Measurements of the Masses, Mixing, and Lifetimes, of B Hadrons at the Tevatron

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

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


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


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


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)


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


DØ Tracker

= - ln (tan(/2))

SMT

SMT + CFTmax = 1.65

SMT regionmax = 2.5


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


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


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


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?


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


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)%


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


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


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.


PID using = (1-p1/p2)q1


B h±h+ Fractions


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


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


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

–


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


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


Bs Ds– lX


Fully Reconstructed Bs

Ds

D*s

and

others

Useful for Bs Mixing

CDF “golden channels”:Bs Ds Ds , K*K, Bs Ds


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


B Oscillation Variables

Opposite side Same side

b–1/3 Q<0

b –

BsK+

(CDF)

b K–

(CDF)

b B0 –

b B– +


Final State Ambiguities in SS Tag


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–)


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 %


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


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


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



Kmass - Kmass

BD0+XB0D*±+X

Dominated by B+ events



•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


• 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


B Hadron Lifetime Ratios


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


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


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


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


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


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


D0 and D*+ Candidates

109k inclusive B D0 candidates

25k Bμ ν D* candidates

Dominated by B+ decays Dominated by B0 decays

+π±



• 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)




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


Decay Modes


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


Angular Projections and fit for Bs

Decay Angular Distribution:

6

1

4

iiii ftgA

dtd

Pd


Decay Angular Distributions


Bd Amplitudes vs BaBar/Belle


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


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


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


CDF Sensitivity Estimate

SM BR(Bs0+-)(3.40.5)×10-9;


Lambda Lifetimes


Constraining Unitarity Triangle

From Colin Gay, FNAL Wine and Cheese, July 16, 2004

Documents

Measurements of the Masses, Mixing, and Lifetimes, of B Hadrons at the Tevatron