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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

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

The Pion Form-Factor

Description: The experimental situation with regard to measurements of the pion charge form factor is reviewed. Both existing data and planned experiments are discussed.
Date: May 1, 2002
Creator: Blok, H.P.; Huber, G.M. & Mack, D.J.
Partner: UNT Libraries Government Documents Department

The origins of quark-hadron duality: How does the square of the sum become the sum of the squares?

Description: Bloom-Gilman duality demonstrates empirically that the electroproduction of N*'s at low momentum transfers averages smoothly around the scaling curve measured at large momentum transfers. The latter is proportional to the sum of the squares of the constituent charges whereas the former involves the coherent excitation of resonances and is driven by the square of summed constituent charges. We determine the minimal necessary conditions for this equality to be realized so that duality can occur and consider the implications for a range of processes that may be studied soon at CEBAF.
Date: January 30, 2001
Creator: Close, Frank E. & Isgur, Nathan
Partner: UNT Libraries Government Documents Department

Electroproduction of $Λ$(1405)

Description: The electroproduction of K{sup +} {Lambda}(1405) was studied by analyzing the E1F data set collected in Hall B at Jefferson Lab. The analysis utilized the decay channel {Sigma}{sup +} {pi}{sup -} of the {Lambda}(1405) and p{pi}{sup 0} of the {Sigma}{sup +}. Simulations of background, {Lambda}(1405) and {Lambda}(1520) production according to PDG values were performed by using standard CLAS analysis tools adapted for the E1F run. Fits of the acceptance-corrected simulations were made to the acceptance-corrected data to determine contributions from signal and background processes. The line shape of {Lambda}(1405) varies with the four momentum transfer, Q{sup 2}, and does not match the line shape based on PDG resonance parameters. It corresponds approximately to predictions of a recent two-pole meson-baryon picture of this state.
Date: April 1, 2012
Creator: Haiyun Lu, Reinhard Schumacher, Brian Raue, Marianna Gabrielyan
Partner: UNT Libraries Government Documents Department


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

Measurement of the gamma gamma* to eta_c transition form factor

Description: The authors study the reaction e{sup +}e{sup -} {yields} e{sup +}e{sup -} {eta}{sub c}, {eta}{sub c} {yields} K{sub S}K{sup {+-}}{pi}{sup {-+}} and obtain {eta}{sub c} mass and width values 2982.2 {+-} 0.4 {+-} 1.6 MeV/c{sup 2} and 31.7 {+-} 1.2 {+-} 0.8 MeV, respectively. They find {Lambda}({eta}{sub c} {yields} {gamma}{gamma}){Beta}({eta}{sub c} {yields} K{bar K}{pi}) = 0.374 {+-} 0.009 {+-} 0.031 keV, and measure the {gamma}{gamma}* {yields} {eta}{sub c} transition form factor in the momentum transfer range from 2 to 50 GeV{sup 2}. The analysis is based on 469 fb{sup -1} of integrated luminosity collected at PEP-II with the BABAR detector at e{sup +}e{sup -} center-of-mass energies near 10.6 GeV.
Date: April 28, 2010
Creator: Lees, J.P.; Poireau, V.; Prencipe, E.; Tisserand, V.; /Annecy, LAPP; Garra Tico, J. et al.
Partner: UNT Libraries Government Documents Department

Quasifree (e,e'p) Reactions and Proton Propagation in Nuclei

Description: The (e,e'p) reaction was studies on targets of C, Fe, and Au at momentum transfers squared Q{sup 2} of 0.6, 1.3, 1.8 and 3.3 GeV{sup 2} in a region of kinematics dominated by quasifree electron-proton scattering. Missing energy and missing momentum distributions are reasonably well described by plane wave impulse approximation calculations with Q{sup 2} and A dependent corrections that measure the attenuation of the final state protons.
Date: June 1, 1998
Creator: Abbott, David; Ahmidouch, A.; Amatuni, Ts.A.; Armstrong, C.; Arrington, J.; Assamagan, J.A. et al.
Partner: UNT Libraries Government Documents Department

Euclidean responses of 4He at high momentum transfer

Description: The Euclidean proton and nucleon responses of <sup>4</sup>He at <I>q</I>=10 fm<sup>-1</sup>, evaluated with the correlated Glauber approximation using a realistic nucleon-nucleon interaction and nonrelativistic kinematics, are compared to those obtained from the Green's function Monte Carlo approach. The results show that final state interactions play a crucial role even at this large value of q, and that their effect can be quantitatively accounted for with the correlated Glauber approximation.
Date: July 1, 1995
Creator: Carlson, Joseph; Benhar, Omar; Schiavilla, Rocco & Pandharipande, Vijay
Partner: UNT Libraries Government Documents Department

The Pion Charge Form Factor Through Pion Electroproduction

Description: The goal of Jefferson Lab experiment E01-004 (F?-2) was the measurement of the longitudinal and transverse cross sections via pion electroproduction from hydrogen and deuterium for the purpose of extracting the charged pion form factor using pole dominance. The data were taken at two values of Q2 (1.60 and 2.45 GeV/c)2. In order to attain full coverage in R?, charged pions were detected in parallel kinematics (along the direction of momentum transfer, q), and at ±3 degrees off the direction of momentum transfer. For each Q2 data were taken for two values of the virtual photon polarization, ?, respectively. All data were taken at a fixed center of mass energy, W=2.22 GeV. The longitudinal and transverse pieces of the cross section were separated using the Rosenbluth separation method.
Date: April 1, 2006
Creator: Horn, Tanja
Partner: UNT Libraries Government Documents Department

Coherent rho 0 photoproduction in bulk matter at high energies

Description: The momentum transfer {Delta}k required for a photon to scatter from a target and emerge as a {rho}{sup 0} decreases as the photon energy k rises. For k &gt; 3 x 10{sup 14} eV, {Delta}k is small enough that the interaction cannot be localized to a single nucleus. At still higher energies, photons may coherently scatter elastically from bulk matter and emerge as a {rho}{sup 0}, in a manner akin to kaon regeneration. Constructive interference from the different nuclei coherently raises the cross section and the interaction probability rises linearly with energy. At energies above 10{sup 23} eV, coherent conversion is the dominant process; photons interact predominantly as {rho}{sup 0}. We compute the coherent scattering probabilities in slabs of lead, water and rock, and discuss the implications of the increased hadronic interaction probabilities for photons on ultra-high energy shower development.
Date: January 9, 2009
Creator: Couderc, Elsa & Klein, Spencer
Partner: UNT Libraries Government Documents Department

Semileptonic Form-factors from B-&gt; K* gamma Decays in the Large Energy Limit

Description: Making use of the measurement of the $B\to K^*\gamma$ branching ratio together with the relations following from the limit of high recoil energy, we obtain stringent constraints on the values of the form-factors entering in heavy-to-light $B\to V\ell\ell'$ processes such as $B\to K^*\ell^+\ell^-$, $B\to K^*\nu \bar\nu$ and $B\to \rho\ell\nu$ decays. We show that the symmetry predictions, when combined with the experimental information on radiative decays, specify a severely restricted set of values for the vector and axial-vector form-factors evaluated at zero momentum transfer, $q^2=0$. These constraints can be used to test model calculations and to improve our understanding of the $q^2$-dependence of semileptonic form-factors. We stress that the constraints remain stringent even when corrections are taken into account.
Date: November 21, 2000
Creator: Burdman, Gustavo & Hiller, Gudrun
Partner: UNT Libraries Government Documents Department

Elastic scattering of the long-lived hadrons

Description: The authors propose to measure the elastic scattering of the charged hadrons {pi}{sup {+-}}, K{sup {+-}}, p and {bar p} over a region of momentum transfer up to about 1 GeV/c. Special attention will be given to the Coulomb interference region. This experimental program is based on the use of novel detectors of high spatial resolution which we have developed.
Date: December 1, 1970
Creator: Atac, M.; Dolnick, C.; Gollon, P.; Lach, J.; MacLachlan, J.; Roberts, A. et al.
Partner: UNT Libraries Government Documents Department

Strategy for understanding gas-solid riser hydrodynamics and other LANL status items

Description: The talk presents the status of work in progress in the area of momentum transport theory in turbulent gas-solid multiphase flow. Previous installments have reported details of the theory, and validation results. This talk provides a grand overview of how the details of dynamic simulations in 3D, 2D, 1D and 0D, all fit together to form a consistent strategy for understanding gas-solid riser hydrodynamics. The circulating fluidized bed is the canonical example for showing how the strategy works. Performance of the procedure is shown by comparison to data recently obtained by Sandia National Laboratory. Status of other LANL efforts is also mentioned.
Date: January 1, 2002
Creator: Kashiwa, B. A.
Partner: UNT Libraries Government Documents Department

Flow Visualization of Forced and Natural Convection in Internal Cavities

Description: The general goal of this program is to develop innovative flow visualization methods and reliable predictive techniques for the energy, mass, and momentum transfer in the presence of surface reactions for the passivation treatment operations of SNF elements.
Date: June 1, 2000
Creator: Crepeau, John C.; Clarksean, Randy; McEligot, Donald M. & Guezennec, Yann G.
Partner: UNT Libraries Government Documents Department

Importance of Coulomb Corrections In Extraction of the Proton Form Factors

Description: Results of recent polarization transfer experiments indicate that the ratio of the proton's electric to magnetic form factor decreases with increasing momentum transfer, yet the polarization transfer results are in sharp disagreement with the many Rosenbluth separation results. In this paper, it will be shown that the inclusion of a Coulomb correction to the Rosenbluth separation data slightly reduces this discrepancy.
Date: June 1, 2003
Creator: Higinbotham, Douglas
Partner: UNT Libraries Government Documents Department


Description: The second part of the sixth RHIC Spin Collaboration (RSC) meeting was held on November 15, 2001 at Brookhaven National Laboratory. Previous meetings have elaborated on the new generation of proton spin-structure studies (e.g. gluon polarization and flavor separation of q and {bar q} polarizations via real W{sup {+-}} production) enabled by studying polarized proton collisions at energies and momentum transfers where perturbative QCD models are expected to be applicable. The focus of this meeting was on many of the experimental issues that must be resolved to achieve these physics goals. This summary is written with the benefit of hindsight following the completion of the first-ever run of a polarized proton collider. This first run can be considered as a successfully completed milestone of the RHIC Spin Collaboration. Other milestones remain important. Long term machine items were identified in Waldo Mackay's talk, the most important being the completion of the spin rotator magnets that will be installed in 2002 to allow the flexible orientation of the proton beam polarization at the PHENM and STAR experiments. At the meeting Waldo discussed a stronger partial snake magnet for the AGS as a means of producing highly polarized proton beams to inject into RHIC. Developments subsequent to this meeting suggest that a superconducting helical dipole magnet may be feasible for the AGS, and is likely to be needed to achieve the 70% beam polarization in RHIC. Longer term items were also presented, including potential increases in luminosity by the addition of electron cooling to RHIC and the possibility of increasing the collision energy by {approx}20% by replacement of the DX magnets. These items could be considered for a second generation of RHIC spin experiments. The other topics covered at the meeting were related to polarimetry and to the absolute calibration of the proton ...
Date: November 15, 2001
Creator: Bland, L. & Saito, N.
Partner: UNT Libraries Government Documents Department

The Upgrade of CEBAF to 12 GeV: Physics Motivations and Technical Aspects

Description: The Continuous Electron Beam Accelerator Facility, CEBAF, makes use of electron and photon beams with an energy up to 6 GeV to investigate the electromagnetic structure of mesons, nucleons, and nuclei. We discuss the physics motivation for upgrading the facility to a maximum energy of 12 GeV and some of the key technological aspects of the upgrade.
Date: August 1, 2002
Creator: Mecking, Bernhard & Cardman, Larry
Partner: UNT Libraries Government Documents Department

Exclusive photon-photon processes

Description: Exclusive gamma gamma right arrow hadron pairs are among the most fundamental processes in QCD, providing a detailed examination of Compton scattering in the crossed channel. In the high momentum transfer domain (s, t, large, Theta cm for t/s fixed), these processes can be computed from first principles in QCD, yielding important information on the nature of the QCD coupling data and the form of hadron distribution amplitudes. Similarly, the transition form factors gamma star gamma, gamma star gamma right arrow pi(o), Eta (0), Eta`, Eta(c)... provide rigorous tests of QCD and definitive determinations of the meson distribution amplitudes Phi H(x,Q). We show that the assumption of a frozen coupling at low momentum transfers can explain the observed scaling of two-photon exclusive processes.
Date: July 1, 1997
Creator: Brodsky, S.J.
Partner: UNT Libraries Government Documents Department

Radiative corrections for (e,e{prime}p) reactions at GeV energies

Description: A general framework for applying radiative corrections to (e,e{prime}p) coincidence reactions at GeV energies is presented, with special emphasis to higher-order Bremsstrahlung effects, radiation from the scattered hadron, and the validity of peaking approximations. The sensitivity to the assumptions made in practically applying radiative corrections to (e,e{prime}p) data is extensively discussed. The general framework is tested against experimental data of the {sup 1}H(e,e{prime}p) reaction at momentum transfer values larger than 1.0 (GeV/c){sup 2}, where radiative processes become a dominant source of uncertainty. The formulas presented here can easily be modified for any other electron-induced coincidence reaction.
Date: May 1, 2000
Creator: Ent, R.; Filippone, B. W.; Makins, N. C. R.; Milner, R. G.; O'Neill, T. G. & Wasson, D. A.
Partner: UNT Libraries Government Documents Department

Virtual Compton Scattering on the proton at high s and low t

Description: Virtual Compton Scattering (VCS) at low transferred momenta to the proton (t) and sufficiently high c.m. energies (s) may be used to (a) study Q{sup 2}-dependence of leading t-channel exchanges and (b) look for onset of scaling behavior with increasing Q{sup 2}. The author discusses the implications for perturbative and nonperturbative QCD and suggests possible experiments.
Date: August 1, 1996
Creator: Afanasev, Andrei
Partner: UNT Libraries Government Documents Department