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Flavourphysik im Standardmodell und dessen Erweiterungen

English title Flavour physics in the standard model and its extensions
Applicant Greub Christoph
Number 163154
Funding scheme Project funding
Research institution Institut für Theoretische Physik Universität Bern
Institution of higher education University of Berne - BE
Main discipline Theoretical Physics
Start/End 01.11.2015 - 31.10.2017
Approved amount 363'684.00
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Keywords (7)

SUSY contributions to rare decays; rare B-decays; Determination of CKM matrix elements; renormalization group improvements; effective field theory; QCD corrections to electroweak processes; new physics contributions to flavour observables

Lay Summary (German)

Lead
Die Berechnung eines seltenen Zerfalls eines B-Mesons soll im Rahmen des Standardmodells systematisch verfeinert werden. Zudem werden wir im Standardmodell einen wichtigen Hintergrundprozess zu einem seltenen Zerfall des Muons berechnen. Die beiden genannten seltenen Prozesse sind interessant, weil sie sehr sensitiv sind auf neue Physik. Zudem werden wir verschiedene weitere Zerfallsprozesse von B-Mesonen im Rahmen des minimalen supersymmetrischen Standardmodells (MSSM) untersuchen, um gewisse zentrale Parameter dieses Modells besser bestimmen zu können.
Lay summary

In diesem Projekt geht es um "seltene'' Zerfälle von Leptonen und von schweren Quarks, insbesondere dem b-quark. Das Wort "selten'' bedeutet, dass es sich um Prozesse handelt, die im Rahmen des Standardmodells (SM) stark unterdrückt sind, weil sie dort erst auf dem 1-loop Niveau induziert werden. In vielen Erweiterungen des SM können im loop neue schwere Teilchen propagieren, welche zu zusätzlichen Beiträgen in den Zerfallsraten führen. Um tatsächlich Abweichungen vom SM etablieren zu können, sind sehr genaue Berechnungen notwendig.

In den zwei Unterprojekten A) und B) verfeinern wir die SM-Rechnungen für die Verzweigungsverhältnisse 
b -> s gamma gamma und mu^+ -> e^+ (e^+ e^-) nu_e nu_mu, indem wir Techniken verwenden wie z.B. die Zerlegung des Zerfallsamplituden in Masterintegrale. In den zwei Unterprojekten C) und E) geht es um die Berechnung von mehreren Observablen in der B-Meson Physik in supersymmetrischen Erweiterung des SM. Diese Unterprojekte zielen darauf ab, ein besseres Verständnis über die Struktur der Fermionen und deren skalaren Partnerteilchen zu gewinnen. Die Bearbeitung der Unterprojekte C) und E) wird zu genaueren Einschränkungen der Parameter führen. In einem weiteren Unterprojekt D) betrachten wir eine ganze Klasse von Theorien, welche sich im Niederenergiebereich auf ein erweitertes Standardmodell reduzieren. Dieses erweiterte Modell besteht aus dem gewöhnlichen SM und aus einer Liste von Operatoren der Dimension 6, welche aus SM Feldern zusammengesetzt sind und welche invariant sind unter der Standardmodell-Eichgruppe. Ziel ist es, die Gewichte (Wilson-Koeffizienten) dieser Operatoren festzulegen durch Vergleichen von geeigneten gemessenen Observablen mit deren theoretischen Voraussagen.

 

 

Direct link to Lay Summary Last update: 03.11.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
B physics Beyond the Standard Model at One Loop: Complete Renormalization Group Evolution below the Electroweak Scale
Aebischer Jason, Fael Matteo, Greub Christoph, Virto Javier (2017), B physics Beyond the Standard Model at One Loop: Complete Renormalization Group Evolution below the Electroweak Scale, in JHEP, 09, 158-158.
Improved analysis of the (O7, O7) contribution to ¯ B → X s γ γ at O(αs)
Asatrian H. M., Greub C., Kokulu A. (2017), Improved analysis of the (O7, O7) contribution to ¯ B → X s γ γ at O(αs), in Phys. Rev., D95(5), 053006-053006.
Next-to-leading order prediction for the decay μ→e(e+e−)νν-
Fael M., Greub C. (2017), Next-to-leading order prediction for the decay μ→e(e+e−)νν-, in JHEP, 01, 084-084.
The MSSM without Gluinos; an Effective Field Theory for the Stop Sector
Aebischer Jason, Crivellin Andreas, Greub Christoph, Yamada Youichi (2017), The MSSM without Gluinos; an Effective Field Theory for the Stop Sector, in Eur. Phys. J., C77(11), 740-740.
(O8, O8) contribution to B → X s γ γ at O (αs)
Asatrian H. M., Greub C., Kokulu A. (2016), (O8, O8) contribution to B → X s γ γ at O (αs), in Phys. Rev., D93(1), 014037-014037.
1-Loop Matching of gauge invariant dim-6 operators for B decays
Aebischer Jason, Crivellin Andreas, Fael Matteo, Greub Christoph (2016), 1-Loop Matching of gauge invariant dim-6 operators for B decays, in Proceedings, 16th International Conference on B-Physics at Frontier Machines (BEAUTY 2016): Marseill, BEAUTY2016, 064-064.
Matching of gauge invariant dimension-six operators for b → s and b → c transitions
Aebischer Jason, Crivellin Andreas, Fael Matteo, Greub Christoph (2016), Matching of gauge invariant dimension-six operators for b → s and b → c transitions, in JHEP, 05, 037-037.
Precision tests via radiative μ and τ leptonic decays
Fael Matteo, Passera Massimo (2016), Precision tests via radiative μ and τ leptonic decays, in Proceedings, 12th International Symposium on Radiative Corrections (Radcor 2015) and LoopFest XIV (R, RADCOR2015, 091-091.
Radiative τ leptonic decays and the possibility to determine the τ dipole moments
Fael Matteo (2016), Radiative τ leptonic decays and the possibility to determine the τ dipole moments, in Proceedings, Workshop on Flavour changing and conserving processes 2015 (FCCP2015): Anacapri, Capri , 118, 01012-01012.

Collaboration

Group / person Country
Types of collaboration
M. Misisak (University of Warsaw) Poland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
M. Passera (INFN Padova) Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
A. Crivellin (CERN) Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
A. Yeghiazaryan (Yerevan Physics Institute) Armenia (Europe)
- in-depth/constructive exchanges on approaches, methods or results
A. Ali (DESY) Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Y. Yamada Japan (Asia)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
H. Asatrian (Yerevan Physics Institute) Armenia (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
U. Nierste (Karlsruhe Inst. of Technology,KIT)) Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
ITP Univ. Bern Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Physics of the Standard Model and Beyond Talk given at a conference owards next-to-leading logarithmic predictions for the decay B -> X_s gamma gamma 25.09.2017 Tbilisi State University, Georgia Greub Christoph;
15th Conference on Flavor Physics and CP Violation (FPCP 2017) Poster B physics beyond the Standard Model at one loop 05.06.2017 Prag, Czech Republic Fael Matteo;
PSI2016 - Physics of fundamental Symmetries and Interactions Talk given at a conference NLO prediction for μ → eννγ and μ → eeeνν decays in the SM 17.10.2016 Villigen, Switzerland Fael Matteo;
Standford Linear Accelerator Center (SLAC), theory group Individual talk Towards NLL in B -> X_s gamma gamma and about tree-level contributions to B -> X_d gamma 27.07.2016 Stanford, United States of America Greub Christoph;
CLFV2016 - 2nd International Conference on Charged Lepton Flavor Violation Poster NLO corrections to μ→eννγ and μ→eeeνν decays in the SM 20.06.2016 Charlottesville, Virginia, United States of America Fael Matteo;
PLANCK 2016 Talk given at a conference NLO SQCD corrections to the decay of top-squarks to charm and neutralino 23.05.2016 Valencia, Spain Aebischer Jason;
BEAUTY 2016 Talk given at a conference Matching of gauge invariant dimension 6 operators for b->s and b->c transitions 01.05.2016 Marseille, France Aebischer Jason;
SCALARS 2015 Talk given at a conference NLO SQCD corrections to the decay of top-squarks to charm and neutralino 03.12.2015 Warschau, Poland Aebischer Jason;


Associated projects

Number Title Start Funding scheme
150057 Physik der schweren Quarks 01.11.2013 Project funding
175449 Flavourphysik im Standardmodell und dessen Erweiterungen 01.11.2017 Project funding
150057 Physik der schweren Quarks 01.11.2013 Project funding

Abstract

This project on flavour physics (in the lepton sector and the quark sector) embraces a major direction of research that will be under investigation at the Institute for Theoretical Physics at the University of Bern. The main focus of this proposal is on multi-loop calculation for flavour observables in the lepton and the quark sector of the Standard Model (SM) and the Minimal Supersymmetric Standard Model (MSSM). The proposal is divided into several subprojects1. Precision calculations in the standard modelA) Determination of the SM mu^+ -> e^+ (e^+ e^-) nu_e \bar{nu}_mu branching ratio at next-to-leading order for the Mu3e experiment at PSIB) Interference contribution of O_{1,2} and O_7 to B -> X_s gamma gamma in the SM2. Precision calculations in the MSSMC) Next-to-leading logarithmic corrections to light stop masses in the MSSM with a scale hierarchyD) Effective field theory analysis of b -> s transitions with gauge invariant dimension 6 operatorsE) Two-loop electroweak contributions to quark-quark-Higgs couplings in the MSSMThe goal of the first part is the precise calculation of the SM contributions to these flavour-changing neutral current (FCNC) processes. This is important in order to identify and quantify possible new physics contributions and/or to obtain more stringent bounds on the flavour parameters.The second part aims at a better understanding of the flavour-structure of the MSSM. On the one hand, this limits the allowed parameter-space of the MSSM which gives important constraints for model building. On the other hand one can correlate the MSSM predictions for rare decays and judge whether the MSSM could explain possible deviations from the SM predictions.
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