CP Violation in the Quark Sector: What Have We Learned?

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

Patricia Burchat, Stanford University World Summit on Physics Beyond the Standard Model Galapagos Islands, June 22-25, 2006

1 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 3 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 B Factories bu = B− Hadron machines bs = Bs (Tevatron, bc = Bc LHC) bud = Λb · · ·

7 ≈ 1, 000, 000, 000 BB pairs served...

CLEO 10M

BABAR 360M

Belle 600M

... 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 0 W χ˜

µ ˜ e˜ νµ νe µ x x γ γ e

− 2 2 → 13 ∆mν −50 B(µ eee) could be of order 10 Suppressed by M 2 ≤ 10 ! ! W " with “New Physics” (e.g., MSSM).

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

10 0 W χ˜ − τ ντ ν! ! τ˜ !˜ x x 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 W K, K∗, Kπ, ... b t d, s !

χ˜0 q˜

12 Keeping track of it all...

Charmless B Branching Fractions Review of Particle Physics K0K0 CLEO CDF K+K0 HFAG Belle PDG2004 00 • 0 0 BABAR New Avg. April 2006 K+ K+ + + K 0 0 + K 0K 0 + 0 K + 0K 0 0 K +0 K+0 + + + + K KSKS K (NR) !+ K00 + K+0 K + + + K KSKSKS + !K+ K 0 0 + !K K + ! K +f + 0 + 0 0 K KK K + + K 0+ K KK + + 0 + + 0 K f0(980) 0 K+f (980) K 0 K0 + + K K + 0 + K 0 0 + 0 K0(1430) + K0(1430) 0 + 0.0 10.0 K0(1430) + 20.0 a1 + 0 K 0 + Heavy Flavor Averaging Group K + + K 0 • 0K + 0K 0.0 50.0 100.0 Branching Ratio x 106

• CKMﬁtter Group (primarily frequentist)

• UTﬁt Group (primarily Bayesian)

13 (B X ! ) + B ! s d (B Xs` ` ) ! B ! HFAG CLEO HFAG Belle April 2006 BABAR April 2006 + PDG2004 New Avg. 0 CLEO Belle BABAR + p Kl l PDG2004 New Avg. + K0 K + K+ Ke e

+ 0 + K K e e + + K+ K 0 + K0 K 0 K+e+e K2(1430) + + K(892)l l K2(1430) + K+0 K(892)

0 + 0 + K K(892) 0 + K (892)++ K + + + K(892)e e K 0 + + 0 K(892) e e K + + K0+0 K(892) e e

+ + K(892) sl l + 0 s K(892) + + se e K1(1270) s 1/10 0.0 5.0 10.0 0.0 40.0 80.0 Branching Ratio x 106 Branching Ratio x 106

14 b → sγ

BaBar ’05

Cleo ’01

Belle ’04

Neubert ’04

Buras et al. ’02

x 10-4 0 0.5 1 1.5 2 2.5 3 3.5 4 b " s! Branching Fraction

BaBar ’05 * + - ∗ + − Belle ’04 B →K lKl ! ! Ali ’02 Zhong ’02

+ - + − B →Kl lK! !

-5 !10 0 0.05 0.1 0.15 0.2 0.25 Branching Fraction

15 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.

16 B0 → π+K−

P B0 → π+K− + Is ( ) = 0 π P (B0 → π−K+)? B b Vub W s − ∗ K Vus t V V ∗ tb ts u u d

17 B0 → π+K−

0 + Two diagrams with π diﬀerent weak phases ... B b Vub W s − ∗ K Vus t V V ∗ tb ts u u d

18 B0 → π+K−

0 + and diﬀerent (uncalculable) π strong phases. B b Vub W s − ∗ K Vus t V V ∗ tb ts u u d

19 Direct CP Violation

2 700 2 700 600 K!"! Belle 600 K!"! 500 500 400 400 300 300 Entries/2MeV/c Entries/2MeV/c 200 200 100 100 0 0 5.2 5.25 5.3 5.2 5.25 5.3 2 2 Mbc (GeV/c ) Mbc (GeV/c ) 700 700 600 World600Average: ! ! ! ! 500 0K " 500 K " Γ(B → π+K−) − Γ(B0 → π−K+) 400 400 0 + − 0 − + Entries/20MeV B → π K Entries/20MeV B → π K 300 Γ( 300) + Γ( ) 200 = −0.200108 ± 0.017 100 100 0 0 0 0.5 0 0.5 20 #E (GeV) #E (GeV) CP Asymmetries Measured in

RCP areAsymmetry B inDecays Charmless B Decays

+1.0 CLEO HFAG Belle + BABAR + 0 APRIL 2006 CDF 0 K + PDG2004 K + New Avg. + K

) ) + + 0 0 0 0 B B K + 0 K + ( ( K + + 0 0 + + + + + Γ Γ K K 0 K K + K K K K + ! + − 0 s ` + ! K + ) ) s` K B B ( ( 0.0 Γ Γ

S + K + S + 0 + K + K K K K

0 0 + 0 f + K + K + K + -1.0

21 CP Asymmetry in Charmless B Decays

+1.0 CLEO HFAG Belle + BABAR + 0 APRIL 2006 CDF 0 K + CP Asymmetries Measured in PDG2004 K + New Avg. K RCP areAsymmetry B inDecays Charmless B Decays + + + 0 0 0 +1.0 0 CLEO K HFAG + Belle 0 K + + K + BABAR + 0 APRIL+ 2006 0 0 + CDF 0 K + + + + + K PDG2004 + K K 0 New Avg. K K + K K + K + ) ) K + K + ! 0 0 0 0 B B K + 0 0 K + + ( ( K + ` ! K + s 0 0 + + + + + + Γ Γ K K 0 s` K K + K K K K + ! + − 0 K s ` + ! K + ) ) s` K B B ( ( 0.0

Γ Γ 0.0

S + K + S + 0 + K + K K S K K + K + 0 S 0 0 + + 0 + 0 K f + + K K K + K + K K K + 0 -1.0 0 0 22 + 0 f + K + K + K + -1.0 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.

23 The Quark Mixing Matrix and the Unitarity Triangle

d s b u ∗ V V ∗ ub ud α V V c tb td γ β t ∗ VcbVcd

apply unitarity constraint to these two columns

24 CP Violation observed in interference between decays with and without mixing.

World Average: sin 2β = 0.69 ± 0.03

25 History of Statistical Uncertainty on sin2β in BABAR

Statistical error on ﬁrst measurement (2000)

Expected reduction in statistical error due to increase in data sample size: 1 N BB ! ( )

26 History of Statistical Uncertainty on sin2β in BABAR

27 The angle α: B → ππ: large penguin contributions; many ambiguities. B → ρπ: use interference in Dalitz plot. B → ρρ: small penguin contributions; longitudinal polarization dominates.

+15 ◦ α = (100− 9 )

+ 5 ◦ α = (97−16)

28 The angle γ from B+ → D(∗)K(∗)+: ! + 0(∗) + ! r ≡ A(B →D K ) Depends on B ! 0(∗) !. ! A(B+→D K+ !

GLW: B → DCP K ADS: B → DK±π± K

B → D 0 + − K GGSZ: Ks π π ; Dalitz analysis ⇒ measure γ and rB.

0 + − D → Ks π π

29 CKM Fit: Angles Only

30 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.

31 Modes that are sensitive to new physics through loops: W b t s φ, η!, ... 0 s B 100 Belle 0 B0 ! "#K0 q=+1 d K 80 q=$1 S,L 60

40 400 Entries / 1.5 ps 2 350 Belle 20 300 0

250 0.5 200 0 150

100 Asymmetry -0.5 Entries / 0.0025 GeV/c 50 0 ! 0 B → η Ks 0 -7.5 -5 -2.5 0 2.5 5 7.5 5.2 5.22 5.24 5.26 5.28 5.3 2 -%f&t(ps) Mbc (GeV/c ) 32 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...

Average (loop diagrams) CP - violating Asymmetry 0.50 ± 0.06

33 Theoretical Predictions -- QCD Factorization

[Beneke, hep-ph/0505075 2 colors  2 ways to estimate theory errors] Beneke

[Cheng,Chua,Son i, hep- Cheng, Chua, Soni ph/0506268] Δsin2β

sin 2βeff − sin 2β

34 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.

35 0 b µ+ B , Z 0 t Bs d, s W µ−

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

H− h0, A0, H0

36 Upper Limits on Branching Fractions in Units of 10−7 0 + − + − B → µ µ Bs → µ µ 5 5

4 4

3 3

2 2

1 1

0 0 le D 0 Bel CDF CDF BABAR

+ − LHCb: ≈ 30 Bs → µ µ events per year for expected SM branching fraction of ≈ 4 × 10−9. 37 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.

38 +0.42 −1 CDF: ∆ms = (17.33−0.21 ± 0.07) ps ) 35 World average (prel.) hood i 30 combined data (from measured A) kel i l expectation for !m =" (A=0) ( s 25 ln expectation for signal at !ms (A=1) !

-5

-10 10 11 12 13 14 15 16 17 18 19 20 -1 !ms (ps )

∆ms measured to ≈ 2% precision (∆ms/Γ ≈ 25). c.f., ∆md measured to 1% precision (∆md/Γ ≈ 0.8).

39 40 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.

41 − − B → τ ντ now observed

Belle

signal 40 Events / 0.1 GeV 30

0 0 0.5 1

EECL (GeV) − − +3.0 −5 World average: B(B → τ ντ ) = (10.4−2.7) × 10 − − −5 CKM ﬁt + LQCD: B(B → τ ντ ) = (9.6 ± 1.5) × 10

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

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

44 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.

45 !V ! ! ub ! !K ∆md ∆md ! Vcb ! ∆ms

sin(2β + γ)

sin 2β cos 2β B → ρ/ω γ B → K∗ γ angle α angle γ K → πνν B → τντ

46 Tree- dominated

versus

Loop- dominated

47 CP- Violating

versus

CP- Conserving

48 “Theory-free” (only angles)

versus

QCD-based (no angles)

49 The Future

1. 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. −4 [Sample result: B(Bs → γγ) < 0.56 × 10 .] 2. Hadron machines: Tevatron, LHCb, ATLAS, CMS

• Bs mixing (∆ms, ∆Γs, βs),