23 research outputs found

    Test of exotic scalar and tensor interactions in K_e3 decay using stopped positive kaons

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    The form factors of the decay K+ --> pi0 e+ nu (K_e3) have been determined from the comparison of the experimental and Monte Carlo Dalitz distributions containing about 10^5 K_e3 events. The following values of the parameters were obtained: lambda_+ = 0.0278 +- 0.0017(stat) +- 0.0015(syst), f_S/f_+(0) = 0.0040 +- 0.0160(stat) +- 0.0067(syst) and f_T/f_+(0) = 0.019 +- 0.080(stat) +- 0.038(syst). Both scalar f_S and tensor f_T form factors are consistent with the Standard Model predictions of zero values.Comment: 10 pages, 5 figures, contributed to the proceedings of NANP Conference, Dubna, June 19-23, 200

    A new limit of T-violating transverse muon polarization in the K+π0μ+νK^{+}\to\pi^{0}\mu^{+} \nu decay

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    A search for T-violating transverse muon polarization (PTP_T) in the K+π0μ+νK^{+}\to \pi^{0}\mu^{+}\nu decay was performed using kaon decays at rest. A new improved value, PT=0.0017±0.0023(stat)±0.0011(syst)P_T= -0.0017\pm 0.0023 (stat)\pm 0.0011 (syst), was obtained giving an upper limit, PT<0.0050| P_T | < 0.0050. The T-violation parameter was determined to be Imξ=0.0053±0.0071(stat)±0.0036(syst)\xi = -0.0053 \pm 0.0071(stat)\pm 0.0036(syst) giving an upper limit, |Imξ<0.016\xi| <0.016.Comment: 5 pages, 4 figure

    Mass Bounds on a Very Light Neutralino

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    Within the Minimal Supersymmetric Standard Model (MSSM) we systematically investigate the bounds on the mass of the lightest neutralino. We allow for non-universal gaugino masses and thus even consider massless neutralinos, while assuming in general that R-parity is conserved. Our main focus are laboratory constraints. We consider collider data, precision observables, and also rare meson decays to very light neutralinos. We then discuss the astrophysical and cosmological implications. We find that a massless neutralino is allowed by all existing experimental data and astrophysical and cosmological observations.Comment: 36 pages, 13 figures, minor modification in astro-physical bounds. EPJC versio

    Measurement of the K+π+ννˉK^+\to\pi^+\nu\bar{\nu} Branching Ratio

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    Experiment E949 at Brookhaven National Laboratory studied the rare decay \K+π+ννˉK^+\to\pi^+\nu\bar{\nu} and other processes with an exposure of 1.77×10121.77\times 10^{12} K+K^+'s. The data were analyzed using a blind analysis technique yielding one candidate event with an estimated background of 0.30±0.030.30\pm0.03 events. Combining this result with the observation of two candidate events by the predecessor experiment E787 gave the branching ratio {\calB}(K^+\to\pi^+\nu\bar{\nu})=(1.47^{+1.30}_{-0.89})\times 10^{-10}, consistent with the Standard Model prediction of (0.74±0.20)×1010(0.74\pm0.20)\times 10^{-10}. This is a more detailed report of results previously published in Physical Review Letters.Comment: 99 pages, 32 figures, 12 tables. Added authors, corrected typos and modify the text suggested by the referees. Accepted for publication in PR

    Further search for the decay K+π+ννˉK^+ \to \pi^+ \nu \bar \nu in the momentum region P < 195 MeV/c

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    We report the results of a search for the decay K+π+ννˉK^+ \to \pi^+ \nu \bar \nu in the kinematic region with π+\pi^+ momentum 140<P<195140 < P < 195 MeV/c using the data collected by the E787 experiment at BNL. No events were observed. When combined with our previous search in this region, one candidate event with an expected background of 1.22±0.241.22 \pm 0.24 events results in a 90% C.L. upper limit of 2.2×1092.2 \times 10^{-9} on the branching ratio of K+π+ννˉK^+ \to \pi^+ \nu \bar \nu. We also report improved limits on the rates of K+π+X0K^+ \to \pi^+ X^0 and K+π+X1X2K^+ \to \pi^+ X^1 X^2 where X0,X1,X2X^0, X^1, X^2 are hypothetical, massless, long-lived neutral particles.Comment: 5 pages, 3 figures, Accepted for publication in Phys. Rev.

    Towards the european strategy for particle physics: The briefing book

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    This document was prepared as part of the briefing material for the Workshop of the CERN Council Strategy Group, held in DESY Zeuthen from 2nd to 6th May 2006. It gives an overview of the physics issues and of the technological challenges that will shape the future of the field, and incorporates material presented and discussed during the Symposium on the European Strategy for Particle Physics, held in Orsay from 30th January to 2nd February 2006, reflecting the various opinions of the European community as recorded in written submissions to the Strategy Group and in the discussions at the Symposium
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