status and characterization of compass rich-1

Silvia DALLA TORRESilvia DALLA TORRE

Playa del Carmen, 30/11-5/12/2004 - 5Playa del Carmen, 30/11-5/12/2004 - 5thth RICH Workshop RICH Workshop 11

STATUS AND CHARACTERIZATION STATUS AND CHARACTERIZATION OF COMPASS RICH-1OF COMPASS RICH-1

on-line image from on-line image from RICH-1 event RICH-1 event displaydisplay

INSTITUTIONS:INSTITUTIONS:Trieste, INFN and University, ICTPTrieste, INFN and University, ICTPTurin, INFNTurin, INFN and Universityand UniversityBielefeld, UniversityBielefeld, UniversityCERN supportCERN support

OUTLINE:OUTLINE:

RICH-1 in COMPASSRICH-1 in COMPASS recall the main characteristiucs recall the main characteristiucs

(4 talks in Pylos !)(4 talks in Pylos !) hardware newshardware news detector performancesdetector performances

S. Dalla TorreS. Dalla TorreINFN – TRIESTEINFN – TRIESTE

on behalf of the COMPASS RICH groupon behalf of the COMPASS RICH group

Playa del Carmen, 30/11-6/12/2004 - 5Playa del Carmen, 30/11-6/12/2004 - 5thth RICH Workshop RICH Workshop



With the muon beam With the muon beam **

Gluon Polarization Gluon Polarization G/GG/G

transverse spin distribution transverse spin distribution

functions functions TTqq (x) (x)

Flavor dependent polarizedFlavor dependent polarized

quark helicity densities quark helicity densities q(x)q(x)

physicsphysics

Diffractive VM-ProductionDiffractive VM-Production

** Data collected Data collected

COMPASSCOMPASS

With hadron beamsWith hadron beams

Primakoff-Reactions Primakoff-Reactions **- polarizability of and K

glueballs and hybridsglueballs and hybrids

charmed mesons and baryonscharmed mesons and baryons- semi-leptonic decays- double-charmed baryons

understanding theunderstanding the non-perturbative non-perturbative physics physics of the nucleonof the nucleon



SM1 dipoleSM1 dipole

SM2 dipole

Polarised Target

HCAL1

Muon-filter1,MW1

Micromegas,DC,SciFi

Gems,SciFi,DCs,straws

MWPC Gems Scifi

trigger-hodoscopes

Silicon

COMPASS COMPASS SPECTROMETERSPECTROMETER

RICH_1

BMS

Gem_11

ECAL2,HCAL2

straws,MWPC,Gems,SciFi

straws

Muon-filter2,MW2

DW45

SciFi

Veto

Beam: 160 GeV µ+

2 . 108 µ/spill

(4.8 s/16.2s)

P ~ 80%



COMPASS RICH-1 - DESIGNCOMPASS RICH-1 - DESIGN

from the experiment design:from the experiment design:

hadron PID up to ~50 GeV/chadron PID up to ~50 GeV/c LARGE acceptance (large LARGE acceptance (large

size): size):

H: 500 mrad H: 500 mrad

V: 400 mrad V: 400 mrad

able to stand trigger rates able to stand trigger rates

up to 100 KHzup to 100 KHz beam rate up to 10beam rate up to 1088 Hz Hz minimize materialminimize material

++ detector designed in 1996 detector designed in 1996

radiator:radiator:

CC44FF1010

5 m

5 m

6 m6 m3 m3 m

photon photon detectors:detectors:CsI MWPCCsI MWPC

mirrormirrorwallwall

vesselvessel

radiator:radiator:

CC44FF1010

detection of detection of VUVVUV photons photons(165-200 nm)(165-200 nm)



PHOTON DETECTIONPHOTON DETECTIONphoton photon

detectorsdetectors (PD) : (PD) :

5.3 m5.3 m22 MWPCs MWPCs

(8 chambers)(8 chambers)

with with CsI CsI

photocathodephotocathode

read-out:read-out:

84,000 analog84,000 analog

read-out ch.sread-out ch.s

with extended with extended

local intelligencelocal intelligence

MWPCs with MWPCs with

CsI photocathodesCsI photocathodes

2 CsI 2 CsI photocathodes,photocathodes,60 x 60 cm60 x 60 cm2 2 eacheach



photocathodephotocathodestoringstoring

glove box to glove box to handle handle photocathodesphotocathodes

photocathode photocathode transportation transportation systemsystem

MWPCs WITH LARGE SIZE MWPCs WITH LARGE SIZE PHOTOCATHODES, PHOTOCATHODES, COMPASS EXPERIENCECOMPASS EXPERIENCE

CsI: hygroscopicCsI: hygroscopic,,water degrades QEwater degrades QE never never exposed to airexposed to air(max 50 ppm O(max 50 ppm O2 ,2 ,

routinely: 10 ppm)routinely: 10 ppm)

marble tablemarble table with x,y with x,y movement and microscopemovement and microscopeto solde to solde anode wireanode wire and for and fordimensional checksdimensional checks (gaps, (gaps, planarity within 100 planarity within 100 m)m)



PHOTON DETECTORs PHOTON DETECTORs behaviour in the behaviour in the

experimentexperiment

wire defect,wire defect,diameter 20 diameter 20 mm

some PDs exhibit some PDs exhibit electrical instabilities electrical instabilities when when exposed to radioactive ratesexposed to radioactive rates (*)(*),,

LONG RECOVERY TIME ! (~ 1 d)LONG RECOVERY TIME ! (~ 1 d)

Instabilities related toInstabilities related to – local tiny defects – local tiny defects

2001 - 2 good PDs / 8 2001 - 2 good PDs / 8 2002 - 5 good PDs / 82002 - 5 good PDs / 82003, 2004 – segmented HV supply: 2003, 2004 – segmented HV supply: 97% MWPC surface good 97% MWPC surface good

(*) with (*) with beams :beams : MIP flux : ~ 5 x 10MIP flux : ~ 5 x 1055 / s / m / s / m2 2 (similar for all PDs)(similar for all PDs) ph. flux : up to 3 x 10ph. flux : up to 3 x 1055 / s / cm / s / cm2 2



RICH-1 mirror systemRICH-1 mirror system‘‘VUV mirror wallVUV mirror wall’, ’,

21 m21 m22,116 mirrors,116 mirrors

radius: 6.6 mradius: 6.6 m

average on 126 mirror average on 126 mirror units units at productionat production

2000 = @ COATING2000 = @ COATING

refl

ecta

nce

refl

ecta

nce

wave lengthwave length

reflectance stable in timereflectance stable in time

20020022

20020011

20020000



MIRROR WALL MECHANICS:MIRROR WALL MECHANICS:light, stiff and adjustablelight, stiff and adjustable

mirror wall mechanics, mirror wall mechanics, assembledassembled

the elements of this the elements of this modular structuremodular structure

mirror wall mirror wall mechanics, mechanics, assembling assembling

assembly jigassembly jig

mirror rear sidemirror rear side

individual individual mirror supportmirror support

regulationregulationfor angular for angular alignment,alignment,2 orthog. 2 orthog. movementsmovements

THICKNESSTHICKNESSmechanics: mechanics: 2.5 % X2.5 % X0 0

mirrorsmirrors ~5.5 % X ~5.5 % X0 0

STABILITY:STABILITY:after an initial deformation after an initial deformation ~1 mrad, stable: 0.1 mrad ~1 mrad, stable: 0.1 mrad

over ~ 3.5 yover ~ 3.5 y



Gas System for:Gas System for:• P constant +/- 0.1 mbar P constant +/- 0.1 mbar to limit to limit P on - P on - vessel windowsvessel windows quartz platesquartz plates He beam pipeHe beam pipe• gas filtering (remove Hgas filtering (remove H22O, OO, O22 ) )• filling with / recovering Cfilling with / recovering C44FF1010

RICH-1 CRICH-1 C44FF1010 GAS GAS SYSTEMSYSTEM

PLC and PLC and electrical electrical installationinstallation compressors compressors

filtersfilters

liquidliquidstoragestoragetanktank

liquifierliquifier

vesselvessel



PRESENT (>2002) GAS PRESENT (>2002) GAS PERFORMANCESPERFORMANCES

gas (atm. P) gas (atm. P)

leak rate = 90 l/dleak rate = 90 l/d

extremely reduced leak rateextremely reduced leak ratevessel volume ~ 85 mvessel volume ~ 85 m33

total o-rings : ~ 100 mtotal o-rings : ~ 100 m

very good transparency very good transparency (better than design)(better than design)-gas cleaning, see O. Ullaland’s talkgas cleaning, see O. Ullaland’s talk-on-line filters, separate functions:on-line filters, separate functions:

-Cu catalyst, ~ 40Cu catalyst, ~ 4000C for OC for O22

-5A molecular sieve, ~ 105A molecular sieve, ~ 1000C for HC for H22OO

transmission transmission through 1,87 m,through 1,87 m,corresponding to:corresponding to:

HH22O:O: ~1 ppm~1 ppm, ,

OO2: 2: ~3 ppm~3 ppm

typicaltypical

wavelength (nm)wavelength (nm)

tran

smis

sio

ntr

ansm

issi

on

CC44FF1010 : N2 = 95 : 5 : N2 = 95 : 5stabile !stabile !



PREDICTING ON-LINE (n-1)PREDICTING ON-LINE (n-1)

[(n-1)[(n-1)measmeas – (n-1) – (n-1) calcal] / (n-1)] / (n-1)

(n-1) (n-1) calcal from measured P, T from measured P, Tcontinuous linecontinuous line

(n-1) (n-1) measmeas from off-line data analysis from off-line data analysisredred dots dots

prediction at ‰ level prediction at ‰ level

to allow quasi-online data processing, a must: to allow quasi-online data processing, a must: COMPASS data rate = 3 TB/dayCOMPASS data rate = 3 TB/day



RICH-1 RAW RICH-1 RAW INFORMATIONINFORMATION

an event, an event, calibration runcalibration run

low intensity: low intensity: 101077/sec/sec

an event, an event, standard run standard run

nominal intensity: nominal intensity: 4 x104 x1077/sec/sec



RICH-1 CENTRAL REGION RICH-1 CENTRAL REGION

0.4

0.6

0.8

1

102

103

104

screens-pipe-hole

screens-REDpipe-NOhole

NOscreens-pipe-hole

screens-NOpipe-hole

NOscreens-NOpipe-hole

Noscreens-NOpipe-Nohole

solid-mirror-wall

Distance from Beam (mm)Distance from Beam (mm)

Effi

cien

cy M

onit

or

Effi

cien

cy M

onit

or

PID efficiency PID efficiency fromfromMonteCarlo MonteCarlo (beam halo off)(beam halo off)

2 combinated effects: - beam halo2 combinated effects: - beam halo - central dead zones - central dead zones

all dead zonesall dead zones

only photon detector only photon detector dead zones dead zones

photons generatedphotons generated

by the beam haloby the beam halo

overlap of event images overlap of event images



““SINGLE PHOTON” SINGLE PHOTON” PERFORMANCES PERFORMANCES

hit hit (mrad)(mrad)

ring ring (m

rad)(m

rad)

all particlesall particles

selecting particles according to polar selecting particles according to polar

angle and producing angle and producing ringring slices slices information on:information on:• resolutionresolution• number of detected photons number of detected photons • backgroundbackground

exampleexample

NUMBER OF PHOTONS NUMBER OF PHOTONS

n. of ph.s n. of ph.s

background background

rings with < 5 ph.s rings with < 5 ph.s not reconstructednot reconstructed

fit above 36 mradfit above 36 mrad

adding up regions 3-6adding up regions 3-6

particleparticle<30 mrad<30 mrad

30-60 mrad30-60 mrad

120-150 mrad120-150 mrad 150-180 mrad150-180 mrad

IS THE NUMBER OF IS THE NUMBER OF PHOTONS UNDERSTOOD ? PHOTONS UNDERSTOOD ?

Very low beam intensity ~ 4106/spillthreshold at 3 HV = 2000 V eff. Nph ~ 21

expected: 22

=6.3 =6.5

<nPH>=21.3 - 3

<nPH>=20.5 - 3

ring centres ring centres of the selected of the selected particles particles



RICH-1 RESOLUTIONRICH-1 RESOLUTION

measured from measured from reconstructed ringsreconstructed rings

RIN

GR

ING (

mra

d)

(m

rad

)

COMPARISON OF COMPARISON OF RING RESOLUTIONRING RESOLUTIONDIRECTLY DIRECTLY MEASURED MEASURED (reconstructed (reconstructed rings) AND rings) AND CALCULATEDCALCULATED FROM SINGLE FROM SINGLE PHOTON RESOLUTION:PHOTON RESOLUTION:FULL DETECTOR UNDERSTANDINGFULL DETECTOR UNDERSTANDING

single photon resolutionsingle photon resolution

ph

oto

n

ph

oto

n (

mra

d)

(m

rad

)

p (GeV/c)p (GeV/c)ring resolutionring resolution

calculated from single calculated from single photon resolutionphoton resolution

particleparticle (mrad) (mrad)

2.5 2.5 /K/Ksep. up to 40 GeV/csep. up to 40 GeV/c



PID with COMPASS RICH-PID with COMPASS RICH-11

momentum (GeV/c)

C

h (mrad)

0 10 20 30 40 50 60

0

10

20

30

40

50

60

Cherenkov angle vs. momentumfor reconstructed rings (24 runs)

K p

(x30)(x150)

KK

pp

particleparticle> 25 mrad> 25 mrad

p (GeV/c) > pp (GeV/c) > pthrthr(K) + 2 (K) + 2 GeV/cGeV/c

PID EFFICIENCYPID EFFICIENCY

±± from from KKss decays decays

p> thr. (= on average p> thr. (= on average 0 0 photons ) photons ) p> thr. + 0.5 GeV/c (=on av. p> thr. + 0.5 GeV/c (=on av. 55 det. ph.s) det. ph.s) p> thr. + 1.2 GeV/c (=on av.p> thr. + 1.2 GeV/c (=on av.88 det. ph.s) det. ph.s) p> thr. + 2 GeV/c (=in m. p> thr. + 2 GeV/c (=in m. 1010 det. ph.s) det. ph.s)

0-30 mrad0-30 mrad

 = = 12.4 GeV/c12.4 GeV/c

 = = 9.3 GeV/c9.3 GeV/c

 = = 7.1GeV/c7.1GeV/c

 = = 5.8 GeV/c5.8 GeV/c

 = = 4.9 GeV/c4.9 GeV/c

 = = 4.3 GeV/c4.3 GeV/c




90-120 mrad90-120 mrad

MOMENTUM SPECTRA IN MOMENTUM SPECTRA IN particleparticle BINS BINS

particleparticle(mrad)(mrad)

E

FF

ICIE

NC

YE

FF

ICIE

NC

Y



KK±± from from decaydecay (sample purity: (sample purity: 84%84% ) )

p> thr. + 2. GeV/cp> thr. + 2. GeV/c (= on av. (= on av. 55 det. ph.s) det. ph.s)

EFFICIENCY, learning EFFICIENCY, learning curvecurve

±± da decadimenti da decadimenti KKss

(sample purity: (sample purity: 94%94% ) )

p> thr. + 0.5 GeV/c p> thr. + 0.5 GeV/c (= on av. (= on av. 55 det. ph.s) det. ph.s)

software software upgrade upgrade


E

FF

ICIE

NC

YE

FF

ICIE

NC

Y


E

FF

ICIE

NC

YE

FF

ICIE

NC

Y

PD PD stabilitystability

gasgasquality quality



2002 : Seff(*)= 151 (8) 2003: Seff = 674 (17)

(*) Seff =S/(1+B/S)

A remarkable example:A remarkable example:G/G open charm-signalG/G open charm-signal D D00 & D & D00 withoutwithout microvertex detector microvertex detector

RICH-1 in COMPASS RICH-1 in COMPASS PHYSICSPHYSICS

20022002 2003 (2004) 2003 (2004)

SSeffeff//dayday * 4.9 * 4.9

Preliminary Preliminary



CONCLUSIVE REMARKSCONCLUSIVE REMARKS

COMPASS RICH-1 is fully operativeCOMPASS RICH-1 is fully operative plateau performances since 2003

COMPASS RICH-1COMPASS RICH-1 designed ~ mid 90’s challenging requirements concerning

transversal size and rates (beam, trigger)

large size VUV gas RICH limitationslimitations for the operation of for the operation of large size CsI photocathodeslarge size CsI photocathodes

coupled to gas detectors coupled to gas detectors in radioactive environmentsin radioactive environments have have been encounteredbeen encountered

““single photon” resolution is satisfactory (~ parameter design)single photon” resolution is satisfactory (~ parameter design) ““ring resolution” limited by physical backgroundring resolution” limited by physical background

ring resolution allows 2.5 / K separation up to 40 GeV/c

central for COMPASS physics (demonstrated in polarized DIP)central for COMPASS physics (demonstrated in polarized DIP)

status and characterization of compass rich-1

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