359 Matching Results

Search Results

Advanced search parameters have been applied.

Theoretical studies in high energy nuclear physics. Progress report

Description: This paper is a progress report for the period 1-1-93 to 6-30-95 on a project primarily directed at the application of high energy physics techniques to nuclear structure studies, and the ability to study hadron dynamics through interactions with nuclear targets. This work has included the first legitimate QCD calculations of hard coherent diffractive processes off nucleon (nuclear) targets which established novel features of color transparency phenomenon not anticipated in the previous intuitive or QCD inspired model calculations and predicted the fast increase of the cross section for electroproduction of {rho}-mesons with increase of the energy, which was confirmed very recently by the first HERA data on this reaction. First theoretical demonstration that color transparency phenomenon for the hard diffractive processes follow from QCD in the kinematics when both x{yields}0 and Q{sup 2}{yields}{infinity}. Establishing the pattern of color (cross section) fluctuations in hadrons. Confirmed by the FNAL inelastic diffraction data. Finding that in realistic quark, skyrmion models of a hadron large momentum transfer elastic lepton-hadron scattering occurs through formation of small spatial size configurations. Discovering a novel class of color transparency sensitive double interaction processes which is complementary to quasielastic reactions originally suggested by S. Brodsky and A. Mueller. Adopting ideas suggested elsewhere for hadron initiated reactions they developed a method for taking into account nuclear correlations in (e,e{prime}p) reactions. Such an approach gives practical possibility to overcome ambiguities of optical model approximation used before and to reliably interpret color transparency effects at intermediate Q{sup 2}.
Date: August 1, 1995
Partner: UNT Libraries Government Documents Department

Review of {alpha}{sub s} measurements

Description: Determinations of {alpha}{sub s} are reviewed. Current results are limited to a precision of around 3--20%, largely by theoretical uncertainties. All measurements are consistent with a world average value of 0.118 {+-} 0.005 and there is no evidence of any discrepancy between low-Q{sup 2} and high-Q{sup 2} results. 71 refs., 1 fig., 1 tab.
Date: October 1, 1996
Creator: Burrows, P.N.
Partner: UNT Libraries Government Documents Department

Pole term and gauge invariance in deep inelastic scattering

Description: In this paper the authors reconcile two contradictory statements about deep inelastic scattering (DIS) in manifestly covariant theories: (1) the scattering must be gauge invariant, even in the deep inelastic limit, and (2) the pole term (which is not gauge invariant in a covariant theory) dominates the scattering amplitude in the deep inelastic limit. An ``intermediate'' answer is found to be true. They show that, at all energies, the gauge dependent part of the pole term cancels the gauge dependent part of the rescattering term, so that both the pole and rescattering terms can be separately redefined in a gauge invariant fashion. The resulting, redefined pole term is then shown to dominate the scattering in the deep inelastic limit. Details are worked out for a simple example in 1+1 dimensions.
Date: March 1, 1998
Creator: Batiz, Zoltan & Gross, Franz
Partner: UNT Libraries Government Documents Department

Compton scattering and nonforward parton distributions

Description: The hard exclusive electroproduction processes provide new information about hadronic structure accumulated in nonforward parton distributions. The NFPD's are universal hybrid functions having the properties of parton densities, hadronic form factors and distribution amplitudes. They give a unified description of various hard exclusive and inclusive reactions. The basic supplier of information about nonforward parton distributions is deeply virtual Compton scattering which offers a remarkable example of Bjorken scaling phenomena in exclusive processes. Wide-angle real Compton scattering is an ideal tool to test angle-dependent scaling laws characteristic for soft overlap mechanism. Hard meson electroproduction is the best candidate to see pQCD hard gluon exchange in exclusive reactions.
Date: November 1, 1998
Creator: Radyushkin, A.V.
Partner: UNT Libraries Government Documents Department

The parton distribution functions in the limit x{sub BJ} {yields} 1

Description: We review both the counting rule and the influence of the evolution in Q{sub 2} for the large {chi}{sub Bj} behavior of the valance quark distribution functions. Based on a factorization procedure we present a more general perturbative treatment to compute this behavior. A complete analysis is performed in the scalar {phi}{sub [6]}{sup 3}-theory for the parton distribution function of the ``meson,`` which shows that logarithmical corrections arise from the distribution amplitude and that the reference momentum square Q{sub 0}{sup 2} is fixed by {chi}{sub Bj}.
Date: May 1, 1994
Creator: Mueller, D.
Partner: UNT Libraries Government Documents Department

Consequences of unitarity and analyticity for weak interactions

Description: One considers the implications of the fact that weak two body scattering amplitudes, when calculated to all orders in any renormalizable model, should exhibit unitary, analytic, ''Mandelstam'' behavior. One discusses from this point of view, the existence of neutral currents, the suppression of $nu$/sub $mu$/e elastic scattering, and the possibility of lepton hadron resonances. A brief review is given of the predictions for lepton--lepton scattering of two models in which Mandelstam behavior is explicitly realized. (auth)
Date: January 1975
Creator: Dicus, D. A. & Teplitz, V. L.
Partner: UNT Libraries Government Documents Department

Progress report of a research program in experimental and theoretical high energy physics, 1 January 1992--31 May 1992

Description: This report discusses research at Brown University in experimental and theoretical high energy physics. Some of the research programs conducted are: interactions of leptons and hadrons form accelerator and astrophysical sources; hadron interactions with hydrogen and heavier nuclei; large volume detector at the Gran Sasso Laboratory; GEM collaboration at SSC; and hadron colliders and neutrino physics. (LSP)
Date: June 1, 1992
Creator: Brandenberger, R.; Cutts, D.; Fried, H. M.; Guralnik, G.; Jevicki, A.; King, K. et al.
Partner: UNT Libraries Government Documents Department

Theoretical Aspects of Lepton-Hadron Scattering

Description: In this paper, I will emphasize two points on Theoretical Aspects of Lepton-Hadron Scattering: (1) The crucial importance of testing the ``exact`` sum rules as tests of the local current algebra. Discrepancies, if found, between experiment and theory cannot be ``interpreted away`` in terms of more complex parton wave functions for the hadronic ground state. The three sum rules of interest are those of Adler, Bjorken, and Gross and Llewellyn-Smith. (2) An understanding of the corrections to scaling in QCD and what they teach us.
Date: January 1992
Creator: Drell, Sidney D.
Partner: UNT Libraries Government Documents Department

Same-Sign Dilepton Production by Neutrinos

Description: There has been considerable experimental work on same-sign dilepton production in neutrino interactions over the past 10 years. However, the situation is still unclear. Most experiments do have evidence for an excess of candidates but there is a lack of independent statistically significant results. Present experiments at the Tevatron may provide important new information. However the recent revision of older results and the lower rates from recent experiments indicate that real progress will be difficult. Furthermore, the problems encountered with ..pi../K background subtractions argue for a multi-target experiment. Also, given the conflict with present c anti c calculations, a high statistics bubble chamber experiment would be useful to establish the presence/absence of c anti c events at the presently measured production rates. 13 refs., 6 figs., 2 tabs.
Date: November 7, 1985
Creator: Murtagh, Michael J.
Partner: UNT Libraries Government Documents Department

An historical review of lepton proton scattering

Description: In this talk I will try to review some of the early experiments in the field of electron-proton scattering, concentrating mostly on the inelastic scattering experiments at SLAC. Ordinarily, those experiments would be covered in the first five or ten minutes of the talks by Professor Scuilli and Drell, but this is a special year, and I will feel free to reminisce about the early days in a somewhat personal way.
Date: June 1, 1992
Creator: Taylor, R.
Partner: UNT Libraries Government Documents Department

Elastic scattering of muon neutrinos at BNL

Description: In this paper measurement of the purely leptonic reactions: nu/sub ..mu../e ..-->.. nu/sub ..mu../e and anti nu/sub ..mu../e ..-->.. anti nu/sub ..mu../e, and the semileptonic reactions: nu/sub ..mu../p ..-->.. nu/sub ..mu../p and anti nu/sub ..mu../p ..-->.. anti nu/sub ..mu../p are presented and discussed in terms of the standard model. The data also places limites of interest on the magnitudes of a possible neutrino charge radius and a neutrino magnetic moment.
Date: February 1, 1987
Creator: Abe, K.; Ahrens, L.A.; Amako, K.; Aronson, S.H.; Beier, E.W.; Callas, J.L. et al.
Partner: UNT Libraries Government Documents Department

Production of like sign dimuon events by neutrinos

Description: A sample of 46 ..mu../sup -/..mu../sup -/ events was obtained in studying high energy neutrino interactions at Fermilab. The analysis of these data yields a prompt rate, N/sup prompt/(..mu../sup -/..mu../sup -/)/N/sup prompt/(..mu../sup -/..mu../sup +/), of 0.12 +- 0.05 for P/sub ..mu../ > 10 GeV/c. The ..mu../sup -/..mu../sup -/ events are predominately of hadronic origin. 9 references.
Date: January 1, 1978
Creator: Gilchriese, M.G.D.
Partner: UNT Libraries Government Documents Department

Nuclear dependence of structure functions in the shadowing region of deep inelastic scattering

Description: A discussion of nuclear shadowing in deep inelastic lepton scattering is presented. We show that the parton recombination model suggests that shadowing should begin to occur at larger values of Bjorken x as A increases. This expectation as well as that of weak dependence on Q/sup 2/, and the trend of the x dependence of the shadowing phenomenon are consistent with recent data. Shadowing at small x is combined with nuclear bound state effects, responsible for nuclear dependence at larger x, to provide description of the A dependence of the structure function for the entire range of x. 21 refs., 5 figs.
Date: July 27, 1988
Creator: Berger, E.L. & Qiu, Jianwei
Partner: UNT Libraries Government Documents Department

Inclusive vector meson production in. nu. /sub. mu. /D charged current interactions

Description: From hadronic systems induced in 3571 charged-current neutrino-deuterium interactions in the FNAL 15-foot diameter bubble chamber, invariant mass distributions (..pi../sup +/..pi../sup -/) and (K/sub s//sup 0/..pi../sup + -/) have been used to study inclusive production of vector meson resonances. Inclusive rates from a pure isoscalar target are determined to be 0.05 +- 0.01 K*/sup +/(890) per charged-current event and 0.19 +- 0.04 rho/sup 0/ per charged-current event. Inclusive K*(890)/sup + -/ production is found to be predominantly K*/sup +/(890) in the current fragmentation region. The ratios (rho/sup 0//event) from neutron targets and from proton targets separately are, respectively, 0.18 +- 0.06 and 0.21 +- 0.08. For deuteron targets, trends in the dependence of (rho/sup 0//event) on variables Y/sub R/, W, p/sub T/, and Q/sup 2/ are found to be similar to those observed in rho/sup 0/ production from anti ..nu../sub ..mu../p collisions.
Date: January 1, 1980
Creator: Chang, C.C.; Mann, W.A. & Napier, A.
Partner: UNT Libraries Government Documents Department

Calorimetry in ZEUS: Lessons for the future

Description: The storage ring facility HERA, under construction at the DESY Laboratory, will collide 30 GeV e/sup /minus// with 820 GeV protons when the machine is first turned on in 1990. Four interaction regions being provided. Subsequently either e/sup /minus// or e beams can be used and a facility for producing longitudinal polarization of the electrons at the interaction points will be provided. Both the center-of-mass energy ( s = 314 GeV) and the momentum transfer (Q/sub max/S /approximately/ 10V GeVS) are substantially higher than in any deep inelastic scattering studies to date. The HERA program will be the natural extension of both the neutrino and the muon scattering experiments done at CERN and Fermilab. With the design luminosity of 1.5 10T cm/sup /minus/2/ sec/sup /minus/1/ experiments with 200 pb/sup /minus/1/ of integrated luminosity will be possible. HERA will be the first electron-quark collider. The energy is substantially higher than LEP, and the events will be cleaner than those resulting from p/bar p/ collisions. It provides the third leg that will support the physics stool of the 1990s. In neutral current events, the z exchange graph is comparable in strength to the photon exchange and the charged current events will provide unique insights into the W coupling. There will be substantial rates of heavy quark production. Two detectors are under construction: H1 uses a large solenoid with a liquid argon calorimeter inside the coil, ZEUS uses a smaller magnet with uranium-scintillator calorimeters outside of the coil. 4 refs., 11 figs.
Date: January 1, 1988
Creator: Derrick, M.
Partner: UNT Libraries Government Documents Department

W- and Z-boson production at ep colliders

Description: We briefly summarize the results of a comprehensive study of W and Z production in high energy ep collisions. The processes ep [yields] vWX[sup [plus minus]]X, ep [yields] vW[sup [minus]]X, ep [yields] eZX and ep [yields] vZX are investigated. The region of small momentum transfer in eW and eZ production, with a fermion exchanged in the u-channel, is treated using the photon structure function approach, and carefully matched to the deep inelastic region. Low momentum photon exchange contributions to vW and eZ production, where the proton either stays intact or is transformed into a nucleon resonance, are calculated using form factors and structure functions fitted directly to experimental data.
Date: April 1, 1992
Creator: Baur, U.
Partner: UNT Libraries Government Documents Department

Is there a way to measure the deep-inelastic cross-section using wide-band neutrino beams

Description: A method is described for extracting the value of the neutrino flux in a wide-band beam exposure based on computed differential cross-sections for resonance production and quasielastic scattering of neutrinos on nucleons. The resonance production cross-sections, computed by means of a relativistic quark model, are in excellent agreement with measurements of various neutrino-induced exclusive final states performed so far and also with data from inclusive deep-inelastic neutrino interactions. The theoretical uncertainty inherent in the method is estimated to be about 10% and is roughly equal to the systematic error which plagues the measurements of the neutrino flux in present-day narrow-band beams. Before the first Tevatron narrow-band beam data becomes available in a few years time, if at all, this method provides the only reliable way of ''measuring'' the total neutrino cross-section with the existing wide-band beam data, thus extending the measured energy range by nearly a factor of two.
Date: January 1, 1987
Creator: Belusevic, R. & Rein, D.
Partner: UNT Libraries Government Documents Department

A possible early experimental test for a large G(x,QS)

Description: A proposal that the net spin carried by gluons in a polarized proton may be very large compared to 1/2 has recently received considerable theoretical attention. There exists a unique opportunity to test for this dramatic possibility using an existing experimental setup. We urge the consideration of a precision measurement (+-10 b) of sigma/sub L//sup jet/(pp; p0, s) at p0S = 5 GeVS and s = 400 GeVS using the Fermilab polarized beam facility. 10 refs.
Date: October 6, 1988
Creator: Sivers, D. & Ramsey, G.
Partner: UNT Libraries Government Documents Department