Cherenkov Detectors for b Physics

Sacha Kopp

University of Texas at Austin

cosC = 1/(n)

C“radiator”

“photo-detector”

2/30

Good Ol’ Days of Cherenkov Counters

ThresholdCounter

Velocity Selector

“Fitch Counter”

3/30

Ring-Imaging Cherenkov Detectors (RICH)

• First detectors: DELPHI “RICH” at LEP SLD “CRID” at SLC

• Both TMAE-based TPC’s, dual radiator

Original proposal in J. Séguinot & T. Ypsilantis, Nucl. Instr. Meth. 142, 377 (1977)

figures from J. Séguinot CERN-89-12

4/30

BaBar “Detector of Internally-Reflected Cherenkov-light (DIRC)”

5/30

DIRC Principle ee

t ~ 300 nsabout collision time

t ~ 8 nsabout collision timefigures from J. Schwiening, Nucl. Instr. Meth. A502, 67 (2003)

6/30

BaBar DIRC Performance

figures from B. Ratcliff, RICH2004 Conference

7/30

Belle DetectorSC solenoid 1.5T

CsI(Tl) 16X0

TOF counter

8GeV e -

Si vtx. det.3 lyr. DSSD

μ/KL detection14/15 lyr. RPC+Fe

Tracking + dE/dxsmall cell + He/C2H5

3.5GeV e +

Aerogel Cherenkov cnt.n=1.015~1.030

AK=0.101±0.025±0.005

3.9

8/30

Particle Identification at Belle

slide taken from Blair Ratcliff, RICH 2004 Conference

p/K/π separation is based on Likelihood ratio:

LR(K)=L(K)+L(π)

L(K)

9/30

CLEO-IIIRICH

Detector

• Fit inside existing CsI calorimeter (102 cm ID)

• Limit to 13% X0

• Needed <20 cm depth 0.0

0.2

0.4

0.6

0.8

1.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

eKp

Che

renk

ov A

ngle

(ra

d)

Momentum (GeV/c)

C = 12.8 mrad in LiF

• Coverage for daughters of B mesons produced at rest: pmax ~ 2.65 GeV/c

10/30

Photon Detectors

Charged Particle

Cherenkov Photon

Nitrogen Expansion Volume

Carbon Fiber Support Tube

LiF Crystal

LiF + TEA Detector

11/30

0

20

40

60

80

100

2 4 6 8 10 12

Wavelength (nm)

Tra

nsm

issi

on

orQ

uant

um E

ffic

ienc

y (%

)

Photon Energy (eV)

LiF

CaF2

He+TEA

CH4+TEA

C* (6.42)C* (7.48)

C*(7.94)

N* (8.30)

620 310 207 155 124 103

ROYGBIV

O2

H2O

• Alkali-halide crystals low dispersion (n/ = 0.0023 nm-1): cosC = 1/n() Can fabricate with good transparency, large sizes (after many yrs’ effort)

• Sole example in world: previous effort by Sauli @ FNAL E605, npe ~ 1-2

12/30

• Images are conic intersections distorted and truncated by refractive effects.

• Total internal reflection for trk < 6° sawtooth radiatorAlso reduces chromatic aberrations

Radiator Optics

Image in photon detectors:

charged track

Sawtooth image in detectors:

primary arcssecondary arcs (+1 reflection)

charged track

emerging

internally reflected radiator

photon detector

charged track charged track

reflected emerging

4mm

Planar radiator Sawtooth radiator

A. Efimov and S. Stone, Nucl. Instr. Meth. A371, 79 (1996)

13/30

14/30

Anode Wires

1 mm

e-CH +TEA gas4CaF Window2

4.5 mm

Window Frame

Cathode Pads

• Multiwire chamber 20246 cm2

• CH4 + TEA gas (no blinds/cloisons)

• Total 15 m2 of chambers

• <8% “dead area”

• No observed aging of components from corrosive TEA

• Cathode pad readout (80% coupling)

• Achieve effective gain ~ 105

Photon Detector MWPCs

S.K. & Georg Viehhauser

15/30

Single Photo-electron Detection• Assume:

electronics = 400 e

chamber gain ~ 40,000

• Charged ptcles ionize ~ 62 e-/cm in CH4

• Single ’s: large statistical fluctuations.• Gain limit g~105 due to feedback

(R.Arnold et al, Nucl. Instr. Meth. A270, 255 (1980).

originally seen by H. Schlumbohm, Z. Phys. 151, 563 (1958)

• Analog readout of signal accurate clustering in RICH identification of charged

particles

4

/1dze

ggz

= e4/g

= 96%

16/30

Readout Electronics

• VA_RICH chip variation of chip used for Si tracking detectors (input Cdet)

daisy-chain multiple chips into one VME controller input protection (protect against chamber sparking) dynamic range 650,000 e

Marina Artuso

17/30

Electronics Performance

• 230,400 channels in CLEO RICH onboard sparsification.

• Coherent noise subtraction was an improvement, also adopted for CsI incoh ~ 2.6 ADC counts ~ 400e

Marina Artuso & Silvia Schuh

18/30

• Parasitic µ beam (> 100 GeV).

• 2 MWPCs as track reference

• Demonstrated npe~12 expected for CLEO-III

Sawtooth works as expected given clarity measurements.

RICH Beam Test

E866 beam dump

MWPC1MWPC2

Trigger counters

Vetocounter

1.5 m

RICHconcrete

N = 13.5N = 13.5

=4.8 mr =4.8 mr

CC

NN

19/30

photo of beam testBeamline

Elliot Lipeles

Ray Mountain

Silvia Schuh

Alex Efimov

20/30

Beam Test Events Planar

Sawtooth

M. Artuso et al Nucl. Instrum. Meth. A441, 374 (2000)

21/30Sheldon Stone

Yuri Maravin

Jeff Cherwinka

Rachid Ayad

Rachid Ayad

22/30

AlexSmith

RayMountain

GeorgViehhauser

SilviaShuh

23/30

Ray Mountain

Jeff Cherwinka

Georg Viehhauser

24/30

First CLEO-III Data

ee ee taken from T. Skwarnicki, BCP Conference, Taipei, Dec. ‘99

25/30

CLEO-III RICH Performance

M. Artuso et al, Nucl. Instrum. Meth. A554: 147-194 (2005)

BDK

BD

Beam Constrained Mass (GeV/c)

A. Bornheim et al, Phys. Rev. D68:052002 (2003)

26/30

LHCb Layout

b Exp’ts at Hadron Machines

CERN LHC Proposed for FNAL Tevatron

• Purpose is to collect large samples to over-constrain Unitarity Triangle and search for New Physics.

27/30

Particle ID in Forward b Experiments

Gas

C4F8O

n=1.00138

LiquidC5F12

n=1.24

(proximity focused)(mirror-focused)

(mirror-focused)BTeV RICH

28/30

-20,000 V

-19,890 V

-15,800 V

ground

Vacuum-based Photodetectors

0pe 1pe

2pe

3pe

BTeV HPD readout with VA_RICH

87 mm

125 mm

e-

+60 VSilicondiode

HPD: DEP PP0380AT

figures from T. Skwarnicki, presentation at DOE review of BTeV

29/30

MAPMTs

Beam(120 GeV p)

Glassmirror

Gas tank:C4F8O

and Argon

Beam Test of BTeV RICH

figures from T. Skwarnicki, presentation at DOE review of BTeVJ.C. Wang

R. MountainS. Blusk

30/30

Looking Back• The CLEO-III/c RICH detector works well

• We all made it through a challenging project working beyond edge of demonstrated technology rising/falling of semiconductor industry learning curve in chambers, crystals, gas systems, electronics, … near-miss not choosing CsI or other photocathode

• I would like to express my gratitude and admiration for my coworkers at Syracuse, and those that followed to make the RICH a success.

• All of us grateful for the job Sheldon did supporting our research encouraging “discussion” spreading infectious enthusiasm maintaining focus providing “guidance” to young turks

• I wish Sheldon & Syracuse group many years of productive research