B Physics in Berkeley
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Transcript of B Physics in Berkeley
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March 6, 2003 Cahn: LBNL B-Physics - HEPAP 1
B Physics in Berkeley
BaBar and CDF
R. Cahn
HEPAP, March 6, 2003
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March 6, 2003 Cahn: LBNL B-Physics - HEPAP 2
LBNL: Doing the Physics From Start to Finish
Conception DesignFabrication
CommissioningOperations/Calibration
Reco/Simulation
Analysis
upgrade
Performance optimization
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Conception
Oddone: Asymmetric B-factory can study CP
Silicon vertex detector can work in hadron collider
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BaBar DesignDIRC barbox
DIRC structure
SVT cone
SVT space frame
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CDF Design
CDF SVX-II Layer-1 Phi Layout & Hybrid
side-by-side
SVXII ladder design
Sense wiresPotential
wires
Cathode
COT cell
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BaBar FabricationWorking with LBNL’s Engineering Division we developed critical instrumentation for BaBar and CDF
AToM
SVT mechanical
TriggerTrack Segment Finder DIRC barrel
Drift Chamber Readout
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CDF Fabrication
Assembly of Central OuterTracker
Fabrication of field sheets for COT at LBL
SVX-3d chip
SVX hybrids
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Commissioning
92.5% of ladders are operating ~85 % collect good data 7.5% bad ladders (ISL cooling) ~ 7% error rate
DIRC angular and time resolutions
Shelkov
CDF
BaBar
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Operations &Calibration at BaBar
Residuals of SVT alignment showed strong azimuthal variation. Mini-DST made it possible to use enough tracks to remove most of it.
SVT removed for access in Summer 2002. Most of few dead modules resuscitated by fixing connections. Valuable experience gained in preparation for major refurbishing in Summer 2005. Kerth
Gritsan
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BaBar Reco/Simulations
• R. Jacobsen: Reconstruction Manager/Offline Computing Co-ordinator (1995-2000)– Sub-system code: DIRC, SVT,
trigger,tracking,alignment• D. Quarrie (NERSC) led database development
– On-line configuration database– Off-line conditions database– Event store
• G. Abrams led on-line computing– Detector control– Calibration
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Performance Optimization
• B physics is precision physics
• Continual improvements in hardware and
software are essential
• Inevitably, those who design and build the
detector are in the best position to propose and implement improvements
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Development of the “Mini” DST for BaBar
• David Brown leads team with NERSC computing professionals
• Mini-DST replaces 20 times larger version• Mini provides access event details• New computing model’s central component• Already improved calibrations, analysis
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Performance Optimization: CDF SVX Trigger
J/ -> trigger on impact parameter compared to high–pt trigger
SVT impact parameterSVT impact parameter
= 48 Online track d0
Level 1:pt>1.5 GeV
Level 2: add SVX 120 impact parameter required
on-line
Cerri
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Upgrades - CDFSVX family of radiation tolerant silicon strip readout chips
First rad-hard chip
Analog pipeline + on-chip ADC
Dead-timeless operation, on-chip common mode subtraction
x10 more rad hard + better noise performance
SVX21996 SVX3
1998
SVX42002
SVX’1990
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Analysis:B Physics Goals
• Precision tests– Angles and sides of unitarity triangle
• Study of decay dynamics– Direct CP violation– QCD/HQET
We claim to have a complete model of the physical phenomena below the TeV domain. Such a sweeping assertions requires real verification. B physics provides the ideal theatre in which to test this claim.
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Measuring theUnitarity Triangle
Vub* Vud Vtb*Vtd
-Vcb*Vcd
Analyses with LBNL
involvement
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Measuring Mixing
LBL-Stanford measurement
In D* l
Measures m_d. Amplitude is not 1.0 because we mistag a fraction w of events.
Mixing provides calibration of tagging. Best done with nonleptonic decays.
B= 1.523 +0.023-0.028 ±0.022 ps
m=0.492 ±0.018 ±0.013 ps-1
LeClerc, Roe
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Mixing at CDF
Goal is measuring Bs mixing.
Toy MC shown
Nonleptonic Bs decays provide ideal basis for mixing. First observation of nonleptonic Bs decays at CDF.
Cerri,
ms measurement is next big step in pinning down
unitarity triangle
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Mixing with SemileptonicDecays at CDF
Semileptonic Bd is warm up exercise. First do inclusive, then full reco.
Semileptonic Bs is check on nonleptonic and means of finding Bs lifetime
Bs->l+Ds X
CDF semileptonic group
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sin 2
sin 2 =0.741 +/- 0.067 +/- 0.033
BaBar flagship measurement.
CDF should become competitive.
Results in Ks may yet upset the picture.
Tree has “no phase.”
Penguin same.
BaBar sin 2 group, Cahn
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sin 2B → : alternative to B →
Tree Penguin
Eventually, do time-dependent Dalitz plot.
For now, treat as stable particle.
Measure coefficients of sin mt , cos m t.
Penguin prohibits clean interpretation.
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B→: sin 2
413 events
147 K events
Shelkov
New results this month
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sin(2 + )
Ds+- is SU(3) variant of
Cabibbo suppressed D+-.
whose BR is needed in the measurement of in D+
Kolomensky, Orimoto
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Vcb
BaBar: Exclusive D* l Gill
CDF: Inclusive
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Direct CP Violation: K
Telnov
New results this month
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B → V V
• For direct CP• For mixing+decay CP: signal&bkgd!• Three decay amplitudes• Two relative strong phases• Angular analysis required
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B →V V
Gritsan, Mir
B+ →0K*+ B+ →0+
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Direct CP Summary
No convincing evidence.
Getting close.
Gritsan
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LBNL: Doing the Physics From Start to Finish
• LBNL pioneered B physics at CDF and BaBar.
• Efforts continue to improve detector performance and analysis capability to meet the challenge of precision B physics.
• Analysis is attacking the unitarity triangle from all sides (and angles).
• Increased luminosity at both experiments promises important new results.
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Extra Slides
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How B’s Mix
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Oscillations
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& CP/CPT Violation in Mixing
• Use fully reconstructed “flavor” and CP eigenstates• Fit time dependence
• Measure or limit and |q/p|2 (i.e. 12 / M12)
• Measure or limit CPT violation
Cahn
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Reconstructing Tracks in BaBar with Few Drift Chamber Hits
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Governance/Direction: BaBar
• Brown:Computing Model Task Force• Cahn: Publications Board, Long-Term Task Force• Kolomensky: Computing Model Task Force• Oddone: Executive Board• Roe: Long-Term Task Force, IFR Task Force, SVT Task Force
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BaBar Commissioning
DIRC angular and time resolutions
DIRC K/ separation
Drift ChamberAverage resolution = 125 um (Design goal was 140 um)
Shelkov
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Oscillations
Mixing: observe final state that is clearly B0 or B0-
CP eigenstate gets contributions from both
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Tagging
0B D
0 ,B DX D K X
0 0, sB D X D D
0 *,B D D K
Secondary lepton
K
Kaon(s)
Soft pions from D* decays
, Fast charged tracks
Primary lepton
b c sW W
Slide:D. MacFarlane
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Operations &Calibrations at BaBar
LBNL engineering key to designing on-line system
Rolling calibrations essential to quick reconstruction.
Each run feeds parameters to the next.
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Commissioning
92.5% of ladders are operating ~85 % collect good data 7.5% bad ladders (ISL cooling) ~ 7% error rate
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CP eigenstates
Decay Time Difference (reco-tag) (ps)
B0 tagB0 tag
0
10
20
30
40
50
60
-8 -6 -4 -2 0 2 4 6 8Decay Time Difference (reco-tag) (ps)
B0 tagB0 tag
0
10
20
30
40
50
60
-8 -6 -4 -2 0 2 4 6 8
z ~ 260 m
0tagB
ee
4S0
recB
0SK
/J
e,
K
Slide:D. MacFarlane
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Mixing Distributions
Decay Time Difference (reco-tag) (ps)
UnMixedMixed
0
10
20
30
40
50
60
-8 -6 -4 -2 0 2 4 6 8
Decay Time Difference (reco-tag) (ps)
UnMixedMixed
0
10
20
30
40
50
60
-8 -6 -4 -2 0 2 4 6 8
(4s)
= 0.55
Reco Bz ~ 65 m
+
t z/c
K0
D-
--
K+
Tag B
z ~ 110 m
resolution
Slide:D. MacFarlane
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Upgrades - BaBar
No to new layer-0. Roe co-chairs committee on long-term SVT options.
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CDF: Operations
Measured signal-to-noiseby layers
Measured signal-to-noiseas function of band-width
Dominguez,Nielsen
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CDF Reco/Simulations
Agreement between MC and measured
Residuals in SVX Layer 2
= 8 micron
SVX efficiency, (PT)
=89.5%
Dominguez
W-M Yao