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Why B physics at pp collider

B physics at the Tevatron S. Donati University and INFN Pisa April 2003 Meeting of the American Physical Society. Why B physics at pp collider. Open wide spectrum of B hadrons B  , B 0 , B s , B c ,  b ,  b bb cross section is 50-100 m b

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Why B physics at pp collider

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  1. B physics at the TevatronS. Donati University and INFN Pisa April 2003 Meeting of the American Physical Society

  2. Why B physics at pp collider Open wide spectrum of B hadrons • B, B0, Bs, Bc, b, b bb cross section is 50-100 mb ~O(105) larger than @(4S)/Z0 BUT: B hadrons are hidden in a 103 larger background (inelastic(pp)  50 mb) • Events more complicated than at (4S) CLEO CLEO CDF Crucial detector components: - Tracking system Excellent pt resolution/Vertexing - Trigger Large bandwidth Strong background reduction - Particle identification

  3. Jan 03 Mar 02 Tevatron pp collider Main Injector (new injection stage for Tevatron) Ability to accelerate and deliver higher intensity of protons More efficient anti-proton production Collision rate: 396 ns crossing time (36x36 bunches)  ~ 2M collisions/sec Center of Mass energy: 1.96 TeV CDF Integrated Luminosity 130 pb-1 (delivered) 100 pb-1 (to tape) B/Charm: ~ 70 pb-1 Today: luminosity ~4.0 x 1031cm-2s-1 4 to 7 pb-1/week delivered Goal: luminosity: ~1032 cm-2s-1 16 pb-1/week delivered In this talk: results with 70 pb-1 for CDF and 40 pb-1 for D0 commiss

  4. CDF Detector in Run II Inherited from Run I: Central Calorimeter (||<1) Solenoid (1.4T) Partially New: Muon system(extended to ||~1.5) Completely New: Tracking System - 3D Silicon Tracker(up to ||~2) - Faster Drift Chamber Time-of-Flight(particle ID) Plug and Forward Calorimeters DAQ & Trigger system(Online Silicon Vertex Tracker: trigger on displaced vertices, first time at hadron collider)

  5. D0 detector in Run II

  6. B Triggers and data samples (New in CDF/Short term upgrade in D0) (Conventional) Displaced trk + lepton (e, ) IP(trk) > 120m Pt(lepton) > 4 GeV Semileptonic modes 2-Track Trig. Pt(trk) > 2 GeV IP(trk) > 100 m Fully hadronic modes Di-Muon (J/) Pt() > 1.5 GeV (CDF) J/ modes down to low Pt(J/)(~ 0 GeV) • - BS mixing • CP asymmetry in 2-body charmless decays • - High statistics lifetime • Sample for tagging • studies, mixing - CP violation - Masses, lifetimes - Quarkonia, rare decays Secondary Vertex B Decay Length Lxy PT(B)  5 GeV Primary Vertex Lxy  450m d = impact parameter

  7. Raw tracks Detector calibration:p scale & B-field correction MASS SCALE: MCDF = MPDG-M(Pt) Use J/ to correct for B field and energy loss: (scale)/scale ~ 0.02% D0 Sanity check with known signals: D0 and  Add B scale correction 1S  Tune missing material 2S Correct for material in GEANT 3S

  8. Mass measurements M(Bs) is already the second best in the world (after CDF RunI) 2.12.9 FIRST CDFII PAPER Ds± - D± mass difference Both D (KK) m = 99.28 ± 0.43 ± 0.27MeV PDG: 99.2 ± 0.5 MeV (CLEO2, E691) Systematics dominated by background modeling See A. Korn’s talk

  9. Background is subtracted Conventional way to B: J/y mm L ~ 40 pb-1 75k J/y  mm CDF triggers on stopped J/y  mm: pt(m)  1.5 GeV/c, pt(J/y )  0 • CDF can measure cross section down to pT = 0 (first at hadron collider) • s(ppgJ/y; pT>0; |h|<0.6) = • 240  1 (stat) 35/28(syst) nb • See Y. Gotra’s Talk

  10. First step: Inclusive B  J/y X Lifetime D0 Run II Preliminary J/y B Estimate B through  D0 Run II Preliminary MC CDF July 2002 (18 pb-1):t=1.5260.0340.035 ps D0 March 2003 (40 pb-1):t=1.5610.0240.074 ps PDG 2002: t= 1.674  0.018

  11. B Lifetimes Heavy Quark Expansion predicts the lifetimes for different B hadron species t(Bc) << t(Xb0) ~ t(Lb) < t(B0) ~ t(Bs) < t(B-) < t(Xb-) < t(Wb) • t(B+)/t(B0) = 1.03-1.07 • t(Bs)/t(B0) = 1.00 + 0.01 • t(Lb)/t(B0) = 0.9-1.0 B+/B0 and Bs/B0 measurements agree with prediction Small discrepancy forLb lifetimes • LEP + CDF Run I

  12. Exclusive B  J/yKLifetime (1) Use exclusively reconstructed BB+gJ/y K+ B0gJ/y K0* (K0* g Kp) Bsg J/yf (fgKK) LbgJ/yL (Lgpp) Simultaneous fitting of MB: Extract signal fraction ct: Extract the lifetime CDF March 2003 (70 pb-1):t(B+)=1.570.070.02 ps D0 March 2003 (40 pb-1):t(B+)=1.76  0.24 ps

  13. Exclusive B  J/yK lifetime (2)(Bs Unique to Tevatron) Important for simultaneous measurement Use control channels: Bu J/ K+and Bd J/ K0* Measurement limited only by statistics Systemat. & statist. errors already @ Run I level = 0.89  0.15 = 1.11  0.09 c, [cm] See K. Anikeev’s Talk

  14. Physics with B0s J/  CDF: largest fully reconstructed sample in the world: 74 11 evts Yield/Lumi = 2 x RunI CP asymmetry measures the weak phase of Vts (angles = 2s ) Expected to be very small:sin(2s ) O(l2)  0.03 Complicated analysis: requires xsand angular analysis to disentangle CP even/odd final states CDF reach : s(sin(2 s )) 0.1 with 2fb–1 (0.03-0.06 with 10fb–1) If asymmetry observed with 2fb–1 signal for NEW Physics We also want to measure the lifetime difference:s = BsH- BsL Current limit (LEP):s / s <0.31 (S.M.:DG/G = 0.05 - 0.20)

  15. Moreabout BgJ/ysignals CDF L0bgJ/yL B0gJ/yK0s CDF~220 events First steps towards sin(2b) Measurement D0 L0bgJ/yL Br.Ratio and Lifetime meas. in progress (see T. Yamashita, R. Madrak’s Talk)

  16. B+/B0 from lepton+displaced track CDF CDF CDF CDF: high statistics semileptonic B samples Excellent calibration samples for B+/B0lifetime, tagging and B0 mixing BglD0X (D0gKp):~10,000 events BglD*+X (D*+gD0p):~1,500 events BglD+X (D+gKpp):~5,000 events Run II yields significantly larger, lower lepton pt threshold possible thanks to i.p trigger

  17. BS from lepton + displaced track Bs Dsl [] l  [[KK] ]lONLY @ Tevatron • HIGH STATISTICS SAMPLE: • Inclusive lifetime:  • Mixing (moderate xs): • good S/N, limited time resolution: back-up sample 385  22 Ds (muon only) Systematics of trigger bias Efficiency vs c ARBITRARY UNITS MC Yield/Lumi ~ Run I x 3 S/N ~ Run I x 2

  18. bfrom lepton+displaced track b cl  [pK] l • Branching Ratio • Measure  • Q2 = m(l) • important for theory • Experimental challenge: • disentangle from decays through excited baryons Time of flight Yield/Lumi = 4 x RunI S/N ~ 2 x Run I dE/dx +

  19. Physics with the hadronic trigger CDF: open access to fully hadronic D and B signals D D D’s from Primary Vertex have d 0 B d(D) D mesons I.P. (d) distribution Reconstructed large (0.5M) D mesons: D K, D0 K, D* D0, Ds  D0 KK, D0 p See K. Stenson’s (Charm Physics review), C. Chen (D x-section), S. Vallecorsa (D Cabibbo supp. decays), M. Campanelli (D orb. excited states) talks for CDF Charm results Direct Charm D0K86.5  0.4 % (stat) D*D087.6  1.1 % (stat) DK89.1  0.4 % (stat) Ds72.4  3.4 % (stat) B fraction  10 - 20 %

  20. Lxy c =  Ingredients for B0s mixing ms/md a Nunmix(t) – Nmix(t) Amix(t) = = Dcos(mst) g b Nunmix(t) + Nmix(t) • Reconstruct the final state(use fully rec. B0s → D-sπ+(3π)) with good S/B (thanks to precise tracking, vertexing, PID) ;  = PT(B) / M(B) 2. Measure proper decay time: Current limit: ms 14.4 ps-1 Error on B momentum, ~ 15% (semileptonic) negligible (~ 0.5%) for fully reconstructed final states 60 fs (SVX II detector) 45 fs (also Layer 00 is used) 3. Identify the flavor of Bsat production: B-flavor tagging algorithms

  21. First steps towards B0s mixingin CDF Bs Ds(*) []   [[KK] ]  Fully reconstructed Bs is consistent with Bd Dcontrol sample Collect more data and understand tagging See S. DaRonco’s Talk

  22. B Flavor Tagging “Identify the flavor of B at production” OST (opposite side tagging): B’s produced in pairs  measure flavor of opposite B JETQ:sign of the weighted average charge of opposite B-Jet SLT:identify the soft lepton from semileptonic decay of opposite B SST (same side tagging): B0 (B0) is likely to be accompanied close by a + () Search for the track with minimum PTREL b d d u u B0 + D2 “tagging effectiveness”  2% Figure of merit: = efficiency ; D = “Dilution” = 1 – 2Pmistag Effective size of sample is reduced byD2

  23. NEW in CDF: “Kaon b-taggers” • Exploit K/ separation of new TOF • Well suited for strange B mesons b s s u u B0s Same Side K: aB0s(B0s) is likely to be accompanied close by aK+(K) from fragmentation K+ Opposite Side K: due to bcs it is more likely that a B meson contains in final state a K than a K+  to identify a B0s look for a K from the decay of the opposite B D0 Run II Preliminary For CDF studies see A. Ratikin and T. Moulik’s Talks

  24. Physics with B0 h+h- 300 eventsin 65 pb-1 of CDF Hadronic Trigger data with very good S/B B0 h+h-is a mixture of Bdpp; BdKp; BsKp; BsKK • Strategy for disentangling channels: • Invariant mass shape (M ~25 MeV) • Kinematical variables • Particle Identification • Oscillation of CP asymmetry ( inv.mass) CDF II simulation • Can soon perform interesting measurements: • Relative B. Ratios: Bdpp/Kp ; BsKK/Kp • Direct CP asymmetries in BdKp (self tagging) • CP asymmetries in Bdpp(with b-tagging) • Later on: CKM angle —sum BdK BsKK Bd BsK 

  25. Disentangling the B0h+h-contributions Use M vs (1-p1/p2)q1 B0d pp B0d K-p+ B0d K+p- B0s K+p- B0s K-p+ B0s KK Expected fraction res. (MC 65 pb-1) B0dKp(0.6): 0.062 (stat) B0 dpp(0.15):  0.056 (stat) B0sKK(0.2):  0.045 (stat) B0 sKp(0.05): 0.036 (stat) ACP(B0dKp): 0.14 (PDG-2002: 0.06) Use K/ separation dE/dx 1.16 See M. Morello’s talk

  26. u W+ p+ b d B0 p u d d b ms/md a Angle  from B0h+h- g b B0 +has two (comparable) decay amplitudes: Penguin Tree W+ d p+ u u,c,t B0 g d u p d direct CP CP from mixing alone ACP(t) =ACPdircos(Dmd t) +ACPmixsin(Dmd t) ACPdir, ACPmixfunctions of,, d,(d ei P / Tdecay amplitude) R. Fleischer(PLB 459 (1999) 306): Assume U-spin symmetry (d  s) Similar relation holds for Bs K+K(Dmdreplaced byDms) The 4 asymmetries can be expressed as function of , and P/T amplitude ratio Parameters can be extracted from fit of meas. of ACP(t) for Bd and BsKK Expected (2fb-1) accuracy: () = ±10(stat) ±3(syst) (SU(3) breaking effects)

  27. Hadronic b c signal b  c  [pK]  Largest fully rec. hadronic channel • Measure mass, lifetime, polarization • Precise Lifetime Discrepancy with theory: Is it valid for baryons? pK Mass [GeV] NO PID YET See Y. Li’s Talk pK Mass [GeV]

  28. Conclusions • The upgraded CDF/D0 detectors are taking new data • Great B physics potential, we have results on: • Masses, lifetimes in the BJ/y K exclusive channels • and production cross sections • New impact parameter trigger (CDF-only): huge/clean • semileptonic/all hadronic B signals (and also Charm): • Large and clean BglDX reconstructed in CDF • (excellent for lifetime, tagging and md meas.) • B0s → D-sπ+: first ingredient towardsms • B0h+h-: important results awaiting on our way to g • (B0sKK, CP in B0dKp) • Lots of Beauty (and Charm) at the Tevatron

  29. Backup Slides

  30. Jan 03 Mar 02 CDF Integrated Luminosity Data used for Today’s results Mar 02 – Jan 03 130 pb-1 (delivered) 100 pb-1 (to tape) B/Charm: ~ 70 pb-1 commissioning

  31. B physics prospects(with 2fb-1) Both competitive and complementary to B -factories • Bs mixing: Bs →Dsπ(Ds3π)(xsup to 60, with xd meas. one side of U.T.) • Angle : B0→ J/ψ Ks(refine Run1 meas. up to (sen2)  0.05) • CP violation, angleγ: B0→ ππ(πK), Bs→ KK(Kπ) • Angle s and s/ s : Bs→ J/ψ(probe for New Physics) • Precise Lifetimes, Masses, BRfor all B-hadrons: Bs, Bc, Λb … (CDF observed: Bc → J/ψ e(). Now hadronic channels Bc → Bs X can be explored) • HF cross sections (beauty and charm) • Stringent tests of SM … or evidence for new physics !!

  32. 1 B 1   » ) + ( sin (2 ) e D N S 2 ms/md a Sin(2) in B0J/y Ks g b N(B0)(t) - N(B0)(t) ACP(t) = =Dsin(2b)sin(Dmd t) N(B0)(t) + N(B0)(t) In Run1 measured: B0  J/ Ks ; J/   sin(2b)=0.79±0.39±0.16 (400 events) sin(2b)=0.91±0.32±0.18 (+60 B0   (2S) Ks) With 2fb-1 can refine this measurement Although: no way to compete with B-Factories ! N(J/ Ks) from scaling Run I data: • x 20 luminosity 8,000 • x 1.25 tracks at L1 trigger 10,000 • x 2 muon acceptance 20,000 • Trigger on J/  e+e+ 10,000 Stat. Error: Expect: s(sin2b)  0.05 Systematic ~ 0.5xStatistical (scales with control sample statistics) Combined eD2: from 6.3% to 9.1%(Kaon b-tag) Same S/B = 1

  33. Tevatron Performance 3.8 x 1031 • Tevatron operations • Startup slow, but progress steady ! • Now:L ~3.5 x 1031 cm-2s-1 • integrating ~ 6. pb-1/week • … still factor 2-3 below planned values • additional improvements (~10-20%) expected from Jan. 3weeks shutdown Initial Luminosity July ‘01 Now • CDF operations • Commissioning: Summer 2001 • Physics data since February 2002 • Running with >90% Silicon integrated • since July 2002 On-tape Luminosity 110 pb -1 • Luminosity (on-tape): • ~20pb-1until June (analyses in this talk) • Additional 90pb-1 July – December • Reach 300- 400 pb-1 by October 2003 July ‘02 Feb ‘02

  34. Quadrant of CDF II Tracker TOF:100ps resolution, 2 sigma K/ separation for tracks below 1.6 GeV/c (significant improvement of Bs flavor tag effectiveness) TIME OF FLIGHT COT: large radius (1.4 m) Drift C. • 96 layers, 100ns drift time • Precise PT above 400 MeV/c • Precise 3D tracking in ||<1 (1/PT) ~ 0.1%GeV –1; (hit)~150m • dE/dx info provides 1 sigma K/ separation above 2 GeV • SVX-II + ISL: 6 (7) layers of double-side silicon (3cm < R < 30cm) • Standalone 3D tracking up to ||= 2 • Very good I.P. resolution: ~30m (~20 m with Layer00) LAYER 00: 1 layer of radiation-hard silicon at very small radius (1.5 cm) (achievable: 45 fs proper time resolution inBs Dsp )

  35. CDF II Trigger System 3 levels: 5 MHz (pp rate) 50 Hz (disk/tape storage rate) almost no dead time (< 10%) • XFT: “EXtremely Fast Tracker” • 2D COT track reconstruction at Level 1 • PT res. DpT/p2T = 2% (GeV-1) • azimuthal angle res. Df = 8 mrad • SVT: “Silicon Vertex Tracker” • precise 2D Silicon+XFT tracking at Level 2 • impact parameter res. d = 35 m • Offline accuracy !! CAL MUON CES COT SVX XFT XCES Matched to L1 ele. and muons XTRP enhanced J/ samples L1 CAL L1 TRACK L1 MUON GLOBAL L1 SVT L2 CAL CDF II can trigger on secondary vertices !! Select large B,D samples !! GLOBAL LEVEL 2 TSI/CLK

  36. COT track ( 2 parameters) 5 SVX coordinates beam spot d Impact Parameter (transverse projection) SVT: Triggering on impact parameters ~150 VME boards • Combines COT tracks (from XFT) with Silicon Hits (via pattern • matching) • Fits track parameters in the transverse plane (d, , PT)with offline res. • All this in ~15ms ! • Allows triggering on displaced impact parameters/vertices • CDF becomes a beauty/charm factory

  37. B triggers: conventional Needspecialized triggers (bb) /(pp)  10-3 CDF Run1, lepton-based triggers: • Di-leptons (, PT 2 GeV/c): B  J/ X, J/   • Single high PT lepton ( 8 GeV/c): B  l  D X Suffer of low BR and not fully rec. final state Nevertheless, many important measurements by CDF 1: B0d mixing, sin(2), B lifetimes, Bc observation, … • Now enhanced, thanks to XFT (precise tracking at L1) : • Reduced (21.5 GeV/c) and more effective PT thresholds • Increased muon and electron coverage • Also J/  ee

  38. XFT performance Efficiency curve: XFT threshold at PT=1.5 GeV/c  = 96.1 ± 0.1 % (L1 trigger) XFT: L1 trigger on tracks better than design resolution pT/p2T = 1.65% (GeV-1)  = 5.1 mrad Offline track XFT track 11 pb-1 53.000 J/  

  39. SVT performance • I.P. resolution as planned • d = 48 m = 35m  33 m intrinsic D0  Kp used as online monitor of the hadronic SVT triggers transverse beam size • Efficiency S/B  1 90% soon 80%

  40. TOF performance • TOF resolution (110ps) within 10% of design value Background reduction in KK: Low PT (< 1.5 GeV/c) track pairs before and after a cut on TOF kaon probability x20 bkg reduction, 80% signal efficiency with TOF PID S/N = 1/2.5 S/N = 1/40

  41. CDF J/y cross section 0<pt<0.25 GeV 5.0<pt<5.5 GeV 10.0<pt<12.0 GeV s(ppgJ/y; pT>0; |h|<0.6) =240  1 (stat) 35/28(syst) nb

  42. D0 K D0 KK D0  5670180 2020110 56320490 K mass KK mass  mass Lots of charm from hadronic triggers: With ~10 pb-1 of “hadronic trigger” data: Relative Br. Fractions of Cabibbo suppressed D0 decays : Already competitive with CLEO2 results (10fb-1 @ (4S)) !!!!! (DKK)/(DK) = 11.17  0.48(stat)  0.98 (syst) % (D )/(DK) = 3.37  0.20(stat)  0.16(syst) % O(107) fully reconstructed decays in 2fb-1 •  Foresee a quite interesting charm physics program: • D cross sections, • CP asymmetries and Mixing in D sector, Rare decays, …

  43. B0s mixing: expectations with 2fb-1 xs = ms(B0s) Bs Ds, Ds  Ds  , K*K,  • Signal: 20K (fp only) - 75K (all) events • with SVT hadronic trigger • BR (Ds ) = 0.3 % ; BR (Ds   ) = 0.8 % • Resolution: • (c)= 45 fs (with Layer00) • eD2 = 11.3% (with TOF) • S/B: 0.5-2 (based on CDF I data) S.M. allowed range: 20. < Xs < 35. 5s sensitivity up to: Xs = 63 (S/B = 2/1) Xs = 53 (S/B = 1/2) Can do a precise measurement … or evidence for new physics !

  44. Projections for xs reach with 2fb-1 Optimistic: S/B =2/1 Conservative: S/B =1/2 Xs = 42-63 Xs = 32-53 MC simulation: accounts also for SVT cuts on proper time acceptance, non-Gaussian tails in proper time resolution function

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