Eldorado Collection:
http://hdl.handle.net/2003/51
2024-03-29T06:01:06ZRare radiative charm decays in and beyond the standard model
http://hdl.handle.net/2003/41130
Title: Rare radiative charm decays in and beyond the standard model
Authors: Adolph, Nico
Abstract: This thesis comprises a study of rare radiative |Δc| = |Δu| = 1 transitions within
and beyond the standard model of particle physics. For the 18 three-body decays
D → P1 P2 ɣ with 𝑃 = π, K decay amplitudes are derived using Low’s theorem, QCD
factorization and heavy hadron chiral perturbation theory. Standard model predictions for
branching ratios, CP asymmetries as well as forward-backward asymmetries are determined.
Moreover, the effects of new physics in the coefficients of the electromagnetic dipole
operators are investigated respecting the current constraints. The photon polarization in
Ds→ K1(→ Kπ π) ɣ decays is studied with respect to new physics effects in the dipole
coefficients. Within the standard model, the polarization parameter agrees with the SM-
like partner decay 𝐷+ → 𝐾1 (→ 𝐾π π)) ɣ up to U-spin breaking corrections. The existence
of partner decays allows to construct a null test which does not require precise knowledge
of the hadronic K1 → Kπ π decay. Finally, different ways to test the standard model with
rare radiative decays of charm baryons are discussed. Based on the approximate SU(3)𝐹
symmetry of QCD as well as its subgroups, relations between partner decays are worked
out. Branching ratios, CP asymmetries as well as the photon polarizations are considered
as observables and the potential of new physics effects is estimated. Methods for the
extraction of the photon polarization from two-body decays Bc → B ɣ of polarized charm
baryons as well as from decay chains Bc → B(→ B′ 𝑃 ) ɣ with self-analyzing hyperons 𝐵
are presented.2022-01-01T00:00:00ZExploiting the phenomenology of flavourful Z′ models
http://hdl.handle.net/2003/41120
Title: Exploiting the phenomenology of flavourful Z′ models
Authors: Bause, Rigo
Abstract: This thesis comprises recent studies on extensions of the standard model (SM) involving a heavy
Z’ boson. In the SM, flavour-changing neutral current (FCNC) quark transitions only appear at loop level and are highly suppressed. This puts forward flavourful Z’ models, where the new gauge boson couples non-universally to the known quarks and leptons at tree level. The models are able address the persistent deviations of the SM seen in observables of rare B-meson decays referred to as the
B-anomalies. By supplementing the particle content of the SM with new scalars and vector-like fermions, the occurrence of putative Landau poles present in general Z’ scenarios can be averted. We discuss dedicated models in the context of the B-anomalies that allow for a stable and predictive theory up to the Planck scale. Moreover, flavour rotations also enable FCNC transitions in the charm sector, where the resonance pollution in branching ratios of semileptonic decays demands null test observables sensitive to physics beyond the SM. We investigate effects in such decays and present unique correlations to CP-violating observables in hadronic decays, accessible with future measurements by the LHCb and Belle II experiments. Recent studies involving dineutrino modes are discussed as well. We exploit an interplay between neutrino and charged lepton couplings within the SM effective field theory approach that connects decays of opposite flavour sectors. In doing so, we derive limits on diverse sets of dineutrino branching ratios and find novel tests of lepton universality using data from global fits of the B-anomalies.; Die vorliegende Dissertation umfasst Studien zur Erweiterung des Standardmodells durch ein schweres Z’-Boson. Flavour-verändernde neutrale Ströme (FCNCs) von Quarkübergängen treten im Standardmodell in höheren Ordnungen auf und sind stark unterdrückt. Die Implementation von
Z’-Modellen ermöglicht solche Übergänge auf Baumgraphen-Niveau, induziert durch nicht-universelle Kopplungen an die bekannten Quarks und Leptonen. Dies liefert eine mögliche Erklärung der Diskrepanzen zwischen theoretischer Vorhersage und Messung in Observablen von seltenen B-Meson-Zerfällen, den sogenannten B-Anomalien. Das Auftreten von Landau-Polen in eben solchen Theorien kann durch das Hinzufügen von neuen Teilchen zum Standardmodell-Spektrum abgewendet
werden. In dieser Arbeit untersuchen wir ausgewählte Modelle, die eine direkte Erklärung der
B-Anomalien liefern und zusätzlich eine stabile Vorhersagekraft durch Abwesenheit von Polen und Instabilitäten bis zur Planck-Skala innehaben. Auch in seltenen charm Zerfällen können erhebliche Beträge zu FCNCs durch das Z’-Boson generiert werden. In diesem Sektor spielt das Aufstellen von null tests des Standardmodells, sensitiv zu Effekten neuer Physik, eine besondere Rolle, da unter anderem semi-leptonische Verzweigungsverhältnisse durch die Verunreinigung von auftretenden Resonanzen schwer zugänglich sind. Wir befassen uns deshalb außerdem mit der Erforschung von Effekten neuer Physik in diesen Zerfällen und erarbeiten eindeutige Korrelationen zwischen CP-verletzenden Observablen, welche mit zukünftigen Messungen von den Experimenten LHCb und Belle II überprüft werden können. Wir präsentieren außerdem neue Studien zu Teilchenzerfällen in zwei Neutrinos. Durch das Zusammenspiel zwischen Kopplungen von geladenen Leptonen und Neutrinos unter Zuhilfenahme der effektiven Feldtheorie des Standardmodells bestimmen wir obere Grenzen an eine Vielzahl von Neutrino-Verzweigungsverhältnissen, und entwickeln neue Tests der Lepton-Universalität.2022-01-01T00:00:00Z|Δc| = |Δu| = 1 transitions in and beyond the standard model
http://hdl.handle.net/2003/41012
Title: |Δc| = |Δu| = 1 transitions in and beyond the standard model
Authors: Golz, Marcel
Abstract: This thesis comprises a study of rare semileptonic |Δc|=|Δu|=1 transitions in the Standard Model and beyond. The Standard Model phenomenology of three-body meson decays D→ Pll, as well as three- and four-body charmed baryon decays B0 → B1 (→ B2 π) ll, is analyzed and branching ratios are found to be dominated by resonances. Physics effects beyond the Standard Model are studied model-independently as well as in the framework of leptoquark- and flavorful, anomaly-free Z’-models. Resonance dominance is shown to be overcome or even used as a catalyst in analyses of clean null-test observables, where any signal indicates new physics. Null tests are based on angular observables, CP-conservation, lepton flavor universality and charged lepton flavor conservation. Already a subset of four angular observables in three- and four-body rare charm baryon decays are sufficient to disentangle beyond Standard Model effects in dipole and (axial) vector Wilson coefficients, whereas (semi-)leptonic rare meson decays D→ (P)ll are shown to control (pseudo-)scalar and (pseudo-)tensor effects. A global view on connections between different flavor sectors is put forward in the context of flavor summed dineutrino branching ratios. Indirect tests of lepton flavor universality and charged lepton flavor conservation are presented for the charm sector, where dineutrino modes already pose null tests of the Standard Model. In |Δb|=|Δs|=1 transitions, the first evidence for the violation of lepton flavor universality is found in muon over electron ratios of B-meson branching fractions. Complementing the direct probes, dineutrino modes are shown to test charged lepton flavor indirectly in the correlation of B → Pνν and B → Vνν. Similarly, indirect flavor probes in other quark sectors are also commented on.2022-01-01T00:00:00ZFlavorful new physics models in the light of the B decay anomalies
http://hdl.handle.net/2003/40564
Title: Flavorful new physics models in the light of the B decay anomalies
Authors: Loose, Dennis
Abstract: Current experimental data on the flavor observables R_K and R_K^* shows evidence for a
violation of lepton universality – an essential feature of the Standard Model of particle
physics. Together with several deviations seen in other b -> sµ^+ µ^− observables as well as
R_D and R_D^*, these results constitute the so-called B decay anomalies. In this thesis we
investigate new physics models that provide potential solutions to these anomalies and
put a special emphasis on their flavor structure. To this end, we consider an A4 x U(1)_FN
based flavor symmetry, which addresses the SM flavor puzzle, and study patterns that it
imposes on the couplings of leptoquark models. We find that flavorful leptoquarks provide
good explanations of R_K^(*) , while constraints from rare kaon decays and charged lepton
flavor violating processes are too strong to allow to accommodate the deviations in R_D^(*).
As another consequence of the imposed flavor structure, flavorful leptoquarks are light
enough to be produced at current and future hadron colliders. We compute estimates
for the production cross sections of the S_3 , V_1 and V_3 leptoquarks in different flavor
scenarios, focusing on single production, which is sensitive to the leptoquark coupling
and its flavor structure. We find that future hadron colliders with higher center of mass
energies are needed to cover the full parameter space and determine leptoquark mass
bound for benchmark scenarios.2021-01-01T00:00:00ZFlavorful models for asymptotic safety
http://hdl.handle.net/2003/40279
Title: Flavorful models for asymptotic safety
Authors: Hormigos Feliu, Clara
Abstract: In this thesis we study asymptotically safe models with implications for flavor physics. We show that the Yukawa couplings necessary to generate ultraviolet fixed points could link a new sector to the Standard Model, generating a rich phenomenology. Most prominently, we find that for theories with heavy vector-like leptons and singlet scalars the discrepancies in the anomalous magnetic moments of the electron and the muon can be simultaneously explained without explicitly breaking lepton flavor universality. We study implications for the models at colliders, and propose targeted observables and null tests which exploit the flavor structure of the new sector. We finally show that, in asymptotically safe theories where the Standard Model is extended with an additional U(1) gauge symmetry, large hierarchies in the Yukawa sector can be generated through renormalization group running. Employing non-universal charge assignments, we find that the observed fermion masses and quark mixing patterns can be reproduced to the order of magnitude.; In dieser Arbeit untersuchen wir asymptotisch sichere Modelle mit Implikationen für Flavorphysik. Wir zeigen, dass die Yukawa-Kopplungen, die zur Erzeugung ultravioletter Fixpunkte notwendig sind, einen neuen Sektor mit dem Standardmodell verknüpfen können, wodurch eine reichhaltige Phänomenologie entsteht. Vor allem finden wir heraus, dass für Theorien mit schweren vector-like Leptonen und Singulett-Skalaren die Diskrepanzen in den anomalen magnetischen Momenten des Elektrons und des Myons gleichzeitig erklärt werden können, ohne die Leptonflavoruniversalität explizit zu brechen. Wir untersuchen Implikationen für die Modelle an Collidern und schlagen gezielte Observablen und Nulltests vor, die die Flavorstruktur des neuen Sektors ausnutzen. Schließlich zeigen wir, dass in asymptotisch sicheren Theorien, in denen das Standardmodell um eine zusätzliche U(1)-Eichsymmetrie erweitert wird, durch Renormierungsgruppenlaufen große Hierarchien im Yukawa-Sektor erzeugt werden können. Unter Verwendung von nicht-universellen Ladungen finden wir, dass die beobachteten Fermionenmassen und Quark-Mischungsmuster in der Größenordnung reproduziert werden können2021-01-01T00:00:00ZSynergies of flavor anomalies with top-quark physics in the Standard Model Effective Field Theory and direct searches
http://hdl.handle.net/2003/40278
Title: Synergies of flavor anomalies with top-quark physics in the Standard Model Effective Field Theory and direct searches
Authors: Bißmann, Stefan
Abstract: This thesis comprises a study on opportunities for physics beyond the Standard Model (BSM)
guided by the flavor anomalies. Aiming at linking the top-quark sector of the Standard Model
Effective Field Theory (SMEFT) to the anomalies in b → s transitions, we perform a global fit
to top-quark data detailing on the validity of the SMEFT framework, and highlight benefits
and challenges of combining multiple measurements in a combined fit. To combine top-quark
and beauty data we perform a first joined fit of three SMEFT Wilson coefficients to tt̄γ and
b → sγ data. We work out the steps needed for linking top-quark and B physics within
SMEFT, and demonstrate how the complementarity of both sectors enhances constraints
significantly. Extending our setup, we analyze semileptonic four-fermion operators, which
are of high interest in the context of anomalies seen in b → sμ+μ− data, in a combined fit
to top-quark, Zbb, and B-physics observables using present data as well as future scenarios
of HL-LHC, Belle II, and a future lepton collider. We observe powerful synergies between
top-quark and beauty physics, which open new directions for model-independent searches. To
complement our analysis, we investigate the possibility that BSM physics can be well within
the reach of the LHC while still accommodating the anomalies within the lepton anomalous
magnetic moments and lifting several shortcomings of the Standard Model (SM). The models
are an asymptotically safe extension of the SM featuring potentially light vector-like leptons
and additional scalars with a non-trivial flavor structure. We perform a detailed study of
implications for discovery at the LHC exploiting unique flavor signatures to construct null-
tests of the SM, and find that Run 2 data can be sufficient to detect BSM physics, indicating
that new physics might be just around the corner.; Diese Dissertation beinhaltet eine Studie zur Entdeckung von Physik jenseits des Standard
Modells (BSM) geleitet durch die Flavor-Anomalien. Mit dem Ziel, den Top-Quark Bereich
der Standard Model Effective Field Theory (SMEFT) mit den Anomalien in b → s Übergän-
gen zu verbinden, führen wir zunächst einen globalen Fit an Top-Quark Messungen durch,
in dem wir die Gültigkeit des SMEFT-Ansatzes sowie Vorteile und Herausforderungen, die
in der Kombination verschiedener Datensätze entstehen, diskutieren. Anschließend führen
wir eine erste kombinierte Analyse von Top-Quark und Beauty Daten durch und fitten drei
SMEFT Wilson Koeffizienten an tt̄γ and b → sγ Daten. Wir beschreiben die notwendigen
Schritte für die Analyse und zeigen, wie Unterschiede in der Sensitivität die Resultate deutlich
verbessern. Wir erweitern diese Studie und betrachten semileptonische Operatoren, die im
starken Zusammenhang zu den Anomalien in b → sμ+μ− Messungen stehen, in einem Fit an
Top-Quark, Zbb, und B-Physik Observablen im Kontext aktueller Messungen sowie mehrerer
Zukunftsszenarien für HL-LHC, Belle II, und einem Lepton Collider. Unsere Analyse zeigt
eine starke Verbindung von Top-Quark und Beauty Observablen auf, die neue Möglichkeiten
für modellunabhängige Fits ermöglichen. Um unsere Analyse abzurunden, untersuchen wir
den Fall, dass BSM Physik am LHC produziert werden könnte. Diese neue Physik kann sowohl
die Anomalien in den magnetischen Momenten der Leptonen erklären als auch mehrere Prob-
leme des Standard Modells beheben. Wir betrachten dazu zwei asymptotisch sichere Modelle
mit vektorartigen Leptonen und Skalaren mit einer nicht-trivialen Falvorstruktur und führen
eine detaillierte Analyse für eine Entdeckung am LHC durch. Wir konstruieren Nulltests und
stellen fest, dass der Run 2 Datensatz ausreichen könnte, um BSM Physik zu entdecken.2021-01-01T00:00:00ZFixed points in supersymmetric extensions of the Standard Model
http://hdl.handle.net/2003/39282
Title: Fixed points in supersymmetric extensions of the Standard Model
Authors: Moch, Kevin
Abstract: In this work, we are searching for supersymmetric extensions of the Standard Model (SM) of particle physics which are asymptotically safe. Such models are well-defined at all energy scales and provide hints for the scale at which supersymmetry gets broken. The combination of supersymmetry and asymptotic safety hereby turns out to strongly restrict the space of possible models. Within extensions of the minimal supersymmetric SM (MSSM), we perturbatively find candidates which all have a specific field content and low supersymmetry-breaking scales. For extensions of the MSSM with an extended gauge sector, we find models for which these scales appear at much larger energies. We then investigate whether the perturbatively found models are in agreement with non-perturbative results obtained from superconformal field theories. The exact supersymmetric Novikov-Shifman-Vainshtein-Zakharov beta functions suggest that these models are not asymptotically safe beyond perturbation theory. Finally, we present a model for which the non-perturbative results suggests that the SM can be UV-completed by this model. We also study perturbatively whether the fixed point needed for this UV-completion is physical.2020-01-01T00:00:00ZMassive two- and three-loop calculations in QED and QCD
http://hdl.handle.net/2003/38377
Title: 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.2019-10-15T00:00:00ZProbing the standard model with rare charm decays
http://hdl.handle.net/2003/36043
Title: 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.2017-01-01T00:00:00ZThree-loop QCD corrections from massive quarks to deep-inelastic structure functions and operator matrix elements
http://hdl.handle.net/2003/35170
Title: 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.2016-01-01T00:00:00ZO(α 3 s) contributions to the heavy flavor Wilson coefficients of the structure function F 2(χ, Q²) at Q² >> m²
http://hdl.handle.net/2003/34119
Title: 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.2015-01-01T00:00:00ZCollider physics in anticipation of new TeV-scale phenomena
http://hdl.handle.net/2003/33004
Title: Collider physics in anticipation of new TeV-scale phenomena
Authors: Sedello, Henning2014-03-27T00:00:00Z3-loop contributions to heavy flavor Wilson coefficients of neutral and charged current DIS
http://hdl.handle.net/2003/31817
Title: 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.2014-01-13T00:00:00ZProbing Flavor and CP in Decays of Beauty and Charm
http://hdl.handle.net/2003/30420
Title: Probing Flavor and CP in Decays of Beauty and Charm
Authors: Schacht, Stefan2013-07-16T00:00:00ZMellin moments of heavy flavor contributions to F 2 (x, Q 2 ) at NNLO
http://hdl.handle.net/2003/26524
Title: 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 QCD
http://hdl.handle.net/2003/26046
Title: 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 nucleon
http://hdl.handle.net/2003/21580
Title: 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 quarks
http://hdl.handle.net/2003/2397
Title: 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.2000-05-22T00:00:00Z