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Mu-Lin Yan

Publications and source records attributed to Mu-Lin Yan.

At least 55 records · Page 3Linked to original sources

Improved Gell-Mann--Okubo Relations and SU(3) Rotation Excitations of Baryon States

The corrections to the Gell-Mann--Okubo relations of baryon masses are presented in the SU(3) Skyrme model. These corrections are calculated up to the second order in flavor breaking at the skyrmion quantum mechanics. The results are compatible with the experimental data. They could be regarded as a signal of existence of the SU(3) rotation excitation states of baryons: 27-let (with spin 1/2 or 3/2), 10*-let (with spin 1/2) and 35-let (with spin 3/2).

hep-ph

CP-violating asymmetry in $Λ\to pπ$ in the Skyrme model

We study the CP-violating asymmetry in nonleptonic decay $Λ\to pπ$. By employing the Skyrme model to calculate this decay amplitude contributed by the gluonic diploe operator, we find a possible large CP-violating asymmetry could be expected, which is consistent with the previous study.

hep-ph

$ρ-ω-$Interference in $J/ψ-$Decays and $ρ\to π^+π^-π^0$ Decay

We study $ρ-ω-$interference by analyzing $J/ψ\to π^+π^-π^0π^0$. PDG-2002 data on $J/ψ$ decays into $PP$ and $PV$ ($P$ denotes pseudoscalar mesons; $V$, vector mesons) are used to fit a generic model which describes the $J/ψ$ decays. From the fits, we obtain anomalously large branching ratio $Br(ρ^0\to π^+π^-π^0)\sim 10^{-3}-10^{-2}$. A theoretical analysis for it is also provided, and the prediction is in good agreement with the anomalously large $Br(ρ^0\to π^+π^-π^0)$. By the fit, we also get the $η-η'-$mixing angle $θ=-19.68^o\pm 1.49^o$ and the constituent quark mass ratio $m_u/m_s\sim 0.6$ which are all reasonable.

hep-ph

Remarks on 't Hooft's Brick Wall Model

A semi-classical reasoning leads to the non-commutativity of the space and time coordinates near the horizon of Schwarzschild black hole. This non-commutativity in turn provides a mechanism to interpret the brick wall thickness hypothesis in 't Hooft's brick wall model as well as the boundary condition imposed for the field considered. For concreteness, we consider a noncommutative scalar field model near the horizon and derive the effective metric via the equation of motion of noncommutative scalar field. This metric displays a new horizon in addition to the original one associated with the Schwarzschild black hole. The infinite red-shifting of the scalar field on the new horizon determines the range of the noncommutativ space and explains the relevant boundary condition for the field. This range enables us to calculate the entropy of black hole as proportional to the area of its original horizon along the same line as in 't Hooft's model, and the thickness of the brick wall is found to be proportional to the thermal average of the noncommutative space-time range. The Hawking temperature has been derived in this formalism. The study here represents an attempt to reveal some physics beyond the brick wall model.

gr-qc

The Scale on Chiral Symmetry Breaking

We study the relation between the scale of chiral symmetry spontaneously breaking and constituent quark mass. We argue that this relation partly reveals strong interaction origination of chiral symmetry breaking. We show that the relation can be obtained via checking unitarity region of low-energy effective field theory of QCD. This effective field theory must manifestly include consistent quark mass as parameter. Thus we derive this effective field theory from naive chiral constituent quark model. The phenomenological value obtained by this method agree with usual one determined by pion decay constant.

hep-ph

$K_L \to γν> \barν$ decay beyond the standard model

The decay $K_L \to γν\barν$ is investigated beyond the standard model. Interestingly, the upper limit of the CP-conserving and CP-violating branching ratios of the decay, induced from the possible extensions of the standard model, would be larger than the corresponding branching ratios given in the standard model respectively, and it is expected that the CP-violating part could be enhanced.

hep-ph

Resummation Study on Decay $ρ\toππ$ in $U(2)_L\times U(2)_R$ Chiral Theory of Mesons

We improve $O(p^4)$ calculation in $U(2)_L\times U(2)_R$ chiral theory of mesons by resummation calculation for vector mesons physics and restudy decay $ρ\toππ$. A complete and compact expression for $f_{ρππ}(p^2)$ (up to $O(p^\infty)$) is obtained, from which an important non-perturbative conclusion is given based on convergence and unitarity consideration.

hep-ph

Resummation Studies on Vector Meson Decays and Chiral Symmetry Spontaneously Breaking in Chiral Constituent Quark Model

We study on-shell decays of light vector meson resonances $ρ$, $K^*$ and $ϕ$ in the framework of chiral constituent quark model using resummation calculations. Such studies are necessary for showing that chiral dynamics works well at this energy scale. The effective action is derived by proper vertex method, where resummation of all orders of momentum expansion is accomplished. The loop effects of pseudoscalar meson are also taken into account, which play an important role at this energy scale. The numerical results agree well with the experimental data. A new method to explore the Chiral Symmetry Spontaneously Breaking (CSSB) is proposed. It is found that the unitarity of the effective meson theory resulted from resummation derivations demands an upper-limit to the momentum of vector meson. This upper-limit, being critical point, is just the energy scale of CSSB, and is found to be flavor-dependent.

hep-ph

Quantum Integrable System with Multi-components in Two-Dimension

A quantum N-body problem with 2-component in (2+1)-dimension deduced from integrable model in (2+1) dimension is investigated. The Davey-Stewartson 1(DS1) system[Proc. R. Soc. London, Ser. A {\bf 338}, 101 (1974)] is an integrable model in two dimensions. A quantum DS1 system with 2 colour-components in two dimensions has been formulated. This two-dimensional problem has been reduced to two one-dimensional many-body problems with 2 colour-components. The solutions of the two-dimensional problem under consideration has been constructed from the resulting problems in one dimensions. For latters with the $δ$-function interactions and being solved by the Bethe-Yang ansatz, we introduce symmetrical and antisymmetrical Young operators of the permutation group and obtain the exact solutions for the quantum DS1 system. The application of the solusions is discussed.

cond-mat.stat-mech

Isospin Symmetry Breaking in ρ\toπγDecay

In terms of effective field theory and mixed propagator approach, we show that there is a larger hidden effect of isospin breaking in $ρ^0\toπ^0γ$ decay due to an $ω$ exchange, $ρ^0\toω\toπ^0γ$. The branching ratio is predicted as $B(ρ^0\toπ^0γ)=(11.67\pm 2.0)\times 10^{-4}$, which is much larger than Partcile Data Group's datum $(6.8\pm 1.7)\times 10^{-4}$ and one of charged mode, $B(ρ^\pm\toπ^\pmγ)=(4.5\pm 0.5)\times 10^{-4}$.

hep-ph

On the Mixed Propagator Approach to $ρ-ω$ Mixing

Mixed Propagator (MP) approach to $ρ-ω$ mixing is discussed. It is found that under the pole-approximation assumption the results of MP approach is not compatible both with the effective Lagrangian theory and with the experiment measurement criterion. To overcome these inconsistent, we propose a new MP approach in which the physical states of $ρ$ and $ω$ are determined by the requirement of experimental measurement to meson resonance. In terms of this new MP approach, the EM pion form factor $F_π$ and form factors of $ρ^0 \to π^0 γ$ and of $ω\to π^0 γ$ are derived. The results of $F_π$ are in good agreement with data. The form factor of $ρ^0 \to π^0 γ$ exhibits a hidden charge-asymmetry enhancement effect which agree with the prediction of the effective Lagrangian theory.

hep-ph

Quantum integrable system with two color components in two dimensions

The Davey-Stewartson 1(DS1) system[9] is an integrable model in two dimensions. A quantum DS1 system with 2 colour-components in two dimensions has been formulated. This two-dimensional problem has been reduced to two one-dimensional many-body problems with 2 colour-components. The solutions of the two-dimensional problem under consideration has been constructed from the resulting problems in one dimensions. For latters with the $δ$-function interactions and being solved by the Bethe ansatz, we introduce symmetrical and antisymmetrical Young operators of the permutation group and obtain the exact solutions for the quantum DS1 system. The application of the solusions is discussed.

cond-mat.stat-mech

Noncommutative QED and Muon Anomalous Magnetic Moment

The muon anomalous $g$ value, $a_μ=(g-2)/2$, is calculated up to one-loop level in noncommutative QED. We argue that relativistic muon in E821 experiment nearly always stays at the lowest Landau level. So that spatial coordinates of muon do not commute each other. Using parameters of E821 experiment, $B=14.5$KG and muon energy 3.09GeV/c, we obtain the noncommutativity correction to $a_μ$ is about $1.57\times 10^{-9}$, which significantly makes standard model prediction close to experiment.

hep-th

Quantum entropy of the Kerr black hole arising from gravitational perturbation

The quantum entropy of the Kerr black hole arising from gravitational perturbation is investigated by using Null tetrad and t Hooftś brick-wall model. It is shown that effect of the gravitonś spins on the subleading correction is dependent of the square of the spins and the angular momentum per unit mass of the black hole, and contribution of the logarithmic term to the entropy will be positive, zero, and negative for different value of $a/r_+$.

gr-qc

Effect of spins on the quantum entropy of black holes

By using the Newman-Penrose formalism and 't Hooft brick-wall model, the quantum entropies of the Kerr-Newman black hole due to the Dirac and electromagnetic fields are calculated and the effects of the spins of the photons and Dirac particles on the entropies are investigated. It is shown that the entropies depend only on the square of the spins of the particles and the contribution of the spins is dependent on the rotation of the black hole, except that different fields obey different statistics.

gr-qc

$K^*(892)$ Electromagnetic Mass Anomaly

Electromagnetic masses of neutral $K^*(892)$ may be larger than one of charged $K^*(892)$. It is unusual and is called $K^*$-EM-mass anomaly. We review the studies on this issue, and point out that $K^*$-mass splitting can be measured in BES accurately.

hep-ph

Chiral Expansion Theory at Vector Meson Scale

We study physics on $ρ(770)$ and $ω(782)$ in framework of chiral constituent quark model. The effective action is derived by proper vertex method, which can capture all order information of chiral expansion. The $N_c^{-1}$ expansion is also studied systematically. It is shown that the momentum expansion at vector meson energy scale converges slowly, and the loop effects of pseudoscalar meson play an important role at this energy scale. We provide a method to prove the unitarity of S-matrix in any low-energy effective theory of QCD. Phenomenologically, we study decays for $ρ\toππ$, $ρ\to e^+e^-$, $ω\toπ^+π^-$, $ρ^\pm\toγπ^\pm$ and $ω\toγπ^0$, $ρ^0-ω$ mixing and their mass splitting, pion form factor, $I=l=1$ phase shift and light quark masses at vector meson energy scale. These results include all order contribution of vector meson momentum expansion and is up to next to leading order of $N_c^{-1}$ expansion. All of these theoretical predictions agree with data very well. The unitarity of S-matrix yielded by this framework is examined. The Breit-Winger formula for resonance propagator is derived.

hep-ph

Chiral Expansion at Energy Scale of $ρ$-Mass

We study chiral expansion at $m_ρ$-scale in framework of chiral constituent quark model. The lowest vector meson resonsances are treated as composited fields of constituent quarks. We illustrate that, at energy scale of $ρ$-meson mass, the chiral expansion expansion converges slowly. Therefore, it is possible to construct a well-defined chiral effective field theory at this energy scale, but high order correction of chiral expansion must be included simultanously. The one-loop correction of pseudoscalar mesons is also studied systematically. The unitarity of the model is examined and Breit-Wigner formula for $ρ$-meson is obtained. The prediction on on-shell $ρ\toππ$ and $ρ\to e^+e^-$ decays agree with data very well.

hep-ph