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arXiv 1705.09403hep-ph
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轻子数破坏$B$介子衰变对重-轻混合$|U_{μN}|^2$的灵敏度极限

Sensitivity limits on heavy-light mixing $|U_{μN}|^2$ from lepton number violating $B$ meson decays

Gorazd Cvetic, C. S. Kim

备注：
revtex, 20 pages, 6 figures; v4: typos in Eqs.(10), (11) and (17b) corrected; the correct expressions had been used in calculations, results unchanged
发表信息：
Phys. Rev. D 96, 035025 (2017)
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摘要：

我们考虑了LHCb和Belle-Ⅱ实验中可能探测到的轻子数破坏衰变$B \to μ^{\pm} μ^{\pm} π^{\mp}$和$B \to D^{(*)} μ^{\pm} μ^{\pm} π^{\mp}$，以及Belle-Ⅱ实验中可能探测到的$B \to μ^{\pm} μ^{\pm} e^{\mp} ν$和$B \to D^{(*)} μ^{\pm} μ^{\pm} e^{\mp} ν$衰变。预计产生的$B$介子总数是LHCb升级的$4.8 \times 10^{12}$和Belle-II的$5 \times 10^{10}$。在上述衰变未被探测到的情况下，我们导出了重无菌中微子与亚电子伏轻中微子混合参数$|U_{μN}|^2$的新的上界（灵敏度极限），它是$1.75 \ {\rm GeV} < M_N < 5.0 \ {\rm GeV}$区间内无菌中微子质量的函数.我们考虑到探测器内的无菌中微子$N$衰变的概率，作为有效的探测器长度$L=2.3 \ m$在LCHb升级和$L=1 \ m$在Belle-II。在区间$1.75 \ {\rm GeV} < M_N < 3 \ {\rm GeV}$中，最严格的界限可以用LHCb升级时的衰变$B \to μ^{\pm} μ^{\pm} π^{\mp}$来获得。LHCb升级的灵敏度极限一般比Belle-II更严格，主要是因为LHCb升级中产生的$B$介子的数量预计比Belle-II大大约两个数量级。我们的结论是，LHCb升级和Belle-II实验有可能找到一个新的重马约拉纳中微子$N$，或显着提高灵敏度限制（上限）的重轻混合参数$|U_{μN}|^2$，特别是在质量范围$1.75 \ {\rm GeV} < M_N < 3 \ {\rm GeV}$。这项工作是我们以前关于这个问题的工作的继续和改进[1]。

英文摘要：

We consider the lepton number violating decays $B \to μ^{\pm} μ^{\pm} π^{\mp}$ and $B \to D^{(*)} μ^{\pm} μ^{\pm} π^{\mp}$ which may be detected at LHCb and Belle-II experiments; and $B \to μ^{\pm} μ^{\pm} e^{\mp} ν$ and $B \to D^{(*)} μ^{\pm} μ^{\pm} e^{\mp} ν$ decays which may be detected at Belle-II experiment. The projected total number of produced $B$ mesons is $4.8 \times 10^{12}$ at LHCb upgrade and $5 \times 10^{10}$ at Belle-II. For the case that the above decays are not detected, we deduce the new upper bounds (sensitivity limits) for the mixing parameter $|U_{μN}|^2$ of heavy sterile neutrino with sub-eV light neutrino, as a function of the sterile neutrino mass in the interval $1.75 \ {\rm GeV} < M_N < 5.0 \ {\rm GeV}$. We take into account the probability of decay of the sterile neutrino $N$ within the detector, taking as the effective detector length $L=2.3 \ m$ at LCHb upgrade and $L=1 \ m$ at Belle-II. In the interval $1.75 \ {\rm GeV} < M_N < 3 \ {\rm GeV}$, the most stringent bounds can be obtained with the decays $B \to μ^{\pm} μ^{\pm} π^{\mp}$ at LHCb upgrade. The sensitivity limits are expected to be in general more stringent at LHCb upgrade than at Belle-II, principally because the number of produced $B$ mesons in LHCb upgrade is expected to be by about two orders of magnitude larger than at Belle-II. We conclude that the LHCb upgrade and Belle-II experiments have the potential to either find a new heavy Majorana neutrino $N$, or to improve significantly the sensitivity limits (upper bounds) on the heavy-light mixing parameter $|U_{μN}|^2$, particularly in the mass range $1.75 \ {\rm GeV} < M_N < 3 \ {\rm GeV}$. This work is a continuation and refinement of our previous work [1] on the subject.

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