Hadronic Interaction Models Research Articles

Measurement of prompt charged-particle production in pp collisions at sqrt{mathrm{s}} = 13 TeV

The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at a centre-of-mass energy of sqrt{s} = 13 TeV. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of 5.4 nb−1. The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges pT ∈ [80, 10 000) MeV/c and η ∈ [2.0, 4.8) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.

Simulation and Parameterization of Longitudinal Development using Different Hadronic Interaction Models

The importance of investigating ultra-high energy cosmic ray particles interactions was investigated in this work. Different hadronic interaction models such as (SIBYLL, EPOS, and QGSJET) were used air showers simulation AIRES program (version 19.04.00). Also, the shower size of Extensive Air Showers (EAS) was calculated by estimating the longitudinal development. Moreover, the longitudinal development simulation of the two primary particles (iron nuclei and proton) was performed, taking into account their primary energies effect as well the zenith angle for charged particles that produced in the EAS, with energies (1017 and 1019) eV. At such extremely high energies (1017 and 1019) eV, new parameters as a function of the primary energy were obtained by fitting the longitudinal development curves of EAS using the Lorentz function. Comparison of the results showed a good agreement between the values obtained from the parameterized longitudinal development using Lorentz function with experimental results by Pierre Auger EAS observatory as well the simulated results by Sciutto for the primaries iron nuclei as well proton, with the electrons and the charged muons secondary particles of high energies.

Reconstruction of Air-Shower Parameters through Lateral Distribution Function of Ultra-High Energy Particles

In this study, the necessity of the simulation study for exploring the interactions of ultra-high energy particles cosmic rays was examined. Different hadronic interaction models such as (SIBYLL, QGSJET, and EPOS) were simulated by using air showers simulation AIRES system (version 19.04.00). Also, the charged particle density of Extensive Air Showers (EAS) was calculated by estimating the lateral distribution function (LDF). Moreover, the LDF simulation of the two primary particles (proton and iron nuclei) was performed, taking into account their primary energies effect and the zenith angle of charged particles that produced in the EAS, within the energy range (10^17-10^19) eV. At extremely high energies (10^17, 10^18, and 10^19) eV, new parameters as a function of the primary energy were obtained by fitting the lateral distribution curves of EAS using Sigmoidal function (Logistic model). Comparison of the results showed a good agreement between the values obtained from the parameterized LDF using Sigmoidal function with experimental results by AGASA EAS observatory for the primaries proton as well iron nuclei, with the production of (electron positron) pair and the charged muons secondary particles at high energy about 10^19 eV and (theta = 0 degree).

Comparison of validation methods of simulations for final state interactions in hadron production experiments

Neutrino cross section and oscillation measurements depend critically on modeling of hadronic final state interactions (FSI). Often, this is one of the largest components of uncertainty in a measurement. This is because of the difficulty in modeling strong interactions in nuclei in a consistent quantum-mechanical framework. FSI models are most often validated using hadron-nucleus data which introduces further uncertainties. The alternative is to use transparency data where the hadron starts propagating from inside the nucleus and the probability of interaction is measured as a function of hadron energy. This work examines the relationship between the $\pi^+$ and proton total reaction cross section and transparency from a simulation viewpoint.

Mass Composition of UHECRs from Xmax 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 Xmax 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 Xmax distributions, which we compare with the experimental Xmax 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 (≳70%) by protons and He nuclei in the energy range investigated lgE(eV) = [17.8–19.3] (Auger) and lgE(eV) = [18.2–19.0] (TA). The indirect comparisons between the Xmax 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 (lgE(eV)∼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.

Energetics of ultrahigh-energy cosmic-ray nuclei

Energetics of the ultrahigh-energy cosmic rays (UHECRs) generated in the universe is crucial for pinning down their candidate sources. Using the recent Auger data on UHECR spectra, we calculate the UHECR energy generation rate density for different species of nuclei at the injection, considering intermediate and heavy nuclei as well as protons, through scanning over source parameters on the spectral index, maximum energy and redshift evolution. We find the resulting UHECR energy generation rate density to be $\approx(0.2-2)\times$10$^{44}$~erg~Mpc$^{-3}$~yr$^{-1}$ at $10^{19.5}$~eV with a nontrivial dependence on the spectral index. Nuclei other than protons and irons favor hard spectral indices at the injection, and the required value of energy budget is smaller for intermediate nuclei. Given significant uncertainties in hadronic interaction models and astrophysical models for the Galactic-extragalactic transition, our results can be regarded as conservative. The composition data on $X_{\rm max}$ give additional constraints, but the results are consistent within the model uncertainties.

Surface detectors for IceCube-Gen2

The IceCube-Gen2 Neutrino Observatory will feature an in-ice optical array, a larger in-ice radio detector array, and a surface cosmic-ray air-shower array.The surface array will consist of stations based on the experience from the planned IceTop enhancement, each station having four pairs of scintillator panels, three radio antennas and a central hub hosting electronics for data readout and time digitization.In the currently proposed implementation, a surface station will be located in the proximity of each of the 120 in-ice optical strings. Together with the in-ice optical array, the designed array will help to test hadronic interaction models and will extend IceTop's measurement of the energy spectrum and mass composition beyond 10 PeV. The array will also serve as a background veto for down-going candidate neutrino events. In addition, the surface stations will be fundamental to characterize the atmospheric component of the in-ice spectrum (i.e. atmospheric neutrinos and muons) and may serve as a cross calibration tool for the in-ice radio array.In this presentation the physics motivations for the surface array, and the proposed implementation plan will be reviewed.

Deep-learning based reconstruction of the shower maximum X max using the water-Cherenkov detectors of the Pierre Auger Observatory

The atmospheric depth of the air shower maximum X max is an observable commonly used for the determination of the nuclear mass composition of ultra-high energy cosmic rays.Direct measurements of X max are performed using observations of the longitudinal shower development with fluorescence telescopes.At the same time, several methods have been proposed for an indirect estimation of X max from the characteristics of the shower particles registered with surface detector arrays.In this paper, we present a deep neural network (DNN) for the estimation of X max. The reconstruction relies on the signals induced by shower particles in the ground based water-Cherenkov detectors of the Pierre Auger Observatory.The network architecture features recurrent long short-term memory layers to process the temporal structure of signals and hexagonal convolutions to exploit the symmetry of the surface detector array.We evaluate the performance of the network using air showers simulated with three different hadronic interaction models. Thereafter, we account for long-term detector effects and calibrate the reconstructed X max using fluorescence measurements. Finally, we show that the event-by-event resolution in the reconstruction of the shower maximum improves with increasing shower energy and reaches less than 25 g/cm2 at energies above 2 × 1019 eV.

Effect of the uncertainty in the hadronic interaction models on the estimation of the sensitivity of the Cherenkov telescope array

Imaging atmospheric Cherenkov telescopes (IACTs) are ground-based indirect detectors for cosmic gamma rays with energies above tens of GeV. The major backgrounds for gamma-ray observations in IACTs are cosmic-ray charged particles. The capability to reject these backgrounds is the most important factor determining the gamma-ray sensitivity of IACT systems. Monte Carlo simulations are used to estimate the residual background rates and sensitivity of the systems during the design and construction phase. Uncertainties in the modeling of high-energy hadronic interactions of cosmic rays with nuclei in the air propagate into the estimates of residual background rates and subsequently into the estimated instrument sensitivity. We investigate the influence of the difference in the current hadronic interaction models on the estimated gamma-ray sensitivity of the Cherenkov Telescope Array using four interaction models (QGSJET-II-03, QGSJET-II-04, EPOS-LHC, and SIBYLL2.3c) implemented in the air shower simulation tool CORSIKA. Variations in background rates of up to a factor 2 with respect to QGSJET-II-03 are observed between the models, mainly due to differences in the π 0 production spectrum. These lead to ∼30% differences in the estimated gamma-ray sensitivity in the 1–30 TeV region, assuming a 50 h observation of a gamma-ray point-like source. The presented results also show that IACTs have a significant capability in the verification of hadronic interaction models.

Depth of shower maximum and mass composition of cosmic rays from 50 PeV to 2 EeV measured with the LOFAR radio telescope

We present an updated cosmic-ray mass composition analysis in the energy range $10^{16.8}$ to $10^{18.3}$ eV from 334 air showers measured with the LOFAR radio telescope, and selected for minimal bias. In this energy range, the origin of cosmic rays is expected to shift from galactic to extragalactic sources. The analysis is based on an improved method to infer the depth of maximum $X_{\rm max}$ of extensive air showers from radio measurements and air shower simulations. We show results of the average and standard deviation of $X_{\rm max}$ versus primary energy, and analyze the $X_{\rm max}$-dataset at distribution level to estimate the cosmic ray mass composition. Our approach uses an unbinned maximum likelihood analysis, making use of existing parametrizations of $X_{\rm max}$-distributions per element. The analysis has been repeated for three main models of hadronic interactions. Results are consistent with a significant light-mass fraction, at best fit $23$ to $39$ $\%$ protons plus helium, depending on the choice of hadronic interaction model. The fraction of intermediate-mass nuclei dominates. This confirms earlier results from LOFAR, with systematic uncertainties on $X_{\rm max}$ now lowered to 7 to $9$ $\mathrm{g/cm^2}$. We find agreement in mass composition compared to results from Pierre Auger Observatory, within statistical and systematic uncertainties. However, in line with earlier LOFAR results, we find a slightly lower average $X_{\rm max}$. The values are in tension with those found at Pierre Auger Observatory, but agree with results from other cosmic ray observatories based in the Northern hemisphere.

Measurement of the Fluctuations in the Number of Muons in Extensive Air Showers with the Pierre Auger Observatory.

We present the first measurement of the fluctuations in the number of muons in extensive air showers produced by ultrahigh energy cosmic rays. We find that the measured fluctuations are in good agreement with predictions from air shower simulations. This observation provides new insights into the origin of the previously reported deficit of muons in air shower simulations and constrains models of hadronic interactions at ultrahigh energies. Our measurement is compatible with the muon deficit originating from small deviations in the predictions from hadronic interaction models of particle production that accumulate as the showers develop.

Sub-TeV hadronic interaction model differences and their impact on air showers

In the sub-TeV regime, the most widely used hadronic interaction models disagree significantly in their predictions for post-first interaction and ground-level particle spectra from cosmic ray induced air showers. These differences generate an important source of systematic uncertainty in their experimental use. We investigate the nature and impact of model uncertainties through a simultaneous analysis of ground level particles and first interaction scenarios. We focus on air shower primaries with energies close to the transition between high and low energy hadronic interaction models, where the dissimilarities have been shown to be the largest and well within the range of accelerator measurements. Interaction models are shown to diverge as several shower scenarios are compared, reflecting intrinsic differences in the model theoretical frameworks. Finally, we discuss the importance of interactions in the energy regime where the switching between models occurs (<1 TeV) and the effect of the choice of model on the number of hadronic interactions within cosmic ray induced air showers of higher energies.

Simulation study on the effects of diffractive collisions on the prediction of the observables in ultra-high-energy cosmic-ray experiments

AbstractThe mass composition of ultra-high-energy cosmic rays is important for understanding their origin. Owing to our limited knowledge of the hadronic interaction, the interpretations of the mass composition from observations include several open problems, such as the inconsistent interpretations of $\langle X_{\mathrm{max}}\rangle $ and $\langle X_{\mathrm{max}}^{\mu}\rangle $. Furthermore, a large difference between the predictions exists in the hadronic interaction models. Diffractive collision is one of the proposed sources of the uncertainty. In this paper, we discuss the effect of the detailed characteristics of diffractive collisions on the observables of ultra-high-energy cosmic-ray experiments, focusing on three detailed characteristics. These are the cross-sectional fractions of different collision types, the diffractive-mass spectrum, and diffractive-mass-dependent particle production from the diffractive dissociation system. We demonstrate that the current level of uncertainty in the cross-sectional fraction can affect $\langle X_{\mathrm{max}}\rangle $ by 8.9 $\mathrm{g/cm^2}$ and $\langle X_{\mathrm{max}}^{\mu}\rangle $ by 9.4 $\mathrm{g/cm^2}$, whereas the other details of diffractive collisions exhibit relatively minor effects.

Identical pion and kaon femtoscopy in EPOS 3 with and without the hadronic afterburner UrQMD

Femtoscopy is an effective instrument to study the size and dynamics of the system created in heavy-ion collisions. In particular, a decreasing dependence of system size on increasing pair momentum and particle mass could be interpreted as an evidence of the strong collective flow. Such phenomena are naturally modeled by hydrodynamics. The large data sample collected in Pb–Pb collisions at by the ALICE collaboration enables femtoscopic measurements for pions and kaons. In this paper, the ALICE data are compared with calculations within the EPOS 3 hadronic interaction model, which is based on a (3+1)D viscous hydrodynamical evolution and employs the UrQMD cascade to describe the hadronic phase. The femtoscopic radii for pions and kaons are considered as a function of pair transverse momentum/mass and collision centrality. The obtained results show the importance of the hadronic rescattering phase at LHC energies.

Muons with threshold 1 GeV in extensive air showers with energy greater than 5 EeV

The paper presents an analysis of the characteristics of muons with a threshold greater than 1 GeV in showers with energies greater than 5 EeV and zenith angles less than 60 degrees. The analysis is based on the registration data of extensive air showers of the Yakutsk array. Estimation of muons at different distances from the shower core, fraction of muons ρμ /ρ μ+e at a distance of 600 m are obtained. Calculations of the fraction of muons are performed using the QGSjetII-04 hadronic interaction model for different primary nuclei, and compared with the data. Mass composition of primary particles is estimated by muon component. Several showers were found in the sample, with a low content of muons which possibly is produced by ultrahigh energy gamma rays.

Composition determination of cosmic rays from the muon content of the showers

The origin and nature of ultra high energy cosmic rays remains being a mystery. However, great progress has been made in recent years due to the observations performed by the Pierre Auger Observatory and Telescope Array. In particular, it is believed that the composition information of the cosmic rays as a function of the energy can play a fundamental role for the understanding of their origin. The best indicators for primary mass composition are the muon content of extensive air shower and the atmospheric depth of the shower maximum. In this work we consider a maximum likelihood method to perform mass composition analyses based on the number of muons measured by underground muon detectors. The analyses are based on numerical simulations of the showers. The effects introduced by the detectors and the methods used to reconstruct the experimental data are also taken into account through a dedicated simulation that uses as input the information of the simulated showers. In order to illustrate the use of the method, we consider AMIGA (Auger Muons and Infill for the Ground Array), the low energy extension of the Pierre Auger Observatory that directly measures the muonic content of extensive air showers. We also study in detail the impact of the use of different high energy hadronic interaction models in the composition analyses performed. It is found that differences of a few percent between the predicted number of muons have a significant impact on composition determination.

Through the looking-glass with ALICE into the quark-gluon plasma: A new test for hadronic interaction models used in air shower simulations

Recently, the ALICE Collaboration reported an enhancement of the yield ratio of strange and multi-strange hadrons to charged pions as a function of multiplicity at mid-rapidity in proton-proton, proton-lead, lead-lead, and xenon-xenon scattering. ALICE observations provide a strong indication that a quark-gluon plasma is partly formed in high multiplicity events of both small and large colliding systems. Motivated by ALICE's results, we propose a new test for hadronic interaction models used for analyzing ultra-high-energy-cosmic-ray (UHECR) collisions with air nuclei. The test is grounded in the almost equal column-energy density in UHECR-air collisions and lead-lead collisions at the LHC. We applied the test to post-LHC event generators describing hadronic phenomena of UHECR scattering and show that these QCD Monte Carlo-based codes must be retuned to accommodate the strangeness enhancement relative to pions observed in LHC data.

Hadronic interaction model sibyll 2.3d and extensive air showers

We present a new version of the hadron interaction event generator Sibyll. While the core ideas of the model have been preserved, the new version handles the production of baryon pairs and leading particles in a new way. In addition, production of charmed hadrons is included. Updates to the model are informed by high-precision measurements of the total and inelastic cross sections with the forward detectors at the LHC that constrain the extrapolation to ultra-high energy. Minimum-bias measurements of particle spectra and multiplicities support the tuning of fragmentation parameters. This paper demonstrates the impact of these changes on air shower observables such as $X_{\rm max}$ and $N_\mu$, drawing comparisons with other contemporary cosmic ray interaction models.

Astrophysical Background and Dark Matter Implication Based on Latest AMS-02 Data

Abstract The cosmic-ray (CR) positrons and antiprotons are often regarded as the collision products of CR nucleons with the interstellar medium. However, the predicted fluxes of CR positrons and antiprotons by the conventional models are not consistent with the experimental data from PAMELA, Fermi-LAT, AMS-02, etc. In this work, we choose the latest AMS-02 data to analyze the astrophysical background of CR positrons and antiprotons. QGSJET-II-04 is chosen as the hadronic interaction model. The GALPROP package is used to solve the propagation equation numerically. The results show that the predicted flux of CR positrons at low energies is consistent with AMS-02 data in the reacceleration and convection–diffusion (DCR) model. In the DCR model and the hadronic interaction model, QGSJET-II-04, the excess of CR antiprotons at low energies is excluded. The dark matter interpretation of the positron excess is analyzed with the total fluxes of CR electrons and positrons from AMS-02. The predicted best-fit mass of dark matter ranges from 400 GeV to 4 TeV. Moreover, in the above models the predicted flux of CR protons is completely consistent with AMS-02 data, which matches the hardening feature above 330 GeV.

Studies on the response of a water-Cherenkov detector of the Pierre Auger Observatory to atmospheric muons using an RPC hodoscope

Extensive air showers, originating from ultra-high energy cosmic rays, have been successfully measured through the use of arrays of water-Cherenkov detectors (WCDs). Sophisticated analyses exploiting WCD data have made it possible to demonstrate that shower simulations, based on different hadronic-interaction models, cannot reproduce the observed number of muons at the ground. The accurate knowledge of the WCD response to muons is paramount in establishing the exact level of this discrepancy. In this work, we report on a study of the response of a WCD of the Pierre Auger Observatory to atmospheric muons performed with a hodoscope made of resistive plate chambers (RPCs), enabling us to select and reconstruct nearly 600 thousand single muon trajectories with zenith angles ranging from 0̂ to 55̂. Comparison of distributions of key observables between the hodoscope data and the predictions of dedicated simulations allows us to demonstrate the accuracy of the latter at a level of 2%. As the WCD calibration is based on its response to atmospheric muons, the hodoscope data are also exploited to show the long-term stability of the procedure.