在轻子数自发破缺的模型中，出现了无质量的戈德斯通玻色子--Majoron（$J$）。在R宇称自发破缺的超对称模型中，计算了发射带电轻子衰变Br（$μ\to e J$）和Br（$μ\to e J γ$）的Majoron分支比的理论允许范围. Br（$μ\to eJ$）在最轻的中性伴子衰变主要是不可见的参数空间的同一区域中是最大的。因此，Br（$μ\to eJ$）的测量潜在地提供了与加速器搜索互补的关于R奇偶违反的信息。我们还简要地讨论了现有的界限和未来的改进带电轻子的Majoron耦合的前景。
英文摘要：
In models where the breaking of lepton number is spontaneous a massless Goldstone boson, the Majoron ($J$), appears. We calculate the theoretically allowed range for the branching ratios of Majoron emitting charged lepton decays, such as Br($μ\to e J$) and Br($μ\to e J γ$), in a supersymmetric model with spontaneous breaking of R-parity. Br($μ\to eJ$) is maximal in the same region of parameter space for which the lightest neutralino decays mainly invisibly. A measurement of Br($μ\to eJ$) thus potentially provides information on R-parity violation complementary to accelerator searches. We also briefly discuss existing bounds and prospects for future improvements on the Majoron coupling to charged leptons.
tau -> pi pi pi nu_tau decays and the a_1(1260) off-shell width revisited
τ-> pi pi pi nu_tau衰变是由轴向矢量流的强子化驱动的。在共振手征理论中，考虑到大Nc展开，这一过程已在参考文献[1]中得到了研究。[1]的文件。根据后来的发展，我们在这里修改了以前的工作，包括一个新的离壳宽度为最轻的a_1共振，提供了一个很好的描述tau -> π nu_tau光谱和分支比。我们还考虑了ρ（1450）共振在这些观测值中的作用。因此，我们带来了一个整体的描述tau -> pi pi pi nu_tau过程与我们目前的实验知识非常一致。
We reconsider the issue of the search for a nonzero electric dipole form factor (EDM) $d_τ(s)$ using optimal observables in $τ^+τ^-$ production by $e^+ e^-$ collisions in the center-of-mass energy range from the $τ$-pair threshold to about $\sqrt{s} \sim 15$ GeV. We discuss the general formalism of optimal observables and apply it to two $CP$-odd observables that are sensitive to the real and imaginary part of $d_τ(s)$, respectively. We compute the expectation values and covariances of these optimal $CP$ observables for $τ$-pair production at $\sqrt{s}=10.58$ GeV with subsequent decays of $τ^\…
If light new physics with lepton-flavor-violating couplings exists, the prime discovery channel might not be $\ell\to\ell'γ$ but rather $\ell\to\ell' X$, where the new boson $X$ could be an axion, majoron, familon or Z' gauge boson. The most conservative bound then comes from $\ell\to\ell'+\mathrm{inv}$, but if the on-shell $X$ can decay back into leptons or photons, displaced-vertex searches could give much better limits. We show that only a narrow region in parameter space allows for displaced vertices in muon decays, $μ\to e X, X\to γγ, ee$, whereas tauon decays can have much more interesti…
We assess the status of past and future experiments on lepton flavor violating (LFV) muon and tau decays into a light, invisible, axion-like particle (ALP), $a$. We propose a new experimental setup for MEG II, the MEGII-fwd, with a forward calorimeter placed downstream from the muon stopping target. Searching for $μ\to e a$ decays MEGII-fwd is maximally sensitive to LFV ALPs, if these have nonzero couplings to right-handed leptons. The experimental set-up suppresses the (left-handed) Standard Model background in the forward direction by controlling the polarization purity of the muon beam. The…
