Search for the decay K→πν in the momentum region P<195 MeV/c

Plans for Kaon Physics at BNL

“…One might even speculate, based on our experience with the higher rates in 2002, that it would be possible to take more instantaneous beam in the future, allowing us to take better advantage of the higher proton intensity being delivered by the AGS. There is also the potential of increasing the sensitivity in the kinematic region below the K π2 peak; this region was background limited in E787 analyses [19], including the recently published result on the 1997 data [20], but it is hoped that improvements made in E949 to the photon veto system will make this kinematic region viable. Analysis of the 2002 data in this region is currently in progress.…”

Further search for the decayK+→π+νν¯<

“…As discussed in [15], the background in Region 2 was found to be dominated by K π2 events in which the charged pion underwent a nuclear interaction near the kaon decay vertex, most probably on a carbon nucleus in the target plastic scintillator. The scattering of the pion reduced its kinetic energy into the signal region and removed the directional correlation with the photons from The total background in the analysis of the 1996 data set was measured to be 0.73±0.18 in the same search region [15].…”

“…It is therefore important to obtain higher statistics for this decay and to extend the measurement to other regions of phase space. In an earlier paper [15], we reported the results from the kinematic search region below the K + → π + π 0 (K π2 ) peak with π + momentum, 140 < P < 195 (MeV/c) (Region 2), using the data collected by the E787 experiment during the 1996 run. In this letter, we present results for the same kinematic region from additional data collected during the 1997 run.…”

“…The scattering of the pion reduced its kinetic energy into the signal region and removed the directional correlation with the photons from The total background in the analysis of the 1996 data set was measured to be 0.73±0.18 in the same search region [15]. The errors include both statistical and systematic uncertainties.…”

“…The contribution from these processes to the total background was small compared to scattered K π2 decays. The techniques used to measure these backgrounds were discussed in [15]. TABLE II: Acceptance factors used in the measurement of K + → π + νν in Region 2.…”