measurements of the masses, mixing, and lifetimes, of b hadrons at the tevatron
DESCRIPTION
Measurements of the Masses, Mixing, and Lifetimes, of B Hadrons at the Tevatron. Mike Strauss The University of Oklahoma The Oklahoma Center for High Energy Physics for the CDF and D Ø Collaborations. Outline. B Physics at the Tevatron B Resonances B 0 oscillations B Lifetimes - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Measurements of the Masses, Mixing, and Lifetimes, of B Hadrons at the Tevatron](https://reader036.vdocuments.mx/reader036/viewer/2022062422/56812e95550346895d943a21/html5/thumbnails/1.jpg)
Mike Strauss
The University of OklahomaThe Oklahoma Center for High Energy Physics
for the CDF and DØ Collaborations
Measurements of the Masses, Mixing, and Lifetimes, of B
Hadrons at the Tevatron
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Mike Strauss The University of Oklahoma 2
• B Physics at the Tevatron
• B Resonances
• B0 oscillations• B Lifetimes
• Exclusive Decays• Lifetime Ratios and Differences
Outline
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Mike Strauss The University of Oklahoma 3
Tevatron Luminosity
• ~0.5 fb–1 delivered this year
• Detectors collect data at typically 85% efficiency
• These analyses use 150–350 pb–1
• About 150 pb–1 of data has been recorded and is currently being analyzed
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Mike Strauss The University of Oklahoma 4
Why B Physics?
Understanding the structure of flavour dynamics is crucial
3 families, handedness, mixing angles, masses, …
any unified theory will have to account for it Weak decays, especially mixing, CP violating and rare decays,
provide insight into short-distance physics Short distance phenomena are sensitive to beyond-SM effects CKM matrix determines the charged weak decays of quarks,
tree level diagrams, one-loop transitions… Lifetime measurements probe QCD at large distances and
give information on form factors and quark models
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Mike Strauss The University of Oklahoma 5
B Physics at the Tevatron
Large production cross sectionsAll B Hadrons produced (Best Bs and b)
Larger inelastic cross section (S/B 10-3)Specialized Triggers:
Single lepton triggersDilepton triggers (e.g. J/+) L1 Track triggers L2 displaced track trigger for CDF
(ppbb) 150 b at 2 TeV
(e+ebb) 7 nb at Z0
(e+ebb) 1 nb at (4S)
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Mike Strauss The University of Oklahoma 6
Silicon vertex tracker, Axial solenoid, Central tracking,High rate trigger/DAQ, Calorimeter, Muon system
Excellent muon ID; || < 2Excellent calorimetry Tracking acceptance || < 2-3L3 trigger on impact parameter
Detectors
L2 trigger on displaced vertexesLow p particle ID (TOF and dE/dx)Excellent mass resolution
CDF DØ
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Mike Strauss The University of Oklahoma 7
DØ Tracker
= - ln (tan(/2))
SMT
SMT + CFTmax = 1.65
SMT regionmax = 2.5
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Mike Strauss The University of Oklahoma 8
Silicon Microstrip Tracker (SMT)
6 Barrels
12 F-disks 4 H-disks
Barrels F-disks H-disks
Dble+sngle sided
Double
sided
Single
sided
Stereo angle 0o, 2o, 90o ±15o ±7.5o
Channels ~400K ~250K ~150K
Inner radius 2.7 cm 2.6 cm 9.5 cm
Outer radius 9.4 cm 10.5 cm 26 cm
Multi-layer barrel cross-section
3m2 of silicon
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Mike Strauss The University of Oklahoma 9
Tracking Performance
pT spectrum of soft pion candidate in D*D0
Tracks are reconstructedstarting from pT = 180 MeV
Muon in J/ events
Coverage of Muon system is matched by L3/offline tracking
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Mike Strauss The University of Oklahoma 10
SMT Resolution and dE/dx
Impact Parameter Resolution
(DCA) 53 m @ PT = 1 GeVand 15 m @ higher PT
Can provide: K/ separation for Ptot< 400 MeV p/ separation for Ptot<700 MeV
NOT yet used for PID
SMT dE/dx
MC Data
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Mike Strauss The University of Oklahoma 11
Belle’s Discovery of X(3872)
X J/
MX = 3872.0 0.6 (stat) 0.5 (sys)
• No signal in Xc1 decay• Mass doesn’t fit easily into
charm spectroscopy models• Near D0 D*0 threshold• Charmonium? A loosely
bound meson state?
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Mike Strauss The University of Oklahoma 12
730 730 90 candidates 90 candidates ~~12 12 effect effect
MXX = 3871.3 = 3871.3 0.7 (stat) 0.7 (stat)
0.4 (sys) MeV/c0.4 (sys) MeV/c22
X(3872)
CDF and DØ have confirmed Belle’s discovery of the X(3872)
M = 774.9 3.1(stat) 3.0 (sys) MeV/c2
M +M(J/) = 3871.8 4.3 MeV/c2
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Mike Strauss The University of Oklahoma 13
Long Lifetime fraction of X(3872)
Is the X charmonium, or something else?
(2S): 28.3±1.0(stat) ±0.7(syst)%
(2S): X(3872):
X(3872): 16.1±4.9(stat) ±2.0(syst)%
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Mike Strauss The University of Oklahoma 14
X(3872) – (2S) comparison
Is the X charmonium, or something else?
pT>
15 G
eV/c
|y|<
1
cos
<0.
4
dl<
0.1
Iso
=1
cos
<0.
4
DØ multi-parameter comparison
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Mike Strauss The University of Oklahoma 15
First Observation of BS
BR(Bs) = 1.4 ± 0.6(stat) ± 0.2(syst) ± 0.5(BR)×10-5
• Charmless BVV decay not yet observed• Dominated by penguin contributions• Cuts optimized on Bs J/
• BR error on this decay is dominant systematic uncertainty
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Mike Strauss The University of Oklahoma 16
B h±h+ Fractions
• h, h = , K
• Motivation is to construct many charmless two body decays for CP studies
• Hadronic B trigger using SVT
• dE/dx and used for PID
• Signal reconstructed with vertex constrained fit
• Fractions measured with unbinned likelihood fit using MID1, ID2.
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Mike Strauss The University of Oklahoma 17
PID using = (1-p1/p2)q1
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Mike Strauss The University of Oklahoma 18
B h±h+ Fractions
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Mike Strauss The University of Oklahoma 19
B h±h+ Fractions
syststat
KBBR
BBR
d
d 05.006.024.0
01.008.004.0
00
00
CP
KBNKBN
KBNKBNA
dd
dd
Assuming Bs K+K- is 100% CP even, s/s = 0.12±0.06, s=d,
syststat
KKBBRf
BBRf
ss
dd 07.012.048.0
syststat
KBBRf
KKBBRf
dd
sd 07.008.050.0
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Mike Strauss The University of Oklahoma 20
Search for B0(s,d)+–
SM BR(Bs0+-)(3.40.5)×10-9; BR(Bd
0+-)(1.50.9)×10-10
BR(Bs0+–): < 7.5×10-7
at 95% CL (CDF)
BR(Bd0+–): < 1.9×10-7 at 95% CL
Expected BG: 1.05 ± 0.30
BR(Bs0+–): < 4.2×10-7
at 95% CL (DØ)
Expected BG: 3.7 ± 1.1 events
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Mike Strauss The University of Oklahoma 21
Observation of B**
• B Spectroscopy: • B (Jp = 0–)
• B* (Jp = 1–) – decays to Bγ (100%)
• ΔM = M(B*) – M(B) = 46 MeV/c2
• The B** consists of four separate states• 2 narrow states B1 (1+) and B2* (2+), decay via D-wave;
• 2 wide states B0* (0+) and B1' (1+), decay via S-wave;
• None of these individual states are well established
• Decay channels used: • Bd**B±+; B**+Bd+; B**B* B (γ)
• B J/ K±; Bd J/ K*0; Bd J/ K0s
–
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Mike Strauss The University of Oklahoma 22
Distinct Narrow B** States
M(B1) = 5724 ± 4 ± 7 MeV /c2
M(B2*) – M(B1) = 23.6 ± 7.7 ± 3.9 MeV/c2
350 pb–1
• The first direct measurement of masses and splitting between B2
* and B1
• M(B*) = M(B) + 46 MeV
()
B1B() B2*B () B2*B
Sum of 3 decay modes
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Mike Strauss The University of Oklahoma 23
Observation of BC J/X
Combined unbinned likelihood fit made to mass and lifetime
95±12±11 candidatesMBc) = 5.95 ± 0.34 GeV/c2
-0.13+0.14
Bc) = 0.448 ± 0.121 ps-0.096+0.123
First 5 measurement
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Mike Strauss The University of Oklahoma 24
Bs Ds– lX
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Mike Strauss The University of Oklahoma 25
Fully Reconstructed Bs
Ds
D*s
and
others
Useful for Bs Mixing
CDF “golden channels”:Bs Ds Ds , K*K, Bs Ds
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Mike Strauss The University of Oklahoma 26
Bd Mixing
• In SM Bd mixing is explained by box diagrams
• Constrains Vtd CKM matrix element
• Mixing frequency md has been measured with high precision at e+e– B factories (0.502 0.007 ps-1)
md measurement at Hadron Colliders
• Confirms initial state flavor tagging for later use in Bs and ms measurements
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Mike Strauss The University of Oklahoma 27
B Oscillation Variables
Opposite side Same side
b–1/3 Q<0
b –
BsK+
(CDF)
b K–
(CDF)
b B0 –
b B– +
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Mike Strauss The University of Oklahoma 28
Final State Ambiguities in SS Tag
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Mike Strauss The University of Oklahoma 29
md = 0.443 0.052(stat) 0.030(sc) 0.012(syst) ps-1
B0 Mixing with SS Tag
A = (NRS – NWS )/(NRS + NWS )NRS:N(B0+)NWS:N(B0–)
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Mike Strauss The University of Oklahoma 30
md = 0.488 0.066(stat) 0.044(syst) ps-
1
B0 Mixing with SS Tag
BD*X, D*D0
Preliminary
Visible Proper Decay Length:xM = Lxy MB c /pT
D
Tagging purity: 55.8 ± 0.7 ± 0.8 %
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Mike Strauss The University of Oklahoma 31
md = 0.506 0.055(stat) 0.049(syst) ps-
1
Decay Mode:•BD*X, D*D0
Tagging:•muon pT > 2.5 GeV/c•cos B < 0.5•Tagging efficiency:
4.8 ± 0.2 %•Tagging purity:
73.0 ± 2.1 % •Fit procedure
• Binned 2 fit
B0 Mixing with OS Tag
Preliminary
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Mike Strauss The University of Oklahoma 32
B0 Mixing with Combined Tag
• Uses Bl D(*)
• Lepton plus SVT trigger• Combines:
• Same Side Pion Tagging• Opposite Side Muon Tagging• Opposite Side Jet Charge Tagging
• With and without vertex tagging• Ten subsamples
• Tagged with SST• Tagged with OST (3 samples)• Tagged with SST and OST that agree (3 samples)• Tagged with SST and OST that don’t agree (3 sample)
• Tagging priority is determined
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Mike Strauss The University of Oklahoma 33
Efficiency and Dilution
md = 0.536 0.037(stat) 0.009 (sc) 0.015(syst) ps-1
Preliminary
Channel (%) D(%) D2(%)
Only SST 25.89 0.17 12.45 1.46 0.401 0.028Only SMT 1.17 0.04 29.13 2.26 0.099 0.016
SST and SMT (agree) 1.34 0.04 40.12 2.42 0.216 0.027SST and SMT (disagree) 1.22 0.04 17.31 2.79 0.037 0.012
Only JQT-SecVtx 2.73 0.06 20.11 1.57 0.110 0.017SST and JQT-SecVtx (agree) 3.38 0.07 31.76 1.99 0.341 0.043
SST and JQT-SecVtx (disagree) 3.19 0.07 7.86 2.19 0.020 0.010
Only JQT-High Pt 16.13 0.14 4.85 0.65 0.038 0.010
SST and JQT-High Pt (agree) 15.70 0.14 17.20 1.57 0.464 0.084
SST and JQT-High Pt (disagree) 16.08 0.14 7.65 1.61 0.094 0.040Total 86.86 0.33 1.820 0.114
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Mike Strauss The University of Oklahoma 34
B0 Mixing with Combined Tag
Kmass - Kmass
BD0+XB0D*±+X
Dominated by B+ events
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Mike Strauss The University of Oklahoma 35
B0 Mixing with Combined Tag
•Soft muon tag•If not tagged by muon:
•Opposite side jet charge•Soft Pion
D0 “asymmetry”
Soft muon tag
Jet charge and pion
md = 0.456 0.034(stat) 0.025(syst) ps-1
Preliminary
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Mike Strauss The University of Oklahoma 36
• Naive quark spectator model: a 1 3 decay process common to all B hadrons.
• (NLO) QCD Heavy Quark Expansion predicts deviations in rough agreement with data
• Experimental and theoretical uncertainties are comparable
• Lifetime differences probe the HQE to 3rd order in QCD / mb
• Goal: measure the ratios accurately
B Hadron Lifetimes
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Mike Strauss The University of Oklahoma 37
B Hadron Lifetime Ratios
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Mike Strauss The University of Oklahoma 38
b Lifetime
New Measurement from DØ
bJ/ 0
DØ Preliminary
b) = 1.221 ± 0.043 ps-0.179+0.217
(b)/(Bd0) = 0.874 ± 0.028-0.142
+0.169
CDF Preliminary from 2003:
b) = 1.25 ± 0.26 ± 0.10 ps
DØ
DØ
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Mike Strauss The University of Oklahoma 39
Bs Lifetime using BsJ/
Improvements since 2003: • Selection minimizes
stat syst • 12 parameter maximum
likelihood fit • 240 pb-1
CDF DØ
DØ analysis is similar to this CDF “improved” analysis
250 pb-1 Preliminary
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Mike Strauss The University of Oklahoma 40
Bs Lifetime using BsJ/
Bs) = 1.369±0.100 ps-0.010+0.008
CDF DØ
Bs) = 1.444 ±0.020 ps-0.090+0.098
Uses one exponential decay in the fit
250 pb-1
Preliminary
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Mike Strauss The University of Oklahoma 41
Bd Lifetimes Using Bd J/ Ks*0
Bd0) = 1.473 ±0.023 ps
250 pb-1
-0.050+0.052
Bs)/B0) = 0.980 ±0.003-0.070+0.075
Preliminary
CDF DØ
B0) = 1.539±0.051±0.008 ps
Bs)/B0) = 0.890±0.072
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Mike Strauss The University of Oklahoma 42
B+ Lifetime Using B J/ K+
B+) = 1.662±0.033±0.008 ps
B+)/B0) = 1.080±0.042 Most systematic uncertainties cancel in the ratio
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Mike Strauss The University of Oklahoma 43
Lifetime Ratio (B+)/(B0)
Novel Analysis Technique using B Dc(*)X
• Directly measure ratio instead of individual lifetimes• Split D0 Ksample:
• D*+ (with slow mainly from B0
• D0 mainly from B+
B0
PV ν
D0
μ+ K+
π-
μD0
π-
D*-
86% B0
12% B+ 2% BS
16% B02% BS
82% B+
D*+
D0
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Mike Strauss The University of Oklahoma 44
D0 and D*+ Candidates
109k inclusive B D0 candidates
25k Bμ ν D* candidates
Dominated by B+ decays Dominated by B0 decays
+π±
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Mike Strauss The University of Oklahoma 45
Lifetime Ratio (B+)/(B0)
• Measure N(D*+)/N(D0) in bins of VPDL
• In both cases fit D0 signal to extract N
• Use slow pion only to distinguish B0 from B+ (not in vertexing, K-factors etc., to avoid lifetime bias)
(B+)/(B0) = 1.093 ± 0.021(stat) ± 0.022(syst)
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Mike Strauss The University of Oklahoma 46
Lifetime Ratio (B+)/(B0)
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Mike Strauss The University of Oklahoma 47
B Decay Angular Amplitudes
• Uses Bs J/ ; Uses Bd J/ K*0
• Allows measurement of many parameters including polarization amplitudes and s = 1/L – 1/H
ssss
Ls
ssssHs
BBBqBpB
BBBqBpB
2
12
1CP odd
CP even
L
sHss
Ls
Hss
BBB
BBB
2
12
1Initial particle
orantiparticle
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Mike Strauss The University of Oklahoma 48
Decay Modes
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Mike Strauss The University of Oklahoma 49
Transversity Angles
• The J/rest frame• KK defines (x,y) plane
• K+(K) defines +y direction• polar & azimuthal
angles of +
• helicity angle of (K*)
Extract polarization amplitudes:A0: LongitudinalA, A: Transverse
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Mike Strauss The University of Oklahoma 50
Angular Projections and fit for Bs
Decay Angular Distribution:
6
1
4
iiii ftgA
dtd
Pd
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Mike Strauss The University of Oklahoma 51
Decay Angular Distributions
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Mike Strauss The University of Oklahoma 52
Bd Amplitudes vs BaBar/Belle
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Mike Strauss The University of Oklahoma 53
Bs and Bd Amplitudes
For Bd0
A0 = 0.750 ± 0.017 ± 0.012A|| = (0.473 ± 0.034 ± 0.006) ×
ei(2.86 ± 0.22 ± 0.04) |A┴| = (0.482 ± 0.104 ± 0.014) ×
ei(0.15 ± 0.15 ± 0.04)
For Bs0
A0 = 0.784 ± 0.039 ± 0.007A|| = (0.510 ± 0.082 ± 0.013)×
ei(1.94 ± 0.36 ± 0.03)
|A┴ | = 0.354 ± 0.098 ± 0.003
DØ results coming soon
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Mike Strauss The University of Oklahoma 54
Bs Mass and Lifetime Projections
L = 1.05 ± 0.02 ps
= 0.47 ± 0.01 ps–1
= 0.65 ± 0.01
+0.16–0.13
H = 2.07 ± 0.03 ps+0.58–0.46
+0.19–0.24
+0.25–0.33
Unconstrained fit
ms= 125 ps–1
Using SM and constrained fit:+65–55
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Mike Strauss The University of Oklahoma 55
Conclusions
• The Tevatron is working great, producing many B hadrons.
• We now have about 500 pb-1
• DØ and CDF are measuring many properties of B hadrons that nicely complement those measured at “B factories”
• More exciting results are expected in the future
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Mike Strauss The University of Oklahoma 56
CDF Sensitivity Estimate
SM BR(Bs0+-)(3.40.5)×10-9;
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Mike Strauss The University of Oklahoma 57
Lambda Lifetimes
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Mike Strauss The University of Oklahoma 58
Constraining Unitarity Triangle
From Colin Gay, FNAL Wine and Cheese, July 16, 2004