The BTeV Experiment: Physics and Detector FPCP 2003 K. Honscheid Ohio State University

FPCP 2003K. HonscheidOhio State

The BTeV Experiment:Physics and Detector

FPCP 2003K. Honscheid

Ohio State University


B Physics Today

CKM Picture okay

CP Violation observed

No conflict with SM

Vud Vus Vub

VCKM = Vcd Vcs Vcb

Vtd Vts Vtb

sin(2) = 0.734 +/- 0.054

>1011 b hadrons

(including Bs)


B Physics at Hadron Colliders

Energy 2 TeV 14 TeVb cross section ~100 b ~500 b

c cross section ~1000 b ~3500 bb fraction 2x10-3 6x10-3

Inst. Luminosity 2x1032 >2x1032

Bunch spacing 132 ns (396 ns) 25 nsInt./crossing <2> (<6>) <1>Luminous region 30 cm 5.3 cm

Tevatron LHC

Large cross sectionsTriggering is an issueAll b-hadrons produced (B, Bs, Bc, b-baryons)


Detector Requirements

From F. Teubert

•Trigger, trigger, trigger •Vertex, decay distance•Momentum•PID•Neutrals (, 0)


Forward vs. Central Geometry

b production angle

b production angle

230b

100b

Multi-purpose experiments requirelarge solid angle coverage.

Central Geometry (CDF, D0, Atlas, CMS)

Dedicated B experiments can takeadvantage of

Forward geometry(BTeV, LHCb)


The BTeV Detector

Beam Line


Pixel Vertex Detector

Reasons for Pixel Detector:• Superior signal to noise• Excellent spatial resolution -- 5-10 microns depending on angle, etc• Very Low occupancy• Very fast • Radiation hardSpecial features:• It is used directly in the L1 trigger• Pulse height is measured on every channel with a 3 bit FADC• It is inside a dipole and gives a crude standalone momentum

Doublet


The Pixel Detector II

Vacuum System


Simulated B Bbar, Pixel Vertex Detector


Generate Level-1 accept if “detached” tracks in the BTeV pixel detector satisfy:

2

2.0

25.02

b

mb

pT

(GeV/c)2

cm

L1 vertex trigger algorithm

b

p p

B-meson


Level 1 vertex trigger architecture

FPGA segment trackers

Merge

Trigger decision to Global Level 1

Switch: sort by crossing number

track/vertex farm(~2500 processors)

30 station pixel detector


Efficiencies and Tagging

For a requirement of at least 2 tracks detached by more than 6, we trigger on only 1% of the beam crossings and achieve the following trigger efficiencies for these states (<2> int. per crossing):

Decay efficiency(%) Decay efficiency(%)

B +- 63 Bo K+- 63

Bs DsK 74 Bo J/ Ks 50

B- DoK- 70 Bs J/K* 68

B- Ks- 27 Bo K*

74%

1%

Impact Parameter in units of Impact Parameter in units of

Trigger Efficiency-Minimum Bias EventsTrigger EfficiencyBsDsKE

F

F

I

C

I

E

N

C

Y

E

F

F

I

C

I

E

N

C

Y

N=1

N=2

N=3

N=4

N=1

N=2

N=3

N=4


The Physics Goals

There is New Physics out there: Baryon Asymmetry of Universe & by Dark MatterHierarchy problemPlethora of fundamental parameters…

B Experiments at Hadron Colliders are well positioned to:

Perform precision measurements of CKM Elements withsmall model dependence.Search for New Physics via CP phasesSearch for New Physics via Rare DecaysHelp interpret new results found elsewhere (LHC, neutrinos)Complete a broad program in heavy flavor physics

Weak decay processes, B’s, polarization, Dalitz plots, QCD…

Semileptonic decays including b

b & c quark ProductionStructure: B(s) spetroscopy, b-baryon statesBc decays


Importance of Particle Identification

BTeV RICH Detector

Gas

Liquid


Measuring Using Bo

A Dalitz Plot analysis gives both sin(2) and cos(2)(Snyder & Quinn)

Measured branching ratios are:

(B = ~10-5

(B + = ~3x10-5

(B <0.5x10-5

Snyder & Quinn showed that 1000-2000 tagged events are sufficient

Not easy to measure0 reconstruction

Not easy to analyze9 parameter likelihood fit

Slow 0’s

Nearly empty( polarization)

Dalitz Plot for Bo


Yields for BoBased 9.9x106 background events

Bo+-

5400 events, S/B = 4.1

Booo

780 events, S/B = 0.3

o

Background Signal

mB (GeV) mB (GeV)

Booo


Our Estimate of Accuracy on

Geant simulation of Bo(for 1.4x107 s)

Example:1000 Bo signal + backgroundsWith input =77.3o

minimum 2

non-resonantnon- bkgrd

resonantnon- bkgrd

(gen)

Rres Rnon(recon)

77.3o 0.2 0.2 77.2o 1.6o

77.3o 0.4 0 77.1o 1.8o

93.0o 0.2 0.2 93.3o 1.9o

93.0o 0.4 0 93.3o 2.1o

111.0o 0.2 0.2 111.7o 3.9o

111.0o 0.4 0.2 110.4o 4.3o


Rare b Decays Search for New Physics in Loop diagrams

New fermion like objects in addition to t, c or uNew Gauge-like objects in addition to W, Z or g

Inclusive Rare Decays including bs bd bs+

Exclusive Rare Decays such as BBK*+ Dalitz plot & polarization

+-

BoK*


Electromagnetic CalorimeterThe main challenges include

• Can the detector survive the high radiation environment ?• Can the detector handle the rate and occupancy ?• Can the detector achieve adequate angle and energy resolution ?BTeV will have a high resolution PbWO4 calorimeter• Developed by CMS for use at the LHC• Large granularity

Block size 2.7 x 2.7 x 22 cm3 (25 Xo)~23000 crystals

• Photomultiplier readout (no magnetic field)• Pre-amp based on QIE chip (KTeV)• Energy resolution

Stochastic term 1.6%Constant term 0.55%

• Position resolution E

x/m3526 m217


PbWO4 Calorimeter Properties

Property ValueDensity(gm/cm2) 8.28Radiation Length(cm) 0.89Interaction Length(cm) 22.4Light Decay time(ns) 5(39%) (3components) 15(60%)

100(1%)Refractive index 2.30Max of light emission 440nmTemperature Coefficient (%/oC) -2Light output/Na(Tl)(%) 1.3Light output(pe/MeV) into 2” PMT 10

Property ValueTransverse block size 2.7cm X 2.7 cmBlock Length 22 cmRadiation Length 25Front end Electronics PMTInner dimension +/-9.8cm (X,Y)Energy Resolution: Stochastic term 1.6% (2.3%) Constant term 0.55%Spatial Resolution: Outer Radius 140 cm--215 cm

$ drivenTotal Blocks/arm 11,500

Ex

/m3526 m217


Electromagnetic Calorimeter Tests

Block from China’s Shanghai Institute

• Resolution (energy and position) close to expectations

• This system can achieve CLEO/BaBar/BELLE-like performance in a hadron Collider environment!


Muon System

track from IP

toroid(s) / iron

~3 m

2.4 m halfheight

Provides Muon ID and TriggerTrigger for interesting physics statesCheck/debug pixel trigger

fine-grained tracking + toroid

Stand-alone mom./mass trig.Momentum “confirmation”

Basic building block: Proportional tube “Planks”


BTeV data compared to Burdman et al calculation

Dilepton invariant mass distributions,forward-backward asymmetrydiscriminate among the SM and various supersymmetric theories.(Ali, Lunghi, Greub & Hiller, hep-ph/0112300)

One year for K*+-, enough to determine if New Physics is present

Polarization in BoK*o+-

Ali et. al, hep-ph/9910221


Summary

Heavy quark physics at hadron colliders provides a unique opportunity to

measure fundamental parameters of the Standard Model with no or only small model dependencediscover new physics in CP violating amplitudes or rare decays.interpret new phenomena found elsewhere (e.g. LHC)

Some scenarios are clear others will be a surprise

This program requires a general purpose detector like BTeV with

an efficient, unbiased trigger and a high performance DAQa superb charged particle tracking systemgood particle identificationexcellent photon detection


Additional Transparencies


Physics Reach (CKM) in 107 s Reaction B(B)

(x10-6)# of Events

S/B Parameter Error or (Value)

Bs Ds K- 300 7500 7 - 8o

Bs Ds- 3000 59,000 3 xs (75)

BoJ/KS J/+ - 445 168,000 10 sin(2) 0.017

BoJ/Ko, Ko 7 250 2.3 cos(2) ~0.5

B-Do (K+-) K- 0.17

170 1

B-Do (K+K-) K- 1.1 1,000 >10 13o

BsJ/ 330 2,800 15

BsJ/ 670 9,800 30 sin(2 0.024

Bo+- 28 5,400 4.1

Booo 5 780 0.3 ~4o Reaction B(B)

(x10-6)# of Events

S/B Parameter Error

B-KS -

12.1 4,600 1 <4o +

BoK+- 18.8

62,100 20 Theory err.

Bo+- 4.5 14,600 3 Asymmetry 0.030

BoK+ K- 17 18,900 6.6 Asymmetry 0.020


A simplified trigger comparison

From U. Egede


Unitarity TrianglesUnitarity Triangles

Bd0

Bd0

Bd0 DK*0

BS0 DSK

Bd0 D*

BS0 DS

Bd0 J/ KS

0

BS0 J/

From N. Harnew


Pixel Test Beam Results

Track angle (mr)

No changeafter 33 Mrad(10 years, worst case, BTeV)

Analog output of pixel amplifier before and after 33 Mrad irradiation.0.25 CMOS design verified radiationhard with both and protons.


Forward Tracker

Predicted performance -Momentum resolution is better than 1% over full momentum and angle range

Prototype Straw tracker being constructed for FNALbeam test summer/fall 2002

DrawingOf forwardMicrostriptracker


HPD Schematic for BTeV RICH

HPD Tube HPD Pixel array HPD Pinout

Pulse Height from163 pixel prototypeHPD. Note pedestal,1, 2, 3 pe peaks


Prop Tube Planks

3/8” diameter Stainless steel tubes (0.01” walls)“picket fence” design 30 (diameter) gold-plated tungsten wireManifolds are brass soldered to tubes (RF sheilding important!)Front-end electronics: use Penn ASDQ chips, modified CDF COT cardTry “D0 fast gas” 88% Ar - 10% CF4 - CO2 or 50% Ar – 50% Eth.

Basic Building Block: Proportional Tube “Planks”


Plank Cosmic Ray Tests

Cosmic Ray Test Stand


BTeV Data Acquisition Architecture

B TeV d etec to r

L 1 m uon

L 1 vertex

G loba lL evel-1

L eve l-1

L ev el 2 /3 C ro ss in g S w itch

D a ta L o g g in g

F ron t-end e lec tron ics

L eve l-1 B uffe rs

L eve l-2 /3 B uffe rs

I n f o r m a tio n T r a n s fe r C o n t r o l H a r d w a r e

IT C H

L eve l-2 /3 P rocessor F a rm

#1

#2

#m -1

#m

RDY

Crossing #N

Req. data for crossing #N

L eve l-3 accep t

G L 1 accep t

P IX

> 2 x 10 channe ls7

800 GB/s7.6 MHz

L1 rate reduction: ~1/100

L2/3 rate reduction: ~1/20

4 KHz 200 MB/s

The BTeV Experiment: Physics and Detector FPCP 2003 K. Honscheid Ohio State University

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Transcript of The BTeV Experiment: Physics and Detector FPCP 2003 K. Honscheid Ohio State University