0000000000216863
AUTHOR
A. Zinchenko
showing 18 related works from this author
Measurement of Kμ30 form factors
2007
Abstract This Letter reports on a new high precision measurement of the form factors of the K L → π ± μ ∓ ν μ decay. The data sample of about 2.3 × 10 6 events was recorded in 1999 by the NA48 experiment at CERN. Studying the Dalitz plot density we measured a linear, λ + ′ = ( 20.5 ± 2.2 stat ± 2.4 syst ) × 10 −3 , and a quadratic, λ + ″ = ( 2.6 ± 0.9 stat ± 1.0 syst ) × 10 −3 term in the power expansion of the vector form factor. No evidence was found for a second order term for the scalar form factor; the linear slope was determined to be λ 0 = ( 9.5 ± 1.1 stat ± 0.8 syst ) × 10 −3 . Using a linear fit our results were: λ + = ( 26.7 ± 0.6 stat ± 0.8 syst ) × 10 −3 and λ 0 = ( 11.7 ± 0.7 s…
Search for heavy neutrinos at the NA48/2 and NA62 experiments at CERN
2018
© The Authors, published by EDP Sciences. The NA48/2 experiment at CERN has collected large samples of charged kaons decaying into a pion and two muons for the search of heavy nuetrinos. In addition, its successor NA62 has set new limits on the rate of charged kaon decay into a heavy neutral lepton (HNL) and a lepton, with = e, µ, using the data collected in 2007 and 2015. New limits on heavy neutrinos from kaon decays into pions, muons and positrons are presented in this report.
UTSW Small Animal Positron Emission Imager
2006
A Small Animal Imager (SAI) for PET has been designed, built, tested in phantoms, and applied to investigations in mice and rats. The device uses principles based on gamma-ray induced scintillation in crossed fiber optic detectors connected to Position Sensitive Photomultiplier Tubes (PSPMT). Each detector consists of an epoxied stack of 28 layers of 135 round 1 mm BCF-10 scintillating plastic fibers. The overlap region forms a 13.5times13.5times2.8 cm3 detector volume. Scintillating light from the fibers is detected by two (X and Y directions) Hamamatsu R-2486 PSPMTs with 16 anode wires in each of two orthogonal directions. A centroid-finding algorithm gives the position of a light cluster…
Search for neutralino pair production at root s = 189 GeV
2001
A search for pair-production of neutralinos at a LEP centre-of-mass energy of 189 GeV gave no evidence for a signal. This limits the neutralino production cross-section and excludes regions in the parameter space of the Minimal Supersymmetric Standard Model (MSSM).
Observation of the rare decay K-S -> pi(0)e(+)e(-)
2003
A search for the decay Ks->pi0e+e- has been made by the NA48/1 experiment at the CERN SPS accelerator. Using data collected during 89 days in 2002 with a high-intensity Ks beam, 7 events were found with a background of 0.15 events. The branching fraction BR(Ks->pi0e+e-, m(ee) > 0.165 GeV/c^2) = (3.0^{+1.5}_{-1.2}(stat) +/-0.2 (syst)) x 10^{-9} has been measured. Using a vector matrix element and a form factor equal to one, the measurement gives BR(Ks->pi0e+e-) = (5.8^{+2.9}_{-2.4}) x 10^{-9}.
Search for heavy charged scalars in Z$^0$ Decays
1990
Using a sample of Z0's corresponding to about 12 000 events, we have searched for the production of charged scalars, primarily charged Higgs particles, decaying into c̄scs̄, τν+jets, and τντν. The average detection efficiency is 20%. No candidate was found in the leptonic modes. Masses in the range up to 30-36 GeV/c2 are excluded, extending the mass domain covered by previous e+e- machines.
Measurement of the branching ratio of the decay Ξ0→Σ+μ−ν¯μ
2013
Abstract From the 2002 data taking with a neutral kaon beam extracted from the CERN-SPS, the NA48/1 experiment observed 97 Ξ 0 → Σ + μ − ν ¯ μ candidates with a background contamination of 30.8 ± 4.2 events. From this sample, the BR ( Ξ 0 → Σ + μ − ν ¯ μ ) is measured to be ( 2.17 ± 0.32 stat ± 0.17 syst ) × 10 − 6 .
First observation and measurement of the decay K±→π±e+e−γ
2008
Abstract Using the full data set of the NA48/2 experiment, the decay K ± → π ± e + e − γ is observed for the first time, selecting 120 candidates with 7.3 ± 1.7 estimated background events. With K ± → π ± π D 0 as normalisation channel, the branching ratio is determined in a model-independent way to be Br ( K ± → π ± e + e − γ , m e e γ > 260 MeV / c 2 ) = ( 1.19 ± 0.12 stat ± 0.04 syst ) × 10 −8 . This measured value and the spectrum of the e + e − γ invariant mass allow a comparison with predictions of chiral perturbation theory.
First observation and study of the K± → π±π0e+e− decay
2018
The NA48/2 experiment at CERN reports the first observation of the K-+/- -> pi(+/-)pi(0)e(+)e(-) decay from an exposure of 1.7 x 10(11) charged kaon decays recorded in 2003-2004. A sample of 4919 candidates with 4.9% background contamination allows the determination of the branching ratio in the full kinematic region, BR(K-+/- -> pi(+/-)pi(0)e(+)e(-)) = (4.24 +/- 0.14) x 10(-6). The study of the kinematic space shows evidence for a structure dependent contribution in agreement with predictions based on chiral perturbation theory. Several P- and CP-violating asymmetries are also evaluated.
Search for K+→ π+νν¯ at NA62
2018
Flavour physics is one of the most powerful fields for the search of new physics beyond the Standard Model. The kaon sector with the rare decay K+ → π+νν̅ provides one of the cleanest and most promising channels. NA62, a fixed target experiment at the CERN SPS, aims to measure BR (K+ → π+νν̅) with 10% precision to test the Standard Model validity up to an energy scale of hundreds of TeV. NA62 had dedicated data taking for the K+ → π+νν̅ measurement in 2016 and 2017 and will continue in 2018. Here preliminary results on a fraction of 2016 dataset are presented. The analysis of the complete 2016 data sample is expected to achieve the SM sensitivity.
The ALICE experiment at the CERN LHC
2008
Journal of Instrumentation 3(08), S08002 (2008). doi:10.1088/1748-0221/3/08/S08002
Search for the dark photon in π0 decays
2015
A sample of $1.69\times 10^7$ fully reconstructed $\pi^0\to\gamma e^+e^-$ decay candidates collected by the NA48/2 experiment at CERN in 2003--2004 is analysed to search for the dark photon ($A'$) production in the $\pi^0\to\gamma A'$ decay followed by the prompt $A'\to e^+e^-$ decay. No signal is observed, and an exclusion region in the plane of the dark photon mass $m_{A'}$ and mixing parameter $\varepsilon^2$ is established. The obtained upper limits on $\varepsilon^2$ are more stringent than the previous limits in the mass range $9~{\rm MeV}/c^2<m_{A'}<70~{\rm MeV}/c^2$. The NA48/2 sensitivity to the dark photon production in the $K^\pm\to\pi^\pm A'$ decay is also evaluated.
Search for heavy neutral lepton production in K+ decays
2018
A search for heavy neutral lepton production in $K^+$ decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the $10^{-7}$ to $10^{-6}$ level are established on the elements of the extended neutrino mixing matrix $|U_{\ell 4}|^2$ ($\ell=e,\mu$) for heavy neutral lepton mass in the range $170-448~{\rm MeV}/c^2$. This improves on the results from previous production searches in $K^+$ decays, setting more stringent limits and extending the mass range.
Search for direct CP-violation in K±→π±π0π0 decays
2006
Abstract A search for direct CP-violation in K ± → π ± π 0 π 0 decay based on 47.14 million events has been performed by the NA48/2 experiment at the CERN SPS. The asymmetry in the Dalitz plot linear slopes A g = ( g + − g − ) / ( g + + g − ) is measured to be A g = ( 1.8 ± 2.6 ) × 10 −4 . The design of the experiment and the method of analysis provide good control of instrumental charge asymmetries in this measurement. The precision of the result is limited by statistics and is almost one order of magnitude better than that of previous measurements by other experiments.
Study of the leptonic decays of the Z0 boson
1990
Measurements are presented of the cross section ratios Rℓ = σℓ(e+e-→ℓ+ℓ -)/σhh(e+e-→hadrons) for ℓ = e, μ and τ using data taken from a scan around the Z0. The results are Re = (5.09±0.32±0.18)%, Rμ = (4.96±0.35±0.17)% and Rτ,=(4.72±0.38± 0.29)% where, for the ratio Re, the t-channel contribution has been subtracted. These results are consistent with the hypothesis of lepton universality and test this hypothesis at the energy scale s ∼ 8300 GeV2. The absolute cross sections σℓ(e+e-→ℓ +ℓ-) have also been measured. From the cross sections the leptonic partial widths Γe = (83.2±3.0±2.4) MeV, (ΓeΓμ) 1/2=(84.6±3.0±2.4) MeV and (ΓeΓτ) 1/2=(82.6±3.3±3.2) MeV have been extracted. Assuming lepton un…
The ALICE Collaboration
2009
The production of mesons containing strange quarks (KS, φ) and both singly and doubly strange baryons ( , , and − + +) are measured at mid-rapidity in pp collisions at √ s = 0.9 TeV with the ALICE experiment at the LHC. The results are obtained from the analysis of about 250 k minimum bias events recorded in 2009. Measurements of yields (dN/dy) and transverse momentum spectra at mid-rapidity for inelastic pp collisions are presented. For mesons, we report yields (〈dN/dy〉) of 0.184 ± 0.002(stat.) ± 0.006(syst.) for KS and 0.021 ± 0.004(stat.) ± 0.003(syst.) for φ. For baryons, we find 〈dN/dy〉 = 0.048 ± 0.001(stat.) ± 0.004(syst.) for , 0.047 ± 0.002(stat.) ± 0.005(syst.) for and 0.0101 ± 0.0…
Precise measurement of the K±→π±e+e− decay
2009
Abstract A sample of 7253 K ± → π ± e + e − ( γ ) decay candidates with 1.0% background contamination has been collected by the NA48/2 experiment at the CERN SPS, which allowed a precise measurement of the decay properties. The branching ratio in the full kinematic range was measured to be BR = ( 3.11 ± 0.12 ) × 10 − 7 , where the uncertainty includes also the model dependence. The shape of the form factor W ( z ) , where z = ( M e e / M K ) 2 , was parameterized according to several models, and, in particular, the slope δ of the linear form factor W ( z ) = W 0 ( 1 + δ z ) was determined to be δ = 2.32 ± 0.18 . A possible CP violating asymmetry of K + and K − decay widths was investigated,…
Precision measurement of the ratio of the charged kaon leptonic decay rates
2013
A precision measurement of the ratio RK of the rates of kaon leptonic decays K+- --> e nu and K+- --> mu nu with the full data sample collected by the NA62 experiment at CERN in 2007-2008 is reported. The result, obtained by analysing ~150000 reconstructed K+- --> e nu candidates with 11% background contamination, is RK = (2.488+-0.010)*10^{-5}, in agreement with the Standard Model expectation.