1. 1 October 25 th, 2002Gerhard Raven, NNV 2002 CP Violation: Observing Matter-Antimatter Asymmetries NNV meeting October 25 th 2002 Gerhard Raven Vrije Universiteit Amsterdam & NIKHEF 1964 1999 

2. 2 October 25 th, 2002Gerhard Raven, NNV 2002 Searches for Anti-Matter in the Universe Universe around us is matter dominated –Absence of anti-nuclei amongst cosmic rays in our galaxy –Absence of intense  ray emission due to annihilation of distant galaxies in collision with antimatter Anti-Matter Spectrometer

3. 3 October 25 th, 2002Gerhard Raven, NNV 2002 Matters dominates the visible universe Where has the anti-matter gone? In 1966, Andrei Sakharov showed that the generation of a net baryon number requires: 1.Baryon number violating processes (e.g. proton decay) 2.Non-equilibrium state during the expansion 3.Violation of C and CP symmetry Standard Model CP-violation is very unlikely to be sufficient to explain matter asymmetry in the universe –It means there is something beyond the SM in CP violation somewhere, so a good place for further investigation All searches for primordial antimatter have only yielded limits:

4. 4 October 25 th, 2002Gerhard Raven, NNV 2002 Three Important Symmetries Parity, P –Parity reflects a system through the origin. Converts right-handed coordinate systems to left-handed ones. –Vectors change sign but axial vectors remain unchanged x   x, L  L Charge Conjugation, C –Charge conjugation turns a particle into its anti-particle e   e   K   K  Time Reversal, T –Changes, for example, the direction of motion of particles t  t CPT Theorem –One of the most important and generally valid theorems in local quantum field theory. –All interactions are invariant under combined C, P and T –Implies particle and anti-particle have equal masses and lifetimes  

5. 5 October 25 th, 2002Gerhard Raven, NNV 2002 Weak Force breaks C, breaks P, but it conserves CP (really?) 1957,  -decay of 60 Co: Weak Interaction breaks both C and P symmetry maximally! Despite the maximal violation of C and P symmetry, the combined operation, CP, seemed exactly conserved But, in 1964, Christensen, Cronin, Fitch and Turlay observed CP violation in decays of Neutral Kaons! W+W+ e+Re+R L WW eReR L WW eLeL R W+W+ e+Le+L R P C

6. 6 October 25 th, 2002Gerhard Raven, NNV 2002 The neutral Kaon system and CP violation Kaons are mesons (qq bound states) with Strangeness = ±1. The neutral kaons are: and can be produced by the strong interaction (which conserves Strangeness) via, e.g.: But K 0 and K 0 are not the mass eigenstates. It was long thought that those were given by the following states of definite CP (because of their decay properties): A state produced as K 0 or K 0 can be seen as a superposition of K S and K L

7. 7 October 25 th, 2002Gerhard Raven, NNV 2002 Two very different kaons While the K 0 and K 0 are charge conjugate states, the K S and K L are not, and they have different decay modes and lifetimes K S and K L decay to 2 or 3 pions, one can show that the 2  final state has CP  1, and the 3  state has CP  1 Because the mass of 3 pions is very close to the mass of the kaon, the 2  and 3  final states have very different phase space factors leading to very different lifetimes of the K S and K L Wonderful for experiments! Easy to separate K S from K L CP  1 CP  1

8. 8 October 25 th, 2002Gerhard Raven, NNV 2002 Discovery of CP violation in K 0 decay In 1964, Cronin, Fitch et al. observed the long lived K L (which was presumed to be CP-odd) decaying into    , which is a CP -even final state! –This decay occurs only ~0.2% of the time The long lived particle is therefore not a CP eigenstate, implying Weak Interaction violates CP We now refer to the two different neutral kaons K L and K S as : K 1 and K 2 are the CP even and odd eigenstates, not K S and K L

9. 9 October 25 th, 2002Gerhard Raven, NNV 2002 Tagged K 0 and K 0 production: pp  K + K 0  -  K + (  +  - )  - K - K 0  +  K - (  +  - )  + How to tell matter from anti-matter A(K S )     (t) A(K L ) K 0 (t=0) Opposite signs for K L -K S interference term between K 0 and K 0 If CP were conserved, K L wouldn’t decay to    , and there would be no interference… -A(K S )     (t) A(K L ) K 0 (t=0) CP D.Banner et al., PRD 1973 CPLEAR, PLB 1999 K0K0 K0K0 (K 0 -K 0 )/(K 0 +K 0 ) decaytime /  KS

10. 10 October 25 th, 2002Gerhard Raven, NNV 2002 Kobayashi and Maskawa and CP Violation Proposed an bold explanation of CP violation in K decay based on the minimal Standard Model and dynamics within : –CP violation appears only in the charged current weak interaction of quarks –There is a single source of CP Violation  Complex Quantum Mechanical Phase in the coupling matrix –Need at least three Generations of Quarks to allow this at that time only u,d,s known! –CP is not an approximate symmetry, large phase differences possible 1972

11. 11 October 25 th, 2002Gerhard Raven, NNV 2002 The weak decay of quarks and leptons The weak interaction can change the flavour of quarks and leptons –Leptons only change into the other lepton in the same generation –But quarks can change into a quark of any charge changing generation  WW e  WW  b WW c b WW u

12. 12 October 25 th, 2002Gerhard Raven, NNV 2002 The weak coupling of quarks The coupling strength at the vertex is given by gV ij –g is the universal Fermi weak coupling –V ij depends on which quarks are involved –For leptons, the coupling is just g For 3 generations, the V ij can be written as a 3x3 matrix –This matrix is referred to as the CKM matrix (Cabibbo, Kobayashi, Maskawa) We can view this matrix as rotating the quark states from a basis in which they are mass eigenstates to one in which they are weak eigenstates b WW c gV cb d s b dsbdsb d’ s’ b’ = uctuct

13. 13 October 25 th, 2002Gerhard Raven, NNV 2002 CP violation and the SM: the CKM matrix With 3 families, the CKM matrix is a 3  3 complex unitary matrix –18 parameters, with 9 constraints, 6 of which can be represented as triangles in the complex plane, e.g. –With 6 quarks, 5 (relative) phases are unphysical and can be ‘rotated away’ be redefining the quark fields Requires 18-9-5=4 independent parameters to describe it: –3 real numbers & 1 complex non-trivial phase –It is the non-trivial phase which is responsible for all CP violation –All CP violating observables are due to interference –CP violation is “built” into the Standard Model iff  3 generations 

14. 14 October 25 th, 2002Gerhard Raven, NNV 2002 Intermezzo: LEP @ CERN Maybe the most important result from LEP: “There are three generations of light neutrinos” L3L3 Aleph Opal Delphi Geneva Airport “Cointrin” MZMZ

15. 15 October 25 th, 2002Gerhard Raven, NNV 2002 Unitarity of the CKM matrix The CKM Matrix: Wolfenstein Parameterization Complex phase λ =V us = sin(  Cabibbo ) = 0.2205 ±0.0018 A =V cb / λ 2 = 0.83±0.06 = Measurements are usually summarized by plotting their constraints on the  -  plane ds* = 0 (K system) sb* = 0 (B system) db* = 0 (B system) All triangles have the same area:  A 6  Out of 6 triangles, the “db*” one (together with the “tu*” one) is “special”: It has all sides O( 3 ) And thus large angles

16. 16 October 25 th, 2002Gerhard Raven, NNV 2002 From CKM matrix to CP Observables CP  D + D – | H | B 0  = |A|e + i   D + D – | H | B 0  = |A|e - i  B0B0 The phase shift due to any single side of the triangle is not observable, but relative phase shifts between sides are: | B 0  f | 2 – | B 0  f | 2 = – 4 | A 1 | | A 2 | sin(  1 –  2 ) sin(  1 –  2 ) (  i = non-CKM phase of A i ) CP f B0B0 f | A 1 | e +i   e +i   | A 2 | e +i   e +i   | A 1 | e - i    e +i   | A 2 | e - i    e +i           A2A2 A1A1 B 0  f          A1A1 A2A2 B 0  f Reflecting a quark process involving W bosons in the CP mirror induces a CP-violating phase shift in the transition amplitude: V cd V cb *  V cd * V cb | B 0  D + D - | 2 – | B 0  D - D + | 2 = 0

17. 17 October 25 th, 2002Gerhard Raven, NNV 2002 How can we measure the angles? What are the theoretical requirements for an observable interference sensitive to unitarity triangle angles? –At least two interfering amplitudes –with different CKM phases (sides of the triangle) –and with different non-CKM phases What conditions lead to a large observable asymmetry? –asymmetry = (| A | 2 – | A | 2 ) / (| A | 2 + | A | 2 )  (triangle area) / (length of sides)  B system should have much larger asymmetries than kaons! What kinds of interference can we calculate? –In order to extract unitarity triangle angle(s) (  1 –  2 ) from a measurement, we must know the value of the non-CKM phase shift (   –   ): asymmetry  sin(  1 –  2 ) sin(  1 –  2 ) –When these phase shifts are due to long-distance QCD effects, they are generally not calculable (but it may be possible to measure them). This is the reason why the asymmetry measurements in K decays are hard to interpret! Need a ‘clean’ non-CKM phase!

18. 18 October 25 th, 2002Gerhard Raven, NNV 2002 Produce an bb bound state,  (4S), in e + e - collisions: e + e -   (4S)  B 0 B 0 and sometimes observe an B 0 B 0 event! ~17% of B 0 and B 0 mesons mix before they decay:  m ~ 0.5/ps,  B ~ 1.5 ps B 0 B 0 mixing: ARGUS, 1987 first hint of a really large m top ! |B 0 (t)   cos(  m t/2) |B 0  + i e +2i  mixing sin(  m t/2) |B 0  |B 0 (t)   cos(  m t/2) |B 0  + i e -2i  mixing sin(  m t/2) |B 0 

19. 19 October 25 th, 2002Gerhard Raven, NNV 2002 CP violation in the inference between mixing and decay Neutral B meson mixing provides an error-free source of non-CKM phase shift, by 90 o ( i ): B 0 (t) f CP B0B0 cos(  mt/2)  i sin(  mt/2) e +2i  mixing B0B0 A e +i  decay A e -i  decay CP B 0 (t) f CP B0B0 cos(  mt/2)  i sin(  mt/2) e - 2i  mixing B0B0 A e -i  decay A e +i  decay Sin(2  mix -2  decay ) = 0.75 This leads to a time-dependent CP asymmetry with a very clean interpretation directly in terms of CKM phases!

20. 20 October 25 th, 2002Gerhard Raven, NNV 2002 Golden Decay Mode: B 0  J/  K 0 S 2  mixing - 2  decay =arg{ } Theoretically clean way to measure  Clean experimental signature Branching fraction: O(10 -4 ) “Large” compared to other CP modes! Time-dependent CP asymmetry   CP = +1 B 0  J/  K 0 L   CP = -1 B 0  J/  K 0 S B 0   (2s) K 0 S B 0   c1 K 0 S “Golden Modes” J/  K0SK0SK0SK0S B0B0B0B0

21. 21 October 25 th, 2002Gerhard Raven, NNV 2002 The Quest for CP Violation in the B System ATLASATLASBTEV CLEO 3 B A B AR BELLE 2007? 1999 2000 2007 2002 Mission Statement Obtain precision measurements in the domain of the charged weak interactions for testing the CKM sector of the Standard Model, and probing the origin of the CP violation phenomenon 2002

22. 22 October 25 th, 2002Gerhard Raven, NNV 2002 B meson production BaBar & BelleD0/CDFHERA-BLHCb PEP-II/KEKBTevatronHERALHC mode e+e-e+e- pppApp Start datataking 19992002200?2007  s (GeV) 10.4 = M  (4S) 20004214000  bb /  qq 1/41/10001/10000001/160 N qq /s (Hz) 2020k10M13M N bb /s (Hz) 520 100000 (  m) 260450900010000 Branching ratios CP-channels: 10 -4 and smaller: Must produce MANY B mesons e + e - B factories: clean events easy trigger (  >99% for all B) only B + and B d produced Hadron colliders: huge b production rate low s bb /s inel -> triggering! large B flight distance excellent proper time resolution both B d and B s

23. 23 October 25 th, 2002Gerhard Raven, NNV 2002 B Meson Production: the “easy” way… Electron-Positron collider: e + e -   (4s)  B 0 B 0 –Only 4s resonance can produce B meson pair –Low B 0 production cross-section: ~1 nb –Clean environment, coherent B 0 B 0 production B-Factory approach B 0 B 0 threshold BB threshold CESR CLEO

24. 24 October 25 th, 2002Gerhard Raven, NNV 2002  (4S): Coherent B 0 B 0 production B 0 B 0 system evolves coherently until one of them decays (EPR!) –CP/Mixing oscillation clock only starts ticking at the time of the first decay, relevant time parameter  t: –B mesons have opposite flavour at time  t=0 –Half of the time CP B decays first (  t<0) Integrated CP asymmetry is 0: Coherent production requires time dependent analysis At t cp =0 B0B0 B0B0 At t=0 B0B0 B0B0 t = t CP - t OtherB Coherent Incoherent -- ++ ++ --  t(ps) t(ps)

25. 25 October 25 th, 2002Gerhard Raven, NNV 2002 A Symmetric Collider won’t work… CP asymmetry is a time-dependent process –A CP   t between two B decays,  t ~ ps –In reality one measures decay distance between two B decays In symmetric energy e + e - collider, where  (4S) produced at rest, daughter B’s travel ~ 20  m –Too small a distance to discern with today’s detector technology  l  40  m B tag B CP 5.3 GeV e+e+

26. 26 October 25 th, 2002Gerhard Raven, NNV 2002 Solution: Boost the CMS! Coherent BB pair z Start the Clock This can be measured using a silicon vertex detector! (  )  (4S) = 0.56

27. 27 October 25 th, 2002Gerhard Raven, NNV 2002 PEP-II: B Factory @ SLAC PEP-II: Asymmetric B Factory @ SLAC  = 0.56,  s = M  (4S) HERLER Energy (GeV)9.03.1 Number of bunches1658 Beam Current (A)1.02.1 Peak L ( 10 33 cm -2 s -1 or nb -1 /s)4.6 Collisions every 4.2 ns.. fortunately most collisions don’t result in an interaction Linac LER HER

28. 28 October 25 th, 2002Gerhard Raven, NNV 2002 BaBar and Belle: available data Both experiments started data taking in 1999 only 2 weeks apart After 3 years, both experiments ~90M BB each out to 360M qq events on tape size of BaBar database: ~650TB >1000M fully simulated MC events (Geant4) LEP: ~3M qq events per experiment… CP samples are O(1000) (or much less!) events

29. 29 October 25 th, 2002Gerhard Raven, NNV 2002 The Roadmap to sin2  z Exclusive B Meson Selection and Vertex Reconstruction Exclusive B Meson Selection and Vertex Reconstruction Tag Vertex Reconstruction Flavour Tagging e+e+ K-K- Measurements B ± /B 0 Lifetimes B 0 B 0 -Mixing CP-Asymmetries sin(2  ) Ingredient a)Reconstruction of B mesons in flavour eigenstates b)Tag B vertex reconstruction c)Flavour Tagging (+ a + b) d)Reconstruction of B mesons in CP eigenstates (+ a + b + c) Higher precision Increasing complexity

30. 30 October 25 th, 2002Gerhard Raven, NNV 2002  (2S) K s   +  -   +  - Example of a Fully Reconstructed Event B 0  D* +  - fast  D 0  + soft  K -  + ‘’fish eye’’ view fast soft B 0 (  t) At  t=0 (i.e. when the D*  decay happened), the ‘CP’ B was/would have been a B 0 EPR! In general, use charges of identified leptons, kaons, soft pions from the “the rest of the event” to tag B flavour

31. 31 October 25 th, 2002Gerhard Raven, NNV 2002 B meson selection at  (4S) m ES EE sidebands signal region  E [MeV] m ES [GeV/c 2 ] Two main kinematic variables for exclusively reconstructed B candidates: i)  E = E B cms -  s/2 There are exactely 2 B mesons produced, nothing else A signal B candidate must carry (in the CMS) half the CMS energy ii) M ES =  s/4-p B 2 Invariant mass, substituting the measured B energy with the better- known  s/2. J/  K s (    - )

32. 32 October 25 th, 2002Gerhard Raven, NNV 2002 The CP Sample ModeNtagPurity (%) J/  K s (    - )97496.5 J/  K s (     )17088.5  (2s)K s 15096.9 cKscKs 8094.5 cKscKs 13263.4 (cc)K s 150692.2 J/  K L 98855.2 J/  K *0 (K s  0 ) 14781.2 All CP264178.2 B 0  J/  K 0 S   (2s) K 0 S   c1 K 0 S   c K 0 S  J/  K * (K 0 S  0 )

33. 33 October 25 th, 2002Gerhard Raven, NNV 2002  t Spectrum of CP events perfect flavour tagging & time resolution Mistag fractions w And Resolution function R CP PDF realistic mis-tagging & finite time resolution Mixing PDF measured from fully reco’d flavour sample, B 0 -> D (*)+  -, … (~10x more events)

34. 34 October 25 th, 2002Gerhard Raven, NNV 2002 All analysis were done “blind” to eliminate possible experimenters’ bias –In general, measurements of a quantity “X” are done with likelihood fits – blinding done by replacing “X” with “X+R” in likelihood fits –R is draw from a Gaussian with a width a several times the expected error –Random number sequence is “seeded” with a “blinding string” –The reported statistical error is unaffected –It allows all systematic studies to be done while still blind –Example: the BaBar sin(2  ) result for ICHEP02 was “unblinded” 2 weeks before paper was submitted to hepex/PRL! Blind Analysis

35. 35 October 25 th, 2002Gerhard Raven, NNV 2002 “Golden” and J/  K L “Golden” and J/  K L sin2  = 0.741  0.067 (stat)  0.033 (syst) sin2 = 0.755  0.074 sin2 = 0.723  0.158 hep-ex/0207042, Accepted by PRL BaBar

36. 36 October 25 th, 2002Gerhard Raven, NNV 2002 Compilation of sin2  Measurements World average ~13  significant CP is broken in B decays sin2  = 0.73  0.06 CP asymmetry in B  J/  K S,L is large

37. 37 October 25 th, 2002Gerhard Raven, NNV 2002 Interpretation of the Result One solution for  is consistent with measurements of sides of the unitarity triangle Method as in Höcker et al, hepex/0104062 (see also many other recent global CKM analyses) Error on sin2  is still dominated by statistics and will decrease ~1/ for the forseeable future… The KM mechanism has successfully survived its first precision test!

38. 38 October 25 th, 2002Gerhard Raven, NNV 2002 What Next? These 2 measurements both depend on the B d mixing diagram… Which could be ‘polluted’ by physics beyond the SM! b d s s s d Same  decay as J/  K S : should measure same sin(2  ) only if no ‘new’ contribution to this process KSKS   B0B0 To hunt for and disentangle contributions from ‘new physics’ beyond the SM, need to Measure all angles ‘cleanly’ (no theoretical uncertainties!) 1 down, 2 to go… In redundant ways (they may not be!) Consider many B s modes Improve the measurements of the ‘sides’

39. 39 October 25 th, 2002Gerhard Raven, NNV 2002 The TEVATRON: B s mixing! 0.1 40 x s D D - - ZERO CDF TEVATRON Run II has started (finally) Main Injector added Much improved CDF and D0 detectors B physics reach: B s  D s  (B s mixing) B s  J/  (angle  ) B s  D s K (angle  )  m s = x s /  ~ 27 Current limit (LEP, SLD):  m s > 14.4/ps (95%CL) hint at 17.5/ps?

40. 40 October 25 th, 2002Gerhard Raven, NNV 2002 The Next Generation Precision tests of the consistency of the KM picture requires MANY more B decays, Access to B s decays A dedicated B-physics experiment at the LHC: LHCb

41. 41 October 25 th, 2002Gerhard Raven, NNV 2002 A Dedicated B detector: LHCb @LHC, B mesons are mainly produced forward A detector designed for Measurements of  and  Exploration of the B s sector Very rare B decays See parallel session talks: Bart Hommels Hella Snoek Marko Zupan

42. 42 October 25 th, 2002Gerhard Raven, NNV 2002 LHCb contribution after 1 year of running: From B factories

43. 43 October 25 th, 2002Gerhard Raven, NNV 2002 Summary and Outlook CP is not a symmetry of nature! CP violation is a pure QM effect due to interference We can make an absolute (not just relative!) statement of what is matter, and what is anti-matter After almost 40 years, CP violation has been observed in a system other than kaons: B decays CP violation is not something specific to kaons! CP is very much broken in B decays And we can finally make a quantitative interpretation The KM ‘ansatz’ has survived its first real test… In the coming years, additional measurements in B-decays, at PEP-II, KEK-B, the Tevatron, and ultimately at the LHC will tell us whether there is more to CP than “just KM” Exciting times ahead!

44. 44 October 25 th, 2002Gerhard Raven, NNV 2002 CP Violation Saves The World! People around the world are grateful to particle physicists today as a doomed visit from the Planet-X delegation was called off at the last minute after it was found they were made of anti-matter. “I never thought this CP stuff was useful”, one physicst was overheard saying, ”but they claimed that sin(2  ) = - 0.78, and we are sure we agreed on all the sign conventions so there was only one option left…” ?? X or X?

45. 45 October 25 th, 2002Gerhard Raven, NNV 2002 BACKUP SLIDES

46. 46 October 25 th, 2002Gerhard Raven, NNV 2002 Sources of interferences Higher  resonances, with different strong phases, might spoil the measurement Measurement of sin2  with B->  m ES BABAR (20.7 fb -1 ) prelim  Exploit interferences in the 3  final state o Fit to the time-dependent Dalitz plot o In principle, extract  without ambiguity  Need at least 1,500 events with B/S<2 o     needed, but color-suppressed

47. 47 October 25 th, 2002Gerhard Raven, NNV 2002 Prospects for Measuring  decays to extract – CPV in mixing/decay – clean theoretically, pure tree amplitudes – no penguin pollution – …but time-dependent CP asymmetries at the few % level decays to extract  – interference Original construction by Gronau & Wiler:

48. 48 October 25 th, 2002Gerhard Raven, NNV 2002  m d Measurement in Comparison Precision  m d measurement (3%) with B flav sample is still statistically limited Systematic error under control (2%) –Dominated by uncertainty on  B –Followed by resolution fcn and tagging-vertexing correlations. Theoretical hadronic uncertainties limit extraction of |V td | (PDG 2000)

49. 49 October 25 th, 2002Gerhard Raven, NNV 2002 Measurement of sin2  3. Reconstruct Inclusively the vertex of the “other” B meson (B TAG ) 4. Determine the flavour of B TAG to separate B 0 and B 0 5. compute the proper time difference  t 6. Fit the  t spectra of B 0 and B 0 tagged events (4s)  = 0.56 Tag B  z ~ 110  m Reco B  z ~ 65  m -- zz t  z/c K0K0  KS0KS0 -- ++ 1. Fully reconstruct one B meson in CP eigenstate (B REC ) 2. Reconstruct the decay vertex ++

50. 50 October 25 th, 2002Gerhard Raven, NNV 2002

51. 51 October 25 th, 2002Gerhard Raven, NNV 2002 B 0 B 0 mixing: ARGUS, 1987 Fully reconstructed mixed event and dilepton studies demonstrate mixing Integrated luminosity 1983-87: –103 pb -1

52. 52 October 25 th, 2002Gerhard Raven, NNV 2002

53. 53 October 25 th, 2002Gerhard Raven, NNV 2002 Control Sample: Fully-Reconstructed B flavour events Cabibbo -favored hadronic decays “Open Charm” decays [GeV/c 2 ] Color suppressed decays into charmonium final states Select “self-tagging” decays

54. 54 October 25 th, 2002Gerhard Raven, NNV 2002 B d     +  B s  D s  K   LHCb contributions to CP violation

55. 55 October 25 th, 2002Gerhard Raven, NNV 2002 Sin(2  ) Likelihood Fit Simultaneous unbinned maximum likelihood fit to  t spectra to both flavour and CP samples 35 total free parameters All  t parameters and mistag rates extracted from data Correct estimate of the uncertainty due to statistical error in resolution fcn parameters and mistag rates Fit Parameters sin2  1 Mistag fractions for B 0 and B 0 tags8 Signal resolution function8 Empirical description of background  t17 B lifetime fixed to the PDG value  B = 1.548 ps Mixing Frequency fixed to the PDG value  m d = 0.472 ps -1 Global correlation coefficient for sin2b: 14% tagged flavour sample tagged CP samples Driven by

56. 56 October 25 th, 2002Gerhard Raven, NNV 2002 CP violation in mixing Mixing between B 0 and B 0 can be described can by effective Hamiltonian:  12 describes B 0  f  B 0 via on-shell states Unlike the kaon system, this is rare: the branching ratios of CP states is very small M 12 describes B 0  f  B 0 via off-shell states CP violation can occur in the interference between the on-shell and off- shell amplitudes, and leads to However, for B 0 mesons,  12 is very small: mixing is dominated by  m=2M 12 Little CP sensitivity…  Prob(B 0  B 0 )  Prob(B 0  B 0 )  |q/p|  1 Time evolution of a state produced as a pure B 0 : In the SM:

57. 57 October 25 th, 2002Gerhard Raven, NNV 2002 The BaBar Detector Cerenkov Detector (DIRC) 144 quartz bars 11000 PMs 1.5 T solenoid Electromagnetic Calorimeter 6580 CsI(Tl) crystals Drift Chamber 40 layers Instrumented Flux Return iron / RPCs (  / neutral hadrons) Silicon Vertex Tracker 5 double sided layers e + (3.1 GeV) e - (9 GeV) SVT: 97% efficiency, 15  m z hit resolution SVT+DCH:  (p T )/p T = 0.13 %  p T + 0.45 % DIRC: K-  separation: 4.2  @ 3.0 GeV/c  2.5  @ 4.0 GeV/c EMC:  E /E = 2.3 %  E -1/4  1.9 %

58. 58 October 25 th, 2002Gerhard Raven, NNV 2002 Reconstruct B rec vertex from charged B rec daughters Determine B Tag vertex from charged tracks not belonging to B rec B rec vertex and momentum beam spot and  (4S) momentum High efficiency (97%) Average  z resolution is 180  m ( ~  ct = 260  m) Conversion of  z to  t takes into account the (small) B momentum in  ( 4S) frame  t resolution function measured directly from data Vertex and  t Reconstruction Beam spot Interaction Point B REC Vertex B REC daughters B REC direction B TAG direction TAG Vertex TAG tracks, V 0 s z

59. 59 October 25 th, 2002Gerhard Raven, NNV 2002 Systematic Errors Signal resolution and vertex reconstruction 0.014 Resolution model, outliers, residual misalignment of the Silicon Vertex Detector Factor of 3 smaller compared to last publication  Tagging 0.007  possible differences between B CP and B flavour samples Backgrounds 0.022 (overall) Signal probability, fraction of B + background in the signal region, CP content of background Total 0.05 for J/  K L channel; 0.09 for J/  K *0 Monte Carlo statistics used for validation: 0.014 External parameters (  B and  m): 0.014 Total: 0.04 for total sample Error/SampleKSKS KLKL K *0 Total Statistical0.100.190.560.09 Systematic0.040.060.100.04

60. 60 October 25 th, 2002Gerhard Raven, NNV 2002 Mixing with Dilepton Events Very precise mixing measurement –Select events with 2 high momentum leptons in run 1 Sample contains ~50% B + Fraction of B + is a free parameter –Largest syst. are B 0 lifetime and resolution function param’zn  m d =0.493±0.012±0.009 ps -1 Submitted to PRL: hep-ex/01 12 045 20 fb -1

61. 61 October 25 th, 2002Gerhard Raven, NNV 2002 Search for Direct CP To probe new physics (only use  CP =-1 sample that contains no CP background) | | = 0.92 ± 0.06 (stat) ± 0.02 (syst) No evidence of direct CP violation due to decay amplitude interference (S CP unchanged in Value) Without SM Prejudice : If more than one amplitude present then | | might be different from 1

62. 62 October 25 th, 2002Gerhard Raven, NNV 2002 Neutral and Charged B Meson Lifetimes Simultaneous unbinned maximum likelihood fit to B 0 /B + samples All  t characteristics (both signal and bkgd) determined from data Precision measurements: 2 % statistical error 1.5 % systematic error  t (ps)  0 = 1.546  0.032  0.022 ps   = 1.673  0.032  0.022 ps   /  0 = 1.082  0.026  0.011  t RF parameterization,  t outlier description Common resolution function for B + and B 0 20 fb -1 PRL 87 (2001)  t distribution well described! bkgd signal +bkgd outliers

63. 63 October 25 th, 2002Gerhard Raven, NNV 2002 Check “null” control sample: B Flavour Events Treat B flavour sample as CP No asymmetry seen: “sin2  ” = 0.00 Analysis doesn’t create artificial asymmetries Sample “sin2  ” B o flavour 0.00 ± 0.03 B+B+ -0.02 ± 0.03

64. 64 October 25 th, 2002Gerhard Raven, NNV 2002 Consistency Checks Subsamples Various Vtx reconstructions

65. 65 October 25 th, 2002Gerhard Raven, NNV 2002 A few words about J/  K* 0 (K S  0 ) J/  K* 0 (K S  0 ) angular components: A ||,A 0 : CP = +1 A  : CP = -1 (define R  = |A  | 2 )  CP asymmetry diluted by D  = (1 - 2R  )  R  = (16.0 ± 3.2 ± 1.4) % (B A B AR, to appear in PRL)  Last year, just used R  as an additional dilution  Now, perform full angular analysis instead: O 1D: Treat R  as dilution  2D: Use  tr  4D: Full angular analysis

66. 66 October 25 th, 2002Gerhard Raven, NNV 2002 The time and angle dependent decay rate is given by The angular terms depend on the transversity angles  and amplitudes A x These amplitudes are functions of the strong phases D( , A x ) suffers from the sign ambiguity under Floating cos(2  ) does not change the value of sin(2  ): fit is not very sensitive to cos(2  ) The effect seems large, but it is statistical: J/  K* 0 and cos(2  ) rad ±0.7 (syst)

67. 67 October 25 th, 2002Gerhard Raven, NNV 2002 CP violating observables for B mesons As mentioned, need at least two amplitudes with different phases In B decays, we can consider two different types of amplitudes: –Those responsible for decay –Those responsible for mixing This gives rise to three possible manifestations of CP violation: –Direct CP violation interference between two decay amplitudes –Indirect CP violation interference between two mixing amplitudes –CP violation in the interference between mixed and unmixed decays d b WW d u u d   B0B0 B0B0 B0B0 b bd d u,c,tu,c,t u,c,tu,c,t WW WW

68. 68 October 25 th, 2002Gerhard Raven, NNV 2002 B 0 and B 0 tagged events and Asymmetry Plot The curve looks vertically shifted; is this a problem? NO! –The Likelihood is normalized to the sum of all tagged events –The asymmetry is made from the projection of the Likelihood for B 0 and B 0 tagged –Since the actual number of the 2 flavours is not identical in data there is a vertical shift 471 B 0 and 524 B 0 tagged golden events 7530 B 0 and 7394 B 0 tagged B flavour events The weighted average of the fit B 0 and B 0 tagged events only is right on: 0.747 +/- 0.088 –The fit is not sensitive to the individual normalization One can make the plot ‘pretty’ by renormalizing the Likelihood curve to the actual numbers

69. 69 October 25 th, 2002Gerhard Raven, NNV 2002 “Renormalized”  t spectrum and Asymmetry Likelihood curve projection Likelihood curve normalized to the actual # of observed B 0 and B 0 tags in data

70. 70 October 25 th, 2002Gerhard Raven, NNV 2002 Mistag Rates: The numbers Tagging Category Efficiency  (%) Mistag Fraction w(%) B 0 /B 0 diff.  w(%) Q=  (1-2w) 2 (%) Lepton 11.1  0.2 8.6  0.9 0.6  1.57.6  0.4 Kaon34.7  0.418.1  0.7-0.9  1.114.1  0.6 NT1 7.7  0.222.0  1.5 1.4  2.32.4  0.3 NT214.0  0.337.3  1.3-4.7  1.90.9  0.2 All67.5  0.525.1  0.8  (sin2  )  1/  Q Mistag fraction as determined from simultaneous fit to B flav sample

71. 71 October 25 th, 2002Gerhard Raven, NNV 2002 B d decays and the Unitarity Triangle B d    ,    , … B d  J/  K s, D* + D* -,… B  D* , DK, K  B , ,  l,  l,… B d  B d, B d   B  D ( * ) l,D ( * ) ,…

72. 72 October 25 th, 2002Gerhard Raven, NNV 2002 Resolution Function Parameters S core 1.19  0.07 b core (lepton) 0.01  0.07 b core (Kaon)-0.24  0.04 b core (NT1)-0.20  0.08 b core (NT2)-0.21  0.06 S tail 3.0 (fixed) b tail -2.5  1.7 S outlier 8 ps (fixed) f tail 0.05  0.04 f outlier 0.004  0.002

73. 73 October 25 th, 2002Gerhard Raven, NNV 2002 SLAC B Factory Performance PEP-II delivered : 77.7 fb -1 B A B AR recorded : 73.8 fb -1 (incl. 7.9 fb -1 off peak) PEP-II top luminosity: 4.5 x 10 33 cm -2 s -1 (design 3.0 x 10 33 ) Average BaBar logging efficiency: > 95% Analysis Samples (on peak) –Run1: 20.7 /fb –Run2a: 9.0 /fb –Run2b: 26.7 /fb –Total: 56.4 /fb 30/fb used for mixing 21/fb used for lifetime off-peak 56/fb used for CP

74. 74 October 25 th, 2002Gerhard Raven, NNV 2002 sin2 ,  B and  m Fixed ,  m to PDG 2000:  B = 1.548 ps,  m = 0.472 ps -1 Dependence of sin2  on ,  m: sin2  = 0.75 - 0.31(  m-0.472 ps -1 ) - 0.62(  B -1.548 ps)

75. 75 October 25 th, 2002Gerhard Raven, NNV 2002  B Measurements in BaBar e -|  t|/  Either B rec or B tag can decay first (this analysis) BaBar/ Belle  t resolution e -t/  true  t B production point known eg. from beam spot LEP/SLD/C DF/D0… Need to disentangle resolution function from physics ! measured  t Resolution function Resolution fcn + lifetime Resolution Function + Lifetime  = = 

76. 76 October 25 th, 2002Gerhard Raven, NNV 2002 Comparison of Lifetime Ratio Measurements (99-01)

77. 77 October 25 th, 2002Gerhard Raven, NNV 2002 Mixing Likelihood Fit Fit Parameters  m d 1 Mistag fractions for B 0 and B 0 tags8 Signal resolution function(scale factor,bias,fractions)8+8=16 Empirical description of background  t19 B lifetime fixed to the PDG value  B = 1.548 ps Unbinned maximum likelihood fit to flavour-tagged neutral B sample 44 total free parameters All  t parameters extracted from data

78. 78 October 25 th, 2002Gerhard Raven, NNV 2002 Mixing Likelihood Fit Result  m d =0.516±0.016±0.010 ps -1 PRL CL=44% 29.7 fb -1 At  t=0 only unmixed events produced (EPR!):  can extract mistag rate from data! ~1-2w

79. 79 October 25 th, 2002Gerhard Raven, NNV 2002  t Distribution of Mixed and Unmixed Events perfect flavour tagging & time resolution realistic mis-tagging & finite time resolution w: the fraction of wrongly tagged events  m d : oscillation frequency + -

80. 80 October 25 th, 2002Gerhard Raven, NNV 2002  m d : Cross Checks and Systematic Errors

81. 81 October 25 th, 2002Gerhard Raven, NNV 2002 event-by-event  (  t) from vertex errors Resolution Function (RF) – 2 models: –Sum of 3 Gaussians (mixing + CP analyses) –Lifetime-like bias (lifetime analysis)  t Signal Resolution high flexibility small correlation with  B) zz Signal MC (B 0 )  t  (meas-true)   t tracks from long-lived D’s in tag vertex  asymmetric RF ~0.6 ps

82. 82 October 25 th, 2002Gerhard Raven, NNV 2002 Sin 2  statistical error vs. time ICHEP00 Winter 01 LP01 Winter 02 Still improving faster than statistics: improved resolution, improved efficiency, additional modes, …