Engineering topics

Dalpiaz, P.

Publications and source records attributed to Dalpiaz, P..

5 records

DOE OSTI2024

Development of a new CEDAR for kaon identification at the NA62 experiment at CERN

The NA62 experiment at CERN utilises a differential Cherenkov counter with achromatic ring focus (CEDAR) for tagging kaons within an unseparated monochromatic beam of charged hadrons. The CEDAR-H detector was developed to minimise the amount of material in the path of the beam by using hydrogen gas as the radiator medium. The detector was shown to satisfy the kaon tagging requirements in a test-beam before installation and commissioning at the experiment. The CEDAR-H performance was measured using NA62 data collected in 2023.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2024

First observation and study of the $K^± → π^0π^0μ^±ν$ decay

The NA48/2 experiment at CERN reports the first observation of the $K^± → π^0π^0μ^±$ν decay based on a sample of 2437 candidates with 15% background contamination collected in 2003–2004. The decay branching ratio in the kinematic region of the squared dilepton mass above 0.03 GeV 2 /c 4 is measured to be (0.65 ± 0.03) × 10 –6 . The extrapolation to the full kinematic space, using a specific model, is found to be (3.45 ± 0.16) × 10 –6 , in agreement with chiral perturbation theory predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Measurement of the $K^{+} → π^{+} γγ$ decay

A sample of 3984 candidates of the $K^{+} → π^{+} γγ$ decay, with an estimated background of 291 ± 14 events, was collected by the NA62 experiment at CERN during 2017–2018. In order to describe the observed di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be (9.61 ± 0.17) x 10 -7 . The first search for production and prompt decay of an axion-like particle with gluon coupling in the process $K^{+} → π^{+} a$, $a → γγ$ is also reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Improved calorimetric particle identification in NA62 using machine learning techniques

Measurement of the ultra-rare $K^+$ → $π$ +$ν$$\overline{ν}$ decay at the NA62 experiment at CERN requires high-performance particle identification to distinguish muons from pions. Calorimetric identification currently in use, based on a boosted decision tree algorithm, achieves a muon misidentification probability of 1.2×10 -5 for a pion identification efficiency of 75% in the momentum range of 15–40 GeV/c. In this work, calorimetric identification performance is improved by developing an algorithm based on a convolutional neural network classifier augmented by a filter. Muon misidentification probability is reduced by a factor of six with respect to the current value for a fixed pion-identification efficiency of 75%. Alternatively, pion identification efficiency is improved from 72% to 91% for a fixed muon misidentification probability of 10 -5 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2023

Search for K + decays into the π + e + e - e + e - final state

The first search for ultra-rare K + decays into the π + e + e - e + e - final state is reported, using a dataset collected by the NA62 experiment at CERN in 2017–2018. An upper limit of 1.4 x 10 -8 at 90% CL is obtained for the branching ratio of the K + → π + e + e - e + e - decay, predicted in the Standard Model to be (7.2 ± 0.7) x 10 -11 . Upper limits at 90% CL are obtained at the level of 10 -9 for the branching ratios of two prompt decay chains involving pair-production of hidden-sector mediators: K + → π + aa,a → e + e - and K + → π + S,S → A'A',A' → e + e - .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗