نتایج جستجو برای: fragmentation theory

تعداد نتایج: 814990  

2004

We present a calculation of single and double spin asymmetries for inclusive hadron production in hadronic collisions. Our approach is based on Leading Order (LO) perturbative QCD and generalized factorization theorems, with full account of intrinsic parton momentum, k⊥, effects. This leads to a new class of spin and k⊥dependent distribution and fragmentation functions. Limiting ourselves to co...

2005
Laura Stephenson

The field of landscape ecology is an emerging complex area of study encompassing numerous concepts and principles. Landscapes are intricate systems and must remain balanced if ecosystem collapse is to be avoided. However, habitat fragmentation in landscapes of differing characteristics is threatening to upset such interconnectedness. It is the purpose of this investigation to explore the theory...

2005
Xin-Nian Wang

Recent progresses in the study of jet modification in hot medium and their consequences in high-energy heavy-ion collisions are reviewed. In particular, I will discuss energy loss for propagating heavy quarks and the resulting modified fragmentation function. Medium modification of the parton fragmentation function due to quark recombination are formulated within finite temperature field theory...

1997
J P Ma

By expanding functions of parton fragmentation into a heavy hadron in the inverse of the heavy quark mass m Q we attempt to factorize them into perturbative-and nonperturba-tive parts. In our approach the nonperturbative parts can be defined as matrix elements in heavy quark effective theory, the shape of the functions is predicted by perturbative QCD. In this work we neglect effect at order of...

2008
Jens C. Zahnow Joeran Maerz Ulrike Feudel

The incorporation of particle inertia into the usual mean field theory for particle aggregation and fragmentation in fluid flows is still an unsolved problem. We therefore suggest an alternative approach that is based on the dynamics of individual inertial particles and apply this to study steady state particle size distributions in a paradigmatic 2d flow. We show how a fractal structure, typic...

Journal: :Science 2003
Jianguo Wu Jianhui Huang Xingguo Han Zongqiang Xie Xianming Gao

Habitat fragmentation is the primary cause of the loss of biodiversity and ecosystem services, but its underlying processes and mechanisms remain poorly understood. Studies of islands and insular terrestrial habitats are essential for improving our understanding of habitat fragmentation. We argue that the Three-Gorges Dam, the largest that humans have ever created, presents a unique grand-scale...

2008
K. Chase A. Mekjian

A model for the fragmentation of a nucleus is developed. Parallels of the description of this process with other areas are shown which include Feynman's theory of the λ transition in liquid Helium, Bose condensation, and Markov process models used in stochastic networks and polymer physics. These parallels are used to generalize and further develop a previous exactly solvable model of nuclear f...

1994
L. Randall

We present a detailed analysis of the use of heavy quark fragmentation into heavy hadrons for testing the heavy quark effective theory through comparison of the measured fragmentation parameters of the c and b quarks. Our analysis is entirely model independent. We interpret the known perturbative evolution in a way useful for exploiting heavy quark symmetry at low energy. We first show consiste...

2007
Richard C. Canfield Alexander J. B. Russell

We explore the properties of the fragmentation of magnetic flux in solar active regions. We apply gradient-based tessellation to magnetograms of 59 active regions to identify flux fragments. First, we find that the distribution function of flux fragments in these regions is highly consistent with lognormal form, which is the most direct evidence yet obtained that repeated random bifurcation dom...

2004
G. Corcella

I study bottom quark fragmentation in the Standard Model Higgs decay H → b ¯ b, within the framework of perturbative fragmentation functions. I resum large collinear logarithms ln(m 2 H /m 2 b) in the next-to-leading logarithmic (NLL) approximation, using the DGLAP evolution equations. Soft contributions to the MS coefficient function and to the initial condition of the perturbative fragmentati...

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