Lecture III. Measurement of sin 2 in B K 0 S. Measurement of sin 2 in B + -, B + - Measurement of in B DK. Direct CP Violation

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1 Lecture III Measurement of sin 2 in BK S Measurement of sin 2 in BK S Measurement of sin 2 in B + -, B + - Measurement of in BDK Direct CP Violation Model-independent Test for New Physics Prospects

2 Strategy for CP Asymmetry Measurements e ( 4S) + e B rec B tag J / K S 1.Exclusive B Meson Reconstruction z K = Measure t t z/ z/<> c 2. B-Flavor Tagging

3 Charmonium & Tag Samples CP sample 437 tagged events 2877 tagged events BABAR J/K S & related modes J/ K L signal J/ X background Non-J/ background control sample m ES (GeV/c) >64 tags E [MeV] m ES (GeV/c) Control sample has same s mistag rate, t t resolution as CP sample (t error dominated by recoil side) use in fit as well

4 Tagging the 2 nd B and t t Reconstruction Tagging 2 nd B Tagging quality Q = ( 1 2) 2 Error on sin2 depends on tagging quality (sin 2 ) Parameters extracted from B-flavor sample using a neural net Achieve Q=3.5±.4% t reconstruction Get B rec vertex from charged daughter tracks z (B rec )=65 μm B rec momentum Determine B tag vertex from remaining charged tracks B tag vertex & B tag momentum Average z z resolution: 18 μm m (t( t resolution:.6ps) 1 Q

5 B J/ K S Flavor tag: b ce e e - K S J / e +

6 sin 2 2 Results from B (cc)k S(L) Modes B B cck S Belle 773 tagged events (227 M BB) 5261 tagged events (368 M BB) sin 2=.722±.4±.23 =.95±.31±.13 sin 2 1 =.652±.39±.2 =1.5±.13±.18

7 sin 2 2 Results from b(cc)s b Modes.69±.3.27±.28 sin 2 2 World average is.69±.3 BABAR/Belle average is.685±.32 = ( ) (ambiguity lifted) cosine term is consistent with zero C=.27±.28

8 CP Violation in bsss Penguins In the Standard Model, CP asymmetries from BJ/ J/K S & BK S modes yield the same value of sin 2 2 But contributions from new physics processes, e.g. Supersymmetry may modify these asymmetries in different ways Since BK S and related modes are suppressed by penguin loops, they are sensitive to new physics contributions in loops, which may carry new phases deviation from nominal sin 22 Standard Model B K e.g. from SUSY:

9 sin 2 2 from BB K BABAR has measured the CP asymmetries in BK S & BK L modes In BB events BABAR observed 114±12 K S & 98±18 K L events B K S B The CP asymmetry measurements yield: B S K +.7 = +.5 ±.25.4 C K = +. ±.23 ±.5 A fcp (t) = S sin m t C cos m t

10 Comparison of sin 2 2 Results.69±.3 For BJ/ J/K S modes BABAR & Belle results deviate by >1standard deviation For BK S & related modes BABAR & Belle results are consistent.5±.6 See discrepancy of 2.6 standard dev. between BK S & BJ/ J/K S modes

11 Measurements of sin2 Interference of buud b decay w&w/ow/o B B mixing yields angle tree penguin B B mixing Thus we need to measure t-dependent CP asymmetries of b uud processes, such as B,,, B + - However, penguin pollution complicates extraction of measure sin 22 eff Since 1, CP asymmetry has form A (t) = C cos m d t + S sin m d t ) 2 Events / (4 MeV/c ± 52 events (a) mes (GeV/c 2 )

12 Complication from Penguins S measures 2 eff = 2+2,, where can be determined using the Gronau-London method The decays B + -, +, are related by SU(2) Have isospin relations between amplitudes A +-, A +, A Central observation is that states can have I=2 or, while gluonic penguins only contribute to I = (I( = rule) + is pure I = 2, so only tree amplitude A + = A - B isospin analysis Need to measure: C +-, C (amplitudes in Cos terms for + - & ), & A, A + Effective isospin analysis requires A & A very large, or very small! Phys. Rev. Lett. 65, 3381 (199)

13 CP Asymmetry in BB + - hep-ex/ BB events B tag BB events B tag 666± events S =.3 ±.17 ±.3 C =.9 ±.15 ±.4 S =.67 ±.16 ±.6 C =.56 ±.12 ±.6

14 Results for B ± ± and B B + K + hep-ex/41237 B B + + bkg 379±41 events B( A CP + ) ( + = (5.8 ±.6 ± ) =.1± Weak constraint.4) 1.1 ± 6.2 B( 61±18 events ) = (1.17 ±.32 ±.1) 1 C =.12 ±.56 ± 67 < <

15 BABAR s Measurement from B + - From study of B penguin amplitude can be constrained We don t t see B B(B B(B ) < % C.L. + ) = (33 ± 4 ± 5) 1 6 yielding model uncertainty of eff - < 11 on extraction B B 1 - CL α (deg) = [1 ± 7 exp ± 11 peng ] o S( ) =.33 ± C( + ) =.3 ±.18 ±.9

16 From combined,, results constrain to: = [ ] o Best constraints from B Mirror solutions are disfavored CKM indirect constraint yields: = [ ] o Very good agreement Summary on

17 Measuring in BDK (*) Modes The angle is measurable via interference between B - D K - & B - D K - decays, where the D /D decay to common final state 2 m KS + V cb A V V cb * us * V us 3 2 m KS A V V * ub cs V ub + * V cs i e r B (*) = A(B- D (*) K - ) A(B - D (*) K - ) Color suppressed ~.1-.3 Different methods: most promising is a D K S + - Dalitz plot analysis in B - D (K S + - )K - Error on becomes smaller for larger values of r (*) B ()~38 for r B ~.1 & ()~2 for r B ~.2

18 Results for Combining all 3 methods for B - D (*) K (*)- yields first measurement of A few years ago this was thought to be impossible From combined analysis = [ ] o From indirect constraints = [ ] o measurements obtained from 2 independent methods are in excellent agreement Results for r (*) (*) B : +.36 r B = r * +.34 B =.12.57

19 Status of Unitarity Triangle Allowed region is determined from UT sides & sin 22 Both angles,, & UT sides are in good agreement Allowed UT region agrees with Standard Model prediction Look for New Physics as correction to Standard Model

20 Observation of Direct CP in B K ± - We observe decay asymmetry between B K + - & B K BB events BB events B K + - B K A K # ±.3 stat ±.9 syst ±.22 stat ±.8 syst ~5 This effect is not seen in B + K + & B - K - A CP =.49 ±.4 (BABAR & Belle average)

21 Model-independent Analysis of BB Mixing New Physics may affect both B d B d mixing, changing size of m Bd and introducing new CP-violating phase in a CP (Ks)=S Ks This is based on the scenario discussed by Y. Nir in the BABAR physics book (Y. Okada has discussed similar ideas) Yossi considered measurements of V ub /V cb,m Bd, a Ks, a In the presence of new physics: i) b uud : a =a CP ( + ) b ccs : a Ks =a CP ( K s ) remain primarily tree level ii) There would be a new contribution to KK mixing constraint: small (ignore new parameters) K iii) Unitarity of the 3 family CKM matrix is maintained if there are no new quark generations

22 Model-independent Analysis of BB Mixing Under these circumstances new physics effects can be described by 2 parameters: r d, d B d B d full H eff B d H SM eff B d = (r d ei d ) 2 Thus, New Physics parameters modify the parameterization of following observables m Bd = C t R 2 2 t r d A = sin (2 +2 Ks d ) A = sin (2-2 + d ) Extend 2 function to include new parameters r d, d

23 New Physics in B B Mixing Nir Agashe, et al.

24 Prospects Due to recent decision by DOE PEP II will run till end of 28 expected integrated luminosity will be Ldt~1ab -1, (5 fb -1 by summer 26) KEKB has a short term program till 28 with similar integrated luminosity, and a long term plan that gets Ldt~1ab -1 by 214 (not approved), based on peak luminosity of cm -2 s -1 To be competitive with LHCb one needs a peak luminosity of cm -2 s -1 LHCb is expected to come on 28 with 5% efficiency main emphasis will be on B s physics B-physics capabilities in ATLAS & CMS are rather limited SLAC will focus on ILC, but within BABAR efforts remain for 1 36 cm -2 s -1 super B-factory joint experiment with super KEKB? new project (study at Frascati based on linear collider)?

25 Global CKM fit: 28 (V ub ) = 6.5% (m s ) = 5% (sin2) =.19 ( ) = 8o ( ) = 1 o

26 The World is not CP Symmetric