The Relative Fluxes of Protons and Helium Nuclei up to 100GeV/n

TheRelativeFluxesofProtonsandHeliumNucleiupto100GeV/nS.P. Swordy1, S.W. Barwick2, J.J. Beatty3, C.R. Bower4, C. Chaput5S. Coutu5, G. de Nolfo3, D. Ficenec, J. Knapp1, D.M. Lowder6S. McKee5, D. M uller1, J.A. Musser4, S.L. Nutter, E. Schneider2K.K. Tang7, G. Tarle5, A.D. Tomasch, E. Torb et11.University of Chicago, Enrico Fermi Institute, Chicago, IL 606372.University of California at Irvine, Dept.of Physics, Irvine, CA 927173.Washington University, Dept.of Physics, St.Louis, MO 631304.Indiana University, Dept.of Physics, Bloomington, IN 474055.University of Michigan, Dept.of Physics, Ann Arbor, MI 481096.University of California at Berkeley, Dept.of Physics, Berkeley, CA 947207.University of Utah, Dept.of Physics, Salt Lake City, UT 84112AbstractThe high energy antimatter telescop e (HEAT) was own for 29 hourson a high altitude ballo on in May 1994. Although the primary goal of thisexp eriment was the measurement of electron and p ositron abundances athigh energy, a large sample of data containing high energy protons andhelium nuclei was also collected.The magnet sp ectrometer of HEAT hasb een used to analyze these data and determine the ratio of the uxes overa range of rigidities from 10GV to 200GV. This ratio is compared to asimple prediction based on a leaky-b ox mo del and recent predictions fromnon-linearsho ckacceleration.Theprotonandheliumenergysp ectrahave also b een determined and are compared to existing measurements.1Intro ductionThe HEAT-einstrument combines a magnet sp ectrometer with a transitionradiation detector and a lead/scintillatorelectromagnetic calorimeter (EMC)todiscriminateefromthemuchlargeruxofhadrons[1].Theinstrumentistriggeredbyacoincidenceb etweenplasticscintillationcounterswhicharealso used for determining the charge of relativistic particles by a measurementoftheenergy-loss.SinceprimarygoalHEAT-eisto studyelectronsthe main trigger requires the equivalent of 0.5GeV electromagnetic shower en-ergy dep osition in the lower 70% of the EMC. Protons and helium nuclei alsoo ccasionallypro duceatriggersignalresultingfromhadronicinteractionsthe EMC or by uctuationsinthesingleparticleenergyloss.Asmall( 4%)prescaledsampleofeventswhichtriggertheshowercounteratalolevelcorresp onding to a single non-interacting proton are also included in the data.Theprobabilityforahadronicshowertriggerisfoundtob eessentiallyin-dep endentofparticleenergyab ove10GeV/nbyacomparisonwiththese