Precise measurement of Br($K^+ \to \pi^+ \nu \bar{\nu}$) at CERN SPS

TL;DR

This paper proposes an experiment at CERN SPS to precisely measure the rare decay Br($K^+ o \pi^+ u ar{ u}$), aiming to improve CKM matrix element determination and test the Standard Model.

Contribution

It introduces a new experimental setup to measure the rare decay with high precision, enabling more accurate CKM parameter extraction.

Findings

Targeted collection of ~80 decay events within two years

Achieving a signal to background ratio of 10:1

Expected ~10% accuracy in determining $V_{td}$

Abstract

An experimental proposal to measure Br($K^+ \to \pi^+ \nu \bar{\nu}$) has been submitted at the CERN SPSC. The goal is to collect ~80 $K^+\to \pi^+ \nu \bar{\nu}$ events with signal to background ratio of 10:1 in two years of data taking. This will allow determination of the CKM parameter $V_{td}$ with ~10% accuracy.