heavy flavor production at the tevatron jennifer pursley the johns hopkins university on behalf of...
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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