B Production and Decay at DØ Brad Abbott University of Oklahoma BEACH 2004 June 28-July 3.
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B Production and Decay at DØ
Brad Abbott
University of Oklahoma
BEACH 2004
June 28-July 3
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B physics at DØ• Will be presenting latest results on:
– D**
– B**
– Bs
(1S) production
– X(3872)
• Keys to DØ B physics program– Muon system and trigger
– Silicon vertex detector and fiber tracker
L= 115 – 250 pb-1
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SMTSMT
SMT
Muon System and Tracker • New forward muon system with ||<2 and good shielding • 4-layer Silicon and 8 doublet-layer Fiber Trackers in 2 T
magnetic field
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Observation of B D** X
• D** are orbitally excited D meson states
• In heavy quark limit– Two narrow states (D-wave)
– Two broad states(S-wave)
• Search for narrow states via– D0
1(2420) D*+ -
– D*02(2460) D*+ -
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D0 sample
• D10 and D2*0 observed in
several experiments, most recently by BaBar/Belle in B- D**0 -
• DØ is studying D10 and
D2*0 in B semileptonic
decays
• Start with B D0 X (D0 K)
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D* sample
• Add a pion (charge correlated with the muon) with PT>0.18 GeV
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D**
• Measure invariant mass of D*- + system
• See merged D10(2420)
and D2*0 (2460)
Wrong sign combinations
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Interference effectsTwo interfering Breit-Wigner D** states with mass/width as measured by Belle (no resolution effects included)
Work in progress to extract separate amplitude for eachstate and relative phase of interference.
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Branching ratio• Take experimentally measured number of D1
0 and D2*0 : N(D1)+N(D2*)=523 40
• Measure branching ratio of B D**(narrow) X, normalizing to known branching ratio (B D*+ X)
• Br(B {D10,D2*0} X • Br({D1
0,D2*0} D*+ -) = 0.280 0.021(stat) ± 0.088 (sys) %
• Compare to LEP measurement of total D** Br (B D*+ X) = (0.48 0.10)%
• ~ half the rate through narrow states
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Future measurements
= 0.4-0.7 predicted by HQET
World average =0.4 ± 0.15
DØ can measure:• R• Br(B D1X )• Br(B D*2 X)• Interference effects• Helicity
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B**
• Heavy quark symmetry predicts 4 B*J states JP = 0+, 1+ , 1+ , 2+
• Parity and angular momentum require B*J to decay to B* or B
• B** provide a good test of heavy quark symmetry• Many properties of the B** unknown• Large B cross section at Tevatron allows for
precise measurements with large statistics
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B**
• Search for B**d B+ -
B+ J/ K+ • Allows one to charge
correlate the pion and the B to reduce combinatoric background
115 pb-1
PDG Average 5.698 0.008 GeV
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Additional Channels
• Are adding in more decays to increase statistics
• B**+ Bd
– Bd J/ K*
– Bd J/ KS
• With increased statistics should be able to resolve the narrow B** states.
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Bd,s
• Forbidden at
Tree Level in SM
BR(Bd l+l-) BR(Bs l+l-)
e (3.4 ± 2.3) 10-15 (8.0 ± 3.5) 10-14
(1.5 ± 0.9) 10-10 (3.4 ± 0.5) 10-9
(3.1 ± 1.9) 10-8 (7.4 ± 1.9) 10-7
Theoretical predictions
Experimental limits at 90% CL
BR(Bd l+l-) BR(Bs l+l-)
e < 5.9 10-6 < 5.4 10-5
< 1.5 10-7 < 5.8 10-7
< 2.5 % < 5.0%
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Bs in SUSY(Two Higgs-Doublet Model)
• BR depends only on charged Higgs mass and tan
• BR increases as tan4 (tan6) in 2HDM (MSSM)
• R parity violating models can give tree level contributions
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Dimuon Data sample
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Cut optimization
• Signal box is blinded
• Use a random grid search optimizing the ratio
Ba 2/
= reconstruction efficiency of signal MCB= expected background extrapolated from sidebandsa = number of sigmas corresponding to confidence level (set to 2 for this analysis, corresponding to ~ 95% CL
(Following proposal fromG. Punzi physics/0308063 Test of hypothesis and limits)
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Discriminating variables• Isolation of the muon pair
• Opening angle between momentum vector of pair and vector pointing from primary vertex to vertex
• Decay lengthBox not opened yet180 pb-1
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Expected upper limit
• Since box not opened, calculate expected upper limit
• Expected signal normalized to B+J/K+
• Expect 7.3 ± 1.8 background events in signal region
• Current expected limit using Feldman-Cousins:
Br(Bs ) < 1.0 10-6 @ 95% CL (stat + sys) Reoptimization still in progress.
Further improvements expected
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(1S) Production• Measuring the (1S) production cross section
provides a test of our understanding of the production mechanism of heavy quarks
• Extend measurement of (1S) cross section to rapidities of 1.8
• Color octet model predicts an increase in transverse polarization with increasing PT
(Measurements so far are inconclusive)
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Analysis• Measure the (1S) cross-section as a function
of PT in three rapidity regions
0< |y| <0.6 0.6<|y|<1.2 1.2<|y|<1.8
Signal fit to 3 Gaussians (1S), (2S), (3S) Background: 3rd order polynomial
m((2/3S) = m((1S) + mpdg((2/3S)- (1S))((2/3S) = ((1S) + m (2/3S)/m((1S))* ((1S))
5 parameters: m, (1S)Number of (1S), (2S), (3S)
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Normalized cross section
159 pb-1
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Normalized Cross section
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Normalized cross section
• Normalized cross section shows little dependence on rapidity
• Good agreement with published results
• Absolute cross section nearly ready
• Next: Polarization measurement
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X(3872) J/ + -
• First observed by Belle B+ K+ X(3872) decays• Signal confirmed by CDF, DØ and BaBar• Nature of X(3872) unknown• Theories include:
– Another charmonium state– D D* molecular state
• Since the X(3872) lies very close in mass to the Ψ(2S) charmonium state, and has a common decay mode (X J/, we compare production and decay properties of these two states through this decay mode
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X(3872)
M=774.9 ± 3.1 (stat) 3.0 (sys) MeV
522 ± 100 X candidates
Significance = 5.2
230 pb-1
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• Separate data into different regions
• Compare (2S) yield to X yield in different regions
• Study production and decay characteristics
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• a) PT > 15 GeV• b) |y| <1• c) |cos()| < 0.4• d) decay length < 0.01 cm• e) isolation=1• f) |cos ()| < 0.4
(: boost one of the pions and the X(3872) into dipion rest frame.
is the angle between them)
• To within uncertainties, production of X(3872) found to be consistent with the production of the Y(2S) I.e producted both directy and via B decays,
• Future: look for radiative decays and charge analog of X
Compare2||))3872((
1||))3872((
yXN
yXN
2||))2((
1||))2((
ySN
ySN
Submitted to PRL: hep-ex/0405004
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Summary
• Observation of B D** X
• Observation of B**
• Sensitivity to Bs
• Normalized Upsilon(1S) Cross section
• Observation of X(3872)
• Many new analyses on the way