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Lepton flavour violation in an effective-field theory approach with dimension 6 operators

English title Lepton flavour violation in an effective-field theory approach with dimension 6 operators
Applicant Signer Adrian
Number 160156
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Theoretical Physics
Start/End 01.04.2015 - 31.03.2018
Approved amount 337'740.00
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All Disciplines (2)

Discipline
Theoretical Physics
Particle Physics

Keywords (4)

Phenomenology; Standard Model effective field theory; Quantum field theory; Lepton-flavour violation

Lay Summary (German)

Lead
Mit der Entdeckung des Higgs Bosons ist der letzte Baustein des Standard Modells experimentell bestätigt worden. Obwohl das Standard Modell ist eine äusserst erfolgreiche Theorie der Teilchenphysik ist, gibt es Phänomene wie Dunkle Materie oder Teilchen-Antiteilchen Asymmetrie, die damit nicht erklärt werden können. Die Suche nach 'Neuer Physik', d.h.. Physik jenseits des Standard Modells ist daher ein zentraler Pfeiler der Forschung in der Teilchenphysik. In diesem Projekt wird eine spezielle Klasse von Prozessen detailliert untersucht, die sehr strikte Tests des Standard Modells erlauben. Insbesondere werden Zerfälle von Leptonen untersucht. Leptonen sind Materieteilchen, die der starken Wechselwirkung nicht unterliegen, und dadurch besonders geeignet sind, um detaillierte theoretische Berechungen mit experimentellen Resultaten zu vergleichen.
Lay summary

Im Standard Modell kommen Leptonen in drei Arten ('Flavours') vor, Elektronen, Muonen und Tau-Leptonen. Diese mischen nicht miteinander, abgesehen von einem vernachlässigbaren Effekt via Neutrinomassen. Insbesondere ist der Zerall eines Muons in ein Elektron und ein Photon im Standard Modell verboten. Würde ein solcher 'Lepton-Flavour-Verletzender' Prozess experimentell nachgewiesen, wäre dies ein klarer Hinweis auf Neue Physik. Dieser und verwandte Muon Zerfälle werden am Paul Scherrer Institut intensiv untersucht. Gleichzeitig gibt es  ähnliche Prozesse, die am Large Hadron Collider am CERN untersucht werden.

Ziel dieses Projektes ist einen einheitliche theoretische Behandlung all dieser Prozesse. Dazu werden allgemeine Erweiterungen des Standard Modelles betrachtet, die mit den wohlbekannten Symmetrien der Natur verträglich sind. Dadurch können Zusammenhänge hergestellt werden zwischen verschiedenen solchen Prozessen, ohne dass man sich auf spezielle Modelle einschränken muss. Allfällige positive Resultate der experimentellen Suche können für Vorhersagen für andere Prozesse benutzt werden. Falls keine Abweichung vom Standard Modell gefunden wird, führt dies zu sehr einschneidenden Bedingungen, die Physik jenseits des Standard Modells erfüllen muss.

 

Direct link to Lay Summary Last update: 13.04.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Low- and high-energy phenomenology of a doubly charged scalar
Crivellin Andreas, Ghezzi Margherita, Panizzi Luca, Pruna Giovanni Marco, Signer Adrian (2019), Low- and high-energy phenomenology of a doubly charged scalar, in Physical Review D, 99(3), 035004-035004.
Fully differential NLO predictions for the radiative decay of muons and taus
Pruna G.M., Signer A., Ulrich Y. (2017), Fully differential NLO predictions for the radiative decay of muons and taus, in Physics Letters B, 452-458.
To $${d}$$ d , or not to $${d}$$ d : recent developments and comparisons of regularization schemes
Gnendiger C., Signer A., Stöckinger D., Broggio A., Cherchiglia A. L., Driencourt-Mangin F., Fazio A. R., Hiller B., Mastrolia P., Peraro T., Pittau R., Pruna G. M., Rodrigo G., Sampaio M., Sborlini G., Bobadilla W. J. Torres, Tramontano F., Ulrich Y., Visconti A. (2017), To $${d}$$ d , or not to $${d}$$ d : recent developments and comparisons of regularization schemes, in The European Physical Journal C, (7), 471-471.
Renormalisation-group improved analysis of μ → e processes in a systematic effective-field-theory approach
Crivellin A., Davidson S., Pruna G. M., Signer A. (2017), Renormalisation-group improved analysis of μ → e processes in a systematic effective-field-theory approach, in Journal of High Energy Physics, (5), 117-117.
Fully differential NLO predictions for the rare muon decay
Pruna G.M., Signer A., Ulrich Y. (2017), Fully differential NLO predictions for the rare muon decay, in Physics Letters B, 280-284.
Leptonic CP violation in the charged sector and effective field theory approach
Pruna Giovanni Marco (2017), Leptonic CP violation in the charged sector and effective field theory approach, in Proceedings, 15th Conference on Flavor Physics and CP Violation (FPCP 2017), Prague, Czech RepublicPoS FPCP2017 (2017) 016, SISSA.
Lepton-flavour violating decays in theories with dimension 6 operators
Pruna Giovanni Marco, Signer Adrian (2016), Lepton-flavour violating decays in theories with dimension 6 operators, in EPJ Web of Conferences, 01031-01031.

Collaboration

Group / person Country
Types of collaboration
CERN Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
CNRS Lyon, Sacha Davidson France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
ALPS 2018 Talk given at a conference Searches for a doubly charged scalar at LHC and future colliders 17.04.2018 Obergurlg, Austria Ghezzi Margherita;
ALPS 2018 Talk given at a conference Charged lepton flavor violation 16.04.2018 Obergurlg, Austria Signer Adrian;
Rencontres de Moriond Talk given at a conference The doubly charged scalar: current status and perspectives 20.03.2018 La Thuile, Italy Ghezzi Margherita;
BSM direct searces Meeting (CLIC working group) Talk given at a conference "See-saw mediators in t-channel” 21.02.2018 CERN / Videoconference, Switzerland Ghezzi Margherita;
Joint Rome Seminar, Sapienza University of Rome Talk given at a conference The Effective Field Theory approach to new physics: two explicit examples 21.12.2017 Rome, Italy Ghezzi Margherita;
Milan Christmas meeting Talk given at a conference "The Effective Field Theory approach to new physics: two explicit examples" 20.12.2017 Milano, Italy Ghezzi Margherita;
SHiP Open Colloquium Talk given at a conference Lepton flavour violation in muon decays 09.11.2017 CERN Geneva, Switzerland Signer Adrian;
NUFACT 2017 Talk given at a conference SMEFT and charged lepton flavour violation 25.10.2017 Uppsala, Sweden Pruna Giovanni Marco;
FCCP 2017 Flavour changing and conserving processes Talk given at a conference Charged lepton flavour violation: precise background calculation and effective field theoretical interpretation 07.10.2017 Anacapri, Italy Pruna Giovanni Marco;
Muon-electron scattering: theory kickoff workshop Talk given at a conference Preliminary considerations on the NP sensitivity of low-energy mu-e scattering data 04.10.2017 Padova, Italy Pruna Giovanni Marco;
ACFI Workshop: Neutrinos at the high-energy frontier Talk given at a conference Charged lepton-flavour violation 20.07.2017 Amherst, United States of America Signer Adrian;
Irish Quantum Foundations 2017 Talk given at a conference Recent theoretical developments in the study of charged lepton flavour violation 05.06.2017 Dublin, Ireland Pruna Giovanni Marco;
FPCP 2017 - Flavour Physics and CP Violation Talk given at a conference Leptonic CP Violation 05.06.2017 Prague, Czech Republic Pruna Giovanni Marco;
HEFT 2017 Talk given at a conference Charged lepton-flavour violation with effective theories 22.05.2017 Durham, Great Britain and Northern Ireland Signer Adrian;
BLV 2017 Talk given at a conference Lepton-flavour violating processes 15.05.2017 Cleveland, United States of America Signer Adrian;
IFAE 2017 - Incontri di Fisica delle Alte Energie Talk given at a conference Standard Model and low-energy experiments: from lepton flavour to dark photon searches 19.04.2017 Trieste, Italy Pruna Giovanni Marco;
Current Trends in Flavour Physics - GDR Intensity Frontier Talk given at a conference Charged Lepton Flavour Violation in effective field theories with dimension 6 operators 29.03.2017 Paris, France Pruna Giovanni Marco;
NuPhys 2016 Talk given at a conference Lepton Flavour Violation 12.12.2016 London, Great Britain and Northern Ireland Pruna Giovanni Marco;
NUFACT 2016 Talk given at a conference On the interrelationship among neutrino physics, leptonic g-2, EDMs and lepton flavor violation 21.08.2016 Quy Nhon, Vietnam Pruna Giovanni Marco;
MIAPP workshop Talk given at a conference Low-energy cLFV and precision physics 01.06.2016 Munich, Germany Signer Adrian;
FCCP 2015 Flavour changing and conserving processes Talk given at a conference Lepton-flavour violating decays in theories with dimension 6 operators 10.10.2015 Anacapri, Italy Pruna Giovanni Marco;


Associated projects

Number Title Start Funding scheme
178967 NNLO calculations for leptons 01.10.2018 Project funding (Div. I-III)

Abstract

With the discovery of the Higgs boson at the Large Hadron Collider(LHC) the Standard Model (SM) is complete. However, it is generallyaccepted that the SM cannot be the ultimate theory and there is a hugeexperimental and theoretical effort ongoing in scrutinizing the SM.The study of charged lepton-flavour violating (cLFV) processes plays aparticularly important role in the search for physics beyond theStandard Model (BSM). LFV processes like $\mu^+ \to e^+ \gamma$,$\mu^+ \to e^+ e^- e^+ $ or muon conversion in the field of a nucleus,$\mu^- N \to e^- N$ are not allowed in the SM. However, in many BSMtheories such processes are expected to happen.For a large number of cLFV processes there are very stringentexperimental limits and a large effort is ongoing to increase thesensitivity further. This allows to extract a wealth of informationon possible BSM scenarios with a reach in energy scale that is wellbeyond the reach of direct searches. To obtain a more completepicture, it is crucial to combine the analyses of low energymeasurements with experimental results obtained at higher energiessuch as LEP and LHC.Typically, the experimental results for such processes are used toobtain constraints on particular BSM models. The aim of this projectis to take a much more general and model independent approach by usingthe SM effective field theory (SMEFT) framework. In the SMEFT, ageneral parameterization of BSM physics compatible with Lorentzinvariance and gauge symmetries is given by higher-dimensionaloperators. The coefficients of these operators are treated as unknowncouplings that contain the information on the underlying theory thatlies beyond the SM. With enough information available on thesecoefficients it is feasible to decisively narrow down the options onpossible BSM scenarios.The main goal of this proposal is to perform a complete study of allcLFV processes including all relevant dimension~6 operators. With acombined analysis we plan to obtain constraints on a large number ofcoefficients of these operators. Linking loop calculations withrenormalization-group evolution, constraints from different energyscales will be combined in a way consistent with quantum fieldtheory. Once the constraints are known, they can also be used to shedlight on classes of explicit BSM models and be transformed intoconstraints on parameters of these models.
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