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Parton Distributions and Spin-Orbital Correlations

Description: In this talk, I summarize a recent study showing that the large-x parton distributions contain important information on the quark orbital angular momentum of nucleon. This contribution could explain the conflict between the experimental data and the theory predictions for the polarized quark distributions. Future experiments at JLab shall provide further test for our predictions.
Date: September 24, 2007
Creator: Yuan, Feng
Partner: UNT Libraries Government Documents Department

Global polarization measurement in Au+Au collisions

Description: The system created in non-central relativisticnucleus-nucleus collisions possesses large orbital angular momentum. Dueto spin-orbit coupling, particles produced in such a system could becomeglobally polarized along the direction of the system angular momentum. Wepresent the results of Lambda and anti-Lambda hyperon global polarizationmeasurements in Au+Au collisions at sqrt sNN=62.4 GeV and 200 GeVperformed with the STAR detector at RHIC. The observed globalpolarization of Lambda and anti-Lambda hyperons in the STAR acceptance isconsistent with zero within the precision of the measurements. Theobtained upper limit, lbar P Lambda, anti-Lambda rbar<= 0.02, iscompared to the theoretical values discussed recently in theliterature.
Date: August 2, 2007
Creator: Abelev, B.I.; Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett,J.; Anderson, B.D. et al.
Partner: UNT Libraries Government Documents Department

ISOMERIC-YIELD RATIOS IN NUCLEAR REACTIONS. (WITH A COMPILATION OF EXPERIMENTAL DATA)

Description: Experimertal procedures are briefly described for the determination of the ratios of cross sections for the formation of isomeric states in nuclear reactions. Much avatlable experimertal data on isomeric yield ratios in nuclear reactions is compiled. Some of the collected data are discussed in terms of angular-momentum effects in nuclear reactions. (230 references).
Date: September 1, 1962
Creator: Wing, J.
Partner: UNT Libraries Government Documents Department

Application of the Von Kármán momentum theorem to turbulent boundary layers

Description: Report presenting a study of the Von Kármán momentum theorum with respect to its application to turbulent boundary layers in a positive pressure gradient. The results indicate that the streamwise derivative of the turbulent longitudinal momentum may be large near the separation and therefore should be considered when the momentum theorum is used for turbulent boundary layers near separation.
Date: December 1951
Creator: Bidwell, Jerold M.
Partner: UNT Libraries Government Documents Department

A cascade-general-momentum theory of operation of a supersonic propeller annulus

Description: Report presenting a cascade-general-momentum theory method for calculating the operating conditions of a supersonic propeller annulus throughout the flight Mach number range. General flow patterns about the cascade and adjustments to free-stream conditions are discussed.
Date: January 5, 1953
Creator: Klawans, Bernard B. & Vogeley, Arthur W.
Partner: UNT Libraries Government Documents Department

Transverse momentum and centrality dependence of high-ptnon-photonic electron suppression in Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV

Description: The STAR collaboration at RHIC reports measurements of theinclusive yield of non-photonic electrons, which arise dominantly fromsemi-leptonic decays of heavy flavor mesons, over a broad range oftransverse momenta (1.2<pt<10 gevc) in pp, dAu, and AuAucollisions at sqrt sNN = 200 GeV. The non-photonic electron yieldexhibits unexpectedly large suppression in central AuAu collisions athigh pt, suggesting substantial heavy quark energy loss at RHIC. Thecentrality and \pt dependences of the suppression provide constraints ontheoretical models of suppression.
Date: July 11, 2006
Creator: Abelev, B.I.; Adams, J.; Aggarwal, M.M.; Ahammed, Z.; Amonett,J.; Anderson, B.D. et al.
Partner: UNT Libraries Government Documents Department

NUCLEAR SHAPES AT HIGH ANGULAR MOMENTUM

Description: Multiplicities as a function of {gamma}-ray energy have been measured for continuum {gamma}-ray spectra produced in argon- and calcium-induced reactions. A peak sometimes occurs in the multiplicity spectrum, indicating a correlation between {gamma}-ray energy and multiplicity (spin). This correlation can be explained by rotational motion of the nucleus, suggesting basically prolate nuclear shapes. Absence of structure in the multiplicity spectrum is interpreted to indicate non-collective motion, and hence spherical or oblate shapes.
Date: December 1, 1977
Creator: Deleplanque, M.A.; Lee, I.Y.; Stephens, F.S.; Diamond, R.M. & Aleonard, M.M.
Partner: UNT Libraries Government Documents Department

Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris

Description: Proposals for ground-based laser remediation of space debris rely on the creation of appropriately directed ablation-driven impulses to either divert the fragment or drive it into an orbit with a perigee allowing atmospheric capture. For a spherical fragment, the ablation impulse is a function of the orbital parameters and the laser engagement angle. If, however, the target is irregularly shaped and arbitrarily oriented, new impulse effects come into play. Here we present an analysis of some of these effects.
Date: February 4, 2010
Creator: Liedahl, D A; Libby, S B & Rubenchik, A
Partner: UNT Libraries Government Documents Department

System-size independence of directed flow at the RelativisticHeavy-Ion Collider

Description: We measure directed flow (v{sub 1}) for charged particles in Au + Au and Cu + Cu collisions at {radical}s{sub NN} = 200 GeV and 62.4 GeV, as a function of pseudorapidity ({eta}), transverse momentum (p{sub t}) and collision centrality, based on data from the STAR experiment. We find that the directed flow depends on the incident energy but, contrary to all available model implementations, not on the size of the colliding system at a given centrality. We extend the validity of the limiting fragmentation concept to v{sub 1} in different collision systems, and investigate possible explanations for the observed sign change in v{sub 1}(p{sub t}).
Date: September 20, 2008
Creator: Coll, STAR
Partner: UNT Libraries Government Documents Department

Electron-pair excitations and the molecular Coulomb continuum

Description: Electron-pair excitations in the molecular hydrogen continuum are described by quantizing rotations of the momentum plane of the electron pair about by the pair's relative momentum. A helium-like description of the molecular pi.Joto double ionization is thus extended to higher angular momenta of the electron pair. A simple three-state superposition is found to account surprisingly well for recent observations of noncoplanar electron-pair, molecular-axis angular distributions.
Date: January 1, 2009
Creator: Colgan, James
Partner: UNT Libraries Government Documents Department

Systemsize dependence of associated yields in hadron-triggered jets

Description: We present results on the system size dependence of high transverse momentum di-hadron correlations at {radical}s{sub NN} = 200 GeV as measured by STAR at RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like correlation yields at small angular separation ({Delta}{phi} {approx} 0, {Delta}{eta} {approx} 0) for all systems and centralities. Previous measurements have shown that the away-side yield is suppressed in heavy-ion collisions. We present measurements of the away-side suppression as a function of transverse momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found to be similar in Cu+Cu and Au+Au collisions at a similar number of participants. The results are compared to theoretical calculations based on the parton quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will provide important constraints on medium density profile and energy loss model parameters.
Date: July 5, 2010
Creator: Collaboration, STAR & Abelev, Betty
Partner: UNT Libraries Government Documents Department

Analysis of some parameters used in correlating blowing-type boundary-layer control data

Description: Report presenting an examination of the limitations of the use of jet momentum coefficient as a correlating factor in comparing tests of blowing-type boundary-layer control. Theoretical and experimental data indicate that it should be an acceptable parameter where the duct pressures are large.
Date: September 26, 1956
Creator: Kelly, Mark W.
Partner: UNT Libraries Government Documents Department

PARTON DISTRIBUTIONS AND SPIN-ORBITAL CORRELATIONS.

Description: In this talk, the author summarizes a recent study showing that the large-x parton distributions contain important information on the quark orbital angular momentum of nucleon. This contribution could explain the conflict between the experimental data and the theory predictions for the polarized quark distributions. Future experiments at JLAB shall provide further test for our predictions.
Date: May 21, 2007
Creator: FENG,Y.
Partner: UNT Libraries Government Documents Department

Study of Collective Beam Instabilities using a Correleation-moment Analysis

Description: A general formalism for treating simultaneously the transverse coupled bunch and transverse coupled mode instabilities is presented. In this approach, the equations of motion of a coupled multi-bunch beam are expanded to yield a system of equations involving correlation-moments of the transverse and longitudinal motions. After a proper truncation, the system of equations is closed and can be solved. This approach allows us to formulate within one framework several known instability mechanisms including the single bunch mode coupling instability, the coupled bunch instability, the mode coupling instability, and the coupled mode coupled bunch instability as particular cases.
Date: October 24, 2006
Creator: Heifets, S. A. & Chao, A. W.
Partner: UNT Libraries Government Documents Department

Effects of momentum conservation on the analysis of anisotropic flow

Description: We present a general method for taking into account correlations due to momentum conservation in the analysis of anisotropic flow. Momentum conservation mostly affects the first harmonic in azimuthal distributions, i.e., directed flow. It also modifies higher harmonics, for instance elliptic flow, when they are measured with respect to a first harmonic event plane such as one determined with the standard transverse momentum method. Our method is illustrated by application to NA49 data on pion directed flow.
Date: February 5, 2002
Creator: Borghini, N.; Dinh, P.M.; Ollitrault, J.-Y.; Poskanzer, A.M. & Voloshin, S.A.
Partner: UNT Libraries Government Documents Department

Emittance compensation studies of photoinjector beams with angular momentum

Description: Beam dynamics studies on the FNPL photo injector that seek to optimize the transport of intense electron beams with large values of canonical angular momentum have been performed. These studies investigate the effect of solenoid emittance compensation on beams that evolve under the combined influence of intense space charge forces and large angular momentum. We present details of experimental measurements and supporting simulations of beam envelope evolution.
Date: May 19, 2003
Creator: Lidia, Steven
Partner: UNT Libraries Government Documents Department

Drell-Yan Lepton Pair Azimuthal Asymmetry in Hadronic Processes

Description: We study the azimuthal asymmetry in the Drell-Yan lepton pair production in hadronic scattering processes at moderate transverse momentum region, taking into account the contributions from the twist-three quark-gluon correlations from the unpolarized hadrons. The contributions are found to dominate the asymmetry, and are not power suppressed by qt/Q at small qt where qt and Q are the transverse momentum and invariant mass of the lepton pair. Accordingly, the Lam-Tung relation will be violated at this momentum region, and its violation depends on the twist-three functions. However, at large transverse momentum qt~;;Q, the Lam-Tung relation still holds because all corrections are power suppressed by Lambda2/qt2 ~;; Lambda2/Q2 where Lambda is the typical nonperturbative scale.
Date: January 22, 2009
Creator: Zhou, Jian; Yuan, Feng & Liang, Zuo-Tang
Partner: UNT Libraries Government Documents Department