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Photoproduction of hybrid mesons

Description: In this contribution the author discusses prospects for photoproducing hybrid mesons at CEBAF, based on recent model results and experimental indications of possible hybrids. One excellent opportunity appears to be a search for I = 1, J{sup PC} = 2{sup +{minus}} ``b{sub 2}{sup o}`` hybrids in (a{sub 2}{pi}){sup o} through diffraction photoproduction. Other notable possibilities accessible through {pi}{sup +}; {pi}{sub J}{sup +}(1770) in f{sub 2}{pi}{sup +} and (b{sub 1}{pi}){sup +}; {pi}{sup +}(1800) in f{sub 0}{pi}{sup +}, f{sub 2}{pi}{sup =}, {rho}{sup +}{omega} and ({rho}{pi}){sup +}; a{sub 1} in f{sub 1}{pi}{sup +} and f{sub 2}{pi}{sup +}; and {omega} in ({rho}{pi}){sup o}, {omega}{eta} and K{sub 1}K.
Date: November 1, 1998
Creator: Barnes, T.
Partner: UNT Libraries Government Documents Department

Background Enhancement of CPT Reach at an Asymmetric Phi Factory

Description: Photoproduction of neutral-kaon pairs is studied from the perspective of CP and CPT studies. Interference of the P and S waves, with the former due to diffractive phi production and the latter to f{_}0/a{_}0 production, is shown to enhance the CPT reach. Results are presented of Monte Carlo studies based on rates expected in future experiments.
Date: June 1, 2001
Creator: Isgur, Nathan; Kostelecky, Alan & Szczepaniak, Adam
Partner: UNT Libraries Government Documents Department

ENERGY RECEPTION AND TRANSFER IN PHOTOSYNTHESIS

Description: The basic information about the path of carbon in photosynthesis is reviewed together with the methods that were used to discover it. This has led to the knowledge of what is required of the photochemical reaction in the form of chemical species. Attention is then directed to the structure of the photochemical apparatus itself insofar as it is viewable by electron microscopy, and some principoles of ordered structure are devised for the types of molecules to be found in the chloroplasts. From the combination of these, a structure for the grana lamella is suggested and a mode of function proposed. Experimental test for this mode of function is underway; one method is to examine photoproduced unpaired electrons. This is discussed.
Date: September 23, 1958
Creator: Calvin, Melvin
Partner: UNT Libraries Government Documents Department

Biological Systems for Hydrogen Photoproduction

Description: This presentation summarizes NREL biological systems for hydrogen photoproduction work for the DOE Hydrogen and Fuel Cells Program Annual Merit Review and Peer Evaluation Meeting, May 14-18, 2012. General goal is develop photobiological systems for large-scale, low cost and efficient H{sub 2} production from water (barriers AH, AI and AJ). Specific tasks are: (1) Address the O{sub 2} sensitivity of hydrogenases that prevent continuity of H{sub 2} photoproduction under aerobic, high solar-to-hydrogen (STH) light conversion efficiency conditions; and (2) Utilize a limited STH H{sub 2}-producing method (sulfur deprivation) as a platform to address or test other factors limiting commercial algal H{sub 2} photoproduction, including low rates due to biochemical and engineering mechanisms.
Date: May 1, 2012
Creator: Ghirardi, M. L.
Partner: UNT Libraries Government Documents Department

Investigations of the dynamics and electromagnetic interactions of few-body systems. Progress report, June 30, 1994--September 30, 1995

Description: This progress report summarizes the work of The George Washington University (GW) nuclear theory group during the period 1 July 1994 - 30 September 1995 under DOE Grant No. DE-FG02-95-ER40907 mainly dealing with photonuclear reactions and few-body problems of nuclei. This report contains: papers published or in press, submitted for publication, and in preparation; invited talks at conferences and meetings; invited talks at universities and laboratories; contributed papers or abstracts at conferences; visitors to the group; and research progress by topic.
Date: October 1, 1995
Creator: Lehman, D.R.
Partner: UNT Libraries Government Documents Department

Probing the strange nature of the nucleon with phi photoproduction

Description: The presence inside the nucleon of a significant component of strange-antistrange quark pairs has been invoked to explain a number of current puzzles in the low energy realm of QCD. The {sigma} term in {pi}N scattering is a venerable conundrum which can be explained with a 10%--20% admixture. The spin crisis brought on by the EMC result and follow on experiments was first interpreted as requiring a large strange content of s quarks whose spin helped cancel the contribution of the u and d quarks to the nucleon spin, again of order 10%. Excess phi meson production in p{anti p} annihilation at LEAR has also been explained in terms of up to a 19% admixture of s{anti s} pairs. Charm production in deep-inelastic neutrino scattering would appear to provide evidence for a 3% strange sea. It is clear that a definite probe of the strange quark content would be an invaluable tool in unraveling a number of mysteries. The longitudinal beam target asymmetry in {psi} photoproduction is a particularly sensitive probe of that content. It is explored here.
Date: March 6, 1997
Creator: Lowry, M.M.
Partner: UNT Libraries Government Documents Department

Spin-dependent Drell-Yan and double prompt photon production to NLO QCD

Description: We present the complete O({alpha}{sub s}{sup 2}) radiative corrections to the (non singlet) polarized Drell Yan cross section for the production of a lepton pair with a nonzero qT. The helicity of the incoming states is arbitrary. In the case of double photon, results for the longitudinal asymmetries and on the pT behavior of the cross section are also given (to O({alpha}{sub em}{sup 2}{alpha}{sub s})) in the central rapidity region of the tagged photon.
Date: September 1, 1997
Creator: Chang, Sanghyeon; Coriano, C.; Field, R.D. & Gordon, L.E.
Partner: UNT Libraries Government Documents Department

Reaction theories for N* excitations in {pi}N and {gamma}N reactions

Description: The importance of developing reaction theories for investigating N* physics is illustrated in an analysis of pion photoproduction on the nucleon. It is shown that the {gamma}N {leftrightarrow} {Delta} transition amplitudes predicted by the constituent quark model are in agreement with the values extracted from the {gamma}N {r_arrow} {pi}N data only when the contributions from the reaction mechanisms calculated using a dynamical approach are taken into account in the analysis.
Date: December 31, 1996
Creator: Lee, T. S. H.
Partner: UNT Libraries Government Documents Department

Electromagnetic production of vector mesons at low energies

Description: The authors have investigated exclusive photoproduction of light vector mesons ({omega}, {rho} and {phi}) on the nucleon at low energies. In order to explore the questions concerning the so-called missing nucleon resonances, they first establish the predictions from a model based on the Pomeron and meson exchange mechanisms. They have also explored the contributions due to the mechanisms involving s- and u-channel intermediate nucleon state. Some discrepancies found at the energies near threshold and large scattering angles suggest a possibility of using this reaction to identify the nucleon resonances.
Date: May 17, 2000
Creator: Oh, Y.; Titov, A. I. & Lee, T.-S. H.
Partner: UNT Libraries Government Documents Department

IEA Agreement on the production and utilization of hydrogen: 1996 annual report

Description: The annual report includes an overview of the IEA Hydrogen Agreement, including a brief summary of hydrogen in general. The Chairman's report provides highlights for the year. Sections are included on hydrogen energy activities in the IEA Hydrogen Agreement member countries, including Canada, European Commission, Germany, Japan, Netherlands, Norway, Spain, Sweden, Switzerland, and the US. Lastly, Annex reports are given for the following tasks: Task 10, Photoproduction of Hydrogen, Task 11, Integrated Systems, and Task 12, Metal Hydrides and Carbon for Hydrogen Storage.
Date: January 31, 1997
Creator: Elam, Carolyn C. (National Renewable Energy Lab, Golden, CO (US)) (ed.)
Partner: UNT Libraries Government Documents Department

Isolated prompt photon production

Description: We show that the conventionally defined partonic cross section for the production of isolated prompt photons is not an infrared safe quantity. We work out the case of e{sup +}e{sup -} {yields} {gamma} + X in detail, and we discuss implications for hadron reactions such as p{bar p} {yields} {gamma} + X.
Date: August 15, 1997
Creator: Berger, E.L.; Guo, Xiaofeng & Qiu, Jianwei
Partner: UNT Libraries Government Documents Department

Polarized double photon production in QCD to order {alpha}{sub s}

Description: We present a complete order {alpha}{sub s} analysis of the process pp {r_arrow}{gamma}{gamma} + X with polarized initial states, previously studied by us with leading order structure functions. We include in our calculation new sets of parton densities evolved in NLO QCD, such as those of Gehrmann and Stirling and of Glueck et al., which incorporate the new anomalous dimensions of Mertig and Van Neerven in the evolution equation. A detailed phenomenological analysis is also given which includes the photon isolation. Our results indicate that the asymmetries, although not very large, should be substantial enough at RHIC energies to be measurable in future planned experiments.
Date: March 1996
Creator: Coriano, C. & Gordon, L. E.
Partner: UNT Libraries Government Documents Department

Measurement of direct photons in 200{center_dot}A GeV {sup 32}S + Au collisions

Description: Two years ago at the 10th Winter Workshop on Nuclear Dynamics, we reported preliminary results from our measurements of photons in reactions of 200{center_dot}A GeV {sup 32}S ions with Au nuclei. The results had been presented earlier at Quark Matter `93. For central collisions we reported a small, but statistically significant, excess of photons over those that can be accounted for by the two-photon decay branches of neutral pions and eta mesons and by the small photon contributions from other radiative decays. This paper is, in a sense, a sequel to the 1994 presentation. Here we present the final WA80 single `direct` photon results, and we discuss their implications for various theoretical calculations. 13 refs., 2 figs., 1 tab.
Date: April 1, 1996
Creator: Plasil, F. & Collaboration, The WA80
Partner: UNT Libraries Government Documents Department

Exclusive electroproduction of phi mesons at 4.2 GeV

Description: We studied the exclusive reaction ep {yields} e{prime}p{prime}{phi} using the {phi} {yields} K{sup +} K{sup -} decay mode. The data were collected using a 4.2 GeV incident electron beam and the CLAS detector at Jefferson Lab. Our experiment covers the range in Q{sup 2} from 0.7 to 2.2 GeV{sup 2}, and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of {phi} production on the proton. Our measurement shows the expected decrease of the t-slope with the vector meson formation time c{Delta}{tau} below 2 fm. At c{Delta}{tau}= 0.6 fm, we measure b{sub {phi}} = 2.27 {+-} 0.42 GeV{sup -2}. The cross section dependence on W as W{sup 0.2{+-}0.1} at Q{sup 2} = 1.3 GeV{sup 2} was determined by comparison with {phi} production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction.
Date: January 1, 2001
Creator: Lukashin, K.; E.S., Smith. & others], CLAS Collaboration
Partner: UNT Libraries Government Documents Department

Proton and deuteron structure functions in muon scattering at 470 GeV

Description: The proton and deuteron structure functions F{sub 2}{sup p} and F{sub 2}{sup d} measured in inelastic muon scattering with an average beam energy of 470 GeV. The data were taken at Fermilab experiment 665 during 1991-1992 using liquid hydrogen and deuterium targets. The F{sub 2} measurements are reported in the range 0.0008 < x < 0.6 and 0.2 < Q{sup 2} < 75 GeV{sup 2}. These are the first precise measurements of F{sub 2} in the low x and Q{sub 2} range of the data. The E665 data overlap in x with the HERA data, and there is a smooth connection in Q{sup 2} between the two data sets. At high Q{sup 2} the E665 measurements are consistent with QCD-evolved leading twist structure function models. The data are qualitatively described by structure function models incorporating the hadronic nature of the photon at low Q{sup 2}. The Q{sup 2} and the W dependence of the data measure the transition in the nature of the photon between a point-probe at high Q{sup 2} and a hadronic object at low Q{sup 2}.
Date: May 1, 1995
Creator: Kotwal, A.V. & Collaboration, E665
Partner: UNT Libraries Government Documents Department

Correlations between D and Dbar mesons in high energy photoproduction

Description: Over 7000 events containing a fully reconstructed D{bar D} pair have been extracted from data recorded by the FOCUS photoproduction experiment at Fermilab. Preliminary results from a study of correlations between D and {bar D} mesons are presented. Correlations are used to study perturbative QCD predictions and investigate non-perturbative effects. We also present a preliminary result on the production of {psi}(3770).
Date: November 13, 2002
Creator: Gottschalk, Erik E
Partner: UNT Libraries Government Documents Department

2-pi Photoproduction from CLAS and CB-ELSA - The Search for Missing Resonances

Description: 2-pi-photoproduction is one of the promising reactions to search for baryon resonances that have been predicted but have not yet been observed. The gamma-rho --&gt; rho-pi{sup 0}-pi{sup 0}(CB-ELSA) and the gamma-rho --&gt; rho-pi{sup +}-pi{sup -} (CLAS) data show interesting resonance structures. A partial wave analysis (PWA) has to be done to determine which baryon resonances contribute what their quantum numbers and their relative couplings to the different accessible rho-2-pi-channels and to the photon are. First preliminary PWA-results on the lowest energy rho-pi{sup 0}-pi{sup 0} data (sq rt s&lt;1.8 GeV)look very promising. From an extension of this analysis to higher energies combining the rho-pi{sup 0}-pi{sup 0} and the rho-pi{sup +}-pi{sup -}-data, one can expect; interesting results on resonances decaying into Delta-pi, N-rho, N(pi-pi)s, N*-pi, and Delta*-pi.
Date: October 1, 2003
Creator: Thoma, Ulrike
Partner: UNT Libraries Government Documents Department

Photoproduction of charm pairs

Description: A large sample of events containing fully and partially reconstructed pairs of charmed D mesons has been studied by the Fermilab photoproduction experiment FOCUS (FNAL-E831). Correlations between photoproduced D and {bar D} mesons are used to study heavy quark production dynamics. Correlation results are presented for fully and partially reconstructed pairs of charmed D mesons. The results are compared to Monte Carlo predictions based on a recent version of PYTHIA with default settings.
Date: September 2, 2003
Creator: Gottschalk, Erik E
Partner: UNT Libraries Government Documents Department

The Leading Particle Effect from Heavy-Quark Recombination

Description: The leading particle effect in charm hadroproduction is an enhancement of the cross section for a charmed hadron D in the forward direction of the beam when the beam hadron has a valence parton in common with the D. The large D+/D- asymmetry observed by the E791 experiment is an example of this phenomenon. We show that the heavy-quark recombination mechanism provides an economical explanation for this effect. In particular, the D+/D- asymmetry can be fit reasonably well using a single parameter whose value is consistent with a recent determination from charm photoproduction.
Date: May 1, 2002
Creator: Braten, Eric; Jia, Yu & Mehen, Thomas
Partner: UNT Libraries Government Documents Department

Detailed comparison of next-to-leading order predictions for jet photoproduction at HERA.

Description: The precision of new HERA data on jet photoproduction opens up the possibility to discriminate between different models of the photon structure. This requires equally precise theoretical predictions from perturbative QCD calculations. In the past years, next-to-leading order calculations for the photoproduction of jets at HERA have become available. Using the kinematic cuts of recent ZEUS analyses, we compare the predictions of three calculations for different dijet and three-jet distributions. We find that in general all three calculations agree within the statistical accuracy of the Monte Carlo integration yielding reliable theoretical predictions. In certain restricted regions of phase space, the calculations differ by up to 5%.
Date: June 2, 1999
Creator: Harris, B. W.; Klassen, M. & Vossebeld, J.
Partner: UNT Libraries Government Documents Department