A novel approach for deducing the mass composition of cosmic rays from lateral densities of EAS particles

Abstract

A Monte Carlo (MC) simulation study of cosmic ray (CR) extensive air showers (EAS) has been carried out in the energy regime of the KASCADE experiment. From the characteristics of lateral distributions of electrons and muons of simulated EAS, some important EAS observables are extracted by a novel approach, and their CR mass-sensitivity is demonstrated. The study takes into account the issue of the experimental lateral density profiles of EAS electrons and muons after introducing the notion of the local age and segmented slope parameters, aimed to extract information on CR mass composition from observed data. The estimated lateral shower age and slope from the analysis of the KASCADE data (KCDC) agrees with the idea of a gradual change of CR mass composition from light to heavy around the knee.PACS numbers: 96.50.sd, 95.75.z, 96.50.S

Explaining the characteristics of lateral shower age of cosmic ray extensive air showers

“…Instead of taking multiple local ages belonging to a shower, a systematically chosen single age parameter was found appropriate to deal with some important issues such as composition, energy etc. on the PCRs [5,[7][8]. The minimum value of the LAP that was noticed at a particular radial distance between the first and the second maxima in the s local versus r curves appears very effective in several recent works [7][8].…”

“…The minimum value of the LAP that is assigned to a shower, is discussed below. Let us recall the feature of the LAP from both the simulations and observations in recent works [5,[7][8]. It was found that the parameter or the LDD of shower electrons exhibits some kind of scaling behavior if one studies the variation of the parameter with the radial distance from the EAS core [5].…”

“…Some current and recent works have revisited several conceptual issues in connection with the shower age particularly for protons/nuclei generated showers [4][5][6][7][8] and references therein. Basically the trace of the shape/form of the lateral distribution of shower electrons (i.e.…”

“…This indicates that the lateral shower age varies with the radial distance, which is in character the shower age at a point, and was labeled as the local age parameter (LAP) by Capdevielle and Gawin [11]. To assign a single age parameter to each shower, some works took the minimum value of the LAP from its variation against the radial distance [5,8] while some other works took some sort of averaging of different LAPs falling between the first minima and the second maxima [5,[7][8]11].…”

“…It is noteworthy to mention that the s parameter estimated from the above two distinctive methods is adjudged an important parameter for studying the primary cosmic rays (PCRs). These parameters have been used to correlate with other EAS observables to identify the nature of the shower initiating PCR particles [7][8]. The parameter also provides a basic relationship between the slope of the LDF and the crucial CR mass sensitive parameter 'the depth of shower maximum' (X max ) in the ultra-high-energy (UHE) range.…”