Measurement of ϕ 2 /α using

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1 Measurement of ϕ 2 /α using Decays at elle and aar lexander Somov CKM 6, Nagoya 26 Introduction (CP violation in decays Measurements in φ 2 constraint from an Isospin analysis

2 CP Violation in decays Tree Penguin d (π u b W u,c,t b u - (π - d d d W d u (π u d - (π - N N ( ( N N ( ( cos( m t S sin( m t Direct CPV Mixing induced CPV Tree only Tree Penguin S sin(2 φ 2 S ~ sin( 1 δ 2 direct CP violation sin(2 φ eff determine φ 2 using isospin analysis

3 φ 2 /α measurement Three main decays used for the extraction of φ 2 ( α π π relatively clean signal, large penguin contribution m π not a CP eigenstate, time-dependent Dalitz analysis dvantages of : small penguin contribution due to relatively small.37 6 r ( ( [abar, hep-ex/6797] relatively large measured branching fraction for b u process r( r( π π ~ 4.4

4 CP analysis in decays Complications: is a VV state 3 helicity states (three helicity amplitudes should be considered longitudinal polarization H H ( 1 CP even H H ( 1 CP even 2 H H ( 1 CP odd H 2 H Fortunately, longitudinal polarization dominates f L aar: hep-ex/6798 f L elle: PRL96, f L PDG

5 CP analysis in decays (cont d Complications (cont d: Dirty final state π π π π ; Γ( 15 MeV large backgrounds I 1 contribution due to finite width of [.F.Falk, Z.Ligeti, Y. Nir, H.Quinn PRD69, 1152, 24] Contribution from EW penguin

6 Constraint on φ 2 /α Extract φ 2 using an Isospin analysis (similar to π π analysis - model independent approach The penguin contribution can also be bound using flavor SU(3 relations [M.eneke, M.Gronau, J.Rohrer, M.Spranger hep-ph/645] [M.Gronau, O.F.Hernandez,D.London,J.L.Rosner, Phys.Rev.D5,4529,1994]

7 Isospin analysis in (ππ Measure and S : eff S sin(2 φ φ φ δ ππ 1 ππ 2 2 eff 2 Use isospin relations [M.Gronau and D.London, Phys.Rev.Letter. 65, 199] Two amplitude triangles: 2, 2 2 2δ ~ 2 ~ ~ 6 unknowns, and 5 observables: r s,, S ( 2, not yet measured CP asymmetries in ~ ~ ~ ( ( ( ( ( ( Calculate confidence level applying R-fit method (see next talks [J.Charles et. l. Eur.Phys.J.C41:1-131, 25 ]

8 Common features of measurements small branching fractions: Large background S/ ~ O(1% ll types of background contribute: continuum, b c and b u continuum is a dominant background. Use Fisher or neural nets (aar to discriminate Multiple candidates in the same event. est candidates selection based on best π mass and best χ 2 of the vertex fit. Events with misreconstructed pions, SCF. Use separate PDFs. Several variables used to separate signal from backgrounds: m bc, E, m ππ, cos θ, event topology, flavor, t

9 nalysis strategy aar Determine signal yield, polarization, CP parameters simultaneously using a multidimensional fit. Loose cuts on kinematical variables more signal events in the fit. Use PDFs for all variables to discriminate against background - PDF shapes, correlations among variables (sometimes fits exhibit small bias elle Relatively stringent cuts on kinematical variables. Separate fits for event yields, polarization, and CP parameters. - larger statistical errors

10 M bc - E - LR fit results NEW elle results (preliminary 535 Million pairs Events / 2 MeV bc M (GeV/c Events / 2 MeV E (GeV Events / 2 MeV Events / 2 MeV Fit results: N evt in the fit N ππ 567 LR fit projection high quality tag high quality tag bc M (GeV/c E (GeV

11 S t (ps Million pairs.16.21( stat.7( syst ( stat.6 ( syst Events / (1.25 ps Events / (1.25 ps t (ps Raw symmetry / (2.5 ps t (ps t (ps -5 5 t (ps Events / (1.25 ps Events / (1.25 ps CP fit results Signal true PDF t /τ e { 1 q( cos( m t S sin( m t} 1 4τ fit for two parameters, S long P q f 2% f 35 % High quality tag t (ps Raw symmetry / (2.5 ps Low quality tag Preliminary

12 fit results 1 R preliminary (GeV/c 2 m ES high-purity events (a 5 E (GeV Million pairs Events / (5 MeV/c 2 Events / (3 MeV 2 (c cos θ 1 m ES E cos(θ i 1 5 (b m (GeV/c 2 π π Events / (.188 Events / (5 MeV r f L ( m(π π (d Updated this summer hep-ex/6792 Simultaneous fit for the yield, polarization, and CP parameters C and S N Previous elle: (PRL 96,17181, r 3. 4 Previous (PRL 95,4185, 25 aar: 21 f L (PRL 95,4185, 25 f L r

13 CP symmetries Tags Tags R preliminary tags tags symmetry (a background Signal true PDF (b (c t(ps C S P long q e t /τ 4τ { ( q(.15( stat hep-ex/6792 S sin( m t C cos( m t} stat.6( syst ( syst

14 Measurements in decays NEW measurements last summer, hep-ex/ Million pairs Extract signal yield, polarization and charge asymmetry using an extended unbinned (7-dimensional ML fit to m ES, E, m(ππ, cosθ, x N Events / 2 MeV 8 (a (GeV/c 2 m ES (b Events / 2 MeV/c 2 Simultaneous fit for the yield, polarization, and charge asymmetry N total E (GeV 8 (d Events / 5 MeV/c 2 Events / 45 MeV/c 2 39 N (c m(π π (GeV/c m(π π (GeV/c 2

15 Measurements in decays (cont d elle results (old, PRL 91, (23 85 Million pairs N events E (GeV Determine signal yield from a fit to E distribution Obtain polarization from a simultaneous fit to background subtracted cos θ cos θ distributions Determine charge asymmetry from separate fits to E distributions of and candidates Events/32 MeV ackground subtracted m(π π and m(π π ackground subtracted cos θ cos θ Data MC E Yield cosθ hel( H : H 11 : E yield / 1MeV/c 2 E Yield M(π π (GeV/c 2 Data MC E yield / 1MeV/c 2 M(π π (GeV/c cosθ hel(

16 results 232 Million pairs 85 Million pairs HFG r f L (1 CP Previous aar measurement: r ( f.97.4 Phys. Rev. Lett. 91, L CP (23

17 Evidence for 348 Million pairs hep-ex/6797 Use an unbinned extended ML fit to extract signal yield and polarization 8 dimensional fit: m ES, E, m(ππ 1,2, cosθ 1,2, event topology, flavor tags total number of events in the fit 6518, N( Main components in the fit signal, ε 24.2% continuum background (use neural network and tagging information float parameter values b c background b u background - similar topology: a 1 π (dominant peaking background, f, f f - other modes: K *,, π,, remaining float normalization

18 Evidence for (cont d R Preliminary 6 R Preliminary 5 4 hep-ex/6797 Events / (.2 GeV Events / (.1 GeV m ES 1 E 3 background m ES (GeV E (GeV N ( syst r ( ( ( syst f L ( syst Sourses of dominant systematic errors: PDF shapes, interference with a 1 π, fit bias Results statistically consistent with previous aar measurements, PRL 94, (25 r < at 9% CL

19 - last minute results! m ES (a (b E Events /(.2 GeV Events /(.1 GeV 384 Million pairs N ( syst m ES (GeV (c m ππ (GeV E (GeV (d Events /(.2 GeV Events /(.2 background m ππ cos θ r ( (1.7.33( stat.19( syst 1 6 hel ππ hep-ex/61221 (12/11/26 submitted to PRL f L.87 13( stat.4( syst

20 Constraint on φ 2 /α ranching fractions and polarization fractions used in the calculations (HFG, ug. 26 OLD ( ( > ( f L ( ( f L ( ( f L ( ( ( ( ( Caveats N ignore interference with ππ, π π π π, a 1 π ignore possible I 1 contribution neglect EW penguin (all believed to be small The isospin triangle is closed with new measurements of r(, r(, r(,

21 Constraint on φ 2 /α (cont d CKM f i t t e r CKM6 (W (R (elle & (R Generally, Isospin analysis allows to extract φ 2 /α with 8-fold ambiguity (S is not measured. We have 6 unknowns and 5 measurements. leads to plateau on 1-CL plot the plateau width depends on r(.6 If r(, Isospin triangles squashes.4.2 Squashed Isospin triangles at elle due to large r( 31.7 no plateau, 2-fold ambiguity α (deg 71 < φ 2 / α < 113 o at 68% CL ( CL CL

22 Summary Several new results during this year: Measurement of CP asymmetries in at elle Measurement of branching fractions, polarization fractions, and CP asymmetries in and decays at aar First evidence for decays at aar From an Isospin analysis ϕ 2 /α is constrained as 71 < 2 / α < o φ 113 at 68% CL New measurements are awaited to improve our knowledge on ϕ 2 /α (elle first results on r( will appear soon

23 ackup slides

24 Summary of systematic errors pairs 1 6 Value pairs 1 6 Value r f L (C S pairs 1 6 Value pairs 1 6 Value r f L CP pairs 1 6 Value r

25 Mixing induced CP violation (sin 2φ 2 2 /α q p f CP * V ud V ub * td tb * V ud V ub φ 2 arg V V φ 2 (α * V td V tb CP S sin( m t S sin 2φ 2 φ 3 (γ φ 1 (β * V cd V cb Tree W b u d * V ub V ud d u d (π - (π - Mixing V tb * V td b d t W W t d b

B Factories. Alan Watson University of Birmingham, UK

B Factories. Alan Watson University of Birmingham, UK Towards (φ ) and γ (φ ) at the 2 3 B Factories Alan Watson University of Birmingham, UK The Unitarity Triangle Source of CP in the Standard Model 1 λ 2 /2 λ Aλ 3 (ρ iη) V CKM λ 1 λ 2 /2 Aλ 2 Αλ 3 (1 ρ