The HADES RICH High Acceptance Di-Electron Spectrometer

RICH 2002 @ PylosR. Gernhäuser (TU-München)

The The HADESHADES RICH RICH High High AcceptanceAcceptance Di-Electron Spectrometer Di-Electron Spectrometer

• The HADES Spectrometer• Special requirements • RICH setup

– Mirror– Window– Photon detector

• Preliminary results from 12C-12C [1.0 AGeV]

• Outlook

For the HADES Collaboration


Motivation

SIS / GSI : heavy ion, proton,pion beams

0 3 0 T 80 MeV

HADES: systematic dilepton spectroscopy• meson prod. in A / pA : T = 0 MeV

• meson prod. in p / pp : 0 , T = 0 MeV

• meson prod. in AA : T = 80MeV

Properties of hadrons in strong int. matter: M, vs , B, T, V

Vector meson , , spectral functions measurements

Hadron’s structure: VDM, Form factors, vector meson-nucleon inter.

Dalitz and two-body decays, pN, N reactions


Magnet SC. toroid ( 6 coils) in

Lepton Identification RICH C4F10 + gas Phot. Det.

CsI - cathode

META TOF scintillator wall + Pre-Shower detector

p/ identification META and tracking

Tracking p – measurement, vertex

reconstruction

MDC Drift chambers x ~ 80 m ()

High High AcceptanceAcceptance Di-Electron Spectrometer Di-Electron Spectrometer


experiment hall CsI based MWPC

with gas radiator

Design ConstraintsDesign Constraints

101

20det thr

radlNN

cmlrad 40~;10thr

beam intensity108/s

central collisions105/s

ch. particles < 200/evt

lepton pairs 103/s

Meson Mass (MeV/c2)

(MeV/c2)

dominant decay

e+e-/

769 150 2 4.5 10-5

783 8.5 2 7.1 10-5

1019 4.5 2K 2.9 10-4

N0 ~ 100

fast

high granularity

hadron blind

Trigger device


Fast Photon DetectorFast Photon Detector

Pad cathode

Anode w ires 20 m

Cathode w ires 50 m

G ate w ires 20 m

2 ,4m m

3,0m m

7,0m m

6,6m m

1,65m m

3,3m m

U =+2,5 kVanod

U =0Vcath

U =500Vgate

U =0Vpcath

e-

UV

Ph

oto

n

PC B

CsI+RSGconnector

CH 4

6 sector shaped MWPCs with 2.4 mm gap 5*104 < gain < 1*105 @ 2450V signal coupling on several pads solid CsI photon converter on special

substrate material (RSG)


Photon Detector ShapePhoton Detector Shape

– 4712 pads/sector, individually shaped

4.5 mm < y < 7 mm, x = 6.6mm– GASSIPLEX based FE-electronics

– 10s conversion time

rin

g r

adiu

s [p

ads]

polar angle [°]

A trigger device for ~ 1 particles

constant ring radius


MirrorMirrorØ 150 cm, R = 871 mm, d = 2 mmPoly – Carbon

–rad. length X0 = 28cm

–18 panels polished

Float Glass

–rad. length X0 = 14cm

–6 panels, molded

J. Friese (Saturday afternoon)


CaFCaF22 - Window - Window

Crystal window Ø = 140cm

64 CaF2 hexagonal crystals

Ø = 20cm,

d = 5mm p < 5mbar


The Eye of HADESThe Eye of HADES

Commissioning in 2001

Full HADES Setup (! outer tracking)

108 events C – C 1-2 AGeV

400m Carbon fiber

radiator shell


Typical PatternTypical PatternData Nov. 2001, C - C @ E = 1 AGeV


RICH online Lepton ID RICH online Lepton ID

• Ring recognition algorithm (fixed radius)– Ring radius (+) inner and outer veto

regions (-)– Threshold on positive and negative

quality parameters

Typical AlgorithmJ. Lehnert (Sunday morning)

Reference of qualitative and quantitative

detector response needed


Calibration MeasurementCalibration Measurement(OEM online efficiency measurement)(OEM online efficiency measurement)

beam

calibrated light source!Photons produced by 600 AMeV 12C beam particles passing two different solid radiatorspad plane

tank

window

mirror

tank shell

target

radiator gas

detector gas

beam

field plane

photon detector


OEM resultsOEM results

N0 > 90

Radial distribution of photons represents spectral sensitivity of the detector

L. Fabbietti (Sunday morning)

200 nm

145 nm

200 nm

163 nmsingle 12C hit

beam pipe shadow


Dominant Dilepton Dominant Dilepton SourceSourcess

e+

e-Conversion

e+

e-

0

Dalitz

7 M events C+C @1.0 AGeV

opening angle [°]

cut on opening angle

combinatory pairs negligible


The Ring PropertiesThe Ring PropertiesRings from single leptons

e+e- pair with 1 track/ring

Th. Eberl (Sunday afternoon)

momentum [MeV/c]

po

lar

an

gle

[°]

Efficiency of Ring recognition


Lepton ID with TOF and RICHLepton ID with TOF and RICH

TOF[ns]

preliminary

Data: Nov01C-C 2.0 AGeV

q*m

om

entu

mq

*mo

men

tum


Lepton ID online -Lepton ID online - offlineoffline

Full HADES simulation

and data analysis

RQMD ev.generator

q* momentum [e*MeV/c]

Ne/N

+pr

elim

inar

y

Correlation of rings found by hardware or software image

processing

A. Toia (Sunday morning)


OutlookOutlook

•HADES comes into operation

(e/p sep., LVL2 trig., tracking)

•3 MDC layer will be completed this summer (p3% for /)Phase I (2002 – 2003) : (acc. proposals S200 ,S262)

Continuum below M inv < 600 MeV/c2 ; 0 Dalitz in C+C (more statistics)

High statistics e+,e- production in HI reactions C+ C @ 1 – 2 AGeV

(compare to DLS)

e+e- production in - p - p @ 0.8 – 1.3 GeV/c

(below and above threshold for

e+e- pair acceptances pp pp pp e+e-

The HADES RICH High Acceptance Di-Electron Spectrometer

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