RICH 2004, Playa del Carmen, G.Vasileiadis The HESS Experiment G.Vasileiadis GAM-Univ.Montpellier II For the HESS Collaboration

RICH 2004, Playa del Carmen, G.Vasileiadis 2 Outline HESS Collaboration / Site The Physics Detection Concept Experimental Goals The Instrument  Telescope(s) / Camera  Electronics / Trigger Data Analysis Physics Results Perspectives

RICH 2004, Playa del Carmen, G.Vasileiadis 3 HESS Collaboration / Site 3 continents 8 countries 19 institutions 69 physicists 100 engineers and technicians MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Ruhr-Univ. Bochum Univ. Hamburg Landessternwarte Heidelberg Univ. Kiel LLR, Ecole Polytechnique, Palaiseau PCC, College de France, Paris LPNHE-Paris, Univ. Paris VI-VII CEA Saclay CESR Toulouse LAOG Grenoble Observatoire de Paris GAM, Montpellier Durham Univ. Charles Univ., Prag Yerewan Physics Inst. Dublin Inst. for Adv. Studies Univ. Namibia, Windhoek Univ. Potchefstroom Namibia (Gamsberg) /1800m Alt.

RICH 2004, Playa del Carmen, G.Vasileiadis 4 The Physics Cosmic ray origin and acceleration Supernova remnants Starburst galaxies Unidentified galactic sources/surveys Clusters of galaxies Astrophysics of compact objects AGNs Micro-Quasars & Stellar-mass black holes Pulsars Gamma ray bursts Cosmology Diffuse extragalactic radiation fields via cutoff in AGN spectra and AGN halos Clusters of galaxies Astroparticle physics Neutralino annihilation in DM halos

RICH 2004, Playa del Carmen, G.Vasileiadis 5 Detection Concept

RICH 2004, Playa del Carmen, G.Vasileiadis 6 Experimental Goals Dynamic Range up to few Tev Energy threshold from 100 Gev Energy Resolution 10-20% Fast Trigger (70 ns actually) Good Collection Efficiency

RICH 2004, Playa del Carmen, G.Vasileiadis 7 Instrumentation / Telescope  Mirror Dishes : 4 x 107 m 2  Diameter 12 m  Focal Length 15 m  Telescope Separation 120 m  Mirror : 380 x 60 circular facets  Ground Glass, Aluminized and Quartz coated  PSF 1.3’ / 0.38 mrad  Pointing Precision 8”  Field View 5 o (1.4m)  Pixel Size 2.8 mrad  960 Photomultipliers  Camera weight 900 kgr  3-cable control to rest of system

RICH 2004, Playa del Carmen, G.Vasileiadis 8 Instrumentation / Camera 60 Drawers of 16 PMTs each (photonis XP2960 : QE ~25% borosilicafe window) Active DC-DC base converters (0-1600V) Slow Control Card (HV,Current,Temperature monitoring) Two R/O Analog Memory Cards (x8 PMTS) Winston Cone Plate (~70% Eff.)

RICH 2004, Playa del Carmen, G.Vasileiadis 9 Instrumentation / Camera (R/O) ARS0 Connection to photo-tubes Trigger channels Analogue Fpga 8 x comparators Adder Enable/disable (4 channels) output local trigger Fanout signal entry Amplifications Buffers 12 bits ADC Digital Multiplexor Readout channels

RICH 2004, Playa del Carmen, G.Vasileiadis 10 Instrumentation / Camera-R/O (cnt.) Analogue Memory ARS0 Analogue Memory ARS0 built for ANTARES experiment (SEI-Dapnia) 5 buffers /chip, 128 cells per channel. 1 GHz Readout ~ 1 Mhz Controlled by two parameters Readout window (~16 ns) Readout delay (50-70 ns) Readout : Sampling or integrated charge mode

RICH 2004, Playa del Carmen, G.Vasileiadis 11 Instrumentation / Camera-R/O (cnt) Acquisition Speed limited by : Readout of the analogue memories+Digi (273  s). Data transfer on the drawer's busses (141  s). Readout by the CPU. Single  e 2x10 5 of gain

RICH 2004, Playa del Carmen, G.Vasileiadis 12 Data Analysis / StereoScopy Shower detected from different angles: Better discrimination between gammas and hadronic background Determination of the gamma- ray origin on the sky Determination of the shower impact parameter on the ground better energy resolution Factor of two less Muon Triggers compare to single telescope, resulting in lower threshold hadrons muons gamma

RICH 2004, Playa del Carmen, G.Vasileiadis 13 Data Analysis / Reconstruction Geometrical Determination of the Shower Impact point on the ground Source Position on the Camera ( Angular resolution from 0.1 o to 0.06 o )

RICH 2004, Playa del Carmen, G.Vasileiadis 14 Data Analysis / Muon Rejection

RICH 2004, Playa del Carmen, G.Vasileiadis 15 Data Analysis / Interpretation Angle  between image axis and source image; signal has  < o Sky plot or angle  between shower axis and direction to source; signal has  < o Source  0.2 o  2 ( Degr. 2 ) H.E.S.S. Crab Nebula preliminary Background flat in  2 Co G Source  Reconstru cted Shower Axis

RICH 2004, Playa del Carmen, G.Vasileiadis 16 Data Analysis / DataSets ~ 350 Hz~ 2 kHzCT 1, 2, 3, 4 (2 out of 4) Since Dec ~ 210 Hz~ 2 kHzCT 2, 3, 4 (2 out of 3) Oct. – Nov ~ 110 Hz~ 2 kHzCT 2, 3 (coincidence) Aug. – Sept ~ 30 Hz~ 250 HzCT 2, 3 (independent) Mar. – July ~ 250 HzCT 3July 2002 – Feb System rateTelescope rateTelescopesTime Increased Single-telescope rate  decreased threshold Increased System rate  increased collection area

RICH 2004, Playa del Carmen, G.Vasileiadis 17 Physics Results / CRAB Nebula  October 2003 (3 telescopes)  Live time: 4h1m53s  Mean zenith angle (Z): 47°  Energy Threshold: 325 GeV (at this Z)  Standard Analysis:  Significance: 53.5  (26.6  /hr-0.5)  Excess: 10.8 ± 0.2 .min -1  Signal easily detected, stable in time Preliminary

RICH 2004, Playa del Carmen, G.Vasileiadis 18 Physics Results / Sensitivity Crab: F(>1 TeV) = (1.35±0.45) ×10 -8 m -2 s -1 At 20º zenith angle, full array, after selection cuts Sensitivity:: 0.01 Crab in ≈25 hrs 0.05 Crab in ≈1 hr 0.10 Crab in ≈20 min 0.50 Crab in ≈75 sec 1.00 Crab in ≈30 sec Threshold (trigger, selected): (105,125) GeV at 0º (115,145) GeV at 20º (265,305) GeV at 45º (785,925) GeV at 60° with current standard analysis (threshold = peak in event rate for Crab-like spectrum)

RICH 2004, Playa del Carmen, G.Vasileiadis 19 Physics Results / RXJ  2003: 18.1 hrs with 2 tels  (250 GeV thres)  2004 data (under analysis)  Skymap  Hard cuts (background- free)  800 GeV Threshold  --> 20 Sigma  First resolved TeV source!

RICH 2004, Playa del Carmen, G.Vasileiadis 20 Physics Results / RXJ (X-Ray correlation) Courtesy of Y. Uchiyama ASCAHESS

RICH 2004, Playa del Carmen, G.Vasileiadis 21 Physics Results / RXJ (Spectra) Hard Spectrum from WHOLE SNR (H.E.S.S.) (cf. CANG spectrum for NW rim) dN/dE ~ E /-0.1+/0.15 F(1-10TeV) ~ 3x erg/cm 2 /s (~1 Crab) Extends to 10 TeV --> 100 TeV particles Clouds (n~100 cm -3 ) NW region --> E p ~ /n erg --> 2004 data (>50h)....spectral imaging, energy resolved morphology

RICH 2004, Playa del Carmen, G.Vasileiadis 22 Physics Results / Galactic Center (1) Observations with 2 tels (2003 ~16h) Tight cuts (600 GeV) Count map (back. free) - Steady emission - Steady emission - Point src. - Point src. Size < 4.2 arcmin Size < 4.2 arcmin - Position consistent with - Position consistent with SgrA* < 20 arcsec SgrA* < 20 arcsec - No E-dependence on - No E-dependence on position position Aharonian et al. (2004) astro-ph//

RICH 2004, Playa del Carmen, G.Vasileiadis 23 Physics Results / Galactic Center (2) 21cm Radio

RICH 2004, Playa del Carmen, G.Vasileiadis 24 Physics Results / Galactic Center (3) Rate: 0.34 ph/min Rate: 0.3 ph/min Aharonian & Neronov 2004 [astro-ph/ ] HESS: F ~ E (Jun/Jul 03) E (Jul/Aug 03)

RICH 2004, Playa del Carmen, G.Vasileiadis 25 Perspectives / HESS II ?!  28m telescope  Centre of Phase I array  Push threshold --> 10 GeV  Development underway

RICH 2004, Playa del Carmen, G.Vasileiadis 26 Summary  H.E.S.S. Phase I (4-tel) operational (since Dec. 2003)  Most sensitive Gamma-ray detector: 0.05 Crab in 1 hour (5  )  First resolved Gamma-image: RXJ  Discovery of Gamma-rays from the Galactic center  Great potential for a census of Galactic sources  H.E.S.S. Phase II &