Large N_c Expansion in Chiral Quark Model of Mesons

We study SU(3)_L\timesSU(3)_R chiral quark model of mesons up to the next to leading order of $1/N_c$ expansion. Composite vector and axial-vector mesons resonances are introduced via non-linear realization of chiral SU(3) and vector meson dominant. Effects of one-loop graphs of pseudoscalar, vector and axial-vector mesons is calculated systematically and the significant results are obtained. We also investigate correction of quark-gluon coupling and relationship between chiral quark model and QCD sum rules. Up to powers four of derivatives, chiral effective lagrangian of mesons is derived and evaluated to the next to leading order of $1/N_c$. Low energy limit of the model is examined. Ten low energy coupling constants $L_i(i=1,2,...,10)$ in ChPT are obtained and agree with ChPT well.Comment: 49 pages, latex file, 6 eps figure

Noncommutative QED and Muon Anomalous Magnetic Moment

The muon anomalous $g$ value, $a_\mu=(g-2)/2$, 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 $a_\mu$ is about $1.57\times 10^{-9}$, which significantly makes standard model prediction close to experiment.Comment: revtex, 6 page, 5 figure

Rigorous Effective Field Theory Study on Pion Form Factor

We study $e^+e^-\to\pi^+\pi^-$ cross section and phase shift of $I=l=1$ $\pi-\pi$ scattering below 1GeV in framework of chiral constituent quark model. The results including all order contribution of the chiral perturbation expansion and all one-loop effects of pseudoscalar mesons, but without any adjust parameters. Width of $\rho$ predicted by the model strongly depends on transition momentum-square $q^2$. We show that the mass pamameter of $\rho$-meson in its propagator is very different from its physical mass due to momentum-dependent width of $\rho$. The mass difference between $\rho^0$ and $\omega$ are predicted successfully. The rigorous theoretical prediction on $e^+e^-\to\pi^+\pi^-$ cross section and the phase shift in $I=l=1$ $\pi-\pi$ scattering agree with data excellentlly.Comment: revtex file, 10 pages, 4 eps figure

Chiral Expansion Theory at Vector Meson Scale

We study physics on $\rho(770)$ and $\omega(782)$ 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 $\rho\to\pi\pi$, $\rho\to e^+e^-$, $\omega\to\pi^+\pi^-$, $\rho^\pm\to\gamma\pi^\pm$ and $\omega\to\gamma\pi^0$, $\rho^0-\omega$ 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.Comment: revtex file, 36 pages, 10 eps figure

Probing Light Stop Pairs at the LHC

In this work, we study the light stop pair signals at the LHC. We explore the SUSY parameter space with non-universal gaugino and third generation masses at the GUT scale. Recent LHC SUSY search results based on 35pb$^{-1}$ and 1fb$^{-1}$ of data are implemented to put the limits on stop pair events. The dark matter relic density and direct detection constraints are also taken into account. Detailed simulations on the signals and background for some benchmark points are performed, and it is found that the stop pair signals usually escape the LHC search if the present cut conditions are used. We also explore the potential and sensitivity of ILC to probe such scenarios. It is found that the ILC can detect them with an integrated luminosity of a few tens of fb$^{-1}$.Comment: 35pages, 13figure

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.Comment: 6 pages, 1 figure

Human migration patterns in large scale spatial with the resume data

Researches on the human mobility have made great progress in many aspects, but the long-term and long-distance migration behavior is lack of in-depth and extensive research because of the difficult in accessing to household data. In this paper, we use the resume data to discover the human migration behavior on the large scale scope. It is found that the asymmetry in the flow structure which reflects the influence of population competition is caused by the difference of attractiveness among cities. This flow structure can be approximately described by the gravity model of spatial economics. Besides, the value of scaling exponent of distance function in the gravity model is less than the value of short-term travel behavior. It means that, compared with the short-term travel behavior, the long-term human migration behavior is less sensitive. Moreover, the scaling coefficients of each variable in the gravity model are investigated. The result shows that the economic level is a mainly factor on the migration

Light stop/sbottom pair production searches in the NMSSM

In this work, we study the constraints on the scenario of light stops and sbottoms in the next-to-minimal supersymmetric standard model (NMSSM), especially by a 125 GeV Higgs boson discovery and the LHC bounds on supersymmetry. The constraints from dark matter detections are also taken into account. From the parameter scan, we find that the NMSSM can well accommodate a light Higgs boson around 125 GeV and decay patterns. We would like to stress that the LHC direct supersymmetry searches with b-tagging are very powerful and can set strong bounds on many NMSSM parameter points with light stops and sbottoms. We find $\tilde {t}\to b\tilde{\chi}^+_1$ is a very promising channel for light stop detection if the mass splitting between $\tilde{\chi}^+_1$ and $\tilde{\chi}^0_1$ is very small. It is also pointed out that in order to close the parameter space of light stops and sbottoms, new search strategies for signal channels such as $p p \to {\tilde t_1} {\tilde t_1} \to t {\bar t} h h \tilde{\chi}^0_1 \tilde{\chi}^0_1$ and $p p \to {\tilde b_1} {\tilde b_1} \to t {\bar t} W^+ W^- \tilde{\chi}^0_1 \tilde{\chi}^0_1$ may be necessary.Comment: 43 pages, 18 fig

Resummation Study on Decay ρ→ππ\rho\to\pi\pi in U(2)L×U(2)RU(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 $\rho\to\pi\pi$. A complete and compact expression for $f_{\rho\pi\pi}(p^2)$ (up to $O(p^\infty)$) is obtained, from which an important non-perturbative conclusion is given based on convergence and unitarity consideration.Comment: 5 pages, 2 figure

Relativistic corrections to the form factors of BcB_c into SS-wave Charmonium

We investigate the form factors of $B_c$ meson into $S$-wave charmonium within the nonrelativistic QCD effective theory and obtain the next-to-leading order relativistic corrections to the form factors, where both the $B_c$ meson and the charmonium are treated as the nonrelativistic bound states. Treating the charm quark as a light quark in the limit \ $m_c/m_b\to 0$, some form factors are identical at the maximum recoil point, which are consistent with the predictions in the heavy-quark effective theory and the large-energy effective theory. Considering that the branching ratios of $B^+_c \to J/\psi D_s^+$ and $B^+_c \to J/\psi D_s^{*+}$ have been measured by the LHCb and ATLAS Collaborations recently, we employ the form factors of $B_c$ meson into $S$-wave charmonium at the next-to-leading order accuracy to these two decay channels and obtain more precise predictions of their decay rates. Numerical results indicate that the factorizable diagrams dominate the contribution in these two channels, while the colour-suppressed and the annihilation diagrams contribute less than 10 percent. Our results are consistent with the LHCb and ATLAS data.Comment: 10 pages, 2 figures and 2 tables. The typos are corrected and more discussions are adde