Searching for New Physics at the B factories:
Title
Measurements of sin2β at BaBar
Gabriella Sciolla
Massachusetts Institute of Technology
Representing the BaBar Collaboration
Beauty 2005 - Assisi, June 20-24, 2005
BaBar and PEP-II
„
BaBar detector
„
e+
„
PEP-II asymmetric B factory
„
„
e+
„
9.0 GeV e- beam
3.1 GeV e+ beam
Peak luminosity
„
„
4π collider detector
9.1 x 1033 cm-2s-1
Integrated luminosity
„
Delivered: >268 fb-1
Most results in this talk are
based on 227 M BB events
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
2
The Beauty of the Unitarity Triangle
(ρ,η)
α
Vub* Vud
VcdVcb*
Vtb*Vtd
VcdVcb*
β
γ
(0,0)
(1,0)
Two ways of looking for New Physics:
„
„
Compare measurement of sides and angles
Measure angles in channels with different sensitivity to New Physics
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
3
The three roads to β
„
Charmonium modes:
„
„
„
c
b
c
J/ψ KS, ψ(2S) KS, χc1 KS, ηc KS
J/ψ KL
J/ψ K*0 (K*0 → KS π0)
s
d
d
d
„
„
„
c
Open-charm modes:
D*+ D*−, D*+ D−, D+ D−
b
c
d
d
Penguin-dominated modes:
„
„
„
φ K0, K+ K− KS, KS KS KS
η′ KS
KS π0, ω KS, f0(980) KS
G. Sciolla – M.I.T.
d
Measurements of sin(2β) at BaBar
d
4
CP violation in interference between
mixing and decays
t
t =0
B0
mixing
~ e−2iβ
0
B
„
„
N (B 0 (t ) → f CP ) − N (B 0 (t ) → f CP )
ACP (t ) =
N (B 0 (t ) → f CP ) + N (B 0 (t ) → f CP )
= S f sin(∆mt ) − C f cos(∆mt )
AfCP
de
fCP (ηf)
c ay
AfCP
Cf =
1− λf
2
1+ λf
2
Sf =
q Af
λf = ⋅
p Af
2 Im λ f
1+ λf
2
When only one diagram contributes to the final state:
Example: B0Æ J/ΨKS:
⎛ Vtb*Vtd ⎞
λ =ηf ⎜
* ⎟
V
V
0
⎝ tb td ⎠ Bmix
⎛ Vcs*Vcb ⎞
⎛ Vcd* Vcs ⎞
−i2β
e
=
−
⎜
⎟
⎜
⎟
*
*
0
⎝ VcsVcb ⎠ decay ⎝ Vcd Vcs ⎠ K mix
⎧C f = 0
⎨
⎩S f = Im λ
c
b
c
d
ACP (t ) = −ηf sin 2 β sin(∆mt )
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
d
d
5
How to measure the CP asymmetry
.
N ( B 0 (t ) → fCP ) − N ( B0 (t ) → fCP )
ACP (t ) =
N ( B 0 (t ) → fCP ) + N ( B0 (t ) → fCP )
e-
Flavor tagging
Q=(30.5 ± 0.5)%
B0
Υ(4S)
eExclusive B
reconstruction
e+
µ+
B0
µ- π
∆z~ βγc ∆t
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
π+
Precise ∆t determination
6
Phys. Rev. Lett. 94, 161803 (2005)
The golden mode for sin2β:
B0Æ charmonium
„
„
„
Theoretically clean
Experimentally clean
Relatively large BF (~10-4)
K0
c
b
c
d
d
d
CP sample:
J/ψ K s , Ψ(2s)K s , χcK s , ηcK s
J/ψ K L
NCP =−1 = 4370
N CP =+1 = 2788
mES [GeV]
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
∆E [MeV]
7
Phys. Rev. Lett. 94, 161803 (2005)
The golden mode for sin2β:
CP fit in BÆ charmonium K0
Unbinned maximum likelihood fit to ∆t distribution
CP=-1
CP=+1
sin(2β) = 0.722 ± 0.040stat ± 0.023syst
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
8
SM test in B0 Æ charmonium K0
cos(2β)<0
„
Compare sides and angles
„
„
cos(2β)>0
Ambiguity resolved measuring
sign(cos2β) in B0ÆJ/ΨK*
„
„
Both BaBar and Belle results used
cos(2β)=-0.68 excluded at
86.6%CL [PRD 71 (2005)032005]
Excellent agreement with
constraints from the sides
„
Another SM triumph?
.
SM test #2:
Compare β in various channels
G. Sciolla – M.I.T.
Measurements Measurements
of sin(2β) at BaBar of
angles NOT included in9 fit
The bÆccd trees:
B0 Æ open charm
u,c,t
„
„
Tree measures sin2β from bÆccd transitions
Penguin expected to be small in SM (< few %)
New Physics could have large effects
„
D*D*: as large as ∆β = 0.6 [Grossman and Worah, 1997]
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
10
New
The open charm trees:
Recent update: B0 Æ D*+D*„
Vector-vector final state:
„
„
BaBar
Preliminary
CP-even and CP-odd admixture
Transversity analysis measures fCP-even
N D *D * = 391 ± 28
CCP+ = +0.06 ± 0.17 ± 0.03
-SCP+ = 0.75 ± 0.25 ± 0.03
fCP+ = (87.5 ± 4.4 ± 0.7)%
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In good agreement with SM
Measurements of sin(2β) at BaBar
11
hep-ex/0505092
The open charm trees:
B0 Æ D(*)± D±
D*+D-
D*-D+
Updated
D+DUpdated
New
-S
0.54 ± 0.35 ± 0.07
0.29 ± 0.33 ± 0.07
0.29 ± 0.63 ± 0.06
C
0.09 ± 0.25 ± 0.06
0.17 ± 0.24 ± 0.04
0.11 ± 0.35 ± 0.06
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
12
The key to New Physics:
The Penguin Modes
Decays dominated by gluonic penguin diagrams
0
„ The typical example: B ÆφKS
NP
SM
d
d
„
„
„
d
b
d
)23
~ +(δRR
bR
~
g
sR
d
s
s
s
d
No tree level contributions
In SM, top quark dominates the loop: C~0; S~sin2β
Impact of New Physics could be significant
„
„
d
~
g
New particles could participate in the loop Æ new CPV phases
Low branching fractions
„
Measure ACP in as many bÆsqq penguins as possible!
„
φ K0, K+ K− KS, η′ KS, KS π0, KS KS KS, ω KS, f0(980) KS
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
13
Phys. Rev. D 71, 091102(R) (2005)
The golden penguin: B0 Æ φK0
N φK S = 114 ± 12
N φK L = 98 ± 18
Combined φKS and φKL fit:
G. Sciolla – M.I.T.
0.07
S φK = +0.50 ± 0.25 +−0.04
0
C φK = 0.00 ± 0.23 ± 0.05
0
Measurements of sin(2β) at BaBar
14
Phys. Rev. D 71, 091102(R) (2005)
Related channel: B0Æ K+K-KS
„
„
For non resonant B0ÆK+K-KS decays, ηCP = 2 feven- 1
feven measured from angular moment analysis of the K+K- system
feven
NK
+
K −K S
A 2S
= 2
= 0.89 ± 0.08 ± 0.06
A S + AP2
= 452 ± 28
sin 2 βKeff+K −K 0 = +0.55 ± 0.22stat ± 0.04 syst ± 0.11CP
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
15
hep-ex/0502013 (accepted by PRL)
A new golden penguin: B0ÆKSKSKS
„
Theoretically clean
„
„
Penguin dominated CP=+1 eigenstate
Experimentally challenging
„
B decay vertex uses KS pseudo-particles
and beam spot constraint
N K S K S K S = 88 ± 10
0.32
−S K S K S K S = +0.71 +−0.38
± 0.04
G. Sciolla – M.I.T.
0.28
C K S K S K S = −0.34 +−0.35
± 0.05
16
Measurements of sin(2β) at BaBar
Phys. Rev. Lett. 94, 191802 (2005)
The silver penguin: B0 Æ η’KS
„
„
Relative large BF ~ 6 x 10-5
Theoretically less clean than φKS
„
Tree diagram possible
… but Cabibbo and color suppressed…
„
|∆S| =|SΨK-SPenguin|~ 0.01QCDFact Æ 0.1SU(3)
Nη ' K S = 804 ± 40
Sη′Ks = 0.30 ± 0.14 ± 0.02
Cη′Ks = −0.21 ± 0.10 ± 0.02
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
17
The challenging penguins:
B0Æπ0KS, f0KS,
hep-ex/0503011
hep-ex/0408095
hep-ex/0503018
ωKS
B0Æπ0KS:
„
„
„
„
dominated by b → sdd
b → suu tree contribution are non negligible (∆S ~ 0.1 – 0.2)
Experimental challenge: BCP decay vertex reconstruction (σ∆t~1ps)
B0Æf0KS:
„
„
In SM dominated by b → sss
B0ÆωKS:
„
„
„
In SM dominated by b → sdd
But tree can be relatively large
B0Æπ0KS
+ 0.30
-ηf S
0.35 −0.33 ± 0.04
C
0.06 ± 0.18 ± 0.03
G. Sciolla – M.I.T.
B0Æf0KS
+0.95
+ 0.23
− 0.32
± 0.10
-0.24 ± 0.31 ± 0.15
Measurements of sin(2β) at BaBar
B0ÆωKS
+0.50
+ 0.34
−0.38
± 0.02
+ 0.29
-0.56 −0.27 ± 0.03
18
“sin2β” in penguins: BaBar only
• Although each
measurement is
compatible with J/ΨKS,
a trend is visible
• η’KS has the most
significant shift
(~2.9 σ if theory
uncertainties neglected)
… but statistical errors are
still large…
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
19
“sin2β” in penguins: BaBar + Belle
Statistical fluctuation or
first •signs
of Newof
Physics?
Average
BaBar
and Belle results
• Boxes are SM expected
ranges for -ηfSf from
Beneke, hep-ph/0505075
• Shift still significant…
SJ/Ψ - Spenguins > 3 σ
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
20
Summary and Conclusion
„
Precision measurements of sin2β in many different
channels are a powerful probe for New Physics
„
„
„
„
New Physics or statistical fluctuations?
„
„
B0Æ charmonium K0: our calibration point (σsin2β ~ 0.04)
B0Æ open charm: no smoking guns so far
B0Æ penguin modes: intriguing shifts observed
Time and data will tell…
Goals for BaBar luminosity
„
„
Summer 2006: 500 fb-1
Summer 2008: 1 ab-1
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
21
Backup slides -------------------------------------------------------------------
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
22
Transversity analysis
• D*+D*- is not a CP eigenstate
• sum of L=0, 2 (CP even) and L=1 (CP odd)
• CP odd fraction R⊥ determined by transversity analysis
1 dΓ
3
3
= (1 − R⊥ )sin 2 θ tr + R⊥ cos 2 θ tr
Γ d cos θ tr 4
2
z
θ1
θ tr
π+
π-
o
D
2
| A⊥ |
R⊥ =
| A0 |2 + | A|| |2 + | A⊥ |2
D*y
D*+
x
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
o
D
φ tr
23
D*D analysis
SM expectations
„ D+D•C = 0
• S = − sin 2 β
„
D*D
• C D *+D − = −C D *−D +
• S D *+D − = − X sin(2 β + δ ) and S D *−D + = − X sin(2 β − δ )
with:
• X= 1-CD2 *−D +
• δ =difference of strong phases for B 0 → D * +D − and B 0 → D *−D +
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
24
cos and sin fits in penguin modes
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
25
hep-ex/0503011
The challenging penguins: B0Æπ0 KS
„
In SM these decays are dominated by b → sdd
„ b → suu tree contribution are non negligible
„
„
„
∆S ~ 0.1 in model dependent QCD calculations
∆S ~ 0.2 in SU(3)
Experimentally challenging
„
„
BCP decay vtx from KS and beam spot
KS tracks with > 3 SVT: σ∆t~1ps
Nsig = 300 ± 23
„
Unbinned max likelihood fit:
SK
CK
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Sπ
0
0.30
= +0.35 +−0.33
± 0.04
Sπ
0
= +0.06 ± 0.18 ± 0.03
Measurements of sin(2β) at BaBar
26
Two more penguins:
B0Æ f
hep-ex/0408095
hep-ex/0503018
0Æ ωK
K
and
B
0 S
S
B0Æ f0KS dominated by bÆ sss
2
Events/(1.5 MeV/c )
f 0 (980) = cos ϕ s ss + sin ϕ s
40
35
30
25
20
15
10
5
0
5.23
uu + dd
, ϕ s = −48o ± 6o
2
0
preliminary
0
5.25
5.26
Tree contamination can be relatively large
N ω K S = 92 ± 13
A BAR
N f K S =B153
± 19
5.24
B0 → ωKS : dominated by b → sdd
5.27
5.28
5.29
2
m ES (GeV/c )
23
− ηCP × S f 0 K S = +0.95 +−00..32
± 0.10
G. Sciolla – M.I.T.
34
− ηCP × SωK S = +0.50 +−00..38
± 0.0227
Measurements of sin(2β) at BaBar
Results presented at Moriond 2005
The Other Trees:
Recent update: B Æ D*+D*„
Vector-vector final state:
„
„
BaBar
Preliminary
CP-even and CP-odd admixture
Transversity analysis measures fodd
„ fodd = (12.5 ± 4.4 ± 0.7)%
CCP+ = +0.04 ± 0.14 ± 0.02
-SCP+ = 0.65 ± 0.26 +0.09-0.07 ± 0.04
Æ Good agreement with SM
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
28
Penguins vs tree
G. Sciolla – M.I.T.
Measurements of sin(2β) at BaBar
29