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Selected Topics on Open Charm Physics at CLEO-c

 (3770) D 0 D 0 D 0 K +  - , D 0 K - e + . . K -. K +.  -. e +. Selected Topics on Open Charm Physics at CLEO-c. Main topics: Overview the CLEO-c experiment and its physics program Absolute Hadronic D 0 and D + Branching Fractions

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Selected Topics on Open Charm Physics at CLEO-c

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  1. (3770)D0D0 D0K+-, D0K-e+  K- K+  - e+ Selected Topics on Open Charm Physics at CLEO-c Main topics: • Overview the CLEO-c experiment and its physics program • Absolute Hadronic D0 and D+ Branching Fractions • Preliminary Results for Absolute Branching Fractions and Form Factor Measurements in and Batbold Sanghi Purdue University (CLEO Collaboration) Selected Topics on Open Charm Physics from CLEO-c

  2. CLEO-c and the CKM Matrix • The CKM matrix provides the only mechanism for CP violation in the SM • An important goal of flavor physics is to measure and (over)constrain the parameters in the CKM matrix (4 parameters) to test the SM • Non-perturbative hadronic effects limit our ability to extract fundamental parameters from experimental measurements • CLEO-c provides unique measurements in the charm sector that test theory and help reduce hadronic uncertainties • CLEO-c tested theory can then be applied to B decay processes to extract CKM matrix elements (especially Vub and Vtd) Recent status Status with theory errors reduced) Selected Topics on Open Charm Physics from CLEO-c

  3. An example of a test of Lattice QCD • Measure form factors in D  l at CLEO-c Theories of Strong Interactions (LQCD) • validate LQCD calculations for form factors • use LQCD to extract Vub from Bl Selected Topics on Open Charm Physics from CLEO-c

  4. An example of a test of Lattice QCD • m is well measured • But |Vtd| from m has a large uncertainties from fB Theories of Strong Interactions (LQCD) • validate theoretical calculations fB ~fB (LQCD)/ fD (LQCD) fD • Use fB to extract |Vtd| • measure fD in D  l Selected Topics on Open Charm Physics from CLEO-c

  5. CLEO-c impact l Vus/Vus =1% l Vud/Vud 0.1% Vub/Vub 15% e B n n K n n p p  Vcb/Vcb 5% Vcd/Vcd 7% Vcs/Vcs =16% l l D n B n l D K D n p Vtb/Vtb 29% Vtd/Vtd =36% Vts/Vts 39% W t b Bd Bd Bs Bs CLEO-c + Lattice QCD +B factories + ppbar CLEO-c + Lattice QCD +B factories CLEO-c • I will focus on two CLEO-c analyses that have impact on Vcd, Vcs, Vub and Vcd: D semileptonic B’s and form factors in (Analysis by Purdue and SMU, my main thesis topic) D hadronic branching fractions (Analysis by Cornell, Purdue and CMU) Including: and D and Ds leptonic branching fraction Selected Topics on Open Charm Physics from CLEO-c

  6. The CLEO-c detector Over 20 years of data taking at Y(4S) Started data taking in the fall of 2003 An event taken at (4S) Note: Log Scale P/P = 0.6% at 1GeV E/E = 2% at 1GeV = 5% at 100MeV Excelent electron and hadron ID • The main components of the CLEO-c detector were developed for B physics at the Y(4S). • Minor modifications • Replaced silicon with 6 layer inner drift chamber • B field 1.5 T 1.0 T • Advantages at (3770) • Pure DD, no additional particle • Low multiplicity • High tagging efficiency Selected Topics on Open Charm Physics from CLEO-c

  7. CLEO-c data samples Three generations of CLEO-c analyses at the (3770): • Oct-03 through Jan-04: Luminosity = 56 pb 1 all results are published(D hadronic branching fraction) • Sep-04 through Apr-05: Luminosity = 225 pb1 most analyses are on-going(D semileptonic B’s and form factors) • Future running: projected total Luminosity = 750 pb1 CLEO-c is also collecting data above the DsDsbarproduction threshold (goal 750 pb1) and lower energies at the (2S). Selected Topics on Open Charm Physics from CLEO-c

  8. Absolute Hadronic D0 and D+ Branching Fractions • Introduction and Overview of the Analysis • Measurements of Absolute Hadronic Branching Fractions • Summary Selected Topics on Open Charm Physics from CLEO-c

  9. Overview of Technique K- + e- e- e+ e+ p- p- K+ K+ Double tagged D Single tagged D • Use 3 D0modes and 6 D+ modes • K-+, K-+,0, K-+ ,+ - • K-+ +, K-+ +0, Ks+ , Ks+ 0, Ks+ 0, Ks+++ , K-K+ + • Reference modes D "K-p+ and K-p+p+ normalize many B measurements from other experiments. Selected Topics on Open Charm Physics from CLEO-c

  10. Overview of Technique • Determine separately the and yields • 18=2(3+6) single tags(ST) and 45(=32 + 62) double tag yields(DT) • In a combined 2 fitter (physics/0503050), we extract 9 branching ratios and and yields : • Include both statistical and systematic errors (with correlations): • All experimental inputs treated consistently. • Efficiency, cross-feed, background corrections performed directly in fit. • Some systematic errors for and completely cancelled • Branching fractions are independent of L and cross-sections. • The main variables used in the reconstruction are: Selected Topics on Open Charm Physics from CLEO-c

  11. Yield Fits DT signal shape Detector resolution ISR & beam energy • Unbinned ML fits to MBC (1D for ST, 2D for DT) • Signal function includes ISR, y(3770) line shape, beam energy smearing, and detector resolution. • Signal parameters from DT fits, then apply to ST. • Background: phase space (“ARGUS function”). • D and D yields and efficiencies separated.c • Two dimensional fit allows to separate • ISR and beam energy spread (causes correlated shifts in the mass of the two D’s) • Detector resolution (uncorrelated among these D’s ) MBC (log scale) for ST modes: All D0 DT 2484±51 All D+ DT 1650±42 Selected Topics on Open Charm Physics from CLEO-c

  12. Systematic uncertainties K found (MC) K not found (MC) K-p+p0, etc. p+p- • Dominant error: MC simulation of tracking, K0S, and p0 finding efficiencies: • Correlated errors among all particles of a given type add up quickly. • Missing mass technique measure syst errors by comparing data and MC: • Fully reconstruct entire event, but deliberately leave out one particle. • Fraction of MM peak where the last particle is found = efficiency. Example: K- efficiency from D0"K-p+ e ≈ 91% in fiducial volume Selected Topics on Open Charm Physics from CLEO-c

  13. Fit Results (PRL 95,121801) • Precision comparable to PDG-04. • Statistical errors: ~2.0% neutral, ~2.5% charged from total DT yields. • s(systematic) ~ s(statistical). • Many systematic errors are measured in data and will be improved with time. • Our MC simulation includes FSR • Using efficiencies without FSR would lead to lower B. • NDD includes continuum and resonant production. The CLEO-c measurement is the single most precise measurement for every mode Selected Topics on Open Charm Physics from CLEO-c

  14. Comparisons with other measurements Other direct meas. B(D0"K-p+) Overall C.L 25.9% B(D+"K- p+p+) • Reasonable agreement with PDG for all modes • Measurements and errors normalized to PDG. • PDG numbers are correlated among modes • PDG global fit includes ratios to K-p+ or K-p+p+. • No FSR corrections in PDG measurements • Our measurements are also correlated (through statistics and efficiency systematics). Selected Topics on Open Charm Physics from CLEO-c

  15. Results for D cross sections • Using a measurement of the luminosity of the data sample (55.8/pb), we obtain • Our cross sections are in good agreement with BES [Phys.Lett. B 241, 278(1990) ] and higher than those of MARKIII [Phys.Rev.Lett. 60, 89 (1988) ] • CLEO-c inclusive: PRL 96, 092002 Selected Topics on Open Charm Physics from CLEO-c

  16. Absolute Branching Fractions and Form Factor Measurements in and • Introduction and Overview of the Analysis • Measurements of Absolute Branching Fractions • Measurements of Form Factors • Summary Selected Topics on Open Charm Physics from CLEO-c

  17. Introduction • Semileptonic decays are an excellent laboratory to study • Weak physics • QCD physics • Gold-plated modes are P  P semileptonic transitions as they are the simplest modes for both theory and experiment: • Cabibbo favored : • Cabibbo suppressed : • Main goals of the analysis: • Measure efficiency-corrected absolutely-normalized decay rate distributions and form factors • Measure form factor parameters to test LQCD and model predictions • We analyze both D0 and D+ decays. By isospin invariance • . • . This is a nice cross check and adds statistics to improve statistical precision. Selected Topics on Open Charm Physics from CLEO-c

  18. Overview of the analysis  K- K+  - e+ (3770)D0D0 D0K+-, D0K-e+ • Reconstruct one of the two D’s in a hadronic decay channel. It is called a tagging D or a tag. Two key variables in the tagging D reconstruction are: • Reconstruct from theremaining tracks and showers the observable particles in the final state of a semileptonic decay. • Define an observable that can be used to separate signal and background as where Emiss and Pmiss are the missing energy and momentum in the event, approximating the neutrino E and P. The signal peaks at zero in U. • Branching fractions are obtained as Obtained from Fits toU Obtained from Fits toMbc Selected Topics on Open Charm Physics from CLEO-c

  19. D0 and D+ tag yields in 281/pb of DATA Examples of Mbc for tag modes in the data ~30% event tagging efficiency ~20% event tagging efficiency Tagging provides a beam of D mesons allowing semileptonic decays to be reconstructed with no kinematic ambiguity Selected Topics on Open Charm Physics from CLEO-c

  20. Measurements of Absolute Semileptonic Branching Fractions Selected Topics on Open Charm Physics from CLEO-c

  21. Fits to U in 281 pb-1 of Data for N~7000 • Main backgrounds for • Main backgrounds for • Electron fakes from kaons N~700 Selected Topics on Open Charm Physics from CLEO-c

  22. Fits to U in 281 pb-1 of Data for • Main backgrounds for • Main Backgrounds for N~2900 N~290 Selected Topics on Open Charm Physics from CLEO-c

  23. Preliminary Results for BFs Selected Topics on Open Charm Physics from CLEO-c

  24. Comparisons with other experiments and projections for 750 pb-1 Statistically limited Systematically limited Reasonable agreement Selected Topics on Open Charm Physics from CLEO-c

  25. Measurements of Semileptonic Form Factors Selected Topics on Open Charm Physics from CLEO-c

  26. Two Fitting Methods: Fit A and Fit B • The observed decay rate is related to the true decay rate in the following way: in terms of Acceptance and Smearing functions. The fit has to take into account both effects. We have developed and tested two types of fits. • Fit A is a fit to efficiency-corrected and absolutely-normalized d/dq2distributions. This fit is a good match for CLEO-c data as the q2 resolution is excellent. Fit A is our primary fit as the main goal of our analysis is to obtain d/dq2 and f+(q2). • Fit B is a fit to the observed decay rate according to a procedure described in D.M.Schmidt, R.J.Morrison and M.S.Witherell in Nucl. Instr. and Meth. A328 547(1993).The technique makes possible a (multidimensional) fit to variables modified by experimental acceptance and resolution. This method has been used by CLEO several times before, for example, to measure form factor ratios in ce and BD*l. • Both fitting methods were tested using large Monte Carlo samples. Two fits provide cross-checks. Selected Topics on Open Charm Physics from CLEO-c

  27. q2 resolutions and Raw q2 distributions q2 resolution Raw q2 distribution q2 ~ 0.012GeV2 D0→K-e+ν D0→K-e+ν 7000 events S/B > 300/1 CLEOIII(Y(4S): q2 ~ 0.4 GeV2 CLEO-c((3770)): q2 ~ 0.012GeV2 Note the background in blue q2 ~ 0.011GeV2 D0→π-e+ν D0→π-e+ν 700 events S/B ~40/1 Selected Topics on Open Charm Physics from CLEO-c

  28. Efficiency corrected and absolutely normalized decay rates (DATA) Subtracting background and applying efficiency corrections (matrices) we find absolute decay rates in bins of q2 (The bin width is equal q2max/10, the last bins for D0e+ and D+0e+ are 2 and 3 times wider): D0→K-e+ν D+→Kse+ν D0→π-e+ν D+→π0e+ν Selected Topics on Open Charm Physics from CLEO-c

  29. Efficiency corrected and absolutely normalized decay rates (DATA) The spectra on the last slide are tabulated here: These rates can be fit to any form factor model w/o knowing CLEO acceptance and resolution Selected Topics on Open Charm Physics from CLEO-c

  30. Form Factor Models • Simple pole model : • Modified pole model (BK) [Phys.Lett.B 52, 478,417(2000) ] : • Series parameterization [.Becher and R.Hill, hep-ph/0509090] • ISGW2 [Phys.Rev.D 52,2783,(1985) ] : Selected Topics on Open Charm Physics from CLEO-c

  31. Tests of Fit A and B D0 - e+  700 events C-R Prediction Our Fits D0 K- e+  7000 events • The fitting techniques were tested by making ensembles of fits to mock data samples with the number of signal events equal to the expected number of events in the data. We have tested: • Fits for all 4 form factor models • simultaneous fits to isospin conjugate modes • fit with two free parameters [f+(0)Vcs and a form factor shape parameter] Example: The fitter is consistent with being unbiased. • The efficiency of fits is tested using the Cramer-Rao inequality: The fitter is consistent with being fully efficient. Mpole (GeV) Selected Topics on Open Charm Physics from CLEO-c

  32. Example of a fit (DATA) Modified Pole (BK) Model: D0→K-e+ν D+→Kse+ν D0→π-e+ν D+→π0e+ν Selected Topics on Open Charm Physics from CLEO-c

  33. D0→Ke+ν q2 (GeV2) f+(q2)Vcs D+→KSe+ν D0→πe+ν f+(q2)Vcd D+→π0e+ν q2 (GeV2) DATA Cross Check 1 By isospin invariance: The plots show: The q2 spectra for isospin conjugate modes are consistent. Selected Topics on Open Charm Physics from CLEO-c

  34. Cross check 2: Hadron & Electron Spectra & W Helicity cosW • Quantities that are not constrained in the fit are well described D+→Kse+ν D0→π-e+ν D+→π0e+ν D0→K-e+ν Hadron Momentum Electron Momentum Selected Topics on Open Charm Physics from CLEO-c

  35. Systematic Uncertainties for Form Factor Shape Parameters • Systematic uncertainties that are independent of q2 (ex: tag Mbc fit function) do not change the decay rate shape and hence have a negligible contribution to the shape parameter uncertainty • Systematic effects correlated with the hadron (K/KS//0) momentum, change the decay rate distribution and lead to modest systematic uncertainties Kaon momentum vs q2 PK(GeV) eff Kaon ID efficiency q2 (GeV) PK ~ 100MeV Few events Lepton momentum vs q2 Our studies indicate that the total systematic uncertainty is much smaller than the statistical uncertainty for each semileptonic mode Pe(GeV) This correlation is not as strong as the hadron momentum correlation q2 (GeV) Selected Topics on Open Charm Physics from CLEO-c

  36. Fit results with two parameters • The shape parameters for modified pole, simple pole model and series parameterizationwith two parameters : • The normalization parameter for modified pole model and series parameterization with two parameters : Selected Topics on Open Charm Physics from CLEO-c

  37. Comparison with Other Measurements D → π e+ ν D → K e+ ν • First measurements of form factors for the D+ modes; • CLEO-c is the most precise for D→πe+ Selected Topics on Open Charm Physics from CLEO-c

  38. Comparison with Other Measurements D → π e+ ν D → K e+ ν • First measurements of form factors for the D+ modes; • CLEO-c is the most precise for D→πe+ Selected Topics on Open Charm Physics from CLEO-c

  39. Confidence levels for fits results with 2 parameters • The confidence levels for fits with 2 parameters : • Which parameterization does the data prefer? The confidence levels for all parameterizations are comparable, as the functional forms for the parameterization are similar and the shape parameters are not fixed. However, the CLEO-c data exclude the ISGW2 (K/) , pole (K) and modified pole (K) parameterizations when the shape parameters are fixed to the physical values. Selected Topics on Open Charm Physics from CLEO-c

  40. Data vs. physical basis for shape parameters • #1: ISGW2 Form factor shape parameters in the data for ISGW2 are inconsistent with the model predictions • #2: Pole • #3: Modified Pole Because the data do not support the physical interpretation of these three parameterizations we use the series parameterization Selected Topics on Open Charm Physics from CLEO-c

  41. Fit results with 3 parameters • Our main form factor shape and intercept results are for the series parameterization : • The series is expected to converge rapidly, so only the 1st few terms are expected to be measurable: we test for three Selected Topics on Open Charm Physics from CLEO-c

  42. Interpretation • The fit results for 2 and 3 parameters are consistent with each other; • Noticeable improvement for 2 for D→Ke+νwith 3 parameters; • The  modes do not show this trend as they lack the statistics to probe the third term in the expansion; • For D → Ke+ν the 3rd term b2 is a order of magnitude larger than b1. This cannot be interpreted as a lack of convergence if the series because both are consistent with zero indicating that the data does not yet have the sensitivity to determine three parameters simultaneously. Selected Topics on Open Charm Physics from CLEO-c

  43. Comparison Between Parameterizations  Data --- Simple pole --- Modified Pole --- Series with 2 par  Series with 3 par D+→Kse+ν D0→K-e+ν D0→π-e+ν D+→π0e+ν • Data and Fit results are normalized to the fit results for the series parameterization with 3 parameters. Selected Topics on Open Charm Physics from CLEO-c

  44. Form Factors as a Stringent Test of LQCD Vcd = 0.22380.0029(CKM unitarity, i.e Vcd = Vus) LQCD • Plotted LQCD results (blue) are recent results of FNAL+MILC unquenched three flavor LQCD [C. Aubin et al., PRL 94 011601 (2005)] • Lattice systematic uncertainties dominate: • The green lines are our fits to CLEO-c data • The dashed lines show 1 (stat+syst) regions DATA FIT Vcs = 0.97450.0008(CKM unitarity) LQCD DATA FIT Selected Topics on Open Charm Physics from CLEO-c

  45. D0→K-e+ν D0→π-e+ν Projections for  and f+(0) In these plots, the central values for our projections are equal to the central values from the LQCD results The anticipated precision for a larger 750 pb1 data sample to be collected in the future Selected Topics on Open Charm Physics from CLEO-c

  46. Vcs(d) and f+(0) determination • Using Vcs = 0.97450.0008 (CKM unitarity) Vcd = 0.22380.0029 (CKM unitarity, i.e Vcd = Vus) • Using LQCD results [C. Aubin et al., PRL 94 011601 (2005)]: Selected Topics on Open Charm Physics from CLEO-c

  47. Summary for D semileptonic studies • I have shown preliminary results for DK/ e+ branching fractions and form factor measurements from the 280/pb data sample collected at (3770). Results of this analysis include: • the most precise branching fraction measurements for these decays • the most precise or first measurements of form factors for these modes • the most precise or first measurements of the efficiency corrected and absolutely normalized decay rates • a stringent test of LQCD calculations of semileptonic form factors Selected Topics on Open Charm Physics from CLEO-c

  48. In summary, CLEO-c provides: • unique input to test LQCD, the theory capable of solving strongly couple field theory equations, and • input to other experiments that help improve their measurements Thank you Selected Topics on Open Charm Physics from CLEO-c

  49. Fit A: a 2 fit to efficiency corrected d/dq2 • A brief description of the procedure for making Fit A: • Create an N x N efficiency matrix, where N is the number of q2 bins • Invert the efficiency matrix • Measure raw background subtracted q2 distributions • Use the inverted efficiency matrix to obtain efficiency-corrected and absolutely-normalized d/dq2 (or the form factor) • We make fits for form factor parameters to efficiency-corrected and absolutely-normalized d/dq2 (or the form factor), using the 2 fitter which includes both statistical and systematic errors (with correlations) : • bin migrations, background uncertainty, and efficiency corrections. - the decay rate estimated from a form factor - the correlation matrix - the decay rate • The low number of events in the high q2 bins can lead to biases in 2 fits, we find that the Bias, if any, is SMALL [~0.10(stat. data) ] Selected Topics on Open Charm Physics from CLEO-c

  50. Efficiency Matrices • We use 10 q2 bins for and . For and we use 9 and 8 bins, respectively. The last bin for these two modes are two or three times wider than other bins. 10 bins Full efficiency matrix for Do not need to read these tables Efficiency matrices in a truncated form for 10 bins 9 bins 8 bins Selected Topics on Open Charm Physics from CLEO-c

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