Measurements of the UT Angle a from BABAR Carlos A. Chavez University of Liverpool On behalf of the BABAR collaboration The 12th International Symposium on Particles Strings and Cosmology PASCOS 2006 The Ohio State University. Wednesday, September 13, 2006 The University of Liverpool

Outline B → +−, ± 0 , 00 B → +−, ±0, 00 B0 → ()0 Introduction to the CKM angle  Analysis techniques, BABAR results and their implications for  : B → +−, ± 0 , 00 B → +−, ±0, 00 B0 → ()0 Summary All these are new results based on 347 million of BB pairs (except ±0 uses 232 million) University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

How to measure a ? Defined as : Need to look for : B mesons decaying to CP eigenstates through transitions Tree Need to measure : ACP Indirect CP Direct CP @ Tree level: ACP (t )  sin(2a) ; Direct ACP = 0 University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

How to measure a ? (2) Penguin Tree + Carries a different phase compared to tree level Tree + Penguins: ACP (t )  sin(2aeff); aeff = a +D ; direct ACP ≠ 0 We measure then need to bound University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool Isospin analysis in B →  , ρρ M. Gronau, D. London, Phys. Rev. Lett. 65, 3381 (1990) 6 unknowns  → 6 observables (there is no vertex to measure S00)  → 5 observables (or 7, when both C00 and S00 are measured)  → there are 3 such relations (one for each polarization state) 4-fold ambiguity in 2Δ : due to orientation of triangles Neglecting EW penguins, A ± 0 is a pure tree mode, and so the two triangles share a common side: University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool Analysis Techniques Signal selection B candidate’s energy and mass Particle identification /K separation (Cherenkov light detector) Signal Background K+K- K+p- p+p- Background 12 σ  /K separation at 1.5 GeV/c, 2 σ at 4.5 GeV/c Calibration sample: B− → −D0, D0 → +K− From p+p- Monte-Carlo Event Shape variables for background suppression p* h+ q* e- e+ e- e+ h- Background events from light quark have jet-like topology B signal B events are spherical University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool BABAR results: B0 → +− (1) hep-ex/0607106 Simultaneous ML fit to B0 → +−, K+−, +K−, K+K− ( 347 Million of BB pairs ) Using DIRC Cherenkov angle to separate  / K, additional  / K / KK separation from ΔE N+− = 675 ± 42 B0 tags signal background mES Δt B0 tags _ asymmetry sPlot: Builds a histogram of x excluding it from the Maximum-Likelihood fit, assigning a weight to each event, keeping all signal events, getting rid of all background events, and keeping track of the statistical errors in each x bin M. Pivk and F. R. Le Diberder, “sPlot: a statistical tool to unfold data distributions,” Nucl. Instrum. Meth. A 555, 356 (2005) [arXiv:physics/0402083]. University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool BABAR results: B0 → +− (2) hep-ex/0607106 3.6 σ evidence for CP violation is observed S = −0.53 ± 0.14 ± 0.02 C = −0.16 ± 0.11 ± 0.03 The result (S,C) = (0.0, 0.0) is excluded at a 99.97 % C.L. (3.6 σ) University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

BABAR results: B → ±0, 0 0 hep-ex/0607106 (using 347 Million of BB pairs) Simultaneous ML fit to B+ → +0, K+0, using DIRC Cherenkov angle to separate  / K In B0 → 00 we measure branching fraction and time-integrated direct CP asymmetry (In addition to 0 → , we use merged 0 and  → e+e− conversions) N±0 = 572 ± 53 N00 = 140 ± 25 ±0 mES mES 00 sPlot - qq background signal B± → ±0 background Br±0 = (5.12 ± 0.47 ± 0.29)  10−6 Br00 = (1.48 ± 0.26 ± 0.12)  10−6 C00 = −0.33 ± 0.36 ± 0.08 University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

a from B →  results |Δ |   = 0 excluded at Only the B → branching fractions and isospin-triangle relations are used in arriving at these constraints on Δ = | − eff| and on  itself  near 0 is disfavored by other experimental information (rp) |Δ |   = 0 excluded at 1−C.L. = 4.4  10−1 |Δ | < 41º at 90% C.L. BaBar-CONF-06/039 or hep-ex/0607106 University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

B →  angular analysis fL(B0 → +−)WA= 0.967+0.023  is a vector-vector final state An angular analysis is required to separate the CP content “helicity frame” pure CP = +1 transverse is not a CP eigenstate Fortunately, the helicity-zero state in B →  decays is dominant (fL close to 1): fL(B0 → +−)WA= 0.967+0.023 −0.028 fL(B± → ±0)WA= 0.96 ± 0.06 Heavy Flavor Averaging Group, April 2006, http://www.slac.stanford.edu/xorg/hfag/rare/winter06/polar/index.html We have the same situation as in B →pp decays University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

BABAR results: B0 → +− N+− = 615 ± 57 B0 tags ΔΕ mES B0 tags hep-ex/0607098 N+− = 615 ± 57 (using 347 Million of BB pairs) B0 tags ΔΕ B0 tags _ mES sum of backgrounds BABAR preliminary  helicity m±0 asymmetry distributions for the highest-purity tagged events Δt (ps) Br +− = (23.5 ± 2.2 ± 4.1)  10−6 Slong = −0.19 ± 0.21+0.05 −0.07 fL(B0 → +−) = 0.977 ± 0.024+0.015 −0.013 Clong= −0.07 ± 0.15 ± 0.06 Important to reduce systematics: hep-ex/0605024, accepted by PRD Br (B0 → a± )  Br (a± →  +  − ± ) < 30  10−6 (90% C.L.) 1 University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool BABAR results: B0 → 00 hep-ex/0607097 N00 = 98+32 ± 22 −31 3.0  significance (using 347 Million of BB pairs) ΔΕ mES 0f0 00 Results are statistically consistent with the previous analyses Br00 = (1.16 +0.37 ± 0.27)  10−6 −0.36 fL(B0 → 00)= 0.86+0.11 ± 0.05 −0.13 The main systematic errors are dominated by interference with B0 → a± (1260)  (where a± (1260) →    ±  ±) and by PDF parameter uncertainties 1 1 University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool BABAR results: B± → ±0 hep-ex/0607092 (Based on 232 million BB pairs) N±0 = 390 ± 49 BABAR preliminary BABAR preliminary mES continuum + BB backgrounds ΔΕ Br±0 = (16.8 ± 2.2 ± 2.3)  10−6 fL(B± → ±0) = 0.905 ± 0.042+0.023 −0.027 The systematic error is dominated by modeling of backgrounds, signal misreconstruction, and by statistical PDF uncertainties The latest BABAR measurement in B± → ±0 allows the  isospin triangle to close University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool a from B →  results Only the B → branching fractions, polarization fractions and isospin-triangle relations are used in arriving at these constraints on Δ =  − eff and  itself Δ BABAR preliminary  BABAR preliminary |Δ | < 21º at 90% C.L. [74, 117]º at 68.3% C.L. |Δ | < 18º at 68% C.L. Improvement in the precision of the the  isospin analysis will be possible with the determination of both C and S from B0 →00 (need more data) BaBar-CONF-06/27, BaBar-CONF-06/016 University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

B0 → ()0 Dalitz-plot analysis rp is not a CP eigenstate In principle we can use an isospin-pentagon analysis method, but is not suitable with current statistics A. Snyder and H. Quinn, Phys. Rev. D, 48, 2139 (1993) Time-dependent Dalitz-plot analysis assuming isospin symmetry Monte Carlo Interference in the corners of the Dalitz plot provides information on strong phases between resonances allowing the extraction of the angle a with no ambiguity r0p0 Measures the time-dependent decay rate B0 (B0 ) using: r+p− r−p+ Fitting for 27 coefficients of the bilinear form factors in the time-dependent decay rate. The resonances  (770) ,  (1450) and  (1700) are all included in this analysis University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

Time & flavor integrated A = −0.142 ± 0.041 ± 0.015 BABAR results: B0 → ()0 (1) BaBar-CONF-06/037 ΔΕ minimum of the three di-pion invariant masses mES data projection of the fit result signal misreconstruction expected B background continuum background NN output Δt/(Δt) m'  ' S = 0.01 ± 0.12 ± 0.028 C = 0.154 ± 0.090 ± 0.037 Time & flavor integrated A = −0.142 ± 0.041 ± 0.015 A & C are transformed into more physically Intuitive quantities A = 0.03 ± 0.07 ± 0.03 +− quasi-two-body approach (ignoring interference): ΔS = 0.06 ± 0.13 ± 0.029 A = −0.38+0.15 ± 0.07 −0.16 −+ ΔC = 0.377 ± 0.091 ± 0.021 University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool BABAR results: B0 → ()0 (2) + − = arg(A+*A−) : The constraint on  from B0 → ()0 is relatively weak but has no ambiguity Relative phase between the amplitudes of B0 → −+ and B0 → +− + − [5, 63]º at 68.3% C.L. [75, 152]º at 68.3% C.L.  BaBar-CONF-06/037 University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

Global constraint on    [86, 114]º Frequentist interpretation of constraints on  using B → , ,  measurements: 97.5°   [86, 114]º at 68.3% C.L. CKMfitter Group (J. Charles et al.), Eur. Phys. J. C41, 1-131 (2005), [hep-ph/0406184], http://ckmfitter.in2p3.fr Belle excludes  in the range [9, 81]º at 95.4% C.L. from their latest B →  measurements University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool Summary The BaBar experiment has improved the precision in several measurements related to the extraction of  , and has observed evidence of CP violation in B0 → +− The decay process B0 → 00 The branching fractions and CP parameters in B0 → 00 and B0 → 00 decays are crucial to make a precision measurement of  at the B-Factories When extracting  from all BaBar measurements, the frequentist approach (CKMfitter) differs from the Bayesian one (UTfit) significantly. The larger of the 68.3% C.L. intervals is   [86, 114]º (CKMfitter), and gives a solution at 97.5° Improved measurements of  from BaBar are expected in the future, more data and improvements to the analysis techniques are underway University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool Backup Slides University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool The CKM Matrix & CP Violation 3x3 unitary matrix: 3 real parameters, 1 phase: only source of CPV in SM CKM matrix describes mixing between flavor and weak eigenstates in the Standard Model. Unitarity implies Wolfenstein parameterization This talk (1,0) (0,0) (,) CP violating phases University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool How to measure a ? Decays sensitive to a B0-B0 mixing Tree level Time dependent cp asymmetry: Can be written as: Indirect CP relevant to a Direct CP University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

University of Liverpool B tagging & vertexing BCP (4S) Btag Accurate measurement of Dt requires accurate measurement of the decay vertices. Resolution in Dt is dominated by the tagging side. Determine resolution parameters from a large sample of fully reconstructed B events. For time-dependent analyses we must know the flavor of BCP when Btag decays (t=0). This is done by looking at the decay products of Btag. For instance, leptons and kaons. The ”mistag” rate dilutes the measured asymmetry. University of Liverpool Carlos A. Chavez PASCOS 2006, OSU

Global constraint on    [164, 176]º at 68.3% C.L. 169.7° Constraint on  from Bayesian interpretation using B → , ,  measurements CKM fit no  in fit 169.7°   [164, 176]º at 68.3% C.L. UTfit group (M. Ciuchini et al), JHEP 0107 (2001) 013, [hep-ph/0012308], http://utfit.roma1.infn.it University of Liverpool Carlos A. Chavez PASCOS 2006, OSU