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.
We review the present understanding of etaprime and eta meson physics and these mesons as a probe of gluon dynamics in low-energy QCD. Recent highlights include the production mechanism of eta and etaprime mesons in proton-nucleon collisions from threshold to high-energy, the etaprime effective mass shift in the nuclear medium, searches for possible eta and etaprime bound states in nuclei as well as precision measurements of eta decays as a probe of light-quark masses. We discuss recent experimental data, theoretical interpretation of the different measurements and the open questions and chall…
Pion and eta electroproduction data are jointly analyzed for the first time, up to a center-of-mass energy of 1.6 GeV. The framework is a dynamical coupled-channel model, based on the recent Jülich-Bonn-Washington analysis of pion electroproduction data for the same energy range. Comparisons are made to a number of single-channel eta electroproduction fits. By comparing multipoles of comparable fit quality, we find some of these amplitudes are well determined over the near-threshold region, while others will require fits over an extended energy range.
Anomalous enhancement of a penguin hadronic matrix element in B->K eta'
我们估计了在大N_c极限下真空产生的π ^0,η和η '的密度矩阵元。因此,我们发现QCD轴向反常导致了对通常的味SU(3)关系的高度非平凡的修正,即B^0-> K^0 π ^0,B^0-> K^0 eta和B^0-> K^0 eta'衰变振幅之间的关系。这些修正可以解释为什么B-> K η '分支比比B-> K π大6倍。
π质量差在K+ --> pi 0 pi 0 pi+衰变的pi 0 pi 0不变质量分布中产生一个明显的尖点。正如Cabibbo最初指出的那样,尖点的精确测量可以让人们以高精度确定S波π介子-π介子散射长度。我们提出了非相对论性的有效场论框架,允许以一种简单的方式来确定这个尖点的结构,包括辐射校正的影响。同样的形式主义的其他衰变通道,特别是埃塔和埃塔'衰变的应用程序,也进行了讨论。
Relevance of final state interactions in eta'->eta pi pi decays
在这次演讲中,我们对eta '->eta pi pi Dalitz图分布进行了研究。分支比的大小在1/Nc展开的框架内在U(3)手性微扰理论和共振手性理论内被适当地理解。尽管如此,为了实现对达利兹斜率参数的适当描述,必须将π介子环的么正性效应考虑在内。在考虑了末态相互作用后,我们的预测与现有的实验测量结果一致,尽管与以前的理论估计存在一些明显的差异。
The study of the properties of pion pairs emitted in pp Central Production Experiments (CEP) shows that a) scalar and tensor mesons production dominates at increasing energies and that 2++ production is suppressed by selecting events with low four momentum transfer square -t at both proton vertices and b) pion+pion- decays of the f0(1370) meson are directly observable as an isolated peak over a vanishing background between 1.1 and 1.6 GeV in measurements at high energies and low -t. Together with the measurements of the decay branching ratios of the f0(1370) into sigma sigma, rho rho, pion pio…
The enhancement of the decay Upsilon(1D) -> eta Upsilon(1S) by the axial anomaly in QCD
结果表明,Uppersons(1^3D_1)-> eta Uppersons(1 S)和Uppersons(1^3D_2)-> eta Uppersons(1 S)的衰变率应与最近文献中讨论的Uppersons(1D)-> pi pi Uppersons(1 S)的衰变率相当,甚至可能超过。这种现象的原因是所讨论的eta跃迁被QCD中味单重态轴流反常的贡献所增强。
We investigate the magnetism of QCD matter and pion mass under magnetic field considering the contribution from the tensor-type spin polarization and the anomalous magnetic moment (AMM) of quarks. It is found that the tensor-type spin polarization (TSP) induces the magnetic catalysis of chiral condensate and diamagnetism (negative magnetic susceptibility) of quark matter at low temperature, both neutral and charged pion masses increase quickly with magnetic field in the case of TSP. The anomalous magnetic moment (AMM) of quarks induces magnetic inhibition and a magnetic dependent AMM causes in…
In order to characterize the transverse momentum spectra of positive pions measured in the ALICE experiment, two thermal approaches are utilized; one is based on degeneracy of non-perfect Bose-Einstein gas and the other imposes an {\it ad-hoc} finite pion-chemical potential. The inclusion of missing haron states and the out-of-chemical equilibrium greatly contribute to the excellent characterization of pion production. The excellent reproduction of the experimental data can be understood as a manifestation of not-yet-regarded anomalous pion-production, which likely contribute to the long-stand…