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Charged and neutral kaons are formed by impact of pulsed lasers on ultra-dense hydrogen H(0). This superfluid material H(0) consists of clusters of various forms, mainly of the chain-cluster type H2N. Such clusters are not stable above the transition temperature from superfluid to normal matter. In the case studied here, this transition is at 525 K for D(0) on an Ir target, as reported previously. Mesons are formed both below and above this temperature. Thus, the meson formation is not related to the long chain-clusters H2N but to the small non-superfluid cluster types H3(0) and H4(0) which still exist on the target above the transition temperature. The nuclear processes forming the kaons take place in such clusters when they are transferred to the lowest s = 1 state with H-H distance of 0.56 pm. At this short distance, nuclear processes are expected within 1 ns. The superfluid chain-cluster phase probably has no direct importance for the nuclear processes. The clusters where the nuclear processes in H(0) take place are thus quite accurately identified. [ABSTRACT FROM AUTHOR]

A large-acceptance spectrometer, Neutral Kaon Spectrometer 2 (NKS2), was newly constructed to explore various photoproduction reactions in the gigaelectronvolt region at the Laboratory of Nuclear Science (LNS, currently ELPH), Tohoku University. The spectrometer consisted of a dipole magnet, drift chambers, and plastic scintillation counters. NKS2 was designed to separate pions and protons in a momentum range of less than 1 GeV/ c , and was placed in a tagged photon beamline. A cryogenic H 2 /D 2 target fitted to the spectrometer were designed. The design and performance of the detectors are described. The results of the NKS2 experiment on analyzing strangeness photoproduction data using a 0.8–1.1 GeV tagged photon beam are also presented. [ABSTRACT FROM AUTHOR]

The KOTO experiment at J-PARC, Japan, aims to observe the rare neutral kaon decay mode KL\rightarrow \pi ^{0}\nu \bar {\nu } . After the first experimental run in May 2013 at a 24-kW beam power, the KOTO data acquisition (DAQ) system was upgraded in 2015 to provide efficient and reliable data collection at higher beam intensities. Lossless data compression in the analog-to-digital converter modules was implemented to reduce the size of data packets, resulting in a threefold increase in data collection rate. A new software trigger on a 47-node cluster was designed to use Infiniband hardware with message passing interface protocol to establish a mesh network inside the computer clusters for parallel data processing. The upgrade to the KOTO DAQ system was commissioned in 2015 and successfully collected data with a beam intensity of up to 42 kW. In preparation for increasing beam intensities in future runs, the hardware trigger upgrades using the reconfigurable clustering element platform technology are under development. [ABSTRACT FROM AUTHOR]

A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D 0 → K − K + is performed using pp collision data, corresponding to an integrated luminosity of 3 fb − 1 , collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The flavour of the charm meson at production is determined from the charge of the pion in D ⁎ + → D 0 π + and D ⁎ − → D ‾ 0 π − decays. The time-integrated CP asymmetry A CP ( K − K + ) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D 0 → K − π + , D + → K − π + π + and D + → K ‾ 0 π + decays used as calibration channels. It is found to be A CP ( K − K + ) = ( 0.14 ± 0.15 (stat) ± 0.10 (syst) ) % . A combination of this result with previous LHCb measurements yields A CP ( K − K + ) = ( 0.04 ± 0.12 (stat) ± 0.10 (syst) ) % , A CP ( π − π + ) = ( 0.07 ± 0.14 (stat) ± 0.11 (syst) ) % . These are the most precise measurements from a single experiment. The result for A CP ( K − K + ) is the most precise determination of a time-integrated CP asymmetry in the charm sector to date, and neither measurement shows evidence of CP asymmetry. [ABSTRACT FROM AUTHOR]

We compute the hadronic matrix elements of the four-quark operators relevant for $$ {K}^0-{\overline{K}}^0 $$ mixing beyond the Standard Model. Our results are from lattice QCD simulations with n = 2 + 1 flavours of domain-wall fermion, which exhibit continuum-like chiral-flavour symmetry. The simulations are performed at two different values of the lattice spacing ( a ∼ 0 .08 and a ∼ 0 .11 fm) and with lightest unitary pion mass ∼ 300 MeV. For the first time, the full set of relevant four-quark operators is renormalised non-perturbatively through RI-SMOM schemes; a detailed description of the renormalisation procedure is presented in a companion paper. We argue that the intermediate renormalisation scheme is responsible for the discrepancies found by different collaborations. We also study different normalisations and determine the matrix elements of the relevant four-quark operators with a precision of ∼ 5% or better. [ABSTRACT FROM AUTHOR]

In quantum mechanics, the measurer (subject) plays important roles influencing the state of an object under experimental observation. That implies the necessity of inclusion of the subject (observers) at the moment of observation in the final theory. What is "the observer" that makes the state of object jump into one of the eigenstates? By observing the observer at the moment of observation phenomenologically, we find that there exists a state of observers which is common, at the moment of observation, to all observers and which may be described by physics terminologies such as vacuum and ground state in extended sense to other fields of science. This state of observers satisfies the requirements of the universality and reproducibility which are necessary for any object studied in physics. Taking the entangled two neutral kaons as an example, we show how it could be included in quantum mechanics. [ABSTRACT FROM AUTHOR]

The KLOE experiment at the DAΦNE ϕ-factory performed precise studies of charged and neutral kaon physics, low energy QCD, as well as tests of CP and CPT invariance. For the new run, the KLOE has been upgraded by adding new tagger systems for the γ γ physics, the inner tracking chamber and two calorimeters in the final focusing region. We are also improving on kaon identification techniques, in particular algorithms for the KS meson tagging. In this article, we discuss the impact of the improved tagging procedure on studies of the KS decays. [ABSTRACT FROM AUTHOR]