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

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

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

P. Camarri - WAPP Darjeeling, India - Dec The gamma-ray spectrum eV Satellites Cerenkov Telescopes EAS arrays HAFC EAS arrays 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 Extragalactic sources  Active Galactic Nuclei (blazars)  Gamma Ray Bursts Cosmological γ –ray Horizon  Probe of the Extragalactic Background Light (EBL) Absolute necessity of multiwavelength observations

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

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

P. Camarri - WAPP Darjeeling, India - Dec Satellite vs Ground-based detectors Satellite:  lower energy  primary detection  small effective area ~1m 2 lower sensitivity  large duty-cycle  large cost  low bkg Ground based:  higher energy  secondary detection  huge effective area ~10 4 m 2 higher sensitivity  Small/large duty-cycle  low cost  high bkg

P. Camarri - WAPP Darjeeling, India - Dec

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10 Statistical significance Excess of events coming from the source over the estimated background standard deviations

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

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

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

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

P. Camarri - WAPP Darjeeling, India - Dec Why an EAS array ? Provides synoptic view of the sky Sees an entire hemisphere every day Large fov & high duty-cycle GRBs Transient astrophysics Extended objects New sources 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 Darjeeling, India - Dec A new-generation EAS array Low energy threshold < 500 GeV Increased sensitivity Φ  Φ crab  <10 -1 Φ crab The Goal High-altitude operation Secondary-photon conversion Increase the sampling (~1%  100%) The Solution Improves angular resolution Lowers energy threshold

P. Camarri - WAPP Darjeeling, India - Dec The ARGO-YBJ experiment ARGO detects air-shower particles at ground level wide field of view gamma-ray telescope which operates in “scanning mode”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 Excellent complement to AGILE/GLAST to extend satellite measurements at > 100 GeV This low energy threshold is achieved by:  operating at very high altitude (4300 m asl)  using a “full-coverage” detection surface

P. Camarri - WAPP Darjeeling, India - Dec 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 The ARGO-YBJ experiment Tibet AS γ ARGO The Yangbajing Cosmic Ray Laboratory VHE  -Ray Astronomy  -Ray Burst Physics Cosmic-Ray Physics 4300 m above the sea level

P. Camarri - WAPP Darjeeling, India - Dec Pads = 1 RPC (2.80  1.25 m 2 ) Gas Mixture: Ar/ Iso/TFE = 15/10/75, HV = 7200 V 78 m 99 m74 m 111 m Layer of RPC covering  5600 m 2 (  92% active surface) (+ 0.5 cm lead converter) + sampling guard-ring Central Carpet: 130 Clusters 1560 RPCs Strips BIG PAD ADC RPC Read-out of the charge induced on “Big-Pads” 12 RPC =1 Cluster ( 5.7  7.6 m 2 ) 8 Strips = 1 Pad (56  62 cm 2 )

The ARGO-YBJ Resistive Plate Chambers P. Camarri - WAPP Darjeeling, India - Dec 2011 Gas mixture: C 2 H 2 F 4 /Ar/iC 4 H 10 = 75/15/10 Operated in streamer mode Time resolution ~ 1.5 ns 23

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

Analog read-out 0 Fs: > 1300/m 2 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/m P. Camarri - WAPP Darjeeling, India - Dec

Detector Pixels Cluster = DAQ unit = 12 RPCs RPC Strip Strip = Strip = SPACE PIXEL, 6.5 x 62 cm 2, BigPa d BigPad = BigPad = CHARGE readout PIXEL, 120 x 145 cm 2, 3120 Pad Pad = Pad = TIME PIXEL, 56 x 62 cm 2, σ t ≈1 ns P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec 2011 Operational Modes Object: flaring phenomena (high energy tail of GRBs, solar flares) detector and environment monitor Recording the counting rates (N hit ≥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. :  Scaler 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)  Shower Mode: INDEPENDENT DAQ 28

P. Camarri - WAPP Darjeeling, India - Dec

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

P. Camarri - WAPP Darjeeling, India - Dec

 -ray astronomy Crab Nebula Mrk 421 MGRO Cygnus region and more… no γ/h discrimination applied so far P. Camarri - WAPP Darjeeling, India - Dec

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

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

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

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec

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

Conclusions (2)  -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 TeV  -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 ~10 16 eV. P. Camarri - WAPP Darjeeling, India - Dec

P. Camarri - WAPP Darjeeling, India - Dec A few references 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