Higher Order Calculations for Low Energy Precision Physics

Nils Hermansson Truedsson

Higher Order Calculations for Low Energy Precision Physics

Bidragets översatta titel : Högre ordningars beräkningar för precisionsfysik vid låga energier

Nils Hermansson Truedsson

Forskningsoutput: Avhandling › Doktorsavhandling (sammanläggning)

185 Nedladdningar (Pure)

Sammanfattning

Denna sammanläggningsavhandling berör beräkningar som behövs för precisionsfysik vid låga energier inom Standardmodellen, särskilt högre ordningars korrektioner. I avhandlingens två första artiklar introduceras beräkningar på ordning p8 i kiral störningsräkning, vilket är en effektiv fältteori för QCD vid låga energier. De sista två artiklarna handlar om myonens anomala magnetiska moment och de hadronbidrag som står för den största delen av osäkerheten i den teoretiska förutsägelsen av nämnda magnetiska moment.

Artikel I: Här beräknas pionens massa och sönderfallskonstant på ordning p8 i kiral störningsräkning. En mindre numerisk studie visar att dessa överensstämmer väl med lägre ordningars beräkningar för fysikaliska kvarkmassor.

Artikel II: I denna artikel härleds Lagrangefunktionen för mesoner på ordning p8 i kiral störningsräkning. Detta görs för två, tre samt ett godtyckligt antal kvarksmaker. Detta görs genom att explicit konstruera alla av symmetrin tillåtna operatorer samt generera alla möjliga relationer mellan dessa. Från detta system av relationer tas därefter en minimal bas fram.

Artikel III: Här undersöks de korrektioner från ändlig-volymapproximationen inom gitterstudier som uppkommer när elektromagnetiska effekter inkluderas till vakuumpolarisationens hadronbidrag. Detta är viktigt för att minska det teoretiska felet på myonens anomala magnetiska moment. Vi visar att ändlig-volymkorrektionerna är mindre än förväntade, och i princip inte behöver korrigeras för givet nuvarande eftersökta precision.

Artikel IV: I denna artikel härleder vi modelloberoende begränsningar för lågenergimodeller av en viss typ av hadronbidrag till myonens magnetiska moment, detta från störningsmässig QCD. Detta görs genom att introducera en operatorproduktexpansion i ett externt elektromagnetiskt fält, vars första term är en kvarkloop och nästa innehåller ett kondensat relaterat till magnetiska egenskaper hos QCD-vakuumet. Detta senare bidrag visas vara undertryckt med nästan en faktor tusen, och är därför försumbart.

Bidragets översatta titel	Högre ordningars beräkningar för precisionsfysik vid låga energier
Originalspråk	engelska
Kvalifikation	Doktor
Tilldelande institution
Handledare	Bijnens, Johan, handledare Rathsman, Johan, Biträdande handledare
Tilldelningsdatum	2019 sep. 20
Förlag	Lund University, Faculty of Science
ISBN (tryckt)	978-91-7895-213-7
ISBN (elektroniskt)	978-91-7895-214-4
Status	Published - 2019

Bibliografisk information

Defence details
Date: 2019-09-20
Time: 10:00
Place: Lundmarksalen, Astronomihuset, Sölvegatan 27, Lund
External reviewer(s)
Name: Pineda, Antonio
Title: Associate Professor
Affiliation: Grup de Física Teòrica, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
---

Ämnesklassifikation (UKÄ)

Subatomär fysik

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Effektiv fältteori, Kiral störningsräkning, Myonens anomala magnetiska moment, Gitter-gaugeteori, Ändlig-volymkorrektioner

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NilsHermanssonTruedssonweb

4 Artikel i vetenskaplig tidskrift

Short-distance constraints for the HLbL contribution to the muon anomalous magnetic moment
Hermansson Truedsson, N., Bijnens, J. & Rodríguez Sánchez, A., 2019 nov. 10, I: Physics Letters B. 798, 134994.
Forskningsoutput: Tidskriftsbidrag › Artikel i vetenskaplig tidskrift › Peer review

Öppen tillgång
Electromagnetic finite-size effects to the hadronic vacuum polarization
Bijnens, J., Harrison, J., Hermansson Truedsson, N., Janowski, T., Juettner, A. & Portelli, A., 2019, I: Physical Review D - Particles, Fields, Gravitation and Cosmology. 100, 1, 014508.
Forskningsoutput: Tidskriftsbidrag › Artikel i vetenskaplig tidskrift › Peer review

Öppen tillgång
The order p ⁸ mesonic chiral Lagrangian
Bijnens, J., Hermansson-Truedsson, N. & Wang, S., 2019, I: Journal of High Energy Physics. 2019, 1, 102.
Forskningsoutput: Tidskriftsbidrag › Artikel i vetenskaplig tidskrift › Peer review

Öppen tillgång

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abstract = "This thesis concerns higher order calculations needed for precision physics in the low energy region of particlephysics. Of the four papers it contains, the first two introduce calculations at order p8 in the power countingof chiral perturbation theory, which is an effective field theory of QCD at low energies. The remaining twopapers concern the hadronic contributions to the muon anomalous magnetic moment, or muon g − 2, which areresponsible for the main uncertainty in the theoretical prediction of the quantity.Paper I. The pion mass and decay constant are calculated at order p8 within two-flavour chiral perturbationtheory. A small numerical study of the quark mass dependence is performed, and there is good agreement withlower order results at the physical point.Paper II. The order p8 mesonic chiral Lagrangian is derived for two, three as well as a general number of flavours.This is done by explicitly creating all operators allowed by the relevant symmetries, and finding a minimal basis ofoperators. Special cases where some of the external fields are set to zero are also considered.Paper III. The finite volume effects from the next-to-leading order electromagnetic corrections to the hadronicvacuum polarisation are here calculated in QEDL. This is needed for precision calculations of the muon g − 2on the lattice. The analytic results are compared to lattice simulations as well as numerical lattice perturbationtheory. There is good agreement between the methods, and it is found that the electromagnetic corrections aresuppressed to such an extent that they for moderately sized lattices and pion masses in principle can be neglectedfor the currently sought precision on the hadronic vacuum polarisation.Paper IV. Short-distance constraints on the hadronic light-by-light contribution to the muon g − 2 are herederived. Such constraints are useful for the matching of hadronic models valid at low energies to the high energyregion. In particular, the 4-point function entering into the hadronic light-by-light piece is calculated as a 3-pointfunction in the presence of an external electromagnetic field. We show that the quark loop is the first term in anoperator product expansion, and also consider the next term containing the condensate ⟨q σαβ q⟩ which is relatedto the magnetic susceptibility of the QCD vacuum. This latter contribution is found to be negligible due to thesuppression in quark masses and sizes of the condensates.",

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N2 - This thesis concerns higher order calculations needed for precision physics in the low energy region of particlephysics. Of the four papers it contains, the first two introduce calculations at order p8 in the power countingof chiral perturbation theory, which is an effective field theory of QCD at low energies. The remaining twopapers concern the hadronic contributions to the muon anomalous magnetic moment, or muon g − 2, which areresponsible for the main uncertainty in the theoretical prediction of the quantity.Paper I. The pion mass and decay constant are calculated at order p8 within two-flavour chiral perturbationtheory. A small numerical study of the quark mass dependence is performed, and there is good agreement withlower order results at the physical point.Paper II. The order p8 mesonic chiral Lagrangian is derived for two, three as well as a general number of flavours.This is done by explicitly creating all operators allowed by the relevant symmetries, and finding a minimal basis ofoperators. Special cases where some of the external fields are set to zero are also considered.Paper III. The finite volume effects from the next-to-leading order electromagnetic corrections to the hadronicvacuum polarisation are here calculated in QEDL. This is needed for precision calculations of the muon g − 2on the lattice. The analytic results are compared to lattice simulations as well as numerical lattice perturbationtheory. There is good agreement between the methods, and it is found that the electromagnetic corrections aresuppressed to such an extent that they for moderately sized lattices and pion masses in principle can be neglectedfor the currently sought precision on the hadronic vacuum polarisation.Paper IV. Short-distance constraints on the hadronic light-by-light contribution to the muon g − 2 are herederived. Such constraints are useful for the matching of hadronic models valid at low energies to the high energyregion. In particular, the 4-point function entering into the hadronic light-by-light piece is calculated as a 3-pointfunction in the presence of an external electromagnetic field. We show that the quark loop is the first term in anoperator product expansion, and also consider the next term containing the condensate ⟨q σαβ q⟩ which is relatedto the magnetic susceptibility of the QCD vacuum. This latter contribution is found to be negligible due to thesuppression in quark masses and sizes of the condensates.

AB - This thesis concerns higher order calculations needed for precision physics in the low energy region of particlephysics. Of the four papers it contains, the first two introduce calculations at order p8 in the power countingof chiral perturbation theory, which is an effective field theory of QCD at low energies. The remaining twopapers concern the hadronic contributions to the muon anomalous magnetic moment, or muon g − 2, which areresponsible for the main uncertainty in the theoretical prediction of the quantity.Paper I. The pion mass and decay constant are calculated at order p8 within two-flavour chiral perturbationtheory. A small numerical study of the quark mass dependence is performed, and there is good agreement withlower order results at the physical point.Paper II. The order p8 mesonic chiral Lagrangian is derived for two, three as well as a general number of flavours.This is done by explicitly creating all operators allowed by the relevant symmetries, and finding a minimal basis ofoperators. Special cases where some of the external fields are set to zero are also considered.Paper III. The finite volume effects from the next-to-leading order electromagnetic corrections to the hadronicvacuum polarisation are here calculated in QEDL. This is needed for precision calculations of the muon g − 2on the lattice. The analytic results are compared to lattice simulations as well as numerical lattice perturbationtheory. There is good agreement between the methods, and it is found that the electromagnetic corrections aresuppressed to such an extent that they for moderately sized lattices and pion masses in principle can be neglectedfor the currently sought precision on the hadronic vacuum polarisation.Paper IV. Short-distance constraints on the hadronic light-by-light contribution to the muon g − 2 are herederived. Such constraints are useful for the matching of hadronic models valid at low energies to the high energyregion. In particular, the 4-point function entering into the hadronic light-by-light piece is calculated as a 3-pointfunction in the presence of an external electromagnetic field. We show that the quark loop is the first term in anoperator product expansion, and also consider the next term containing the condensate ⟨q σαβ q⟩ which is relatedto the magnetic susceptibility of the QCD vacuum. This latter contribution is found to be negligible due to thesuppression in quark masses and sizes of the condensates.

KW - Effective Field Theory, Chiral Perturbation Theory, The Muon Anomalous Magnetic Moment, Lattice Gauge Theory, Finite Volume Effects

KW - Fysicumarkivet A:2019:Hermansson

KW - Effektiv fältteori, Kiral störningsräkning, Myonens anomala magnetiska moment, Gitter-gaugeteori, Ändlig-volymkorrektioner

M3 - Doctoral Thesis (compilation)

SN - 978-91-7895-213-7

PB - Lund University, Faculty of Science

ER -

Higher Order Calculations for Low Energy Precision Physics

Sammanfattning

Bibliografisk information

Ämnesklassifikation (UKÄ)

Fria nyckelord

Tillgång till dokument

Fingeravtryck

Forskningsoutput

Short-distance constraints for the HLbL contribution to the muon anomalous magnetic moment

Electromagnetic finite-size effects to the hadronic vacuum polarization

The order p 8 mesonic chiral Lagrangian

Citera det här

The order p ⁸ mesonic chiral Lagrangian