It is known that the Standard Model does not describe all phenomena related to subatomic particles. This thesis presents feasibility studies of the measurement of eta meson decay using WASA-at-COSY detector which tests predictions of the Standard Model. The aim of this thesis is to estimate the time of measurement for which the current branching ratio limit of eta -> 4pi0 decay can be improved. In order to estimate the time of measurement Monte Carlo simulations were performed. Kinematics of the pp -> ppeta -> pp4pi0 -> pp8gamma reactions were simulated using PLUTO program. Next, by means of the GEANT3 program the response of the WASA-at-COSY detector was simulated for each particle. Received signals were analysed in RootSorter software package based on ROOT. Studies of the reaction with many gamma quanta in the exit channel required the investigation of WASA-at-COSY calorimeter functioning. Tests of a cluster building algorithm with emphasis on merging and splitting of detected signals were done. The obtained result shows that only about 3% of eta -> 4p0 decays can be properly reconstructed. The identification of the eta -> 4pi0 -> 8gamma decay was based on the invariant mass method for both pi0 and eta mesons. As a result, the resolution of the invariant mass determination of the eta meson was established to sigma = 31 MeV/c2. The acceptance of the WASA-at-COSY detector for pp -> ppeta -> pp4pi0 -> pp8gamma reaction was determined to Aeta=(Neta detected) / (Neta produced) = 1.5%. The time of measurement for obtaining a statistical precision equal to the current branching ratio limit for Tbeam = 1.3 GeV is about 13 hours. It was also established that the lower the excess energy in the eta production is the shorter the time of the measurement needed.
Studies of the $η$ meson with WASA at COSY and KLOE-2 at DA$Φ$NE
KLOE-2和WASA-at-COSY实验的基本动机之一是检验基本对称性，并在基态介子的强子和轻子衰变中，特别是在$η$介子的衰变中寻找标准模型之外的现象。在COSY，这些介子产生于质子或氘束与氢或氘丸靶的碰撞，而在DA $Φ$ NE $η$介子来源于$ϕ$介子的辐射衰变或来自碰撞电子和正电子之间交换的虚伽马量子的融合。这一贡献包括KLOE-2和WASA-at-COSY使用的实验技术的简要描述，以及一些物理方面的激励调查的生产和衰变的$η$介子。
We report on the investigation of the rare decay $η\rightarrowπ^0+\text{e}^++\text{e}^-$ which is of interest to study both $C$ violation in the electromagnetic interaction and to search for contributions from physics beyond the Standard Model, since the allowed decay via a two-photon intermediate state is strongly suppressed. The experiment has been performed using the WASA-at-COSY installation, located at the COSY accelerator of the Forschungszentrum Jülich, Germany. In total $3\times10^7$ events of the reaction $\text{p}+\text{d}\rightarrow{^3\text{He}}+η$ have been recorded at an excess en…
Hadronic interaction of the eta meson with two nucleons
COSY-11协作组进行了旨在确定接近运动学阈值的p p-> p p eta反应的激发函数和相空间布居的实验。利用较冷的同步加速器COSY和高分辨率零度磁谱仪的随机冷却质子束获得的精确数据允许观察到显着偏差-在激发函数和两粒子不变质量的形状上-与基于反应相空间均匀填充假设的预测。比较p p--> p p eta和p p--> p p eta-prime反应的激发函数的形状，可以以与模型无关的方式区分源自质子-质子和质子-η相互作用的影响。为了进行比较，使用了在COSY和其他实验室进行的实验的完整数据集。
In May-June 2014, the experiment devoted to the search for the bound state of the $η$ meson and $^3$$He$ nucleus has been performed at COSY accelerator in Research Center Jülich in Germany with WASA-at-COSY facility. The excitation functions for $pd\rightarrow^3$$He2γ$, $pd\rightarrow^3$$He6γ$, $pd\rightarrow pppπ^{-}$, $pd\rightarrow ppnπ^{0}$, $pd\rightarrow dnπ^{-}$, $pd\rightarrow dpπ^{0}$, $pd\rightarrow pd$, and $pd\rightarrow ppn$ reactions have been measured in the vicinity of the $η$ meson production threshold. The experiment was carried out using COSY ramped proton beam and deuterium…
The $η$ and $η$' mesons are almost unique in the particle universe since they are Goldstone and the dynamics of their decays are strongly constrained. Because the $η$ has no charge, decays that violate conservation laws can occur without interfering with a corresponding current. The integrated η-meson samples collected in earlier experiments amount to $\sim10^{9}$ events, dominated by the WASA-at-Cosy experiment. A new experiment, REDTOP (Rare Eta Decays with a TPC for Optical Photons), is being proposed, either at the proton Delivery Ring of Fermilab or at the Proton Synchrotron of CERN, with…
Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high degree of the polarized proton beam of COSY, the reaction pp{\to} ppη has been measured close to threshold to explore the analyzing power Ay. The angular distribution of Ay is determined with the precision improved by more than one order of magnitude with respect to previous results allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q = 15 MeV signaling s wave production with no evidence for higher p…
