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University of Nebraska - Lincoln

2008

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Articles 1 - 30 of 130

Full-Text Articles in Physics

Search For The Standard Model Higgs Boson In The Missing Energy And Acoplanar B-Jet Topology At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration Dec 2008

Search For The Standard Model Higgs Boson In The Missing Energy And Acoplanar B-Jet Topology At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory R. Snow, D0 Collaboration

Kenneth Bloom Publications

We report a search for the standard model Higgs boson in the missing energy and acoplanar b-jet topology, using an integrated luminosity of 0.93 fb-1 recorded by the D0 detector at the Fermilab Tevatron pp Collider. The analysis includes signal contributions from ppZHννbb, as well as from WH production in which the charged lepton from the W boson decay is undetected. Neural networks are used to separate signal from background. In the absence of a signal, we set limits on σ (ppVH) x B(H → bb) at the 95% C.L. of 2.6 ...


Measurement Of BS0 Mixing Parameters From The Flavor-Tagged Decay BS0J/Ψφ, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Dec 2008

Measurement Of BS0 Mixing Parameters From The Flavor-Tagged Decay BS0 → J/Ψφ, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

From an analysis of the flavor-tagged decay Bs0J/ ψφ we obtain the width difference between the Bs0 light and heavy mass eigenstates, ΔΓs = 0.19 ± 0.07 (stat)-0.01+0.02 (syst) ps-1, and the CP-violating phase, φs = -0.57-0.30+0.24(stat)-0.02+0.08(syst). The allowed 90% CL intervals of ΔΓs and φs are 0.06 < ΔΓs < 0.30 ps-1 and -1.20< φs < 0.06, respectively. The data sample corresponds to an integrated luminosity of 2.8 fb-1 accumulated with the D0 detector at the Fermilab Tevatron collider.


Search For Third Generation Scalar Leptoquarks Decaying Into ΤB, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Dec 2008

Search For Third Generation Scalar Leptoquarks Decaying Into ΤB, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We have searched for third generation leptoquarks (LQ3) using 1.05 fb-1 of data collected with the D0 detector at the Fermilab Tevatron Collider operating at √s = 1.96 TeV. We set a 95% C.L. lower limit of 210 GeV on the mass of a scalar LQ3 state decaying solely to a b quark and a τ lepton.


Observation Of The Doubly Strange B Baryon ΩB-, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Dec 2008

Observation Of The Doubly Strange B Baryon ΩB-, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We report the observation of the doubly strange b baryon Ωb- in the decay channel Ωb-J/ψΩ-, with J/ψ → μ+μ- and Ω- → ΛK- → (pπ-)K-, in pp collisions at √s = 1.96 TeV. Using approximately 1.3 fb-1 of data collected with the D0 detector at the Fermilab Tevatron Collider, we observe 17:8 ± 4.9(stat) ± 0.8(syst) Ωb- signal events at a mass of 6.165 ± 0.010(stat) ± 0.013(syst) GeV. The significance of the observed signal is 5.4 σ, corresponding to a probability of ...


Effective-Range Theory For An Electron In A Short-Range Potential And A Laser Field, M. V. Frolov, N. L. Manakov, Anthony F. Starace Dec 2008

Effective-Range Theory For An Electron In A Short-Range Potential And A Laser Field, M. V. Frolov, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

The time-dependent effective-range (TDER) theory introduced by Frolov et al. [Phys. Rev. Lett. 91, 053003 (2003)] and used in numerous applications for processes involving a linearly polarized intense laser field is presented in detail for the general problem of an electron, initially bound in a short-range potential, interacting with a laser field of arbitrary polarization. The TDER theory combines the well-known effective-range theory for a weakly bound electron in a short-range potential with the quasistationary, quasienergy state (QQES) or Floquet formulation for an electron interacting with a harmonic, time-dependent field, such as a monochromatic laser field. We present the basic ...


Search For Neutral Higgs Bosons In Multi-B-Jet Events In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Nov 2008

Search For Neutral Higgs Bosons In Multi-B-Jet Events In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. This production mode can be enhanced in the minimal supersymmetric standard model (MSSM). The search is performed in the three b quark channel using multijet triggered events corresponding to an integrated luminosity of 1 fb-1. No statistically significant excess of events with respect to the predicted background is observed and limits are set in the MSSM parameter space.


Search For Anomalous Wtb Couplings In Single Top Quark Production, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Nov 2008

Search For Anomalous Wtb Couplings In Single Top Quark Production, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

In 0.9 fb-1 of pp collisions, the D0 Collaboration presented evidence for single top quark production in events with an isolated lepton, missing transverse momentum, and two to four jets. We examine these data to study the Lorentz structure of the Wtb coupling. The standard model predicts a left-handed vector coupling at the Wtb vertex. The most general lowest dimension, CP-conserving Lagrangian admits right-handed vector and left- or right-handed tensor couplings as well. We find that the data prefer the left-handed vector coupling and set upper limits on the anomalous couplings. These are the first direct constraints ...


Measurement Of The Electron Charge Asymmetry In PpW + X + X Events At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Nov 2008

Measurement Of The Electron Charge Asymmetry In Pp → W + X → Eν + X Events At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of the electron charge asymmetry in ppW + X + X events at a center of mass energy of 1.96 TeV using 0.75 fb-1 of data collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron transverse momentum and pseudorapidity in the interval (-3.2, 3.2) and is compared with expectations from next-to-leading order calculations in perturbative quantum chromodynamics. These measurements will allow more accurate determinations of the proton parton distribution functions.


Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo Nov 2008

Temperature Dependence Of The Training Effect In Exchange Coupled Ferromagnetic Bilayers, Christian Binek, Srinivas Polisetty, Sarbeswar Sahoo

Christian Binek Publications

The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning (CoPtCrB) layer in proximity of a soft ferromagnetic pinned (CoCr) layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in ...


Measurement Of The Forward-Backward Charge Asymmetry And Extraction Of Sin2ӨWEff In PpZ/Γ* +XE+E- + X Events Produced At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Nov 2008

Measurement Of The Forward-Backward Charge Asymmetry And Extraction Of Sin2ӨWEff In Pp → Z/Γ* +X → E+E- + X Events Produced At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a measurement of the forward-backward charge asymmetry (AFB) in ppZ/γ* +Xe+e- + X events at a center-of-mass energy of 1.96 TeV using 1.1 fb-1 of data collected with the D0 detector at the Fermilab Tevatron collider. AFB is measured as a function of the invariant mass of the electron-positron pair, and found to be consistent with the standard model prediction. We use the AFB measurement to extract the effective weak mixing angle sin2ӨWeff = 0.2326 ± 0.0018 (stat) ± 0.0006 (syst).


Regulating Self-Organizing Nanostructures Via External Mechanism, Jiangyu Li, Q. G. Du, Stephen Ducharme Nov 2008

Regulating Self-Organizing Nanostructures Via External Mechanism, Jiangyu Li, Q. G. Du, Stephen Ducharme

Stephen Ducharme Publications

Self-organizing nanostructures are ubiquitous in both natural and synthetic materials. They are not only appealing scientifically, by revealing the intrinsic atomic and molecular interactions that might be difficult to detect otherwise, but may also hold the key for the development of novel functional structures and devices. For their technological potential to be fully realized, the size, morphology, and distribution of the self-organizing nanostructures must be regulated. In this paper, we investigate the principles under which the self-organizing nanostructures can be regulated via external mechanisms. Using nanomesa and nanowell formation in polyvinylidene fluoride trifluoroethylene copolymer film as an example, we demonstrate ...


Measurement Of The Polarization Of The Ү(1S) And Ү(2S) States In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration Oct 2008

Measurement Of The Polarization Of The Ү(1S) And Ү(2S) States In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, D0 Collaboration

Kenneth Bloom Publications

We present a study of the polarization of the Ү(1S) and Ү(2S) states using a 1.3 fb-1 data sample collected by the D0 experiment in 2002–2006 during run II of the Fermilab Tevatron Collider. We measure the polarization parameter α = (σT - 2σL), where σT and σL are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum (pTҮ) for the Ү(1S) and Ү(2S). Significant pTҮ-dependent longitudinal polarization is observed for the Ү ...


Precise Measurement Of The Top-Quark Mass From Lepton + Jets Events, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration Oct 2008

Precise Measurement Of The Top-Quark Mass From Lepton + Jets Events, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration

Kenneth Bloom Publications

We measure the mass of the top quark using top-quark pair candidate events in the lepton + jets channel from data corresponding to 1 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron collider. We use a likelihood technique that reduces the jet energy scale uncertainty by combining an in situ jet energy calibration with the independent constraint on the jet energy scale (JES) from the calibration derived using photon þ jets and dijet samples. We find the mass of the top quark to be 171.5 ± 1.8(stat) + JES) ± 1.1(syst) GeV.


Observation Of Zz Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration Oct 2008

Observation Of Zz Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration

Kenneth Bloom Publications

We present an observation for ZZ → ℓ+-ℓ‘+ℓ‘- (ℓ, ℓ‘ = e or μ ) production in pp collisions at a center-of-mass energy of √s = 1.96 TeV. Using 1.7 fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider, we observe three candidate events with an expected background of 0.14+0.03 -0.02 events. The significance of this observation is 5.3 standard deviations. The combination of D0 results in this channel, as well as in ZZ → ℓ+-vv, yields a significance of 5.7 standard deviations and a combined cross ...


Observation Of Zz Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration Oct 2008

Observation Of Zz Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration

Kenneth Bloom Publications

We present an observation for ZZ → ℓ+-ℓ‘+ℓ‘- (ℓ, ℓ‘ = e or μ ) production in pp collisions at a center-of-mass energy of √s = 1.96 TeV. Using 1.7 fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider, we observe three candidate events with an expected background of 0.14+0.03 -0.02 events. The significance of this observation is 5.3 standard deviations. The combination of D0 results in this channel, as well as in ZZ → ℓ+-vv, yields a significance of 5.7 standard deviations and a combined cross ...


Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, Sarbeswar Sahoo, Christian Binek Oct 2008

Quenching Of The Exchange Bias Training In Fe/Cr2o3/Fe Trilayer, Sarbeswar Sahoo, Christian Binek

Christian Binek Publications

Exchange bias (EB) and its associated training effects are studied in an epitaxial Fe(10 nm)/Cr2O3(2.7 nm)/Fe(10 nm) trilayer heterostructure grown by molecular beam epitaxy. The EB decreases linearly with increasing temperature from T = 5 K to T = 50 K. It changes sign and becomes positive within 50 K < T < 200 K, finally changing back to regular EB for T<200K up to the highest measured temperature of T = 395 K. Remarkably, the latter is far above the bulk Néel temperature TN = 307 K. EB training effects occur only at 5 K < T < 50 K. We show that this training can be quenched by subjecting the system to DC magnetic field, µ0HDC <= 7 T. The applied field most likely induces a temperature dependent spin-flop transition. Upon its removal the antiferromagnetic Cr2O3 pinning layer evolves uniformly into its quasi-equilibrium spin configuration thus leading to quasi-equilibrium EB.


The Anisotropic Band Structure Of Layered In4Se3(001), Yaroslav B. Losovyj, L. Makinistian, E. A. Albanesi, A. G. Pethukov, Jing Liu, P. Galiy, O. R. Dveriy, Peter A. Dowben Oct 2008

The Anisotropic Band Structure Of Layered In4Se3(001), Yaroslav B. Losovyj, L. Makinistian, E. A. Albanesi, A. G. Pethukov, Jing Liu, P. Galiy, O. R. Dveriy, Peter A. Dowben

Peter Dowben Publications

There is discernable and significant band dispersion along both high symmetry directions for cleaved ordered surfaces of the layered In4Se3(001). The extent of dispersion of approximately 1 eV is observed along the surface chain rows, and about 0.5 eV perpendicular to the surface “furrows,” consistent with theoretical expectations. A possible surface state exists at the surface Brillouin zone edge, in the direction perpendicular to the chains, in a gap of the projected bulk band structure. Excluding the possible surface state, the experimental hole mass is 5.5 times greater along the chains than perpendicular to ...


ZzL+L-V+V- Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration Oct 2008

Zz → L+L-V+V- Production In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, D0 Collaboration

Kenneth Bloom Publications

We describe a search for Z boson pair production in pp collisions at √s = 1.96 TeV with the D0 detector at the Fermilab Tevatron Collider using a data sample corresponding to an integrated luminosity of 2.7 fb-1. Using the final state decay ZZ → ℓ+-v+v- (where ℓ = e or μ) we find a signal with a 2.6 standard deviations significance (2.0 expected) corresponding to a cross section of σ(ppZZ + X) = 2.01 ± 0.93(stat) ± 0.29(sys) pb.


Why Are Ferroelectric Polymers Difficult To Find – And Difficult To Verify, Stephen Ducharme Sep 2008

Why Are Ferroelectric Polymers Difficult To Find – And Difficult To Verify, Stephen Ducharme

Stephen Ducharme Publications

The field of electrets encompasses a wide range of materials that maintain an external electric field due to alignment of internal electric dipoles or trapped charge, or both [1]. Polymers incorporating molecular dipoles constitute an important class of electrets, and so it is fitting that we consider the conditions under which such a polymer can also be considered a ferroelectric [2]. Further, because ferroelectric polymers have many uses, it is fruitful to consider how their properties depend on molecular structure [3].


Search For Long-Lived Particles Decaying Into Electron Or Photon Pairs With The D0 Detector, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration Sep 2008

Search For Long-Lived Particles Decaying Into Electron Or Photon Pairs With The D0 Detector, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration

Kenneth Bloom Publications

In this Letter we report on a search for long-lived particles that decay into final states with two electrons or photons. Such long-lived particles arise in a variety of theoretical models, such as hidden valleys and supersymmetry with gauge-mediated breaking. By precisely reconstructing the direction of the electromagnetic shower we are able to probe much longer lifetimes than previously explored. We see no evidence of the existence of such long-lived particles and interpret this search as a quasi model-independent limit on their production cross section, as well as a limit on a long-lived fourth generation quark.


Magnetoelectric Effect At The Fe3O4 /Batio3 (001) Interface: A First-Principles Study, Manish K. Niranjan, Julian P. Velev, Chun-Gang Duan, Sitaram S. Jaswal, Evgeny Y. Tsymbal Sep 2008

Magnetoelectric Effect At The Fe3O4 /Batio3 (001) Interface: A First-Principles Study, Manish K. Niranjan, Julian P. Velev, Chun-Gang Duan, Sitaram S. Jaswal, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

Multiferroic heterostructures comprising ferroelectric and ferro(ferri)magnetic constituents have recently attracted considerable interest due to the strong coupling between magnetic and electric properties which may have interesting applications. Here we investigate the magnetoelectric coupling at the ferrimagnetic/ ferroelectric Fe3O4 /BaTiO3 (001) interfaces within the framework of density-functional theory. The coupling in this system originates from the interface bonding sensitive to atomic displacements at the interface and leads to the change in the interface magnetization when the polarization of the ferroelectric layer reverses. We consider two types of interface terminations of Fe3O4 which ...


Electrically Controlled Magnetism, Christian Binek, Xi He, Yi Wang, Sarbeswar Sahoo Sep 2008

Electrically Controlled Magnetism, Christian Binek, Xi He, Yi Wang, Sarbeswar Sahoo

Christian Binek Publications

Manipulation of magnetically ordered states by electrical means is a promising approach towards novel spintronics devices. We report on the electric control of surface magnetism in Cr2O3 thin films and uniaxial anisotropy in ferroelectric/ferromagnetic heterostructures, respectively. Artificial magnetoelectricity is realized in a BaTiO3/Fe heterostructure. Here, thermally induced coercivity changes of the Fe hysteresis loop are used to derive the stress imposed by the ferroelectric BaTiO3 substrate on the adjacent Fe film. Electrically induced coercivity changes give rise to a giant magnetoelectric susceptibility in the vicinity of the magnetic coercive field.


Surface Magnetoelectric Effect In Ferromagnetic Metal Films, Chun-Gang Duan, Julian P. Velev, Renat F. Sabirianov, Ziqiang Zhu, Junhao Chu, Sitaram S. Jaswal, Evgeny Y. Tsymbal Sep 2008

Surface Magnetoelectric Effect In Ferromagnetic Metal Films, Chun-Gang Duan, Julian P. Velev, Renat F. Sabirianov, Ziqiang Zhu, Junhao Chu, Sitaram S. Jaswal, Evgeny Y. Tsymbal

Evgeny Tsymbal Publications

A surface magnetoelectric effect is revealed by density-functional calculations that are applied to ferromagnetic Fe(001), Ni(001), and Co(0001) films in the presence of an external electric field. The effect originates from spin-dependent screening of the electric field which leads to notable changes in the surface magnetization and the surface magnetocrystalline anisotropy. These results are of considerable interest in the area of electrically controlled magnetism and magnetoelectric phenomena.


Interface Effects In Spin-Polarized Metal/Insulator Layered Structures, Julian P. Velev, Peter A. Dowben, Evgeny Y. Tsymbal, Stephen J. Jenkins, A. N. Caruso Sep 2008

Interface Effects In Spin-Polarized Metal/Insulator Layered Structures, Julian P. Velev, Peter A. Dowben, Evgeny Y. Tsymbal, Stephen J. Jenkins, A. N. Caruso

Evgeny Tsymbal Publications

Recent advances in thin-film deposition techniques, such as molecular beam epitaxy and pulsed laser deposition, have allowed for the manufacture of heterostructures with nearly atomically abrupt interfaces. Although the bulk properties of the individual heterostructure components may be well-known, often the heterostructures exhibit novel and sometimes unexpected properties due to interface effects. At heterostructure interfaces, lattice structure, stoichiometry, interface electronic structure (bonding, interface states, etc.), and symmetry all conspire to produce behavior different from the bulk constituents. This review discusses why knowledge of the electronic structure and composition at the interfaces is pivotal to the understanding of the properties of ...


Search For Scalar Leptoquarks And T-Odd Quarks In The Acoplanar Jet Topology Using 2.5 Fb−1 Of Pp Collision Data At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration Sep 2008

Search For Scalar Leptoquarks And T-Odd Quarks In The Acoplanar Jet Topology Using 2.5 Fb−1 Of Pp Collision Data At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration

Kenneth Bloom Publications

A search for new physics in the acoplanar jet topology has been performed in 2.5 fb−1 of data from pp collisions at √s = 1.96 TeV, recorded by the DØ detector at the Fermilab Tevatron Collider. The numbers of events with exactly two acoplanar jets and missing transverse energy are in good agreement with the Standard Model expectations. The result of this search has been used to set a lower mass limit of 205 GeV at the 95% C.L. on the mass of a scalar leptoquark when this particle decays exclusively into a quark and a neutrino ...


Threshold Effects On Plateau Electron Angular Distributions In Above-Threshold Detachment, Katarzyna Krajewska, Ilya I. Fabrikant, Anthony F. Starace Aug 2008

Threshold Effects On Plateau Electron Angular Distributions In Above-Threshold Detachment, Katarzyna Krajewska, Ilya I. Fabrikant, Anthony F. Starace

Anthony F. Starace Publications

Rates of above-threshold detachment (ATD) of H (s-electron) and F (p-electron) ions, calculated using the Sturmian-Floquet quasienergy approach, are investigated as a function of intensity for the case that the laser field intensity passes across ponderomotively shifted detachment thresholds. Pronounced enhancements of both detached electron angular distributions and fixed-angle ATD spectra in the low- and mid-energy plateau region are found at near-threshold laser intensities. These enhancements are sensitive to the initial state symmetry (i.e., the s or p symmetry) of the valence electron and occur in a narrow angular interval that is far from the polarization axis ...


Search For Higgs Bosons Decaying To Tau Pairs In Pp Collisions With The D0 Detector, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration Aug 2008

Search For Higgs Bosons Decaying To Tau Pairs In Pp Collisions With The D0 Detector, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration

Kenneth Bloom Publications

We present a search for the production of neutral Higgs bosons φ decaying into τ+ τ- final states in pp collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of approximately 1 fb-1, were collected by the D0 experiment at the Fermilab Tevatron Collider. Limits on the production cross section times branching ratio are set. The results are interpreted in the minimal supersymmetric standard model yielding limits that are the most stringent to date at hadron colliders.


Search For Pair Production Of Doubly Charged Higgs Bosons In The H++H-- → Μ+Μ+Μ-Μ- Final State, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration Aug 2008

Search For Pair Production Of Doubly Charged Higgs Bosons In The H++H-- → Μ+Μ+Μ-Μ- Final State, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration

Kenneth Bloom Publications

We report the results of a search for pair production of doubly charged Higgs bosons via ppH++H--X → μ+μ+μ-μ-X at √s = 1.96 TeV.We use a data set corresponding to an integrated luminosity of 1.1 fb-1 collected from 2002 to 2006 by the D0 detector at the Fermilab Tevatron Collider. In the absence of an excess above the standard model background, lower mass limits of M(H±±L) > 150 GeV/c2 and M(H±±R) > 127 GeV/c2 at 95% C.L. are set, respectively, for left-handed and right-handed ...


Observation Of The Suppression Of The Flux Of Cosmic Rays Above 4 X 1019 Ev, J. Abraham, Gregory Snow, The Pierre Auger Collaboration Aug 2008

Observation Of The Suppression Of The Flux Of Cosmic Rays Above 4 X 1019 Ev, J. Abraham, Gregory Snow, The Pierre Auger Collaboration

Gregory Snow Publications

The energy spectrum of cosmic rays above 2.5 x 1018 eV, derived from 20 000 events recorded at the Pierre Auger Observatory, is described. The spectral index γ of the particle flux, J/ E- γ , at energies between 4 x 1018 eV and 4 x 1019 eV is 2.69 ± 0.02(stat) ± 0.06(syst), steepening to 4.2 ± 0.4(stat) ± 0.06(syst) at higher energies. The hypothesis of a single power law is rejected with a significance greater than 6 standard deviations. The data are consistent with the prediction by Greisen and ...


Measurement Of The Inclusive Jet Cross Section In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration Aug 2008

Measurement Of The Inclusive Jet Cross Section In Pp Collisions At √S = 1.96 Tev, V. M. Abazov, Kenneth A. Bloom, Gregory Snow, Dø Collaboration

Kenneth Bloom Publications

We report on a measurement of the inclusive jet cross section in pp collisions at a center-of-mass energy √s = 1.96 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider corresponding to an integrated luminosity of 0.70 fb-1. The data cover jet transverse momenta from 50 to 600 GeV and jet rapidities in the range -2.4 to 2.4. Detailed studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented, and the cross section measurements are found to be in good agreement with next-to-leading order QCD calculations.