Digital Commons Network^™

Large-Qt W-Boson Production At The Tevatron, Nikolaos Kidonakis, Agustín Sabio Vera

Faculty Articles

The production of W bosons at large transverse momentum at the Tevatron is dominated by soft-gluon corrections. In this talk we present a calculation of these corrections at next-to-next-to-leading order. The corrections enhance the transverse momentum distribution of the W while reducing the scale dependence.

Read More: http://www.worldscientific.com/doi/abs/10.1142/S0217751X05026236

Strain Induced Half-Metal To Semiconductor Transition In Gdn, Chun-Gang Duan, Renat F. Sabirianov, Jianjun Liu, Wai-Ning Mei, Peter A. Dowben, John R. Hardy

Physics Faculty Publications

We investigate the electronic structure and magnetic properties of GdN as a function of unit cell volume. Based on the first-principles calculations of GdN, we observe that there is a transformation in the conduction properties associated with the volume increase: first from half-metallic to semimetallic, then ultimately to semiconducting. We show that applying stress can alter the carrier concentration as well as mobility of the holes and electrons in the majority spin channel. In addition, we found that the exchange parameters depend strongly on lattice constant, thus the Curie temperature of this system can be enhanced by applying stress or …

Collinear And Soft Resummation In The Large-X Limit, Nikolaos Kidonakis

Faculty Articles

I discuss general unified formulas for resumming collinear and soft contributions to QCD hard scattering cross sections at laxge x. Expansions of the resummed cross sections to next-to-next-to-next-to-leading order are also shown along with applications of the formalism.

Erratum: Nonrelativistic Qed Approach To The Bound-Electron G Factor (Phys. Rev. Lett. (2004) 93 (150401)), Krzysztof Pachucki, Ulrich D. Jentschura, Vladimir A. Yerokhin

Physics Faculty Research & Creative Works

No abstract provided.

Modelling Continuum Optical And Ultraviolet Polarization Of Active Galactic Nuclei, René W. Goosmann, C. Martin Gaskell

Department of Physics and Astronomy: Faculty Publications

We present results from a new Monte Carlo radiative transfer computer code, STOKES, developed to model polarization induced by scattering off free electrons and dust grains. STOKES is freely available on the web and can be used to model scattering in a wide variety of astrophysical situations. For edge-on (type-2) viewing positions, the polarization produced by a dusty torus alone is largely wavelength-independent.

This is because the torus is optically thick and the change in albedo with wavelength is slight. Wavelength-independent polarization therefore does not necessarily imply electron scattering. We are able to fully explain wavelength independent type-2 polarization without …

Top Quark And Charged Higgs Production At Hadron Colliders, Nikolaos Kidonakis

Faculty Articles

I present a brief theoretical update on top quark pair production at the Tevatron and give values of the NNLO-NNNLL cross section for both m_t=175 and 178 GeV. I then present a calculation of the cross section for charged Higgs production in association with a top quark at the LHC, including NNLO soft-gluon corrections.

Ferromagnetism In Nanocrystalline Epitaxial Co:Tio2 Thin Films, Aswini K. Pradhan, D. Hunter, J.B. Dadson, T.M. Williams, Kai Zhang, K. Lord, B. Lasley, Rakhim R. Rakhimov, Jun Zhang, David J. Sellmyer, U.N. Roy, Y. Cui, A. Burger, C. Hopkins, N. Pearson, A.L. Wilkerson

David Sellmyer Publications

We report on the observation of remarkable room-temperature ferromagnetism in nanocrystalline epitaxial Co:TiO₂ films grown on sapphire (0001) substrates by a pulsed-laser deposition technique using high-density targets. The films were characterized by x-ray measurements, atomic force microscopy, micro-Raman, electron-paramagnetic resonance, and magnetization studies. The films exhibit three-dimensional islandlike growth that contains nanocrystalline particles. Our experimental results suggest that the remarkable ferromagnetism in Co:TiO₂ films is controlled either by the interstitial Co²⁺ ions or small clusters, which are mainly present at the interface and on the surface of the films. Our work clearly indicates that Co interstitials and …

Erratum: Computing The M = 1 Diocotron Frequency Via An Equilibrium Calculation In Non-Neutral Plasmas, Ross L. Spencer

Faculty Publications

Equation 14 in this paper contains errors.

Black Hole Thermodynamics From Near-Horizon Conformal Quantum Mechanics, Horacio E. Camblong

Physics and Astronomy

The thermodynamics of black holes is shown to be directly induced by their near-horizon conformal invariance. This behavior is exhibited using a scalar field as a probe of the black hole gravitational background, for a general class of metrics in D spacetime dimensions (with D≥4). The ensuing analysis is based on conformal quantum mechanics, within a hierarchical near-horizon expansion. In particular, the leading conformal behavior provides the correct quantum statistical properties for the Bekenstein-Hawking entropy, with the near-horizon physics governing the thermodynamics from the outset. Most importantly: (i) this treatment reveals the emergence of holographic properties; (ii) the conformal coupling …

Fine Structure Of Beta Decay Endpoint Spectrum, Joseph Schechter, Samina S. Masood, Salah Nasri

Physics - All Scholarship

We note that the fine structure at the endpoint region of the beta decay spectrum is now essentially known using neutrino oscillation data, if the mass of one neutrino is specified. This may help to identify the effects of nonzero neutrino masses in future experiments. An exact treatment of phase space kinematics is used. This work is independent of theoretical models. Additional restrictions due to the assumption of a so-called "complementary ansatz" for the neutrino mass matrix are also discussed.

Preheating In New Inflation, Mariel Desroche, Gary Felder, Jan M. Kratochvil, Andrei Linde

Physics: Faculty Publications

During the last ten years a detailed investigation of preheating was performed for chaotic inflation and for hybrid inflation. However, nonperturbative effects during reheating in the new inflation scenario remained practically unexplored. We investigate preheating in new inflation, using a combination of analytical and numerical methods. We find that the decay of the homogeneous component of the inflaton field and the resulting process of spontaneous symmetry breaking in the simplest models of new inflation usually occurs almost instantly: for the new inflation on the GUT scale it takes only about 5 oscillations of the field distribution. The decay of the …

Lattice Thermal Conductance In Nanowires At Low Temperatures: Breakdown And Recovery Of Quantization, Y. Tanaka, F. Yoshida, S. Tamura

Dartmouth Scholarship

The quantization of lattice thermal conductance g normalized by g0=π2k2BT/3h (the universal quantum of thermal conductance) was recently predicted theoretically to take an integer value over a finite range of temperature and then observed experimentally in nanowires with catenoidal contacts. The prediction of this quantization by Rego and Kirczenow [Phys. Rev. Lett. 81, 232 (1998)] relies on a study of only dilatational (longitudinal) vibrational mode in the wires. We study the thermal conductance in catenoidal wires by explicitly calculating the transmission rates of the six distinct vibrational modes (four acoustic and two low-lying optical modes) and applying the Landauer …

Estimation Of (N, F) Cross Sections By Measuring Reaction Probability Ratios, C. Plettner, H. Ai, C. W. Beausang, L. A. Bernstein, L. Ahle, H. Amro, M. Babilon, J. T. Burke, J. A. Caggiano, R. F. Casten, J. A. Church, J. R. Cooper, B. Crider, G. Gurdal, A. Heinz, E. A. Mccutchan, K. Moody, J. A. Punyon, J. Qian, J. J. Ressler, A. Schiller, E. Williams, W. Younes

Physics Faculty Publications

Neutron-induced reaction cross sections on unstable nuclei are inherently difficult to measure due to target activity and the low intensity of neutron beams. In an alternative approach, named the “surrogate” technique, one measures the decay probability of the same compound nucleus produced using a stable beam on a stable target to estimate the neutron-induced reaction cross section. As an extension of the surrogate method, in this paper we introduce a new technique of measuring the fission probabilities of two different compound nuclei as a ratio, which has the advantage of removing most of the systematic uncertainties. This method was benchmarked …

Correlation Length And Chirality Of The Fluctuations In The Isotropic Phase Of Nematic And Cholesteric Liquid Crystals, Jacob J. Krich , '00, Mark B. Romanowsky , '03, Peter J. Collings

Physics & Astronomy Faculty Works

Light-scattering measurements of the correlation length in the isotropic phase of a nematic liquid crystal reveal a temperature dependence following Landau-de Gennes theory for the isotropic phase with a bare correlation length smaller than has been measured in other liquid crystals. Similar measurements in a cholesteric liquid crystal demonstrate that the correlation length in the isotropic phase is larger than typically found in nematics and that the chirality of the fluctuations in the isotropic phase is slightly higher than the chirality of the cholesteric phase. Landau-de Gennes theory of the cholesteric phase describes the chirality in the cholesteric phase well …

Search For Zz And Zw Production In Pp̅ Collisions At √S=1.96 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a search for ZZ and ZW vector boson pair production in pp̅ collisions at √s =1.96 TeV using the leptonic decay channels ZZ→_llνν, ZZ→_{lll′ l′}, and ZW→_lll′ν. In a data sample corresponding to an integrated luminosity of 194 pb^-1 collected with the Collider Detector at Fermilab, 3 candidate events are found with an expected background of 1.0±0.2 events. We set a 95% confidence level upper limit of 15.2 pb on the cross section for ZZ and ZW production, compared to the standard model prediction of 5.0±0.4 pb.

Klystron Linearizer For Use With 1.2 Mw 476 Mhz Klystrons In Pep-Ii Rf Systems, J. Fox, T. Mastorides, D. Teytelman, D. Van Winkle, Y. Zhou

Physics

The direct and comb loop feedback around the RF cavities in PEP-II is critical in reducing longitudinal instabilities driven by the cavity impedance. The non-linear 1.2 MW klystron is in the signal path for these feedback loops. As a result, the effective small-signal gain of the klystron at 85% saturation reduces the impedance control by factors of 5 to 20 as compared to a linear power amplifier. A klystron linearizer circuit has been developed which operates in series with the power amplifier and acts to equalize the small and large signal gains through the combination. The technique must implement a …

Direct Visualization Of Dislocation Dynamics In Grain Boundary Scars, Mark Bowick, Peter Lipowsky, Jan H. Meinke, David R. Nelson, Andreas R. Bausch

Physics - All Scholarship

Mesoscale objects with unusual structural features may serve as the analogues of atoms in the design of larger-scale materials with novel optical, electronic or mechanical behaviour. In this paper we investigate the structural features and the equilibrium dynamics of micron-scale spherical crystals formed by polystyrene particles adsorbed on the surface of a spherical water droplet. The ground state of sufficiently large crystals possesses finite-length grain boundaries (scars). We determine the elastic response of the crystal by measuring single-particle diffusion and quantify the fluctuations of individual dislocations about their equilibrium positions within a scar determining the dislocation spring constants. We observe …

Spin Glass Or Random Anisotropy?: The Origin Of Magnetically Glassy Behavior In Nanostructured Gdal2, P. M. Shand, C. C. Stark, D. Williams, Marco Morales Torres, T. M. Pekarek, Diandra Leslie-Pelecky

Diandra Leslie-Pelecky Publications

Initially crystalline GdAl₂ was mechanically milled for long times to produce a highly chemically disordered phase with approximately 8-nm grains. Analysis of dc magnetization measurements using an Arrott plot and the approach to saturation suggest the presence of significant random anisotropy. ac susceptibility measurements showed that the shift in the peak temperature with frequency usually seen in magnetically glassy and superparamagnetic systems was virtually undetectable in the 10–1000-Hz frequency range. Based on these results, we believe that this material represents an interacting system with random anisotropy, where the anisotropy is the result of surface and interface asymmetries. ©2005 American …

Anisotropic Exchange, Ralph Skomski, Arti Kashyap, Jian Zhou, David J. Sellmyer

David Sellmyer Publications

The origin and physical nature anisotropic exchange interactions is investigated. Emphasis is on nonrelativistic exchange anisotropies, as encountered, for example, in intermetallics with layered crystal structures. The summation of site-resolved exchange interactions is analyzed, and it is shown that Ruderman–Kittel-type long-range exchange yield converging exchange-stiffness expressions down to atomic length scales. In general, the resulting exchange stiffness is anisotropic, even if the interaction is mediated by an isotropic free electron gas. The determination of the mean-field Curie temperature from pair-exchange interactions requires the diagonalization of an interaction matrix, as opposed to simple site averaging.

Enhanced Coercivity In Thermally Processed (Nd,Dy)(Fe,Co,Nb,B) 5.5/ Α-Fe Nanoscale Multilayer Magnets, W. Liu, Xingzhong Li, J Ping Liu, X.K. Sun, C.L. Chen, Ralph Skomski, Z.D. Zhang, David J. Sellmyer

David Sellmyer Publications

Structural and magnetic properties of laminated (Nd,Dy)(Fe,Co,Nb,B)_5.5/Fe nanocomposites are investigated. Normally, the addition of the soft phase to the hard phase enhances the remanence but deteriorates the permanent-magnet performance of the material by reducing the coercivity. In the present system, the coercivity increases to 1608 kA/m (20.2 kOe) in thermally processed Nd–Dy–Fe–Co–Nb–B(15 nm)/Fe(4 nm) multilayered nanocomposites, which is higher than that of the single-layer hard-magnetic film. The abnormally high coercivity is achieved by annealing at relatively high temperature, which breaks the laminated structure of the as-deposited multilayer. A likely physical explanation of the enhanced coercivity is the introduction …

Magnetic Materials For Finite-Temperature Quantum Computing, Ralph Skomski, J. Zhou, A.Y. Istomin, Anthony F. Starace, David J. Sellmyer

Anthony F. Starace Publications

The potential use of interacting magnetic nanodots for quantum computing (qubit) operations is investigated by model calculations. The quantum entanglement of the low-lying ferromagnetic states, as quantified by the concurrence, exhibits a resonant peak whose position and width depend on parameters such as dot anisotropy, interdot exchange, and external field gradient. The maximum operation temperature is proportional to the magnetocrystalline anisotropy of the dot material. A specific condition is that the dots are sufficiently small so that the interatomic exchange ensures a coherent magnetization state and quantum coherence at finite temperatures. From a material point of view, there is a …

Molecular Hydrogen In Star-Forming Regions: Implementation Of Its Microphysics In Cloudy, G. Shaw, Gary J. Ferland, N. P. Abel, P. C. Stancil, P. A. M. Van Hoof

Physics and Astronomy Faculty Publications

Much of the baryonic matter in the universe is in the form of H₂, which includes most of the gas in Galactic and extragalactic interstellar clouds. Molecular hydrogen plays a significant role in establishing the thermal balance in many astrophysical environments and can be important as a spectral diagnostic of the gas. Modeling and interpretation of observations of such environments requires a quantitatively complete and accurate treatment of H₂. Using this microphysical model of H₂, we present illustrative calculations of prototypical astrophysical environments. This work forms the foundation for future investigations of these and …

Measurement Of Charged-Particle Multiplicities In Gluon And Quark Jets In Pp̅ Collisions At √S =1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report the first largely model independent measurement of charged particle multiplicities in quark and gluon jets, N_q and N_g, produced at the Fermilab Tevatron in pp̅ collisions with a center-of-mass energy of 1.8 TeV and recorded by the Collider Detector at Fermilab. The measurements are made for jets with average energies of 41 and 53 GeV by counting charged particle tracks in cones with opening angles of θ _c=0.28, 0.36, and 0.47 rad around the jet axis. The corresponding jet hardness Q=E_jet θ _c varies in the range from 12 to 25 GeV. At …

Transverse-Momentum PT Correlations On (Η,Φ) From Mean-PT Fluctuations In Au–Au Collisions At √SNn = 200 Gev, J. Adams, M.M. Aggarwal, Z. Ahammed, J. Amonett, B.D. Anderson, D. Arkhipkin, G.S. Averichev, S.K. Badyal, Y. Bai, J. Balewski, O. Barannikova, L.S. Barnby, J. Baudot, S. Bekele, V.V. Belaga, A. Bellingeri-Laurikainen, R. Bellwied, J. Berger, B.I. Bezverkhny, S. Bharadwaj, A. Bhasin, A.K. Bhati, V.S. Bhatia, H. Bichsel, J. Bielcik, J. Bielcikova, A. Billmeier, L.C. Bland, C.O. Blyth, S-L. Blyth, B.E. Bonner, M. Botje, A. Boucham, J. Bouchet, A.V. Brandin, A. Bravar, M. Bystersky, R.V. Cadman, X.Z. Cai, H. Caines, M. Calderón De La Barca Sánchez, J. Castillo, O. Catu, D. Cebra, Z. Chajecki, P. Chaloupka, S. Chattopadhyay, H.F. Chen, J.H. Chen, Y. Chen, J. Cheng, M. Cherney, A. Chikanian, H.A. Choi, W. Christie, J.P. Coffin, T.M. Cormier, M.R. Cosentino, J.G. Cramer, H.J. Crawford, D. Das, S. Das, M. Daugherity, M.M. De Moura, T.G. Dedovich, M. Dephillips, A.A. Derevschikov, L. Didenko, T. Dietel, S.M. Dogra, W.J. Dong, X. Dong, J.E. Draper, F. Du, A.K. Dubey, V.B. Dunin, J.C. Dunlop, M.R. Dutta Mazumdar, V. Eckardt, W.R. Edwards, L.G. Efimov, V. Emelianov, J. Engelage, G. Eppley, B. Erazmus, M. Estienne, P. Fachini, J. Faivre, R. Fatemi, J. Fedorisin, K. Filimonov, P. Filip, E. Finch, V. Fine, Y. Fisyak, K.S.F. Fornazier, J. Fu, C.A. Gagliardi, L. Gaillard, J. Gans, M.S. Ganti, F. Geurts, V. Ghazikhanian, P. Ghosh, J.E. Gonzalez, H. Gos, O. Grachov, O. Grebenyuk, D. Grosnick, S.M. Guertin, Y. Guo, A. Gupta, N. Gupta, T.D. Gutierrez, T.J. Hallman, A. Hamed, D. Hardtke, J.W. Harris, M. Heinz, T.W. Henry, S. Hepplemann, B. Hippolyte, A. Hirsch, E. Hjort, G.W. Hoffmann, M.J. Horner, H.Z. Huang, S.L. Huang, E.W. Hughes, T.J. Humanic, G. Igo, A. Ishihara, P. Jacobs, W.W. Jacobs, M. Jedynak, H. Jiang, P.G. Jones, E.G. Judd, S. Kabana, K. Kang, M. Kaplan, D. Keane, A. Kechechyan, V.Yu. Khodyrev, B.C. Kim, J. Kiryluk, A. Kisiel, E.M. Kislov, J. Klay, S.R. Klein, D.D. Koetke, T. Kollegger, M. Kopytine, L. Kotchenda, K.L. Kowalik, M. Kramer, P. Kravtsov, V.I. Kravtsov, K. Krueger, C. Kuhn, A.I. Kulikov, A. Kumar, R. Kh. Kutuev, A.A. Kuznetsov, M.A.C. Lamont, J.M. Landgraf, S. Lange, F. Laue, J. Lauret, A. Lebedev, R. Lednicky, C-H. Lee, S. Lehocka, M.J. Levine, C. Li, Q. Li, Y. Li, G. Lin, S.J. Lindenbaum, M.A. Lisa, F. Liu, H. Liu, J. Liu, L. Liu, Q.J. Liu, Z. Liu, T. Ljubicic, W.J. Llope, H. Long, R.S. Longacre, M. Lopez-Noriega, W.A. Love, Y. Lu, T. Ludlam, D. Lynn, G.L. Ma, J.G. Ma, Y.G. Ma, D. Magestro, S. Mahajan, D.P. Mahapatra, R. Majka, L.K. Mangotra, R. Manweiler, S. Margetis, C. Markert, L. Martin, J.N. Marx, H.S. Matis, Yu.A. Matulenko, C.J. Mcclain, T.S. Mcshane, F. Meissner, Yu. Melnick, A. Meschanin, M.L. Miller, N.G. Minaev, C. Mironov, A. Mischke, D.K. Mishra, J. Mitchell, B. Mohanty, L. Molnar, C.F. Moore, D.A. Morozov, M.G. Munhoz, B.K. Nandi, S.K. Nayak, T.K. Nayak, J.M. Nelson, P.K. Netrakanti, V.A. Nikitin, L.V. Nogach, S.B. Nurushev, G. Odyniec, A. Ogawa, V. Okorokov, M. Oldenburg, D. Olson, S.K. Pal, Y. Panebratsev, S.Y. Panitkin, A.I. Pavlinov, T. Pawlak, T. Peitzmann, V. Perevoztchikov, C. Perkins, W. Peryt, V.A. Petrov, S.C. Phatak, R. Picha, M. Planinic, J. Pluta, N. Porile, J. Porter, A.M. Poskanzer, M. Potekhin, E. Potrebenikova, B.V.K.S. Potukuchi, D. Prindle, C. Pruneau, J. Putschke, G. Rakness, R. Raniwala, S. Raniwala, O. Ravel, R.L. Ray, S.V. Razin, D. Reichhold, J.G. Reid, J. Reinnarth, G. Renault, F. Retiere, A. Ridiger, H.G. Ritter, J.B. Roberts, O.V. Rogachevskiy, J.L. Romero, A. Rose, C. Roy, L. Ruan, M.J. Russcher, R. Sahoo, I. Sakrejda, S. Salur, J. Sandweiss, M. Sarsour, I. Savin, P.S. Sazhin, J. Schambach, R.P. Scharenberg, N. Schmitz, K. Schweda, J. Seger, I. Selyuzhenkov, P. Seyboth, E. Shahaliev, M. Shao, W. Shao, M. Sharma, W.Q. Shen, K.E. Shestermanov, S.S. Shimanskiy, E. Sichtermann, F. Simon, R.N. Singaraju, N. Smirnov, R. Snellings, G. Sood, P. Sorensen, J. Sowinski, J. Speltz, H.M. Spinka, B. Srivastava, A. Stadnik, T.D.S. Stanislaus, R. Stock, A. Stolpovsky, M. Strikhanov, B. Stringfellow, A.A.P. Suaide, E. Sugarbaker, M. Sumbera, B. Surrow, M. Swanger, T.J.M. Symons, A. Szanto De Toledo, A. Tai, J. Takahashi, A.H. Tang, T. Tarnowsky, D. Thein, J.H. Thomas, A.R. Timmins, S. Timoshenko, M. Tokarev, T.A. Trainor, S. Trentalange, R.E. Tribble, O.D. Tsai, J. Ulery, T. Ullrich, D.G. Underwood, G. Van Buren, N. Van Der Kolk, M. Van Leeuwen, A.M. Vander Molen, R. Varma, I.M. Vasilevski, A.N. Vasiliev, R. Vernet, S.E. Vigdor, Y.P. Viyogi, S. Vokal, S.A. Voloshin, W.T. Waggoner, F. Wang, G. Wang, G. Wang, X.L. Wang, Y. Wang, Y. Wang, Z.M. Wang, H. Ward, J.W. Watson, J.C. Webb, G.D. Westfall, A. Wetzler, C. A. Whitten Jr., H. Wieman, S.W. Wissink, R. Witt, J. Wood, J. Wu, N. Xu, Z. Xu, Z.Z. Xu, E. Yamamoto, P. Yepes, I.-K. Yoo, V.I. Yurevich, I. Zborovsky, H. Zhang, W.M. Zhang, Y. Zhang, Z.P. Zhang, C. Zhong, R. Zoulkarneev, Y. Zoulkarneeva, A.N. Zubarev, J.X. Zuo

Physics

We present first measurements of the pseudorapidity and azimuth (η, ϕ) binsize dependence of event-wise mean transverse-momentum ⟨p_t⟩ fluctuations for Au–Au collisions at √s_NN = 200 GeV. We invert that dependence to obtain p_t autocorrelations on differences (η_∆, ϕ_∆) interpreted to represent velocity/temperature distributions on (η, ϕ). The general form of the autocorrelations suggests that the basic correlation mechanism is parton fragmentation. The autocorrelations vary rapidly with collision centrality, which suggests that fragmentation is strongly modified by a dissipative medium in the more central Au–Au collisions relative to peripheral or p–p collisions.

Measurements Of Bottom-Antibottom Azimuthal Production Correlations In Proton-Antiproton Collisions At √S =1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have measured the azimuthal angular correlation of b[overline b] production, using 86.5 pb^-1 of data collected by Collider Detector at Fermilab (CDF) in pp̅ collisions at sqrt(s)=1.8 TeV during 1994–1995. In high-energy pp̅ collisions, such as at the Tevatron, bb̅ production can be schematically categorized into three mechanisms. The leading-order (LO) process is "flavor creation," where both bb and b̅ quarks substantially participate in the hard scattering and result in a distinct back-to-back signal in final state. The "flavor excitation" and the "gluon splitting" processes, which appear at next-leading-order (NLO), are known to make a comparable contribution to …

Nondipole Effects In The Triply Differential Cross Section For Double Photoionization Of He, Andrei Y. Istomin, N. L. Manakov, A. V. Meremianin, Anthony F. Starace

Department of Physics and Astronomy: Faculty Publications

Lowest-order nondipole effects are studied systematically in double photoionization (DPI) of the He atom. Ab initio parametrizations of the quadrupole transition amplitude for DPI from the 1S0 state are presented in terms of the exact two-electron radial matrix elements. Analytic expressions for these matrix elements within lowest-order perturbation theory (LOPT) in the interelectron interaction are also given. The corresponding parametrizations for the dipole-quadrupole triply differential cross section (TDCS) are presented for the case of an elliptically polarized photon. A general analysis of retardation-induced asymmetries of the TDCS including the circular dichroism effect at equal energy sharing is presented. Numerical LOPT …

Study Of Deep Inelastic Inclusive And Diffractive Scattering With The Zeus Forward Plug Calorimeter, S. Chekanov, M. Derrick, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida, Margarita C. K. Mattingly, N. Pavel, A. G. Yagües Molina, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, A. Montanari, R. Nania, F. Palmonari, A. Pesci, A. Polini

Faculty Publications

Deep inelastic scattering and its diffractive component, ep → e′ γ* p → e′ X N, have been studied at HERA with the ZEUS detector using an integrated luminosity of 4.2 pb-1. The measurement covers a wide range in the γ* p c.m. energy W (37-245 GeV), photon virtuality Q2 (2.2-80 GeV2) and mass MX (0.28-35 GeV). The diffractive cross section for MX > 2 GeV rises strongly with W; the rise is steeper with increasing Q2. The latter observation excludes the description of diffractive deep inelastic scattering in terms of the exchange of a single pomeron. The ratio of diffractive …

A Direct Comparison Of Conceptual Learning And Problem Solving Ability In Traditional And Studio Style Classrooms, Chance Hoellwarth, Matthew J. Moelter, Randall D. Knight

Physics

We present data on student performance on conceptual understanding and on quantitative problem-solving ability in introductory mechanics in both studio and traditional classroom modes. The conceptual measures used were the Force Concept Inventory and the Force and Motion Conceptual Evaluation. Quantitative problem-solving ability was measured with standard questions on the final exam. Our data compare three different quarters over the course of 2 years. In all three quarters, the normalized learning gain in conceptual understanding was significantly larger for students in the studio sections. At the same time, students in the studio sections performed the same or slightly worse on …

A Secrecy Primer, David Hafemeister

Physics

As more countries acquire the scientific knowledge to build nuclear weapons, the U.S. response should not be heightened secrecy but a renewed commitment to strengthening political safeguards.

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix: Neutronic Evaluation Of Zro2-Mgo Inert Fuels, E. Fridman, S. Kolesnikov, E. Shwageraus, A. Galperin

Fuels Campaign (TRP)

This report presents the results of the Task 4, defined in working program as: evaluation of reactivity feedback coefficients. Three main parameters of the Fertile-Free Fuel (FFF) lattices were evaluated: Moderator Temperature Coefficient (MTC), Fuel Temperature Coefficient due to Doppler Effect (DC), and soluble Boron reactivity worth (BW).

One of the major design challenges associated with utilization of FFF is deterioration of the temperature coefficients and control materials reactivity worth caused by high thermal cross-section of Pu and consequent hardening of the neutron spectrum. The purpose of the investigation reported in this section is to estimate the potential of addition …