Optimization of tracker configuration for the CEPC

TL;DR

This paper optimizes the tracker configuration for the CEPC collider, balancing cost and resolution for various physics channels, and finds that optimal radii vary with the specific measurement goals and particle distributions.

Contribution

It introduces a method to determine the optimal tracker radius for the CEPC based on resolution and cost constraints, considering different physics channels.

Findings

Optimal tracker radii range from 1.59m to 1.97m depending on the resolution goal.

Tracks prefer smaller radii and longer lengths due to resolution degradation in the forward region.

The optimal configuration shows weak dependence on construction cost variations.

Abstract

We investigate the tracker configuration optimization for the Circular Electron Position Collider (CEPC), a proposed Higgs and $Z$ factory. Fixing the construction cost comparable to that of the baseline detector design and considering the benchmark channels ($Z\rightarrow f\bar{f}$, $WW$ fusion with $H\rightarrow f\bar{f}$, $ZH\rightarrow\nu\bar{\nu}f\bar{f}$, and $t\bar{t}\rightarrow b\bar{b}\mu\nu_\mu ud$) of various operating modes of the CEPC, we obtain the optimal tracker radius that provides the best average resolution of the track momentum or jet energy. The optimal tracker radii for track momentum resolution range from 1.59\,m to 1.73\,m and for jet energy resolution from 1.82\,m to 1.97\,m, depending on the benchmark channels. Compared to the jets, the tracks prefer a smaller radius and a longer length because the track momentum resolution degrades more significantly than jet energy resolution in the forward region. The benchmark channel for $Z$-pole prefers a smaller radius and longer length compared to other benchmark channels because the final state particles at the $Z$-pole have a more forward distribution. We also analyze the scaling behavior of the optimal tracker configuration at floating construction cost and observe a weak dependence.