Optimal New Physics estimation in presence of Standard Model backgrounds

Abstract

In this work, we develop a numerical technique for the optimal estimation of the new physics (NP) couplings applicable to any collider process without any simplifying assumptions. This approach also provides a way to measure the quality of the NP estimates derived using standard $χ^2$ analysis and can be used to gauge the advantages of various modalities of collider design. We illustrate the techniques and arguments by considering the pair production of heavy charged fermions at an $e^+e^-$ collider.

Figures (7)

• Figure 1: Pair-production of heavy charged fermions ($\psi^+\psi^-$) and their subsequent decay at an $e^+ \, e^-$ collider.
• Figure 2: Normalized $\slashed{E}$ distribution (left) and $\Delta R(\ell^+\ell^-)$ (right) for signal and dominating backgrounds of the reaction in Fig. \ref{['fig:productn']}; see text for details. We assumed $\sqrt{s} = 500$ GeV, $m_{\psi^{\pm}} = 210$ GeV (consistent with LEP bound L3:2001xsz) and $m_{\psi_1} = 60$ GeV.
• Figure 3: Effects of cuts on the 1$\sigma$ surfaces for 3 different hypotheses: signal only with $\mathcal{C}_1+\mathcal{C}_2$ applied (green); and signal+background after $\mathcal{C}_1$ (light read), and $\mathcal{C}_1+\mathcal{C}_2$ (blue) -- see the text for details.
• Figure 4: Comparison of 1$\sigma$ regions between standard approach (cyan) and OOT (brown) for three different hypotheses.
• Figure 5: Comparison of 1$\sigma$ surfaces for different CM energy and beam polarization.