Les effets des opérateurs liés aux anomalies axiale et de trace de QCD et de QED dans les désintégrations faibles des mésons sont analysés dans deux régimes extrêmes: tout d'abord lorsque les densités anomales de gluons et de photons sont générées à courte distance par une boucle de quark lourd, ensuite lorsqu'elles sont générées à longue distance par des corrections fortes associées aux quarks légers u, d et s. A courte distance, l'ensemble des corrections de type pingouin à une interaction effective à quatre quarks arbitraire est obtenu à partir de l'expansion en la masse inverse du propagateur d'un quark lourd plongé dans un champ de jauge classique. Une suppression des effets anomaux est ainsi mise en évidence dans le Modèle Standard. Un nouvel ensemble d'opérateurs de dimension huit décrivant les effets du quark charmé dans les désintégrations des kaons est également établi. A longue distance, les effets anomaux associés aux quarks légers dans les désintégrations faibles hadroniques et radiatives des kaons sont analysés dans le formalisme des Lagrangiens chiraux. Une contribution potentiellement importante de l'opérateur d'anomalie de trace est ainsi mise en évidence. Les implications d'une éventuelle dominance des anomalies sont également étudiées.

In a recent paper we studied the effect of new-physics operators with different Lorentz structures on the semileptonic Λb → Λcτν¯τ decay. This decay is of interest in light of the R(D(∗)) puzzle in the semileptonic B¯ → D(∗)τν¯τ decays. In this work we add tensor operators to extend our previous results and consider both model-independent new physics (NP) and specific classes of models proposed to address the R(D(∗)) puzzle. We show that a measurement of R(Λc) = B[Λb → Λcτν¯τ ]/B[Λb → Λcℓν¯ℓ] can strongly constrain the NP parameters of models discussed for the R(D(∗)) puzzle. We use form factors from lattice QCD to calculate all Λb → Λcτν¯τ observables. The Λb → Λc tensor form factors had not previously been determined in lattice QCD, and we present new lattice results for these form factors here.

Der Autor hat das pastor-Softwarepaket für automatisierte Gitterstörungstheorie im Schrödingerfunktional entwickelt. Das pastor-Paket besteht aus zwei Bausteinen, die die Erzeugung von Vertexfunktionen und Feynmandiagrammen übernehmen. Ausgehend von recht generischen Formulierungen der Gitterwirkungen für Fermionen und Gluonen, die dem Vertexgenerator in symbolischer Form übergeben werden, erzeugt dieser Feynmanregeln zu beliebiger Ordnung in der nackten Kopplung. Dabei kann sowohl ein triviales als auch ein Abelsches Hintergrundfeld verwendet werden. Die vom zweiten Teil von pastor, einem Code-Generator, erzeugten Programme greifen auf den Vertexgenerator zu und berechnen alle Terme der perturbativen Entwicklung für eine Klasse von Schrödingerfunktional-Observablen bis zur Einschleifenordnung. Verbesserungsterme der Ordnung a werden dabei berücksichtigt. Wir werden die für die Funktionen der beiden Teile von pastor relevanten Algorithmen detailliert beschrieben und die Korrektheit unserer Implementierung mit einer Reihe von Vergleichen mit perturbativen und nichtperturbativen Daten belegen. Wir werden darauf die Nützlichkeit von pastor Anhand einiger Beispiele aus dem Abgleich von Heavy Quark Effective Theory mit Quantenchromodynamik demonstrieren. Wir haben unter Anderem eine Einschleifenrechnung zweier Kandidaten für Observablen, die aller Voraussicht nach in Zukunft für den Abgleich verwendet werden, zügig und mit geringem Aufwand durchgeführt. Dies zeigt die Stärken eines Softwarepakets für automatisierte Störungsrechnungen. Unsere Resultate werden als nützliche Richtschnur für zukünftige nichtperturbative Berechnungen dienen. / The author developed the pastor software package for automated lattice perturbation theory calculations in the Schrödinger functional scheme. The pastor code consists of two building blocks, dealing with the generation of Feynman rules and Feynman diagrams respectively. Accepting a rather generic class of lattice gauge and fermion actions, passed to the code in a symbolic form as input, a low level part of pastor will generate Feynman rules to an arbitrary order in the bare coupling with a trivial or an Abelian background field. The second, high level part of pastor is a code generator whose output relies on the vertex generator. It writes programs that evaluate Feynman diagrams for a class of Schrödinger functional observables up to one loop order automatically, the relevant O(a) improvement terms are taken into account. We will describe the algorithms used for implementation of both parts of the code in detail, and provide cross checks with perturbative and non-perturbative data to demonstrate the correctness of our code. We demonstrate the usefulness of the pastor package through various applications taken from the matching process of heavy quark effective theory with quantum chromodynamics. We have e.g. completed a one loop analysis for new candidates for matching observables timely and with rather small effort, highlighting two advantages of an automated software setup. The results that were obtained so far will be useful as a guideline for further non-perturbative studies.

Effective field theories can be used to describe measurements at e⁺e⁻ colliders over a wide kinematic range while allowing reliable error predictions and systematic extensions. We show this in two physical situations. First, we give a factorization formula for the e⁺e⁻ thrust distribution dσ/dτ with thrust T and τ = 1 − T based on soft collinear effective theory. The result is applicable for all τ, i.e. in the peak, tail, and far-tail regions. We present a global analysis of all available thrust distribution data measured at center-of-mass energies Q = 35 to 207 GeV in the tail region, where a two parameter fit to the strong coupling constant α(s)(m(Z)) and the leading power correction parameter Ω₁ suffices. We find α(s)(m(Z)) = 0.1135 ± (0.0002)expt ± (0.0005)hadr ± (0.0009)pert, with x²/dof = 0.91, where the displayed 1-sigma errors are the total experimental error, the hadronization uncertainty, and the perturbative theory uncertainty, respectively. In addition, we consider cumulants of the thrust distribution using predictions of the full spectrum for thrust. From a global fit to the first thrust moment we extract α(s)(m(Z)) and Ω₁. We obtain α(s)(m(Z)) = 0.1140 ± (0.0004)exp ± (0.0013)hadr ± (0.0007)pert which is compatible with the value from our tail region fit. The n-th thrust cumulants for n ≥ 2 are completely insensitive to Ω₁, and therefore a good instrument for extracting information on higher order power corrections, Ω'(n)/Qⁿ, from moment data. We find (˜Ω₂)^1/2 = 0.74 ± (0.11)exp ± (0.09)pert GeV. Second, we study the differential cross section dσ/dx of e⁺e⁻-collisions producing a heavy hadron with energy fraction x of the beam energy in the center-of-mass frame. Using a sequence of effective field theories we give a definition of the heavy quark fragmentation function in the endpoint region x → 1. From the perspective of our effective field theory approach we revisit the heavy quark fragmentation function away from the endpoint and outline how to develop a description of the heavy quark fragmentation function valid for all x. Our analysis is focused on Z-boson decays producing one B-meson. Finally, we will give a short outlook of how we want to apply our approach to determine the leading nonperturbative power corrections of the b-quark fragmentation function from LEP experiments.

Lepton pairs resulting from the decay of heavy flavor mesons are an important tool to probe the hot and dense matter created in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider. Due to their large mass, heavy quarks are produced in the earliest stages of the collision and will, therefore, experience the full evolution of the system. The yield of heavy flavor mesons can be measured through their semi-leptonic decay channel by constructing like-sign and unlike-sign lepton pairs. Cross section measurements in p + p collisions provide a test of perturbative quantum chromodynamics (pQCD) theory in addition to a crucial baseline measurement to study the hot and cold nuclear matter effects present in heavy ion collisions. For the first time, the b¯b cross section in p+p collisions at √s = 500 GeV is measured. The results are based on the yield of high mass, like-sign dimuons measured in the PHENIX muon arm acceptance (1.2 < |y| < 2.2). The extrapolated total cross section is 25.2 ± 3.2 (stat) +11.4 -9.5 µb (sys). The cross section is comparable to pQCD calculation within uncertainties.

Lepton pairs resulting from the decay of heavy flavor mesons are an important tool to probe the hot and dense matter created in nucleus-nucleus collisions at the Relativistic Heavy Ion Collider. Due to their large mass, heavy quarks are produced in the earliest stages of the collision and will, therefore, experience the full evolution of the system. The yield of heavy flavor mesons can be measured through their semi-leptonic decay channel by constructing like-sign and unlike-sign lepton pairs. Cross section measurements in p + p collisions provide a test of perturbative quantum chromodynamics (pQCD) theory in addition to a crucial baseline measurement to study the hot and cold nuclear matter effects present in heavy ion collisions. For the first time, the b¯b cross section in p+p collisions at √s = 500 GeV is measured. The results are based on the yield of high mass, like-sign dimuons measured in the PHENIX muon arm acceptance (1.2 < |y| < 2.2). The extrapolated total cross section is 25.2 ± 3.2 (stat) +11.4 -9.5 µb (sys). The cross section is comparable to pQCD calculation within uncertainties.

Nesta dissertação discutimos a medida RAA desenvolvida para análise de observáveis de colisão núcleo-núcleo (AA), tendo em vista sua implementação em colisões próton-próton (pp). No contexto das colisões hadrônicas de altíssimas energias, o RAA compara quantidade de observáveis duros medidos em colisões AA com a quantidade do mesmo observável em colisões pp. As qualidades destas colisões são descritas pela teoria do modelo de Glauber, em que projeção analítica da produção esperada de quarks pesados (observável duro) é realizada para colisões nucleares por meio da sobreposição de colisões pp independentes. Esta projeção analítica é comparada no RAA à medida de quarks pesados em estado final de colisões AA, e desvios em relação à distribuição de momentos da seção de choque calculada teoricamente são interpretados como decorrentes da presença de plasma de quarks e glúons (PQG) na colisão medida. O plasma de quarks e glúons é o objeto de interesse do campo de estudos em que esta pesquisa se insere. Considerado presente em colisões AA centrais desde 2000, o plasma de quarks e glúons é o estado da matéria mais energético possível, em que os pártons produto da colisão se comportam livremente por breves instantes e sofrem expansão hidrodinâmica. Este processo acontece nos estágios inacessíveis da colisão. Algumas das medidas indiretas que indicam formação de plasma em colisões AA são detectadas em colisões de sistemas pequenos, pp e pA desde 2010. Ainda não foi medida supressão de provas duras no PQG. As tentativas de medir PQG em sistemas pequenos pelo método do RAA tem sido feitas por meio da comparação RpA, também definida pelo modelo de Glauber. Na presente pesquisa buscamos extrapolar o funcionamento do RAA para medidas em colisões pp. Como o núcleo em Glauber é formado por sobreposição de prótons, a resolução da descrição da colisão na teoria é discutida. Além disso verificamos que a concepção de que colisões pp não formam ambiente de PQG é importante para o estabelecimento da comparação RAA. Entendemos que as hipóteses sobre a física de estágios inacessíveis da colisão previstas pela teoria de Glauber são diferentes das hipóteses decorrentes de medidas de coletividade em sistemas pequenos. Propomos alternativamente comparações experimentais simples entre quantidades parecidas medidas em colisões pp que podem conter informações sobre supressão de observáveis duros em colisões pp de alta multiplicidade sem o uso de quantidades teóricas. / This master thesis adresses the measurement RAA, developed for the analysis of nucleus-nucleus (AA) collisions, aiming to implement the measure for proton-proton (pp) collisions. In the context of high energy hadronic collisions, RAA compares hard observables measured in AA collisions with the same observable measured in pp collisions. These collisions traits are described by the Glauber model, where an analitical projection of the expected heavy quark production (hard observable) is calculated through the superimposition of independent pp collisions. In RAA, that analitical projection is compared to the actual final state AA collisions measurements, and deviations with relation to the momentum distribution of the theoriticaly calculated cross section are regarded as arising from interaction of the heavy quark with a quark gluon plasma (QGP) formed in the measured collision. The quark gluon plasma is the fields object of interest in which this reasearch is undertaken. Since 2000, QGP is measured and presumed in central AA colissions.The quark gluon plasma is the most energetic state of nuclear matter, in which partons behave as deconfined matter and undergo hydrodynamic expansion. That happends in the first inaccessible stages of the collisions. Some of the indirect measurements that point to the formation of QGP in AA collisions have been detected small systems, pp and pA, since 2010. Is yet to be measured hard probes PQG supression in these systems. Current attempts to evaluate this supression have been made with the RpA comparison, also defined with the Glauber model. In this study, we attempt to extrapolate the RAA operation to pp collision measurements. As the nucleus in Glauber is modeled as a superimposition of pp collisions, the theory\'s resolutuon in describing AA collisions is discussed. We also notice that the concept of pp collisions not formimg QGP is relevant for RAA comparisons. We appreciate that the theoretical hipothesis on the physics of the inaccessible first stages of collisions as foreseen with the Glauber model are different than the hipothesis that stem from collectivity in small systems. We propose alternatively simple experimental comparisons between similar quantities measured in pp collisions without the use of theoretical quantities.

No description available.

We study the masses of the low-lying charm and bottom mesons within the framework of heavy-hadron chiral perturbation theory. We work to third order in the chiral expansion, where meson loops contribute. In contrast to previous approaches, we use physical meson masses in evaluating these loops. This ensures that their imaginary parts are consistent with the observed widths of the D-mesons. The lowest odd- and even-parity, strange and non-strange mesons provide enough constraints to determine only certain linear combinations of the low-energy constants (LECs) in the effective Lagrangian. We comment on how lattice QCD could provide further information to disentangle these constants. Then we use the results from the charm sector to predict the spectrum of odd- and even-parity of the bottom mesons. The predicted masses from our theory are in good agreement with experimentally measured masses for the case of the odd-parity sector. For the even-parity sector, the $B$-meson states have not yet been observed; thus, our results provide useful information for experimentalists investigating such states. The near degeneracy of nonstrange and strange scalar $B$ mesons is confirmed in our predictions using $\mathrm{HHChPT}$. Finally,we show why previous approaches of using $\mathrm{HHChPT}$ in studying the mass degeneracy in the scalar states of charm and bottom meson sectors gave unsatisfactory results. Interactions between these heavy mesons are treated using effective theories similar to those used to study nuclear forces. We first look at a strongly-interacting channel which produces a bound or virtual state and a dimer state which couples weakly to a weakly-interacting channel to produce a narrow resonance. We also look at the short-range interactions in two channels. We consider two cases: two channels where one has a strong $s$-wave interaction which produces bound or virtual states, and a dimer state which couples weakly to weakly-coupled channels which in turn can produce narrow resonances. For each of these systems, we use well-defined power-counting schemes. The results can be used to investigate resonances in the charmonium and bottomonium systems. We demonstrate how the method can be applied to the $X(3872)$. The widths of the $X(3872)$ for decay processes to $\bar{D}^0 D^{*0}$ and $\bar{D}^0D^0\pi$ are calculated. We use these results to obtain the line shapes of the $X(3872)$ under different assumptions about the nature of this state.