追踪FCC-he中异常的$tqg$和$tqγ$风味变化相互作用
Tracing the anomalous $tqg$ and $tqγ$ flavor changing interactions at the FCC-he
摘要：
在质子-电子模式下，研究了在未来圆形对撞机上通过$e^-p\to e^-tj$过程的顶夸克与胶子和光子的变味中性流（FCNC）耦合.专注于解开可能存在的不同耦合的影响，我们利用散射电子的存在，其角分布是敏感的耦合类型。通过衰变轻子的角分布获得的顶夸克极化为识别耦合的性质提供了额外的处理。此外，我们还证明了电子束极化在区分胶子和光子的左手和右手耦合方面的潜力。考虑到在2 ab $^{-1}$积分光度下，束流能量为$E_{e(p)} = 60~(50000)$ ~GeV的$e^-p$对撞机，耦合可以在$10^{-2}$水平上与相应的${\rm BR}(t\to uγ)\le 4 - 7 \times 10^{-6}$和${\rm BR}(t\to cγ) \le 1-2 \times 10^{-5}$分支分数进行探测，这取决于耦合是右手还是左手。胶子耦合的相应极限导致了${\rm BR}(t\to ug)\le 1.7 \times 10^{-5}$和${\rm BR}(t\to cg) \le 3-4 \times 10^{-5}$。
英文摘要：
We investigate the possible presence of Flavor Changing Neutral Current (FCNC) couplings of the top quark with gluon and photon through $e^-p\to e^-tj$ process at the Future Circular Collider in the proton-electron mode (FCC-he). Focusing on disentangling the effects of different couplings that could be present, we exploit the presence of the scattered electron, the angular distribution of which is sensitive to the type of coupling involved. Top quark polarisation accessed through the angular distribution of the decay lepton provides additional handle in identifying the nature of the couplings. Further, we demonstrate the potential of electron beam polarisation in distinguishing the left-handed and right-handed couplings of both gluon and photon separately. Considering an $e^-p$ collider of beam energies of $E_{e(p)} = 60~(50000)$~GeV at 2~ab$^{-1}$ integrated luminosity, couplings can be probed at the level of $10^{-2}$ with the corresponding branching fractions of ${\rm BR}(t\to uγ)\le 4 - 7 \times 10^{-6}$ and ${\rm BR}(t\to cγ) \le 1-2 \times 10^{-5}$, depending on if the coupling is right-handed or left-handed. The corresponding limits on the gluon couplings lead to ${\rm BR}(t\to ug)\le 1.7 \times 10^{-5}$ and ${\rm BR}(t\to cg) \le 3-4 \times 10^{-5}$.
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