1. Experimental Aspects of CP Violation Daniel Cronin-Hennessy TASI June 2003

2. Daniel Cronin-Hennessy CP NO Research Associate University of Rochester CLEO collaboration at LEPP (Cornell)

3. Short Bio  1995 Joined CDF collaboration at Fermilab top (1.8 TeV pp collider: q q  t t )  During Run 1  Focus was tests of Perturbative QCD (  s ) via analysis of W boson produced in association with jets.  1999 Joined CLEO collaboration at CESR bottom  (10.58 GeV e+e- collider Y(4S)  BB)  During CLEOIII  Improved CKM matrix element extractions with HQET  Future CLEO-c (3 GeV) charm  Lattice QCD, glueballs, and hybrids

4. Goals  How we know what we know  Show experimental techniques  The phenomenology used to interpret data  Accent role of Symmetry  both in theory and in experiment  Connect Observables to CKM formalism  Convey importance CP Violation

5. Authors versus Time Carl Anderson 1933

6. Authors versus Time J H Christenson 1964 J W Cronin V L Fitch R Turlay

7. Authors versus Time CLEO ~ 150 Recent list

8. Authors versus Time CDF ~ 400 1995

9. Authors versus Time BaBar ~ 600

10. Timeline 1933 1957 1964 1974 1977 1982 1987 1989 Anderson Wu Cronin&Fitch Brookhaven Fermilab CESR DORIS CESR Standford e+ P(C) Viol CP Viol J/  cc) Y(bb) Bmeson BMixiing charmless B decay(Vub) 1995 2000 2001 Fermilab CERN/Fermilab KEKB/PEPII TOP Direct CP Violation CP Violation in B 1928 1956 1972 Dirac Lee&Yang KM e+ P Violation CP viol from mixing matrix

11. Background (positron)  Carl Anderson 1933  Wilson Chamber- condensation around ions. Ions generated from passing charged particle.  Device immersed in high B field (15 kG)  14 cm diameter

12. Background (positron)  B field into page  qvXB  the sign of charge  Negative particle moving down or positive particle moving up  6mm Lead plate (dark band) placed in middle of chamber to break up-down symmetry  Ionization loss in lead  radius of curvature of track is smaller in 2 nd half of track. Positive charged track.

13. Background (positron)  Positive track but why not Proton  Energy of proton (upper portion) is.3 MeV. Range of proton is about 5 mm at this energy. The track is 10 times this length (5 cm).  Conclusions after detailed study Q < 2 Qproton M < 20 Melectron Particle (positron) identified with the anti-particle of electron Electron should be renamed negatron (from symmetry considerations) symmetry does not drive all physics

14. Background (positron) The idea that each particle has an anti- particle has empirical basis We can reasonably ask where antimatter has gone if we have basis for its existence. Symmetry of mathematics driving the interpretation of physical reality 5 years earlier Dirac’s wave equation manifested negative energy solutions. These solutions were not discarded as unphysical mathematical artifacts but interpreted as antiparticle partners to the positive solutions

15. Where are the anti-protons? Astro-physicists count photons. 3 degree cosmic background radiation permeates all space. It is the cooled (red shifted ) remnant of the early universe. Astro-physicists measure abundances: hydrogen, helium, etc. (baryon number) We could detect antimatter if it were there ( Signature photons from matter + anti-matter annihilation not detected) Results Current limits on anti-matter < 0.0001*observed matter Observed universe Baryon number to photon number ~ 10-9 For every billion photons there is one baryon Assuming baryon + anti-baryon annihilation accounts for current photons in Universe  1 baryon for every 1 billion baryon-antibaryon pair survived Without this asymmetry we would not be here.

16. Where are the positrons (anti-protons etc) ? Sakharov’s (1967) conditions for generating Anti-matter matter asymmetry Baryon number violation (another story) Must be able to get rid of baryons CP asymmetry Must be imbalance in baryon violation between baryons and anti-baryons Universe must be out of thermal equilibrium So that time reversed process can not restore symmetry.

17. Symmetries (C )  Charge conjugation (C)  C changes particle to anti-particle  Examples  Charge Conjugation on electron = positron  C e - = e + (shorthand)  C p = p  C  + =  -  C =

18. Symmetries (P)  Parity (P) Mirror symmetry  Inverts spatial coordinates  x  -x ; y  -y ; z  -z  Effect on other observables  Velocity (v)  P v = - v ( reverses direction)  Spin (s)  P s = s ( does not change)  Helicity  P Right-handed = Left-handed Right-handed means thumb Of righthand points in direction of motion Left-handed means thumb of left hand Points in direction of motion

19. C and P P P C C Left Anti- Left Right Anti- Right CP  Participates in weak interaction  No electric charge, No color charge  NEVER observed  C and P in weak interactions is violated

20. The  -  puzzle  Pre – 1956  Two particles with similar characteristics (such mass and lifetime) are only different in the decays.     parity +1 (-1*-1*(-1) 0 )     parity –1  Seemed obvious that  if  and  are the same particle they should have the same intrinsic parity  T.D. Lee & C.N. Yang point out no evidence favoring parity conservation in weak decays – must test.

21. A Test of Parity (Wu, 1957)  Align Cobalt 60 nuclear spin  Look for electrons from beta decay  60 Co  60 Ni + e- anti-  Beta decay  n  p + e- anti-  d  u + e- anti-  Electrons emitted opposite to direction of nuclear spin (parity operation would reverse direction of electron but not the the nuclear spin).

22. C and P P P C C Left Anti- Left Right Anti- Right CP  Participates in weak interaction  No electric charge, No color charge  NEVER observed  C and P in weak interactions is violated maximally

23. The Neutral Kaon system  K 0 (d anti-s) K 0 (anti-d s)  Strange particles produced via strangeness conserving process.   S=0 (-1 +1)  Decays weakly (violating strangeness) long lived and large difference in lifetimes between the neutral Ks  Proposal  Assuming CP  K 1 ~ K 0 + K 0 CP K 1 = K 0 + K 0 = K 1 (CP=1)  K 2 ~ K 0 – K 0 CP K 2 = K 0 – K 0 = K 2 (CP=-1)  K 1  2  (CP =1)  K 2  3  (CP = -1)  Without 2  decay open to K 2 expect increased lifetime: Long lived Neutral K (15 meters) Short lived (2.8 cm)

24. CP Violation Observed K2K2 57 Ft to target collimator Decay Volume (He) Spectrometer   Signal K 2  2  Bck K 2  3  Use angle (q) between 2p and beam axis K 1 decay long before detector Regeneration of K 1 in collimator inconsistent with vertex distribution 494-509 MeV cos  484-494 MeV504-514 MeV cos  M K =.498 MeV

25. CP Violation Observed  Christenson, Cronin, Fitch & Turlay 1964  Observed CP violating decay K 2  2  17 meters from production point (> 600 times lifetime of short lived neutral Kaon)  Occurred in about 1 in 500 decays.  Interpretation: Physicals states were not eigenstates of CP but asymmetric mixing of K 0 and anti-particle.  K short ~ K 1 +  K 2  K long ~ K 2 +  K 1  K short ~ (1+  ) K 0 + (1-  ) K 0  K long ~ (1+  ) K 0 – (1-  ) K 0  Asymmetric mixing at level of 0.2%

26. Counting K long decays Part of what particle physicists do is just count the number of times a particular particle decays to a particular final state Example: Given 10000 Klong particles 2108 times I see the Klong decay to  0  0  0 1258 times I see the Klong decay to  +  -  0 1359 times I see the Klong decay to  -  + 1350 times I see the Klong decay to  +  - 1950 times I see the Klong decay to  - e + 1937 times I see the Klong decay to  + e - 38 times I see the Klong decay to other Note that  - e +  and  + e -  are connected by CP CP (  - e + ) =  + e -

27. Counting K long decays Example: Given 10000 Klong particles 1950 times I see the Klong decay to  - e + 1937 times I see the Klong decay to  + e - If CP were an exact symmetry I expect the same number of  - e +  and  + e -  decays.  We observe different numbers 1950 and 1937  = N(K L  e +  -) – N(K L  e -  + ) = 0.0033 N(K L  e +  -) + N(K L  e -   )

28. CP Violation in Neutral Kaon a = amp(K 0  f) a = amp(K 0  f)  = (a-a) / (a+a)  = amp(K L  f )/amp(K S  f) K short ~ (1+  ) K 0 + (1-  ) K 0 K long ~ (1+  ) K 0 – (1-  ) K 0  = (1+  ) a - (1-  )a = (a-a) +  (a+a) =  +  (1+  ) a + (1-  )a  (a+a) + (a-a) 1+   =  +  (mixing) + (direct CP violation – Process dependent)  |  +- | != |  00 |

29. Observable for Direct CP Violation  +- /  00 = amp(K L   +  - )/amp(K S   +  - ) =  +  ’ amp(K L   0  0 )/amp(K S   0  0 )  – 2  ’ Actual measurement:  (K L   +  - )/  (K S   +  - ) ~ 1 + 6 Re(  ’/  )  (K L   0  0 )/  (K S   0  0 )  ’ small compared to .  already small  difficult measurement!

30. K mixing (quark mixing) K0  K0 (Standard Model) K0 s d s d u,c,t W W

31. quark mixing  CKM matrix relates quark mass eigenstates to weak eigenstates  Fundamental Standard Model parameters – must be measured.  Measurement of these electro-weak parameters complicated by QCD (we observe hadrons not quarks)  The formalism that provides a viable framework for extracting CKM elements is Heavy Quark Effective Theory HQET.

32. Parameterized by 3 rotation angles(  ij ) and a phase (  ) S ij =sin  ij CP Violation:  3 generations required for non-Real matrix  Quark mass not degenerate (u,c,t) (d,s,b)   not 0 or 

33. rewrite in terms of the Wolfenstein parameters A  Taking advantage of small value of 2 ~order 4

34. Unitarity Triangle Unitarity Algebra 0,0  1,0 a gb CP

35. Implications of CPV via CKM matrix  At least 3 generations of quarks  Charm quark not known at time of proposal  2 generations can not provide required phase  Same mechanism that describes CPV in Kaon system predicts (possibly larger) CPV in B meson system.  Direct CPV predicted  In contrast to other competing mechanisms such as superweak (  S=2, K 0  K 0 ).

36. Keeping Score (CKM constraints)   

37. Observed particles:

38. hidden bottom  1977, Fermilab  400 GeV protons on nuclear targets  Examined  pair mass  Broad peak observed (1.2 GeV) at 9.5 GeV  Eventually interpreted as 2 peaks  Had observed the Y and Y’.  Bound states of bb quarks.  PRL 39 p252 ‘77

39. The Y system 1980 CESR online. e+ e- collisions in the 10 GeV energy range Resonance structures very similar to the cc (J/  ) observations just a few years earlier.

40. The Y as a B laboratory  e + e -   (4S)  BB (  ~ 1.0 nb) e + e -  qq (  ~ 3.0 nb)  Broad (14 MeV >> narrow Y,Y’,Y’’)  Lepton production  Spherical topology  Just above 2 times B meson mass (5.279 GeV).  B’s nearly at rest

41. The Y as a B laboratory R2 (shape) qq BB

42. B mixing B0  B0 (Standard Model) B0 b d b d u,c,t W W

43. B Mixing B D V cb B 0  D + e - B 0  D - e + BB  BB or BB Signature: Same sign leptons e + e + or e - e - 1987 (ARGUS/DESY)

44. Observation of top  1995 D0 and CDF at FERMILAB  1.8 GeV pp collisions  Ignoring sea quarks and gluons: (uud) + (uud)  u u  t t (production)  t  b W (V tb ) (decay no bound states)

45. Observation of top Top decays fast (due to large mass). No time for bound state formation. t t signals (t  b W) b l + (dilepton) b j j (lepton + jets) b l - b l - b j j (6 jets) b j j Background W + jet production

46. Observation of top Lepton: electron - (well measured in tracking and electromagnetic calorimeter) muon - tracking chambers behind shielding Neutrino: Large (20-30 GeV) missing transverse energy. W boson: coincidence of above with consistent transverse mass. Jets: clusters of energy in hadronic calorimeter B-jets: algorithm identifying displaced vertex from long lived b quark (and/or) soft lepton in jet from semileptonic decay of b quark.

48. W and Jets

49. Top mass W+4jet sample With b-tagged jets Reconstruct top mass (7%). Mass top ~ 175 GeV Currently best known quark mass (few%).

50. Keeping Score (CKM constraints) B0 b db d t t  mdmd

51. Part II  Extractrion of a CKM matrix elements  Observation of CPV in B system  Observation of Direct CPV  How does the standard model do?

52. B Decays Hadronic Semileptonic Radiative B  X H B  X H l B  X H  B  D  (K  ) Exclusive Inclusive Exclusive Inclusive Experimentally B  D l B  X c l B  K*  B  X s  “Easy” B   l B  X u l Heavy Quark Exp Heavy Quark Exp Theoretically Factorization clean

53. c u d b  c d u b W Still need QCD corrections Perturbative Non-Perturbative Hard gluon (Short distance) Soft gluon (Long distance)  s , 1 & 2 B  D e W e ]D]D c B[B[ b Just right? W bc u d ]] ]D]DB[B[ B  D  Very difficult B Decay

54. Heavy Quark Limit B meson ~ a heavy quark + “light degrees of freedom” b ~ 1/m b (m b ~ 5GeV) Typical energy exchanges ~  QCD (.1 GeV) l ~  /  QCD l >> Q  point charge (can not resolve mass) flavor blind Chromo-magnetic moment g/(2 m Q )  spin blind Heavy quark symmetry will provide relations between different heavy flavor mesons (B  D) and mesons with different spin orientations (B  B*, D  D*)  QCD is in non-perturbative regeme (no  s expansion for bound state effects). Heavy Quark Effective Theory systematically provides symmetry breaking corrections in expansion (  QCD /m Q )

55.  HQET+OPE allows any inclusive observable to be written as a double expansion in powers of a s and 1/M B : O(1/M)  energy of light degrees of freedom O(1/M 2 ) 1 -momentum squared of b quark 2 hyperfine splitting (known from B/B * and D/D * DM) O(1/M 3 )  1,  2,  1,  2,  3,  4 ~(.5 GeV) 3 from dimensional considerations  G sl = |V cb | 2 ( A(a s,,b o a s 2 )+B(a s )  /M B + C 1 /M B 2 +… )  , 1 combined with the G sl measurements  better |V cb | 2

56. b  s   Moments u, c, t

57. b  s   Moments u, c, t Xs

58. b  s   Moments radiative tail u, c, t

59. Back to CMK Elements   sl (B Meson Semileptonic Decay Width) Calculated from B meson branching fraction and lifetime measurements (CLEO, CDF, BaBar, Belle …) It is the first approximation to the b quarks decay width Free quark decay width b quark motion – increased b lifetime P fermi  M hyperfine splitting

60. Strategy  Bound state corrections needed.  Extract , 1, 2 from independent observables   (e.g. average photon energy B  Xs  )  1 (e.g. width of photon energy)  2 (e.g. D and D* mass difference)  Once determined can be used in extraction of CKM elements (e.g. V ub and V cb )  Over constrain in order to check size of higher order terms

61. Photon Energy Moments  Always require high energy photon 2.0 < E  < 2.7 GeV |cos  | < 0.7  Naïve strategy: Measure E  spectrum for ON and OFF resonance and subtract  But, must suppress huge continuum background! [veto is not enough]   0   and     Three attacks:  Shape analysis  Pseudoreconstruction  Leptons

62. Photon Energy Moments

66. HQET Predictions for moments of (inclusive) Hadronic Mass, Photon Energy & Lepton Energy 6 constraints for 2 parameters BXs BXs  B  X c l

67. Consistency Among Observables   and  ellipse extracted from 1 st moment of B  X s  photon energy spectrum and 1 st moment of hadronic mass 2 distribution(B  X c ). We use the HQET equations in MS scheme at order 1/M B 3 and  s 2  o.  MS Expressions: A. Falk, M. Luke, M. Savage, Z. Ligeti, A. Manohar, M. Wise, C. Bauer  The red and black curves are derived from the new CLEO results for B  X lepton energy moments.  MS Expressions: M.Gremm, A. Kapustin, Z. Ligeti and M. Wise, I. Stewart (moments) and I. Bigi, N.Uraltsev, A. Vainshtein(width)  Gray band represents total uncertainty for the 2 nd moment of photon energy spectrum. CLEO Preliminary

68. V cb In MS scheme, at order 1/M B 3 and  s 2  o  = 0.35 + 0.07 + 0.10 GeV 1 = -.236 + 0.071 + 0.078 GeV 2 |V cb |=(4.04 + 0.09 + 0.05 + 0.08) 10 -2  sl , 1 Theory

69. MomentCLEODELPHI(prelim) B A B AR(prelim) 0.251±0.023±0.062 (E l >1.5GeV)0.534±0.041±0.074 Versus E L ) 2 >.576±0.048±0.163 (E l > 1.5GeV)1.23±0.16±0.15 ) 3 > 2.97±0.67±0.48 <E y  2.346         0.0226  <E  1.7810+0.0007+0.0009 (E l > 1.5 GeV) 1.383       0.192       0.029  R0R0 0.6187+0.0014 +0.0016 (E l > 1.5 GeV) Global Analysis: hep-ph/0210027 Bauer,Ligeti,Luke & Manohar

70. |V ub | from Lepton Endpoint (using b  s  )  |V ub | from b  u  We measure the endpoint yield Large extrapolation to obtain |V ub | High E cut leads to theoretical difficulties (we probe the part of spectrum most influenced by fermi momentum)  GOAL: Use b  s   to understand Fermi momentum and apply to b  u  for improved measurement of |V ub | Kagan-Neubert DeFazio-Neubert

71. Convolute with light cone shape function. b g s g (parton level) B g X s g (hadron level) B g lightquark shape function, SAME (to lowest order in L QCD /m b ) for b g s g a B g X s g and b g u ln a B g X u ln. b g u l n (parton level ) B g X u l n (hadron level) Fraction of b ® uln spectrum above 2.2 is 0.13 ± 0.03

72.  Method for partial inclusion of subleading corrections: Neubert Published With subleading corrections  Subleading corrections large C. Bauer, M. Luke, T. Mannel A. Leibovich, Z. Ligeti, M. Wise |V ub | from Lepton Endpoint (using b  s  ) |V ub | = (4.08 + 0.34 + 0.44 + 0.16 + 0.24)10-3 The 1 st two errors are from experiment and 2 nd from theory PRL 88 231803 ‘02 CLEO

73. |Vub| measurements

74. Keeping Score (CKM constraints)  |V ub | mdmd

75. CP Violation Measurement in B System  Approximately 4 decades after observation of CPV in Kaon System  Three quark generation model well established  constraints from B mixing and CKM element magnitudes nicely consistent  K meson and B meson measurements consistent  NO CP violation yet observed in B meson system!  By 1999 CLEO experiment has accumulated luminosity larger than all other collider experiments combined. Ten Million BB pairs.  Still no hope of measuring CP violation as predicted by SM. SM predicts direct CPV and CPV in mixing small. Best first measurement is interference between decays to CP eigenstates with and without mixing. = B0 f f Time dependent asymmetry

76. CP Violation Measurement in B System PEPII Electron at 9 GeV Positrons at 3.1 GeV KEKB Electrons 8 GeV Positrons 3 GeV 4 fb-1/week  10 Million BB pairs in 3 weeks  Recall B mesons produced via symmetric e+e- collisions yields B mesons nearly at rest (Y(4S) ~ 2 M B )  Require fast B mesons (displaced vertex) to extract time of decay.  Hadronic collider produce boosted B meson but statistics low.  Require “simple” design change for e+e-  asymmetric collisions.  Enter BaBar and Belle

77. PEPII

78. CP Violation Measurement in B System  Symmetric e+e- collisions at Y(4S)   is ~.05 (  z ~.025 mm)  With BaBar parameters   is ~.5 (  z ~.25 mm)  Resolution ~.15 mm

79. CP Violation Measurement in B System  CP Final state (example):  B  J/  K short (BR = 0.05%)  J/   l + l - (e + e -,  +  - ) (BR 11%)  K short   +  -,  0  0 (BR ~100%)  Second “Tagging” B  Provides second vertex (  z)  Provides flavor tag (65% eff in tagging)  High momentum leptons  B 0 (B 0 )  l + (l - )  Kaon charge (K +, K - )  Soft pion (D + *  D 0  + )  88 Million BB pairs  740 B 0 tags and 766 B 0 tags

80. CP Violation Measurement in B System M ES  M ES : Beam Energy substituted mass  sqrt(E beam 2 -p B 2 )  Consistent with known M B  DE: E beam -E B  B candidate energy consistent with expected B meson energy   All in CM frame EE

81. CP Violation Measurement in B System Observable:  z =  c  t A is amplitude for decay: Even with |q/p| and |A/A| ~ 1 CP Violation possible via interference with and without mixing  Im( )=0

82. f =J/  K short b Vcb c c  sK0K0 Vcs* B0B0 B0B0 Vtb Vtd K0K0 K0K0 Vsc Vcd

83. Connection to  plane 0,0  1,0  ((1-  ) 2 +  2 ) 1/2 (1-  ) 

84. Results BaBar and Belle average Sin(2  )=0.734 + 0.055

85. Keeping Score (CKM constraints) BaBar and Belle average Sin(2  )=0.734 + 0.055  Sin(2  )  |V ub | mdmd CP Violation observed. Constraints consistent with previous measurements

86.  Constraints Including Uncertainties

87. Bottom plot shows constraints With ~few% theoretical uncertainties  required to see “beyond” standard model.

88. Direct CP Violation No (unambiguous) measurement of direct CP violation from B mesons Direct CP Violation has been observed in Kaon system.

89. Direct CP Violation (Kaon)  Re(  ’/  )  Requires very accurate measurements of 4 processes K long   +  - K long   0  0 K short   +  - K short   0  0

90. Observable for Direct CP Violation  +- /  00 = amp(K L   +  - )/amp(K S   +  - ) =  +  ’ amp(K L   0  0 )/amp(K S   0  0 )  – 2  ’ Actual measurement:  (K L   +  - )/  (K S   +  - ) ~ 1 + 6 Re(  ’/  )  (K L   0  0 )/  (K S   0  0 )  ’ small compared to .  already small  difficult measurement!

91. Direct CP Violation NA31  NA48 CERN E731  E832 FermiLab

92. KTeV Vacuum beam = K long Regenerator beam = K long +  K short CsI Cal Resolution = 0.7% (15GeV) Position Resolution = 1 mm (can identify parent beam) K long   0  0 (2.5 M events) Systematics Acceptance difference for K long & K short Must be well modelled.

93. Accounting for K long component in Regenerator beam

94. Re(  ’/  ) Results Direct CP violation observed Superweak Theory fails SM Model predictions consistent but has large uncertainties

95. Re(  ’/  ) Results

96. Summary  Standard Model performance  Excellent  3 quark generations well established  CP Violation in B mesons observed  Direct CP violation in Kaons observed  CKM constraints in quantitative agreement no known significant deviations  The math works but do we understand the source of CP violation?  Understanding of Higgs sector and mass generation may help  If the Standard Model continues in its success how do we explain the quantity of observed matter?