Publications (60)25.3 Total impact
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Article: Antennas for the Detection of Radio Emission Pulses from Cosmic-Ray induced Air Showers at the Pierre Auger Observatory
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ABSTRACT: The Pierre Auger Observatory is exploring the potential of the radio detection technique to study extensive air showers induced by ultra-high energy cosmic rays. The Auger Engineering Radio Array (AERA) addresses both technological and scientific aspects of the radio technique. A first phase of AERA has been operating since September 2010 with detector stations observing radio signals at frequencies between 30 and 80 MHz. In this paper we present comparative studies to identify and optimize the antenna design for the final configuration of AERA consisting of 160 individual radio detector stations. The transient nature of the air shower signal requires a detailed description of the antenna sensor. As the ultra-wideband reception of pulses is not widely discussed in antenna literature, we review the relevant antenna characteristics and enhance theoretical considerations towards the impulse response of antennas including polarization effects and multiple signal reflections. On the basis of the vector effective length we study the transient response characteristics of three candidate antennas in the time domain. Observing the variation of the continuous galactic background intensity we rank the antennas with respect to the noise level added to the galactic signal.09/2012; -
Article: Critical fluctuations of the proton density in A+A collisions at $158A$ GeV
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ABSTRACT: Studies of QCD suggest the existence of a critical point in the phase diagram of strongly interacting matter. Close to this point, according to recent theoretical investigations, the net-proton density carries the critical fluctuations of the chiral order parameter. Using intermittency analysis in the transverse momentum phase space of protons produced around midrapidity in the 12.5% most central C+C, Si+Si and Pb+Pb collisions at the maximum SPS energy of 158$A$ GeV we find evidence of power-law fluctuations for the Si+Si and Pb+Pb data. The fitted power-law exponent approaches the value expected for critical fluctuations. This suggests that the freeze-out states of these two systems are located in the phase diagram in the neighbourhood of the chiral critical point.08/2012; -
Article: The Rapid Atmospheric Monitoring System of the Pierre Auger Observatory
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ABSTRACT: The Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 10^17 eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by optical telescopes at the Observatory. To correct the observations for variations in atmospheric conditions, atmospheric monitoring is performed at regular intervals ranging from several minutes (for cloud identification) to several hours (for aerosol conditions) to several days (for vertical profiles of temperature, pressure, and humidity). In 2009, the monitoring program was upgraded to allow for additional targeted measurements of atmospheric conditions shortly after the detection of air showers of special interest, e.g., showers produced by very high-energy cosmic rays or showers with atypical longitudinal profiles. The former events are of particular importance for the determination of the energy scale of the Observatory, and the latter are characteristic of unusual air shower physics or exotic primary particle types. The purpose of targeted (or "rapid") monitoring is to improve the resolution of the atmospheric measurements for such events. In this paper, we report on the implementation of the rapid monitoring program and its current status. The rapid monitoring data have been analyzed and applied to the reconstruction of air showers of high interest, and indicate that the air fluorescence measurements affected by clouds and aerosols are effectively corrected using measurements from the regular atmospheric monitoring program. We find that the rapid monitoring program has potential for supporting dedicated physics analyses beyond the standard event reconstruction.08/2012; -
Article: Pion emission from the T2K replica target: method, results and application
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ABSTRACT: The T2K long-baseline neutrino oscillation experiment in Japan needs precise predictions of the initial neutrino flux. The highest precision can be reached based on detailed measurements of hadron emission from the same target as used by T2K exposed to a proton beam of the same kinetic energy of 30 GeV. The corresponding data were recorded in 2007-2010 by the NA61/SHINE experiment at the CERN SPS using a replica of the T2K graphite target. In this paper details of the experiment, data taking, data analysis method and results from the 2007 pilot run are presented. Furthermore, the application of the NA61/SHINE measurements to the predictions of the T2K initial neutrino flux is described and discussed.07/2012; -
Article: System-size and centrality dependence of charged kaon and pion production in nucleus-nucleus collisions at 40A GeV and158A GeV beam energy
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ABSTRACT: Measurements of charged pion and kaon production are presented in centrality selected Pb+Pb collisions at 40A GeV and 158A GeV beam energy as well as in semi-central C+C and Si+Si interactions at 40A GeV. Transverse mass spectra, rapidity spectra and total yields are determined as a function of centrality. The system-size and centrality dependence of relative strangeness production in nucleus-nucleus collisions at 40A GeV and 158A GeV beam energy are derived from the data presented here and published data for C+C and Si+Si collisions at 158A GeV beam energy. At both energies a steep increase with centrality is observed for small systems followed by a weak rise or even saturation for higher centralities. This behavior is compared to calculations using transport models (UrQMD and HSD), a percolation model and the core-corona approach.07/2012; -
Article: First proton–proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at GeV
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ABSTRACT: On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |η|<0.5, we obtain dN ch/dη=3.10±0.13(stat.)±0.22(syst.) for all inelastic interactions, and dN ch/dη=3.51±0.15(stat.)±0.25(syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton–antiproton interactions at the same centre-of-mass energy at the CERN Sp [`(p)]\overline{\mathrm{p}} S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.European Physical Journal C 04/2012; 65(1):111-125. · 3.63 Impact Factor -
Article: Production of pions, kaons and protons in pp collisions at with ALICE at the LHC
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ABSTRACT: The production of π +, π −, K+, K−, p, and [`(p)]\overline{\mathrm{p}} at mid-rapidity has been measured in proton-proton collisions at Ös = 900GeV\sqrt{s} = 900~\mathrm{GeV} with the ALICE detector. Particle identification is performed using the specific energy loss in the inner tracking silicon detector and the time projection chamber. In addition, time-of-flight information is used to identify hadrons at higher momenta. Finally, the distinctive kink topology of the weak decay of charged kaons is used for an alternative measurement of the kaon transverse momentum (p t) spectra. Since these various particle identification tools give the best separation capabilities over different momentum ranges, the results are combined to extract spectra from p t=100MeV/c to 2.5 GeV/c. The measured spectra are further compared with QCD-inspired models which yield a poor description. The total yields and the mean p t are compared with previous measurements, and the trends as a function of collision energy are discussed.European Physical Journal C 04/2012; 71(6):1-22. · 3.63 Impact Factor -
Article: Charged-particle multiplicity measurement in proton–proton collisions at and 2.36 TeV with ALICE at LHC
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ABSTRACT: Charged-particle production was studied in proton–proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9TeV and 2.36TeV in the pseudorapidity range |η|<1.4. In the central region (|η|<0.5), at 0.9TeV, we measure charged-particle pseudorapidity density dNch/dh = 3.02±0.01(stat.)+0.08-0.05(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.02\pm 0.01(\mathit{stat.})^{+0.08}_{-0.05}(\mathit{syst.}) for inelastic interactions, and dNch/dh = 3.58±0.01(stat.)+0.12-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.58\pm0.01(\mathit{stat.})^{+0.12}_{-0.12}(\mathit{syst.}) for non-single-diffractive interactions. At 2.36TeV, we find dNch/dh = 3.77±0.01(stat.)+0.25-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=3.77\pm0.01(\mathit{stat.})^{+0.25}_{-0.12}(\mathit{syst.}) for inelastic, and dNch/dh = 4.43±0.01(stat.)+0.17-0.12(syst.)\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta=4.43\pm0.01(\mathit{stat.})^{+0.17}_{-0.12}(\mathit{syst.}) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7%±0.5%(stat.)+5.7-2.8%(syst.)24.7\%\pm0.5\%(\mathit{stat.})^{+5.7}_{-2.8}\%(\mathit{syst.}) for inelastic and 23.7%±0.5%(stat.)+4.6-1.1%(syst.)23.7\%\pm0.5\%(\mathit{stat.})^{+4.6}_{-1.1}\%(\mathit{syst.}) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton–antiproton data and to model predictions.European Physical Journal C 04/2012; 68(1):89-108. · 3.63 Impact Factor -
Article: Antideuteron and deuteron production in midcentral Pb+Pb collisions at 158A GeV
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ABSTRACT: Production of deuterons and antideuterons was studied by the NA49 experiment in the 23.5% most central Pb+Pb collisions at the top CERN Super Proton Synchroton (SPS) energy of √sNN=17.3 GeV. Invariant yields for d̅ and d were measured as a function of centrality in the center-of-mass rapidity range −1.2<y<−0.6. Results for d̅ (d) together with previously published p̅ (p) measurements are discussed in the context of the coalescence model. The coalescence parameters B2 were deduced as a function of transverse momentum pt and collision centrality.Phys. Rev. C. 04/2012; 85(4). -
Article: A search for ultra-high energy neutrinos in highly inclined events at the Pierre Auger Observatory
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ABSTRACT: The Surface Detector of the Pierre Auger Observatory is sensitive to neutrinos of all flavours above 0.1 EeV. These interact through charged and neutral currents in the atmosphere giving rise to extensive air showers. When interacting deeply in the atmosphere at nearly horizontal incidence, neutrinos can be distinguished from regular hadronic cosmic rays by the broad time structure of their shower signals in the water-Cherenkov detectors. In this paper we present for the first time an analysis based on down-going neutrinos. We describe the search procedure, the possible sources of background, the method to compute the exposure and the associated systematic uncertainties. No candidate neutrinos have been found in data collected from 1 January 2004 to 31 May 2010. Assuming an E^-2 differential energy spectrum the limit on the single flavour neutrino is (E^2 * dN/dE) < 1.74x10^-7 GeV cm^-2 s^-1 sr^-1 at 90% C.L. in the energy range 1x10^17 eV < E < 1x10^20 eV.02/2012; -
Article: Description of Atmospheric Conditions at the Pierre Auger Observatory using the Global Data Assimilation System (GDAS)
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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 Malarg\"ue and averaged monthly models, the utility of the GDAS data is shown.01/2012; -
Article: Search for Point-like Sources of Ultra-high Energy Neutrinos at the Pierre Auger Observatory and Improved Limit on the Diffuse Flux of Tau Neutrinos
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ABSTRACT: The surface detector array of the Pierre Auger Observatory can detect neutrinos with energy E ν between 10 17 eV and 10 20 eV from point-like sources across the sky south of +55° and north of –65° declinations. A search has been performed for highly inclined extensive air showers produced by the interaction of neutrinos of all flavors in the atmosphere (downward-going neutrinos), and by the decay of tau leptons originating from tau neutrino interactions in Earth's crust (Earth-skimming neutrinos). No candidate neutrinos have been found in data up to 2010 May 31. This corresponds to an equivalent exposure of ~3.5 years of a full surface detector array for the Earth-skimming channel and ~2 years for the downward-going channel. An improved upper limit on the diffuse flux of tau neutrinos has been derived. Upper limits on the neutrino flux from point-like sources have been derived as a function of the source declination. Assuming a differential neutrino flux k PS · E –2 ν from a point-like source, 90% confidence level upper limits for k PS at the level of ##IMG## [http://ej.iop.org/icons/Entities/ap.gif] ≈ 5 × 10 –7 and 2.5 × 10 –6 GeV cm –2 s –1 have been obtained over a broad range of declinations from the searches for Earth-skimming and downward-going neutrinos, respectively.The Astrophysical Journal Letters. 01/2012; 755(1):L4. -
Article: Measurement of Production Properties of Positively Charged Kaons in Proton-Carbon Interactions at 31 GeV/c
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ABSTRACT: Spectra of positively charged kaons in p+C interactions at 31 GeV/c were measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is based on the full set of data collected in 2007 with a graphite target with a thickness of 4% of a nuclear interaction length. Interaction cross sections and charged pion spectra were already measured using the same set of data. These new measurements in combination with the published ones are required to improve predictions of the neutrino flux for the T2K long baseline neutrino oscillation experiment in Japan. In particular, the knowledge of kaon production is crucial for precisely predicting the intrinsic electron neutrino component and the high energy tail of the T2K beam. The results are presented as a function of laboratory momentum in 2 intervals of the laboratory polar angle covering the range from 20 up to 240 mrad. The kaon spectra are compared with predictions of several hadron production models. Using the published pion results and the new kaon data, the K+/\pi+ ratios are computed.12/2011; -
Article: The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory
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ABSTRACT: We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than $60^\circ$, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the ~2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for.11/2011; -
Article: The Lateral Trigger Probability function for the Ultra-High Energy Cosmic Ray Showers detected by the Pierre Auger Observatory
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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 degs. 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 using events simultaneously observed by the fluorescence and the surface detector of the Pierre Auger Observatory (hybrid events). We validate the Monte-Carlo results showing how LTP functions from data are in good agreement with simulations.11/2011; -
Article: Search for signatures of magnetically-induced alignment in the arrival directions measured by the Pierre Auger Observatory
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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.11/2011; -
Article: The Pierre Auger Observatory II: Studies of Cosmic Ray Composition and Hadronic Interaction models
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ABSTRACT: Studies of the composition of the highest energy cosmic rays with the Pierre Auger Observatory, including examination of hadronic physics effects on the structure of extensive air showers.07/2011; -
Article: The Pierre Auger Observatory III: Other Astrophysical Observations
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ABSTRACT: Astrophysical observations of ultra-high-energy cosmic rays with the Pierre Auger Observatory07/2011; -
Article: The Pierre Auger Observatory IV: Operation and Monitoring
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ABSTRACT: Technical reports on operations and monitoring of the Pierre Auger Observatory07/2011; -
Article: The Pierre Auger Observatory V: Enhancements
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ABSTRACT: Ongoing and planned enhancements of the Pierre Auger Observatory07/2011;
Top co-authors
Top Journals
Institutions
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2011
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Karlsruhe Institute of Technology
Eggenstein-Leopoldshafen, Baden-Wuerttemberg, Germany
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2006–2011
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Warsaw University of Technology
- Faculty of Physics
Warsaw, Masovian Voivodeship, Poland
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2010
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University of Oslo
- Department of Physics
Oslo, Oslo, Norway
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