Michele Iacovacci (Napoli), CSNII, LNGS 4 Giugno 09 ARGO-YBJ

Experimental Hall At present the detector is completely mounted .The central carpet of 78x74 m2 is operating since July 2006 with an inclusive trigger Npad > 20, the trigger rate is about 4 kHz and the compressed data flow is 2.5 MB/s. Layer (92% active surface) of Resistive Plate Chambers (RPC), covering a large area (5850 m2) + sampling guard ring (20% instrumented) up to 110x100 m2

Detector Pixels ... to be put in operation Strip Strip =SPACE PIXEL, 6 x 62 cm2, 124800 Pad Pad =TIME PIXEL, 60 x 62 cm2, 15600 σt≈1 ns BigPad BigPad =CHARGE readout PIXEL, 120 x 145 cm2, 3120 Cluster = DAQ unit = 12 RPCs RPC ... to be put in operation

Data Taking in 2008

Analog Readout Calibration System: DAC linearity Single Channel Calibration 800 Channel: Calibration Parameters New LV Power Supplies

Analog Readout Event 31 m 35 m 3500 part

ARGO Papers (last 6 months) Title Journal Date Status Scaler Mode Technique for the ARGO-YBJ detector. Astroparticle Physics End 2008 Pubblished Software timing calibration of the ARGO-YBJ detector Beginning 2009 "Search for Gamma Ray Bursts with the ARGO-YBJ detector in Scaler Mode" Astrophysical Journal May 2009 in Press "Proton-air cross section measurement with the ARGO-YBJ cosmic ray experiment" Physical Review D April 2009 Submitted "ARGO-YBJ constraints on very high energy emission from GRBs" May 2009 Accepted "Temperature Effect on RPC Performance in the ARGO-YBJ Experiment" NIM

ICRC09 - ARGO Contributions

Mrk 421 - June 2008 Flare NPAD > 100 3 days average ARGO 1 day average ASM/RXTE

Mrk 421 SED June 11-13 7 Crab units Measured flux in agreement with theoretical expectations

Localized region of CR excess  0.06% 424 days  0.1% N PAD > 40 Proton median energy  2 TeV

ARGO-YBJ Milagro Abdo et al., Phys Rev. Lett, 101, 221101, 2008

pbar/p ratio

GRB Sample Total number of GRBs analyzed: 66 With known redshift: 11 Long duration GRBs (> 2s): 59 Short duration GRBs (≤ 2s): 7 The widest sample of GRBs studied at ground in the GeV - TeV energy region. Only fluence upper limits 10-5 erg cm-2

Total p-p cross section

Conclusioni L’esperimento Argo-YBJ sta continuando la fase di presa dati stabile, secondo il programma previsto e con alto duty cycle (> 90%), da Dicembre 2007 La collaborazione e’ impegnata nell’analisi dei dati e sta producendo diversi articoli e numerose presentazioni a conferenze. Il programma di lavoro dei prossimi mesi prevede il completamento dell’apparato con l’istallazione del sistema di lettura analogico; questo impegno comporta una forte presenza presso il Laboratorio in Tibet. Sono inoltre necessari e urgenti interventi di manutenzione in quanto nell’ultimo anno l’accesso in Tibet e’ stato difficile ed episodico. Per sostenere queste attivita’ e’ necessario lo sblocco del sub-judice sul capitolo delle Missioni Estere.