cp violation in the quark sector: what have we learned?

CP violation in the quark sector:What have we learned?

Patricia Burchat, Stanford UniversityWorld Summit on Physics Beyond the Standard Model

Galapagos Islands, June 22-25, 20061

Notes for Printed Version of Presentation

• I delivered this presentation on June 22, 2006, at the World Summit on Physics Beyond the Standard Model in San Cristobal Island, Galapagos.

• I deliberately do not put much distracting text on my presentation slides. Therefore, the logic of the presentation may not be clear from this printed version.

• This talk is not intended to be a review of heavy-flavor physics or CP violation.

• For summarizing our current knowledge of results, I have relied heavily on the invaluable compilations by the Heavy Flavor Averaging Group, the CKMfitter Group, and the UTfit Group.

• For most decays, I include the minimum number of Standard-Model or New-Physics Feynman diagrams needed to make a pedagogical point, rather than all possible diagrams.

• This talk was prepared with Keynote and LaTeX Equation Editor (Mac OS X).

2

Last year’s World Summit on Evolution was a natural for the Galapagos.

How can we compete??

• Evidence for CP Violation: difference in the time evolution of matter and anti-matter.

• Evidence for Neutrino Mass: evolution of neutrino flavor in space and time.

• Evidence for Dark Energy: unexpected evolution of the expansion rate of the universe.

4

Back to the Skeptics Society

Excerpt from http://www.skeptic.com/about_us/discover_skepticism.html:

Some people believe that skepticism is the rejection of new ideas, or worse, they confuse “skeptic” with “cynic” and think that skeptics are a bunch of grumpy curmudgeons unwilling to accept any claim that challenges the status quo. This is wrong. Skepticism is a provisional approach to claims. It is the application of reason to any and all ideas — no sacred cows allowed. In other words, skepticism is a method, not a position. Ideally, skeptics do not go into an investigation closed to the possibility that a phenomenon might be real or that a claim might be true. When we say we are “skeptical,” we mean that we must see compelling evidence before we believe.

5

Ideas to treat with healthy skepticism...

• Supersymmetry: solution to the large quantum corrections to the Higgs mass.

• R-parity conservation in SUSY: prevents proton decay -- and provides attractive Dark Matter candidate.

• Cosmological Constant: solution to Dark Energy mystery?

Motivation for best possible experimental investigation...

6

bd = B0

bu = B−

bs = Bs

bc = Bc

bud = Λb

· · ·

B FactoriesHadron

machines(Tevatron,

LHC)

7

Belle600M

BABAR360M

CLEO10M

≈ 1, 000, 000, 000 BB pairs served...

... plus ≈ 1, 000, 000, 000 cc pairs

and ≈ 1, 000, 000, 000 τ+τ− pairs

8

Outline

• Radiative decays

• Direct CP violation

• The angles α, β, γ

• CP violation in b → sss decays with loops

• B(s) → µ+µ−

• Two recent results:

1. Observation of Bs mixing

2. Observation of B → τν

• Putting it all together.

9

B(µ → eee) could be of order 10−13

with “New Physics” (e.g., MSSM).

e

e

e

µx

χ0

µ e

γ

Experimental Results: B(µ → eγ) < 1.2×10−11, B(µ → eee) < 1.0×10−12

Suppressed by(

∆m2

ν

M2

W

)2

≤ 10−50!

e

e

e

µ

W

νµ νex

γ

10

W

τ−

ντ ν!x !

γ !

!

τ−

x

χ0

τ !

γ

!

!

!

Experimental Results (BABAR and Belle):

B(τ → µγ) < 0.7 × 10−7

B(τ → eγ) < 1.1 × 10−7

B(τ → eee, µµµ, eµµ, µee) < (1 − 3) × 10−7

11

d, u

B

d, u

B

W

b t d, s

!

!

b d, sχ

0

q

!

!

K, K∗, Kπ, ...

12

Keeping track of it all...

• Review of Particle Physics

• Heavy Flavor Averaging Group

• CKMfitter Group (primarily frequentist)

• UTfit Group (primarily Bayesian)

0.0 50.0 100.0

PDG2004BABARBelle

CLEO

New Avg.

HFAG

April 2006

Branching Ratio x 106

Charmless B Branching Fractions

CDF

0.0 10.0 20.0

13

PDG2004

BABARBelle

CLEO

New Avg.

0.0 40.0 80.0

!

HFAG

April 2006


0.0 5.0 10.0

PDG2004

BABARBelle

CLEO

New Avg.

HFAG

April 2006


B Xs

14

0 0.5 1 1.5 2 2.5 3 3.5 4 Branching Fraction! s"b

BaBar ’05

Cleo ’01

Belle ’04

Neubert ’04

Buras et al. ’02

-4x 10

b → sγ

0 0.05 0.1 0.15 0.2 0.25

-510!

Branching Fraction

-l

+Kl

-l

+l*

KBaBar ’05Belle ’04Ali ’02Zhong ’02

B → K∗!+!−

B → K!+!−

15

Outline





• B(s) → µ+µ−





16

W

W

d

d

b

b

d

u

u

u

u

s

s

d

t

B0 π

+

K−

π+

K−

B0

Is P (B0→ π+K−) =

P (B0→ π−K+)?

VtbV

∗

ts

V∗

us

Vub

B0→ π+K−

17

W

W

d

d

b

b

d

u

u

u

u

s

s

d

t

B0 π

+

K−

π+

K−

B0

VtbV

∗

ts

V∗

us

Vub

B0→ π+K−

Two diagrams with different weak phases ...

18

W

W

d

d

b

b

d

u

u

u

u

s

s

d

t

B0 π

+

K−

π+

K−

B0

VtbV

∗

ts

V∗

us

Vub

B0→ π+K−

and different (uncalculable) strong phases.

19

Direct CP Violation

0

100

200

300

400

500

600

700

5.2 5.25 5.3

Mbc (GeV/c2)

En

trie

s/2

Me

V/c

2

K!"!

0

100

200

300

400

500

600

700

5.2 5.25 5.3

Mbc (GeV/c2)

En

trie

s/2

Me

V/c

2

K!"!

0

100

200

300

400

500

600

700

0 0.5

#E (GeV)

En

trie

s/2

0M

eV

K!"!

0

100

200

300

400

500

600

700

0 0.5

#E (GeV)

En

trie

s/2

0M

eV

K!"!

Belle

World Average:

Γ(B0→ π+K−) − Γ(B0 → π−K+)

Γ(B0→ π+K−) + Γ(B0 → π−K+)

= −0.108 ± 0.017

20

+1.0

0.0

-1.0

CP Asymmetry in Charmless B Decays

HFAG

APRIL 2006

PDG2004

BABARBelle

CLEO

New Avg.

CDF

Γ(B

)−

Γ(B

)

Γ(B

)+

Γ(B

)CP Asymmetries Measured in

Rare B Decays

21

+1.0

0.0

-1.0


HFAG

APRIL 2006

PDG2004

BABARBelle

CLEO

New Avg.

CDF

+1.0

0.0

-1.0


HFAG

APRIL 2006

PDG2004

BABARBelle

CLEO

New Avg.

CDFΓ(B

)−

Γ(B

)

Γ(B

)+

Γ(B

)CP Asymmetries Measured in

Rare B Decays

22

Outline





• B(s) → µ+µ−





23

The Quark Mixing Matrix and the Unitarity Triangle

u

c

t

d s b

apply unitarity constraint to these two columns

V∗

ubVud V∗

tbVtd

V∗

cbVcd

α

βγ

24

CP Violation observed in interference

between decays with and without

mixing.

sin 2β = 0.69 ± 0.03

World Average:

25

History of Statistical Uncertainty on sin2β in BABAR

Expected reduction in statistical errordue to increase in data sample size:

1√

N(BB)

Statistical error on first measurement (2000)

26

History of Statistical Uncertainty on sin2β in BABAR

27

The angle α:B → ππ: large penguin contributions; many ambiguities.

B → ρρ: small penguin contributions; longitudinal polarization dominates.

B → ρπ: use interference in Dalitz plot.

α = (97+ 5−16)

◦

α = (100+15− 9)◦

28

The angle γ from B+→ D(∗)K(∗)+:

Depends on rB ≡

∣

∣

∣

A(B+→D

0(∗)K

+)

A(B+→D

0(∗)K+

∣

∣

∣

.

GGSZ: B → DK0sπ+π−K;

D → K0sπ+π−

Dalitz analysis ⇒ measure γ and rB .

GLW: B → DCP K

ADS: B → DK±π±K

29

CKM Fit: Angles Only

30

Outline





• B(s) → µ+µ−





31

Belle

W

d

b

d

st

B0

s

s

K0

S,L

Modes that are sensitive to new physics through loops:

φ, η′, ...

B0 ! "#K

0

0

20

40

60

80

100q=+1

q=$1

Entr

ies / 1

.5 p

s-0.5

0

0.5

-7.5 -5 -2.5 0 2.5 5 7.5

-%f&t(ps)

Asym

metr

y

Belle

0

50

100

150

200

250

300

350

400

5.2 5.22 5.24 5.26 5.28 5.3

Mbc

(GeV/c2)

Entr

ies / 0

.0025 G

eV

/c2

B0→ η′K0

s

32

CP - violating AsymmetryAverage (loop diagrams)0.50 ± 0.06

Difference between asymmetry from tree and loop diagrams:

2.5 σ(stat).But each “loop” mode

has (different) additional

sub-dominant diagrams, which brings in

theoretical uncertainties...

33

Beneke

Cheng, Chua, Soni

sin 2βeff − sin 2β

Δsin2β

[Beneke, hep-ph/05050752 colors 2 ways toestimate theory errors]

[Cheng,Chua,Soni, hep-ph/0506268]

Theoretical Predictions -- QCD Factorization

34

Outline





• B(s) → µ+µ−





35

bt

Z

W

W µ+

µ−d, s

B0,

B0

s

bt

W

µ+

µ−d, s

B0,

B0

s

h0, A0, H0

H−

Standard Model prediction: B(Bs → µ+µ−) = (3.35 ± 0.32) × 10−9

36

0

1

2

3

4

5BA

BAR

Belle

CD

F

B0→ µ+µ− Bs → µ+µ−

0

1

2

3

4

5

D0

CD

F

Upper Limits on Branching Fractions in Units of 10−7

LHCb: ≈ 30 Bs → µ+µ− events per year forexpected SM branching fraction of ≈ 4 × 10−9.

37

Outline





• B(s) → µ+µ−





38

-10

-5

0

5

10

15

20

25

30

35

10 11 12 13 14 15 16 17 18 19 20

!ms (ps

-1)

!ln

(lik

elih

ood

)

combined data (from measured A)

expectation for !ms=" (A=0)

expectation for signal at !ms (A=1)

World average (prel.)

c.f.,∆md measured to 1% precision (∆md/Γ ≈ 0.8).

∆ms measured to ≈ 2% precision (∆ms/Γ ≈ 25).

CDF: ∆ms = (17.33+0.42−0.21 ± 0.07) ps−1

39

Outline





• B(s) → µ+µ−





41

B−

→ τ−ντ now observed

(GeV)ECLE

0 0.5 1

Ev

en

ts / 0

.1 G

eV

0

10

20

30

40

50

Belle

signal

World average: B(B− → τ−ντ ) = (10.4+3.0−2.7) × 10−5

CKM fit + LQCD: B(B− → τ−ντ ) = (9.6 ± 1.5) × 10−5

42

Theoretical Input• Uncertainties on all non-angle CKM

measurements now dominated by theoretical uncertainties from non-perturbative parameters (e.g., decay constants and bag parameters).

Lattice QCD• “Staggered fermion” technique plus “4th-root of

determinant” technique looks promising for reducing light quark masses to their physical values.

• Two new related methods, “domain wall fermions” and “overlap fermions”, promising but in infancy.

43

Lattice QCD ... ... with “staggered fermions”

B−

→ τ−ντ and ∆md both depend on fB .Therefore, constraints are correlated.

44

Outline





• B(s) → µ+µ−





45

sin 2β cos 2β

sin(2β + γ)

angle α angle γ B → τντK → πνν

B → ρ/ω γ

B → K∗ γ

∣

∣

∣

Vub

Vcb

∣

∣

∣

εK ∆md ∆md

∆ms

46

Tree-dominated

versus

Loop-dominated

47

CP-Violating

versus

CP-Conserving

48

“Theory-free”(only angles)

versus

QCD-based(no angles)

49

The Future1. B Factories:

• 1 billion BB pairs recorded now (not all analyzed yet).

• 4 billion BB pairs expected by end of 2008.⇒ ≥ factor of 2 improvement in statistical uncertainties+ new analyses.

• Belle recorded ≈ 2 fb−1 in a three-day engineering run at the Υ(5S)and may return to this energy in the future.[Sample result: B(Bs → γγ) < 0.56 × 10−4.]

2. Hadron machines: Tevatron, LHCb, ATLAS, CMS

• Bs mixing (∆ms, ∆Γs, βs),

• radiative decays and leptonic decays of B and Bs,

• CKM angle γ from B and Bs decays, ...

50

Now

Expectedin 2010

51

CP violation in the quark sector:What have we learned?

βα

γ

52

Bayesian Reality, by the UTfit group

Frequentist Reality by the CKMfitter Group

Polar Coordinates VIII

by Frank Stella

Sinjerli Variation

by Frank Stella

53

What have we really learned?

• The B Factories and hadron machines are providing enormous data samples that allow us to explore the heavy-flavor sector with unprecedented precision.

• Many new analysis techniques have been developed to allow us to probe more and more decays that are potentially sensitive to new physics.

• If NEW PHYSICS is out there, then it must have a very special flavor and CP structure to evade all the existing searches.

• Continue to confront new theoretical ideas and hints of discrepancies in experimental results with healthy skepticism.

54

cp violation in the quark sector: what have we learned?

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