438 research outputs found
Positron source: first 50 nanoseconds
No full textThese results use the program ETRANS written by Harvey Lynch. ETRANS steps positrons produced in the target through a series of elements simulating the magnetic and accelerting fields of the flux concentrator, DC solenoids, and accelerating cavities. 13 figures, 1 table
Recommended from our members
Experimental test of exchange degeneracy in hypercharge exchange reactions. [Helicity-flip and nonflip amplitudes, angular distribution, quark model]
No full textTwo pairs of line-reversed reactions ..pi../sup +/P ..-->.. K/sup +/..sigma../sup +/, K/sup -/p ..-->.. ..pi../sup -/..sigma../sup +/ and ..pi../sup +/p ..-->.. K/sup +/Y*/sup +/(1385), K/sup -/p ..-->.. ..pi../sup -/Y*/sup +/(1385) provide an experimental test of exchange degeneracy in hypercharge exchange reactions. From their study it is concluded that in contrast to the lower energy data, the 11.5 results for the two pairs of reactions are consistent with exchange degeneracy predictions for both helicity-flip and nonflip amplitudes. The Y(1385) decay angular distributions indicate that the quark model and Stodolsky--Sakurai predictions are in agreement with the main features of the data. However, small violations are observed at small momentum transfer. While the Y(1385) vertex is helicity-flip dominated, the nonvanishing of T/sub 3/2 - 1/2/ and T/sub -3/2 1/2/ suggests some finite helicity nonflip contribution in the forward direction. 23 references. (JFP
Recommended from our members
Polarized electron beams at SLAC
No full textSLAC has successfully accelerated high energy polarized electrons for the Stanford Linear Collider and fixed polarized nuclear target experiments. The polarized electron beams at SLAC use a gallium arsenide (GaAlAs for E-142) photon emission source to provide the beam of polarized electrons with polarization of approximately 28% (41% for E-142). While the beam emittance is reduced in the damping ring for SLC operation a system of bend magnets and superconducting solenoids preserve and orient the spin direction for maximum longitudinal polarization at the collision point. The electron polarization is monitored with a Compton scattering polarimeter, and was typically 22% at the e[plus]e[minus] collision point for the 1992 run. Improvements are discussed to increase the source polarization and to reduce the depolarization effects between the source and the collision point
Production of pi+, K+, K0, K*0, phi, p and Lambda0 in hadronic Z0 decays
No full textWe have measured the differential production cross sections as a function of scaled momentum xp=2p/Ec.m. of the identified hadron species π+, K+, K0, K*0, φ, p, Λ0, and of the corresponding antihadron species in inclusive hadronic Z0 decays, as well as separately for Z0 decays into light (u, d, s), c and b flavors. Clear flavor dependences are observed, consistent with expectations based upon previously measured production and decay properties of heavy hadrons. These results were used to test the QCD predictions of Gribov and Lipatov, the predictions of QCD in the modified leading logarithm approximation with the ansatz of local parton-hadron duality, and the predictions of three fragmentation models. The ratios of production of different hadron species were also measured as a function of xp and were used to study the suppression of strange meson, strange and non-strange baryon, and vector meson production in the jet fragmentation process. The light-flavor results provide improved tests of the above predictions, as they remove the contribution of heavy hadron production and decay from that of the rest of the fragmentation process. In addition we have compared hadron and antihadron production as a function of xp in light quark (as opposed to antiquark) jets. Differences are observed at high xp, providing direct evidence that higher-momentum hadrons are more likely to contain a primary quark or antiquark. The differences for pseudoscalar and vector kaons provide new measurements of strangeness suppression for high-xp fragmentation products. ©1999 The American Physical Society
Spin rotation schemes at the ILC for two interaction regions and positron polarization with both helicities
No full textThis note describes a spin rotation scheme for the ILC that allows the polarization spin vector of the electron and positron beams to be tuned independently for two Interaction Regions (IR). The correct spin direction for a particular IR can be selected by directing the beam into one of two parallel spin rotation beam lines located between the damping ring and the linac. With suitable fast kicker magnets, it is possible to rapidly switch between these parallel beam lines, so that polarized beams can be delivered to two IRs on a pulse train by pulse train basis. A similar scheme can be employed in the insertion beam line to the positron damping ring, to allow rapid helicity switching for polarized positrons
Measurement of the decays and
No full textWe have observed the decays B-->phi K and phi K^* in a sample of over 45 million B mesons collected with the BABAR detector at the PEP-II collider. The measured branching fractions are BF(B^+ --> phi K^+) = (7.7^{+1.6}_{-1.4}+/- 0.8) x 10^{-6}, BF(B^0 --> phi K^0) = (8.1^{+3.1}_{-2.5}+/- 0.8) x 10^{-6}, BF(B^+ --> phi K^{*+}) = (9.7^{+4.2}_{-3.4}+/- 1.7) x 10^{-6} and BF(B^0 --> phi K^{*0}) = (8.6^{+2.8}_{-2.4}+/- 1.1) x 10^{-6}. We also report the upper limit BF(B^+ --> phi pi^+) 1.4 x 10^{-6}$ (90% CL)
Book reviews [1986, Vol. 13, no. 1]
No full textBooks reviewed are: Robert R. Locke, The End of the Practical Man: Entrepreneurship and Higher Education in Germany, France and Great Britain, 1880-1940. Review by O. Finley Graves; F. Sewell Bray, Precision and Design in Accountancy Reviewed by Edward N. Coffman; Richard P. Brief, ed. Dicksees Contribution to Accounting Theory Reviewed by Walker Fesmire; Leslie G. Campbell, International Auditing: A Comparative Survey of Professional Requirements in Australia, Canada, France, West Germany, Japan, the Netherlands, the UK and the USA. Reviewed by O. Ronald Gray; Sir Hugh Cooke. A Summary of the Principal Legal Decisions Affecting Auditors Reviewed by Raymond T. Holmes, Jr.; Hawawini, G. A. and Ashok, V., eds. The History of Interest Approximations Reviewed by Charles E. Boynton IV; McCraw, Thomas K. Prophets of Regulation Reviewed by Robert Bricker; D. R. Myddleton, On A Cloth Untrue: Inflation Accounting : The Forward Way Reviewed by B. A. Coda; Beresford Worthington. Professional Accountants Reviewed by Katherine S. Moffeit; CAPSULE COMMENTS: Barbara D. Merino Edwards, J. R., ed. British Company Legislation and Company Accounts, 1844-1974. The Institute of Chartered Accountants in England and Wales Library Catalogue, 1913. The Institute of Chartered Accountants in England and Wales Library Catalogue, 1937. Papers and Proceedings of the American Association of University Instructors in Accounting
Notes on the rf system for the SLC positron source
No full textThe proposed arrangement of accelerator structures, waveguide feeds and klystrons is shown. A 50 MW klystron at 20-3C will provide power for the high-field capture section immediately following the target. About 1 meter downstream of this section there will be a standard girder of four 3.05-meter SLAC constant gradient accelerator sections. These will be powered by a klystron at station 20-3D. Current thinking is that this will also be a 50 MW tube, but 35 MW might well be sufficient. Both stations will be SLEDded. The length of the rectangular waveguide feed to the capture section will be approximately 132 ft, and the attenuation will be about 0.97 db. The corresponding numbers for the feed to the standard girder are 153 ft and 1.07 db. In CN-268 dated 6/22/84: Positron Source: First 50 Nanoseconds, K. Moffeit shows that good positron acceptance requires very high accelerating fields (on the order of 70 MV/m) in the first meter following the target. Various ways of approaching this gradient in a 1-meter section have been examined
- …
