Impact of Charm Physics on CKM. David Asner Carleton University

Transcription

1 Impact of Charm Physics on CKM David Asner Carleton University

2 Outline 1) Review Benefits of Threshold Running 2) Discuss Two Roles of Charm Physics Precision Decay Rates, Spectra Leptonic, Semileptonic, Hadronic Decays Standard Model suppressed processes D Mixing, CPV and Rare Decays 3) Review results from CLEO-c, B-factories Emphasis on CKM relevant measurements 4) Consider future prospects 2

3 Dsig Charm at Threshold e + e + e - ψ(3770) DD e! D tag Pure DD, no additional particles (E D = E beam ) σ(dd) = 6.4 nb (Y(4S)->BB ~ 1 nb) Low multiplicity ~ 5-6 charged particles/event high tagging efficiency:~22% of D s Compared to ~0.1% of B s at Y(4S)! + ψ(3770) is to charm what ϒ(4S) is to beauty! " K + A little luminosity goes a long way: # events in 100 pb charm factory with 2D s reconstructed ~ # events in 500 fb ϒ(4S) with 2B s reconstructed! "! +! (3770) $ D Increased statistics is NOT an advantage of threshold running. Cross section is 3x D $ higher than 10 GeV but luminosity is more than 100x lower K " + + # + + D # 3 K! CLEO-c DATA ", D $ K " " # + # #

4 Two Roles of Charm Physics 1) Precision CKM physics - desire % level Leptonic Decays Decay Constants, f D, f Ds, f D /f Ds Enables precision V td, V ts Semileptonic Decays Measure V cd, V cs Form Factor analysis enables precision V ub Inclusive spectra important for V cb Hadronic Decays Normalizes scale of B physics Important for V cb 2) Standard Model suppressed processes D mixing CP Violation Rare Decays Benefit from low bkgd at threshold Threshold Data Essential Benefits from statistics at 10 GeV Quantum correlated threshold data important 4

5 Exploiting Quantum Correlation For CKM physics Measure relative strong phase between D 0 K-π+ and D 0 K-π+ Impacts charm mixing at B-factories/LHCb Charm hadronic BF at Threshold Needed for γ/φ 3 measurement with ADS method CP asymmetry in B DK, D Kπ etc. Reduce systematic error on γ /φ 3 CP tagged Dalitz plots Additionally Time integrated sensitivity to D mixing Unique sensitivity to CP violation 5

6 Precision CKM 6

7 Precision CKM:Why Do We Measure ρ,η?? We don t really care what ρ,η are we care if results from different measurements of them are the same! -- Is the theory internally consistent? -- Or is there a hint of new physics For several measurements theoretical precision is the limiting factor: Charm physics can help! 7

8 ! Precision Quark Flavor Physics The discovery potential of B physics At BABAR/Belle/CDF/D0/ LHC-b is limited by systematic errors from QCD: l ν B π! B d B d 8

9 ! Precision Quark Flavor Physics The discovery potential of B physics At BABAR/Belle/CDF/D0/ LHC-b is limited by systematic errors from QCD: l ν B π! B d B d D system- CKM elements known to <1% by unitarity l ν DB π measurements of absolute rates for D leptonic & a wide variety of semileptonic decays yield decay constants & form factors to test and hone QCD techniques into precision theory which can then be applied to the B system. D l ν + Br(B D)~100% absolute D hadronic rates normalize B physics important for Vcb (scale of triangle) - also normalize D physics 9

10 Leptonic Charm Decays & Decay Constants D+ µν CLEO Phys.Rev. Lett. 95 (2005) D s + µν, τν CLEO hep-ex/ ICHEP06 (preliminary) D s + µν BABAR hep-ex/ submitted to PRL See also talk tomorrow in WG 2/3 by S. Stone Semileptonic + Leptonic D Decays CLEO 10

11 Leptonic Decays: D (s) l + ν Introduction: Pseudoscalar decay constants _ c and q can annihilate, probability is to wave function overlap Example : (s) or cs In general for all pseudoscalars: m 2! GF fp m M # $ + l l l P ( V 2 ) Qq 8" M P %(P & ) = 1 ' * + Calculate, or measure if V Qq is known 11

12 BABAR: D s µν + µ! "# Select e+e- cc events with high momentum D 0, D+, D s, D* + close to B kinematic end-point Search for D s * γ Ds γµν in the recoil Measure B(Ds µν)/b(ds φπ)=0.143±0.018 Use B(D s φπ) = (4.71±0.46)% BABAR PRD71 (2005) Find B(D s µν) = (6.74 ± 0.83 ± 0.26 ± 0.66)x ) ) ± f Ds = (281 ± 17 ± 6 ± 14) MeV BABAR 230 fb -1 12

13 D s Data at CLEO-c σ(d S D S *) = 0.9 nb at E cm ~4.17 GeV 13

14 D S+ µ + ν + τ + ν, τ + π + ν: Distinguish by energy deposition in calorimeter: (i) Clear D S+ µ + ν at zero missing mass (ii) events <0.2 GeV 2 are mostly D S τ + ν, τ π + ν (iii) No D S + ν seen 64 events <0.3GeV in CC 24 events D S+ µ + ν and τ + ν (200pb -1, D Tagged) D S+ τ + ν, τ + e + νν: BR product ~1.3%; large compared with expected B(D S + Xe + ν) 8% Signal candidates: 1) e + opposite D S - tag 2) no other tracks 3) Σ calorimeter energy < 400 MeV 400 MeV Signal >0.3GeV in CC 12 events Xe + ν Sum both µν and τν, τ πν: B eff (D S+ µ + ν) = (0.664±0.076±0.028)% B(D S + τ + ν) =(7.1±1.4±0.03)% B(D S+ τ + ν) = (6.29±0.78±0.52)% 14

15 Decay Constants, Combined Results CLEO combined result (preliminary) f Ds = (280.1±11.6±6.0) MeV Γ(D S+ τ + ν)/γ (D S+ µ + ν): CLEO: 9.9±1.7±0.7, Standard Model: 9.72 consistent with lepton universality D + µ + ν D " K! Signal CLEO published from D µν f D+ =(222.6± )MeV: f Ds /f D +=1.26±0.11±0.03 Or using Unquenched Lattice Gauge prediction of 1.24±0.07 find V cd /V cs =0.22±

16 Hadronic Charm Decays D 0, D + Hadronic BF CLEO presented at HQL06 D s Hadronic BF CLEO hep-ex/ ICHEP06 B(D s φπ) BABAR PRD (2005) D s Kππ Dalitz Plot Analysis BABAR presented at DPF06 16

17 D 0 K - π +,D + K - π + π + at the ψ" (CLEO-c) 281 pb -1 D 0 or D 0 230,225 D 0 & D 0 13,575±120 D + or D - 167,086 D + & D - 8,867±97 Double Tags B(D + K - π + π + ) (%) Error(%) Source B(D 0 K - π + ) (%) Error(%) Source 9.2±0.1± CLEO-c (281 pb -1 ) 3.87±0.04 ± CLEO-c (281 pb -1 ) 9.2± PDG ± PDG ± PDG ± PDG06 17

18 D s Single Tag Yields 18

19 D s Double Tag Yields 19

20 Absolute B Results for D S pb -1 About ±6% error Compare with BABAR B(D s φπ)=(4.71± 0.46)% 20

21 Comparison of BABAR & CLEO-c 123 M BB pairs B D*D* s Fully reconstruct D*+γ Shown above is the denominator in BF Normalization of D s important for B-factories B-factories measure B(D s µν)/b(d s φπ) Measurements at threshold & 10 GeV very different 21

22 D s+ K + K - π + (BABAR) 22

23 The Real B(D S φπ + ) You can use a Dalitz plot fit (i.e. BABAR) to get the fraction of φπ. This is not the same procedure that was done in the past of merely cutting on the K + K - invariant mass about the φ. The BABAR Dalitz plot analysis has the φπ + fraction of K + K - π + =0.379±0.018 Dividing the CLEO number for B(D S K + K - π + ) by B(φ K + K - )=.491, gives B(D S φπ + )=(4.3±0.5)% This is the branching ratio that is most appropriate to compare with theoretical calculations 23

24 Semileptonic Charm Decays Form Factors, V cs & V cd D 0 /D + Xev D 0 πe/µν, Ke/µν Belle PRL 97:061804,2006 D 0/+ πeν, Keν D 0 Keν D 0 πµν, Kµν BES hep-ex/ D+ Kµν BES hep-ex/ CLEO accepted by PRL hep-ex/ CLEO - presented at ICHEP06 BABAR hep-ex/ ICHEP06 See also talk tomorrow in WG 2/3 by S. Stone Semileptonic + Leptonic D Decays CLEO And Talk on Friday in WG 1 by M. Artuso Status + Future Perspectives on V cs and V cd 24

25 Inclusive Semileptonic Results mode D 0 Xe + ν Σ i Β i (D 0 Xe + ν) D + Xe + ν Σ i Β i (D + Xe + ν) Branching Fraction (6.46 ± 0.17 ± 0.13)% (6.1 ± 0.2 ± 0.2)% (16.13 ± 0.20 ± 0.33)% (15.1 ± 0.5 ± 0.5)% CLEO-c 281pb -1 " " SL Consistent with the known exclusive modes saturating the inclusive branching fractions. B SL = # = ± ± D D D SL SL B 0 0!! D D D Extrapolated below 0.2 GeV Consistent with isospin symmetry Electron vs D Tag D 0 Kπ, D + Kππ 25

26 Exclusive Semileptonic Decays Either take V cq from other information & test theory, or use theory & measure V cq V cs use D K(K*)lν to measure form-factor shapes to distinguish among models & test lattice QCD predictions V cd use D π(ρ)lν Use D πlν (& ρlν) to get form-factor for B πlν (& ρlν) and use HQET to get V ub See WG2 Session on Exclusive V ub later today 26

27 D 0 /D + K/πeν CLEO-c (281 pb -1 ) With D tagging Untagged: Neutrino Reconstruction 40% common samples! 1347± ± ± ±84 295± ±55 450± ±88 U = E miss P miss (GeV) Plots Integrated over all q 2 27

28 D 0 K/π e/µν Belle (282 fb -1 ) Fully recontruct e + e - cc D 0 Κeν 1318 ± 37 stat ± 7 syst data data remaining signal fake-d 0 bkg D 0 πeν 126 ± 12 stat ± 3 syst D 0 Κµν data hadronic bkg D 0 πµν 1249 ± 37 stat ± 25 syst data MC Klν bkg Κ /ρlν bkg 106 ± 12 stat ± 6 syst m ν ² / GeV² 1/7 statistics of CLEO-c with 1000x Luminosity 28

29 Exclusive Branching Ratio Summary 29

30 Form Factor Fit (CLEO-c & Belle) CLEO-c Belle σ(q²) = GeV²/c² σ(q²) = GeV²/c² 30

31 Form Factors D Ke + ν D πe + ν Decay Mode CLEO-c (av. D 0 & D + ) tagged untagged Belle (D 0 ) BABAR (D 0 ) D Κeν 1.96±0.03± ±0.03± ±0.04 ± ±0.016 ±0.020 D πeν 1.95±0.04± ±0.03± ±0.08±

32 Form Factors & Tests of LQCD D 0 " + # K e! Assuming V cs = Use independent measure of V cx Compare data & lattice determination of f + (0). Belle D 0 $ " # e +! Assuming V cd = Belle. 32

33 Use Lattice to extract V cs & V cd Preliminary CLEO-c semileptonic widths Γ(D Keν e ) =(8.7±0.16) x10-2 ps-1 Γ(D πeν e )= (0.76 ±0.03)x10-2 ps-1 FNAL-MILC-HRQCD (PRL 94, (2005)) Γ(D Keν e )/ V cs 2 and Γ(D πeν e )/ V cd 2 Uncertainties Expt:<2% ~4% LQCD: 10% CLEO-c Preliminary D πeν V cx ± (stat) ± (syst) ± ± PDG ± (ν ν interactions) D Keν ± ± ± ± (charm exclusive sl width, smaller data sample) Best direct determination of V cs See talk on Friday in WG 1 by M. Artuso Status + Future Perspectives on V cs and V cd 33

34 Charm Impact on γ/φ 3 Charm Mixing Doubly-Cabibbo Suppressed Decay Strong Phases CP Tagged Dalitz Plots 34

35 Mixing & Strong Phase at Threshold C = 1 e + e γ* D 0 D 0 Not all final states allowed. Apparent Bs different from incoherent (isolated) decay. interference forbidden in absence of mixing maximal constructive interference forbidden by CP conservation K π + K π + CP+ K l + ν CP+ CP+ K + π K + π K π + K π + K π + K + l ν K + l ν K + l ν K + l ν CP- CP- CP- CP+ CP- Interf. of D 0 and D 0 to same f: DCSD: <D 0 K π + >/<D 0 K π + > = re iδ Κπ Mixing: y = (Γ 2 -Γ 1 )/2Γ Time-integrated rates probe r, cos δ, and y (at first order!). SL decays tag flavor (if no mixing) other D decays as if isolated. Disentangle DCSD and mixing. See PRD (2006) Goals: first measurement of cosδ Kπ, constrain y. 35

36 Previous Results (Oct 2005) PANIC 05 prelim. results: 281 pb -1. No systematics. Only one CP- mode. With r 2 constrained to world average, cosδ Κπ =1.08±0.66. Use BF constraints then σ(y)~0.03 & σ(cosδ Κπ )~0.5 In progress: Added 70% more CP K 0 S η, K0 S ω Added K 0 L π0. Technique tested with Quantum Correlated MC. Expect in 281 pb -1 σ(y)~0.015 & σ(cosδ Κπ )~0.3 Expect in 281 pb -1 σ(y)~0.01 & σ(cosδ Κπ )~ Param. N D 0 D 0 y r 2 rz R M B(K π + ) B(K K + ) B(π π + ) B(K 0 S π0 π 0 ) B(K 0 S π0 ) B(X e + ν) Value (1.09 ± 0.04)x ± ± ± (1.74 ± 1.47)x10-3 (3.80 ± 0.29)% (0.357 ± 0.029)% (0.125 ± 0.011)% (0.932 ± 0.087)% (1.27 ± 0.09)% (6.21 ± 0.42)% <D 0 K π + >/<D 0 K π + > = re iδ Κπ z = 2cosδ Κπ PDG04 or CLEO-c (1.01 ± 0.02)x ± (3.74 ± 0.18)x10-3 PDG + Belle + FOCUS < ~1x10-3 (3.91 ± 0.12)% (0.389 ± 0.012)% (0.138 ± 0.005)% (0.89 ± 0.41)% (1.55 ± 0.12)% (6.87 ± 0.28)% 36

37 Determing γ/φ 3 with Direct CPV 1) B +- D ( * ) CP K( * )+ Gronau-London-Wyler 2) B + D 0 Kπ h+ Atwood-Dunietz-Soni 3) B + D 0( * ) CP K( * )+, D 0 K S π + π - Dalitz Method Giri et al., Bondar et al. D mixing is fortunately small enough to ignore ADS requires δ Kπ - phase between D 0 Kπ & D 0 Kπ Dalitz method requires proper amplitude/phase description of D 0 K S π + π -. Benefits from CP tagged Dalitz plots 37

38 CP Tagged Dalitz Plots CP tagged Dalitz plots can reduce systematic uncertainty on γ/φ 3. CLEO-c data is a source of CP tagged Dalitz plots Preliminary yields for CP tagged D0 K S π + π - in 281 pb -1 Extrapolate to 750 pb -1 expected New! Use kinematic constraints to reconstruct K L π + π - c i = 1 2 ( M ( M! i! i! + M M + i + i ) ) ( K i + K K i K! i! i ) -i i CLEO-c will detemine c i by counting yields in bin i for flavor and CP tags K i - flavor tag yield in bin i M i ± - CP± yield in bin i 38

39 CP Tagged K S ππ (CLEO-c Data) K S π 0 cuts: < ΔE < GeV/c < M BC < GeV/c 2 ΔE (K S ππ) M bc (K S ππ) KK, ππ,, K S ππ cuts: < ΔE < 0.03 GeV/c < M BC < GeV/c 2 Slide 9 Very low background ΔE (K S ππ) M bc (K S ππ) 39

40 CP Tagged K S ππ Dalitz Plots (CLEO-c Data) K S ππ yields by tag: K S π = 95 KK = 66 ππ = 27 no ρ 0 ρ 0 Clearly statistics starved! Use kinematic constraints to add modes with K L K L π + π - K L π 0 K L π 0 π 0 40

41 Reconstructing K L Kπ vs K L ππ Motivation is clear - more statistics Method straight forward Reconstruct D (Tag) on one side Bkgd ~5% Compute (missing mass) 2 on other Additional CP tags - shown today K L π 0 vs K S π + π - K L π 0 vs K S ππ KK vs K L ππ K S π 0 vs K L π + π - K + K - vs K L π + π - π + π - vs K L π + π - Modes with 2π 0 s also promising K L π 0 π 0 vs K S π + π - K S π 0 vs K L ππ ππ vs K L ππ K S π 0 π 0 vs K L π + π - MM 2 (GeV) 2 41

42 CP Tagged K L π + π - Dalitz Plots CP+ Tags CP- Tags M(K L π + ) 2 no ρ 0 M(K L π + ) 2 ρ 0 M(K L π - ) 2 M(π+ π - ) 2 M(K L π - ) 2 M(π + π - ) 2 CP- tagged K L ππ Dalitz plots have enhanced K L ρ 0 (CP+) CP+ tagged K L ππ Dalitz plots have no K L ρ 0 42

43 Double Dalitz Tags K S π + π - vs K L π + π - (CLEO-c Data) M(K S π + ) 2 M(K L π + ) 2 M(π + π - ) 2 M(π + π - ) 2 43

44 Impact of CLEO-c Φ 3 error vs. D CP statistics [1] # of events (CLEO-c) KK K S π+π pb K S π+π- 750 pb pb ππ K S π K L π K L π+π- 750 pb Sys. Error on γ/φ 3 Stat. Error on γ/φ CP tags in 281 pb o sys. err. ~1500 CP tags expected in 750 pb -1 ~4 o sys. err. ~1700 double Dalitz tags expected in 750 pb -1 Impact on sys. err under study # of B+ DK+, D K S π+π- # of CP tagged D K S π+π- [1] Bondar, Poluektov [hep-ph/ ] 44

45 CKM Impact of Charm Measurements Leptonic Charm Decays D+ µ+ν, D s + µ+ν,τ+ν Measure decay constants f D, f Ds Improved f B possible from f D measurement + LQCD Important for V td and V ts Semileptonic Charm Decays Measurements of V cs and V cd Test theoretical form factor models Impacts prediction of form factors for B meson decays Important for V ub and V cb Hadronic Charm Decays D 0 Kπ, D + Kππ, D s+ φπ Important for V cb Multibody Charm Decays D 0 K S,L ππ, Important for γ/φ 3 f D :CLEO-c ~8% 4-5% BESIII expect ~1-2% f Ds: CLEO-c ~6% (200 pb-1) BABAR ~8% (230 fb-1) Expect 3% each BESIII expect ~1-2% CLEO-c Vcs <2%, Vcd <4%, Expect<2% BESIII improvement depends on sys err. B-factories contribute to Klν, πlν FF Expect CLEO-c 1-2% D,D + BF Cosδ ± CLEO-c 4% Ds Currently BABAR 10% on φπ CLEO-c 6% on KKπ 4% CP tagged K S ππ + K L ππ: improve γ/φ 3 6 o <4 o at CLEO-c 45

46 Closing Provacative Thoughts How much more charm data do we need? How precisely do we need to measure CKM parameters? Want to measure f D /f Ds to 1% use double ratio (f B /f Bs )/(f D /f Ds ) from LQCD to get f B /f Bs and interpret Δm d /Δm s Needs O(100 fb -1 ) at threshold BESIII will accumulate 0(10 fb -1 ) Same level of FF analyses as Ke 3, Ke 4 For Ke 4 Na48/2, E K each Charm phase space is larger, perhaps need 1M events Needs O(10 2 to 10 3 fb -1 ) at threshold Sys. Err on γ/φ 3 to 1 o Needs ~20 fb -1 for K S,L ππ - okay for BESIII Other modes (πππ 0, KKπ 0 etc.) will require more threshold data We should consider seriously the option of running SuperB at charm threshold Requires ~(5-10)% of running time distraction from ϒ(4S) 46

47 The End 47

48 A Tribute to Bernie Gittelman 1936-Nov. 25, 2006 A hero of flavor physics Pioneered e- storage rings at SLAC First to measure B semileptonic decays Led CLEO II project 48

49 BABAR & FOCUS Form Factors LQCD CLEO-c Belle Unquenched LQCD Quenched LQCD Simple pole model DATA FIT LQCD DATA FIT 49