HESS-II - Rencontres de Moriond

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HESS-II - Rencontres de Moriond

Rencontres de Moriond 2009

HESS-II

Yvonne Becherini

APC, Paris

for the H.E.S.S. Collaboration

07 . 02 . 09 Yvonne Becherini, APC Paris 1


● 2002: first telescope installed

● January 2004: begin regular

stereoscopic operation of the

4-telescope H.E.S.S. system

● 2004-2009:

➔ 63 purely physics papers

➔ 52 published sources (the

majority are first

detections)

● 2010: beginning of a new era

HESS-II

– Scientific motivations

– Status of the construction

– Preliminary performance

H.E.S.S. history

Crab Flux

HESS

PKS 2155-304

28 th July 2006

12 detected AGNs, 9 discoveries

07 . 02 . 09 Yvonne Becherini, APC Paris 2


Scientific motivations for HESS-II: lowering the threshold

● First goal: lower the threshold

to about 30 GeV

E thres∝ B t / A

A mirror area, Ω angular size

ε photon detection efficiency

B night­sky noise

Δ t integration window

● A big mirror area is needed

Choice to build a new ~ 600 m 2

telescope (the biggest ever built)

07 . 02 . 09 Yvonne Becherini, APC Paris 3


Tiny absorption expected : access to

more distant objects

Intrinsic source characteristics

Stronger EBL / QG constraints

Advantage of lower threshold

Could distinguish between hadronic and leptonic

scenarios, for instance in the case of

RXJ1713.7-3946

(SNR, binaries, ...)

Access to pulsar emission:

Polar cap vs. Outer gap vs. Striped wind

Fermi

Predictions for Fermi

07 . 02 . 09 Yvonne Becherini, APC Paris 4


Scientific motivations for HESS-II: gain in sensitivity

● Second goal: enhance the sensitivity in the current energy domain by a factor of 2

● Access to various new phenomena, undetectable for the moment with the current

instruments and the standard analysis methods

● Starburst galaxies and ULIRG have a predicted very high energy -ray flux which is

slightly under the current sensitivities (upper limits are approaching the current

theoretical predictions)

● No signal from the cluster of galaxies either (D. Nedbal)

07 . 02 . 09 Yvonne Becherini, APC Paris 5


H.E.S.S. (2004)

Veritas (W. Benbow)

100 h 2009!

115 h Cen A

130 h SN1006

A word on the sensitivity

Re-aluminisation of the H.E.S.S. mirrors is

foreseen for the HESS-II operation

K. Bernlör

07 . 02 . 09 Yvonne Becherini, APC Paris 6


How to achieve these goals: HESS-II

● Parabolic mirror, surface of 596 m 2 , focal length = 36 m

● High resolution camera 2048 pixels (0.07°)

● 3.5° FoV

● Automatic procedure for focusing on the shower maximum

● Installation of the telescope end 2009

● Data taking runs in the upgraded configuration for 2010

07 . 02 . 09 Yvonne Becherini, APC Paris 7


24 m

Steel structure

The biggest telescope ever built

f = 36m

d = 36m

Drive arc

07 . 02 . 09 Yvonne Becherini, APC Paris 8

40 m


The HESS-II camera

Dummy camera Real camera

P. Manigot

● 2048 pixels (0.07°)

● 16 PMTs = 1 Drawer

● New electronics (SAM Saclay)

– Save charge and time

– Expected timing resolution

of the order of 1 ns

● Trigger based on superimposed sectors

07 . 02 . 09 Yvonne Becherini, APC Paris 9


Snapshots of the test phase at Walvis bay (Namibia) in 2008

Test mounting of the dish structure

07 . 02 . 09 Yvonne Becherini, APC Paris 10


Snapshots of the test phase at Walvis bay (Namibia) in 2008

Dummy mirror

07 . 02 . 09 Yvonne Becherini, APC Paris 11


Snapshots of the test phase at Walvis bay (Namibia) in 2009

Test mounting of the camera arms on the dish

07 . 02 . 09 Yvonne Becherini, APC Paris 12


Test of “autofocus” and camera unloading (Annecy)

H.E.S.S. Collaboration

Facsimile of HESS-II

camera support “nose”

07 . 02 . 09 Yvonne Becherini, APC Paris 13


A preliminary estimate of the performance at low energy [30-100 GeV]

● Simulations with 100% efficiency in the H.E.S.S.

telescopes

● From stereo back to MONO !!

● Low energy single telescope reconstruction:

1 electron for every 1 GeV at shower max.

● Images at 30 GeV → only few pixels available

● As soon as a even a small image is present in a second

small telescope turn on the stereo reconstruction


(more efficient)

● “Hillas” based analysis on the events hitting the

HESS-II telescope only

● The image given by a

has an elliptical shape

● No stereoscopy = no direct geometrical

source position estimate

– Estimate of the source position

(via parametrisation or NN) and

calculation of the shower kinematic

parameters

● No timing yet (in this analysis)

07 . 02 . 09 Yvonne Becherini, APC Paris 14


A preliminary estimate of the performance at low energy [30-100 GeV]

● Simulations with 100% efficiency in the H.E.S.S.

telescopes

● From stereo back to MONO !!

● Low energy single telescope reconstruction:

1 electron for every 1 GeV at shower max.

● Images at 30 GeV → only few pixels available

● As soon as a even a small image is present in a second

small telescope turn on the stereo reconstruction


(more efficient)

100 GeV, 500 ps, pulse

maximum

● “Hillas” based analysis on the events hitting the

HESS-II telescope only

● The image given by a

has an elliptical shape

● No stereoscopy = no direct geometrical

source position estimate

– Estimate of the source position

(via parametrisation or NN) and

calculation of the shower kinematic

parameters

● No timing yet (in this analysis)

07 . 02 . 09 Yvonne Becherini, APC Paris 15


Analysis cuts for the analysis in the [30-100 GeV] range

● Hadron rejection cut with Fisher

algorithm in TMVA (more MVA

algorithms are being tested by the

analysis WG)

– Input: nominal distance, Hillas

length & width, total charge in the

event

CUT : Fisher response > 0.1

Currently 70% efficiency on signal, 18% on bkg

● Image shape cut

– Reject events at the border of the

camera or too close to the source

direction (round images)

0.45° < Nominal distance < 1°

07 . 02 . 09 Yvonne Becherini, APC Paris 16


Mono with

cuts

Expected preliminary mono-telescope performance

● Angular resolution between 0.28° and

0.24° as a function of the energy

Mono pre-cuts

Hybrid

pre-cuts

● Additional cut on the angular resolution

– 2 < 0.13 deg 2

Mono pre-cuts

~ 4 · 10 4 m 2

Mono with

cuts

● Energy estimate through Neural Networks :

the energy resolution varies from 40% to 10% as a function of the energy,

the bias spans from +40% to −40% (further work needed!)

Hybrid

pre-cuts

07 . 02 . 09 Yvonne Becherini, APC Paris 17


● Great physics potential with HESS-II

● Expected results on :

– Detection of

more distant AGNs

– Detection of -ray pulsars

– Differentiate leptonic / hadronic

models in several source

classes

● Could give results on currently

undetectable sources thanks to

the enhanced sensitivity in the

stereo mode

Conclusions

● Construction under way

● New analysis methods for low energy

and Hybrid configurations

are under development

● First data in the new configuration

expected for 2010

● Results expected rapidly

after first light

07 . 02 . 09 Yvonne Becherini, APC Paris 18


M. Renaud

Number of expected galactic sources with HESS-II

07 . 02 . 09 Yvonne Becherini, APC Paris 19

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