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University of Nebraska - Lincoln

2012

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Articles 1 - 30 of 96

Full-Text Articles in Physics

Ferroelectric Instability Under Screened Coulomb Interactions, Yong Wang, Xiaohui Liu, John D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal Dec 2012

Ferroelectric Instability Under Screened Coulomb Interactions, Yong Wang, Xiaohui Liu, John D. Burton, Sitaram S. Jaswal, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

We explore the effect of charge carrier doping on ferroelectricity using density functional calculations and phenomenological modeling. By considering a prototypical ferroelectric material, BaTiO3, we demonstrate that ferroelectric displacements are sustained up to the critical concentration of 0.11 electron per unit cell volume. This result is consistent with experimental observations and reveals that the ferroelectric phase and conductivity can coexist. Our investigations show that the ferroelectric instability requires only a short-range portion of the Coulomb force with an interaction range of the order of the lattice constant. These results provide a new insight into the origin of ferroelectricity ...


High-Order-Harmonic-Generation Spectroscopy With An Elliptically Polarized Laser Field, M. V. Frolov, N. L. Manakov, T. S. Sarantseva, Anthony F. Starace Dec 2012

High-Order-Harmonic-Generation Spectroscopy With An Elliptically Polarized Laser Field, M. V. Frolov, N. L. Manakov, T. S. Sarantseva, Anthony F. Starace

Anthony F. Starace Publications

Analytic formulas describing high-order-harmonic generation (HHG) by atoms in an intense laser field with small ellipticity are obtained quantum mechanically in the tunneling limit. The results show that factorization of the HHG yield in terms of an electron wave packet and the photorecombination cross section (PRCS) is valid only for s states of a bound atomic electron, whereas the HHG yield for p states involves two different atomic parameters. For the latter case, elliptic HHG spectroscopy enables one to retrieve both the energy and angular dependence of the PRCS of the target atom, as we illustrate for the case of ...


Threshold Effects In Strong-Field Ionization: Energy Shifts And Rydberg Structures, Katarzyna Krajewska, Ilya I. Fabrikant, Anthony F. Starace Nov 2012

Threshold Effects In Strong-Field Ionization: Energy Shifts And Rydberg Structures, Katarzyna Krajewska, Ilya I. Fabrikant, Anthony F. Starace

Anthony F. Starace Publications

The behavior of strong-field ionization rates of neutral atoms in the vicinity ofmultiphoton ionization thresholds is analyzed using formal collision theory.Our approach,which accounts nonperturbatively for effects of an intense laser field, shows that the ionization rates have a nearly constant behavior below and above each multiphoton threshold and that between such thresholds there are an apparently finite number of rapid oscillations due to resonances with laser-field-modified Rydberg states. This pattern is typical for any atomic target, as we illustrate specifically for hydrogen and neon atoms. The flat behavior of the ionization yield near multiphoton thresholds gives the appearance ...


Electron-Phonon Coupling And Structural Phase Transitions On Au/Mo(112), Keisuke Fukutani Nov 2012

Electron-Phonon Coupling And Structural Phase Transitions On Au/Mo(112), Keisuke Fukutani

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

The electronic structures, many-body interactions and Fermi surface topologies of Au/Mo(112) were investigated in detail and were found to play important roles in the newly discovered order-disorder structural phase transition of the system. First, the high-resolution angle-resolved photoemission spectroscopy was utilized to characterize the electronic band structure of Mo(112) in far greater details than before. This elucidated the existence of several surface-derived states and their dispersion relations in high precisions near the Fermi level, as well as the symmetries of the bulk and surface electronic states, which are in good quantitative agreement with the ab-initio calculations. Such ...


Enhanced Asymmetry In Few-Cycle Attosecond Pulse Ionization Of He In The Vicinity Of Autoionizing Resonances, Jean Marcel Ngoko Djiokap, S. X. Hu, Wei-Chao Jiang, Liang-You Peng, Anthony F. Starace Sep 2012

Enhanced Asymmetry In Few-Cycle Attosecond Pulse Ionization Of He In The Vicinity Of Autoionizing Resonances, Jean Marcel Ngoko Djiokap, S. X. Hu, Wei-Chao Jiang, Liang-You Peng, Anthony F. Starace

Anthony F. Starace Publications

By solving the two-active-electron, time-dependent Schrödinger equation in its full dimensionality, we investigate the carrier-envelope phase (CEP) dependence of single ionization of He to the He+(1s) state triggered by an intense few-cycle attosecond pulse with carrier frequency ω corresponding to the energy ћω = 36 eV. Effects of electron correlations are probed by comparing projections of the final state of the two-electron wave packet onto field-free highly correlated Jacobi matrix wave functions with projections onto uncorrelated Coulomb wave functions. Significant differences are found in the vicinity of autoionizing resonances. Owing to the broad bandwidths of our 115 and 230 as ...


Propagation Of Ultrasound Through Freshly Excised Human Calvarium, Armando Garcia Noguera Jul 2012

Propagation Of Ultrasound Through Freshly Excised Human Calvarium, Armando Garcia Noguera

Engineering Mechanics Dissertations & Theses

The propagation of ultrasound through complex biological media, such as the human calvarium, poses a great challenge for modern medicine. Several ultrasonic techniques commonly used for treatment and diagnosis in most of the human body are still difficult to apply to the human brain, in part, because of the properties of the skull. Moreover, an understanding of the biomechanics of transcranial ultrasound may provide needed insight into the problem of blast wave induced traumatic brain injury (TBI). In the present study, the spatial variability of ultrasonic properties was evaluated for relevant frequencies of 0.5, 1, and 2.25 MHz ...


Fourier Transform Infrared Spectroscopy And Wide-Angle X-Ray Scattering: Investigations On Polypropylene–Vapor-Grown Carbon Nanofiber Composites, Mircea Chipara, John Hamilton, Alin Cristian Chipara, Tom George, Dorina Magdalena Chipara, Elamin E. Ibrahim, Karen Lozano, David J. Sellmyer Jul 2012

Fourier Transform Infrared Spectroscopy And Wide-Angle X-Ray Scattering: Investigations On Polypropylene–Vapor-Grown Carbon Nanofiber Composites, Mircea Chipara, John Hamilton, Alin Cristian Chipara, Tom George, Dorina Magdalena Chipara, Elamin E. Ibrahim, Karen Lozano, David J. Sellmyer

David Sellmyer Publications

Fourier transform infrared (FTIR) spectroscopy and wide-angle X-ray scattering (WAXS) investigations of isotactic polypropylene (iPP)–vapor-grown carbon nanofiber (VGCNF) composites containing various amounts of VGCNFs ranging between 0 and 20 wt %. are reported. The FTIR investigations were focused on the regularity bands of iPP. The FTIR data indicated a drop in the isotac­ticity index as the concentration of nanofibers was increased; this suggested a decrease in the crystallinity. WAXS measurements revealed a dominating α1 phase, with a small admixture of γ phase or mesophase. The loading of the polymeric matrix with car­bon nanofibers (CNFs) did not induce ...


New View Of The Occupied Band Structure Of Mo(112), Keisuke Fukutani, Hirokazu Hayashi, I. N. Yakovkin, Tula R. Paudel, Takafumi Habuchi, Daisuke Hirayama, Jian Jiang, Hideaki Iwasawa, Kenya Shimada, Ning Wu, Evgeny Y. Tsymbal, Yaroslav B. Losovyj, Peter A. Dowben Apr 2012

New View Of The Occupied Band Structure Of Mo(112), Keisuke Fukutani, Hirokazu Hayashi, I. N. Yakovkin, Tula R. Paudel, Takafumi Habuchi, Daisuke Hirayama, Jian Jiang, Hideaki Iwasawa, Kenya Shimada, Ning Wu, Evgeny Y. Tsymbal, Yaroslav B. Losovyj, Peter A. Dowben

Evgeny Tsymbal Publications

We present a comprehensive examination of the occupied surface-weighted band structure of Mo(112) along the two high-symmetry directions of the surface Brillouin zone, both from theoretical and experimental perspectives. The band structures are found to be significantly different for the states along the two high-symmetry directions and for the states with even and odd reflection parities with respect to the mirror planes. The present study suggests the existence of a number of surface-weighted bands along both high-symmetry directions. The complexity of the band structure near the Fermi level may impose potential difficulties in experimental determination of the electronphonon coupling ...


Mechanical Writing Of Ferroelectric Polarization, Haidong Lu, C.-W. Bark, D. Esque De Los Ojos, J. Alcala, Chang-Beom Eom, G. Catalan, Alexei Gruverman Apr 2012

Mechanical Writing Of Ferroelectric Polarization, Haidong Lu, C.-W. Bark, D. Esque De Los Ojos, J. Alcala, Chang-Beom Eom, G. Catalan, Alexei Gruverman

Alexei Gruverman Publications

Ferroelectric materials are characterized by a permanent electric dipole that can be reversed through the application of an external voltage, but a strong intrinsic coupling between polarization and deformation also causes all ferroelectrics to be piezoelectric, leading to applications in sensors and high-displacement actuators. A less explored property is flexoelectricity, the coupling between polarization and a strain gradient. We demonstrate that the stress gradient generated by the tip of an atomic force microscope can mechanically switch the polarization in the nanoscale volume of a ferroelectric film. Pure mechanical force can therefore be used as a dynamic tool for polarization control ...


Ultrafast Intense-Field Photoionization And Photofragmentation Of Systematic Series Of Substituted Organic Molecules, Timothy D. Scarborough Apr 2012

Ultrafast Intense-Field Photoionization And Photofragmentation Of Systematic Series Of Substituted Organic Molecules, Timothy D. Scarborough

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

The abundance and relevance of organic molecules similar to benzene makes their study important. Studying the interactions of such molecules with intense light fields has implications for the generation of short-wavelength radiation, attosecond science, high-harmonic generation, and many other fields. However, the computing power necessary to complete fully ab initio calculations describing molecules of this size does not exist; this leaves theoretical studies to rely on assumptions and approximations just to calculate the energies of the ground state. Including any sort of dynamics in these calculations is prohibitively complicated, and this makes experimental observations important. Since many organic molecules are ...


An Exploration Of Neutron Detection In Semiconducting Boron Carbide, Nina Hong Apr 2012

An Exploration Of Neutron Detection In Semiconducting Boron Carbide, Nina Hong

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

The 3He supply problem in the U.S. has necessitated the search for alternatives for neutron detection. The neutron detection efficiency is a function of density, atomic composition, neutron absorption cross section, and thickness of the neutron capture material. The isotope 10B is one of only a handful of isotopes with a high neutron absorption cross section—3840 barns for thermal neutrons. So a boron carbide semiconductor represents a viable alternative to 3He. This dissertation provides an evaluation of the performance of semiconducting boron carbide neutron detectors grown by plasma enhance chemical vapor deposition (PECVD) in order ...


Robert Fuller Obituary From American Association Of Physics Teachers Apr 2012

Robert Fuller Obituary From American Association Of Physics Teachers

Robert G. Fuller Publications and Presentations

Fuller’s contributions to education will have a continuing impact through the projects he helped lead and the many books and articles he authored or co-authored. AAPT joins the UNL and the physics education community in recognizing the lasting legacy of Dr. Robert G. Fuller.


Resonant Phenomena In Laser-Assisted Radiative Attachment Or Recombination, A. N. Zheltukhin, A. V. Flegel, M. V. Frolov, N. L. Manakov, Anthony F. Starace Mar 2012

Resonant Phenomena In Laser-Assisted Radiative Attachment Or Recombination, A. N. Zheltukhin, A. V. Flegel, M. V. Frolov, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

Resonant enhancements are predicted in cross sections σn for laser-assisted radiative attachment or electron–ion recombination accompanied by absorption of n laser photons. These enhancements occur for incoming electron energies at which the electron can be attached or recombined by emitting μ laser photons followed by emission of a spontaneous photon upon absorbing n + μ laser photons. The close similarity between rescattering plateaus in spectra of resonant attachment/recombination and of high-order harmonic generation is shown based on a general parametrization for σn and on numerical results for e−H attachment.


Analytic Theory Of High-Order-Harmonic Generation By An Intense Few-Cycle Laser Pulse, M. V. Frolov, N. L. Manakov, A. M. Popov, O. V. Tikhonova, E. A. Volkova, A. A. Silaev, N. V. Vvedenskii, Anthony F. Starace Mar 2012

Analytic Theory Of High-Order-Harmonic Generation By An Intense Few-Cycle Laser Pulse, M. V. Frolov, N. L. Manakov, A. M. Popov, O. V. Tikhonova, E. A. Volkova, A. A. Silaev, N. V. Vvedenskii, Anthony F. Starace

Anthony F. Starace Publications

We present a theoretical model for describing the interaction of an electron, weakly bound in a short-range potential, with an intense, few-cycle laser pulse. General definitions for the differential probability of above-threshold ionization and for the yield of high-order-harmonic generation (HHG) are presented. For HHG we then derive detailed analytic expressions for the spectral density of generated radiation in terms of the key laser parameters, including the number N of optical cycles in the pulse and the carrier-envelope phase (CEP). In particular, in the tunneling approximation, we provide detailed derivations of the closed-form formulas presented briefly by M. V. Frolov ...


Berry Phase From A Randomly Fluctuating Magnetic Field, Ralph Skomski Feb 2012

Berry Phase From A Randomly Fluctuating Magnetic Field, Ralph Skomski

Ralph Skomski Publications

The quantum-mechanical Berry phase due to a randomly fluctuating magnetic field is calculated by exploiting an analogous random-walk problem in polymer physics. The phase depends on the time correlations of the magnetic field, despite the adiabatic nature of the Berry phase. A probability distribution for the phase is obtained, and how this phase could affect the magnetotransport in granular magnetic nanostructures is briefly discussed.


Ferroelectric And Multiferroic Tunnel Junctions, Evgeny Y. Tsymbal, Alexei Gruverman, Vincent Garcia, Manuel Bibes, A. Barthélémy Feb 2012

Ferroelectric And Multiferroic Tunnel Junctions, Evgeny Y. Tsymbal, Alexei Gruverman, Vincent Garcia, Manuel Bibes, A. Barthélémy

Evgeny Tsymbal Publications

The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fi elds of physics, as well as creating sub-fi elds on its own. Spin-dependent tunneling in magnetic tunnel junctions has aroused considerable interest and development. In parallel with this endeavor, recent advances in thin-fi lm ferroelectrics have demonstrated the possibility of achieving stable and switchable ferroelectric polarization in nanometer-thick fi lms. This discovery opened the possibility of using thin-fi lm ferroelectrics as barriers in magnetic tunnel junctions, thus merging the fi elds of magnetism, ferroelectricity, and spin-polarized transport ...


Magnetoelectric Interactions Between An Organic Ferroelectric And A Transition Metal Ferromagnet, Abhijit Mardana Jan 2012

Magnetoelectric Interactions Between An Organic Ferroelectric And A Transition Metal Ferromagnet, Abhijit Mardana

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

The interaction between ferromagnetic and ferroelectric films, the magnetoelectric effect, is a fascinating fundamental research area as well as having potential applications in magnetic data storage devices. We have investigated magnetoelectric coupling effects in thin film heterostructures, consists of metallic ferromagnet, cobalt, and the polymer ferroelectric [P(VDF-TrFE) 70:30]. The work described here encompasses changes in ferroelectric polarization with magnetic field as well as changes in the magnetic anisotropy with ferroelectric polarization.

In samples of Co overlayers on P(VDF-TrFE), in which the Co is not constrained by the substrate, the polarization shows a large change on application of ...


Zɤ Production And Limits On Anomalous Zzɤ And Zɤɤ Couplings In Pp̅ Collisions At √S= 1.96, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory R. Snow, D0 Collaboration Jan 2012

Zɤ Production And Limits On Anomalous Zzɤ And Zɤɤ Couplings In Pp̅ Collisions At √S= 1.96, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of pp̅ →Zɤ→ℓ+-ɤ(ℓ=e, µ) production with a data sample corresponding to an integrated luminosity of 6.2 fb-1 collected by the D0 detector at the Fermilab Tevatron pp Collider. The results of the electron and muon channels are combined, and we measure the total production cross section and the differential cross section dσ/dpɤT, where pɤT is the momentum of the photon in the plane transverse to the beam line. The results obtained are consistent with the standard model predictions from next-to-leading order calculations. We use the ...


Search For Heavy Long-Lived Charged Particles In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For Heavy Long-Lived Charged Particles In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

The result of a search for heavy long-lived charged particles produced in pp collisions at √s = 7 TeV at the LHC is described. The data sample has been collected using the CMS detector and corresponds to an integrated luminosity of 5.0 fb−1. The inner tracking detectors are used to define a sample of events containing tracks with high momentum and high ionization energy loss. A second sample of events, which have high-momentum tracks satisfying muon identification requirements in addition to meeting high-ionization and long time-of-flight requirements, is analyzed independently. In both cases, the results are consistent with the ...


Search For The Standard Model Higgs Boson Decaying Into Two Photons In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For The Standard Model Higgs Boson Decaying Into Two Photons In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a center-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 fb−1. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data ...


Imaging Of Isolated Molecules With Ultrafast Electron Pulses, Christopher J. Hensley, Jie Yang, Martin Centurion Jan 2012

Imaging Of Isolated Molecules With Ultrafast Electron Pulses, Christopher J. Hensley, Jie Yang, Martin Centurion

Martin Centurion Publications

Imaging isolated molecules in three dimensions with atomic resolution is important for elucidating complex molecular structures and intermediate states in molecular dynamics. This goal has so far remained elusive due to the random orientation of molecules in the gas phase. We show that threedimensional structural information can be retrieved from multiple electron diffraction patterns of aligned molecules. The molecules are aligned impulsively with a femtosecond laser pulse and probed with a femtosecond electron pulse two picoseconds later, when the degree of alignment reaches a maximum.


Generation Of Tunable, 100–800 Mev Quasi-Monoenergetic Electron Beams From A Laser-Wakefield Accelerator In The Blowout Regime, Sudeep Banerjee, Nathan D. Powers, Viswanathan Ramanathan, I. Ghebregziabher, Kevin J. Brown, C. Maharjan, Shouyuan Chen, A. Beck, E. Lefebvre, Serguei Y. Kalmykov, Bradley Allan Shadwick, Donald Umstadter Jan 2012

Generation Of Tunable, 100–800 Mev Quasi-Monoenergetic Electron Beams From A Laser-Wakefield Accelerator In The Blowout Regime, Sudeep Banerjee, Nathan D. Powers, Viswanathan Ramanathan, I. Ghebregziabher, Kevin J. Brown, C. Maharjan, Shouyuan Chen, A. Beck, E. Lefebvre, Serguei Y. Kalmykov, Bradley Allan Shadwick, Donald Umstadter

Donald Umstadter Publications

In this paper, we present results on a scalable high-energy electron source based on laser wakefield acceleration. The electron accelerator using 30–80 TW, 30 fs laser pulses, operates in the blowout regime, and produces high-quality, quasi-monoenergetic electron beams in the range 100–800 MeV. These beams have angular divergence of 1–4 mrad, and 5%–25% energy spread, with a resulting brightness 1011 electrons mm-2 MeV-1 mrad-2. The beam parameters can be tuned by varying the laser and plasma conditions. The use of a high-quality laser pulse and appropriate target conditions enables optimization of beam ...


Search For Large Extra Dimensions In Dimuon And Dielectron Events In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For Large Extra Dimensions In Dimuon And Dielectron Events In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

Results are presented from a search for large, extra spatial dimensions in events with either two isolated muons or two isolated electrons. The data are from proton–proton interactions at √s = 7 TeV collected with the CMS detector at the LHC. The size of the data sample corresponds to an integrated luminosity of approximately 2 fb−1. The observed dimuon and dielectron mass spectra are found to be consistent with standard-model expectations. Depending on the number of extra dimensions, the 95% confidence level limits from the combined μμ and ee channels range from Ms > 2.4 TeV to M ...


Measurement Of The Cp-Violating Phase Φsj/ᴪφ Using The Flavor-Tagged Decay B0s→J/ᴪφ In 8 Fb-1 Of Pp̅ Collisions, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow Jan 2012

Measurement Of The Cp-Violating Phase Φsj/ᴪφ Using The Flavor-Tagged Decay B0s→J/ᴪφ In 8 Fb-1 Of Pp̅ Collisions, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

We report an updated measurement of the CP-violating phase, ΦsJ/ᴪΦ, and the decay-width difference for the two mass eigenstates, ∆Ӷs, from the flavor-tagged decay B0s → J/ᴪΦ. The data sample corresponds to an integrated luminosity of 8.0 fb-1 accumulated with the D0 detector using pp̅ collisions at √s= 1.96 TeV produced at the Fermilab Tevatron collider. The 68% Bayesian credibility intervals, including systematic uncertainties, are ∆Ӷs = 0.163 + 0.065-0.064 ps-1 and ΦsJ/ᴪΦ= -0.55+0.38-0.36. The p-value for the Standard ...


Ultrafast Resonance-Enhanced Multiphoton Ionization In The Azabenzenes: Pyridine, Pyridazine, Pyrimidine, And Pyrazine, Timothy D. Scarborough, David B. Foote,, Cornelis J. Uiterwaal Jan 2012

Ultrafast Resonance-Enhanced Multiphoton Ionization In The Azabenzenes: Pyridine, Pyridazine, Pyrimidine, And Pyrazine, Timothy D. Scarborough, David B. Foote,, Cornelis J. Uiterwaal

C.J.G.J. Uiterwaal Publications

We report on the ultrafast photoionization of pyridine, pyridazine, pyrimidine, and pyrazine. These four molecules represent a systematic series of perturbations into the structure of a benzene ring which explores the substitution of a C–H entity with a nitrogen atom, creating a heterocyclic structure. Data are recorded under intense-field, single-molecule conditions. The pulses (50 fs, 800 nm) are focused into the molecular vapor, and ion mass spectra are recorded for intensities of ∼1013 W/cm2 to ∼1015 W/cm2. We measure ion yields in the absence of the focal volume effect without the need for ...


Search For Universal Extra Dimensions In Pp Collisions, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow Jan 2012

Search For Universal Extra Dimensions In Pp Collisions, V. M. Abazov, Kenneth A. Bloom, Daniel R. Claes, Kayle Devaughan, Aaron Dominguez, Michael Eads, Ioannis Katsanos, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb-1, collected by the D0 detector at a pp̅ center-of-mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R-1 > 260 GeV in a minimal UED model.


Measurement Of Isolated Photon Production In Pp And Pbpb Collisions At √Snn = 2.76 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, Jose Lazo-Flores, Helena Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Measurement Of Isolated Photon Production In Pp And Pbpb Collisions At √Snn = 2.76 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, Jose Lazo-Flores, Helena Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

Isolated photon production is measured in proton–proton and lead–lead collisions at nucleon–nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |η| < 1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET -differential yields, scaled by the number of incoherent nucleon–nucleon collisions, is consistent with unity for all PbPb reaction centralities.


Search For Narrow Resonances In Dilepton Mass Spectra In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For Narrow Resonances In Dilepton Mass Spectra In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search for narrow, high-mass resonances decaying to electron or muon pairs has been performed using pp collision data collected at √s = 7 TeV by the CMS experiment in 2011. The data sample corresponds to an integrated luminosity of approximately 5 fb−1. The event yields observed in the signal regions are consistent with predictions of the standard model backgrounds, and upper limits on the cross section times branching fraction for a resonance decaying to dileptons are extracted from a shape analysis of the dilepton invariant mass distribution. The resulting mass limits at 95% confidence level are 2330 GeV for ...


Search For Heavy Majorana Neutrinos In Μ±Μ± +Jets And E±E± + Jets Events In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow Jan 2012

Search For Heavy Majorana Neutrinos In Μ±Μ± +Jets And E±E± + Jets Events In Pp Collisions At √S = 7 Tev, Cms Collaboration, Ekaterina Avdeeva, Kenneth A. Bloom, S. Bose, J. Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, J. Keller, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory Snow

Kenneth Bloom Publications

A search is performed for heavy Majorana neutrinos (N) using an event signature defined by two samesign charged leptons of the same flavour and two jets. The data correspond to an integrated luminosity of 4.98 fb−1 of pp collisions at a centre-of-mass energy of 7 TeV collected with the CMS detector at the Large Hadron Collider. No excess of events is observed beyond the expected standard model background and therefore upper limits are set on the square of the mixing parameter, |VℓN|2, for ℓ = e,μ, as a function of heavy Majorana-neutrino mass. These are the ...


Inclusive Search For Squarks And Gluinos In Pp̅ Collisions At √S= 7 Tev, S. Chatrchyan, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, T. Kelly, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory R. Snow Jan 2012

Inclusive Search For Squarks And Gluinos In Pp̅ Collisions At √S= 7 Tev, S. Chatrchyan, Kenneth A. Bloom, S. Bose, Jamila Butt, Daniel R. Claes, Aaron Dominguez, Michael Eads, P. Jindal, J. Keller, T. Kelly, Ilya Kravchenko, J. Lazo-Flores, H. Malbouisson, Sudhir Malik, Gregory R. Snow

Kenneth Bloom Publications

A search is performed for heavy particle pairs produced in √s= 7 TeV proton-proton collisions with 35 pb-1 of data collected by the CMS experiment at the LHC. The search is sensitive to squarks and gluinos of generic supersymmetry models, provided they are kinematically accessible, with minimal assumptions on properties of the lightest superpartner particle. The kinematic consistency of the selected events is tested against the hypothesis of heavy particle pair production using the dimensionless razor variable R, related to the missing transverse energy Emiss T . The new physics signal is characterized by a broad peak in the ...