Heavy B Hadrons at Tevatron
Andrei Nomerotski (Fermilab)
D
Tevatron
Main Injector
and Recycler
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
1
Introduction
 Tevatron produces B hadrons inaccessible at Bfactories

Previous results mostly from LEP and Run I Tevatron
 Cross sections are large but so are the backgrounds
 (bb) 100b at 2 TeV ((bb)  1nb at B factories)

Mostly soft Pt processes : Triggers are very important
 In Run II, Tevatron has two experiments doing Bphysics : CDF and DZero


Take data the third year
Both had major upgrades for Run II

With magnetic field and Tracker DZero is much better suited
for B-physics than before
 With 0.5 fb-1 per experiment on tape Tevatron
has world largest samples of heavy B hadrons
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
2
DZero Detector
 Excellent coverage of Tracking and Muon Systems
 2 T Solenoid, polarity inversed weekly
 Quiet Muon Trigger with muon Pt measurement at Level1 by
toroids
 Fine segmentation Calorimeter and Preshower
SMT H-disks
FPCP2004, Daegu
SMT F-disks SMT barrels
Andrei Nomerotski (Fermilab)
3
CDF Detector
 Large Tracking volume in
magnetic field – excellent
mass resolution
 Particle ID capabilities :
TOF, dE/dx in drift
chamber
 Large bandwidth (50
kHz) Level1 Trigger and
Displaced Track Silicon
Trigger at Level2

Access to purely
hadronic B samples
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
4
Datasets
 Tevatron performance progressed very well in 2004
 0.5 fb-1 per experiment by September 2004
 Typical analyses use ½ of total luminosity
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
5
Will talk about
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Bs and Lb Mass Measurements at CDF
Observation of narrow B** mesons at DZero
Observation of Bc at DZero
Branching Fractions of hadronic modes Bs and Lb
(CDF)
Semileptonic samples of Bs and Lb (DZero)
Bs oscillations (DZero)
Bs and Lb lifetimes (DZero/CDF)
Summary
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
6
Bs and Lb Masses (1)
 Taking advantage of good mass resolution CDF
greatly improved mass accuracy for Bs and Lb
 Possible after careful calibration of the mass scale
of the tracker



Material
Field
Track errors
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
7
Bs and Lb Masses (2)
 World’s best single measurements
 In agreement with previous results
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
8
B** Spectroscopy : Theory
 B** are orbitally (L=1) exited states of B meson
 In general there are two wide states and two
narrow states


Narrow states decay through D-wave
Wide states decay through S-wave
 Properties of B** are very similar to D** mesons
For charm mesons, M(D*)-M(D) ~ 140-145 MeV
 For bottom, M(B*)-M(B) ~ 46 MeV
Theory: Splitting within a doublet has 1/m_Q corrections
 For non-strange charm, M(D**)-M(D) ~550-600 MeV
Expect similar behavior for B mesons
 M( D*2)-M(D1) ~ 32-37 MeV
Expect this to be ~ 10-15 MeV for M(B*2)-M(B1)

FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
9
DZero : D** in Semileptonic B Decays
Observed merged D10(2420) and D2*0(2460)
wrong-sign combinations
D*- + mass
Preliminary result on product branching ratio
Br(B  {D10,D2*0}   X)  Br({D10,D2*0}  D*+ -) = 0.280  0.021 (stat)  0.088 (syst) %
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
10
B** Spectroscopy : Experiment
 B** have been observed before at LEP and
CDF in Run I but the narrow states haven’t
been resolved
Experiment
B reconstruction
BJ mass (MeV)
BJ width
ALEPH
exclusive
5695±18
53±16
CDF
(μD)+π
5710±20
-----
DELPHI
inclusive B + π
5732±21
145±28
OPAL
inclusive B + π
5681±11
116±24
 DZero observed B** in B+ modes using
exclusive B decay channels
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
11
DZero : B** analysis (1)
2826±93
7217±127
L = 350 pb-1
Used exclusive B
meson samples with
J/psi in final state
624±41
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
12
DZero : B** analysis (2)
 Add charged pion coming from the Primary Vertex to
exclusively reconstructed B
 Since ΔM between B**+ and B**0 is expected to be
small compared to resolution all channels are combined
 Dominant decay modes



B*2  B  or B*
B1  B*
B*  B g
 Since photon is not reconstructed two narrow B**
states produce three peaks in ΔM
 In addition there are wide states which cannot be
distinguished from non-resonant background
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
13
First Observation of Separated States
From fit:
N = All B**
536±114
events
~7σ signif.
273±59 events
B1  B  ; B  Bg
*
*
Interpreting the peaks
*
B

B

2
as
*
*
*
B2  B  ; B  Bg
FPCP2004, Daegu
131±30 events
Andrei Nomerotski (Fermilab)
14
DZero : B** analysis (4)
 Fitting DM distribution


Three relativistic Breit-Wigner functions convoluted with
Gaussian resolution
Theory motivated assumptions : G1 = G2 and equal Br for
two B*2 decay modes
 Results
M(B1)
= 5724 ± 4(stat) ± 7(syst) MeV
M(B*2-B1) = 23.6 ± 7.7(stat) ± 3.9(syst) MeV
G
f1
= 23 ± 12(stat) ± 9(syst) MeV
= 0.51 ± 0.11(stat) ± 0.21(syst)
f1 is relative yield of B1 meson

Systematic errors are dominated by fit assumptions and for G by
uncertainty of mass resolution
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
15
DZero : B** analysis (5)
 Consistency checks:
 Separate fits for neutral
and charged B
Neutral B**

No signal if charged pion is
not coming from Primary
Vertex
Charged B**
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
16
DZero: Bc Meson (1)
 Last of ground state mesons
to be definitively observed
 Theory


Lifetime 0.3 - 0.5 ps
Mass 6.4 ± 0.3 GeV
 Only previous evidence : CDF
Run I result
20.4+6.2
signal
- 5.5
mass 6.4 ± 0.39 ± 0.13 GeV
t=
+0.18
0.46- 0.16
FPCP2004, Daegu
0.03 ps
Andrei Nomerotski (Fermilab)
17
DZero: Bc Meson (2)
 Use tri-muon final state

J/y and tight third  form a
good vertex
 Select 231 J/y  X candidates
 Bc is not fully reconstructed 
backgrounds are very important


Bkg with fake muon estimated with
J/y+track data control sample
separated into prompt and nonPV
prompt components
bb/cc backgrounds are small due to
vertex requirement

-
+
+
Bc+
 Include contributions to signal
from


Feed-down from Bc  y(2S)  0 X
Bc  J/ y  0 X
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
18
Dzero : Bc Meson (3)
 Plot invariant mass of
three muons


Not exclusive reconstruction
Use MC to get mass
template shapes
 Do combined likelihood fit to
invariant mass and pseudoproper time distribution
 Number of Bc candidates:
95±12±11
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
19
DZero: Bc Meson (4)
Results of the fit :
Mass log likelihood
Mass :
5.95
+0.14
- 0.13
± 0.34 GeV
Lifetime :
+0.12
0.45 - 0.10 ± 0.12 ps
Main systematics
 Mass : signal sample
composition, MC signal
modeling, fraction of
prompt bkg
 Lifetime : Bias from
vertexing algorithm,
fraction of prompt bkg
 Both could be improved
Mass, GeV
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
20
Bc : Other Properties
 Fragmentation process b Bc + c
dominated production

Charm quark should form weakly decaying
charmed hadron in vicinity of Bc
b
b
c
c
 Measured probability to have muon
within f ± 90o of Bc candidate


5 ± 2 % for signal sample
1% for background sample
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
21
Branching Rates for Bs and Lb
 Poorly known – see PDG summary below
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
22
CDF : Br for hadronic modes
 CDF collected excellent hadronic samples of Bs
and Lb decays using Track Trigger
 Measured Br of several decay modes
 Earlier results


Br(BsDs)/Br(B0D)=1.4±0.2(stat)±0.5(syst)
Br(LbLc) = 6.0±1.0(stat)±0.8(syst)±2.1(Br) x10-3
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
23
CDF : Br (Bs  ff)
 Charmless BVV decay
 Track Trigger :


Two oppositely charged tracks with Pt > 2 GeV at Level 1
Impact Parameter > 0.12 mm at Level 2
 Normalized to Bs J/y f decay
 Br(Bs  ff) = (1.4+-0.6(stat)+-0.2(syst)+-0.5(Br)) 10-5
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
24
CDF : Charmless Lbgp and LbgpK decays
 Charmless Lb decays may have large direct CPV
 Proceeds via CKM suppressed and/or penguin (QCD,EW)

Expected Br ~ (1-2) 10-6
 Normalized to B  hh process
 Search window in M()
optimizes separation from
B  hh


772 ±13 events expected
767 observed
 Br(Lb  hh) < 22
x
10-6
M()
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
25
DZero : Bs semileptonic modes
 Excellent yield for all semileptonic modes

Collected by Single Muon Triggers without online lifetime cuts
 Used for Bs oscillations and lifetime measurements
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
26
Oscillated BS candidate
 Opposite Side Muon tagging applied to semileptonic BS sample

Re performance of taggers see G.Borissov’s talk
 Example of tagged BS candidate



Two same sign muons are detected
MKK=1.019 GeV, MKKπ=1.94 GeV
PT(μBs)=3.4 GeV; PT(μtag)=3.5 GeV
Tagging muon
Y, cm
μ+
BS
μ+
D-S
K+
πK-
X, cm
φ
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
27
DZero : Bs Mixing Projections

Plan to use both semileptonic and
hadronic Bs samples



More statistics in semileptonics
Better proper decay time resolution in
hadronics (no )
Have access to hadronic Bs sampe
triggering on opposite side muon

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Muon is used as high purity tag
Work in progress - see signals
Also hardware upgrades in 2005
 L3 bandwidth will be increased from 50
to 100 Hz in 2005



Semileptonic sample limited by L3 and
offline CPU – expect large gain in yield
Upgrade to 250 Hz under review
Partial silicon upgrade


New beampipe with smaller diameter
Add another innermost layer of silicon
(Layer0) with analog cable readout
Layer0 + L3 BW upgrades
No upgrades
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
28
DZero: Lb  Lc  sample
 Reconstructs Lb  Lc  in two Lc decay modes

L c  Ks p
350 pb-1

Lc  L 
 Samples will be used for lifetime
ratio measurements
350 pb-1
Lc mass agrees with PDG
Second peak interpreted as
Lc  S  ; S  L g
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
29
B Hadron Lifetimes
 Naive quark spectator model
predicts equal lifetimes for all B
hadrons (but Bc)
 (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 LQCD / mb
 Goal: measure the ratios
accurately
Dzero: Recent result from semileptonic modes
t(B+)/t(B0) = 1.093  0.021 (stat)  0.022 (syst)
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
30
Exclusive modes : Bs Lifetime
 J/y modes are golden at the Tevatron since they allow
for simple di-lepton trigger with low Pt threshold
CDF : BsJ/y f ( KK) based on 240 pb-1

12 parameter maximum likelihood fit
t(Bs) = 1.369 ±
+0.008
0.100 -0.010
FPCP2004, Daegu
ps
Andrei Nomerotski (Fermilab)
31
DZero : Exclusive Bs Sample
DZero accumulated the largest sample of exclusive
Bs  J/y f decays

J/y  

f  KK
250 pb-1
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
32
DZero : Bs Lifetime
 Use two similar topologies BsJ/y f and BdJ/y Ks*0 to measure
lifetime ratio
 Simultaneous Likelihood fit to mass and lifetime distribution
250 pb-1
250 pb-1
BdJ/y Ks*0
BsJ/y f
t(Bs) = 1.444 +0.098
±0.020 ps
-0.090
t(Bd0) = 1.473 +0.052
-0.050 ±0.023 ps
t(Bs)/t(B0) = 0.980 +0.075
±0.003
-0.070
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
33
DZero : Lb Lifetime
 Reconstruct Lb J/y L
 Use process with similar
topology Bd0  J/y Ks to
measure the ratio
 Result is statistically limited
t(Lb) = 1.221 +0.217
±0.043 ps
-0.179
t(Bd0) = 1.397 +0.107
-0.098 ±0.031 ps
t(Lb)/t(B0) = 0.874 +0.169
±0.028
-0.142
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
34
Summary
 So far Tevatron experiments were doubling samples every year
– that may continue
300
12
DRAFT June04
-1
Peak
200
30
-2
Total Integrated Luminosity (fb)
10
-1
Peak Luminosity (x10 cm sec )
250
8
Phases
Total
150
6
100
4
50
2
0
9/29/03
0
9/29/04
9/30/05
10/1/06
10/2/07
10/2/08
10/3/09
 Exciting prospects for heavy B hadrons
 Expect great improvement in accuracy of lifetime and Br
measurements
 Measurement of DGs, Dms within reach
 There are still particles to discover in this sector: Xb, Sb, Wb ,
doubly heavy baryons
 Be ready for new results
Date
FPCP2004, Daegu
Andrei Nomerotski (Fermilab)
35