131 research outputs found
Factorization Approach for Top Mass Reconstruction at High Energies
Using effective theories for jets and heavy quarks it is possible to prove
that the double differential top-antitop invariant mass distribution for the
process in the resonance region for c.m. energies much
larger than the top mass can factorized into perturbatively computable hard
coefficients and jet functions and a non-perturbative soft function. For
invariant mass prescriptions based on hemispheres defined with respect to the
thrust axis the soft function can be extracted from massless jet event shape
distributions. This approach allows in principle for top mass determinations
without uncertainties from hadronization using the reconstruction method and to
quantify the top mass scheme dependence of the measured top quark mass value.Comment: Talk given at 2007 International Linear Collider Workshop (LCWS07 and
ILC07), Hamburg, Germany, 30 May - 3 Jun 2007, 7 pages, 4 figures, title
modifie
Factorization of e+e- Event Shape Distributions with Hadronic Final States in Soft Collinear Effective Theory
We present a new analysis of two-jet event shape distributions in soft
collinear effective theory. Extending previous results, we observe that a large
class of such distributions can be expressed in terms of vacuum matrix elements
of operators in the effective theory. We match these matrix elements to the
full theory in the two-jet limit without assuming factorization of the complete
set of hadronic final states into independent sums over partonic collinear and
soft states. We also briefly discuss the relationship of this approach to
diagrammatic factorization in the full theory.Comment: 21 pages. Journal version. Defined an explicit thrust axis operator;
clarified meaning of a delta function operato
The Resummed Photon Spectrum in Radiative Upsilon Decays
We present a theoretical prediction for the photon spectrum in radiative
Upsilon decay including the effects of resumming the endpoint region, E_\gamma
-> M_\Upsilon/2. Our approach is based on NRQCD and the soft collinear
effective theory. We find that our results give much better agreement with data
than the leading order NRQCD prediction.Comment: 4 pages, 6 figure
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Single and multiple rates of nonequilibrium diffusive mass transfer at the laboratory, field, and regional scales in the Culebra Member of the Rustler Formation, New Mexico
Recommended from our members
Bulldozer blades and colliding submarine mountain chains : constraints on central Oregon convergent margin tectonics from magnetics and gravity
Magnetic and gravity modelling was completed along two E-W transects offshore central Oregon. These models indicate that the backstop-forming western edge of the Siletz terrane has a seaward dip of approximately 40° to 49° at 44°48'N, shallowing to ~28° at 44°1 1 'N. This is a well-determined result, given available a priori information,
to a depth of ~7 km. The edge of the Siletz terrane may continue to descend at these dips to the JdF plate, but alternate geometries for the lowermost portion of the backstop are also consistent with the potential field data. The magnetic data also require progressive eastward demagnetization of the subducting JdF crust, which is most likely due to heating of the descending oceanic plate to the Curie temperature. Our southern transect reveals that Heceta Bank is cored by relatively high-density sediments (~2.54 g/cc), consistent with the model proposed by Kulm and Fowler (1974) for submarine bank formation in the Oregon convergent margin. On the basis
of magnetic, gravity, and velocity data, we tentatively interpret a deeply buried, linear aseismic ridge to be present beneath the accretionary complex from about 45°N to 42°N. This ridge may collide with the backstop beneath Heceta Bank and may play a role, in concert with imbricate thrust faulting, in the formation of Heceta Bank's high density core. We also speculate that differences in depth to the JdF plate due to juxtaposition of different-aged crust across pseudofaults which intersect the coast at
Nehalem and Heceta Banks may be a factor in the construction of these topographic highs
Top Jets in the Peak Region: Factorization Analysis with NLL Resummation
We consider top-quarks produced at large energy in e+e- collisions, and
address the question of what top-mass can be measured from reconstruction. The
production process is characterized by well separated scales: the
center-of-mass energy, Q, the top mass, m, the top decay width, Gamma_t, and
also LambdaQCD; scales which can be disentangled with effective theory methods.
In particular we show how the mass measurement depends on the way in which soft
radiation is treated, and that this can shift the mass peak by an amount of
order Q LambdaQCD/m. We sum large logs for Q >> m >> Gamma_t > LambdaQCD and
demonstrate that the renormalization group ties together the jet and soft
interactions below the scale m. Necessary conditions for the invariant mass
spectrum to be protected from large logs are formulated. Results for the
cross-section are presented at next-to-leading order with next-to-leading-log
resummation, for invariant masses in the peak region and the tail region. Using
our results we also predict the thrust distribution for massive quark jets at
NLL order for large thrust. We demonstrate that soft radiation can be precisely
controlled using data on massless jet production, and that in principle, a
short distance mass parameter can be measured using jets with precision better
than LambdaQCD.Comment: 92 pages, 22 figs, typos corrected, journal versio
Hadronic production calculated in the NRQCD factorization formalism
The NRQCD factorization formalism of Bodwin, Braaten, and Lepage prescribes
how to write quarkonium production rates as a sum of products of short-distance
coefficients times non-perturbative long-distance NRQCD matrix elements. We
present, in the true spirit of the factorization formalism, a detailed
calculation of the inclusive cross section for hadronic production. We
find that in addition to the well known {\it color-singlet} production
mechanisms, there are equally important mechanisms in which the pair
that forms the is initially produced in a {\it color-octet} state, in
either a , , or angular-momentum
configuration. In our presentation, we emphasize the ``matching'' procedure,
which %is the method that allows us to determine the short-distance
coefficients appearing in the factorization formula. We also point out how one
may systematically include relativistic corrections in these calculations.Comment: 25 pages, 3 postscript figures, use Revtex and epsfig.sty We fixed
some typos, added some text regarding a reference, and changed some
equations. The file will be available at http://phenom.physics.wisc.edu
Jets from Massive Unstable Particles: Top-Mass Determination
We construct jet observables for energetic top quarks that can be used to
determine a short distance top quark mass from reconstruction in e+ e-
collisions with accuracy better than Lambda_{QCD}. Using a sequence of
effective field theories we connect the production energy, mass, and top width
scales, Q>> m>> Gamma, for the top jet cross section, and derive a QCD
factorization theorem for the top invariant mass spectrum. Our analysis
accounts for: alpha_s corrections from the production and mass scales,
corrections due to constraints in defining invariant masses, non-perturbative
corrections from the cross-talk between the jets, and alpha_s corrections to
the Breit-Wigner line-shape. This paper mainly focuses on deriving the
factorization theorem for hemisphere invariant mass distributions and other
event shapes in e+e- collisions applicable at a future Linear Collider. We show
that the invariant mass distribution is not a simple Breit-Wigner involving the
top width. Even at leading order it is shifted and broadened by
non-perturbative soft QCD effects. We predict that the invariant mass peak
position increases linearly with Q/m due to these non-perturbative effects.
They are encoded in terms of a universal soft function that also describes soft
effects for massless dijet events. In a future paper we compute alpha_s
corrections to the jet invariant mass spectrum, including a summation of large
logarithms between the scales Q, m and Gamma.Comment: 54 pages, 10 figures, typos corrected, figures update
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Tracer tests in a fractured dolomite: 2. Analysis of mass transfer in single-well injection-withdrawal tests
We investigated multiple-rate diffusion as a possible explanation for observed behavior in a suite of single-well injection-withdrawal (SWIW) tests conducted in a fractured dolomite. We first investigated the ability of a conventional double-porosity model and a multirate diffusion model to explain the data. This revealed that the multirate diffusion hypothesis/model is consistent with available data and is capable of matching all of the recovery curves. Second, we studied the sensitivity of the SWIW recovery curves to the distribution of diffusion rate coefficients and other parameters. We concluded that the SWIW test is very sensitive to the distribution of rate coefficients but is relatively insensitive to other flow and transport parameters such as advective porosity and dispersivity. Third, we examined the significance of the constant double-log late time slopes (−2.1 to −2.8), which are present in several data sets. The observed late time slopes are significantly different than would be predicted by either conventional double-porosity or single-porosity models and are believed to be a distinctive feature of multirate diffusion. Fourth, we found that the estimated distributions of diffusion rate coefficients are very broad, with the distributions spanning a range of up to 3.6 orders of magnitude. Fifth, when both heterogeneity and solute drift are present, late time behavior similar to multirate mass transfer can occur. Although it is clear that multirate diffusion occurs in the Culebra, the number of orders of magnitude of variability may be overestimated because of the combined effects of drift and heterogeneity.Keywords: Hydrology, Groundwater transportKeywords: Hydrology, Groundwater transpor
Color-Octet Fragmentation and the psi' Surplus at the Tevatron
The production rate of prompt 's at large transverse momentum at the
Tevatron is larger than theoretical expectations by about a factor of 30. As a
solution to this puzzle, we suggest that the dominant production
mechanism is the fragmentation of a gluon into a pair in a pointlike
color-octet S-wave state, which subsequently evolves nonperturbatively into a
plus light hadrons. The contribution to the fragmentation function from
this process is enhanced by a short-distance factor of relative
to the conventional color-singlet contribution. This may compensate for the
suppression by , where is the relative momentum of the charm quark in
the . If this is indeed the dominant production mechanism at large
, then the prompt 's that are observed at the Tevatron should
almost always be associated with a jet of light hadrons.Comment: 9 pages, LaTe
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