Delayed hadrons in extensive air showers: Evidence for the iron-group nuclei in primary cosmic-ray flux at energies approx. 10/sup 13/--10/sup 15/ eV
The distribution of arrival time of energetic hadrons in the near-core region of air showers of energies approx.10/sup 4/--10/sup 6/ GeV relative to the shower front has been studied experimentally at mountain altitude. The observed rate of hadron events with (i) energy >50 GeV in the calorimeter, (ii) associated shower particle density >18 m/sup -2/, and (iii) a signal > or =5 equivalent particles in a plastic scintillator T/sub 3/ of area 0.54 m/sup 2/ placed under 220 g cm/sup -2/ of absorber in the calorimeter is found to be 1.85 x 10/sup -3/ m/sup -2/sr/sup -1/sec/sup -1/. Of these events a fraction (0.55 +- 0.05)% have shown the signal from T/sub 3/ to be delayed by 15 nsec or greater relative to shower particles. Monte Carlo simulations of experimental observations have shown that these requirements on energy and shower density enhance the sensitivity of the observed rate to the contributions due to showers initiated by heavy nuclei. Calculations also show that observed delayed hadrons are mostly associated with showers due to heavy nuclei. For interpretation of observed features two models for primary composition have been considered. In the first model the power-law spectra for protons and lighter nuclei are assumed to have spectral index ..gamma../sub p/ and the heavy (iron group) nuclei the index ..gamma../sub Fe/. An agreement between the expectation and observation requires the values of ..gamma../sub p/ and ..gamma../sub Fe/ to be significantly different as -2.68 and -2.39 in the energy range approx.10/sup 3/--10/sup 6/ GeV. In the second model the spectral index ..gamma.. is assumed to be the same for all components and the spectra steepen by 0.5 at the same rigidity R/sub c/. It is found that the values of ..gamma.. and R/sub c/ should be -2.55 and 10/sup 5/ GV/c, respectively, to match the observations.
- Research Organization:
- Department of Physics and Astronomy, University of Maryland, College Park, Maryland 20742
- OSTI ID:
- 6719238
- Journal Information:
- Phys. Rev. D; (United States), Vol. 26:5
- Country of Publication:
- United States
- Language:
- English
Similar Records
CONSTRAINTS ON COSMIC RAYS, MAGNETIC FIELDS, AND DARK MATTER FROM GAMMA-RAY OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES WITH VERITAS AND FERMI
Hadronic interactions at energies around 10/sup 3/ TeV inferred fromthe large-scale emulsion-chamber experiment at Mt. Fuji
Related Subjects
GENERAL PHYSICS
COSMIC NUCLEI
ISOTOPE RATIO
EXTENSIVE AIR SHOWERS
DELAYED PROTONS
PRIMARY COSMIC RADIATION
CALORIMETERS
IRON
MONTE CARLO METHOD
PLASTIC SCINTILLATORS
SCALING LAWS
BARYONS
COSMIC RADIATION
COSMIC SHOWERS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
HADRONS
IONIZING RADIATIONS
MEASURING INSTRUMENTS
METALS
NUCLEI
NUCLEONS
PHOSPHORS
PROTONS
RADIATIONS
SECONDARY COSMIC RADIATION
SHOWERS
TRANSITION ELEMENTS
640101* - Astrophysics & Cosmology- Cosmic Radiation