 450 million events are collected with a high-energy (E > 10 GeV) trigger. In addition, calibration data acquisition and low-energy trigger modes, as well as an ultra-heavy trigger mode, are consistently scheduled around the ISS orbit. By combining all operation modes with the excellent-quality on-orbit data collected thus far, it is expected that a five-year observation period will provide a wealth of new and interesting results.
... Detailed calibration achieved a fine energy resolution of 2% or better in the energy region from 20 GeV to 20 TeV (<3% for 10-20 GeV). The validity of our simulation has been checked with beam test data [23][24][25]. Regarding temporal variations occurring during long-term observations, each detector component is calibrated by modeling variations of the minimum ionizing particles (MIP) peak obtained from noninteracting particles (protons or helium) recorded with a dedicated trigger mode. ...
First results of a cosmic-ray electron and positron spectrum from 10 GeV to 3 TeV is presented based upon observations with the CALET instrument on the International Space Station starting in October, 2015. Nearly a half million electron and positron events are included in the analysis. CALET is an all-calorimetric instrument with total vertical thickness of 30 X0 and a fine imaging capability designed to achieve a large proton rejection and excellent energy resolution well into the TeV energy region. The observed energy spectrum over 30 GeV can be fit with a single power law with a spectral index of −3.152±0.016 (stat+syst). Possible structure observed above 100 GeV requires further investigation with increased statistics and refined data analysis.
The relative abundance of cosmic ray nickel nuclei with respect to iron is by far larger than for all other transiron elements; therefore it provides a favorable opportunity for a low background measurement of its spectrum. Since nickel, as well as iron, is one of the most stable nuclei, the nickel energy spectrum and its relative abundance with respect to iron provide important information to estimate the abundances at the cosmic ray source and to model the Galactic propagation of heavy nuclei. However, only a few direct measurements of cosmic-ray nickel at energy larger than ∼3 GeV/n are available at present in the literature, and they are affected by strong limitations in both energy reach and statistics. In this Letter, we present a measurement of the differential energy spectrum of nickel in the energy range from 8.8 to 240 GeV/n, carried out with unprecedented precision by the Calorimetric Electron Telescope (CALET) in operation on the International Space Station since 2015. The CALET instrument can identify individual nuclear species via a measurement of their electric charge with a dynamic range extending far beyond iron (up to atomic number Z=40). The particle's energy is measured by a homogeneous calorimeter (1.2 proton interaction lengths, 27 radiation lengths) preceded by a thin imaging section (3 radiation lengths) providing tracking and energy sampling. This Letter follows our previous measurement of the iron spectrum [1O. Adriani et al. (CALET Collaboration), Phys. Rev. Lett. 126, 241101 (2021).PRLTAO0031-900710.1103/PhysRevLett.126.241101], and it extends our investigation on the energy dependence of the spectral index of heavy elements. It reports the analysis of nickel data collected from November 2015 to May 2021 and a detailed assessment of the systematic uncertainties. In the region from 20 to 240 GeV/n our present data are compatible within the errors with a single power law with spectral index -2.51±0.07.
The bismuth germanium oxide (BGO) electromagnetic calorimeter, which is characterized by a large detection energy range of 5 GeV–10 TeV for high-energy cosmic-ray electrons/positrons (CREs) and γ-rays, is the key sub-detector of the Dark Matter Particle Explorer (DAMPE). A careful and comprehensive calibration is essential for conducting accurate detector energy measurement. In this study, we present a method based on the ATmospheric Muon Neutrino Calculation 3-dimensional version (ATMNC3) software package, which achieves a stable and homogenous inter-calibration in orbit for the DAMPE calorimeter.
The CALorimetric Electron Telescope (CALET) is a space mission installed on the International Space Station (ISS) in August 2015. In addition to high precision measurements of the electron spectrum up to TeV scale, CALET will also investigate the mechanism of cosmic-ray (CR) acceleration and propagation in the Galaxy, by performing direct measurements of the energy spectra and elemental composition of CR nuclei from H to Fe, and the abundance of trans-iron elements up to about Z = 40. The instrument consists of two layers of segmented plastic scintillators to identify the particle charge, a thin (3 radiation lengths) tungsten-scintillating fiber calorimeter providing accurate particle tracking, and a thick (27 radiation lengths) calorimeter made of lead-tungstate crystal logs. In this paper, we discuss the analysis procedure developed to reconstruct and select carbon and oxygen nuclei in cosmic rays and present the preliminary measurement of their energy spectra based on the analysis of the data collected from October 2015 to February 2018.
The DArk Matter Particle Explorer (DAMPE) developed in China was designed to search for evidence of dark matter particles by observing primary cosmic rays and gamma rays in the energy range from 5 GeV to 10 TeV. Since its launch in December 2015, a large quantity of data has been recorded. With the data set acquired during more than a year of operation in space, a precise time-dependent calibration for the energy measured by the BGO ECAL has been developed. In this report, the instrumentation and development of the BGO Electromagnetic Calorimeter (BGO ECAL) are briefly described. The calibration on orbit, including that of the pedestal, attenuation length, minimum ionizing particle peak, and dynode ratio, is discussed, and additional details about the calibration methods and performance in space are presented.
A satellite-borne, high energy cosmic ray detector, named the DArk Matter Particle Explorer (DAMPE), was developed in China. The major scientific objectives of the DAMPE mission are observing primary cosmic rays and gamma rays in an energy range from 5 GeV to 10 TeV, to find evidence of the existence of dark matter particle. An electromagnetic calorimeter(ECAL), which contains 308 Bismuth Germanate(BGO) crystal bars, has been built for the DAMPE mission. The performance of 60-cm long BGO crystal bars has been studied with cosmic rays. Electron and ion beam test results of the BGO ECAL are also presented in this paper.
A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200 GeV the positron fraction no longer exhibits an increase with energy.
The Alpha Magnetic Spectrometer experiment onboard the International Space Station has recently provided cosmic ray electron and positron data with unprecedented precision in the range from 0.5 to 350 GeV. The observed rise in the positron fraction at energies above 10 GeV remains unexplained, with proposed solutions ranging from local pulsars to TeV-scale dark matter. Here, we make use of this high quality data to place stringent limits on dark matter with masses below ∼300 GeV, annihilating or decaying to leptonic final states, essentially independent of the origin of this rise. We significantly improve on existing constraints, in some cases by up to 2 orders of magnitude.
The rise of the cosmic ray positron fraction with energy, as first observed
with high confidence by PAMELA, implies that a large flux of high energy
positrons has been recently (or is being currently) injected into the local
volume of the Milky Way. With the new and much more precise measurement of the
positron fraction recently provided by AMS, we revisit the question of the
origin of these high energy positrons. We find that while some dark matter
models (annihilating directly to electrons or muons) no longer appear to be
capable of accommodating these data, other models in which ~1-3 TeV dark matter
particles annihilate to unstable intermediate states could still be responsible
for the observed signal. Nearby pulsars also remain capable of explaining the
observed positron fraction. Future measurements of the positron fraction by AMS
(using a larger data set), combined with their anticipated measurements of
various cosmic ray secondary-to-primary ratios, may enable us to further
discriminate between these remaining scenarios.
While the Vela pulsar and its associated nebula are often considered as the archetype of a system powered by a ~104 year old isolated neutron star, many features of the spectral energy distribution of this pulsar wind nebula (PWN) are both puzzling and unusual. Here we develop a model that for the first time relates the main structures in the system, the extended radio nebula (ERN) and the X-ray cocoon through continuous injection of particles with a fixed spectral shape. We argue that diffusive escape of particles from the ERN can explain the steep Fermi-LAT spectrum. In this scenario Vela X should produce a distinct feature in the locally measured cosmic ray (CR) electron spectrum at very high energies. This prediction can be tested in the future using the Cherenkov Telescope Array. If particles are indeed released early in the evolution of PWNe and can avoid severe adiabatic losses, PWN provides a natural explanation for the rising positron fraction in the local CR spectrum.
We report cosmic-ray proton and helium spectra in energy ranges of 1-120 GeV nucleon-1 and 1-54 GeV nucleon-1, respectively, measured by a flight of the Balloon-borne Experiment with Superconducting Spectrometer (BESS) in 1998. The magnetic rigidity of the cosmic ray was reliably determined by highly precise measurement of the circular track in a uniform solenoidal magnetic field of 1 T. Those spectra were determined within overall uncertainties of ±5% for protons and ±10% for helium nuclei including statistical and systematic errors.
Precision measurements of the electron component in the cosmic radiation provide important information about the origin and propagation of cosmic rays in the Galaxy. Here we present new results regarding negatively charged electrons between 1 and 625 GeV performed by the satellite-borne experiment PAMELA. This is the first time that cosmic-ray e⁻ have been identified above 50 GeV. The electron spectrum can be described with a single power-law energy dependence with spectral index -3.18 ± 0.05 above the energy region influenced by the solar wind (> 30 GeV). No significant spectral features are observed and the data can be interpreted in terms of conventional diffusive propagation models. However, the data are also consistent with models including new cosmic-ray sources that could explain the rise in the positron fraction.
One of the most essential but uncertain processes for producing cosmic-rays
(CRs) and their spectra is how accelerated particles escape into the
interstellar space. We propose that the CR electron spectra at >~TeV energy can
provide a direct probe of the CR escape complementary to the CR nuclei and
gamma-rays. We calculate the electron spectra from a young pulsar embedded in
the supernova remnant (SNR), like Vela, taking into account the
energy-dependent CR escape. SNRs would accelerate and hence confine particles
with energy up to 10^{15.5}eV. Only energetic particles can escape first, while
the lower energy particles are confined and released later. Then the observed
electron spectrum should have a low energy cutoff whose position marks the age
of the pulsar/SNR. The low energy cutoff is observable in the $\gtrsim {\rm
TeV}$ energy window, where other contaminating sources are expected to be few
due to the fast cooling of electrons. The spectrum looks similar to a dark
matter annihilation line if the low energy cutoff is close to the high energy
intrinsic or cooling break. The future experiments such as CALET and CTA are
capable of directly detecting the CR escape features toward revealing the
origin of CRs.
Evidences of non-thermal X-ray emission and TeV gamma-rays from the supernova remnants (SNRs) has strengthened the hypothesis that primary Galactic cosmic-ray electrons are accelerated in SNRs. High energy electrons lose energy via synchrotron and inverse Compton processes during propagation in the Galaxy. Due to these radiative losses, TeV electrons liberated from SNRs at distances larger than ~1 kpc, or times older than ~10^5 yr, cannot reach the solar system. We investigated the cosmic-ray electron spectrum observed in the solar system using an analytical method, and considered several candidate sources among nearby SNRs which may contribute to the high energy electron flux. Especially, we discuss the effects for the release time from SNRs after the explosion, as well as the deviation of a source spectrum from a simple power-law. From this calculation, we found that some nearby sources such as the Vela, Cygnus Loop, or Monogem could leave unique signatures in the form of identifiable structure in the energy spectrum of TeV electrons and show anisotropies towards the sources, depending on when the electrons are liberated from the remnant. This suggests that, in addition to providing information on the mechanisms of acceleration and propagation of cosmic-rays, specific cosmic-ray sources can be identified through the precise electron observation in the TeV region. Comment: 32 pages, 6 figures, submitted to ApJ
This biennial review summarizes much of Particle Physics. Using data from previous editions, plus 1900 new measurements from 700 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review.
We have revised the calculation of the flux of atmospheric neutrinos based on a three-dimensional scheme with the realistic IGRF geomagnetic model. The primary flux model has been revised, based on the AMS and BESS observations, and the interaction model updated to DPMJET-III. With a fast simulation code and computer system, the statistical errors in the Monte Carlo study are negligible. We estimate the total uncertainty of the atmospheric neutrino flux prediction is reduced to ≲10 % below 10 GeV. The ``three-dimensional effects'' are found to be almost the same as the study with the dipole magnetic field, but the muon-curvature effect remains up to a few tens of GeV for horizontal directions. The uncertainty of the absolute normalization of the atmospheric neutrino is still large, above 10 GeV, due to the uncertainty of the primary cosmic ray flux above 100 GeV. However, the zenith angle variation is not affected by these uncertainties.
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CALET is a detector planned to be on-board the Japanese Experiment Module Exposed Facility (JEM-EF) of the International Space Station. The CALET mission aims at revealing unsolved problems in high energy phenomena of the Universe by carrying out a precise measurement of the high energy electrons in 1 GeV–20 TeV, the gamma-rays in 20 MeV to a few TeV and the nuclei in a few 10 GeV–1000 TeV. The main detector is composed of imaging calorimeter (IMC), total absorption calorimeter (TASC), silicon pixel array (SIA) and anti-coincidence detector (ACD) to detect various kinds of particles in very wide energy range. The total absorber thickness is 31 radiation lengths for electromagnetic particles and 1.4 interaction mean free paths for protons. Monte Carlo simulation study has been carried out for optimization of the detector performance in observing each kind of particles. We obtained following performance about the observation of very high energy (>100 GeV) electrons, which is a main target of the CALET experiment: (1) Effective geometrical factor is about 7000 cm2 sr. (2) Energy resolution is better than a few %. (3) Angular resolution is better than 0.1°. (4) Proton rejection power is ∼105 with the electron detection efficiency better than 95%. We also present the simulated performance of the CALET experiment in observing other particles.
The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight STS-91 (June 1998) in a 51.7° orbit at altitudes between 320 and 390km.
A search for antihelium nuclei in the rigidity range 1-140GV was performed. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of <1.1×1E-6 was obtained.
The high energy proton, electron, positron, helium, antiproton and deuterium spectra were accurately measured.
For each particle and nuclei two distinct spectra were observed: a higher energy spectrum and a substantial second spectrum. Positrons in the second spectrum were found to be much more abundant than electrons. Tracing particles from the second spectra shows that most of them travel for an extended period of time in the geomagnetic field, and that the positive particles (p and e+) and negative ones (e-) originate from two complementary geographic regions. The second helium spectrum flux over the energy range 0.1-1.2GeV/nucleon was measured to be (6.3+/-0.9)×10^-3(m^2ssr)^-1. Over 90 percent of the helium flux was determined to be 3He at the 90% confidence level.
Galactic cosmic ray scattering and energy loss through solar wind interaction