Highlights from ARGO-YBJ

Transcription

1 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

2 The ARGO-YBJ experiment An unconventional EAS-array exploiting the full coverage approach at very high altitude, with the aim of studying VHE γ-ray Astronomy Gamma Ray Burst Physics Cosmic Ray Physics Longitude East Latitude North 90 Km North from Lhasa (Tibet) 4300 m above the sea level Tibet ASγ The Yangbajing Cosmic Ray Laboratory ARGO Vulcano Workshop 2010 G. Di Sciascio 2

3 The ARGO-YBJ experiment International Collaboration: Chinese Academy of Science (CAS) Istituto Nazionale di Fisica Nucleare (INFN) INFN and Dpt. di Fisica Università, Lecce INFN and Dpt. di Fisica Universita, Napoli INFN and Dpt. di Fisica Universita, Pavia INFN and Dpt di Fisica Università Roma Tre, Roma INFN and Dpt. di Fisica Univesità Tor Vergata, Roma INAF/IFSI and INFN, Torino INAF/IASF, Palermo and INFN, Catania IHEP, Beijing Shandong University, Jinan South West Jiaotong University, Chengdu Tibet University, Lhasa Yunnan University, Kunming ZhengZhou University, ZhengZhou Hong Kong University, Hong Kong Vulcano Workshop 2010 G. Di Sciascio 3

4 Experimental Hall & Detector Layout 99 m 74 m time resolution ~1-2 ns (pad) space resolution = strip Central Carpet: 130 Clusters 1560 RPCs Strips 78 m 1 CLUSTER = 12 RPCs ( m 2 ) 10 Pads (56 x 62 cm 2 ) for each RPC 8 Strips (6.5 x 62 cm 2 ) for each Pad Gas Mixture: Ar/ Iso/TFE = 15/10/ 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

5 INDIPENDENT DAQ Operational Modes 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 (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

6 Number of fired Strips Shower mode: Space pixel: 7 62 cm 2 (single strip) Time pixel: cm 2 (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

7 Stable data taking since Nov with full detector Average duty cycle ~ 90% Trigger rate ~ pad threshold Dead time 4% 220 GB/day transferred to IHEP/CNAF data centers Vulcano Workshop 2010 G. Di Sciascio 7

8 Detector performance Moon Shadow & Angular Resolution Vulcano Workshop 2010 G. Di Sciascio 8

9 The Moon Shadow Cosmic rays are hampered by the Moon Deficit of cosmic rays in the direction of the Moon Size of the deficit Position of the deficit Angular Resolution Pointing Error Geomagnetic Field: positively charged particles are deflected towards the West. Ion spectrometer Z E( TeV ) Moon diameter ~0.5 deg 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

10 All data: s.d. N > 100 θ < 50 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

11 Moon Shadow analysis Measured angular resolution Measured EW displacement Vulcano Workshop 2010 G. Di Sciascio 11

12 Sun shadow 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 Displacement of the Sun shadow correlates with the SMMF 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

13 Cosmic Ray Physics Antiproton/proton ratio measurement Light-component spectrum of primary CRs Vulcano Workshop 2010 G. Di Sciascio 13

14 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

15 Upper limit on p/p by ARGO-YBJ Preliminary Vulcano Workshop 2010 G. Di Sciascio 15

16 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 CREAM p+he EAS-TOP + MACRO Horandel p+he CNO < 2% CREAM He CREAM p ARGO data agree with CREAM results ARGO preliminary Evidence that the proton spectrum is flatter than in the lower energy region Vulcano Workshop 2010 G. Di Sciascio 16

17 Anisotropy & γ-ray astronomy Large & Medium Scale Anisotropy Search for point like sources AGN Follow Up Flaring Vulcano Workshop 2010 G. Di Sciascio 17

18 Intermediate scale anisotropy 584 days: 2007 Dec Nov events Cosmic rays excess 0.06% 0.1% r.a.=360 r.a.=0 N PAD > 40 Proton median energy 2 TeV Smoothing radius = 5 Vulcano Workshop 2010 G. Di Sciascio 18

19 MILAGRO ~ Galactic Plane ~ Geminga Heliotail Proton median energy 10 TeV Multiple explanations were proposed: 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 ARGO-YBJ Proton median energy Vulcano Workshop 2010 G. Di Sciascio 19 2 TeV

20 Large scale anisotropy ARGO-YBJ DATA: 2008 and 2009 Tail-in Loss-cone Cygnus region Vulcano Workshop 2010 G. Di Sciascio 20

21 Tibet AS M. Amenomori et.al. Science, 2006 Vulcano Workshop 2010 G. Di Sciascio 21

22 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 PRD Vulcano Workshop 2010 G. Di Sciascio 22

23 All sky survey result 3 sources with significance >5σ in 825 days (Jul. 06 Oct. 09) Crab 14.5 σ, Mrk σ, MGRO σ Mean = Sigma = Crab Mrk Vulcano Workshop 2010 G. Di Sciascio

24 Crab Nebula N PAD Events /day E med (TeV) > ~14.5 s.d. in ~800 days NO selection NO γ/h discrimination Absolute measurement ~50 % Crab/year dn/de = ( ) E ev cm 2 s 1 TeV 1 Vulcano Workshop 2010 G. Di Sciascio 24

25 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 TEST data Full DAQ Swift (15-50 kev) Vulcano Workshop 2010 G. Di Sciascio 25

26 δ (deg) 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 (110 hours) 6σ 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

27 Mrk421: 2008 emission ARGO Gamma Rays vs X-rays Correlation coefficient = 0.64 ASM/RXTE 10 days average N PAD > 100 days from Vulcano Workshop 2010 G. Di Sciascio 27

28 Mrk421 energy spectrum 2008 days : when the source was in active state Integral flux (E > 1 TeV) ev cm 2 s 1 2 Crab EBL from Primack et al. AIP conf. Proc. 745, 23, 2005 Power law spectrum + EBL absorption : dn/de = ( ) E e - (E) ev cm 2 s 1 TeV 1 Vulcano Workshop 2010 G. Di Sciascio 28

29 Mrk421 - June 2008 flare A set of simultaneous measurements covering 12 decades from optical to TeV energies was performed during the flaring activity in first half of June 2008 in Donnarumma et al., ApJ 691 L13 (2009) data from: GASP-WEBT (R-band; May 24 to June 23) SWIFT (UVOT & XRT; June 12-13) AGILE (E > 100 MeV; June 9-15) MAGIC and VERITAS (E> 400 GeV; May 27 - June 8) GASP- WEBT SWIFT RXTE SWIFT SuperAGILE complemented by publicy-available data from RossiXTE/ASM (2-12 kev) and Swift/BAT (15-50 kev). 2 flaring episodes were reported: June 3-8 and June 9-15 AGILE MAGIC VERITAS No VHE data after June 8 the moonlight hampered the Cherenkov telescopes measurements! Vulcano Workshop 2010 G. Di Sciascio 29

30 Mrk421 - June 2008 flare N PAD > days average June 5-7, 3.0 June 11-13, 4.2 ~18 h on source Expected from theoretical SED 1 day average Vulcano Workshop 2010 G. Di Sciascio 30

31 Mrk421 - June 2008 flare G. Aielli et al. ApJL 714 (2010) L208 The spectrum slope is consistent with that measured by Whipple in 2000/2001 observing a similar flare, suggesting that the relation spectral index flux is a long term property of the source. The integral flux above 1 TeV during June is ~6 Crab units: one of the most powerful flare ever observed by Mrk421. EBL from Raue, M. & Mazin, D., 2008, Int. J. Mod. Phys. D17, 1515 dn/de = ( ) (E/2.5) e - (E) ev cm 2 s 1 TeV 1 Vulcano Workshop 2010 G. Di Sciascio 31

32 Feb. 2010: strong Mrk421 flare ARGO observed a strong TeV γ-ray flare from Mrk421 during Feb at 6σ. VERITAS reported similar observation in Atel #2443. The flux exceeded 3 Crab units for the duration of the observations. The peak flux (16 Feb.) is >10 Crab units. The flux measured by ARGO is consistent with VERITAS evaluation. For the first time an EASarray observed a TeV flare at 5σ on a daily basis Feb. 16 Feb. 17 Feb. 18 Feb. Vulcano Workshop 2010 G. Di Sciascio 32

33 MGRO Pulsar Wind Nebula discovered by Milagro, confirmed by HESS and VERITAS. HESS: intrinsic extension is 0.34 deg, spectrum index is -2.1 up to 20TeV without cutoff. Milagro: extension is <2.6 deg, spectrum cut-off at about 14 TeV and its flux is higher than HESS result. ARGO preliminary: extension ~0.6-1 deg. Our data seems to support the Milagro spectrum. Vulcano Workshop 2010 G. Di Sciascio 33

34 Cygnus region Milagro VERITAS Tibet ASγ R=1.5 deg Fermi LAT ARGO-YBJ No detection at 5σ, but with 2 years data ARGO is observing some signals from 2 TeV sources. Vulcano Workshop 2010 G. Di Sciascio 34

35 Conclusions ARGO-YBJ detector taking data since November 2007 with excellent performance First results on γ-ray astronomy Crab Nebula spectrum in agreement with other measurements Continuous monitor of Markarian 421 All sky survey Limits on GeV fluence from GRBs Cosmic Rays & Particle Physics Large & Medium scale anisotropies Solar physics p-p cross section Limit on antiproton flux Light component spectrum measurement Multicore EAS with large transverse momentum Vulcano Workshop 2010 G. Di Sciascio 35

36 Vulcano Workshop 2010 G. Di Sciascio 36

37 IMF measurement with ARGO-YBJ Vulcano Workshop 2010 G. Di Sciascio 37

38 Scaler mode Number of GRBs analysed: 83 With known redshift: 14 Long duration GRBs (>2s): 73 Short duration GRBs ( 2s): 10 GRB in the ARGO FOV since Dec 2004 to Sep 2009 No evidence of coincident signal over the GRB T90 duration In stacked analysis no evidence for any integral effect Vulcano Workshop 2010 G. Di Sciascio 38

39 Upper Limits in the GeV Energy Range GRBs with known redshift Fluence upper limits (99% c.l.) obtained with differential spectral indexes ranging from the value measured by satellites to 2.5. Vulcano Workshop 2010 G. Di Sciascio 39

40 Proton-Air cross section Idea: measurement of shower rate at fixed energy angle as a function of the zenith I() I)0( e oh sec 1 h 0 q Where is not the p interaction lenght mainly because of inelasticity, shower fluctuations and detector resolution. = k int, where k is determined by MC and depends on: hadronic interactions detector features and location (atm. depth) actual set of experimental observables analysis cuts energy threshold etc. int Data Full MC p-air (mb)= / int(g/cm 2 ) Vulcano Workshop 2010 G. Di Sciascio 40

41 Vulcano Workshop 2010 G. Di Sciascio 41 Extending the energy range with the analog readout Phys. Review D80 (2009)

42 Vulcano Workshop 2010 G. Di Sciascio 42

43 Moon shadow: East-West projection The higher the energy the lower the West displacement induced by the Earth magnetic field. Vulcano Workshop 2010 G. Di Sciascio 43