M. Menichelli

Observations of cosmic ray electrons and positrons using an imaging calorimeter

A ballon-borne magnet spectrometer system was flown for 5.5 hr at an altitude of more than 117,00 feet from Prince Albert, Saskatchewan (Canada), on 1989 September 5, when the Newark neutron monitor rate was 2952. The instrument was a modified version of the one used to observe antiprotons in 1979. The most significant modification was the addition of an imaging calorimeter, 7.33 radiation lengths thick. Inclusion of the calorimeter has significantly improved the ability to distinguish electrons and positrons from the other constituents of the cosmic rays. The absolute electron flux has been determined in the energy interval 1.3-26 GeV. The electron spectrum at the top of the atmosphere was found to be J(sub e-) = 177E(exp -(3.15+/-0.13)) electrons/ sq m/(sr s GeV) in the energy range 4.0-26 GeV. Below 4 GeV, the spectrum showed flattening, which is consistent with the effect of solar modulation. The e(+)/(e(+)+e(-)) ratio was found to be (0.11 +/- 0.03) in the energy range 5.2-13 GeV.

Measurement of the positron to electron ratio in the cosmic rays above 5-GeV

As part of a series of experiments to search for antimatter in cosmic rays, the New Mexico State University balloon-borne magnet spectrometer was configured for a flight to study positrons. Two completely new instruments, a transition radiation detector and a silicon-tungsten imaging calorimeter, were added to the magnet spectrometer. These two detectors provided a proton rejection factor better than 3 × 104. This instrument was flown from Fort Sumner, New Mexico, at an average depth of 4.5 g cm-2 of residual atmosphere for a period of 25 hr. We report here the measured fraction of positrons e+/(e+ + e-) from ~5 to 60 GeV at the top of the atmosphere. Our measurements do not show any compelling evidence for an increase in this ratio with energy, and our results are consistent with a constant fraction of 0.078 ± 0.016 over the entire energy region.

Measurement of Cosmic-Ray Antiprotons from 3.7 to 19 GeV

The antiproton-to-proton ratio,p ¯/p, in cosmic rays has been measured in the energy range 3.7‐19 GeV. This measurement was carried out using a balloon-borne superconducting magnetic spectrometer along with a gas Cerenkov counter, an imaging calorimeter, and a time-of-flight scintillator system. The measuredp ¯/p ratio was

Absolute spectrum and charge ratio of cosmic ray muons in the energy region from 0.2 GeV to 100 GeV at 600 m above sea level

We have determined the momentum spectrum and charge ratio of muons in the region from 250 MeV/c to 100 GeV/c using a superconducting magnetic spectrometer. The absolute differential spectrum of muons obtained in this experiment at 600 m above sea level is in good agreement with the previous measurements at sea level. The differential spectrum can be represented by a power law with a varying index, which is consistent with zero below 450 MeV/c and steepens to a value of −2.7 ± 0.1 between 20 and 100 GeV/c. The integral flux of muons measured in this experiment span a very large range of momentum and is in excellent agreement with the earlier results. The positive to negative muon ratio appears to be constant in the entire momentum range covered in this experiment within the errors and the mean value is 1.220 ± 0.044. The absolute momentum spectrum and the charge ratio measured in this experiment are also consistent with the theoretical expectations. This is the only experiment which covers a wide range of nearly 3 decades in momentum from a very low momentum.

Performance of a balloon-borne magnet spectrometer for cosmic ray studies

Abstract This paper summarizes the performance characteristics of the balloon-borne magnet spectrometer operated by New Mexico State Universitys Particle Astrophysics Laboratory. Particular emphasis has been placed on the rigidity resolution, including both random and systematic errors of the magnetic spectrometer system. Measurement of the performance characteristics has been greatly enhanced through the use of an imaging calorimeter as an independent aid in the identification of cosmic rays.

WiZard SiW imaging calorimeter: a preliminary study on its particle identification capability during a balloon flight in 1993

Abstract The WiZard Collaboration is engaged in a program to study the antimatter components of the cosmic rays. A silicon-tungsten (WiW) imaging calorimeter has been developed as part of this program. We present its performance and preliminary results, obtained during a balloon flight on September 8, 1993. The flight was dedicated to the measurement of the positron spectrum in the energy range 4–50 GeV and took place from Ft. Sumner, New Mexico.

Momentum spectra of atmospheric pions, muons, electrons and positrons at balloon altitudes

Momentum spectra of pions, muons, electrons and secondary positrons have been measured at an atmospheric depth of 5: 8gc m 2 with the same instrument. Data was collected by the Matter Antimatter Space Spectrometer of the New Mexico State University in a balloon flight in September 1991 at the rigidity cut-off of 4 : 5G V c 1 in Fort Sumner, New Mexico. The first measurement of the positive muon spectrum in the range 0:15 GeV c 1 to 2 GeVc 1 is reported in this paper. The spectral index above 3 GeV c 1 of the negative muon momentum spectrum of this measurement is 2:39 0:05 in agreement with analytical cascade calculations which assume a primary proton kinetic energy spectrum with a slope of 2:740:02 in the corresponding kinetic energy range. In the momentum interval 300-700 MeV c 1 , both negative and positive muon fluxes turn out to be larger than calculated fluxes by a factor of about 1.4. The measurement of the secondary electron and positron energy spectra allows a reliable subtraction of the atmospheric background from the primary electron and positron fluxes which are affected by large uncertainties in most of the experiments. The energy spectra of the secondary particles reported here have the same systematic errors implying a higher relative accuracy with respect to those measurements made in different flights.

Temperature dependence of time resolution and electronic noise in a silicon detector telescope

Abstract We have constructed a silicon detector time-of-flight spectrometer operating at low temperature with an overall time resolution of 115.2 ± 2.0 ps at −50°C for minimum ionizing particles with unitary charge. We report the measurement of the overall time resolution of the telescope versus temperature in several relevant experimental conditions from −50 to 20°C. An extensive experimental study of the noise components of the detector and of the electronic readout as a function of the temperature is also given. We present an analysis of the measured noise components in order to account for the improvement of time resolution when the temperature varies from 20 to −50°C. Future developments of cold silicon strip detectors for time-of-flight determination are considered.

Leakage current and capacity variation with temperature in silicon detectors of a space calorimeter

Abstract Leakage current and capacity dependence on temperature have been measured in the range − 30°C t

WiZard 2: a proposal to complement WiZard detector with two further modules of tracking calorimeter and an accurate spark counter t.o.f. system

Among the several existent proposals for the cosmic antimatter search, the Wi#x005A-0304;ard project for the U.S. Space Station Freedom shows the greatest interest. A possible upgrading of the Wi#x005A-0304;ard apparatus, called Wi#x005A-0304;ard 2, is presented in order to sensibly improve the capability of detecting antihelium nuclei in the cosmic radiation.SummaryAmong the several existent proposals for the cosmic antimatter search, the Wi#x005A-0304;ard project for the U.S. Space Station Freedom shows the greatest interest. A possible upgrading of the Wi#x005A-0304;ard apparatus, called Wi#x005A-0304;ard 2, is presented in order to sensibly improve the capability of detecting antihelium nuclei in the cosmic radiation.RiassuntoFra tutte le varie proposte esistenti nell’ambito della ricerca di antimateria cosmica, il progetto Wi#x005A-0304;ard per la Stazione Spaziale americana Freedom si dimostra del piú grande interesse. Si presenta un possibile ampliamento dell’apparato Wi#x005A-0304;ard allo scopo di migliorare sensibilmente la capacità di rivelare nuclei di antielio nella radiazione cosmica.Among the several existent proposals for the cosmic antimatter search, the Wi#x005A-0304;ard project for the U.S. Space Station Freedom shows the greatest interest. A possible upgrading of the Wi#x005A-0304;ard apparatus, called Wi#x005A-0304;ard 2, is presented in order to sensibly improve the capability of detecting antihelium nuclei in the cosmic radiation. Fra tutte le varie proposte esistenti nell’ambito della ricerca di antimateria cosmica, il progetto Wi#x005A-0304;ard per la Stazione Spaziale americana Freedom si dimostra del piu grande interesse. Si presenta un possibile ampliamento dell’apparato Wi#x005A-0304;ard allo scopo di migliorare sensibilmente la capacita di rivelare nuclei di antielio nella radiazione cosmica.