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Strong interaction at low energy, flavour physics and the search for new physics

English title Strong interaction at low energy, flavour physics and the search for new physics
Applicant Colangelo Gilberto
Number 175791
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 01.11.2017 - 31.03.2021
Approved amount 579'492.00
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Keywords (4)

effective field theories; dispersion relations; isospin symmetry breaking; chiral perturbation theory

Lay Summary (Italian)

Lead
“Our future discoveries must be looked for in the sixth place of decimals.”"Le nostre scoperte future andranno cercate nella sesta cifra decimale"Cosi` scrisse A. Michelson nel 1894, e oggi possiamo dire che questo e` pratica quotidiana nella fisica delle particelle. Grazie alle peculiarita` della fisica quantistica particelle che ancora non abbiamo mai osservato perche' troppo pesanti per essere generate nelle collisioni di acceleratori esistenti, possono rendersi visibili generando piccoli contributi in grandezze che conosciamo e misuriamo. Per identificare questi piccoli contributi e` necessario innanzitutto fare misure sufficientemente precise e in secondo luogo fare calcoli teorici altrettanto precisi per tutti i contributi di particelle che conosciamo. Questo progetto di ricerca si propone questo scopo per il momento di dipolo magnetico del muone.
Lay summary
Obiettivo di questo progetto e` quello di migliorare la precisione
delle predizioni teoriche del modello standard per il momento di dipolo 
magnetico del muone che sta per essere rimisurato al "Fermilab" negli USA. 
L'obiettivo della nuova misura e` una riduzione di un fattore 4 dell'errore 
sperimentale. La precisione della misura attuale e` arrivata a 0.6 parti 
per milione e i calcoli teorici hanno raggiunto una precisione simile. 
Un miglioramento sul fronte sperimentale va quindi accompagnato da un 
analogo miglioramento teorico.

Diversi gruppi di teorici in tutto il mondo stanno investendo tempo e 
risorse nel cercare di migliorare questi calcoli. Anche il nostro 
dell'universita` di Berna si impegnato su questo fronte ed e` riuscito a 
sviluppare un nuovo metodo sistematico per calcolare un contributo che 
finora era stato stimato solo sulla base di modelli. Questo contributo, che e` 
noto con il nome di "hadronic light-by-light", e` uno dei due maggiormente 
responsabili dell'incertezza teorica. L'approccio sviluppato ha il vantaggio 
di essere sistematico, ma e` anche notevolmente complicato. Il completamento di
questo calcolo entro i prossimi tre anni e` l'obiettivo di questo progetto.

Se i valori centrali, sia della misura sperimentale, sia del calcolo teorico
verranno confermati, e gli errori ridotti di un fattore 4 su entrambi i 
fronti questo rappresentera` una chiara evidenza sperimentale dell'esistenza
di nuove particelle, non incluse nel modello standard (la teoria che descrive
in maniera matematicamente consistente tutte le particelle finora osservate
e le loro interazioni), ed ancora mai osservate. Questa sarebbe una scoperta
di fondamentale importanza e darebbe nuovo stimolo alla ricerca di queste 
particelle agli acceleratori di alte energie.
Direct link to Lay Summary Last update: 02.11.2017

Responsible applicant and co-applicants

Employees

Publications

Publication
Constraints on the two-pion contribution to hadronic vacuum polarization
Colangelo Gilberto, Hoferichter Martin, Stoffer Peter (2021), Constraints on the two-pion contribution to hadronic vacuum polarization, in Phys. Lett. B, 814, 136073-136073.
Dispersion relations for hadronic light-by-light and the muon g-2
Procura Massimiliano, Colangelo Gilberto, Hoferichter Martin, Stoffer Peter (2020), Dispersion relations for hadronic light-by-light and the muon g-2, 234, 01013-01013, Springer, EPJ Web of Conferences 234, 01013-01013.
FLAG Review 2019: Flavour Lattice Averaging Group (FLAG)
Aoki S., others (2020), FLAG Review 2019: Flavour Lattice Averaging Group (FLAG), in Eur. Phys. J. C, 80(2), 113-113.
The anomalous magnetic moment of the muon in the Standard Model
Aoyama T., others (2020), The anomalous magnetic moment of the muon in the Standard Model, in Phys. Rept., 887, 1-166.
The Belle II Physics Book
Kou E, Urquijo P, Altmannshofer W, Beaujean F, Bell G, Beneke M, Bigi I I, Bishara F, Blanke M, Bobeth C, Bona M, Brambilla N, Braun V M, Brod J, Buras A J, Cheng H Y, Chiang C W, Ciuchini M, Colangelo G, Crivellin A, Czyz H, Datta A, De Fazio F, Deppisch T, et al. (2019), The Belle II Physics Book, in Progress of Theoretical and Experimental Physics, 2019(12), 123C01.
Hadronic contributions to the muon anomalous magnetic moment
Procura Massimiliano, Colangelo Gilberto, Hoferichter Martin, Stoffer Peter (2019), Hadronic contributions to the muon anomalous magnetic moment, in PoS, 336, 186-186.
Report from Working Group 4: Opportunities in Flavour Physics at the HL-LHC and HE-LHC
Cerri A., others (2019), Report from Working Group 4: Opportunities in Flavour Physics at the HL-LHC and HE-LHC, in CERN Yellow Rep. Monogr., 7, 867-1158.
Two-pion contribution to hadronic vacuum polarization
Colangelo Gilberto, Hoferichter Martin, Stoffer Peter (2019), Two-pion contribution to hadronic vacuum polarization, in JHEP, 02, 006-006.
Two-pion contributions to the muon g-2
Stoffer Peter, Colangelo Gilberto, Hoferichter Martin (2019), Two-pion contributions to the muon g-2, in PoS, CD2018, 084-084.
Dispersion relations for hadronic light-by-light scattering and the muon g-2
Procura Massimiliano, Colangelo Gilberto, Hoferichter Martin, Stoffer Peter (2018), Dispersion relations for hadronic light-by-light scattering and the muon g-2, in EPJ Web Conf., 166, 00014-00014.
Dispersive analysis of η→3π
Colangelo Gilberto, Lanz Stefan, Leutwyler Heinrich, Passemar Emilie (2018), Dispersive analysis of η→3π, in Eur. Phys. J. C, 78(11), 947-947.
Hadronic light-by-light contribution to (g-2)μ: a dispersive approach
Colangelo Gilberto, Hoferichter Martin, Procura Massimiliano, Stoffer Peter (2018), Hadronic light-by-light contribution to (g-2)μ: a dispersive approach, in EPJ Web Conf., 175, 01025-01025.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Ultimate Precision at Hadronic Colliders Talk given at a conference Hadronic light-by-light (HLbL) from disperive/analytic methods 25.11.2019 Paris, France Colangelo Gilberto;
Physics of fundamental symmetries and interactions - PSI2019 Talk given at a conference Convener: G. Colangelo, talk F. Hagelstein: Pseudoscalar contribution to the muon g-2, Poster J. Monnard: Dispersive treatment of the EM radiative corrections to the pion vector form factor 21.10.2019 Villigen, Switzerland Hagelstein Franziska; Monnard Joachim; Colangelo Gilberto;
Frontiers of QCD Talk given at a conference Dispersive treatment of the hadronic light-by-light contribution to the Muon g-2 26.09.2019 Tbilisi, Georgia Colangelo Gilberto;
New physics at the low-energy precision frontier Talk given at a conference Progress in g-2 theory 16.09.2019 Orsay, France Colangelo Gilberto;
XIX Internatioaln Conference on Science, Art and Culture - The Proton Radius Talk given at a conference Lower bound on the proton radius & proton-polarizability effects in muonic hydrogen 15.09.2019 Veli Losinj, Croatia Hagelstein Franziska;
INT-19-74W Workshop Hadronic contributions to (g-2)μ Talk given at a conference Summary HLbL analytic (G.Colangelo), Pion contribution from Schwinger sum rule (F. Hagelstein) 09.09.2019 Seattle, United States of America Hagelstein Franziska; Colangelo Gilberto;
Seminar talk at TRIUMF, Vancouver Individual talk Hadronic Corrections to Muon Anomalies 04.09.2019 Vancouver, Canada Hagelstein Franziska;
15th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU 2019) Talk given at a conference Hadronic Corrections to Muon Anomalies 02.06.2019 Pittsburgh, United States of America Hagelstein Franziska;
Muon g-2 Elba Physics Workshop Talk given at a conference Hadronic corrections to Muon g-2 27.05.2019 Elba, Italy Colangelo Gilberto;
International Workshop on e+e- collisions from Phi to Psi Talk given at a conference Dispersive approach to the hadronic light-by-light contribution to the muon g-2 / Dispersive analysis of the two-pion contribution to the hadronic vacuum polarization to the (g−2)μ 25.02.2019 Novosibirsk, Russia Colangelo Gilberto;
SFB-School 2018 Talk given at a conference Pseudoscalar-Meson Contributions to the Muon g-2 via Schwinger’s Sum Rule 04.09.2018 Mainz, Germany Hagelstein Franziska;
Second Plenary Workshop of the Muon g-2 Theory Initiative Talk given at a conference Dispersive approach to hadronic light-by-light: An overview (G. Colangelo) / Pseudoscalar-Meson Contributions via the Schwinger Sum Rule (F. Hagelstein) 18.06.2018 Mainz, Germany Colangelo Gilberto; Hagelstein Franziska;
Advances in Lattice Field Theory Talk given at a conference Lattice results and phenomenology: the FLAG review 08.03.2018 Zürich, Switzerland Colangelo Gilberto;
The Evaluation of the Leading Hadronic Contribution to the Muon Anomalous Magnetic Moment Talk given at a conference Hadronic corrections to g-2 via Schwinger's sum rule 19.02.2018 Mainz, Germany Hagelstein Franziska;


Associated projects

Number Title Start Funding scheme
178915 Short-distance constraints on the hadronic light-by-light contribution to the muon g-2 01.04.2018 Project funding
200553 Strong interaction at low energy, Muon g-2 and the search for new physics 01.10.2021 Project funding
163280 Strong interaction at low energy, flavour physics and the search for new physics 01.11.2015 Project funding

Abstract

At the present high-energy frontier (LHC) the window for possiblediscoveries of new particles is still open but rapidly closing down. Onthe other hand hints of possible discrepancies between Standard Model (SM)and experiment are all coming from precision measurements: there areseveral from LHCb and others at lower-energy experiments. In thecurrent particle physics landscape, the high-precision frontier isattracting considerable attention.One of the most resistant hints of a discrepancy with the SM remains thatof the $(g-2)$ of the muon. As it first showed up, the discrepancy betweenmeasurement and SM prediction was called a ``harbinger of new physics'',but now that the bounds on the masses of all beyond-the-Standard-Model(BSM) particles have moved up as a consequence of the unsuccessful searchesat the LHC, the same discrepancy has become a true puzzle. To clarify it, anew generation of $(g-2)_\mu$ measurements has been planned: the FermilabMuon $(g-2)$ experiment has just started running and a new experiment (Muon$g-2$/EDM experiment), based on a completely different experimentalconcept, is currently being developed at J-Parc in Japan.On the theory side, similar efforts are being put forward, in particularfor the hadronic contributions which are responsible for almost 100\% ofthe uncertainty in the SM prediction. We have recently proposed a newapproach to the so-called hadronic light-by-light scattering (HLbL)contribution to the $(g-2)_\mu$, based on dispersion relations, which aimsat a model-independent evaluation and at significantly reduceduncertainties with respect to earlier model calculations. Such an approachhas been deemed to be ``impossible'' for this particular contribution. In aseries of papers we have written in the last four years we have laid downthe theoretical basis for such an approach and have recently produced thefirst numerical estimate for part of the HLbL contribution. In thefollowing three years, we will concentrate our efforts in completing thisvery complex calculation and in carefully assessing the final uncertainty.The Fermilab experiment is aiming to release the first number for$(g-2)_\mu$ at the end of 2018, but the final result will take a few moreyears. The goal of this project is to significantly improve the accuracy ofthe theoretical evaluation of hadronic contributions to this quantitybefore the Fermilab experiments will produce its final result.
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