T. Kubo

Vidence for CP-violating asymmetries in B0→π +π- decays and constraints on the CKM angle φ2

We present an improved measurement of CP-violating asymmetries in B-0-->pi(+)pi(-) decays based on a 78 fb(-1) data sample collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We reconstruct one neutral B meson as a B-0-->pi(+)pi(-) CP eigenstate and identify the flavor of the accompanying B meson from inclusive properties of its decay products. We apply an unbinned maximum likelihood fit to the distribution of the time intervals between the two B meson decay points. The fit yields the CP-violating asymmetry amplitudes A(pipi) = +0.77 +/-0.27(stat) +/-0.08(syst) and S-pipi = -1.23+/-0.41(stat) (+0.08)(-0.07)(syst), where the statistical uncertainties are determined from the Monte Carlo pseudoexperiments. We obtain confidence intervals for CP-violating asymmetry parameters A(pipi) and S-pipi based on a frequentist approach. We rule out the CP-conserving case, A(pipi) = S-pipi = 0, at the 99.93% confidence level. We discuss how these results constrain the value of the Cabibbo-Kobayashi-Maskawa (CKM) angle phi(2).

Magnet system for the KEKB main ring

Abstract KEKB is a two-ring electron–positron collider with asymmetric energies of 8 and 3.5 GeV to study CP violation in B meson decay. In KEKB, there are 21 types of magnets; about 1600 in total. About 430 dipole and quadrupole magnets were recycled from TRISTAN, the preceding program. All quadrupole magnets are equipped with vertical and horizontal steering dipole magnets. The number of steering magnets is about 1700. There are 212 sextupole magnets, and all of them are fixed on remotely controlled movers to adjust their positions to the beam passage. All main dipole magnets have back-leg coils to steer beams precisely. All quadrupole and sextupole magnets are equipped with correction coils to have a capability for beam-based alignment. Also one-turn coils are installed as well to each magnetic pole of the main magnets to monitor the magnetic flux in the case of trouble. The magnetic field in all magnets was measured and its quality strictly checked. After field measurement, the magnets were installed and precisely aligned. A cooling water system and a power supply system for these magnets were constructed. Magnet design was started in 1994, and construction of the two rings was completed in November 1998. The parameters of the magnets and the construction of the KEKB magnet system are described. Some of the problems experienced during this construction work are also presented.

Accelerator plan for a light‐source study at the TRISTAN MR

A three‐month operation with a beam is scheduled for the autumn of 1995 at the TRISTAN MR for the sake of light‐source development and research programs using it. The lattice will be modified so as to enable the installation of an undulator 5.4 m long and achieve a very low‐emittance beam of 5 nm at 10 GeV. The emittance damping wigglers will enhance the radiation‐damping rate, which will stabilize the coherent beam instabilities as well as reduce the emittance more. A considerable number of accelerating cavities will be removed from the ring in order to minimize the impedance of the higher‐order modes of the cavities that may cause coupled‐bunch instabilities and limit the intensity of the stored beam. For the stability of the light beam, a local feedback system will be applied to the electron orbit in the MR. The beam emittance will be measured by detecting the angular distribution of the Compton scattering of laser photons from the beam electrons. To measure the beam emittance in an independent way, vi...

Superconducting quadrupole magnet system for TRISTAN mini-beta insertions

Superconducting quadrupoles for the mini-beta insertions were installed close to every interaction point and their performances were tested successfully. The system consists of four subsystems, which can be operated individually at the local control rooms located near the subsystems and/or at the remote central cryogenic control room.<<ETX>>

Field measurement of superconducting quadrupole magnets for TRISTAN mini-beta insertions

Eight superconducting quadrupole magnets for TRISTAN minibeta insertions (QCS) have been measured by the rotating coil method before installation in the TRISTAN electron-positron colliding ring. Following the alignment of the magnet to the measuring system by use of a movable QCS-support, harmonics and field gradients were measured as functions of current and the median plane was determined for each magnet. Details of the measuring systems and results of the measurements are presented. The results of the field measurements show that the relative errors of the integral field gradient can be kept within +or-0.001 for all the magnets and that the higher multipole components are small enough for the tolerance required to the QCS.<<ETX>>

Digital Simulation for TRISTAN AR Magnet Power Supply and Control System

The TRISTAN AR Magnet Power Supply is the system for exciting the magnets to accelerate the electron and positron beam from 2.5 GeV to 8 GeV. To estimate its performance the digital simulation was performed using DDS (Digital Dynamics Simulator). The simulation method and the result are described.

Software System for the Operation of the TRISTAN-AR Power Supply

Many power supplies ranging from 1 KVA to 4 MVA are controlled remotely through the serial CAMAC data way. The programs for their operation have been combined to form a software system which includes functions such as current monitoring, interlock and status surveillance, current pattern data generation, current fine adjustment, data transfer and so on.

Power Supply Control Programs for the TRISTAN AR

The power supplies of the TRISTAN Accumulation Ring (AR) have been operated under the KEK NODAL system[1] since November 1983. This report describes the details of control programs and some discussions.

Lattice Upgrade Plan for Crab Crossing at the KEKB Rings

We plan to install two superconducting crab cavities into the rings at January, 2006. In our plan, we will install one crab cavity per one ring into the NIKKO straight section where the cryogenic infrastructure is already operated for the superconducting accelerating cavities. For crab crossing, we have to enlarge the horizontal beta function(200m for HER) and have to adjust the horizontal phase advance between the interaction point and the crab cavity. In this paper, we will report the lattice modified for the crab crossing and the study results about the single beam dynamics.

Steering Magnet Power Supply Control System for the TRISTAN AR

The closed orbit distortion of TRISTAN Accumulation Ring (AR) is corrected by the steering magnets1-2 (correction dipole magnets). These magnets are excited by the bipolar power supplies with the rated power of about 1 KVA. The power supplies are controlled remotely through the serial camac dataway3. The camac modules which include the microprocessor are developed for this system and these modules send out the reference current patterns to the individual power supply.