Search

NA62 is a new generation kaon experiment at the CERN SPS aiming at studying rare and forbidden decays. One of main challenges of the experiment is the suppression of background decay channels with branching ratios up to 10 orders of magnitude higher than the signal and with similar experimental signatures. To provide such suppression, a powerful particle identification (PID) is needed. A key element of PID in NA62 is the Ring Imaging Cherenkov (RICH) detector. The RICH has successfully operated during the 2016–2018 data taking periods, being essential in the measurement of the branching ratio of the K + → π + ν ν ̄ decay. The detector was also used for searches for lepton number violation in 3-track kaon decays. The results on the π / μ and π /e separation directly measured with the data for the aforementioned decays are presented. [ABSTRACT FROM AUTHOR]

The OKA detector is described, and recently published results of experimental searches for a heavy neutrino and investigations of the Ke3 -decay form factors are reported. Incident-beam characteristics, the detector configuration and its major subsystems, and triggering conditions are discussed. Physical motivations for these experimental studies are provided, and the event-selection procedures are briefly described. [ABSTRACT FROM AUTHOR]

NA62 is the last generation kaon experiment at CERN SPS aiming to study the decay K + → π + ν ν ¯ . The goal of the experiment is to measure the decay branching ratio, O ( 10 − 10 ) , with 10% precision collecting about 100 K + → π + ν ν ¯ events in three years of data taking and assuming a 10% signal acceptance. The weak signal and the huge background make the experiment very challenging. The NA62 detector must be able to reject background events from decay channels with branching ratios up to 10 orders of magnitude higher than the signal one and with similar experimental signature. In order to achieve the designed goal, good Particle Identification (PID), kinematic rejection and precise timing are required. The key element of the PID in NA62 is the Ring Imaging Cherenkov detector (RICH) to identify pions and muons and to measure the particle arrival time. After a pilot run in 2014, installation and commissioning of the detector were completed in 2015, when also the first physics run took place. Results on the detector performance will be presented together with preliminary results from the 2015 and 2016 physics runs. [ABSTRACT FROM AUTHOR]

The NA62 experiment recorded a large sample of K + → μ + ν μ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range 2 × 10 − 6 to 10 − 5 have been set on the squared mixing matrix element | U μ 4 | 2 between muon and heavy neutrino states, for heavy neutrino masses in the range 300–375 MeV/ c 2 . The result extends the range of masses for which upper limits have been set on the value of | U μ 4 | 2 in previous production search experiments. [ABSTRACT FROM AUTHOR]

A search for the K + → μ − ν e + e + decay, forbidden within the Standard Model by either lepton number or lepton flavour conservation depending on the flavour of the emitted neutrino, has been performed using the dataset collected by the NA62 experiment at CERN in 2016–2018. An upper limit of 8.1 × 10 − 11 is obtained for the decay branching fraction at 90% CL, improving by a factor of 250 over the previous search. [ABSTRACT FROM AUTHOR]

The absolute branching ratio of the K + → π + π − π + ( γ ) decay, inclusive of final-state radiation, has been measured using ∼17 million tagged K + mesons collected with the KLOE detector at DAΦNE, the Frascati ϕ -factory. The result is: BR ( K + → π + π − π + ( γ ) ) = 0.05565 ± 0.00031 stat ± 0.00025 syst a factor ≃ 5 more precise with respect to the previous result. This work completes the program of precision measurements of the dominant kaon branching ratios at KLOE. [ABSTRACT FROM AUTHOR]

We analyze the role of the left-left squark mixing in the rare decay within the minimal supersymmetry with a large β. A Higgs boson mass of 125 GeV has been taken into account leading to correlation between stop masses and trilinear soft supersymmetry breaking coupling . We find that measurable effects, similar to that of the well known LR squark mixing terms, are possible for large combined with the off-diagonal LL-insertions. Precise measurements of the decay rate are expected from the ongoing NA62 experiment at CERN. We emphasize that the effect we present can put certain limits on the left-left flavor changing structure of the squark mass matrix. [ABSTRACT FROM AUTHOR]

Abstract: Recent results and future prospects of particle physics experiments with neutral and charged -meson (kaon) decays are reviewed. Topics include CP violation, rare decays, leptons in kaon decays, tests of CPT and quantum mechanics, radiative decays, hadrons in kaon decays, basic observables, and CKM unitarity, and exotic searches. Experimental techniques developed for the kaon decay experiments are discussed. [Copyright &y& Elsevier]

It is well known that the study of flavour physics and CP violation is very important to critically test the Standard Model and to look for possible signature of new physics beyond it. The observation of CP violation in kaon system in 1964 has ignited a lot of experimental and theoretical efforts to understand its origin and to look for CP violation effects in other systems besides the neutral kaons. The two B-factories BABAR and BELLE, along with other experiments, in the last decade or so made studies in flavour physics and CP violation a very interesting one. In this article we discuss the status and prospectives of the flavour physics associated with the strange, charm and bottom sectors of the Standard Model. The important results in kaon sector will be briefly discussed. Recently, mixing in the charm system has been observed, which was being pursued for quite some time without any success. The smallness of the mixing parameters in the charm system is due to the hierarchical structure of the CKM matrix. Interestingly, so far we have not found CP violation in the charm system but in the future, with more dedicated experiments at charm threshold, the situation could change. Many interesting observations have been made in the case of bottom mesons and some of them show some kind of deviations from that of the Standard Model expectations which are mainly associated with the b → s flavour changing neutral current transitions. It is long believed that the B s system could be the harbinger of new physics since it is a system in which both bottom and strange quarks are the constituents. Recently, D0 and CDF announced their result for the B s mixing which is claimed to be the first possible new physics signature in the flavour sector. We plan to touch upon all important issues pointing out both theoretical and experimental developments and future prospects in this review article. [ABSTRACT FROM AUTHOR]

Abstract: We study the decays in one-loop two-flavour Chiral Perturbation Theory. We provide arguments why the calculation of the coefficient of the pionic chiral logarithm is unique and then perform the calculation. As a check we perform the reduction of the known three-flavour result. Our result can be used to perform the extrapolation to the physical pion mass of direct lattice QCD calculations of at fixed or . The underlying arguments are expected to be valid for heavier particles and other processes as well. [Copyright &y& Elsevier]

Abstract: We have measured the absolute branching ratio of the decay, using ∼20 million tagged mesons collected with the KLOE detector at DAΦNE, the Frascati ϕ-factory. Signal counts are obtained from the fit of the distribution of the momentum of the charged decay particle in the kaon rest frame. The result, inclusive of final-state radiation, is . [Copyright &y& Elsevier]

Abstract: The decay rate of relative to the rate of has been measured by the NA48 Collaboration in a neutral kaon beam originating from 400 GeV proton-Be interactions at the CERN SPS. The result is , compatible with 1 in agreement with the Standard Model prediction at tree level. It implies . [Copyright &y& Elsevier]

Abstract: We present a measurement of the ratio of the decay rates , denoted as . The analysis is based on data taken during a dedicated run in 1999 by the NA48 experiment at the CERN SPS. Using a sample of 47 000 and five million decays, we find . From this we derive the branching ratio of the CP violating decay and the CP violation parameter . Excluding the CP conserving direct photon emission component , we obtain the results and . [Copyright &y& Elsevier]

Abstract: The () decay has been measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A sample containing 125 events was obtained. The partial branching ratio was found to be , which is in good agreement with theoretical predictions. [Copyright &y& Elsevier]

The J-PARC facility, which will be ready in 2008, is being constructed to perform a number of experiments including nuclear physics, kaon decays and neutrino oscillation. The expected data acquisition rate ranges from 500 Hz to 10 kHz, which is significantly higher than those used in the existing small experiments at KEK. We have developed a new data acquisition system that can be used in a wide range of experiments at J-PARC. The system consists of a KEK-VME crate, a readout platform module and peripheral modules. The readout platform module is highly modularized, having four slots to install daughter cards for digitization and three PCI mezzanine card (PMC) slots for on-board data processing and other purposes. The performance of the platform module and a model setup of the data acquisition system are reported [ABSTRACT FROM PUBLISHER]

The KLOE experiment at DAΦNE has collected data for an integrated luminosity of ~ 1.3 fb-1 from e+e- collisions at center-of-mass energy around the ϕ-meson peak, W ~1.02 GeV. A selection of results obtained from a sample of 450 pb-1 of data acquired during year 2001 and 2002 is presented. Studying tagged KS and KL-mesons produced in the reaction e+e-→ϕ→KS KL we measured the branching ratio of the decay KS→πeν, the upper limit on the decay KS→π0π0π0, and the main KL decay branching ratios. Exploiting the initial state radiation in the reaction e+e-→π+π-γ, we extracted the hadronic cross-section as a function of the squared center-of-mass energy sπ of the π π system, in the range 0.35 < sπ < 0.95 GeV2. [ABSTRACT FROM AUTHOR]

I review briefly various models and ways of quantum-gravity induced CPT violation, and discuss in some detail their phenomenology, in particular precision CPT tests in neutral mesons, and hydrogen/antihydrogen spectroscopy. As I shall argue, severe constraints can be placed in CPT violating parameters, with sensitivities that can safely exclude models with effects suppressed by a single power of Planck mass. [Copyright &y& Elsevier]

We present the result of the first measurement of the T-violating transverse muon polarization PT in the decay K+→μ+νγ. This polarization is sensitive to new sources of CP-violation in the Higgs sector. Using data accumulated in the period 1996–1998 we have obtained PT=(−0.64±1.85(stat)±0.10(syst))×10−2 which is consistent with no T-violation in this decay. [Copyright &y& Elsevier]

The Ring Imaging Cherenkov detector of the NA62 experiment at the CERN SPS is a key element of particle identification in the NA62 experimental strategy. According to the NA62 requirements, the RICH identifies π + and μ + in the momentum range between 15 and 35 GeV/c with a muon rejection factor of O(10 2), measures the arrival time of charged particles with a precision better than 100 ps and is one of the main components of the NA62 trigger system. After the commissioning in 2014–2015, the RICH detector has been successfully operated during the 2016, 2017 and 2018 data taking periods of NA62. The main design aspects and operational characteristics of the NA62 RICH are described and results on its performance, directly measured with data, are presented. [ABSTRACT FROM AUTHOR]

The Ring Imaging Cherenkov detector of the NA62 experiment at CERN SPS was commissioned in 2014, but the optimal performance was achieved in 2016 after the precise mirror alignment with reconstructed tracks. The measurement and monitoring of basic performance parameters is discussed: ring radius resolution, ring centre resolution, single hit resolution and mean number of hits per ring. The performance is measured with 2016 data on the positron sample. Different contributions to the resolutions are calculated. [ABSTRACT FROM AUTHOR]