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Title: Two aspects of one loop structure: Unitarity delay in the Standard Model and modular invariance in string theory

Abstract

We study two aspects of one loop structures in quantum field theories which describe two different areas of particle physics: the one loop unitarity behavior of the Standard Model of electroweak interactions and modular invariance of string model theory. Loop expansion has its importance in that it contains quantum fluctuations due to all physical states in the theory. Therefore, by studying the various models to one loop, we can understand how the contents of the theory can contribute to physically measurable quantities and how the consistency at quantum level restricts the physical states of the theory, as well. In the first half of the thesis, we study one loop corrections to the process {ital e}{sup +}{ital e}{sup {minus}} {yields} {ital W}{sup +}{ital W}{sup {minus}}. In this process, there is a delicate unitarity-saving cancellation between s-channel and t-channel tree level Feynman diagrams. If the one loop contribution due to heavy particles corrects the channels asymmetrically, the cancellation, hence unitarity, will be delayed up to the mass scale of these heavy particles. We refer to this phenomena as the unitarity delay effect. Due to this effect, cross section below these mass scales can have significant radiative corrections which may provide an appropriatemore » window through which we can see the high energy structure of the Standard Model from relatively low energy experiments. In the second half, we will show how quantum consistency can restrict the physical states in string theory. 53 refs., 13 figs.« less

Authors:
Publication Date:
Research Org.:
Stanford Linear Accelerator Center, Menlo Park, CA (USA)
Sponsoring Org.:
DOE/ER
OSTI Identifier:
5580440
Report Number(s):
SLAC-349
ON: DE90000889; TRN: 89-025992
DOE Contract Number:
AC03-76SF00515
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ELECTRON-POSITRON INTERACTIONS; STANDARD MODEL; STRING MODELS; CROSS SECTIONS; FEYNMAN DIAGRAM; PARTITION FUNCTIONS; RADIATIVE CORRECTIONS; RIEMANN SPACE; SUPERSYMMETRY; W MINUS BOSONS; W PLUS BOSONS; BOSONS; COMPOSITE MODELS; CORRECTIONS; DIAGRAMS; ELEMENTARY PARTICLES; EXTENDED PARTICLE MODEL; FUNCTIONS; INTERACTIONS; INTERMEDIATE BOSONS; INTERMEDIATE VECTOR BOSONS; LEPTON-LEPTON INTERACTIONS; MATHEMATICAL MODELS; MATHEMATICAL SPACE; PARTICLE INTERACTIONS; PARTICLE MODELS; QUARK MODEL; SPACE; SYMMETRY; UNIFIED GAUGE MODELS; 645400* - High Energy Physics- Field Theory; 645203 - High Energy Physics- Particle Interactions & Properties-Theoretical- Weak Interactions & Properties

Citation Formats

Ahn, C. Two aspects of one loop structure: Unitarity delay in the Standard Model and modular invariance in string theory. United States: N. p., 1989. Web. doi:10.2172/5580440.
Ahn, C. Two aspects of one loop structure: Unitarity delay in the Standard Model and modular invariance in string theory. United States. doi:10.2172/5580440.
Ahn, C. Tue . "Two aspects of one loop structure: Unitarity delay in the Standard Model and modular invariance in string theory". United States. doi:10.2172/5580440. https://www.osti.gov/servlets/purl/5580440.
@article{osti_5580440,
title = {Two aspects of one loop structure: Unitarity delay in the Standard Model and modular invariance in string theory},
author = {Ahn, C.},
abstractNote = {We study two aspects of one loop structures in quantum field theories which describe two different areas of particle physics: the one loop unitarity behavior of the Standard Model of electroweak interactions and modular invariance of string model theory. Loop expansion has its importance in that it contains quantum fluctuations due to all physical states in the theory. Therefore, by studying the various models to one loop, we can understand how the contents of the theory can contribute to physically measurable quantities and how the consistency at quantum level restricts the physical states of the theory, as well. In the first half of the thesis, we study one loop corrections to the process {ital e}{sup +}{ital e}{sup {minus}} {yields} {ital W}{sup +}{ital W}{sup {minus}}. In this process, there is a delicate unitarity-saving cancellation between s-channel and t-channel tree level Feynman diagrams. If the one loop contribution due to heavy particles corrects the channels asymmetrically, the cancellation, hence unitarity, will be delayed up to the mass scale of these heavy particles. We refer to this phenomena as the unitarity delay effect. Due to this effect, cross section below these mass scales can have significant radiative corrections which may provide an appropriate window through which we can see the high energy structure of the Standard Model from relatively low energy experiments. In the second half, we will show how quantum consistency can restrict the physical states in string theory. 53 refs., 13 figs.},
doi = {10.2172/5580440},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Aug 01 00:00:00 EDT 1989},
month = {Tue Aug 01 00:00:00 EDT 1989}
}

Technical Report:

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  • We prove the modular invariance and thus the finiteness of the five-point amplitudes in closed superstrings. The complicated algebra necessary is considerably simplified by making use of the results of Frampton, Moxhay, and Ng for the open superstring.
  • The new features of a supersymmetric standard model in the presence of heavy families are studied. The minimal set of Higgs fields, the desert between the electroweak and the grand unification scale and perturbative values of the dimensionless parameters throughout this region are assumed. Using the numerical as well as the approximate analytic solution of the renormalization group equations, the evolution of all the parameters of the theory are studied in the case of large Yukawa couplings for the fourth family. The desired spontaneous symmetry breaking of the electroweak symmetry takes place only for a rather unnatural choice of themore » initial values of certain mass parameters at the grand unification scale. If it is gravitino mass smaller than 200 GeV the vacuum expectation values of the Higgs fields emerge necessarily in an interplay of the tree level Higgs potential and its quantum corrections and are approximately equal. The qurak masses of the fourth family are roughly 135 GeV, while the mass of the fourth charged lepton has an upper bound of 90 GeV. Further characteristic features of this scenario are one light neutral Higgs field of mass 50 GeV and gluino masses below 75 GeV. If the gravitino mass is higher than 200 GeV one obtains a scaled up version of the well-known three family, heavy top scenario with quark masses between 40 and 205 GeV and all superparticle masses heavier than 150 GeV except the photino, gluino, one chargino and one neutralino. The gauge-invariant theory of the free bosonic open string is generalized to treat closed strings and superstrings. All of these theories can be written as theories of string differential forms defined on suitable spaces. All of the bosonic theories have exactly the same structure; the Ramond theory takes an analogous first-order form. We show explicitly, how to gauge-fix each action to the light-cone gauge and to the Feynman-Siegel gauge.« less
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