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Cosmic-Ray Detection at the ARGO-YBJ observatory

Cosmic-Ray Detection at the ARGO-YBJ observatory. P. Camarri University of Roma “Tor Vergata ” INFN Roma Tor Vergata. TeV gamma-ray astronomy. TeV γ -ray astronomy: science topics. The gamma-ray spectrum. Cerenkov Telescopes. EAS arrays. HAFC EAS arrays. Satellites.

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Cosmic-Ray Detection at the ARGO-YBJ observatory

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  1. Cosmic-Ray Detection at the ARGO-YBJ observatory P. Camarri University of Roma “Tor Vergata” INFN Roma Tor Vergata

  2. TeV gamma-ray astronomy P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  3. TeV γ-ray astronomy: science topics P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  4. The gamma-ray spectrum Cerenkov Telescopes EAS arrays HAFC EAS arrays Satellites 106 109 1012 1015 1018 eV 1 MeV 1 GeV 1 TeV 1 PeV 1 EeV -ray sources: naturally multiwavelength Physics targets for -ray astronomy • Galactic sources • Supernova Remnants • Plerions • Shell type SNR • Pulsars • Diffuse emission from the galactic disk • Unidentified Sources Absolute necessity of multiwavelength observations • Extragalactic sources • Active Galactic Nuclei (blazars) • Gamma Ray Bursts • Cosmological γ–ray Horizon • Probe of the Extragalactic Background Light (EBL) P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  5. TeV γ-rays: production processes P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  6. TeV γ-rays: production processes P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  7. Satellite vs Ground-based detectors • Satellite: • lower energy • primary detection • small effective area ~1m2 • lower sensitivity • large duty-cycle • large cost • low bkg • Ground based: • higher energy • secondary detection • huge effective area ~104 m2 • higher sensitivity • Small/large duty-cycle • low cost • high bkg P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

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  10. Statistical significance Excess of events coming from the source over the estimated background standard deviations P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  11. CRAB( >1 TeV) 2 ·10-11 ph/cm2·s In addition… Cosmic Ray showers γ-ray showers bkg( >1 TeV) · (= 1 msr) 1.5 ·10-8 nuclei/cm2·s … fortunately, some difference does exist !! Ground based -Ray Astronomy requires a severe control and rejection of the BKG. The main drawback of ground-based measurements …background showers induced by primary Cosmic Rays No possible veto with an anticoincidence shield as in satellite experiments P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

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  15. Classical EAS arrays Air Cherenkov Telescopes detection of the Cherenkov light from charged particles in the EAS detection of the charged particles in the shower High energy threshold ( 50 TeV) Moderate bkg rejection ( 50 %) Modest sensitivity ( Fcrab) Modest energy resolution High duty-cycle (> 90 %) Large field of view (~2 sr) Very low energy threshold ( 60 GeV) Good background rejection (99.7 %) High sensitivity (< 10-2Fcrab) Good energy resolution Low duty-cycle (~ 5-10 %) Small field of view D < 4° Detecting Extensive Air Showers The classical solution for ground based –ray astronomy P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  16. The birth of TeV γ-ray astronomy Discovery of the emission of photons with E > 0.7 TeV coming from the Crab Nebula by the Whipple Cherenkov telescope in 1989: 50 h per 5σ HESS: 30 seconds ! P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  17. The TeV sky P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  18. Provides synoptic view of the sky • Sees an entire hemisphere every day • Large fov & high duty-cycle • GRBs • Transient astrophysics • Extended objects • New sources Why an EAS array ? Excellent complement to satellites ACTs can monitor only a limited number of sources / year at stated sensitivity A sensitive EAS array is needed to extend the FERMI/GLAST measurements at > 100 GeV. P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  19. The Goal • Low energy threshold < 500 GeV • Increased sensitivity ΦΦcrab <10-1 Φcrab The Solution • High-altitude operation • Secondary-photon conversion • Increase the sampling (~1%  100%) Improves angular resolution Lowers energy threshold A new-generation EAS array P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  20. Excellent complement to AGILE/GLAST to extend satellite measurements at > 100 GeV The ARGO-YBJ experiment • ARGO detects air-shower particles at ground level • ARGO is a wide field of view gamma-ray telescope which operates in “scanning mode” • ARGO is optimized to work with showers induced by primaries of energy E > a few hundred GeV This low energy thresholdis achieved by: • operating atvery highaltitude (4300 m asl) • using a“full-coverage” detection surface P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  21. The Yangbajing Cosmic Ray Laboratory ARGO Tibet ASγ The ARGO-YBJ experiment Longitude 90° 31’ 50” East Latitude 30° 06’ 38” North 90 Km North from Lhasa (Tibet) An Extensive Air Shower detector exploiting the full-coverage approach at very high altitude, with the goal of studying • VHE g-Ray Astronomy • g-Ray Burst Physics • Cosmic-Ray Physics 4300 m above the sea level P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  22. 12 RPC =1 Cluster ( 5.7 ´ 7.6 m2 ) 99 m 74 m Central Carpet: 130 Clusters 1560 RPCs 124800 Strips 78 m 111 m Layer of RPC covering 5600 m2 (  92% active surface) (+ 0.5 cm lead converter) + sampling guard-ring 8 Strips = 1 Pad (56 ´ 62 cm2) 10 Pads = 1 RPC (2.80 ´ 1.25 m2) Gas Mixture: Ar/ Iso/TFE = 15/10/75, HV = 7200 V BIG PAD Read-out of the charge induced on “Big-Pads” ADC P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011 RPC

  23. The ARGO-YBJ Resistive Plate Chambers Gas mixture: C2H2F4/Ar/iC4H10 = 75/15/10 Operated in streamer mode Time resolution ~ 1.5 ns P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  24. Shower recostruction time (ns) meters Arrival time vs position Fired pads on the carpet P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  25. Analog read-out It is crucial to extend the dynamics of the detector for E > 100 TeV, when the strip read-out information starts to become saturated. Max fs: 6500 part/m2 0 4000 0 3500 3000 2500 ARGO event 2000 1500 1000 500 Fs: 4000 -> 1300/m2 P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  26. Strip =SPACE PIXEL, 6.5 x 62 cm2, 124800 Pad =TIME PIXEL, 56 x 62 cm2, 15600 BigPad =CHARGE readout PIXEL, 120 x 145 cm2, 3120 Cluster = DAQ unit = 12 RPCs σt≈1 ns RPC Pad BigPad Strip Detector Pixels P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

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  28. Shower Mode: Detection of Extensive Air Showers (direction, size, core …) Coincidence of different detector units (pads) within 420 ns Trigger : ≥ 20 fired pads on the central carpet (rate ~3.6 kHz) • Object: • Cosmic Ray physics (above ~1 TeV) • VHE γ-astronomy (above ~300 GeV) • Scaler Mode: Recording the counting rates (Nhit ≥1, ≥2, ≥3, ≥4) for each cluster at fixed time intervals (every 0.5 s) lowers the energy threshold down to ≈ 1 GeV. No information on the arrival direction and spatial distribution of the detected particles. • Object: • flaring phenomena (high energy tail of GRBs, solar flares) • detector and environment monitor Operational Modes INDEPENDENT DAQ P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

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  30. Size of the deficit • Position of the deficit Angular Resolution Pointing Error Ion spectrometer Energy calibration The Moon Shadow Cosmic rays are hampered by the Moon Deficit of cosmic rays in the direction of the Moon Geomagnetic Field: positively charged particles deflected towards the West and negatively charged particles towards the East. Moon diameter ~0.5 deg The observation of the Moon shadow can provide a direct check of the relation between size and primary energy P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

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  32. g-ray astronomy • Crab Nebula • Mrk 421 • MGRO 1908+06 • Cygnus region • and more… no γ/h discrimination applied so far P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  33. γ/h discrimination • Some algorithms developed based on • 2-D topology • Time profile • Time distribution • Q factor = 1.2 - 3 depending on the number of fired pads • Very heavy, fine tuning needed • Many months for data reprocessing P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

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  39. Cosmic-Ray Physics • Spectrum of the light component (1-100 TeV) • Medium and large scale anisotropies • The anti-p/p ratio P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

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  44. The Earth-Moon system as a spectrometer The shadow of the Moon can be used to put limits on antiparticle flux. In fact, if proton are deflected towards West, antiprotons are deflected towards East. If the displacement is large and the angular resolution small enough we can distinguish between the 2 shadows. If no event deficit on the antimatter side is observed an upper limit on antiproton content can be calculated. P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  45. (under peer reviewing for publication on PRD) P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  46. Conclusions (2) • g-ray astronomy in the energy range above ~300 GeV can only be investigated by ground-based Cherenkov and EAS detectors. • The ARGO-YBJ experiment, a full-coverage EAS array at high altitude, is giving very nice results in TeVg-ray astronomy and cosmic-ray physics at E > 1 TeV. By exploiting the analog read-out of its RPCs, it will be possible to study the energy region around the “knee” up to ~1016eV. P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

  47. A few references http://tevcat.uchicago.edu/reviews.html G. Di Sciascio and L.Saggese, Towards a solution of the knee problem with high altitude experiments Invited contribution to the Book "Frontiers in Cosmic Ray Research", 2007 Nova Science Publishers, New York, Ed. I.N. Martsch, Chapter 3, pp. 83 - 130. P. Camarri - WAPP 2011 - Darjeeling, India - Dec 2011

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