Searcharxiv⌕ Search

arXiv subjects

H. Jung

Publications and source records attributed to H. Jung.

At least 73 records · Page 4Linked to original sources
arXiv2015

HERAFitter, Open Source QCD Fit Project

HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum Chromodynamics (QCD). It encodes results from a wide range of experimental measurements in lepton-proton deep inelastic scattering and proton-proton (proton-antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework covers a large number of the existing methods and schemes used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to help visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides facilities for fits of dipole models and transverse-momentum dependent PDFs. The package can be used to study the impact of new precise measurements from hadron colliders. This paper describes the general structure of HERAFitter and its wide choice of options.

hep-ph↗
arXiv2014

TMDlib and TMDplotter: library and plotting tools for transverse-momentum-dependent parton distributions

Transverse-momentum-dependent distributions (TMDs) are central in high-energy physics from both theoretical and phenomenological points of view. In this manual we introduce the library, TMDlib, of fits and parameterisations for transverse-momentum-dependent parton distribution functions (TMD PDFs) and fragmentation functions (TMD FFs) together with an online plotting tool, TMDplotter. We provide a description of the program components and of the different physical frameworks the user can access via the available parameterisations.

hep-ph↗
arXiv2014

Precision DIS data and TMD parton distributions

General formulations of QCD factorization for hadronic collisions extend the notion of ordinary parton distributions to transverse-momentum dependent (TMD) parton density and parton decay functions. We discuss the use of the recent high-precision deep-inelastic scattering (DIS) measurements for determination of TMD distributions. These are relevant for both low-pT and high-pT physics in hadron collisions. We comment on applications to multi-jet final states associated with electroweak gauge boson production at the LHC.

hep-ph↗
arXiv2014

The CCFM uPDF evolution uPDFevolv

uPDFevolv is an evolution code for TMD parton densities using the CCFM evolution equation. A description of the underlying theoretical model and technical realization is given together with a detailed program description, with emphasis on parameters the user may want to change

hep-ph↗
arXiv2014

Hadroproduction of electroweak gauge boson plus jets and TMD parton density functions

If studies of electroweak gauge boson final states at the Large Hadron Collider, for Standard Model physics and beyond, are sensitive to effects of the initial state's transverse momentum distribution, appropriate generalizations of QCD shower evolution are required. We propose a method to do this based on QCD transverse momentum dependent (TMD) factorization at high energy. The method incorporates experimental information from the high-precision deep inelastic scattering (DIS) measurements, and includes experimental and theoretical uncertainties on TMD parton density functions. We illustrate the approach presenting results for production of W-boson + n jets at the LHC, including azimuthal correlations and subleading jet distributions.

hep-ph↗
arXiv2014

Higgs boson as a gluon trigger: the study of QCD in high pile-up environments

In the forthcoming high-luminosity phase of the LHC many of the most interesting measurements for precision QCD studies are hampered by large pile-up conditions, especially at not very high transverse momenta. However, with the recently discovered Higgs boson, which couples in the heavy top limit directly to gluons, we have access to a novel production process to probe QCD by a colour-singlet current. In this study we compare observables in Higgs boson and Drell-Yan production and investigate whether measuring ratios or subtractions can yield results that are stable in high pile-up environments, and yet sensitive to (small-$p_{\text{T}}$) QCD physics in gluon fusion processes. We present results of Monte Carlo event generator calculations for a few specific examples.

hep-ph↗
arXiv2014

Transverse momentum dependent gluon density from DIS precision data

The combined measurements of proton's structure functions in deeply inelastic scattering at the HERA collider provide high-precision data capable of constraining parton density functions over a wide range of the kinematic variables. We perform fits to these data using transverse momentum dependent QCD factorization and CCFM evolution. The results of the fits to precision measurements are used to make a determination of the nonperturbative transverse momentum dependent gluon density function, including experimental and theoretical uncertainties. We present an application of this density function to vector boson + jet production processes at the LHC.

hep-ph↗
arXiv2013

Higgs as a gluon trigger

In the forthcoming high-luminosity phase at the LHC many of the most interesting measurements for precision QCD studies are hampered by conditions of large pile-up, particularly at not very high transverse momenta. We study observables based on measuring ratios of color-singlet currents via Higgs boson and Drell-Yan production, which may be accessed also at large pile-up, and used for an experimental program on QCD physics of gluon fusion processes in the LHC high-luminosity runs. We present results of Monte Carlo calculations for a few specific examples.

hep-ph↗
arXiv2013

Nonperturbative corrections and showering in NLO-matched event generators

We study contributions from nonperturbative effects and parton showering in NLO event generators, and present applications to jet final states. We find pT-dependent and rapidity-dependent corrections which can affect the shape of observed jet distributions at the LHC. We illustrate numerically the kinematic shifts in longitudinal momentum distributions from the implementation of energy-momentum conservation in collinear shower algorithms.

hep-ph↗
arXiv2013

Longitudinal momentum shifts, showering and nonperturbative corrections in matched NLO-shower event generators

Comparisons of experimental data with theoretical predictions for collider processes containing hadronic jets rely on shower Monte Carlo event generators to include corrections to perturbative calculations from hadronization, parton showering, multiple parton collisions. We examine current treatments of these corrections and propose alternative methods to take into account nonperturbative effects and parton showering in the context of next-to-leading-order (NLO) event generators. We point out sizeable parton-showering corrections to jet transverse energy spectra at high rapidity, and discuss kinematic shifts in longitudinal momentum distributions from initial state showering in the case both of jet production and of heavy mass production at the Large Hadron Collider.

hep-ph↗
arXiv2013

A Large Hadron Electron Collider at CERN

This document provides a brief overview of the recently published report on the design of the Large Hadron Electron Collider (LHeC), which comprises its physics programme, accelerator physics, technology and main detector concepts. The LHeC exploits and develops challenging, though principally existing, accelerator and detector technologies. This summary is complemented by brief illustrations of some of the highlights of the physics programme, which relies on a vastly extended kinematic range, luminosity and unprecedented precision in deep inelastic scattering. Illustrations are provided regarding high precision QCD, new physics (Higgs, SUSY) and electron-ion physics. The LHeC is designed to run synchronously with the LHC in the twenties and to achieve an integrated luminosity of O(100) fb$^{-1}$. It will become the cleanest high resolution microscope of mankind and will substantially extend as well as complement the investigation of the physics of the TeV energy scale, which has been enabled by the LHC.

hep-ex↗
arXiv2013

On the Relation of the LHeC and the LHC

The present note relies on the recently published conceptual design report of the LHeC and extends the first contribution to the European strategy debate in emphasising the role of the LHeC to complement and complete the high luminosity LHC programme. The brief discussion therefore focuses on the importance of high precision PDF and $α_s$ determinations for the physics beyond the Standard Model (GUTs, SUSY, Higgs). Emphasis is also given to the importance of high parton density phenomena in nuclei and their relevance to the heavy ion physics programme at the LHC.

hep-ex↗
arXiv2012

Collinearity approximations and kinematic shifts in partonic shower algorithms

We study kinematic effects due to the approximation of on-shell, collinear partons in shower Monte Carlo event generators. We observe that the collinearity approximation, combined with the requirements of energy-momentum conservation, gives rise to a kinematic shift, event by event, in longitudinal momentum distributions. We present numerical results in the case of jet and heavy flavor production processes measured at the LHC.

hep-ph↗
arXiv2012

Jet production and the inelastic pp cross section at the LHC

We suggest that, if current measurements of inclusive jet production for central rapidities at the LHC are extended to lower transverse momenta, one could define a visible cross section sensitive to the unitarity bound set by the recent determination of the inelastic proton-proton cross section.

hep-ph↗
arXiv2012

A Large Hadron Electron Collider at CERN: Report on the Physics and Design Concepts for Machine and Detector

The physics programme and the design are described of a new collider for particle and nuclear physics, the Large Hadron Electron Collider (LHeC), in which a newly built electron beam of 60 GeV, up to possibly 140 GeV, energy collides with the intense hadron beams of the LHC. Compared to HERA, the kinematic range covered is extended by a factor of twenty in the negative four-momentum squared, $Q^2$, and in the inverse Bjorken $x$, while with the design luminosity of $10^{33}$ cm$^{-2}$s$^{-1}$ the LHeC is projected to exceed the integrated HERA luminosity by two orders of magnitude. The physics programme is devoted to an exploration of the energy frontier, complementing the LHC and its discovery potential for physics beyond the Standard Model with high precision deep inelastic scattering measurements. These are designed to investigate a variety of fundamental questions in strong and electroweak interactions. The physics programme also includes electron-deuteron and electron-ion scattering in a $(Q^2, 1/x)$ range extended by four orders of magnitude as compared to previous lepton-nucleus DIS experiments for novel investigations of neutron's and nuclear structure, the initial conditions of Quark-Gluon Plasma formation and further quantum chromodynamic phenomena. The LHeC may be realised either as a ring-ring or as a linac-ring collider. Optics and beam dynamics studies are presented for both versions, along with technical design considerations on the interaction region, magnets and further components, together with a design study for a high acceptance detector. Civil engineering and installation studies are presented for the accelerator and the detector. The LHeC can be built within a decade and thus be operated while the LHC runs in its high-luminosity phase. It thus represents a major opportunity for progress in particle physics exploiting the investment made in the LHC.

physics.acc-ph↗
arXiv2012

Forward Z-boson production and the unintegrated sea quark density

Drell-Yan production in the forward region at the Large Hadron Collider is sensitive to multiple radiation of QCD partons not collinearly ordered, emitted over large rapidity intervals. We propose a method to take account of these radiative contributions via a factorization formula which depends on the unintegrated, or transverse momentum dependent, splitting function associated with the evolution of the initial-state sea quark distribution. We analyze this formula numerically, and point out kinematic effects from the initial-state transverse momentum on the vector boson spectrum.

hep-ph↗