Some topics on D and Ds decays Zheng-Tao Wei Nankai University 2010高能物理学会第八届全国会员代表大会, 2010.4.17-21, 南昌

η-η’ mixing from D and Ds decays Summary H.W. Ke, X.Q. Li, Wei, PRD 80, 015002 (2009); PRD 80, 074030 (2009); arXiv:0912.4094. Introduction fDs puzzle f0(980) from Ds decays η-η’ mixing from D and Ds decays Summary

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)

Leptonic decays of D(Ds)->lν Simple in theory, tree dominated, one mesondecay constants Clean in experiment.  Precision test of lattice QCD.

Experiment HPQCD+UKQCD (unquenched) in 2007 PRL (2008) Rosner, et al., PDG08

A Puzzle? Most model predictions are smaller than exp. 3σ deviations between experiment and lattice results.

Light-front method Dirac’s three forms of Hamiltonian dynamics ( S. Brodsky et al., Phys.Rep.301(1998) 299 )

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. ψ(xi, k┴i ) is independent of the bound state momentum.

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 β determines the confinement scale.

The pseudoscalar meson decay constant is with Model I: fD=200 MeV, fDs=230 MeV; Model II: fD=221 MeV, fDs=270 MeV.

It is not difficult to adjust parameters β to fit the data. One prediction is that D->τν is 1.2*10^{-3 }, which will be observed soon.

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

Chared Higgs model in 2HDM is excluded due to 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).

Structure of f0(980) from Ds decays Mass: below 1GeV Isosinglet scalar meson state.

What are the components of f0(980)? Four quark state: qq qbarqbar; Jaffe (1977) φ->f0γ; Kkbar molecular state; Weinstein and Isgar (1982) close to the threshold of Kkbar, J/ψ->φππ 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 σ(f0(600)).

Advantages of using Ds semi-leptonic decays sbar sbar Ideal place to determine the ssbar component of f0(980). Small strong uncertainties compared to the exclusive modes.

Scenario of quark-antiquark structure In literature, the mixing angle φ (233)o, f0->ππ, Scadron et al. (2009) φ= (1426)o , φ->f0γ, f0->γγ, Anisovich et al. (2002) (325)o , Ds->f0+M, El-Bennich et al. (2009) They favor that ssbar is dominant.

Using LFQM, Ds->f0(980) form factors are calculated. The ssbar is not the dominant component.

η- η’ mixing from D and Ds decays η- η’ mixing plays an important role: Chiral symmetry breaking QCD anomaly 1997, B->η’K anomaly. In the SU(3) quark model, where θ is the nonet mixing angle with the range of -10o to -23o.

Another form is also widely used, The relation between the two mixing form Mixing angle θ=-11.7o corresponds to φ=43.0o. Rosner (2009)

The mixing angle (by fit): φ=(39.31.0)o, Feldmann (1999)

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 η-η’ mixing . The ssbar component is not dominant in f0(980). Our result on η-η’ mixing is consistent with the previous study.