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Experiments for the laser guiding studies has been carried out with the 30-fs 100-TW Ti:sapphire laser pulse interaction with the underdense plasma produced by a long-slab (1.2 times 10 mm2) gas jet and an ablative laser-triggered discharged capillary. Formation of an extremely long plasma channel with a length (~10 mm) 10 times above the Rayleigh length is observed when the laser pulse power is much higher than the critical power for relativistic self-focusing. The long-self-guiding- channel formation is accompanied by the electron acceleration with a low transverse emittance (< 0.87pi mm mrad) and high electric current (~10 nC/shot), as well as the generation of a quasi- monoenergetic electron bunch with an energy of ~80 MeV. In order to continuously elongate the plasma channel, a 4-cm- scale discharged capillary was used. We successfully demonstrated laser-plasma acceleration of high-quality electron beams up to nearly semigigaelectronvolts. Our results exactly verified the prediction of laser wakefield acceleration through a centimeter- scale plasma channel in the "blowout bubble" regime, where a microscale plasma cavity produced through the ultrarelativistic laser-plasma interactions plays an essential role in the self- injection and acceleration of electrons.

Based on 58 million BESII J / ψ events, the K ¯ ∗ ( 892 ) 0 K + π − channel in K + K − π + π − is studied. A clear low mass enhancement in the invariant mass spectrum of K + π − is observed. The low mass enhancement does not come from background of other J / ψ decay channels, nor from phase space. Two independent partial wave analyses have been performed. Both analyses favor that the low mass enhancement is the κ , an iso-spinor scalar resonant state. The average mass and width of the κ in the two analyses are 878 ± 23 −55 +64 MeV / c 2 and 499 ± 52 −87 +55 MeV / c 2 , respectively, corresponding to a pole at ( 841 ± 30 −73 +81 ) − i ( 309 ± 45 −72 +48 ) MeV / c 2 .

An overview of the KEKB accelerators is given as an introduction of the following articles in this issue, first by summarizing the basic features of the machines, and then describing the improvements of the performance since the start of the physics experiment.

KEKB has been operated since December, 1998, to deliver BB pairs for a physics detector. In this paper,we describe the commissioning procedure of KEKB.

A computor control system of magnets in the low energy separated beams in KEK is reported. The system consists of five CAMAC crates and a central minicomputor. The CAMAC crates are connected by a CAMAC Serial Highway. The transmission is 128 k bytes/sec byte serial mode. Compared to the manual remote control arrangement, improvements in beam line operation can be identified.

An N-to-N token ring network of twenty-four minicomputers controls the TRISTAN accelerator complex. The computers are linked by optical fiber cables with 10 Mbps transmission speed. The software system is based on the NODAL, a multi-computer interpreter language developed at CERN SPS. Typical messages exchanged between computers are NODAL programs and NODAL variables transmitted by the EXEC and the REMIT commands. These messages are exchanged as a cluster of packets whose maximum size is 512 bytes. At present, eleven minicomputers are connected to the network and the total length of the ring is 1.5 km. In this condition, the maximum attainable throughput is 980 kbytes/s. The response of a pair of an EXEC and a REMIT transactions which transmit a NODAL array A and one line of program `REMIT A' and immediately remit the A is measured to be 95+0.039x ms, where x is the array size in byte. In ordinary accelerator operations, the maximum channel utilization is 2%, the average packet length is 96 bytes and the transmission rate is 10 kbytes/s.

The KEK NODAL system, which is based on the NODAL devised at the CERN SPS, works on an optical-fiber token ring network of twenty-four minicomputers (Hitachi HIDIC 80's) to control the TRISTAN accelerator complex, now being constructed at KEK. KEK NODAL retains main features of the original NODAL: the interpreting scheme, the multi-computer programming facility, and the data-module concept. In addition, it has the following characteristics: (1) fast execution due to the compiler-interpreter method, (2) a multicomputer file system, (3) a full-screen editing facility, and (4) a dynamic linkage scheme of data modules and NODAL functions. The structure of the KEK NODAL system under PMS, a real-time multitasking operating system of HIDIC 80, is described; the NODAL file system is also explained.

The results of the measurements of the characteristics of two low energy separated beams, K2 and K3, are reported. The performances of the electrostatic separators used in those beams are also presented.

A computer control and monitor system was constructed to handle power supplies of the beam line magnets. The interface modules are installed in CAMAC crates linked by a CAMAC serial highway. The structure and performance of the system are presented.

We summarize here the outline of our system. (1) Distributed computer control scheme is adopted. (2) Twenty-five 16-bit mini-computers are connected by 10 Mbps optical fiber cables to form an N-to-N ring network. (3) NODAL interpreter and compiler are used throughout the program development of the system. (4) CAMAC serial highways are used as the means of communication between the mini-computers and the devices. (5) TRISTAN system is controlled from a single control center.