S. Dubynskiy, M. B. Voloshin
We consider transitions from the resonance X(3872) to the chi_{cJ} states of charmonium with emission of one or two pions as a means of studying the structure of the X resonance. We find that the relative rates for these transitions to the final states with different J significantly depend on whether the initial state is a pure charmonium state or a four-quark/molecular state.
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The chiral symmetry of QCD requires energy-dependent pionic strong interactions at low energies. This constraint, however, is not fulfilled by the usual Breit--Wigner parameterization of pionic resonances, leading to masses larger than the real ones. We derive relations between nonleptonic three-body decays of the $B$-meson into a $D$-meson and a pair of light pseudoscalar mesons based on SU(3) chiral symmetry. Employing effective field theory methods, we demonstrate that taking into account the final-state interactions, the experimental data of the decays $B^-\to D^+π^-π^-$, $B_s^0\to \bar{D}…
The radiative transitions from the neutral exotic $Z_c(4020)^0$ resonance to $X(3872)$ with emission of a photon and the pionic transitions from the charged $Z_c(4020)^\pm$ to $X(3872)$ and a charged pion $π^\pm$ are considered for both charmoniumlike states being charmed meson-antimeson molecules. The underlying processes for these transitions are the decays of the charmed vector meson to pseudoscalar plus a photon or a pion. It is found that the discussed transition rates typically amount to a branching fraction of several permil with a peak at the vector meson pair threshold.
We estimate the partial widths for the radiative and pionic transitions from the $D_{s1}(2460)$ to the $D_{s0}(2317)$ in a molecule scenario, in which the $D_{s1}(2460)$ and $D_{s0}^\ast(2317)$ are considered as hadronic molecule states of $DK$ and $D^\ast K$, respectively. The partial widths for the $D_{s1}(2460) \to D_{s0}^\ast(2317) π^0$ and $D_{s1}(2460) \to D_{s0}^\ast(2317) γ$ are evaluated to be about $0.19 \sim 0.22$ keV and $3.0 \sim 3.1$ keV, respectively. In addition, the ratio of the $D_{s1}(2460) \to D_{s0}(2317) γ$ and $D_{s1}(2460) \to D_{s}^\ast π^0$ is estimated to be about $(…
Utilizing the Langevin scenario for the linear sigma model we investigate the effect of friction and white noise on the evolution and stability of collective pionic fields in heavy ion collisions. We find that the smaller the volume the more stable pionic fluctuations become (the avergae mass increases). On the other hand the variance of the mass square increases even more, so for a system preheated in 10 fm3 volume individual trajectories do become unstable during a rapid one dimensional expansion in contrast to the ensemble averaged solution. This result supports the idea of looking for diso…
Motivated by recent results by lattice analysis, we assume that the spin-1 mesons of $\left( ρ, ω, a_1, ρ', ω', b_1, f_1, h_1\right)$ make a representation of $\mathbf{16}$ of U(4) emergent symmetry in two-flavor QCD when the chiral symmetry is not broken. We study the decay properties of the spin-1 mesons by using a chiral model with an SU(4)$\times$U(1) hidden local symmetry. We first show that, since the SU(4) symmetry is spontaneously broken together with the chiral symmetry, each coupling of the interaction among one pion and two spin-1 mesons is proportional to the mass difference of the…
The pionic decay of a possible d'-dibaryon in the process d' --> pi + N + N is studied in the microscopic quark shell model and with a single-quark transition operator describing the transition q --> pi + q'. For the d' with quantum numbers J^P=0^-, T=0, we employ a six-quark shell-model wave function with a spatial s^5p [51]_X-configuration with N=1 harmonic oscillator quanta. It is shown that the pionic decay width depends strongly on the mass and size of the d'. In the case that the calculated d' mass is close to the experimental one a small pionic decay width of 0.04 MeV is obtained. This …
We discuss a model for heavy mesons where the light quark (u or d) moves in the colour electric field from a heavy quark (c or b) placed in the center of the bag. We calculate energy spectra for pionic and photonic transitions from excited states. The transition amplitudes and the branching ratios between electromagnetic and pionic transitions compares favorable with the limited amount of known experimental data.
We report on ongoing work to determine the pion-cloud contribution to the electromagnetic $N\rightarrowΔ$ transition form factors. The starting point is an $SU(6)$ spin-flavor symmetric constituent-quark model with instantaneous confinement that is augmented by dynamical pions which couple directly to the quarks. This system is treated in a relativistically invariant way within the framework of point-form quantum mechanics using a multichannel formulation. The first step is to determine the electromagnetic form factors of the bare particles that consist only of three quarks. These form factors…
The energy level displacements of the excited nl states of pionic hydrogen and the contribution of the ns -> 1s transitions and the (pi^-p)_Coul -> 1s transitions of the pi^-p pair, coupled by the attractive Coulomb field in the S-wave state with a continuous energy spectrum, to the shift of the energy level of the ground state of pionic hydrogen, caused by strong low-energy interactions, are calculated within a quantum field theoretic, relativistic covariant and model-independent approach developed in nucl-th/0306047.
It is well known that neutrinoless double decay is going to play a crucial role in settling the neutrino properties, which cannot be extracted from the neutrino oscillation data. It is, in particular, expected to settle the absolute scale of neutrino mass and determine whether the neutrinos are Majorana particles, i.e. they coincide with their own antiparticles. In order to extract the average neutrino mass from the data one must be able to estimate the contribution all possible high mass intermediate particles. The latter, which occur in practically all extensions of the standard model, can, …
Pionic transitions of the spin-2 partner of $X(3872)$ to $χ_{cJ}$
本文以非相对论有效场论计算$X(3872)$的自旋-2伙伴$X_2$到$χ_{c1,2}$的单、双 pion 跃迁，给出宽度、分支比及近似不依赖参数的特征比值。
Pionic transitions from $Z_c(4020)$ to $D$ wave charmonia
利用有效拉格朗日方法研究粲介子圈对Z_c(4020)到D波粲偶素π跃迁的贡献，发现其分支比远小于到h_c的跃迁，故在πψ(1^3D_J)中寻找Z_c(4020)不可行，4.04和4.13 GeV峰不来自Z_c(4020)，需精确测量e+e-→π+π-ψ(3770)以揭示其本质。
Pionic and radiative transitions from $T_{c\bar{s}0}^+(2900)$ to $D_{s1}^+(2460)$ as a probe of the structure of $D_{s1}^+(2460)$
通过比较$T_{c\bar{s}0}^+(2900)$到$D_{s1}^+(2460)$的π和辐射跃迁宽度，发现分子框架下宽度远大于粲-奇异介子框架，且宽度比可作为区分$D_{s1}^+(2460)$结构的探针。
The emission of pions produced within a dense, strongly-interacting system of matter in the presence of strong radial flow and absorption is described using a relativistic optical model formalism, replacing the attenuated or unattenuated plane waves of earlier emission function approaches with ``distorted wave'' solutions to a relativistic wave equation including a complex optical potential. The resulting distorted-wave emission function model (DWEF) is used in numerical calculations to fit HBT correlations and the resonance-corrected pion spectrum from central-collision STAR Au+Au pion data a…
We study the electromagnetic transitions of the Roper N(1440) resonance. Our results, when combined with the previously obtained for the mass and the pionic strong decay widths of the Roper, show that within a non-relativistic constituent quark model scheme, a comprehensible understanding of the Roper phenomenology can be achieved. They also seem to support the view of the Roper as a radial excitation of the nucleon, though more experimental data are needed to reach a definitive conclusion.
We consider the two flavor Nambu--Jona-Lasinio model within the RPA framework to evaluate the masses of the $σ$ and $π^0$ mesons and the $π^0$ decay constant in the presence of a magnetic field at vanishing temperatures and baryonic densities. The present work extends other RPA applications by fully considering the external momenta, which enter the integrals representing the magnetized polarization tensor, so that more accurate results can be obtained in the evaluation of physical quantities containing pionic contributions. As we show, this technical improvement generates results which agree w…
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