The BTeV Experiment:
Physics and Detector
FPCP 2003
K. Honscheid
Ohio State University
FPCP 2003
K. Honscheid
Ohio State
B Physics Today
CKM Picture okay
VCKM =
Vud
Vus
Vub
Vcd
Vcs
Vcb
Vtd
Vts
Vtb
CP Violation observed
sin(2b) = 0.734 +/- 0.054
>1011 b hadrons
No conflict with SM
FPCP 2003
K. Honscheid
Ohio State
(including Bs)
B Physics at Hadron Colliders
Energy
b cross section
c cross section
b fraction
Inst. Luminosity
Bunch spacing
Int./crossing
Luminous region
Tevatron
LHC
2 TeV
~100 mb
~1000 mb
2x10-3
2x1032
132 ns (396 ns)
<2> (<6>)
30 cm
14 TeV
~500 mb
~3500 mb
6x10-3
>2x1032
25 ns
<1>
5.3 cm
Large cross sections
Triggering is an issue
All b-hadrons produced (B, Bs, Bc, b-baryons)
FPCP 2003
K. Honscheid
Ohio State
Detector Requirements
FPCP 2003
K. Honscheid
Ohio State
•Trigger, trigger, trigger
•Vertex, decay distance
•Momentum
•PID
•Neutrals (g, p0)
From F. Teubert
Forward vs. Central Geometry
Multi-purpose experiments require
large solid angle coverage.
Central Geometry
(CDF, D0, Atlas, CMS)
Dedicated B experiments can take
advantage of
Forward geometry
(BTeV, LHCb)
bg
FPCP 2003
K. Honscheid
Ohio State
100mb
230mb
The BTeV Detector
Beam Line
FPCP 2003
K. Honscheid
Ohio State
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 hard
Special 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
FPCP 2003
K. Honscheid
Ohio State
The Pixel Detector II
Vacuum System
FPCP 2003
K. Honscheid
Ohio State
Simulated B Bbar, Pixel Vertex Detector
FPCP 2003
K. Honscheid
Ohio State
L1 vertex trigger algorithm
Generate Level-1 accept if
satisfy:
2
“detached” tracks in the BTeV pixel detector
pT2  0.25
(GeV/c)2
b  m
b  0 .2
cm
p
p
b
FPCP 2003
K. Honscheid
Ohio State
B-meson
Level 1 vertex trigger architecture
30 station pixel detector
FPGA segment trackers
Switch: sort by crossing number
track/vertex farm
(~2500 processors)
Merge
Trigger decision to
Global Level 1
FPCP 2003
K. Honscheid
Ohio State
Efficiencies and Tagging
Trigger EfficiencyBsDsK
E
Trigger Efficiency-Minimum Bias Events
E
N=1
F
F
F
F
I
N=2
74%
I
N=2
C
C
I
N=3
I
E
E
N
N=1
N=4
N
C
C
Y
Y
Impact Parameter in units of 
N=3
1%
N=4
Impact Parameter in units of 
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):
FPCP 2003
K. Honscheid
Ohio State
Decay
efficiency(%)
B  p+p 63
Bs  DsK
74
B-  DoK70
B-  Ksp27
Decay efficiency(%)
Bo  K+p63
Bo  J/y Ks
50
Bs  J/yK*
68
Bo  K*g
40
The Physics Goals
There is New Physics out there:
Baryon Asymmetry of Universe & by Dark Matter
Hierarchy problem
Plethora of fundamental parameters
…
B Experiments at Hadron Colliders are well positioned to:
Perform precision measurements of CKM Elements with
small model dependence.
Search for New Physics via CP phases
Search for New Physics via Rare Decays
Help 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 Lb
b & c quark Production
Structure: B(s) spetroscopy, b-baryon states
Bc decays
FPCP 2003
K. Honscheid
Ohio State
Importance of Particle Identification
BTeV RICH Detector
Gas
FPCP 2003
K. Honscheid
Ohio State
Measuring a Using Borp  p+p-po
A Dalitz Plot analysis gives
both sin(2a) and cos(2a)
(Snyder & Quinn)
Measured branching ratios are:
B(B-rop-)
Nearly empty
(r polarization)
~10-5
=
B(Bor-p+ + r+p-) = ~3x10-5
B(Boropo) <0.5x10-5
Snyder & Quinn showed that
1000-2000 tagged events are
sufficient
Not easy to measure
p0 reconstruction
Not easy to analyze
9 parameter likelihood fit
FPCP 2003
K. Honscheid
Ohio State
Slow p0’s
Dalitz Plot for Borp
Yields for Borp
Based 9.9x106 background events
Bor+p5400 events, S/B = 4.1
Boropo
780 events, S/B = 0.3
Background
p
o
FPCP 2003
K. Honscheid
Ohio State
g
Boropo
Signal
g
mB (GeV)
mB (GeV)
Our Estimate of Accuracy on a
Geant simulation of Borp, (for 1.4x107 s)
a (gen)
Rres
Rnon
a (recon)
Da
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
minimum c2
Example:
1000 Borp signal + backgrounds
With input a=77.3o
FPCP 2003
K. Honscheid
Ohio State
non-resonant
non-rp bkgrd
resonant
non-rp bkgrd
Rare b Decays
Search for New Physics in Loop diagrams
New fermion like objects
in addition to t, c or u
New Gauge-like objects
in addition to W, Z or g
Inclusive Rare Decays including
g, l+l-
bsg
bdg
bsl+l-
Exclusive Rare Decays such as
Brg, K*g
BK*l+lDalitz plot & polarization
FPCP 2003
K. Honscheid
Ohio State
BoK*g
Electromagnetic Calorimeter
The 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
  3526mm / E  217mm
x
FPCP 2003
K. Honscheid
Ohio State
PbWO4 Calorimeter Properties
Property
Density(gm/cm2)
Radiation Length(cm)
Interaction Length(cm)
Light Decay time(ns)
(3components)
Value
8.28
0.89
22.4
5(39%)
15(60%)
100(1%)
Refractive index
2.30
Max of light emission 440nm
Temperature
Coefficient (%/oC) -2
Light output/Na(Tl)(%) 1.3
Light output(pe/MeV)
into 2” PMT
10
FPCP 2003
K. Honscheid
Ohio State
Property
Transverse block size
Block Length
Radiation Length
Front end Electronics
Inner dimension
Energy Resolution:
Stochastic term
Constant term
Spatial Resolution:
Outer Radius
Total Blocks/arm
Value
2.7cm X 2.7 cm
22 cm
25
PMT
+/-9.8cm (X,Y)
1.6% (2.3%)
0.55%
  3526mm / E
x
 217mm
140 cm--215 cm
$ driven
11,500
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!
FPCP 2003
K. Honscheid
Ohio State
Muon System
Provides Muon ID and Trigger
Trigger for interesting physics
states
Check/debug pixel trigger
fine-grained tracking + toroid
Stand-alone mom./mass trig.
Momentum “confirmation”
Basic building block: Proportional
tube “Planks”
~3 m
toroid(s) / iron
track from IP
FPCP 2003
K. Honscheid
Ohio State
2.4 m
half
height
Polarization in BoK*om+mBTeV data compared to Burdman et al calculation
Dilepton invariant mass distributions,
forward-backward asymmetry
discriminate among the SM and
various supersymmetric theories.
Ali et. al, hep-ph/9910221
(Ali, Lunghi, Greub & Hiller, hep-ph/0112300)
FPCP 2003
K. Honscheid
Ohio State
One year for K*l+l-, enough to determine if New Physics is present
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 dependence
discover 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 DAQ
a superb charged particle tracking system
good particle identification
excellent photon detection
FPCP 2003
K. Honscheid
Ohio State
Additional Transparencies
FPCP 2003
K. Honscheid
Ohio State
Physics Reach (CKM) in 107 s
Reaction
B(B)
(x10-6)
S/B
Parameter
Error or
(Value)
Bs Ds K-
300
7500
7
g - 2c
8o
Bs Ds p-
3000
59,000
3
xs
(75)
445
168,000
10
7
250
2.3
B-Do (K+p-) K-
0.17
170
1
B-Do (K+K-) K-
1.1
1,000
>10
BoJ/y KS
J/y l+ l -
BoJ/y Ko, Ko  p l n
BsJ/y h,
330
2,800
15
BsJ/y h
670
9,800
30
Bor+p-
28
5,400
4.1
Boropo
5
780
0.3
Reaction
B(B)
(x10-6)
FPCP 2003
K. Honscheid
Ohio State
# of
Events
# of
Events
S/B
sin(2b)
0.017
cos(2b)
~0.5
13o
g
sin(2c)
0.024
a
~4o
Parameter
Error
B-KS p-
12.1
4,600
1
BoK+p-
18.8
62,100
20
Bop+p-
4.5
14,600
3
Asymmetry
0.030
BoK+ K-
17
18,900
6.6
Asymmetry
0.020
<4o +
g
Theory err.
A simplified trigger comparison
FPCP 2003
K. Honscheid
Ohio State
From U. Egede
Unitarity Triangles
Bd0  p+ pBd0  r p
BS0  DS p
Bd0  DK*0
BS0  DSK
Bd0  D* p, 3p
Bd0  J/y KS0
dg  c
FPCP 2003
K. Honscheid
Ohio State
BS0  J/y f
From N. Harnew
Pixel Test Beam Results
No change
after 33 Mrad
(10 years, worst
case, BTeV)
Analog output of pixel amplifier before
and after 33 Mrad irradiation.
0.25m CMOS design verified radiation
hard with both g and protons.
Track angle (mr)
FPCP 2003
K. Honscheid
Ohio State
Forward Tracker
Prototype Straw tracker
being constructed for FNAL
beam test summer/fall 2002
FPCP 2003
K. Honscheid
Ohio State
Predicted performance Momentum resolution is better
than 1% over full momentum and
angle range
Drawing
Of forward
Microstrip
tracker
HPD Schematic for BTeV RICH
HPD Tube
HPD Pixel array
HPD Pinout
Pulse Height from
163 pixel prototype
HPD. Note pedestal,
1, 2, 3 pe peaks
FPCP 2003
K. Honscheid
Ohio State
Prop Tube Planks
Basic Building Block: Proportional Tube “Planks”
3/8” diameter Stainless steel
tubes (0.01” walls)
“picket fence” design
30 m (diameter) gold-plated
tungsten wire
Manifolds are brass soldered to
tubes
(RF sheilding
important!)
Front-end electronics: use Penn
ASDQ chips, modified CDF COT
card
Try “D0 fast gas”
88% Ar 10% CF4 - CO2 or 50% Ar –
50% Eth.
FPCP 2003
K. Honscheid
Ohio State
Plank Cosmic Ray Tests
Cosmic Ray Test Stand
FPCP 2003
K. Honscheid
Ohio State
BTeV Data Acquisition Architecture
BTeV detector
Front-end electronics
7.6 MHz
800 GB/s
7
> 2 x 10 channels
m
PIX
Level-1
L1 muon
Global
Level-1
L1 vertex
Level-1 Buffers
Information Transfer
Control Hardware
L1 rate reduction: ~1/100
GL1 accept
ITCH
Req. data for
crossing #N
Crossing #N
Level 2/3 Crossing Switch
RDY
#1
L2/3 rate reduction: ~1/20
Level-2/3 Processor
Farm
#2
#m-1
#m
Level-2/3 Buffers
Level-3 accept
Data Logging
4 KHz
FPCP 2003
K. Honscheid
Ohio State
200 MB/s