arXiv subjects
Publications and source records attributed to F. Hautmann.
This article gives an introduction to transverse momentum dependent (TMD) parton distribution functions and their use in shower Monte Carlo event generators for high-energy hadron collisions, and describes recent progress in the treatment of sea quark effects within a TMD parton-shower framework.
We present recent QCD calculations of energy flow distributions associated with the production of jets at wide rapidity separations in high-energy hadron collisions, and discuss the role of these observables to analyze contributions from parton showering and from multiple parton collisions.
We observe that at the Large Hadron Collider, using forward + central detectors, it becomes possible for the first time to carry out calorimetric measurements of the transverse energy flow due to "minijets" accompanying production of two jets separated by a large rapidity interval. We present parton-shower calculations of energy flow observables in a high-energy factorized Monte Carlo framework, designed to take into account QCD logarithmic corrections both in the large rapidity interval and in the hard transverse momentum. Considering events with a forward and a central jet, we examine the energy flow in the interjet region and in the region away from the jets. We discuss the role of these observables to analyze multiple parton collision effects.
At the LHC, using forward + central detectors, it becomes possible for the first time to carry out measurements of the transverse energy flow due to ``minijets" accompanying production of two jets separated by a large rapidity interval. We discuss parton-shower calculations of energy flow observables in a high-energy factorized Monte Carlo framework, and comment on the role of these observables to study high parton multiplicity effects.
We give a brief introduction to the topics discussed at the ISMD 2010 Symposium (Antwerp, 2010) on forward physics at the LHC and its interplay with cosmic rays physics.
Proceedings of the 13th International Conference on Elastic and Diffractive Scattering (Blois Workshop) - Moving Forward into the LHC Era
This talk discusses basic aspects of forward production of jets in pp collisions at high energy, including i) issues on QCD factorization for hard processes at large rapidities, and ii) the role of forward jet measurements at the LHC to investigate contributions to parton showers from large-angle gluon radiation and from multiple parton interactions.
For high-pT forward processes at the Large Hadron Collider (LHC), QCD logarithmic corrections in the hard transverse momentum and in the large rapidity interval may both be quantitatively significant. The theoretical framework to resum consistently both kinds of logarithmic corrections to higher orders in perturbation theory is based on QCD high-energy factorization. We present numerical Monte Carlo applications of this method to final-state observables associated with production of one forward and one central jet. By computing jet correlations in rapidity and azimuth, we analyze the role of corrections to the parton-showering chain from large-angle gluon radiation, and discuss this in relationship with Monte Carlo results modeling interactions due to multiple parton chains.
CASCADE is a full hadron level Monte Carlo event generator for ep, γp and p\bar{p} and pp processes, which uses the CCFM evolution equation for the initial state cascade in a backward evolution approach supplemented with off - shell matrix elements for the hard scattering. A detailed program description is given, with emphasis on parameters the user wants to change and variables which completely specify the generated events.
If large-angle multigluon radiation contributes significantly to parton showers associated with heavy boson production at the LHC, appropriate parton branching methods are required for realistic Monte Carlo simulations of final states. We report on a study illustrating such effects in the case of central scalar-boson production. We comment on the possible impact of such studies on the modeling of multi-parton interactions.
At the Large Hadron Collider (LHC) it will become possible for the first time to investigate experimentally the forward region in hadron-hadron collisions via high-$p_T$ processes. In the LHC forward kinematics QCD logarithmic corrections in the hard transverse momentum and in the large rapidity interval may both be quantitatively significant. We analyze the hadroproduction of forward jets in the framework of QCD high-energy factorization, which allows one to resum consistently both kinds of corrections to higher orders in QCD perturbation theory. We compute the short-distance matrix elements needed to evaluate the factorization formula at fully exclusive level. We discuss numerically dynamical features of multi-gluon emission at large angle encoded in the factorizing high-energy amplitudes.
If large-angle multigluon radiation gives significant contributions to parton showers in the LHC high-energy region, appropriate generalizations of parton branching methods are required for Monte Carlo simulations of exclusive high-multiplicity final states. We discuss the use in this context of transverse-momentum dependent kernels which factorize in the region of high energies. We give examples based on ep and p pbar multi-jet data, and point to possible developments for distributions associated with massive final states at the LHC.
We discuss high-pT production processes at forward rapidities in hadron-hadron collisions, and describe recent results from using QCD high-energy factorization in forward jet production at the LHC.
We discuss jet production at forward rapidities at the LHC. In this region QCD logarithmic corrections in the hard transverse momentum and in the large rapidity interval may both be quantitatively significant. We describe results of using high-energy factorization techniques, which allow one to take into account both kinds of corrections to higher orders in QCD.
Proceedings of ISMD08
We discuss coherent QCD radiation from space-like parton branching and its effects on multi-jet final states at high-energy hadron colliders. Coherence effects for small longitudinal momentum fractions x are not included in the branching algorithms of standard shower Monte Carlo event generators. On the other hand, they are taken into account only partially in perturbative next-to-leading-order calculations for multi-jets. Such effects are present to all orders in alpha_s and can become logarithmically enhanced with \sqrt{s} / E_T, where E_T is the hardest jet transverse energy. We present results of summing coherence effects to all orders by parton-branching Monte Carlo methods based on transverse-momentum dependent matrix elements.
We report on studies of multi-parton corrections from nonlocal operator expansion. We discuss relations between eikonal-line matrix elements and parton distributions, and present an illustration for initial-state collinear evolution.
We investigate parton-branching methods based on transverse-momentum dependent (TMD) parton distributions and matrix elements for the Monte Carlo simulation of multi-particle final states at high-energy colliders. We observe that recently measured angular correlations in ep final states with multiple hadronic jets probe QCD coherence effects in the space-like branching, associated with finite-angle gluon radiation from partons carrying small longitudinal momenta, and not included in standard shower generators. We present Monte Carlo calculations for azimuthal two-jet and three-jet distributions, for jet multiplicities and for correlations in the transverse-momentum imbalance between the leading jets. We discuss comparisons with current experimental multi-jet data, and implications of corrections to collinear-ordered showers for LHC final states.