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1Chunhui Chen, University of Pennsylvania
Heavy Flavor Production and Heavy Flavor Production and Cross Sections at the TevatronCross Sections at the Tevatron
(Run II results only)
Chunhui ChenUniversity of Pennsylvania
For CDF and D0 Collaboration
Beauty 2003 October 14-18, 2003 Pittsburg, USA
2Chunhui Chen, University of Pennsylvania
Outline
• Tevatron and CDF/D0 upgrade• Prompt charm meson production cross section • Inclusive J/ cross section • b cross section• b-jet cross section • Conclusion
3Chunhui Chen, University of Pennsylvania
Tevatron Run IIThe Tevatron is a proton-antiproton collider with 980 GeV/beam
1.80TeV in Run I
36 bunches p 36 bunches p_
396 ns bunch crossing time
66 in Run I
Tevatron Performance: L~5.0 x 1031 cm-2s-1 9 pb-1/weekLint~300 pb-1 delivered by Tevatron
Goal: L~1032 cm-2s-1
3.5s in Run I
4Chunhui Chen, University of Pennsylvania
The upgraded detectors
•New tracking: silicon and fibers in magnetic field•Upgraded muon system•Upgraded DAQ/trigger (displaced track soon)
•New silicon detector new drift chamber•Upgraded calorimeter, •Upgraded DAQ/trigger, esp. displaced-track trigger•New TOF PID system
5Chunhui Chen, University of Pennsylvania
Heavy Flavor Production X-Section
B cross section measured from Run Iat Tevatron is consistently higher than NLO QCD
Theoretical development still ongoing.Ex: fragmentation effect …….
Experimental Approaches:Experimental Approaches:More cross section measurement -- energy at 1.96TeV -- lower pT(B)
Study bb correlation
Measure charm production cross section
6Chunhui Chen, University of Pennsylvania
CDF Silicon Vertex Trigger (SVT)
Read out Silicon information and reconstruct tracks online at ~10’s KHz
Collect large amount and fully reconstructed B,D Hadrons:
Tracks from B, D displaced from primary vertex
Using track impact parameterInformation to make trigger decision
Primary Vertex
Secondary Vertex
BDecay LengthLxy
Lxy 450mPT(B) 5 GeV
d = impact parameter
OnlineTrackImpactParam.
35m33m resolbeam 48m
7Chunhui Chen, University of Pennsylvania
Prompt Charm Meson X-Section5.85.80.3pb0.3pb-1-1
Measure prompt charm meson production cross section
Data collected by SVT triggerfrom 2/2002-3/2002
Large and clean signalMeasurement not limited by statistics
8Chunhui Chen, University of Pennsylvania
Separate Prompt/Secondary Charm
Direct Charm Meson Fraction:Direct Charm Meson Fraction:DD00: f: fDD=86.5±0.4±3.5=86.5±0.4±3.5%%D*D*++: : ffDD=88.1±1.1±3.9%=88.1±1.1±3.9%DD++: f: fDD=89.1±0.4±2.8%=89.1±0.4±2.8%DD++
ss: f: fDD=77.3±4.0±3.4%=77.3±4.0±3.4%
Tail due to BD
Detector I.P. resolution Measured from data
Need to separate direct D and BD decay• Direct D point back to collision point I.P.=0• Secondary D not point back to PV I.P.0
Most reconstructed charm mesons are direct
Separate prompt and secondarySeparate prompt and secondarycharm based on theircharm based on their impact parameter distributionimpact parameter distribution..
9Chunhui Chen, University of Pennsylvania
Prompt Charm Meson X-Sections
Integral cross section: (|Y|Integral cross section: (|Y|1)1)
bpDbpDbpDbpD
Ts
T
T
T
22.005.075.0)1|Y|GeV,8,(7.01.03.4)1|Y|GeV,6,(8.01.02.5)1|Y|GeV,6,*(
5.12.03.13)1|Y|5.5GeV,,( 0
bpB T 6.06.3)1|Y|6GeV,,(
Determine trigger and reconstruction efficiency from data and MCMeasure charm meson pT spectrum
CDF I
Prompt charm cross section result submitted to PRL hep-ex/0307080
10Chunhui Chen, University of Pennsylvania
Differential Charm Meson X-Section
Calculation from M. Cacciari and P. Nason: Resummed perturbative QCD (FONLL)JHEP 0309,006 (2003)
CTEQ6M PDFMc=1.5GeV,
Fragmentation: ALEPH measurementRenorm. and fact. Scale: mT=(mc
2+pT2)1/2
Theory uncertainty: scale factor 0.5-2.0
D*+ also include calculation from B.A. Kniehl(private communication)
11Chunhui Chen, University of Pennsylvania
Comparison with Theory Ratio of the measured to the predicted cross section
Measured cross section higher : similar to B
I CDF XBpp
PRL89:122003,2002
Not incompatible with uncertaintiespT shape consistent for D mesons
12Chunhui Chen, University of Pennsylvania
Inclusive J/ Cross SectionCDF: Lower pT trigger
threshold for : pT()≥1.5GeV
J/ acceptance down to pT=039.739.7±2.3±2.3 pb pb-1-1
00ppTT(J/(J/))0.25GeV0.25GeV
D0: Larger y acceptance for
114 pb114 pb-1-1
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Inclusive J/ Cross Section
bsyststatJyXJpp )()(02.008.4)6.0|)/(|,/( 60.048.0
D0: 4.74 pbD0: 4.74 pb-1-1CDF: 39.7CDF: 39.7±2.3±2.3 pb pb-1-1
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Extract Contribution from b J/X
The J/ inclusive cross section includes contribution from•Direct production of J/•Decays from excited charmonium: (2S)J/+-, ……•Decays of b-hadrons: B J/X, ……
b hadrons have long lifetime, J/ decayed from b hadronsWill be displaced from primaryvertex
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Extract Contribution from b J/X
012.0010.0010.0097.0
GeV5.125.1
b
T
f
p006.0006.0005.0143.0
GeV5.50.5
b
T
fp
008.0007.0012.0279.0
GeV1210
b
T
fp
A unbinned maximum likelihood fit to the flight path of theJ/ in the r plane to extract the b fraction
16Chunhui Chen, University of Pennsylvania
b Hadron Differential Cross Section
)/(/)/()/,( JdpJBrXJHXHppd Tbb
But:We can not extract b fraction when bhadron is at restWe want total b hadron cross sectionWe want b cross section as a function of b hadron transverse momentum
Hb denote both b hadron and anti b hadron
|Y(Hb)|<0.6
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b Hadron Differential X-Section
Bottom decays transfer about 1.7GeV pT to the J/
We can probe b near pT=0 if we can measure b fraction
of J/ with pT below this value.
Unfold pT(Hb) from pT(J/) using MC
Iterate to obtain the correct pT spectrum
b-hadron X-section d/dpT(Hb)
Assume a b-hadron pT spectrum
b-hadron differential and total X-section
New b-hadron pT spectrum
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b Hadron Differential X-Section
)(/)/()/,( bTbb HdpJBrXJHXHppd
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Total b Quark Production X-Section
nb)(7.4)(5.05.24)/()/()6.0||,(
syststatJBrXJHBryXHppd bb
b)(8.3)(4.00.18)6.0||,( syststatyXbppd
b)(2.6)(6.04.29)0.1||,( syststatyXbppd
MC extract to high Y region
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b-jet X-Section
+ jet sample Using pT spectrum to fit the b and
non b content as a function of jet ET
D0: 4.8 pbD0: 4.8 pb-1-1
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Conclusion
• Large amount data collected by both CDF and D0 already surpass the run I statistics• New Charm, Bottom cross section results• Lots of analysis in progress:
J/, (2S) cross section and polarizationUpsilon cross section and polarizationUpdated b cross section ……
• Tevatron will contribute the knowledge of heavy flavor production• Stay tuned