The evolution of the cosmic ray primary composition in the energy range 106–107 GeV (i.e. the “knee” region) is studied by means of the e.m. and muon data of the Extensive Air Shower EAS-TOP array ...(Campo Imperatore, National Gran Sasso Laboratories). The measurement is performed through: (a) the correlated muon number (Nμ) and shower size (Ne) spectra, and (b) the evolution of the average muon numbers and their distributions as a function of the shower size. From analysis (a) the dominance of helium primaries at the knee, and therefore the possibility that the knee itself is due to a break in their energy spectrum (at EkHe=(3.5±0.3)×106 GeV) are deduced. Concerning analysis (b), the measurement accuracies allow the classification in terms of three mass groups: light (p,He), intermediate (CNO), and heavy (Fe). At primary energies E0≈106 GeV the results are consistent with the extrapolations of the data from direct experiments. In the knee region the obtained evolution of the energy spectra leads to: (i) an average steep spectrum of the light mass group (γp,He>3.1), (ii) a spectrum of the intermediate mass group harder than the one of the light component (γCNO≃2.75, possibly bending at EkCNO≈(6–7)×106 GeV), (iii) a constant slope for the spectrum of the heavy primaries (γFe≃2.3–2.7) consistent with the direct measurements. In the investigated energy range, the average primary mass increases from 〈lnA〉=1.6–1.9 at E0≃1.5×106 GeV to 〈lnA〉=2.8–3.1 at E0≃1.5×107 GeV. The result supports the standard acceleration and propagation models of galactic cosmic rays that predict rigidity dependent cut-offs for the primary spectra of the different nuclei. The uncertainties connected to the hadronic interaction model (QGSJET in CORSIKA) used for the interpretation are discussed.
Ground arrays for UHECR shower detection based on traditional counters, water Cerenkov tanks or scintillator modules, are unavoidably limited by the saturation suffered by the counters nearest to the ...shower axis. Reducing to a negligible level the amount of events recorded with saturated counters should be mandatory in a future UHECR ground array. The use of the signals extracted from the internal dynodes of the used photomultipliers can offer an elegant and inexpensive way to increase the dynamic range of such detectors. The viability of this technique has been explored studying in laboratory the performances of a sample of 3 Hamamatsu R5912-MOD photomultipliers. Exploiting the signal from the fifth dynode, a linear response up to an equivalent anodic peak current larger than 1A (at gain G = 2 times 10 super(5)) has been measured for all the studied PMTs. The feasibility of this technique in the frame of a new ground array for UHECR studies should be verified with a larger sample of photomultipliers.
We show that new detectors dedicated to direct measurements of charged cosmic ray (CR) nuclei at energies > 100 GeV/n could determine the diffusion coefficient power index δ through the measurement ...of the boron-to-carbon ratio with an uncertainty of about 10-15 %. Space-based or satellite detectors will be able to determine d with very high accuracy even in the case of important systematic errors. We also find that no uncertainties other than those on δ affect the determination of the acceleration slope α, so that measures of light primary nuclei performed with the same experiments will provide valuable information also on the acceleration mechanisms.
The present white paper is submitted as part of the “Snowmass” process to help inform the long-term plans of the United States Department of Energy and the National Science Foundation for high-energy ...physics. It summarizes the science questions driving the Ultra-High-Energy Cosmic-Ray (UHECR) community and provides recommendations on the strategy to answer them in the next two decades.
The flux of cosmic ray hadrons at the atmospheric depth of 820 g
cm
−2 has been measured by means of the EAS-TOP hadron calorimeter (Campo Imperatore, National Gran Sasso Laboratories, 2005 m ...a.s.l.).
The hadron spectrum is well described by a single power law:
S
h
(E
h
)=(2.25±0.21±0.34
sys
)×10
−7
E
h
1000
(−2.79±0.05)
m
−2
s
−1
sr
−1
GeV
−1
overthe energy range 30 GeV–30 TeV. The procedure and the accuracy of the measurement are discussed.
The primary proton spectrum is derived from the data by using the CORSIKA/QGSJET code to compute the local hadron flux as a function of the primary proton spectrum and to calculate and subtract the heavy nuclei contribution (basing on direct measurements). Over a wide energy range
E
0=0.5–50 TeV its best fit is given by a single power law:
S(E
0)=(9.8±1.1±1.6
sys
)×10
−5
E
0
1000
(−2.80±0.06)
m
−2
s
−1
sr
−1
GeV
−1
The validity of the CORSIKA/QGSJET code for such application has been checked using the EAS-TOP and KASCADE experimental data by reproducing the ratio of the measured hadron fluxes at the two experimental depths (820 and 1030 g
cm
−2 respectively) at better than 10% in the considered energy range.
The present white paper is submitted as part of the "Snowmass" process to help inform the long-term plans of the United States Department of Energy and the National Science Foundation for high-energy ...physics. Further, it summarizes the science questions driving the Ultra-High-Energy Cosmic-Ray (UHECR) community and provides recommendations on the strategy to answer them in the next two decades.
Cosmic Ray Energetics And Mass (CREAM) is a balloon-borne experiment designed to perform direct measurements of cosmic ray composition over the elemental range from proton to iron to the supernova ...energy scale of
10
15
eV
in a series of balloon flights using the new Ultra Long Duration Balloon (ULDB) capability under development by NASA. The first flight of CREAM will take place at the end of 2004 from Antarctica. The instrument includes a sampling tungsten/scintillating fiber calorimeter preceded by a graphite target with scintillating fiber hodoscopes, a pixelated silicon charge detector, a transition radiation detector and a segmented timing-based particle-charge detector. The thin ionization calorimeter has been designed to operate in the range of energies from a few hundred GeV to 1
PeV providing imaging capability in the reconstruction of the showers originating from the interaction of primary nuclei in the carbon target. A twin calorimeter for the second CREAM payload has been built and tested at CERN. Its construction technique and preliminary test results are presented.
We discuss the potentials of several experimental configurations dedicated to direct measurements of charged cosmic ray (CR) nuclei at energies ≳100
GeV/n. Within a two-zone propagation model for ...stable CRs, we calculate light primary and secondary nuclei fluxes for different diffusion and acceleration schemes. We show that the new detectors exploiting the long and ultra long duration balloon flights could determine the diffusion coefficient power index
δ through the measurement of the boron-to-carbon ratio with an uncertainty of about 10–15%, if systematic errors are low enough. Only space-based or satellite detectors will be able to determine
δ with very high accuracy even in the case of important systematic errors, thanks to the higher energy reach and the less severe limitations in the exposure. We show that no uncertainties other than those on
δ affect the determination of the acceleration slope
α, so that measures of light primary nuclei, such as the carbon one, performed with the same experiments, will provide valuable information on the acceleration mechanisms.
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