picture erice - tu dresdenschubert/talks/erice-0209.pdf · 2002. 9. 23. · 23 sept 2002 k. r....

K. R. Schubert (TU Dresden), QHN Erice23 Sept 2002 1

Picture Erice


Title page New Results onCP Violation in

B-Meson Decays

K. R. Schubert, TU DresdenQuarks in Hadrons and Nuclei

Erice, 23 Sept 2002

Old Results on CPV in K and B Decays Explanation in the Standard ModelPEP-II and KEK-B, BABAR and BelleSearch for CPV in other B Decay ModesLuminosity expectations


Discovery of CP Violation:1964 by Christenson, Cronin, Fitch and Turlay in the π+ π−

decay of K0 = 11S0 sd. „Strange particle“ with transitions K0↔K0 and onlytwo states with exponential decay laws: KS = pK0 + qK0 ,

KL = pK0 - qK0 .CP symmetry ⇔ |p|=|q|,Observed 1964: |p|>|q|.Simplest demonstration today:

CPV discovery I

( ) ( ) ...

...

LeRLLReLRR

RLRLRL

eeuuCPeeCPCP

µµ ννµννµ

νν−−++

+−

→Γ=→Γ

===CP Symmetry of the Weak Interaction:

Strictly obeyedfrom 1957 to 1964

1999


CP-Violating Asymmetry: Explanation of this CP-Violation in the Standard Model:

CPV discovery IICPLEAR

( )

ttK

t

LS

LS

eetme

KNKNKNKNtA

Γ−−+

Γ−

−+Γ+Γ−

−+

−+−+

−+−+

+

−⋅∆−=

→+→→−→

=

2

2/)(

00

00

)( cos2)()()()(

η

ϕη

ππππππππ

( ) 0)5.03.43(31002.027.2 ±−−+ ⋅⋅±= ieη

The 4x3 weak interaction couplings are complex,g = g0

.Vij (CKM). Their interference leads toΓ(K0 → K0) < Γ(K0 → K0).


Expected CPV in B decays

For 37 years, the K0 was the only system in particle physicswith CP violation. In summer 2001, decays of B0 mesonsshowed the second evidence. Search for CPV(B) could beplanned well because of clear Standard Model expectation:

( ) ( )( ) ( ) ( ) ( ).arg;sin2sin

//// **

0000

0000

cdcbtbtdBSS

SS VVVVtmKJBKJBKJBKJBA =∆⋅=

→Γ+→Γ→Γ−→Γ

= ββψψψψ

β(CKM) given by St.Model. Early B experiments (ARGUS, CLEO) measure ∆mB = 0.47/ps and |Vub| ⇒ sin2β = 0.2-1.0;sin2β = 0.5-0.8 if CPV(K) has only St.Model origin.However, 3.107 B mesons required! Most promising method:

e+

e-γ

ge Y(4S),10.56 GeVB0

B0

c sgw

K0

J/ψ

gs

g

Wgw

c

d

dgs

b

b

ge


PEP-II

The B-Meson Factory PEP-II at SLAC:design 1988, approval 1993, start 1998

yes9.0 / 3.1E [GeV] e- / e+

308135Lint [pb-1/day]4.6 x 10333 x 1033L [cm-2 s-1]980 / 1680610 / 2140I [mA] e- / e+

reachedPlan

βγ = 0.55


KEKB

(on same time scale)

βγ = 0.43

achieved: 7.35 x 1033


View ino KEKB tunnel

KEKBin theTRISTANtunnel,L=3.0 km

PEP-II:L=2.2 km


Lumi in BABAR & Belle

91/fb in PEP-II85/fb in KEKB

σ(e+e-→Y4S)= 1.1 nb ⇒

N(BB) = 100Min PEP-II,95M in KEKB.

In practice ≈ 90% of thatbecause of runsoff-resonance.

L

I(LER)I(HER)

Typical very good day in PEP-II


Cont. Subtraction & 2-particle coherence

ϒ Resonances= n3S1bb states, JPC=1- -

BB

- -

ϒ(4S)→B0B0(50%), B+B-(50%). Strong decay conserves C&P.Neutral final state is coherent 2-particle state, (BoBo-BoBo)/√2,Single B state created when first B of the pair decays

ttttt decaydecayproductiondecay ∆=−⇒− )()( 1222


The BABAR Detector:

BABAR Detector

(4) ElectromagneticCalorimeter (6) Instrumented

Iron Yoke(3) Cerenkov-Detector

(5) 1.5 T Solenoid

(2) Drift Chamber

(1) Silicon Vertex Detectore-

e+


BABAR picture & Collaboration

73 institutes

USAItaly FranceUKGermanyCanadaRussiaChinaNorway

516 authors


Belle Detector

≈ 300 physicists, 49 institutes, 14 countries: Australia, Austria, China, Germany, India, Korea, Japan, Philippines, Poland, Russia, Slovenia, Switzerland, Taiwan, USA


BABAR Si Vx Tracker

BABAR Silicon Vertex Tracker: βγ cτ(B) = 260 µm,π βγ c /∆m(B0) = 1 mm,

R=14cm

σz ≈ 70 µm for fully reconstructed B mesons

σz ≈ 180 µm forB0 meson tags


A fully reconstructed eventϒ

CP eigenstate, decay at t1,either from B0 or from B0

flavour eigenstate,here from B0,decay at t2, „tags“ the flavour

of the other B at time t2

A fully reconstructed event:

Such events are very rare, o(10-6), therefore BABAR and Belle use inclusive tagging for CP asymmetry measurement.


T dependence of asymmetry( ) ( )( ) ( ) ( )[ ]tagdecay

SS

SS ttmKJBKJBKJBKJBA −∆⋅=

→Γ+→Γ→Γ−→Γ

= sin2sin////

0000

0000

βψψψψ

Integral of A over all ∆t is zero. Therefore it is necessary to measure the ∆t dependence (and - for technical reasons - to boost the ϒ4S.)

B0B0

∆t/τ

Γ B0

B0

Incoherent case:

B0 dec.B0 tags

B0B0

∆t/τ

Γ B0 decaysB0 tags

Because of coherence:

Searched CP-Asymmetry:


Prinzip der sin2beta MessungMeasurement of time-dependent CP-Asymmetry:

4: Flavour Determination of the other B Meson (“tag”)

1, 2, 3: B Reconstruction into CP Eigenstate

Υ(4S)

( ) ( ) ( )( ) ( ) ( ) tt-t~t) msin(2sinD

/B/B

/B/Bt~A~

0000

0000

∆∆∆⋅∆∆⋅⋅=Ψ→Γ+Ψ→Γ

Ψ→Γ−Ψ→Γ=∆ ∫ dr

KJKJ

KJKJ

SS

SS β

e+

βγ = 0.55

6: Determination of ∆t = ∆z/βγc 7: Determination of the ∆z reso-lution function5: Determination of the fraction w of mistags

Dilution D = (1-2w) reduces observed asymmetry.

8: sin2β Fit to both Time Distributions


Newest BABAR results (7/02):

ccKSmodes:

J/ψKL: Ncand = 132Purity = 63 %

ηc(KKπ)KS


One more mode:

J/psi K*

D = 0.68 ± 0.07


Tagging quality and result

28.1 ± 0.765.6 ± 0.5total0.9 ± 0.231.6 ± 0.920.0 ± 0.3Inclusive6.7 ± 0.420.9 ± 0.819.8 ± 0.3Kaon II10.7 ± 0.49.9 ± 0.716.7 ± 0.2Kaon and π(soft)7.9 ± 0.33.3 ± 0.69.1 ± 0.2Lepton

Q (%)Mistag fraction (%)Efficiency (%)Tagging Category

Tag quality Q = Σ εi (1-2wi)2 ( )sig

bg

sig NN

QN+⋅

⋅≈⇒ 19.12sin βσ

Result July 2002 with 90 M ϒ(4S), 2641 tagged events:

sin2β =0.741± 0.067± 0.033

-5 0 5 ∆t [ps] -5 0 5 ∆t [ps]


BABAR asymmetry, all and golden

σ(sin2β)

Submitted to PRL,

hep-ex/0207042


Belle results

July 2002Results with 78/fb,85 M ϒ(4S)


All sin2beta results

13σ effect


Explanation in the Standard ModelHiggs mechanism gives mass to doublets .The partners d‘i of ui are related to the mass eigenstates diby a unitary rotation in family space.Matrix V was introduced into the Standard Model by M. Kobayashi and T. Maskawa 1973, now called VCKMbecause of N. Cabibbo‘s d‘ = cosθ . d + sinθ . s in 1963.

'ii dWu +↔

′

′

′

=

′ b

tsc

du

du

i

i

jiji dVd ='

bVsVdVbbVsVdVsbVsVdVd

tbtstd

cbcscd

ubusud

++=

++=

++=

'

'

'

bVsVdVbbVsVdVsbVsVdVd

tbtstd

cbcscd

ubusud

***'

***'

***'

++=

++=

++=

owing to CPT symmetry.

Higgs mixes antiquarks differently than quarks if VCKM is not real; more precisely ifThis is the origin of CP violation in the Standard Model.

( ) 0Im ** ≠= iljljkik VVVVJ


Wolfenstein and unitarity triangle

Wolfenstein 1984:

A, λ, ρ, η are 4 of 18 „free parameters“ of the St. Model.6 unitarity conditions of V can be drawnas triangles, e.g.:

.;1)1(

2/1

)(2/162

23

22

32

ηλληρλ

λλλ

ηρλλλ

AJAiA

A

iA

V ≈

−−−−−

−−

≈

.1//

,033*

*3*

≈+

=+−

λλ

λ

AVAV

VVAVV

tdub

tbtdubud

ρ

η

1

Vub*/Aλ3

Vtd/Aλ3

β

Area of this triangle is J/2.Measurements of λ, A, ρ2+η2,

and (1−ρ)2+η2 giveλ = 0.22 ± 1% , A = 0.83 ± 4%,

lJl ≈ 3 • 10 –5 . St. Model violates CP symmetry.0


ckm-Lfit-0208-1

Γ(B→ρlν)∆Γ(B→Xulν)

η maxL, 1σ, 2σLfitckm


ckm-Lfit-0208-2

maxL, 1σ, 2σ∆m(Bd

0)∆m(Bs

0)

J≠0,Standard Model

violates CP with > 3σ,concluded fromCP conserving

measurements only.

ηLfitckm


ckm-Lfit-0208-3

maxL, 1σ, 2σ

ε(K0)

ηLfitckm


ckm-Lfit-0208-4

maxL, 1σ, 2σ

Combined Fit

ηLfitckm


ckm-Lfit-0208-5

Previous fit without sin2β

sin2β

maxL, 1σ, 2σηLfitckm


ckm-Lfit-0208-6Fit with all experimentsexcept sin2β:

Fit with all experiments,B → ρlν, B → Xulν, ∆md, ∆ms, ε(K), sin2β:

(λ = 0.220 ± 0.002)(A = 0.85 ± 0.04)ρ = 0.20 ± 0.11η = 0.35 ± 0.06

J = (2.9 ± 0.6) .10-5

maxL, 1σ, 2σηLfitckm


ckm-Lfit-0208-7

sin2β from BABAR, Belle, LHCb∆ms from CDF, D0, LHCbB→ργ/B→K*γ BABAR,Belle

Vub from BABAR, Belle,and Theory!

and Theory!

ηLfitckm

Future?

(Falsification of the Standard Model?)


Search for CP Violation in other B-Meson Decays

1. CP Violation in B0B0 Oscillations, Re ε(B0):

CPV in Bbbar Mixing

))(())((

))(())(()(

tNtN

tNtNtA

∆+∆

∆−∆=∆

±±−+

±±−+

llll

llll

A

∆m(B0) = (0.499 ± 0.010 ± 0.012) h ps-1

007.006.998.00036.00029.00012.0

)||1/()Re( 2

±±=

±±+=+

pq

BB εε

A(∆t) with 20/fb:

βγ =0.55 ϒ(4S) <∆z> = 250 µm

B0

l+

l-

B0

))(())(())(())(()(tNtNtNtNtACP ∆+∆

∆−∆=∆ −−++

−−++

llll

llll


B0→φK0S : Pure penguin, tree highly suppressedB0→φK0

S : Pure penguin, tree highly suppressed2.

A = sin2β in St.M, but new physics may change A.

CPV in B to phi Ks

51 events

( ) 600 108.05.21.3

1.8 −⋅

±

−+

=Φ→ KBB

BABAR: A(φKS) = -0.19 ± 0.52 ± 0.09 1.8σ from ccK0

Belle: A(φKS) = -0.73 ± 0.64 ± 0.18 2.3σ from ccK0

Combined: -0.40 ± 0.41 2.7σ from ccK0


( ) ( )( ) ( )fBfB

fBfBA→Γ+→Γ→Γ−→Γ

=Search for Direct CPV(B)3. Condition: Final state f is reached by two diagrams,

( ) ( )( ) ( )2121

22

21

212121

coscos2sinsin2

δδφφδδφφ

−−++−−

=aaaaA with 2 different weak φ

and two different strong δ

8 ± 135.3 ±8.3 -3.5 ± 7.639 ± 6 ± 2K*+ γ

1.8 ± 4.3-0.9 ± 2.71010 ± 30 ± 50J/ψ K+

18 ± 2446 ± 15 (*) 2 ± 9 (**)

-17 ± 10 K0π+

-4 ± 16-7 ± 6 -10 ±517.9 ±0.9 ±0.7K+π-2 ± 36 10.4 ±1.5 ±0.8K0π0

-29 ± 23-4 ± 19 -9 ± 9 12.8 ±1.2 ±1.0K+π0

31 ± 31 -3 ± 18 5.5 ±1.0 ±0.6π+π0

A(CLEO)%

A(Belle)%

A(BABAR)%

B(BABAR)10-6

Mode

(*) 24/fb (**) 78/fband in more modes ...


4 types of CPVNo CPV(B) effect seen - except sin2β - with > 3σ.Some effects with 2 to 3 σ come and go,

small statistics does not give Gaussian σ.

( )( )

( )( )

( ) 120

0

0

0

−≠−=→→

→→

= +−+

−+βα

ψ

ππ

ππππ effi

S

S

K

eKccBAKccBA

BABA

rr

There are four types of CP Violation seen and expected:

1) in flavour oscillations M0↔M0, Re(εK), Re(εB),2) in interference between oscillations and decay, Im(εK),

3) direct CPV in decays into one final state, Re(ε‘K), A(B→πK)...page 35

4) Direct CPV in decays into > 2 final states, Im(ε‘K),

( )( ) ( )[ ]ββ 2sinIm2

0

0

=−=→⋅→⋅

= −Kcc

i

S

SKcc re

KccBApKccBAqr


4. Search for CPV(B→π+π-)

Decay functions f+(f-) for tag = B0(B0):

For weak phase from tree T only:

With additional phase from penguin P: d

ud

d

b

d

t

d

duu

W

g

W

αγ β

( ) ( ) ( )[ ]tmCtmStf ∆⋅∆⋅∆⋅∆⋅±Γ

=∆± cossin14

m

α2sin,0 == SC

.2sin,0 effSC α=≠

b u


CPV(B→π+π-) II

BABAR with 81/fbJuly 2002Preliminary:

S = 0.02±0.34±0.05C = -0.30±0.25±0.04

S = 0 ⇒ no type-2 CPV,αeff = 900 ± 110.

C = 0 ⇒ no type-3 CPV,

αeff = 900 ± 110, β = 250 ± 3.50

⇒ Type-4 CPV only with 2.3σ.


Belle with 42/fb, March 2002:

CPV(B→π+π-) Belle

S = -1.21 ± ± , ≠ 0 with 3.2σ

C = -0.94 ± ± 0.09 , ≠ 0 with 3.0σ

0.380.17

0.160.13

0.310.25


CPV(B→π+π-) IV

Belle value is outsidethe physical boundary.Average not very relevant.Therefore, here, only onediscussion of the result:

S

-C

S2+C2<1


PEP-II Luminosity Expectations

Peak Lumi[1033/cm2/s]

IntegratedLumi

[events/fb]

(from David MacFarlane, BABAR, August 2002)

Similar expectations for KEK-B.


CPV Precision estimates(from David MacFarlane, BABAR, August 2002)

As important as more precision on CPV observables:|Vub| from b→ulν and |Vtd| from B →ργ for testingif all observed CPV fits into Standard Model.0.5 - 2/ab: σ(Vub) = 5%, σ(Vtd) = 10%.


Summary• Owing to the unexpectedly good performance of the e+e-

storage rings PEP-II and KEK-B, the experiments BABAR and Belle have now analysed ≈ 90 M BB pairs each, establishing CP Violation in B meson decays with ≈ 13σ.

• Owing to the unexpectedly good performance of the e+e- storage rings PEP-II and KEK-B, the experiments BABAR and Belle have now analysed ≈ 90 M BB pairs each, establishing CP violation in B meson decays with ≈ 13σ.

• The observed asymmetry sin2β = 0.734 ± 0.055 isin perfect agreement with the Standard Model, which naturally contains CPV if 6 quarks with m(qi) ≠ m(qk).

• There are no other CP(B) asymmeties with significance> 3.2σ. If no surprises, the next significant measurementswill require 5 to 20 times more data than now available.

• There are no known limitations in storage ring physicswhich exclude that 5 - 20 times higher luminosities can be achieved at both PEP-II and KEK-B during this decade.


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picture erice - tu dresdenschubert/talks/erice-0209.pdf · 2002. 9. 23. · 23 sept 2002 k. r....

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