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Direct electron pair production in. pi. /sup -/p interactions at 16 GeV/c and a model for direct lepton and photon production at low P/sub T/

Description: The production of prompt electron-positron pairs in 16 GeV/c ..pi../sup -/p collisions has been measured using the LASS spectrometer at SLAC. An excess of events is observed above the estimated contributions of direct and Dalitz decay of known resonances in the kinematic range defined by 0.1 less than or equal to x less than or equal to 0.45, 0 less than or equal to P/sub T/ less than or equal to 0.8 GeV/c and 0.2 less than or equal to M(e/sup +/e/sup -/) less than or equal to 0.7 GeV/c/sup 2/. The excess signal decreases slowly with increasing M, but exhibits very steep x and P/sub T//sup 2/ dependence. The contribution of this signal to the e/sup +/e/sup -//..pi../sup +/..pi../sup -/ and ..gamma../..pi.. ratios is discussed. Detailed comparisons are made between e/sup +/e/sup -/ distributions and the corresponding low mass ..mu../sup +/..mu../sup -/ distributions, and a simple production mechanism is proposed which describes the 16 GeV/c data well. The implications for direct photon production are presented, and it is shown that the model provides simultaneously a good description of the experimental data on the (e/..pi..) and (..mu../..pi..) ratios for p/sub T/ < 1 GeV/c.
Date: July 1, 1981
Creator: Blockus, D.; Dunwoodie, W. & Leith, D.W.G.S.
Partner: UNT Libraries Government Documents Department

Design of an electron beam spectral modification system

Description: We report the design of a spectral modification system (SMS) for use with the proposed NEAL linac-pulse stretcher ring, cw electron beam facility. The SMS allows tailoring of the energy distribution of electrons in beams produced by a pulsed linac operating in the transient beam loading (TBL) regime. Modification of the energy distribution of electrons injected into the pulse strecher ring will increase the duty factor of current extracted from the ring and improve the efficiency of the extraction process. Physically, the SMS consists of an anisochronous, achromatic magnetic lattice followed by a pair of traveling-wave accelerating sections. For beams in the energy range of 500 MeV to 4 GeV, TBL ripple on the energy envelope of microsecond long beam spills is expected to be reduced from 1% peak-peak to less than 0.01% while the desired width of the energy profile due to the phase extent of the microbunches in the beam spill is preserved.
Date: October 1, 1981
Creator: Sheppard, J.C.; York, R.C.; Norum, B.E. & McCarthy, J.S.
Partner: UNT Libraries Government Documents Department

Exclusive processes in quantum chromodynamics

Description: Large momentum transfer exclusive processes and the short distance structure of hadronic wave functions can be systematically analyzed within the context of perturbative QCD. Predictions for meson form factors, two-photon processes ..gamma gamma.. ..-->.. M anti M, hadronic decays of heavy quark systems, and a number of other related QCD phenomena are reviewed.
Date: June 1, 1981
Creator: Brodsky, S.J. & Lepage, G.P.
Partner: UNT Libraries Government Documents Department

Crystal Ball evidence for new states

Description: Evidence for three new particles observed in the Crystal Ball detector is presented. The first particle, at 3592 MeV, is seen inclusively in ..gamma.. transitions from psi', and is thus a candidate for eta/sub c/'. The other two, at 1440 and 1640 MeV, are best seen in exclusive decays of psi involving a prompt ..gamma.., and are thus candidates for bound states of two gluons. Detailed reasons are presented to support the contention that these states are distinct from previously observed candidates such as E(1420). Alternative hypotheses are discussed.
Date: September 1, 1981
Creator: Coyne, D.G.
Partner: UNT Libraries Government Documents Department

Initial-state interactions, factorization, and the Drell-Yan process

Description: It is shown that initial state interactions violate the factorization conjecture for the Drell-Yan process order by order in perturbation theory. Also, the effects of elastic and inelastic initial state interactions on the observed cross sections are discussed.
Date: December 1, 1981
Creator: Bodwin, G.T.; Brodsky, S.J. & Lepage, G.P.
Partner: UNT Libraries Government Documents Department

Baryon production at PEP

Description: Measurements of inclusive ..lambda.. + anti ..lambda.. production for 1.0 less than or equal to p less than or equal to 10.0 GeV/c and p + anti p production for 0.4 less than or equal to p less than or equal to 2.0 GeV/c show significant baryon production in e/sup +/e/sup -/ annihilation at E/sub cm/ = 29 GeV. ..lambda.. + anti ..lambda.. production represents 0.2 ..lambda..'s or anti ..lambda..'s per PEP event while the observed p + anti p production implies all baryon-antibaryon pair production is occurring at least as often as 0.6 per event, depending on the yet to be measured p + anti p production at high momentum. Comparisons are made with the first theoretical attempts to account for baryon production at these energies.
Date: September 1, 1981
Creator: Goldhaber, G. & Weiss, J.M.
Partner: UNT Libraries Government Documents Department

Quantum chromodynamics and hadronic interactions at short distances

Description: A brief introduction to QCD and asymptotic freedom is given. A new method to avoid scheme and scale ambiguities in perturbative QCD predictions is discussed. A detailed discussion of light-cone perturbation theory and the Fock state expansion of hadronic wavefunctions is given. The QCD equation of motion is also discussed. Measures of the hadronic wavefunction (form factors, magnetic moments, etc.), and the QCD analysis of high momentum transfer exclusive processes are discussed. It is also shown how meson distribution amplitudes can be measured in ..gamma gamma.. ..-->.. M anti M reactions. The connection of the Fock state basis to leading and higher twist contributions to deep inelastic scattering is given. How many different QCD processes are interelated through the hadronic Fock states is discussed, and a novel type of QCD subprocess - direct coupled hadron-induced reactions is considered. A new prediction for the proton form factor is also given. Also, a simple phenomenology of hadron wavefunctions is introduced, and present constraints on the form and normalization of the valence meson and nucleon Fock states are discussed. An important conclusion is that the valence Fock state as defined at equal time or the light cone appears to have a significantly smaller radius than that of the physical hadron; higher Fock states thus play an essential role in low momentum transfer phenomenology. Applications to quark jet diffraction excitation and the hidden heavy quark Fock state structure of hadrons are also discussed. 83 references. (WHK)
Date: January 1, 1981
Creator: Brodsky, S.J.; Huang, T. & Lepage, G.P.
Partner: UNT Libraries Government Documents Department

Summary talk

Description: To sum it all up: 1. QCD has made its mark and is here to stay with its J = 1 gluons. 2. A quantitative determination of the strong coupling constant ..cap alpha../sub s/, and scale parameter, ..lambda.., remains for the future. The reliable processes from the theoretical point of view for determining their values will be R or the study of the 3-gluon decays of heavy onia still to be discovered. 3. Very deep questions such as the scale of grand unification and the hierarchy problem. viz. why is the weak interaction lifetime of the neutron so many orders of magnitude shorter than the proton decay lifetime, or why is the grand unification scale so much larger than the weak vector boson mass, remain beyond our understanding. 4. All theories, as so eloquently described in Professor Okun's beautiful talk, lead us to expect to observe evidence of scalars in the ee annihilation process, whether they arise from dynamical or spontaneous symmetry breaking.
Date: January 1, 1981
Creator: Drell, S.D.
Partner: UNT Libraries Government Documents Department

Recent results from SPEAR

Description: Recent results from SPEAR include measurements of Cabibbo-suppressed decay modes of the tau (Mark II), and a limit on the decay J/psi ..-->.. ..gamma.. + axion (Crystal Ball).
Date: August 1, 1981
Creator: Porter, F.C.
Partner: UNT Libraries Government Documents Department

Recent results from the Crystal Ball

Description: During the past year, the Crystal Ball experiment has continued the investigation of e/sup +/e/sup -/ interactions at SPEAR. In the course of the year, we have slightly more than doubled the available datasets at the J/psi (to 2.2 x 10/sup 6/ produced J/psi) and the psi' (to 1.8 x 10/sup 6/ produced psi') resonances, and have increased the data in the 5.2 to 7.4 GeV center-of-mass (E/sub c.m./) region. The present discussion is limited to recent results obtained with the J/psi and psi' datasets, primarily dealing with transitions among the charmonium bound states.
Date: September 1, 1981
Creator: Porter, F.C.
Partner: UNT Libraries Government Documents Department

Beam parametr measurements for the SLAC linear collider

Description: A stable, closely-controlled, high-intensity, single-bunch beam will be required for the SLAC Linear Collider. The characteristics of short-pulse, low-intensity beams in the SLAC linac have been studied. A new, high-intensity thermionic gun, subharmonic buncher and S-band buncher/accelerator section were installed recently at SLAC. With these components, up to 10/sup 11/ electrons in a single S-band bunch are available for injection into the linac. the first 100-m accelerator sector has been modified to allow control of short-pulse beams by a model-driven computer program. Additional instrumentation, including a computerized energy analyzer and emittance monitor have been added at the end of the 100-m sector. The beam intensity, energy spectrum, emittance, charge distribution and the effect of wake fields in the first accelerator sector have been measured. The new source and beam control system are described and the most recent results of the beam parameter measurements are discussed.
Date: January 1, 1981
Creator: Clendenin, J.E.; Blocker, C. & Breidenbach, M.
Partner: UNT Libraries Government Documents Department

Fundamental tests and measures of the structure of matter at short distances

Description: Recent progress in gauge field theories has led to a new perspective on the structure of matter and basic interactions at short distances. It is clear that at very high energies quantum electrodynamics, together with the weak and strong interactions, are part of a unified theory with new fundamental constants, new symmetries, and new conservation laws. A non-technical introduction to these topics is given, with emphasis on fundamental tests and measurements. 21 references.
Date: July 1, 1981
Creator: Brodsky, S.J.
Partner: UNT Libraries Government Documents Department

Exclusive final states from photon-photon collisions at SPEAR

Description: Studies of exclusive final states produced by the two-photon process have been made at SPEAR by the Mark II and by the Crystal Ball Collaborations. Measurements of ..pi../sup +/..pi../sup -/ and ..pi../sup 0/..pi../sup 0/ production in the mass region 500 MeV/c/sup 2/ < m/sub ..pi pi../ < 2000 MeV/c/sup 2/ are presented. These data include strong signals from the well-known f(1270) meson. The A/sub 2/(1310) has been observed via its ..pi../sup 0/ eta decay mode and its partial width to ..gamma gamma.. has been determined. A measurement of the cross section for the reaction ..gamma gamma.. ..-->.. ..pi../sup +/..pi../sup -/..pi../sup +/..pi../sup -/ is reported. This channel is found to be small just above the four pion threshold, but exhibits a large enhancement near the rho/sup 0/rho/sup 0/ threshold.
Date: May 1, 1981
Creator: Burke, D.L.
Partner: UNT Libraries Government Documents Department

Exceptional groups and elementary-particle structures

Description: A new finite-dimensional quantum mechanical space is constructed over the complex octonionic plane using the recently developed algebraic techniques of Jordan pairs and inner ideals. The automorphism group of this structure is E/sub 6/ x U(1), realized on precisely two E/sub 6/ irreps which is abstracted as a (topless) model for grand unification.
Date: September 1, 1981
Creator: Biedenharn, L.C. & Truini, P.
Partner: UNT Libraries Government Documents Department

CID thermionic gun system

Description: A new high-current thermionic gun has been installed on the CID injector at SLAC and brought into operation. The gun and pulser system generate three nanosecond pulses of about six amps peak which, when bunched in the subharmonic buncher system, produce in excess of 10/sup 11/ electrons in a single S-band accelerated bunch. Preliminary operation of the gun is described, and details of the avalanche cathode drive pulser are presented.
Date: October 1, 1981
Creator: Koontz, R.F.
Partner: UNT Libraries Government Documents Department

Coordinate measurement by current division: a simple system for multichannel detectors

Description: A simple current-division scheme is described based on an unorthodox connection of the 733 amplifier chip: a common-base input can be obtained by grounding the normal inputs and driving a gain control terminal. With ganged multiwire chambers detecting cosmic rays in the proportional region, under realistic operating conditions (charge approx. 2 picocoulombs per gap), the resolution is about 2% of full length. Calibration procedures are discussed, as are the effects of changing various parameters.
Date: August 1, 1981
Creator: Gottschalk, B.
Partner: UNT Libraries Government Documents Department

Polarization of a stored electron beam

Description: Synchrotron radiation by a point charge is a familiar subject in classical electrodynamics. Perhaps less familiar are some quantum mechanical corrections to the classical results. Some of those quantum aspects of synchrotron radiation are described. One of the quantum effects leads to the expectation that electrons in a storage ring will polarize themselves to 92% - a surprisingly high value. A semi-classical derivation of the quantum effects is given. An effort has been made to minimize the need of using quantum mechanics. Results are put together to derive a final expression of beam polarization. Conditions under which the expected 92% polarization is destroyed are found and attributed to depolarization resonances. The various depolarization mechanisms are first illustrated by an idealized example and then systematically treated by a matrix formalism. It is shown that the strength of depolarization is specified by a key quantity called the spin chromaticity. Finally as an application of the obtained results, an estimate of the achievable level of beam polarization for two existing electron storage rings, SPEAR and PEP, is given.
Date: July 1, 1981
Creator: Chao, A.W.
Partner: UNT Libraries Government Documents Department

Oxide effects on photoemission from high current GaAs photocathodes

Description: During four years of on line operation of the SLAC polarized electron gun (PEGGY) and polarized LEED (PLEED) system, we have observed and characterized the failure modes of the GaAs (100) photocathodes (PC's) used in these systems. Several modes are observed. Gradual decreases in electron polarization and intensity are attributed to the physisorption of CO/sub 2/ on the PC's during running at LN/sub 2/ temperatures. Such PC's can be rejuvenated by warming to 90K, i.e., above the CO/sub 2/ desorption temperature. These PC's recover 90% of their original intensity. A second well-characterized failure mode results from overheating the PC during in-situ heat cleaning prior to activation. In this mode, As is preferentially evaporated from the GaAs, leaving a Ga/sub 2/O/sub 3/ layer on the surface. This effect has been studied by AES sputter profiling which indicates that the substantial thickness of the oxide layer blocks photoemission. These PC's may only be recovered by chemically removing the oxide layer. A third mode which is not as well characterized appears for thin Ga oxide layers. Properties of these PC's include reduced emission and the presence of a cutoff bias level. Such PC's are also not recoverable in-situ.
Date: March 1, 1981
Creator: Garwin, E.L.; Kirby, R.E.; Sinclair, C.K. & Roder, A.
Partner: UNT Libraries Government Documents Department

nu. N,. mu. N interactions: structure functions, higher twist

Description: Data on deep inelastic scattering of leptons by nucleons and nuclei have been accumulated for several years. Results exist from several experiments with electron, muon, neutrino beams. In this talk I shall review the most recent experiments which measured nucleon structure functions with ..nu.. and ..mu.. beams. In particular, I will summarize the results on R = sigma/sub L//sigma/sub T/ measurement, on F/sub 2/(x,Q/sup 2/), and xF/sub 3/(x,Q/sup 2/), and their interpretation in terms of QCD, including both gluon radiation and higher twist phenomena.
Date: October 1, 1981
Creator: Matteuzzi, C.
Partner: UNT Libraries Government Documents Department

Minimal relativistic three-particle equations

Description: A minimal self-consistent set of covariant and unitary three-particle equations is presented. Numerical results are obtained for three-particle bound states, elastic scattering and rearrangement of bound pairs with a third particle, and amplitudes for breakup into states of three free particles. The mathematical form of the three-particle bound state equations is explored; constraints are set upon the range of eigenvalues and number of eigenstates of these one parameter equations. The behavior of the number of eigenstates as the two-body binding energy decreases to zero in a covariant context generalizes results previously obtained non-relativistically by V. Efimov.
Date: July 1, 1981
Creator: Lindesay, J.
Partner: UNT Libraries Government Documents Department

Moving to a total VM environment

Description: The Stanford Linear Accelerator Center is a single purpose laboratory operated by Stanford University for the Department of Energy. Its mission is to do research in High Energy (particle) physics. This research involves the use of large and complex electronic detectors. Each of these detectors is a multi-million dollar device. A part of each detector is a computer for process control and data logging. Most detectors at SLAC now use VAX 11/780s for this purpose. Most detectors record digital data via this process control computer. Consequently, physics today is not bounded by the cost of analog to digital conversion as it was in the past, and the physicist is able to run larger experiments than were feasible a decade ago. Today a medium sized experiment will produce several hundred full reels of 6250 BPI tape whereas a large experiment is a couple of thousand reels. The raw data must first be transformed into physics events using data transformation programs. The physicists then use subsets of the data to understand what went on. The subset may be anywhere from a few megabytes to 5 or 6 gigabytes of data (30 or 40 full reels of tape). This searching would be best solved interactively (if computers and I/0 devices were fast enough). Instead what we find are very dynamic batch programs that are generally changed every run. The result is that on any day there are probably around 50 to 100 physicists interacting with a half dozen different experiments who are causing us to mount around 750 to 1000 tapes a day. This has been the style of computing for the last decade. Our going to VM is part of our effort to change this style of computing and to make physics computing more effective.
Date: August 11, 1981
Creator: Johnston, T.Y.
Partner: UNT Libraries Government Documents Department

Measurements of R/sub hadron/ at 5 less than or equal to E/sub c. m. / less than or equal to 8 GeV as a test of QCD

Description: The hadron yield in e/sup +/e/sup -/ annihilation normalized to the lowest order ..mu..-pair cross section (R/sub h/) is measured with systematic errors of +-6 to 8%, using the Crystal Ball detector at SPEAR. In the energy range of this measurement (5.2 to 7.0 GeV), the prediction of QCD for R/sub h/, calculated to second order, is tested.
Date: July 1, 1981
Creator: Bloom, E.D.
Partner: UNT Libraries Government Documents Department