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Accelerator and Detector

Accelerator and Detector. KEK-B accelerator. Two separate rings: 8GeV(e - )/3.5GeV(e + ). Finite crossing angle. Design luminosity = 10 34 cm -2 sec -1. Achieved lum =1.06  10 34 cm -2 sec -1. Belle logged: 158 fb -1. KEKB Collider.

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Accelerator and Detector

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  1. Accelerator and Detector

  2. KEK-B accelerator Two separate rings: 8GeV(e-)/3.5GeV(e+) Finite crossing angle Design luminosity = 1034 cm-2sec-1 Achieved lum =1.06 1034 cm-2sec-1 Belle logged: 158 fb-1 KEKB Collider

  3. Future upgrade planned for 2005 [luminosity:factor of 2 ] For a finite crossing angle  Geometrical luminosity loss  Beam instability Without crab cavities: 22mrad With crab cavities: Complete overlap of beams Crab cavities Head-on collision

  4. Belle Detector Aerogel Cherenkov cnt. n=1.015~1.030 SC solenoid 1.5T 3.5GeV e+ CsI(Tl) TOF counter 8GeV e- Tracking + dE/dx Si vtx. det. 3 lyr. DSSD m / KL detection 14/15 lyr. RPC+Fe

  5. Particle identification • Particle identification: ACC, TOF , dE/dx from CDC PID(K) = = pKdE/dx pKTOF pKACC • Very good in a wide momentum range

  6. Upgrade (fall-2003): New beam-pipe SR mask SR mask No SR mask New beam-pipe is longer , 16cm 24cm

  7. Upgrade (fall-2003): New beam-pipe HER Downstream Double walled Be beampipe HER QCSLE LER mask LER QC2 QCSRP QC1 BC3 HER Upstream Removed for new beam-pipe

  8. Upgrade (fall-2003): New beam-pipe SR mask SR mask No SR mask New beam-pipe is longer , 16cm 24cm

  9. Upgrade (fall-2003): cont… • More synchrotron radiation protection LER HER QC1 QC2 LER mask BC3 Saw tooth shape No SR hits Beam-pipe

  10. Upgrade (fall-2003): New beam-pipe SR mask No SR mask New beam-pipe is longer , 16cm 24cm

  11. Upgrade (fall-2003): SVD2 • Increase the number of layers , 3 layers  4 layers • smaller radius for inner-most layer • Better vertex resolution (  1/distance 1st detection layer)

  12. Upgrade (fall-2003): New Vertex Detector(SVD2)

  13. An event with new Vertex Detector

  14. CP violation and Unitarity of CKM matrix What is ? g

  15. Standard Model lagrangian for q-W interaction Lint(t) =  d3x (LqW(x) + L†qW(x)) LqW(x)= VijUi  ( 1- 5) Dj W Dj (x ) = Ui (x ) = V= (CKM matrix) Experimentally, V has a hierarchical structure. ( = 0.22)

  16. Transformation of Lint under CP exchanges particle (n)  antiparticle ( n ) CP: flips momentum sign ( p  -p ) keeps the spin z-component () the same   under CP, LqW transforms as CP LqW(x) P†C† =  ud Vij (Ui (x’) ( 1- 5) Dj(x’) W(x’))†  * x ’ =( t , -x) If ud can be chosen such that ud Vij = Vij * (1) * * Then, Lint(t) becomes invariant under CP: • CP LqW(x) P†C† =L†qW(x) • CP Lint(t) P†C† = d3x CP (LqW(x) + LqW(x)) P†C† = d3x (LqW(x) + LqW(x) ) = Lint(t)

  17. Condition for CP invariance ud Vij = Vij * * Condition (1) is equivalent to rotating the quark phases to make Vij all real In general, there are 5 phase differences for 6 quarks  5 elements of VCKM can be set to real always + 3 phases can be related to Euler angles There is one phase which cannot be removed CP violation

  18. Wolfenstein parameterization Wolfenstein parameterization

  19. What is the angle  ? Orthogonality of d-colmn and b-column: * * * VudVub + VcdVcb + VtdVtb = 0 ⃔ * * VtdVtb VudVub  ⃔ ⃔   * VcdVcb a * ⃔ = arg  b * -b  = arg CKM fitter: 39°   80° @ 95% C.L

  20. Methods to extract the angle  s u b - K - Vub o - - D u c Vcb b - c B - s o B D - K - - - - u u u u • One needs interference between D0K- and D0K- D0 and D0 decay to common final state Example: K+K-, KS0 etc ( CP eigenstates) KS+- Dalitz analysis K*K (singly Cabibbo suppressed mode) K+- ( doubly Cabibbo suppressed mode) I will discuss

  21. (*)- B -> D K - - CP (Gronau , London and Wyler) PLB 253(1991)483 PLB 265(1991)172

  22. Gronau-London-Wyler method to extract  - B- DCPK- where Dcp  (D0 ± D0 ) - • Amp(B- DCPK-) = Amp(B-  D0K-) + Amp(B-  D0K-) - KS0, KS, KS, KS, KS’ K+K-, +- D0 and D0 CP + modes  2 diagrams CP - modes s u b -  K - Vub o - - D u c Vcb - b B c s * o - =arg(Vub) D - B K - - - - u u u u Color-favored Color-suppressed ~  Vcb ~Vub

  23. GLW method cont… Strong final-state-interaction phase: B-  D0K- relative to B-  D0K- isei _ _ • Amp(B- DCPK-) = |Amp(B-  D0K-)| + |Amp(B-  D0K-)| ei(+) _ • Amp(B+ DCPK+)= |Amp(B+ D0K+)| + |Amp(B- D0K+)| ei(-) — A(B- D0K-) A(B- DCPK-)  — A(B- D0K-) = A(B+ D0K+) - A(B+ DCPK+) A(B+ D0K+)

  24. GLW method cont… _ • Amp(B- DCPK-) = |Amp(B-  D0K-)| + |Amp(B-  D0K-)| ei(+) _ • Amp(B+ DCPK+)= |Amp(B+ D0K+)| + |Amp(B- D0K+)| ei(-) — A(B- D0K-) A(B- DCPK-)   — A(B- D0K-) = A(B+ D0K+) - A(B+ DCPK+)  A(B+ D0K+) Reconstruct the two triangles   Non-vanishing strong phase (  0)  Direct CP violation

  25. GLW method cont… One can measure  even if =0( No strong phase) no direct CPV One needs to measure the sides and reconstruct triangle  — A(B- D0K-) A(B- DCPK-)  — A(B- D0K-) = A(B+ D0K+) - A(B+ DCPK+) A(B+ D0K+)

  26. Problem: Color-suppressed mode B- D0K- B- D0K-  and  K+- K+- — A(B- D0K-)  How to measure ? - Ratio of amplitudes ~ 1  Good or Bad ? Method of Atwood, Dunietz and Soni

  27. Theoretical solution One can instead measure: R1,2 = DCP Dnon-CP R /R = 1 + r2  2r cos()cos() B(B-  D1,2K-) + C.C DCP where R = B (B-  D1,2-) + C.C R1 + R2 = 2( 1 + r2) r = |BKD|/|BKD| 2 In principle one can obtain r Useful inequality: Sin2 < R 1,2 R1 or R2 < 1.0 (assuming small r )

  28. Solution - B (B-  D1,2K-) B(B+  D1,2K+)  2r sin()sin() A1,2 = = R1,2 + B (B-  D1,2K-) B (B+  D1,2K+) 4 measurements : A1,2 and R1,2 But A1R1= - A2R 2 r = |BKD|/|BKD| 3 independent measurements  3 unknowns ( r , , ) Solve !

  29. Variables to identify signal B  f1….. fn Energy and absolute value of momentum is known: EB = Ebeam = 5.29 GeV E  PB = = 0.34 GeV/c • Requires that the candidates satisfy   EB = |PB| =| | Mbc Peaks at: 0.0 GeV 5.279 GeV  Instead of EB and PB , we historically use Energy difference  M ~ 2.5 MeV ~  10 better inv mass Beam constrained mass bc

  30. Hadronic cross sections @(4S) peak energy channel (nb) 1.05 1.39 0.35 0.35 1.30 (4S) uu dd ss cc Hadronic total 4.44 ~ 76% is qq 2 jet-type (“ continuum events”) The continuum is monitored by taking data just below the (4S) resonance (60 MeV) off (4S)  x on (4S)(Belle) KEK-B operates here • Rare decay background is usually dominated by continuum

  31. Suppressing continuum events • Variables to distinguish signal from continuum events • CosB signal ~ sin2 continuum ~ flat B B e+ e- Continuum BB Signal

  32. Suppressing continuum signal  • Fisher discriminant of variables x = (x1…….xn) • F =  .x : constants to be chosen to maximize separation(S)between signal and background , S = func (FS , FB ) • = 0    continuum Xi = Fox-Wolfram moments continuum signal Get values of ’s

  33. Suppressing continuum Most effective way to suppress the continuum events  Combine Fisher discriminant(F) and cosB Likelihood ratio (LR) _ _ L(BB) LR(BB) = _ L(BB) + L(qq) continuum _ _ _ signal L(BB) = L(BB)(F) x L(BB)(cosB) _ { 0 for continuum events _ LR(BB) peak at: 1 for signal(BB) events Performance( B- D0[K-+]- ) : LR > 0.4 keeps 87.5% signal removes 73% continuum LR

  34. Results for calibration mode B- D0K-(-) @78fb-1 /K separation by Aerogel Cherenkov Counter ( with dE/dx, and TOF) Prompt Kaon is reconstructed with pion mass assumption shifts E by -49 MeV Allows simple cuts/fits : B-  D0 K- B-  D0 - 347.5±21 6058±88 B-  D0 - 134.4±14.7 B-D0*-, D0- continuum B-D0*K-, D0K*- D00, D0 D00, D0 R = = 0.077 ± 0.005(stat) ± 0.006(sys)

  35. Results for B- D1K-(-) mode CP-even For B- D0[K+K-]K- B- D0[+-]K-  23 background  100 B- K+K-K- B- K-+- Can be estimated from D0 sideband data  included in systematic error 47.3±8.9 683.4±32.8 15.6±6.4 R = =0.093±0.018±0.008 Double ratio R1 = 1.21 ±0.25 (stat)±0.14 (sys) 22.1±6.1 25±6.5 CP asymmetry A1 = +0.06 ± 0.19 (stat)±0.04(sys)

  36. Results for B- D2K-(-) mode CP-odd For B- D0[KS]K- where +-0 background For B- D0[K*-+]K- where K*-KS- and + +0 KS- invariant mass difference> 75 MeV 52.4±9.0 648.3±31.0 R = =0.108±0.019±0.007 6.3±5.0 Double ratio R2 = 1.41 ±0.27 (stat)±0.145(sys) 29.9±6.5 20.5±5.6 CP asymmetry A2 = - 0.19 ± 0.17 (stat)±0.05(sys) A1,2and R1,2 are useful quantities for determining 

  37. Measuring  using B- DCPK- mode Using the measured value of and R1,2 A1,2 We find: R1 R2 r = |BKD|/|BKD| r2 = = 0.31  0.21 2 Just 1.5 away from physical boundary: r2 =0 otherwise r would be imaginary A lot more statistics needed for this method to be useful This corresponds to r = 0.57 0.19 very unlikely (theory: 0.1 0.2)

  38. Measurement of “r” s u b - K - Vub o - - D u c Vcb b - c B - s o D - B K - - - - u u u u r =

  39. Measurement of “r” using B0 D0K0 mode s c b K- o - D - Vcb Vcb u u o B b o B- c o K D s - - - - u u d d BF(B0D0K0)=(5.0±1.3)  10-5 r =  (CKM factor)(color factor)  r  0.2 0.45 ??  Color factor= ~ ~ 0.4

  40. Measuring  using B- DCPK- mode Assume we measured r = 0.2 , what would be? A1,2 =0 R1,2 = 1.4 1 + r2  2r cos()cos() |A1,2|=0.25 1.2 R2(-1) A1,2 =  2r sin()sin() R1,2 1.0 R1(-1) R1,2 Taken from Gronau 0.8 A1,2 =0 0.6  (degrees) At 1, the angle  <33 or  >   > Excluded by CKM fit

  41. *- Additional modes: B- DCPK mode Same principle as B- -> DCPK- decay: K- to be replaced by K*- First step: Flavor specific modes D0 K-+ , K-+0 , K-+-+ Only KS- is used (K-0 could be included worry: handling background) 169.5±15.4 16 

  42. *- Consistency check: B- D0K mode Yields in KS- mass and helicity bins • Points with error bars  data •  • Hatched histogram  Signal Monte Carlo Fit to E for each bin

  43. *- B- DCPK mode 13.1 ± 4.3 B- D1K*- 4.3 7.2 ± 3.6 2.4 B- D2K*- A1 = -0.02 ± 0.33(stat) ± 0.07(sys) CP asymmetries : A2 = 0.19± 0.50(stat) ± 0.04(sys) Cannot now constrain  -> need more data

  44. Additional modes: Atwood, Dunietz and Soni method K- K- Doubly Cabibbo Suppressed Cabibbo Allowed K+- D0 D0 1  Maximum Interference B- B- Measure B- DK- in two decay modes of D: e.gK+- and KS0 ( their CP conjugates) [B- (K+-)K-] [B+ (K-+)K+] [B- (KS0)K-] [B+ (KS0)K+] Solve for   ,  ,  and r K+- KS0

  45. Additional modes: ADS method @78fb-1 Only ~ 10-12 events, Cabibbo-suppressed D0K down by ~1/15 E E Promising method but requires lots & lots of data

  46. Other related decay modes

  47. B-D0(KS+-)K- Dalitz analysis - Previously: B- DCPK- where DCP =(D0  D0 ) both D0 and D0 decays to CP eigenstates ( K+K-..) - D0K0p+p- DKSp+p- D0K0p+p- Amp(B+ ->DK+) = f(m+2,m-2) + r. ei( + ) f(m-2 , m+2 ) where m+/-2= M2(KS+/-) r = |BKD|/|BKD| f( m+2,m-2) =  ak. ei Ak(m+2,m-2) + b ei -> both 2-body resonances and non-res component

  48. Simple example Suppose allDKS+p- decays are via K*p D0K*+p- D0K*-p+ KS p+ KS p- M(KS p+)2 Dalitz plot interference M(KS p-)2

  49. Reality is more complex ( & better) D0KS p+p- many amplitudes & strong phases(13) lots of interference K*p KSs KSf2 KSr

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