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BELLE
��
�
� From — Status and Prospects
Tim GershonIPNS, KEK
Workshop on the CKM Unitarity TriangleApril 6, 2003
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE Introduction
� ��� �� � �� � � �� � � �
(0,0) (1,0)
(ρ,η)
φ1
φ2φ3
VudVub*
VcdVcb*
VtdVtb*
VcdVcb*
� Require interference between
� �� &
� �� processes� � � ��
is a good place to look– Relatively abundant processes with relatively clean signals� So what is the problem?– Smallness of
� �� amplitude relative to
� ��
– Efficiency to reconstruct
�
� So what is the solution?� Measure
� �� �� � �! " �$#% & ' ' at
�factories, so why not
� �)( �* �� ! " �#+ , ' ' ?Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE Notation & Disclaimers
As is common in
�
physics, different notations exist in the literatureI will use ��� Amplitude to a
�
specific final state,
�
� � Rate to a
�
specific final state,
�
�
Direct CP asymmetry,
� � ��� � � �� �
�� � � �� �
�
Branching fraction,
� � �� � � � �
�
�
Ratio of suppressed to favoured amplitudes
Disclaimers
� I apologise in advance for any bias towards Belle &
�
-factories
� All results are preliminary unless you can find them in a journal
� Not enough space to give references � � � sorry!
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE The GLW Method
Access
� ��� �� via interference between
� � � � � �
&
� � � � � � �
by reconstructing
�
decays to
��
eigenstates
�� (
��
even) &
� � ( ��odd)
� � � � �� ��� � � � � � � � �� ��� � �s
b
u
c
uW
uu
u
c
s
b
u
W
s
b
u
c
uW
uu
u
c
s
b
u
W
COLOUR ALLOWED COLOUR SUPPRESSED
K−)
D0K−)
0
φφ
δ
δ3
3
(B− DCP2A
(B−
(B− D K−)
A
A
����� �� � ���� �� � ! " #� �� $ � ! "% &(' )+* $, - �.� �� / - � �� �� 01 � "#� �� $ 01 � "% &(' )+* $ � � / �� � 2 � ��� �� � ! "#� �� $ � ! "% &(' )+* $, - �.� �� / 2 � �.� �� 01 � "#� �� $ 01 � "% &(' )+* $
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE Problems With The GLW Method
� ��� ��� is small, early predictions of� ��
�
� � � observation of COLOUR SUPPRESSED
� � � ��� �
, etc. (Belle, BaBar, CLEO)
� � � � � ��
(?)
� Hard to measure
� � � � since
� � � � � �� � � � � � � �� �
� � � � � � � � � �
instead measure
� � � �� ��� � � ��� � � � � �� � �� � � ��� � � � � �
� ��� � � � � � � �� � �� � � � � � � �
where
� �
indicates the
�
is reconstructed in a “flavour-specific” mode
��� � � � !"# $ �% !"# &'( )* !"# + &'( ), -/. 021 + � $ � � � !"# $43 % !"# &'( )* !"# + &'( ), -. 021 +
� Measure
� �5� ��� ,
� � � ��� ,� ,� �, note that
� �5� ��� � � �� � � � � � �
3 independent measurements & 3 unknowns (
� � � � ,
6 � � � ,
� ��� �� )
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � �� Results - BaBar
� BaBar have studied
� � � �
with� �� �� �
(� �� �
with� � � � � �
No
�� identification
-id required
(GeV)KE∆-0.1 -0.05 0 0.05 0.1
Eve
nts/
0.00
58 G
eV
0
20
40
60
80
100
120K0 D→B
π0 D→B
bkg
BABAR
(GeV)KE∆-0.1 -0.05 0 0.05 0.1
Eve
nts/
0.01
15 G
eV
0
5
10
15
20
25K0 D→B
π0 D→B
bkg
BABAR
� �
�� � � � ���� � � �� � � � �� � ��� ��� � ��
� � � ��
� � � ��� � �
NB.
peak around
�
, � peak around
� � � ��� �
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � �� Results - Belle
� Belle have updated results using� � � � � �
for� � � ��� � � � �
;
� � � �� �� � �� � �� � �� � � �
� � � � � � � � � �
��
�
∆E (GeV)
Even
ts / 1
0 MeV
∆E (GeV)
Even
ts / 1
0 MeV
�
� �
∆E (GeV)
Even
ts / 1
0 MeV
∆E (GeV)
Even
ts / 1
0 MeV
�
�� �
∆E (GeV)
Even
ts / 1
0 MeV
∆E (GeV)
Even
ts / 1
0 MeV
��� � ��� � � �� � �� �� � ��
��� � ��� � � �� � �� �� � � �
� �"! #$ % &')( ' * + ')( ,- + ')( ' .
�/�"0 #1$ %32 ' ( ,4 + ')( ,5 + ')( ' 6
NB.
7
peak around 8 � � 93: ;
,
< peak around
�
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE Extensions and Alternatives to the GLW Method
� � � � � � �
–
� � � � � � �� � � �
measured by CLEO, Belle
– Belle:
� � �
events with
� � � � � �
in� � � � � � (cf.
�� � � � � � � � � �
with
� � � � � �
in� � � � � � )
� � � � � � (non-resonant)– both amplitudes colour allowed � large
� � � �– non-resonant branching fraction not yet observed
u
cbs
uu
u
u u
bs
u
u
u
c
u
� � � � � � Dalitz plot analysis– General extension of above– Beneficial if different contributions interfere
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE More Extensions and Alternatives to the GLW Method
� ADS method– Use interference between
� � � � � � �
&
� � � � � �
� � � � � � � � � �SUPPRESSED
�
FAVOURED FAVOURED
�
SUPPRESSED
– Comparable amplitudes � � � large
�
– Product branching fractions become very small (below
� � �
)
� � � � � � � � � � �
– both amplitudes colour suppressed � � � large�
s
b
d
c
uW
dd
u
c
s
b
d
Ws
b
d
c
uW
dd
u
c
s
b
d
W
– These modes observed by Belle–
� � � � � � �
tags flavour of
� do not need flavour tagging– Can also study time-dependence � � � more later
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � � � � ��� � �
Results - Belle
Results with
� � � � �
0
5
10
15
20 D0K-0
0
10
20
-0.2 -0.1 0 0.1 0.2
D0K-*0
∆E (GeV)
Events/(0.01 GeV) 0
5
D*0K−0
0
5
10 D*0K−*0
0
20D−0K−*0
0
10
−0.2 −0.1 0 0.1 0.2
D−*0
K−*0
∆E (GeV)
Events/(0.01 GeV)
� ��� � � � � � � � � ��� � �� �
� � � � �� � �
� ��� � � � � � � � � � �� � � ��
� � � � �� � �
� ��� � � � � � � � � � � � � � � �
� ��� � � � � � � � � � � � � � � � �
� ��� � � � � � � � � � � � � � � �
� ��� � � � � � � � � � � � � � � � � �
If
��� �� � is large, hope to see hints for
� � � � � � � � � �
soon
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE Yet Another Extension of the GLW Method
� Consider
� � � � �
with
� � �� � � �
� �� �� �
Dalitz plot has contributions from:
� � � � � � � � � � � � � � � � �� �
� � � � � � � � � � � � � � � � � � �� �
� � � � �� � � � � � ��
�� � � � � �
� � � � � �� � � � � � � ��
�� � � � � �
� � � and many other possible modes
� Study
�� � � �
Dalitz plots for
� � � � �&
� � � � �
� � � enough information to extract
� � � �� cleanly
� Can use other multibody final states of
�decay
� Can do the same for
� � � � � � � � � �
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � ��
� �
Dalitz Plot Analysis - CLEO
Note that
� � �� � � �
Dalitz plot analysis has been done by CLEO
� NOT from�
decay!
� 5299 candidates
� �
� �background
� “wrong-sign”
� � � � � � �
observed (
� � � � significance)� “
�
”� ��
�
� � � �
error on the phase difference
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE Time-dependent
� � � � �
� Note that in any mode discussed so far, can replace � � �
&
� �
�
becomes
� � � � �� � � usually not worth considering
� BUT let’s make an exception for
� � � � � (no
� � equivalent)
d
b-
d
c-
u
d-
B0
D*-
π+
VcbVud
� favoured �
d-
b
d-
c
u-
d
B0-
D*+
π-
VcbVud
d
b-
d
u-
d-
c
B0
π-
D*+
VubVcd
� suppressed �
d-
b
d-
u
d
c-
B0-
π+
D*-
VubVcd
� Time evolution: (
��� � � �� � � � � � �� )
�� � � �� � � ���� � � ��� �� � � ���� � ! � � " � �� � ! � � "$#% &�' (' ) " � � � � & *,+ �- . � / � � " & * + �' (' ) "0
�21� ,� � �� � � ���� � � ��� �� � � �3�� � ! � � " � �� � ! � � "$#% &�' (' ) " � � � � & *,+ �- . � / � � " & *,+ �' (' ) "0
�4� ,� � �� � � ���� � � ��� �� � � ���� � ! � � " � �� � ! � � " #% &�' (' ) " � � � � & *,+ �- . � / � � " & *,+ �' (' ) "0
�21� � � �� � � � ��� � � ��� �� � � �3�� � ! � � " � �� � ! � � "$#% &�' (' ) " � � � � & *,+ �- . � / � � " & * + �' (' ) "0
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � � � � �� �� � ��� �� �
Time-dependent
� � � analysis accesses � ��� � � �� � � � ��� �� �
� � � since � ��� � � �� � �
is measured � � � � ��
BUT precise measurement of � ��� � � �� � � � � � �� �
may not precise� ��� ��
Take � ��� � � �� � � � �� ��
– measure � ��� � � �� � � � � � �� � ��
�
� � � � ��� �� � � �
On the other hand– measure � ��� � � �� � � � � � �� � ��
�� � �
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � �
�� � ����������� �� � � � �� � � ���������� �
��
�
� Cannot extract
� � � � from
� � � data
� Clean measurement in principle from
� � � � � � � � � � � � � � � � � �
� Instead use
� � � � � ��� � �
� � � � � � � ��� � � � �� � � � � � � � � � � �
� � � � �
��
� ������ � � ��
� � ���� �
� BaBar and Belle have measured
� � "! # $ %&(' ) * +
, , , limiting systematic is
� - % *' $ . ) *0/
� Belle has measured
� - % *' $ . ) *1/
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
��� � � ���� �
Both BaBar and Belle also measure
! $ % ' �
(not relevant to this discussion)B
aBar
Even
ts/2
0 M
eV B0→Ds+π-
Data
MDssidebandsCombinatorial
charmless
B0→D-π+
B0→D-ρ+
∆E(GeV)
B0→Ds-K+
0
5
10
15
012
-0.25 0
0
2.5
5
7.5
10
-0.2 -0.1 0 0.1 0.2
Bel
le 0
2
4
6
8
10 Ds+K-
0
2
4
6
-0.2 -0.1 0 0.1 0.2
Ds+π-
∆E (GeV)
Events/(0.01 GeV)
���� ��� ���� � � ��� � ���� � �� � ���� "! # $ #! # # $ #! � %� #� &
� �� �� ��'� � � �� � ��'� � �� � ��� #! () � � *+� � * � $ #! + � #� &
Belle measures
� � %&�' $ . )& +-, ./0 0 12 3 45 67 1 / 378 459 : 178 :0 12 3 45 6 7 1 / 378 45
5.200 5.225 5.250 5.275 5.3000
20
40
60
Mbc(GeV)
#entry
/2.5M
eV
0
200
400
600
800
1000
1200
1400
1600
1800
1.86 1.88 1.9 1.92 1.94 1.96 1.98 2 2.02 2.04 2.06
#event
/2MeV
Mmiss GeV
rejectreject
side band side band
� � %&�' $ . )& +, �<; , = > ? � , ;@ * #! AB& #! # C +ED F � & � G � �� � H � , � > > ? � , � � =
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � Analysis Techniques
Method Usage Pro ConFull reconstruction BaBar & Belle �� &
��� Good
� ��
Low efficiencyPartial reconstruction, any tag BaBar �� Very large statistics Poor
� ��
Partial reconstruction, lepton tag Belle
��� Large statistics, clean tag Poor
� ��
)2
Missing Mass (GeV/c1.8 1.81 1.82 1.83 1.84 1.85 1.86 1.87 1.88
)2Ev
ents
/(2 M
eV/c
0
500
1000
1500
2000
2500
3000
)2
Missing Mass (GeV/c1.8 1.81 1.82 1.83 1.84 1.85 1.86 1.87 1.88
)2Ev
ents
/(2 M
eV/c
0
500
1000
1500
2000
2500
3000
Decay Time Difference (ps)
BaBar
−15 −10 −5 0 5 10 15
Even
ts/(0
.8 p
s)
1
10
102
103
Decay Time Difference (ps)−15 −10 −5 0 5 10 15
Even
ts/(0
.8 p
s)
1
10
102
103
1.78 1.80 1.82 1.84 1.86
D0 missing mass (GeV/c 2)
0
200
400
600
800
1000
1200
Entri
es/0.
0021
GeV
/c2
DATAFitUn−peaked BackgroundPeaked Background
Belle
−0.2
0
0.2
0.4
0.6
0.8
1
−1500 −1000 −500 0 500 1000 1500
∆z (µm)A(∆
z)
� � � �
,
�� �� � � �
events
��� � ��� � �� � � � � �� � � � � � � � !
"� � � �
,
"� "� �# �
events
$&% � � � �� ' � � � � �( � � � � )� � ! * +
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � � � � -� /F � -�� /;
- Monte Carlo Studies
Can generate Monte Carlo with any
� ��� ,
��� , � �� - > . �� % � . ��� %# /
using EvtGen
This example uses
� partial reconstruction
� lepton tag
� � � �� �� � �
sample
INPUT MEASURED�� ��� � �! � � � "# $ * � "&% $* * ' ��� % & #! #) ( & #! #) ( $ #! # B
� � ��� � �! � � � "# $ * � "&% $* & ' ��� % & #! # (( & #! # C # $ #! # )
) Asymmetric peaks in same flavour modes ) Shifted means of mixing asymmetry
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � � � � -� /F � -�� /;
- Experimental Considerations
� High precision vertexing requiredshift in
��� of � F�� � $ shift in
> � ��� � �� - > . � � % � . �� %# ? ��� /
of � F
Partial reconstruction (lepton tag) very sensitive to charge dependencies
� Background contains
% ), % ��� % ,
% ��� %� , etc.$ same quark level process & same
�
violating effectPartial reconstruction techniques need sophisticated background treatment
� Kaon tags often come from
% � � % ), % � � % ,% ��� %� , etc.$ same
�
violating effect on the tag sideFull reconstruction & partial reconstruction (any tag) sensitive
� Different techniques are complementary
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� , � - �/ �,
� - �/ � F
� Similar modes also access � �� - > . �� % � . ��� %# /
� % ), % ,
%� can only be studied using full reconstruction
� %� ,
%� � are
! $ � �
decays and contain extra information
– 3 helicity/transversity statesG ; ��� � �� ; �� � �, relative amplitudes & phases,
> . � � % � . ��� %#
– Total of 11 parameters$ can in principle be obtained from time-dependent angular analysis
– Interference between helicity amplitudes
� do not need to measure
� � � �– What is the best way to do this fit?
B
D*
D
π
ρ
π
π+
−
0
θθDρ
0
+
−
χ
*
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � � Polarization
� CLEO have measured
��� � �, � , � �� ? � , � F� ? � , � F >
��
�
���
�
? Can analyze
% � in same way as
% � ), replacing
> �� � � � �� - .� ? � �� / $ - > �� � F / > �� � � � �� - .� ? � � �/
– Complications if helicity states have different
� � � �,
� � �
– Beneficial for partial reconstruction where angular ( �) resolution may be poor
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE
� � �/
� � � F Partial Reconstruction - BaBar
Large signal yields, but very large backgrounds
%�
)2
Missing Mass (GeV/c1.845 1.85 1.855 1.86 1.865 1.87 1.875
) 2
Eve
nts
/ (
0.00
12 G
eV/c
0
500
1000
1500
2000
2500
3000
a)
)2
) (GeV/c+π0πm(0.5 0.6 0.7 0.8 0.9 1
) 2
Eve
nts
/ (
0.02
48 G
eV/c
0
500
1000
1500
2000
2500
3000
b)
)2
) (GeV/c+π0πm(0.5 0.6 0.7 0.8 0.9 1
) 2
Eve
nts
/ (
0.02
48 G
eV/c
0
500
1000
1500
2000
2500
3000
Fisher Discriminant−4.5 −4 −3.5 −3 −2.5 −2 −1.5 −1 −0.5
Eve
nts
/ (
0.17
2 )
0
1000
2000
3000
4000
5000
c)
Fisher Discriminant−4.5 −4 −3.5 −3 −2.5 −2 −1.5 −1 −0.5
Eve
nts
/ (
0.17
2 )
0
1000
2000
3000
4000
5000
Decay Time Difference (ps)−15 −10 −5 0 5 10 15
Eve
nts
/ (
0.6
ps
)
1
10
102
103
Decay Time Difference (ps)−15 −10 −5 0 5 10 15
Eve
nts
/ (
0.6
ps
)
1
10
102
103
Decay Time Difference (ps)−15 −10 −5 0 5 10 15
Eve
nts
/ (
0.6
ps
)
1
10
102
103
d)
� > � � � & $ � � > � ? > � �events
�� �, F ,� F� ? � , �� � ? � , � =� � �
%� �
mmiss(Gev/c 2)
En
trie
s/(2
Mev
/c)
� > � � � & $ F � � � � ? F > � �
events
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003
BELLE Prospects for
� -�� /; Measurement
Mode Summer 2003 (
F � � � � &
)
F � � � � � &
% �� �& � � � � � ��� � � , F >
,
� � � � , F �
Observe D
�
V (if
� � � �, �)
�� � � � � , �� $ . �� %# � ; � �
% �� #
Search for
"! # $ % # �� #
Search for
"! # $ % �� �� #
%� ) ' � � � � � � "# $ * � " % $* $ ' ��� % %�� #! ( - � �� - > . � � % � . ��� %# / / � � , F �
PARTIAL REC. Assume
� ��� &
' ��� known, may hit systematics limit%� ' � � � � � � "# $ * � " % $* $ ' ��� % %�� "! � - � �� - > . � � % � . ��� %# / / � � , ; �
PARTIAL REC. Worse than
�� � due to background, not
# # �
polarized% ��� % ) � ' � � � � � � "# $ * � " % $* $ ' ��� % %�� #! ( - � �� - > . � � % � . ��� %# / / � � , F �
FULL REC. All modes combined
� Dalitz plot & time-dependent angular analyses also look promising
� Clearly a long an arduous journey ahead of us to measure
. �� %#
� The first steps are being taken
, , , in some cases the path ahead is clear
, , , there may yet be surprises along the way
� Reason to be optimistic about prospects with
F � � � � � &
Tim Gershon Workshop on the CKM Unitarity Triangle April 6, 2003