No abstract

We construct a kink solution on a non-BPS D-brane using Berkovits' formulation of superstring field theory in the level truncation scheme. The tension of the kink reproduces 95% of the expected BPS D-brane tension. We also find a lump-like solution which is interpreted as a kink-antikink pair, and investigate some of its properties. These results may be considered as successful tests of Berkovits' superstring field theory combined with the modified level truncation scheme.

Superconducting helical dipole magnets will be used in the Brookhaven Relativistic Heavy Ion Collider (RHIC) to maintain polarization of proton beams and to perform localized spin rotations at the two major experimental detector regions. Requirements for the helical dipole system are discussed, and magnet prototype work is reported. SNAKES AND SPIN ROTATORS IN RRICThe Relativistic Heavy Ion Collider at Brookhaven National Laboratory allows for the unique possibility of colliding high energy polarized proton beams. To maintain polarization during the acceleration process, two full "Siberian Snakes" are to be inserted on opposite sides of the RHIC lattice for each of the two counter-rotating rings. In addition, other magnetic components --spin rotators --will be located on each side of the two major interaction points (again, far each ring) which allow the spin orientation to be altered from the vertical direction to the longitudinal direction. Superconducting magnets are used in order to contain the magnetic elements for a Snake within a 10 m longitudinal space so as to fit within available room in the RHIC lattice. The use of a helical dipole field as part of a Siberian Snake in a synchrotron was fust suggested by Courant [l]. A system made completely of four identical length helices was first proposed by Ptitsin and Shatunov [2]. Four right-handed helical dipole magnets, each 2.4 m long and operating near 4 T or less can produce a Siberian Snake for RHIC. The strong helical fields reduce the orbit excursions normally produced by interleaved horizontal and vertical dipole magnets. Hence, the magnet apertures can be similar to those found elsewhere in RHIC. Furthermore, a combination of right-handed and lefthanded helical dipole magnets also within a 10 m space can perform the desired local 90" rotations of the spin at the major detector regions. The twisting current distribution introduces intrinsic nonlinear terms into the field. To first order, the trajectory through the helical field above is just I . I Helical Magnets for Spin ControlWe see that for a complete 360" helix, the effect on the particle trajectory is simply a vertical "shift" in the orbit by an amount S = -B&k(Bp). We also note that the handedness of the helix is given by the sign of k, positive is right-handed, negative is left-handed. By pairing identical length 360" helical magnets of the same strength but opposite field directions (or, equivalently, with equal strength but opposite handedness), the overall orbit distortion outside the system will be zero. With four magnets, this allows one to choose two independent field strengths far control of the spin rotation angle and axis of rotation. A third parameter is needed to completely define the rotation, but by providing the system with reflection symmetry, the axis of rotation is constrained to lie in the horizontal plane.The spin precession through a helical dipole magnet is most easily found by using the spinor formalism and solving the equation of motion for the fmt-order feld expre...

Studies of radioactive ions (RI) is the most intensively developing field of the low-energy nuclear physics. In this paper the concept and the scientific agenda of prospective accelerator and storage ring facility for the RI beam (RIB) research are proposed for the large-scale international project based at the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research. The motivation for the new facility is discussed and its characteristics are briefly presented, showing to be comparable to those of the advanced world centers, the socalled "RIB factories". In the project the emphasis is made on the studies with the short-lived RIBs in storage rings. A unique feature of the project is the possibility to study the electron-RI interactions in the collider experiment for determination of fundamental properties of the nuclear matter, in particular, electromagnetic form-factors of exotic nuclei.

No abstract