Search

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]

The results obtained by measuring the inclusive distributions of the Feynman variable x and the transversemomentum for the production of K mesons in proton-nucleus interactions at 70 GeV/ c for three targets (C, Si, and Pb) are presented. The mass-number ( A) dependence of the cross section for K -meson production is studied. The measured value of the exponent α in the formula σ ∼ A agrees within the errors with its counterpart at higher energies. With the aid of the A dependence, the measured yield of K mesons at x = 0 is compared with the yield of K and K mesons in the proton-proton reaction at 70 GeV/ c. The inclusive spectra of longitudinal and transverse variables for K-meson production are contrasted against the predictions of the FRITIOF and UrQMD models. [ABSTRACT FROM AUTHOR]

Abstract: At large momentum transfers the photon interacts with the charges and spins of the constituent partons in a hadron. It is expected that the neutral kaon can acquire finite electromagnetic form factors because its wave function is affected by the order of magnitude difference between the mass of the strange quark and that of the down quark, or flavor breaking. We report on the first measurement of the form factor of neutral kaons at the large timelike momentum transfer of by measuring the cross section for at using CLEO-c data with an integrated luminosity of 586 pb−1. We obtain , with a 90% C.L. interval of . This is nearly an order of magnitude smaller than , and indicates that the effect of breaking is small. In turn, this makes it unlikely that the recently observed strong violation of the pQCD prediction, , which is based on the assumption of similar wave functions for the pions and kaons, can be attributed to breaking alone. [Copyright &y& Elsevier]

Abstract: The KLOE Collaboration recently reported bounds on the directional dependence of the lifetime of the short-lived neutral kaon with respect to the dipole anisotropy of the cosmic microwave background. We interpret their results in an effective field theory framework developed to probe the violation of Lorentz invariance in the weak interaction and previously applied to semileptonic processes, in particular β decay. In this approach a general Lorentz-violating tensor is added to the standard propagator of the W boson. We perform an exploratory study of the prospects to search for Lorentz violation in nonleptonic decays. For the kaon, we find that the sensitivity to Lorentz violation is limited by the velocity of the kaons and by the extent to which hadronic effects can be calculated. In a simple model we derive the decay rate and calculate the asymmetry for the lifetime. Using the KLOE data, limits on the values of are determined. [Copyright &y& Elsevier]

Photoproduction of the neutral kaon on the deuteron has been investigated at the Research Center for Electron Photon Science, Tohoku University. We constructed the Neutral Kaon Spectrometer-2 for the detection of charged particles from the decay of the neutral kaon and the hyperon. We obtained a momentum distribution of K with the inclusive measurement. It was consistent with the previous measurement. The total cross section of γ + d → K + Λ + p was estimated from the measured integral cross section of γ + d → Λ + X. The total cross section with respect to the photon energy was compared with the theoretical calculations. It favored the Saclay-Lyon A model calculation with the ratio of the neutral to charged coupling constants of the axial-vector meson, K, as ~ −1.5. The energy dependence and the magnitude of the total cross section were similar to the total cross section of γ + p → K Λ. [ABSTRACT FROM AUTHOR]

Double charged pion photoproductions from the deuteron have been studied at Research Center for Electron Photon Science (ELPH), Tohoku University. Tagged photon beams in an energy range of 0.67 ≤ E ≤ 1.08 GeV were impinged on the liquid deuteron target. Produced charged particles were observed with the Neutral Kaon Spectrometer2 (NKS2). The γ d → π π d process was clearly separated among the three charged tracks. We obtained the photon energy dependence of the normalized yields of this process. [ABSTRACT FROM AUTHOR]

The kaon nucleus (KN) interaction in dense nuclear matter is predicted to be repulsive and increasing with density. However, determined values for this potential are not yet consistent with each other (Benabderrahmane et al., Phys Rev Lett 102:182501, ; Agakishiev et al., Phys Rev C 82:044907, ; Büscher et al., Eur Phys J A 22:301-317, ). We analyze $K^0_S$ mesons identified with the HADES detector in p+p and p+ Nb reactions at 3.5 GeV kinetic beam energy. To determine the KN potential at normal nuclear density we propose to compare the $K^0_S$ differential distributions in p+ Nb and p+p collisions. High statistics of low p-kaons ( p < 100 MeV/c) ensure the sensitivity of our measurements to the nuclear matter effects. We present the data analysis method and first results. [ABSTRACT FROM AUTHOR]

Abstract: Photoproduction of the from the deuteron and the carbon nucleus has been investigated at the Laboratory of Nuclear Science, Tohoku University in Sendai. The Neutral Kaon Spectrometer and the Neutral Kaon Spectrometer 2 were developed to detect pairs coming from the decay of the . The resulting momentum spectra for inclusive photoproduction were compared with theoretical calculations based on isobar models for , utilizing the spectator hypothesis. An upgrade of the inner detectors to enhance the acceptance for the coincidence measurement of the and Λ is underway. We expect that the exclusive and kinematically complete measurement of the reaction will provide us with direct access to the center-of-mass observables that are important for further understanding the mechanism for strangeness photoproduction. [Copyright &y& Elsevier]

Abstract: The kaon photo-production process on 12C has been studied by measuring neutral kaons in the photon energy range of 0.8–1.1 GeV. Neutral kaons were identified by the invariant mass constructed from two charged pions emitted in the decay channel. The differential and integrated cross sections in the threshold photon energy region were obtained. The obtained momentum spectra were compared with a Spectator model calculation using elementary amplitudes of kaon photo-production given by recent isobar models. The present results provide the first information on the reaction, which is expected to play an important role in constructing models of strangeness production by electromagnetic interactions. The experimental results show that the cross section of is of the same order as that of and suggest that a slightly backward angular distribution is favored in the process. [Copyright &y& Elsevier]

The KLOE-2 experiment continues and extends the program of its predecessor KLOE in the field of discrete symmetry tests with the K meson system, among other studies which comprise light meson spectroscopy, dark matter searches and γγ physics. Together, KLOE and KLOE-2 have recorded the largest sample (almost 8 fb− 1) of e+e− collisions at the energy equal to ϕ meson mass, amounting to 2.4 × 1010 of produced ϕ mesons. We report on the latest results and ongoing analyses of KLOE and KLOE-2 concerning discrete symmetry tests and measurements of symmetry-violating observables. A measurement of the CPT violation sensitive asymmetry in semileptonic decays of K˙S with 1.7 fb− 1 of KLOE data will be presented, which improves the sensitivity w.r.t. previous measurements about twice. Moreover, status of direct tests of T and CPT in transitions of neutral kaons performed with the ϕ →K˙SK˙L → πeν, 3π0(2π) processes will be reported, followed by the search of the CP-violating decay K˙S → 3π0 using the data recently acquired by KLOE-2. [ABSTRACT FROM AUTHOR]

In this paper a method to perform direct T and CPT symmetry tests is briefly discussed, exploiting the Einstein-Podolsky-Rosen correlations of neutral kaon pairs produced at a ø-factory. The KLOE-2 experiment at DAΦNE, the Frascati ø-factory, could make statistically significant tests of this type. [ABSTRACT FROM AUTHOR]