Highlights from ARGO-YBJ G. Di Sciascio INFN – Sez. Roma “Tor Vergata” On behalf of the ARGO-YBJ Collaboration Vulcano Workshop 2010 – May 25, 2010
The ARGO-YBJ experiment An unconventional EAS-array exploiting the Longitude 90° 31’ 50” East full coverage approach at very high altitude, Latitude 30° 06’ 38” North with the aim of studying 90 Km North from Lhasa (Tibet) VHE γ -Ray Astronomy Gamma Ray Burst Physics 4300 m above the sea level Cosmic Ray Physics The Yangbajing Cosmic Ray Laboratory ARGO Tibet AS γ Vulcano Workshop 2010 G. Di Sciascio 2
The ARGO-YBJ experiment International Collaboration: Chinese Academy of Science (CAS) Istituto Nazionale di Fisica Nucleare (INFN) INFN and Dpt. di Fisica Università, Lecce IHEP, Beijing INFN and Dpt. di Fisica Universita’, Napoli Shandong University, Jinan INFN and Dpt. di Fisica Universita’, Pavia South West Jiaotong University, Chengdu INFN and Dpt di Fisica Università “Roma Tre”, Roma Tibet University, Lhasa INFN and Dpt. di Fisica Univesità “Tor Vergata”, Roma Yunnan University, Kunming INAF/IFSI and INFN, Torino ZhengZhou University, ZhengZhou INAF/IASF, Palermo and INFN, Catania Hong Kong University, Hong Kong Vulcano Workshop 2010 G. Di Sciascio 3
Experimental Hall & Detector Layout time resolution ~1-2 ns (pad) space resolution = strip Central Carpet: 99 m 74 m 130 Clusters 1560 RPCs 124800 Strips 8 Strips 10 Pads (6.5 x 62 cm 2 ) (56 x 62 cm 2 ) 1 CLUSTER = 12 RPCs for each Pad for each RPC (5.7 7.6 m 2 ) Gas Mixture: Ar/ Iso/TFE = 15/10/75 78 m 111 m HV = 7200 V Single layer of Resistive Plate Chambers (RPCs) with a full coverage (92% active surface) of a large area (5600 m 2 ) + sampling guard ring (6700 m 2 in total) Vulcano Workshop 2010 G. Di Sciascio 4
Operational Modes Shower Mode: Detection of Extensive Air Showers (direction, size, core …) INDIPENDENT DAQ 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 (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. Object: • flaring phenomena (high energy tail of GRBs, solar flares) • detector and environment monitor Vulcano Workshop 2010 G. Di Sciascio 5
Shower mode: Number of fired Strips 62 cm 2 (single strip) Space pixel: 7 62 cm 2 Time pixel: 56 (8 ORed strips = 1 Pad) Time resolution: ≈ 1 ns The size of pixels, the time resolution and the full coverage allow reconstruction with unprecedent details
• Stable data taking since Nov. 2007 with full detector • Average duty cycle ~ 90% • Trigger rate ~3.6 kHz @ 20 pad threshold • Dead time 4% • 220 GB/day transferred to IHEP/CNAF data centers Vulcano Workshop 2010 G. Di Sciascio 7
Detector performance Moon Shadow & Angular Resolution Vulcano Workshop 2010 G. Di Sciascio 8
The Moon Shadow Deficit of cosmic rays in Cosmic rays are hampered by the Moon the direction of the Moon Size of the deficit Angular Resolution Position of the deficit Pointing Error Geomagnetic Field : positively charged particles are deflected towards the West. 0 1 . 6 Z Ion spectrometer Moon diameter ~0.5 deg E ( TeV ) The observation of the Moon shadow can provide a direct check of the relation between size and primary energy West displacement Energy calibration Vulcano Workshop 2010 G. Di Sciascio 9
All data: 2006 → 2009 θ < 50° N > 100 55 s.d. PSF of the detector 3200 hours on-source 9 standard deviations / month The deficit surface is the convolution of the PSF of the detector and the widespread Moon disc. Vulcano Workshop 2010 G. Di Sciascio 10
Moon Shadow analysis Measured angular resolution Measured EW displacement Vulcano Workshop 2010 G. Di Sciascio 11
Sun shadow Displacement of the Sun shadow correlates with the SMMF Sun at maximum → shadow is washed out Sun at minimum → good shadow & SMF symmetric between NS EW shift due to GMF NS shift due to IMF The displacement of the Sun shadow is a good measurement of the IMF, especially in a this particular quiet phase between 23 th and 24 th cycles. Vulcano Workshop 2010 G. Di Sciascio 12
Cosmic Ray Physics • Antiproton/proton ratio measurement • Light-component spectrum of primary CRs Vulcano Workshop 2010 G. Di Sciascio 13
p/p ratio at TeV energies Using data on Moon shadow, limits on antiparticle flux can be derived. Protons are deflected towards West, antiprotons are deflected towards East → 2 symmetric shadows expected . 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. Vulcano Workshop 2010 G. Di Sciascio 14
Upper limit on p/p by ARGO-YBJ Preliminary Vulcano Workshop 2010 G. Di Sciascio 15
Light-component spectrum of CRs Measurement of the light-component (p+He) spectrum of primary CRs in the energy region (5 – 250) TeV via a Bayesian unfolding procedure CNO < 2% CREAM p+He EAS-TOP + MACRO Horandel p+He CREAM p ARGO data agree with CREAM results CREAM He ARGO preliminary Evidence that the proton spectrum is flatter than in the lower energy region Vulcano Workshop 2010 G. Di Sciascio 16
Anisotropy & γ -ray astronomy • Large & Medium Scale Anisotropy • Search for point like sources • AGN Follow Up – Flaring Vulcano Workshop 2010 G. Di Sciascio 17
Intermediate scale anisotropy 584 days: 2007 Dec. – 2009 Nov. Cosmic rays excess 0.06% 9 ·10 10 events 0.1% r.a.=0 r.a.=360 N PAD > 40 Proton median energy 2 TeV Smoothing radius = 5 Vulcano Workshop 2010 G. Di Sciascio 18
~4 ·10 -4 ~6 ·10 -4 MILAGRO Ga Galacti tic Pl Plane He Heliotail tail Ge Gemi minga Proton median energy 10 TeV Multiple explanations were proposed: ARGO-YBJ Salvati & Sacco, A&A 485 (2008) 527 Drury & Aharonian, Astrop. Phys. 29 (2008) 420. K. Munakata ,AIP Conf Proc Vol 932, page 283 Salvati, A&A 513 (2010) A28 Proton median energy 2 TeV Vulcano Workshop 2010 G. Di Sciascio 19
Large scale anisotropy ARGO-YBJ DATA: 2008 and 2009 Loss-cone Tail-in Cygnus region Vulcano Workshop 2010 G. Di Sciascio 20
Tibet AS M. Amenomori et.al. Science, 2006 Vulcano Workshop 2010 G. Di Sciascio 21
1D anisotropy for different energies Fit function: Agree with diffusion model: larger amplitude for higher energy. 0.7 TeV 1.5 TeV 3.9 TeV G. Guillian et. al. 2007 PRD Vulcano Workshop 2010 G. Di Sciascio 22
All sky survey result • 3 sources with significance >5 σ in 825 days (Jul. 06 – Oct. 09) • Crab 14.5 σ , Mrk421 12 σ , MGRO1908+06 5.4 σ 2.1 10 -3 Mean = -9.3 Mrk421 Crab Sigma = 1.008 0.002 23 Vulcano Workshop 2010 G. Di Sciascio
Crab Nebula ~14.5 s.d. in ~800 days ~ 50 % N PAD Events /day E med (TeV) Crab/year NO selection 40 – 100 128 24 0.85 NO γ /h discrimination 100 – 300 17.9 6.3 1.8 Absolute measurement > 300 9.2 2.3 5.2 dN/dE = (3.73 0.80) ·10 -11 · E – 2.67 0.25 ev cm – 2 s – 1 TeV – 1 Vulcano Workshop 2010 G. Di Sciascio 24
Mrk421 Total significance: 12 s.d. in ~800 days Mrk421 is characterized by a strong flaring activity both in X-rays and in TeV γ– rays. Different flares observed by ARGO-YBJ in TeV range Swift (15-50 keV) Full TEST DAQ data Vulcano Workshop 2010 G. Di Sciascio 25
Mrk 421: July 2006 flare ARGO started recording data with the full central carpet during the X-ray flare of Mrk421 in July 2006 Commissioning Phase Evidence for TeV emission in coincidence with a X-ray flare days 187-245 ( 110 hours ) δ (deg) ≈ 6 σ Mrk421 ASM / RXTE Flux 3-4 Crab N pad > 60 E γ 50 ~ 1.6 TeV, E γ mode ~ 500 GeV R.a. (deg) Vulcano Workshop 2010 G. Di Sciascio 26
Mrk421: 2008 emission ARGO Gamma Rays vs X-rays Correlation coefficient = 0.64 ASM/RXTE days from 1-1-08 10 days average N PAD > 100 Vulcano Workshop 2010 G. Di Sciascio 27
Mrk421 energy spectrum 2008 days 41 – 180: when the source was in active state Integral flux (E > 1 TeV) 4.9 2.0 10 -11 ev cm – 2 s – 1 2 Crab EBL from Primack et al. AIP conf. Proc. 745, 23, 2005 Power law spectrum + EBL absorption : 1.7) · 10 -11 E – 2.51 0.29 e - (E) ev cm – 2 s – 1 TeV – 1 dN/dE = (7.5 Vulcano Workshop 2010 G. Di Sciascio 28
Recommend
More recommend
