The large values of the transverse single spin asymmetry, A_N, seen in forward pi0 production from polarized proton collisions have stimulated important questions and have been studied in QCD based transverse spin models. We report the first RHIC measurement of A_N for the two photon mass region of the eta meson. The eta peak for meson energies greater than 50 GeV (Feynman x_F >0.5) was observed in the STAR Forward Pion Detectors, along with pi0 mesons, at pseudo-rapidity of 3.65 in sqrt{s}=200 GeV pp collisions. The pi0 transverse asymmetry, which has already been reported in detail by the STAR collaboration, is compared to the transverse asymmetry in the eta mass region. The surprising observation is that in this kinematic region, the eta asymmetry is larger than the already large pi0 asymmetry.
Neutral pions and eta mesons as probes of the expanding hadronic fireball in nucleus-nucleus collisions at SIS
中性介子和η介子的生产轻，中等质量，和重核碰撞在0.8 A GeV和2.0 A GeV之间的光束能量的框架内进行了讨论，假设在强子化学和热冻结平衡，分别。从相对粒子产额的温度为56-90 MeV和重子化学势为780-675 MeV的化学冻结。中性π介子和η介子的中快度谱与得到的温度是一致的，如果，此外，测量的碰撞区的横向膨胀被考虑在内。与AGS和SPS数据的类似分析结果相反，推导出的冻结参数远低于强子气体和夸克-胶子等离子体之间的相边界。
Transverse Single Spin Asymmetries and Cross-Sections for Forward pi0 and eta Mesons at Large Feynman-x in sqrt(s)=200 GeV polarized p+p Collisions at STAR
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.
The $ηN$ final state is isospin-selective and thus provides access to the spectrum of excited nucleons without being affected by excited $Δ$ states. To this end, the world database on eta photoproduction off the proton up to a center-of-mass energy of $E\sim 2.3$ GeV is analyzed, including data on differential cross sections, and single and double polarization observables. The resonance spectrum and its properties are determined in a combined analysis of eta and pion photoproduction off the proton together with the reactions $πN\to πN$, $ηN$, $KΛ$ and $KΣ$. For the analysis, the so-called Jüli…
High transverse momentum inclusive neutral pion production in d+Au collisions at RHIC
给出了在赝快度范围0 < eta γ，sqrt（sNN）= 200 GeV的d+Au碰撞中高pT中性π介子产生的初步结果< 1. Photons from the decay pi0->，γ是在RHIC STAR实验的Barrel电磁量能器中探测到的。详细描述了分析过程，发现结果与早期的STAR研究结果和次领先阶微扰QCD计算吻合良好。
Experimental observations of strikingly large transverse single-spin asymmetries (TSSAs) opened a window into quark and gluon dynamics present in hadronic collisions, revealing large spin-momentum correlations within nucleons and in the process of forming hadrons. Though originally measured in lower energy fixed target experiments, they have been found to persist in collisions with momentum transfer well into the perturbative regime of quantum chromodynamics (QCD) and yet their origin remains poorly understood. TSSA measurements have allowed for the development of both transverse momentum depe…
Coherent photoproduction of the neutral pion and eta meson on the deuteron, $γ{d}${$\to$}$π^0η{d}$, has been experimentally studied at incident photon energies ranging from the reaction threshold to 1.15 GeV. The total cross section demonstrates a rapid rise below 1 GeV. The data are underestimated by the existing theoretical calculations based on quasi-free $π^0 η$ photoproduction on the nucleon followed by deuteron coalescence. At the same time, the data are rather well reproduced by the calculations taking into account the final-state interaction. We have also measured for the first time th…
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。
