Searching for displaced vertices with a gaseous tracker for a future e$^+$e$^-$ Higgs factory

TL;DR

This study investigates the detection of long-lived particles at a future electron-positron collider using a gaseous tracker, demonstrating potential for observing displaced vertices across various lifetimes and challenging scenarios.

Contribution

It provides the first full simulation analysis of LLP detection prospects with the ILD detector at the ILC, focusing on displaced vertex signatures in a gaseous TPC.

Findings

Expected limits on LLP production cross section across a wide lifetime range.

Feasibility of detecting displaced vertices for soft and highly boosted LLP scenarios.

Demonstration of the gaseous tracker’s capability for LLP searches.

Abstract

This paper presents results of the first full simulation study addressing prospects for observation of long-lived particles (LLPs) with the International Large Detector (ILD), operating at the International Linear Collider (ILC) at $\sqrt{s}=250$ GeV. Neutral LLP production, resulting in a displaced vertex signature inside the ILD's time projection chamber (TPC), is considered. We focus on scenarios interesting from the experimental perspective and perform a search based on displaced vertex finding inside the TPC volume. Two experimentally challenging scenarios are explored: the first involving very soft final states due to a small mass splitting between a heavy LLP and the dark matter particle to which it decays, and the second with production of a light and therefore highly boosted LLP resulting in almost colinear vertex tracks. The expected limits on the signal production cross section are presented for a wide range of the LLP proper lifetimes corresponding to $c\tau$ from 0.1 mm to 10 km.