Heavy Flavor Production at the Tevatron Jennifer Pursley The Johns Hopkins University on behalf of...
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Transcript of Heavy Flavor Production at the Tevatron Jennifer Pursley The Johns Hopkins University on behalf of...
Heavy Flavor Production at the
TevatronJennifer Pursley
The Johns Hopkins Universityon behalf of the CDF and D0 Collaborations
Beauty 2006 - University of Oxford, UK September 25-29, 2006
J. Pursley, Beauty 06 2
BRAND NEW RESULT! b(*)± search
B hadron relative fragmentation fractions
B + cross section using B + → J/ K+
(1S) production cross section b→ J/J/ search and production
upper limit
Focus of this talk
See many other CDF and D0 talks for more interesting b and c results from the Tevatron!
J. Pursley, Beauty 06 3
Triggers and Data Samples Analyses use between
160 pb-1 and 1.1 fb-1 of data
Trigger paths used by these analyses: Di-Muon (J/) [CDF + D0] Displaced track + lepton
(e, ) [CDF] 2 track trigger [CDF]
Skipping all detector and Tevatron review!
D0
J. Pursley, Beauty 06 4
b Motivation b only established B baryon Enough statistics at Tevatron to
probe other heavy baryons Next accessible baryons:
b: b{qq}, q = u,d; JP = SQ + sqq
= 3/2+(b*)
= 1/2+ (b) HQET extensively tested for Qq
systems; interesting to check predictions for Qqq systems
Baryon spectroscopy also tests Lattice QCD and potential quark models
J. Pursley, Beauty 06 5
Reconstructing b With 1.1 fb-1, world’s
largest sample of b:
~3000 Use 2 track trigger to
reconstruct:
b decays at primary vertex
Combine b with a prompt
track to make a b candidate
b Mass Plot
J. Pursley, Beauty 06 6
b Search Methodology Separate b
- and b+:
(+ c.c.)
(+ c.c.)
Search for resonances in mass difference: Q = m(b) - m(b) – m
Use reconstructed b mass →
remove b mass systematic
error Unbiased optimization
Optimize b cuts with b signal
region blinded: 30 <
Q < 100 MeV/c2
b backgrounds: b Hadronization + Underlying
Event – Dominant! B meson Hadronization Combinatorial Bkg
Fix background contributions from data or PYTHIA Monte Carlo
J. Pursley, Beauty 06 7
b Observation Observe signals consistent with
lowest lying charged b states With unbinned likelihood fit,
measure events
And mass difference values:
J. Pursley, Beauty 06 8
b Fragmentation Fractions Measure flavor dependence
of fragmentation process for b quarks (non-perturbative)
Reconstruct semi-leptonic decays of B 0, B -, Bs
0, and b0
in 360 pb-1 of data ℓ –D 0, ℓ –D +, ℓ –D *+, ℓ – Ds
+, ℓ – c+
Use Particle ID likelihood cuts (important for c
+ signal) Determine sample comp.
from charm hadron BRs Indirect semi-lep decays and
excited B hadrons explicitly included
J. Pursley, Beauty 06 9
Fragmentation Fraction Results
fu, fd, fs, f = probability to result in B -, B 0, Bs0, b
0
Use B hadron transverse momentum (pT) threshold of 7 GeV/c
Agrees with world average of fragmentation fraction of B - relative to B 0
fb differs from LEP by ~2.2
J. Pursley, Beauty 06 10
B+ Production Cross Section
8197 ± 239 B ± mesons total Divide in 5 bins of pT and
measure differential cross section as a function of pT, in units of nb/GeV/c
Integrated cross section for pT ≥ 25 GeV/c = 21.7 ± 3.7 nb
Using 740 pb-1 of data, reconstruct B+ → J/ K+
To be submitted to PRD very soon…
J. Pursley, Beauty 06 11
Total B+ Production Cross Section
Combined stat & syst errors
Agrees with previous Tevatron measurements 1.8 TeV cross section
increased by 10% Also within the range of
FONLL theoretical predictions with fu = 0.389 CTEQ6M fits to parton
distribution functions
J. Pursley, Beauty 06 12
(1S) Production With 160 pb-1, reconstruct
(1S) → +-
Unresolved (2S) and (3S) signals
Previous studies at CDF limited to at √s = 1.8 TeV
Divide into three rapidity regions:
J. Pursley, Beauty 06 13
(1S) Diff. Cross Section
Little variation between rapidity regions
Also consistent with previous CDF measurement
Allows a more precise determination of parameters of bottomonium production models
Phys. Rev. Lett. {94},232001 (2005)
J. Pursley, Beauty 06 14
Search for b → J/ J/ Spin-singlet bb bound
state b yet to be observed
(pp → b X) ~ b at Tevatron energy scale
Look for b decay into
J/ J/ in 1.1 fb-1
Large uncertainty in expected BR
Expect between 0.2 and 20 events with both J/ decaying to + -
Reconstruct as 3 + track
J. Pursley, Beauty 06 15
b → J/ J/ Results Expected 3.6 bkg events; observe 3 events Set upper limit for production cross section:
J. Pursley, Beauty 06 16
First observation of lowest lying charged b states! With m(b) = 5619.7 ± 1.2 (stat) ± 1.2 (syst) MeV/c2,
Precision measurements of b production properties b fragmentation fractions (1S) and B + production cross sections Upper limit on b → J/ J/ production
More results on the way…
Summary
J. Pursley, Beauty 06 18
b SystematicsParameterParameter TrackingTracking b b
Sample Sample CompComp..
b b
Ha+UEHa+UE
Norm.Norm.
b b
Ha+UE Ha+UE ShapeShape
b b Ha+UE Ha+UE
ReweightReweightDet. Det. Reso.Reso.
b b Nat. Nat.
WidthWidthTotalTotal
bb-- Q Q
(Mev/c(Mev/c22))0.06
-0.06
0.00
-0.03
0.009
-0.002
0.000
-0.011
0.04
-0.0004
0.0
-0.011
0.009
-0.005
0.07
-0.07
bb+ + Q Q
(Mev/c(Mev/c22))0.06
-0.06
0.03
0.0
0.013
-0.013
0.013
0.0
0.0
-0.11
0.0
-0.014
0.01
-0.02
0.07
-0.13
bb**--bb
Q Q
(Mev/c(Mev/c22))0.06
-0.06
0.05
0.0
0.14
-0.13
0.04
0.0
0.32
0.0
0.02
0.0
0.07
-0.07
0.37
-0.16
bb-- events events 0.0
0.0
0.7
0.0
2.2
-2.2
0.3
0.0
7.4
0.0
0.3
0.0
3.4
-3.4
8.5
-4.0
bb++ events events 0.0
0.0
3.3
0.0
2.1
-2.1
1.2
0.0
2.3
-1.8
0.3
0.0
1.8
-2.0
5.0
-3.4
bb*-*- events events 0.0
0.0
0.4
0.0
4.8
-4.7
0.3
0.0
14.7
0.0
0.1
0.0
1.7
-1.7
15.6
-5.0
bb*+*+ events events 0.0
0.0
7.3
0.0
4.8
-4.8
2.8
0.0
4.6
-2.9
0.2
0.0
0.8
-0.8
10.3
-5.7
J. Pursley, Beauty 06 19
b Fit Likelihood Ratios
HypothesisHypothesis (-ln £) 1/LR
““NULL” vs. “4 NULL” vs. “4 Peak”Peak”
44.7 2.6e19
““2 Peak” vs. “4 2 Peak” vs. “4 Peak”Peak”
14.3 1.6e6
No No bb- - PeakPeak 10.4 3.3e4
No No bb+ + PeakPeak 1.1 3
No No bb*- *- PeakPeak 10.1 2.4e4
No No bb*+ *+ PeakPeak 9.8 1.8e4