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2009

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Articles 1 - 30 of 734

Full-Text Articles in Physics

Partial Wave Analysis Of The Reaction Γp→Pω And The Search For Nucleon Resonances, M. Williams, Gerard P. Gilfoyle, Et. Al. Dec 2009

Partial Wave Analysis Of The Reaction Γp→Pω And The Search For Nucleon Resonances, M. Williams, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

An event-based partial wave analysis (PWA) of the reaction γp → pω has been performed on a high-statistics dataset obtained using the CLAS at Jefferson Lab for center-of-mass energies from threshold up to 2.4 GeV. This analysis benefits from access to the world’s first high-precision spin-density matrix element measurements, available to the event-based PWA through the decay distribution of ω → π +π −π0. The data confirm the dominance of the t-channel π0 exchange amplitude in the forward direction. The dominant resonance contributions are consistent with the previously identified states F15(1680) and …

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Differential Cross Sections And Spin Density Matrix Elements For The Reaction Γp→Pω, M. Williams, Gerard P. Gilfoyle, Et. Al. Dec 2009

Differential Cross Sections And Spin Density Matrix Elements For The Reaction Γp→Pω, M. Williams, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

High-statistics differential cross sections and spin-density matrix elements for the reaction γp → pω have been measured using the CEBAF large acceptance spectrometer (CLAS) at Jefferson Lab for center-of-mass (c.m.) energies from threshold up to 2.84 GeV. Results are reported in 112 10-MeV wide c.m. energy bins, each subdivided into cos θωc.m. bins of width 0.1. These are the most precise and extensive ω photoproduction measurements to date. A number of prominent structures are clearly present in the data. Many of these have not previously been observed due to limited statistics in earlier measurements.

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A High-Yield Synthesis Of Chalcopyrite Cuins2 Nanoparticles With Exceptional Size Control, Aaron Thurber, Alex Punnoose Dec 2009

A High-Yield Synthesis Of Chalcopyrite Cuins2 Nanoparticles With Exceptional Size Control, Aaron Thurber, Alex Punnoose

Physics Faculty Publications and Presentations

We report high-yield and efficient size-controlled syntheses of Chalcopyrite CuInS2 nanoparticles by decomposing molecular single source precursors (SSPs) via microwave irradiation in the presence of 1,2-ethanedithiol at reaction temperatures as low as 100◦C and times as short as 30 minutes. The nanoparticles sizes were 1.8nm to 10.8 nm as reaction temperatures were varied from 100◦C to 200◦C with the bandgaps from 2.71 eV to 1.28 eV with good size control and high yields (64%–95%). The resulting nanoparticles were analyzed by XRD, UV-Vis, ICP-OES, XPS, SEM, EDS, and HRTEM. Titration studies by 1H NMR using SSP 1 with 1,2-ethanedithiol …

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Classical Modeling Of Non-Sequential Double Ionization: Recollision, Time-Delayed Ionization, Drift, And Possible Reattachment, Stanley L. Haan, Z. S. Smith, K. N. Shomsky, P. W. Plantinga Dec 2009

Classical Modeling Of Non-Sequential Double Ionization: Recollision, Time-Delayed Ionization, Drift, And Possible Reattachment, Stanley L. Haan, Z. S. Smith, K. N. Shomsky, P. W. Plantinga

University Faculty Publications and Creative Works

We employ 3d classical ensembles to study Non-Sequential Double Ionization (NSDI) of atoms by strong laser fields at visible and infrared wavelengths. We consider in particular the wavelength dependence of final electron drift directions and the net momentum spectra parallel to the laser polarization. We find that as the wavelength is increased the spectrum transitions from a singlet to a doublet, then to a triplet, and finally back to a doublet. We also show that electrons that escape the central potential-energy well during the pulse may nonetheless be bound to the nucleus after laser turnoff.

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Photoassociation Spectroscopy Of Purely Long-Range Krypton Molecules, Z. Smith, J. Banister, R. Norman, K. Hoogeboom Dec 2009

Photoassociation Spectroscopy Of Purely Long-Range Krypton Molecules, Z. Smith, J. Banister, R. Norman, K. Hoogeboom

University Faculty Publications and Creative Works

Photoassociation spectra for purely long-range (PLR) krypton molecules are both computed and measured. The photoassociation laser is tuned just red of the 5s[3/2]2-5p[5/2]2 transition at 810.6 nm, over a frequency range in which fourteen different PLR potential wells support hundreds of vibrational bound states. In the experiment, laser light is directed into a cloud of magneto-optically trapped 84Kr atoms, and the emission of both ultraviolet photons and ions is monitored. Peaks in these signals are observed for laser frequencies within 200 MHz of the atomic resonance. Ongoing work is aimed at improving the experimental signal and understanding the degree of …

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Photoassociation Spectroscopy Of Purely Long-Range Krypton Molecules, Z. Smith, J. Banister, R. Norman, K. Hoogeboom Dec 2009

Photoassociation Spectroscopy Of Purely Long-Range Krypton Molecules, Z. Smith, J. Banister, R. Norman, K. Hoogeboom

University Faculty Publications and Creative Works

Photoassociation spectra for purely long-range (PLR) krypton molecules are both computed and measured. The photoassociation laser is tuned just red of the 5s[3/2]2-5p[5/2]2 transition at 810.6 nm, over a frequency range in which fourteen different PLR potential wells support hundreds of vibrational bound states. In the experiment, laser light is directed into a cloud of magneto-optically trapped 84Kr atoms, and the emission of both ultraviolet photons and ions is monitored. Peaks in these signals are observed for laser frequencies within 200 MHz of the atomic resonance. Ongoing work is aimed at improving the experimental signal and understanding the degree of …

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Reevaluating The Cosmological Origin Of Dark Matter, Scott Watson Dec 2009

Reevaluating The Cosmological Origin Of Dark Matter, Scott Watson

Physics - All Scholarship

The origin of dark matter as a thermal relic offers a compelling way in which the early universe was initially populated by dark matter. Alternative explanations typically appear exotic compared to the simplicity of thermal production. However, recent observations and progress from theory suggest that it may be necessary to be more critical. This is important because ongoing searches probing the microscopic properties of dark matter typically rely on the assumption of dark matter as a single, unique, thermal relic. On general grounds I will argue that non-thermal production of dark matter seems to be a robust prediction of physics …

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Measured Optical Constants Of Copper From 10 Nm To 35 Nm, David D. Allred, Nicole Brimhall, Nicholas Herrick, Justin Peatross, R. Steven Turley, Michael Ware Dec 2009

Measured Optical Constants Of Copper From 10 Nm To 35 Nm, David D. Allred, Nicole Brimhall, Nicholas Herrick, Justin Peatross, R. Steven Turley, Michael Ware

Faculty Publications

We use laser high-order harmonics and a polarization-ratioreflectance technique to determine the optical constants of copper and oxidized copper in the wavelength range 10-35 nm. This measurement resolves previously conflicting data sets, where disagreement on optical constants of copper in the extreme ultraviolet most likely arises from inadvertent oxidation of samples before measurement.

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Fractal Location And Anomalous Diffusion Dynamics For Oil Wells From The Ky Geological Survey, Keith Andrew, Karla M. Andrew, Kevin A. Andrew Dec 2009

Fractal Location And Anomalous Diffusion Dynamics For Oil Wells From The Ky Geological Survey, Keith Andrew, Karla M. Andrew, Kevin A. Andrew

Physics & Astronomy Faculty Publications

Utilizing data available from the Kentucky Geonet (KYGeonet.ky.gov) the fossil fuel mining locations created by the Kentucky Geological Survey geo-locating oil and gas wells are mapped using ESRI ArcGIS in Kentucky single plain 1602 ft projection. This data was then exported into a spreadsheet showing latitude and longitude for each point to be used for modeling at different scales to determine the fractal dimension of the set. Following the porosity and diffusivity studies of Tarafdar and Roy[1] we extract fractal dimensions of the fossil fuel mining locations and search for evidence of scaling laws for the set of deposits. The …

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Viscosity Dependent Liquid Slip At Molecularly Smooth Hydrophobic Surfaces, Sean P. Mcbride, Bruce M. Law Dec 2009

Viscosity Dependent Liquid Slip At Molecularly Smooth Hydrophobic Surfaces, Sean P. Mcbride, Bruce M. Law

Physics Faculty Research

Colloidal probe atomic force microscopy is used to study the slip behavior of 18 Newtonian liquids from two homologous series, the n-alkanes and n-alcohols, at molecularly smooth hydrophobic n-hexadecyltrichlorosilane coated surfaces. We find that the slip behavior is governed by the bulk viscosity η of the liquid, specifically, the slip length b∼ηx with x∼0.33. Additionally, the slip length was found to be shear rate independent, validating the use of Vinogradova slip theory in this work.

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Partially Coherent Standard And Elegant Laguerre-Gaussian Beams Of All Orders, Fei Wang, Yangjian Cai, Olga Korotkova Dec 2009

Partially Coherent Standard And Elegant Laguerre-Gaussian Beams Of All Orders, Fei Wang, Yangjian Cai, Olga Korotkova

Physics Articles and Papers

Partially coherent standard and elegant Laguerre-Gaussian (LG) beams of all orders are introduced as a natural extension of coherent standard and elegant LG beams to the stochastic domain. By expanding the LG modes into a finite sum of Hermite-Gaussian modes, the analytical formulae are obtained for the cross-spectral densities of partially coherent standard and elegant LG beams in the source plane and after passing through paraxial ABCD optical system, based on the generalized Collins integral formula. A comparative study of the propagation properties of the partially coherent standard and elegant LG beams in free space is carried out via a …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner Dec 2009

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Mikhail Khenner

Mathematics Faculty Publications

A mathematical model for the evolution of pulsed laser-irradiated, molten metallic films has been developed using the lubrication theory. The heat transfer problem that incorporates the absorbed heat from a single laser beam or the interfering laser beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the reflectivity, the peak laser beam …

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A 236-Ghz Fe3+ Epr Study Of Nanoparticles Of The Ferromagnetic Room-Temperature Semiconductor Sn1-XFeXO2 (X = 0.005), Sushil K. Misra, S. I. Andronenko, Alex Punnoose, Dmitry Tipikin, J. H. Freed Dec 2009

A 236-Ghz Fe3+ Epr Study Of Nanoparticles Of The Ferromagnetic Room-Temperature Semiconductor Sn1-XFeXO2 (X = 0.005), Sushil K. Misra, S. I. Andronenko, Alex Punnoose, Dmitry Tipikin, J. H. Freed

Physics Faculty Publications and Presentations

High-frequency (236 GHz) electron paramagnetic resonance (EPR) studies of Fe3+ ions at 255 K are reported in a Sn1-xFexO2 powder with x = 0.005, which is a ferromagnetic semiconductor at room temperature. The observed EPR spectrum can be simulated reasonably well as the overlap of spectra due to four magnetically inequivalent high-spin (HS) Fe3+ ions (S = 5/2). The spectrum intensity is calculated, using the overlap I(BL) + (I(HS1) + I(HS2) + I(HS3) + I(HS4)) 9 x e-0.00001xB, where B is the magnetic field intensity …

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Are Periodic Solar Wind Number Density Structures Formed In The Solar Corona?, N. M. Viall, Harlan E. Spence, J. Kasper Dec 2009

Are Periodic Solar Wind Number Density Structures Formed In The Solar Corona?, N. M. Viall, Harlan E. Spence, J. Kasper

Physics & Astronomy

[1] We present an analysis of the alpha to proton solar wind abundance ratio (AHe) during a period characterized by significant large size scale density fluctuations, focusing on an event in which the proton and alpha enhancements are anti-correlated. In a recent study using 11 years (1995–2005) of solar wind observations from the Wind spacecraft, N. M. Viall et al. [2008] showed that periodic proton density structures occurred at particular radial length-scales more often than others. The source of these periodic density structures is a significant and outstanding question. Are they generated in the interplanetary medium, or are they a …

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Systematic Analysis Of Double-Ionization Dynamics Based On Four-Body Dalitz Plots, Daniel Fischer, Michael Schulz, Katharina R. Schneider, Marcelo F. Ciappina, Tom Kirchner, Aditya H. Kelkar, S. Hagman, Manfred Grieser, Kai Uwe Kuhnel, Robert Moshammer, Joachim Hermann Ullrich Dec 2009

Systematic Analysis Of Double-Ionization Dynamics Based On Four-Body Dalitz Plots, Daniel Fischer, Michael Schulz, Katharina R. Schneider, Marcelo F. Ciappina, Tom Kirchner, Aditya H. Kelkar, S. Hagman, Manfred Grieser, Kai Uwe Kuhnel, Robert Moshammer, Joachim Hermann Ullrich

Physics Faculty Research & Creative Works

We report on an experimental and theoretical systematic study of double ionization of helium by ion impact in terms of four-particle Dalitz plots. Several collision systems covering abroad range of perturbation parameters η (projectile charge to speed ratio) were investigated. With increasing η we observe a systematic trend from features, characteristic to correlated double-ionization mechanisms, to signatures of higher-order processes not requiring electron-electron correlations [the mechanism called "two-step-two projectile-electron interaction" (TS-2)]. The data for the largest η can qualitatively be amazingly well described by a simple model only including the TS-2 mechanism.

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Morphology Of The Dayside Ionosphere Of Mars: Implications For Ion Outflows, Jane L. Fox Dec 2009

Morphology Of The Dayside Ionosphere Of Mars: Implications For Ion Outflows, Jane L. Fox

Physics Faculty Publications

Significant fluxes of tailward streaming ions have been detected in the Martian wake by instruments on spacecraft. Imposing outward fluxes at the top of a model will produce dayside ion density profiles that are characterized by smaller scale heights than those of diffusive equilibrium. We determine the maximum outward fluxes of ions, and those implied by radio occultation data, by constructing ∼180 models, with upward velocity boundary conditions in the range from 0 to (7–8) × 105 cm s−1 in small increments. As the upward velocity is increased, the topside ion or electron densities decrease until eventually the …

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Modeling Of Metal-Ferroelectric-Insulator-Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, Stephen Ducharme Dec 2009

Modeling Of Metal-Ferroelectric-Insulator-Semiconductor Structures Based On Langmuir–Blodgett Copolymer Films, Timothy J. Reece, Stephen Ducharme

Stephen Ducharme Publications

Among the ferroelectric thin films used in field-effect transistor devices; the ferroelectric copolymer of polyvinylidene fluoride PVDF –CH2–CF2–, with trifluoroethylene TrFE –CHF–CF2–, has distinct advantages, including low dielectric constant, low processing temperature, low cost, and compatibility with organic semiconductors. The operation of a metal-ferroelectric insulatorsemiconductor structure with PVDF-TrFE as the ferroelectric layer was analyzed and optimized by numerical solution of the Miller and McWhorter model. A model device consisting of 20 nm PVDF/TrFE on a 10-nm-thick high-k dielectric buffer exhibits a memory window of 5 V with an operating voltage of 15 V. The operating voltage can be reduced to …

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Self-Organized Criticality In Sheared Suspensions, L. Corté, Sharon J. Gerbode, W. Man, D. J. Pine Dec 2009

Self-Organized Criticality In Sheared Suspensions, L. Corté, Sharon J. Gerbode, W. Man, D. J. Pine

All HMC Faculty Publications and Research

Recent studies reveal that suspensions of neutrally buoyant non-Brownian particles driven by slow periodic shear can undergo a dynamical phase transition between a fluctuating irreversible steady state and an absorbing reversible state. Using a computer model, we show that such systems exhibit self-organized criticality when a finite particle sedimentation velocity vs is introduced. Under periodic shear, these systems evolve, without external intervention, towards the shear-dependent critical concentration ϕc as vs is reduced. This state is characterized by power-law distributions in the lifetime and size of fluctuating clusters. Experiments exhibit similar behavior and, as vs is reduced, …

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Transition From N-Type To P-Type Destroys Ferromagnetism In Semiconducting Sn1-XCoXO2 And Sn1-XCrXO2 Nanoparticles, C. Van Komen, A. Punnoose, M. S. Seehra Dec 2009

Transition From N-Type To P-Type Destroys Ferromagnetism In Semiconducting Sn1-XCoXO2 And Sn1-XCrXO2 Nanoparticles, C. Van Komen, A. Punnoose, M. S. Seehra

Physics Faculty Publications and Presentations

This work reports strong correlations between the structural, magnetic and electronic properties of room temperature ferromagnets (RTFM) Sn1-xCoxO2 and Sn1-xCrxO2 for x = 0 to 0.1. The samples prepared by the sol-gel chemical method show RTFM for x < xL with the limiting concentration xL = 0.01 for Co doping and xL = 0.025 for Cr doping. As doping level x is increased from x = 0, the magnetic moment per ion, μ, increases and the lattice volume VL decreases up to x = xL. …

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Perturbation Theory Analysis Of Attosecond Photoionization, Anthony F. Starace, Evgeny A. Pronin, M. V. Frolov, N. L. Manakov Dec 2009

Perturbation Theory Analysis Of Attosecond Photoionization, Anthony F. Starace, Evgeny A. Pronin, M. V. Frolov, N. L. Manakov

Anthony F. Starace Publications

Ionization of an atom by a few-cycle attosecond xuv pulse is analyzed using perturbation theory (PT), keeping terms in the transition amplitude up to second order in the pulse electric field. Within the PT approach, we present an ab initio parametrization of the ionized electron angular distribution (AD) using rotational invariance and symmetry arguments. This parametrization gives analytically the dependence of the AD on the carrier envelope phase (CEP), the polarization of the pulse, and on the ionized electron momentum direction, p^ . For the general case of an elliptically polarized pulse, we show that interference of the first- and …

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Nonlinear Evolution Of Baryon Acoustic Oscillations From Improved Perturbation Theory In Real And Redshift Spaces, Atsushi Taruya, Takahiro Nishimichi, Shun Saito, Takashi Hiramatsu Dec 2009

Nonlinear Evolution Of Baryon Acoustic Oscillations From Improved Perturbation Theory In Real And Redshift Spaces, Atsushi Taruya, Takahiro Nishimichi, Shun Saito, Takashi Hiramatsu

Physics Faculty Research & Creative Works

We study the nonlinear evolution of baryon acoustic oscillations in the matter power spectrum and correlation function from the improved perturbation theory (PT). Based on the framework of renormalized PT, which provides a nonperturbative way to treat the gravitational clustering of large-scale structure, we apply the closure approximation that truncates the infinite series of loop contributions at one-loop order, and obtain a closed set of integral equations for power spectrum and nonlinear propagator. The resultant integral expressions are basically equivalent to those previously derived in the form of evolution equations, and they keep important nonperturbative properties which can dramatically improve …

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Pair Creation Rates For One-Dimensional Fermionic And Bosonic Vacua, T Cheng, M R. Ware, Q Su, Rainer Grobe Dec 2009

Pair Creation Rates For One-Dimensional Fermionic And Bosonic Vacua, T Cheng, M R. Ware, Q Su, Rainer Grobe

Faculty publications – Physics

We compare the creation rates for particle-antiparticle pairs produced by a supercritical force field for fermionic and bosonic model systems. The rates obtained from the Dirac and Klein-Gordon equations can be computed directly from the quantum-mechanical transmission coefficients describing the scattering of an incoming particle with the supercritical potential barrier. We provide a unified framework that shows that the bosonic rates can exceed the fermionic ones, as one could expect from the Pauli-exclusion principle for the fermion system. This imbalance for small but supercritical forces is associated with the occurrence of negative bosonic transmission coefficients of arbitrary size for the …

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Investigation Of Velocity Profiles In Anatomically Realistic Renal Artery Flow Phantoms By Physiological Flow Experimentation, Deepa Chari Dec 2009

Investigation Of Velocity Profiles In Anatomically Realistic Renal Artery Flow Phantoms By Physiological Flow Experimentation, Deepa Chari

Masters

Renal Artery stenosis is one of the major causes of curable renovascular hypertension.An early investigation of renal artery stenosis helps in the management of renovascular hypertension by alternative, less-invasive methods such as drug treatments, thereby reducing the risk involved in the surgery. Therefore an early investigation of renal artery stenosis has been always an attractive goal for the physicians. The renal artery stenosis affects the blood velocity profile in the renal artery. These profiles can be investigated by quantitative Doppler Ultrasound measurements obtained by flow experimentations and can be used as a tool for the identification of renal artery stenosis. …

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Four-Body Model For Transfer Excitation, Allison L. Harris, Jerry Peacher, Don H. Madison, James Colgan Dec 2009

Four-Body Model For Transfer Excitation, Allison L. Harris, Jerry Peacher, Don H. Madison, James Colgan

Physics Faculty Research & Creative Works

We present here a four-body model for transfer-excitation collisions, which we call the four-body transfer-excitation (4BTE) model. Each two-body interaction is explicitly included in the 4BTE model, allowing us to study the effects of individual two-body interactions. We apply our model to fully differential cross sections for proton+helium collisions, and study the effect of the incident projectile-atom interaction, the scattered projectile-ion interaction, the projectile-nuclear interaction, and electron correlation within the target atom.

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Multi-Leptons With High Transverse Momentum At Hera, F. D. Aaron, H. Abramowicz, I. Abt, L. Adamczyk, M. Adamus, M. Aldaya Martin, C. Alexa, K. Alimujiang, V. Andreev, S. Antonelli, P. Antonioli, A. Antonov, B. Antunovic, M. Arneodo, A. Asmone, V. Aushev, O. Bachynska, S. Backovic, A. Baghdasaryan, A. Bamberger, A. N. Barakbaev, G. Barbagli, G. Bari, F. Barreiro, E. Barrelet, W. Bartel, D. Bartsch, M. Basile, K. Begzsuren, O. Behnke, J. Behr, Margarita C. K. Mattingly Dec 2009

Multi-Leptons With High Transverse Momentum At Hera, F. D. Aaron, H. Abramowicz, I. Abt, L. Adamczyk, M. Adamus, M. Aldaya Martin, C. Alexa, K. Alimujiang, V. Andreev, S. Antonelli, P. Antonioli, A. Antonov, B. Antunovic, M. Arneodo, A. Asmone, V. Aushev, O. Bachynska, S. Backovic, A. Baghdasaryan, A. Bamberger, A. N. Barakbaev, G. Barbagli, G. Bari, F. Barreiro, E. Barrelet, W. Bartel, D. Bartsch, M. Basile, K. Begzsuren, O. Behnke, J. Behr, Margarita C. K. Mattingly

Faculty Publications

Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0.94 fb-1. The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e+p collision data with a scalar sum of the lepton transverse momenta above 100GeV while 1.94 ± 0.17 events are expected. Such events are not observed in e-p collisions for which 1.19 ± 0.12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in …

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Measurement Of J/Ψ Helicity Distributions In Inelastic Photoproduction At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann Dec 2009

Measurement Of J/Ψ Helicity Distributions In Inelastic Photoproduction At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita C. K. Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, F. Cindolo, M. Corradi, G. Iacobucci, A. Margotti, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, S. De Pasquale, G. Sartorelli, A. Zichichi, D. Bartsch, I. Brock, H. Hartmann

Faculty Publications

The J/ψ decay angular distributions have been measured in inelastic photo-production in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb-1. The range in photon-proton centre-of-mass energy, W, was 50 < W < 180 GeV. The J/ψ mesons were identified through their decay into muon pairs. The polar and azimuthal angles of the μ+ were measured in the J/ψ rest frame and compared to theoretical predictions at leading and next-to-leading order in QCD. © SISSA 2009.

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Leading Proton Production In Deep Inelastic Scattering At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, F. Cindolo, M. Corradi, P. Giusti, G. Iacobucci, A. Margotti, T. Massam, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, F. Palmonari, S. De Pasquale, G. Sartorelli Dec 2009

Leading Proton Production In Deep Inelastic Scattering At Hera, S. Chekanov, M. Derrick, S. Magill, B. Musgrave, D. Nicholass, J. Repond, R. Yoshida, Margarita Mattingly, P. Antonioli, G. Bari, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, F. Cindolo, M. Corradi, P. Giusti, G. Iacobucci, A. Margotti, T. Massam, R. Nania, A. Polini, S. Antonelli, M. Basile, M. Bindi, L. Cifarelli, A. Contin, F. Palmonari, S. De Pasquale, G. Sartorelli

Faculty Publications

The semi-inclusive reaction e+p→e+Xp was studied with the ZEUS detector at HERA with an integrated luminosity of 12.8 pb -1. The final-state proton, which was detected with the ZEUS leading proton spectrometer, carried a large fraction of the incoming proton energy, xL > 0.32, and its transverse momentum squared satisfied p 2T < 0.5GeV2; the exchanged photon virtuality, Q2, was greater than 3GeV2 and the range of the masses of the photon-proton system was 45 < W < 225GeV. The leading proton production cross section and rates are presented as a function of xL, p2 T , Q2 and the Bjorken scaling variable, x. © SISSA 2009.

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(E,2e) Study Of Two-Center Interference Effects In The Ionization Of N₂, Leigh R. Hargreaves, Christopher J. Colyer, Mark A. Stevenson, B. Lohmann, Ola A. Al-Hagan, Don H. Madison, Chuangang Ning Dec 2009

(E,2e) Study Of Two-Center Interference Effects In The Ionization Of N₂, Leigh R. Hargreaves, Christopher J. Colyer, Mark A. Stevenson, B. Lohmann, Ola A. Al-Hagan, Don H. Madison, Chuangang Ning

Physics Faculty Research & Creative Works

A number of previous studies have suggested the possibility of two-center interference effects in the single ionization of diatomic molecules such as H2 and N2. While interference effects have been successfully observed in the ionization of H2, to date evidence for interference in N2 ionization has yet to be conclusively demonstrated. This study presents triply differential cross sections for electron impact ionization of N2, measured using the (e,2e) technique. The data are probed for signatures of two-center interference effects. Evidence for interference manifesting in the cross sections is observed.

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