Hashim, N O

CERN Document Server

29th International Cosmic Ray Conference Pune (2005) 6, 1316Momentum spectrum of cosmic muons at a depth of 320 mweN.O. Hashim , C. Grupen , S. Luitz, A. Mailov , F. Maciuc, A.-S. Mu¨ller,A. Putzer, H.-G. Sander, S. Schmeling  , M. Schmelling, R. Tcaciuc ,H. Wachsmuth  , Th. Zieglerand K. Zuber(a) Fachbereich Physik, Universit¤at Siegen, D-57068 Siegen, Germany(b) SLAC M/S 41, 2575 Sand Hill Rd, Menlo Park, CA 94025, USA(c) Max-Planck-Institut f¤ur Kernphysik, D-69029, Heidelberg, Germany(d) Institut f¤ur Synchrotronstrahlung, FZ Karlsruhe, D-76021 Karlsruhe, Germany(e) Kirchhoff-Institut f¤ur Physik, Universit¤at Heidelberg, D-69120 Heidelberg, Germany(f) Fachbereich Physik, Universit¤at Mainz, D-55099 Mainz, Germany(g) CERN, CH-1211 Geneva 23, Switzerland(h) Department of Physics, Princeton University, Princeton NJ 08544, USA(i) Experimental Physik IV, Universit¤at Dortmund, D-44221 Dortmund, GermanyPresenter: N.O. Hashim (hashim@hep.physik.uni-siegen.de), ger-hashim-NO-abs1-he11-oralCosmic muons are produced through interactions of primary cosmic radiation in the atmosphere. They are acomponent of extensive air showers which can also be measured underground. The CosmoALEPH experimentused the ALEPH detector at the European Laboratory for Particle Physics, CERN, to measure cosmic muonevents at a depth of 320 mwe underground. The momentum spectrum and charge ratio of the cosmic muons aremeasured. The results are compared with the expectations from MC simulations based on different hadronicinteraction models.1. IntroductionSince their discovery, great progress has been achieved in the field of cosmic ray physics particularly towardsthe understanding of the origin, transport and acceleration mechanisms of the high energy particles that con-stitute primary cosmic rays, their interaction processes in the galactic and extra galactic media, and also inthe Earth’s atmosphere[1]. The interaction of primary cosmic ray particles in the Earth’s atmosphere leads tothe production of a cascade of secondary particles or Extensive Air Showers (EAS) with various components- electromagnetic, hadronic, muon and neutrino components. There is a large number of models to describethese interactions.Many cosmic ray experiments have used a variety of observables in EAS that provide an understanding of thehadronic interactions and also shed some light on the chemical composition of the primary particles. The muonflux at the surface provides a useful tool for the calculations of neutrino fluxes, the reconstruction of EAS andit can serve as a test of various interaction models.The CosmoALEPH detector, which was one of the experiments in CosmoLEP[2, 3] used the ALEPH detector atthe European Laboratory for Particle Physics, CERN, to measure the muonic component of EAS. Preliminaryresults[4] have recently shown that the momentum spectrum and charge ratio for cosmic muons measuredby CosmoALEPH are well within the world average [5]. This work reports on further improvements in thereconstruction of the cosmic muon events and data analysis.2. Experimental SetupThe ALEPH detector and its applicability as a tool for cosmic ray measurements has been well described[6, 7, 8, 9]. It was located at a depth of 320 mwe, which corresponds to an energy cut-off of about 70 GeV for14 N.O. Hashim et alvertical muons. For measurements of cosmic muon events, the hadron calorimeter HCAL and time projectionchamber TPC have been used. The trigger efficiency for HCAL is about 85% for vertical muons and a spatialresolution of about 160 	 m in the TPC allows the measurements of up to 3 TeV. A total of about 1.1 millioncosmic muon events from dedicated cosmic runs is analysed in this work. The data are compared with MonteCarlo simulations.3. Data Selection and AnalysisA total of 65,946 vertical cosmic muons, zenith angle  up to 10  , with momentum greater than 5 GeV mea-sured in ALEPH was selected for analysis. The muon energies at the surface E  are extrapolated from theirrespective energies measured in ALEPH E  at the depth R using the relation,ﬀﬂﬁﬃ! "$#&%('*),+-.ﬀﬂﬁﬃ! "which takes into account the energy losses due to ionisation, bremsstrahlung and direct electron pair productiondescribed by the terms  0/213/547698:+9;=<?>-@BA and:CD1 CECEFG;=<>@HA respectively[1].The momentum spectra arecorrected for geometrical acceptance and effects of the angular distribution around the vertical using a MonteCarlo simulation. The data are then corrected for the track reconstruction efficiency which is estimated tobe about 79%. The momentum spectrum is unfolded using Bayesian technique [10] taking into account thedetector resolution and energy losses in the overburden. This is achieved by a complete simulation of cosmicmuon events in the CosmoALEPH experiment using the following programs; CORSIKA[11] for air showersimulations, GEANT[12] for muon transport and interactions in ALEPH including the overburden. A detaileddescription is in preparation [13].4. Results and DiscussionThe preliminary momentum spectrum and the charge ratio for vertical muons at the surface are shown in Figure1. The data are similar to results of earlier experiments and a recent compilation [5]. The charge ratio, R  ,of positive to negative muons obtained has an average value of 1.278 I 0.011. Only statistical uncertaintiesare shown. Systematic uncertainties are expected to be below 10%. A comparison with the Monte CarloSimulations based on different hadronic interaction models is shown on Figure 2. The MC simulations arenormalised to the selected number of events in the data. The slope of the number of muons at the surfacepredicted by the models agrees very well with our data. However, some systematic effects are evident in thecalculations of the charge ratio. SIBYLL, which is known to generate a relatively lower muon content[14, 15],shows systematically higher values for the muon charge ratio compared to our measurements. A similar trendis observed by the L3+C experiment [16] which was also one of the cosmic ray experiments at LEP. The muonflux is closely related to the neutrino flux and the muon charge ratio is a sensitive observable for precision testsof muon and neutrino production in EAS [17].5. OutlookThe preliminary results show a momentum spectrum that is consistent with previous measurements and thecharge ratio is well described by Monte Carlo simulations. This work shows that the charge ratio for cosmicMomentum spectrum of cosmic muons ... 150.10.20.30.40.50.610 2 10 3Hayman 1962Barber 1968Appleton 1971CosmoALEPH (preliminary)Allkofer 1971Nandi 1972Ayre 1972L3+C 2004 Rastin 1972Pµ(GeV/c)Φ·P3  (GeV/c)2  [ 1/sec cm2  sr ]00.511.522.533.51.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4CosmoALEPH( preliminary)log10 Pµ(GeV/c)Muon charge ratio RµHebbeker and Timmermans (2002)Figure 1. Momentum spectrum and charge ratio for vertical muons compared with other experiments[5, 18].10 210 310 410 510 61.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4CosmoALEPH( preliminary)VENUS 4.12QGSJET 01DPMJET 2.55SIBYLL 2.1log10 Pµ(GeV/c)Number of muons at the surface Nµ00.511.522.533.51.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4CosmoALEPH( preliminary)VENUS 4.12QGSJET 01DPMJET 2.55SIBYLL 2.1log10 Pµ(GeV/c)Muon charge ratio RµFigure 2. Number of vertical muons at the surface and their charge ratio compared with MC simulations based on differenthadronic interaction models.muons measured in CosmoALEPH is indeed an observable in EAS that can be used for testing theoreticalhadronic interaction models. Further work is in progress to compare the data with updated models for highenergy interactions such as QGSJET-II [19] and NEXUS 3 [20] which will be included in the next version ofCORSIKA[15, 21]. A more detailed analysis of the detector acceptance and trigger efficiency as function ofmuon momentum for inclined muons is in progress.16 N.O. Hashim et al6. AcknowledgementsOne of the authors (NOH) gratefully acknowledges the funding from the German Academic Exchange Service,DAAD. The authors gratefully acknowledge the help of the ALEPH collaboration, in particular the shift crewmembers of ALEPH, without whose support the data taking could not have been possible. The data analy-sis of the CosmoALEPH experiment has been funded by the Deutsche Forschungsgemeinschaft under grantDFG/Gr/1796/1-3.References[1] C. Grupen. Astroparticle Physics. Springer-Verlag, Berlin Heidelberg, 2005. 441 p.[2] H. Wachsmuth, Proposal to search for cosmic ray coincidences in the LEP-Detectors, Draft, 16 December1993, CosmoLEP-Note 94.000.[3] A. Ball, G. Bonvicini, C. Grupen et al., CERN/LEPC 94-10, LEPC/M, 1994, p 109[4] D. Zimmermann et al. The cosmic muon spectrum and charge ratio in CosmoALEPH. NIM A 525 (2004)pp 141 - 143.[5] T. Hebbeker and C. Timmermans. A compilation of high energy atmospheric muon data at sea levelAstropart. Phys. 18 (2002) p 107-127.[6] ALEPH collaboration. Performance of the ALEPH detector at LEP. NIM A 360 (1995) pp 481-506.[7] M. Schmelling et al. Studying extendend air showers with CosmoALEPH. First Arctic Workshop onCosmic Ray Muons, Sodankylae, Finnland, April 24-29, 1999.[8] H. Besier et al. Cosmic ray physics with the ALEPH detector. NIM A 454 (2000) pp 201 - 206.[9] C. Grupen et al. Measurements of the muon component of extensive air showers at 320 m.w.e. under-ground. NIM A 510 (2003) pp 190-193[10] G. D’Agostini. A multidimensional unfolding method based on Bayes’ theorem. NIM A 362 (1995) pp487-498.[11] D. Heck et al. CORSIKA: A Monte Carlo code to simulate extensive air showers. FZKA 6019,Forschungszentrum Karlsruhe (1998)[12] CERN. GEANT 3.21. Detector description and simulation tool. CERN Library Long Write-up W5013,CERN, GENEVA. 1994.[13] N.O. Hashim et al. Simulation of cosmic muon events in CosmoALEPH. In preparation.[14] J.R. Ho¨randel et al. Test of High Energy Hadronic Interaction Models using EAS Data. Proc. 26th Int.Cosmic Ray Conference, Salt Lake City 1 (1999) p 131 (and FZKA 6345, Forschungszentrum Karlsruhe(1999))[15] D. Heck. The influence of hadronic interaction models on simulated air showers: A phenomenologiccomparison. Lecture Notes. VIHKOS CORSIKA School 2005. May 29 - June 5 2005. Freudenstadt,Germany.[16] P. Le Coultre, on behalf of the L3+C collaboration. L3+C - The atmospheric muon momentum spectrum.Nucl. Phys. B (Proc. Suppl.) 145 (2005) pp 136-140.[17] J. Wentz et al. The relevance of the muon charge ratio for the atmospheric neutrino anomaly. J.Phys. G:Nucl. Part. Phys. 27 (2001) pp 1699-1708.[18] The L3 Collaboration. Measurement of the atmospheric muon spectrum from 20 to 3000 GeV. CERN-PH-EP-2004-023. June 1, 2004.[19] S. Ostapchenko. Non-linear effects in high energy hadronic interactions. hep-ph/0501093 Jan. 2005.[20] K. Werner et al. A new string model: NEXUS 3. hep-ph/0306151 June 2003[21] D. Heck et al. Influence of low-energy hadronic interaction programs on air shower simulations withCORSIKA. Proc. 28th ICRC, Tsukuba, Japan, 1 (2003) p 279.

Momentum spectrum of cosmic muons at a depth of 320 mwe

Abstract

Similar works

Full text

Available Versions

CERN Document Server