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About 10,000 papers for “Parton”

parton

B. Pasquini, S. Boffi, B. Pasquini · 2008

Cited by 0

Parton-parton scattering at two-loops

Maria Elena Tejeda Yeomans · Durham e-Theses (Durham University) · 2001

We present an algorithm for the calculation of scalar and tensor one- and two-loop integrals that contribute to the virtual corrections of 2 →2 partonic scattering. First, the tensor integrals are related to scalar integrals that contain an irreducible propagator-like structure in the numerator. Then, we use Integration by Parts and Lorentz Invariance recurrence relations to build a general system of equations that enables the reduction of any scalar integral (with and without structure in the numerator) to a basis set of master integrals. Their expansions in e = 2-D/2 have already been calculated and we present a summary of the techniques that have been used to this end, as well as a compilation of the expansions we need in the different physical regions. We then apply this algorithm to the direct evaluation of the Feynman diagrams contributing to the O(α4/8) one- and two-loop matrix-elements for massless like and unlike quark-quark, quark-gluon and gluon-gluon scattering. The analytic expressions we provide are regularised in Convensional Dimensional Regularisation and renormalised in the MS scheme. Finally, we show that the structure of the infrared divergences agrees with that predicted by the application of Catani's formalism to the analysis of each partonic scattering process. The results presented in this thesis provide the complete calculation of the one- and two-loop matrix-elements for 2 2 processes needed for the next-to-next-to-leading order contribution to inclusive jet production at hadron colliders.

Cited by 2Open access

Parton-parton scattering at two-loops

Tejeda Yeomans, M.E. · OpenGrey (Institut de l'Information Scientifique et Technique) · 2001

Abstract We present an algorithm for the calculation of scalar and tensor one- and two-loop integrals that contribute to the virtual corrections of 2 #-># 2 partonic scattering. First, the tensor integrals are related to scalar integrals that contain an irreducible propagator-like structure in the numerator. Then, we use Integration by Parts and Lorentz Invariance recurrence relations to build a general system of equations that enables the reduction of any scalar integral (with and without structure in the numerator) to a basis set of master integrals. Their expansions in #epsilon# = 2 - D/2 have already been calculated and we present a summary of the techniques that have been used to this end, as well as a compilation of the expansions we need in the different physical regions. We then apply this algorithm to the direct evaluation of the Feynman diagrams contributing to the O(#alpha#_s"4) one- and two-loop matrix-elements for massless like and unlike quark-quark, quark-gluon and gluon-gluon scattering. The analytic expressions we provide are regularised in Convensional Dimensional Regularisation and renormalised in the MS-bar scheme. Finally, we show that the structure of the infrared divergences agrees with that predicted by the application of Catani's formalism to the analysis of each partonic scattering process. The results presented in this thesis provide the complete calculation of the one- and two-loop matrix-elements for 2 #-># 2 processes needed for the next-to-next-to-leading order contribution to inclusive jet production at hadron colliders. (author)

Cited by 0Open access

Parton Correlations in Double Parton Scattering

Tomas Kasemets, Sergio Scopetta · Advanced series on directions in high energy physics · 2018

Double parton scattering events are directly sensitive to the correlations between two partons inside a proton and can answer fundamental questions on the connections between the proton constituents. In this chapter, the different types of possible correlations, our present knowledge of them, and the processes where they are likely to be important, are introduced and explained. The increasing integrated luminosity at the LHC and the refinements of the theory of double parton scattering, lead to interesting prospects for measuring, or severely constraining, two-parton correlations in the near future.

Cited by 0Open access

Elastic Parton-Parton Scattering from AdS/CFT

Rho, Mannque, Sin, Sang-Jin, Zahed, Ismail · arXiv (Cornell University) · 1999

Using the AdS/CFT correspondence and the eikonal approximation, we evaluate the elastic parton-parton scattering amplitude at large $N$ and strong coupling $g^2N$ in N=4 SYM. We obtain a scattering amplitude with a Regge behavior that unitarizes at large $\sqrt{s}$.

Cited by 0Open access

Can We Measure Parton-Parton Cross Sections?

James D. Bjorken · Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields · 1973

Multiple-core production in hadron-hadron collisions directly measures (in the context of the parton model) differential cross sections for parton-parton collisions. To obtain \ensuremath{\sim}20% accuracy in reconstruction of the parton-parton kinematics requires transverse momentum of the cores \ensuremath{\gtrsim} 5 GeV/c. Experiments at NAL as well as the CERN ISR appear feasible. What might be learned from such studies is discussed.

Cited by 37Open access

On parton showers and multi parton interaction

Driesch, Martin von den · DESY (CERN, DESY, Fermilab, IHEP, and SLAC) · 2016

In high energy hadron-hadron collisons (like for example at LHC) Drell Yan processes are important. For a precise determination of the inclusive crosssection higher order calculations must be taken into account. In the region of phase space near threshold (where soft gluon emission dominates) largedouble logarithmic corrections become important. Thus it is necessary to perform a resummation to all orders in perturbation theory. In this thesiswe analyze the energy fraction in Drell Yan processes. For that we apply a new parton shower formalism that was originally developed in [1]. It willbe shown that the result is equivalent (under certain conditions) to a result given in [2] where the distribution of the energy fraction has been derived by standard resummation techniques. The goal is to confirm the reliability of this new formalism. Further also a comparison with the Monte Carlo eventgenerator PYTHIA will be done.We further investigate a jet algorithm that should detect multi parton interactions. It will be shown that this algorithm works for an idealised casebut that it cannot detect multi parton interaction in a realistic scenario.

Cited by 0Open access

Parton Shower based on TMD parton distributions

Schmitz, Melanie, Hautmann, Francesco, Jung, Hannes et al. · DESY (CERN, DESY, Fermilab, IHEP, and SLAC) · 2019

We present a parton shower based on Transverse Momentum Dependent (TMD)parton distributions obtained with the Parton Branching method. We investigatehow well the TMD parton shower reproduces the TMD parton distributions.Applications of the TMD parton shower to LHC processes will be presented.

Cited by 0

On parton showers and multi parton interaction

M. von den Driesch · DESY Publication Database (PUBDB) (Deutsches Elektronen-Synchrotron) · 2016

In high energy hadron-hadron collisons (like for example at LHC) Drell Yan processes are important. For a precise determination of the inclusive cross section higher order calculations must be taken into account. In the region of phase space near threshold (where soft gluon emission dominates) large double logarithmic corrections become important. Thus it is necessary to perform a resummation to all orders in perturbation theory. In this thesis we analyze the energy fraction in Drell Yan processes. For that we apply a new parton shower formalism that was originally developed in [1]. It will be shown that the result is equivalent (under certain conditions) to a result given in [2] where the distribution of the energy fraction has been derived by standard resummation techniques. The goal is to confirm the reliability of this new formalism. Further also a comparison with the Monte Carlo event generator PYTHIA will be done. We further investigate a jet algorithm that should detect multi parton interactions. It will be shown that this algorithm works for an idealised case but that it cannot detect multi parton interaction in a realistic scenario. In hochenergetischen Hadron-Hadron Kollisionen (wie z.B. am LHC) sind Drell Yan Prozesse wichtig. Fur eine prazise Bestimmung des inklusiven Wirkungsquerschnittes mussen Rechnungen hoherer Ordnung berucksichtigt werden. In der Region nahe an der Grenze des Phasenraumes (wo weiche Gluonenemission dominiert) werden grose doppelte Logarithmen wichtig. Es ist daher notwendig, eine Resummation in allen Ordnungen der Storungstheorie durchzufuhren. In dieser Arbeit analysieren wir den Energieanteil in Drell Yan Prozessen. Dafur wenden wir einen neuen Partonschauerformalismus an, der urprunglich in [1] entwickelt wurde. Es wird gezeigt, dass das Resultat unter bestimmten Bedingungen aquivalent zu einem anderen Resultat von [2] ist, wo die Verteilung des Energieanteils mit Standardresummationtechniken hergeleitet wurde. Das Ziel ist, die Zuverlassigkeit des neuen Formalismus zu bestatigen. Desweiteren wird auch ein Vergleich mit dem Monte Carlo Generator PYTHIA gemacht werden. Wir untersuchen desweiteren einen Jetalgorithmus, der Multipartonwechselwirkungen ausfindig machen soll. Es wird gezeigt werden, dass dieser Algorithmus fur ein idealisiertes Szenario funktioniert, aber dass er Multipartonwechselwirkungen nicht in einem realistischen Szenario bestimmen kann.

Cited by 0Open access

Multiple parton interactions and generalized parton distributions

Diehl, M. · DESY (CERN, DESY, Fermilab, IHEP, and SLAC) · 2010

Multi-parton interactionsgenerically take place in hadron-hadron collisions effect averages out in sufficiently inclusive quantities but do affect final state properties estimated to be important for many processes at LHC see e.g.Procs. of the Workshop on HERA and the LHC, 2005 and 2008

Cited by 0Open access

Parton distributions

Petronzio, Roberto · CERN Document Server (European Organization for Nuclear Research) · 1978

Cited by 0

parton, n.

Oxford University Press eBooks · 2023

Cited by 0

Két parton

George Gömöri, Zsuzsa Beney · World Literature Today · 2001

Cited by 0

Parton models

Alison M. Thomson · Durham e-Theses (Durham University) · 1975

We discuss the successes and failures of the naive quark and Parton models and offer a possible remedy for the resonance symmetry versus vertex symmetry dilemma. Using the concept of current and constituent quarks related by a general Melosh-type transformation, we calculate matrix elements for excitation of the baryon octet ground state by weak and electromagnetic currents and find that the theory compares well with experiment except in the low ῲ region. Here some further SU (6) breaking mechanism is necessary for a good fit. An alternative to the current and constituent quarks idea is to attempt a relativistic treatment of quarks, assuming current and constituent quarks to be fundamentally identical. Several models are discussed and a new model for mesons is presented. The solutions are similar to those obtained in other models apart from the inclusion of spin-orbit coupling terms, which have not previously appeared naturally in relativistic wave functions. We calculate some decay widths and find reasonable agreement with the data.

Cited by 0Open access