论文标题
异常和偶然对称性：在$L_μ$-L_τ$下为标量leptoquark充电
Anomalies and accidental symmetries: charging the scalar leptoquark under $L_μ$-$L_τ$
论文作者
论文摘要
尽管$ S_3 $标量leptoquark提出了$ b \ to s \ ell \ ell $ floes Anomalies的可能的树级解释，但它遇到了两个概念性问题，通常被模型建造者忽略了。首先，$ s_3 $的量子数允许可renormalissable的diquark运算符，该二夸克操作员将触发快速质子衰变，除非将其耦合调出。其次，人们期望Leptoquark与Leptons具有通用的耦合，这需要调整以避免在违反Lepton风味的情况下进行严格的实验界限。通过测量$ u（1）$当前在标准型号（SM）费米子上充当$l_μ-l_τ$的电流，并且在该型号的leptoquark符合$ -1 $的情况下，人们可以解决这两个问题。额外的$ u（1）$在某种程度上自发折断，与巨大的$ z^\ prime $量表玻色子和标量sm singlet $φ$相关，在介导异常$ b $ erson衰减方面没有任何直接作用。通过计算一环质量校正，我们表明这对颗粒可以在更高的质量尺度上隐藏，而不会破坏希格（Higgs）或leptoquark质量。因此，测量$l_μ-l_τ$的唯一低能遗物是Lagrangian的意外全局对称结构。另一方面，我们通常发现，将$ b \介导为s \ ell \ ell $ $异常的$ S_3 $ leptoquark不能比几个TEV重得多，而不会诱导大型Higgs质量校正。
While the $S_3$ scalar leptoquark presents a possible tree-level explanation of the $b \to s \ell \ell$ flavour anomalies, it suffers from two conceptual problems which are often disregarded by model-builders. Firstly, the quantum numbers of the $S_3$ allow for a renormalisable diquark operator that would trigger rapid proton decay unless its coupling were tuned away. Secondly, one expects the leptoquark to have generic couplings to leptons, which require tuning to avoid stringent experimental bounds on lepton flavour violation. By gauging a $U(1)$ current that acts as $L_μ- L_τ$ on the Standard Model (SM) fermions, and under which the leptoquark has charge $-1$, one can remedy both these problems. The additional $U(1)$, which is spontaneously broken at some high scale, is associated with a massive $Z^\prime$ gauge boson and a scalar SM singlet $Φ$, which play no direct role in mediating the anomalous $B$ meson decays. By computing one- and two-loop mass corrections, we show that this pair of particles can be hidden away at much higher mass scales without destabilising either the Higgs or the leptoquark masses. The only low-energy relic of gauging $L_μ- L_τ$ is thus the accidental global symmetry structure of the lagrangian. On the other hand, we find quite generally that an $S_3$ leptoquark that mediates the $b \to s \ell \ell$ anomalies cannot be much heavier than a few TeV without itself inducing large Higgs mass corrections.
