1,209 research outputs found
Next-to-leading order predictions for WW + 1 jet distributions at the LHC
We present numerical results for the production of a pair in
association with a jet at the LHC in QCD at next-to-leading order (NLO). We
include effects of the decay of the massive vector bosons into leptons with
spin correlations and contributions from the third generation of massive
quarks. The calculation is performed using a semi-numerical method for the
virtual corrections, and is implemented in MCFM. In addition to its importance
{\it per se} as a test of the Standard Model, this process is an important
background to searches for the Higgs boson and to many new physics searches. As
an example, we study the impact of NLO corrections to jet production
on the search for a Higgs boson at the LHC.Comment: 21 pages, 9 figures; v3 published versio
The Stellar-Disk Electric (Short) Circuit: Observational Predictions for a YSO Jet Flow
We discuss the star-disk electric circuit for a young stellar object (YSO)
and calculate the expected torques on the star and the disk. We obtain the same
disk magnetic field and star-disk torques as given by standard
magnetohydrodynamic (MHD) analysis. We show how a short circuit in the
star-disk electric circuit may produce a magnetically-driven jet flow from the
inner edge of a disk surrounding a young star.
An unsteady bipolar jet flow is produced that flows perpendicular to the disk
plane. Jet speeds of order hundreds of kilometres per second are possible,
while the outflow mass loss rate is proportional to the mass accretion rate and
is a function of the disk inner radius relative to the disk co-rotation radius.Comment: 6 pages, 8 figures, Accepted for publication in Astrophysics & Space
Scienc
Pedestrian Solution of the Two-Dimensional Ising Model
The partition function of the two-dimensional Ising model with zero magnetic
field on a square lattice with m x n sites wrapped on a torus is computed
within the transfer matrix formalism in an explicit step-by-step approach
inspired by Kaufman's work. However, working with two commuting representations
of the complex rotation group SO(2n,C) helps us avoid a number of unnecessary
complications. We find all eigenvalues of the transfer matrix and therefore the
partition function in a straightforward way.Comment: 10 pages, 2 figures; eqs. (101) and (102) corrected, files for fig. 2
fixed, minor beautification
Levinson's Theorem for Dirac Particles
Levinson's theorem for Dirac particles constraints the sum of the phase
shifts at threshold by the total number of bound states of the Dirac equation.
Recently, a stronger version of Levinson's theorem has been proven in which the
value of the positive- and negative-energy phase shifts are separately
constrained by the number of bound states of an appropriate set of
Schr\"odinger-like equations. In this work we elaborate on these ideas and show
that the stronger form of Levinson's theorem relates the individual phase
shifts directly to the number of bound states of the Dirac equation having an
even or odd number of nodes. We use a mean-field approximation to Walecka's
scalar-vector model to illustrate this stronger form of Levinson's theorem. We
show that the assignment of bound states to a particular phase shift should be
done, not on the basis of the sign of the bound-state energy, but rather, in
terms of the nodal structure (even/odd number of nodes) of the bound state.Comment: Latex with Revtex, 7 postscript figures (available from the author),
SCRI-06109
Next-to-Leading order Higgs + 2 jet production via gluon fusion
We present phenomenological results for the production of a Higgs boson in
association with two jets at the LHC. The calculation is performed in the limit
of large top mass and is accurate to next-to-leading order in the strong
coupling, i.e. Comment: 13 pages, 6 figures; v2: references added, modified acknowledgments,
final version as published in JHE
Understanding the scabbling of concrete using microwave energy
This paper reports on the use of microwave energy to scabble concrete. While the technique is not new, little information exists relating to the controllability of the process, the effect of different types of concrete and the performance and durability of the scabbled concrete post treatment. Concrete blocks supplied by the UK Sellafield nuclear site were treated with microwave energy using a 15kW system, operating at 2.45GHz. The effect of aggregate type (Whinstone, Gravel and Limestone); standoff distance; and effect of surface coating were studied to determine their influence on the systems performance, in terms of mass and area removal rates. Complimentary modelling studies were undertaken relating the power density of the microwave energy to observed scabbling profile. Mass and area removal rates averaged 11.3gs-1 and 3cms-1 respectively on treating large areas to a depth of 25mm. The process was shown to not adversely affect structural properties of the specimens after treatment
Three point SUSY Ward identities without Ghosts
We utilise a non-local gauge transform which renders the entire action of
SUSY QED invariant and respects the SUSY algebra modulo the gauge-fixing
condition, to derive two- and three-point ghost-free SUSY Ward identities in
SUSY QED. We use the cluster decomposition principle to find the Green's
function Ward identities and then takes linear combinations of the latter to
derive identities for the proper functions.Comment: 20 pages, no figures, typos correcte
Direct Extraction of QCD Lambda MS-bar from e+e- Jet Observables
We directly fit the QCD dimensional transmutation parameter, Lambda MS-bar,
to experimental data on e+e- jet observables, making use of next-to-leading
order (NLO) perturbative calculations. In this procedure there is no need to
mention, let alone to arbitrarily vary, the unphysical renormalisation scale
mu, and one avoids the spurious and meaningless ``theoretical error''
associated with standard alpha_s determinations. PETRA, SLD, and LEP data are
considered in the analysis. An attempt is made to estimate the importance of
uncalculated next-NLO and higher order perturbative corrections, and power
corrections, by studying the scatter in the values of Lambda MS-bar obtained
for different observables.Comment: 46 pages, 22 figure
FTIR autecological analysis of bottom-ice diatom taxa across a tidal strait in the Canadian Arctic
A recent study demonstrated that an Arctic tidal strait, where a shoaled and constricted waterway increases
tidally driven sub-ice currents and turbulence, represents a âhotspotâ for ice algal production due to
a hypothesized enhanced ocean-ice nutrient supply. Based on these findings, we sampled the bottom-ice
algal community across the same tidal strait between the Finlayson Islands within Dease Strait, Nunavut,
Canada, in spring 2017. Our objective was to examine cellular responses of sea-ice diatoms to two expected
nutrient supply gradients in their natural environment: (1) a horizontal gradient across the tidal strait and (2)
a vertical gradient in the bottom-ice matrix. Two diatom taxa, Nitzschia frigida and Attheya spp. in bottomice sections (0â2, 2â5, and 5â10 cm) under thin snow cover (<5 cm), were selected for Fourier Transform
Infrared (FTIR) spectrochemical analysis for lipid and protein content. Results from the FTIR technique
strongly supported the existence of a horizontal nutrient gradient across the tidal strait of the Finlayson
Islands, while estimates of particulate organic carbon and chlorophyll a concentrations were difficult to
interpret. The larger N. frigida cells appeared to be more sensitive to the suspected horizontal nutrient
gradient, significantly increasing in lipid content relative to protein beyond the tidal strait. In contrast,
the epiphytic diatoms, Attheya spp., were more sensitive to the vertical gradient: above 2 cm in the
bottom-ice matrix, the non-motile cells appeared to be trapped with a depleted nutrient inventory and
evidence of a post-bloom state. Application of the FTIR technique to estimate biomolecular composition of
algal cells provided new insights on the response of the bottom-ice algal community to the examined spatial
gradients that could not be obtained from conventional bulk measurements alone. Future studies of sea ice
and associated environments are thus encouraged to employ this technique
Higgs Boson Production in Association with Three Jets
The scattering amplitudes for Higgs + 5 partons are computed, with the Higgs
boson produced via gluon fusion in the large top-quark mass limit. A
parton-level analysis of Higgs + 3 jet production via gluon fusion and via
weak-boson fusion is presented, and the effectiveness of a central-jet veto is
analysed.Comment: 26 pages, 4 Postscript figures, uses JHEP3.cl
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