Results for "S. S. Vogt"

total 158539took 0.14s
On non-singlet physical evolution kernels and large-x coefficient functions in perturbative QCDSep 11 2009We study the large-x behaviour of the physical evolution kernels for flavour non-singlet observables in deep-inelastic scattering, where x is the Bjorken variable, semi-inclusive e^+ e^- annihilation and Drell-Yan lepton-pair production. Unlike the corresponding ... More
On Third-Order Timelike Splitting Functions and Top-Mediated Higgs Decay into HadronsSep 25 2007We employ relations between spacelike and timelike deep-inelastic processes in perturbative QCD to calculate the next-to-next-to-leading order (NNLO) contributions to the timelike quark-quark and gluon-gluon splitting functions for the evolution of flavour-singlet ... More
$J/ψ$ and $ψ'$ suppression by comovers in Pb+Pb collisionsSep 30 1996Measurements of $\psi$ and $\psi'$ production at the CERN SPS are compared to predictions based on a hadronic model of charmonium suppression. Detailed information is presented to facilitate comparison to other analyses. Sensitivity of these conclusions ... More
Charmonium Suppression by Comover Scattering in Pb+Pb CollisionsJun 27 1996Sep 25 1996The first reports of $\psi$ and $\psi'$ production from experiment NA50 at the CERN SPS are compared to predictions based on a hadronic model of charmonium suppression. Data on centrality dependence and total cross sections are in good accord with these ... More
Threshold Resummation of the Structure Function F_LFeb 13 2009The behaviour of the quark coefficient function for the longitudinal structure function F_L in deep-inelastic scattering is investigated for large values of the Bjorken variable x. We combine a highly plausible conjecture on the large-x limit of the physical ... More
Consequences of Nuclear Shadowing for Heavy Quarkonium Production in Hadron-Nucleus InteractionsJul 11 1994We study nuclear shadowing in $J/\psi$ and $\Upsilon$ production in hadron-nucleus interactions and in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider. %We define the regions in $x_f$ where nuclear shadowing ... More
Higher-order threshold resummation for semi-inclusive e^+e^- annihilationAug 19 2009The complete soft-enhanced and virtual-gluon contributions are derived for the quark coefficient functions in semi-inclusive e^+e^- annihilation to the third order in massless perturbative QCD. These terms enable us to extend the soft-gluon resummation ... More
NNLO Time-like Splitting Functions in QCDJul 02 2008We review the status of the calculation of the time-like splitting functions for the evolution of fragmentation functions to the next-to-next-to-leading order in perturbative QCD. By employing relations between space-like and time-like deep-inelastic ... More
Higher-Order Soft Corrections to Lepton Pair and Higgs Boson ProductionAug 25 2005Nov 12 2006Utilizing recent three-loop results on the quark and gluon splitting functions and form factors, we derive the complete threshold-enhanced third-order (N^3LO) QCD corrections to the total cross sections for the production of lepton pairs and the Higgs ... More
Inhomogeneous Shadowing Effects on J/ψProduction in dA CollisionsMay 15 2003We study the effect of spatially homogeneous and inhomogeneous shadowing on $J/\psi$ production in deuterium-nucleus collisions. We discuss how the shadowing and its spatial dependence may be measured by comparing central and peripheral $dA$ collisions. ... More
Comments on "Perspectives on Galactic Dynamics via General Relativity"Dec 22 2005In this comment we question some arguments presented in astro-ph/0512048 to refuse the presence of an singular mass surface layer. In particular, incorrect expressions are used for the disk's surface mass density. We also point out that the procedure ... More
Presence of exotic matter in the Cooperstock and Tieu galaxy modelOct 26 2005We analyze the presence of an additional singular thin disk in the recent General Relativistic model of galactic gravitational field proposed by Cooperstock and Tieu. The physical variables of the disk's energy-momentum tensor are calculated. We show ... More
Relativistic Models of GalaxiesJul 18 2005A special form of the isotropic metric in cylindrical coordinates is used to construct what may be interpreted as the General Relativistic versions of some wellknown potential-density pairs used in Newtonian gravity to model three-dimensional distributions ... More
Exact General Relativistic Perfect Fluid Disks with HalosAug 11 2003Using the well-known ``displace, cut and reflect'' method used to generate disks from given solutions of Einstein field equations, we construct static disks made of perfect fluid based on vacuum Schwarzschild's solution in isotropic coordinates. The same ... More
QCD and Intrinsic Heavy Quark Predictions for Leading Charm and Beauty HadroproductionMay 05 1994Recent experiments at Fermilab and CERN have observed a strong asymmetry between the hadroproduction cross sections of leading $D$ mesons, containing projectile valence quarks, and nonleading charmed mesons, without projectile valence quarks. The observed ... More
Nuclear Shadowing and High-$p_T$ Hadron Spectra in Relativistic Heavy Ion CollisionsNov 22 2002We explore how nuclear modifications to the nucleon parton distributions affect production of high-$p_T$ hadrons in heavy ion collisions. We perform a leading order calculation of the high-$p_T$ charged pion, kaon and proton spectra using standard fragmentation ... More
Exact General Relativistic Discs and the Advance of PerihelionMay 20 2008The advance of perihelion for geodesic motion on the galactic plane of some exact general relativistic disc solutions is calculated. Approximate analytical and numerical results are presented for the static Chazy-Curzon and the Schwarzschild discs in ... More
Exact General Relativistic Rotating Disks Immersed in Rotating Dust Generated from van Stockum SolutionsNov 14 2006A class of exact general relativistic rotating thick disks surrounded by rotating dust is constructed by applying the ``displace, cut, fill and reflect'' method on the van Stockum class of metrics. Two particular solutions are considered in detail. We ... More
Analytical Potential-Density Pairs for Flat Rings and Toroidal StructuresJun 04 2009The Kuzmin-Toomre family of discs is used to construct potential-density pairs that represent flat ring structures in terms of elementary functions. Systems composed of two concentric flat rings, a central disc surrounded by one ring and a ring with a ... More
A General Relativistic Model for the Gravitational Field of Active Galactic Nuclei Surrounded by a DiskSep 28 2004An exact but simple general relativistic model for the gravitational field of active galactic nuclei is constructed, based on the superposition in Weyl coordinates of a black hole, a Chazy-Curzon disk and two rods, which represent matter jets. The influence ... More
Triaxial Analytical Potential-Density Pairs for GalaxiesMay 11 2007We present two triaxial analytical potential-density pairs that can be viewed as generalized versions of the axisymmetric Miyamoto and Nagai and Satoh galactic models. These potential-density pairs may be useful models for galaxies with box-shaped bulges. ... More
Gliese 581g as a scaled-up version of Earth: atmospheric circulation simulationsOct 22 2010Apr 05 2011We use three-dimensional simulations to study the atmospheric circulation on the first Earth-sized exoplanet discovered in the habitable zone of an M star. We treat Gliese 581g as a scaled-up version of Earth by considering increased values for the exoplanetary ... More
Exact Relativistic Static Charged Perfect Fluid DisksSep 28 2004Using the well-known ``displace, cut and reflect'' method used to generate disks from given solutions of Einstein field equations, we construct static charged disks made of perfect fluid based on the Reissner-Nordstr\"{o}m solution in isotropic coordinates. ... More
On the Solutions of the Lorentz-Dirac EquationJul 01 2003We discuss the unstable character of the solutions of the Lorentz-Dirac equation and stress the need of methods like order reduction to derive a physically acceptable equation of motion. The discussion is illustrated with the paradigmatic example of the ... More
Charmed Hadron Asymmetries in the Intrinsic Charm Coalescence ModelDec 13 1995Fermilab experiment E791, measuring charmed hadron production in $\pi^- A$ interactions at 500 GeV with high statistics, has observed a strong asymmetry between the hadroproduction cross sections for leading $D$ mesons which contain projectile valence ... More
Potential-density pairs for bent barsDec 27 2010A method is presented to bend a thin massive line when the curvature is small. The procedure is applied to a homogeneous thin bar with two types of curvatures. One of them mimics a galactic bar with two spiral arms at its tips. It is showed that if the ... More
Intrinsic Charm Contribution to Double Quarkonium HadroproductionMar 02 1995Double $J/\psi$ production has been observed by the NA3 collaboration in $\pi N$ and $p N$ collisions with a cross section of the order of 20-30 pb. The $\psi \psi$ pairs measured in $\pi^- $ nucleus interactions at 150 and 280 GeV$/c$ are observed to ... More
Analytical potential-density pairs for barsAug 14 2010An identity that relates multipolar solutions of the Einstein equations to Newtonian potentials of bars with linear densities proportional to Legendre polynomials is used to construct analytical potential-density pairs of infinitesimally thin bars with ... More
Newtonian and General Relativistic Models of Spherical Shells - IIJun 11 2010A family of potential-density pairs that represent spherical shells with finite thickness is obtained from the superposition of spheres with finite radii. Other families of shells with infinite thickness with a central hole are obtained by inversion transformations ... More
Newtonian and General Relativistic Models of Spherical ShellsNov 25 2009A family of spherical shells with varying thickness is derived by using a simple Newtonian potential-density pair. Then, a particular isotropic form of a metric in spherical coordinates is used to construct a General Relativistic version of the Newtonian ... More
New Models of General Relativistic Static Thick DisksJan 31 2005New families of exact general relativistic thick disks are constructed using the ``displace, cut, fill and reflect'' method. A class of functions used to ``fill'' the disks is derived imposing conditions on the first and second derivatives to generate ... More
Analytical potential-density pairs from complex-shifted Kuzmin-Toomre discsAug 06 2009The complex-shift method is applied to the Kuzmin-Toomre family of discs to generate a family of non-axisymmetric flat distributions of matter. These are then superposed to construct non-axisymmetric flat rings. We also consider triaxial potential-density ... More
On Multipolar Analytical Potentials for GalaxiesMar 09 2006We present analytical potential-density pairs in three dimensions for the gravitational field of galaxies, obtained by thickening the multipolar expansion up to the quadrupole term. These may be interpreted as generalizations of the Miyamoto and Nagai ... More
The Kinematics of Intermediate Redshift Mg II AbsorbersJun 01 2001[Abridged] We present 23 quasar absorption line systems selected by the MgII doublet with W_r(2796)>0.3 Ang over the redshift range 0.4<z<1.2. The kinematics are studied at ~6 km/s resolution to a 5-sigma detection threshold of 0.015 Ang. Most absorbers ... More
Structure and Magnetism of the mono-layer hydrate Na0.3NiO2 0.7H2OJan 20 2007The mono-layer hydrate (Ni-MLH) Na0.3NiO2 0.7H2O was synthesized with an average Ni valence close to one in the bi-layer hydrate (Ni-BLH) Na0.3NiO2 1.3H2O. A weak unsaturated ferromagnetism and divergence of the magnetic susceptibilities of field and ... More
Differences between charged-current coefficient functionsAug 28 2007Second- and third-order results are presented for the structure functions of charged-current deep-inelastic scattering in the framework of massless perturbative QCD. We write down the two-loop differences between the corresponding crossing-even and -odd ... More
The Small-x Evolution of Unpolarized and Polarized Structure FunctionsOct 21 1996A brief overview is presented of recent developments concerning resummed small-x evolution, based upon the renormalization group equation. The non-singlet and singlet structure functions are discussed for both polarized and unpolarized deep-inelastic ... More
The Evolution of Unpolarized and Polarized Structure Functions at Small $x$Aug 28 1996Aug 29 1996A survey is given of recent developments on the resummed small-$x$ evolution, in a framework based on the renormalization group equation, of non--singlet and singlet structure functions in both unpolarized and polarized deep--inelastic scattering. The ... More
On Small-x Resummations for the Evolution of Unpolarized and Polarized Non--Singlet and Singlet Structure FunctionsJul 15 1996A brief survey is given of recent results on the resummation of leading small-x terms for unpolarized and polarized non--singlet and singlet structure function evolution.
On top-pair hadro-production at next-to-next-to-leading orderMar 28 2012Jun 27 2012We study the QCD corrections at next-to-next-to-leading order (NNLO) to the cross section for the hadronic pair-production of top quarks. We present new results in the high-energy limit using the well-known framework of k_t-factorization. We combine these ... More
On the Next-to-Next-to-Leading Order Evolution of Flavour-Singlet Fragmentation FunctionsJul 12 2011We present the third-order contributions to the quark-gluon and gluon-quark timelike splitting functions for the evolution of fragmentation functions in perturbative QCD. These quantities have been derived by studying physical evolution kernels for photon- ... More
Photon-Parton Splitting Functions at the Next-to-Next-to-Leading Order of QCDNov 09 2005We have calculated the splitting functions governing the evolution of the unpolarized parton distributions of the photon at the next-to-next-to-leading order (NNLO) of massless perturbative QCD. The results, presented here mainly in terms of compact and ... More
The Three-Loop Splitting Functions in QCDJul 28 2004We have computed the next-to-next-to-leading-order (NNLO) contributions to the evolution of unpolarized parton distributions in perturbative QCD. In this talk, we briefly recall why this huge computation was necessary and outline how it was performed. ... More
Third-order QCD results on form factors and coefficient functionsAug 29 2006We summarize recent higher-order QCD results based, directly or indirectly, on the Mellin-space computation of the next-to-next-to-leading-order splitting functions governing the evolution of hadronic parton distributions. Specifically, we briefly present ... More
Charmonium Production and Corona EffectNov 21 2011We study the centrality dependence to be expected if only charmonium production in the corona survives in high energy nuclear collisions, with full suppression in the hot, deconfined core. To eliminate cold nuclear matter effects as far as possible, we ... More
The Halo from the Outside In: QSO Absorption LinesJan 24 1996Studies of high resolution quasar absorption lines (QALs), arising from gas in local and z < 1.5 galaxies, provide direct probes of the kinematic, chemical, and ionization conditions and evolution of Milky Way-like galaxies. Inferences drawn from these ... More
NNLO splitting and coefficient functions with time-like kinematicsSep 04 2006Sep 04 2006We discuss recent results on the three-loop (next-to-next-to-leading order, NNLO) time-like splitting functions of QCD and the two-loop (NNLO) coefficient functions in one-particle inclusive e+e- annihilation. These results form the basis for extracting ... More
Third-order QCD corrections to the charged-current structure function F_3Dec 22 2008We compute the coefficient function for the charge-averaged W^(+/-)-exchange structure function F_3 in deep-inelastic scattering (DIS) to the third order in massless perturbative QCD. Our new three-loop contribution to this quantity forms, at not too ... More
Flavour changing effects on e^+ e^- -> H b \bar{s}, H \bar{b} s in the MSSMNov 02 2005Jul 20 2007Flavour changing effects originating from the exchange of scalar particles in the processes e^+ e^- -> H b \bar{s}, H \bar{b} s, with H = h^0, H^0, A^0, are investigated in the Minimal Supersymmetric Standard Model with non-minimal flavour violation at ... More
Next-to-Next-to-Leading Order Evolution of Non-Singlet Fragmentation FunctionsApr 06 2006We have investigated the next-to-next-to-leading order (NNLO) corrections to inclusive hadron production in e^+e^- annihilation and the related parton fragmentation distributions, the `time-like' counterparts of the `space-like' deep-inelastic structure ... More
Sudakov Resummations at Higher OrdersNov 09 2005We summarize our recent results on the resummation of hard-scattering coefficient functions and on-shell form factors in massless perturbative QCD. The threshold resummation has been extended to the fourth logarithmic order for deep-inelastic scattering, ... More
Relativistic ring modelsJan 30 2014Relativistic thick ring models are constructed using previously found analytical Newtonian potential-density pairs for flat rings and toroidal structures obtained from Kuzmin-Toomre family of discs. In particular, we present systems with one ring, two ... More
On the Resummation of the $α\ln^2 z Terms for QED Corrections to Deep-Inelastic $ep$ Scattering and $e^+e^-$ AnnihilationNov 02 1996The resummation of the $\alpha \ln^2(z)$ non-singlet contributions is performed for initial state QED corrections. As examples, the effect of the resummation on neutral-current deep-inelastic scattering and the $e^+ e^- \rightarrow \mu^+ \mu^-$ scattering ... More
Sub-Saturn Planet Candidates to HD 16141 and HD 46375Apr 24 2000Precision Doppler measurements from the Keck/HIRES spectrometer reveal periodic Keplerian velocity variations in the stars HD 16141 and HD 46375. HD 16141 (G5 IV) has a period of 75.8 d and a velocity amplitude of 11 m/s, yielding a companion having Msini ... More
On gamma_5 in higher-order QCD calculations and the NNLO evolution of the polarized valence distributionJun 15 2015We discuss the prescription for the Dirac matrix gamma_5 in dimensional regularization used in most second- and third-order QCD calculations of collider cross sections. We provide an alternative implementation of this approach that avoids the use of an ... More
The Quark Form Factor at Higher OrdersJul 04 2005We study the electromagnetic on-shell form factor of quarks in massless perturbative QCD. We derive the complete pole part in dimensional regularization at three loops, and extend the resummation of the form factor to the next-to-next-to-leading contributions. ... More
Understanding Bottom ProductionAug 12 2002We describe calculations of b b-bar production to next-to-next-to-leading order (NNLO) and next-to-next-to-leading logarithm (NNLL) near threshold in pp interactions. Our calculations are in good agreement with the b b-bar total cross section measured ... More
Synthesis and Structure of the Monolayer Hydrate K03CoO2 x 04H2OMar 07 2005The monolayer hydrate (MLH) K03CoO2 x 04H2O was synthesized from K06CoO2 by extracting K+ cations using K2S2O8 as an oxidant and the subsequent intercalation of water between the layers of edge-sharing CoO6 octahedra. A hexagonal structure (space group ... More
How To Find Charm in Nuclear Collisions at RHIC and LHCApr 19 1996Measurements of dilepton production from charm decay and Drell-Yan processes respectively probe the gluon and sea quark distributions in hadronic collisions. In nucleus-nucleus collisions, these hard scattering processes constitute a `background' to thermal ... More
Three-Loop Results for Quark and Gluon Form FactorsAug 04 2005We study the photon-quark-quark and Higgs-gluon-gluon form factors for on-shell massless quarks and gluons in perturbative QCD. Previous third-order results for the quark case are extended by calculating the fermion-loop contributions up to the finite ... More
Towards the NNLO evolution of polarised parton distributionsJul 08 2008We report on the first calculation of the structure function g_1 in polarised deep-inelastic scattering to the third order in massless perturbative QCD. The calculation follows the dispersive approach already used for the corresponding unpolarised cases ... More
Three-loop results and soft-gluon effects in DISSep 05 2003Sep 15 2003We have calculated the fermionic contributions to the flavour non-singlet structure functions in deep-inelastic scattering (DIS) at third order of massless perturbative QCD. We discuss their implications for the threshold resummation at the next-to-next-to-leading ... More
Impact Parameter Dependence of $J/ψ$ and Drell-Yan Production in Heavy Ion Collisions at $\sqrt{s_{NN}} = 17.3$ GeVSep 01 1998In heavy-ion collisions, $J/\psi$ and Drell-Yan production are expected to be affected by nuclear modifications to the free nucleon structure functions. If these modifications, known as shadowing, are proportional to the local nuclear density, the per ... More
Charm Quark Production in Non-central Heavy Ion CollisionsJun 30 1997Jul 03 1997The effect of gluon shadowing on charm quark production in large impact parameter ultrarelativistic heavy ion collisions is investigated. Charm production cross sections are calculated for a range of non-central impact parameters which can be accurately ... More
GJ 581 update: Additional Evidence for a Super-Earth in the Habitable ZoneJul 18 2012We present an analysis of the significantly expanded HARPS 2011 radial velocity data set for GJ 581 that was presented by Forveille et al. (2011). Our analysis reaches substantially different conclusions regarding the evidence for a Super-Earth-mass planet ... More
The Three-Loop Splitting Functions in QCD: The Helicity-Dependent CaseSep 17 2014We present the next-to-next-to-leading order (NNLO) contributions to the main splitting functions for the evolution of longitudinally polarized parton densities of hadrons in perturbative QCD. The quark-quark and gluon-quark splitting functions have been ... More
Approximate N^3LO Higgs-boson production cross section using physical-kernel constraintsAug 26 2014Oct 06 2014The single-logarithmic enhancement of the physical kernel for Higgs production by gluon-gluon fusion in the heavy top-quark limit is employed to derive the leading so far unknown contributions, ln^{5,4,3}(1-z), to the N^3LO coefficient function in the ... More
On the next-to-next-to-leading order QCD corrections to heavy-quark production in deep-inelastic scatteringMay 25 2012Aug 08 2016The contribution of quarks with masses m >> Lambda_QCD is the only part of the structure functions in deep-inelastic scattering (DIS) which is not yet known at the next-to-next-to-leading order (NNLO) of perturbative QCD. We present improved partial NNLO ... More
On higher-order flavour-singlet splitting and coefficient functions at large xAug 05 2010We discuss the large-x behaviour of the splitting functions P_qg and P_gq and of flavour-singlet coefficient functions, such as the gluon contributions C_2,g and C_L,g to the structure functions F_2,L, in massless perturbative QCD. These quantities are ... More
Higher-order predictions for splitting functions and coefficient functions from physical evolution kernelsJan 20 2010We have studied the physical evolution kernels for nine non-singlet observables in deep-inelastic scattering (DIS), semi-inclusive e^+e^-annihilation and the Drell-Yan (DY) process, and for the flavour-singlet case of the photon- and heavy-top Higgs-exchange ... More
Higher-Order Corrections in Threshold ResummationJun 28 2005Nov 12 2006We extend the threshold resummation exponents G^N in Mellin-N space to the fourth logarithmic (N^3LL) order collecting the terms alpha_s^2 (alpha_s ln N)^n to all orders in the strong coupling constant as. Comparing the results to our previous three-loop ... More
Sudakov Resummation and Finite Order Expansions of Heavy Quark Hadroproduction Cross SectionsMay 04 2001We resum Sudakov threshold enhancements in heavy quark hadroproduction for single-heavy quark inclusive and pair-inclusive kinematics. We expand these resummed results and derive analytical finite-order cross sections through next-to-next-to-leading order. ... More
Threshold Effects in Charm HadroproductionDec 12 2002Feb 20 2003We describe calculations of $c \bar c$ production to next-to-next-to-leading order (NNLO) and next-to-next-to-leading logarithm (NNLL) near threshold in $pp$ and $\pi^- p$ interactions. We study the relevance of these calculations for existing $c \bar ... More
First results for three-loop deep-inelastic structure functions in QCDNov 19 2002As a first step towards the complete calculation of deep-inelastic scattering at third order of massless perturbative QCD, we have computed the fermionic (nf) contributions to the flavour non-singlet structure functions in unpolarized electromagnetic ... More
Systematic study of (g,n) reaction rates for Z>=78 isotopesSep 02 2004Jan 06 2005The (g,n) reaction rates of the isotopes 196,198,204-Hg and 204-Pb have been determined using the photoactivation technique in an energy region relevant for p process nucleosynthesis. The systematic study of the ground-state (g,n) reaction rates on even-even ... More
Spatial Variation of Nuclear Structure Functions and Heavy Quark ProductionMay 14 1998We explore how nuclear modifications to the free nucleon structure functions (also known as shadowing) affect heavy quark production in collisions at different impact parameters. We assume that the nuclear modifications arise from a density dependent ... More
The Effect of Shadowing on Initial Conditions, Transverse Energy and Hard Probes in Ultrarelativistic Heavy Ion CollisionsSep 17 1999The effect of shadowing on the early state of ultrarelativistic heavy ion collisions is investigated along with transverse energy and hard process production, specifically Drell-Yan, $J/\psi$, and $\Upsilon$ production. We choose several parton distributions ... More
On Higgs-exchange DIS, physical evolution kernels and fourth-order splitting functions at large xDec 02 2009We present the coefficient functions for deep-inelastic scattering (DIS) via the exchange of a scalar phi directly coupling only to gluons, such as the Higgs boson in the limit of a very heavy top quark and n_f effectively massless light flavours, to ... More
Next-to-next-to-leading order QCD corrections to the photon's parton structureOct 25 2001Nov 29 2001The next-to-next-to-leading order (NNLO) corrections in massless perturbative QCD are derived for the parton distributions of the photon and the deep inelastic structure functions F_1^gamma and F_2^gamma. We present the full photonic coefficient functions ... More
Chemical short range order obtained from the atomic pair distribution functionJan 23 2002Many crystalline materials show chemical short range order and relaxation of neighboring atoms. Local structural information can be obtained by analyzing the atomic pair distribution function (PDF) obtained from powder diffraction data. In this paper, ... More
Non-singlet coefficient functions for charged-current deep-inelastic scattering to the third order in QCDJun 28 2016We have calculated the coefficient functions for the structure functions F_2, F_L and F_3 in nu-nubar charged-current deep-inelastic scattering (DIS) at the third order in the strong coupling alpha_s, thus completing the description of unpolarized inclusive ... More
Shadowing Effects on Particle and Transverse Energy ProductionJul 15 1999The effect of shadowing on the early state of ultrarelativistic heavy ion collisions and transverse energy production is discussed. Results are presented for RHIC Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV and LHC Pb+Pb collisions at $\sqrt{s_{NN}} ... More
Theoretical Uncertainties in the QCD Evolution of Structure Functions and their Impact on $α_s(M_Z^2)$Sep 01 1996Sep 02 1996The differences are discussed between various next-to-leading order prescriptions for the QCD evolution of parton densities and structure functions. Their quantitative impact is understood to an accuracy of 0.02\%. The uncertainties due to the freedom ... More
A calculation of the three-loop helicity-dependent splitting functions in QCDMay 14 2014We have calculated the complete matrix of three-loop helicity-difference (`polarized') splitting functions Delta P_ik^(2), i,k = q,g, in massless perturbative QCD. In this note we briefly discuss some properties of the polarized splitting functions and ... More
Threshold-improved predictions for charm production in deep-inelastic scatteringAug 05 2010We have extended previous results on the threshold expansion of the gluon coefficient function for the charm contribution to the deep-inelastic structure function F_2 by deriving all threshold-enhanced contributions at the next-to-next-to-leading order. ... More
The third-order QCD corrections to deep-inelastic scattering by photon exchangeApr 26 2005We compute the full three-loop coefficient functions for the structure functions F_2 and F_L in massless perturbative QCD. The results for F_L complete the next-to-next-to-leading order description of unpolarized electromagnetic deep-inelastic scattering. ... More
The Longitudinal Structure Function at the Third OrderNov 08 2004Nov 09 2004We compute the complete third-order contributions to the coefficient functions for the longitudinal structure function F_L, thus completing the next-to-next-to-leading order (NNLO) description of unpolarized electromagnetic deep-inelastic scattering in ... More
The Three-Loop Splitting Functions in QCD: The Singlet CaseApr 14 2004We compute the next-to-next-to-leading order (NNLO) contributions to the splitting functions governing the evolution of the unpolarized flavour-singlet parton densities in perturbative QCD. The exact expressions are presented in both Mellin-N and Bjorken-x ... More
The Three-Loop Splitting Functions in QCD: The Non-Singlet CaseMar 17 2004We compute the next-to-next-to-leading order (NNLO) contributions to the three splitting functions governing the evolution of unpolarized non-singlet combinations of quark densities in perturbative QCD. Our results agree with all partial results available ... More
The QCD Splitting Functions at Three Loops: Methods and ResultsAug 05 2004We have computed the complete next-to-next-to-leading order (NNLO) contributions to the splitting functions governing the evolution of unpolarized parton densities in perturbative QCD. Our results agree with all partial results available in the literature. ... More
Non-Singlet Structure Functions at Three Loops: Fermionic ContributionsSep 10 2002We compute the fermionic (n_f) contributions to the flavour non-singlet structure functions in unpolarized electromagnetic deep-inelastic scattering at third order of massless perturbative QCD. Complete results are presented for the corresponding nf-parts ... More
On the Spatial and Kinematic Distributions of Mg II Absorbing Gas in <z>=0.7 GalaxiesMay 29 1996(Abridged) We present HIRES/Keck spectra having resolution 6 km/s of Mg II 2796 absorption profiles which arise in the gas associated with 15 identified galaxies over the redshift range 0.5 < z < 0.9. Using non-parametric rank correlation tests, we searched ... More
Charge transfer in the high dielectric constant materials CaCu3Ti4O12 and CdCu3Ti4O12Sep 16 2002The cubic perovskite-related ceramic CaCu3Ti4O12 has a very high static dielectric constant ~10000 at room temperature (RT), which drops to about 100 below about 100 K. Substituting Cd for Ca reduces the RT value of the dielectric constant by over an ... More
Planetary Companions Around Two Solar Type Stars: HD 195019 and HD 217107Oct 26 1998We have enlarged the sample of stars in the planet search at Lick Observatory. Doppler measurements of 82 new stars observed at Lick Observatory, with additional velocities from Keck Observatory, have revealed two new planet candidates. The G3V/IV star, ... More
Dynamical Mass Estimates for the Halo of M31 from Keck SpectroscopyAug 09 2000The last few months have seen the measurements of the radial velocities of all of the dwarf spheroidal companions to the Andromeda galaxy (M31) using the spectrographs (HIRES and LRIS) on the Keck Telescope. This paper summarises the data on the radial ... More
A Planetary Companion to the Nearby M4 Dwarf, Gliese 876Jul 29 1998Doppler measurements of the M4 dwarf star, Gliese 876, taken at both Lick and Keck Observatory reveal periodic, Keplerian velocity variations with a period of 61 days. The orbital fit implies that the companion has a mass of, M = 2.1 MJUP /sin i, an orbital ... More
High-Redshift Superwinds as the Source of the Strongest Mg II Absorbers: A Feasibility AnalysisAug 03 2001We present HIRES/Keck profiles of four extremely strong (W_r > 1.8 A) Mg II absorbers at 1 < z < 2. The profiles display a common kinematic structure, having a sharp drop in optical depth near the center of the profile and strong, black-bottomed absorption ... More
The GJ 876 Planetary System -- A Progress ReportJul 21 2004We present an updated analysis of the GJ 876 planetary system based on an augmented data set that incorporates 65 new high-precision radial velocities obtained with the Keck telescope from 2001 to 2004. These new radial velocities permit a more accurate ... More
Temperature dependent total scattering structural study of CaCu3Ti4O12Mar 11 2003X-ray and neutron powder diffraction data as a function of temperature are analyzed for the colossal dielectric constant material CaCu3Ti4O12. The local structure is studied using atomic pair distribution function analysis. No evidence is found for enhanced ... More
A transportable optical lattice clock with $7\times10^{-17}$ uncertaintySep 20 2016We present a transportable optical clock (TOC) with $^{87}$Sr. Its complete characterization against a stationary lattice clock resulted in a systematic uncertainty of ${7.4 \times 10^{-17}}$ which is currently limited by the statistics of the determination ... More