Probe Anomalous $tq\gamma$ couplings through Single Top Photoproduction at the LHC

Abstract

In this work we study the constraints on the anomalous $tq\gamma$ ($q=u$, $c$) couplings by photon-produced leading single top production and single top jet associated production through the main reaction $pp\to p\gamma p\to pt\to pW(\to \ell {\nu }_{\ell })b+X$ and $pp\to p\gamma p\to ptj\to pW(\to \ell {\nu }_{\ell })bj+X$ assuming a typical LHC multipurpose forward detectors in a model independent effective lagrangian approach. Our results show that: for the typical detector acceptance $0.0015<{\xi }_1<0.5$, $0.1<{\xi }_2<0.5$ and $0.0015<{\xi }_3<0.15$ with a luminosity of 2 ${\mathrm{fb}}^{-1}$, the lower bounds of ${\kappa }_{tq\gamma }$ through leading single top channel (single top jet channel) are 0.0096 (0.0115), 0.0162 (0.0152) and 0.0098 (0.0122), respectively, correspond to $\mathrm{Br}(\mathrm{t}\to \mathrm{q}\gamma )\sim 3\times 10^{-5}$. With a luminosity of 200 ${\mathrm{fb}}^{-1}$, the lower bounds of ${\kappa }_{tq\gamma }$ are 0.0031 (0.0034), 0.0051 (0.0047) and 0.0031(0.0038), respectively, correspond to $\mathrm{Br}(\mathrm{t}\to \mathrm{q}\gamma )\sim 4\times 10^{-6}$. We conclude that both channels can be used to detect such anomalous $tq\gamma$ couplings and the detection sensitivity on ${\kappa }_{tq\gamma }$ can be improved.

Comments: 37pages, 10 figures, 6 tables, to appear in Nuclear Physics B