Physics Commons^™

Search For New Heavy Particles In The Wz0 Final State In Pp̅ Collisions At √S = 1.8 Tev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present the first general search for new heavy particles, X, which decay via X → WZ⁰ → eν + jj as a function of M_x and Γ(X) in pp̅ collisions at √s =1.8 TeV. No evidence is found for production of X in 110 pb^-1 of data collected by the Collider Detector at Fermilab. General cross section limits are set at the 95% C.L. as a function of mass and width of the new particle. The results are further interpreted as mass limits on the production of new heavy charged vector bosons which decay via W′ …

Study Of B0 → J/Ψk(*)0Π+Π- Decays With The Collider Detector At Fermilab, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report a study of the decaysB⁰ →J/ψK^(*)0π⁺π^-, which involve the creation of a uu̅ or dd̅ quark pair in addition to a b̅→ c̅(cs̅) decay. The data sample consists of 110 pb^-1 of pp̅ collisions at √s=1.8 TeV collected by the CDF detector at the Fermilab Tevatron collider during 1992–1995. We measure the branching fractions to be Ɓ(B⁰ → J/ψK^(*)0π⁺π^-) = (6.6 ± 1.9 ± 1.1) x 10^-4 and Ɓ(B⁰ → J/ψK^(*)0π⁺π …

Subjet Multiplicity Of Gluon And Quark Jets Reconstructed With The K ┴ Algorithm In Pp̅ Collisions, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

The DØ Collaboration has studied for the first time the properties of hadron-collider jets reconstructed with a successive-combination algorithm based on relative transverse momenta (k _┴) of energy clusters. Using the standard value D=1.0 of the jet-separation parameter in the k _┴ algorithm, we find that the p_T of such jets is higher than the E_T of matched jets reconstructed with cones of radius R=0.7, by about 5 (8) GeV at p_T ≈'90 (240) GeV. To examine internal jet structure, the k _┴ algorithm is applied within D=0.5 jets to resolve any …

High-Energy Ion Generation In Interaction Of Short Laser Pulse With High-Density Plasma, Y. Sentoku, V. Y. Bychenkov, K. Flippo, Anatoly Maksimchuk, K. Mima, G. Mourou, Z. M. Sheng, Donald Umstadter

Donald Umstadter Publications

Multi-MeV ion production from the interaction of a short laser pulse with a high-density plasma, accompanied by an underdense preplasma, has been studied with a particle-in- cell simulation and good agreement is found with experiment. The mechanism primarily responsible for the acceleration of ions is identified. Comparison with experiments sheds light on the ion-energy dependence on laser intensity, preplasma scale length, and relative ion energies for a multi-species plasma. Two regimes of maximum ion-energy dependence on laser intensity, I, have been identified: subrelativistic, μ I ; and relativistic, μ √I. Simulations show that the energy of the …

The Intermediate-Period Cepheid Strip Stars, Edward G. Schmidt

Edward Schmidt Publications

To explore the population of variable stars that fall between RR Lyrae stars and classical Cepheids, we have obtained extensive photometric observations for 56 stars with periods between 0.6 and 1.0 days. For these stars and an additional 10, we have examined the form and stability of the light curves to explore the variety of types of stars in this period regime. We conclude that the majority of the sample are Bailey type ab RR Lyrae stars. However, a surprising number that possibly exhibit the Blazhko effect are found. There are a half-dozen other stars that do not appear to …

Nontunneling High-Order Harmonics From Ultra-Intense Laser-Driven Tightly Bound Systems, S. X. Hu, Anthony F. Starace, W. Becker, W. Sandner, D. B. Milosevic

Anthony F. Starace Publications

High-order harmonic emission is investigated by numerical solution of the weakly relativistic, two-dimensional Schrödinger equation for the case of ultra-intense laser-driven tightly bound systems (for example, multiply charged ions such as O⁷⁺ exposed to laser fields of the order of 10¹⁸ W cm^-2 at 248 nm). In contrast to their usual substantial decrease, the low-order harmonics having an energy less than the ionization potential exhibit a high efficiency (i.e. intense) plateau with a well defined cutoff. The shape of this plateau is found to depend on the shape of the binding potential. A classical “surfing” mechanism for …

Search For Gluinos And Scalar Quarks In Pp̅ Collisions At √S = 1.8 Tev Using The Missing Energy Plus Multijets Signature, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have performed a search for gluinos (g̃) and scalar quarks (q̃,/i>) in a data sample of 84 pb^-1 of pp̅ collisions at √s =1.8 TeV, recorded by the Collider Detector at Fermilab. We investigate the final state of large missing transverse energy and three or more jets, a characteristic signature in R-parityconserving supersymmetric models. The analysis has been performed “blind,” in that the inspection of the signal region is made only after the predictions from standard model backgrounds have been calculated. Comparing the data with predictions of constrained supersymmetric models, we exclude gluino …

Measurement Of The Strong Coupling Constant From Inclusive Jet Production At The Tevatron P̅P Collider, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report a measurement of the strong coupling constant, α_s(M_z ), extracted from inclusive jet production in pp̅ collisions at √s =1800 GeV. The QCD prediction for the evolution of α_s with jet transverse energy E_T is tested over the range 40 TE_T for the renormalization scale. The data show good agreement with QCD in the region below 250 GeV. The value of α_s at the mass of the Z⁰ boson averaged over the range 40 < T < 250 GeV is found to be α_s(M_z )= 0.1178 ± 0.0001(stat)_-0.0095^+0.0081 (expt. syst). The associated theoretical uncertainties …

Effects Of Surface Morphology On Magnetic Properties Of Ni Nanowire Arrays In Self-Ordered Porous Alumina, H. Zeng, Stevem A. Michalski, Roger D. Kirby, David J. Sellmyer, L. Menon, Supriyo Bandyopadhyay

David Sellmyer Publications

Ni nanowire arrays were produced by electrodeposition of Ni into self-assembled porous anodic alumina templates. With different anodization voltages, the wires show different surface morphologies. The temperature dependence of the coercivity and activation volume of wires with regular shape can be explained by thermal activation over an energy barrier with a 3/2 power dependence on the field. The wires with irregular surface morphologies show abnormal temperature dependences of the coercivity and activation volume. Possible mechanisms for these behaviors are discussed.

White-Light-Induced Fragmentation Of Toluene, A. M. Müller, B. Witzel, Cornelis J. Uiterwaal, J. Wanner, K.-L. Kompa

C.J.G.J. Uiterwaal Publications

We investigate the influence of continuum generation on the photofragmentation dynamics of the toluene molecule. By sending an 80-fs Ti:sapphire laser beam through a 2-mm-thick CaF₂ plate we show that even moderately broadened laser frequency spectra considerably increase the degree of fragmentation, while it is nearly absent without continuum generation. The measured broadening of the frequency spectra and the known Raman-active vibrational modes of toluene afford an explanation in terms of a stimulated Raman scattering scheme, in which the molecule absorbs large amounts of vibrational energy.

Specification Of Jecp/Sp: Stereographic Projection With An Application For Specimen Orientation Adjustment Using Tem Holders, Xingzhong Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

1. Purpose of the program 2. Graphic user interface and program design 3. Crystallographic principle and implementation 4. System requirement 5. Installation and user instruction 6. How to contact the author 7. References

1. Purpose of the program JECP/SP is a computer program in Java Electron Crystallography Package. JECP is developed for quantitative electron diffraction and image processing, the package is designed and written by Dr. XingZhong Li. JECP/SP provides the all necessary functions of stereographic projection for regular application and furthermore it can be used to minimized the difficulties encountered when tilting highly beam-sensitive, or small-grain-size specimens with known …

Selected Reflection Imaging: A Useful Tool For Imaging Nanocomposite Magnetic Materials, Yi Liu, Y. Qiang, M. Yu, J. Ping Liu, David J. Sellmyer

David Sellmyer Publications

The great strength of transmission electron microscope (TEM) is its capability to access to both real space (imaging) and reciprocal space (diffraction). Selected reflection imaging (SRI) can relate the diffraction of nanostructured materials with the image, providing information otherwise not possible. The experimental set up of SRI is given by Liu and Sellmyer [I]. In this paper we present some new measurements on nanocomposite magnetic materials.

Implications Of Single-Particle Experiments For Track Theory, Therapy And Radiation Protection, Robert Katz, Francis Cucinotta

Robert Katz Publications

‘‘Because the predominant exposure of cells in humans is to single isolated tracks, a critical question is what effects a single track is capable of producing and with what probabilities.’’ ‘‘Most of the current biophysical models. . . make the clear prediction that a single track can produce virtually all of the detrimental stochastic effects of interest.’’ ‘‘But one model, in particular (the amorphous track model of Katz and coworkers), disagrees fundamentally that a single low LET track has the ability to cause the cellular changes.’’ ‘‘This model leads to very dramatic differences in the predicted risk at low doses. …

Holographic Recording Of Fast Events On A Ccd Camera, Zhiwen Liu, Martin Centurion, George Panotopoulos, John Hong, Demetri Psaltis

Martin Centurion Publications

We report on holographic recording of nanosecond events on a conventional CCD camera. Three frames of an air-discharge event, with resolution of 5.9 ns and frame interval of 12 ns, are recorded in a single CCD frame. Each individual frame is reconstructed by digital filtering of the CCD frame, since successively recorded holograms are centered at different carrier frequencies in the spatial frequency domain.

Jecp/Ed Manual, Xingzhong Li

Nebraska Center for Materials and Nanoscience: Faculty Publications

JECP/ED is a Java program with graphic interface for simulating electron diffraction pattern. It is designed and written by Dr. Xingzhong in University of Nebraska- Lincoln. This is verision 12-2002. It can be used for simulating electron diffraction zone pattern(ZOLZ with/without FOLZ), it allows to select zone axis, high voltage, sample thickness in the simulation, optional to show index, intensity and Laue center, featureed with manuniplating the pattern with slightly tilting, 360 degree rotation, zoom. The diffraction intensity is calculated on the basis of the kinematical theory. The program is extended to simulate electron diffraction with a precession of incident …

Unifying Lectures, Recitations & Laboratories As A Part Of The Humanized Physics Project, Vicki L. Plano Clark, Robert G. Fuller

Robert G. Fuller Publications

As a part of our work in the Humanized Physics Project, we have made the content of the physics laboratories the keystone of our physics content coverage. After having selected an appropriate human application of physics for the laboratory each week, we have shaped the lecture, recitation and homework assignments to support the laboratory. Our poster will provide examples from both semesters of our general physics course.

Cross Section And Heavy Quark Composition Of Γ+Μ Events Produced In Pp̅ Collisions, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We present a measurement of the cross section and the first measurement of the heavy flavor content of associated direct photon + muon events produced in hadronic collisions. These measurements come from a sample of 1.8 TeV pp̅ collisions recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily due to the Compton scattering process cg→cγ , with the final-state charm quark producing a muon. The cross section for events with a photon transverse momentum between 12 and 40 GeV/c is measured to be 46.8±6.3±7.5 pb, which is two standard deviations below the …

Neutron Powder Diffraction Studies Of The La0.65Pb0.35Mno3 Perovskite, Camelia Borca, Shireen Adenwalla, Sy-Hwang Liou, Q.L. Xu, J. L. Robertson, Peter A. Dowben

Peter Dowben Publications

The structure of La_0.65Pb_0.35MnO₃ has been studied by neutron powder diffraction. From the temperature dependence of the lattice parameters, we observe that La_0.65Pb_0.35MnO₃ remains single phase in the temperature interval from 25 to 400 K, with a rhombohedral (R3c) structure. The collinear Mn spins suffer a thermally driven reorientation transition close to the Curie temperature, as obtained from powder samples (using neutron diffraction) and from thin films [using ferromagnetic resonance (FMR)]. The reorientation transition may indicate the presence of local Jahn–Teller (JT) lattice distortions, which are prevented from …

Structural Transition In (C60)N Clusters, W. Branz, N. Malinowski, Axel Enders, T. P. Martin

Axel Enders Publications

The structure of (C₆₀) _n clusters (n = 1– 150) was investigated by heating them to definite temperatures in a helium bath (heating cell) with subsequent characterization in a time-of-flight mass spectrometer. The intensity anomalies in the resulting mass spectra reflect particularly stable configurations that resisted evaporation. However, the set of enhanced peaks (magic numbers) turned out to be temperature dependent. Clusters heated to a moderate temperature of 490 K yielded mass spectra indicating the presence of icosahedral structures that can be characterized by a set of unusually strong peaks, namely n = 13, 19, 23, 26, …

Adsorbate And Thermally Induced Spin Reorientation Transition In Low-Temperature-Grown Fe/Cu(001), D. Peterka, Axel Enders, G. Haas, K. Kern

Axel Enders Publications

Adsorbate and thermally induced changes of the spin reorientation transition in Fe wedges grown at 140 K on Cu(001) substrates are investigated by the magneto-optical Kerr effect and Kerr microscopy. The adsorption of oxygen causes a complete reorientation of the easy axis of magnetization into the film plane. In contrast to that carbon monoxide decreases the critical thickness for the reorientation transition of the film by 0.7 monolayer down to 3.6 monolayers, while films thinner than 3.6 monolayers remain magnetized perpendicularly. These adsorbate-induced changes can be ascribed to a change in the surface magnetic anisotropy. Also annealing of the films …

The Magnetism-Nanostructure Interface In Advanced Magnetic Materials, David J. Sellmyer

David Sellmyer Publications

The critical relationship between microstructure and nanostructure of materials and their magnetic properties has been appreciated for decades. Electromagnetic machinery, permanent magnets, and data recording and electronic devices all have seen steady and sometimes spectacular advances over this period. At the present time the most interesting research in magnetism and magnetic materials arises from new developments in structuring materials on the nanometer length scale. This talk will present recent advances and challenges in furthering this work, with particular attention paid to extremely high density magnetic recording films, exchange-coupled high-energy-product permanent-magnet materials, high-temperature permanent-magnet materials, and self-organized and patterned magnetic nanoarrays.

Elemental Mapping Of Co-Pr Nanostructured Powders By Eels Image Filtering, Yi Liu, C. Nelson, H. Tang, David J. Sellmyer

David Sellmyer Publications

In current extremely high density recording media design, the signal to noise ratio SNR is related to the number of magnetic grains N in a recording bit by
SNR = 10 log_l0 N .................................... (1)
In earlier studies we have found that a metallurgical grain can act as a magnetic grain when grains are magnetically decoupled by a non-magnetic phase [1,2]. Alternatively, several metallurgical grains can be exchange-coupled together when they are small [3]. An ideal morphology is one in which the non-magnetic atoms are segregated at the grain boundaries forming the non-magnetic phase while keeping the grains closely …

Determination Of Hexadecapole Moments For The 3p4(1D) Core Of Argon Ii Excited In Polarized E--Ar Collisions, B. G. Birdsey, H. M. Al-Khateeb, Timothy J. Gay

Timothy J. Gay Publications

We report on measurements of the integrated Stokes parameters of the light emitted from four well-LS coupled states of the 3p⁴(¹D)4p manifold of Aril, following the simultaneous ionization and excitation of neutral argon by polarized electrons. As for all states, the state multipoles of J can be expanded in terms of the total orbital (L ) and the total spin (S) state multipoles. By splitting each L and S state multipole into multipoles for the core and outer electron, we have experimentally obtained for the first time the normalized integrated state multipole of rank 4 (hexadecapole …

Progress With Optically Pumped Sources Of Polarized Electrons, Mark A. Rosenberry, Herman Batelaan, J. P. Reyes, Timothy J. Gay

Timothy J. Gay Publications

We report our work in developing new "turn-key" sources of polarized electrons. These sources operate by extracting the electrons from a discharge and polarizing them through optical pumping. Preliminary work demonstrates that beams of 4 μA with greater than 20% polarization are possible. Such devices could enormously simplify the running of many experiments in the fields of atomic structure, magnetic materials and biophysics.

Multipole Expansions Of Irreducible Tensor Sets And Some Applications, N. L. Manakov, A. V. Meremianin, Anthony F. Starace

Anthony F. Starace Publications

A formal multipole expansion of tensor functions dependent on several vector parameters is obtained in an invariant differential form. We apply this result to derive multipole expansions of finite rotation matrices in terms of finite sums of bipolar harmonics. The multipole expansion in terms of bipolar harmonics of unit vectors r₁ and r₂ are analyzed for functions of the type f (r)Y_lm( r) (with r = r₁ − r₂), which are important in two-center problems. As another example of the application of the multipole expansion technique, reduction formulae are obtained for tensor constructions …

Phase And Absorption Gratings For Electrons, Hong Gao, Glen Gronniger, Daniel Friemund, Alex Cronin

Department of Physics and Astronomy: Faculty Publications

We report the experimental realization of phase and absorption gratings for electrons. Phase gratings made with standing waves of light with a periodicity of 266 nm are used to diffract 380 eV electrons [1]. Material gratings of 100 and 200 nm periodicity are used to diffract 500 eV electrons. We are exploring the possibility to use these gratings for low energy electron interferometry.