arXiv subjects

Nicusor Arsene

Publications and source records attributed to Nicusor Arsene.

15 recordsLinked to original sources

arXiv2025

Cosmic-Ray Mass Composition around the Knee via Principal Component Analysis

In this paper, we apply Principal Component Analysis (PCA) to experimental data recorded by the KASCADE experiment to reconstruct the mass composition of cosmic rays around the \textit{knee} region. A set of four extensive air shower parameters sensitive to the primary particle mass ($LCm$, $N_{\mu}$, $N_{e}$, and lateral shower $age$) was considered, whose coordinates were transformed into a new orthogonal basis that maximally captures the data variance. Based on the experimental distributions of the first two principal components (PCA0 vs.\ PCA1) and full Monte Carlo simulations of the KASCADE array considering five types of primary particles (p, He, C, Si, and Fe) and three hadronic interaction models (EPOS-LHC, QGSjet-II-04, and SIBYLL~2.3d), we obtained the evolution of the abundance of each primary species as a function of energy, as well as the evolution of the mean logarithmic mass with energy. We found that the reconstruction of the mass composition resulting from this comprehensive analysis significantly reduces dependence on the hadronic interaction model used in the simulation process, even though the initial input parameters are model-dependent. Moreover, the results support the idea that around the \textit{knee} region, the abundance of the light component (protons) decreases, while the heavy component shows a slight increase. The evolution of $\langle \ln (A) \rangle$ as a function of energy derived from this analysis shows excellent agreement with recent results from the LHAASO--KM2A experiment and aligns very well with the predictions of the data-driven GSF model.

astro-ph.HE↗

arXiv2023

Cosmic ray mass composition at the knee using azimuthal fluctuations of air shower particles detected at ground by the KASCADE experiment

The presence of hadronic sub-showers causes azimuthal non-uniformity in the particle distributions on the ground in vertical air showers. The $LCm$ parameter, which quantifies the non-uniformity of the signal recorded in detectors located at a given distance on a ring around the shower axis, has been successfully introduced as a gamma/hadron discriminator at PeV energies \cite{Conceicao:2022lkc}. In this work, we demonstrate that the $LCm$ parameter can effectively serve as a mass composition discriminator in experiments that employ a compact array of detectors, like KASCADE. We reconstruct the $LCm$ parameter distributions in the energy range $\lg(E/\rm eV) = [15.0 \text{ - } 16.0]$ using measurements from the KASCADE experiment, with intervals of $\lg(E/\rm eV) = 0.2$, which are then fitted with MC templates for five primary nuclei species p, He, C, Si, and Fe considering three hadronic interaction models: QGSjet-II-04, EPOS-LHC and SIBYLL 2.3d. We find that the $LCm$ parameter exhibits minimal dependence on the specific hadronic interaction model considered. The reconstructed fractions of individual species demonstrate a linear decrease in the abundance of protons and He nuclei with increasing energy, while the heavier components become prevalent above the \textit{knee} as predicted by all three hadronic interaction models. Our findings indicate that the abundance of particle types as a function of energy aligns with different astrophysical models that link the \textit{knee} to the acceleration and propagation of cosmic rays within the Galaxy. Furthermore, they also demonstrate excellent agreement with three more recent data-driven astrophysical models. These findings suggest that the $LCm$ parameter could be a valuable tool for forthcoming measurements of the LHAASO experiment to enhance our knowledge about the origin and acceleration mechanisms of cosmic rays.

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arXiv2021

Mass Composition of UHECRs from $X_{\rm max}$ Distributions Recorded by the Pierre Auger and Telescope Array Observatories

In this paper we infer the mass composition of the ultra high energy cosmic rays (UHECRs) from measurements of $X_{\rm max}$ distributions recorded at the Pierre Auger (2014) and Telescope Array (TA) (2016) Observatories, by fitting them with all possible combinations of Monte Carlo (MC) templates from a large set of primary species (p, He, C, N, O, Ne, Si and Fe), as predicted by EPOS-LHC, QGSJETII-04 and Sibyll 2.1 hadronic interaction models. We use the individual fractions of nuclei reconstructed from one experiment in each energy interval to build equivalent MC $X_{\rm max}$ distributions, which we compare with the experimental $X_{\rm max}$ distributions of the other experiment, applying different statistical tests of compatibility. The results obtained from both experiments confirm that the mass composition of the UHECRs is dominated ($\gtrsim$$70\%$) by protons and He nuclei {in the energy range investigated $\lg E (\rm eV)$ = [17.8--19.3] (Auger) and $\lg E \rm (eV)$ = [18.2--19.0] (TA).} The indirect comparisons between the $X_{\rm max}$ distributions recorded by the two experiments show that the degree of compatibility of the two datasets is good, even excellent in some high energy intervals, especially above the ankle ($\lg E (\rm eV) \sim 18.7$). However, our study reveals that, at low energies, further effort in data analysis is required in order to harmonize the results of the two experiments.

hep-ph↗

arXiv2021

Fitting fractions of the $X_{\rm max}$ distributions at ultra high energies

The mass composition of ultra high-energy cosmic ray (UHECRs) can be inferred from measurements of $X_{\rm max}$ distributions by fitting them with Monte Carlo (MC) predictions for different primary species of nuclei in each energy interval. On the basis of Monte Carlo (MC) simulations, we show that an appropriate approach is to fit the observed $X_{\rm max}$ distributions with all possible combinations of elements from a large set of primaries (in our case p, He, C, N, O, Ne, Si and Fe), and to find the "best combination" of elements which best describe the observed $X_{\rm max}$ distributions. We apply this method to the $X_{\rm max}$ distributions recorded by the Pierre Auger (2014) and Telescope Array (TA) (2016) Observatories in the energy range $\lg E (\rm eV) =$ [17.8 - 19.3] and $\lg E (\rm eV) =$ [18.2 - 19.0], respectively, by employing MC predictions of the QGSJETII-04 hadronic interaction model. The results obtained from both data sets suggest that the mass composition of UHECRs is dominated by protons and He nuclei ($\gtrsim 70\%$) which present a modulation of their abundances as a function of primary energy, but keeping their sum roughly constant. We performed an indirect comparison between the two data sets measured by the two experiments and found a good degree of compatibility in some energy bins around and above the \textit{ankle} ($\lg E (\rm eV) \sim 18.7$), but worsening at lower energies. We consider that the current approach, completed with predictions of different hadronic interaction models, can be used in further studies on mass composition to obtain a more accurate image of the evolution of the individual fractions of nuclei as a function of energy on the basis of experimental $X_{\rm max}$ distributions.

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arXiv2020

Restoration of azimuthal symmetry of muon densities in extended air showers

At ground level, the azimuthal distribution of muons in inclined Extensive Air Showers (EAS) is asymmetric, mainly due to geometric effects. Several EAS observables sensitive to the primary particle mass, are constructed after mapping the density of secondary particles from the ground plane to the shower plane (perpendicular to the shower axis). A simple orthogonal projection of the muon coordinates onto this plane distorts the azimuthal symmetry in the shower plane. Using CORSIKA simulations, we correct for this distortion by projecting each muon onto the normal plane following its incoming direction, taking also into account the attenuation probability. We show that besides restoring the azimuthal symmetry of muons density around the shower axis, the application of this procedure has a significant impact on the reconstruction of the distribution of the muon production depth and of its maximum, $X_{\rm max}^μ$, which is an EAS observable sensitive to the primary particle mass. Our results qualitatively suggest that not including it in the reconstruction process of $X_{\rm max}^μ$ may introduce a bias in the results obtained by analyzing the actual data on the basis of Monte Carlo simulations.

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arXiv2020

UHECRs mass composition from $X_{\rm max}$ distributions

The atmospheric depth where the energy deposit profile of secondary particles from extensive air showers (EAS) reaches its maximum, $X_{\rm max}$, is related to the primary particle mass. The mass composition of the ultra-high energy cosmic rays (UHECRs) can be inferred from measurements of $X_{\rm max}$ distributions in each energy interval, by fitting these distributions with Monte Carlo (MC) templates for four primary species (p, He, N and Fe). On the basis of simulations, we show that a high abundance of some intermediate elements in the $X_{\rm max}$ distributions, e.g. Ne or Si, may affect the quality of the fit and also the reconstructed fractions of different species with respect to their true values. We propose a method for finding the "best combination" of elements in each energy interval from a larger set of primaries (p, He, C, N, O, Ne, Si and Fe) which best describes the $X_{\rm max}$ distributions. Applying this method to the $X_{\rm max}$ distributions measured by the Pierre Auger Observatory (2014), we found that the "best combination" of elements which best describe the data suggest the presence of Ne or Si in some low energy bins for the EPOS-LHC model.

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arXiv2016

Simulation study of the correlation ($X_{max}^μ$, $N^μ$) in view of obtaining information on primary mass of the UHECRs

In this paper we study, using Monte Carlo simulations, the possibility to discriminate the mass of the Ultra High Energy Cosmic Rays (UHECRs) by combining information obtained from the maximum $X_{max}^μ$ of the muon production rate longitudinal profile of Extensive Air Showers (EAS) and the number of muons, $N^μ$, which hit an array of detectors located in the horizontal plane. We investigate the sensitivity of the 2D distribution $X_{max}^μ$ versus $N^μ$ to the mass of the primary particle generating the air shower. To this purpose we analyze a set of CORSIKA showers induced by protons and iron nuclei at energies of $10^{19}$eV and $10^{20}$eV, at five angles of incidence, $0^{\circ}$, $37^{\circ}$, $48^{\circ}$, $55^{\circ}$ and $60^{\circ}$. Using the simulations we obtain the 2D Probability Functions $Prob(X_{max}^μ,N^μ \ | \ p)$ and $Prob(X_{max}^μ,N^μ \ | \ Fe)$ which give the probability that a shower induced by a proton or iron nucleus contributes to a specific point on the plane ($X_{max}^μ$, $N^μ$). Then we construct the probability functions $Prob(p\ | \ X_{max}^μ,N^μ)$ and $Prob(Fe \ | \ X_{max}^μ,N^μ)$ which give the probability that a certain point on the plane ($X_{max}^μ$, $N^μ$) corresponds to a shower initiated by a proton or an iron nucleus, respectively. Finally, a test of this procedure using a Bayesian approach, confirms an improved accuracy of the primary mass estimation in comparison with the results obtained using only the $X_{max}^μ$ distributions.

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arXiv2016

Quantum production of black holes at colliders

We investigate black hole production in pp collisions at the Large Hadron Collider by employing the horizon quantum mechanics for models of gravity with extra spatial dimensions. This approach can be applied to processes around the fundamental gravitational scale and naturally yields a suppression below the fundamental gravitational scale and for increasing number of extra dimensions. The results of numerical simulations performed with the black hole event generator BLACKMAX are here reported in order to illustrate the main differences in the number of expected black hole events and mass distributions.

hep-ph↗

arXiv2016

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.

astro-ph.HE↗

arXiv2016

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.

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arXiv2015

Measurement of the cosmic ray spectrum above $4{\times}10^{18}$ eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-γ}$ with index $γ=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.

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arXiv2015

An improved limit to the diffuse flux of ultra-high energy neutrinos from the Pierre Auger Observatory

Neutrinos in the cosmic ray flux with energies near 1 EeV and above are detectable with the Surface Detector array of the Pierre Auger Observatory. We report here on searches through Auger data from 1 January 2004 until 20 June 2013. No neutrino candidates were found, yielding a limit to the diffuse flux of ultra-high energy neutrinos that challenges the Waxman-Bahcall bound predictions. Neutrino identification is attempted using the broad time-structure of the signals expected in the SD stations, and is efficiently done for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for "Earth-skimming" neutrino interactions in the case of tau neutrinos. In this paper the searches for downward-going neutrinos in the zenith angle bins $60^\circ-75^\circ$ and $75^\circ-90^\circ$ as well as for upward-going neutrinos, are combined to give a single limit. The $90\%$ C.L. single-flavor limit to the diffuse flux of ultra-high energy neutrinos with an $E^{-2}$ spectrum in the energy range $1.0 \times 10^{17}$ eV - $2.5 \times 10^{19}$ eV is $E_ν^2 dN_ν/dE_ν< 6.4 \times 10^{-9}~ {\rm GeV~ cm^{-2}~ s^{-1}~ sr^{-1}}$.

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arXiv2014

$X_{max}^μ$ vs. $N^μ$ from Extensive Air Showers as estimator for the mass of primary UHECR's. Application for the Pierre Auger Observatory

We study the possibility of primary mass estimation for Ultra High Energy Cosmic Rays (UHECR's) using the $X_{max}^μ$ (the height where the number of muons produced on the core of Extensive Air Showers (EAS) is maximum) and the number $N^μ$ of muons detected on ground. We use the 2D distribution - $X_{max}^μ$ against $N^μ$ in order to find its sensitivity to the mass of the primary particle. For that, we construct a 2D Probability Function $Prob(p,Fe \ | \ X_{max}^μ,N^μ)$ which estimates the probability that a certain point from the plane $(X_{max}^μ$, $N^μ)$ corresponds to a shower induced by a proton, respectively an iron nucleus. To test the procedure, we analyze a set of simulated EAS induced by protons and iron nuclei at energies of $10^{19} eV$ and $20^{\circ}$ zenith angle with CORSIKA. Using the Bayesian approach and taking into account the geometry of the infill detectors from the Pierre Auger Observatory, we observe an improvement in the accuracy of the primary mass reconstruction in comparison with the results obtained using only the $X_{max}^μ$ distributions.

astro-ph.HE↗

arXiv2014

Quantum Black Holes Effects on the Shape of Extensive Air Showers

We investigate the possibility to find a characteristic TeV scale quantum black holes decay signature in the data recorded by cosmic rays experiments. TeV black holes can be produced via the collisions of ultra high energetic protons (E > $10^18$ eV) with nucleons the from atmosphere. We focus on the case when the black holes decay into two particles moving in the forward direction in the Earth reference frame (back-to-back in the center of mass reference frame) and induce two overlapping showers. When reconstructing both the energy and the shape of the resultant air shower, there is a significant difference between showers induced only via standard model interactions and showers produced via the back-to-back decay of black holes as intermediate states.

hep-ph↗

arXiv2014

Back-to-Back Black Holes decay Signature at Neutrino Observatories

We propose a decay signature for non-thermal small black holes with masses in the TeV range which can be discovered by neutrino observatories. The black holes would result due to the impact between ultra high energy neutrinos with nuclei in water or ice and decay instantaneously. They could be produced if the Planck scale is in the few TeV region and the highly energetic fluxes are large enough. Having masses close to the Planck scale, the typical decay mode for these black holes is into two particles emitted back-to-back. For a certain range of angles between the emitted particles and the center of mass direction of motion, it is possible for the detectors to measure separate muons having specific energies and their trajectories oriented at a large enough angle to prove that they are the result of a back-to-back decay event.

hep-ph↗