# Project

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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 Colangelo Gilberto 137518 Project funding Institut für Theoretische Physik Universität Bern University of Berne - BE Theoretical Physics 01.11.2011 - 31.10.2013 354'989.20
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### Keywords (5)

Standard model; Strong interactions; Effective field theories; Dispersion relations; Search for new physics

### Lay Summary (English)

Lay summary
Since several years the particle physics community is trying to find
effects which cannot be explained by the "standard model" - the generally
accepted theory of particle interactions. This effort is carried out along
two main alleys: the high-energy and the high-precision ones. By increasing
the energy of the events observed in laboratory one tries to produce new
particles, not present in the standard model. By increasing the precision
of the measurements of the decays of known particles one tries to see
deviations from what the standard model predicts -- in this case the
evidence of new particles is only indirect.

The goal of this project is to improve the precision of the theoretical
calculations of quantities which have been and will be measured with
increasing accuracy. Only in this manner one can obtain convincing evidence
of new effects from precise experimental measurements. The difficulty of
the theoretical calculations lies in the presence of strong interactions --
although we have a theory which we believe describes them exactly (quantum
chromodynamics, QCD), often we are not yet able to calculate observables,
within this theory, to the desired level of precision.

We will use methods like effective field theories or dispersion relations
and collaborate with colleagues which use the numerical approach to deal
with the strong interactions (lattice QCD).

One of the goals of the project is to improve the evaluation of hadronic
contributions to the gyromagnetic ratio of the muon. This quantity has been
measured with very high accuracy (to about $0.6$ parts per million for
$(g-2)_\mu$) and is different by more than three standard deviations from
what the standard model predicts. The most delicate part of the
standard-model calculations is precisely the hadronic contribution, whose evaluation
we aim to improve.

 Direct link to Lay Summary Last update: 21.02.2013

### Responsible applicant and co-applicants

Name Institute
 Colangelo Gilberto Institut für Theoretische Physik Universität Bern

### Employees

Name Institute
 Procura Massimiliano Institut für Theoretische Physik Universität Bern

### Publications

Publication
Aoki Sinya, Aoki Yasumichi, Bernard Claude, Blum Tom, Colangelo Gilberto, others (2014), Review of lattice results concerning low energy particle physics, in European Physical Journal C, C74, 2890.
Hoferichter Martin, Colangelo Gilberto, Procura Massimiliano, Stoffer Peter (2014), Virtual photon-photon scattering, in International Journal of Modern Physics: Conference Series, 35, 1460400.
Chang Hsi-Ming, Procura Massimiliano, Thaler Jesse, Waalewijn Wouter J. (2013), Calculating Track Thrust with Track Functions, in Phys.Rev., D88, 034030-034030.
Chang Hsi-Ming, Procura Massimiliano, Thaler Jesse, Waalewijn Wouter J. (2013), Calculating Track-Based Observables for the LHC, in Phys.Rev.Lett., 111, 102002-102002.
Colangelo Gilberto, Passemar Emilie, Stoffer Peter (2012), A Dispersive Treatment of $K_{\ell4}$ Decays, in EPJ Web Conf., 37, 05006-05006.
Hoferichter Martin, Kubis Bastian, Sakkas Dimitrios (2012), Extracting the chiral anomaly from gamma pi --> pi pi, in Phys.Rev., D86, 116009-116009.
Colangelo G., Procura M., Rothen L., Stucki R., Tarrus Castella J. (2012), Factorization of chiral logarithms in the pion form factors, in PoS, QNP2012, 131-131.
Colangelo G. (2012), FLAG phase 2, status and prospects, in PoS, Lattice 2012, 021-021.
Procura Massimiliano, Waalewijn Wouter J. (2012), Fragmentation in Jets: Cone and Threshold Effects, in Phys.Rev., D85, 114041-114041.
Colangelo G., Procura M., Rothen L., Stucki R., Tarrus Castella J. (2012), On the factorization of chiral logarithms in the pion form factors, in JHEP, 1209, 081-081.
Caprini I., Colangelo G., Leutwyler H. (2012), Regge analysis of the pi pi scattering amplitude, in Eur.Phys.J., C72, 1860-1860.
Colangelo Gilberto, Lanz Stefan, Leutwyler Heinrich, Passemar Emilie (2011), Determination of the light quark masses from eta ---> 3pi, in PoS, EPS-HEP2011, 304-304.

### Collaboration

Group / person Country
Types of collaboration
 PD Dr. Bastian Kubis, University of Bonn Germany (Europe)
 - in-depth/constructive exchanges on approaches, methods or results- Exchange of personnel
 FLAG (Flavour Lattice Averaging Group) Switzerland (Europe)
 - in-depth/constructive exchanges on approaches, methods or results- Publication
 Prof. Johan Bijnens, University of Lund Sweden (Europe)
 - in-depth/constructive exchanges on approaches, methods or results
 Prof. Urs Wenger, ITP, Uni 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
 Workshop QCD@LHC2013 Talk given at a conference Calculating track-based observables using track functions 02.09.2013 Hamburg, Germany Procura Massimiliano;
 CHIPP Annual Plenary Meeting Talk given at a conference Overview: theoretical particle physics in Switzerland 24.06.2013 Sursee, Switzerland Colangelo Gilberto;
 International Workshop "MesonNet Meeting" Talk given at a conference eta -> 3 pi and the determination of Q 17.06.2013 Prag, Czech Republic Colangelo Gilberto;
 Int. Workshop on Determination of the Fundamental Parameters of QCD Talk given at a conference Low energy QCD I: status of chiral perturbation theory 18.03.2013 Singapur, Singapore Colangelo Gilberto;
 University of Vienna Individual talk eta -> 3 pi and the determination of the quark mass ratio Q 22.01.2013 Wien, Austria Colangelo Gilberto;
 University of Basel Individual talk Determination of the light quark masses 29.11.2012 Basel, Switzerland Colangelo Gilberto;
 STRONGnet 2012 Workshop Talk given at a conference FLAG phase 2: status and prospects 15.10.2012 Madrid, Spain Colangelo Gilberto;
 Konferenz "Xth Quark Confinement and the Hadron Spectrum" Talk given at a conference Factorization of leading chiral logarithms in the pion form factors 08.10.2012 Garching, Germany Procura Massimiliano;
 Klausurtagung des Graduiertenkollegs "Symmetry Breaking in Fundamental Interactions" Talk given at a conference Introduction to chiral perturbation theory 24.09.2012 Mainz, Germany Colangelo Gilberto;
 The 7th International Workshop on Chiral Dynamics Talk given at a conference A scrutiny of hard pion chiral perturbation theory (Procura) A Dispersive Treatment of Kl4 Decays (Stoffer) 06.08.2012 Newport News, United States of America Stoffer Peter;
 The 30th International Symposium on Lattice Field Theory Talk given at a conference FLAG phase 2: status and prospects 24.06.2012 Cairns, Australia Colangelo Gilberto;
 12th International Workshop on Meson Production, Properties and Interaction Talk given at a conference A Dispersive Treatment of Kl4 Decays 31.05.2012 Krakow, Poland Stoffer Peter;
 MesonNet Workshop on Meson Transition Form Factors Talk given at a conference A Dispersive Treatment of Kl4 Decays 29.05.2012 Krakow, Poland Stoffer Peter;
 Sixth International Conference on Quark and Nuclear Physics (QNP2012) Talk given at a conference Factorization of chiral logarithms in the pion form factors 16.04.2012 Palaiseau, France Stucki Ramon;
 Konferenz "47th Rencontres de Moriond" Talk given at a conference Flavour and Lattice: FLAG activities 03.03.2012 La Thuile (Aostatal), Italy Colangelo Gilberto;
 PhD Winter School 2012 Talk given at a conference Hard pion chiral perturbation theory 22.01.2012 Engelberg, Switzerland Stucki Ramon;

### Associated projects

Number Title Start Funding scheme
 126798 Strong interaction at low energy, flavour physics and the search for new physics 01.11.2009 Project funding
 117848 Strong interaction at low energy, flavour physics and the search for new physics 01.11.2007 Project funding
 149272 Strong interaction at low energy, flavour physics and the search for new physics 01.11.2013 Project funding

### Abstract

After the start of the operations at the LHC and a first year of running,the particle physics community is still looking for hints, if not of a goodand clear signal, of physics beyond the standard model (SM). There areseveral hints coming from flavour physics, but none of them is conclusiveyet. In the latter field, more than ever, progress is achieved by severalsmall improvements both on the experimental as well as on the theoreticalside, whose common aim is to accumulate and make clearer the evidence ofdeviations from the SM.After the completion of a generation of high-precision experiments inflavour physics, a new series of yet higher precision experiments is beingprepared: NA62 at CERN, Project X and the new $(g-2)_\mu$ experiment atFermilab, kaon-physics experiments at JPARC, as well as the SuperBfactories in Japan and in Italy (I mention only the experiments which haveto do with hadronic physics and omit those investigating flavour violationsin the leptonic sector). These experiments call for improved theoreticalcalculations to match the level of precision they aim at.The main goal of this project is to improve our calculations ofstrong--interaction effects for low-energy observables which are ofinterest in flavour physics. In this way we can, as a minimal goal,increase the precision of our knowledge of fundamental parameters of the SMwhich we determine from experiments or, in the best case, detect signals ofphysics beyond the SM. The tools we use to deal with strong interactionsare: chiral perturbation theory (CHPT), nonrelativistic effective fieldtheory (NREFT), dispersion relations and numerical lattice calculations.Although we do not directly perform the latter, we apply effective fieldtheory methods which help in doing the necessary extrapolations before onecan use the numerical results in connection with phenomenology. At thelevel of precision now reached in calculating low-energy strong interactioneffects, isospin violations matter -- NREFT and ChPT are the tools whichallow us to take these effects also into account.
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