Acoustoelectric pumping through a ballistic point contact in the presence of magnetic fields

The acoustoelectric current, J, induced in a ballistic point contact (PC) by a surface acoustic wave is calculated in the presence of a perpendicular magnetic field, B. It is found that the dependence of the current on the Fermi energy in the terminals is strongly correlated with that of the PC conductance: J is small at the conductance plateaus, and is large at the steps. Like the conductance, the acoustoelectric current has the same functional behavior as in the absence of the field, but with renormalized energy scales, which depend on the strength of the magnetic field, | B|.Comment: 7 page

Comments on gluon scattering amplitudes via AdS/CFT

In this article we consider n gluon color ordered, planar amplitudes in N=4 super Yang Mills at strong 't Hooft coupling. These amplitudes are approximated by classical surfaces in AdS_5 space. We compute the value of the amplitude for a particular kinematic configuration for a large number of gluons and find that the result disagrees with a recent guess for the exact value of the amplitude. Our results are still compatible with a possible relation between amplitudes and Wilson loops. In addition, we also give a prescription for computing processes involving local operators and asymptotic states with a fixed number of gluons. As a byproduct, we also obtain a string theory prescription for computing the dual of the ordinary Wilson loop, Tr P exp[ i\oint A ], with no couplings to the scalars. We also evaluate the quark-antiquark potential at two loops.Comment: 27 pages, 9 figures,v3:minor correction

Magnetic edge states of impenetrable stripe

The electron motion in a strong perpendicular magnetic field close to the impenetrable stripe is considered by making use of the singular integral equation technique. The energy spectrum is calculated and compared with the energy spectrum of the round antidot.Comment: REVTeX4 format, 9 pages with 9 figures (*.eps

Coherent quantum transport in narrow constrictions in the presence of a finite-range longitudinally polarized time-dependent field

We have studied the quantum transport in a narrow constriction acted upon by a finite-range longitudinally polarized time-dependent electric field. The electric field induces coherent inelastic scatterings which involve both intra-subband and inter-sideband transitions. Subsequently, the dc conductance G is found to exhibit suppressed features. These features are recognized as the quasi-bound-state (QBS) features which are associated with electrons making transitions to the vicinity of a subband bottom, of which the density of states is singular. Having valley-like instead of dip-like structures, these QBS features are different from the G characteristics for constrictions acted upon by a finite-range time-modulated potential. In addition, the subband bottoms in the time-dependent electric field region are shifted upward by an energy proportional to the square of the electric field and inversely proportional to the square of the frequency. This effective potential barrier is originated from the square of the vector potential and it leads to the interesting field-sensitive QBS features. An experimental set-up is proposed for the observation of these features.Comment: 8 pages, 4 figure

An overview of trace elements in soils of Keana-Awe Brine-Fields, Middle Benue Trough, Nigeria

The objective of this study was to determine the concentration of trace elements in soils of Keana-Awe brine-fields. Composite soil samples were randomly collected at a depth of 0–15 cm and were analysed for molybdenum, zinc, arsenic, lead, cobalt, chromium, copper, barium and nickel using Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Quantification of the degree of soil contamination by these trace elements was carried out using the enrichment factor (EF) and the geo-accumulation index (Igeo). The data were subjected to principal component analysis (PCA). The average concentrations were 1.56 ppm molybdenum, 1116.42 ppm zinc, 23.80 ppm arsenic, 71.40 ppm lead, 17.64 ppm cobalt, 237.35 ppm chromium, 24.16 ppm copper, 254.67 ppm barium and 143.71 ppm nickel. Cobalt, nickel and chromium showed positive loadings in component 1 with a total variance of 29.56%. Zinc, copper and lead showed positive loadings in component 2 with a total variance of 18.79%, while copper showed negative loading in component 3 with a total variance of 14.79%. Considering the concentration of trace elements in the soils and statistical analyses, we conclude that soils of the study area were severely enriched in molybdenum, cobalt, chromium, copper, barium, nickel, while arsenic and zinc are in excessive concentrations in the soils. These trace elements could have originated from geogenic and anthropogenic sources.DHE

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary

This paper constructs the reduction of heterotic $M$-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and for the boundary conditions on the bulk fields. Some general features of dualisation on a manifold with boundary are used to explain the origin of some topological terms in the action. The effect of gaugino condensation on the fermion boundary conditions leads to a `twist' in the chirality of the gravitino which can provide an uplifting mechanism in the vacuum energy to cancel the cosmological constant after moduli stabilisation.Comment: 16 pages, RevTe