Some topics on D and Ds decays

1
Some topics on D and Ds decays
Zheng-Tao Wei Nankai University
2010?????????????????, 2010.4.17-21, ??
2
H.W. Ke, X.Q. Li, Wei, PRD 80, 015002
(2009) PRD 80, 074030 (2009)
arXiv0912.4094.

• Introduction
• fDs puzzle
• f0(980) from Ds decays
• ?-? mixing from D and Ds decays
• Summary

3
Introduction

• Charm physics has been entered into a
• second Golden age .
• 1. D0-D0bar mixing (2007)
• 2. New charmed resonances, DsJ, X, Y ,
  Z.

Non-pertuebative QCD and New Physics
X. Li, X. Liu, Wei, FP (2009)
4

• Leptonic decays of D(Ds)-gtl?

• Simple in theory, tree dominated,
• one meson?decay constants
• Clean in experiment.

? Precision test of lattice QCD.
5

• HPQCDUKQCD (unquenched) in 2007

PRL (2008)
Experiment
Rosner, et al., PDG08
6
A Puzzle?

• Most model predictions are smaller than exp.
• 3s deviations between experiment and lattice
  results.

7
Light-front method
Diracs three forms of Hamiltonian dynamics( S.
Brodsky et al., Phys.Rep.301(1998) 299 )
8

• Advantage of LF framework

• LF method provides an appropriate
  non-perturbative
• method to treat the low energy hadron
  phenomenon.
• LF Fock space expansion provides a convenient
  description
• of a hadron in terms of the fundamental
  quark and gluon
• degrees of freedom.
• The LF wave functions is Lorentz invariant.
• ?(xi, k-i ) is independent of the bound
  state momentum.

9

• Basic assumptions of LF quark model

• Valence quark contribution dominates.
• The quark mass is constitute mass which absorbs
• some dynamic effects.
• LC wave functions are Gaussian.

Choose Gaussian-type wave function
The parameter ß determines the confinement scale.
10

• The pseudoscalar meson decay constant is

with
Model I fD200 MeV, fDs230 MeV Model II
fD221 MeV, fDs270 MeV.
11

• It is not difficult to adjust parameters ß to
  fit the data.
• One prediction is that D-gtt? is 1.210-3 ,
• which will be observed soon.

12

• The semi-leptonic modes are chosen to have the
• same quark diagrams as the leptonic decays.

13

• New physics scenarios

• Chared Higgs model in 2HDM is excluded due to
• its destructive interference effects.
• Lepto-quark model
• Unparticle physics

Dobrescu, et al., PRL (2008) Chen, et al., PRD
(2007).
14
Structure of f0(980) from Ds decays
Mass below 1GeV Isosinglet scalar meson state.
15

• What are the components of f0(980)?

• Four quark state qq qbarqbar Jaffe (1977)
• f-gtf0?
• Kkbar molecular state Weinstein and Isgar
  (1982)
• close to the threshold of Kkbar, J/?-gtfpp
  and Ds decays.
• f0 has a large ssbar component.
• glueball? Jaffe, et al., (1976).
• lattice calculation does not support it.
• Conventional quark model with qqbar component,
• mix with s(f0(600)).

16

• Advantages of using Ds semi-leptonic decays

c
s
f0(980)
Ds
sbar
sbar

• Ideal place to determine the ssbar component
  of f0(980).
• Small strong uncertainties compared to the
  exclusive modes.

17

• Scenario of quark-antiquark structure

In literature, the mixing angle f
(23?3)o, f0-gtpp, Scadron et al. (2009)
f
(142?6)o , f-gtf0?, f0-gt??, Anisovich et al. (2002)
(32?5)o , Ds-gtf0M, El-Bennich et al. (2009)

• They favor that ssbar is dominant.

18
Using LFQM, Ds-gtf0(980) form factors are
calculated.

• The ssbar is not the dominant component.

19
(No Transcript)
20
?- ? mixing from D and Ds decays

• ?- ? mixing plays an important role

• Chiral symmetry breaking
• QCD anomaly
• 1997, B-gt?K anomaly.

In the SU(3) quark model,
where ? is the nonet mixing angle with the range
of -10o to -23o.
21
Another form is also widely used,
The relation between the two mixing form
Mixing angle ?-11.7o corresponds to f43.0o.
Rosner (2009)
22

• The mixing angle (by fit)

f(39.3?1.0)o, Feldmann (1999)
23
(No Transcript)
24
(No Transcript)
25
Summary

• The fDs puzzle can be explained in SM with the
• light-front approach.
• The semi-leptonic decay of D and Ds provides a
  clean
• way to determine the mixing parameter in
  f0(980)
• and ?-? mixing .
• The ssbar component is not dominant in
  f0(980).
• Our result on ?-? mixing is consistent with
  the
• previous study.