123100999
Differential cross sections of neutral pion photoproduction from hydrogen in the energy region from 390 MeV to 975 MeV
The differential cross sections of the reaction γp→π0p have been measured at photon energies between 390 MeV and 975 MeV with an energy step of 20 or 25 MeV. The angular region covers 11 angles between 15° and 130° in the c.m.s. A combination of a magnetic spectrometer and photon detector was used for the measurement in the angular region from 50° to 130°. At forward angles of 15°, 35° and 50°, π0 mesons were detected using a π0 detector consisting of a pair of photon detectors. The data obtained with two different detection systems overlap at the angle of 50° and coincide with each other within the experimental error. The results are compared with those of phenomenological partial-wave analyses.
3231612
Neutral-pion photoproduction on the deuteron.
Large-angle cross sections for ..gamma..d..--> pi../sup 0/d are systematically measured in a photon energy range between 500 and 1000 MeV. A good fit is obtained by use of a Glauber model calculation which includes the dibaryon resonances /sup 3/F/sub 3/(2.26) and /sup 1/G/sub 4/(2.51), but the fit has an unusual nature in the role of resonance and nonresonance contributions.
41583508
(d,2He) reactions at Ed=260 MeV as a possible probe to nuclear spin-isospin excitation.
The ([ital d],[sup 2]He) reactions on light nuclei were studied at [ital E][sub [ital d]]=260 MeV with a large solid-angle, wide momentum-acceptance spectrometer. The data indicated the direct one-step nature of the reaction at this energy. Observed excitation-energy spectra for [ital N]=[ital Z] nuclei compared well with those from the ([ital p],[ital n]) reactions at similar momentum transfer. The peaks corresponding to the 0[sup +][r arrow]1[sup +] transitions showed angle dependence characteristic of [Delta][ital L]=0. The 0[degree] ([ital d],[sup 2]He) cross sections were found to be proportional to the Gamow-Teller [beta]-decay strengths.
119944717
A large acceptance spectrometer using wire chambers
Abstract A large acceptance magnetic spectrometer has been constructed for an experiment on the π 0 -photoproduction off hydrogen and proton Compton scattering with the 1.3 GeV electron synchrotron at the Institute for Nuclear Study, University of Tokyo. The spectrometer system consists of four multiwire proportional chambers, six wire spark chambers and scintillation counters. The system has worked smoothly under high background events from electromagnetic processes. The performance, construction and monitoring system of the spectrometer are described.
124095029
Measurement of large-angle cross-sections for coherent pion photoproduction on deuteron
SummaryCoherent pion photoproduction from deuteron is studied by measuring the differential cross-sections at c.m. angles between 90° and 130° in a photon energy range from 500 to 1000 MeV. The experimental data are compared with a model calculation which takes into account two kinds of contributions, the nonresonant contribution consisting of pion photoproduction from single nucleons and pion rescattering and that from the dibaryon resonances3F3(2.26) and1G4(2.51). The model predictions for the photon asymmetry σ and the deuteron polarizationiT11 are also presented.RiassuntoSi studia la fotoproduzione coerente del pione dal deuterone misurando le sezioni d'urto differenziali ad angoli del centro di massa compresi tra 90° e 130° in un intervallo d'energia dei fotoni pari da 500 a 1000 MeV. Si confrontano i dati sperimentali con un calcolo di un modello che consideri due tipi di contributi, il contributo non risonante che consiste nella fotoproduzione di pioni da singoli nucleoni e rescattering di pioni., e quello dalle risonanze del dibarione3F3(2.26) e1G4(2.51). Si presentano anche le previsioni del modello per l'asimmetria σ dei fotoni e la polarizzazione dei deuteroniiT11.--РезюмеИсследуется когерентное фоторождение пионов на дейтоне, посредством измерения поперечных сечений в области углов от 90° до 130° в системе центра масс и в области энергий фотонов от 500 до 1000 МэВ. Экспериментальные данные сравниваются с модельными вячислениями, которые учитывают два типа вкладов: нерезонансный вклад, состоящий из фоторождения пионов на отдельных нуклонах, и перерассеяние пиона и вклад от дибарионных резонансов3F3(2.26) и1G4(2.51). Так же приводятся модельные предсказания для фотонной асимметрии σ и поляризации дейтонаiT11.
523124
Development of a 56 mm aperture superconducting dipole model magnet for LHC
A 56 mm single aperture superconducting dipole model magnet, which is one of the frameworks of the LHC collaboration between KEK and CERN, has been developed. A central field of 8.65 T is provided at a load line ratio of 90% with a 5 block coil wound with NbTi superconducting cables. The magnet has a straight section of 0.8 m and a total length of 1.2 m. The distinctive features of the magnet are a magnetically symmetrical configuration being applicable to the twin aperture magnet and mechanical consideration sharing the magnetic forces with a high manganese steel collar and a horizontally split iron yoke. The magnet showed almost no training at 4.4 K. The first quench current at 1.8 K was 91% of the short sample I/sub c/ and the magnet reached a central magnetic field of 8.8 T. Finally it could be excited with the current of more than 99% of the short sample limit which corresponds to a central field of 9.63 T.
42191029
Multipole analysis for absolute magnetic field measured by multi-probe pulsed-NMR method
For accelerator dipole magnets, the study on multipole coefficients in a local region is useful for understanding magnet characteristics and checking construction procedure. The multi-probe pulsed-NMR method is a candidate for measurement of the local multipole coefficients. For the absolute fields measured by the multi-probe pulsed-NMR method, a rigorous application of the Fourier expansion is found to yield multipole coefficients. It is made clear that the direction of the dipole field is unable to be determined by the Fourier expansion alone. For estimating alignment accuracy of pulsed-NMR probes, the relationship between errors of multipole coefficients and those of probe position is derived by the Fourier expansion method. For applying of multi-probe pulsed-NMR method to accelerator dipole magnets, we designed and fabricated a field measuring system using two probes. The probes had NMR coils wound around glass ampoules with a diameter of about 1.4 mm. The NMR signal was processed with a phase lock loop circuit to produce the NMR frequency. Dipole field uniformity and multipole coefficients were measured at 0.35 T for a 1.5 m long dipole magnet. It was confirmed that the field data by this NMR system had an accuracy of 10/sup -6/.
123208138
PRESENT STATUS OF THE KEKB B-FACTORY
The KEKB B-factory is an energy-asymmetric e+edouble-ring collider at KEK. It has been operated since December 1998, and has recently marked the peak luminosity of 7.35 /nb/s which is the highest value in the history of colliders. By several improvements such as solenoid windings in LER, new moving-chamber masks in HER, etc., the luminosity performance of KEKB has been significantly upgraded last year. This paper mainly describes the progress after the summer shutdown in 2001. 1 OVERVIEW The luminosity performance of KEKB, both peak and integrated luminosities, has been almost doubled in a year, as shown in Fig. 1. The main beam parameters at the peak record are listed in Table 1, compared with those about a year ago. While the main optical parameters, ex, β ∗ x,y, σz, and the number of bunches were almost unchanged, the beam-beam parameters increased as the bunch current increased. The total beam currents are now mainly limited by heating of the IR masks closest to the IP, due to both HOM and synchrotron light.
118396687
Tidal Instability and Superhump by a Wave-Wave Resonant Model
On a disk deformed to a non-axisymmetric form, a set of oscillations can be excited by their resonant interaction through the disk deformation (Kato et al. 2011). This resonant instability process has been proposed to suggest a possible cause of the high-frequency quasi-periodic oscillations (HF QPOs) observed in black-hole lowmass X-ray binaries. In the present paper, we examine whether the above-mentioned wave-wave resonant process can describe the tidal instability and superhump in dwarf novae. The results show that the process seems to well describe the observations. If this process is really the cause of the tidal instability and superhump, a two-armed oscillation with high frequency roughly on the magnitude of three times the orbital frequency is present on disks, although its expected amplitude may be small.
89614487
High energy electron acceleration by stochastic acceleration mechanism
A stochastic acceleration mechanism which explains the high energy electron acceleration by intense laser pulses is analyzed by Fokker‐Planck approach. The Fokker‐Planck equation describing is derived from the equation of motion of electrons interacting with filamented laser field. The time evolution of electron distribution function, energy distribution, effective temperature are obtained for initially rest plasma. The acceleration of 10 MeV electron beam is examined and shown to be effective.