Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Dramatic progress has been made over the last decade in the numerical study of quantum chromodynamics (QCD) through the use of improved formulations of QCD on the lattice (improved actions), the development of new algorithms, and the rapid increase in computing power available to lattice gauge theorists. In this article simulations of full QCD are described using the improved staggered quark formalism, ''asqtad'' fermions. These simulations were carried out with two degenerate flavors of light quarks (up and down) and with one heavier flavor, the strange quark. Several light quark masses, down to about three times the physical light quark mass, and six lattice spacings have been used. These enable controlled continuum and chiral extrapolations of many low energy QCD observables. The improved staggered formalism is reviewed, emphasizing both advantages and drawbacks. In particular, the procedure for removing unwanted staggered species in the continuum limit is reviewed. Then the asqtad lattice ensembles created by the MILC Collaboration are described. All MILC lattice ensembles are publicly available, and they have been used extensively by a number of lattice gauge theory groups. The physics results obtained with them are reviewed, and the impact of these results on phenomenology is discussed. Topics includemore » the heavy quark potential, spectrum of light hadrons, quark masses, decay constants of light and heavy-light pseudoscalar mesons, semileptonic form factors, nucleon structure, scattering lengths, and more.« less

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Nonperturbative QCD Simulations with 2+1 Flavors of Improved Staggered Quarks

We assess the current phenomenological status of transverse momentum dependent (TMD) parton distribution functions (PDFs) and fragmentation functions (FFs) and study the effect of consistently including perturbative QCD (pQCD) evolution. Our goal is to initiate the process of establishing reliable, QCD-evolved parametrizations for the TMD PDFs and TMD FFs that can be used both to test TMD factorization and to search for evidence of the breakdown of TMD factorization that is expected for certain processes. In this article, we focus on spin-independent processes because they provide the simplest illustration of the basic steps and can already be used in direct tests of TMD factorization. Our calculations are based on the Collins-Soper-Sterman (CSS) formalism, supplemented by recent theoretical developments which have clarified the precise definitions of the TMD PDFs and TMD FFs needed for a valid TMD-factorization theorem. Starting with these definitions, we numerically generate evolved TMD PDFs and TMD FFs using as input existing parametrizations for the collinear PDFs, collinear FFs, nonperturbative factors in the CSS factorization formalism, and recent fixed-scale fits. We confirm that evolution has important consequences, both qualitatively and quantitatively, and argue that it should be included in future phenomenological studies of TMD functions. Our analysis is also suggestive of extensions to processes that involve spin-dependent functions such as the Boer-Mulders, Sivers, or Collins functions, which we intend to pursue in future publications. At our website [http://projects.hepforge.org/tmd/], we have made available the tables and calculations needed to obtain the TMD parametrizations presented herein.

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Transverse momentum dependent parton distribution and fragmentation functions with QCD evolution

We perform a detailed investigation of multiple hard interactions in hadron- hadron collisions. We discuss the space-time, spin and color structure of multiple interac- tions, classify different contributions according to their power behavior and provide several elements required for establishing all-order factorization. This also allows us to analyze the structure of Sudakov logarithms in double hard scattering. We show how multiparton distributions can be constrained by connecting them with generalized parton distributions and by calculating their behavior at large transverse parton momenta.

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Elements of a theory for multiparton interactions in QCD

theta dependence of SU(N) gauge theories in the presence of a topological term

We discuss in detail a method to study transverse momentum dependent parton distribution functions (TMDs) using lattice QCD. To develop the formalism and to obtain first numerical results, we directly implement a bilocal quark-quark operator connected by a straight Wilson line, allowing us to study T-even, ''process-independent'' TMDs. Beyond results for x-integrated TMDs and quark densities, we present a study of correlations in x and k{sub perpendicular}. Our calculations are based on domain wall valence quark propagators by the LHP Collaboration calculated on top of gauge configurations provided by the MILC Collaboration with N{sub f}=2+1 asqtad-improved staggered sea quarks.

Exploring quark transverse momentum distributions with lattice QCD

We discuss in detail a method to study transverse momentum dependent parton distribution functions (TMDs) using lattice QCD. To develop the formalism and to obtain first numerical results, we directly implement a bilocal quark-quark operator connected by a straight Wilson line, allowing us to study T-even, ‘‘process-independent’’ TMDs. Beyond results for x-integrated TMDs and quark densities, we present a study of correlations in x and k?. Our calculations are based on domain wall valence quark propagators by the LHP Collaboration calculated on top of gauge configurations provided by the MILC Collaboration with Nf ¼ 2 þ 1 asqtad-improved staggered sea quarks.

We present preliminary results for the axial and tensor charge of the nucleon obtained from simulations with N f = 2 clover fermions. A comparison with chiral perturbation theory is attempted.

Axial and tensor charge of the nucleon with dynamical fermions

Generalized parton distributions encompass a wealth of information concerning the three-dimensional quark and gluon structure of the nucleon, and thus provide an ideal focus for the study of hadron structure using lattice QCD. The special limits corresponding to form factors and parton distributions are well explored experimentally, providing clear tests of lattice calculations, and the lack of experimental data for more general cases provides opportunities for genuine predictions and for guiding experiment. We present results from hybrid calculations with improved staggered (Asqtad) sea quarks and domain wall valence quarks at pion masses down to 350 MeV.

Hadron structure with light dynamical quarks

This is a review of progress in hadron structure physics from lattice QCD. Recent results on the structure of the nucleon and the pion in terms of (transition) form factors, moments of distribution amplitudes and (generalized) parton distribution functions are presented. These observables allow us to investigate a number of fundamental physics questions related to e.g. the distribution of charge and momentum in hadrons, the spin structure of the nucleon and the pion, and correlations between spin, orbital angular momentum and coordinate degrees of freedom. Chiral extrapolations of selected lattice results are presented and compared to results from experiment and phenomenology. We conclude that lattice simulations already today strongly contribute to our understanding of the structure of hadrons.

Philipp Hagler

Papers

Exploring quark transverse momentum distributions with lattice QCD

Exploring quark transverse momentum distributions with lattice QCD

Axial and tensor charge of the nucleon with dynamical fermions

Hadron structure with light dynamical quarks

Progress in hadron structure physics on the lattice