Experimental Aspects of CP Violation Daniel Cronin-Hennessy TASI June 2003.
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Transcript of Experimental Aspects of CP Violation Daniel Cronin-Hennessy TASI June 2003.
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?