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Search Results: 1 - 10 of 68074 matches for " Feng-Kun Guo "
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Isospin and a possible interpretation of the newly observed X(1576)
Feng-Kun Guo,Peng-Nian Shen
Physics , 2006, DOI: 10.1103/PhysRevD.74.097503
Abstract: Recently, the BES collaboration observed a broad resonant structure X(1576) with a large width being around 800 MeV and assigned its $J^{PC}$ number to $1^{--}$. We show that the isospin of this resonant structure should be assigned to 1. This state might be a molecule state or a tetraquark state. We study the consequences of a possible $K^*(892)$-${\bar \kappa}$ molecular interpretation. In this scenario, the broad width can easily be understood. By using the data of $B(J/\psi\to X\pi^0)\cdot B(X\to K^+K^-)$, the branching ratios $B(J/\psi\to X\pi^0)\cdot B(X\to \pi^+\pi^-)$ and $B(J/\psi\to X\pi^0)\cdot B(X\to K^+K^-\pi^+\pi^-)$ are further estimated in this molecular state scenario. It is shown that the $X\to \pi^+\pi^-$ decay mode should have a much larger branching ratio than the $X\to K^+K^-$ decay mode has. As a consequence, this resonant structure should also be seen in the $J/\psi\to \pi^+\pi^-\pi^0$ and $J/\psi\to K^+K^-\pi^+\pi^-\pi^0$ processes, especially in the former process. Carefully searching this resonant structure in the $J/\psi\to \pi^+\pi^-\pi^0$ and $J/\psi\to K^+K^-\pi^+\pi^-\pi^0$ decays should be important for understanding the structure of X(1567).
More kaonic bound states and a comprehensive interpretation of the D_{sJ} states
Feng-Kun Guo,Ulf-G. Mei?ner
Physics , 2011, DOI: 10.1103/PhysRevD.84.014013
Abstract: The leading order interaction between a Goldstone boson and a matter field is universally dominated by the Weinberg-Tomozawa term. Based on this observation, we predict a rich spectrum of bound states of a kaon and a heavy meson. We argue that if the lifetime of an excited heavy meson is significantly longer than the range of forces, then the finite width of that state can be neglected in a first approximation. Then, the D_{s0}^*(2317), D_{s1}(2460), D_{sJ}(2860) and D_{sJ}(3040) are generated as DK, D^*K, D_1(2420)K and D^*(2600)K bound states, respectively. In addition to the remarkable agreement with the measured masses, the decay patterns of the D_{sJ}(2860) and D_{sJ}(3040) can also be understood. Two more D_{sJ} states, and kaonic bound states with the bottom mesons as well as the doubly charmed baryon are also predicted.
Examining coupled-channel effects in radiative charmonium transitions
Feng-Kun Guo,Ulf-G. Mei?ner
Physics , 2011, DOI: 10.1103/PhysRevLett.108.112002
Abstract: Coupled-channel effects due to coupling of charmonia to the charmed and anticharmed mesons are of current interest in heavy quarkonium physics. However, the effects have not been unambiguously established. In this paper, a clean method is proposed in order to examine the coupled-channel effects in charmonium transitions. We show that the hindered M1 radiative transitions from the 2P to 1P charmonia are suitable for this purpose. We suggest to measure one or more of the ratios Gamma(h_c'-->chi_{cJ} gamma)/Gamma(chi_{cJ}'-->chi_{cJ} pi^0) and Gamma(chi_{cJ}'-->h_c gamma)/Gamma(chi_{cJ}'-->chi_{cJ} pi^0), for which highly nontrivial and parameter-free predictions are given. The picture can also be tested using both unquenched and quenched lattice calculations.
Anomalous decays of eta' and eta into four pions
Feng-Kun Guo,Bastian Kubis,Andreas Wirzba
Physics , 2011, DOI: 10.1103/PhysRevD.85.014014
Abstract: We calculate the branching ratios of the yet unmeasured eta' decays into four pions, based on a combination of chiral perturbation theory and vector-meson dominance. The decays eta' --> 2(pi+ pi-) and eta' --> pi+ pi- 2pi0 are P-wave dominated and can largely be thought to proceed via two rho resonances; we predict branching fractions of (1.0+-0.3)*10^-4 and (2.4+-0.7)*10^-4, respectively, not much lower than the current experimental upper limits. The decays eta' --> 4pi0 and eta --> 4pi0, in contrast, are D-wave driven as long as conservation of CP symmetry is assumed, and are significantly further suppressed; any experimental evidence for the decay eta --> 4pi0 could almost certainly be interpreted as a signal of CP violation. We also calculate the CP-violating amplitudes for eta' --> 4pi0 and eta --> 4pi0 induced by the QCD theta-term.
Light quark mass dependence in heavy quarkonium physics
Feng-Kun Guo,Ulf-G. Mei?ner
Physics , 2012, DOI: 10.1103/PhysRevLett.109.062001
Abstract: The issue of chiral extrapolations in heavy quarkonium systems is discussed. We show that the light quark mass dependence of the properties of heavy quarkonia is not always suppressed. For quarkonia close to an open flavor threshold, even a nonanalytic chiral extrapolation is needed. Both these nontrivial facts are demonstrated to appear in the decay widths of the hindered M1 transitions between the first radially excited and ground state P-wave charmonia. The results at a pion mass of about 500 MeV could deviate from the value at the physical pion mass by a factor of two. Our findings show the necessity of performing chiral extrapolations for lattice simulations of heavy quarkonium systems.
Cumulants of the QCD topological charge distribution
Feng-Kun Guo,Ulf-G. Mei?ner
Physics , 2015, DOI: 10.1016/j.physletb.2015.07.076
Abstract: The distribution of the QCD topological charge can be described by cumulants, with the lowest one being the topological susceptibility. The vacuum energy density in a theta-vacuum is the generating function for these cumulants. In this paper, we derive the vacuum energy density in SU(2) chiral perturbation theory up to next-to-leading order keeping different up and down quark masses, which can be used to calculate any cumulant of the topological charge distribution. We also give the expression for the case of SU(N) with degenerate quark masses. In this case, all cumulants depend on the same linear combination of low-energy constants and chiral logarithm, and thus there are sum rules between the N-flavor quark condensate and the cumulants free of next-to-leading order corrections.
Extracting $ππ$ $S$-wave scattering lengths from cusp effect in heavy quarkonium dipion transitions
Xiao-Hai Liu,Feng-Kun Guo,Evgeny Epelbaum
Physics , 2012, DOI: 10.1140/epjc/s10052-013-2284-2
Abstract: Charge-exchange rescattering $\pi^+\pi^-\to \pi^0\pi^0$ leads to a cusp effect in the $\pi^0\pi^0$ invariant mass spectrum of processes with $\pi^0\pi^0$ in the final state which can be used to measure $\pi\pi$ $S$-wave scattering lengths. Employing a non-relativistic effective field theory, we discuss the possibility of extracting the scattering lengths in heavy quarkonium $\pi^0\pi^0$ transitions. The transition $\Upsilon(3S)\to\Upsilon(2S)\pi^0\pi^0$ is studied in details. We discuss the precision that can be reached in such an extraction for a certain number of events.
Could the near-threshold $XYZ$ states be simply kinematic effects?
Feng-Kun Guo,Christoph Hanhart,Qian Wang,Qiang Zhao
Physics , 2014, DOI: 10.1103/PhysRevD.91.051504
Abstract: We demonstrate that the spectacular structures discovered recently in various experiments and named as $X$, $Y$ and $Z$ states cannot be purely kinematic effects. Their existence necessarily calls for nearby poles in the $S$--matrix and they therefore qualify as states. We propose a way to distinguishing kinematic cusp effects from genuine $S$--matrix poles: the kinematic threshold cusp cannot produce a narrow peak in the invariant mass distribution in the elastic channel in contrast with a genuine $S$--matrix pole.
Where is the χ_{c0}(2P)?
Feng-Kun Guo,Ulf-G. Mei?ner
Physics , 2012, DOI: 10.1103/PhysRevD.86.091501
Abstract: Although the analysis of the BaBar Collaboration prefers J^P=0^+ for the X(3915), it is difficult to assign the X(3915) to the \chi_{c0}(2P). We show that there is an indication of the \chi_{c0}(2P) with a mass around 3840 MeV and width of about 200 MeV in the Belle and BaBar data for \gamma \gamma --> D\bar D.
Baryon electric dipole moments from strong CP violation
Feng-Kun Guo,Ulf-G. Mei?ner
Physics , 2012, DOI: 10.1007/JHEP12(2012)097
Abstract: The electric dipole form factors and moments of the ground state baryons are calculated in chiral perturbation theory at next-to-leading order. We show that the baryon electric dipole form factors at this order depend only on two combinations of low-energy constants. We also derive various relations that are free of unknown low-energy constants. We use recent lattice QCD data to calculate all baryon EDMs. In particular, we find d_n = -2.9\pm 0.9 and d_p = 1.1\pm 1.1 in units of 10^{-16} e \theta_0 cm. Finite volume corrections to the moments are also worked out. We show that for a precision extraction from lattice QCD data, the next-to-leading order terms have to be accounted for.
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