139 research outputs found

    Rare kaon decays (NA48/2 and NA62)

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    The rare decay K±π±γγK^\pm\to\pi^\pm\gamma\gamma has been recently measured from data samples collected by the NA48/2 and NA62 experiments at CERN. These measurements are presented, including model-independent spectrum measurements and fits to the Chiral Perturbation Theory description.Comment: talk given at the EPS HEP conference, 18-24 July 2013, Stockholm, Swede

    Neutral pion form factor measurement at NA62

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    The NA62 experiment at CERN collected a large sample of charged kaon decays with a highly efficient trigger for decays into electrons in 2007. The kaon beam represents a source of tagged neutral pion decays in vacuum. A measurement of the electromagnetic transition form factor slope of the neutral pion in the time-like region from 1.05×1061.05\times10^6 fully reconstructed π0\pi^0 Dalitz decay is presented. The limits on dark photon production in π0\pi^0 decays from the earlier kaon experiment at CERN, NA48/2, are also reported.Comment: Talk given at ICHEP 2016, Chicago, 3-10 August 2016. arXiv admin note: text overlap with arXiv:1609.0295

    Kaon experiments at CERN: recent results and prospects

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    The NA48/2 and NA62-RKR_K experiments at the CERN SPS collected large samples of charged kaon decays in flight in 2003--07. The data analysis is still on-going (with over 20 publications produced so far); the recent results from these experiments are presented. A new upper limit on the rate of a lepton number violating decay K±πμ±μ±K^\pm\to\pi^\mp\mu^\pm\mu^\pm is reported: B<8.6×1011\mathcal{B} < 8.6\times 10^{-11} at 90\% CL. Searches for heavy sterile neutrino N4N_4 and neutral scalar resonances (χ\chi) in K±πμμK^\pm\to\pi\mu\mu decays are reported. Upper limits on the products B(K±μ±N4)B(N4πμ±)\mathcal{B}(K^\pm\to\mu^\pm N_4)\mathcal{B}(N_4\to\pi^\mp\mu^\pm) and B(K±π±χ)B(χμ+μ)\mathcal{B}(K^\pm\to\pi^\pm \chi)\mathcal{B}(\chi\to\mu^+\mu^-) are set in the range 101010^{-10} to 10910^{-9} for resonance lifetimes up to 100~ps. A preliminary measurement of the electromagnetic transition form factor slope of the π0\pi^0 from 1.05×1061.05\times 10^6 fully reconstructed π0γe+e\pi^0\to\gamma e^+e^- decays is presented: the obtained result a=(3.70±0.53stat±0.36syst)×102a = (3.70 \pm 0.53_\text{stat} \pm 0.36_\text{syst})\times 10^{-2} represents the first observation of a non-zero slope in the time-like region of momentum transfer.Comment: Contribution to proceedings of MESON 2016 conference (Krakow, 2-6 June 2016

    New results from the NA48/2 experiment at CERN SPS: radiative nonleptonic kaon decays

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    The NA48/2 experiment at the CERN SPS carried out data taking in 2003 and 2004. Analysis of the selected data samples of 7,146 K±π±e+eK^\pm\to\pi^\pm e^+e^- decay candidates with 0.6% background, 1,164 K±π±γγK^\pm\to\pi^\pm\gamma\gamma candidates with 3.3% background, and 120 K±π±γe+eK^\pm\to\pi^\pm\gamma e^+e^- candidates with 6.1% background allowed precise measurements of branching fractions and other characteristics of these rare kaon decays.Comment: Talk given at 22nd Rencontres de Physique de La Vallee d'Aoste, La Thuile, Aosta Valley, Italy, 24 Feb-1 Mar 2006. 15 pages, 4 figure

    Searches for lepton flavour and lepton number violation in kaon decays

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    Searches for lepton flavour and lepton number violation in kaon decays by the NA48/2 and NA62 experiments at CERN are presented. A new measurement of the helicity suppressed ratio of charged kaon leptonic decay rates $RK=BR(Ke2)/BR(Kmu2) to sub-percent relative precision is discussed. An improved upper limit on the lepton number violating K+- --> pi-+mu+-mu+- decay rate is also presented.Comment: Talk given at Moriond EW 2011 conference (La Thuile, Italy, March 2011

    Precision study of K^\pm\to\pi^\pm\pi^0\pi^0 and K^\pm\to\pi^\pm\pi^+\pi^- Dalitz plot distributions by NA48/2

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    The NA48/2 experiment at the CERN SPS has collected an unprecedented sample of K±3πK^\pm\to3\pi decays. The high statistics and the good resolution of the detectors allow a unique investigation of the detailed phase space distributions of these decays. The effects of final state pion rescattering observed in the Dalitz plot distribution of the K±π±π0π0K^\pm\to\pi^\pm\pi^0\pi^0 decays turned out to be a powerful tool for extraction of the S-wave ππ\pi\pi scattering lengths. The large statistics also allowed a precise measurement of the Dalitz plot slope parameters for the K±3π±K^\pm\to3\pi^\pm decays.Comment: Talk given at Kaon'07 Conference, LNF, Frascati, Italy, 21--25 May, 2007. A version revised by PoS refere

    Search for the dark photon in π0\pi^0 decays

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    A sample of 1.69×1071.69\times 10^7 fully reconstructed π0γe+e\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 (AA') production in the π0γA\pi^0\to\gamma A' decay followed by the prompt Ae+eA'\to e^+e^- decay. No signal is observed, and an exclusion region in the plane of the dark photon mass mAm_{A'} and mixing parameter ε2\varepsilon^2 is established. The obtained upper limits on ε2\varepsilon^2 are more stringent than the previous limits in the mass range 9 MeV/c2<mA<70 MeV/c29~{\rm MeV}/c^2<m_{A'}<70~{\rm MeV}/c^2. The prospects of the dark photon search in the K±π±AK^\pm\to\pi^\pm A' decay are also discussed.Comment: Contribution to the proceedings of the PLANCK 2015 conference, Ioannina, Greece, 25-29 May 201

    Kaon programme at CERN: recent results

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    Searches for lepton flavour and lepton number violation in kaon decays by the NA48/2 and NA62 experiments at CERN are presented. A precision measurement of the helicity-suppressed ratio RK of the K --> e nu and K --> mu nu decay rates has been performed using the full data set collected by the NA62 collaboration in 2007. The data sample amounted to 145,958 reconstructed K --> e nu candidates with 11.0% background contamination. The result is RK = (2.488 +- 0.010) X 10^{-5}, which is in agreement with the Standard Model expectation. An improved upper limit on the lepton number violating K+- --> pi-+ mu+- mu+- decay rate is also presented.Comment: Talk given at the EPS HEP 2011 conference (Grenoble, 21-27 July 2011
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