Exclusive J/Ψ Vector-Meson production in high-energy nuclear collisions: a cross-section determinaton in the Colour Glass Condensate effective field theory and a feasibility study using the STARlight Monte Carlo event generator

Includes bibliographical references.The cross-section calculation for exclusive J /Ψ vector-meson production in ultra-peripheral heavy ion collisions is approached in two ways. First, the setup for a theoretical calculation is done in the context of the Colour Glass Condensate effective field theory. Rapidity-averaged n-point correlators are used to describe the strong interaction part of this process. The JIMWLK equation can be used to predict the energy evolution of a correlator. In order to facilitate practical calculations, an approximation scheme must be employed. The Gaussian Truncation is one such method, which approximates correlators in terms of new 2-point functions. This work takes the first step beyond this truncation scheme by considering higher-order n-point functions in the approximation. An expression for the cross-section is written, which takes parametrised 2- and 4-point correlators as input. This expression can be used as the basis for a full cross-section calculation. The second part of the thesis is a feasibility study using Monte Carlo simulations done by the STARlight event generator. A prediction is made for how many exclusive J /Ψ vector-mesons are expected to be detected by ATLAS in a data set corresponding to 160 μb−1 total integrated luminosity. It is found that the muon reconstruction efficiencies for low pT muons is too poor in ATLAS to do this analysis effectively. On the order of 150 candidate events are expected from all the Pb-Pb collision data collected in 2011. The feasibility study acts as a preliminary investigation for a full cross-section measurement using ATLAS collision data. Once this is completed, it can be compared with the theoretical prediction for the cross-section

JIMWLK and beyond : From concepts to observables

Volume: 112 Host publication title: 6th International Conference on Physics Opportunities at an Electron-Ion ColliderThe Color Glass Condensate and its associated evolution equation, the JIMWLK equation have applications to many observables far beyond totally inclusive observables. The phenomenology is so rich that little has been done to explore beyond scaling behavior of correlators. We show first examples that exemplify the considerations necessary to access additional information both experimentally and theoretically and demonstrate that the Wilson line correlators appearing throughout make it imperative to consistently take into account that one is dealing with correlators of group elements and demonstrate how this imposes physical and phenomenological constraints. Similar considerations apply also to jet observables at finite N-c.Peer reviewe

Initial Stages 2021

The Colour Glass Condensate effective field theory is a useful framework for studying heavy ion collisions at ultra-relativistic energies, such as those reached at the Large Hadron Collider. In this framework, we study the rapidity evolution of Wilson lines that appear explicitly in cross section expressions. The next-to-leading order BK (Balitsky-Kovchegov) equation for the 2-point Wilson line correlator involves 6-point correlators of Wilson lines. These correlators are typically calculated only in the large-Nc limit. I will present a fully analytic calculation of these correlators in the finite-Nc case, using the Gaussian Approximation. We use these results to find the relative importance of finite-Nc corrections to the next-to-leading order (NLO) evolution equation. I will also present some results from our study of the correlators that appear in the NLO BK equation and the equation itself

10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions

The Colour Glass Condensate effective field theory is a useful framework for studying heavy ion collisions at ultrarelativistic energies, such as those reached at the Large Hadron Collider at CERN. In this framework, we study the rapidity evolution of Wilson lines that appear explicitly in cross section expressions. The next-to-leading order BK (Balitsky-Kovchegov) equation for the 2-point Wilson line correlator involves 6-point correlators of Wilson lines. These correlators are typically calculated only in the large-Nc limit. I will present a fully analytic calculation of these correlators in the finite Nc case, using the Gaussian Truncation. We use these results to find the relative importance of finite Nc corrections to the next-to-leading order evolution equation. We show numerically that the finite Nc corrections are negligible, as expected

Nonlinear evolution in the colour glass condensate

The Colour Glass Condensate is used as an effective theory to study Quantum Chromodynamics at high energies in various scattering processes. Several evolution equations are discussed, in particular the JIMWLK (Jalilian-Marian–Iancu– McLerran–Weigert–Leonidov–Kovner) equation. This is studied in two equivalent pictures, namely the Fokker–Planck formalism and the Langevin formalism. From the latter, we show how BFKL (Balitsky–Fadin–Kuraev–Lipatov) dynamics emerge in the dilute limit. This is discussed further in Paper [II]. From the Fokker–Planck formalism, we use the Gaussian Approximation scheme to study several different types of correlators of fundamental Wilson lines. The 6-point correlators that appear in the next-to-leading order BK (Balitsky–Kovchegov) equation are calculated – their numerical implementation is covered in Paper [III]. Finally, the Gaussian Approximation is extended as a means to derive an evolution equation for the so-called odderon. Simple correlators are also calculated to see how their parametric equations are modified. The extended approximation scheme and the numerical implementation of the odderon are studied further in Paper [I].Kvanttiväridynamiikan ilmiöitä eri sirontaprosesseissa kuvataan värilasikondensaatiksi kutsutulla efektiivisellä kenttäteorialla. Tutkimuksen kohteena ovat erilaiset evoluutioyhtälöt, erityisesti JIMWLK (Jalilian-Marian–Iancu–McLerran– Weigert–Leonidov–Kovner) -yhtälö. JIMWLK-yhtälöä tutkitaan kahdesta eri lähestymistavasta, kirjoittaen se joko Fokker–Planck-muotoon tai Langevin-yhtälöksi. Lähtien yhtälön Langevin-muodosta osoitetaan, että heikon vuorovaikutuksen rajalla siitä voidaan johtaa BFKL (Balitsky–Fadin–Kuraev–Lipatov) -dynamiikka kuvaava yhtälö. Tätä käsitellään tarkasti artikkelissa [II]. Toisaalta Fokker–Planckmuotoa käytetään laskemaan fundamentaaliesityksen Wilson viivojen korrelaattoreita soveltaen Gaussista approksimaatiota. Väitöskirjassa lasketaan sellaiset 6-pistekorrelaattorit, joita tarvitaan BK (Balitsky–Kovchegov) -evoluutioyhtälön ratkaisemiseen alinta seuraavassa kertaluvussa. Analyyttiset tulokset ja niiden numeerinen toteutus on raportoitu artikkelissa [III]. Gaussista approksimaatiota laajentaen johdetaan myös evoluutioyhtälö niin kutsutulle odderonille ja määritetään, miten odderon-kontribuutio vaikuttaa Wilsonin viivojen korrelaattoreiden lausekkeisiin. Näin johdetut korrelaattorit ja niiden numeerinen toteutus on esitetty artikkelissa [I]

JIMWLK and beyond: From concepts to observables

The Color Glass Condensate and its associated evolution equation, the JIMWLK equation have applications to many observables far beyond totally inclusive observables. The phenomenology is so rich that little has been done to explore beyond scaling behavior of correlators. We show first examples that exemplify the considerations necessary to access additional information both experimentally and theoretically and demonstrate that the Wilson line correlators appearing throughout make it imperative to consistently take into account that one is dealing with correlators of group elements and demonstrate how this imposes physical and phenomenological constraints. Similar considerations apply also to jet observables at finite Nc