Würzburg 2018 – scientific programme

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T: Fachverband Teilchenphysik

T 88: Flavor Physik III

T 88.7: Talk

Thursday, March 22, 2018, 18:00–18:15, Z6 - SR 2.006

Photon rejection at the NA62 experiment for the measurement of K⁺ → π⁺ ν ν and the search for π⁰ → invisible decays — •Letizia Peruzzo — Johannes Gutenberg University Mainz

In September 2016 the NA62 experiment at CERN began its physics data taking to collect in three years around 100 K⁺→π⁺νν events and measure the branching ratio with a precision of about 10%.
Well predicted inside the Standard Model, BR(K⁺→π⁺νν)=(8.4±1.0)·10⁻¹¹, this decay is closely related to the CKM matrix elements |V_td| and |V_ts| and any deviation from the theoretical branching ratio would be a clear sign of physics beyond the Standard Model.
The suppression of the main K⁺ decays, which have branching fractions several orders of magnitude higher than the K⁺→π⁺νν signal, is crucial for the success of NA62. A rejection power of 10⁻¹² on the decay K⁺ → π⁺ π⁰ (BR∼21%) is required using kinematic O(10⁻⁴) and π⁰ rejection O(10⁻⁸).
A direct spin-off of the K⁺→π⁺νν measurement is the search for the decay π⁰→ invisible where the π⁰ is tagged by K⁺→π⁺π⁰ decays. The same signature of π⁰→ invisible with respect to the K⁺→π⁺νν signal allows to perform the two measurements using the same dataset and analysis.
This talk describes the analysis of the photon rejection using the NA62 data collected in 2016.