Electrical and mechanical properties of Bi-2223/Ag tapes made by TIRT technique

Multi-core Bi-2223/Ag tapes with various number of filaments (21–162), different filament architecture and their changing orientation to the tape plane have been made by the tape-in-rectangular tube (TIRT) process. The transport current properties of TIRT tape samples with “parallel” and “perpendicular” filaments have been measured. The transversal Ic distribution obtained by spatially resolved transport measurements (“magnetic knife”) measurement illustrates that filament quality of TIRT tapes is better at the tape edges as in its centre. The Ic degradation due to bending shows a different behaviour for parallel and perpendicular filaments which is attributed to the difference in filament density and crack propagation

MesonNet 2013 International Workshop. Mini-proceedings

The mini-proceedings of the MesonNet 2013 International Workshop held in Prague from June 17th to 19th, 2013, are presented. MesonNet is a research network within EU HadronPhysics3 project (1/2012 -- 12/2014). The web page of the conference, which contains all talks, can be found at http://ipnp.mff.cuni.cz/mesonnet13Comment: 106 pages, 53 contributions. Mini-proceedings of the MesonNet 2013 International Workshop. Editors: K. Kampf, A. Kupsc, and P. Masjua

Latest Results of the OSQAR Photon Regeneration Experiment for Axion-Like Particle Search

The OSQAR photon regeneration experiment searches for pseudoscalar and scalar axion-like particles by the method of "Light Shining Through a Wall", based on the assumption that these weakly interacting sub-eV particles couple to two photons to give rise to quantum oscillations with optical photons in strong magnetic field. No excess of events has been observed, which constrains the di-photon coupling strength of both pseudoscalar and scalar particles down to $5.7 \cdot 10^{-8}$ GeV$^{-1}$ in the massless limit. This result is the most stringent constraint on the di-photon coupling strength ever achieved in laboratory experiments.Comment: 6 pages, 5 figures. appears in Proceedings of the 10th PATRAS Workshop on Axions, WIMPs and WISPs (2014

Workshop summary:Kaons@CERN 2023

Kaon physics is at a turning point – while the rare-kaon experiments NA62 and KOTO are in full swing, the end of their lifetime is approaching and the future experimental landscape needs to be defined. With HIKE, KOTO-II and LHCb-Phase-II on the table and under scrutiny, it is a very good moment in time to take stock and contemplate about the opportunities these experiments and theoretical developments provide for particle physics in the coming decade and beyond. This paper provides a compact summary of talks and discussions from the Kaons@CERN 2023 workshop, held in September 2023 at CERN

Workshop summary -- Kaons@CERN 2023

Kaon physics is at a turning point -- while the rare-kaon experiments NA62 and KOTO are in full swing, the end of their lifetime is approaching and the future experimental landscape needs to be defined. With HIKE, KOTO-II and LHCb-Phase-II on the table and under scrutiny, it is a very good moment in time to take stock and contemplate about the opportunities these experiments and theoretical developments provide for particle physics in the coming decade and beyond. This paper provides a compact summary of talks and discussions from the Kaons@CERN 2023 workshop.Comment: 54 pages, Summary of Kaons@CERN 23 workshop, references and clarifications adde

Search for π⁰ decays to invisible particles

The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson

Searches for lepton number violating K+ decays

The NA62 experiment at CERN reports a search for the lepton number violating decays K+→π−e+e+ and K+→π−μ+μ+ using a data sample collected in 2017. No signals are observed, and upper limits on the branching fractions of these decays of 2.2 x 10^-10 and 4.2 x 10^-11 are obtained, respectively, at 90% confidence level. These upper limits improve on previously reported measurements by factors of 3 and 2, respectively

Recent results in kaon physics

A review of the present experimental status of the K → πνν (Kπνν) and other kaon decay analyses at experiments NA62 (CERN) and KOTO (J-PARC) is given. The Kπνν decay is one of the best candidates among the rare meson decays for indirect searches for new physics in the mass ranges complementary to those accessible by current accelerators. The Standard Model (SM) prediction of the branching fraction (B) of the Kπνν decay is lower than 10−10 in both neutral and charged modes. The NA62 experiment aims to measure the B of the charged mode with better than 10% precision. Three candidate events, compatible with the SM prediction, have been observed from a sample of 2.12×1012 K+ decays collected in 2016 and 2017 by NA62. More than twice the statistics is available in the 2018 dataset currently being analysed. The KOTO experiment in Japan aims to measure B(KL → π0νν) using a technique similar to NA62, but with much lower momentum. In the first dataset taken in 2015 zero signal candidate events were observed. The current status of the analysis of the 2016-2018 dataset with 1.4 times more data is presented. Finally, the most recent results of other physics analyses at the NA62 experiment are summarised

Measurement of the very rare K + → π+νν¯ decay

The NA62 experiment reports the branching ratio measurement BR(K+→π+νν¯)=(10.6−3.4+4.0|stat±0.9syst)×10−11 at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016–2018. This provides evidence for the very rare K+→π+νν¯ decay, observed with a significance of 3.4σ. The experiment achieves a single event sensitivity of (0.839 ± 0.054) × 10−11, corresponding to 10.0 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. This measurement is also used to set limits on BR(K+→ π+X), where X is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample