Lattice phenomenology of minimal walking technicolor

As results from the Large Hadron Collider (LHC) begin to shed light on the physics of the electroweak scale, which has been of primary interest to theorists for many years, we have entered a phase where critical judgement of the many models of electroweak symmetry breaking (EWSB) that have been developed in recent years will be possible. As this process continues, those models which are not additionally constrained by emerging data attract increased scrutiny and interest. In this respect, technicolor models, in which EWSB occurs dynamically through the spontaneous chiral symmetry breaking in a new strongly coupled sector, are the subject of growing research activity. The focus of this work is a program of investigation of Minimal Walking Technicolor (MWT), a candidate theory for the new strongly coupled sector of a model of dynamical EWSB using Lattice Gauge Theory (LGT) techniques. We have performed an improved comprehensive study of mesonic spectral observables within MWT, with emphasis on nite volume e ects arising from nite temporal and spatial boundaries. Our results clarify the role of nite volume e ects in such studies, while con rming the near-conformal behaviour of the theory in the infra-red, and indicating a relatively small value of the mass anomalous dimension, in agreement with other studies. We also describe a calculation of the leading order hadronic vacuum polarisation contribution to the anomalous magnetic moment of the muon from a lattice simulation of 2+1 avour lattice QCD using Domain Wall Fermions (DWF). We investigate in detail a number of systematic uncertainties involved in this calculation, determining how to e ectively bring them under control, and obtain a result in close agreement with previous determinations from LGT studies, from calculations based on independent experimental data, and from experimental measurements. We present a preliminary calculation of the contribution to the electroweak S parameter from MWT, using a mixed-action simulation involving the DWF action used for the valence sector combined with gauge con gurations generated using the Wilson fermion action for sea quarks

Improved Lattice Spectroscopy of Minimal Walking Technicolor

We present a numerical study of spectroscopic observables in the SU(2) gauge theory with two adjoint fermions using improved source and sink operators. We compare in detail our improved results with previous determinations of masses that used point sources and sinks and we investigate possible systematic effects in both cases. Such comparison enables us to clearly assess the impact of a short temporal extent on the physical picture, and to investigate some effects due to the finite spatial box. While confirming the IR-conformal behaviour of the theory, our investigation shows that in order to make firm quantitative predictions, a better handle on finite size effects is needed.Comment: 33 pages, 30 figures, 18 table

Mass corrections in string theory and lattice field theory

Kaluza-Klein compactifications of higher dimensional Yang-Mills theories contain a number of four dimensional scalars corresponding to the internal components of the gauge field. While at tree-level the scalar zero modes are massless, it is well known that quantum corrections make them massive. We compute these radiative corrections at 1-loop in an effective field theory framework, using the background field method and proper Schwinger-time regularization. In order to clarify the proper treatment of the sum over KK--modes in the effective field theory approach, we consider the same problem in two different UV completions of Yang-Mills: string theory and lattice field theory. In both cases, when the compactification radius $R$ is much bigger than the scale of the UV completion ($R \gg \sqrt{\alpha'},a$), we recover a mass renormalization that is independent of the UV scale and agrees with the one derived in the effective field theory approach. These results support the idea that the value of the mass corrections is, in this regime, universal for any UV completion that respects locality and gauge invariance. The string analysis suggests that this property holds also at higher loops. The lattice analysis suggests that the mass of the adjoint scalars appearing in $\mathcal N=2,4$ Super Yang-Mills is highly suppressed due to an interplay between the higher-dimensional gauge invariance and the degeneracy of bosonic and fermionic degrees of freedom.Comment: 27 page

Lattice Determination of the Hadronic Contribution to the Muon g−2g-2 using Dynamical Domain Wall Fermions

We present a calculation of the leading order hadronic contribution to the anomalous magnetic moment of the muon for a dynamical simulation of 2+1 flavour QCD using domain wall fermions. The electromagnetic 2-point function is evaluated on the RBC-UKQCD lattice gauge configurations and this is fitted to a continuous form motivated by models of vector dominance. We determine a robust and reliable technique for performing this fit, allowing us to extract the most accurate results possible from our ensembles. This combined with data at very light quark masses produces the result a_\mu^{(2)had}=641(33)(32) x 10^{-10} at the physical point, where the first uncertainty is statistical, and the second is an estimate of systematics, which is in agreement with previous results. We outline various methods by which this calculation can and will be improved in order to compete with the accuracy of alternative techniques of deducing this quantity from experimental scattering data.Comment: 18 pages, 1

Lattice phenomenology of minimal walking technicolor

As results from the Large Hadron Collider (LHC) begin to shed light on the physics of the electroweak scale, which has been of primary interest to theorists for many years, we have entered a phase where critical judgement of the many models of electroweak symmetry breaking (EWSB) that have been developed in recent years will be possible. As this process continues, those models which are not additionally constrained by emerging data attract increased scrutiny and interest. In this respect, technicolor models, in which EWSB occurs dynamically through the spontaneous chiral symmetry breaking in a new strongly coupled sector, are the subject of growing research activity. The focus of this work is a program of investigation of Minimal Walking Technicolor (MWT), a candidate theory for the new strongly coupled sector of a model of dynamical EWSB using Lattice Gauge Theory (LGT) techniques. We have performed an improved comprehensive study of mesonic spectral observables within MWT, with emphasis on nite volume e ects arising from nite temporal and spatial boundaries. Our results clarify the role of nite volume e ects in such studies, while con rming the near-conformal behaviour of the theory in the infra-red, and indicating a relatively small value of the mass anomalous dimension, in agreement with other studies. We also describe a calculation of the leading order hadronic vacuum polarisation contribution to the anomalous magnetic moment of the muon from a lattice simulation of 2+1 avour lattice QCD using Domain Wall Fermions (DWF). We investigate in detail a number of systematic uncertainties involved in this calculation, determining how to e ectively bring them under control, and obtain a result in close agreement with previous determinations from LGT studies, from calculations based on independent experimental data, and from experimental measurements. We present a preliminary calculation of the contribution to the electroweak S parameter from MWT, using a mixed-action simulation involving the DWF action used for the valence sector combined with gauge con gurations generated using the Wilson fermion action for sea quarks.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Improved Spectroscopy of Minimal Walking Technicolor

We present an improved study of spectroscopic observables in the $SU(2)$ Yang-Mills theory with two adjoint fermions. We make an improvement on the precision of previous results which clarify the scale of finite volume effects present. This analysis adds to the evidence for near-conformal dynamics of this theory, while indicating a preference for a low anomalous mass dimension of the massless theory