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  1. v2 B physics at Belle (and beyond) Summary: Aurelio Bay LPHE/IPEP • CP violation and B physics, introduction • KEK-B and the BELLE detector • Results from Belle: constraining the UT • Beyond 2007 (LHCb) Colloquium, PSI January 2004

  2. + - e p n provides an absolute definition of + charge - + e p n - N % 0.3  - + + - e N p n e p n + N - + + - N e e p n p n July 1964: J. H. Christenson, J. W. Cronin, V. L. Fitch et R. Turlay small CP violation with K0 mesons CP violation S. Bennet, D. Nygren, H. Saal, J. Steinberg, J. Sunderland (1967): K 0 L { CP MIRROR K 0 L 0 K is its own antiparticle L CP symmetry implies identical rates. Instead... Asymmetry =

  3. K0 K0 CPLear Processes should be identical but CPLear finds that neutral kaon decay time distribution  anti-neutral kaon decay time distribution Other experiments: NA48, KTeV, KLOE f factory in Frascati, ...

  4. Andrej Sakarov 1967 e+e- annihilation from the center of the Galaxy Starting from a perfectly symmetric Universe: 3 rules to induce matter-antimatter asymmetry during evolution Baryogenesis 1) $ processes which violate baryonic number conservation: B(t=0) = 0 B(today)>0 B violation is unavoidable in GUT. 2) Interactions must violate C and CP. C violated in Weak Interactions. CP violation observed in K and B decays . 3) System must be out of thermal equilibrium OK: Universe expands. rate compatible with secondary production !

  5. How to generate CPV Hamiltonian H = H0 + HCPV with HCPV responsible for CP violation. Let's take HCPV = gH + g*H† where g is some coefficient. The second term is required by hermiticity. CPHCPVCP† = CP(gH + g*H†)CP† = gH† + g*H CP is violated, HCPVCPHCPVCP† if gH + g*H† gH† + g*H The conclusion is that CP is violated if g  g* CP violation is associated to the existence of a complex component in the hamiltonian.

  6. CPV and the Standard Model .2 L= LW,Z + LH + LFermions + Linteraction LFermions contains the (Yukawa) mass terms: MU and MD complex matrices, diagonalized by a couple of non-singular matrices, to get the physical mass values:

  7. CPV and the Standard Model .3 After the transformation (idem for D quarks) e.m. and neutral currents unaffected. The charged currents are modified: u W Vus "mixing matrix" V unitary s

  8. u W Vus s CPV and the SM .4 Parameters Vij are used to calculate the transitions quark(i)  quark(j) first introduced by N. Cabibbo for i,j=u, d, s The c introduced in 1970 (GIM), discovered in 1974. VCabibbo= • Cabibbo~ 12° VCabibbo is real. CPV implies that some of the Vijare complex ! In 1972 Kobayashi & Maskawa show that, in order to generate CP violation (i.e. to get a complex phase), V must be (at least) 3x3  prediction of the three quark families of the SM: (u, d), (c, s), (t, b)

  9. phase: change sign under CP CKM matrix l = sin(qCabibbo) ~ 0.22 + O(l4) Wolfestein (1983) parametrized by 4 real numbers (not predicted by the SM). Need to measure them. down strange beauty up 0.97 0.22 0.002 charm 0.22 0.97 0.03 top 0.004 0.03 1 Magnitude ~

  10. CKM matrix From direct measurements, no unitarity imposed: s(|Vij|)/|Vij| ~ down strange beauty up 0.1% 1% 17% charm 7% 15% 5% top 20% ?% 29%

  11. down strange beauty up 0 0 115° charm 0 0 0 top 25° 0 0 down strange beauty up 0 0 -115° charm 0 0 0 top -25° 0 0 CKM matrix .2 + O(l4) Wolfestein (1983) Phase ~

  12. SM UnitarityVji*Vjk=dik VudVub + VcdVcb + VtdVtb = 0 Im a(f2) VtdVtb * * VudVub The Unitary Triangle g(f3) b(f1) * Re VcdVcb CKM Matrix and the Unitary Triangle(s) + O(l4)

  13. SM UnitarityVji*Vjk=dik VudVub + VcdVcb + VtdVtb = 0 Im h a(f2) The Unitary Triangle g(f3) b(f1) Re r 1 CKM Matrix and the Unitary Triangle(s) + O(l4) after normalization by VcdVcb*=Al3 Area h  CPV !

  14. a b quark t quark ~Vub g b ~Vtd decays ~Vcb oscillations CP asymmetries Experimental program: measure sides and angles * CP violated in the SM => the area of triangle 0 * Any inconsistency could be a signal of the existence of phenomena not included in the SM Use B mesons phenomenology

  15. B factories qq qq u,c,t b s,d W u,c,t b d B0 W W B0 u,c,t d b The B mesons family M (B-) ≈ M (B0) ≈ ≈ 5279 MeV/c2 lifetime ≈ 1.5 10-12 s + antiparticles loop decay W u,c b direct decay mixing/oscillation

  16. s s ? ? d d + + B0 b b d d W W d d b b New Physics ...may modify rates and inject new phases in the processes. For instance: Vts s s Vtb* c ??? ??? f W f b b t squark d s s K0 d K0 New FCNC ( MSSM has 43 additional CP violating phases ! )

  17. (Open a parenthesis: masses & mixings In the SM, CPV is related to the mass generation mechanism for the fermions. The fermionic system is far to be understood. Is there any "periodicity" in the mass spectrum? Similar question for the mixing matrices.

  18. ? H (CKM) (NMS) V Lepton-quark mass relations first (?) discussed by A. Buras, J. Ellis, M.K. Gaillard and D.V. Nanopoulos, Nucl. Phys. B135 (1978) 66 Any horizontal symmetry ? CPV, n mix., baryogenesis: hep-ph/0108216v2 * Neutrino mix and CPV in B: hep-ph/0205111v2 Bs-Bs mixing in SO(10) SUSY GUT linked to nm nt mix. hep-ph/0312145 ...close the parenthesis)

  19. 24% Y(4s) 76% continuum 8 GeV electrons 3.5GeV positron  production of (4s) (10.58GeV/c2)  = 0.425 (4s)  B0 B0  B+ B- KEK-B IP: sx77µm sy  2µm sz  4mm s(E*beam) = 2.6 MeV Ldt ~ 180 fb–1 at (4S)+off res(~10%)

  20. KEK-B year 2003: crossing the(psychological) barrier of 1034 cm-2s-1 Luminosity trend in the last 30 years Peak luminosity cm-2 s-1 24 I 20004: 24h integrated lumi record: 730.3 pb-1

  21. Started in 1999 ~300 physicists from ~60 institutes in 14 countries. Has collected ~150 million BB pairs Belle experiment Aerogel Cherenkov n=1.015~1.030 SC solenoid 1.5T 3.5GeV e+ CsI(Tl) 16X0 E/E ~ 1.8% @1GeV TOF counter 8GeV e- Central Drift Chamber He/C2H5 (Pt/Pt)2=(0.0019 Pt)2+(0.0030)2 Particle ID : dE/dx in CDCdE/dx =6.9% TOFTOF = 95ps Aerogel Cerenkov ACC Efficiency = ~90%, Fake rate = ~6% 3.5GeV/c m / KL detection 14/15 layers of RPC+Fe  : efficiency > 90% <2% fake at p > 1GeV/c Si Vertex detector 3 layers  mid 2003 now 4 layers Impact parameter resolution  55m for p=1GeV/c

  22. Micro-vertex detector

  23. event Belle x z 1 mm

  24. dE/dx TOF Barrel ACC cut Endcap ACC p (GeV/c) Particle ID in Belle Particle ID uses information from ACC, TOF, dE/dx( CDC)

  25. a ~Vub ~Vtd g b ~Vcb Analysis and results • Continuum rejection • Kinematics at the Y(4s) • The Unitary triangle: • determination of Vub • " Vcb • " Vtd • " b • " a • " g • No time for other topics

  26. 24% Y(4s) 76% continuum Build Likelihood L for B and qq hypothesis using event shape variables and cos qB BB cut qq Continuum rejection from event topology which is ~spherical for BB, jet like for continuum and angular distributions 0 0.2 0.4 0.6 0.8 1

  27. GeV/c2 0.2 DE 0 -0.2 Mbc 5.2 5.24 5.28 GeV/c2 How to find a B meson?Kinematics variables at the Y(4S) Gather candidates B daughters and calculate its (pB,EB) Boost to c.m. Example: B- D0p- "beam constrained mass"

  28. B0 World Average: |Vcb| (inclusive) (42.0  0.6  0.8) 10-3 |Vcb| (exclusive) (40.2 +2.1) 10-3 -1.8 Determination of Vcb D0p+ Vcb W- q c b D*+ d g(y) known function of y F(y) hadronic form factor plus ~5% error on F(1) (Moriond excl. D*: CLEO: 46.9 10-3 BABAR: 48.2 10-3)

  29. Vub W b u hep-ex/0305037, with neutrino reconstruction |Vub| (10-3) = 3.960.17(stat) 0.44(syst) 0.29(theo) 0.34(bc) 0.26(bu) Determination of Vub bc bu Exemple: use lepton momentum distribution from inclusive semileptonic decays 0 1 2 3 Lepton momentum (in c.m.) GeV/c Less than 10% of the spectrum background free Average(inclusive) Vub=(4.12±0.13±0.60)10-3

  30. Vtd B0 Starting from a pure sample of B0, for instance, a B0component builds up in a time scale of a few ps: t b d B0 B0 W W t d b Determination of Vtd Probability 1 B0 measure oscillation frequency 0 3 6 9 ps

  31. * B0 and B0 oscillate coherently (QMentangled state). When the first decays, the other is known to be of the opposite flavour. * Tag B flavour from semileptonic B0 X-l+n B0 X+l-n region of B0 & B0 coherent evolution t ~ Dz/cbg Dmd with di-lepton events * KEK-B boost  <Δz>  cβγt ~ 200 m e+ n (4s) m- X n Y Dz z z1 z2

  32. Missing mass N GeV2 -12 -8 -4 0 Dmd from di-lepton events .2 Background: B+ X0l+n B- X0l-n Selection strategy of the "soft pion tag" B0 D*-l+n Br3%  D0p- Br70% (Frederic Ronga, PhD thesis, 2003) • Event selection: • - 1st lepton P*> 1.8 GeV • 1 pion of opposite sign P* < 1 GeV • 2nd lepton P*> 1.3 GeV • - cut on Mn2

  33. SS OS -2 -1 0 1 2 -2 -1 0 1 2 Dz (mm) Dz (mm) Dz (mm) 0 1 2 Dmd from di-lepton events .3 Get Dz distributions for "Same Sign" and "Opposite Sign" leptons couples and fit for Dmd... OS SS J/  l+ l- to infer resolution

  34. average F. Ronga HEP-PH/0206171 Dmd and Vtd B decay constant Bag parameter { ~20% error !  |Vtd | ~ (8±2)10-3 From: F. Ronga, PhD Thesis, Lausanne XII 2003

  35. Excluded area has <0.05 CL UT sides The Unitary Triangle inferred from its sides and from K0 data From K0 Dmd & Dms 0 1 Vub/Vcb

  36. c J/y c Vcb b s B0 Ks d c b B0 d } SM: sin2b bfrom B0J/y Ks Golden Channel CKM phase = 0 J/y c Vcb Vtd Vtb d s CKM phase  0 ! B0 Ks Vtb Vtd Interference between the 2 amplitudes gives a "time-dependent CPV"

  37. c J/y c Vcb b s B0 Ks d c b s } } SM: 0 sin2b Any "direct" CP violation ? CKM phase = 0 J/y t Vtb c Vts CKM phase = 0 B0 d Ks No "direct CPV" expected in SM in B J/y Ks, but who knows ?...

  38. Need to "tag" the flavour: B0 or B0. B0 and B0 oscillate coherently (QMentangled state)  use the other side to infer the flavour (4s) J/Y Ks Dz z1 z2 z e fCP n D region of B0 & B0 coherent evolution Time dependent asymmetry measurement ftag t ~ Dz/cbg

  39. b ccsreconstruction b ccs(J/KL excluded) B 0 J/KL 140 fb-1, 152MBB pairs 5417 events are used in the fit. pB GeV/c

  40. A large CP asymmetry has been observed! mainly tag and vtx reconstruction Belle: SCP = 0.733 ± 0.057 ± 0.028 BABAR: SCP = 0.741 ± 0.067 ± 0.033 World average: SCP = 0.736 ± 0.049 ACP~ 0, compatible with no direct CPV SM: SCP = sin(2b) =>b =23.7° (or 66.3°) J/KL J/KLv is OK

  41. SM & KM model is verified ! sin2b(Belle, 140 fb-1) = 0.733±0.057±0.028 sin2b(BaBar, 81 fb-1)= 0.741±0.067±0.033 sin2b(World Av.) =0.736±0.049 b = 23.7°± 2.1° = 66.3°± 2.1°

  42. UT with sin2b The Unitary Triangle fit including sides, K0 data, and sin2b

  43. s s B0 B0 d d d d b sss, a B0f Ks puzzle ? b to s transition is second order (gluonic penguin). Prediction from SM: ~ same value of sin(2b) as in ccs because no additional phase from the loop. s Vts W Vtb* f b t s Ks s ??? ??? f c b unless new physics enters the loop. For instance: squark s

  44. sin2b(ccs) 5.2 5.4 5.28 GeV/c2 B0 fKS B0f Ks .2 6811 signals 106 candidates in the fit purity = 0.640.10 efficiency = 27.3% Beam-Energy Constrained Mass BaBar

  45. Ks u K+ u p+ D0 s s p- Ks b b B+ p+ c c K+ B+ u D0 u p- D0 and D0 decay to same final state  mixed state is produced: gfrom BD0K D0 Ks p+p- See A.Giri, Yu.Grossman, A.Soffer, J.Zupan hep-ph/0303187 a, d, g unknown Dalitz's analysis with variables and

  46. 3 2 1 0.5 1 1.5 2 2.5 3 gfrom BD0K D0 Ks p+p- .2 D0Ksp+p- as a sum of 2 body decays a = 0.33±0.10±0.03±0.03 d = 162° +20-25 ±12°±24° g = 95° +25-20 ±13°±10° Fit Dalitz plot with a, d, g as free parameters 90%CL: 61°< g < 142° very preliminary

  47. Belle: very, very preliminary

  48. d p - u W W d - p t g afromB0pp Consider B0p+p- first: without penguin contributions: App= 0 Spp= sin(2b+2g)= -sin(2a) This is not the case: large "penguin pollution" expected (but intrinsically interesting..!) Isospin analysis needed for the extraction of a. Need to measure alsoB0p0p0, B+p+p0,...

  49. B0p+p- App0 continuum p+p- Kp syst. primarily from background fraction charmless 3-body B decay Submitted to Phys Rev from ~231 p+p- : App= +0.58 0.15 0.07 Spp= -1.00 ± 0.21 ± 0.07 BABAR: App = 0.30 ± 0.25 ± 0.04 Spp = 0.02 ± 0.34 ± 0.05 hep-ex/0401029

  50. B0p+p-.2 Belle BaBar direct CVP