ARGO-YBJ Results in cosmic-ray physics and astrophysics P. Camarri University of Roma “Tor Vergata” and INFN Roma Tor Vergata On behalf of the ARGO-YBJ Collaboration Workshop on Astroparticle Physics (WAPP 2010) Ooty, India - Dectember 14 th – 16 th, 2010

SciNeGHE Workshop 2010G. Di Sciascio2 Longitude 90° 31’ 50” East Latitude 30° 06’ 38” North 90 Km North from Lhasa (Tibet) An unconventional EAS-array exploiting the full coverage approach at very high altitude to detect small air showers at an energy threshold of a few hundreds of GeV. The ARGO-YBJ experiment Tibet ASγ ARGO The Yangbajing Cosmic Ray Laboratory 4300 m above the sea level ~ 600 g/cm 2

The ARGO-YBJ Collaboration WAPP 2010P. Camarri3 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 International Collaboration: Chinese Academy of Science (CAS) Istituto Nazionale di Fisica Nucleare (INFN)

Experimental Hall & Detector Layout RPC SciNeGHE Workshop 2010G. Di Sciascio4 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) time resolution ~1-2 ns (pad) space resolution = strip 10 Pads (56 x 62 cm 2 ) for each RPC 8 Strips (6.5 x 62 cm 2 ) for each Pad 1 CLUSTER = 12 RPCs 78 m 111 m 99 m74 m (5.7  7.6 m 2 ) Gas Mixture: Ar/ Iso/TFE = 15/10/75 HV = 7200 V Central Carpet: 130 Clusters 1560 RPCs Strips

ARGO-YBJ

Experimental Hall

Detector Pixels Cluster = DAQ unit = 12 RPCs RPC Strip Strip = Strip = SPACE PIXEL, 6 x 62 cm 2, BigPad BigPad = BigPad = CHARGE readout PIXEL, 120 x 145 cm 2, 3120 Pad Pad = Pad = TIME PIXEL, 60 x 62 cm 2, σ t ≈1 ns

ARGO-YBJ: a multi-purpose experiment WAPP 2010P. Camarri8 by 2 operational modes:  scaler mode (counting rate, > 1 GeV)  shower mode (full reconstruction, > 300 GeV) Sky survey -10º  δ  70º above 300 GeV (  -sources, anisotropies) High exposure for flaring activity (  -sources, GRBs, solar flares) CR physics 1 TeV  10 4 TeV p/p ratio at TeV energies Solar and heliospheric physics p + He spectrum at low energies Knee region p-air and p-p cross sections Anisotropies Multicore events

WAPP 2010P. Camarri9 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

Analog read-out 0 Fs: > 1300/m 2 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

0.1 PeV 1 PeV A. Surdo part/m 2

WAPP 2010P. Camarri12 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

WAPP 2010P. Camarri13 Detector performance  Angular resolution  Pointing accuracy  Energy scale calibration  Long-term stability Moon Shadow analysis:

WAPP 2010P. Camarri14 The Moon Shadow technique Geomagnetic Field: positively charged particles are deflected towards the West. Ion spectrometer The observation of the Moon shadow may provide a direct check of the relation between size and primary energy Cosmic rays are blocked by the Moon Deficit of cosmic rays in the direction of the Moon Moon diameter ~0.5 deg Size of the deficit Position of the deficit Angular Resolution Pointing Error Energy calibration West displacement

Moon Shadow History WAPP 2010P. Camarri.15 G.W. Clark, (Phys. Rev , 1957 ): “The Sun and Moon must cast a shadow in the flux of high energy primary CRs” J. Linsley and J. Lloyd-Evans (ICRC1985), following Watson's suggestion, independently explored the possibility to use the Moon or Sun shadows as mass spectrometers to measure the charge composition of CRs. In particular J. Linsley first discussed the idea to measure the CR antiprotons abundance exploiting the separation of the p and antip shadows. In 1990 Urban et al. carried out detailed calculations of this effect proposing this method as a way to search for antimatter in CRs at TeV energies. CYGNUS 1991: first Moon shadow observation.

Ground-based observations WAPP 2010P. Camarri16 The effect of the Moon (Sun) on CRs was first noted by Clark in However the first observation of a shadowing effect had to wait for the results of CYGNUS in reasons for this long delay:  Poor angular resolution of EAS-arrays. The performance of the detector has to cope with the angular radius of the Moon or Sun (≈0.26 deg) and only at the beginning of the 90s the angular resolutions of EAS-arrays reached the 1 deg level.  High energy threshold (>100 TeV) of detectors  poor statistics. Advantage of ARGO-YBJ Good angular resolution and pointing Low energy threshold Real sensitivity to the Earth magnetic field No sensitivity to GMF  no shadow displacement

The observed Moon Shadow WAPP 2010P. Camarri17 With the ARGO-YBJ detector we can observe the Moon shadow even without subtracting the background contribution. All data: 2006 → 2009 N > 100θ < 50° 3200 hours on-source

CRIS Workshop 2010G. Di Sciascio18 The statistical significance N > s.d.  9 standard deviations / month PSF of the detector 3200 hours on-source θ < 50° The deficit surface is the convolution of the PSF of the detector and the widespread Moon disc. All data: 2006 → 2009

WAPP 2010P Camarri19 Moon Shadow analysis Measured angular resolution Measured EW displacement Relation multiplicity – primary energy Δα = º · N -0.68

WAPP 2010P. Camarri20 Cosmic Ray Physics Antiproton/proton ratio measurement Light-component spectrum of primary CRs

Motivation for CR p search WAPP 2010P. Camarri21 for the understanding of CR origin and propagation in the Galaxy. to investigate the matter/antimatter symmetry in the Universe to investigate the existence of Dark Matter. The study of CR antiprotons provides an useful tool Theoretical models Secondary production. Secondary production. Most of the CR observed near the Earth are secondaries produced in collisions of HE CRs with interstellar medium: p + N → + X Direct production by exotic sources o Primordial Black Hole (PBH) evaporation o DM neutralino annihilation o Extragalactic sources in antimatter domains DM E 0.7

Antiprotons from anti-galaxies WAPP 2010P. Camarri22 The mean lifetime of a CR in the galaxy decreases with energy as E -δ with δ = diffusion coefficient. Antip assumed to be primary and produced/accelerated in an antimatter domain as the protons are in our galaxy. The antip/proton ratio at high energies would go ~E δ, the antip being mainly extragalactic and the protons galactic. Taking δ = 0.7, antip could make up to ~1% of the CR flux at an energy of ~500 GeV and even ~50% at higher energies. In 1985 (19 th ICRC ) Wolfendale & Stecker discussed the question: Does antimatter play an equal role with respect to matter in the formation of galaxies ? E 0.7 Important observational implications Hypothesis:

p/p ratio at TeV energies WAPP 2010P. Camarri23 Using the data on the 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 the antiproton content can be calculated.

The likelihood method for the estimate of the u.l. WAPP 2010P. Camarri24 A fraction r of the simulated events is assumed to be antip. In such a way, the number of events hampered by the Moon in a certain time remains unchanged. The N i measured events are represented in black. The expected events E i are calculated by subtracting the new simulated signal from the background (red points).  New MC signal:  Likelihood function: antip p

The likelihood method for the estimate of the u.l. WAPP 2010P. Camarri25 The corresponding upper limit according to the unified Feldman & Cousins approach (1998) are: The r-values which maximize the likelihood are: for 40 < N < 100 for N > 100 r min = ± r min = ± r u.l. = (90% c.l.) r u.l. = (90% c.l.)

Upper limits on p/p by ARGO-YBJ WAPP 2010P. Camarri26 5% at 1.4 TeV at 90% c.l. 6% at 5 TeV at 90% c.l. In this energy range the p fraction in CR is ≈70% In the few-TeV energy range these limits are the lowest available In the few-TeV energy range these limits are the lowest available. Antigalaxies contribution for different diffusion coefficients, 0.6, 0.7 Heavy DM contribution (Cirelli) Secondary production

Light-component spectrum of CRs WAPP 2010P. Camarri27 Measurement of the light-component (p+He) spectrum of primary CRs in the energy region (5 – 250) TeV via a Bayesian unfolding procedure. The contribution of heavier nuclei to the trigger is a few % ARGO data agree with CREAM results Evidence that the proton spectrum is flatter than in the lower energy region CREAM p+He EAS-TOP + MACRO Horandel p+He CREAM p CREAM He ARGO preliminary For the first time direct and ground-based measurements overlap for a wide energy range thus making possible the cross-calibration of the experiments.

WAPP 2010P. Camarri28 Cosmic rays excess  0.06%  0.1% N > days: 2007 Dec. – 2009 Nov. Proton median energy  2 TeV Smoothing radius = 5° Intermediate scale anisotropy 9 ·10 10 events r.a.=0° r.a.=360°

WAPP 2010P. Camarri29 Proton median energy  2 TeV ARGO-YBJ Heliotail Geminga Galactic Plane ~6 ·10 -4 ~4 ·10 -4 Proton median energy  10 TeV MILAGRO 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 Lazarian & Desiati (2010)

Large scale anisotropy Tail-in Loss-cone Cygnus region ARGO-YBJ DATA: 2008 and 2009 WAPP P. Camarri

31 Tibet AS  M. Amenomori et.al. Science, 2006 WAPP 2010P. Camarri

Fit function: Preliminary results agree with other measurements (G. Guillian et. al PRD). 1D anisotropy for different energies WAPP G. Di Sciascio 0.7 TeV 1.5 TeV 3.9 TeV 3.6·10 -4, 63º 6.8·10 -4, 41º 9.0·10 -4, 35º ARGO preliminary

Proton-air cross section measurement Use the shower frequency vs (sec  -1) The lenght  is not the p interaction lenght mainly because of collision inelasticity, shower fluctuations and detector resolution. It has been shown that  = k int, where k is determined by simulations and depends on:  hadronic interactions  detector features and location (atm. depth)  actual set of experimental observables  analysis cuts  energy,...  p-Air (mb) = / int (g/cm 2 ) for fixed energy and shower age. Take care of shower fluctuations Constrain X DO = X det – X 0 or X DM = X det – X max Select deep showers (large X max, i.e. small X DM ) Exploit detector features (space-time pattern) and location (depth). Then: X max X0X0 X rise X DM h0h0 

Weather effects, namely the atmospheric pressure dependence on time, have been shown to be at the level of 1 % h 0 MC = g/cm 2 ( 4300m a.s.l. standard atm.) h 0 MC / h 0 = ± Experimental data Clear exponential behaviour Full consistency with MC simulation at each selection step

The proton-air cross section Extending the energy range with the analog readout Phys. Rev. D 80, (2009) WAPP 2010P. Camarri

Phys. Rev. D 80, (2009) WAPP 2010P. Camarri

Sun shadow 37 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. 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 WAPP 2010P. Camarri

Solar wind and IMF radial velocity at emission v r + run rotation Archimedean spiral EARTH x y … so a charged particle that passes through the IMF experiences a B y that changes once or twice from positive to negative (two- or four-sector structure). Consenquently the sun shadow will be seen oscillating once or twice along the north-south direction in a solar rotation period, or Carrington period. Carrington period

IMF measurement with ARGO-YBJ 39  time lag 1.6 days  Parker model :By near the earth Submitted to ApJ, November 2010

Conclusions ARGO-YBJ has been running uninterruptedly for over 3 years with its complete layout. The results in cosmic-ray physics are going to be the most accurate so far between ~ 1 TeV and ~ 100 TeV, and specifically: – Moon shadow and ratio – p – p cross section at c.m. energies not directly obtained at colliders – Anisotropy – IMF studies WAPP 2010P. Camarri

External and internal temperature ARGO-YBJ General Meeting - Lecce, July , 2010 T (°C) Every point in all the plots is the 1-hour average of the parameter. External temperature Internal temperature

Barometric pressure ARGO-YBJ General Meeting - Lecce, July , 2010 mb

Effects of T, p changes ARGO-YBJ General Meeting - Lecce, July , 2010 Effective voltage: related to the changes in the RPC gas density due to T, p changes Here we chose the reference values T ref = 15 °C = K p ref = 600 mb (by C.Y. Wu) V Effective voltage trend in 2010 A very strong correlation between the detector behaviour and the effective voltage is confirmed.