Experimental Aspects of CP Violation

Daniel Cronin-Hennessy

TASI June 2003

Daniel Cronin-Hennessy

CP

NO NO

Research Associate University of RochesterCLEO collaboration at LEPP (Cornell)

Short Bio 1995 Joined CDF collaboration at Fermilab top

(1.8 TeV pp collider: q q t t ) During Run 1 Focus was tests of Perturbative QCD (s) via analysis of

W boson produced in association with jets.

1999 Joined CLEO collaboration at CESR bottom (10.58 GeV e+e- collider Y(4S)BB)

During CLEOIIIImproved CKM matrix element extractions with HQET

Future CLEO-c (3 GeV) charmLattice QCD , glueballs, and hybrids

Goals How we know what we know

Show experimental techniques The phenomenology used to interpret data

Accent role of Symmetry both in theory and in experiment

Connect Observables to CKM formalism Convey importance CP Violation

Authors versus Time

Carl Anderson 1933

Authors versus Time

J H Christenson 1964 J W Cronin V L FitchR Turlay

Authors versus Time

CLEO ~ 150Recent list

Authors versus TimeCDF ~ 400 1995

Authors versus Time

BaBar ~ 600

Timeline

1933 1957 1964 1974 1977 1982 1987 1989

Anderson Wu Cronin&Fitch Brookhaven Fermilab CESR DORIS CESR Standford

e+ P(C) Viol CP Viol J/cc) Y(bb) Bmeson BMixiing charmless B decay(Vub)

1995 2000 2001Fermilab CERN/Fermilab KEKB/PEPIITOP Direct CP Violation CP Violation in B

1928 1956 1972 Dirac Lee&Yang KM e+ P Violation CP viol from mixing matrix

Background (positron) Carl Anderson 1933 Wilson Chamber-

condensation around ions. Ions generated from passing charged particle.

Device immersed in high B field (15 kG)

14 cm diameter

Background (positron) B field into page qvXB the sign of charge Negative particle moving

down or positive particle moving up

6mm Lead plate (dark band) placed in middle of chamber to break up-down symmetry

Ionization loss in lead radius of curvature of track is smaller in 2nd half of track. Positive charged track.

Background (positron) Positive track but why not Proton Energy of proton (upper portion)

is .3 MeV. Range of proton is about 5 mm at this energy. The track is 10 times this length (5 cm).

Conclusions after detailed study Q < 2 Qproton M < 20 MelectronParticle (positron) identified with the

anti-particle of electron Electron should be renamed negatron

(from symmetry considerations) symmetry does not drive all physics

Background (positron) The idea that each particle has an

anti-particle has empirical basis We can reasonably ask where

antimatter has gone if we have basis for its existence.

Symmetry of mathematics driving the interpretation of physical reality 5 years earlier Dirac’s wave equation

manifested negative energy solutions.

These solutions were not discarded as unphysical mathematical artifacts but interpreted as antiparticle partners to the positive solutions

Where are the anti-protons?

Astro-physicists count photons. 3 degree cosmic background radiation permeates all space. It is the cooled (red shifted ) remnant of the early universe.

Astro-physicists measure abundances: hydrogen, helium, etc. (baryon number)

We could detect antimatter if it were there ( Signature photons from matter + anti-matter annihilation not detected)

Results Current limits on anti-matter < 0.0001*observed matter Observed universe Baryon number to photon number ~ 10-9

For every billion photons there is one baryon

Assuming baryon + anti-baryon annihilation accounts for current photons in Universe 1 baryon for every 1 billion baryon-antibaryon pair survived

Without this asymmetry we would not be here.

Where are the positrons (anti-protons etc) ?

Sakharov’s (1967) conditions for generating Anti-matter matter asymmetry

Baryon number violation (another story) Must be able to get rid of baryons

CP asymmetry Must be imbalance in baryon violation between baryons and anti-

baryons Universe must be out of thermal equilibrium

So that time reversed process can not restore symmetry.

Symmetries (C )

Charge conjugation (C) C changes particle to anti-particle

Examples Charge Conjugation on electron = positron C e- = e+ (shorthand) C p = p C + = -

C =

Symmetries (P) Parity (P) Mirror symmetry Inverts spatial coordinates

x -x ; y -y ; z-z Effect on other observables

Velocity (v) P v = - v ( reverses direction)

Spin (s) P s = s ( does not change)

Helicity P Right-handed = Left-handed

Right-handed means thumbOf righthand points in direction of motion

Left-handed means thumb of left hand Points in direction of motion

C and P

P

P

C C

Left

Anti- Left

Right

Anti- Right

CP

Participates in weak interaction No electric charge, No color charge NEVER observed C and P in weak interactions is violated

The - puzzle Pre – 1956

Two particles with similar characteristics (such mass and lifetime) are only different in the decays.

parity +1 (-1*-1*(-1)0) parity –1

Seemed obvious thatif and are the same particle they should have the same intrinsic parity

T.D. Lee & C.N. Yang point out no evidence favoring parity conservation in weak decays – must test.

A Test of Parity (Wu, 1957) Align Cobalt 60 nuclear spin Look for electrons from beta decay

60Co60Ni + e- anti- Beta decay

n p + e- anti- d u + e- anti-

Electrons emitted opposite to direction of nuclear spin (parity operation would reverse direction ofelectron but not the the nuclear spin).

C and P

P

P

C C

Left

Anti- Left

Right

Anti- Right

CP

Participates in weak interaction No electric charge, No color charge NEVER observed C and P in weak interactions is violated maximally

The Neutral Kaon system K0 (d anti-s) K0 (anti-d s) Strange particles produced via strangeness conserving

process. S=0 (-1 +1)

Decays weakly (violating strangeness) long lived and large difference in lifetimes between the neutral Ks

Proposal Assuming CP K1 ~ K0 + K0 CP K1 = K0 + K0 = K1 (CP=1) K2 ~ K0 – K0 CP K2 = K0 – K0 = K2 (CP=-1)

K1 2 (CP =1) K2 3 (CP = -1)

Without 2 decay open to K2 expect increased lifetime: Long lived Neutral K (15 meters) Short lived (2.8 cm)

CP Violation Observed

K2

57 Ft to target

collimatorDecay Volume(He)

Spectrometer

Spectrometer

Signal K22 Bck K23

Use angle (q) between 2p and beam axis

K1 decay long before detector

Regeneration of K1 in collimator inconsistent with vertex distribution

494-509 MeV

cos

484-494 MeV 504-514 MeV

cos cos

MK = .498 MeV

CP Violation Observed Christenson, Cronin, Fitch & Turlay 1964 Observed CP violating decay K22 17 meters from

production point (> 600 times lifetime of short lived neutral Kaon)

Occurred in about 1 in 500 decays. Interpretation: Physicals states were not eigenstates of CP

but asymmetric mixing of K0 and anti-particle. Kshort ~ K1 + K2

Klong ~ K2 + K1

Kshort ~ (1+) K0 + (1-) K0

Klong ~ (1+) K0 – (1-) K0

Asymmetric mixing at level of 0.2%

Counting Klong decays Part of what particle physicists do is just count the number of

times a particular particle decays to a particular final state

Example: Given 10000 Klong particles 2108 times I see the Klong decay to 0 0 0

1258 times I see the Klong decay to + - 0

1359 times I see the Klong decay to - + 1350 times I see the Klong decay to + - 1950 times I see the Klong decay to - e+ 1937 times I see the Klong decay to + e- 38 times I see the Klong decay to other

Note that - e+ and + e- are connected by CPCP (- e+ ) =+ e-

Counting Klong decays

Example: Given 10000 Klong particles 1950 times I see the Klong decay to - e+ 1937 times I see the Klong decay to + e-

If CP were an exact symmetry I expect the same number of

- e+ and + e- decays.We observe different numbers 1950 and 1937 = N(KL e+ -) – N(KL e- + ) = 0.0033

N(KL e+ -) + N(KL e- )

CP Violation in Neutral Kaon a = amp(K0 f) a = amp(K0f) = (a-a) / (a+a) = amp(KL f )/amp(KS f)

Kshort ~ (1+) K0 + (1-) K0

Klong ~ (1+) K0 – (1-) K0

= (1+) a - (1-)a = (a-a) + (a+a) = + (1+) a + (1-)a (a+a) + (a-a) 1+

= + (mixing) + (direct CP violation – Process

dependent)

|+-| != |00|

Observable for Direct CP Violation +- /00

= amp(KL+-)/amp(KS+-) = +’

amp(KL00)/amp(KS00) – 2’ Actual measurement:

(KL+-)/(KS+-) ~ 1 + 6 Re(’/)

(KL00)/(KS00)

’ small compared to . already small difficult measurement!

K mixing (quark mixing) K0 K0 (Standard Model)

K0 K0

s

d s

d

u,c,t

u,c,t

W W

quark mixing

bsd

VVVVVVVVV

bsd

tbtstd

cbcscd

ubusud

'

'

'

CKM matrix relates quark mass eigenstates to weak eigenstates

Fundamental Standard Model parameters – must be measured.

Measurement of these electro-weak parameters complicated by QCD (we observe hadrons not quarks)

The formalism that provides a viable framework for extracting CKM elements is Heavy Quark Effective Theory HQET.

VVVVVVVVV

tbtstd

cbcscd

ubusud

132313231223121323122312

132313231223121323122312

1313121312

ccescsscesccss

csesssccessccs

escscc

ii

ii

i

Parameterized by 3 rotation angles(ij) and a phase ()Sij =sinij

CP Violation:3 generations required for non-Real matrixQuark mass not degenerate (u,c,t) (d,s,b) not 0 or

1)1(2

1

)(2

1

23

2

2

3

2

AiA

A

iA

132313231223121323122312

132313231223121323122312

1313121312

ccescsscesccss

csesssccessccs

escscc

ii

ii

i

rewrite in terms of the Wolfenstein parametersA Taking advantage of small value of 2

22.0||12 usVs)81.(23

2 AsA

~order 4

)(3 iAVub

)1(3 iAVtd

Unitarity Triangle

VVVVVVVVV

tbtstd

cbcscd

ubusud

Unitarity

VV tbtd*

VV cbcd*

VV ubud*

Algebra

0,0

1,0

||

||

VV

cb

uba

g bCP

0*** VVVVVV tbtdcbcdubud

0))1(()(1 ii

Implications of CPV via CKM matrix

At least 3 generations of quarksCharm quark not known at time of proposal2 generations can not provide required phase

Same mechanism that describes CPV in Kaon system predicts (possibly larger) CPV in B meson system.

Direct CPV predicted

In contrast to other competing mechanisms such as superweak (S=2, K0 K0) .

Keeping Score (CKM constraints)

Observed particles:

hidden bottom

1977, Fermilab 400 GeV protons on nuclear

targets Examined pair mass Broad peak observed (1.2

GeV) at 9.5 GeV Eventually interpreted as 2

peaks Had observed the Y and Y’. Bound states of bb quarks. PRL 39 p252 ‘77

The Y system 1980 CESR online. e+ e- collisions in the 10

GeV energy range Resonance structures very similar to the cc

(J/) observations just a few years earlier.

The Y as a B laboratory e+e- (4S) BB ( ~ 1.0 nb) e+e- qq ( ~ 3.0 nb) Broad (14 MeV >> narrow Y,Y’,Y’’) Lepton production Spherical topology Just above 2 times B meson mass (5.279 GeV). B’s nearly at rest

The Y as a B laboratory

R2 (shape)

qqBB

B mixing B0 B0 (Standard Model)

B0 B0

b

d b

d

u,c,t

u,c,t

W W

B Mixing

B DVcb

B0 D+ e-

B0 D- e+

BB BB or BB

Signature:Same sign leptonse+e+ or e-e-

1987 (ARGUS/DESY)

Observation of top 1995 D0 and CDF at FERMILAB 1.8 GeV pp collisions Ignoring sea quarks and gluons:

(uud) + (uud)

u u t t (production) t b W (Vtb) (decay no bound states)

Observation of topTop decays fast (due to large mass). No time forbound state formation. t t signals (tb W) b l+ (dilepton) b j j (lepton + jets) b l- b l- b j j (6 jets) b j j

Background W + jet production

Observation of topLepton:

electron - (well measured in tracking and electromagnetic

calorimeter) muon - tracking chambers behind shieldingNeutrino: Large (20-30 GeV) missing transverse energy. W boson: coincidence of above with consistent transverse

mass.Jets: clusters of energy in hadronic calorimeterB-jets: algorithm identifying displaced vertex from long

lived b quark (and/or) soft lepton in jet from semileptonic decay of b quark.

W and Jets

Top massW+4jet sample With b-tagged jets

Reconstruct top mass (7%). Mass top ~ 175 GeV

Currently best known quark mass (few%).

Keeping Score (CKM constraints)

)1(3 iAVtd

))1(|| 22 tdV

B0 B0

b

db

d

t

t

md

Part II Extractrion of a CKM matrix

elements Observation of CPV in B system Observation of Direct CPV How does the standard model do?

B DecaysHadronic Semileptonic Radiative

BXH B XH l BXH

BD (K ) Exclusive Inclusive Exclusive Inclusive

Experimentally BD l BXc l BK* BXs

“Easy” B l BXu l

Heavy Quark Exp Heavy Quark Exp Theoretically

Factorization clean

c

u

d

b c d u

b

W

Still need QCD corrections Perturbative Non-Perturbative

Hard gluon (Short distance) Soft gluon (Long distance) s , 1 & 2

B D e

W

e

]D

c

B[b

Just right?

W

b c

u

d]

]DB[

B D

Very difficult

B Decay

Heavy Quark Limit B meson ~ a heavy quark + “light degrees of freedom”

b ~ 1/mb (mb ~ 5GeV)

Typical energy exchanges ~ QCD (.1 GeV) l ~ /QCD l >> Q point charge (can not resolve mass) flavor blind Chromo-magnetic moment g/(2 mQ) spin blind

Heavy quark symmetry will provide relations between different heavy flavor mesons (B D) and mesons with different spin orientations (BB* , DD*)

QCD is in non-perturbative regeme (no s expansion for bound state effects).

Heavy Quark Effective Theory systematically provides symmetry breaking corrections in expansion (QCD/mQ)

HQET+OPE allows any inclusive observable to be written as a double expansion in powers of as and 1/MB:

O(1/M) energy of light degrees of freedomO(1/M2) 1 -momentum squared of b quark

2 hyperfine splitting (known from B/B* and D/D* DM)

O(1/M3) 1, 2, 1, 2, 3, 4 ~(.5 GeV)3 from dimensional considerations

Gsl = |Vcb|2 (A(as,,boas2)+B(as)/MB+ C1/MB

2+…)

, 1 combined with the Gsl measurements better |Vcb|2

)1

()(),(32

221

2

22

MO

ME

MD

MC

MBAObservable sss

b s Moments

)

1(

94

33

12

3313))(175.1954.01()(620.0385.01

2 47

222

34321

3212

02

0M

OCMM

C

MMM

mE

BBDBB

ss

B

ssb

)

1(

12

3

12

32))(05412.005083.0()(01024.000815.0

12 4321

3212

02

02

122

MO

MMMMMEE

BBB

ss

B

ss

BB

u, c, t

b s Moments

)

1(

94

33

12

3313))(175.1954.01()(620.0385.01

2 47

222

34321

3212

02

0M

OCMM

C

MMM

ME

BBDBB

ss

B

ssB

)

1(

12

3

12

32))(05412.005083.0()(01024.000815.0

12 4321

3212

02

02

122

MO

MMMMMEE

BBB

ss

B

ss

BB

u, c, t

Xs

b s Moments

)

1(

94

33

12

3313))(175.1954.01()(620.0385.01

2 47

222

34321

3212

02

0M

OCMM

C

MMM

ME

BBDBB

ss

B

ssB

)

1(

12

3

12

32))(05412.005083.0()(01024.000815.0

12 4321

3212

02

02

122

MO

MMMMMEE

BBB

ss

B

ss

BB

radiative tail

u, c, t

Back to CMK Elements

sl (B Meson Semileptonic Decay Width) Calculated from B meson branching fraction and lifetime

measurements (CLEO, CDF, BaBar, Belle …) It is the first approximation to the b quarks decay width

)]/1(474.7185.3946.0648.11[192

||)3689.0()( 3

22

21

2

2

3

522

BBBBB

BcbFcs MO

MMMM

MVGlXB

Free quarkdecay width

b quark motion –increased b lifetime

Pfermi

M hyperfine splitting

)]/1(2

9

21[

192

||)( 3

22

21

3

522

Bbb

bubFus MOradiative

mm

mVGlXB

Strategy Bound state corrections needed. Extract , 1, 2 from independent observables

(e.g. average photon energy BXs ) 1 (e.g. width of photon energy)

2 (e.g. D and D* mass difference)

Once determined can be used in extraction of CKM elements (e.g. Vub and Vcb)

Over constrain in order to check size of higher order terms

Photon Energy Moments

Always require high energy photon 2.0 < E < 2.7 GeV |cos | < 0.7

Naïve strategy: Measure E spectrum for ON and OFF resonance and subtract

But, must suppress huge continuum background![veto is not enough] 0 and

Three attacks: Shape analysis Pseudoreconstruction Leptons

Photon Energy Moments

Photon Energy Moments

Photon Energy Moments

Photon Energy Moments

HQET Predictions for moments of (inclusive) Hadronic Mass, Photon Energy & Lepton Energy

6 constraints for 2 parameters

BXs BXc l BXc l

Consistency Among

Observables

and ellipse extracted from 1st moment of B Xs photon energy spectrum and 1st moment of hadronic mass2 distribution(B Xc ). We use the HQET equations in MS scheme at order 1/MB

3 and s

2 o. MS Expressions: A. Falk, M. Luke, M.

Savage,Z. Ligeti, A. Manohar, M. Wise, C. Bauer

The red and black curves are derived from the new CLEO results for B X lepton energy moments. MS Expressions: M.Gremm, A. Kapustin, Z.

Ligeti and M. Wise, I. Stewart (moments) and I. Bigi, N.Uraltsev, A. Vainshtein(width)

Gray band represents total uncertainty for the 2nd moment of photon energy spectrum.

CLEOPreliminary

Vcb

In MS scheme, at order 1/MB3

and s2o

= 0.35 + 0.07 + 0.10 GeV1= -.236 + 0.071 + 0.078 GeV2

|Vcb|=(4.04 + 0.09 + 0.05 + 0.08) 10-2

sl , 1 Theory

)]/1(474.7185.3946.0648.11[192

||)3689.0()( 3

22

21

2

2

3

522

BBBBB

BcbFcs MO

MMMM

MVGlXB

Moment CLEO DELPHI(prelim)

BABAR(prelim)

<m2H - m2

D> 0.251±0.023±0.062 (El>1.5GeV) 0.534±0.041±0.074 Versus EL

<(m2H- <m2

H>)2 > .576±0.048±0.163 (El > 1.5GeV) 1.23±0.16±0.15

<(m2H- <m2

H>)3 > 2.97±0.67±0.48

<Ey 2.346

0.0226

<E 1.7810+0.0007+0.0009 (El > 1.5 GeV) 1.383

0.192

0.029

R0 0.6187+0.0014 +0.0016 (El > 1.5 GeV)

Global Analysis: hep-ph/0210027 Bauer,Ligeti,Luke &

Manohar

|Vub| from Lepton Endpoint (using b s

)

|Vub| from b u We measure the endpoint

yield Large extrapolation to obtain |

Vub|

High E cut leads to theoretical difficulties (we probe the part of spectrum most influenced by fermi momentum)

GOAL: Use b s to understand Fermi momentum and apply to b ufor improved measurement of |Vub|

Kagan-Neubert DeFazio-Neubert

Convolute with light cone shape function.

b g s g(parton level)

B g Xs g(hadron level)

B g lightquark shape function, SAME (to lowest order in LQCD/mb) for b g s g a B g Xs g and b g u ln a B g Xu ln.

b g u l n(parton level)

B g Xu l n(hadron level)

Fraction of b ® uln spectrum above 2.2 is

0.13 ± 0.03

Method for partial inclusion of subleading corrections: Neubert

•Published

•With subleading corrections

Subleading corrections large C. Bauer, M. Luke, T. Mannel A. Leibovich, Z. Ligeti, M. Wise

|Vub| from Lepton Endpoint (using b s

) |Vub| = (4.08 + 0.34 + 0.44 + 0.16 + 0.24)10-3

The 1st two errors are from experiment and 2nd from theory

PRL 88 231803 ‘02

CLEO

|Vub| measurements

Keeping Score (CKM constraints)

)(3 iAVub

)(|| 22 ubV

|Vub|

md

CP Violation Measurement in B System

Approximately 4 decades after observation of CPV in Kaon System

Three quark generation model well establishedconstraints from B mixing and CKM element magnitudes nicely consistentK meson and B meson measurements consistent NO CP violation yet observed in B meson system!

By 1999 CLEO experiment has accumulated luminosity larger than all other collider experiments combined. Ten Million BB pairs.

Still no hope of measuring CP violation as predicted by SM. SM predicts direct CPV and CPV in mixing small. Best first measurement is interference between decays to CP eigenstates with and without mixing.

=B0

fB0 f

B0

B0

Time dependent asymmetry

CP Violation Measurement in B System

PEPIIElectron at 9 GeVPositrons at 3.1 GeV

KEKBElectrons 8 GeVPositrons 3 GeV

4 fb-1/week 10 Million BB pairs in 3 weeks

Recall B mesons produced via symmetric e+e- collisions yields B mesons nearly at rest (Y(4S) ~ 2 MB)Require fast B mesons (displaced vertex) to extract time of decay.Hadronic collider produce boosted B meson but statistics low.Require “simple” design change for e+e- asymmetric collisions.Enter BaBar and Belle

PEPII

CP Violation Measurement in B System

Symmetric e+e- collisions at Y(4S) is ~ .05 (z ~ .025 mm)

With BaBar parameters is ~ .5 (z ~ .25 mm) Resolution ~ .15 mm

CP Violation Measurement in B System

CP Final state (example): B J/Kshort (BR = 0.05%)

J/ l+ l- (e+e-, +-) (BR 11%) Kshort + - , 0 0 (BR ~100%)

Second “Tagging” B Provides second vertex (z) Provides flavor tag (65% eff in tagging)

High momentum leptons B0 (B0) l+ (l-) Kaon charge (K+, K-) Soft pion (D+* D0 +)

88 Million BB pairs 740 B0 tags and 766 B0 tags

CP Violation Measurement in B System

MES

MES: Beam Energy substituted

mass sqrt(Ebeam

2-pB2)

Consistent with known MB

DE: Ebeam-EB

B candidate energy consistent with expected B meson energy

All in CM frame

E

CP Violation Measurement in B System

Observable: z = ct

))(())((

))(())((00

00

ftft

ftft

BBBB

aphysphys

physphys

f

AA

f

f

fcp p

q BBB qpL

00 BBB qpL

00

A is amplitude for decay:Even with |q/p| and |A/A| ~ 1 CP Violation possiblevia interference with and without mixing Im()=0

)sin(Im~1

)sin(Im2)cos()1(

||

||2

2

t

f

ttfm

mma Bf

BfB

f

AA

f

f

fcp p

q f =J/ Kshort

b Vcb c

c

s K0Vcs*

i

i

VV

VVVV

VVVV

VVVV

td

td

tbtd

tbtd

cdcs

cdcs

cscb

cscb

1

1~~~ **

*

*

*

*

*

B0 B0

Vtb Vtd

K0 K0

Vsc Vcd

Connection to plane

0,0

1,0

((1-)2+2)1/2

(1-)

2222

22

)1(

)1(2

)1(

)1(

1

1~

ii

i

)2sin()sin()cos(2)1()1(

)1(2)Im(

2222

Results

)sin()2sin(~)sin(Im~ tt mma BBff

BaBar and Belle averageSin(2)=0.734 + 0.055

Keeping Score (CKM constraints)

BaBar and Belle averageSin(2)=0.734 + 0.055

Sin(2)

|Vub|

md

CP Violation observed.Constraints consistentwith previous measurements

Constraints Including Uncertainties

Constraints Including Uncertainties

Bottom plot shows constraints With ~few% theoretical uncertainties required to see“beyond” standard model.

Direct CP Violation No (unambiguous) measurement of direct CP

violation from B mesons

Direct CP Violation has been observed in Kaon system.

Direct CP Violation (Kaon) Re(’/) Requires very accurate

measurements of 4 processes

Klong + -

Klong 0 0

Kshort + -

Kshort 0 0

Observable for Direct CP Violation +- /00

= amp(KL+-)/amp(KS+-) = +’

amp(KL00)/amp(KS00) – 2’ Actual measurement:

(KL+-)/(KS+-) ~ 1 + 6 Re(’/)

(KL00)/(KS00)

’ small compared to . already small difficult measurement!

Direct CP Violation

NA31 NA48 CERN

E731 E832 FermiLab

KTeV

Vacuum beam = Klong

Regenerator beam = Klong+Kshort

CsI Cal Resolution = 0.7% (15GeV)Position Resolution = 1 mm (can identify parent beam)

Klong 0 0 (2.5 M events)

SystematicsAcceptance difference for Klong & Kshort Must be well modelled.

Accounting for Klong component in Regenerator beam

Re(’/) Results

Direct CP violation observed

Superweak Theory fails

SM Model predictions consistent but has large uncertainties

Re(’/) Results

Summary Standard Model performance

Excellent 3 quark generations well established CP Violation in B mesons observed Direct CP violation in Kaons observed CKM constraints in quantitative agreement no known

significant deviations The math works but do we understand the source of CP

violation? Understanding of Higgs sector and mass generation may help

If the Standard Model continues in its success how do we explain the quantity of observed matter?