Palm tree and CKM

G. Sciolla – M.I.T.Beauty in the Standard Model and

Beyond 1

Palm tree and CKM Beauty in the Standard Model and Beyond

Gabriella Sciolla (MIT)

CIPANP 2006 - Puerto Rico - May 30 - June 3, 2006


Beyond 2

Palm tree and CKMBeauty in the Standard Model and Beyond

Gabriella Sciolla (MIT)

CIPANP 2006 - Puerto Rico - May 30 - June 3, 2006


Beyond 3

Outline

The beauty of B physics CP violation in the B system and the Unitarity Triangle

Standard Model measurements Sensitivity to New Physics

Measurements of CP violation in B decays The experiments Measurement of the angles and sides of the Unitarity

Triangle

What have we learned? Summary and conclusion


Beyond 4

CP violation What is CP?

Why is CP violation interesting? Crucial ingredient to explain the matter-dominated universe

A. Sakharov (1967) CP violation is expected in the Standard Model

Until recently, one of the least tested aspect of the theory Many new sources of CP violation Beyond the Standard Model

Sensitive to New Physics

C: Charge ConjugationParticle Anti-particle

P: ParityInverts space coordinates

CP = C × P


Beyond 5

CP violation in the Standard Model Discovered by Fitch and Cronin in 1964 in KL decays Introduced in Standard Model in 1973 by Kobayashi and

Maskawa In KM mechanism, CP violation originates from a complex

phase in the quark mixing matrix (CKM matrix)

)(

1)1(2

11

)(2

11

6

23

22

32

O

AiA

A

iA

VVV

VVV

VVV

V

tbtstd

cbcscd

ubusud

b c

W-cbV

A, (Cabibbo angle): very well measured: poorly known until recentlyFirst goal of CP violation studies:

Precise determination of the parameters and


Beyond 6

Pros and Cons of CKMPros:

Elegant and simple explanation of CPV in SM It is very predictive: only one CPV phase It accommodates all experimental results

Indirect CP violation in K and KLl Direct CP violation in K CP violation in the B system

Cons: nB/n predicted by CKM « observed value

…by orders of magnitude!

New sources of CPV must exist besides CKM!

.

CP violation as a probe for New Physics:Measure CP violation in channels theoretically well understood

and look for deviations w.r.t. SM expectations


Beyond 7

Unitarity of CKM implies: V†V = 1 6 unitarity conditions Of particular interest:

All sides are ~ O(1) possible to measure both sides and angles! CP asymmetries in B meson decays measure and Sides from semileptonic B decays, B mixing, rare B decays

The Unitarity Triangle

0VVVVVV *tbtd

*cbcd

*ubud

*

*ub ud

cd cb

V V

V V

*

*tb td

cd cb

V V

V V


Beyond 8

Standard Model or New Physics?

Two ways of looking for New Physics: Compare measurement of sides and angles

2 measurements define the apex; >2 test Standard Model All pieces of the puzzle must fit: inconsistencies mean New

Physics Measure same quantity in channels with different

sensitivity to NP E.g.: measure in modes mediated by different decay

diagrams

Precision and redundancy are essential!


Beyond 9

The experiments: B factories BaBar (SLAC) and Belle (KEK)

e+e- asymmetric collisions . (4S) resonance

Advantages of the B factories No need for bb trigger

Very clean environment:

High luminosity Peak luminosity > 1034 cm-2s-1

Integrated luminosity 350/600 fb-1 (BaBar/Belle)

10.58 GeVs

+ -e e (4s) BB

bb : ~ 1 : 4 qq

350/600 fb-1 (BaBar/Belle)


Beyond 10

The experiments: Tevatron experiments CDF and D0 at Fermilab

.

Challenges of the Tevatran Special trigger necessary for B events

High multiplicity events Advantages of the Tevatron

Large number of B produced

L~1032 cm-2s-1 but high x-sections

Integrated luminosity: >1 fb-1

All b hadrons are produced BS , b , BC ,…

pp collisions at s ~ 2 TeV

bb : ~ 1 : 1000 inelastic

Complementary to B factories


Beyond 11

The measurements

*

*ub ud

cd cb

V V

V V

*

*tb td

cd cb

V V

V V

The angle


Beyond 12

BfCP exclusivereconstruction

How to measure the CP asymmetry

.

e-

Flavor taggingQ=(30.5 0.5)%

(4S)

B0

B0

e-

+

-

e+

+

-

Precise t determination

z~ c t


Beyond 13

CP violation at the B factories

0 0

0 0

( ( ) ) ( ( ) )( )

( ( ) ) ( ( ) )

sin( ) cos( )

CP CPCP

CP CP

ff

N B t f N B t fA t

N B t f N B t f

S mt C mt

2

2

1

1

f

f

f

C

2

2Im

1

f

f

f

S ff

f

Aqλ

p A

i2e~

0B

0B

CPf

mixin

g

decay

0t t

CPfA

CPfA

(f

)

When only one diagram contributes to the final state, ||=1

0

Imf

f

C

S

ACP(t) = ± Im sin(mt)

(CP violation in interference between mixing and decays in B0 )


Beyond 14

CP violation in B0 decays: sin2For some modes, Im is directly and simply

related to the angles of the Unitarity Triangle.

Example: B0J/KS: the “golden mode”

Theoretically clean Experimentally clean Relatively large BF (~10-4)

ACP(t) = sin2 sinmt

0 0

* * *2

* * *

mix mix

itb td cs cb cd cs

tb td cs cb cd csB decay K

V V V V V Ve

V V V V V V

0B

/J

SK


Beyond 15

The golden mode for sin2: sin2 in B0 J/ KS

Belle 386 fb-1

mES [GeV/c2]

sin(2) = 0.685 ± 0.032 WA EPS

2005

Belle 386 fb-1

B0J/ KS Belle 386 fb-1

t [ps]

t [ps]

sin(2)= 0.652 ± 0.039 ± 0.020


Beyond 16

Unitarity Triangle constraints

sin2 vs indirect UT constraints: very good agreement!

New Physics does not show up in the golden mode SM reference Compare with sin2 in independent modes with different sensitivity to NP

CKM mechanism is the dominant source of CPV at low energies

95% CL from sides


Beyond 17

The key to New Physics:

The Penguin Modes

Decays dominated by gluonic penguin diagrams The typical example: B0KS

No tree level contributions: theoretically clean SM predicts: ACP(t) = sin2sin(mt)

Impact of New Physics could be significant New particles could participate in the loop new CPV phases

Low branching fractions (10-5) Measure ACP in as many bsqq penguins as possible!

φ K0, K+ K− KS, η′ KS, KS π0, KS KS KS, ω KS, f0(980) KS

d d

SM NP


Beyond 18

The golden penguin: B0 K0

N(Ks)=180 ± 16Belle 386 fb-1

Belle 386 fb-1

Belle 386 fb-1 B0KS

B0KL

0

0

0.44±0.27±0.05

-0.14±0.17±0.07K

K

S

CBelle 386 fb-1


Beyond 19

The silver penguin: B0 ’KS

Larger BF ~ 6 x 10-5 but theoretically slightly less clean than KS

Sη′Ks = 0.30 ± 0.14 ± 0.02

Cη′Ks = −0.21 ± 0.10 ± 0.02

' 804 40SKN

BaBar 210 fb-

1

BaBar 210 fb-

1

BaBar 210 fb-

1


Beyond 20

“sin2” in penguins

A trend is visible although each

measurement is compatible with J/KS…

Most significant shift in ’KS ~2.1

Naïve average: 0.50±0.06 ~2.5

… statistical errors still large…

BaBar + Belle average

Penguin modes

Golden mode

J/KS


Beyond 21

The measurements

*

*ud ub

cd cb

V V

V V

*

*td tb

cd cb

V V

V V

The angle

ubud

tbtdargVV

VV


Beyond 22

sin2in Tree diagram dominates

Relatively large Branching Fraction (B0 → ) = (25.2 ± 3.7 )×106

Penguin contribution small (B0 → ) < 1.1×106 (90%C.L.)

Vector-vector final state: is CP defined? In principle admixture of CP+ and CP- eigentastes…

ACP(t) = sin2 sinmt

*

*

*

*

)1(ubud

ubud

tdtb

tdtb

VV

VV

VV

VV

b du

u

W

gtbV *

tdV

Penguin

ubud

tbtdargVV

VV

b uu

d

W

ubV

Tree


Beyond 23

Is CP defined in ? Vector-vector final state

3 possible L states

Measure fraction of longitudinal polarization in angular analysis

021.0 029.0 014.0978.0

LfBaBar 210 fb-

1

S wave (L=0, CP even)

P wave (L=1, CP odd), only transverse polarization

D wave (L=2, CP even)

~ 100% longitudinally polarized CP even eigenstate


Beyond 24

CP asymmetry in B0 →

09.018.003.0

024.033.0 008.0 014.0

C

S

BaBar 210 fb-

1

0 tagsB

0 tagsB

BaBar 210 fb-

1

BaBar 210 fb-

1


Beyond 25

Combined constraints on

Average of BaBar and Belle +15

-9 = 105 °cfr: CKM fit

+5-16 = 97 °


Beyond 26

The measurements

*

*ud ub

cd cb

V V

V V

*

*td tb

cd cb

V V

V V

The angle

cbcd

ubudargVV

VV


Beyond 27

The angle .

0

+ 0 + + 0 +

0

Use interference between and with both

D and D decaying

B D K B D K

same final stto t athe e f

Cabibbo allowed Cabibbo and color suppressed

cbcd

ubudargVV

VV

NB: only tree diagrams: 100% Standard Model

B

B


Beyond 28

from B → DK GWL (Gronau, Wyler, London)

D CP eigenstate Theoretically clean Small interference: needs more data

ADS (Atwood, Dunietz, Soni) is doubly Cabibbo suppressed

Larger interference Needs more data

Dalitz method (Giri, Grossman, Soffer, Zupan) Exploits interference pattern in Dalitz plot in DKS

Combines many modes statistical advantage Small systematics due to Dalitz model Currently

most sensitive

( )A D f

D0KS+-

See talk by M. Verderi


Beyond 29

Summary of measurements Direct measurement on

BaBar + Belle, all methods combined

Indirect constraints:

65 20 deg

61.1 4.5 degUTFit


Beyond 30

The left side: Rb

*

*ub ud

cd cb

V V

V V

*

*tb td

cd cb

V V

V Vubb

cb

VR

V

1.31.221.7 degrees

NB: is the best measured quantity in the Unitarity Triangle

precise measurement of Rb is needed for accurate tests of SM


Beyond 31

Semileptonic B Decays

Sensitive to hadronic effects Theory error not negligible

Prob(bc)/Prob(bu)~50 Vcb precisely measured (2%) Vub is the challenge

b

,u c

, cub bV V

Parton level

W l

22 5

2( )

192F

ub b

Gb u V m

22 5

2( )

192F

ub b

Gb u V m

B

uX

b

u

ubVB

, cuX X

Hadron level

l


Beyond 32

Two approaches to Vub

Inclusive B Xul Hadronic final state is not

specified

bc l background is suppressed using kinematical variables

Partial rate is measured

theoretical uncertainties ~5%

Inclusive B Xu l

B

uXubV

Exclusive B l

B

W

ubV

Exclusive B l Better S/B but lower branching

fraction (10-4)

Needs form factor calculation from Lattice QCD

uncertainty of ~ 12%

l- ll-


Beyond 33

|Vub| from Inclusive B Xu l

Close collaboration between theorists and experimentalists led to

c.f.r.: precision on : 5.5%

World Average 4.45 0.33

2/dof = 5.5/6

Precision on Vub: 7.4%


Beyond 34

The last side of the triangle: Rt

*

*ub ud

cd cb

V V

V V|| *

*

cbcd

tdtb

VV

VV tdt

ts

VR

V


Beyond 35

The measurement of Rt

Bs/Bd oscillations

Theory error <5% md is precisely measured But Bs mixing is very hard…

1 tdt

ts

VR

V

( )td sV

( )td sV

b

b

( )d s

( )d s

t

t

W0( )d sB 0

( )d sBW

2

d td

s ts

m V

m V


Beyond 36

History of BS mixing 6 experiments, > 10 years of work

Then early this Spring… D0: double sided limit on mS

CDF: first observation of BS mixing

Dec 2005


Beyond 37

BS mixing at the Tevatron

. .

. .

Reconstruction of BS decay in hadronic or SL modes

Flavor taggingQSST~4%QOST~1%

Time reconstruction(ct)~26-70 m

Talk on Fri by Matthew Jones


Beyond 38

D0 result

. .

. .

BsμDs: 5601±102

ms < 21 ps-1 @ 90% CL assuming Gaussian errors

Most probable value of ms = 19 ps-1


Beyond 39

CDF result

Probability of random fluctuation: ~0.5%

0.42 0.008td0.007

ts

-10.2117.33 0.07 ps

V 0.208

VSm

3,700 events


Beyond 40

Impact of mS on Unitarity

Triangle


Beyond 41

Conclusion Standard Model: precision

Tremendous improvement in and Precision ~ 0.05

First quantitative test of CPV in SM CKM is the dominant source of CPV

New Physics: redundancy Sides vs angles in agreement with SM First signs of NP in sin2 in penguins?

More statistics will help: Analyzed: ~500 fb-1 Available: ~1 ab-1

By 2008: > 2 ab-1 .

BaBar+BelleCP-violating

measurements

CP-conserving measurements

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