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Alba Cappa Universita’ and INFN Torino

Čerenkov Light Measurements for the EUSO Experiment. Alba Cappa Universita’ and INFN Torino. Rencontres de Moriond – Very High Energy Phenomena in the Universe La Thuile, March 12-19, 2005. CONTENTS:. the ULTRA experiment for EUSO the ULTRA detector simulated and collected data

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Alba Cappa Universita’ and INFN Torino

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  1. Čerenkov Light Measurements for the EUSO Experiment Alba Cappa Universita’ and INFN Torino Rencontres de Moriond – Very High Energy Phenomena in the Universe La Thuile, March 12-19, 2005

  2. CONTENTS: • the ULTRA experiment for EUSO • the ULTRA detector • simulated and collected data • data analysis • conclusions Alba Cappa - Very High Energy Phenomena in the Universe

  3. EUSO : an UHECRs observatory UHECRs spectrum EUSO will provide to solve some problems of Fundamental Physics and HE astrophysics: • do the GZK cut-off exist? • investigation of the highest energy processes in the Universe through the detection and investigation of the Extreme Energy component of the cosmic radiation (EECRs / UHECRs with E > 5×1019 eV); • arrival direction and small-scale clustering will provide informations on the origin of EECRs and magnetic fields; • HE neutrino astronomy will probe the boundaries of the extreme Universe and the nature and distribution of EECRs sources. Alba Cappa - Very High Energy Phenomena in the Universe

  4. The EUSO project EUSO will look downwards to the Earth atmosphere. It will see the fluorescent UV traces isotropically produced by the charged secondary particles along the EAS development. EUSO will detect also the Cherenkov light emitted in a narrow cone centered on the shower axis and hitting the Earth surface, where it’s partially diffused. EUSO geometrical design Cherenkov signal image of a shower from a UHE primary on the EUSO focal surface: fluorescent and Cherenkov signals. EUSO focal surface Alba Cappa - Very High Energy Phenomena in the Universe

  5. ULTRA facility in the EUSO framework ? reflection/diffusion coefficient ULTRA UV Light Transmission and Reflection in the Atmosphere ULTRA goals: measurement of the EAS characteristics and associated Cherenkov light diffused by various surfaces. Alba Cappa - Very High Energy Phenomena in the Universe

  6. ULTRA : a supporting activity for the EUSO project UVscope UV optical unit for Cherenkov light detection ULTRA: hybrid system ETscope EAS telescope, scintillator’s array UVscope and ETscope work in coincidence to detect the EAS and the Cherenkov light generated and reflected/diffused back by the Earth surface. ETscope detector: characterization of the triggering EAS (shower size, arrival direction, core position) and comparison with the results of the simulations. Alba Cappa - Very High Energy Phenomena in the Universe

  7. ST4 ST3 B-UP B-DW ST5 L=54 m ST2 ST1 The ULTRA setup • 2003/2004 Experimental Setup • 4+1 counting stations • distance between modules = 35/54 m • standard NIM & CAMAC electronics / ACQ by Labview • 4-fold coincidence 150 ns • threshold: 0.3 VEM • 2 couples of “Belenos” (Cherenkov light detectors) near to the central station, pointing to zenith and nadir. ETscope @ LPSC Grenoble 216 m a.s.l. - 990 g/cm2 ETscope @ Mont Cenis 1970 m a.s.l. - 805 g/cm2 Alba Cappa - Very High Energy Phenomena in the Universe

  8. The ETscope detector Scintillator NE102A80x80 cm2 x 4 cm Expected Light Yield ~40 p.e./m.i.p. 2 PMTs High/Low Gain HG pmt Saturation ~40 VEM / 0.64 m2 LG pmt Saturation ~400 VEM / 0.64 m2 • Procedures for the triggering events: • event by event for each station the following characteristics are known: • arrival time • deposited energy in the scintillator (number of VEMs) • position of the detectors arrival direction (q,f) shower size Ne (Eo) core position RECONSTRUCTION Alba Cappa - Very High Energy Phenomena in the Universe

  9. SIMULATIONS (I) • Procedures for the simulated events: • event by event for each station the following characteristics are known: • deposited energy in the scintillator (number of VEMs) • position of the detectors • true values for size and core position shower size Ne (Eo) core position resolution in the reco RECONSTRUCTION of the internal events very important also for the reconstruction of the real data the ones having the core inside the array: UVscope FOV is limited to the dimensions of ETscope area Alba Cappa - Very High Energy Phenomena in the Universe

  10. SIMULATIONS (II) EAS simulation: CORSIKA simulations of EAS with QGSJET hadronic interaction model: • primary particles type: protons; • 2000 events for each energy and primary inclination; • two observation levels: 0m asl, 2000m asl. Alba Cappa - Very High Energy Phenomena in the Universe

  11. SIMULATIONS (III) detector simulation: a Monte Carlo program simulate the detector response to the showers generated by CORSIKA, for different geometrical configurations (the experimental conditions used in the measurement campaigns @ Grenoble, @ Mont-Cenis, @ Capo Granitola). optimization of the detector: study of the effective area calculation of the threshold energy measurement of the expected counting rate From the simulations we can predict the detector side that is required to have the best measurement conditions @ the observation level of interest. Alba Cappa - Very High Energy Phenomena in the Universe

  12. SIMULATIONS (IV) E(GeV) E(GeV) • Some results for: • effective area for internal events • effective area • convolution between the effective area and the CR spectrum Aint(m2) Aeff(m2) Capo Granitola (spring-summer 2005 campaign): Grenoble (winter 2004-05 campaign): Mont-Cenis (2004 campaign): AeffAE-γ(m2) Alba Cappa - Very High Energy Phenomena in the Universe

  13. Čerenkov light measurement (I) in this measurement campaign, we are interested to the detect em component in coincidence with diffused Cherenkov light. For this reason (and due to high beckground in Grenoble), we used a surface with a very high reflectivity coefficient. 2004 CAMPAIGN top oriented unit Tyvec Refecting-Diffusing Surface 2+2 optical units (Belenos-up & down) located near to the ETscope central station (1.5 cm Ø pmt + fresnel lens) / triggered by EAS events FOV = 30o bottom oriented unit Alba Cappa - Very High Energy Phenomena in the Universe

  14. The ETscope data@ LPSC • Measurement campaigns: • 2004 (Mont-Cenis, Grenoble) • winter 2004-2005 (Grenoble) • I will show the data analysis of the 2004 campaign @ Grenoble 937 events collected in 38.4 hours TRIGGER CONDITIONS: Data selected requiring the triggering of the central detector and the Belenos-up or the Belenos-down. Requiring a signal over threshold on the Belenos-up high energy shower are selected, and even higher requiring the Belenos-down. Alba Cappa - Very High Energy Phenomena in the Universe

  15. Cherenkov light measurement (II) green: trigger of central station + Belenos-up red: trigger of Belenos-down LPSC size spectrum <Log10Ne> 5.25±0.02 5.65±0.04 6.26±0.20 LPSC zenith angle < θ(°) > 23.1±0.4 11.6±0.7 16.7±3.2 Alba Cappa - Very High Energy Phenomena in the Universe

  16. Cherenkov light measurement (III) blue points:Cherenkov l.d.f. obtained from events with core located within 20 meters to central station (absolute single-pe calibration used) background level: 3000 photons /(m2 ns sr) (10 x Mont-Cenis background) green line: CORSIKA Simulation for 1016 eV proton, with wavelength in 300-400 nm band. Alba Cappa - Very High Energy Phenomena in the Universe

  17. UP Oriented Unit (1) vs Event Number Twilight UP Oriented Unit (2) vs Event Number Cherenkov light measurement (IV) The signal measured by the Belenos-up shows the excellent correlation between the two detectors. Yellow points are the twilight, well visible at the end of two measurement nights. Alba Cappa - Very High Energy Phenomena in the Universe

  18. Reflection coefficient measurement • Data: May-June 2004, 6 events selected • Due to low ADC gain and wrong ADC calibration in May only June data are available: 2 surviving events in Dt=17 h used to a very preliminary estimation on the reflected light. • background level used • top/bottom units relative normalization applied compatible with tyvec reflectivity and detector acceptance Alba Cappa - Very High Energy Phenomena in the Universe

  19. CONCLUSIONS • 2004 campaigns (Mont-Cenis @ 1970m asl, Grenoble @ 200m asl), measured: • em component; • direct Cherenkov light; • 2 events of diffuse Cherenkov light; • background evaluation; • winter 2004-2005 (Grenoble): • more statistics, analysis of the events is still in progress; • UVscope characterization; • spring/summer 2005 (Capo Granitola @ sea level- Sicily): • final measurements with UVscope; • direct Cherenkov light detection. Alba Cappa - Very High Energy Phenomena in the Universe

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