Measurement of the CKM angle b at Ba

Measurement of the CKM angle b at Ba. Bar Roberto Covarelli (University-INFN Perugia, Italy) on behalf of the Ba. Bar collaboration Phenomenology Symposium – Madison – May 2007 PHENO ‘ 07 Roberto Covarelli 1

CP violation and the b angle • CP violation in the Standard Model (SM) Non-null apex of the unitarity triangle (h ≠ 0) CP-odd phase in the CKM matrix • How to measure it? in B 0 meson system CP violation effect in the interference between mixing and decay: • Time-dependent asymmetry: . PHENO ‘ 07 Roberto Covarelli Difference of mass eigenstates 2

CP violation at the Y(4 S) Dt ~ Dz/<bg>c <bg> ~ 0. 55 In all modes considered in this talk the SM expectations are: Cf = 0 PHENO ‘ 07 Sf = ± sin 2 b Roberto Covarelli 3

Many ways of measuring b… Large tree amplitude Low penguin pollution PHENO ‘ 07 Both tree and penguin amplitudes Cabibbosuppressed: small BF’s Roberto Covarelli No tree: sensitivity to New Physics particles in the loop 4

1) b → ccs (charmonium) + Color-suppressed tree. Gluonic penguin (same weak phase) • Theoretical uncertainties on DSf = Sf – sin 2 b: • Experimentally clean • BF = O(10 -3) ÷ O(10 -4) • Still “golden-plated” channels • In the SM: Apenguin << Atree – Factorization + non-perturbative QCD: • DSJ/y. Ks = (-2. 2 ± 2. 2) · 10 -4 • DSJ/y. Ks = (9. 3 +3. 6 -4. 6) · 10 -4 [Boos et al. , PRD 70, 036006 (2004)] [Li and Mishima, hep-ph/0610120] – Model-independent data-driven calculation: DS is constrained using measurements of the SU(3)-related process B 0 → J/ 0 : DSJ/y. Ks = (0. 000 ± 0. 012) [Ciuchini et al. , PRL 95, 221804 (2005)] [Ciuchini at CKM 2006] PHENO ‘ 07 Roberto Covarelli 5

sin 2 b from B 0 → (cc)K(*)0 (I) • “Reference” sin 2 b measurement ( O(%) uncertainty ) • Improvements with respect to previous Ba. Bar measurements: – Using full Ba. Bar statistics: 383 · 106 BB pairs – Alternative Dt fit configurations added to the nominal one (all even/odd modes together): • Fit of sin 2 b and | | for each mode separately • Fit of sin 2 b and | | for J/ K 0 (KS + KL) and J/ KS only – Now including J/ K*0 (KS 0) and J/ KL in the | | measurement – Reduction of systematic error related to backgrounds Sample Nevents Purity (%) CP-odd 6873 92 CP-even 4730 55 K*0 1056 66 J/ PHENO ‘ 07 DE distribution after B mass constraint CP odd Roberto Covarelli CP even 6

sin 2 b from B 0 → (cc)K(*)0 (II) CP odd sin 2 b = 0. 714 0. 032(stat) 0. 018(syst) | | = 0. 952 0. 022(stat) 0. 017(syst) • • ~5% total uncertainty on sin 2 b | | result compatible with 1 at 1. 7 s sin 2 b result split in sub-modes: CP even hep-ex/0703021, submitted to PRL PHENO ‘ 07 Roberto Covarelli 7

2) b → ccd transitions + Cabibbo-suppressed tree. Gluonic penguin (different weak phase) • BF(B 0 → D(*)) = O(10 -4) • Expected penguin contribution negligible: 2 -10% [Z. -Z. Xing, Phys. Rev. D 61, 014010 (2000)] • beff (i. e. b angle as effectively measured in such processes) sensitive to New Physics in loops: beff – b up to 0. 6 in supersymmetric models [Y. Grossman and M. Worah, Phys. Lett. B 395, 241 (1997)] PHENO ‘ 07 Roberto Covarelli 8

Recent results: B 0 → D+D • Claim of a large CP violation measurement by Belle in B 0 → D+D-: . (CDD, SDD) ≠ (0, 0) at 4. 1 s [hep-ex/0702031, submitted to PRL] • Ba. Bar does not confirm observation: 364 · 106 BB pairs D. Lange at Moriond 2007, PRELIMINARY background sin 2 beff = 0. 54 0. 34(stat) 0. 06(syst) C = 0. 11 0. 22(stat) 0. 07(syst) PHENO ‘ 07 Roberto Covarelli 9

B 0 → D*+D- and B 0 → D+D* • Not a CP eigenstate: need to define C+-/C-+ and S+-/S-+ that depend on the strong phase difference between the two processes. 364 · 106 BB pairs • General relation: • If penguin contribution is negligible: beff = b, C+- = – C-+ • Signal of CP violation: sin 2 b ≠ 0 C+- = 0. 18 0. 15(stat) 0. 04(syst) C-+ = 0. 23 0. 15(stat) 0. 04(syst) S+- = -0. 79 0. 21(stat) 0. 06(syst) S-+ = -0. 44 0. 22(stat) 0. 06(syst) PHENO ‘ 07 S+- ≠ – S-+ B 0 → D*+D- Roberto Covarelli D. Lange at Moriond 2007, PRELIMINARY B 0 → D+D*- 10

Recent results: B 0 → D(*)0 h 0 • Used modes: h 0 = 0, h, w • b → cud transition: D 0 = D 0 CP → K+K-, KS 0, KSw hep-ex/0703019, submitted to PRL – No penguin contribution theoretically clean – Very small contribution from DCS decays (b → ucd) CP even Nsig = 131 16 CP odd Nsig = 209 23 CP even 383 · 106 BB pairs CP odd Combined fit sin 2 beff = 0. 56 0. 23(stat) 0. 05(syst) C = -0. 23 0. 16(stat) 0. 04(syst) PHENO ‘ 07 Roberto Covarelli Separate fits 11

Summary of b → ccd (cud) • B 0 → D+ D- • B 0 → D*+D- , D+D*- – No evidence of CP violation measured – ~3 s disagreement between Ba. Bar and Belle results B 0 → D + D - – Hints of CPV when combining Babar and Belle results: S+- ≠ – S-+ at ~ 4 s • B 0 → D(*)0 h 0 (first measurement) – Both sin 2 beff and C consistent with SM expectations PHENO ‘ 07 Roberto Covarelli 12

Resolving the b ambiguity • When extracting b from sin 2 b, twofold ambiguity left in the r-h positive quadrant • cos 2 b is measured from timedependent analyses of J/ K*, D 0 h 0, D*+D*-KS • Recent Ba. Bar results: – Time-dependent Dalitz analysis of B 0 → D(*)0 h 0 (D 0 → KS + -) hep-ex/0607105, PRELIMINARY cos 2 b > 0 at 87% CL Integrals over Dalitz phase – Time-dependent Dalitz analysis of space: 0 → D*+D*-K : positive under B S certain theoretical (Js 2/J 0)cos 2 b > 0 at 94% CL Phys. Rev. D 74, 091101 (2006) assumptions PHENO ‘ 07 Roberto Covarelli 13

3) b in penguins: motivations • Pure b → sss transitions include a Flavor Changing Neutral Current: in the SM they must proceed through a penguin diagram • b → dds (and similar): theoretical calculation predict penguin-dominated SUSY SM SUSY coupling: - mass-suppressed (~ 1/M 2) - coupling-enhanced (~ a. S/a. W) • Quark-squark coupling adds unknown SUSY phases to the mixing phase 2 b ACP(Dt) sensitive to presence of new particles in the loop • Caveat: interpretation of beff – b not completely clean in all cases due to hadronic uncertainties PHENO ‘ 07 Roberto Covarelli 14

Dalitz analysis of B 0 → K+K-K 0 • Time-dependent Dalitz analysis: – Taking for the first time into account interference between high and low KK mass (close to f resonance) regions 347 · 106 BB pairs K+K-KS KS → + - hep-ex/0607112, PRELIMINARY PHENO ‘ 07 Combined (whole Dalitz plot): beff = 0. 361 0. 079(stat) 0. 037(syst) C = 0. 034 0. 079(stat) 0. 025(syst) Roberto Covarelli 15

B 0 → KS KS KS and B 0 → h’K 0 • B 0 → K S K S: hep-ex/0702046, Submitted to PRL – Challenging vertex reconstruction (beam-spot constraint used) • B 0 → h’ K 0: – Large BF (~6 · 10 -5) – Many h’ reconstruction modes Phys. Rev. Lett. 98, 031801 (2007) (a) Evidence of CPV with > 5 s significance sin 2 beff = 0. 71 0. 24(stat) 0. 04(syst) C = 0. 02 0. 21(stat) 0. 05(syst) PHENO ‘ 07 sin 2 beff = 0. 58 0. 10(stat) 0. 03(syst) C = -0. 16 0. 07(stat) 0. 03(syst) Roberto Covarelli 16

Conclusions • Measurements of the CKM angle b have reached the O(%) precision: – CP violation well established in B 0 -meson system – Main input in unitarity triangle fits b = (21. 3 1. 0)o (World Average) • New results from Ba. Bar: – sin 2 b update on B 0 → (cc)K(*)0 with 383 million B pairs – b ambiguity broken by cos 2 b measurements – New results on B → D(*) and B → D(*)0 h 0 • Evidence for CPV in B 0 → D*+D • 3 s puzzle in B 0 → D+D- (Ba. Bar-Belle) – Hints of difference between sin 2 b in trees and penguins persist (DS = sin 2 beff – sin 2 b < 0) but handle averages with care … PHENO ‘ 07 Roberto Covarelli 17

Backup slides PHENO ‘ 07 Roberto Covarelli 18

Penguin averaging … • Averaging over all s-penguin modes assumes that contributions with non-zero weak phases to the decay amplitudes can be neglected. This assumption may be significantly violated due to doubly CKMsuppressed Vub penguin amplitudes, and, in some cases, doubly CKM-suppressed and color-suppressed Vub tree amplitudes that contribute to the decay amplitude. • Recent theoretical analyses indicate that it is reasonable to expect that, while the modes φK 0, η′K 0 and KS KS KS have theoretical uncertainties of the order of 0. 05 or smaller, these can be significantly larger for the other modes (in particular for non-ssresonance modes: π0 KS, ρ0 KS, ωKS and K+K-K 0). [Heavy Flavor Averaging Group webpage] PHENO ‘ 07 Roberto Covarelli 19