125,620 research outputs found
Dolly Parton, gender, and country music
Book review of: Dolly Parton, Gender, and Country Music. Leigh H. Edwards. Bloomington: Indiana University Press, 2018, 265 pp., $21.00, 978-0-2530-3155-6 (paper)
Perturbative QCD correlations in multi-parton collisions
We examine the role played in double parton interactions (DPI) by the
parton--parton correlations originating from perturbative QCD parton
splittings. Also presented are the results of the numerical analysis of the
integrated DPI cross sections at Tevatron and LHC energies. To obtain the
numerical results the knowledge of the single-parton GPDs gained by the HERA
experiments was used to construct the non-perturbative input for generalized
double parton distributions. The perturbative two-parton correlations induced
by three-parton interactions contribute significantly to resolution of the
longstanding puzzle of an excess of multi-jet production events in the
back-to-back kinematics observed at the Tevatron.Comment: 16 pages, 13 figure
Parton correlations in double parton scattering
Double parton scattering events are directly sensitive to the correlations
between two partons inside a proton and can answer fundamental questions on the
connections between the proton constituents. In this chapter, the different
types of possible correlations, our present knowledge of them, and the
processes where they are likely to be important, are introduced and explained.
The increasing integrated luminosity at the LHC and the refinements of the
theory of double parton scattering, lead to interesting prospects for
measuring, or severely constraining, two-parton correlations in the near
future.Comment: Prepared for: Multiple Parton Interactions at the LHC, Eds. P.
Bartalini and J. R. Gaunt, World Scientific, Singapore; v2: references adde
Initial State Parton Showers Beyond Leading Order
We derive a new method for initial-state collinear showering in Monte-Carlo
event generators which is based on the use of unintegrated parton correlation
functions. Combined with a previously derived method for final-state showering,
the method solves the problem of treating both the hard scattering and the
evolution kernels to be used in arbitrarily non-leading order. Although we only
treat collinear showering, so that further extensions are needed for QCD, we
have discovered several new results: (1) It is better to generate exact parton
kinematics in the hard scattering rather than with the subsequent parton
showering, and similarly at each step of the showering. (2) Parton showering is
then done conditionally on the exact energy-momentum of the initiating parton.
(3) We obtain a factorization for structure functions in terms of parton
correlation functions so that parton kinematics can be treated exactly from the
beginning. (4) We obtain two factorization properties for parton correlation
functions, one in terms of ordinary parton densities and one, suitable for
event generation, in terms of parton correlation functions themselves.Comment: 45 page
Parton recombination effect in polarized parton distributions
Parton recombination corrections to the standard spin-dependent
Altarelli-Parisi evolution equation are considered in a nonlinear evolution
equation. The properties of this recombination equation and its relation with
the spin-averaged form are discussed.Comment: 25 pages, 1 figure, to be published in Nucl. Phys. B. Appendix is
correcte
Calculation of W b bbar Production via Double Parton Scattering at the LHC
We investigate the potential to observe double parton scattering at the Large
Hadron Collider in p p -> W b bbar X -> l nu b bbar X at 7 TeV. Our analysis
tests the efficacy of several kinematic variables in isolating the double
parton process of interest from the single parton process and relevant
backgrounds for the first 10 inverse fb of integrated luminosity. These
variables are constructed to expose the independent nature of the two
subprocesses in double parton scattering, pp -> l nu X and pp -> b bbar X. We
use next-to-leading order perturbative predictions for the double parton and
single parton scattering components of W b bbar and for the pertinent
backgrounds. The next-to-leading order contributions are important for a proper
description of some of the observables we compute. We find that the double
parton process can be identified and measured with significance S/sqrt(B) ~ 10,
provided the double parton scattering effective cross section sigma_{eff} ~ 12
mb.Comment: 21 pages, 9 figures; v2: improved presentation and figures, version
published in Phys. Rev.
Parton distribution functions in the context of parton showers
When the initial state evolution of a parton shower is organized according to
the standard "backward evolution'' prescription, ratios of parton distribution
functions appear in the splitting probabilities. The shower thus organized
evolves from a hard scale to a soft cutoff scale. At the end of the shower, one
expects that only the parton distributions at the soft scale should affect the
results. The other effects of the parton distributions should have cancelled.
This means that the kernels for parton evolution should be related to the
shower splitting functions. If the initial state partons can have non-zero
masses, this requires that the evolution kernels cannot be the usual MSbar
kernels. We work out what the parton evolution kernels should be to match the
shower evolution contained in the parton shower event generator Deductor, in
which the b and c quarks have non-zero masses.Comment: 33 pages, 6 figure
Computation of Mini-Jet Inclusive Cross Sections
We apply the theory of parton-parton total cross sections at large ``s", due
to Lipatov and collaborators, to compute the inclusive cross section for jets
which accompany a large ``s" parton scattering process.Comment: 13 page
- …