Publications (179)70.53 Total impact

Article: Recent NA48/2 and NA62 results
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ABSTRACT: The NA48/2 Collaboration at CERN has accumulated and analysed unprecedented statistics of rare kaon decays in the $K_{e4}$ modes: $K_{e4}(+)$ ($K^\pm \to \pi^+ \pi^ e^\pm \nu$) and $K_{e4}(00)$ ($K^\pm \to \pi^0 \pi^0 e^\pm \nu$) with nearly one percent background contamination. It leads to the improved measurement of branching fractions and detailed form factor studies. New final results from the analysis of 381 $K^\pm \to \pi^\pm \gamma \gamma$ rare decay candidates collected by the NA48/2 and NA62 experiments at CERN are presented. The results include a decay rate measurement and fits to Chiral Perturbation Theory (ChPT) description.08/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Using the full data set of the NA48/2 experiment, the decay K+ > pi+ e+ e gamma is observed for the first time, selecting 120 candidates with 7.3 + 1.7 estimated background events. With K+ > pi+ pi0D as normalisation channel, the branching ratio is determined in a modelindependent way to be Br(K+ > pi+ e+ e gamma, m_eegamma > 260 MeV/c^2) = (1.19 + 0.12_stat + 0.04_syst) x 10^8. This measured value and the spectrum of the e+ e gamma invariant mass allow a comparison with predictions of Chiral Perturbation Theory.07/2013;  Physics Letters B. 03/2013; 720(s 1–3):105–110.
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ABSTRACT: From the 2002 data taking with a neutral kaon beam extracted from the CERNSPS, the NA48/1 experiment observed 97 Ξ0 → Σ+ μ over(ν, )μ candidates with a background contamination of 30.8 ± 4.2 events. From this sample, the BR (Ξ0 → Σ+ μ over(ν, )μ) is measured to be (2.17 ± 0.32stat ± 0.17syst) × 10 6. © 2013 Elsevier B.V. All rights reserved.Physics Letters, Section B: Nuclear, Elementary Particle and HighEnergy Physics. 01/2013;  [Show abstract] [Hide abstract]
ABSTRACT: From the 2002 data taking with a neutral kaon beam extracted from the CERNSPS, the NA48/1 experiment observed 97 $\Xi^{0}\rightarrow \Sigma^{+} \mu^{} \bar{\nu}_{\mu}$ candidates with a background contamination of $30.8 \pm 4.2$ events. From this sample, the BR($\Xi^{0}\rightarrow \Sigma^{+} \mu^{} \bar{\nu}_{\mu}$) is measured to be $(2.17 \pm 0.32_{\mathrm{stat}}\pm 0.17_{\mathrm{syst}})\times10^{6}$.12/2012;  Physics Letters B. 08/2012; 715(s 1–3):105–115.
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ABSTRACT: A sample of more than one million (Ke4) decay candidates with less than one percent background contamination has been collected by the NA48/2 experiment at the CERN SPS in 20032004, allowing a detailed study of the decay properties. The branching ratio, inclusive of Ke4 decays, is measured to be with a total relative error of 0.8%. This measurement complements the study of S and Pwave hadronic form factors by assigning absolute values to the relative hadronic form factors obtained earlier in a simultaneous analysis of the ππ scattering lengths conducted on the same data sample. The overall form factor normalization is obtained with a total relative precision of 0.6%. © 2012 Elsevier B.V.Physics Letters, Section B: Nuclear, Elementary Particle and HighEnergy Physics. 01/2012; 715(13):105115.  [Show abstract] [Hide abstract]
ABSTRACT: A sample of 7253 K{sup {+}} {yields} {pi}{sup {+}}e{sup +}e{sup }({gamma}) decay candidates with 1.0% background contamination has been collected by the NA 48/2 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) x 10{sup 7}, where the uncertainty includes also the model dependence. The shape of the form factor W(z), where z = (M{sub ee}/M{sub K}){sup 2}, was parameterized according to several models, and, in particular, the slope {delta} of the linear form factor W(z) = W{sub 0}(1 + {delta}z) was determined to be {delta} = 2.32 {+} 0.18. A possible CP violating asymmetry of K{sup +} and K{sup } decay widths was investigated, and a conservative upper limit of 2.1 x 10{sup 2} at 90% CL was established.11/2011; 677(5).  Physics Letters B. 02/2011; 697(2):107–115.
 Physics Letters B. 01/2011; 694(s 4–5):301–309.
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ABSTRACT: The K>pi+pie+e decay mode was investigated using the data collected in 2002 by the NA48/1 Collaboration. With about 23 k K>pi+pie+e events and 59 k K>pi+pipiD0 normalization decays, the K>pi+pie+e branching ratio relative to the K>pi+pipiD0 one was determined to be BR(K>pi+pie+e)/BR(K>pi+pipiD0)=(3.28±0.06±0.04)×102. This result was used to set the upper limit g/gpi+pie+e events, where varphi is the angle between the pi+pi and the e+e decay planes in the kaon centre of mass, was found to be A=(0.4±0.8)%, consistent with zero. These results are in good agreement with a description of the K>pi+pie+e decay amplitude dominated by the CPeven inner bremsstrahlung process.Physics Letters B  PHYS LETT B. 01/2011; 694:301309.  Physics Letters B. 10/2010; 693(3):241–248.
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ABSTRACT: As first observed by the NA48/2 experiment at the CERN SPS, the $\p0p0$ invariant mass (M00) distribution from $\kcnn$ decay shows a cusplike anomaly at M00=2m+, where m+ is the charged pion mass. An analysis to extract the pi pi scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively, has been recently reported. In the present work the Dalitz plot of this decay is fitted to a new empirical parameterization suitable for practical purposes, such as Monte Carlo simulations of K+ > pi+ pi0 pi0 decays. Comment: 9 pages, 3 figures.04/2010;  Physics Letters B. 03/2010; 686(s 2–3):101–108.
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ABSTRACT: As first observed by the NA48/2 experiment at the CERN SPS, the π0π0 invariant mass (M00) distribution from K±→π±π0π0 decay shows a cusplike anomaly at M00=2m+, where m+ is the charged pion mass. An analysis to extract the ππ scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively, has been recently reported. In the present work the Dalitz plot of this decay is fitted to a new empirical parameterization suitable for practical purposes, such as Monte Carlo simulations of K±→π±π0π0 decays.Physics Letters B. 01/2010;  [Show abstract] [Hide abstract]
ABSTRACT: We report results from the analysis of the $\mbox {$\mbox { ($\mbox {$\mbox {) decay by the NA48/2 collaboration at the CERN SPS, based on the total statistics of 1.13 million decays collected in 2003–2004. The hadronic form factors in the S and Pwave and their variation with energy are obtained. The phase difference between the S and Pwave states of the ππ system is accurately measured and allows a precise determination of $\mbox {$\mbox { and $\mbox {$\mbox {, the I = 0 and I = 2 Swave ππ scattering lengths: $\mbox {$\mbox {. Combination of this result with the other NA48/2 measurement obtained in the study of $\mbox {$\mbox { decays brings an improved determination of $\mbox {$\mbox { and the first precise experimental measurement of $\mbox {$\mbox {, providing a stringent test of Chiral Perturbation Theory predictions and lattice QCD calculations. Using constraints based on analyticity and chiral symmetry, even more precise values are obtained: $\mbox {$\mbox { and $\mbox {$\mbox {.European Physical Journal C 01/2010; 70(3):635657. · 5.25 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The decay asymmetries of the weak radiative hyperon decays Ξ0→Λγ and Ξ0→Σ0γ have been measured with high precision using data of the NA48/1 experiment at CERN. From about 52 000 Ξ0→Λγ and 15 000 Ξ0→Σ0γ decays, we obtain for the decay asymmetries αΞ0→Λγ=−0.704±stat0.019±syst0.064 and αΞ0→Σ0γ=−0.729±stat0.030±syst0.076, respectively. These results are in good agreement with previous experiments, but more precise.Physics Letters B. 01/2010;  [Show abstract] [Hide abstract]
ABSTRACT: We report on the measurement of the direct emission (DE) and interference (INT) terms of the $K\pm > \pi \pm \pi^0 \gamma$ decay by the NA48/2 experiment at the CERN SPS. From the data collected during 2003 and 2004 about 600k such decay candidates have been selected. The relative amounts of DE and INT with respect to the internal bremsstrahlung (IB) contribution have been measured in the range 0<T*\pi<80 MeV: Frac_{DE} (0<T*\pi<80 MeV) = (3.32\pm 0.15_{stat} \pm 0.14_{sys})x10^{2} Frac_{INT} (0<T*\pi<80 MeV) = ( 2.35\pm 0.35_{stat} \pm 0.39_{sys})x10^{2}, where T*pi is the kinetic energy of the charged pion in the kaon rest frame. This is the first observation of an interference term in T*\pi decays. In addition, a limit on the CP violating asymmetry in the K^+ and K^ branching ratios for this channel has been determined to be less than 1.5x10^{3} at 90% confidence level.01/2010;  [Show abstract] [Hide abstract]
ABSTRACT: As first observed by the NA48/2 experiment at the CERN SPS, the π0π0 invariant mass (M00) distribution from K±→π±π0π0 decay shows a cusplike anomaly at M00=2m+, where m+ is the charged pion mass. An analysis to extract the ππ scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively, has been recently reported. In the present work the Dalitz plot of this decay is fitted to a new empirical parameterization suitable for practical purposes, such as Monte Carlo simulations of K±→π±π0π0 decays.Physics Letters B  PHYS LETT B. 01/2010; 686(2):101108.  [Show abstract] [Hide abstract]
ABSTRACT: We report on the measurement of the direct emission (DE) and interference (INT) terms of the K ±→π ± π 0 γ decay by the NA48/2 experiment at the CERN SPS. From the data collected during 2003 and 2004 about 600k such decay candidates have been selected. The relative amounts of DE and INT with respect to the internal bremsstrahlung (IB) contribution have been measured in the range MeV: where is the kinetic energy of the charged pion in the kaon rest frame. This is the first observation of an interference term in K ±→π ± π 0 γ decays, thus allowing the normalised electric and magnetic amplitudes to be measured, giving X E =(−24±6) GeV−4, and X M =(254±9) GeV−4. In addition, a limit on the CP violating asymmetry in the K + and K − branching ratios for this channel has been determined to be less than 1.5×10−3 at 90% confidence level.European Physical Journal C 01/2010; · 5.25 Impact Factor
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254  Citations  
70.53  Total Impact Points  
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1993–2010

CERN
Genève, Geneva, Switzerland
