Takao Shinkawa

Further evidence for the decay K+ ---> pi+ neutrino anti-neutrino

Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211<P<229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 pm 0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.

Further Evidence for the DecayK+→π+νν¯

Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211<P<229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 pm 0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.

Search for a Rare Decay Mode K+ ---> pi+ Neutrino anti-neutrino and Axion

Abstract Using stopped kaons, rare decay modes K + → π + ν v and K + → π + a 0 is the light pseudoscalar meson (axion), have been measured. The upper bound of the branching ratio was found to be 1.4 × 10 −7 for K + → π + ν v and 3.8 × 10 −8 for K + → π + a 0 .

Further search for the decay K+-->pi(+)nunu;

A search for additional evidence for the rare kaon decay K^+ -->pi^+ nu nubar has been made with a new data set comparable in sensitivity to the previous exposure that produced a single event.A search for additional evidence for the rare kaon decay K{sup +}{yields}{pi}{sup +}{nu}{nu} (bar sign) has been made with a new data set comparable in sensitivity to the previous exposure that produced a single event. No new events were found in the pion momentum region examined, 211<P<229 MeV/c . Including a reanalysis of the original data set, the backgrounds were estimated to contribute 0.08{+-}0.02 events. Based on one observed event, the new branching ratio is B(K{sup +}{yields}{pi}{sup +}{nu} {nu}(bar sign))=1.5{sup +3.4}{sub -1.2}x10{sup -10} . (c) 2000 The American Physical Society.

A test of transition radiation detectors for a colliding beam experiment

Abstract We have tested transition radiation detectors (TRDs) to separate electrons from pions in the momentum range between 2.0 GeV/c and 7.5 GeV/c. The radiator materials used in this experiment were polypropylene (CH2) fibers and lithium (Li) foils. A Xe filled longitudinal drift chamber of 3 cm depth was used for detecting transition radiation photons. We compared the methods of truncated mean of the total charge measurements and of maximum likelihood as well as cluster counting methods. We obtained 2% electron/pion separation for the CH2 fibers in the configuration of four modules with total length of 32 cm for a typical geometry of a collider experiment.

Measurement of structure-dependent K+ --> m(+)nu(m)gamma decay

We report the first measurement of a structure dependent component in the decay K^+ ->mu^+ nu gamma. Using the kinematic region where the muon kinetic energy is greater than 137 MeV and the photon energy is greater than 90 MeV, we find that the absolute value of the sum of the vector and axial-vector form factors is |F_V+F_A| =0.165 \pm 0.007 \pm 0.011. This corresponds to a branching ratio of BR(SD^+) = (1.33 \pm 0.12 \pm 0.18) \times 10^{-5}. We also set the limit -0.04

Precise Determination of Sin**2-

Measurements of the semileptonic weak neutral-current reactions ..nu../sub ..mu../p..--> nu../sub ..mu../p and nu-bar/sub ..mu../p..-->..nu-bar/sub ..mu../p which yield the absolute differential cross sections dsigma(..nu../sub ..mu../p)/dQ/sup 2/ and dsigma(nu-bar/sub ..mu../p)/dQ/sup 2/ described. The weak-neutral-current parameter, sin/sup 2/theta/sub W/, is determined to be sin/sup 2/theta/sub W/ = 0.220 +- 0.016 (stat)/sub -0.031//sup +0.023/(syst).

\theta^-

Abstract This paper describes the design criteria, construction, and performance of a detector to study neutral and charged current elastic neutrino interactions induced by neutrinos of average energy approximately 1 GeV from the Brookhaven National Laboratory Alternating Gradient Synchrotron.

w From Measurements of the Differential Cross-sections for

A new programmable trigger board and digital mean-timer modules using complex programmable logic device have been introduced to the trigger system of the BNL-E949 experiment. The online dead time was reduced from 4.0% to 1.7% by introducing an on-chip prescaler to the programmable trigger board. The acceptance loss of the online photon veto was reduced from 4.9% to 1.8% by introducing the mean-timer modules.

\nu_\mu p \to \nu_\mu p

We have constructed an endcap photon detector with undoped Cesium Iodide (CsI) crystals for K + →π + νν experiment E787 at Brookhaven National Laboratory (BNL). To reject backgrounds it is essential to have a photon detection system with high efficiency. Good resolution for timing and energy is critical for reducing accidental vetoes in a high-counting-rate environment. The endcap detector is located in a 1 T magnetic field. Fine-mesh photomultiplier tubes are attached directly to the crystals for efficient light collection, and the fast-decay component of the CsI light output is selected by optical filters. The tube gains are monitored with the light from a xenon flash lamp and from light pulsers. The pulse shapes are recorded by transient digitizers based on charged coupled devices (CCDs), which enables precise determination of timing of endcap signals. The construction and performance of the detector are described.The authors have constructed an endcap photon detector with undoped Cesium Iodide (CsI) crystals for K{sup +} {yields} {pi}{sup +}{nu}{bar {nu}} experiment E787 at Brookhaven National Laboratory (BNL). To reject backgrounds it is essential to have a photon detecting system with high efficiency. Good resolution for timing and energy is critical for reducing accidental vetoes in a high-counting-rate environment. The endcap detector is located in a 1 T magnetic field. Fine-mesh photomultiplier tubes are attached directly to the crystals for efficient light collection, and the fast-decay component of the CsI light output is selected by optical filters. The tube gains are monitored with the light from a xenon flash lamp and are monitored with the light from a xenon flash lamp and from light pulsers. The pulse shapes are recorded by transient digitizers based on charged coupled devices (CCDs), which enables precise determination of timing of endcap signals. The construction and performance of the detector are described.We have constructed an endcap photon detector with undoped cesium iodide (CsI) crystals for K/sup +//spl rarr//spl pi//sup +//spl nu//spl nu. >