Picture Erice. 23 Sept 2002 K. R. Schubert (TU Dresden), QHN Erice

Transcription

1 Picture Erice 1

2 K. R. Schubert, TU Dresden Quarks in Hadrons and Nuclei Erice, 23 Sept 22 Title page New Results on CP Violation in B-Meson Decays Old Results on CPV in K and B Decays Explanation in the Standard Model PEP-II and KEK-B, BABAR and Belle Search for CPV in other B Decay Modes Luminosity expectations 2

3 CP Symmetry of the Weak Interaction: + CPν = ν CP e = e CP u = u... Γ ( + + ) ( µ e ν ν = Γ µ e ν )... R L R R el µ R L L erν µ L Discovery of CP Violation: 1964 by Christenson, Cronin, Fitch and Turlay in the π + π decay of K = 1 1 S sd. Strange particle with transitions K K and only two states with exponential decay laws: K S = pk + qk, K L = pk -qk. CP symmetry p = q, Observed 1964: p > q. Simplest demonstration today: L R L R Strictly obeyed from 1957 to 1964 CPV discovery I

4 CP-Violating Asymmetry: Explanation of this CP-Violation in the Standard Model: CPV discovery II CPLEAR η () A t N( K = N( K 2η = + e + π π ) N( K + π π ) + N( K ( Γ +Γ ) t/2 e S Γ t S L + η cos( m + ( 2.27 ±.2) 2 e Γ t 3 + = 1 L K + π π ) + π π ) t ϕ ) i e + (43.3±.5) The 4x3 weak interaction couplings are complex, g = g. V ij (CKM). Their interference leads to Γ(K K ) < Γ(K K ). 4

5 For 37 years, the K was the only system in particle physics with CP violation. In summer 21, decays of B mesons Expected CPV in B decays showed the second evidence. Search for CPV(B) could be planned well because of clear Standard Model expectation: ( B J ψ K S ) Γ( B J / ψ K S ) ( B J / ψ K ) + Γ( B J / ψ K ) Γ A = = sin 2β sin B β = Γ / * td tb cb cd S S * ( m t) ; arg( V V V V ). β(ckm) given by St.Model. Early B experiments (ARGUS, CLEO) measure m B =.47/ps and V ub sin2β =.2-1.; sin2β =.5-.8 if CPV(K) has only St.Model origin. However, B mesons required! Most promising method: g e e + e - γ g e b b Y(4S),1.56 GeV 5 g s g g s B B g w c d d W g w K c s J/ψ

6 The B-Meson Factory PEP-II at SLAC: design 1988, approval 1993, start 1998 PEP-II βγ =.55 E [GeV] e - / e + I [ma] e - / e + L [cm -2 s -1 ] L int [pb -1 /day] Plan 9. / / x reached yes 98 / x

7 (on same time scale) βγ =.43 KEKB achieved: 7.35 x

8 View ino KEKB tunnel KEKB in the TRISTAN tunnel, L=3. km PEP-II: L=2.2 km 8

9 91/fb in PEP-II 85/fb in KEKB σ(e + e - Y4S) = 1.1 nb Typical very good day in PEP-II Lumi in BABAR & Belle L I(LER) I(HER) N(BB) = 1M in PEP-II, 95M in KEKB. In practice 9% of that because of runs off-resonance. 9

10 ϒ Resonances = n 3 S 1 bb states, J PC = Cont. Subtraction & 2-particle coherence BB ϒ(4S) B B (5%), B + B - (5%). Strong decay conserves C&P. Neutral final state is coherent 2-particle state, (B o B o -B o B o )/ 2, Single B state created when first B of the pair decays ( tdecay 2 tproduction 2) ( tdecay 2 tdecay 1) = t 1

11 The BABAR Detector: (4) Electromagnetic Calorimeter (3) Cerenkov- Detector BABAR Detector (5) 1.5 T Solenoid (6) Instrumented Iron Yoke e - e + (2) Drift Chamber (1) Silicon Vertex Detector 11

12 73 institutes BABAR picture & Collaboration USA Italy France UK Germany Canada Russia China Norway 516 authors 12

13 Belle Detector 3 physicists, 49 institutes, 14 countries: Australia, Austria, China, Germany, India, Korea, Japan, Philippines, Poland, Russia, Slovenia, Switzerland, Taiwan, USA 13

14 BABAR Silicon Vertex Tracker: βγ cτ(b) = 26 µm, π βγ c / m(b ) = 1 mm, BABAR Si Vx Tracker R= 14 cm σ z 7 µm for fully reconstructed B mesons σ z 18 µm for B meson tags 14

15 A fully reconstructed event: CP eigenstate, decay at t 1, either from B or from B ϒ A fully reconstructed event flavour eigenstate,here from B, decay at t 2, tags the flavour of the other B at time t 2 Such events are very rare, o(1-6 ), therefore BABAR and Belle use inclusive tagging for CP asymmetry measurement. 15

16 Searched CP-Asymmetry: ( B J / ψ K ) Γ( B J / ψ K ) Γ A = = sin 2β sin Γ S S T dependence of asymmetry ( B J / ψ K ) + Γ( B J / ψ K ) Because of coherence: S S [ m( t t )] decay Incoherent case: tag Γ B dec. B tags B B B decays Γ B B tags B B B t/τ t/τ Integral of A over all t is zero. Therefore it is necessary to measure the t dependence (and - for technical reasons - to boost the ϒ4S.) 16

17 Measurement of Prinzip time-dependent der sin2beta MessungCP-Asymmetry: ( B J / Ψ K ) Γ ( B J / Ψ K ) S S ( B J / Ψ K ) + Γ ( B J / Ψ K ) A ~ ( ~ Γ t ) = = D sin 2 β sin( m t) r d Γ S S ( ~ t - t ) t βγ =.55 Υ(4S) e + 4: Flavour Determination of the other B Meson ( tag ) 1, 2, 3: B Reconstruction into CP Eigenstate 6: Determination of t = z/βγc 7: Determination of the z resolution 5: Determination of the fraction w of mistags function Dilution D = (1-2w) reduces observed asymmetry. 8: sin2β Fit to both Time Distributions 17

18 Newest BABAR results (7/2): cck S modes: η c (KKπ)K S N J/ψK L : cand = 132 Purity = 63 % 18

19 One more mode: J/psi K* D =.68 ±.7 19

20 Tagging Category Lepton Kaon and π(soft) Kaon II Inclusive total Efficiency (%) Mistag fraction (%) 9.1 ± ± ± ± ± ±.8 2. ± Tagging.3 quality 31.6 ±.9 and result 65.6 ±.5 Q (%) 7.9 ± ± ±.4.9 ± ±.7 Tag quality Q = Σ ε i (1-2w i ) 2 σ ( sin 2β ) N Q sig N N bg sig Result July 22 with 9 M ϒ(4S), 2641 tagged events: sin2β =.741 ±.67 ± t [ps] -5 5 t [ps] 2

21 Submitted to PRL, hep-ex/2742 BABAR asymmetry, all and golden σ(sin2β) 21

22 July 22 Results with 78/fb, 85 M ϒ(4S) Belle results 22

23 All sin2beta results 13σ effect 23

24 Explanation in the Standard Model u = Higgs mechanism gives mass to doublets d i d s b. The partners d i of u i are related to the mass eigenstates d i + ' by a unitary rotation d ' in family space. ui W d i = Vij d j i Matrix V was introduced into the Standard Model by M. Kobayashi and T. Maskawa 1973, now called V CKM because of N. Cabibbo s d = cosθ. d + sinθ. s in d s b ' ' ' = = = V ud V V cd td d d d + V us + V + V cs ts s + V s + V s + V ub cb tb b b b + V 24 d s b ' ' ' = = = V * ud V V * cd * td d d d + V + V u * us * cs * ts i s s s + V + V + V * ub c * cb * tb owing to CPT symmetry. Higgs mixes antiquarks differently than quarks if V CKM is not real; more precisely if Im ( * * J = V ) ik V jk V jl Vil This is the origin of CP violation in the Standard Model. b b b t

25 Wolfenstein 1984: V Aλ 1 λ 3 2 λ / 2 (1 ρ iη ) λ 1 λ 2 Aλ / 2 2 Aλ ( ρ iη ) 2 Aλ ; 1 A, λ, ρ, η are 4 of 18 free parameters of the St. Model. 6 unitarity conditions * 3 * of V can be drawn Vud Vub Aλ + Vtd Vtb =, as triangles, e.g.: * 3 3 V / Aλ + V / Aλ 1. η V ub* /Aλ 3 V td /Aλ 3 β 1 ρ ub 3 td J A 2 λ 6 η. Area of this triangle is J/2. Measurements of λ, A, ρ 2 +η 2, and (1 ρ) Wolfenstein and unitarity triangle 2 +η 2 give λ =.22 ± 1%, A =.83 ± 4%, ljl St. Model violates CP symmetry. 25

26 ckm Lfit η maxl, 1σ, 2σ Γ(B ρlν) Γ(B X u lν) ckm-lfit

27 ckm Lfit η maxl, 1σ, 2σ m(b d ) m(b s ) J, Standard Model violates CP with > 3σ, concluded from CP conserving measurements only. ckm-lfit

28 ckm Lfit η maxl, 1σ, 2σ ε(k ) ckm-lfit

29 ckm Lfit η maxl, 1σ, 2σ Combined Fit ckm-lfit

30 ckm Lfit η maxl, 1σ, 2σ sin2β Previous fit without sin2β ckm-lfit

31 ckm Lfit η maxl, 1σ, 2σ (λ =.22 ±.2) (A =.85 ±.4) ρ =.2 ±.11 η =.35 ±.6 J = (2.9 ±.6). 1-5 Fit with all experiments, B ρlν, B X u lν, m d, m s, ε(k), sin2β: Fit with all experiments except sin2β: ckm-lfit

32 ckm Lfit η Future? sin2β from BABAR, Belle, LHCb m s from CDF, D, LHCb B ργ/b K*γ BABAR,Belle and Theory! V ub from BABAR, Belle, and Theory! ckm-lfit-28-7 (Falsification of the Standard Model?) 32

33 Search for CP Violation in other B-Meson Decays 1. CP Violation in B B Oscillations, Re ε(b ): βγ =.55 B ϒ(4S) < z> = 25 µm l - A A( t ) = N ( l N ( l + + l l )( t ) N ( l )( t ) + N ( l ± ± l l ± ± B )( t ) )( t ) l + CPV in Bbbar Mixing A CP ( t) = + N( l l + N( l l + + A( t) with 2/fb: m(b ) = (.499 ±.1 ±.12) h ps -1 )( t) N( l )( t) + N( l l l )( t) )( t) + q Re( ε B ) /(1 + ε ) =.12 ±.29 ±.36 p =.998 ±.6 ±.7 B 2 33

34 2. B φk S : Pure penguin, tree highly suppressed A = sin2β in St.M, but new physics may change A. 51 events B ( B ΦK ) = 8.1 ± CPV in B to phi Ks BABAR: A(φK S ) = -.19 ±.52 ±.9 1.8σ from cck Belle: A(φK S ) = -.73 ±.64 ± σ from cck Combined: -.4 ± σ from cck 34

35 3. Search for Direct CPV(B) A Γ A = Γ ( B f ) Γ( B f ) ( B f ) + Γ( B f ) Condition: Final state f is reached by two diagrams, 2a1a 2 sin ( φ1 φ 2 ) sin ( δ 1 δ 2 ) = 2 2 a + a + 2 cos ( φ φ ) cos ( δ δ ) 1 Mode J/ψ K + K* + γ 2 B(BABAR) ± 3 ± 5 39 ± 6 ± ± ± with 2 different weak φ and two different strong δ -29 ± 23 2 ± 36-4 ± 16 π + π 5.5 ±1. ±.6-3 ± ± 31 K + π 12.8 ±1.2 ±1. -9 ± 9-4 ± 19 K π 1.4 ±1.5 ±.8 K + π ±.9 ±.7-1 ±5-7 ± 6 K π ± 1 46 ± 15 (*) 18 ± 24 and in more modes... A(BABAR) % A(Belle) % 2 ± 9 (**) 5.3 ±8.3 (*) 24/fb (**) 78/fb A(CLEO) % 1.8 ± ± 13

36 No CPV(B) effect seen - except sin2β - with > 3σ. Some effects with 4 types 2 of to CPV 3 σ come and go, small statistics does not give Gaussian σ. There are four types of CP Violation seen and expected: 1) in flavour oscillations M M, Re(ε K ), Re(ε B ), 2) in interference between oscillations and decay, Im(ε K ), r cck 3) direct CPV in decays into one final state, Re(ε K ), A(B πk)...page 35 4) Direct CPV in decays into > 2 final states, Im(ε K ), r r = ππ ψk q A B p A B = + ( π π ) + ( π π ) A B A B ( cck S ) ( cck ) S = ( cck S ) ( cck ) A B A B e 2iβ [ Im( r ) = sin 2β ] S cck = e 2i ( α + β ) eff 1 36

37 4. Search for CPV(B π + π - ) Decay functions f + (f - ) for tag = B (B ): Γ f± cos 4 ( t) = [ 1± S sin( m t) m C ( m t) ] For weak phase from tree T only: C =, S = sin 2α With additional phase from penguin P: C, S = sin 2α. eff b d b g W t W u d u d d d u u d α γ β 37

38 BABAR with 81/fb July 22 Preliminary: S =.2±.34±.5 C = -.3±.25±.4 CPV(B π + π - ) II S = no type-2 CPV, α eff = 9 ± 11. C = no type-3 CPV, α eff = 9 ± 11, β = 25 ± 3.5 Type-4 CPV only with 2.3σ. 38

39 Belle with 42/fb, March 22: CPV(B π + π - ) Belle S = ± ±, with 3.2σ C = -.94 ± ±.9, with 3.σ 39

40 -C S 2 +C 2 <1 CPV(B π + π - ) IV Belle value is outside the physical boundary. Average not very relevant. Therefore, here, only one discussion of the result: S 4

41 PEP-II Luminosity Expectations Integrated Lumi [events/fb] Peak Lumi [1 33 /cm 2 /s] (from David MacFarlane, BABAR, August 22) Similar expectations for KEK-B. 41

42 CPV Precision estimates (from David MacFarlane, BABAR, August 22) As important as more precision on CPV observables: V ub from b ulν and V td from B ργ for testing if all observed CPV fits into Standard Model..5-2/ab: σ(v ub ) = 5%, σ(v td ) = 1%. 42

43 Summary Owing to the unexpectedly good Owing to the unexpectedly performance good performance of the e + e - storage of therings e + e - PEP-II and KEK-B, the experiments storage rings PEP-II and KEK-B, the experiments BABAR BABAR and Belle have now analysed and Belle have now analysed 9 M BB 9 pairs M BB each, pairs establishing each, CP establishing CP Violation in B meson decays with 13σ. violation in B meson decays with 13σ. The observed asymmetry sin2β =.734 ±.55 is in perfect agreement with the Standard Model, which naturally contains CPV if 6 quarks with m(q i ) m(q k ). There are no other CP(B) asymmeties with significance > 3.2σ. If no surprises, the next significant measurements will require 5 to 2 times more data than now available. There are no known limitations in storage ring physics which exclude that 5-2 times higher luminosities can be achieved at both PEP-II and KEK-B during this decade. 43

44 Picture Dirac Theatre 44