Description of BTeV detector Jianchun Wang Syracuse University Representing The BTeV Collaboration...

Description of BTeV detector

Jianchun WangSyracuse University

Representing The BTeV Collaboration

DPF 2000 Aug 9 - 12 , 2000 Columbus, Ohio

DPF 2000 Jianchun (JC) Wang 2

Introduction

BTeV: dedicated beauty and charm experiment at pp collider at Fermilab

Physics goal: mixing, CP violation, rare decays of b- and c- hadronsAccurately determine Standard Model

parametersSearch for physics beyond Standard Model


Characteristics of b Production at Tevatron

Luminosity (leveled) 21032 cm-2s-1

b cross-section 100 µb# of b’s per 107 sec 41011

b fraction ~ 0.15 %c cross-section >500 µbBunch Spacing 132 nsLuminous region length z = 30 cmLuminous region width

x ~y ~ 50 µmInteractions/crossing <2>


A Forward Detector at pp Collider

The higher momentum b are at larger

b production angle

b production angle

b production peaks at large angles with large bb correlation

Pseudo-rapidity

BTeV detector covers forward region, 10-300 mrad


High background ( b/tot ~ 1/500 ), large data rate ( 1kHz ) to be recorded

Detached vertex trigger and background rejection

Deadtimeless trigger and DAQ system

Background from real b event can overwhelm “rare” processes

Excellent particle identification

Radiation hard detector components

Main Challenges


The C0 Interaction Region

C0 collision Hall( 9 m x 24 m )

C0 Assembly Building


The BTeV Detector

Pixel Vertex Detector

Dipole Magnet

Magnet Coil

Beam Pipe

Forward tracking

RICH

PbWO4 EM calorimeter

Muon Toroid


The Pixel Detector

Function: Deliver clean, precise space

points to detached vertex trigger

Provide vertex information for offline analysis

Pixel sensor Eliminate ambiguity problems

with high track density (essential to the detached vertex trigger)

Radiation hard, low noise Easy pattern recognition

Pixels size: 50m 400 m (total 3 107 channels)

Elevation View 10 of 31 Doublet stations

5mm


Silicon Pixel Detector

FPIX2 Readout Chip3-bit analog readoutNoise ~ 100 e0.25m CMOS process

Pixel sensor Size: 50400 m2

Thickness: 250 m Type: n+np+


Support and Cooling

Carbon composite structures include integrated cooling tubes ( by ESLI) Shingled surface, allow the multichip assemblies to overlap Movable structure, adjustable distance between the sensor and the beam Light mass material ( ~ 0.9 % X0 includes the detector)


Pixel Test Beam Results

280 m thick detector bump bonded to custom made electronics chip developed at Fermilab

Excellent resolution ( requirement: 9 m ) Diamond target test, track density higher than BTeV


Decay Time Resolution

• Decay length (from primary vertex to secondary vertex) <L> = c

= 480 m pB/mB (2700 m at pB = 30 GeV)

• Excellent resolution (L 75 m at pB = 30 GeV)

– Reduces background

– Allows detached vertex trigger

• Smallest error near peak (30GeV) pB (GeV)

L (

cm)

B

PB distribution

Decay length error


Detached Vertex Trigger

State efficiency(%) State efficiency(%)

B +- 63 Bo K+- 63

Bs DsK 71 Bo J/ Ks 50

B- DoK- 70 Bs J/K* 68

B- Ks- 27 Bo oo

Idea: finds the primary vertex, selects events that have additional tracks miss it

Requirement: at least 2 tracks detached by more than 6 1% minimum bias

Efficiency: (after the other analyses cuts)


Forward Tracking System

Major functions: Improve P measurement combined with pixel system Reconstruct and measure all parameters for tracks outside the

acceptance of pixel system Project tracks into downstream detectors Provide information for level 2 trigger

Combination of straw-tube chambers and silicon strips (along the beam line, 7 station per arm)

Straw-tube (4mm diameter, x ~ 150 m): small cell for large chamber, no heavy frame near the beam

Silicon strip (100m pitch, x ~ 29 m): near the beam, handle high track density

Momentum resolution ( 0.4% - 0.9% )


Ring Imaging CHerenkov

Goal: /K/p separation from 3 - 70 GeV/c Radiators: freon, aerogel (~ 4cm thick) Photon detector: hybrid photodiodes (HPD)


Hybrid Photo Diode

e

Silicon diode

Pins to readout chip

window with aphoto-cathode at -20 kV

Electrostatic acceleration and focusing of a photo-electron on a silicon diode

Large active area ( ~ 80%), hexagonal close packed, no lens system needed

163 channels, manufactured by DEP

Large HV (20kV) but no current draw


Particle Identification

Rings from Bo+ -High efficiency

with excellent rejection


The PbWO4 EM Calorimeter

Goal: Reconstruction of (B, etc), identification of electron Excellent resolution, radiation hard

PbWO4 crystal Radiation hard Scintillation is fast, 99% of light emitted < 100 ns Lateral size: 25.425.4 mm2 (front), 2626 mm2 (back) Length 22 cm (25 X0)

Photo-multiplier tube (PMT) readout (no magnetic field)

Projective geometry, covers up to 210 mrad (reduce cost)

Total of 2 11,850 crystals needed


Expected Resolution

M(GeV)

0 at 10 GeV

M=2.6MeV

E / E

= 0.77%

BK*

22

E %55.0)GeV(E

%6.1

E

22

x 200)GeV(E

3500)m( Excellent Resolution:


Expected Efficiency

High rate at small radius

resolution and efficiency degrade About 80% efficiency at large radius

BK*


The Muon Detector

Goals:Muon Identification

Trigger on di-muons in level 1, Provides a method of checking detached vertex triggering efficiency

Design: Two Toroids with three sets of position detectorsToroid: 1 m thick, 1.5 Tesla,

absorb hadron, deflect track

position detectors: 1 between toroids, two downstream

To beam center

B

B


The Muon Position Detector

Planks of 3/8" diameter stainless steel proportional tubes

Eight overlapping pie shaped octants

Four views (r, u, v, r)

p / p= 19% 0.6% p

r vu


DAQ Scheme

See Paul Lebrun’s talk7.6MHz crossing rate

2 - 4 kHz

40 KB/event


The Status of BTeV

BTeV submitted a preliminary technical design report in May of 1999 and a full proposal in May of 2000

BTeV is an approved experiment,

Fermilab E897

More information can be found at

http://www-btev.fnal.gov

Description of BTeV detector Jianchun Wang Syracuse University Representing The BTeV Collaboration...

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