A Simple Model for the BFKL-DGLAP Transition in Deep Inelastic Scattering

A simple model is presented, which interpolates between the DGLAP and BFKL regimes in deep inelastic e-p scattering. The model is based on the CCFM and LDC models, and it is simple enough to provide an intuitive picture of the transition region between the two domains. Results are presented for both fixed and running coupling; for fixed coupling the transition between the domains occurs at a constant ratio between ln((k_T)^2) and ln(1/x), while for a running coupling it occurs for constant ratio between ln(ln((k_T)^2)) and ln(1/x).Comment: 1+14 pages, 6 figure

W Production in an Improved Parton-Shower Approach

In the description of the production properties of gauge bosons (W+/W-, Z0, gamma) at colliders, the lowest-order graph normally is not sufficient. The contributions of higher orders can be introduced either by an explicit order-by-order matrix-element calculation, by a resummation procedure or by a parton-shower algorithm. Each approach has its advantages and disadvantages. We here introduce a method that allows the parton-shower algorithm to be augmented by higher-order information, thereby offering an economical route to a description of all event properties. It is tested by comparing with the pT spectrum of W bosons at the Tevatron.Comment: 1+9 pages, 5 eps-figures, submitted to Phys. Lett.

Gluon Distribution Functions in the kT-factorization Approach

At small x, the effects of finite transverse momenta of partons inside a hadron become increasingly important, especially in analyses of jets and heavy-quark production. These effects can be systematically accounted for in a formalism based on kT-factorization and unintegrated distribution functions. We present results for the unintegrated distribution function, together with the corresponding integrated one, obtained within the framework of the Linked Dipole Chain model. Comparisons are made to results obtained within other approaches

High-Energy-Physics Event Generation with PYTHIA 6.1

PYTHIA version 6 represents a merger of the PYTHIA 5, JETSET 7 and SPYTHIA programs, with many improvements. It can be used to generate high-energy-physics `events', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as accurate as possible a representation of event properties in a wide range of reactions. The underlying physics is not understood well enough to give an exact description; the programs therefore contain a combination of analytical results and various models. The emphasis in this article is on new aspects, but a few words of general introduction are included. Further documentation is available on the web.Comment: 1 + 27 pages, submitted to Computer Physics Communication

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

A Matrix-Element-Based Modification of the Parton Shower

The transverse momentum distribution of W \Sigma bosons at hadron colliders is well described by a parton-shower model for small p ? values, but not for large ones. This article is an attempt to give a better description of the distribution by using corrections derived from the matrix-element formalism. The parton shower for qq 0 ! W \Sigma has been modified to resemble the matrix elements of qq ! gW and qg ! q 0 W at large p ? values. Comparisons between different approaches are presented at p s = 1800 GeV. The results are also compared with experimental data from the D0 collaboration at Fermilab. 1 Introduction The Standard Model is the theory which lies at the heart of modern particle physics. In this theory we distinguish between two kinds of particles: matter particles and gauge bosons. (A boson is a particle of integer spin.) The Standard Model describes the matter particles (quarks and leptons) and their interactions. There are four fundamental forces in nature; int..

Gluon distribution functions in the kappa(perpendicular to)-factorization approach

At small x, the effects of finite transverse momenta of partons inside a hadron become increasingly important, especially in analyses of jets and heavy-quark production. These effects can be systematically accounted for in a formalism based on k(perpendicular to)-factorization and unintegrated distribution functions. We present results for the integrated and unintegrated distribution functions obtained within the framework of the Linked Dipole Chain model. Comparisons are made to results obtained within other approaches

Analyses of Electron-Proton and Hadron-Hadron Collisions Using the Linked Dipole Chain Model

In this thesis we perform phenomenological studies of Quantum Chromodynamics, as manifested in deeply inelastic electron-proton (DIS) and high-energy hadron-hadron interactions. Most of the results are obtained using the Linked Dipole Chain model (LDC). This model was originally developed for studies of DIS and is formulated in terms of kT-factorization and un-integrated parton distribution functions. We develop a simple model, based on the CCFM and LDC models, which interpolates between the DGLAP and BFKL regimes in DIS. This model gives an intuitive qualitative picture of the transition region between the DGLAP and BFKL domains. We use an approximate version of the LDC model to obtain qualitative results for the inclusive minijet cross section and transverse energy flow, expected to be relevant in analyses of future high-energy hadron-hadron or nucleus-nucleus collisions. Our results contain a dynamical suppression at small transverse momenta, which corresponds to an effective cutoff which is slowly increasing with the total collision energy. This is in contrast to the traditional approach based on collinear factorization, which results in an inclusive cross section that diverges at small transverse momenta and implies the introduction of a cutoff parameter whose value needs to be adjusted to data. The LDC model is particularly suitable for a description of e.g. the cross section for jets and heavy quarks at very high energies, where the effects of finite transverse momenta of partons inside the hadrons become increasingly important. We obtain results for the LDC integrated and un-integrated gluon distribution functions and compare them with those of other formalisms, e.g. those based on the CCFM model, demonstrating how to make a relevant comparison between the different formalisms. We exploit the symmetric formulation of the LDC model with respect to the photon and proton ends and develop a version of the LDC model for hadronic interactions. In this preliminary analysis, we focus on features of jet and minijet production which are less sensitive to hadronization effects and compare our results to those of the PYTHIA event generator

W Production in an Improved Parton-Shower Approach

In the description of the production properties of gauge bosons (W \Sigma , Z 0 , fl ) at colliders, the lowest-order graph normally is not sufficient. The contributions of higher orders can be introduced either by an explicit order-by-order matrix-element calculation, by a resummation procedure or by a partonshower algorithm. Each approach has its advantages and disadvantages. We here introduce a method that allows the parton-shower algorithm to be augmented by higher-order information, thereby offering an economical route to a description of all event properties. It is tested by comparing with the p ? spectrum of W bosons at the Tevatron. 1 [email protected] 2 [email protected] The W \Sigma and Z 0 bosons have been extensively studied at colliders, in order to test the standard model [1]. In recent years they have also made their debut as backgrounds to other processes of interest: top studies, Higgs searches, and so on. Here it is often the association of the W=Z..