32,166 research outputs found
Polarization Effects in Standard Model Parton Distributions at Very High Energies
We update the earlier work of Refs. arXiv:1703.08562 and arXiv:1712.07147 on
parton distribution functions in the full Standard Model to include gauge boson
polarization, non-zero input electroweak boson PDFs and next-to-leading-order
resummation of large logarithms.Comment: 24 pages, 7 Figures. arXiv admin note: text overlap with
arXiv:1703.08562, arXiv:1806.1015
The check is dead! Long live the check! A Check 21 update
Check 21 legislation has enabled the check clearing system to transform from paper to electronics, and much more rapidly than some had predicted. As a result of competition with other payment methods, check use has been declining since the mid-1990s, but because of the rapid adoption of electronic payment methods, checks are evolving and are unlikely to disappear anytime soon. Checks are still a convenient way to initiate some payments, and electronic processing has only made them more competitive with all types of electronic payments.Checks ; Electronic funds transfers
Standard Model Parton Distributions at Very High Energies
We compute the leading-order evolution of parton distribution functions for
all the Standard Model fermions and bosons up to energy scales far above the
electroweak scale, where electroweak symmetry is restored. Our results include
the 52 PDFs of the unpolarized proton, evolving according to the SU(3), SU(2),
U(1), mixed SU(2) x U(1) and Yukawa interactions. We illustrate the numerical
effects on parton distributions at large energies, and show that this can lead
to important corrections to parton luminosities at a future 100 TeV collider.Comment: 30 pages, 7 figures. Improved treatment of input PDFs at 100 GeV.
Adjusted plotting style to show features more clearly. Main results and
conclusions unchange
Phase Transitions in a Two-Component Site-Bond Percolation Model
A method to treat a N-component percolation model as effective one component
model is presented by introducing a scaled control variable . In Monte
Carlo simulations on , , and simple cubic
lattices the percolation threshold in terms of is determined for N=2.
Phase transitions are reported in two limits for the bond existence
probabilities and . In the same limits, empirical formulas
for the percolation threshold as function of one
component-concentration, , are proposed. In the limit a new
site percolation threshold, , is reported.Comment: RevTeX, 5 pages, 5 eps-figure
Standard Model Fragmentation Functions at Very High Energies
We compute the leading-order evolution of parton fragmentation functions for
all the Standard Model fermions and bosons up to energies far above the
electroweak scale, where electroweak symmetry is restored. We discuss the
difference between double-logarithmic and leading-logarithmic resummation, and
show how the latter can be implemented through a scale choice in the SU(2)
coupling. We present results for a wide range of partonic center-of-mass
energies, including the polarization of fermion and vector boson fragmentation
functions induced by electroweak evolution.Comment: 32 pages, 4 figure
Microwave Scattering and Noise Emission from Afterglow Plasmas in a Magnetic Field
The microwave reflection and noise emission (extraordinary mode) from cylindrical rare‐gas (He, Ne, Ar) afterglow plasmas in an axial magnetic field is described. Reflection and noise emission are measured as a function of magnetic field near electron cyclotron resonance (ω ≈ ω_c) with electron density as a parameter (ω_p < ω). A broad peak, which shifts to lower values of ω_c/ω) as electron density increases, is observed for (ω_c/ω) ≤ 1. For all values of electron density a second sharp peak is found very close to cyclotron resonance in reflection measurements. This peak does not occur in the emission data. Calculations of reflection and emission using a theoretical model consisting of a one‐dimensional, cold plasma slab with nonuniform electron density yield results in qualitative agreement with the observations. Both the experimental and theoretical results suggest that the broad, density‐dependent peak involves resonance effects at the upper hybrid frequency ((ω_h)^2 = (ω_c)^2 + (ω_p)^2) of the plasma
Jet noise suppression by porous plug nozzles
Jet noise suppression data presented earlier by Maestrello for porous plug nozzles were supplemented by the testing of a family of nozzles having an equivalent throat diameter of 11.77 cm. Two circular reference nozzles and eight plug nozzles having radius ratios of either 0.53 or 0.80 were tested at total pressure ratios of 1.60 to 4.00. Data were taken both with and without a forward motion or coannular flow jet, and some tests were made with a heated jet. Jet thrust was measured. The data were analyzed to show the effects of suppressor geometry on nozzle propulsive efficiency and jet noise. Aerodynamic testing of the nozzles was carried out in order to study the physical features that lead to the noise suppression. The aerodynamic flow phenomena were examined by the use of high speed shadowgraph cinematography, still shadowgraphs, extensive static pressure probe measurements, and two component laser Doppler velocimeter studies. The different measurement techniques correlated well with each other and demonstrated that the porous plug changes the shock cell structure of a standard nozzle into a series of smaller, periodic cell structures without strong shock waves. These structures become smaller in dimension and have reduced pressure variations as either the plug diameter or the porosity is increased, changes that also reduce the jet noise and decrease thrust efficiency
Soft-Collinear Messengers: A New Mode in Soft-Collinear Effective Theory
It is argued that soft-collinear effective theory for processes involving
both soft and collinear partons, such as exclusive B-meson decays, should
include a new mode in addition to soft and collinear fields. These
"soft-collinear messengers" can interact with both soft and collinear particles
without taking them far off-shell. They thus can communicate between the soft
and collinear sectors of the theory. The relevance of the new mode is
demonstrated with an explicit example, and the formalism incorporating the
corresponding quark and gluon fields into the effective Lagrangian is
developed.Comment: 22 pages, 5 figures. Extended Section 6, clarifying the relevance of
different types of soft-collinear interaction
Factorization and Resummation for Dijet Invariant Mass Spectra
Multijet cross sections at the LHC and Tevatron are sensitive to several
distinct kinematic energy scales. When measuring the dijet invariant mass m_jj
between two signal jets produced in association with other jets or weak bosons,
m_jj will typically be much smaller than the total partonic center-of-mass
energy Q, but larger than the individual jet masses m, such that there can be a
hierarchy of scales m << m_jj << Q. This situation arises in many new-physics
analyses at the LHC, where the invariant mass between jets is used to gain
access to the masses of new-physics particles in a decay chain. At present, the
logarithms arising from such a hierarchy of kinematic scales can only be summed
at the leading-logarithmic level provided by parton-shower programs. We
construct an effective field theory, SCET+, which is an extension of
soft-collinear effective theory that applies to this situation of hierarchical
jets. It allows for a rigorous separation of different scales in a multiscale
soft function and for a systematic resummation of logarithms of both m_jj/Q and
m/Q. As an explicit example, we consider the invariant mass spectrum of the two
closest jets in e+e- -> 3 jets. We also give the generalization to pp -> N jets
plus leptons relevant for the LHC.Comment: 37 pages, 6 figures; v2: journal versio
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