Particle identification using  Ring Cherenkov detector technology at COMPASS 

M. Finger Jr., M. Finger, M. SluneckaFor the COMPASS RICH group

Charles University

Faculty of Mathematics and Physics

COMPASS

M. Finger SPIN‐Praha‐2010, June 22, 2010

1. 1. COMPASS Experiment at SPS CERN COMPASS Experiment at SPS CERN

2. 2. RIRIng Imaging ng Imaging CHCHerenkov Detectors Basicserenkov Detectors Basics

3. COMPASS RICH3. COMPASS RICH--1 Detector for Particle 1 Detector for Particle Identification 2009/2010 Identification 2009/2010

4. Conclusions 4. Conclusions

SPIN‐Praha‐2010, June 22, 2010M. Finger

Spin observables Spin observables experimentsexperiments

pp e+e−sidis

PH ENIX

@6GeVfar future

PANDA&PAX@GSI-FAIR JLab@12GeV EIC JParc IHEP future TMD pp sidis e+e−

measurements RHIC PAX HERMES COMPASS JLab NUCLOTRON JParc EIC BELLE summary

@RHIC:

@DESY

@CERN

@KEK

@JINRNICA&NUCLOTRON

COMPASS Experiment at SPS COMPASS Experiment at SPS CERN CERN

Prague, December 19, 2006

M. Finger SPIN‐Praha‐2010, June 22, 2010

SM1 dipoleSM1 dipole

SM2 dipolePolarised Target

HCAL1

Muon-filter1,MW1

Micromegas,DC,SciFi

Gems,SciFi,DCs,straws

MWPC Gems Scifi

trigger-hodoscopes

Silicon

THE COMPASS SPECTROMETERTHE COMPASS SPECTROMETER

RICH_1

BMS

Gem_11

ECAL2,HCAL2

straws,MWPC,Gems,SciFi

strawsMuon-filter2,MW2

DW45

SciFi

Veto

Beam:160 GeV µ+

2 . 108

µ/spill(4.8

s/16.8s)Pμ ~ 80%

P. Abbon et al., Nucl. Instr. and Meth. A 567 (2006) 114

E=19

0,100G

eV

HERA

Competition in the world and COMPASS role

Gluons valence quarks valence quarksand sea quarksand gluons

COMPASS JLab 12 GeV, FAIR,…2010 2014

Ix2COMPASS at CERN-SPS

High energy muon beam100/190 GeV

μ+ or μ-change once per daypolar(μ+)=-0.80polar(μ-)=+0.80

2.108 μ per SPS cycle

if intensity × 2, Q2 range up to 11 GeV2

after 2010,which improvementson the muon line ?

Physics program of COMPASS  ‐ 1

• Experiments with hadron beams

– Pion and Kaon polarizabilities 

–Diffractive production of exotic states

– Search for glueballs

– Light meson spectroscopy

– Production of double charmed baryons

• Experiments with muon beam

–ΔG/G 

– g1

– Transverse spin effects

– Flavor decomposition of spin distribution functions

– Vector meson production

– Spin transfer in Λ‐hyperon production

RIRIng Imaging ng Imaging CHCHerenkov Detectorserenkov Detectors

BasicsBasics

Prague, December 19, 2006

A charged particle with a velocity v larger than the velocity of light in a medium emits light.

Pavel A. Cherenkov, Ilja M. Frank, Igor Y. Tamm Nobel Price 1958

COMPASS RICH Detector

M. FingerSPIN‐Praha‐2010, June 22, 2010

Gas Radiator C4F10

Photon detectors

“Reflected particle”

Incoming particle (γ > γt)

Sphericalmirrors

Detector plane’s normal

Mean light axisBeam line

Conical wavefront

COMPASS RICHCOMPASS RICH--1 Detector for 1 Detector for Particle Identification 2009/2010Particle Identification 2009/2010

Prague, December 19, 2006

COMPASS RICH Detector

M. FingerSPIN‐Praha‐2010, June 22, 2010

Gas Radiator C4F10

Photon detectors

“Reflected particle”

Incoming particle (γ > γt)

Sphericalmirrors

Detector plane’s normal

Mean light axisBeam line

Conical wavefront

RICH‐1Ring Imaging Cherenkov

• 80 m3 (3 m C4F10)

• 116 VUV mirrors (3.3 m focal length)

• 5.3 m2 VUV detectors

– MWPC CsI photon‐sensitive cathodes

– 8x8 mm2 pads

• 84k channels of analog read‐out

mirrorwall

photondetectorts

beam

3.3 m

5.3

m

6.6 m

COMPASS

M. Finger SPIN‐Praha‐2010, June 22, 2010

COMPASS

M. Finger SPIN‐Praha‐2010, June 22, 2010

5 m5 m

6 m6 m3 m3 m

photon photon detectors:detectors:CsICsI MWPC MWPC

mirrormirrorwallwall

vesselvessel

radiator:radiator:CC44FF1010

Photon detection Photon detection

5.3 m5.3 m22 MWPCsMWPCs

16 16 CsICsI PhotocathodesPhotocathodes

84,000 analog readout channels84,000 analog readout channels

single photon: σ =1.2 mradring: σ =0.4 mradphotons/ring n ~143σ π /K sep. up to 40 GeV/c

RICH‐1 Photon Photon detectors (PD) : detectors (PD) : MWPCs with CsI MWPCs with CsI photocathodesphotocathodes(5.3 m(5.3 m22),),

84,000 analog 84,000 analog readread‐‐out ch.sout ch.s

COMPASS

M. Finger

an event froman event fromonon‐‐line displayline display

VUV mirror VUV mirror 

wall,  21 mwall,  21 m22,,

116 mirrors116 mirrors

SPIN‐Praha‐2010, June 22, 2010

RICH‐1 Mirror WallCOMPASS

M. Finger SPIN‐Praha‐2010, June 22, 2010

• radiator gas: C4 F10 , good transparency  > 160 nm, low chromaticity• mirror: 20 m2 surface, VUV reflectance (160‐210 nm) > 80%• photon‐detectors: Multi Wire Proportional Chamber, total surface 5.3 m²• angular acceptance: ± 250 mrad horizontal, ± 200 mrad vertical• read‐out: 83.000 channels  (pixels)     

The COMPASS RICH detectorThe COMPASS RICH detector(2003(2003‐‐2004, before upgrade)2004, before upgrade)

5 m5 m

6 m6 m3 m3 m

mirrorwall

vessel

radiator:C4F10

photon detectors:CsI MWPC

identification of π, K and protonsCherenkov thresholds: π ≈ 3 GeV/c

K ≈ 9 GeV/cp ≈ 17 GeV/c

6 m

5 m

3 m

Radiator:C4F10

Mirrorwall

CsIMWPC

2σ π/K separation at 43 GeV/c

particle identification with Compass RICHparticle identification with Compass RICH

without PID

π+ π- π+ K- K+ π- K+ K-

total 5.3*106 3.7*106 2.4*105 3.0*105 8.7*104

Multi Wire Proportional Chambers:(MWPC, in use since 2001)

• CsI photo cathodes • new read‐out system: APV chip(negligible dead time)• time resolution (CsI with MWPC + ro):~ 3 μs   < 40 ns

The upgrade project for 2006 data takingThe upgrade project for 2006 data taking

Fast photon detection:

• Multi Anode PMTs (MAPMT, 576 pc)    • individual telescopes • read‐out

sensitive FE: MAD chiphigh resolution TDC: F1 chip

• time resolution: few ns• no MWPC

Optical system for upgrade RICH‐1 detector

Magnifying Optical system +/- 18/48

Cherenkov Radiation

Input window 48x48 mm in the mirrors focal plane virtually divided into 4x4 regions

4x4 Multichannel Photomultiplayer

with active region18x18 mm

Hamamatsu R7600Hamamatsu R7600‐‐0303‐‐M16 photomultiplierM16 photomultiplier

2  cm

• bialkali photocathode• 18 x 18 mm2 active area• 16 pixel• time resolution 300 ps• UV transparent borosilicate glass window

Effective QE including window losses (collection efficiency not included)

Larger number of detected Cherenkov photons, due to larger wavelength range:

CsI (160 ‐ 200 nm)

Time resolution is useful for correctly assigning hits to rings:

½ detector

Half upgraded detectorHalf upgraded detector‐‐ from insidefrom inside

576 telescopes made of silica lenses576 telescopes made of silica lenses

Telescope system consisting of 2 lenses:

• Purpose: Focussing Cherenkov photons on  MAPMTs (factor 7)

• UV transparent quartz lenses• large geometrical acceptance• minimum image distortion• optimised by Zemax simulation

planar surface

lenses,  spherical surfaces

16 channel MAPMT

aspherical surface

γ5 cm

60 cm

¼ PMT detector

ReadRead‐‐out electronics of 1st quarterout electronics of 1st quarter

MAPMT

MAD4 & roof boards

DREISAM  (TDC‐F1)

60 cm

water cooling

theta(mrad) vs p (GeV/c) - pion, kaon

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70

p (GeV/c)

thet

a (m

rad)

Upgraded RICH resolutionUpgraded RICH resolution

PID capability extended by upgrade

K

ππ

K

p

E. Albrecht et al, NIM A 33 (2003) 127E. Albrecht et al, NIM A 33 (2003) 127

Expected performances:Expected performances:• σph = 2.4 mrad (ß ≈ 1) ‐ before: 1.2 mrad• Nph/ring ≈ 50  (ß ≈ 1) ‐ before: 14• σ ring ≈ 0.4 mrad (ß ≈ 1) ‐ before: 0.6 mrad

• 2σ π/K separation at p ≈ 50 GeV/c‐ before: 43 GeV/c

Performances of upgraded RICH detectorPerformances of upgraded RICH detector

• Nph/ring (ß≈1) > 60  before upgrade: 14

• time resolution < 1 ns before upgrade: 3 µs

• σ ring ≈ 0.3 mrad (ß≈1)  before upgrade: 0.6mrad

•Nph/ring ≈ 50  (ß ≈ 1) ‐ before: 14

• 2σ π/K separation at ph >55 GeV/c before upgrade: 43 GeV/c

• excellent suppression of background from µ halo,

• performances as expected (and better)

Excellent performances:

Fulvio  TESSAROTTO

mirrors and alignmentmirrors and alignment

measurement of mirror alignment

via laser autocollimation

21 m2,  116 mirrors radius: 6.6 m

angular regulation screws 

Fulvio  TESSAROTTO

the vessel and the mirror support the vessel and the mirror support wallwall

Large and accurate mechanics

light front and rear windows

Fulvio  TESSAROTTO

Cassis, 03/05/2010    ‐ 7th International Workshop on 

Ring Imaging Cherenkov Detectors

The CsI photocathodesThe CsI photocathodes

GAS ELECTRON MULTIPLIER (GEM)GAS ELECTRON MULTIPLIER (GEM)Thin metalThin metal‐‐coated polymer foils coated polymer foils 70 70 µµm holes at 140 m holes at 140 µµm pitchm pitch

F. Sauli, NIM A386(1997)531

Manufactured by standard PCB techniquesof precise drilling and Cu etching.

ECONOMIC & ROBUST ECONOMIC & ROBUST

There is need of new technology

Possible solution – closed geometriesto overcome recent limits – fight ion bombardment and photon feedback

GEMs and THGEMs

1mm

Chechik et al. NIM A535 (2004) 303C. Shalem et al. NIM A558 (2006) 475

& NIM A558 (2006) 468

GEM’s principle

Examples of ion blocking schemes from literature

‐ Similar schemes can be adopted with THGEM

multiGEM with multiGEM with Reflective photocathodeReflective photocathode

Electron’s path Ion’s back‐flow

ElectronsElectrons

IonsIons

60 %

40 %

MultiGEM’s:ion blocking + high GAIN

Simulation of avalanche

PerspectivesShort term plans: 

‐ optimize the parameters of the THGEM with photoconverting CsIlayer to achieve maximum photoelectron collection efficiency

‐ optimize the parameters for the (double) THGEM to  be used forthe amplification of the signal to provide large and stable gain‐ produce a set 600 x 600 mm2 THGEMs and assemble them withstesalite spacer frames into first complete “full size” prototype chamber

Possible medium term project:‐ Upgrade of COMPASS RICH (~4m2) with the new photon detectorsin case the COMPASS Collaboration decides for it.

Longer term dream:‐ find a configuration to reduce the ion back‐flow down to <10‐5and operate this large area detectors with visible photoconverter

RIRIng Imaging ng Imaging CHCHerenkov Detectorserenkov Detectors

ConclusionsConclusions

Prague, December 19, 2006

hadron PID from 3 to 60 GeV/cacceptance: H: 500 mrad V: 400 mradtrigger rates: up to ~100 KHzbeam rates up to ~108 Hzmaterial in the beam region: 2.4% Xo

material in the acceptance: 22% Xo

* detector designed in 1996*in operation since 2002*upgraded in 2006

total investment:   ~ 4 M €

radiator:radiator:CC44FF1010

5 m5 m

6 m6 m3 m3 m

MWPC’s + CsI

UV mirrorwall

Al vessel

radiator gas: C4F10

COMPASS RICHCOMPASS RICH--11is a large gaseous  RICH

with two kind of photon detectors

providing: 

PMT’s

beam pipe

The main components

• Al vessel (80 m3 C4F10, 100 m of O‐rings) with light windows• Spherical UV mirrors (21 m2, split in two halves, 116 

mirrors)• Light beam pipe filled with He• 16 fused silica windows (600 mm x 600 mm x 5 mm)• 8 MWPC’s with CsI‐ coated photocathodes (4.3 m2)• 62 k analog r/o channels: APV + GESSICA • 576 MAPMT’s with individual fused silica lens telescopes• 9.2 k TDC channels: MAD + DREISAM + F1• A complex gas circulation and filtering system

RICH PID information

in the Do analysis

without   without   RICH RICH informationinformation

with  RICH information

COMPASS 2006 COMPASS 2006 DDoo peakpeak

freshly released (DIS2010 Conference)

COMPASS COMPASS 2006 data 2006 data with RICH with RICH information, information, zoomedzoomed

Fulvio  TESSAROTTO

withwith withoutwithout PIDPID

RICH PID information in Λ analysis

Λ p π‐ Λ p π+

withwith withoutwithout PIDPID

purity  increased by 6, loss < 3%purity  increased by 6, loss < 3% purity  increased by 7, loss < 3%  purity  increased by 7, loss < 3%  

without                   with  without                   with  p identificationp identification

The keys of the success

• A strong physics case

• A dedicated, highly motivated team and team leader

• A constant support from the Institutes and the Experiment

Thank You for Your AttentionThank You for Your Attention

Prague, December 19, 2006