Fischer, O., Pattnaik, B., & Zurita, J. (2023). Testing Heavy Neutral Leptons in Cosmic Ray Beam Dump experiments. J. High Energy Phys., 07(7), 193–24pp.
Abstract: In this work, we discuss the possibility to test Heavy Neutral Leptons (HNLs) using “Cosmic Ray Beam Dump” experiments. In analogy with terrestrial beam dump experiments, where a beam first hits a target and is then absorbed by a shield, we consider high-energy incident cosmic rays impinging on the Earth's atmosphere and then the Earth's surface. We focus here on HNL production from atmospherically produced kaon, pion and D-meson decays, and discuss the possible explanation of the appearing Cherenkov showers observed by the SHALON Cherenkov telescope and the ultra-high energy events detected by the neutrino experiment ANITA. We show that these observations can not be explained with a long-lived HNL, as the relevant parameter space is excluded by existing constraints. Then we propose two new experimental setups that are inspired by these experiments, namely a Cherenkov telescope pointing at a sub-horizontal angle and shielded by the mountain cliff at Mount Thor, and a geostationary satellite that observes part of the Sahara desert. We show that the Cherenkov telescope at Mount Thor can probe currently untested HNL parameter space for masses below the kaon mass. We also show that the geostationary satellite experiment can significantly increase the HNL parameter space coverage in the whole mass range from 10 MeV up to 2 GeV and test neutrino mixing |U-& alpha;4|(2) down to 10(-11) for masses around 300 MeV.
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Jueid, A., Kip, J., Ruiz de Austri, R., & Skands, P. (2024). The Strong Force meets the Dark Sector: a robust estimate of QCD uncertainties for anti-matter dark matter searches. J. High Energy Phys., 02(2), 119–48pp.
Abstract: In dark-matter annihilation channels to hadronic final states, stable particles – such as positrons, photons, antiprotons, and antineutrinos – are produced via complex sequences of phenomena including QED/QCD radiation, hadronisation, and hadron decays. These processes are normally modelled by Monte Carlo (MC) event generators whose limited accuracy imply intrinsic QCD uncertainties on the predictions for indirect-detection experiments like Fermi-LAT, Pamela, IceCube or Ams-02. In this article, we perform a comprehensive analysis of QCD uncertainties, meaning both perturbative and nonperturbative sources of uncertainty are included – estimated via variations of MC renormalization-scale and fragmentation-function parameters, respectively – in antimatter spectra from dark-matter annihilation, based on parametric variations of the Pythia 8 event generator. After performing several retunings of light-quark fragmentation functions, we define a set of variations that span a conservative estimate of the QCD uncertainties. We estimate the effects on antimatter spectra for various annihilation channels and final-state particle species, and discuss their impact on fitted values for the dark-matter mass and thermally-averaged annihilation cross section. We find dramatic impacts which can go up to O(10%) for the annihilation cross section. We provide the spectra in tabulated form including QCD uncertainties and code snippets to perform fast dark-matter fits, in this github repository.
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Pierre Auger Collaboration(Abreu, P. et al), & Pastor, S. (2010). Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter. Astropart Phys., 34(5), 314–326.
Abstract: Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, 6 x 10(19) eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1 degrees from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is (38(-6)(+7))%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of (69-(+11)(13))%. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation.
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Pierre Auger Collaboration(Abreu, P. et al), & Pastor, S. (2011). The exposure of the hybrid detector of the Pierre Auger Observatory. Astropart Phys., 34(6), 368–381.
Abstract: The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays. It consists of a surface array to measure secondary particles at ground level and a fluorescence detector to measure the development of air showers in the atmosphere above the array. The “hybrid” detection mode combines the information from the two subsystems. We describe the determination of the hybrid exposure for events observed by the fluorescence telescopes in coincidence with at least one water-Cherenkov detector of the surface array. A detailed knowledge of the time dependence of the detection operations is crucial for an accurate evaluation of the exposure. We discuss the relevance of monitoring data collected during operations, such as the status of the fluorescence detector, background light and atmospheric conditions, that are used in both simulation and reconstruction.
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Pierre Auger Collaboration(Abraham, J. et al), & Pastor, S. (2010). A study of the effect of molecular and aerosol conditions in the atmosphere on air fluorescence measurements at the Pierre Auger Observatory. Astropart Phys., 33(2), 108–129.
Abstract: The air fluorescence detector of the Pierre Auger Observatory is designed to perforin calorimetric measurements of extensive air showers created by Cosmic rays of above 10(18) eV. To correct these measurements for the effects introduced by atmospheric fluctuations, the Observatory contains a group Of monitoring instruments to record atmospheric conditions across the detector site, ail area exceeding 3000 km(2). The atmospheric data are used extensively in the reconstruction of air showers, and are particularly important for the correct determination of shower energies and the depths of shower maxima. This paper contains a summary of the molecular and aerosol conditions measured at the Pierre Auger Observatory since the start of regular operations in 2004, and includes a discussion of the impact of these measurements oil air shower reconstructions. Between 10(18) and 10(20) eV, the systematic Uncertainties due to all atmospheric effects increase from 4% to 8% in measurements of shower energy, and 4 g cm(-2) to 8 g cm(-2) in measurements of the shower maximum.
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Pierre Auger Collaboration(Abreu, P. et al), & Pastor, S. (2011). Search for first harmonic modulation in the right ascension distribution of cosmic rays detected at the Pierre Auger Observatory. Astropart Phys., 34(8), 627–639.
Abstract: We present the results of searches for dipolar-type anisotropies in different energy ranges above 2.5 x 10(17) eV with the surface detector array of the Pierre Auger Observatory, reporting on both the phase and the amplitude measurements of the first harmonic modulation in the right-ascension distribution. Upper limits on the amplitudes are obtained, which provide the most stringent bounds at present, being below 2% at 99% C.L. for EeV energies. We also compare our results to those of previous experiments as well as with some theoretical expectations.
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Menjo, H. et al, Faus-Golfe, A., & Velasco, J. (2011). Monte Carlo study of forward pi(0) production spectra to be measured by the LHCf experiment for the purpose of benchmarking hadron interaction models at 10(17) eV. Astropart Phys., 34(7), 513–520.
Abstract: The LHCf experiment aims to improve knowledge of forward neutral particle production spectra at the LHC energy which is relevant for the interpretation of air shower development of high energy cosmic rays. Two detectors, each composed of a pair of sampling and imaging calorimeters, have been installed at the forward region of IP1 to measure pi(0) energy spectra above 600 GeV. In this paper, we present a Monte Carlo study of the pi(0) measurements to be performed with one of the LHCf detectors for proton-proton collisions at root s = 14 TeV. In approximately 40 min of operation at luminosity 0.8 x 10(29) cm(-2) s(-1) during the beam commissioning phase of LHC, about 1.5 x 10(4) pi(0) events are expected to be obtained at two transverse positions of the detector. The backgrounds from interactions of secondary particles with beam pipes and interactions of beam particles with residual gas in the beam pipes are expected to be less than 0.1% of the signal from pi(0)s. We also discuss the capability of LHCf measurements to discriminate between the various hadron interaction models that are used for simulation of high energy air showers, such as DPMJET3.03, QGSJETII-03, SIBYLL2.1 and EPOS1.99.
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Pierre Auger Collaboration(Abreu, P. et al), & Pastor, S. (2011). The Lateral Trigger Probability function for the Ultra-High Energy Cosmic Ray showers detected by the Pierre Auger Observatory. Astropart Phys., 35(5), 266–276.
Abstract: In this paper we introduce the concept of Lateral Trigger Probability (LTP) function, i.e., the probability for an Extensive Air Shower (EAS) to trigger an individual detector of a ground based array as a function of distance to the shower axis, taking into account energy, mass and direction of the primary cosmic ray. We apply this concept to the surface array of the Pierre Auger Observatory consisting of a 1.5 km spaced grid of about 1600 water Cherenkov stations. Using Monte Carlo simulations of ultra-high energy showers the LTP functions are derived for energies in the range between 10(17) and 10(19) eV and zenith angles up to 65 degrees. A parametrization combining a step function with an exponential is found to reproduce them very well in the considered range of energies and zenith angles. The LTP functions can also be obtained from data
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Pierre Auger Collaboration(Abreu, P. et al), & Pastor, S. (2012). Search for signatures of magnetically-induced alignment in the arrival directions measured by the Pierre Auger Observatory. Astropart Phys., 35(6), 354–361.
Abstract: We present the results of an analysis of data recorded at the Pierre Auger Observatory in which we search for groups of directionally-aligned events (or 'multiplets') which exhibit a correlation between arrival direction and the inverse of the energy. These signatures are expected from sets of events coming from the same source after having been deflected by intervening coherent magnetic fields. The observation of several events from the same source would open the possibility to accurately reconstruct the position of the source and also measure the integral of the component of the magnetic field orthogonal to the trajectory of the cosmic rays. We describe the largest multiplets found and compute the probability that they appeared by chance from an isotropic distribution. We find no statistically significant evidence for the presence of multiplets arising from magnetic deflections in the present data.
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Pierre Auger Collaboration(Abreu, P. et al), & Pastor, S. (2012). Description of atmospheric conditions at the Pierre Auger Observatory using the Global Data Assimilation System (GDAS). Astropart Phys., 35(9), 591–607.
Abstract: Atmospheric conditions at the site of a cosmic ray observatory must be known for reconstructing observed extensive air showers. The Global Data Assimilation System (GDAS) is a global atmospheric model predicated on meteorological measurements and numerical weather predictions. GDAS provides altitude-dependent profiles of the main state variables of the atmosphere like temperature, pressure, and humidity. The original data and their application to the air shower reconstruction of the Pierre Auger Observatory are described. By comparisons with radiosonde and weather station measurements obtained on-site in Malargue and averaged monthly models, the utility of the GDAS data is shown.
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