We present a measurement of the branching ratio BR(KS→π±e∓ν̄(ν)) performed using the KLOE detector. KS-mesons are produced in the reaction e+e−→φ→KSKL at the DAΦNE collider. In a sample of ∼5×106 KS-tagged events we find 624±30 semileptonic KS decays. Normalizing to the KS→π+π− count in the same data sample, we obtain BR(KS→πeν)=(6.91±0.37)×10−4, in agreement with the Standard Model expectation.

The design and construction of the large Drift Chamber for the KLOE experiment at the Frascati φ-factory, DAΦNE, are described. The relevant aspects of the various elements of the detector are reviewed together with a description of the track reconstruction program and of the calibration procedures. The performance of the detector based on measurements with cosmic rays and with e+e− colliding beams during DAΦNE commissioning is presented.

A double-level trigger system has been developed for the KLOE experiment. Custom electronics asserts a trigger in a 2μs decision time. The decision is based on the combined information of the electromagnetic calorimeter and the drift chamber. The entire trigger system is continuously monitored, and data flowing from the trigger system have allowed both an efficient online monitoring of the detector and an online luminosity measurement.

Decays of the type B ! D()D() can be used to provide a measurement of the parameter sin2 of the Unitarity Triangle that is complementary to the measurement derived from the mode B0 ! J= K 0 S. In this document we report a measurement of the branching fraction for the decay B0 ! D+D with the BABAR detector. With data corresponding to an integrated luminosity of 20.7 fb 1 collected at the (4S) resonance during 1999-2000, we have reconstructed 38 candidate signal events in the mode B0 ! D+D with an estimated background of 6:2 0:5 events. From these events, we determine the branching fraction to be B(B0 ! D+D )=( 8 : 0 1 :6(stat) 1:2(syst)) 10 4(preliminary).

The main aim of the KLOE experiment at DAΦNE, the Frascati φ-factory, is to study CP violation in the K0–K̄0 system. Requirements on shower detection are very stringent. An hermetic, lead-scintillating fiber sampling calorimeter has been chosen and built. A review of the methods used to calibrate and reconstruct energy and timing is reported in this paper. Emphasis is given to the calibration procedures developed using the 2.4 pb−1 collected in 1999. An energy resolution of 5.7%/E/GeV is achieved together with a linearity in energy response better than 1% above 50 MeV. A time resolution of ∼54 ps/E/GeV is also measured on samples of radiative Bhabha and Φ decays.

The status of the KLOE detector at the Frascati phi -factory DA Phi NE and preliminary results obtained with the data collected in 1999 (similar to 2.4pb(-1), corresponding to about 7 millions phi) are presented.

The KLOE experiment has collected 2.4 pb of integrated luminosity during the commissioning of the DAΦNE φ-factory in 1999. The performance of the detector has been studied using the φ → KLKS decays collected during this period, yielding also first measurements of relevant K parameters such as masses and lifetimes. A clean KS → π π sample is used to select KL → ππ CP-violating decays and KL → KS regeneration events in the detector material. Results on the regeneration probability in a beryllium-alluminum alloy and carbon-fiber plus aluminum composite are presented. Contributed paper ♯ 294 to the XXX International Conference on High Energy Physics, Osaka 27 jul 2 aug 2000.

The main goal of the KLOE experiment is the study of CP violation in the K mesons system, with an accuracy of 10−4 in the measurement of Re(ε′ε). This task imposes strong constraints on the design and operation of the drift chamber, which must reconstruct the charged decays of low momentum KL's and KS's with high efficiency and high resolution. A full-length prototype of the chamber has been built and tested on a 50 GeV/c beam. The analysis of the large sample of data has allowed a detailed study of the time to distance relations as a function of the track parameters and of the peculiar geometry of the drift cell. The detector performance, in terms of efficiency, spatial resolutions and dEdχ resolution, is illustrated and discussed.

The performance of a prototype drift chamber operating in a He-based gas mixture as a specific ionisation detector is presented. In spite of the small number of primary ions, Helium performs quite satisfactorily in measuring energy losses for charged particles: with 50 GeV/c pions, we have measured in a 90% He-10% iC(4)H(10) mixture a relative energy loss resolution of 3.1% with 75 samples 3 cm long, using a modified Truncated Mean technique with 80% accepted fraction.The dependence of the resolution on several parameters such as the operating voltage, the truncation fraction, the number and length of the samples is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.

The CP violation physics program and the detector design are described. The current status of KLOE is summarized.

The status of the construction of the KLOE Drift Chamber is reviewed. With its 4m diameter, it will be the biggest drift chamber ever built. The stringing of 52000 wires is a titanic effort: details are given about the semiautomatic system, the quality tests on wires and the monitoring of end-plates deformations.

For the first time an electrostatic method of wire tension measurement (WTM) is used for drift chamber construction. It became possible due to the use of a digital approach to sense the wire oscillations induced by an alternating potential. The method has excellent signal-to-noise ratio, high accuracy which is well above the stringing requirements and reasonable measuring time. The WTM system implemented in a CAMAC–Machintosh–Labview environment is now in use for the KLOE drift chamber stringing control and for monitoring the end-plate deformation.

A status report on the construction of the drift chamber for the KLOE experiment at the LNF DA Phi NE Phi-factory is given. Physics requirements, detector design performance and its key mechanical features and components are briefly reviewed. The program currently consists of (i) the preparation of final detector components, complemented by (ii) extensive tests of prototypes of critical mechanical parts (like the end plates) and the ''test construction'' of a 1:1 chamber prototype. These two sub-programs are pursued in parallel. Single-component prototype checks include surveys of their shape and size, of accuracy of wire-hole drilling, measurements of their displacement or buckling under nominal load. The ''test construction'' is the debugging of mechanical assembly, survey and alignment of mechanics and of wire-stringing robotics, the actual stringing of a sample 2000 holes drilled on the prototype end plates, the measurement of electrical properties of strung wires, as well as of their mechanical tension. These extensive tests have been successfully completed; they represent an effective hands-on training of the construction group, and will allow a prompt and steady start of the drift chamber wire stringing as all necessary components became available at LNF.