CP Violation in B-Meson Decays - TU Dresdenschubert/talks/edinburgh-0302.pdf · CP Violation in B-Meson Decays CP Violation in the Standard Model ... Properties of the CKM matrix:;

13 Feb 2003 K. R. Schubert (TU Dresden), Colloquium U Edinburgh 1

K. R. Schubert, TU DresdenColloquium U Edinburgh, 13 Feb 03

CP Violationin B-Meson Decays

CP Violation in the Standard ModelExpectations for B-Meson ExperimentsPEP-II and KEK-B, BABAR and BELLEResults and Interpretation


Particle physicists know three systems without particle-antiparticle symmetry:The UniverseMore matter than antimatter. n(N)/n(γ) ≈ 10-9 points toNN annihilation at the end of the „massive-quark gluon“ era;q/q ≈ 1+10-9 requires CP. Standard Model offers this at the end of the „massless“ era, but with q/q ≈ 1+10-20. Extra CP? The Neutral K MesonDiscovery of KL→π+π- by Cronin et al 1964 ⇒ Re(ε) ≈ 10-3,π0π0 ≠ π+π- by NA31/48, E731/KTeV 1988/99 ⇒ lε‘l ≈ 3.10-6.Only CP values till 2001.The Neutral B Meson2002: Measurements of BABAR (90 M BB) and BELLE (85 M BB) in e+e- annihilation at 10.6 GeV show sin2β = 0.73 ± 0.06in agreement with Standard Model CP for K0 and B0 mesons.

The Universe


Paul Adrien Maurice Dirac(1902 – 1984)

Standard Model ofElementary Particle Physics= Extension of Dirac equation by

gauge principle and „zoology“. Dirac 1928:Dirac 1928:

Dirac‘s eq.is C- and P-symmetric.),,,()( ++−−==

−∂=

RLRL eeeexee

eemeieL µµγ

µµµ

α

Aqiiexexe xi

−∂→∂⇒⋅→ )()()(

Weyl 1929:

PC

CPWith electricity,Dirac‘s eq.remains C- and P-symmetric.


Glashow 1961:Invariance of Dirac‘s eq. under local SU(2) + U(1) produces weak and electric interaction byW+, W-, Zo, γ exchange.

P- and C- symmetryare maximally broken;CP symmetry remains.

µµµµ

α

α

σ

νν

ν

BygWgii

exex

xUxex

eeeeofinsteadeande

aa

xi

L

L

L

L

xiRRR

L

L

'2

)()(

)()()(

,

)(

)(

−−∂→∂⇒

→

→

SU(2) invariance requires, because of mee = m(eLeR+eReL) → m ee :

.0)()()()()( ===== νγ memZmWmm


Introduction of a spin-0-doublet Φand spontanuous symmertry breaking

Higgs gives back Dirac‘s electron mass which was taken away by Glashow.

Glashow, Weinberg, Salam 1968:Same Higgs mechanism produces masses for µ andquarks udcs, and gives quark mixing in W exchange.

Higgs 1964:

( ) ( )

( )

( ) eemeeeecv

ehLeeeecvLLxhvx

x

eee

ecLL

RLLR

RLLR

RLLL

LR

=+

++−→⇒

+

→

ΦΦ

ΦΦ

+

ΦΦ−→

),()(

0)()(

int2

1

2

1*2

*1 ν

ν


Kobayashi, Maskawa 1973: Extension 2 → 3 families(discovery of τ-lepton 1975 , c-quark 1974, b 1977)

For gauge invariance, the complex matrices C arbitrary. C(u) can be diagonalized by rotations in family space:

.].

[

)3,3,3,3(

)(

)()(

321,

chdu

uC

du

dCl

lC

LLdulLL

L

LTR

u

L

LR

d

L

LR

l

bosonsSUSUUkinDirac

+

Φ+

Φ+

Φ−

++=

++

⊗⊗

β

βααβ

β

βααββ

βααβ

ε

ν

ν

→

→

→

'''

)(

3

2

1

;00

0000

;L

L

L

L

L

L

t

c

uu

bt

sc

duDubletts

mm

mCv

tcu

uuu


.,, '''LLLLLL bWtsWcdWu +++ ↔↔↔W exchange:

Dublet partners of uc t are not mass eigenstates.Since (uα dα) is one object to be rotated in family space,C(u) and C(d) cannot be diagonalysed simultanuously..

V was introduced into the Standard Model by Kobayashi and Maskawa 1973.Phenomenology for 2 families already by Cabibbo 1963.

Properties of the CKM matrix:

.1;'

'

'

==

=

+VVwithVV

bsd

Vbsd

CKM


bVsVdVb

bVsVdVs

bVsVdVd

tbtstd

cbcscd

ubusud

⋅+⋅+⋅=

⋅+⋅+⋅=

⋅+⋅+⋅=

'

'

'

The matrix Vik is complex. CPT symmetry requires:

Higgs mixes antiquarks in a different way than quarks. This is the origin of CP violation in the Standard Model.Vik

*≠ Vik is necessary, but not sufficient.Because of unobservable quark phases, we must have:

bVsVdVb

bVsVdVs

bVsVdVd

tbtstd

cbcscd

ubusud

⋅+⋅+⋅=

⋅+⋅+⋅=

⋅+⋅+⋅=

***'

***'

***'

.0)(Im ** ≠= jkjlilik VVVVJ


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 ≈

−−−−−

−−

≈

Wolfenstein 1984:

.1//

,033*

*3*

≈+

=+−

λλ

λ

AVAV

VVAVV

tdub

tbtdubud

ρ

η

10

Vub*/Aλ3

Vtd/Aλ3

β

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

and (1−ρ)2+η2 giveλ = 0.223 ± 1% , A = 0.82 ± 4%,

lJl ≈ 3 • 10 –5 . Standard Modelviolates CP symmetry.


ckmLfit-0208-2

Max L, 1σ, 2σηLfitckm

B → ρlν, CLEO, BABAR

b → ulν, CLEO, LEP

∆m(Bs) limit, LEP with ξ from lattice

∆m (B0) value, LEP, BABAR...with fB√BB from lattice

J≠0 with >3σ

There is CP in the Standard Model, concluded from only CP-symmetric observations!1. Does this J explain ε(K0)? 2. What prediction for CP(B0)?

Informations on ρ and η


CPLEAR

( ) ( ) ( )SSLK KKmKmm Γ≈−=∆

Asymmetry betweenπ+π - decays of taggedK0 und K0 as fuction of time between production and decay:

Demonstration of CP(K) in a more recent experiment:CPLEAR 1999, pp → K+π -K0, K- π+ K0; K0,K0 → π+ π-

ttK

t

LS

LS

ee

tme

KNKN

KNKNta

Γ−−+

Γ−

−+Γ+Γ−

−+

−+−+

−+−+

+

−∆⋅∆−=

→+→

→−→=

2

2/)(

00

00

)( cos2

)()(

)()()(

η

ϕη

ππππ

ππππ

( ) ( ) oie 5.03.4331002.027.2 ±−−+ ⋅⋅±=η


ckmLfit-0208-3

η+-(Ko)

η

Lfitckm

Max L, 1σ, 2σ

1. Yes!


Prediction for CP(B0):2.

( ) ( )( ) ( ) ( )[ ]tBm

KJBNKJBNKJBNKJBNASS

SS ∆∆⋅=Ψ→+Ψ→Ψ→−Ψ→

= 00000

0000

sin2sin//// β

where ∆t is the time between B0(B0) production and decay.

η

Fit with lVubl, lVtdl, and η+-

β

Lfitckm


Short History:

1977 Discovery of b in Υ(9.46) = 13S1 bb at FNAL1978 Formation of Υ(9.46) and Υ(10.01) at DESY1980 First B mesons 11S0 bq at Cornell1986-89 „B-Meson Factory“ plans at PSI1987 ARGUS discovery of BoBo oscillations1988 Start of PEP-II studies at SLAC1993 Decisions for PEP-II and KEK-B1995 BABAR „TDR“ & approval7/98 First e+e- collisions in PEP-II5/99 First e+e- events in BABAR7/00 First BABAR & BELLE results at Osaka 10/00 PEP-II reaches design luminosity of 3

•1033/cm2/s3/01 BABAR and BELLE publish sin2β in PRL


SLAC photo← Fixed Target

Experiments

← BABAR

← SLD

← Linac


e-

e+

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

308135Lint [pb-1/day]4.5 x 10 333 x 1033L [cm-2 s-1]980 / 1680610 / 2140I [mA] e- / e+

ReachedDesignyes9.0 / 3.1E [GeV] e- / e+

308135Lint [pb-1/day]4.5 x 10 333 x 1033L [cm-2 s-1]980 / 1680610 / 2140I [mA] e- / e+

ReachedDesign

e-

e+

The B-Meson Factory PEP-II:


KEKB

βγ = 0.43

achieved: 7.35 x 1033


Daily and Integrated Luminosity,October 1999 to February 2003

Design

BABAR

BELLERecorded 107.79/fb


(4) ElectromagneticCalorimeter (6) Instrumented

Iron Yoke(3) Cerenkov-Detector

(5) 1.5 T Solenoid

(2) Drift Chamber

(1) Silicon Vertex Detectore-

e+

The BABAR Detector:


BABAR photo


BABAR Collaboration: 10 Countries, 74 Institutes USA Caltech PasadenaUC, IrvineUC, Los AngelesUC, San DiegoUC, Santa BarbaraUC, Santa CruzU of CincinnatiU of ColoradoColorado StateFlorida A&MU of IowaIowa State ULBNL BerkeleyLLNL LivermoreU of LouisvilleU of MarylandU of MassachusetsMITU of MississippiMount Holyoke CollegeNorthern Kentucky UU of Notre DameORNLU of OregonU of PennsylvaniaPrairie View A&MPrinceton USLACU of South CarolinaStanford UU of TennesseeU of Texas at DallasVanderbilt UU of WisconsinYale U

NetherlandsNIKHEF Amsterdam

Norway U of Bergen

Russia Budker Inst., Novosibirsk

Italy INFN BariINFN FerraraINFN Frascati INFN GenovaINFN MilanoINFN Napoli

CanadaU of British ColumbiaMcGill UU de MontréalU of Victoria

China Inst. of High Energy Physics, Beijing

GermanyRU BochumTU DresdenU Rostock

FranceLAPP AnnecyLAL OrsayU Paris 6 et 7Ecole PolytechniqueCEA Saclay

United Kingdom U of BirminghamU of BristolBrunel UniversityU of EdinburghU of LiverpoolImperial CollegeQueen Mary & Westfield CollegeRoyal Holloway, University of LondonU of ManchesterRutherford Appleton Laboratory

INFN PadovaINFN PaviaINFN PisaINFN Roma INFN TorinoINFN Trieste

≈500 physicists


Dresden Contributions to Calorimeter:

10 % of 6580 CsI(Tl) crystals, and all photodiodes

Optimisation of crystal light yield

Mechanics of readout electronics

Lightpulser system for monitoring

(with Edinburgh and Bochum)

Bhabha calibrationπo calibration

e identification


σz ≈ 70 µm for fully reconstructed B mesons

σz ≈ 180 µm forB0 meson tags

βγ = 0.55, βγ cτ(B) = 260 µm,π βγ c /∆m(B0) = 1 mm,

R=14cm

Silicon Vertex Tracker:


Belle Detector

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


CP state

flavour state

A fully reconstructed event in BABAR:


CP asymmetries in B0 decays:

Decay of ϒ(4S) produces coherent 2-particle state(BoBo-BoBo)/√2 :

Integral of Α over all ∆t is zero ⇒ time dependent and boosted measurement necessary.

Tagging by partially reconstructed,but flavour-specific decays of the second B.

ttttt tagdecproddec ∆=−⇒− )()( ...

( ) ( )( ) ( ) ( )[ ].0000

0000

sin2sin////

proddecaySS

SS ttmKJBKJBKJBKJBA −∆⋅=

→Γ+→Γ→Γ−→Γ

= βψψψψ

Γ

B0B0

∆t/τ


Measurement of time-dependent CP asymmetry:

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

1, 2, 3: B Reconstruction into CP Eigenstate

ϒ( )

( ) ( ) ( )( ) ( ) ( ) 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


Event Selection

N N

in B → J/ψKS

J/ψ → e+e- J/ψ → µ+µ-

π0π0

π+π-

2. K0 Reconstruktion

1. J/ψ Reconstruktion


3. B0 Reconstruction:

More CP Modesin addition toB0 → J/ψ KS :

B0 → ψ(2S) KSB0 → χc1 KSB0 → ηc KSall with CP = -1 and

B0 → J/ψ KL CP = +1

B0 → J/ψ K0*(KSπ0)CPeff = +0.65±0.07

mES

∆E∆E

MeV

mES GeV

J/ψ KS

∆E = E*(J/ψ)+E*(K0) – ECMS/2mES

2 = (ECMS/2)2 – [p(J/ψ)+p(K0)]2


Data 1999-2002: 81/fb on the ϒ(4S) , 90 M BB

CP = -1. N = 1506 after tagging. Purity = S/(S+B) = 94%

Ncand = 132Purity = 63 %

ηc(KKπ)KS

B0 → J/ψ K0L : Only K0

Ldirection measured. Energy from m(B0).

Ntot = 2641 (incl. J/ψK0*)78% purity.


Flavour-Tagging of the CP eigenstate by flavour-specific decays of the other B:Electrons, myons, charged Kaons, or Combi.

4.

4.+5.+6.

6. Determination of ∆t = ∆z/βγc :

5.

Fraction w of mistags determined from the „Flavour Sample“

B0 → J/ψK*0(K+π−),D(*)-π+,D(*)-ρ+...

∆z = zdecay – ztag, with ztag from vertex fit with two or moretracks with small χ2 contribution.


7.

perfect resolution real resolution

∆t/τ ∆t/τ

∆t/τ ∆t/τ

CP sampleswith1 ± sin2β sin∆mt

unmixed

mixed

B0

B0

7. R(∆z)

Flavour sampleswith1 ± cos ∆m t


8.

sin2β =0.741 ± 0.067 ± 0.033

8. sin2β fit to the ∆tdistributions


Belle results

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


OPAL 3.2 ± 0.5

ALEPH 0.84 ± 0.16

CDF 0.79

BABAR 0.741 ± 0.067 ± 0.033

Belle 0.719 ± 0.074 ± 0.035

Mean 0.732 ± 0.055

+ 0.41- 0.44

+ 0.82- 1.04

+ 1.8- 2.0

All results for sin2β:

(13σ)


A new triumph for the Standard Model!

η Fit with lVubl, lVtdl, and η+-

Max L, 1σ, 2σ

sin2β

CP violation in K and Bdecays has its origin inquark mixing producedby Higgs coupling to 6q.

Lfitckm


Fit to all observations:

η Max L, ±1σ, ±2σ

ckmLfit-0212-5

Lfitckm

CKM quark mixing matrix parameters:A = 0.82 ± 0.03, λ = 0.223 ± 0.002, ρ = 0.20 ± 0.10, η = 0.36 ± 0.06, J = (2.9 ± 0.6)10-5.


Conclusions and Prospects:

BABAR from 90 M BB events: sin2β = 0.74 ± 0.07 ± 0.03.BELLE from 85 M BB events: sin2β = 0.72 ± 0.07 ± 0.04.World average sin2β=0.732±0.055 agrees with St.Model.

No hint for New Physics CP, which could help cosmology.

PEP-II & KEK-B work well, both plan to increase BB rates.Next years: Increase significance on sin2β

Precision measurements on ∆m(B0), lVubl, Vcb Search for rare decays like B → K l+l-, B → ρ γ Search for CP in other B decay modes ...

Check and overconstrain the description of theCharged Weak Interaction in the St. Model.

2003 CDF,D0; 2007 ATLAS,CMS,LHCb; BTeV.

Documents

CP Violation in B-Meson Decays - TU Dresdenschubert/talks/edinburgh-0302.pdf · CP Violation in B-Meson Decays CP Violation in the Standard Model ... Properties of the CKM matrix:;