B Physics at D0: An update
Vivek Jain
Cornell University
Oct 1, 2004
1
Outline



Introduction
D0 detector
Recent Results





New states
Rare decays
Lifetimes
Mixing
Conclusions
2
3
Why B physics?




Understanding 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 an insight into short-distance physics
Short distance phenomena are sensitive to beyondSM effects
Test bed for QCD, e.g., form factors, calculations of B
hadron lifetimes, spectroscopy
4
B physics at the Tevatron

At Ecm = 2 TeV
 ( pp  bb )  150b

At Z pole
 (e e  bb )  7nb

At Υ(4S)
 (e e  bb )  1 nb

All species produced,
Bc , Bs , b ...
Environment not as clean as at electron machines
Low trigger efficiencies
5
B Physics Program at D0
 Unique opportunity to do B physics during the current run
 Complementary to program at B-factories (KEK, SLAC, CLEO..)
 BS mixing, S / S
 Rare decays: BS      Large tanβ SUSY models enhance rate
 Beauty Baryons,  b lifetime,  b …
  ( b ) /  ( Bd0 ) expt: 0.80±0.06 (SL modes), theory ~ 0.95
 B C , B ** , B lifetimes, B semi-leptonic, CP violation studies
 b production cross-section: In Run I, measd. Rates x(2-3) higher
 Quarkonia - J / ψ,  production, polarization …
6
DZero Detector
SMT H-disks

Muon system with
coverage |η|<2 and
good shielding
SMT F-disks
SMT barrels
Trackers
Silicon Tracker: |η|<3
Fiber Tracker: |η|<2
Magnetic field 2T
7
CFT
8 Layers: Axial, Stereo (± 3°)
Radius: 20-50 cm
Good S/N. Signal ~ 5-9 pe
Fast enough to be in L1 trigger
Readout by VLPC:
High QE, very low dark noise
Excellent PE resolution
Each pixel has 1mm radius –
well matched to fiber
Operated at 8-9 (± 0.05)°K
8
VLPC performance
Signal ON: LED was
set to ~ 2 pe
9
B  D0μX,
All tracks
σ(DCA)≈53μm @ Pt=1GeV
and better @ higher Pt
D0  K  π 
pT ( )  2 GeV,  ( )  2.2
Analysis cuts – pT>0.7 GeV
data
10
pT spectrum of soft pion candidate
in D*D0
~100 events/pb-1
11
Excellent Lepton Acceptance
Muon ID:
MC: B  Ds μX,
Ds  π 
Overall efficiency (from data)
plateaus at about 85-90%
   0.6 - at pT  4.5 GeV
 0.6    1.2 pT  3.5 GeV

   1.2 - at pT  2.5 GeV
Muon system in Level 1
p T of reconstructed muon
12
Electron ID:
 Calorimeter goes out to   4
 Low pT electron ID is in progress
 At present, we can detect electrons with pT>3 GeV and   1.1
Average efficiency is about 75%
 Working to extend to higher values of  and lower pT
threshold – use for tagging initial state flavour
13
All trigger components have simulation software
14
Triggers for B physics

Robust and quiet di-muon and single-muon triggers
 Large coverage ||<2, p>1.5-5 GeV – depends on Luminosity and trigger

Variety of triggers based on - Muon purity @ L1: 90% - all physics!



L1 Muon & L1 CTT (Fiber Tracker)
L2 & L3 filters
Typical total rates at medium luminosity (40 1030 s-1cm-2)



Di-muons :
50 Hz / 15 Hz / 4 Hz @ L1/L2/L3
Single muons : 120 Hz / 100 Hz / 50 Hz @ L1/L2/L3 (prescaled)
Current total trigger bandwidth
1600 Hz / 800 Hz / 60 Hz @ L1/L2/L3
15
16
Recent Results

Many new analyses used ~ 250-350 pb-1

Single muon triggers have variable prescales, non-trivial to
determine luminosity for analyses using these triggers

Have more data on tape, but not yet analyzed

Details at: www-d0.fnal.gov/Run2Physics/ckm/
17
Basic particles
Plot is for
illustrative
purpose
18
2826±93
7217±127
~ 350 pb-1
624±41
Large exclusive samples
Impact parameter cuts
19
Bs
No IP cuts:
Use for lifetime
Λb
337±25
~ 250 pb-1
Will reprocess w/ tracking
optimized for long-lived part.
(yield will ~50%)
20
Observation of X(3872)
5.2 effect
In 2003, Belle saw a new
particle at  3872 MeV/c2,
observed in B+ decays:
B+  K+ X(3872),
X(3872)  J/ + Belle’s discovery has been
confirmed by CDF and DØ.
DØ (accepted by PRL)
522 ± 100 events
M = 0.7749  0.0031 (stat)  0.003 (syst) GeV/c2
21
Charmonium
(Estia Eichten)
J_PC
22
What kind of particle is the X ?
- charmonium ? 1 ³D3, 2 ³P2 …
- an exotic meson molecule ?
- something else ?
Compare X candidates
to (2S), e.g.
- split into two || regions
- decay length, isolation, helicity
23
No significant differences between
(2S) and X have been observed
yet.
|y|<1
Iso=1
pT>15
Hel(ππ)<0.4
This comparison will be more
useful once we have models of
the production and decay of, e.g.
meson molecules that predict
the observables used in the
comparison.
Hel(μμ)<0.4
dl<0.01 cm
Observation of the charged analog X+  J/ + 0 would rule out charmonium
Observation of radiative decays X   c would favour charmonium
Belle’s results rule out 1 ³D3, 2 ¹P1, ³D2, ¹D2, 0-+, 1++
Use Dzero’s calorimeter to identify low energy 0 and  : work in progress.
24
Spectroscopy: L=1 B (and D) mesons


For Hadrons with one heavy quark, QCD has
additional symmetries as m  
Q
QCD
(Heavy Quark Symmetry)
Spin of the heavy quark decouples and meson
properties are given by the light degrees of freedom
 Each energy level in the spectrum of such mesons
has a pair of degenerate states:
 
jq  sq  L
  
jq , J  jq  sQ
25
Lessons from charm (I)
For non-strange
L=1 Charm mesons
jq = 1/2, 3/2 have
been seen
The wide states were observed
via Dalitz plot analysis in
B  D 
(*)
  300MeV
  25MeV
Belle hep-ex/0307021
26
D** at D0
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) %
measured by normalizing to known Br (B  D*+   X)
27
Lessons from charm (II) – Ds**
Eichten
For L=1 Ds mesons,
preferred decay mode:DK
jq = 3/2 -> DK, D*K
jq = 1/2 below DK threshold,
decay to Ds (*) 0 / Ds (*)
Mass/widths unexpected!
Maybe B** or Bs** have similar
behaviour
28
Probably not the natural
width of these states
Previous results on B**
Previous experiments did not resolve the four states:

<PDG mass> = 5698±8 MeV
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

Theoretical estimates for M(B1)~ 5700 - 5755 and for
M( B * ) ~ 5715 to 5767. Width ~ 20 MeV
2
29
Signal reconstruction (I)

Search for narrow B** - Use B hadrons in the foll.
modes and add   coming from the Primary Vertex




B   J /K 
Bd0  J /K *0 , K *0  K  
Bd0  J /K 0 , K 0    
7217±127 events
2826± 93 events
624± 41 events
Since ΔM between B**+ and B**0 is expected to be
small compared to resolution, we combine all
channels (e.g., ΔM for B+/B0 = 0.33±0.28 MeV)
30
Signal Reconstruction (II)

Dominant decays modes of B1 , B2*
*
*
 B  B  , B  B ( B forbidden by J,P
1
conserv.)
B2*  B* , B*  B
*
 B  B (ratio of the two modes expected to be 1:1)
2


To improve resolution, we measure mass
difference between B1 , B2* and B, ΔM
31
Signal reconstruction (III)
 Now, ΔM(B* - B) = 45.78±0.35 MeV – small
 Thus, if we ignore

, ΔM shifts down ~ 46 MeV,
M ( B  B)  M ( B )  M ( B*)  46MeV
*
2
*
2
 We get three peaks:
  = M( B ) – M(B*) – 46 MeV
1
1
*
  = M( B ) – M(B*) – 46 MeV
2
2
*
  = M( B ) – M(B)
- in correct place
2
3
32
First observation of the separated
states
From fit:
N = All B**
536±114
events
~7σ signif.
273±59 events
*
*
1
B  B  , B  B
Interpreting the peaks as:
(98)
B2*  B
B2*  B* , B*  B
131±30 events
33
Consistency checks:
B0**
B±**

32±36 events
 required to have large
Impact parameter signific.
relative to Primary vertex –
No Signal (as expected)
34
Results of fit - Preliminary
M ( B1 )  5724  4(stat )  7(syst ) MeV / c
2
M ( B )  M ( B1 )  23.6  7.7(stat )  3.9(syst ) MeV / c
*
2
1  2  23  12(stat )  9(syst ) MeV / c
2
2
f1  0.51  0.11(stat )  0.21(syst )
35
Bs   


Standard Model predictions
Exptl. Results 90% (95%) CL
36
Beyond Standard Model
 First proposed by
Babu/Kolda as a probe of
SUSY (hep-ph 9909476)
 Branching fraction depends
on tan(β) and charged Higgs
mass
 Branching fraction
4
6
tan

(tan
)
increases as
in 2HDM (MSSM)
Other models also have
enhanced rates, e.g.,
Dedes, Nierste hep-ph 0108037
mSUGRA
37
Experimental challenge:
(L 200 pb-1)
38
Optimization Procedure – “blind” analysis





~ 80 pb-1 of data was used to optimize cuts
After pre-selection, three additional variables were
used to discriminate bkgd. from signal Isolation : Since most of b-quark’s mom. is carried by
the B-hadron, track population around it is low
 I | p (  ) | /(| p (  ) |  pi ( R  1))
iB
Decay Length significance: Lxy/δLxy – remove
combinatoric background, e.g., fake muons
Pointing angle: Angle, α, between B_s decay vector
and B_s momentum vector
39
Result of optimization
Isolation > 0.56
Pointing angle < 0.20
(rad)
δLxy/ δL > 18.5
Background prediction from sidebands in (MB ± 2σ):
3.7 ± 1.1 events
Punzi (physics/0308063)
40
Opened the box (July 8’ 04)
(L = 240 pb-1)
Nothing remarkable about the four events – look like background!
41
Calculate upper limit (I)

To calculate limit on branching fraction, normalize to
Feldman-Cousins
B   J /K 
B
N ul  K
Br( Bs ) 
. Bs .
N B   
MC: 0.229±0.016
PDG
B 1 ( B  ).B 2 ( J / )
Bd
 
( f b Bs / f bBu,d )  R. Bs
 
MC
0.270±0.034 (PDG)
Since our signal region overlaps Bd, can have contamination
R: theoretical expectation for ratio of Br. frac. of Bd /Bs - set R=0
If R  0 limit will be better
42
Upper Limit - Preliminary
The 95% (90%) C.L. upper limit:
Br( Bs    )  4.6 10


7
7
(3.8 10 )
Currently, the most stringent limit on this decay channel
If we use Bayesian approach, we get 4.7 (3.8)
43
Implications of this result
Excluded by
D0 Run II 240 pb-1
4.6E-7 (95%CL)
Dermisek et al
Hep-ph 0304101
Dark Matter and Bs     
Minimal SO10 with soft SUSY
breaking
Contours of constant
Br( Bs      )
Allowed by Dark Matter
constraints
44
Observation of Bc




Last of ground state mesons
to be definitively observed!
Theory: Lifetime 0.3-0.5 ps
Theory: Mass 6.4 GeV ±0.3
Only previous evidence CDF
RunI result
20.4+6.2
signal
- 5.5
Mass: 6.4±0.39±0.13 GeV
:
+0.18
0.46- 0.16
0.03 ps
45
Take advantage of easy-to-trigger-on final
state – events come via the dimuon triggers
+


Select 231 J/X candidates
+
PV
Bc+
Background estimated with
J/+track data control
sample, separated into
prompt and non-prompt
components
46
Do combined likelihood fit to invariant mass and pseudoproper time distribution:
#signal:
95±12±11
Mass:
+0.14
5.95
-0.13
±0.34 GeV
Lifetime:
0.448
+0.123
±0.121 ps
-0.096
47
Background-only fit:
2log(likelihood) is 60
for 5 degrees of
freedom
48
Other properties:
b
c
c
b
Forms weakly
decaying charmed
hadron
Probability 4th  within  ±90 degrees
of Bc candidate = 5±2%
Probability 4th  within  ±90 degrees
of background = 1%
49
Lifetimes of B hadrons
 Use modes with J/ψ final states, semi-leptonic decays
 Predictions available from theory via OPE calculations
These calculations are rooted in QCD
Expansion is in inverse powers of heavy quark mass
Predictions are semi-quantitative for Charm
For B-hadrons, predictions are on much firmer footing
50
51
(B+)/(B0) from semileptonic decays
Novel idea: Signal with Imp. Param cuts
“D0 sample”: + K+ - + anything
B+ 82 %
B0 16 %
Bs 2 %
“D* sample”: + D0 - + anything
B+ 12 %
B0 86 %
Bs 2 %
Estimates based on measured
branching fractions and isospin relations.
52
VPDL  ( LT / pTD )  M B
Group events into 8 bins of
Visible Proper Decay Length (VPDL):
Measure ri = N(+ D*-)/N(+ D0) in each bin i.
Minimize:
(ri  N .ri (k ))
 
 2 (ri )
k  (  /  0 )  1
e
2
one example VPDL bin
2
Additional inputs to the fit:
- sample compositions (previous slide)
- K-factors (from MC) – missing particles
K = pT(D0) / pT(B)
[separately for different decay modes]
- Relative reconstruction ε for different B decay modes (from MC)
- Slow pion reconstruction ε [flat for pT(D0) > 5 GeV (one of our cuts)]
- Decay length resolution (from MC)
- (B+)
= 1.674  0.018 ps [PDG] – Fix in fit
53
Adding more data
Preliminary result:
(B+)/(B0):
1.093  0.021  0.022
(stat)
(syst)
Syst. dominated by:
- time dependence of slow  reconstruction eff.
- relative reconstruction efficiency CY
- Br(B+  +  D*- + X)
- K-factors
- decay length resolution differences D0  D*
The prelim. DØ meas. is one of the most
precise results
Not updated
54
55
b  J /

 1.221 0.217 (stat)  0.043 (sys) ps
b
 0.179
2D fit: Mass and
Lifetime (100)
Also did,
Bd  J /K s
56
Summary of Λb results
World Average
1.229±0.080 ps
0.798±0.052
Theory: 0.90±0.05
World Average uses semi-leptonic modes
57
2D fit: Mass and
Lifetime
Bs  J /

 1.444 0.098 (stat)  0.020 (sys) ps
Bs
 0.090
Single best measurement
Most existing meas.
use SL mode
Also did,
Bd  J /K *
58
Summary of Bs results
World Average
1.461±0.057 ps
0.951±0.038
Theory: 1.00±0.01
<World> contains final states with different amts. of CP e-states
59
BS Mixing is high priority

Vtd 
 2nd order weak transition

md
mS

ρ<0 disfavoured by current
limit on Δms (>14.4/ps)
L
S
 p B q B
H
S
 p B q B
B
B
0
S
0
S
0
S
0
S
mS  M H  M L
S  L  H
60
Bs CP =+1 & CP = -1 Lifetimes

B0sJ/ψ φ unknown mixture of CP =+1 & CP = -1 states
In Standard Model s/s may be as large as 0.1 ( 
Γs = ( ΓLight + ΓHeavy)/2 ;
ms )
ΔΓs = ΓLight - ΓHeavy
In the case of untagged decay, the CP – specific terms evolve like:

CP - even:
( |A0(0)|2 + |A||(0)|2 ) exp( -ΓLightt)
CP - odd:
|A┴(0)|2 exp( -ΓHeavyt)
Flavor specific final states (e.g. B0slDs ) provide:
Γfs = Γs -
(ΔΓs)2
/ 2Γs + Ό (
(ΔΓs)3
/ Γs )
2
DZ – Beauty’03
61
In progress
Bs Lifetimes,
transversity variable θT
The CP-even and CP-odd components have different decay
distributions.
The distribution in transversity variable θT and its time evolution is:
d(t)/d cosθT ∞ (|A0(t)|2 + |A||(t)|2) (1 + cos2θT) + |A┴(t)|2 2 sin2θT
3 linear polarization states: J/ψ and φ polarization vectors:
longitudinal (0) to the B direction of motion;
transverse and parallel (||) and (┴ ) to each other

DZ – Beauty’03
MC distributions for CP = +1 & CP= -1 for
accepted events (D0)
62
How to measure Δm
PU  PM
A
 cos( ms t )
PU  PM
63
In search of BS oscillations
(“Amplitude method”)
Fit data to
  t
P  e 1  A cos( ms t )
2
Fit for A as a function of ms
Measurement: A = 1
Sensitivity: 1.645A = 1 (95%)
Limit: A < 1 - 1.645A (95%)
Current limit :
ms > 14.4 ps-1 @95% CL
64
Compare A for
Δm=15 ps-1
65
Significance of mixing
measurement

2 /2

(

m


)
ND
S
t
e
2
SB
2
We need:
Final State reconstruction
Ability to measure B decay length
B flavour at decay and production
66
Flavour tagging
 Use flavour-specific decays to get flavour of B at decay
 To get flavour of B at production use
Opposite side
Same side
neutrino
Jet charge
b-hadron
D
PV
Soft lepton
Trigger lepton
Fragmentation
pion
B
Lxy
67
MC
Q0b
(B+ MC)
Require |Q| > 0.2
68
Combined tags analysis - Bd
200pb-1
Data sample split into two sets:
1) Tagged by soft muons (SLT)
2) Tagged by combined jetQ+SST algorithm
Combined algorithm produces non-zero answer if:
– Event not tagged by SLT
– At least one of jetQ and SST gives a non-zero answer
– jetQ and SST give same answer ( better dilution)
69
Combined tagger result
200pb-1
Simultaneous fit to SLT and jetQ+SST asymmetries
SLT
Chief systematics:
• D*  sample composition
• D** pion tagging probability
• Charged B dilution determination
Preliminary results:
md=0.456  0.034 (stat) 0.025 (syst) ps-1
jetQ+SST
D0 = (44.8  5.1) % SLT
D0 = (14.9  1.5) % jetQ+SST
D= (27.9  1.2) % jetQ+SST
 = (5.0  0.2) % SLT
 = (68.3  0.9) % jetQ+SST
70
One can reconstruct
BS
in hadronic and semi-leptonic modes
(*) 
B

D
Hadronic modes, e.g., S
S 
Pros: Very good proper time resolution
Cons: Low branching fraction (  0.5% ), triggers
 Semi-leptonic modes, e.g., BS  DS  
Pros: Large Branching fraction  10% , triggers
Use both Muon & Electron final states
Cons: Poorer proper time resolution
(*)

71
SL modes have large yields
BS  DS  X
DS 
BR= (3.60.9)%
~ 9481 events in 250pb-1
72
BS  DS  X
Ds  K *0 K 
BR= (3.30.9)%
(BR comparable to Ds )
But larger backgrounds
D-  K+ - D-  K* non-resonant D-  K+ - ~ 4933 events in 200 pb-1
 Significant increase in total BS yield
Other DS decays are being studied too
73
Mixed BS candidate in Run 164082 Event
31337864



Two same sign muons are detected
 Tagging muon has η=1.4
 See advantage of muon system with
large coverage
MKK=1.019 GeV, MKKπ=1.94 GeV
PT(μBs)=3.4 GeV; PT(μtag)=3.5 GeV
Tagging muon
Y, cm
μ+
BS
D-S
K+
μ+
πK-
X, cm
74
φ
Progress report:
 Studying electrons as an initial state flavour tag
 Hadronic modes – Bs -> Ds* pi
New triggers online – very effective for hadr. Decays
 If nature is kind, and Δm is on the low side, we could have
a shot at it with the SL mode
Some upgrades are planned:
 Layer 0 – new Silicon layer at r ~ 2.5 cm. Significant
improvement in proper time resolution (mid-2005)
 Double trigger bandwidth/reconstruction farms and write
more data to tape – in proposal stage
75
Conclusions and Outlook
 Lot of progress in the previous year
 Accelerator performing reasonably well.
Expect 500 pb-1 by the end of the calendar year
 B physics group producing competitive results
 Exciting times ahead
76
Backup slides
77
Need to precisely determine the CKM matrix
 d '  Vud Vus Vub  d 
d 
  
 
 
'
ˆ
 s   Vcd Vcs Vcb  s   VCKM  s 
 ' 
b 
 b  Vtd Vts Vtb  b 
 
 

Elements of the CKM matrix can be written as:
 λ – Cabbibo angle (~0.22), A (~0.85),
 ,

(    (1  2 / 2))
Magnitude of CP violation is given by η
78
79


Unitarity of the CKM matrix leads to
relationship between various terms
One such relation:
V V V V V V  0
*
ud ub
*
cd cb
*
td tb
80
Vtd
If CKM matrix is unitary, leads
to triangles in the ρ, η plane
Vub
Vcb
CA:
BA:
81

Study of B hadrons yields



| Vcb |, | Vub / Vcb |, Vtd ,Vts ,
B mixing: Vtd , Vts
η can be inferred from CP violation
Within the SM, CP conserving decays sensitive to
| Vcb |, | Vub / Vcb |, | Vtd | can tell if η is non-zero



 > 0 can be inferred from limit on Bs mixing
Complementary meas. of η, | Vtd |from K  
New phenomena might affect K and B differently
82
Winter 2004
HFAG avg.
(fit does not
include results on
Sin(2β))
83
Pre-shower detectors help in e-ID
SMT+ CFT
ηmax = 1.65
SMT region
ηmax = 2.5
Barrels and Disks
84
SMT
6 barrels: 4 layers SS+DS, 2/90° stereo
|z|<0.6 m, r = 2.7-10 cm
12 central F disks: DS, 144 wedges,
15 stereo
4 forward H disks:
96 wedges,  7.5
z: 1.1/1.2 m
r: 9.5-20 cm
Tracking to η ~ 3 (θ ~ 6°)
793K channels, rad hard to 1 MRad ~ 2-3 fb-1
S/N > 10, 1 MIP ~ 25 ADC counts
Hit resolution ~ 10μ
85
• J/ mass is shifted by 22 MeV
• Observe dependence on Pt and
on material crossed by tracks
• Developed correction procedure
based on field & material model
• Finalizing calibration of
momentum scale using J/, Ks, D0
NOT yet used
86
87
Track triggers very important for B physics
- Trk/muon match at L1
- Trks are fed to L2 Silicon track trigger
- Trk/Pre-shower match
88
Silicon Track Trigger is being commissioned
Trigger is online – as yet not used for physics
CFT outer layer
1-mm road
CFT inner layer
SMT barrels
Performs final silicon cluster
filtering and track fitting
– Lookup table used to convert
hardware (e.g., channel, etc.) to
physical coordinates ( r ,  )
– 8 300-MHz 32-bit integer Texas
Instruments DSPs perform a
linearized track fit
b
 (r )   r  0
r
– Fit using precomputed matrix stored
in lookup table
89
Accelerator performance
# bunches
s
(TeV)
L cm 2 s 1
Bunch x-ing
(ns)
Int./x-ing
Run Ib
Run IIa
Run IIb
6X6
36X36
140X133
1.8
1.96
1.96
1.6E31
8E31
2-5E32
3500
396
132(?)
2.8
2.4
2-5
Currently Linst  4  6E31 cm
2
s
1
Have
1
L

280
pb

90
91
Basic Particles
92
Inclusive B lifetime using B  D 0  X
Standard technique – no IP cuts. Poor S/B
L  12 pb -1
c  438  25(stat ) μm PDG  472  2
93
94
Aside: Where do the B’s go?
Flavour
Tag μ
comes
for
free
Factor
# events for 2 fb-1
 (bb )  150b
3E11
2 b quarks/event
6E11
B(b  Bs(*) )  0.10
6E10
B ( Bs  Ds )  0.003
1.8E8
B( Ds   )  0.04
B(  K  K  )  0.5
7.2E6
3.6E6
Single μ Trig. Eff < 1%
<3.6E4
Reco. Eff. <10%
<3.6E3
95
For L=0, two states with jq=1/2, J=0, 1 - B, B*
 For L=1, get two pairs of degenerate doublets,
jq=1/2, J=0, 1
-
B0* , B '
jq=3/2, J=1, 2
-
*
2
B1 , B
These four L=1 states
are collectively known
as B** or BJ
 HQS also constrains the strong decays of these states
 jq = 1/2 decay via S-wave, hence expected to be wide
 jq = 3/2 decay via D-wave, hence narrow
Strong decays
96
Lessons from Charm (III)


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


M( D2* )-M( D1 ) ~ 32-37 MeV (jq=3/2 doublet)
Could expect this to be ~ 10-15 MeV for M( B *)-M(B )


For non-strange charm, M(D**)-M(D) ~550-600 MeV
Would expect similar behaviour for B mesons
2
1
97
Signal Reconstruction (V)

We fit the ΔM signal with 3 relativistic BreitWigner functions convoluted with Gaussians
N .( f1 * G(1 , 1 )  (1  f1 )( f 2 * G( 2 , 2 )  (1  f 2 ) * G(3 , 2 )))





N: Number of events in the three peaks
f1 : Fraction of B1 in all events
*
*
:
Branching
fraction
of
B

B

f2
2
From theory fix 1  2 and f 2  0.5
From MC fix resolution of ΔM=10.5 MeV
98
Sample composition
B meson lifetimes and branching rates from PDG
K-factor distributions, decay length resolution,
reconstruction efficiencies from MC
12% B+ 2% BS
D* sample
86% B0
16% B0 2% BS
D0 sample
82% B+
99
2D lifetime fits
100
101
Quarkonia at D0
 Have older results on J/Psi production. Will update
- Cross-section as a function of pT and η
 Started to look at Upsilon production characteristics
- We presented a preliminary pT distribution at QWG’03
and more recently at PHENO’04
- Next step is to determine production absolute cross-section
and polarization studies
102
103