New aspects in nucleon-nucleus collisions and EAS properties around 10(6) GeV

At energies higher than 2 x 10 to the 5 GeV, very little information exists on detailed properties of nucleon-nucleon collision; the rare elements are coming from jets, and, as nondirect improvements from gamma-ray families. The results exhibit some conflicting features, or, at least, very large fluctuations like copious production of gamma-rays in opposition to Centauro-like events, sometimes suggest that phase transition to quark gluon plasma occurs in nucleus-nucleus collisions and even in nucleon-nucleus collision. The multicluster phenomenological model (MPM) extrapolated for extensive air showers EAS simulation up to 5 x 10 to the 6 GeV to put in evidence some significant deviation between experimental data and prediction

Topological aspects of age parameter

The well known NKG function is a very useful tool to describe the lateral extension of the electromagnetic component in Extensive Air Showers (EAS); however, in spite of non-negligible qualities (simplicity, normalization by beta function), it doesn't correspond exactly to the natural shape of the lateral electron distribution. Several bias may occur in size estimation if NKG is used without correction. It is shown that the longitudinal age parameter s sub t can be correlated with the information obtained from the lateral electron densities according to the conditions of use of the NKG function

LPM effect and primary energy estimations

The distortion of the electron cascade development under LPM effects is now admitted; it consists of an increase of depth of showers origin, of shower maximum T sum max, a decrease of the number of particles at maximum N sub max and results in a flattening and a widening of the cascade transition curve. Connected with the influence of multiple Coulomb scattering on basic electromagnetic processes (bremsstrahlung, pair production), this effect appears at high energy with a threshold dependent on the density of the medium (more than 10 TeV for lead, more than 10 sup 6 TeV in air). Consequently, the electromagnetic components of hadron induced showers in lead and EAS in air calculated for the same hadronic cascades in the different alternative, including or not the LPM effect are examined here

Multimuons events and primary composition

Nucleon decay detectors at large depths offers now a total area larger than 1000 sq m to registrate muons of energy exceeding 1 TeV. Near complete high energy muon families are detected in those arrays. An extensive 3D Monte-Carlo simulation was conducted in view to understand the spatial distribution of those events and the possible link with elementary act or primary composition. As pion or kaon parents have a very small decay probability at so high energy, multimuon phenomena occurs at high altitude where the atmospheric density is small after the most energetic collisions

Ultra high energy events in ECHOS series and primary energy spectrum

The compilation of ultra high energy jets suggests at present the existence of a bump in primary energy spectrum (with the standard concept of high energy collisions). The pseudo-rapidity distribution exhibits some typical anomalies, more than the (P sub t) behavior, which are (may be) the fingerprints of quark gluon plasma transition. The next results of Emulsion Chamber on Supersonic (ECHOS) will be in both cases determinant to confirm those tendancies, as well as an important effort of the cosmic ray community to develop in that sense a flying emulsion chamber experiment

Behaviour of the EAS Age Parameter in the Knee Energy Region

Analyzing simulated EAS events generated with the CORSIKA code, the characteristics of lateral distribution of electrons in EAS around the knee energy region of the primary energy spectrum have been studied and compared with experimental observations. The differences between the EGS4 and the NKG output of CORSIKA in respect to electron radial density distribution have been investigated. The relation between lateral and longitudinal age parameters has been studied after introducing the notion of the local age parameter that reflects the profile of the lateral distribution of electrons in EAS. The present analysis motivates the inclusion of the lateral shower age in a multiparameter study of EAS to extract information on hadronic interactions and primary composition.Comment: Talk presented at XVI International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI 2010), Batavia, IL, USA (28 June - 2 July 2010). 4 pages, 5 figure

Validity of the estimators of primary energy in giant EAS

A set of hypergeometric gaussian functions, with a consistent relation between age parameter and total size is proposed in the ultra high energy range (above 1 EeV) for electrons, and vertical equivalent muons (vem). This is an important step for a coherent interpretation of hybrid events recorded with both surface array and uorescence telescope. Observing that the extrapolation of the original cosmic ray primary spectrum derived from the size spectrum measured in the Akeno classical EAS array coincides with the spectrum measured recently by the Hires Stereo experiment , we point out a possible overestimation of the primary energy in inclined showers of the surface arrays like AGASA ; this circumstance gives more support to the GZK synopsis

The continuity of the cosmic ray spectra measured by classical and giant EAS arrays

The extrapolation of the original cosmic ray primary spectrum derived from the size spectrum measured in the Akeno classical EAS array coincides with the spectrum measured recently by the Hires Stereo experiment. After revisiting the calibrations carried in the overlapping energy region around $10^{18}eV$, we discuss the consequences of the different approaches in classical arrays and giant surface arrays. The data is obtained from the size spectrum registration in the Akeno experiment with a modest space grid of $30$ to $100$m, instead of $1$km or more in giant arrays using density estimators in place of size and different absorption treatments for inclined cascades. While the analysis of those circumstances suggest a reduction of the energy converted from the estimators in giant surface arrays, the consistency of classical and fluorescence measurements gives more support to the GZK prediction