1 CP Violation Measurements CP Violation Measurements in Hadronic B Decays y at Belle Takeo Higuchi Institute of Particle and Nuclear Studies, KEK The Belle Collaboration Sep.1,2010 T.Higuchi (KEK)
2 B-Factories in the World Accelerator Accelerator Detector Detector Collaboration Collaboration Belle Belle ~400 researchers from Belle (Japan) Belle (Japan) 14 countries/regions 14 co ntries/regions (Japan) (Japan) BaBar (US) BaBar BaBar ~600 researchers from 10 countries/regions / g (US) (US) (US) (US)
3 Integrated Luminosities g • Total recorded luminosity by Belle = 1052.79 fb –1 Total recorded luminosity by Belle 1052.79 fb – Belle finalized data taking on Jun.30 th ,2010. • Total recorded luminosity by BaBar = 558 fb —1 – BaBar finalized data taking in Apr 2008 BaBar finalized data taking in Apr.,2008. • We have recorded > 1.5 ab —1 data. We have recorded > 1.5 ab data. Sep.1,2010 T.Higuchi (KEK)
4 Belle Detector Electromagnetic Calorimeter • CsI (Tl) crystal. K μ Detector K L μ Detector • Energy measurements of γ and e ± . • Sandwich of 14 RPCs and 15 iron plates. σ E E / ~ 1.6% • @ 1 GeV. • μ -ID with iron-punch-through power. • Return path of magnetic flux. p g 3.5 GeV e + + Time-of-Flight Counter • Plastic scintillation counter. • K / π -ID of high range p • K / π -ID of high range p. • Time resolution ~100 ps. 8.0 GeV e – Aerogel Č erenkov Counter • Refractive index n =1.01-1.03. • K / π -ID of middle range p. Central Drift Chamber Silicon Vertex Detector • 8,400 sense wires along the beam direction. g σ ⊕ • Momentum resolution p p / ~ 0.28 p (GeV) 0.3% • Four detection layers. t t t • PID with dE/dx measurement. • Vertex resolution ~ 100 μ m . • 1.5 T magnetic field.
5 History of Belle y Agenda of the 48 th collaboration meeting • Group meeting in Oct. 1993 (Osaka Univ.) Group meeting in Oct. 1993 (Osaka Univ.) Agenda of the first group meeting Agenda of the first group meeting Agenda of the 48 collaboration meeting – The first group meeting. * Group Meeting #1: 7-Oct-1993 (Thu) at Osaka Univ. (Sigma Hall) * Group Meeting #1: 7-Oct-1993 (Thu) at Osaka Univ. (Sigma Hall) 12:00 - 12:10 12:00 - 12:10 Goals of the meeting Goals of the meeting S. Suzuki S. Suzuki (Nagoya) (Nagoya) • Group meeting in Jan. 1994 (Nara Women’s Univ.) 12:10 - 14:10 12:10 - 14:10 Short reports Short reports – Vote for the collaboration name Vote for the collaboration name. Problems at Forward Angles J. Haba Problems at Forward Angles J. Haba g g ( ( (Osaka) (Osaka) ) ) electron collides with electron collides with positron yielding B meson. positron yielding B meson CsI Calorimeter CsI Calorimeter M. Fukushima M. Fukushima (KEK) (KEK) Questions on PID M. Yamauchi Questions on PID M. Yamauchi (KEK) (KEK) • Group meeting in Feb. 1995 (Tohoku Univ.) Group meeting in Feb. 1995 (Tohoku Univ.) PDC/CDC PDC/CDC A. Sugiyama A. Sugiyama g y g y (Nagoya) ( (Nagoya) ( g y ) g y ) Requirements for B->pilnu Requirements for B->pilnu S. Uno S. Uno (KEK) (KEK) – Decision of the Belle group’s logo. “Belle” is French word, which means beauty in Estimation of accuracy of phi-2 Estimation of accuracy of phi-2 Y. Watanabe Y. Watanabe (TIT) (TIT) Proto-typing of the KL Chamber Proto-typing of the KL Chamber A. Yamaguchi A. Yamaguchi (Tohoku) (Tohoku) Belle Belle Peace Peace Beat Beat Bambi Bambi English. The bottom quark is sometimes called English The bottom quark is sometimes called a beauty quark 14:10 - 14:40 14:10 - 14:40 Detector Configuration for LOI Detector Configuration for LOI K. Abe K. Abe (KEK) (KEK) 14:40 - 15:30 14:40 - 15:30 Prcoesses for writing LOI Prcoesses for writing LOI S. Noguchi S. Noguchi (Nara) (Nara) ) ) Time Table for Writing LOI Time Table for Writing LOI S. Suzuki S. Suzuki (Nagoya) (Nagoya)
6 History of Belle y • Dec.,1998 Dec.,1998 Detector construction Detector construction had completed. • Jan 1999 • Jan.,1999 Cosmic-ray event Cosmic-ray event taking had started. The first e + - e – collision of KEKB. + • Feb.,1999 F b 1999 Th fi t lli i f KEKB • May.,1999 The detector had been rolled in to the IR. • Jun.4 th ,1999 The first physics event. … • 9:00am Jun.30 th ,2010 9:00am Jun.30 ,2010 Data taking finished.
7 CKM Matrix and Unitarity Triangle y g W lf Wolfenstein Parameterization t i P t i ti KM ansatz: Irreducible complex phases (in V ub and V td in Wolfenstein parameterization) cause the CP violation. Wolfenstein parameterization) cause the CP violation One of the unitarity conditions: One of the unitarity conditions: i η Unitarity condition forms a untarity Unitarity condition forms a untarity triangle in the complex plane. ( φ 1 φ 2 φ 3 ) = ( β α γ ) ( φ 1 , φ 2 , φ 3 ) ( β , α , γ ) ρ O
_ 8 B 0 - B 0 Mixing and Mixing-Induced CPV g g _ _ V * tb Vtd b d 2 i φ φ _ 2 i t t 2 2 ∝ ∝ V e 1 B 0 B 0 W W td t d b Vtd Vtd V * tb V * tb _ B 0 and B 0 mix with each other through a box diagram shown above. _ Even if B 0 and B 0 decay to the same final state, the phase of the decay amplitude may differ depending on the B flavor at the decay time. B 0 f CP phase == 0 interference interference 2 2 ( ( V V ) ) _ td phase difference = 2 φ 1 B 0 B 0 f CP CPV due to the interference is called “mixing-induced CP violation”.
9 CP Violation in Proper-Time Distribution p + − → ϒ ( (4 ) ) → e e S BB The e + - e – collision produces a pair of B mesons through Υ (4 S ). The mixing-induced CP violation manifests itself in the signed time duration “ Δ t = t BCP – t B tag ”, where • t BCP t … time when one B decays to the CP eigenstate. ti h B d t th CP i t t • t B tag … time when the other B decays to the flavor-specific state. S = 0.65 B tag = B 0 _ − ∆ τ t A = 0.00 B tag = B 0 e 0 B ∆ ∆ = = ∆ ∆ ∆ ∆ P P t t S A S A S S m m t t ( ( ; ; , ) ) [1 [1 ( ( si si n n ± ± d d τ 4 B 0 + ∆ ∆ A cos m t )] d Δ t (ps)
10 B 0 � J / ψ K 0 : Golden Modes for φ 1 ψ φ 1 _ • The B 0 � J / ψ K 0 is mediated by b � ccs tree transition. The B � J / ψ K is mediated by b � ccs tree transition. _ b � ccs tree _ _ c c The decay diagram includes The decay diagram includes J / ψ / ψ b neither V ub nor V td . c B 0 W _ � The φ 1 is accessible. s s 1 d d K 0 d • SM prediction: S = – η CP sin2 φ 1 , A ≈ 0 – Test of Kobayashi-Maskawa theory. � Nobel prize in 2008 Test of Kobayashi Maskawa theory � Nobel prize in 2008 – Check for a NP phase with very precise unitarity tests. Sep.1,2010 T.Higuchi (KEK)
_ 11 B 0 � J / ψ K 0 Reconstruction (535M BB ) ψ ( ) _ from 535 x 10 6 BB pairs p 0 0 J / ψ K S J / ψ K L + data � MC: signal 0 MeV/ c MeV/ c 2 N sig = 7482 � MC: J / ψ K L X Purity 97 % � MC: J / ψ X vents / 1 M CP CP = –1 1 � MC: comb. vents / 50 N sig = 6512 Purity 59 % Ev Ev CP = +1 Beam constrained mass (GeV/ c 2 ) B momentum in Y(4S) CMS (GeV/ c ) Sep.1,2010 T.Higuchi (KEK)
12 0 Event Recorded by Belle B 0 � J/ ψ K S ψ y S Two muons from J/ ψ decay Two pions from K 0 S decay
13 Δ t Reconstruction B rec e – e + e e rec ∆ ≈ ∆ βγ t z c Υ (4 S ) B asc asc Δ z ~ 200 μ m; βγ c ~ 0.425 Δ z ~ 200 μ m; βγ c ~ 0 425 distance ( Δ z ) 2 T T χ ≡ δ δ + δ δ + � h V h h V h Minimizes … Vertex tracks i i i j j j Decay products d h i = i -th track’s helix parameters B V i = Inverse matrix of the i -th track’s error matrix RMS of vertex residual ~ 120 μ m residual distribution == resolution residual distribution == resolution Vertex residual ( μ m)
14 Δ t Resolution Model • Convolution of following 4 items: Convolution of following 4 items: – Detector resolution. – Effect on B – Effect on B asc vertex by secondary tracks. vertex by secondary tracks – Smearing due to kinematical approximation: ∆ ∆ z ∆ � t c βγ ϒ ( ) – Outlier tail. Outlier tail Sep.1,2010 T.Higuchi (KEK)
_ 15 Flavor Tagging (Determine B tag = B 0 / B 0 ) gg g ( ) tag l l K K Measurements are M t B tag decay p p • Particle spices p • Charge p p K K • Momentum, etc… Assign flavor/ambiguity to each particle using measured info. Combine flavors/ambiguities of all particles Combine flavors/ambiguities of all particles. Determine flavor ( q : ± 1) of the B tag and ambiguity ( w :0…1). _ B tag = B 0 B tag = B 0 q (1–2 w ) = –1 ( ) q (1–2 w ) = 0 ( ) q (1–2 w ) = +1 ( ) unambiguous no flavor info. unambiguous
16 Wrong Tagging Probability: w g gg g y Wrong tag probability Wrong tag probability, w , is calibrated using _ the B 0 - B 0 mixing of the g real data. − P P OF SF = = ∆ ∆ A cos m t chg d + + P P OF OF SF SF meas. = − ∆ ∆ A (1 2 )cos m t chg w d ave
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