Speaker
michele iacovacci
(INFN)
Description
By means of the analog readout, the ARGO-YBJ experiment is able to image the very hot region of
the shower core up to particle density of many 10^4/m^2. Exploiting this feature the number of
particles within 10 m from the core and the local age have been carefully studied. This
cascade region is mainly developed from particles produced in the first interactions with pseudorapidity eta > 7, an angular region still out of the reach of the accelerator experiments. We find a systematic shift of the measure
d local age by $\sim$ 0.15-0.20 with respect to the MC expectation, by assuming primary fluxes and composition as given by the Hoerandel model and hadronic interactions as described by QGSJET2. This
effect cannot be taken into account by any
instrumental effect neither by reconstruction biases. Possible explanations of this result involve
both the features of the hadronic interaction as well as the elemental composition of the primary
cosmic rays in the energy range between 50 TeV and 5 PeV.
| Registration number following "ICRC2015-I/" | 817 |
|---|---|
| Collaboration | ARGO-YBJ |
Author
Stefano Mastroianni
(INFN, sec. Naples)
Co-author
michele iacovacci
(INFN)
