论文标题
A $ u $ - Spin Anomaly in Charm CP违规
A $U$-Spin Anomaly in Charm CP Violation
论文作者
论文摘要
最近的LHCB数据表明，衰减模式的直接CP不对称$ d^0 \rightArrowπ^+π^ - $和$ d^0 \ rightArrow k^+k^ - $具有相同的符号，违反了一条即兴的$ u $ -U $ -SPIN限制限制规则，以出乎意料的方式以2.1美元的价格为$ 2.1美元。从新数据中，我们首次确定CKM出版的假想部分，$ u $ -spin Breaking $ΔU= 1 $校正对$ u $ -spin limit lim $ΔU= 0 $ applitude。 $ΔU= 0 $振幅的假想部分由$ΔA_{cp}^{\ mathrm {dir}} $确定。相应的强阶段尚不清楚，将来可以通过时间依赖性测量结果提取。假设$ \ Mathcal {o}（1）由于非扰动剥离而导致$ stront阶段，我们发现$ u $ -spin的比率损坏了$ u $ -spin的限制限制对ckm-subleading振幅的贡献为$（173^{+85} _ {+85} _ { - 74}）$ $ $ $ $ $ $。这大大超过了$ \ sim 30 \％$ $ $ u $ -u $ -spin破裂的标准模型（SM）期望，其显着性为$1.95σ$。如果将来用更多数据确认了这个难题，则在SM中，这将暗示$ u $ -spin扩展在CKM出版的魅力衰减振幅中的细分。另一个解决方案是新的物理模型，它们会产生额外的$ΔU= 1 $运算符，而$ u $ -spin功率扩展完整。后者选项的示例是扩展标量扇区或美味的$ z'$型号。
Recent LHCb data shows that the direct CP asymmetries of the decay modes $D^0\rightarrow π^+π^-$ and $D^0\rightarrow K^+K^-$ have the same sign, violating an improved $U$-spin limit sum rule in an unexpected way at $2.1σ$. From the new data, we determine for the first time the imaginary part of the CKM-subleading, $U$-spin breaking $ΔU=1$ correction to the $U$-spin limit $ΔU=0$ amplitude. The imaginary part of the $ΔU=0$ amplitude is determined by $Δa_{CP}^{\mathrm{dir}}$. The corresponding strong phases are yet unknown and could be extracted in the future from time-dependent measurements. Assuming $\mathcal{O}(1)$ strong phases due to non-perturbative rescattering, we find the ratio of $U$-spin breaking to $U$-spin limit contributions to the CKM-subleading amplitudes to be $(173^{+85}_{-74})\%$. This highly exceeds the Standard Model (SM) expectation of $\sim 30\%$ $U$-spin breaking, with a significance of $1.95σ$. If this puzzle is confirmed with more data in the future, in the SM it would imply the breakdown of the $U$-spin expansion in CKM-subleading amplitudes of charm decays. The other solution are new physics models that generate an additional $ΔU=1$ operator, leaving the $U$-spin power expansion intact. Examples for the latter option are an extended scalar sector or flavorful $Z'$ models.
