ArgoYBJ: further steps for the next thfuture WAPP 2009 Bose Institute, Mayapuri, Darjeeling Dec 12 th 2009 By R. Santonico

Argo is an unprecedented combination of: Large detection area (about 7000 m 2 of RPCs) Full coverage (92%) High granularity (about read out strips) High time resolution (2 ns) High altitude (YBJ 4300 m asl) His purpose is to image the shower front and to lower the threshold energy to a few hundreds GeV

10 Pads = 1 RPC (2.80  1.25 m 2 ) Gas Mixture: Ar/ Iso/TFE = 15/10/75 78 m 99 m74 m 111 m RPC  5600 m 2 (  92% active surface) sampling guard-ring Central Carpet: 130 Clusters 1560 RPCs Strips BIG PAD 1 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 ) BIG PAD2 The ARGO-YBJ detector

Main improvement items: on the analysis An unprecedented detector requires an unprecedented approach to the analysis Shower front reconstruction: -Usually made by fitting the shower front with a conical surface -Can we do better eg using a parabolic surface o fit the front? -Crucial improvement for a good direction reconstruction of very low energy primaries (20-30 hits below 1 TeV) Gamma-hadron discrimination -Not implemented so far in the analysis -Crucial for the γ-ray astrophysics -A strong effort has to be invested to exploit the potential of Argo for the γ/h discrimination

Galactic plane HESS J CRAB MGRO J PSR J days 2007 day 311–2009 day 220 nhit > 40 Smoothing window radius = 1.3°

Percent variation 542 days 2007 day 311–2009 day 220

Moon shadow: all data ( ) N > s.d.  9 standard deviations / month PSF of the detector 2063 hours on-source θ < 50°

Main improvement items: on the detector Analog read out -Allows to study the shower core details in the meter scale -Extends the multiplicity measurements up to densities of several thousend particles per m2 Use radio wave detecting antennas -to complement the information supplied by the RPC carpet with radio signals emitted by cosmic showers -

E  100 TeV StripBig Pad

E  1000 TeV Strip Big Pad

A radio wave antenna for Argo Radio wave signals generated by Extensive Air Showers are random signals of limited duration and wide frequency band They are not easy to be detected by standard “resonating” antennas “Progressive wave” antennas being intrinsically wide band seem to be particularly suitable for their detection A prototype antenna of this kind was tested at YBJ

Argo “big pad” signal vs Antenna signal and its FFT

Next steps The noise below 20 MHz is now well filtered in the prototype antenna A trigger channel searching for coincidences with the RPC carpet will be stably implemented at the beginning of 2010 Crucial to understand what role the antenna can have for a low energy oriented detector like Argo

Conclusions An improvement of the analysis methods will allow Argo to fully express its scientific potential The multiplicity analog read out is extremely promising to study dense shower cores in detail The complementation of the RPC carpet with a radio wave antenna might open a new horizon