High Energy Cosmic Ray Interactions Research Articles

Lateral Distribution Function Estimation of Electrons and Muons using Nishimura-Kamata-Greisen Function

Abstract The density of charged particles in extensive air showers reaching the surface of the Earth was calculated by estimating the lateral distribution function (LDF) of different primary particles at high energies. LDF simulation was performed using the AIRES system (version 19.04.10), a set of programs and subroutines designed to simulate ultra-high-energy air showers resulting from the interaction of cosmic rays with the Earth’s atmosphere. This system includes algorithms for fast simulation and output data management, and can simulate particle showers realistically and manage the related data efficiently. Its aim is to contribute to research on high-energy cosmic ray interactions for two charged particles, like muons and electrons, at very high energies (1016, 1018, and 1019 eV) and taking into account the effect of particles, such as protons, helium nuclei, and iron nuclei, and primary energies and zenith angles (0°, 20°, and 40°). The LDF was also calculated using the Nishimura–Kamata–Greisen function, and good agreement was found with the results produced by the AIRES system for high-energy muons and electrons created by primary particles.

Recent results from LHCb for astroparticle physics

The LHCb experiment is a general-purpose forward spectrometer designed for the study of heavy flavour physics at the LHC. The acceptance in the pseudorapidity range 2 < \eta < 52<η<5 with full tracking and particle identification capabilities down to very small transverse momentum make LHCb also ideal to study hadron production in the forward region. Measuring and modelling these processes is essential for the simulation of interactions of high-energy cosmic rays with matter, like Earth’s atmosphere or the interstellar medium. We present recently published analyses from the LHCb collaboration relevant for this application.

Flare Duty Cycle of Gamma-Ray Blazars and Implications for High-energy Neutrino Emission

Gamma-ray flares of blazars may be accompanied by high-energy neutrinos due to interactions of high-energy cosmic rays in the jet with photons, as suggested by the detection of the high-energy neutrino IceCube-170922A during a major gamma-ray flare from blazar TXS 0506+056 at the ∼3σ significance level. In this work, we present a statistical study of gamma-ray emission from blazars to constrain the contribution of gamma-ray flares to their neutrino output. We construct weekly binned light curves for 145 gamma-ray bright blazars in the Fermi Large Area Telescope Monitored Source List adding TXS 0506+056. We derive the fraction of time spent in the flaring state (flare duty cycle) and the fraction of energy released during each flare from the light curves with a Bayesian blocks algorithm. We find that blazars with lower flare duty cycles and energy fractions are more numerous among our sample. We identify a significant difference in flare duty cycles between blazar subclasses at a significance level of 5%. Then using a general scaling relation for the neutrino and gamma-ray luminosities, with a weighting exponent of γ = 1.0–2.0, normalized to the quiescent gamma-ray or X-ray flux of each blazar, we evaluate the neutrino energy flux of each gamma-ray flare. The gamma-ray flare distribution indicates that blazar neutrino emission may be dominated by flares for γ ≳ 1.5. The neutrino energy fluxes for 1 week and 10 yr bins are compared with the decl.-dependent IceCube sensitivity to constrain the standard neutrino emission models for gamma-ray flares. Finally, we present the upper-limit contribution of blazar gamma-ray flares to the isotropic diffuse neutrino flux.

The γ-Ray Emission of Star-forming Galaxies

Abstract A majority of the γ-ray emission from star-forming galaxies is generated by the interaction of high-energy cosmic rays with the interstellar gas and radiation fields. Star-forming galaxies are expected to contribute to both the extragalactic γ-ray background and the IceCube astrophysical neutrino flux. Using roughly 10 yr of γ-ray data taken by the Fermi Large Area Telescope, in this study we constrain the γ-ray properties of star-forming galaxies. We report the detection of 11 bona fide γ-ray-emitting galaxies and 2 candidates. Moreover, we show that the cumulative γ-ray emission of below-threshold galaxies is also significantly detected at ∼5σ confidence. The γ-ray luminosity of resolved and unresolved galaxies is found to correlate with the total (8–1000 μm) infrared luminosity as previously determined. Above 1 GeV, the spectral energy distribution of resolved and unresolved galaxies is found to be compatible with a power law with a photon index of ≈2.2–2.3. Finally, we find that star-forming galaxies account for roughly 5% and 3% of the extragalactic γ-ray background and the IceCube neutrino flux, respectively.

High energy interactions of cosmic rays

A discussion of a number of important topics related to modeling of high energy cosmic ray interactions is presented. Special attention is devoted to novel theoretical approaches employed in event generators of hadronic interactions and to the impact of experimental data from the Large Hadron Collider (LHC). In relation to studies of ultra-high energy cosmic rays (UHECRs), differences between various predictions for basic characteristics of UHECR-induced extensive air showers in the atmosphere are analyzed and traced down to differences in the respective treatments of hadronic interactions. Possibilities to discriminate between the alternative approaches, based on LHC and UHECR data, are demonstrated and the relation to UHECR primary composition is outlined. Finally, in relation to direct studies of charged cosmic rays, potential improvements of the treatment of cosmic ray interactions at low and intermediate energies are discussed.

Riccardo Giacconi (1931–2018)

Riccardo Giacconi, the “Father of X-ray Astronomy,” Nobel laureate, and one of the most influential figures in astrophysics over the past 60 years, died on December 9, 2018, at the age of 87. With a career spanning the electromagnetic spectrum, Riccardo opened up new windows for observing the universe and revolutionized “big astronomy.” Many in the astronomy community continue to base their research on data from observatories that he conceived, built, and/or directed. Riccardo Giacconi at the rostrum of the Chandra Symposium held in Huntsville, Alabama on September 16, 2003. Image courtesy of NASA/Marshall Space Flight Center. Riccardo’s outstanding scientific capabilities were well matched by his extraordinary leadership and management skills. He had a deep belief in a scientific approach to problem solving and to establishing systematic processes. He insisted that instruments and observatories be built to answer driving scientific questions. Another key to his success was the legendary dedication and drive of the research teams that he assembled, which could be traced directly to Riccardo’s deep commitment to establishing an environment of intellectual honesty and trust. Born in Genoa, Italy, on October 6, 1931, Riccardo received his doctorate in 1954 from the University of Milan. At that time, the only practical way to study high-energy nuclear reactions was through the detection and analysis of the interaction of high-energy cosmic rays, primarily protons, with atomic nuclei in the atmosphere. For his thesis research, he spent about two years at the Testa Grigio Observatory (elevation: 3,500 meters) in the Italian Alps and obtained 80 high-energy cosmic ray detection events. Although he learned much about the conception, design, and building of detectors, Riccardo was frustrated by the lack of “action.” A Fulbright fellowship brought Riccardo to the United States, where he worked at Indiana and Princeton before joining American Science and Engineering … [↵][1]1To whom correspondence may be addressed. Email: htananbaum{at}cfa.harvard.edu. [1]: #xref-corresp-1-1

Opening Remarks ~ Prospects of very high energy cosmic ray interactions for astroparticle physics

Hadronic interactions of very high energy cosmic rays have been studied in various aspects of motivation. In recent decades, mainly motivated by air shower experiments, modelling of very high energy cosmic ray interactions have been greatly improved together with new data obtained from high energy colliders such as the LHC. Regarding recent rapid progress of multi-messenger astronomy, a precise knowledge on secondary particle production by cosmic rays at very high energy is largely indispensable. This would give us a new insight and new motivation to study minimum bias hadronic interactions of very high energy cosmic rays.

High energy cosmic ray interactions and UHECR composition problem

The differences between contemporary Monte Carlo generators of high energy hadronic interactions are discussed and their impact on the interpretation of experimental data on ultra-high energy cosmic rays (UHECRs) is studied. Key directions for further model improvements are outlined. The prospect for a coherent interpretation of the data in terms of the UHECR composition is investigated.

Review of recent forward physics results from the CMS experiment

There is a rich program of forward physics measurements within the CMS Collaboration covering a wide range of topics. In many cases there is a connection to quantities and effects relevant for very high energy cosmic ray interactions. Some of the recent measurements in the fields of exclusive final states, low-pT inclusive and diffractive cross sections, underlying event, multiparton interactions, double parton scattering, final state particle correlations and minimum bias results are briefly summarized here.

Prompt neutrinos from atmospheric charm in the general-mass variable-flavor-number scheme

We present predictions for the prompt-neutrino flux arising from the decay of charmed mesons and baryons produced by the interactions of high-energy cosmic rays in the Earth’s atmosphere, making use of a QCD approach on the basis of the general-mass variable-flavor-number scheme for the description of charm hadroproduction at NLO, complemented by a consistent set of fragmentation functions. We compare the theoretical results to those already obtained by our and other groups with different theoretical approaches. We provide comparisons with the experimental results obtained by the IceCube Collaboration in two different analyses and we discuss the implications for parton distribution functions.

Imaging of underground cavities with cosmic-ray muons from observations at Mt. Echia (Naples)

Muography is an imaging technique based on the measurement of absorption profiles for muons as they pass through rocks and earth. Muons are produced in the interactions of high-energy cosmic rays in the Earth’s atmosphere. The technique is conceptually similar to usual X-ray radiography, but with extended capabilities of investigating over much larger thicknesses of matter thanks to the penetrating power of high-energy muons. Over the centuries a complex system of cavities has been excavated in the yellow tuff of Mt. Echia, the site of the earliest settlement of the city of Naples in the 8th century BC. A new generation muon detector designed by us, was installed under a total rock overburden of about 40 metres. A 26 days pilot run provided about 14 millions of muon events. A comparison of the measured and expected muon fluxes improved the knowledge of the average rock density. The observation of known cavities proved the validity of the muographic technique. Hints on the existence of a so far unknown cavity was obtained. The success of the investigation reported here demonstrates the substantial progress of muography in underground imaging and is likely to open new avenues for its widespread utilisation.

Preface

The 19th International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI 2016), held at the P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow (LPI RAS) from 22 to 28 August 2016, attracted more than 120 participants. The Symposium was carried out under the auspices of the International Union of Pure and Applied Physics (IUPAP) with financial support from the Federal Agency for Scientific Organizations and the Russian Foundation for Basic Research.

Preface

The 19th International Symposium on Very High Energy Cosmic Ray Interactions (ISVHECRI 2016), held at the P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow (LPI RAS) from 22 to 28 August 2016, attracted more than 120 participants. The Symposium was carried out under the auspices of the International Union of Pure and Applied Physics (IUPAP) with financial support from the Federal Agency for Scientific Organizations and the Russian Foundation for Basic Research.

Cosmic Ray Interaction Models: an Overview

I review the state-of-the-art concerning the treatment of high energy cosmic ray interactions in the atmosphere, discussing in some detail the underlying physical concepts and the possibilities to constrain the latter by current and future measurements at the Large Hadron Collider. The relation of basic characteristics of hadronic interactions to the properties of nuclear-electromagnetic cascades induced by primary cosmic rays in the atmosphere is addressed. Experimental studies of high energy cosmic rays (CR) are traditionally performed using the so-called extensive air shower (EAS) techniques: the properties of the primary CR particles are reconstructed from measured characteristics of nuclear-electro-magnetic cascades induced by their interactions in the atmosphere. This naturally implies the importance of detailed Monte Carlo simulations of EAS development, particularly, of its backbone - the cascade of nuclear interactions of both the primary particles and of the secondary hadrons produced. Thus, the very success of experimental studies depends crucially on the validity of hadronic interaction models used in the analysis. Typically, one chooses between two main experimental procedures (1). In the first case, one deals with the information obtained with scintillation detectors positioned at ground. The energy of the primary particle is reconstructed from the measured lateral density of charged particles (mostly, elec- trons and positrons) while the particle type is inferred from the relative fraction of muons, compared to all charged particles at ground. Alternatively, one may study the longitudinal EAS development by measuring fluorescence light produced by excited air molecules at different heights in the atmo- sphere, for which purpose dedicated fluorescence telescopes are employed. In the latter case, the primary energy is related to the total amount of fluorescence light emitted. In turn, the particle type may be determined from the measured position of the so-called shower maximum Xmax - the depth in the atmosphere (in g/cm 2 ) where the number of ionizing particles reaches its maximal value (which is thus the brightest spot on the shower image). Not surprisingly, the observables used to determine the primary particle type - the lateral muon density ρμ and the EAS maximum position Xmax - appear to be very sensitive to details of high energy hadronic interactions. More precisely, Xmax depends strongly on the properties of the primary particle interaction with air nuclei: the inelastic cross section and the forward spectra of secondary hadrons produced. In turn, the EAS muon content is formed in a multi-step cascade process, driven mostly

Heavy quark production in ultra high energy cosmic ray interactions

In this paper we present a comprehensive study of the heavy quark production in ultra high energy cosmic ray interactions in the atmosphere considering that the primary cosmic ray can be either a photon, neutrino or a proton. The analysis is performed using a unified framework – the dipole formalism – and the saturation effects, associated to the physical process of parton recombination, are taken into account. We demonstrate that the contribution of heavy quarks for cosmic ray interactions is in general non-negligible and can be dominant depending of the process considered. Moreover, our results indicate that new dynamical mechanisms should be included in order to obtain reliable predictions for the heavy quark production in pp collisions at ultra high cosmic ray energies.

Experimental Summary: Very High Energy Cosmic Rays and their Interactions

The XVII International Symposium on Very High Energy Cosmic Ray Interactions, held in August of 2012 in Berlin, was the first one in the history of the Symposium, where a plethora of high precision LHC data with relevance for cosmic ray physics was presented. This report aims at giving a brief summary of those measurements and it discusses their relevance for observations of high energy cosmic rays. Enormous progress has been made also in air shower observations and in direct measurements of cosmic rays, exhibiting many more structure in the cosmic ray energy spectrum than just a simple power law with a knee and an ankle. At the highest energy, the flux suppression may not be dominated by the GZK-effect but by the limiting energy of a nearby source or source population. New projects and application of new technologies promise further advances also in the near future. We shall discuss the experimental and theoretical progress in the field and its prospects for coming years.

High energy cosmic-ray interactions with particles from the Sun

Cosmic-ray protons with energies above ${10}^{16}\text{ }\text{ }\mathrm{eV}$ passing near the Sun may interact with photons emitted by the Sun and be excited to a ${\ensuremath{\Delta}}^{+}$ resonance. When the ${\ensuremath{\Delta}}^{+}$ decays, it produces pions which further decay to muons and photons which may be detected with terrestrial detectors. A flux of muons, photon pairs (from ${\ensuremath{\pi}}^{0}$ decay), or individual high energy photons coming from near the Sun would be a rather striking signature, and the flux of these particles is a fairly direct measure of the flux of cosmic-ray nucleons, independent of the cosmic-ray composition. In a solid angle within 15\ifmmode^\circ\else\textdegree\fi{} around the Sun, the flux of photon pairs is about $1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }\mathrm{\text{particles}}/({\mathrm{km}}^{2}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{yr})$, while the flux of muons is about $0.33\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }\mathrm{\text{particles}}/({\mathrm{km}}^{2}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{yr})$. This is beyond the reach of current detectors like the Telescope Array, Auger, KASCADE-Grande, or IceCube. However, the muon flux might be detectable by next-generation air-shower arrays or neutrino detectors such as ARIANNA or ARA. We discuss the experimental prospects in some detail. Other cosmic-ray interactions occurring close to the Sun are also briefly discussed.

LOFAR - A new experiment to record radio emission from cosmic particles

At present, a new digital radio observatory is under construction in the Netherlands and in Europe, the Low Frequency Array (LOFAR) [1]. It is designed as a multi-sensor network to assist scientists in the fields of astronomy, geophysics, and agriculture. The main focus of the astronomy community is to observe the radio Universe in the frequency range from 30 to 240 MHz. The astronomical part of LOFAR is organized in several key science projects, namely: cosmology (the epoch of re-ionization), wide-field surveys, transient detection, cosmic magnetism, the sun, and cosmic rays. The aim of the latter is the detection of radio emission from particle cascades, originating from extremely high-energy particles from outer space. Two main lines of research are followed: (i) the measurement of radio emission from extensive air showers, generated by interactions of high-energy cosmic rays in the atmosphere and (ii) the detection of radio emission of particle cascades in the Moon, originating from ultra high-energy neutrinos and cosmic rays interacting with the lunar surface. The present article gives a short introduction to the key science project “cosmic rays”.

Experimental Efforts on Very High-Energy Cosmic Rays and their Interactions – Conference Summary

Progress reported during the XV International Symposium on Very High-Energy Cosmic-Ray Interactions is summarized. Emphasize is given to experimental work. The actual status, recent results, and their implications on the present understanding of the origin of high-energy cosmic-rays and their interactions are discussed.

New method to measure the attenuation of hadrons in extensive air showers

Extensive air showers are generated through interactions of high-energy cosmic rays impinging the Earth’s atmosphere. A new method is described to infer the attenuation of hadrons in air showers. The numbers of electrons and muons, registered with the scintillator array of the KASCADE experiment, are used to estimate the energy of the shower inducing primary particle. A large hadron calorimeter is used to measure the hadronic energy reaching observation level. The ratio of energy reaching ground level to the energy of the primary particle is used to derive an attenuation length of hadrons in air showers. In the energy range from 106 to 3×107 GeV the attenuation length obtained increases from 170 to 210 g/cm2. The experimental results are compared to predictions of simulations based on contemporary high-energy interaction models.Received 27 March 2009DOI:https://doi.org/10.1103/PhysRevD.80.022002©2009 American Physical Society