J. Kremer

The Cosmic-Ray Antiproton Flux between 3 and 49 GeV

We report on a new measurement of the cosmic ray antiproton spectrum. The data were collected by the balloon-borne experiment CAPRICE98 which was flown on 28-29 May 1998 from Fort Sumner, New Mexico, USA. The experiment used the NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas Ring Imaging Cherenkov (RICH) detector, a time-of-flight system, a tracking device consisting of drift chambers and a superconducting magnet and a silicon-tungsten calorimeter. The RICH detector was the first ever flown capable of mass-resolving charge-one particles at energies above 5 GeV. A total of 31 antiprotons with rigidities between 4 and 50 GV at the spectrometer were identified with small backgrounds from other particles. The absolute antiproton energy spectrum was determined in the kinetic energy region at the top of the atmosphere between 3.2 and 49.1 GeV. We found that the observed antiproton spectrum and the antiproton-to-proton ratio are consistent with a pure secondary origin. However, a primary component may not be excluded.We report on a new measurement of the cosmic ray antiproton spectrum. The data were collected by the balloon-borne experiment CAPRICE98, which was —own on 1998 May 28¨29 from Fort Sumner, New Mexico. The experiment used the NMSU-WiZard/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas Ring Imaging Cherenkov (RICH) detector, a time-of-—ight system, a tracking device consisting of drift chambers and a superconducting magnet, and a silicon-tungsten calorimeter. The RICH detector was the —rst ever —own capable of mass-resolving charge-one particles at energies above 5 GeV. A total of 31 antiprotons with rigidities between 4 and 50 GV at the spectrometer were identi—ed with small backgrounds from other particles. The absolute antiproton energy spectrum was determined in the kinetic energy region at the top of the atmosphere between 3.2 and 49.1 GeV. We found that the observed antiproton spectrum and the antiproton-to-proton ratio are consistent with a pure secondary origin. However, a primary component may not be excluded.

The cosmic-ray proton and helium spectra measured with the CAPRICE98 balloon experiment

A new measurement of the primary cosmic-ray proton and helium fluxes from 3 to 350 GeV was carried out by the balloon-borne CAPRICE experiment in 1998. This experimental setup combines different detector techniques and has excellent particle discrimination capabilities allowing clear particle identification. Our experiment has the capability to determine accurately detector selection efficiencies and systematic errors associated with them. Furthermore, it can check for the first time the energy determined by the magnet spectrometer by using the Cherenkov angle measured by the RICH detector well above 20 GeV n � 1 . The analysis of the primary proton and helium components is described here and the results are compared with other recent measurements using other magnet spectrometers. The observed energy

Measurements of cosmic-ray electrons and positrons by the Wizard/CAPRICE collaboration

Two recent balloon-borne experiments have been performed by the Wizard/CAPRICE collaboration in order to study the electron and positron components in the cosmic radiation. On 1994 August 8-9 the CAPRICE94 experiment flew from norther Canada and on 1998 May 28-29 the CAPRICE98 experiment flew from New Mexico, USA at altitude8 corresponding to 3.9 and 5.5 g/cm2 of average residual atmosphere respectively. The apparatus were equipped with a Ring Imaging Cherenkov (RICH) detector, a time-of-flight system, a superconducting magnet spectrometer with a tracking system and a 7-radiation-length silicon-tungsten imaging calorimeter. The RICH used in 1994 had a solid NaF radiator while in 1998 the RICH had a CbFlO gaseous radiator. We report on the electron and positron spectra and positron fraction at the top of the atmosphere from few hundred MeV to 40 GeV measured by these two experiments.

First Mass-resolved Measurement of High-Energy Cosmic-Ray Antiprotons.

We report new results for the cosmic-ray antiproton-to-proton ratio from 3 to 50 GeV at the top of the atmosphere. These results represent the first measurements, on an event-by-event basis, of mass-resolved antiprotons above 18 GeV. The results were obtained with the NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas-RICH (Ring-Imaging Cerenkov) counter and a silicon-tungsten imaging calorimeter. The RICH detector was the first ever flown that is capable of identifying charge-one particles at energies above 5 GeV. The spectrometer was flown on 1998 May 28-29 from Fort Sumner, New Mexico. The measured p&d1;/p ratio is in agreement with a pure secondary interstellar production.

High-energy deuteron measurement with the CAPRICE98 experiment

We report the first measurement of the deuterium abundance in cosmic rays above 10 GeV nucleon � 1 of kinetic energy. The data were collected by the balloon-borne experiment CAPRICE98, which was flown on 1998 May 28–29 from Fort Sumner, New Mexico. The detector configuration included the NMSU-WiZard/CAPRICE superconducting magnet spectrometer equipped with a gas RICH detector, a silicon-tungsten calorimeter, and a time-of-flight system. By combining the information from the spectrometer and the RICH detector, it was possible to separate deuterons from protons in the kinetic energy range from 12 to 22 GeV nucleon � 1 .I n order to estimate the proton background and the deuteron selection efficiency, we developed an empirical model for the response of the instrument, based on the data collected in this experiment. The analysis procedure is described in this paper, and the result on the absolute flux of deuterium is presented. We found that the deuterium abundance at high energy is consistent with the hypothesis that the propagation mechanism of light nuclei is the same as that of heavier secondary components. Subject headings: balloons — cosmic rays — Galaxy: abundances — ISM: abundances

CAPRICE98: A balloon borne magnetic spectrometer to study cosmic ray antimatter and composition at different atmospheric depths

CAPRICE98 is a superconducting magnetic spectrometer built by the WiZard collaboration. It was launched from Ft. Summer, NM, USA on the 28th of May 1998. For the first time a gas RICH detector has been flown together with a silicon electromagnetic calorimeter. The instrument configuration included a time of flight detector and a drift chamber stack, which were placed in the region of a magnet field, for rigidity measurement. Science objectives for this experiment include the study of antimatter in cosmic rays and that of cosmic ray composition in the atmosphere with special focus on muons.

Performance of the CAPRICE98 balloon borne gas-RICH detector

A RICH counter using a gas radiator ofC 4F10 and a photosensitive MWPC with pad readout has been developed, tested in particle beam at CERN and used in the CAPRICE98 balloon-borne experiment. The MWPC was operated with a TMAE and ethane mixture at atmospheric pressure and used a cathode pad plane to give an unambiguous image ofthe Cherenkov light. The induced signals in the pad plane were read out using the AMPLEX chip and CRAMS. The good efficiency ofthe Cherenkov light collection, the efficient detection ofthe weak signal f rom single UV photons together with a low noise level in the electronics ofthe RICH detector, resulted in a large number ofdetected photoelectrons per event. For b ’ 1 charge one particles, an average of12 photoelectrons per event were detected. The reconstructed Cherenkov angle of50 mrad f a b ’ 1 particle had a resolution of1 :2 mrad (rms). The RICH was flown with the CAPRICE98 magnetic spectrometer and was the first RICH counter ever used in a balloon-borne experiment capable ofidentifying charge one particles at energies above 5 GeV. The RICH provided an identification of

Measurements of primary cosmic-ray hydrogen and helium by the WiZard collaboration

We present the measurements of primary protons and helium nuclei performed by the Wizard Collaboration in different balloon-borne campaigns. A superconducting magnet spectrometer was used in these experiments together with detectors for particle recognition. These combinations of detectors made it possible to perform accurate particle measurements over a large (up to 200 GV for protons) energy interval. We focus in particular on the results from the MASS91 and CAPRICE94 experiments: We find a very good agreement between these two sets of measurements, also in comparison to other recent results. All these results seem to suggest that the normalization of primary cosmic rays may be significantly lower than previously estimated.

The WiZard collaboration cosmic ray muon measurements in the atmosphere

Balloon-borne experiments allow cosmic ray measurements to be performed over large ranges of atmospheric depths. The WiZard Collaboration is involved in a long-range investigation of the cosmic ray muon fluxes in the atmosphere. In this paper, we will discuss the relevance of such measurements to the atmospheric neutrino calculations and will review the results reported by the Collaboration, with particular emphasis on those coming from the latest flight CAPRICE98.