T. Nomura

Improved measurement of the K+ ---> pi+ nu anti-nu branching ratio

An additional event near the upper kinematic limit for K+ to pi+ nu nubar has been observed by Experiment E949 at Brookhaven National Laboratory. Combining previously reported and new data, the branching ratio is B(K+ to pi+ nu nubar)= 1.47 (+1.30, - 0.89) x 10-10 based on three events observed in the pion momentum region 211<P<229 MeV/c. At the measured central value of the branching ratio, the additional event had a signal-to-background ratio of 0.9.

New measurement of the K+-->pi+ nunu branching ratio.

A.V. Artamonov, B. Bassalleck, B. Bhuyan, ∗ E.W. Blackmore, D.A. Bryman, S. Chen, 4 I-H. Chiang, I.-A. Christidi, † P.S. Cooper, M.V. Diwan, J.S. Frank, T. Fujiwara, J. Hu, J. Ives, D.E. Jaffe, S. Kabe, S.H. Kettell, M.M. Khabibullin, A.N. Khotjantsev, P. Kitching, M. Kobayashi, T.K. Komatsubara, A. Konaka, A.P. Kozhevnikov, Yu.G. Kudenko, A. Kushnirenko, ‡ L.G. Landsberg, § B. Lewis, K.K. Li, L.S. Littenberg, J.A. Macdonald, § J. Mildenberger, O.V. Mineev, M. Miyajima, K. Mizouchi, V.A. Mukhin, N. Muramatsu, T. Nakano, M. Nomachi, T. Nomura, T. Numao, V.F. Obraztsov, K. Omata, D.I. Patalakha, S.V. Petrenko, R. Poutissou, E.J. Ramberg, G. Redlinger, T. Sato, T. Sekiguchi, T. Shinkawa, R.C. Strand, S. Sugimoto, Y. Tamagawa, R. Tschirhart, T. Tsunemi, ¶ D.V. Vavilov, B. Viren, Zhe Wang, 3 N.V. Yershov, Y. Yoshimura, and T. Yoshioka

Study of the decay K+→π+νν̄ in the momentum region 140<Pπ<199MeV/c

Experiment E949 at Brookhaven National Laboratory has observed three new events consistent with the decay K+ => pi+,nu,nubar in the pion momentum region 140 pi+,nu,nubar events to seven. Combining this observation with previous results, assuming the pion spectrum predicted by the standard model, results in a branching ratio of (1.73+1.15-1.05)e-10. An interpretation of the results for alternative models of the decay K^ => pi+,nothing is also presented.

Experimental study of the decay KL0→π0νν̄

The first dedicated search for the rare neutral-kaon decay

Measurements of the electron drift velocity and positive-ion mobility for gases containing CF4

K_L^0\to\pi^0\nu\bar{\nu}

Test of BaF2 scintillators coupled to a photomultiplier with a CsTe photocathode

has been carried out in the E391a experiment at the KEK 12-GeV proton synchrotron. The final upper limit of 2.6

New measurement of the

\times 10^{-8}

K^{+} \to \pi^{+} \nu \bar{\nu}

at the 90% confidence level was set on the branching ratio for the decay.

branching ratio

Abstract Measurements of the electron drift velocity and positive-ion mobility for gases containing CF 4 have been performed. The results are presented for four types of gas mixtures containing CF 4 and hydrocarbons: CF 4 +CH 4 , CF 4 +C 2 H 6 , CF 4 +C 3 H 8 and CF 4 +iso-C 4 H 10 . To make a comparison, also positive-ion mobilities for Ar+C 2 H 6 and Ar+C 3 H 8 gas mixtures have been measured. The drift velocities of electrons in a few mixtures are found to exceed 10 cm/μs, twice that in a conventional drift chamber gas such as Ar(50%)+C 2 H 6 (50%). In particular, the electron drift velocity in CF 4 (10%)+CH 4 (90%) is larger than 10 cm/μs, even at a reduced electric field E / P of more than 1 V/(cm Torr). Results on the measurements of the positive ion mobility are consistent with the interpretation that the hydrocarbon ions are the positive ions eventually drifting toward the cathode in the studied gas mixtures. Their mobilities in CF 4 are found to be smaller than those in Ar.

Search for a light pseudoscalar particle in the decay K_{L};{0}-->pi;{0}pi;{0}X.

Basic properties of BaF2 scintillators coupled to a photomultiplier with a CsTe photocathode have been investigated. The signal from the photomultiplier shows a drastic reduction of the slow component of the BaF2 scintillation light while preserving the good properties associated with the fast component.