论文标题
期待Lepton-Fravor-volviolation Alps
Looking forward to Lepton-flavor-violating ALPs
论文作者
论文摘要
我们评估了过去和将来的违反Lepton风味（LFV）MUON和TAU衰减的状态，变成了无形的，无形的轴颗粒（ALP），$ a $。我们为MEGI II（MEGII-FWD）提出了一个新的实验设置，并在MUON停止目标的下游放置了前向量热计。如果$μ\ to a $衰减MEGII-FWD对LFV Alps具有最大敏感性，如果它们与右手lept子具有非零耦合。实验设置通过控制MUON光束的极化纯度来抑制（左手）标准模型背景。将MEGII-FWD的覆盖范围与目前的限制进行了比较，Mu3e和Belle-II的触及范围从$τ\ to \ ell A衰减。我们表明，在MEG II和MU3E中，针对LFV MUON衰减的专门实验运动将能够探究未探索区域的ALP参数空间，远远超出了现有的天体物理约束。我们研究了这些搜索代表性LFV ALP模型的含义，其中光ALP的存在是由中微子质量，强大的CP问题和/或SM风味拼图激励的。在此范围内，我们在低规模的Seesaw设置中讨论了Majoron，并引入了LFV QCD轴，LFV Axiflavon和Leptonic Familon，特别注意LFV Alps构成冷暗物质的情况。
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 reach of MEGII-fwd is compared with the present constraints, the reach of Mu3e and the Belle-II reach from $τ\to \ell a$ decays. We show that a dedicated experimental campaign for LFV muon decays into ALPs at MEG II and Mu3e will be able to probe the ALP parameter space in an unexplored region well beyond the existing astrophysical constraints. We study the implications of these searches for representative LFV ALP models, where the presence of a light ALP is motivated by neutrino masses, the strong CP problem and/or the SM flavor puzzle. To this extent we discuss the majoron in low-scale seesaw setups and introduce the LFV QCD axion, the LFV axiflavon and the leptonic familon, paying particular attention to the cases where the LFV ALPs constitute cold dark matter.
