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Recent results on D meson decays from BES

This paper presents recent results on D meson decays from the BES collaboration at the Institute of High Energy Physics in Beijing, China. The measurements were done using data from the Beijing Electron Positron Collider (BEPC), and the results provide important information about semileptonic and inclusive decays of D mesons.

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Recent results on D meson decays from BES

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  1. Recent results on D meson decays from BES 陈江川(for BES Collaboration) Institute of High Energy Physics, Beijing China 高能物理学会第七届全国会员代表大会暨学术年会 广西 桂林 2006年10月27日-11月1日

  2. Outline • Introduction • Semileptonic decays of D mesons • Inclusive decays of D mesons • Summary

  3. The Beijing Electron Positron Collider (BEPC) L ~ 11031 /cm2sat(3770)peak Ecm~2-5 GeV

  4. BESII Detector VC: xy = 100 m TOF: T = 180 ps  counter: r= 3 cm MDC: xy = 220 m BSC: E/E= 22 % z = 5.5 cm dE/dx= 8.5 %  = 7.9 mr B field: 0.4 T p/p=1.7%(1+p2) z = 3.1 cm

  5. Muon identification can be done by the Muon Counter for the charged track with momentum of great than 0.55 GeV/c dE/dx TOF

  6. (3770) data sample ~18 pb-1 data taken at 3.773 GeV ~7 pb-1 data taken at the region from 3.768 GeV to 3.778 GeV ~8 pb-1 data taken in the energy region from 3.665 to 3.878 GeV The total Luminosity is about 33 pb-1.

  7. Absolute Measurements With the singly tagged D sample, we can do some absolute measurements Singly tagged D sample Near DD-bar production threshold region K+ K+ D D π– tag tag π– π– D- e+ e- e+ e- D D D+

  8. Semileptonic D Decays (1) K+ K+ D D π- tag tag π- π- D- e+ e- e+ e- D0 D+ D D

  9. It is called “Longstanding puzzle” in Charm decay ! Motivation Isospin conservationrequires From PDG Br Is isospin conservation held in the D semileptonic decays? Recently: BES-II published on Phys. Let. B608(2005)24-30 Solved the puzzle in Charm decays ! CLEO-c contributed paper at LP05 reports:

  10. Motivation Branching fractions * From PDG04 Br CKM matrix elements & * Form factors& *

  11. Good track selection Charged track with good helix fit To be consistent with originating from the primary events vertex Vxy <0.02 m & |z| < 0.2 m > 0.1 GeV < 0.08 m & |z| < 0.2 m

  12. Singly tagged D sample Singly tagged modes , , , , , , , , , , , (Throughout the talk, charge conjugation is implied.) PID made by combining TOF, dE/dx & BSC information K : : CL > 0.1% ; CL > CL prob ( , n ) >0.1%, n = 1, 2, 3 1C kinematic fit (mKnπ)

  13. 9 modes Invariant mass distribution for tags Invariant mass distribution for tags

  14. Double-tagged D decays (1) Candidate modes , ; Nγ=0 (on recoil side of the D tag) K+ Combined TOF , dE/dx & BSC information D π- π: tag π- K : D- e+ e- μ: D D+ (or Nhit > 2 on μ counter) Missing energy and momentum selection Should be around zero

  15. data Bckgrd DD-bar Data (subtracted bck) MC

  16. Distribution of the Inv. masses of combinations for the events for which the and are observed in the recoil side Preliminary

  17. Results hep-ex/0610019 & 0610020 • Branching fraction An up limit at 90% C.L is set to be <0.89% Preliminary

  18. Ratio of partial width Preliminary Obtained based on the branching fractions quoted from PDG04 The ratio of Br. for D0 decaysto K(π)μν is:

  19. Semileptonic D Decays (2) K+ K+ D D π- tag tag π- π- D- e+ e- e+ e- D0 D+ D D

  20. Double-tagged D decays (2) Candidate modes Combined TOF and dE/dx information π: K+ K : D π- tag KS0: π- D- Combined TOF , dE/dx & BSC information e+ e- e: D D+ Missing energy and momentum selection νe Should be around zero

  21. Events found in REC. of Dtag

  22. Results: Published in Eur. Phys. J. C47 (2006) 31

  23. Results: Published in Eur. Phys. J. C47 (2006) 31 With the measured branching fractions in this work and quoted from BES-II earlier work, we obtain:

  24. Comparison uncertainty of theoretical prediction

  25. Inclusive Decay Branching Fractionsfor K+ K+ D D π- tag tag π- π- D- e+ e- e+ e- D0 D+ D D K– π – π+ X X=any particles

  26. Motivation • Serving as a check on the sum of the branching fractions for the exclusive D decay. • Providing information about the relative strength of Cabibbo-favored and Cabibbo suppressed D decays.

  27. Double-tagged D decays Candidate modes Combined TOF and dE/dx information K+ π: D π- K : tag π- KS0: D- e+ e- e- D+ D e+ K– D0 D π+ X=any particles π – X The Kπ with maximum CL(K)•CL(π) retained in an event

  28. D0 signal region D0 sideband K+π – K–π+ D– signal region D– sideband K+π – K–π+ K +π – Cabibbo suppressed decay Cabibbo favored decay

  29. Results Published in PLB625 (2005) 196 Cabibbo favored decay: Cabibbo suppressed decay:

  30. Neutral K decay of D: Charged K* Decay of D: KS0 3σ K+ D tag π+π – e+ e- D0 D Removing double counting with sideband background. π – X

  31. Preliminary D0 signal region D+ signal region D0 sideband D+ sideband π+π – π+π –

  32. Preliminary D0 signal region D– signal region D0 sideband D– sideband KS0π – Mass(GeV/c2) KS0π – Mass(GeV/c2) KS0π + KS0π + Mass(GeV/c2) Mass(GeV/c2)

  33. Results The results submitted to PLB Cabibbo favored decay: Cabibbo suppressed decay (at 90% C.L.):

  34. Comparison

  35. Summary hep-ex/0610019 & 0610020 BES measured semileptonic D decay branching fractions • . Preliminary • . The ratio of branching fractions is • .

  36. Summary Published in Eur. Phys. J. C47 (2006) 31 Measured semileptonic D decay branching fractions • . With the measured branching fractions in this work and quoted from BES-II earlier work, we obtain: • .

  37. Summary Published in PLB 625(2005)196 Measured branching fractions for inclusive Cabibbo favored and suppressed decays of D mesons: • . Cabibbo favored decay: Cabibbo suppressed decay:

  38. Summary The results submitted to PLB Cabibbo favored decay: • . Cabibbo suppressed decay (at 90% C.L.): • . Branching fractions of inclusive neutral K decay of D • .

  39. 谢 谢! Thank You!

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