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

The HESS Experiment

G.VasileiadisGAM-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


HESS Collaboration / Site

3 continents 8 countries 19 institutions 69 physicists100 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., PragYerewan Physics Inst.Dublin Inst. for Adv. StudiesUniv. Namibia, WindhoekUniv. Potchefstroom

Namibia (Gamsberg) /1800m Alt.


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


Detection Concept


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


Instrumentation / Telescope

Mirror Dishes : 4 x 107 m2

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 5o (1.4m) Pixel Size 2.8 mrad 960 Photomultipliers Camera weight 900 kgr 3-cable control to rest of system


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.)


Instrumentation / Camera (R/O)

ARS0

Connection to photo-tubes

Trigger channelsAnalogue

Fpga

8 x comparators

Adder

Enable/disable(4 channels)

outputlocal trigger

Fanout signalentry

Amplifications

Buffers

12 bits ADC

Digital

Multiplexor

Readout channels


Instrumentation / Camera-R/O (cnt.)

Analogue MemoryAnalogue MemoryARS0ARS0

Analogue Memory ARS0 built for ANTARES experiment (SEI-Dapnia)

5 buffers /chip, 128 cells per channel.

Sampling @ 1 GHz

Readout ~ 1 Mhz

Controlled by two parameters

Readout window (~16 ns)Readout delay (50-70 ns)

Readout : Sampling or integrated charge mode


Instrumentation / Camera-R/O (cnt)

SvOutPlaceObject

Acquisition Speed limited by :

•Readout of the analogue memories+Digi (273s).•Data transfer on the drawer's busses (141s). •Readout by the CPU.

Single e determination @ 2x105 of gain


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


Data Analysis / Reconstruction

Geometrical Determination of the Shower Impact point on the

ground

Source Position on the Camera ( Angular resolution from 0.1o to 0.06o)


Data Analysis / Muon Rejection


Data Analysis / Interpretation

• Angle between image axis and source image; signal has < 10-20o

• Sky plot or angle between shower axis and direction to source; signal has < 0.1-0.2o

Source

0.2o

2 (Degr.2)

H.E.S.S.Crab Nebulapreliminary

Background flat in 2 CoG

Source Reconstr

ucted Shower

Axis


Data Analysis / DataSets

~ 350 Hz~ 2 kHzCT 1, 2, 3, 4(2 out of 4)

Since Dec. 2003

~ 210 Hz~ 2 kHzCT 2, 3, 4(2 out of 3)

Oct. – Nov. 2003

~ 110 Hz~ 2 kHzCT 2, 3(coincidence)

Aug. – Sept. 2003

~ 30 Hz~ 250 HzCT 2 , 3(independent)

Mar. – July 2003

-~ 250 HzCT 3July 2002 – Feb. 2003

System rateTelescope rateTelescopesTime

Increased Single-telescope rate decreased thresholdIncreased System rate increased collection area


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

Preliminary


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 hrs0.05 Crab in ≈1 hr0.10 Crab in ≈20 min0.50 Crab in ≈75 sec1.00 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)


Physics Results / RXJ 1713.7-3946

2003: 18.1 hrs with 2 2003: 18.1 hrs with 2 telstels

(250 GeV (250 GeV thres) thres)

2004 data (under 2004 data (under analysis) analysis)

SkymapSkymap Hard cuts Hard cuts

(background-free)(background-free) 800 GeV Threshold800 GeV Threshold --> 20 Sigma--> 20 Sigma

First resolved TeV First resolved TeV source!source!


Physics Results / RXJ 1713.7-3946 (X-Ray correlation)

Courtesy of Y. Uchiyama

ASCA HESS


Physics Results / RXJ 1713.7-3946 (Spectra)

Hard Spectrum from WHOLE SNR (H.E.S.S.)(cf. CANG spectrum for NW rim)

dN/dE ~ E-2.19+/-0.1+/0.15

F(1-10TeV) ~ 3x10-11 erg/cm2/s (~1 Crab)

Extends to 10 TeV --> 100 TeV particles

Clouds (n~100 cm-3) NW region --> Ep ~ 10-49/n erg

--> 2004 data (>50h) ....spectral imaging, energy resolved morphology


Physics Results / Galactic Center (1)

Observations with 2 tels (2003 Observations with 2 tels (2003 ~16h) ~16h)

Tight cuts (600 GeV)Tight cuts (600 GeV)Count map (back. free)Count map (back. free)

- Steady emission- Steady emission

- Point src.- Point src. Size < 4.2 arcminSize < 4.2 arcmin

- Position consistent with- Position consistent with SgrA* < 20 arcsecSgrA* < 20 arcsec

- No E-dependence on- No E-dependence on positionposition

Aharonian et al. (2004)astro-ph//0408145



21cm Radio



Rate: 0.34 ph/min

Rate: 0.3 ph/min

Aharonian & Neronov 2004 [astro-ph/0408303]

HESS: F ~ E-2.11+-0.19 (Jun/Jul 03)

E-2.21+-0.09 (Jul/Aug 03)


Perspectives / HESS II ?!

28m telescopeCentre of Phase I array Push threshold --> 10 GeV

Development underway


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 1713-3946Discovery of Gamma-rays from the Galactic centerGreat potential for a census of Galactic sourcesH.E.S.S. Phase II & 5@5.....

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

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