Impact of the PXD on the Vertex Reconstruction of π 0 particles

Transcription

1 Impact of the PXD on the Vertex Reconstruction of π particles Fernando Abudinén 14. May, Why CP-V. Sensitivity to B π π? 2 -Conversions and π e + e 3 Improvement of B Vertex Reco. 4 Summary and Outlook

2 Time-dep. CP-Analysis at B-Factories σ(e + e Hadrons) [nb] Υ(1S) Υ(2S) Υ(3S) Υ(4S) Υ(4S) above BB prod. threshold B-Factory 51 % are B + B 48 % are B B q B,B = 1, 1 continuum background e + e Center-of-Mass Energy [GeV] e Υ(4S) Boost B tag e + B CP l z z 13µm B B at rest in CMS t = z β c π π K β Belle =.425 β Belle II =.284 e + e 1 P Sig ( t, q) = e t /τ B 4τ B [1 + q (A CP cos( m t) + S CP sin( m t))]

3 Time-dependent CP-Analysis B B B B A CP For B ππ: tree and penguin diags. contribute! f f B B S CP f CP i: A CP = S CP = sin(2α) i+f: A CP S CP = 1 A CP sin(2α eff ) b d * V ub + W V ud + W u d u d Isospin I =, 2 2 α eff = α α I α CKM-Triangle β R b d V tb t g * V td d u u d I =

4 3 Active Pi xel Detector Extraction of α angle from B ππ Extr. α through isospin analysis: PhysRevLett A A + = A(B π + π ) 1 2 A + + A = A Ā + + Ā = Ā 1 A α 1 A +- 2 = A - A + A Pure Tree: A + = Ā Isospin analysis requires also S π + π and S π π. S π π needs z 13µm of B π π where π Challenge!

5 4 Active Pi xel Detector Extraction of α angle from B ππ p-value 1 - CL w/out S π π 8 fold ambiguity on α CKM f i t t e r WINTER 12 B ππ (BABAR) B ππ (Belle) B ππ (WA) α (deg) CKM fit 1 - CL Extrapolated to L Belle II = 5ab α ( ) arxiv:hep-ex/7329 with S π π 2 fold ambiguity on α Converted e + e and π e + e req. for z Possible with L Belle II = 5 L Belle and Belle II PXD? α ( )

6 Expected Asymmetry Events / (.22 ps ) t / ps A π π CP =.43 (PDG) S π π CP = 1 A CP sin 2 (α α ).76 5 hep-ex/7339

7 Vertex of -Conversions in B π π y / cm 6 3 e + e Pipe 2 PXD 1 PXD x / cm Υ(4S) B 1 B 2 B 1 generic B 2 π π π (B = 98.82%) π e + e (B = 1.17%) N Belle II = L Belle II B(Υ(4S) B B ) 2 B(B π π ) 5ab 1 1.1nb k events. Accept.: θ [17, 15] ECL: θ [12.4, 155.1]

8 Events with -Conversions % a) If there is an event with -conversions How Many? % b) How many Events have at least one -conversion? Vertex in Events % Beam Pipe 2. % 1st. PXD Layer.6 % 2nd. PXD Layer.5 % Total inside PXD 3.1 % %.8%.1% Number of -Conversions c)... and at least one -conversion or one π e + e decay? π e + e 2. % Total π 5.5 % 7 Requirement: All converted in accept. and not converted in ECL

9 π Kinematics Number of Events/.3 GeV/c p T/ GeV/c 1 5 π Boost θ, e + e θ e+,e Number of Events/ Number of Events/ θ, / Degrees θ e +, e / Degrees

10 π e + e Kinematics 1 Number of Events/.3 GeV/c p/ GeV/c π Boost e + e θ, e + e θ e + e Number of Events/ Number of Events/ θ, e + e / Degrees θ e +, e / Degrees

11 π e + e CMS Kinematics Number of Events/.3 GeV/c p/ GeV/c 1 3 π Boost e + e θ, e + e θ e + e Number of Events/ 1 Number of Events/ θ, e + e / Degrees θ e +, e / Degrees

12 B Vertex Reconstruction Algorithm: Kinematic Vertex Fit Access: RAVE (Reconstruction in a Abstract, Versatile Environment) TNS Vertex Reconstruction with spatial constraint centered at the Beam Spot. τ π.9 as =.1 nm π Vertex ˆ= B Vertex. Q on e ± Tracks: At least one PXD hit. x e x e 6µm BS B z e + 6µm BS B e + z e + e π e + e 11

13 B z-vertex Resolution B π π e + e Events / (.6 cm ) Entries 112 Mean -4.9 µm Std Dev µm Events / (.6 cm ) Entries 556 Mean.2 µm Std Dev 88.5 µm B_Z - Gen. B_Z / cm No PXD Hit required B_Z - Gen. B_Z / cm At least one track (e + or e ) has one PXD Hit

14 B z-vertex Resolution B π π e + e Events / (.6 cm ) Entries 9294 Mean 2.8 µm Std Dev 71.6 µm Events / (.6 cm ) Entries 916 Mean 3.3 µm Std Dev 69.3 µm B_Z - Gen. B_Z / cm No PXD Hit required B_Z - Gen. B_Z / cm At least one track (e + or e ) has one PXD Hit

15 t Resolution Events / (.1 ps ) t = t B CP t B tag B CP π π Entries 1316 Mean.6 ps Std Dev 3.42 ps t - Gen. t / ps No PXD Hit required Events / (.1 ps ) e + e Entries 5861 Mean -.17 ps Std Dev 2.22 ps t - Gen. t / ps At least one track (e + or e ) has one PXD Hit

16 t Resolution t = t B CP t B tag B CP π π e + e Events / (.1 ps ) 4 Entries 9613 Mean -.2 ps 35 Std Dev 1.85 ps Events / (.1 ps ) 4 Entries Mean -.14 ps Std Dev 1.76 ps t - Gen. t / ps t - Gen. t / ps 15 No PXD Hit required At least one track (e + or e ) has one PXD Hit

17 t t t Active Pi xel Detector e +, e e +, e Track Reconstruction / cm σ d.25.2 Gold 2. µm Gold 15. µm Gold 12.5 µm Gold 1. µm Gold 6.6 µm Fit / GeV/c p Gold 2. µm Gold 15. µm Gold 12.5 µm Gold 1. µm Gold 6.6 µm / cm σ z MC p / GeV/c t Gold 2. µm Gold 15. µm Gold 12.5 µm Gold 1. µm Gold 6.6 µm MC p / GeV/c t MC / p Fit p MC p / GeV/c t Gold 2. µm Gold 15. µm Gold 12.5 µm Gold 1. µm Gold 6.6 µm MC p / GeV/c t

18 p t -Distribution of -Daughters e + and e from Number of Events /.1 GeV/c p t =.25 GeV/c p / GeV/c T 17 cm

19 18 Active Pi xel Detector Summary and Outlook Beam Spot constrained kinematic vertex fit reaches higher resolution with PXD Information. Higher t resolution. e ± track fit result to be improved. Check new V Finder tool for e + e.

20 Time of Propagation counter with 2 mm quartz bars MCP-PMT readout K L /µ Detector (outside) RPC Plates and plastic scintillators with SiPM readout Superconducting Magnet homogeneous field of 1.5 T Electromagnetic Calorimeter 8 CsI Crystals, 16 X PMT/APD readout Pixel Vertex Detector 2 layer pixel detector (8MP) technology Silicon Vertex Detector 4 layer double sided strips 2 5 ns shaping time Central Drift Chamber proportional wire drift chamber 15 sense wires in 58 layers Aerogel RICH Proximity focusing RICH with silica aerogel

21 Pixel Vertex Detector Ac or tiv ep ec t i x e l Det active area gaten clearn 76 8 px 25 px m gaten m clearn+1 ( 12.5 mm pixel center) SwitcherB (32 channels gate/clear) DCD-B (analog readout) DHP (digital processing) power 75 μm active area thickness 2 mm / 42 μm rigid frame differential data transmission ( 1.6 Gb/s) ground 2 Background Closest to IP Occupancy ( r 2 ) mounting hole flexible interconnect (polyimide/copper) Inst. Lumi.: LBelle II 4 LBelle conductive layers (Al/Al/Cu) hβibelle II < hβibelle smaller z Pixel Detector needed! Technology most suited Depleted Field Effect Transistor

22 CP-Violation in the SM Why CP-Violation? Matter-Antimatter-Asymm. in the universe larger than in SM. (Sakharov) Why in the B -system? largest CP-V. within the SM. 21 CP-V. in the SM Weak Interaction V CKM d V ud V us V ub d s = V cd V cs V cb s b V td V ts V tb b Wolfenstein-Parameters: λ= sin θ C.2, A, ρ, η λ2 λ Aλ 3 (ρ iη) V CKM = λ λ2 Aλ 2 + O(λ 4 ) Aλ 3 (1 ρ iη)] Aλ 2 1 L Yuk igw µ Jµ cc Jµ cc CP Jµ cc Jµ cc Unitarity: k V ikv jk = V udv ub + V cdv cb + V tdv tb = O(λ 3 ) O(λ 3 ) O(λ 3 )

23 CKM-Triangle η excluded area has CL >.95 sin 2β LHCb sin 2β WA ε K m d & m s m d α ε K CKM f i t t e r La Thuile 215 sol. w/ cos 2β < (excl. at CL >.95) α 22.1 α ρ = ( 1 λ2 2 ) ρ ρ η = V ub ( 1 λ2 2 ) η β