Charm Decays. Karl M. Ecklund

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1 Charm ecays Karl M. Ecklund

2 Outline Results from active experiments BaBar, Belle, CLEO-c, (CF, Ø), FOCUS Guiding principle: Charm s role in flavor physics Hadronic Charm ecays and s branching fractions Leptonic Charm ecays decay constants from (s) µν and s τν Semileptonic Charm ecays branching fractions hadronic form factors and CKM V cs and V cd Many interesting results not shown for lack of time hadronic structure in multibody decays rare decays: CF 0 µµ search presented in session B14 14 Apr 007 K. Ecklund: Charm APS Meeting

3 Charm s role in flavor physics Flavor physics: Overconstrain V CKM Inconsistency new physics Unitarity Triangle Constraints Sin β is theoretically clean V ub is not B mixing is not Hadronic uncertainties confound extraction of weak physics Charm decay measurements can validate QC corrections needed to extract weak physics parameters from experimental observables 14 Apr 007 K. Ecklund: Charm APS Meeting 3

4 V ub from semileptonic B decay q If quarks were like muons: Γ ( b ue ) 5 GFmb ν = 3 19π Rate goes like V ub V But quarks always in hadrons QC form factor f + (q ) needed to extract weak interaction physics ub π dγ dq G 4π F 3 = V p f (q ) 3 ub π + 14 Apr 007 K. Ecklund: Charm APS Meeting 4

5 UT Constraint from V ub V ub from B π l ν: G 4π F 3 = V 3 ub pπ f+ (q ) 14 Apr 007 K. Ecklund: Charm APS Meeting 5 dγ dq Form factor f(q ): Hard to calculate Limits V ub precision Lattice QC can do from first principles πlν to B πlν are both heavy to light decays Precise measurement of πlν can calibrate LQC and allow a precise extraction of V ub from B πlν Absolute rate and shape is a stringent test of theory

6 V td from B 0 -B 0 mixing Mixing rate depends on V td QC correction here is partly decay constant f B probability of wave function overlap ψ(r=0) Hard to small q low energy QC Lattice QC to ~15% Same for meson decay Can measure annihilation decay Belle: PRL 97, 5180 (006) Evidence for B - τ - ν (3.5 σ) f B =9±36±37 MeV (0%) But would like a precise measurement 14 Apr 007 K. Ecklund: Charm APS Meeting 6

7 UT Constraint from B mixing M d = B 1 B f B V d d td 0.50 ps 3 00MeV V td ) σ ( M f d ) ( B BB ) d σ ( σ = 0.5 V M f td d B B B d 0.8% ~15% (LQC) Lattice QC predicts decay constants f & f B Charm sector measurements of f (s) from (s) µν can increase our confidence in the non-perturbative QC calculations of f B needed to interpret m and m s direct measurement of B lν is much harder! Better constraint on V ts /V td from m s / m d still want to check f s /f 14 Apr 007 K. Ecklund: Charm APS Meeting 7

8 CKM Matrix Current V CKM From direct Measurements -no unitarity imposed δvud/vud 0.03% n e ν p δvcd/vcd 10% l ν π δvus/vus =1% l ν π Κ δvcs/vcs =10% l ν Κ δvub/vub 7% l ν B B π δvcb/vcb 5% l ν B d δvtd/vtd =15% B d B s δvts/vts =15% B s δvtb/vtb 0% t W b charm decay measurements: direct access to nd generation elements enable improvements in 3 rd generation elements 14 Apr 007 K. Ecklund: Charm APS Meeting 8

9 CLEO-c Hadronic ecays Presented in session B14 X.Shi e+e- ψ(3770) ( 0 0 or + - ) Just above threshold: no additional particles are produced Fully reconstruct one in the event, e.g. 0 K - π + E < 0 MeV E r p Energy and Momentum Conservation: = = E r p K K + + E r p π π E = M E beam E ( ) = Ebeam p resolution: 7-10 MeV 1.3 MeV 14 Apr 007 K. Ecklund: Charm APS Meeting 9

10 CLEO-c Hadronic ecays Presented in session B14 X.Shi e+e- ψ(3770) ( 0 0 or + - ) Just above threshold: no additional particles are produced Fully reconstruct one in the event, e.g. 0 K - π + E < 0 MeV E r p Energy and Momentum Conservation: = = E r p K K + + E r p π π E = M E beam E ( ) = Ebeam p resolution: 7-10 MeV 1.3 MeV 14 Apr 007 K. Ecklund: Charm APS Meeting 10

11 ouble Tag Events + K - π + π + & - K + π - π - Tagging effectively makes a single beam Can tag % of s produced! N( X i ) B( X i ) = Efficiency N tags 14 Apr 007 K. Ecklund: Charm APS Meeting 11

12 0 Single tagged π 0 K - 0 π + ouble tagged N i = e + N B i = K + B N N ij j i ε ε ε j ij i 0 N π e N N i N ij j N ε i ij ij j = N e + B = ij i j ε ε i K + B 0 π 9 modes, simultaneous χ fit including correlations on N, ε to extract 9 B i & N() j ε ε ε ε ε i =16 65% ij e 56 pb -1 : PRL (005) 81 pb -1 : Preliminary results reported at this meeting (X.Shi) Additional data in hand now (~80 pb -1 ) And from run through Mar 08 (~300 pb -1 ) 14 Apr 007 K. Ecklund: Charm APS Meeting 1

13 CLEO-c hadronic decay results Comparison to other measurements BF( 0 K - π + ) Precision measurements of many 0, + decay modes 14 Apr 007 K. Ecklund: Charm APS Meeting 13

14 Leptonic (s) ecay Measure rate to extract f and f s Useful to calibrate V td /V ts from B (s)0 mixing Γ ( µν ) = GF V 8π cd f m µ M 1 m M µ B( µν ) = Γτ B( τν ) B( s µν ) B( decay constant measures overlap of quark wave functions τν ) Apr 007 K. Ecklund: Charm APS Meeting 14 s

15 81 pb -1 PRL 95, (005) Use 158k tagged - decays Require one µ candidate with MIP-like shower no extra tracks no unmatched showers with E CC > 50 MeV B = (4.40± )x f = (.6± ) MeV -3.4 CLEO-c + µν Number of Events/0.01 GeV signal region: 50 events.8 estimated background K L π + Unquenched Lattice QC 01±3±17 MeV PRL 95, 100 (005) MM (GeV ) (Missing Mass) 14 Apr 007 K. Ecklund: Charm APS Meeting 15

16 BaBar s µν hep-ex/ e + e - s * tag X; tag is fully reconstructed (s) (*) Then look for s * s γ; s µν: M=M(µνγ)-M(µν) signal peak at 143 GeV Measure also s φπ to normalize etailed systematic understanding Γ Γ ( + + ) S µν ( + + ) S φπ = 0.143± ± BF( µν ) = (6.74 ± 0.83± 0.6 ± 0.66) 10 s f s = ( 83 ± 17 ± 7 ± 14)MeV Unquenched Lattice QC 49±3±16 MeV PRL 95, 100 (005) Apr 007 K. Ecklund: Charm APS Meeting 16

17 CLEO-c s µν & s τν; τ πν e + e - s s s=4170 MeV 314 pb -1 Fully Reconstruct 19k s tags (8 modes) Recoil Mass peaks at s * count tags by fit Add a single track µ: MIP-like in Calorimeter π: sometimes E CC >00 MeV MM peaks at 0 for µν and near 0 for τν; τ πν Veto events with extra tracks extra neutral energy Kinematic Fit improved resolution resolve ambiguity: s * s γ on tag or signal side s K* - K 0 s τν; τ πν MM (GeV ) 14 Apr 007 K. Ecklund: Charm APS Meeting 17

18 CLEO-c f s Results E CC <00 MeV arxiv: (to PR) arxiv: (to PRL) B=(0.638±0.059±0.033)% f s =(74±13±7) MeV Unquenched Lattice QC 49±3±16 MeV PRL 95, 100 (005) f s f = 1.3 ± 0.11± 0.04 ULQC 1.4±0.01±0.07 µν τν τ πν τν τ πν electrons E CC >00 MeV 14 Apr 007 K. Ecklund: Charm APS Meeting 18

19 CLEO-c s+ τ + ν; τ + e + νν nd Complementary Analysis with τ + e + νν Signal production of e+: B( s+ τ + ν)b(τ + e + νν)~1.3% Background: B( s+ Xe + ν)~8% Technique: Use s- tags and e + Suppress background no additional tracks and Σ Ecal < 400 MeV No need to find γ from s * B( s+ τ + ν) =(6.9±0.78±0.5)% f s =78±17±1 MeV ICHEP pb -1 near s=4170 MeV 400 MeV Xe + ν 14 Apr 007 K. Ecklund: Charm APS Meeting 19

20 f (s) : Comparison to Theory CLEO results Good agreement with unquenched LQC Calculations Comparable uncertainties already! More data to come! 14 Apr 007 K. Ecklund: Charm APS Meeting 0

21 Semileptonic ecays c V cx d,s Focus on recent results in Pseudoscalar final states: K, π Will not show: ηen/η en/φen (J.Ge) presented in session B14 V e ν ; V =K*,ρ q dγ dq q G 4π F 3 = V p f (q ) 3 cx X + ( p p ) = = M + X M X E X M + r p r p X 14 Apr 007 K. Ecklund: Charm APS Meeting 1

22 Fully reconstructed Belle 0 π - l + ν & 0 K - l + ν e + e - (*) *X events s=10.6 GeV Allows count of 0 independent of decay Neutrino inferred from missing E,p * + 0 π + used to improve S/N Excellent q resolution: σ(q )=0.017 GeV Measure rate directly dγ dq G 4π F 3 = V p f (q ) 3 cx X + PRL (006) 14 Apr 007 K. Ecklund: Charm APS Meeting

23 e + e - cc at s=10.6 GeV Reconstruct * + π + 0 and signal 0 Keν Estimate p and E ν with remaining event & kinematic fits Use Neural Nets to suppress backgrounds e BaBar 0 K - e + ν ν π K high statistics good S/N arxiv: fb -1 δm=m(*)-m() 14 Apr 007 K. Ecklund: Charm APS Meeting 3

24 BaBar f + (q ) 0 K - e + ν arxiv: fb -1 q = ( ) p p X 85k signal/11k background Corrected spectrum compared to LQC 1, FOCUS 1 Aubin et al. PRL 94, (005) PLB607, 33 (005) 14 Apr 007 K. Ecklund: Charm APS Meeting 4

25 CLEO-c πe + ν & Ke + ν Tagged Analysis Preliminary 81 pb -1 Presented by B.Xin Session B14 Neutrino Reconstruction 699±8 6796± ± ±13 95±0 910±55 450±9 5846±88 U = E miss P miss (GeV) extremely clean well separated backgrounds q resolution: σ=0.01 GeV better statistics larger systematic uncertainty ~40% overlap in event samples 14 Apr 007 K. Ecklund: Charm APS Meeting 5

26 0 K - e + ν Form Factor Comparisons Fit ata Single parameter fit modified pole LQC: Aubin et al. PRL (005) Preliminary High statistics test of shape CLEO prefers smaller slope α 14 Apr 007 K. Ecklund: Charm APS Meeting 6

27 0 π - e + ν Form Factor Comparisons CLEO & Belle agree well Compatible with LQC Preliminary 14 Apr 007 K. Ecklund: Charm APS Meeting 7

28 Summary & Conclusions Charm decays are measured with precision Charm measurements complement flavor physics investigations in the b sector aid interpretation of B mixing assist extraction of V CKM especially V ub by constraining QC effects Unquenched Lattice QC decay constant results appear trustworthy but experimental precision exceeds current LQC hints of differences for semileptonic Form factors Keν experimental discrepancy? normalization of form factor 10% uncertainty on V cx Additional data from BaBar, Belle, CLEO more precise results to come! 14 Apr 007 K. Ecklund: Charm APS Meeting 8

29 Additional Slides 14 Apr 007 K. Ecklund: Charm APS Meeting 9

30 CLEO-c s Hadronic results Preliminary hep-ex/ s * s s * s * s s GeV Tagging with s s * s * s γ Partial BF for s φπ interference with f 0 (980) M(KK)=M φ ±10 MeV BF=(1.98 ± 0.1 ± 0.09)% M(KK)=M φ ±0 MeV BF=(.5 ± 0.13 ± 0.1)% 14 Apr 007 K. Ecklund: Charm APS Meeting 30

31 CLEO-c s Hadronic ecays M inv vs. M bc for K - K + π + candidates in MC M bc for s K - K + π + Cut on M bc and use M inv to extract s * s events 14 Apr 007 K. Ecklund: Charm APS Meeting 31

32 Additional Hadronic ecays Additional modes from CLEO-c PRL 96, (006) Single Tag Measurement 0 modes shown on left 14 Apr 007 K. Ecklund: Charm APS Meeting 3