Sensitivity measuring expected on the electromagnetic anomalous couplings in the $t\bar{t}\gamma$ vertex at the FCC-he

Abstract

In this paper, we consider the electroweak production cross-section of a single anti-top-quark, a neutrino and a photon via charged current through the $e^{-}p\to e^{-}\bar{b}\to \bar{t}{\nu }_e\gamma \to \bar{t}(\to W^{-}\to (q{q}^{\prime },l^{-}{\bar{\nu }}_l)+b){\nu }_e\gamma$ signal. Further, we derived the sensitivity expected to the magnetic dipole moment $({\hat{a}}_V)$ and the electric dipole moment $({\hat{a}}_A)$ of the top-quark at the Future Circular Collider Hadron Electron (FCC-he). We present our study for $\sqrt{s}=7.07,10TeV$, $\mathcal{L}=50,100,300,500,1000f{b}^{-1}$, ${\delta }_{sys}=0,3,5\%$ and $P_{e^{-}}=0\%,80\%,-80\%$, respectively. We find that the sensitivity estimated on dipole moments of the top-quark is of the order of magnitude $\mathcal{O}(10^{-1})$ for both hadronic and leptonic decay modes of $W^{-}$: ${\hat{a}}_V=[-0.2308,0.2204]$, $|{\hat{a}}_A|=0.2259$ at $95\%$ C.L. in the hadronic channel with unpolarized electron beam $P_{e^{-}}=0\%$. Our results with polarized electron beam for $P_{e^{-}}=80\%$ and $P_{e^{-}}=-80\%$ are ${\hat{a}}_V=[-0.3428,0.3321]$, $|{\hat{a}}_A|=0.3371$ and ${\hat{a}}_V=[-0.2041,0.1858]$, $|{\hat{a}}_A|=0.1939$ at $95\%$ C.L. in the hadronic channel. The corresponding results for the leptonic channel with $P_{e^{-}}=0\%,80\%-80\%$ are ${\hat{a}}_V=[-0.3067,0.2963]$, $|{\hat{a}}_A|=0.3019$, ${\hat{a}}_V=[-0.4563,0.4456]$, $|{\hat{a}}_A|=0.4505$ and ${\hat{a}}_V=[-0.2695,0.2512]$, $|{\hat{a}}_A|=0.2592$, respectively. The results for ${\hat{a}}_V$ and ${\hat{a}}_A$ in the leptonic channel are weaker by a factor of 0.75 than those corresponding to the hadronic channel. Given these prospective sensitivities we highlight that the FCC-he is potential top-quark factory that is particularly well suited to sensitivity study on its dipole moments and with cleaner environments.

28 pages, 10 figures and 7 tables. arXiv admin note: text overlap with arXiv:1812.08971