To explain the anomALously large decay rate of ∑＋→p＋μ＋μ-, it was proposed that a new mechanism where a light CP-odd pseudoscaJar boson of mAo = 214.3 MeV makes a crucial contribution. Later, some authors have s...To explain the anomALously large decay rate of ∑＋→p＋μ＋μ-, it was proposed that a new mechanism where a light CP-odd pseudoscaJar boson of mAo = 214.3 MeV makes a crucial contribution. Later, some authors have studied the transition π0→e＋e- and γ→γA10 in terms of the same mechanism and their result indicates that with the suggested mass one cannot fit the data. This discrepancy might be caused by experimental error of ∑＋→p＋μ＋μ- because there were only a few events. Whether the mechanism is a reasonable one motivates us to investigate the transitions π0→e＋e-;η（η′）→μ＋μ-;ηc→μ＋μ-;ηb→τ＋τ- within the same framework. It is noted that for π0→ e＋ e-, the standard model （SM） prediction is smaller than the data, whereas the experimental central value of η→μ＋μ- is also above the SM prediction. It means that there should be extra contributions from other mechanisms and the contribution of A may be a possible one. Theoretically calculating the branching ratios of the concerned modes, we would cheek if we can obtain a univers mass for A10 which reconcile the theoretical predictions and data for all the modes. Unfortunately, we find that it is impossible conclude that the phenomenology does not favor such a to have such a mass with the same coupling｜gt｜. Therefore we light A10, even though a small window is still open.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos.11075079and11005079the Special Grant for the Ph.D.Program of Ministry of Eduction of China No.20100032120065
文摘To explain the anomALously large decay rate of ∑＋→p＋μ＋μ-, it was proposed that a new mechanism where a light CP-odd pseudoscaJar boson of mAo = 214.3 MeV makes a crucial contribution. Later, some authors have studied the transition π0→e＋e- and γ→γA10 in terms of the same mechanism and their result indicates that with the suggested mass one cannot fit the data. This discrepancy might be caused by experimental error of ∑＋→p＋μ＋μ- because there were only a few events. Whether the mechanism is a reasonable one motivates us to investigate the transitions π0→e＋e-;η（η′）→μ＋μ-;ηc→μ＋μ-;ηb→τ＋τ- within the same framework. It is noted that for π0→ e＋ e-, the standard model （SM） prediction is smaller than the data, whereas the experimental central value of η→μ＋μ- is also above the SM prediction. It means that there should be extra contributions from other mechanisms and the contribution of A may be a possible one. Theoretically calculating the branching ratios of the concerned modes, we would cheek if we can obtain a univers mass for A10 which reconcile the theoretical predictions and data for all the modes. Unfortunately, we find that it is impossible conclude that the phenomenology does not favor such a to have such a mass with the same coupling｜gt｜. Therefore we light A10, even though a small window is still open.
