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PoS(ICRC2021)105 International th 12–23 July 2021 July 12–23 37 SICS CONFERENCE SICS CONFERENCE Berlin | Germany Berlin Berlin | Germany Conference Ray Cosmic ICRC 2021 THE ASTROPARTICLE PHY ICRC 2021 THEASTROPARTICLE PHY https://pos.sissa.it/ ONLINE [email protected] on behalf of the CALET Collaboration , 0 ), CALET achieves optimal performance for a detailed search 5 10 ∼ and Yosui Akaike ∗ 0, [email protected] International Cosmic Ray Conference (ICRC 2021) Presenter ∗ th for structures in the energythan spectrum. five years without CALET any has majorincreased been interruption, more accumulating and than scientific the double data statistics of since forprecise observed more the measurements latest of events publication has the in all-electronstatistics 2018. spectrum data, up and we In to will this several briefly TeV, as paper discuss about obtained we its with will interpretation. the present high the electron and (all-electron) spectrum.an The imaging instrument, calorimeter consisting and of a a total charge absorption detector, calorimeter,spectrum is well optimized into to the measure TeV region the with all-electron a thickimaging calorimeter of capability. 30 length Due with fine tooutstanding shower- e/p the separation excellent ( resolution (a few % above 10 GeV) and the E-mail: Primary objectives of the CALETpossible (CALorimetric nearby Electron cosmic-ray Telescope) sources mission and are dark to search signatures for with the precise measurement of Waseda Research Institute for and Engineering,17 Waseda Kikuicho, University, Shinjuku, Tokyo, Japan Copyright owned by the author(s) under the terms of the Creative Commons 0 © Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). 37 July 12th – 23rd, 2021 Online – Berlin, Germany Shoji Torii (a complete list of authors can be found at the end of the proceedings) Positron Spectrum with CALET on theStation International Precise Measurement of the Cosmic-Ray Electron and PoS(ICRC2021)105 5 years ∼ Shoji Torii ]. The result 7 ]. In this paper, ] and the Alpha 8 3 sr for high-energy 2 1,040 cm ∼ 2.3 since the last publication [ ∼ 2 ] may require a primary source component of the in 4 from zenith and a geometrical factor of ]. The energy range is extended to 4.8 and TeV, the observed spectrum ]. It was launched on August 19, 2015 with the Japanese carrier H-IIB, ◦ 5 7 45 ∼ ]. 2 , ]. Subsequently, the updated spectrum was published with statistics larger by a factor of 1 6 CALET employs a fully active calorimeter with thirty radiation-length thickness for The Calorimetric Electron Telescope (CALET) is a space experiment on the International Space In addition, the apparent increase of the positron fraction over 10 GeV established by Payload High-energy cosmic-ray provide a unique probe of nearby cosmic accelerators. Elec- 2 compared to the first by using more than 2 years of flight data and the full geometrical acceptance alternating thin layers of Tungsten absorber, optimized in thickness and position, with layers of at normal incidence. It consistscalorimeter of (IMC), a and charge detector a (CHD), twenty-seven radiation-length aIt thick three has total radiation-length a absorption thick field calorimeter of imaging (TASC). view of electrons. CHD, whichplastic identifies scintillator the hodoscopes charge arranged in of two the orthogonal incident layers. , IMC is is a comprised sampling of calorimeter a pair of 2. Instrument we present a preliminary CALET all-electronwith spectrum statistics obtained increased from furthermore observations byis over a compared factor of with othertentative observations, spectral fitting and in the a 10 plausible GeV-4.8and TeV range interpretation including the a Vela is SNR. possible contribution briefly from discussed with its Module - Exposed Facility (JEM-EF).in The the first energy result range ofregion from the [ all-electron 10 spectrum GeV was to published 3∼ TeV as the world’sin first the space high-energy region observation [ upshows to a suppression the of TeV the flux above 1 compatible TeV, with the DAMPE result [ range above 10 GeV. Station (ISS) for long term observations ofthe cosmic-rays, all-electron which spectrum is optimized [ for the measurementdelivered of to the ISS by the HTV-5 Transfer Vehicle, and installed on the Japanese Experiment Magnetic Spectrometer (AMS-02) [ addition to the generally accepted secondary origin. Candidatesastrophysical for () such primary to sources range exotic from ().pairs, it is Since expected these that primary the all-electronfeature sources due (electrons to emit and the electron-positron positrons) primary spectrum source component would of exhibit electrons a and spectral positrons, in the corresponding energy A precise measurement of the electronfeatures spectrum to in provide the the TeV region first might experimental revealsource interesting evidence spectral of [ the possible presence of a nearby cosmic-ray for Antimatter Matter Exploration and nuclei (PAMELA) [ trons rapidly lose energy viagation inverse in Compton the scattering Galaxy. and Since synchrotrona their emission few diffusion during super distance propa- nova above remnants 1 as TeV potential is TeV limited sources to are less located in than the 1 vicinity kpc, of only the . Precise Measurement of the Electron and Positron Spectrum with CALET 1. Introduction PoS(ICRC2021)105 is 3 1% . ∼ Shoji Torii shows the profile of the real time ]. Temporal gain variations occurring 2 10 3 ]. 9 shows a 3.05 TeV-electron candidate and a candidate with comparable energy 1 Examples of TeV event candidates showing energy deposit in each detector channel in the X Z It should be noted that, even with such a detailed calibration, the determining factor for the Since the start of scientific observations on October 13, 2015, smooth and continuous operations While excellent energy resolution inside the TeV region is one of the most important features of Figure ]. Moreover, the very large dynamic range of the energy measurement as presented in Fig. 10 Intrinsic resolution refers to the detector’s capability by design, taking advantage of the thick, fully [ confirmed without saturation of measuredspectra energy are up checked to monthly to 1 confirm PeV for the deposit stability of energy the in extrapolation TASC. usingenergy These four gain resolution ranges. is the calibration uncertainty, as the intrinsic resolution of CALET is during long time observations arecalibration step, also such corrected as the in correction of the position andenergy calibration temperature deposit dependence, procedure. peaks consistency between of The non-interacting errors protonsgain and at helium, ratio each linear measurements, fit error as ofenergy each resolution. well gain range, as As and slope a result, extrapolation, a are very included high in resolution of the 2% estimation or of better is the achieved above 20 GeV a thick calorimeter instrument like CALET, calibrationinto errors account must in be the carefully estimation assessed ofevaluation and of the taken the actual conversion energy factors resolution. between analog-to-digitalensuring Our converter linearity energy units over calibration each and gain includes energy range deposits, the (TASCa has seamless four gain transition ranges for between each neighboring channel), and gain provides ranges [ have being taken place.interruption of observation The by unexpected live accidents.and time the Fig. live fraction time of is the considerably observations [ high being 86 % without any Figure 1: and Y Z views.deposit Left: sum of An 2.89 electron TeV). Right: (or A positron) proton candidate candidate (reconstructed (energy energy deposit of sum 3.05 of3. TeV 2.89 and TeV). energy Observation and Detector Performance hadron background. Together withelectromagnetic showers, the it precision is possible energy to derive measurementsa the electron from straightforward spectrum and total well reliable into absorption analysis. the TeV region of with hodoscope, capable of almost complete absorption of the TeV-electron showers. deposit (2.89 TeV) in the detector.the containment Compared of to the hadron electromagnetic showers,the shower which bottom creates have part a significant of difference leakage, TASC, in allowing for shower an shape, accurate especially electron in identification in the presence of a large Precise Measurement of the Electron and Positron Spectrum with CALET scintillating fibers read-out individually. TASC is a tightly packed lead-tungstate (PbWO4; PWO) PoS(ICRC2021)105 Shoji Torii ] was performed, 12 ] to reconstruct the shower axis ]. A Monte Carlo (MC) program 7 14 Observed spectrum of the de- Figure 3: posited in TASC after calibrations. 4 ]. The analysis has been carried out for the observed events in the full 9 ] is chosen as the hadronic interaction model in the EPICS simulation. 13 ] (EPICS9.20/COSMOS8.00). Using MC event samples of electrons and , 11 Time dependences of the accumulated real The energy of incident electrons is reconstructed using the energy correction function, which In addition to fully contained events, the events incident from the IMC sides and exiting through We use the "electromagnetic shower tracking" algorithm [ In this paper, we report the results obtained by analysis of 1815 days of flight data collected with condition. In order to identify electrons and to study systematic uncertainties in the electron the sides of TASC are used for analysis.of For the events first not crossing hit the IMC CHD, layerlonger we to use than the determine that energy their of deposit charge. vertical depth The of path TASC, length i.e. inside twenty-seven TASC radiation is lengths. converts required the energy to deposit be of TASC and IMC into primary energy for each geometrical are preselected by (1) an off-line trigger confirmation,cut (2) to a geometrical ensure condition, reconstruction (3) a accuracy, track (4)shower quality a development, charge selection and using CHD, (6)electromagnetic (5) cascades. a having a lateral longitudinal shower containment consistent with those expected for GEANT4 simulation employs thewhile hadronic DPMJET3 interaction [ models FTFP_BERT as the list, of each event, taking advantage ofinput the for electromagnetic shower the shape electron and identification, IMC design well-reconstructed concept. and As well-contained single-charged events detector acceptance, by a similar procedure aswas described used in Ref. to [ simulateEPICS physics processes and [ detectorevent response selection based and on event thecontamination reconstruction simulation were efficiencies, package derived. energyand An correction small independent factor, differences analysis and between based background the on MC GEANT4 models [ are included in the systematic uncertainties. The 4. Data Analysis a high-energy shower trigger [ Figure 2: time and live time of the observations since Dec. 2015 gain ranges is crucial for the spectrum measurements in the TeV range. Precise Measurement of the Electron and Positron Spectrum with CALET active total absorption calorimeter. Also important is the fact that the calibration error in the lower PoS(ICRC2021)105 5 % up to Shoji Torii ∼ ] was carried out with ]. The error bars along 7 10 ] as a result of a study of 6 ] and an accompanied paper in 15 5 . 5 ]. Systematic errors include errors in the absolute normalization and 6 ] 16 shows the extended electron and positron spectrum in this analysis using the observed 5 Examples of BDT response distributions in the 476 < E < 599 GeV bin (left) and in the highest . In the final electron sample, the resultant contamination ratios of protons are 4 Comparing with other recent experiments in space (AMS-02, Fermi Large Area Telescope Figure The absolute energy scale was calibrated and shifted by + 3.5% [ The systematic uncertainties are described in details at Ref. [ Calculation of event selection efficiencies, BDT training, and estimation of proton background (Fermi-LAT), and DAMPE), our spectrum shows good agreement with AMS-02 data below 1 TeV. as MC model dependence. Innormalization more could refined be interpretation studies, treated the bytwo latter including components four must their contributions be weights and added asare in nuisance included quadrature parameters, in to the while the total the statistical error first errors. estimate in Conservatively, Fig. all of them is representative of the quadratic sumas of the statistical and one systematic given errors, using inenergy the Ref. dependent same [ definition ones, exceptinclude for those the obtained energy fromdependence, scale BDT dependence stability, uncertainty. on methods trigger of efficiency charge The identification, in and energy of the electron dependent low-energy identification, as errors region, well tracking 5. Electron + Positron Spectrum events with statistics increased by a factorhorizontal of 2.3 and since vertical the last axes publication indicate [ bin width and statistical errors, respectively. The gray band the geomagnetic cutoff energy. Sincea the scale-free full method, dynamic its range validity calibration holds [ regardless of the absolute scale uncertainty. this conference [ Figure 4: region energy , 1196 < E < 4755 GeV bin. (left), including all acceptance conditions . precision of our data, only the fully-contained475 events GeV. Examples are of included in a the BDT lower responsein energy Fig. distribution region below including all acceptance conditions1 are and TeV, shown 10% - 20% infor electrons. the 1 - 4.8 TeV region, while keeping a constant high efficiency of 80 % based on boosted decision trees (BDTs). contamination are carried out separatelyto for obtain each geometrical the condition final andby combined systematics spectrum. in in the our end Considering analysis, and the therefore fact more that statistics the would not lower significantly energy improve region the is dominated Precise Measurement of the Electron and Positron Spectrum with CALET identification, we applied two methods: a simple two-parameter cut and a multivariate analysis PoS(ICRC2021)105 0.026 ± Shoji Torii = 11.64 and 2 ] in the energy j 8 /NDF =11.25/29 which gives a significance 0.178 fits our data well, with 2 ± j 6 , the flux in the 1.4 TeV bin of DAMPE’s spectrum, ], where the gray band indicates the quadratic sum of 6 7 /NDF=54.50/30, which means that the broken power law 2 j 340 GeV with 0.012 by -0.873 ± ± 0.3. A single power-law fit over the same energy range (black ± ] for comparison. 19 0.011 with – ± 17 , 8 , we fit our spectrum with a smoothly broken power-law model [ 6 0.019, which is consistent with other experiments within errors. However, the spectrum Cosmic-ray all-electron spectrum measured by CALET from 11 GeV to 4.8 TeV using the same ± presents one example of fitting a model for the electron and positron origins described in ] (green line) is also presented for comparison, which has the power index of -3.054 7 20 On the other hand, as presented in Fig. Here, we try to explain the CALET energy spectrum observed in a whole energy region. To check if the CALET spectrum is consistent with a possible break at 0.9 as TeV, suggested by =6.58 over the single power law. f Figure of which might imply a peak structure,significance, is including not the compatible systematic errors with from CALET both results experiments. at a level of > 4 sigma the spectral index change ofline) gives 0.7 an index -3.197 is favored with 6.55 sigma significancelaw over [ the single power law.below An a exponentially cutoff cut-off energy power of 2170 GeV DAMPE’s observations, we have adopted exactly thespectrum. same energy In binning Fig. as DAMPE torange show from our 55 GeV topower 4.8 law steepening TeV, while from fixing -3.151 thenumber break of degrees energy of at freedom 914 (NDF) equal GeV( to blue 29. line). This result A is consistent broken with DAMPE regarding be -3.128 is considerably softer from 300 toThe 600 GeV CALET than results the exhibit spectra a measured byto lower DAMPE flux near and 1 than Fermi-LAT. indicating TeV, those the of presence DAMPE of and unknown Fermi-LAT systematic from effects. 300 GeV up energy binning as instatistical our and systematic previous errors publication (not including [ measurements the in uncertainty space on [ the energy scale). Also plotted are direct In the energy region from 40 to 300 GeV, the power-law index of CALET’s spectrum is found to Figure 5: Precise Measurement of the Electron and Positron Spectrum with CALET PoS(ICRC2021)105 Shoji Torii ) are calculated + ,e − ]. The details of this whole-region Tentative spectral fit over a whole region 22 ], which is also used to define the propagation Figure 7: of the CALET observations including the pulsarsthe and Vela SNR above 1 See TeV. details in text. 21 7 ] of the CALET all-electron spectrum with an approx- 7 ]. See text for 8 ]. However, for the highly desired goal of getting conclusive information of 22 All-electron spectrum measured by erg in electron CR above 1 GeV. The spectra by Vela and secondaries (e We gratefully acknowledge JAXA’s contributions to the development of CALET and to the We have extended our previous result [ 48 1. The positron flux of AMS-02 is fitted by contribution from secondaries (red dashed line) + operations onboard the International Space Station. We also wish to express our sincere gratitude of nearby SNRs and pulsars and/or dark matter inspired models. 7. Acknowledgements position, and of the spectral shapeobservations on above the 1 ISS are TeV, approved improved to by continuestatistics the up and better reduction to statistics. of 2024 the (at The systematic least) errors CALET willof based bring systematic on further uncertainties, the increase our analysis. of extended By the all-electron specifyingflux spectrum the measurement together breakdown with provides the essential AMS-02 information positron to investigate spectral features in the framework 6. Summary and Future Prospects imate increase by a factorof of the 2.3 of flux the compatible statistics. with The the data DAMPE in results, the and TeV region the show accuracy a of suppression the break’s sharpness and Figure 6: CALET from 11 GeV to 4.8ergy TeV using binning the as same en- DAMPE’sdetails result of fittings. [ 20 TeV with much more statistics. parameters via calculation of theelectrons nuclei and spectra, positrons concurrently forming providinginterpretation spectra part of of the of all-electron the spectrum the secondary and background itsexplained implications in [ of Ref. the nearby [ source contributionthe are nearby source contribution in the TeV region, we need still to extend the energy spectrum up to several pulsars (dashed-dotted line), and(black the dashed electron line) flux is with fittedpossible cut-off contribution by at from secondaries the 1 + Vela TeV. distant SNR Asx (green SNRs the 10 line), which dominating is source explained by abovewith energy the 1 output numerical TeV, of we propagation 2.08 assume code DRAGON a [ Precise Measurement of the Electron and Positron Spectrum with CALET § PoS(ICRC2021)105 Shoji Torii 628 in this conference. ♯ (CALET Collaboration), As- 4C 0;. 492 in this conference. ♯ 8 (CALET Collaboration), Atroparticle Physics 100, 29 (CALET Collaboration), Advances in Space Research 64 (CALET Collaboration), Poster 4C 0;. 4C 0;. 4C 0;. , Nucl. 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This was supported in part by a PoS(ICRC2021)105 , , , , , , , , , , 7 2 , , 13 15 13 19 13 25 19 15 , , , 6 1 12 12 12 , , , 11 33 11 School of Center for 23 Department RIKEN, 2-1 13 Heliospheric 9 22 40 Shoji Torii Faculty of Sci- , A. Sulaj , S. Okuno , K. Hibino 20 9 , M. Bongi 38 , J. P. Wefel 8 , Y. Katayose 11 2 Institute of Applied , K. Sakai 24 2 , M. L. Cherry 14 , Department of Physics 6 College of Science and 14 15 38 National Institute of Polar , J. F. Krizmanic College of Science, Ibaraki Department of Physics and 24 8 , A. A. Moiseev 44 16 , S. Sugita , T. Hams 7 32 , 15 6 Astroparticle Physics Laboratory, , W. R. Binns 31 , R. Kataoka , G. A. de Nolfo 7 , E. Vannuccini , 23 18 6 Department of Physics and McDonnell Faculty of Science, Shinshu University, , C. Checchia 42 INFN Sezione di Florence, Via Sansone, 8 2 26 14 , S. B. Ricciarini 8 , F. Stolzi 1 , S. Miyake 12 , T. G. Guzik 8 2 , H. S. Krawczynski , 1 Department of Astronomy, University of Maryland, , J. Kataoka 29 33 22 , J. Nishimura , Y. Uchihori , G. Bigongiari 18 41 , B. F. Rauch 2 , , G. Castellini 2 1 13 INFN Sezione di Padova, Via Marzolo, 8, 35131 Padova, Italy, , , P. Spillantini Department of Physics, Catholic University of America, Wash- , S. Gonzi , K. Kohri 17 12 10 39 4 , ICT Advanced Development Center, National Institute , 18 , J.W. Mitchell Faculty of Engineering, Division of Intelligent Systems Engineer- 3 11 7 37 9 , , and W. V. Zober 25 , P. Papini 30 22 , K. Kasahara 2 , E. Berti , 8 , S. Nakahira 5 14 26 , Y. Tsunesada , 1 3 National Institutes for Quantum and Radiation Science and Technology, 4-9-1 , H. Fuke , A. Shiomi 42 15 19 Hakubi Center, Kyoto University, Yoshida Honmachi, Sakyo-ku, Kyoto 606-8501, Department of Electrical and Electronic Systems Engineering, National Institute of , K. Kobayashi 27 Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwa-no-Ha, , N. Cannady , K. Yoshida 5 32 8 15 , Y. Asaoka 38 , S. Torii , L. Pacini 5 , M. H. Israel Division of Mathematics and Physics, Graduate School of Science, Osaka City University, 5 40 37 Department of Physics and Astronomy, University of Denver, Physics Building, Room 211, Collaboration Nagoya University, Furo, Chikusa, Nagoya 464-8601, Japan, 41

, K. Munakata 36 , A. M. Messineo 43 7 35 , Department of Physical , College of Science and Engineering, Ritsumeikan University, 6 , Y. Shimizu 34 , A. W. Ficklin Astroparticle Physics Laboratory, NASA/GSFC, Greenbelt, Maryland 20771, USA, 13 , 12 Department of Physical Sciences, Earth and Environment, University of Siena, via Roma 56, 53100 18 Waseda Research Institute for Science and Engineering, Waseda University, 17 Kikuicho, Shinjuku, 6 , A. Yoshida 12 3 , S. Ozawa , K. Asano , , Y. Kawakubo 4 44 , , J. H. Buckley CALET 17 33 28 , W. Ishizaki , 3 , , T. Terasawa 10 , 21 16 Center for Space Sciences and Technology, University of Maryland, Baltimore County, 1000 Hilltop Circle, 27 19 Faculty of Science and Engineering, Global Center for Science and Engineering, Waseda University, 3-4-1 9 JEM Utilization Center, Human Spaceflight Technology Directorate, Japan Aerospace Exploration Agency, 11 4 , H. M. Motz 35 2 List: , K. Ebisawa University of Pisa, Polo Fibonacci, Largo B. Pontecorvo, 3, 56127 Pisa, Italy, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa, Yokohama, Kanagawa 221-8686, Japan, College of Industrial Technology, Nihon University, 1-2-1 Izumi, Narashino, Chiba 275-8575, Japan 30 17 19 39 , , M. Sasaki , K. Ioka , S. Yanagita , Y. Akaike , P. S. Marrocchesi Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki , N. Ospina 16 38 2 7 20 43 , , 29 INFN Sezione di Pisa, Polo Fibonacci, Largo B. Pontecorvo, 3, 56127 Pisa, Italy, , A. Bruno , T. Tamura 1 6 36 , N. Mori 7 7 5 , N. Kawanaka , 34 6 Department of Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606- 26 Authors 28 Yukawa Institute for , Kyoto University, Kitashirakawa Oiwakecho, Sakyo, Kyoto 606-8502, Japan, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa Department of Physics, University of Florence, Via Sansone, 1, 50019 Sesto, Fiorentino, Italy, Full K. Yamaoka T. Sakamoto M. Takita M. Mori J. F. Ormes P. Maestro C. Kato M. Ichimura G. Collazuol O. Adriani P. Brogi Hirosawa, Wako, Saitama 351-0198, Japan, 3-3-138 Sugimoto, Sumiyoshi, Osaka 558-8585, Japan, Anagawa, Inage, Chiba 263-8555, Japan, University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan Engineering, Department of Physics and252-5258, Mathematics, Japan, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara, Kanagawa of Information and Communications Technology, 4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795, Japan, Shiga 525-8577, Japan, College Park, Maryland 20742, USA, Okubo, Shinjuku, Tokyo 169-8555, Japan, 2112 East Wesley Avenue, Denver, Colorado 80208-6900, USA, ence and Technology, Graduate School of21 Science and Technology„ Hirosaki University, 3, Bunkyo, Hirosaki, Aomoriof 036-8561, Electronic Japan, Information Systems, ShibauraAdvanced Institute Science of and Technology, Engineering, 307 Waseda Fukasaku, University,Research, 3-4-1 Minuma, 10-3, Okubo, Saitama Midori-cho, Shinjuku, 337-8570, Tachikawa, Tokyo Tokyo 169-8555, Japan, 190-8518, Japan, Japan, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan, Japan, 8502, Japan, 305-0801, Japan, NASA/GSFC, Greenbelt, Maryland 20771, USA, Technology, Ibaraki College, 866 Nakane, Hitachinaka, Ibaraki 312-8508, Japan ing, Yokohama National University, 79-5 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan, and Astronomy, Louisiana State University, 202Astronomy, University of Nicholson Padova, Hall, Via Marzolo, Baton18 8, Rouge, 35131 Padova, Louisiana Italy, 70803, USA, 252-5210, Japan, 1 Precise Measurement of the Electron and Positron Spectrum with CALET 1, 50019 Sesto, Fiorentino, Italy, Tokyo 162-0044, Japan, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505, Japan, Center for the Space Sciences, Washington University, One Brookings Drive, St. Louis, Missouri 63130-4899, USA, Research and Exploration in SpacePhysics Sciences (IFAC), National and Research Technology, Council NASA/GSFC, (CNR), Greenbelt, Via Maryland Madonna del 20771, Piano, USA, 10, 50019 Sesto, Fiorentino, Italy, Kashiwa, Chiba 277-8582, Japan, Siena, Italy, Baltimore, Maryland 21250, USA, Physics Laboratory, NASA/GSFC, Greenbelt, Maryland 20771, USA, ington, DC 20064, USA,