TeV Electrons and Positrons Measured by PAMELA Spectrometer
- PDF / 787,054 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 33 Downloads / 161 Views
ELEMENTARY PARTICLES AND FIELDS Experiment
TeV Electrons and Positrons Measured by PAMELA Spectrometer V. V. Mikhailov* (on behalf of the PAMELA Collaboration) National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, 115409 Russia Received August 14, 2019; revised August 14, 2019; accepted August 14, 2019
Abstract—Abstract-The PAMELA magnetic spectrometer was launched onboard the Resurs-DK1 satellite to the Earth polar orbit with altitude of 350–600 km to study the fluxes of cosmic ray particles and antiparticles in a wide energy range. Starting science operation in July 2006, PAMELA spectrometer performed continuous observation without major interruption till January 2016 collected about 10 billion trigger events. New analysis included data for all period of observations in 2006–2016 with improved selection efficiency and it allows to extend measurements of total electron and positron flux in TeV region with better statistic accuracy. In this paper, the observed energy spectrum of electrons and positrons is presented and compared with the other modern measurements. DOI: 10.1134/S1063778819660396
1. INTRODUCTION Measurements of the ratio of the fluxes of positrons to the total flux of electrons and positrons in the PAMELA experiment [1, 2], confirmed by subsequent data from Fermi-LAT and AMS-02 [3, 4] showed that it increases with energy, starting from 5 GeV in contradiction to the “standard” diffusion model of the generation and propagation of cosmic rays. This growth may mean the existence of sources of primary positrons, including those associated with hypothetical dark matter. A gradual hardening of the positron flux centered at energy about 30 GeV can also be understood as the signature of the new source but it is not unique explanation. The shapes of the spectral features observed in the e+ and e− + e+ spectra may be consistent with the hypothesis that they are generated by energy loss effects [5]. To clarify the situation it is clearly necessary to have more data on the electron and positron spectra in the TeV energy range. A huge experimental efforts were undertaken to accurate measurements of cosmic ray electron and positron energy spectrum last years. Measurements of the all electron spectrum up to a maximum energy of 1 and 2 TeV have been obtained by AMS [6] and Fermi-LAT [7]. A spectral suppression above 1 TeV was observed by HESS ground-based Cherenkov telescope and then have been confirmed by two space born experiments CALET [9] and DAMPE [8]. Very recently AMS-2 has provided new very high precision data on positron and electron spectra [10]. The data *
E-mail: [email protected]
cover the an energy range spanning from one GeV under one TeV. Measurements of the fluxes show that the positron spectrum has a possible softening feature for energies above 400 GeV. Positron fraction also has a suppression at that energies. The magnetic spectrometer PAMELA was launched onboard the Resurs-DK1 satellite on the 15th of June 2006 and it was continuously taking data during almost 3200 da
Data Loading...
