Eldorado Collection:http://hdl.handle.net/2003/512020-07-09T09:36:12Z2020-07-09T09:36:12ZMassive two- and three-loop calculations in QED and QCDSchönwald, Kayhttp://hdl.handle.net/2003/383772019-11-14T02:40:46Z2019-11-13T09:01:49ZTitle: Massive two- and three-loop calculations in QED and QCD
Authors: Schönwald, Kay
Abstract: This thesis is devoted to the study of mass effects in higher order radiative corrections within QED
and QCD. The first part of the thesis deals with the process of deep-inelastic scattering. We compute
the full mass dependence of the pure singlet Wilson coefficient in the polarized and unploarized case to next-to-leading order using iterated integrals over square root valued letters. Through explicit expansion in the asymptotic limit we proof the factorization of the heavy Wilson coefficient into massless Wilson coefficient and massive operator matrix element and additionally derive improved asymptotic expressions. We then turn to the calculation of massive operator matrix elements with two masses. We compute missing two-mass contributions to unpolarized operator matrix elements at next-to-next-to-leading order and extend the calculation to polarized operator matrix elements at next-to-leading and next-to-next-to-leading order in the single and two-mass case. For the calculation of these processes we set up new calculational methods.
In the second part of the thesis we deal with QED initial state radiation in electron-positron
annihilation into a neutral vector boson at next-to-next-to-leading order. With the new calculation, which is based on an exact integration of the phase space and a subsequent expansion, we proof the asymptotic factorization of massive external particles for this process and clarify results in the literature.2019-11-13T09:01:49ZProbing the standard model with rare charm decaysBoer, Stefan dehttp://hdl.handle.net/2003/360432017-08-08T02:00:07Z2017-08-07T06:22:03ZTitle: Probing the standard model with rare charm decays
Authors: Boer, Stefan de
Abstract: This thesis comprises a study of rare charm decays in the standard model (SM) and beyond.
Within an effective theory framework, we calculate the SM Wilson coefficients to (partly) next-to-next-to leading logarithmic order in quantumchromodynamics.
The calculation includes matching conditions and the running of the Wilson coefficients in the renormalization group-improved perturbation theory, thereby correcting expressions used in the literature.
Furthermore, a calculation of phenomenological relevant two loop matrix elements of current-current operators is presented.
We work out the phenomenology in the SM for radiative and semileptonic inclusive decays as well as the exclusive decays D -> Pll and D -> V gamma, including non-perturbative effects.
The branching ratios are dominated by resonances, yet we can construct various observables which cleanly probe the SM, e.g. asymmetries, angular observables and lepton flavor violating decays are (approximate) SM null tests.
Beyond the SM physics effects are analyzed model-independently and via leptoquark models, where various constraints and correlations, e.g. through flavor patterns, are worked out.
In addition, we probe the SM by means of the decay Lambda_c -> p gamma, which is accessible at (future) colliders, and investigate the radiative decays in supersymmetric models.2017-08-07T06:22:03ZThree-loop QCD corrections from massive quarks to deep-inelastic structure functions and operator matrix elementsBehring, Arndhttp://hdl.handle.net/2003/351702016-08-05T02:00:10Z2016-08-04T09:40:07ZTitle: Three-loop QCD corrections from massive quarks to deep-inelastic structure functions and operator matrix elements
Authors: Behring, Arnd
Abstract: This thesis discusses higher-order contributions from heavy quarks to inclusive
deep-inelastic lepton-nucleon scattering. In this context, massive operator
matrix elements play an important role: they enter into the heavy flavour Wilson
coefficients through a factorisation relation in the asymptotic limit of large
virtualities. Furthermore, they also enter into the definition of the variable
flavour number scheme for parton distributions.
Here, we present the analytic calculation of of several such massive operator
matrix elements at the 3-loop level in perturbative quantum chromodynamics. In
particular, we review the necessary mathematical and computational methods for
these calculations and give results for the non-singlet and pure-singlet
operator matrix elements including their applications in the structure
functions, sum rules and and the variable flavour number scheme. Through this
calculation we also obtain the pure-singlet and non-singlet anomalous dimensions
at 3-loop order. Moreover, we discuss the calculation of certain representative
Feynman diagrams with ladder and V-topologies, which serve as a testing ground
for the calculational tools. Finally, also all Feynman diagrams of the gluonic
operator matrix element are calculated, which is required in a 3-loop
description of the variable flavour number scheme.2016-08-04T09:40:07ZO(α 3 s) contributions to the heavy flavor Wilson coefficients of the structure function F 2(χ, Q²) at Q² >> m²Wißbrock, Fabian Philipphttp://hdl.handle.net/2003/341192015-08-12T20:16:54Z2015-06-24T11:08:58ZTitle: O(α 3 s) contributions to the heavy flavor Wilson coefficients of the structure function F 2(χ, Q²) at Q² >> m²
Authors: Wißbrock, Fabian Philipp
Abstract: At $O(\alpha_s^3)$ the contribution of a single heavy quark to the unpolarized structure function $F_2(x,Q^2)$ in the asymptotic region $Q^2\gg m^2$ is written as a convolution of the light flavor Wilson coefficents and the process independent massive operator matrix elements. This thesis extends the present description to allow for the presence of two heavy quark flavors and presents the respective renormalization prescription and first analytic results for these contributions. Furthermore the remaining $O(C_{A,F} T_F^2 N_F)$ contributions and various diagrams of more complex topologies have been computed analytically. On the mathematical side different evaluation techniques based on representations in terms of special functions, Mellin-Barnes representations and Hyperlogarithms have been worked out.2015-06-24T11:08:58ZCollider physics in anticipation of new TeV-scale phenomenaSedello, Henninghttp://hdl.handle.net/2003/330042015-08-12T16:45:23Z2014-03-27T12:35:11ZTitle: Collider physics in anticipation of new TeV-scale phenomena
Authors: Sedello, Henning2014-03-27T12:35:11Z3-loop contributions to heavy flavor Wilson coefficients of neutral and charged current DISHasselhuhn, Alexanderhttp://hdl.handle.net/2003/318172015-08-12T23:14:52Z2014-01-13T07:09:23ZTitle: 3-loop contributions to heavy flavor Wilson coefficients of neutral and charged current DIS
Authors: Hasselhuhn, Alexander
Abstract: Die vorliegende Dissertation behandelt die Berechnung höherer Korrekturen zu den Strukturfunktionen der tiefinelastischen Streuung. Insbesondere werden Effekte schwerer Quarks in QCD-Korrekturen auf dem
Drei-Schleifen-Niveau bestimmt. In dem asymtotischen Bereich Q^2 >>m^2 ergeben sich die schweren Wilsonkoeffizienten aus den leichten Wilsonkoeffizienten und den massiven Operatormatrixelementen (OMEs).
Es werden neue Beiträge zu den OMEs A_{gq,Q} und A_{gg,Q} berechnet. Ferner werden Methoden für die computeralgebraische Berechnung von Leiterdiagrammen angegeben, wobei von Darstellungen generalisierter
hypergeometrischer Funktionen und Appell-Funktionen Gebrauch gemacht wird. Hierbei kommen symbolische Summationstechniken zum Einsatz. Für die Berechnung von Graphen mit zwei disjunkten massiven Zyklen werden diese Methoden erweitert um Mellin-Barnes-Integrale und Eigenschaften iterierter Integrale. Schliesslich werden für den Fall
der tiefinelastischen Streuung im geladenen Strom die kompletten Zwei-Schleifen-Korrekturen für die schweren Wilsonkoeffizienten konstruiert und im x- und N-Raum angegeben. Die Ergebnisse sind notwendig für eine präzise Bestimmung der Partondichten (PDFs) und der starken Kopplungskonstante zu Drei-Schleifen-Präzision.; The present thesis presents the calculation of higher order corrections to the structure functions of deep-inelastic scattering.
In particular heavy quark effects in QCD corrections are determined on the 3-loop level. In the asymptotic region Q^2 >> m^2, the heavy flavor Wilson coefficients can be represented in terms of the light flavor Wilson coefficients and the massive operator matrix elements (OMEs). New contributions to the OMEs A_{gq,Q} and A_{gg,Q} are obtained. Furthermore, methods for the computer algebraic computation of ladder diagrams are given, making use of different representations of generalized hypergeometric functions and Appell functions. Here symbolic summation techniques are applied. For the calculation of graphs with two disjoint massive cycles, these methods are altered including Mellin-Barnes integrals and properties of iterated
integrals. Finally, for the process of charged current deep-inelastic scattering, the complete 2-loop corrections to the heavy flavor Wilson coefficients are constructed and given in x-space and Mellin-space.
The results of the thesis are necessary for the precise determination of the parton densities (PDFs) and the strong coupling constant at 3-loop precision.2014-01-13T07:09:23ZProbing Flavor and CP in Decays of Beauty and CharmSchacht, Stefanhttp://hdl.handle.net/2003/304202015-08-12T21:51:25Z2013-07-16T09:02:17ZTitle: Probing Flavor and CP in Decays of Beauty and Charm
Authors: Schacht, Stefan2013-07-16T09:02:17ZMellin moments of heavy flavor contributions to F 2 (x, Q 2 ) at NNLOKlein, Sebastianhttp://hdl.handle.net/2003/265242015-08-13T00:41:12Z2009-11-16T14:13:16ZTitle: Mellin moments of heavy flavor contributions to F 2 (x, Q 2 ) at NNLO
Authors: Klein, Sebastian2009-11-16T14:13:16ZDynamical parton distributions of the nucleon up to NNLO of QCDJiménez Delgado, Pedrohttp://hdl.handle.net/2003/260462015-08-12T20:36:57Z2009-03-12T10:30:08ZTitle: Dynamical parton distributions of the nucleon up to NNLO of QCD
Authors: Jiménez Delgado, Pedro2009-03-12T10:30:08ZThe polarized and unpolarized photon content of the nucleonPisano, Cristianhttp://hdl.handle.net/2003/215802015-08-12T23:55:18Z2005-09-06T05:28:56ZTitle: The polarized and unpolarized photon content of the nucleon
Authors: Pisano, Cristian2005-09-06T05:28:56ZNLO QCD corrections to the polarized photo- and hadroproduction of heavy quarksBojak, Ingohttp://hdl.handle.net/2003/23972015-08-12T23:22:59Z2004-12-06T11:33:12ZTitle: NLO QCD corrections to the polarized photo- and hadroproduction of heavy quarks
Authors: Bojak, Ingo
Abstract: This thesis presents the complete details of our calculation of the next-to-leading order (NLO) QCD corrections to heavy flavor photo- and hadroproduction with longitudinally (circularly) polarized photons and hadrons. The main motivation for investigating these processes is the determination of the polarized gluon density. Corresponding measurements will be available from the COMPASS and RHIC experiments, respectively, in the near future. All methods used in the computation are extensively documented and explained, providing a self-contained introduction to this type of NLO calculations. Some of the employed mathematical tools also may be of general interest, e.g., the series expansion of hypergeometric functions. The relevant parton level results are collected and plotted in the form of scaling functions. However, the simplification of the obtained gluon-gluon virtual contributions has not been completed yet. Thus NLO phenomenological predictions at the hadron level are only given in the case of photoproduction. The theoretical uncertainties of these predictions, in particular with respect to the size of the heavy quark mass, are carefully considered. Also it is shown that cuts on the transverse momentum of the produced heavy flavor can considerably enhance the measured production asymmetries. Finally unpolarized heavy quark production is briefly reviewed in order to derive conditions for a successful extraction of the polarized gluon density from future spin-dependent experimental data.2004-12-06T11:33:12Z