论文标题
稀有衰减$ t \ tocγγ$通过标量leptoquark Doublets
Rare decay $t\to cγγ$ via scalar leptoquark doublets
论文作者
论文摘要
一环对稀有三体风味变化的中性最高夸克decay $ t \ tocγγ$的计算在具有一个或多个标量leptoquark $ su（2）$ doublets的框架中显示了$ 7/6 $。 passarino-veltman积分系数以$ f_ {i，j} $ a Lepton或Quark的形式表示通用衰减$ f_i \ forf_jγγ$不变振幅的分析表达式，从中，从中，$ t \ to complanino-veltman Integral系数从中提供了$ t \ tocγ$和$ \ ell_ el ell的振幅。在场景中，对当前对参数空间的约束进行了分析，只有一个标量LQ DOBLET和LQ耦合的界限是从Muon $ G-2 $异常中获得的，这是LEP $ G-2 $异常，LEPTON风味（LFV）衰减$τ\τ\ toμγ$，以及在理论和实验数据之间避免了toμpodinection和其他约束。对于一个质量为$ 1 $ - $ 1.5 $ tevs的LQ，估计$ {\ rm br}（t \ t \ tocγγ）\ sim 10^{ - 11} $ - $ 10^{ - 12} $是为最大的lq coupling常数的最大允许值而获得的，这意味着该延迟的实验，这意味着未来的实验。我们还考虑了一个带有三个标量双线的方案，最近提议解释$ b $衰减中的Lepton风味普遍性异常以及Muon $ G-2 $异常。尽管这种情况允许向Tau Lepton和$ c $和$ t $ Quarks进行大型LQ耦合，但$ T \与Cγγ$衰减的分支比率也为$ 10^{ - 11} $ - $ 10} $ - $ 10^{ - 12} $ 1.7 TEV的LQ质量。
A calculation of the one-loop contribution to the rare three-body flavor changing neutral current top quark decay $t\to cγγ$ is presented in the framework of models with one or more scalar leptoquark $SU(2)$ doublets with hypercharge $7/6$. Analytical expressions for the invariant amplitude of the generic decay $f_i\to f_jγγ$, with $f_{i,j}$ a lepton or quark, are presented in terms of Passarino-Veltman integral coefficients, from which the amplitudes for the processes $t\to cγγ$ and $\ell_i\to \ell_jγγ$ follow easily. An analysis of the current constraints on the parameter space is presented in the scenario with only one scalar LQ doublet and bounds on the LQ couplings are obtained from the muon $g-2$ anomaly, the lepton flavor violating (LFV) decay $τ\to μγ$ and extra constraints meant to avoid tension between theory predictions and experimental data. For a LQ with a mass in the range of $1$--$1.5$ TeVs, the estimate ${\rm Br}(t\to cγγ)\sim 10^{-11}$--$10^{-12}$ is obtained for the largest allowed values of the LQ coupling constants, which means that this decay would be below the reach of future experimental measurements. We also consider an scenario with three scalar doublets, which was recently proposed to explain the lepton flavor universality violation anomalies in $B$ decays as well as the muon $g-2$ anomaly. Although this scenario allows large LQ couplings to the tau lepton and the $c$ and $t$ quarks, the branching ratio of the $t\to cγγ$ decay is also of the order of $10^{-11}$--$10^{-12}$ for LQ masses of 1.7 TeV.
