Soft resummation and hard evolution: Renormalization group methods in effective theories and multi scalar models

Joel Oredsson

    Forskningsoutput: AvhandlingDoktorsavhandling (sammanläggning)

    174 Nedladdningar (Pure)


    This thesis is composed out of five papers that deal with various problems in
    theoretical particle physics. While paper I is a precision calculation in an
    effective theory of the Standard Model, paper II to V all deal with beyond the
    Standard Model physics. Paper IV is a manual for the tools developed during our
    work on paper II to V.

    Paper I. We calculate the 2-loop soft function for the transverse momentum
    spectrum of a color-neutral final state in proton collisions in the framework of
    Soft-Collinear-Effective Theory. Also the 2-loop beam functions are derived in
    the same framework by a comparison to other works. This framework relies on
    rapidity renormalization group equations to resum logarithms, which gives an
    improved handling of theoretical uncertainties in the resummation. With our
    result, one can perform next-to-next-leading log resummation of the mentioned

    Paper II. In this paper, we show that there is no need to introduce scalar
    kinetic mixing for models containing several identical scalar fields. This is
    shown by an explicit 1-loop calculation of the renormalization group equations
    using a toy model. The calculation is performed in separate renormalization
    schemes; with and without kinetic mixing. We also derive the renormalization
    scale dependent transformations that relate each of these schemes to one

    Paper III. This paper analyzes how breaking an imposed Z2 symmetry spreads
    during renormalization group evolution of the CP~conserved Two-Higgs-Doublet
    Model. We derive the 2-loop renormalization group equations and perform
    numerical parameter scans of several physical scenarios.

    Paper IV. This is a manual for the software 2HDME that was developed to
    perform the numerical calculations in paper III. The code can evolve any
    Two-Higgs-Doublet Model at 2-loop order and perform many tree-level calculations
    such as masses and oblique parameters, but also tests of stability and

    Paper V. In this paper, we use 2HDME in a similar way to paper III, but
    this time with the CP~violating Two-Higgs-Doublet Model. We also implement a
    calculation of the electron's electric dipole moment that we use to constrain
    the amount of CP~violation. We perform several numerical parameter scans of
    scenarios with different levels of Z2 symmetry breaking.
    • Rathsman, Johan, handledare
    • Bijnens, Johan, Biträdande handledare
    Tilldelningsdatum2019 okt. 25
    ISBN (tryckt)978-91-7895-255-7
    ISBN (elektroniskt)978-91-7895-256-4
    StatusPublished - 2019

    Bibliografisk information

    Defence details
    Date: 2019-10-25
    Time: 10:00
    Place: Rydbergssalen, Fysicum, Sölvegatan 14A, Lund
    External reviewer(s)
    Name: Plehn, Tilman
    Title: Professor
    Affiliation: Heidelberg University, Heidelberg, Germany

    Ämnesklassifikation (UKÄ)

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