Transcript Status of sin2b - University of California, San Diego

Sin2 and Beyond :
Recent Measurements and Some
Prognostication
Vivek Sharma
University of California at San Diego
Aspen Center For Physics, August 2001
Outline and Caveats
• Discuss short and incomplete list of results & projections
– Angles: , a (and g ?)
• Bs Mixing at Tevatron
– Direct CPV Searches
– Recoil Side Reconstruction : a new direction at B factories
• Vub, inclusive b-> s gamma , B -> tn etc
• This is not a Babar talk, but I will use many plots from
Babar (easy access, better understanding)
• Predicting the future is dangerous business !
– Try to use real performance, not wild dreams to project
sensitivities
– Use 500 fb-1 (by 2005) as the standard unit based on Bfactory
expectations
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2
Colliders :
Performance and Projections
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3
B Factories in 2001 and Beyond
CESR / CLEO
LP01 analyses
peak  1.25  10 33 cm 2 sec 1
day  73 / pb
PEP-II / BABAR
peak  3.33 10 33 cm 2 sec 1
day  213 .9 / pb
KEK-B / BELLE
peak  4.44  10 33 cm2 sec 1
day  223 .9 / pb
Aggressive plans at KEK/SLAC to keep raising Peak
Luminosity
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4
Minimize Machine
Down time
Luminosity Plans for BABAR & PEP II
Integrated Lumi [fb-1]
500
400
300
200
100
0
1999 2000 2001 2002 2003 2004
mid
2005
Yearly Lumi
2
23
40
70
95
110
70
Cumulative Lumi
2
25
65
135
230
340
410
Peak Lumi
1
2
5
7.5
10
12
17
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Year
Vivek Sharma
18
16
14
12
10
8
6
4
2
0
Peak Lumi [10**33]
Babar and Belle Expect 100 fb-1 samples by summer 2002
Model
Yearly Lumi
Cumulative Lumi
Peak Lumi
Assume
~500 fb-1 by
2005 per
experiment
5
CDF & D0 retooled and taking data: Run2 (2 –15 fb-1)
7/17/2015
Important additions:
Particle Identification (Time of Flight)
7-8 layer Silicon Vertex Detector
Vivek
Sharma for “Flying” Bs
Impact Parameter
Trigger
6
CP Violation Searches
•Time Dependent Measurement: , a
•Time Independent Rate Asymmetries
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CP Definitions
t 0
λ fCP  η fCP
CP eigenvalue
q A fCP

p A fCP
B0
~ e2i
mixing
CP violation results from interference between
decays with and without mixing
amplitude ratio
 e  2i
B
Af CP
CP
0
t
f CP
Af CP
0
 f CP  1  Pr ob( Bphys
( t )  f CP )  Pr ob(B0phys ( t )  f CP )
Time-dependent CP Observable:
A f CP ( t ) 
0
( Bphys
( t )  f CP )  (B0phys ( t )  f CP )
0
( Bphys
( t )  f CP )  (B0phys ( t )  f CP )
 Cf CP  cos (m Bd t )  Sf CP  sin (m Bd t )
cosine term
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sine term
Vivek Sharma
C f CP 
Sf CP 
1  |  f CP | 2
1  |  f CP | 2
 2 Im  f CP
1  |  f CP | 2
8
Golden Channel: B0  J/ K0S/L
Quark Subprocess b  ccs
K0 mixing is required
B  J/ K
B0  J/ K 0
0
0
B0CP  1  J/
B0CP  1  J/
KS0
K 0L
Single weak phase = no direct CPV
A
0
J/ KS, L
(t)   
0  sin
J/ KS, L
c
J/
c
s
d
b
B0 d
|  J/ K S0 ,L |  1
2  sin (m Bd t )
Theoretically clean way to measure sin2
Clear experimental signatures
Relatively large branching fractions
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K0
9
Time-dependent Measure of CP Asymm


J/
(4S)
e
e
B0rec

Exclusive
B Meson
Reconstruction

K S0
0
Btag
K
z

Δ t  Δ z/  βγ  c
B-Flavor Tagging
B0rec  B0flav (flavor eigenstates)
B0rec  B0CP (CP eigenstates)
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Vivek Sharma
lifetime, mixing analyses
CP analysis
10
Effects of CP Asymmetry
Perfect
Experiment,
sin2 = 0.59
Looking for a different t
spectrum in events where
the tag is a B0 or a B0
Visible
asymmetry
ACP
Note: integrated
asymmetry is 0
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CP Analysis: Time Distributions
realistic
mis-tagging probability &
finite time resolution
perfect
flavor tagging &
time resolution
B0tag 
B
0
B0tag 
B
B0tag  B 0
0
B0tag  B0
 e |Δt |/τ Bd

f CP,  ( Δt )  
 ( 1  ηf . (1  2ω). sin 2β. sin( Δm Bd Δt ) )   R
 2τ Bd

"fCP, "  B0tag  B0
"fCP, "  B0tag  B 0
Mixing & CP
Time evolution
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same mis-tagging probability 
and time-resolution function R(  t )
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CP Sample: Non-KL Modes
Present Sample: 725
PRL Sample: 425
Before tagging and
vertexing requirements
NNOW=672
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CP Sample: J/Y KL
Run1+
Run2
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N/(%)
EMC
IFR
Run1
Run2
Run1+Run2
77/52
49/59
128/56
96/68
32/55
129/65
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Fully-Reconstructed B Sample
Flavor eigenstates for mixing
and lifetime measurements
Here determine mistag rates,
t resolutions

Cabibbo-favored hadronic decays
b  c u d “Open Charm” decays

e.g. B 0  D () π  /ρ  /a1

Charmonium Decays b  (c c ) s
Neutral
B Mesons
N
B0 / B 0
 9400
purity 83%
Charged
B Mesons
N
B / B
 8500
purity 85 %
e.g. B  J/ K 
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Likelihood Fit Method
• Global unbinned maximum likelihood fit to data:
• Mistag rates, t resolutions = tagged flavour sample
• sin2 = tagged CP samples
• 45 parameters for mistag rates, t resolution & backgrounds:
floated to obtain an empirical description from data
parameter
#params
sin2
1
Determining
subsample
CP
w & w
42=8
flavour
t resolution
8  2 = 16
flavour and CP
Background t
4+2+3=9
sidebands
Background w 4  2 = 8
sidebands
Background t 3
sidebands
Separate t resolutions
for run1 and run2
Largest correlation
with sin2  : 13%
tB = 1.548 ps and md = 0.472 ps-1 fixed
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Blind analysis !
• The sin2 analysis was done blind to eliminate possible
experimenters’ bias
– The amplitude in the asymmetry ACP(t) was hidden by
arbitrarily flipping its sign and by adding an arbitrary offset
– The CP asymmetry in the t distribution was hidden by
multiplying t by the sign of the tag and by adding an arbitrary
offset
– The blinded aproach allows systematic studies of
tagging, vertex resolution and their correlations to be done
while keeping the value of sin2 hidden
– The result was unblinded 1 week before public announcement
this summer!
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CP= -1 modes Time Distributions
sin2=0.56±0.15
-5
0
Fit projections are from global likelihood fit
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Visible
asymmetry
ACP
5
t(ps)
18
J/Y KL Time Distributions
sin2=0.70±0.34
Visible
asymmetry
ACP
Fit projections are from global fit
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A (t )  (1  2ω).sin 2 .sin( Δm
Raw CP Asymmetries
CP
Kaon tags
All tags
η f  1 modes
(Q=15%)
Visible
ACP
sin2=0.59±0.20
sin2=0.56±0.15
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Bd Δt )
20
“Corrected” Asymmetries
sin 2, fitted in bins of t
BABAR
f   1 modes
BABAR
f   1 modes
sin 2, fitted in bins of t
and multiplied by sin(mBdt)
0.56  sin Δm Bd Δ t
A la Belle and CDF plots
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BaBar Sin2 Fit Results
Cross-checks:
Null result in flavor samples
Consistency of CP
channels P(c2) = 8%
Goodness-of-fit:
P(Lmax>Lobs)>27%
sin2 = 0.59 ± 0.14
Establishes CP violation in B decay
at 4s level
–Probability is < 3 x 10-5 to observe an
equal or larger value if no CP violation
exists
–Corresponding probability for the CP =
-1 modes is 2 x 10-4
–Probability of J/YKL and J/YKS
having the same CP is < 0.1%
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Run1 – Run2 Comparison
Run1-Run2 change for PRL modes: 1.8s
Run2
Run1
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Systematic Errors
• Signal resolution and vertexing = 0.03
– Resolution model, outliers, SVT residual misalignment
• Flavor Tagging = 0.03
– Studies of possible differences between BCP and Bflavor samples
• Background Characterization = 0.02 (overall)
– Signal probability, peaking background, CP content of background
– Total 0.093 for J/Y KL channel; 0.11 for J/Y K*0
Total Systematic Error = 0.05 for full sample
Total Sys
Total Stat
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KS
KL
K*0
Full
0.049
0.151
0.104
0.340
0.162
1.01
0.049
0.137
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24
Search for Direct CP
ACP  C fCP cos md t  S fCP sin md t
(assuming  = 0)
If more than one amplitude present
then || might be different from 1
C f CP 
Sf CP 
1  |  f CP | 2
1  |  f CP | 2
 2 Im  f CP
1  |  f CP | 2
Probing new physics: only use CP=-1 sample
( background Free)
|| = 0.93 ± 0.09 (stat.) ± 0.03 (sys.)
No evidence of direct CP violation due to decay
amplitude interference; none expected
Coefficient of the “sine” term unchanged
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Belle Results : S. Olsen LP01
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Updated World Average
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Comparison with Indirect Measurements
CP Measurements not included in “the Fit”
From Höcker et al, hep-ex/0104062
Many CKM fitters in the
market with
their own religions and
beliefs on error estimations
sin 2β   0.47  0.89 
sin 2α    1  0.5 
γ   34  82 
Sin2 is the
Most precisely
Measured CKM quantity
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28
Prognostication on Sin2
• In the Charmonium Modes
– Add more sub-modes “drops in the bucket” :
• Select Y hadrons, not just Y e+ e- or   ,
• smarter event selection (bremstrahlung recovery)
• Expect for charmonium modes: ssin 2  0.08 for 100 fb 1
– Add new CP modes :
• b sss  B  fKS
s sin 2   0.25 for 500 fb1
– Compare with sin2 from b ccs
• Cabibbo Suppressed B  Y
0
s sin2   0.23 for 500 fb1
– Look for difference in sin2 measured from b ccs
» bound u-quark penguin pollution
• Cabibbo suppressed b ccd  B  D(*+) D(*-)
– May contain (small but unknown) penguin pollution
» D*D* mode requires angular analysis (in progress)
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29
New Modes for “Sin2”
B
0
 f K S0
B0  D D b  ccd
b  sss
~ 11 events
~ 32 events
BABAR
BABAR
B  Y 0
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30
Prognostication on Sin2
• Systematic Error on Sin2Beta
– Is small already
– Almost entirely determined from data, shrinks with data
– Resolution on Z ( or t) largest single source (0.03) of
systematic error so far
• Will be more constrained with better silicon alignment,
reconstruction algorithm and feed back from other Babar
time dependent analyses
– Expect Systematic Error < 0.04, may be 0.03
• Stat. and Systematic error comparable with 225 fb-1
• With 500 fb-1 
s sin 2   0.05
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31
Tevatron Projections : Y-K Kim,LP01
The Most Exciting
Next Measurement
200 pb-1
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32
CP violation in B0   decays
Decay distributions f+(f-) when tag = B0(B0)
e(  t /t )
f ( t ) 
[1  S f sin( m d t )  C f cos( m d t )]
4t
tree diagram
u
b
1||2
Cf 
1||2
penguin diagram
d
u
b
d
2 Im(  )
Sf 
1||2
u
u
For single weak phase
For additional weak phase
q Af

  f e  2 i (   g )   f e 2 ia
p Af
|  |  1  must fit for direct CP
Im ()  sin2a  need to relate
asymmetry to a
C  0, S = sin2aeff
C  0, S = sin2a
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33
15
60
40
0
5.2
5.225
5.25
5.275
5.3
5.2
5.225
GeV/c
BABAR
20
10
5.25
5.275
60
5.3
GeV/c2
mES (Kaon)
BABAR
40
20
NT2
NT1
5.225
kaon
2
30
5.2
BABAR
80
20
mES (Lepton)
0
7/17/2015
lepton
5
Candidates per 2.0 MeV/c2
mES distributions
for the different
tagging categories
BABAR
10
0
Sum of +-/K+-:
No particle ID used
until the fit is performed
Candidates per 2.0 MeV/c2
20
Candidates per 2.0 MeV/c2
9741 two-prong
candidates in 30.4 fb-1
(97% background,
almost entirely from
continuum)
Candidates per 2.0 MeV/c2
CP Data Sample: Likelihood Fit
5.25
5.275
5.3
GeV/c2
mES (NT1)
Vivek
Sharma
0
5.2
5.225
5.25
5.275
mES (NT2)
34
5.3
GeV/c2
L= 30.4 fb-1
15
0
K 
217  18
KK
4.3  64..33
2
+ -
Kp
139 K
3 
B A B AR
20
0
pp
23 
2 K
5
-0.1
00
DE
60
B A B AR
+ -
40
.1
(GeV)
Kp
126 K
3 
20
0
5.25
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10
.3
mES
60
40
B A B AR
+ -
(GeV/c )
Events/20 MeV

2

65 
12
11
15
0
5.25
Events/2 MeV/c
 

pp
20 
1 K
5
Total Yields (fit):

B A B AR
+ -
10
Events/20 MeV
Events/2 MeV/c
For Illustration
purposes:
Events after likelihood
ratio cuts
2
CP Data Sample
2
.3
(GeV/c )
Vivekm
Sharma
ES
-0.1
00
DE35
.1
(GeV)
Lepton Photon 2001
CP Asymmetry Fit and Results
• Extended ML fit to the BRs and CP done
simultaneously:
–
–
–
–

–
5 tagging categories (leptons, K, NT1, NT2, untagged)
8 event species (Sig and Bkg: +- , K+ , K-+ , K+K-)
Discriminating variables (mES, E , F, qc1 , qc2 , t)
Dilutions, R(t) for the signal taken from sin2 analysis
md, B0 lifetime fixed as in sin2 analysis
R(t) for the background taken from sidebands in mES
distribution
Preliminary Results
53
S(    )  0.03 00..56
(stat)  0.11(syst )
45
C(    )  0.25 00..47
(stat)  0.14(syst )
7/17/2015
A CP (K    )  0.07  0.08(stat)  0.02(syst )
Vivek Sharma
36
Measurement of sin2a with B0  +Without penguins: C  0 , S  sin 2a
Penguins are expected to be sizable: |P / T|~ 0.3
C  0, S  sin aeff  sin 2a  F(P / T)
Strategies to extract a from the asymmetry measurement

Isospin analysis (Gronau/London )



Clean theoretically, but challenging experimentally
Need B0   0  0 AND B 0   0  0
When ?
Grossman/Quinn Bound
BF(B   0  0 )
sin Δ 
with Δ  a eff  a

 0
BF(B    )
2

7/17/2015
Theoretical constraints on Penguin pollution ??
Vivek Sharma
37
CP Asymmetry with B0  +- : Future
• Measurement will be statistically limited till 2005
• Major difference in this analysis w.r.t Sin2 is in the
BACKGROUND source : mostly from ucsd (Continnum)
– Hence tagging systematic errors are different
• But much smaller than statistical
• Projections on Sensitivity with 500 fb-1
– CP Asymmetry measurement Error
• s(S)
~ 0.14
• s(C) ~ 0.12
Look forward to establishing CPV in this mode
7/17/2015
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38
B K
and the Estimates of g
Expect significant interference
of tree and penguin amplitudes
A K ~ P  2 eig T
potentially large CP asymmetries
CP-averaged BF measurements can lead to non-trivial
constraints (bounds) on CP angle g
General analysis:
 EW penguins
 SU(3) breaking
 Rescattering (FSI)
Fleischer & Mannel (98)
Gronau, Rosner, London (94, 98)
Neubert & Rosner (98)
Buras & Fleischer (98)
etc.
Experimental test:
 Direct CP violation in B  K modes
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39
B   / K
BF (10 )
6
B0  π  π 
B0  K  π 
B0  K  K 
B  π  π 0
CLEO
9.1
fb1-1
.6
4.3 1.4  0.5
17 .2 12..45  1.2
 1.9 (90 %)
 12.7 (90%)
B   K  π 0 11.6
B   K 0 π  18.2
B0  K 0 π 0
7/17/2015
14.6
3.0
 2.7
 4.6
 4.0
5.9
5.1
1.4
1.3
Branching Fractions,
Summary
BABAR
20.7 fb-1
5.6 22..03  0.4
4.1  1.0  0.7
16.7  1.6  1.3 19.333..24 10..56
 2.5 (90%)
 2.7 (90 %)
5.7 12..80  0.8
 13.4 (90%)
10.8 12..91  1.0
 1.6 18.2
 2.4
3.3
BELLE
10.5 fb-1
8.2
3.3
3.0  2.0
3.1
 2.7  1.2
Vivek Sharma
World
Average
89
4.44 00..86
47
17.37 11..30
16.3 33..35 11..68
70
12 .13 11..67
13.7 54..78 11..98
60
17 .41  22..51
16.0 57..92
66
10 .73  22..66
 2.5
 2.7
40
Ratios of Branching Fractions
BF( B      )
 0.056

0
.
256
0.052
BF( B  K    )
BF( B   K  π 0 )
 0.23
2

1
.
40
 0.22
BF( B  K  π  )
BF ( B  K    )
 0.19

1
.
00
0.15
BF ( B   K   )
1 BF( B  K  π  )
 0.28


0
.
81
 0.17
2 BF( B  K π 0 )
Beneke
Buchalla
Neubert
Sachrajda
7/17/2015
hep-ph/0104110
Vivek Sharma
41
Direct CP Asymmetries in Kp modes
BABAR
K  
A CP (K ± π ) =-0.07±0.08
BABAR
CLEO
BELLE
K  0
A CP (K ± π 0 ) =+0.00±0.18
A CP (K S0 π ± ) =-0.21±0.18
CLEO PRL 85 (2000) 525
CLEO
A CP (K ± π m ) =-0.04±0.16
A CP (K ± π 0 ) =-0.29±0.23
K S0 π 
A CP (K S0 π ± ) =+0.18±0.24
0
+
0
0
Model.5
dependent predictions
exist;
.5
1
possible constraints on CP angle g
7/17/2015
BABAR hep-ex/0105061
BELLE BELLE hep-ex/0106095
+
 
 0.19
A
(K
π
)


0
.
04
CP
0.17
1
22
A CP (K  π 0 )  0.06 00..20
Vivek Sharma
43
A CP (KS0 π  )  0.10 00..34
42
bsg
Flavor-changing neutral currents,
proceeding via penguin diagrams
 Probes top quark couplings Vts
 SM rate predictions:
Chetyrkin et al.
4
(3.28  0.33) 10
PL B400 (1997) 206
 SM predicts small CP asymmetry (<1%)

s
Rates:
ALEPH PL B429 (1999) 169
BF(b  s g) 10 4  3.11  0.80 (stat )  0.72 (syst)
CLEO preliminary
BF(b  s g ) 10 4  2.85  0.35(stat )  0.22 (syst)
50
BF(b  s g) 10 4  3.36  0.53(stat )  0.42 (syst)  00..54
( th ) BELLE hep-ex/0103042
CP Asymmetries:

Non-SM physics may contribute to larger asymmetries
A CP  (0.079  0.108 (stat )  0.022 (add syst) )  (1.0  0.03( mult syst) )
 0.965  A CP (b  s g )  0.02  A CP (b  d g )
CLEO hep-ex/0010075
 0.27  ACP  0.10 (90%CL)
7/17/2015
Vivek Sharma
43
Direct CPV in
Radiative Decays
CLEO
Very little CP-violation
expected in the K*g mode
(window on New Physics)
 Up to ~15% CP-Violation
effect in the suppressed
rg mode (not observed)

72
5
BF(B 0  K 0 γ)  (4.55 00..68

0
.
34
).
10
(stat )
(syst)
89
5
BF(B   K  γ)  (3.76 00..83
(stat )  0.28 (syst) ).10
A CP  0.08  0.13 (stat )  0.03 (syst) CLEO PRL 84, 5283 (2000)
BF(B 0  K 0 γ)  (4.37 0.40( stat )  0.26( syst ) ).105
BF(B   K  γ)  (3.92 0.62
( stat )
0.21( syst ) ).105
ACP  0.035  0.076( stat ) 0.012( syst ) BABAR preliminary
7/17/2015
Vivek Sharma
44
Sin(2g) with B  D/r ?
• Noted by Sachs, Dunietz, Rosner et al as CPV mode
b  cud  B 0  D*  / r 
and
b  ucd  B 0  D*  / r 
B Mixing causes interference, gives asymmetry in each
case. Measures Sin(2g) , no Penguin Pollution
• CP Asymmetry is small ~ 3-5%
• Need to know/measure 
•
– Ratio of two amplitudes (Theory?)
– Expt : B -> Ds   (SU(3)) helps?
• The only good news
– Rates and yields are “enormous” !!
7/17/2015
Vivek Sharma
45
Sin(2g) with B  D/r ?
Large, Clean Data Samples already available
About 100K events in 500 fb-1
7/17/2015
Vivek Sharma
46
Time Evolution of B -> Dpi

4 time-dependent distributions !
7/17/2015
Vivek Sharma
47
Projections
• Experimental Issue : Must measure Small natural
Asymmetry
– Requires extraordinary control over
– B flavor tag
– Time resolution at less than .5% !!
» 3-6 times smaller than current estimates !!
• Background characterization not a problem in excl. modes
• Experiments have begun thinking about these issues
– Still too early to make serious predictions
• Naïve, cursory examination of B -> D*pi mode only with
– No input from theory (); fit for it in time distributions
 s(Sin(2g) ~ 0.15 for 500 fb-1
– If theory helps, then precision is order of magnitude better !
– Recent paper by London, Sinha, Sinha conjectures
• Angular analysis helps B -> D*r more controllable theoretically
– Needs careful investigation
7/17/2015
Vivek Sharma
48
CKM Angle Projections
From SuperBabar Whitepaper,
7/17/2015
Vivek Sharma
49
CKM Elements
From SuperBabar Whitepaper,
7/17/2015
Vivek Sharma
50
A Completely Reconstructed (4S) Event
Example of Recoil Side Physics
All particles accounted for
Nothing Missing !
7/17/2015
Vivek Sharma
51
Recoil Side Physics at B Factories
• A new B-factory era idea (whose time has come): to alleviate model
dependence in key measurements
– Still developing, so think about how it can help your favourite case
• Fully reconstructed, flavor specific sample of B mesons provide a
very clean sample of B tags
• Full B reconstruction of 1 B in (4S) provides:
– Information about flavor of the other ( Recoil side) B => charge
correlation
– Provides precise P vector of the recoiling B ( e.g. B -> t n)
• => daughter particles can be transformed to the B rest frame, not
(4S) CMS
– => Any two body decay produces sharp peaks in momentum spectrum of
daughter particles. (think b -> s g or s g)
– No udsc (continuum background to deal with ..or subtract)
– Half of the event is accounted for => drastically reduced combinatorial
background in studying recoil side B properties
7/17/2015
Vivek Sharma
52
Example : Digging out b -> s gamma
Backgrounds are relatively trivial, once you have one B fully Recoed
7/17/2015
Vivek Sharma
53
Recoil Side Physics at B Factories
• All good things cost !
– In this case reconstruction efficiency will limit the RECO B sample to
use for recoil side study
• How to construct the RecoB sample:
– B decay to hadronic final states provide most precise constraints
• Since every thing is reconstructed
• But each decay mode ~ 0.1-2%
– Larger the multiplicity, worse the reco. Efficiency
» Each  costs ~90%, each 0 in the final state costs 50%
– Semileptonic decays have missing neutrino
• But are relatively prolific (~20%)
– All advantages of the Hadronic sample, except one cant go to the Recoil
B rest frame => no monocromatic spectra
– Hence of limited use
» But good enough to help with b -> u l nu measurements
• Essential experimental requirements are
– Good particle Identification
All B factory detectors have this !
– Good topological vertexing capability etc
7/17/2015
Vivek Sharma
54
Possible Recoil Side Measurements
• Bread and Butter Physics examples
– Inclusive Semileptonic decay rate for B0 and B- (LP01)
– Particle spectra (K, ,  …..)
– Right and Wrong Sign (upper vertex ) Charm production
• Charm species, Rate and spectrum trivially obtained
• More Serious Stuff
–
–
–
–
B -> s g, and b -> s Glue (exclusive and inclusive with reduced modelling)
B -> t n and B  s n n (The ONLY way to get to them!)
Inclusive b -> u l n  Minimal Model dependence
Add your favorite physics
7/17/2015
Vivek Sharma
55
Exclusive Semileptonic Samples
•
B 0  D* n
K
6.1k
~ 1K reconstructed per fb-1
Very High Purity ~80%
 500K fully recoed B in 500 fb-1
K0
5.0k
7/17/2015
K
KS
5.0k
Vivek Sharma
56
B -> D (X) l nu
2.3 K/ fb-1 in D-> Kpi mode
~5K/fb-1 if use all decay modes
 2.5 Million
Recoed B in 500 fb-1
(mostly B-)
7/17/2015
Vivek Sharma
57
Hadronic B Sample
Run I with D0 -, D*0 -, D*0 r-,
D*0 a1-, J/ K-, (2S) K-, cc Kand J/ K-.
B- Sample: 20K in 20 fb-1
This is just a proof of principle!
500K Clean in 500 fb-1
Expect to increase the
reconstruction rate by ~2-3
Expect 1-1.5 M Hadronic B of
each species by 2005
Sample with the largest Set of
Constraints for Recoil side
studies
7/17/2015
Vivek Sharma
58
Example : Precision Vub Measurement
To distinguish bu from bc theoretically:
better
better
q2 spectrum > mhad spectrum > Elepton spectrum
But experimental difficulty is in opposite order
To make major experimental progress in Vub
need powerful suppression of b cl
provided by full reconstruction of companion B
B  D (n )
(*)
B  uln
Study this
Reco this
7/17/2015
Vivek Sharma
59
Inclusive Hadronic Mass Spectrum
Jik Lee@Snowmass
 select b u with mx< mD (~90% acceptance for b u (model ???)
 require: Q(event) =0, 1 lepton/event, missing mass consistent with neutrino
1 ab-1
b  cl n
b  ul n
TRKSIM CLEO
III FAST MC
mn2
1.4 1.7 GeV mhad
 just look at mhad< 1.7 , cut with largest acceptance and hence least theoretical
uncertainty, keep bkgd small with p(lepton)>1.4 GeV
7/17/2015
Vivek Sharma
60
Snowmass Study: Inclusive Vub
 ~100 b ulv events/30 fb-1 : Method attractive with large data samples
year
Ldt
2002 100 fb-1
2005 500 fb-1
2010 2000 fb-1
# bul #b cl Vub Vub
(stat) (sys)
335
127
3.2% 2.2%
1675
635
1.5% 1.5%
6700
2540
0.7% 1.5%
Vub
(expt)
3.9%
2.1%
1.7%
 Systematic error dominated by charm leakage into signal region.






Depends on S/B ratio & B. Assume B = 0.1 B @ 100 fb-1.
S/B can be improved by vertexing.
B can be reduced as Br(B [D*/D**/D/D ] l) and the form factors in these
decays become better measured. B can also be reduced through better
knowledge of D branching ratios.
Assume these improvements lead to B = 0.05 B @ 500 fb-1 or higher Ldt.
Then the systematic error dominates for Ldt
1000 fb-1 .
Br(b ulv) ~ 3.4% , Vub~1.7%
Recall theoretical error is ~ 10%
Jik Lee@Snowmass
7/17/2015
Vivek Sharma
61
Inclusive: endpoint q2 spectrum
 Inclusive q2 endpoint, lose statistics, gain in theoretical certainty
 ~40 b ulv events/30 fb-1 Method attractive with VERY large data samples.
b  cl n
TRKSIM CLEO
III FAST MC
1 ab-1
look at q2 > 11.6 , and 10.8
keep bkgd small with
p(lepton)>1.4 GeV
One experimental advantage
compared to mhad is that S/B
is more favorable
b  ul n
2
7/17/2015
10.8 11.6
S/B: 4/1 18/1
Vivek Sharma
2
q ( GeV )
62
Inclusive: endpoint q2 spectrum
For q2 > 11.6:
year
Ldt
2002 100 fb-1
2005 500 fb-1
2010 2000 fb-1
# bul #b cl Vub
(stat)
127
7
4.6 %
635
36
2.0 %
2538
144
1.0 %
Vub
(sys)
3.0%
1.2%
1.2%
Vub
(expt)
5.5%
2.3%
1.6%
 Systematic error is dominated by charm leakage into signal region for q2>10.8




(S/B ratio & B, same issues as mhad) .
Assume B = 1.0 B @ 100 fb-1, and B = 0.2 B @ 500 fb-1 or higher Ldt.
For q2 > 11.6 (S/B = 18/1), systematic error (tracking and lepton ID)
 1000 fb-1
dominates @ Ldt
2000 fb-1 Br(b ulv) ~ 3.2% , Vub~1.6%.
Recall theoretical uncertainty ~ (5 – 10) %
7/17/2015
Vivek Sharma
63
Snowmass Assessment
Outlook seems good but the method needs detailed
“real life” Detector simulations
7/17/2015
Vivek Sharma
64
Summary of how things can be !
SuperBabar Whitepaper
7/17/2015
Vivek Sharma
65
Detector Not Hermitic : Neutrino Reco?
7/17/2015
Vivek Sharma
66
Recent Developments
• Babar publication was in February 2001
– Sin2 = 0.34  0.20 (stat)  0.05 (syst)
PRL 86 (2001) 2515
• Belle also reported a measurement at the same time
 0.32
– Sin2 = 0.58 0.34 (stat)  0.09 (syst)
 0.10
PRL 86 (2001) 2509
• What has changed since then?
– BABAR has added more data: 23 million BB pairs becomes 32
million now
– Improved reconstruction efficiency
– Improved J/YKL selection
Analysis was re-blinded
*0
– New modes added: cc1KS, J/YK
– Improved resolution of vertex reconstruction for both tag and
reconstructed B
• Similerly Belle has added more data, better
reconstruction
7/17/2015
Vivek Sharma
67
c c K+
Y(2S) K+
J/Y K+
J/Y K*0(K+-)
J/Y Ks(00)
ccKs(+-)
Y(2S) Ks(+-)
J/Y Ks(+-)
Improved Reconstruction Efficiencies
KS Golden modes ~30% larger
than run 1: efficiency improved
7/17/2015
Vivek Sharma
68
Additional Channels: cC1KS
• Major improvements in
cc1KS analysis:
– M(J/Yg)-M(J/Y) cut
tightened / 0 veto
(decrease fake photons)
– Cut on E tightened
(decrease inclusive J/Y
background)
– Relaxed continuum
requirements (not dominant
background)
• Peaking background
reduced by factor ~4 (to
3%)
– With only a 10% efficiency
reduction
7/17/2015
Vivek Sharma
cc2Ks shown to be
absent
69
Run1 – Run2 Comparison
• Change in central value ~1.8s in uncorrelated error
• 30% efficiency improvement for all KS modes
• 15% improvement due to vertexing/alignment
7/17/2015
Vivek Sharma
70