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Cosmic-ray electron spectrum above 100GeV from PPB-BETS experiment in Antarctica

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Abstract

Cosmic-ray electrons have been observed in the energy region from 10 GeV to 1 TeV with the PPB-BETS by a long duration balloon flight using a Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an average altitude of 35 km in January 2004. The PPB-BETS detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead plates. In the study of cosmic-ray electrons, there have been some suggestions that high-energy electrons above 100 GeV are a powerful probe to identify nearby cosmic-ray sources and search for particle dark matter. In this paper, we present the energy spectrum of cosmic-ray electrons in the energy range from 100 GeV to 1 TeV at the top of atmosphere, and compare our spectrum with the results from other experiments.

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... However, it had the merit of extending the energy spectrum measurements far beyond the range accessible to the first category. Examples include the balloon-borne experiments ECC [16], BETS [17], ATIC-2 [18] and PPB-BETS [19]. Moreover, the groundbased Cerenkov telescopes H.E.S.S. [20] and MAGIC [21] also observed cosmic-ray electrons at very high energy. ...
... In parallel, ATIC reported an excess of cosmic-ray electrons over conventional model expectations between 300 and 800 GeV followed by a steepening above 1 TeV [30,31]. Although PPB-BETS also showed a bump-like structure between 100 and 700 GeV [19], Fermi-LAT and H.E.S.S. experiments found no evidence for a prominent peak [32][33][34]. ...
... The novelty here, as aforementioned, is that we used a pure Monte Carlo treatment of the propagation of HECREs from nearby single sources, instead of solving transport equations. [29,106,107], PAMELA [24,108], Fermi-LAT [25,33], AMS-01 [15], ATIC [30], ECC [16], HESS [20,34] and PPB-BETS [19]. ...
Preprint
High-energy cosmic-ray electrons reveal some remarkable spectral features, the most noteworthy of which is the rise in the positron fraction above 10~GeV. Due to strong energy loss during propagation, these particles can reach Earth only from nearby sources. Yet, the exact nature of these sources, which most likely manifest themselves in the observed anomalies, remains elusive. The many explanations put forward to resolve this case range from standard astrophysics to exotic physics. In this paper, we discuss the possible astrophysical origin of high-energy cosmic-ray electrons through a fully three-dimensional time-dependent Monte Carlo simulation. This approach, which takes advantage of the intrinsic random nature of cosmic-ray diffusive propagation, provides valuable information on the electron-by-electron fluctuations, making it particularly suitable for analyzing in depth the single-source scenario.
... Over the last few years a large amount of new high-precision experimental data related to primary electrons and positrons in cosmic rays was obtained in the experiments of a new generation: PPB-BETS [1], ATIC [2,3], PAMELA [4,5,6], Fermi/LAT [7,8,9], H.E.S.S. [10], MAGIC [11]. Some observed features of the data were unexpected and, now compared to the beginning of the 2000's, the situation looks very exciting and intriguing. ...
... In 2007, the data from the Antarctic PPB-BETS experiment was presented at the 30th International Cosmic Ray Conference and published in 2008 [1,36] (see Figure 4). The PPB-BETS spectrum demonstrated, also, a bump-like structure between 100 and 700 GeV which was contradictory to the expectation of the conventional model. ...
... Later, even before 2000, this question was studied several times [85,86,87,88] and hundreds of papers were published following ATIC and PAMELA results. In the electron spectrum, the bump-like feature was considered to be a possible signature of WIMPs annihilation to the electron-positron pairs already in the PPB-BETS paper [1]. However, it was noticed that the statistics were too low to make definite conclusions. ...
Preprint
This review concentrates on the results obtained, over the last ten years, on the astrophysics of high-energy cosmic ray electrons and positrons. The anomalies, observed in the data of recent experiments (possible bump in the electron spectrum and the PAMELA anomaly in the positron fraction) are discussed through the systematic use of simple analytical solutions of the transport equations for cosmic ray electrons. Three main ways of explaining the origin of the anomalies are considered: the conservative way supposing the positrons to be pure secondary particles; the nearby sources like pulsars origin; and the dark matter origin. This review discusses, also, the inability to select the pulsars model or the dark matter model to explain the electron anomalies on the basis of the electron spectra with the usual large energy binning (15\gtrsim15%). It is argued that the signature of nearby pulsars origin of the anomalies against the dark matter origin could be the fine structure of the cosmic ray electron spectrum predicted in the Malyshev et al. paper (2009) and which was observed in the data from the high-resolution ATIC experiment (2009-2011). To date, the high-resolution ATIC data was the only experimental result of this type published in the literature. Therefore, they should be tested by other experiments as soon as possible. Generally, there is, also, rather controversial situations between the data of the majority of recent experiments and, consequently, there is a noted urgent need for new high-precision and high-statistical experiments.
... However, it had the merit of extending the energy spectrum measurements far beyond the range accessible to the first category. Examples include the balloon-borne experiments ECC [16], BETS [17], ATIC-2 [18] and PPB-BETS [19]. Moreover, the ground-based Cerenkov telescopes H.E.S.S. [20] and MAGIC [21] also observed cosmic-ray electrons at very high energy. ...
... In parallel, ATIC reported an excess of cosmic-ray electrons over conventional model expectations between 300 and 800 GeV followed by a steepening above 1 TeV [30,31]. Although PPB-BETS also showed a bump-like structure between 100 and 700 GeV [19], Fermi-LAT and H.E.S.S. experiments found no evidence for a prominent peak [32][33][34]. ...
... It should be stressed here that we used in all these calculations the same combination of the free injection parameters (γ = 2, E cut = 2 TeV, and ηW = 4 × 10 46 erg). The other sources, like B1822-09 and Geminga, also reproduce the [29,106,107], PAMELA [24,108], Fermi-LAT [25,33], AMS-01 [15], ATIC [30], ECC [16], HESS [20,34] and PPB-BETS [19]. observed spectra after, of course, tuning the injection parameters. ...
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High-energy cosmic-ray electrons reveal some remarkable spectral features, the most noteworthy of which is the rise in the positron fraction above 10 GeV. Due to strong energy loss during propagation, these particles can reach Earth only from nearby sources. Yet, the exact nature of these sources, which most likely manifest themselves in the observed anomalies, remains elusive. The many explanations put forward to resolve this case range from standard astrophysics to exotic physics. In this paper, we discuss the possible astrophysical origin of high-energy cosmic-ray electrons through a fully three-dimensional time-dependent Monte Carlo simulation. This approach takes advantage of the intrinsic random nature of cosmic-ray diffusive propagation. It provides valuable information on the electron-by-electron fluctuations, making it particularly suitable for analyzing in depth the single-source astrophysical scenario.
... The best fit to each observable is shown as a solid line, embedded in its 3σ uncertainty band. The result of the analysis shows a quite remarkable agreement with AMS-02 data: this is confirmed by the value of the best-fit chi-squared: Together with our theoretical model, data from AMS-02 [6][7][8], Fermi-LAT [4,5], Pamela [1][2][3], Heat [174][175][176][177], Caprice [178,179], Bets [180,181] and Hess experiments [44,182] are reported. and, in turn, the positron fraction; at lower energies, far SRN are dominating the flux of electrons and of (e + + e − ) (this occurs for energies below about 100 GeV), while secondaries determine the positron flux and the positron fraction (for energies below 10-20 GeV). ...
... By using the calculated fluxes Φ a i (i = 1, . . . , 4 counts the energy bins, a counts the PWN in Fig. 3. Together with our theoretical model, data from AMS-02 [6][7][8], Fermi-LAT [4,5], Pamela [1][2][3], Heat [174][175][176][177], Caprice [178,179], Bets [180,181] and Hess experiments [44,182] are reported. ...
... The fit is performed on all the AMS-02 data simultaneously and the result shown in the figure refers to best-fit configuration for the 5+1 efficiences and the 5+1 spectra indexes. The colors and styles of the lines are the same as in Fig. 3. Together with our theoretical model, data from AMS-02 [6][7][8], Fermi-LAT [4,5], Pamela [1][2][3], Heat [174][175][176][177], Caprice [178,179], Bets [180,181] and Hess experiments [44,182] are reported. modelings and the whole set of AMS-02 data. ...
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We perform a combined analysis of the recent AMS-02 data on electrons, positrons, electrons plus positrons and positron fraction, in a self-consistent framework where we realize a theoretical modeling of all the astrophysical components that can contribute to the observed fluxes in the whole energy range. The primary electron contribution is modeled through the sum of an average flux from distant sources and the fluxes from the local supernova remnants in the Green catalog. The secondary electron and positron fluxes originate from interactions on the interstellar medium of primary cosmic rays, for which we derive a novel determination by using AMS-02 proton and helium data. Primary positrons and electrons from pulsar wind nebulae in the ATNF catalog are included and studied in terms of their most significant (while loosely known) properties and under different assumptions (average contribution from the whole catalog, single dominant pulsar, a few dominant pulsars). We obtain a remarkable agreement between our various modeling and the AMS-02 data for all types of analysis, demonstrating that the whole AMS-02 leptonic data admit a self-consistent interpretation in terms of astrophysical contributions.
... In last few years, many experiments like PAMELA [30,31] have reported the excess in the positron flux (i.e., flux ratio of positron to sum of electron and positron) without any significant excess inp channel (i.e., flux ratio of protons to anti-protons). The peaks in e + e − channel are also observed in ATIC [32] and PPB-BETS [33] balloon experiments at around 1 TeV and 500 GeV respectively. Recently, Dark Matter Particle Explorer (DAMPE) experiment [34] has also observed a sharp peak around ∼ 1.4 TeV favoring the lepto-philic -1 -DM annihilation cross-section of the order of 10 −26 cm 3 /s. ...
... The recent constraints derived from the observation on the dwarf spheroidal satellite galaxies in Fermi-LAT [24][25][26], excess in electron/positron channel around 10 GeV at PAMELA -16 - [30,31], excess in flux of electrons/positrons around 400-500 GeV at ATIC [32] and PPB-BETS [33] balloon experiments and exclusion of quark channels by AMS-02 data [28,29] hints toward the existence of non-baryonic DM. This implies that the direct detection experiments have to be sensitive on the recoil momentum of the atom or an electron in DMatom and/ or DM -electron scattering respectively due to suppressed loop-level interactions of DM with the quarks in the nucleon. ...
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We study the effective interactions of the fermionic, scalar and vector dark matter (DM) with leptons and neutral electroweak gauge Bosons induced by the higher dimensional effective twist-2 tensor operators. We constrain these lepto-philic, τ±\tau^\pm-philic and U(1)YU(1)_Y gauge Boson B-philic effective interactions of DM with the visible world from the WMAP and Planck data. The thermally averaged indirect DM pair annihilation cross-section and the DM-electron direct-detection cross-section for such DM candidates are observed to be consistent with the respective experimental data. Constraining coefficients of the effective operators from the low energy LEP data for the DM \le 80 GeV, we further study their sensitivities in the pair production of such DM \ge 50 GeV in association with mono-photon at the proposed ILC and perform the χ2\chi^2 analysis to obtain the 99.73\% C.L. acceptance contours in the mDMΛeffm_{\rm DM}-\Lambda_{\rm eff} plane from the two dimensional differential distributions of the kinematic observables. We observe that ILC has rich potential to probe the contribution of such effective operators.
... The most interesting topic in this region is an excess compared to a pure powerlaw spectrum. Balloon-borne calorimeter experiments such as ATIC (Chang et al., 2008) and PPB-BETS (Yoshida et al., 2008) observed several extra events in (e À + e + ) spectrum at 300-800 GeV region. Fermi/LAT also observed an excess in (e À + e + ) spectrum (Ackermann et al., 2010), though it was not as distinct as the results of earlier balloon experiments. ...
... We used the data collected in the first half of the observation (trigger threshold: 1 GeV) for the points below 10 GeV, while the other points are derived from the data collected in the second half of the observation (trigger threshold: 5 GeV). For the Monte Carlo estimation we adopted the data of BETS and PPB-BETS (Yoshida et al., 2008) for electrons, AMS-01 (Alcaraz et al., 2000a,b) for protons and helium nuclei, HEAO (Engelmann et al., 1990), ATIC (Panov et al., 2006) and CRN (Mü ller et al., 1991) for other nuclei. We calculated the interaction of these cosmic-rays in the atmosphere with COSMOS, 2 choosing IGRF 2005 3 as geomagnetic field model and US-standard 1976 4 as atmospheric structure model. ...
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... The results of those analyses are consistent with the results presented here. The flux multiplied byẼ 3 is presented in Fig. 3, together with previous measurements [11][12][13][14][15][16][17]. Below ∼10 GeV, the behavior of Φðe þ þ e − Þ is affected by solar modulation. ...
... ðenergyscaleÞ. Also shown are the results from earlier experiments [11][12][13][14][15][16][17]. ...
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... MeV (37) and plotted in figure 33. ...
... . Absolute energy scale Unlike the point-spread function, the absolute energy scale is notoriously difficult to calibrate in orbit due to36 In a sense, there is no such thing as a point source, but in practice the actual angular size for many gamma-ray sources is much (much) smaller than PSF one can realistically achieved.37 Technically, the position is measured at other wavelengths with a much greater accuracy than that achievable in gamma rays, which allows to calibrate not only the point-spread function, but also the absolute pointing accuracy in the sky. ...
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Prepared for the 2014 ISAPP summer school, this review is focused on space-borne and balloon-borne cosmic-ray and gamma-ray detectors. It is meant to introduce the fundamental concepts necessary to understand the instrument performance metrics, how they tie to the design choices and how they can be effectively used in sensitivity studies. While the write-up does not aim at being complete or exhaustive, it is largely self-contained in that related topics such as the basic physical processes governing the interaction of radiation with matter and the near-Earth environment are briefly reviewed.
... Direct measurements of electron and positron cosmic rays (CRs) have been pioneered by various teams such as BETS (Torii et al. 2001), HEAT (DuVernois et al. 2001), ATIC (Chang et al. 2008), PPB-BETS (Yoshida et al. 2008), and PAMELA (Adriani et al. 2011). Recently, the electron and positron CR study (total CR flux, not distinguishing their charge signs) has been greatly advanced with new instruments such as AMS-02 (Aguilar et al. , 2019, Fermi-LAT (Abdollahi et al. 2017), the Calorimetric Electron Telescope (CALET; Adriani et al. 2017Adriani et al. , 2018Torii & Akaike 2021), and DAMPE (Ambrosi et al. 2017). ...
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... The indirect experiments such as FermiLAT [17][18][19], HESS [20], AMS-02 [21,22] etc. are looking for the evidence of excess cosmic rays produced in the DM annihilation to Standard Model (SM) particles photons, leptons, bb and gauge boson pairs etc. Experiments like PAMELA [23,24] in the last several years have reported an excess in the positron flux without any significant excess in the proton to antiproton flux. The peaks in e + e − channel are also observed in ATIC [25] and PPB-BETS [26] balloon experiments at around 1 TeV and 500 GeV respectively. Recently, Dark Matter Particle Explorer (DAMPE) experiment [27] has also observed a sharp peak around ∼ 1.4 TeV favouring the lepto-philic DM annihilation cross-section of the order of 10 −26 cm 3 /s. ...
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... Experiments like PAMELA [23,24] in the last several years have reported an excess in the positron flux without any significant excess in the proton to antiproton flux. The peaks in e + e − channel are also observed in ATIC [25] and PPB-BETS [26] balloon experiments at around 1 TeV and 500 GeV respectively. Recently, Dark Matter Particle Explorer (DAMPE) experiment [27] has also observed a sharp peak around ∼ 1.4 TeV favouring the lepto-philic DM annihilation cross-section of the order of 10 −26 cm 3 /s. ...
Preprint
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... A broad quasi-peak in the (e + + e -) CR spectrum in the vicinity of ~700 GeV was first reliably detected in the ATIC balloon experiment [1] and later confirmed in the PPB-BETS balloon experiment [2]. Considerable changes in the electron (e -) and positron (e + ) CR spectra were subsequently detected in the PAMELA [3][4][5], Fermi-LAT [6,7], and AMS-02 [8,9] satellite experiments. ...
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... On the other hand, ATIC reported an excess of cosmic-ray electrons between 300 and 600 GeV [6,7]. PPB-BETS also showed a similar bump-like structure between 100 and 700 GeV [8]. ...
... Positron fraction in the energy range 0.5 -500 GeV (top-left), all-electron flux in the range 0.5 -1000 GeV (top-right), electron flux in the range 0.5 -700 GeV (bottom-left) and positron flux in the range 0.5 -700 GeV (bottom-right), as measured by the AMS02 experiment. The results from previous experiments are reported for comparison,[12,14,[18][19][20][21][22][23][24][25][26][27][28]. ...
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... No single gamma-ray observatory provides a complete picture of the gamma-ray sky at all energies and spatial scales. The Fermi Gamma-ray Space Telescope (Fermi LAT) can map the entire gamma-ray sky between 300 MeV and 500 GeV over all spatial scales, with an angular resolution that ranges from 0.1 • to 1 • depending Figure 1: Comparison to extant data from AMS-02 [4], Fermi LAT [5], ATIC [6], HEAT [7], CAPRICE [8], BETS [9], and H.E.S.S. [10] of a model considering contributions to the e ± flux from the following categories: e − from distant (> 3 kpc) SNRs (dot-dashed yellow) and local SNRs (dotted green), secondary e ± (long dashed red) and e ± from PWNe (short dashed blue). The model is derived from a simultaneous fit to all AMS-02 data. ...
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... The resolution of incident electron energy is expected below 4% above 10GeV (Fig.7). It is expected that it improves more than PPB-BETS(12∼20%) [3] and BETS(14∼17%). Because bCALET has TASC that is thick active caloriemeter, it is effective not only the energy determine, but also the rejection of proton event at the off-line analysis. ...
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... Interestingly PAMELA's data show a clear feature of such a positron excess but no excess in the anti-protons [3]. While ATIC [4] and PPB-BETS [5] reported unexpected structure in the all-electron spectrum in the range 100 GeV- 1 TeV, the picture has changed with the higher-statistics measurements by Fermi-LAT [6] and HESS [7], leading to a possible slight additional unknown component in the CR e ± flux over and above the standard astrophysical model predictions, like for instance the specific Moskalenko and Strong [8] [9] one. These interesting features have drawn much attention, and many explanations have been proposed: For example, these excesses could be due to an inadequate account of the cosmic ray astrophysical background in previous modeling; They could be due to the presence of new astrophysical sources; They could also originate from annihilations and/or decays of dark matter. ...
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We present an update on CRDB (https://lpsc.in2p3.fr/crdb), the cosmic-ray database for charged species. CRDB is based on MySQL, queried and sorted by jquery and tsorter libraries, and displayed via PHP web pages through AJAX protocol. We review the modifications made on the structure and outputs of the database since the first release (Maurin et al., 2014). For this update, the most important feature is the inclusion of ultra-heavy nuclei (Z>30Z>30), ultra-high energy nuclei (from 101510^{15} to 102010^{20} eV), and limits on anti-nuclei fluxes (Z1Z\leq -1 for A>1A>1); more than 100 experiments, 350 publications, and 40000 data points are now available in CRDB. We also revisited and simplified how users can retrieve data and submit new data. For questions and request, please contact crdb@lpsc.in2p3.fr.
Article
The CALorimetric Electron Telescope (CALET) space experiment, developed by Japan in collaboration with Italy and the United States, is a high-energy astroparticle physics mission installed on the International Space Station (ISS). The primary goals of the CALET mission include investigating on the possible presence of nearby sources of high-energy electrons, studying the details of galactic particle propagation and searching for dark matter signatures. During a two-year mission, extendable to five years, CALET can measure the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma-rays to 10 TeV and nuclei with Z = 1 to 40 up to 1,000 TeV. The instrument consists of two layers of segmented plastic scintillators for cosmic-ray charge identification (CHD), a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 radiation length thick lead-tungstate calorimeter (TASC). CALET has sufficient depth, imaging capabilities and excellent energy resolution to allow for a clear separation between hadrons and electrons and between charged particles and gamma rays. The instrument was launched on August 19, 2015 to the ISS with the H-II Transfer Vehicle 5 (HTV-5) and installed on the Japanese Experiment Module-Exposed Facility (JEM-EF) on August 25. Since the start of operations in mid-October, 2015, a continuous observation has been going on mainly by triggering high energy (>10 GeV) showers without any major interruption. The number of triggered events above 10 GeV is nearly 20 million per month. By using the data obtained during the first two years, we give a summary of CALET observations: (1) Electron + Positron energy spectrum, (2) Proton and Nuclei spectrum, (3) Gamma-ray observation, with results of the performance study on orbit. We also present the results of observations of the electromagnetic counterparts to LIGO-VIRGO gravitational wave events and high-energy counterparts to GRB events measured with the CALET Gamma-ray Burst Monitor (CGBM).
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The results of cosmic rays studies obtained in the AMS experiment in 2011±2015 on the International Space Station are discussed. Research on the energy spectra of electrons and positrons at TeV energies and precision measurements of fluxes were performed. The growth of the positron fraction with energy was observed. Proton and helium spectra were also obtained. A review of theoretical models with possible explanations of the observed phenomena is presented.
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AMS-02 is a large acceptance cosmic ray detector operating on the International Space Station since May 2011. Of the ∼41 billion events collected in the first 30 months of data taking, 10.6 million have been selected as and for the measurement of the ( ) energy spectrum from 0.5 GeV to 1 TeV. In this contribution, the latest result on the ( ) flux measurement with AMS is presented.
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In the last years, space based cosmic ray experiments are delivering very valuable and precise measurements for the understanding of the cosmic ray acceleration and propagation processes. This paper reviews the last measurements on electron and positron cosmic rays highlighting the latest accurate data provided by the AMS experiment
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The Alpha Magnetic Spectrometer has recently released a first set of precise measurements of cosmic rays detected on the International Space Station in the GeV to TeV energy range. The fluxes of positrons, electrons and protons are presented. Neither of the fluxes is compatible with a single power law. Both the electron flux and the positron flux change their behavior at ∼30 GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. Above ∼200 GeV the positron fraction no longer exhibits an increase with energy. The proton flux is progressively hardening above rigidity ∼100 GV. The detailed variation with rigidity of the proton flux spectral index is presented.
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A combined analysis of the recent AMS-02 data on electrons, positrons, electrons plus positrons and positron fraction is presented in a framework where all the astrophysical components that can contribute to the observed fluxes are consistently modeled. A remarkable agreement between our modeling and the AMS-02 data is obtained, demonstrating that the whole AMS-02 leptonicdata can be fully interpreted in terms of astrophysical contributions.
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Very high energy (VHE; E > 30 GeV) cosmic-ray electrons and positrons (CR , ) reaching the Earth from beyond the solar system are important tracers of recent energetic events in our Galactic neighbourhood (1–2 kpc). Spectral measurements of this radiation may help checking standard astrophysical scenarios of CR , origin (e.g., pulsars, SNRs) versus exotic scenarios (e.g., DM particle annihilation). Air-Cherenkov telescopes can contribute to the measurement of the total VHE flux of CR , . This will allow us to consolidate relevant results by, e.g., ATIC, HESS, AMS-02, and Fermi-LAT.
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The fraction of positrons in the electron-positron component of cosmic rays is calculated in a scenario where electrons and positrons are generated by Galactic sources with the same spectral index. It is shown that the proposed scenario allows us to reproduce the existing experimental data on the fraction of positrons if the relative yield of positrons in a source is e +/e − ≈ 0.3.
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The unexpected rise of the positron to electron ratio with energy in the 20 ÷ 100 GeV range has been recently observed by PAMELA. Later, it was also confirmed by Fermi-LAT. In the last experiment it was additionally detected that the positron fraction continues to rise between 100 and 200 GeV. We report the results of new calculations of the positron to electron ratio in the wide energy range. Fractional diffusion model was implemented to describe the particles propagation from sources. It is shown that a self-consistent description of the experimental data can be obtained if we assume that both positrons and electrons are injected into the interstellar medium by the sources with the same spectral exponent p ≈ 2.85. We have also found that the positron to electron ratio increases to a constant value of ~ 0.22 for energies E > 100 GeV. This flattening of the positron fraction obtained in our model for E > 100 GeV can be examined in the near future by the AMS-02 experiment.
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This review concentrates on the results obtained, over the last ten years, on the astrophysics of high-energy cosmic ray electrons and positrons. The anomalies, observed in the data of recent experiments (possible bump in the electron spectrum and the PAMELA anomaly in the positron fraction) are discussed through the systematic use of simple analytical solutions of the transport equations for cosmic ray electrons. Three main ways of explaining the origin of the anomalies are considered: the conservative way supposing the positrons to be pure secondary particles; the nearby sources like pulsars origin; and the dark matter origin. This review discusses, also, the inability to select the pulsars model or the dark matter model to explain the electron anomalies on the basis of the electron spectra with the usual large energy binning ( 15%). It is argued that the signature of nearby pulsars origin of the anomalies against the dark matter origin could be the fine structure of the cosmic ray electron spectrum predicted in the Malyshev et al. paper (2009) and which was observed in the data from the high-resolution ATIC experiment (2009-2011). To date, the high-resolution ATIC data was the only experimental result of this type published in the literature. Therefore, they should be tested by other experiments as soon as possible. Generally, there is, also, rather controversial situations between the data of the majority of recent experiments and, consequently, there is a noted urgent need for new high-precision and high-statistical experiments.
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It is shown that the excesses in the sum of fluxes (e + + e −) in cosmic rays in the energy range (10–1000) GeV and in the flux ratio e +/(e + + e −) in the range > 10 GeV, observed both in recent and old experiments, can be explained by an accelerator of charged particles operating on the heliosphere periphery, in the region beyond the termination shock of the solar wind (∼100 AU). Variations in the value and position of peculiarities in the spectra (e + + e −), as well as increasing ratio of fluxes e +/(e + + e −), can be associated with variations of solar activity (and, as a consequence, of acceleration regimes) on different phases of the 11-years solar cycle. The results of numerical simulation of capture and acceleration of charged particles by packets of plasma waves in the heliospheric magnetic field are presented.
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We introduce new sum rules allowing to determine universal properties of the unknown component of the cosmic rays; we show how they can be used to predict the positron fraction at energies not yet explored by current experiments, and to constrain specific models.
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By combining the recent data from AMS-02 with those from Fermi-LAT, we show the emergence of a charge asymmetry in the electron and positron cosmic-ray excesses, slightly favoring the electron component. Astrophysical and dark matter inspired models introduced to explain the observed excesses can be classified according to their prediction for the charge asymmetry and its energy dependence. Future data confirming the presence of a charge asymmetry, would imply that an asymmetric production mechanism is at play.
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This paper gives a description of a new on-line database http://lpsc.in2p3.fr/cosmic-rays-db and associated on-line tools (data selection, data export, plots, etc.) for charged cosmic-ray measurements. The experimental setups (type, flight dates, techniques) from which the data originate are included in the database, along with the references to all relevant publications. The database relies on the MySQL5 engine. The web pages and queries are based on PHP, AJAX and the jquery, jquery.cluetip, jquery-ui, and table-sorter third-party libraries. In this first release, we restrict ourselves to Galactic cosmic rays with Z<=30 and a kinetic energy per nucleon up to a few tens of TeV/n. This corresponds to more than 200 different sub-experiments (i.e., different experiments, or data from the same experiment flying at different times) in as many publications. We set up a cosmic-ray database and provide tools to sort and visualise the data. New data can be submitted, providing the community with a collaborative tool to archive past and future cosmic-ray measurements. Any help/ideas to further expand and/or complement the database is welcome (please contact crdatabase@lpsc.in2p3.fr).
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Successfully launched in June 2008, the Fermi Gamma-ray Space Telescope, formerly named GLAST, has been observing the high-energy gamma-ray sky with unprecedented sensitivity for more than two years, opening a new window on a wide variety of exotic astrophysical objects. This paper is a short overview of the main science highlights, aimed at non-specialists, with emphasis on those which are more directly connected with the study of fundamental physics---particularly the search for signals of new physics in the diffuse gamma-ray emission and in the cosmic radiation and the study of Gamma-Ray Burst as laboratories for testing possible violations of the Lorentz invariance.
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The CuAAC reaction was used for the development of a click approach to a series of triazole-substituted bipyridinyl deriva-tives. 4,4'-Diethinyl 2,2'-bipyridine and 4,4'-diazido 2,2'-bipyridine were synthesized and tested in the cycloaddition reactions. While 4,4'-diazido 2,2'-bipyridine revealed unreactive in CuAAC reactions, its corresponding N,N'-dioxide afforded the expected cycloaddition product.
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Calorimeters are used in cosmic ray studies for a variety of purposes, such as measurements of particle energy, separation of electrons and hadrons, formation of triggers (signals for activation of instruments), and so on. In this review we consider the methods of energy reconstruct of protons and electrons (for particles with energies exceeding 10 GeV) in calorimeters of various types that are used in astrophysical experiments of cosmic ray studies carried out with balloons and satellites.
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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.
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Cosmic ray antiprotons provide an important probe for the study of cosmic-ray propagation in the interstellar space and to investigate the existence of Galactic dark matter. Cosmic rays are hampered by the Moon, therefore a deficit of cosmic rays in its direction is expected (the so-called Moon shadow). The Earth–Moon system acts as a magnetic spectrometer. In fact, due to the geomagnetic field the center of the Moon shifts westward by an amount depending on the primary cosmic ray energy. Paths of primary antiprotons are therefore deflected in an opposite sense in their way to the Earth. This effect allows, in principle, the search of antiparticles in the opposite direction of the observed Moon shadow.The ARGO-YBJ experiment, in stable data taking since November 2007 with an energy threshold of a few 100s of GeV, is observing the Moon shadow with high statistical significance. Using about 1 year data, an upper limit of the flux ratio in the few-TeV energy region is set to a few percent with a confidence level of 90%.
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The intensity of cosmic-ray electrons is only ∼1% of the protons at 10 GeV, and decreases very rapidly with energy to be ∼0.1% of protons at 1 TeV. Nevertheless, electrons in cosmic-rays have unique features, complementary to all other cosmic-ray nucleonic components, because they enable us to find the origins of cosmic-rays and the properties of their propagation mechanisms in the Galaxy. High-energy electrons lose energy by synchrotron and inverse Compton processes during the propagation in the Galaxy. Since the energy loss rate by these processes is proportional to the square of energy, TeV electrons accelerated in the sources at distances larger than ∼1 kpc, or ages greater than a few 105 yr, cannot reach the solar system. This suggests that some nearby sources leave unique signatures in the form of identifiable structures in the energy spectrum of TeV electrons, and show increases of the flux towards the sources. In this paper, I review the past observations of high-energy cosmic-ray electrons and discuss their astrophysical significance.
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Context: The relation between Galactic cosmic-ray electrons, magnetic fields and synchrotron radiation. Aims: We exploit synchrotron radiation to constrain the low-energy interstellar electron spectrum, using various radio surveys and connecting with electron data from Fermi-LAT and other experiments. Methods: The GALPROP programme for cosmic-ray propagation, gamma-ray and synchrotron radiation is used. Secondary electrons and positrons are included. Propagation models based on cosmic-ray and gamma-ray data are tested against synchrotron data from 22 MHz to 94 GHz. Results: The synchrotron data confirm the need for a low-energy break in the cosmic-ray electron injection spectrum. The interstellar spectrum below a few GeV has to be lower than standard models predict, and this suggests less solar modulation than usually assumed. Reacceleration models are more difficult to reconcile with the synchrotron constraints. We show that secondary leptons are important for the interpretation of synchrotron emission. We also consider a cosmic-ray propagation origin for the low-energy break. Conclusions: Exploiting the complementary information on cosmic rays and synchrotron gives unique and essential constraints on electrons, and has implications for gamma rays. This connection is especially relevant now in view of the ongoing PLANCK and Fermi missions.
Article
The deployment of DeepCore array significantly lowers IceCube's energy threshold to about 10 GeV and enhances the sensitivity of detecting neutrinos from annihilations and decays of light dark matter. To match this experimental development, we calculate the track event rate in DeepCore array due to neutrino flux produced by annihilations and decays of galactic dark matter. We also calculate the background event rate due to atmospheric neutrino flux for evaluating the sensitivity of DeepCore array to galactic dark matter signatures. Unlike previous approaches, which set the energy threshold for track events at around 50 GeV (this choice avoids the necessity of including oscillation effect in the estimation of atmospheric background event rate), we have set the energy threshold at 10 GeV to take the full advantage of DeepCore array. We compare our calculated sensitivity with those obtained by setting the threshold energy at 50 GeV. We conclude that our proposed threshold energy significantly improves the sensitivity of DeepCore array to the dark matter signature for mχ<100m_{\chi}< 100 GeV in the annihilation scenario and mχ<300m_{\chi}<300 GeV in the decay scenario.
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We combine the data from PAMELA and FERMI-LAT cosmic ray experiments by introducing a simple sum rule. This allows to investigate whether the lepton excess observed by these experiments is charge symmetric or not. We also show how the data can be used to predict the positron fraction at energies yet to be explored by the AMS-02 experiment.
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We calculate contained and upward muon flux and contained shower event rates from neutrino interactions, when neutrinos are produced from annihilation of the dark matter in the Galactic Center. We consider model-independent direct neutrino production and secondary neutrino production from the decay of taus, W bosons and bottom quarks produced in the annihilation of dark matter. We illustrate how muon flux from dark matter annihilation has a very different shape than the muon flux from atmospheric neutrinos. We also discuss the dependence of the muon fluxes on the dark matter density profile and on the dark matter mass and of the total muon rates on the detector threshold. We consider both the upward muon flux, when muons are created in the rock below the detector, and the contained flux when muons are created in the (ice) detector. We also calculate the event rates for showers from neutrino interactions in the detector and show that the signal dominates over the background for 150GeV<mχ<1150 {\rm GeV} <m_\chi < 1 TeV for Eshth=100E_{sh}^{th} = 100 GeV. Comment: 13 pages, 14 figures, 3 tables; Fig. 14 replaced and references added; new table and references added, discussion extended, version accepted for publication in Phys Rev D
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Recent data from cosmic ray experiments may be explained by a new GeV scale of physics. In addition the fine-tuning of supersymmetric models may be alleviated by new O(GeV) states into which the Higgs boson could decay. The presence of these new, light states can affect early universe cosmology. We explore the consequences of a light (~ GeV) scalar on the electroweak phase transition. We find that trilinear interactions between the light state and the Higgs can allow a first order electroweak phase transition and a Higgs mass consistent with experimental bounds, which may allow electroweak baryogenesis to explain the cosmological baryon asymmetry. We show, within the context of a specific supersymmetric model, how the physics responsible for the first order phase transition may also be responsible for the recent cosmic ray excesses of PAMELA, FERMI etc. We consider the production of gravity waves from this transition and the possible detectability at LISA and BBO.
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We calculate the muon flux from annihilation of the dark matter in the core of the Sun, in the core of the Earth and from cosmic diffuse neutrinos produced in dark matter annihilation in the halos. We consider model-independent direct neutrino production and secondary neutrino production from the decay of taus produced in the annihilation of dark matter. We illustrate how muon energy distribution from dark matter annihilation has a very different shape than muon flux from atmospheric neutrinos. We consider both the upward muon flux, when muons are created in the rock below the detector, and the contained flux when muons are created in the (ice) detector. We contrast our results to the ones previously obtained in the literature, illustrating the importance of properly treating muon propagation and energy loss. We comment on neutrino flavor dependence and their detection. Comment: 11 pages, 4 figures, 1 table. (v2): figure added, version published in Phys. Rev. D
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We observed atmospheric gamma rays around 10 GeV at balloon altitudes (15–25 km) and at a mountain (2770 m a.s.l). The observed results were compared with Monte Carlo calculations to find that an interaction model (Lund FRITIOF1.6) used in an old neutrino flux calculation was not good enough for describing the observed values. Instead, we found that two other nuclear interaction models, Lund FRITIOF7.02 and DPMJET3.03, gave much better agreement with the observations. Our data will serve for examining nuclear interaction models and for deriving a reliable absolute atmospheric neutrino flux in the GeV region.
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We have performed a series of cosmic-ray electron observations using the balloon-borne emulsion chambers since 1968. While we previously reported the results from subsets of the exposures, the final results of the total exposures up to 2001 are presented here. Our successive experiments have yielded the total exposure of 8.19 m^2 sr day at the altitudes of 4.0 - 9.4 g/cm^2. The performance of the emulsion chambers was examined by accelerator beam tests and Monte-Carlo simulations, and the on-board calibrations were carried out by using the flight data. In this work we present the cosmic-ray electron spectrum in the energy range from 30 GeV to 3 TeV at the top of the atmosphere, which is well represented by a power-law function with an index of -3.28+-0.10. The observed data can be also interpreted in terms of diffusive propagation models. The evidence of cosmic-ray electrons up to 3 TeV suggests the existence of cosmic-ray electron sources at distances within ~1 kpc and times within ~1x10^5 yr ago.
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Measurements of the energy spectra of negative electrons and positrons have been performed with the High-Energy Antimatter Telescope (HEAT) in two balloon flights—1994 May from Fort Sumner, NM, and 1995 August from Lynn Lake, Manitoba. We present the combined data set from these two flights, covering the energy range 1-100 GeV. We compare our data with results from other groups and discuss the data in the context of diffusive propagation models. There is some evidence that primary electrons above 10 GeV and cosmic-ray nuclei exhibit the same energy spectrum at the source, but that the source spectrum becomes harder at lower energy. Within the experimental uncertainties, the intensity of positrons is consistent with a purely secondary origin, due to nuclear interactions in interstellar space.
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We report on a new measurement of the cosmic-ray electron and positron spectra. The data were collected by the balloon-borne experiment CAPRICE94, which was flown from Lynn Lake, Canada, on 1994 August 8-9 at an altitude corresponding to 3.9 g cm-2 of average residual atmosphere. The experiment used the NMSU-WIZARD/CAPRICE94 balloon-borne magnet spectrometer equipped with a solid radiator Ring Imaging Cerenkov (RICH) detector, a time-of-flight system, a tracking device consisting of drift chambers and multiwire proportional chambers, and a silicon-tungsten calorimeter. This was the first time a RICH detector was used together with an imaging calorimeter in a balloon-borne experiment. A total of 3211 electrons, with a rigidity at the spectrometer between 0.3 and 30 GV, and 734 positrons, between 0.3 and 10 GV, were identified with small backgrounds from other particles. The absolute energy spectra were determined in the energy region at the top of the atmosphere between 0.46 and 43.6 GeV for electrons and between 0.46 and 14.6 GeV for positrons. We found that the observed positron spectrum and the positron fraction are consistent with a pure secondary origin. A comparison of the theoretically predicted interstellar spectrum of electrons shows that the injection spectrum of primary electrons is steeper than that of the nucleonic components of cosmic rays. Furthermore, the observed electron and positron spectra can be reproduced from the interstellar spectra by a spherically symmetric model for solar modulation; hence, the modulation is independent of the sign of the particle charge.
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Cosmic-ray electrons have been observed in the energy range from 12 to ~100 GeV with a new balloon-borne payload, the Balloon-borne Electron Telescope with Scintillating Fibers (BETS). This is the first publication of the absolute energy spectrum of electrons measured with a highly granulated fiber calorimeter. The calorimeter makes it possible to select electrons against the background protons by detailed observation of both the longitudinal and the lateral shower development. The performance of the detector was calibrated by the CERN-SPS accelerator beams: electrons from 5 to 100 GeV, protons from 60 to 250 GeV. The balloon observations were carried out twice, in 1997 and 1998, at the Sanriku Balloon Center (Institute of Space and Astronautical Science) in Japan. The observation time was ~13 hr in all at an altitude above 34 km. A total of 1349 electron candidates were collected, and the 628 events with energies above 12.5 GeV, well above the geomagnetic rigidity cutoff of ~10 GV, have been used to compose a differential absolute energy spectrum at the top of the atmosphere. The energy spectrum is described by a power-law index of 3.00 ± 0.09, and the absolute differential intensity at 10 GeV is 0.199 ± 0.015 m-2 s-1 sr-1 GeV-1. The overall shape of the energy spectrum in 10 ~ 100 GeV can be explained by a diffusion model, in which we assume an energy-dependent diffusion coefficient ( E0.3) for an injection spectrum, E-2.4.
Article
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A balloon-borne superconducting magnet spectrometer was used to measure the absolute flux of cosmic-ray electrons. The instrument consisted of a gas Cerenkov detector, a momentum spectrometer, and a lead-scintillator shower counter. In order to determine electron flux in the interstellar medium, observed fluxes for energy loss in the atmosphere and the payload were corrected, taking into account solar modulation effects and bremsstrahlung energy losses. Fluxes were measured at an average atmospheric depth of 5.8 g/sq cm, and the solar modulation was 300 MeV. A cosmic-ray electron flux of 367 E to the exp(3.15 + or -0.2) per sq m/sr s GeV was obtained in the energy range 4.5-63.5 GeV. The uncertainty of the absolute (electron-positron) flux was 10 percent. A summary of the electron data is given in a table.
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The results of a series of emulsion exposures, beginning in Japan in 1968 and continued in the U.S. since 1975, which have yielded a total balloon-altitude exposure of 98,700 sq m sr s, are presented. The data are discussed in terms of several models of cosmic-ray propagation. Interpreted in terms of the energy-dependent leaky-box model, the spectrum results suggest a galactic electron residence time of 1.0(+2.0, -0.5) x 10 to the 7th yr, which is consistent with results from Be-10 observations. Finally, the possibility that departures from smooth power law behavior in the spectrum due to individual nearby sources will be observable in the energy range above 1 TeV is discussed.
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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
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We have observed atmospheric gamma rays from 30GeV to 8TeV, using emulsion chambers at balloon altitudes, accumulating the largest total exposure in this energy range to date, SOT ~ 6.66m^2.sr.day. At very high altitudes, with residual overburden only a few g/cm^2, atmospheric gamma rays are mainly produced by a single interaction of primary cosmic rays with overlying atmospheric nuclei. Thus, we can use these gamma rays to study the spectrum of primary cosmic rays and their products in the atmosphere. From the observed atmospheric gamma ray spectrum, we deconvolved the primary cosmic-ray proton spectrum, assuming appropriate hadronic interaction models. Our deconvolved proton spectrum covers the energy range from 200GeV to 50TeV, which fills a gap in the currently available primary cosmic-ray proton spectra. We also estimated the atmospheric muon spectrum above 30GeV at high altitude from our gamma-ray spectrum, almost without reference to the primary cosmic rays, and compared the estimated flux with direct muon observations below 10GeV.
Article
The CALorimetric Electron Telescope, CALET, mission is proposed for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. The mission goal is to reveal the high-energy phenomena in the universe by carrying out a precise mesurement of the electrons in the range 1 GeV-10 TeV and the gamma-rays in the range 20 MeVto several TeV. The detector will be composed of an imaging calorimeter of scintillating fibers (IMC) and a total absorption calorimeter of BGO (TASC). The total absorber thickness is 36 r.l for electromagnetic particles and 1.8 m.f.p for protons. The total pay-load weight is nearly 2.5 t and the effective geometrical factor for the electrons ∼1.0 m2sr. The CALET has a unique capability to measure the electrons and gamma-rays above 1 TeV since the hadron rejection power can be 106 and the energy resolution for electromagnetic particles is better than a few % above 100 GeV. Therefore, it is promising to detect any change of the energy spectra and a line signature in the energy distribution, as expected from the dark matter.
Article
We have observed cosmic-ray electrons from 10 to 1000 GeV by a long duration balloon flight using Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an altitude of 35 km in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead plates. The geometrical factor of detector is about 600 cm2sr and the total thickness of lead absorber is 9 radiation lengths. The performance of the detector has been confirmed by the CERN-SPS beam test and also investigated by Monte-Carlo simulations. New telemetry system using a commercial satellite of iridium, power supply by solar batteries, and automatic level control using CPU have successfully been developed and operated during the flight. We have collected 5.7 × 103 events over 100 GeV including nearly 100 candidates of primary electrons.
Article
The Polar Patrol Balloon (PPB) experiment is introduced. This campaign will be carried out at Syowa Station in Antarctica during Dec., 2002 to Jan. 2003. The PPB experiment aims at doing long-duration observations with stratospheric zero-pressure balloons by utilizing a stable circumpolar easterly wind around Antarctica. In this experiment, a total of 4 balloons will be launched for the purpose of making astrophysics observations (1 balloon) and upper atmosphere physics observations (3 balloons). The first payload will carry a very sophisticated instrument that will observe primary cosmic-ray electrons in the energy range of 10 GeV - 1TeV. The payloads of the latter 3 flights are identical with each other. They will be launched in as rapid a succession as weather conditions permit to constitute a cluster of balloons during their flights. Such a "Balloon Cluster" is suitable for observing temporal evolution and spatial distribution of various phenomena in various magnetospheric and ionospheric regions and boundaries that the balloons will traverse during their circumpolar trajectory.
Article
We describe a new detector system developed for high-altitude balloon flights to observe the cosmic-ray electrons above 10 GeV. The Balloon borne Electron Telescope with Scintillating (BETS) fibers instrument is an imaging calorimeter which is capable of selecting electrons against the large background of protons. The calorimeter is composed of a sandwich of scintillating optical-fiber belts and lead plates with a combination of three plastic scintillators for shower trigger. The total thickness of lead is 40mm(∼7.1r.l.) and the number of fiber belts is nine. In each belt, alternating layers are oriented in orthogonal (x and y) directions. Two sets of an intensified CCD camera are adopted for read-out of the scintillating fibers in the x and y direction, respectively.The accelerator beam tests were carried out to study the performance of detector for electrons in 1996 and for protons in 1997 at CERN-SPS. The instrument was successfully flown aboard high-altitude balloon in 1997 and 1998. It is demonstrated by the flight data that a reliable identification of the electron component has been achieved in 10–100GeV and the energy spectrum has been obtained.
Article
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.
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Measurements of the cosmic ray flux and electron energy spectrum from 5 GeV to 300 GeV, with an absolute uncertainty in the flux level of + or - 10 percent at low energies and + or - 30 percent at 100 GeV, are described. The measured spectrum appears to represent the competing processes of radiative energy loss in the interstellar medium and leakage out of the Galaxy. In the framework of the leaky box model and diffusion models, the result is most consistent with the picture of cosmic ray electrons spending an average of 10 million years in the Galaxy independent of electron energy, probably propagating in a halo as well as in the galactic disk.
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We propose that cold dark matter is made of Kaluza-Klein particles and explore avenues for its detection. The lightest Kaluza-Klein state is an excellent dark matter candidate if standard model particles propagate in extra dimensions and Kaluza-Klein parity is conserved. We consider Kaluza-Klein gauge bosons. In sharp contrast to the case of supersymmetric dark matter, these annihilate to hard positrons, neutrinos, and photons with unsuppressed rates. Direct detection signals are also promising. These conclusions are generic to bosonic dark matter candidates.
The Alpha Magnetic Spectrometer (AMS) on the International Space Station: part I – results from the test flight on the space shuttle The cosmic-ray electron and positron spectra measured at 1 AU during solar minimum activity The electron spectrum above 20 GeV measured by ATIC-2
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The most likely sources of high-energy cosmic-ray electrons in supernova remnants Emulsion chamber observations of primary cosmic-ray electrons in the energy range 30–1000 GeV The energy spectrum of electrons and cosmic-ray confinement: a new measurement and its interpretation
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