STATE OF HEAVY FLAVOR KAREN GIBSON, UNIVERSITY OF PITTSBURGH

Transcription

1 STATE OF HEAVY FLAVOR KAREN GIBSON, UNIVERSITY OF PITTSBURGH Denver, CO APS April Meeting May 3, 2009

2 2 Flavor Physics Program at Tevatron Has Been Tremendously Successful! Complements excellent programs of BABAR and Belle experiments at the B-factories e + e - colliders produce B s at the Υ(4S) and Υ(5S) Many unique measurements made at Tevatron Observation of B s mixing CP violation in B s J/ψϕ Discovery of b-baryons Several measurements in B 0 and B + systems are approaching sensitivity of BABAR and Belle e.g. lifetimes, direct CPV

3 A Special Time for TeV(atron) 3 Tevatron can contribute uniquely to flavor physics for the next few years Transition between first run of B factories, LHC experiments Consider Tevatron flavor physics program present and future Highlight recent results (from 2008 & 2009) Anticipate results to come Significant statistics can be added to many existing measurements before the end of Run II!

4 Tevatron Performance Has Been Excellent! 4 Delivered > 6 fb -1 of integrated luminosity CDF and D0 experiments have collected >5 fb -1 each Expect ~9 fb -1 delivered integrated luminosity through 2010

5 5 CDF and D0 Detectors Have Different Strengths in Detecting B Hadrons Strong tracking system, ability to trigger on displaced tracks Good mass resolution, high statistics in non-leptonic decays Excellent calorimetry, muon id, reverse direction of B field Large samples of semi-leptonic and forward decays, good direct CPV res.

6 Main Categories of Flavor Physics Results 6 Discussed Today Production Birth of B hadrons Lifetimes Death of B hadrons CP Violation & Rare Decays The curious things in between

7 7 Production B Sandro Botticelli The Birth of Venus c

8 8 Search for New Particles and Measure Production Rates of Known Particles Look for things that we think should be there and also for things that shouldn t Can find some surprises e.g. X, Y, Z charm states Many b-baryons have not been observed until Run II! Observed Σ b ± (2006), Ξ b (2007) and recently Ω b (2008) Measure production rates and crosssections Rel. fragmentation fractions, σ(b + ), σ(b c+ ) BR(B c+ )/σ(b + ) BR(B + )

9 Evidence for New Y(4140) State 9 Find evidence for new state Y(4140) in 2.7 fb -1 of int. lumi. Observed in B + Y(4140)K + Y(4140) J/ψϕ J/ψ µ + µ ϕ K + K Builds on previous discoveries of charm-like states at Belle/BaBar e.g. X(3872), Y(3930) D*D molecule? 4-quark state? N(B + ) ~75 B + J/ψϕK + arxiv: , submitted to PRL

10 Observe 3.8σ Significant Excess 10 Observe 14±5 events Calculate significance to be 3.8σ Near J/ψϕ threshold Similar to Y(3930) J/ψω M = M(µ + µ K + K )-M(µ + µ ) within ±3σ of m(b + ) Assuming S-wave Breit-Wigner m = ±2.9 (stat) ±1.2 (syst) MeV/c 2 Γ = (stat) ± 3.7 (syst) MeV/c 2

11 11 Many b-baryons Have Been Observed Since the Beginning of Run II! Σ (*)± b (2006) Ξ b (2007) Λ b mass [GeV/c 2 ]

12 Observation of Ω b Baryon 12 Announced by D0 on Aug. 29, 2008 Observation made with 1.3 fb -1 of data Builds on previous observation of Ξ b Phys. Rev. Lett. 101, (2008).

13 Observe Significant Ω b Signal 13 Observe 17.8 ± 4.9 (stat) ± 0.8 (syst) events m = ± 0.010(stat) ± (syst) GeV/c 2 Expect GeV/c 2 from theory Calculate significance of 5.4σ f b Ω f ( b Ξ ( b ) Br( Ωb J / ψ Ω ) + 14 = 0.80 ± 0.32( stat) b ) Br( Ξb J / ψ Ξ ) ( syst)

14 Have Observed Most Single b-baryons! 14 Ω b± (2008) Σ (*)± b (2006) Ξ b (2007) Have yet to observe double b-baryon states! Λ b mass [GeV/c 2 ]

15 15 Measurement of Relative B c + Cross Section Updated to 1 fb -1 Measure σ σ ( + ) ( + + B ) c BBc J / ψµ ν ( + ) ( + + B BB J / ψk ) Need to model B +, B c + p T spectrum to calculate relative efficiency between decays

16 Find Good Agreement with Previous 16 B c+ Cross-section Measurement Agrees well with previous results Systematic uncertainty is significantly improved Result pt(b) R B c+ J/ψe + νx (Run II, 360 pb -1 ) >6 GeV/c ±0.045 (st) ±0.066 (sys) (lt) B c+ J/ψµ + νx (Run II, 360 pb -1 ) >4 GeV/c ±0.038 (st) ±0.035 (y) ±0.065 (a)

17 17 Lifetimes B Jacques-Louis David Death of Marat c. 1793

18 Why Measure Lifetimes? 18 Heavy Flavor Averaging Group (HFAG) Test HQE predictions Have previously seen1-2σ discrepancies between lifetime predictions and measurements in B s 0, Λ b 0 Expect τ(b + ) > τ(b 0 ) τ(b s 0 ) > τ(λ b 0 )» τ(b c + ) Because they re there? Fundamental quantity, give complete picture of B s Useful for other measurements (e.g. b-tagging)

19 B s 0 Lifetime Now Agrees with HQE 19 B s 0 D s π + K + ϕ K π + Partially reco. decays double statistics! cτ(b s 0 ) = 455 ± 12 (stat.) ± 7 (syst.) µm Compatible with HQE predictions that cτ(b 0 ) cτ(b s 0 ) (cτ(b 0 ) = ± 2.7, PDG 2008) Data collected with displaced track trigger must correct for trigger bias (use Monte Carlo) www-cdf.fnal.gov/physics/new/bottom/ blessed-bs-lifetime/

20 20 B c + Lifetime Agrees with Theoretical Predictions www-cdf.fnal.gov/physics/new/bottom/ blessed-BC_LT_SemiLeptonic/ CDF: cτ(b c + ) = 142 ± 15 (stat) ± 6 (syst) µm D0: cτ(b c + ) = ± 11 (stat) ± 10 (syst) µm Phys. Rev. Lett. 102, (2009)

21 21 Λ b 0 Lifetime Question Closer to Resolution p K Λ b 0 Λ c + π π + cτ(λ b 0 ) = 420 ± 14 (stat) ± 9 (syst) µm, cτ(λ b 0 ) /cτ(b 0 ) = 0.92± 0.04 PDG 2008 Measure lifetime in displaced track sample www-cdf.fnal.gov/physics/new/bottom/ blessed-lblcpi-ct/

22 22 New Measurements Are in Good Agreement with Predicted Lifetimes New measurements of lifetime are in good agreement with theoretical predictions! Speaker s average World Average

23 23 CP Violation & Rare Decays B Francisco Goya The Third of May

24 CP Violation 24 CP violation is the non-conservation of charge and parity quantum numbers Rate of Rate of

25 Known Amount of CP Violation is Unable to 25 Explain Matter-Antimatter Asymmetry Present sources of CP violation can t account for the amount of matter we observe in the universe! Important to search for new sources of CP violation in places we don t expect Can indicate presence of new particles or forces Maybe with much higher masses than we can observe directly at LHC! matter Where s the anti-matter? Universe antimatter

26 26 There Are Three Types of CP Violation That Can Be Investigated Decay of hadrons direct CPV Only type of CPV for charged mesons Mixing of neutral mesons indirect CPV Semi-leptonic decays of neutral meson Interference between decays with and without mixing B 0 J/ψ K s 0 sin2β Measured precisely by BABAR and Belle B s 0 J/ψϕ sin2β s Use flavor tagging for more powerful measurement of CP phases!

27 Mixing and Decay in B s 0 27 Mixing between particle and anti-particle occurs through the loop processes Oscillations are very fast- ~3 trillion times per second! New particles can contribute to box diagram!

28 Mixing and Decay in B s 0 28 Mixing of B s 0 mesons is governed by Schrodinger eqn. m s = m H m L 2 M 12 [ps -1 ] Γ s = Γ L Γ H 2 Γ 12 cos(ϕ s ) ϕ s = arg( M 12 /Γ 12 ) ~0.004 in SM

29 29 B s0 J/ψϕ Decays Are A Good Place to Look for New Physics Decays of B s0 J/ψϕ gives access to CP violating phase predicted to be nearly zero in Standard Model * J/ψϕ VV ts tb β s = arg ~0.02 * VcsV cb Large phase in b s transition could lead to significant non-zero CP phase New physics could produce large CP phase! G. Hou et al suggest that t quark w/mass ~300 GeV/c 2 1 TeV/c 2 would give β s ~0.5

30 CDF Observes Discrepancy with SM in 30 Flavor-Tagged B s0 J/ψϕ Find 1.8σ (p-value = 7%) discrepancy with SM prediction for β s J/ψϕ = 0.02, Γ s = Expect further improvement in statistical precision shortly! N(B s0 )~3200 N(B s0 )~5200 www-cdf.fnal.gov/physics/new/bottom/ blessed-tagged_bsjpsiphi_update_prelim/

31 31 Similar Discrepancy Observed by D0 in Flavor-Tagged B s0 J/ψϕ D0 result very similar to CDF s! Discrepancy w/sm is 1.7σ, p-value = Trend is identical, ϕ J/ψϕ s 2β s arxiv: v1 D0 finds agreement in strong phase between B s0 J/ψϕ (assuming ϕ s J/ψϕ = 0) and B 0 J/ψ K* 0 Use phases in B 0 J/ψ K* 0 to choose one of two solutions?

32 32 More Significant Discrepancy in Combined B s0 J/ψϕ Result arxiv: v1 New CDF result not included in combination! Expect updates to both CDF and D0 results soon!

33 B(B s0 D ( *) s+ D ( *) s ) Also Gives Access to CP-even Width Difference 33 Measure branching ratio to determine Γ s CP (2.8 fb -1 ) Search for one D s ϕπ, other to D s ϕµν Γ + Γ + Γ H s x L s x CP s s s s f f D D B 2 cos 2 cos ) ( (*) (*) 0 ϕ ϕ B

34 34 Γ CP s /Γ s Measured in B s0 D ( *) s+ D ( *) s Consistent with World Average Measure 0 (*) (*) B ( B D D ) = ± 0.010( stat) ± 0.008( syst) ± 0.007( B) s s s with 3.2σ significance (p-value = ) Assuming x f =0 and Assuming x Γ = Γ CP f =0 and ϕ s = 0 cosϕ s Γ Γ CP s s = 0 (*) (*) 2B( Bs Ds Ds ) 0 (*) (*) 1 B( Bs Ds Ds ) ± 0.021( stat) ± 0.022( syst) Consistent with WA (2007) Γ/Γ = Phys. Rev. Lett. 102, (2009)

35 35 Updated Measurement of B s 0 Semileptonic Asymmetry Measure flavor-specific asymmetry, a s fs, in 5 fb -1 Time-dependent Flavor-tagged Reconstruct B s0 µ + D s X D s ϕπ (K K + )π D s K *0 K a s fs = Γ Γ B B 0 s 0 s ( t) f ( t) f Γ + Γ B B 0 s 0 s ( t) f ( t) f arxiv:

36 36 Measurement Improves Uncertainty by Factor of 2! Extract asymmetry with un-binned maximum likelihood fit Γ Γ B B 0 s 0 s f f Find = = a s fs N N f f A A f f s Γ Γt st s ( 1 a ) e cosh cos( mt) fs 2 Γst cosh cos 2 s Γ st ( 1+ a ) e ( mt) fs = 1.7 ± 9.1 syst ( stat) ( ) 10 Uncertainties improved by factor of 2 over previous direct measurement! Standard model prediction: a s fs = (0.021±0.006) 10 3 s s

37 37 Rare Decays Help Search for Flavor Changing Neutral Currents Search for processes like B 0 µ + µ, B s0 µ + µ D 0 µ + µ Standard Model processes are extremely rare B~ New physics (e.g. SUSY) predicts new sources of FCNC Some processes are forbidden in SM B 0,B s0 e + µ leptoquarks

38 Examples of Rare Decay Processes 38 SM processes New physics processes B 0 + s µ µ B s0 + µ µ D 0 µ + µ D 0 µ + µ

39 B (s)0 µ + µ Branching Ratios 39 Approaching SM Predictions! B s0 µ + 95% CL CDF (2 fb -1 ): B < D0 (5 fb -1 ) expected: B < B 0 µ + 95% CL CDF (2 fb -1 ): B <

40 Other Rare Decays Are Limiting New Physics Parameter Space 40 B s0 e + µ 95% CL CDF (2 fb -1 ): B < B 0 e + µ 95% CL D 0 µ + µ 95% CL CDF (360 pb -1 ): B < CDF (2 fb -1 ): B < Predicted rate ~10-13 m(lq, B s0 ) > 44.6 TeV m(lq, B 0 ) > 55.7 TeV

41 41 Looking to the Future B Neo Rauch The Next Move 2007

42 Many Interesting New and Updated 42 Measurements to Come! Updates to CP violation measurements Expect 2-4x higher yield depending on measurement More flavor-tagged CP violation results Updated lifetimes with higher statistics Updated B J/ψX lifetimes with 2x more data Will give most precise B +, Λ b0 lifetimes to date Observation of new states?

43 43 Valuable Contributions to Study of Bottom and Charm Hadrons Made at Tevatron Exciting time for flavor physics at the Tevatron! Many significant contributions to knowledge of B hadrons has been made Expect many interesting, important updates in the next few years!

44 44 Back-up

45 Y(4140) Selection 45 Optimize S/ (S+B) L xy (B + ) >500 µm Log likelihood ratio of kaon > 0.2 Observe clear sideband subtracted ϕ signal Fit with P-wave relativistic Breit-Wigner Require events to have K + K mass consistent with ϕ m(k + K ) m(ϕ) < 7 MeV/c 2

46 46 Y(4140) Events Are Evenly Distributed in Phase Space See uniform distribution in Dalitz decays All events are within kinematically allowed region determined from MC simulation

47 Investigate Properties of X(3872) 47 First observed by Belle collaboration in 2003 Observed in decay X(3872) J/ψπ + π Nature of particle is still unknown D*D molecule? 4-quark state? Search for mass splitting, measure absolute mass Observation of mass splitting offers evidence of tetraquark No mass splitting makes absolute mass interesting Checks possibility of bound-state D*D www-cdf.fnal.gov/physics/new/bottom/ blessed-x-mass/

48 No Mass Splitting Observed in X(3872) 48 Fit mass with Breit-Wigner convolved with resolution Result consistent with no mass splitting Assign upper limit CL m(x(3872)) < 3.2 (3.6) MeV/c 2 at 90% (95%) C.L.

49 49 Most Precise Measurement of X(3872) Mass m(x(3872)) = (stat) (syst) MeV/c 2 Measured mass is below D*D threshold, although uncertainties are within threshold D*D bound state is still a possibility

50 Selection of X(3872) 50 Use ANN to select events Optimize selection on Monte Carlo (signal) and mass sidebands (background)

51 Mass Splitting of X(3872) 51 Model resolution with Monte Carlo simulation Width scale floats freely in fit

52 Previous Observation of Ξ b 52 In 2007, both CDF and D0 observed the Ξ b and made a precise determination of its mass Ξ b J/ψΞ [µ + µ ][Λ 0 π ], Λ 0 pπ

53 53 Ω Reconstruction Improved with Special Selection Techniques Use boosted decision tree (BDT) to improve identification of Ω signal Veto Ξ Λ 0 π Before BDT After BDT Re-process data with higher IP req. to increase Ξ /Ω acceptance!

54 Cross-Checks of Ω b Signal (1) 54 Check WS events and mass sidebands for spurious excesses None observed!

55 Cross-Checks of Ω b Signal (2) 55 Check lifetime distribution of Ω b candidate events Consistent with B hadron lifetime

56 Cut-based Analysis of Ω b 56 Alternatively, try using simpler cut-based analysis Find 15.7 ± 5.3 (stat) events m = ± GeV/c 2 Signal significance is 3.9σ

57 Ω b Significance Calculation 57 Evaluate significance from likelihood ratio of background only hypothesis (L B ) to signal + background hypothesis (L S+B ) 2 ln L = 2ln L L B S +B

58 58 New Technique Used to Measure B + Lifetime Measured in displaced track sample Novel method for correcting for trigger bias without using Monte Carlo Use acceptance function to correct for trigger bias on event-by-event basis cτ(b + ) = ± 6.8 (stat.) ± 4.5 (syst.) µm, (cτ(b + ) = ± 3.3 µm, PDG 2008) www-cdf.fnal.gov/physics/new/bottom/ blessed-mcfree_blifetime/

59 B s 0 Mass Fit in Lifetime Measurement 59 Perform simultaneous unbinned maximum likelihood fit to mass and lifetime Use partially reconstucted decays to double statistics e.g. B s 0 D s ρ + ( π 0 π + ) ~2200 B s 0 candidates

60 60 Comparison of B s 0 Lifetime with Prev. Results B s0 lifetime is higher than recently measured B s 0 lifetimes in flavor-specific decay modes Expect 50% of Γ L, Γ H in flavor-specific modes

61 61 B c + Lifetime Agrees with Theoretical Predictions B c + µ + µ ν µ + J/ψ Simultaneously fit mass and lifetime cτ(b c + ) = ± 11 (stat) ± 10 (syst) µm arxiv: , submitted to PRL

62 62 B + c Lifetime Agrees with Theoretical Predictions and D0 B c + µ + µ ν J/ψ + B c µ + µ + µ Fit e, µ channels separately, combine L afterwards cτ(b c + ) = 142 ± 15 (stat) ± 6 (syst) µm ν e + J/ψ www-cdf.fnal.gov/physics/new/bottom/ blessed-bc_lt_semileptonic/

63 Measurement of B c + J/ψe + X Lifetime 63 Fit lifetime only, use mass as cross-check Determine all background shapes and normalizations from data if possible, MC otherwise constrain in fit cτ(b c + J/ψe + X ) = (stat) µm c 16

64 Measurement of B c + J/ψµ + X Lifetime 64 Fit lifetime only, use mass as cross-check Determine all background shapes and normalizations from data if possible, MC otherwise constrain in fit cτ(b c + J/ψµ + X ) = (stat) µm c 27

65 Combination of Semilep. B c + Lifetimes 65 Combine -2lnL e, -2lnL µ

66 Unitarity Relations in B 0 /B s 0 66 β s

67 New Physics in B s0 Decays 67 B s0 B s0 oscillations observed by CDF Mixing frequency m s now very well-measured Precisely determines M 12 - in good agreement w/sm pred. Phase of mixing amplitude is still very poorly determined! M 12 = M 12 e iϕ m, where ϕ m = arg( V tb V ts* ) 2 New physics could produce large CP phase!

68 68 Γ/Γ Measured in B s0 D ( *) s+ D ( *) s Consistent with World Average Measure branching ratio to determine Γ (2.8 fb -1 ) Search for one D s ϕπ, other to D s ϕµν Under certain theoretical assumptions, B s0 D ( *) s+ D ( *) s is nearly CP even Find Assuming SM, ϕ s = 0, Γ CP = Γ www-d0.fnal.gov/run2physics/www/results/prelim/b/b53/ Consistent with WA (2007) Γ/Γ=

69 69 New Measurement of Direct CPV in B + J/ψK + (π + ) PRL 100, (2008) SM predicts A CP (B + J/ψK + ) ~ NP might produce asymmetries up to ~0.01 A CP N( B J / ψk ( π )) N( B J / ψk ( π )) ( B J / ψk ( π )) = N( B J / ψk ( π )) + N( B J / ψk ( π )) A CP (B + J/ψK + ) = ± (stat) ± (syst) A CP (B + J/ψπ + ) = 0.09 ± 0.08 (stat) ± 0.03 (syst)