# KLEVER: An experiment to measure \boldmath{${\rm BR}(K_L \to \pi^0 \nu \overline{\nu})$} at the CERN SPS

## TL;DR

The KLEVER experiment is designed to measure the rare decay rate of $K_L$ mesons to improve understanding of CKM unitarity and search for new physics, involving detailed beamline design and background suppression simulations.

## Contribution

This paper presents the ongoing development and simulation efforts for the KLEVER experiment's beamline and target design to enable precise measurement of ${
m BR}(K_L o
u )$.

## Key findings

- Beamline adaptations are necessary from the existing K12 setup.
- Simulations indicate feasible particle flux with background suppression.
- Design considerations support future experimental measurements.

## Abstract

The KLEVER experiment aims to measure ${\rm BR}(K_L \to \pi^0 \nu \overline{\nu})$, supplementing the ongoing NA62 measurement of ${\rm BR}(K^+ \to \pi^+ \nu \overline{\nu})$, to provide new input on CKM unitarity and potentially new physics. KLEVER is undergoing continuous development, with particular efforts focused on the design of the target and the beamline. As described here, adaptations are required relative to the K12 beamline in its current format, and a series of simulations has been performed to ensure that an adequate particle flux can be achieved while simultaneously suppressing problematic backgrounds.