Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station.

M Aguilar,Q Li,C Vannini,M Ionica,H Jinchi,I Cernuda,Y Yang,L Farnesini,J Sandweiss,M Behlmann,K Luebelsmeyer,N Zimmermann,M Willenbrock,P Saouter,V Vagelli,I Guerri,F Cadoux,D Aisa,W Xu,K Whitman,A Rozhkov,S Borsini,M Capell,F Spinella,I Gebauer,L Arruda,J Casaus,G Schwering,C Pizzolotto,L Derome,C Gargiulo,F Pilo,O Kounina,B Alpat,Z Cui,J Hoffman,W Sun,S Zeissler,M Lolli,V Bindi,F Palmonari,R Clavero,Y Li,A Kounine,G Castellini,X Wang,A Barrau,A Zichichi,A Putze,M Habiby,U Becker,R Majka,K Bollweg,T Lomtadze,G Coignet,W Creus,C Huh,Hu Liu,M Vecchi,S Caroff,H Liu,T Urban,C Díaz,P Von Doetinchem,M Pohl,D Cerreta,E Choumilov,F Donnini,S Schael,M Paniccia,B Borgia,C Consolandi,I Lazzizzera,R Battiston,A Schulz Von Dratzig,M Müller,P Zuccon,B Coste,J Berdugo,G Ambrosi,J Marín,L Di Masso,D Tescaro,L Basara,S Xie,K Andeen,M Duranti,R Kossakowski,S Haino,D Grandi,M Orcinha,E Fiandrini,J Gong,W Li,I Rodríguez,F Giovacchini,C Leluc,A Contin,G La Vacca,P Azzarello,M Heil,V Plyaskin,J Wienkenhöver,P Goglov,D Liu,A Oliva,L Morescalchi,T Eronen,P Lipari,S Pensotti,M Incagli,A Alvino,D Maurin,V Choutko,K Kanishev,S Bizzaglia,H Gast,E Laudi,B Bertucci,M Bourquin,A Piluso,G Laurenti,G Gallucci,M Bizzarri,V Vitale,V Formato,X Wu,P Mott,L Barrin,B Beischer,D Rapin,M Velasco,H Chen,M Pauluzzi,M Gervasi,E Pedreschi,E Valente,G Boella,F Spada,M Crispoltoni,N Nikonov,D D’Urso,C Corti,D Haas,A Bachlechner,C Zhang,M Tacconi,V Poireau,W De Boer,N Masi,C Mañá,V Grabski,L Quadrani,F Dimiccoli,J Bazo,S Della Torre,S Vitillo,A Lebedev,F Cervelli,T Siedenburg,C Guandalini,D Rozza,J Torsti,C Palomares,E Finch,A Eline,V Bonnivard,P Nunes,N Attig,G Scolieri,X Qin,S Di Falco,C Goy,M Graziani,A Ghelfi,Z Zhang,A Egorov,F Nozzoli,V Koutsenko,B.r Mellado Garcia ,Z Y Li ,Yongji Yu ,A Fiaßon ,Feng Luo ,X Shi ,S M Ting ,H T Lee ,Junzhou Luo ,R J García-López ,S W Zhang ,Alberto Papi ,N Picot-Clémente ,Yi-Zhong Fan ,W Y Jang ,R Z Sagdeev ,В Жуков ,Alessandro Bartoloni ,Y H Shan ,A I Chen ,Serova Lv ,Yi Han ,Nicola Tomassetti ,L Y Tao ,J S Ricol ,Dong-Chuan Mo ,B Demirköz ,Xudong Cai ,J H Zhang ,X M Qi ,Kexin Guo ,Yu Galaktionov ,Z Weng ,E S Seo ,T S Räihä ,Thierry Martin ,M J Chae ,G M Chen ,J Q Li ,C Delgado Mendez ,T K Nelson ,G Martìnez ,Susann Schmidt ,Z Y Qu ,H L Zhuang ,Min Yang ,Eduardo Cortina Gil ,S I Lim ,R Q Xiong ,J P Vialle ,Zhicheng Tang ,Markus Battarbee ,L Q Wang ,Lin Cheng ,Jiwei Song ,Zhao-Huan Yu ,Z H Li ,Jiawei Yang ,H S Chen ,Q H Ye ,Timothy H Hsieh ,C H Douglas Clark ,P G Rancoita ,Min Xie ,M T Zhang ,R S Wang ,Y H Chang ,T X Li ,Jiangqun Ni ,S S Vaurynovich ,S D Zhang ,M Boschini ,Chengpei Tang ,Samuel C.c Ting ,X M Xia ,Z M Zheng ,X Tang ,N S Xu ,Z H He ,Qiao Meng ,M A Korkmaz ,Э Валтонен ,J D Burger ,Q L Wang ,Chao-Hung Lin ,John Shi ,C Türkoğlu ,S C Lee ,J H Feng ,Z X Wang ,X B Zhang ,Ye Dai ,Z C Huang ,K Han ,S Q Lu ,H L Li ,A Menchaca‐Rocha ,S Rosier‐Lees ,M Lu ,Yao Lu ,D C Son ,Qi Yan ,Rui Pereira ,G N Kim ,F Barão ,Andreas Obermeier ,K S Kim ,H R Wu ,T Kirn ,N H Wang ,M S Krafczyk ,P H Fisher ,F J Eppling ,B S Shan ,H Y Chou ,Ying Shi ,C H Chung ,Th Lippert

doi:10.1103/physrevlett.115.211101

Abstract

Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.

Highlights

Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station
Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin
from 1.9 GV to 3 TV based on 50 million events is presented

Summary

Published by the American Physical Society

A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. In this Letter we report the precise measurement of the helium flux in primary cosmic rays in the rigidity range from 1.9 GV to 3 TV based on data collected by the Alpha Magnetic Spectrometer (AMS) during the first 30 months (May 19, 2011 to November 26, 2013) of operation onboard the International Space Station (ISS). The cutoff was calculated by backtracing [17] particles from the top of the AMS out to 50 Earth’s radii using the most recent IGRF [18] geomagnetic model These procedures resulted in a sample of 5.0 × 107 primary cosmic rays with Z 1⁄4 2, where all the events passed from L1 to L9. Analysis.— The isotropic He flux Φi for the ith rigidity bin (Ri, Ri þ ΔRi) is

Ni AiεiTiΔRi

Spectral Index