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Cosmic ray physics in ALICE

Cosmic ray physics in ALICE. Katherin Shtejer Díaz. For the ALICE Collaboration. LatinoAmerican Workshop on High Energy Physics: Particles and Strings, Havana, 15-21 July 2012. Contents. Motivation Cosmic Rays physics Physics Topics Extensive Air Showers (EAS) Flux of cosmic rays

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Cosmic ray physics in ALICE

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  1. Cosmic ray physics in ALICE Katherin Shtejer Díaz For the ALICE Collaboration LatinoAmerican Workshop on High Energy Physics: Particles and Strings, Havana, 15-21 July 2012

  2. Contents • Motivation • Cosmic Rays physics • Physics Topics • Extensive Air Showers (EAS) • Flux of cosmic rays • ALICE Detector • Main detectors involved in atmospheric muon detection • Tracking and Reconstruction • Forward Muon Spectrometer • Strengths of ALICE for cosmic ray physics • Analyses • Ratio +/- (near-vertical muons) • Ratio +/- (near-horizontal muons) • Muon multiplicity distribution • High muon multiplicity events (february 2010) • High muon multiplicity events (june 2011) • Summary Katherin Shtejer Díaz 2 HEP Havana, 15-21 July 2012

  3. Motivation • Cosmic Rays physics • The understanding of the origin and nature of the most energetic particles that constitute primary cosmic rays and their interaction processes. • Accelerator data and inputs are needed, particularly in the “knee” region of the energy spectrum of cosmic rays. • Mass composition and energy spectrum of primary cosmic rays can be studied with ALICE in an energy range not available from direct measurements with satellites or balloons or from deeper ground arrays. • Flux of cosmic ray muons provides a way of testing the inputs of nuclear cascade models and particle interactions at high energies. • The cosmic ray muon flux provides a useful tool for calculation of neutrino fluxes, which are rather difficult to measure directly. Katherin Shtejer Díaz 3 HEP Havana, 15-21 July 2012

  4. Physics Topics Katherin Shtejer Díaz 4 HEP Havana, 15-21 July 2012

  5. Primary Cosmic Ray (p, He,..., Fe) + Earth's Atmosphere        hadronic cascade  e+ e- e+ e- e+ e- Cherenkov & fluorescence radiation         p,n e- e+ e- e+  neutrino, muon component hadronic component electromagnetic component Extensive Air Showers (EAS) pnucleusanything    Similar processes occur in the decay of kaons producing muons with high momenta ee e-e • All the electromagnetic and hadronic components are absorbed by the overburden rock. • Only muons with E  15 GeV reach ALICE. • For this purpose three detectors are employed as triggers: - ACORDE (A COsmic Ray Detector) - TOF (Time Of Flight) - SPD (Silicon Pixel Detector) ...and - TPC (Time Projection Chamber) for track reconstruction Katherin Shtejer Díaz 5 HEP Havana, 15-21 July 2012

  6.   Knee (1 particle per m2 - year) Ankle (1 particle per Km2 - year) GZK cutoff d  ddddt Flux of cosmics rays - The elemental composition of primary cosmic rays and their sources for energies between the knee (~1015eV) and the Greisen-Zatsepin-Kuzmin (GZK) cutoff (~1020eV) is not well understood, because of the large discrepancies on the way the models predict the inelastic cross sections in this energy range. ALICE may contribute to more data measurements, by registering the high energy muon distribution from cosmic rays, in a cavern 52m underground.  is sensitive to the chemical composition of the primary particles Katherin Shtejer Díaz 6 HEP Havana, 15-21 July 2012

  7. ALICE detector Katherin Shtejer Díaz 7 HEP Havana, 15-21 July 2012

  8. Main detectors involved in atmospheric muon detection Zenith Angle y muon ACORDE z Azimuth Angle x ITS TPC TOF Tracking Chambers Trigger Chambers • ACORDE (ACOsmic Ray Detector) - 60 scintillator modules - trigger given by the coincidence of at least 2 modules (AMU) • TOF (Time Of Flight) - cylindrical Multi-Gap Resistive-Plate Chamber (MRPC) array - cosmic trigger requires one upper pad fired and one pad in the opposite lower side of TOF (OB1) • SPD (Silicon Pixel Detector) - two innermost layers of silicon pixel modules very closed to the interaction point - cosmic trigger given by the coincidence of two signals of muons crossing the top and bottom halves of the external layer (SCO) • Tracking and Trigger Chambers - used for horizontal muons as part of the FMS • TPC (Time Projection Chamber) - for track reconstruction • ALICE located 52 m underground • 28 m of overburden rock (molasse) • Detects atmospheric muons with energies  15 GeV Katherin Shtejer Díaz 8 HEP Havana, 15-21 July 2012

  9. A multi-muon event A muon interaction event up down Tracking and reconstruction (near-vertical muons) A single muon is reconstructed by the TPC as two tracks : up , down One muon is counted by matching the track up with the track down Katherin Shtejer Díaz 9 HEP Havana, 15-21 July 2012

  10. Y Z Forward Muon Spectrometer (Study of near-horizontal muons) A→C y negative Θy = arctan(Py /Pz) Interaction Point A←C y positive • Muon momentum threshold ~ 40GeV/c (due to the rock) • Length of detector ~ 13 m (from first tracking station) Katherin Shtejer Díaz 10 HEP Havana, 15-21 July 2012

  11. Analyses Katherin Shtejer Díaz 11 HEP Havana, 15-21 July 2012

  12. Ratio / (near-vertical muons) • CMS experiment : R = 1.2766 +- 0.0032(stat.) +- 0.0032(syst) P<100 GeV/c • L3+C experiment : R = 1.285 +- 0.003(stat.) +- 0.019 (syst.) P<500 GeV/c • ALICE experiment : R = 1.275 +- 0.006(stat.) +- 0.01 (syst.) P<100 GeV/c Katherin Shtejer Díaz 12 HEP Havana, 15-21 July 2012

  13. ALICE : R =1.27 +- 0.04(stat.) +- 0.1(syst.) 80<P<320 GeV/c (70o-85o) • MUTRON  Surface muon spectrometer at sea level, zenith 86o-90o, year 1984 R = 1.251 +- 0.005 (stat.) 100<P<600 GeV/c • DEIS  Surface muon spectrometer at sea level, zenith 78o-90o, year 1981 R = 1.25 Ratio / (near-horizontal muons) Katherin Shtejer Díaz 13 HEP Havana, 15-21 July 2012

  14. Muon Multiplicity Distribution (Zoom low multiplicity) Comparison with simulation CORSIKA code with QGSJET II Proton primary (relative normalization at 3 muons) Fe primary Data taken February-August 2011 ~ 10 days live time Trigger : ACORDE + TOF Katherin Shtejer Díaz 14 HEP Havana, 15-21 July 2012

  15. High Muon Multiplicity Events (February 2010) Mean Zenith Angle : 40° Mean Azimuth Angle : 212° Density of muons : ~12 /m2 Mean Zenith Angle : 41° Mean Azimuth Angle : 69° Density of muons : ~ 6 /m2 Katherin Shtejer Díaz 15 HEP Havana, 15-21 July 2012

  16. Density (/m2) (1) Estimated Energy (eV) Number of  89 171 276 6 12 18 6x1015 1016 3x1016 High Muon Multiplicity Events (June 2011) Mean Zenith Angle : 26° Mean Azimuth Angle : 193° Density of muons : ~ 17 /m2 (1)Supposing Fe as primary, and the EAS core inside ALICE Katherin Shtejer Díaz 16 HEP Havana, 15-21 July 2012

  17. Summary • ALICE can study atmospheric muons with central detectors and forward muon spectrometer by measuring: number of muons, momentum, charge, direction, arrival time. • Preliminary measurements of Ratio +/- for vertical muons (00-200) with central detectors and for horizontal muons (750-850) with forward muon spectrometer have been presented. • More statistics is required to improve our studies. • More analyses have to be performed of the muon multiplicity distribution and exploit the correlation with various observables in order to study the cosmic ray composition. • Investigate the higher multiplicity events to understand their nature. Katherin Shtejer Díaz 17 HEP Havana, 15-21 July 2012

  18. Inputs from: • Bruno Alessandro (a) • Mario Rodriguez Cahuantzi (b) • Arturo Fernandez Tellez (b) • Mario Sitta (a) (a) Istituto Nazionale di Fisica Nucleare, sezione di Torino, ITALY (b) Benemerita Universidad Autonoma de Puebla, MEXICO Katherin Shtejer Díaz 18 HEP Havana, 15-21 July 2012

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