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Studies of D s decays at BaBar

Studies of D s decays at BaBar. Marco Pappagallo University of Bari & INFN On behalf of the BaBar Collaboration. ICHEP 2010 35 th International Conference on High Energy Physics, Paris, July 22-28, 2010. Outline. Absolute Branching Fractions Measurement

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Studies of D s decays at BaBar

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  1. Studies of Ds decays at BaBar Marco Pappagallo University of Bari & INFN On behalf of the BaBar Collaboration ICHEP 2010 35th International Conference on High Energy Physics, Paris, July 22-28, 2010

  2. Outline • Absolute Branching Fractions Measurement • Ds+ℓ+νℓ(ℓ = e, µ, τ) • Extraction of the Decay Constant fDs • Ds+K+ K-π+ • Amplitude Analysis of Ds decay: • Ds+K+ K-π+ • Ds+π+π-π+ Preliminary NEW Preliminary NEW Phys.Rev.D79:032003,2009 Marco Pappagallo

  3. 521 fb-1 Preliminary Absolute Branching Fractions Measurement Marco Pappagallo

  4. Motivation The measurement of the leptonic decay relative branching fraction can be used to measure the decay constant fDs The global average(HFAG) and the recent unquenched lattice QCD expectations show some disagreement • New preliminary results presented at FPCP2010 • Fermilab/MILC(2010): fDs = 261.4 ± 9.2 • HPQCD(2010): fDs = 247 ± 2 Marco Pappagallo

  5. Analysis strategy • Inclusive Ds candidates • The signal consists of Ds* candidates decaying to Dsγ • The Ds candidate is reconstructed from the four-momentum recoiling against the DKXγ (D = D0(*), D+(*), Λc+; K = Ks, K+,(p); X = π+, π0) • Within this sample, the Ds+ ℓ+νℓ(ℓ = e, µ, τ) events are selected • One more track, identified as e/µ, is required Yields corrected by efficiency to obtain the branching fractions: e+ e- Marco Pappagallo

  6. Fully Inclusive Ds Sample 521 fb-1 • Most Relevant Selection criteria: • p*(Ds) > 3.0 GeV/c • mrecoil(DKX) within ~2.5σ of the Ds* PDG mass value • Eγ > 120 MeV + π0 and η vetoes N.B. mrecoil(DKX) ≡ m(Ds*) mrecoil(DKX γ) ≡ m(Ds) Result of 2D fit mrecoil(DKX γ) vs. nRx(nRx = Number of reconstructed pions in X system) (67.2±1.5)x103 events Total Marco Pappagallo

  7. Results 521 fb-1 Helicity Suppressed PHSP Suppressed Ds+ µ+νµ Ds+ e+νe Ds+ τ+µννντ Ds+ τ+eννντ Background Extra neutral energy in the event The hadronic Ds+K+K-π+ used to cross-check the method Normalization mode of many Ds decays! Very Competitive Measurements! Marco Pappagallo

  8. 384 fb-1 Preliminary Ds+K+K-π+ & Ds+ π+π-π+Dalitz Plot Analysis Marco Pappagallo

  9. Motivation • Charm meson decays are a powerful tool for investigating light quark spectroscopy: • Large coupling to scalar mesons • An initial state well defined JP = 0- • Final spectrum not constrained by isospin and parity conservation Scalar meson candidates are too numerous to fit in a single qq nonet. Some of them may be multiquark, glueball, meson-meson bound state etc…. The f0(980) has still uncertain parameters and interpretations because is just sitting at the KK threshold and strongly coupled to the KK and ππ final states π+/K+ π-/K- PDG08 Ds+→K+K-π+, and Ds+→π+π-π+ decays provide a way to study the coupling of f0(980)† to K+K- and π+π- systems †a0(980)K+K- may be contribute as well Marco Pappagallo

  10. Ds+→K+K-π+ sample 384 fb-1 Inclusive Ds sample obtained with a likelihood selection using vertex separation and p* (1020) 101k events K*(892)0 4σ • No D-wave in K+K- • No K-π+ structure but a small K*0(1430)(~2%) f0(1700) EventsusedtoobtainBkgshape: (-10σ, -6σ) and (6σ, 10σ) Partial Wave Analysis Marco Pappagallo

  11. Partial Wave Analysis at K+K- threshold 384 fb-1 Events weighted by the spherical harmonic Y0ℓ(cos KK)(ℓ=0,1,2) KK π+ Ds+ • Background subtracted • Efficiency corrected • Phase space corrected We extract a phenomenological description of the S-wave to be used in the DP analysis Solid line is the result of a binned fit (Breit-Wigner for the P-wave and a “Breit-Wigner like” function for the S-wave) Marco Pappagallo

  12. Ds+→K+K-π+Dalitz Plot 384 fb-1 Results of an unbinned maximum likelihood fit Reference Mode • K*(892)0 mass and width are floated parameters • f0(980) parameterized by the effective parameterization extracted by the PWA • χ2 computed by an adaptive binning algorithm • Decay dominated by vector intermediated resonances • The total fit fraction closer to 1, due to f0(980) parameterization adopted • K*(892)0 width is 5 MeV lower then PDG08(consistent with CLEO-c analysis) • Contribution from K*1(1410), K2(1430), κ(800), f0(1500), f2(1270), f2’(1525) consistent with zero Marco Pappagallo

  13. Fit result projections 384 fb-1 (1020) (1020) The data are well reproduced in all the projections χ2/ν=1.24 K*(892)0 Marco Pappagallo

  14. Relative Branching Ratios 384 fb-1 Ds+ K+K-K+ SCS Ds+ K+K+π- DCS Marco Pappagallo

  15. Ds+→ π+π-π+ 384 fb-1 f0(980) Phys.Rev.D79:032003,2009 13k events f0(1370)/ρ(1450) f0(980) 4σ χ2/ν=437/(422-64)=1.2 Results of an unbinned maximum likelihood fit Reference Mode • S-wave is the main contribution • Large f2(1270) contribution • Small ρ’s fit fractions Model Independent Partial Wave Analysis Sum of BW’s K-matrix Formalism Marco Pappagallo

  16. π+π- S-wave 384 fb-1 Phys.Rev.D79:032003,2009 • The S-wave shows in both amplitude and phase the expected behavior for the f0(980) • Activity in the region f0(1370) and f0(1500) resonances • The S-wave is small in the f0(600) region Marco Pappagallo

  17. Summary Extraction of the Decay Constant fDs Very Competitive Measurements! Ds+K+K-π+ & Ds+π+π-π+ Dalitz Plot Analysis K+K- and π+π-S-waves extracted by a Model Independent way. Opportunity to obtain new information about f0(980)! • Remarks: • Agreement between K+K-S-wave and π+π-S-waves despite the interferences with the other scalar mesons (especially in the π+π- system) • Agreement between the KK S-waves extracted by D0 and Ds decays. Are f0(980) and a0(980) 4-quark states?* *L. Maiani, A. D. Polosa, and V. Riquer, Phys. Lett.B651, 129 (2007) Marco Pappagallo

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