1. NLO EW corrections to tau pair production via photon fusion in Pb-Pb ultraperipheral collision
- Author
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Jiang, Jun, Lu, Peng-Cheng, Si, Zong-Guo, Zhang, Han, and Zhang, Xin-Yi
- Subjects
High Energy Physics - Phenomenology - Abstract
We study the next-to-leading order (NLO) electroweak (EW) corrections to the $\gamma \gamma \to \tau^+ \tau^-$ process in Pb-Pb ultraperipheral collision (UPC). We find that the EW correction $\delta \sigma_{\mathrm{EW}}$ decreases the total cross section $\sigma_{\mathrm{NLO}} = \sigma_{\mathrm{LO}} + \delta \sigma_{\mathrm{EW}}$ by -3% at Pb-Pb center-of-mass energy $\sqrt{s_{NN}}=5.02$ TeV. The weak correction plays significant role whose contribution is about -4 times of that of QED. The CMS and ATLAS collaborations use the reaction $\gamma\gamma \to \tau^+ \tau^-$ in Pb-Pb and proton-proton UPC to constrain tau's anomalous magnetic moment $a_\tau$. By parameterizing the $\gamma \tau \tau$ vertex with two form factors $F_{1,2}$, the cross section can be written as $\sigma_{a_\tau} = \sigma_{\mathrm{LO}} + \delta \sigma_{a_\tau}$, where $\delta \sigma_{a_\tau}$ is proportional to $a_\tau$. Under this $F_{1,2}$ parametrization scheme, it is found that there is some deviation between the NLO EW correction $\delta \sigma_{\mathrm{EW}}$ and $\delta \sigma_{a_\tau}$ which is derived either by the CMS constraint range on $a_\tau$ or from the precise SM prediction of $a_\tau$. We also find that various differential distributions of the two ratios $\mathrm{d} \sigma_{\mathrm{NLO}}/ \mathrm{d} \sigma_{\mathrm{LO}}$ and $\mathrm{d} \sigma_{a_\tau}/ \mathrm{d} \sigma_{\mathrm{LO}}$ have different lineshapes. This work is significant to precisely study the interaction of $\gamma \tau \tau$ via $\gamma \gamma \to \tau^+ \tau^-$ process., Comment: 18 pages, 6 figures
- Published
- 2024