Matter-Antimatter Asymmetries and CKM Parameters in B A B AR

1. Matter-Antimatter Asymmetries and CKM Parameters in BABAR Representing the BABAR collaboration Meeting of the Particle Physics Program Prioritization Panel (P5) Oct. 6, 2005 Jeffrey D. Richman University of California, Santa Barbara Version 3.0

2. Outline • Where are we in B physics? • A high-precision, benchmark measurement: sin2b from BJ/yK0 • a: a work in progress • A path to g • |Vcb|, |Vub|, heavy-quark masses, and QCD parameters • Perspective and conclusions • Zoltan Ligeti (theory): discussion of theoretical issues & uncertainties; new physics • Luca Silvestrini (theory): new physics sensitivity • Riccardo Faccini: BABAR measurements related to new physics and rare decays, including sin2b from bs penguin modes

3. Exclusive B decays CLEO (1983) B0B0 oscillations ARGUS (1987) Observation of BK* g CLEO II (1993): Loops! Long B lifetime MAC, Mark II (1983) BXu l n and Vub ARGUS, CLEO (1990) BD* l n and Vcb ARGUS, CLEO, LEP, Isgur, Wise +…(>1989): HQET!

4. The Current Era in B Physics Dramatic advances in our knowledge of the CP-violating phase structure of quark interactions. • First achievement: clear and unmistakable evidence for large (order unity) CP violation in the B meson system. • Amazing stream of surprising results and new methods. Many of these would not have appeared in an extrapolation from the past. • Detector technology: can search for essentially any type of B decay. Trigger on all events; Tracking/Vertexing + CsI + PID Some notable or surprising measurements: s, p wave

5. Probing the CKM quark mixing matrix • Angles of triangle: measure from CP asymmetries in B decay • Sides of triangle: measure rates for buln, B0B0 mixing • Other constraints in r,h plane from CP violation in K decay

6. CP asymmetry from interference between mixing and decay BABAR, PRD 70, 012007 (2004) HFAG 1 decay amplitude, |q/p|=1: 1 decay amp: magnitude & strong phase divide out!

7. sin2b as a precision measurement • The ccs sin2b determination belongs to a special class of definitive • measurements in particle physics. • We can achieve high statistical precision before we are limited by systematic uncertainties. • It is a data-driven measurement, with very little dependence on Monte Carlo or theoretical assumptions. • Theoretical uncertainties <1%, so its interpretation is clear (and powerful) [Ligeti, Silvestrini]

8. (cc) KS (CP odd) modes BABAR sin2b from charmonium (227 M BB) J/ψKL (CP even) mode asymmetry is opposite! PRL 94, 161803 (2005), (hep-ex/0408127) sin2b = 0.722  0.040 (stat)  0.023 (sys) |l| = 0.950 +/- 0.031 (stat) +/- 0.013 (sys) hypothesis test (after raw asymmetry shown above is corrected for the dilution)

9. Foundations of the sin2b measurement Dt < 0 Dt > 0 Background Mistag rates= w(tag) Dt resolution function Mixing asymmetry log scale MES(GeV) Si detector alignment, beam spot Signal: 7,730 events (all modes) Control: 72,878 events [D(*) p,r,a1,J/yK*]

10. Dt=trec-ttag fits to BFlav control sample Mixed events log scale Mixed events linear scale Unmixed events log scale Unmixed events linear scale

11. Mistag (w) measurement from BFlav oscillation data Separately determine D for each tag category. D=(1-2w)<1 due to mistags T=2p/Dm Overall tagging performance: tB=1.6 ps

12. Systematic Errors for sin(2b) Some systematics scale with 1/sqrt(N); other partially do.

13. sin2b uncertainties vs. integrated luminosity Current systematic uncertainty Range of estimated systematic error: 1 ab-1 (109) At 1 ab-1, we can improve sin2b by nearly a factor of 2.

14. a: A work in progress Original idea for measuring a: Works if B0p+p- amplitude is dominated by the butree process. If penguins were negligible, we could extract a directly from the time-dependent CP asymmetry for B0p+p- with no additional information.

15. The penguin problem in B0 (B0 )p+p- • In 1998, CLEO performed a search for charmless two-body B decays. Did not observe B0p+p- , but found large B0K+p- rate [CLEO, PRL 80, 3456 (1998)]. • We cannot ignore penguin amplitude in B0p+p-. (In fact, P-T interference produces direct CP violation in B0K+p- and may also in B0p+p-). We still measure S and C, but S isn’t sin2a!

16. I-spin solution to the penguin problem[Gronau & London, PRL, 65, 3381 (1990)] Use I-spin invariance of hadronic matrix elements to relate Bpp amplitudes. Assume that pions are identical particles. triangle relations Penguins: DI=1/2 only, so no contribution to B+p+p0. amplitudes cancel

17. Constraining Da with I-spin relations B+p+p0 is pure tree (no gluonic penguin)triangles have common side after rescaling one set by exp(2ig): • If penguin amp=0, • triangles coincide. • 4-fold discrete ambiguity (can flip both triangles) • take worst case as “penguin error” 2Da Grossman & Quinn, PRD 58, 017504 (1998)

18. Measurements of B0p0p0, B0p+p-, and B+p+p0 Mode B/10-6 (BABAR) B/10-6 (Belle) p0p0 amp. isn’t small compared to the others. BABAR PRL 94, 181802 (2005) BABAR Red triangles: B+ and B0 decays Purple triangles: B- and B0 decays Difference: CP violating interference between T and P amplitudes.

19. Huge program on B decays to charmless hadronic final states... Bigger than pp BABAR, PRL 94, 131801 (2005) (10-6)

20. The investigation of Brr • BABAR has made intensive effort to study the Brr modes: • Measurement of B+r+r0 , B0 r0r0 limit [PRL 91, 171802 (2003).] • 1st observation of Br+r- and polarization measurement [PRD 69, 031102 (2004)] • First time-dependent CP asymmetry measurement and confirmation of polarization. [PRL 93, 231801 (2005)] • Updated time-dependent CP asymmetry measurement with Run 1-4 data. [hep-ex/0503049 PRL] • Limit on B0r0r0 branching fraction [PRL 94, 131801 (2005)] B/10-6 (Belle) Mode B/10-6 (BABAR) BABAR, PRL 94, 131801 (2005)

21. Measurement of CP asymmetry for Br+r- Is the rr system in a CP eigenstate? If not, get effective dilution of CP asymmetry. BABAR, PRL 95, 041805 (2005) B0 tags 232 M BB̅ B0 tags Angular analysis  almost pure CP=+1 ! Dt(ps) Would like to see S, C with 5x data!

22. a: combining the BABAR measurements B pp B  PRL, 94, 181802 (2005) PRL 95, 041805 (2005) α = 100º  13º 1s [29º;61º] excluded @ 90% C.L. 79º< α <123º @ 90% C.L Bp+p-p0 Dalitz hep-ex/ 0408089 1-C.L. CKM fit excluding a measurements

23. Projections for a measurement in Br+r- Current a measurement from Brr Multiple unresolved solutions within each peak. 1s 90% C.L. Projected a measurements from Brr for 1 ab-1 +1s B(Br0r0) unchanged • The uncertainty on a depends • critically on B(Br0r0). • Scenarios: • use current central value • +1s • - 1s -1s

24. Critical issue for a measurement: Br0r0 I-spin triangle for Brr (current measurements) Projected 1s uncertainties on a Projected 2s uncertainties on a

25. Goals and issues for the a program Bpp Resolve issues with S and C: Belle observes significant direct CP violation in Bpp; BABAR doesn’t. BABAR and Belle values of Bp0p0 are higher than theoretical expectations (and differ by x2) and are not precisely measured. Brp Complicated Dalitz-plot measurement; currently disfavors one of the solution regions allowed from Brr. Will this hold up with more data? Brr Need to observe Br0r0. Value is critical in constraining the I-spin triangle and determinining penguin-induced uncertainty on a. Is I-spin conserved? Does the triangle close? Non-resonant background: studies indicate is small effect but more data would allow more detailed investigation. Improve measurements of S and C…also investigate Ba1+p-

26. A path to g color suppressed How can we get interference? Need D0 f and D0 f.(Compare with B0J/yK0.) Some observations: • Uses charged B decays; method is based on a direct CP asymmetry. Issues: strong phase d, rB=|A(bu)/A(bc)| =0.1-0.2 • Uses tree diagrams: no loops/mixing diagrams, no penguin/new physics issues. Together with |Vub|, gives CKM test with trees only.

27. g(GLW method): B-DCPK-, DCPfCP D0(D0) fCP = CP eigenstate from singly-Cabibbo-suppressed decay. [Gronau & London, PLB 253, 483 (1991), Gronau & Wyler, PLB 265, 172 (1991)]. Large rate, but interference is small: rB << 1

28. CFD g (ADS method): B-  [ D0K+p -; D0K+p -]K- Atwood, Dunietz, & Soni, PRL 78, 3257 (1997), PRD 63, 036005 (2001) DCSD Interference is large: rB, rD comparable, but overall rate is small!

29. g (Dalitz plot): B-  [D0Ksp+p-; D0Ksp+p-]K-, Giri, Grossman, Soffer, & Zupan, PRD 68, 054018 (2003), Bondar (Belle), PRD 70, 072003 (2004) 2 |M-|2 = Relatively large BFs; all charged tracks; only 2-fold g ambiguity. Interference depends on Dalitz region: (CP), (DCSD) • g ambiguity only 2-fold (g ↔ g+p)

30. Fitting the D0KSp+p- Dalitz plot BABAR hep-ex/0504039 Use continuum data D*+D0p+ (91.5 fb-1) CA K*(892) Nevts = 82 K Purity: 97% r(770) • Issue: contribution of • broad, s-wave resonances • Orig. method: 2 BWs • New: K-matrix Anisovich & Saratev Eur. Phys. J A16, 229 (2003) DCS K*(892) c2/dof3824/3022=1.27

31. B+/-D0K+/-:KS p+p- Dalitz plot distributions B+D0K+ B-D0K- B+D0K+ B-D0K- Differences between B+ and B- signifies direct CP violation. Above, D0 is super- position of D0 and D0 Good S/B, but needs more data.

32. g: BABAR and Belle results (Dalitz method) hep-ex/04110439, 0504013 hep-ex/0504039, 0507101 non-K* Importance of rB … The error on g is very sensitive to the value of rB. Other methods (ADS, GLW) help us to measure rB. (degrees) 0.1 0.2

33. rB measurements from ADS channels Most measurements using interference with DCSD D0 decay indicate rB<0.2.

34. Projected uncertainty on g for rB = 0.1 Projected sys error due to D0 Dalitz plot We will be able to improve the error on g by at least a factor of 2.

35. Surprises in semileptonic B decays • Two complementary experimental and theoretical approaches • Exclusive decays: measure (and predict) the rate for specific exclusive modes, usually in restricted region of phase space. • Inclusive decays: use as much of phase space as possible to minimize theoretical input. Extract non-perturbative QCD parameters from data. Goal: |Vij| (exclusive) = |Vij| (inclusive)!

36. |Vcb|and the atomic physics of B mesons Extract |Vcb |, quark masses, and non-perturbative QCD parameters from measured inclusive lepton-energy spectrum and hadron recoil mass spectrum (masses, QCD params given below: “kinetic scheme”). Yields |Vcb | to about 2%. (lattice QCD goal: 3% for BD*ln) chromomagnetic expec value Darwin term spin-orbit kinetic expectation value Benson, Bigi, Mannel & Uraltsev, hep-ph/0410080 BABAR, PRL 93, 011803 (2004) Gambino & Uraltsev, Eur.Phys.J. C34, 181 (2004)

37. Why measuring |Vub | is hard Large bc background; suppression cuts introduce dependence on theory predictions for kinematic distributions. Lepton spectrum endpoint analysis Fully reconstructed B recoil analysis p BABAR Breco e- (hep-ex/0509040) D* e+ n continuum data (off res) Xu l Brecoil BABAR bc subtraction bu

38. |Vub |: inclusive measurements • Key CKM constraint • Use mb and QCD parameters extracted from inclusive BXcln and BXsg spectra. • Many methods with uncertainties around 10%. • Uncertainty from mb has been reduced to 4.5%. • With more data, the |Vub| uncertainties could be pushed down to 5%-6.5%. Eℓ endpoint Eℓvs. q2 mX mXvs. q2 mb, theory expt

39. Measuring |Vub| using Bpln and lattice QCD B0p+ l-nform-factor predictions f+(q2) is relevant form factor for Bpln (l=e, m) Fermilab/MILC HPQCD At fixed q2, lepton momentum spectrum is exactly known in this mode, since only one form factor. HPQCD: hep-lat/0408019 restricted q2 range Fermilab/MILC: hep-lat/0409116

40. Experiment vs. Lattice: DKln form factor

41. Measuring |Vub| using Bpln Projection to 1 ab-1 (data taken to be on BK fit curve from present measurement). BABAR PRD 72, 051102 (2005) In the high q2 region alone, we will measure the branching fraction with an uncertainty of (6-7)% , or (3-3.5)% uncertainty on |Vub |. Lattice theorists expect to reach 6%, so exclusive/inclusive will be similar.

42. Perspective/Conclusions Four major measurement programs related to determining the values of fundamental Standard Model CKM parameters.

43. Perspective/Conclusions • Many measurements are now multidimensional: extract not only the • quantity of interest, but also critical information that is difficult • to get from theory. Examples: • a and g measurements are data-driven: isospin triangle, rB, etc. • b-quark mass and other QCD parameters are now well determined from Vcb studies; this information is used as input for the Vub measurement. • CKM measurements go hand-in-hand with other parts of the BABAR physics program: • Enormous program of hadronic rare B decay studies • Search for departures from CKM pattern using bs decays • Studies of electroweak penguin and leptonic decays • Charm physics, including searches for mixing and CP violation. These are great ideas and measurements: this is a great physics program!

44. Backup slides

45. CP Asymmetries: formulas and definitions no net oscillation no net oscillation net oscillation net oscillation For DG/G <<1,

46. Behavior of time-dependent CP asymmetries Linear scale Non-exponential decay law for a specific final state! Log scale

47. Angles of the unitarity triangle Consider two complex numbers z1 and z2.

48. The CKM matrix and its mysterious pattern (Wolfenstein parametrization) • The SM offers no explanation for this numerical pattern. • But SM framework is highly predictive: • Unitarity triangle: (Col 1)(Col 3)* =0 etc. • Only 4 independent parameters: A, l, r, h • One independent CP-violating phase parameter

49. Comments on B physics history (see slide 3) • Exclusive B decays: Reconstruction of bc modes requires charm meson reconstruction. The product branching fractions for BD(*)X, D(*)K(np) modes are typically of the order 10-4 to 10-5, so large data samples are needed. The 1st exclusive B signal from CLEO was made by summing over several different modes. • Long B lifetime: showed that Vcb was smaller than expected. We began to see the larger pattern of the CKM matrix outside the 2x2 Cabibbo sector: Vcb is proportional to l2 , not l. This measurement also demonstrated the critical importance of high-precision tracking and provided a strong impetus to the development of Si vertex detectors. • BB oscillations: this critical discovery was made by ARGUS. The oscillation period is about 12.6 ps (6.3 ps for maximal probability to oscillate), which is about 8x larger than the mean decay time of 1.6 ps. CP violation in mixing is a very small effect in B decays, since the off-shell intermediate states such as tt completely dominate over on-shell intermediate states. CP violation requires interference between these two paths. This simplifies the BABAR/Belle CP violation measurements, which are based on a different effect: the interference between mixing and decay amplitudes.

50. Comments on B physics history (see slide 3) • Observation of charmless semileptonic B decays by ARGUS and CLEO was a critical discovery. The measured value of Vub/Vcb maps out an annular region in the r-h plane. The consistency between this region and the BB mixing and eK regions provided an early test of the CKM framework. In the Vub measurement, the lepton spectrum endpoint region was used, because backgrounds from bcln decays are suppressed compared with buln, where the lepton can be more energetic. Later measurements use a variety of techniques to increase the phase space region used and to thereby decrease theoretical uncertainties. • The observation of BK*g by CLEO was a major discovery, demonstrating the presence of loop processes at the rate expected in the SM. BABAR/Belle are studying a very large number loop processes in both exclusive and inclusive measurements. These processes provide a powerful probe of physics beyond the SM through virtual effects. • Vcb measurements were given a strong boost by the development of Heavy Quark Effective Theory (HQET). This and subsequent theoretical advances have substantially improved our understanding of the dynamics of B decays.