Recent results and D meson production and decays

Recent results and D meson production and decays Medina Ablikim BES Collaboration IHEP, Beijing Topical Seminar on Frontier of Particle Physics 2005 Heavy Flavor Physics 13 -17 August, Beijing 1

Outline v Semileptonic decays of D mesons v Leptonic decay of D+ meson v DD-bar Cross Section at 3. 773 Ge. V v Evidence for v Summary 2

I. Semileptonic D Decays Phys. Lett. B 597(2004)39 Phys. Lett. B 608(2005)24 Motivation § Absolute measurements § Form factors & § CKM matrix elements & § Isospin conservation implies: From PDG 04 Br 3

Method data @ around 3. 773 Ge. V Double-tagged method K Near DDbar production threshold region e+ K π π e- e 4

Singly tagged D samples Singly tagged modes , , , PID made by combining TOF & d. E/dx information : CL prob ( > 0. 1% ; K : CL , i ) > 0. 1 %, > CL i = 1, 2, 3 5

Invariant mass distribution for tags 6

Doubly tagged D decays , ; PID : Missing energy and momentum 7

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Monte Carlo simulation n n Detection efficiency Background subtraction Mode 9

Results Ø Branching fractions (%) Experiment BES MARK III PDG 04 10

Ø Form factors Different theoretical predictions QCDSR Phys. Rev. D 66, 114002, 2000 Nucl. Phys. Prog. Suppl. 83, 28 6, 2000 LQCD(1) LQCD(2) Nucl. Phys. B 619, 565, 2001 BES CLEO Theoretical predictions are in the range from 0. 7 to 1. 4. See J. D. Richman et al. , Rev. Mod. Phys. , Vol. 67, No 4, 1995 11

Ø CKM matrix elements BES(QCDSR ) BES(LQCD(1)) BES(LQCD(2)) Input BES MARK III 12

Ø Ratio of partial widths BES MARK III PDG 04 Obtained based on the branching fractions quoted from PDG 04 BES result favors that the isospin conservation holds in D meson semi-leptonic decays 13

II. Leptonic D+ Decay Phys. Lett. B 610(2005)183 Motivation The effect of strong interaction can be parameterized by Lattice gauge, potential models bag model, QCD sum rule …, calculation predict the value of The f. D measurement will allow comparison with theoretical calculation to improve theory Mixing experiment Lattice predicts f. B/f. D with small errors. Precision measurement of f. D precision estimate of f. B 14

Method Single tags Double-tagged method e+ KDtag D+ D D- π+ π+ e- Require one additional charged track and no additional photons Neutrino carries energy and momentum away Should be around zero data @ around 3. 773 Ge. V 15

Candidate evens 3 events in the signal region Monte Carlo simulation 16

Background Ø method 1 Ø method 2 1 hadronic track in the recoil of the tags MC sample 27 times larger than data Nb = 0. 33+/-0. 11 13 events in the D-mass region Results Nb=0. 31+/- 0. 09 17

III. DD-bar Cross Section at 3. 773 Ge. V Motivation Phys. Lett. B 603(2004)130 Ø (3770) production cross section at peak based on (3770) resonance parameters: Ø DD-bar cross section MARK-III measured the observed DDbar cross section (at Ecm = 3. 768 Ge. V) production cross section Ø discrepancy & 18

Method Single-tagged method Near DDbar production threshold region Dtag e+ D+ D D- K- π+ π+ e- data @ 3. 773 Ge. V 19

From Monte Carlo PDG 20

Radiative correction Assuming that (3770) decay exlusively into PR D 62 (2000)012002 -1 sampling function (Kuraev and Fadin) Using (3770) resonance parameters quoted from PDG 2002 Radiative correction factor: 21

Tree level cross section 22

IV. Evidence for Phys. Lett. B 605(2005)63 Motivation Ø discrepancy & about 40% of psi(3770) does not decay to DD-bar ? Ø theoretical prediction 23

Selection of candidate data @ around 3. 773 Ge. V 4 good charged tacks per event is identified by combining d. E/dx, TOF, BSC & Muon Search for in two different ways 24

Ø Recoil mass of data MC Fitting to the mass distribution with three Gaussian functions plus a first order Polynomial gives, events mainly bg from 25

Open histogram is for e+e- channel, Ø Kinematic fit The events of histogram in yellow is for mu+mu- channel were fitted to the hypothesis of (mainly) requiring Fitting to the mass distribution with three Gaussian functions plus a first order polynomial gives, The histogram is psi(3686), while error bar is the psi(3686)+psi(3770) Monte Carlo The events passed K. F. bg from 26

V. Summary u. Measured the form factors & ratio of partial widths u. Observed 3 D+ leptonic decay events, and obtained u. BES measured the DD-bar Cross Section at 3. 773 Ge. V to be u. BES observed hadronic transition of in first time and measured the partial width to be 28

Thank You！ 29