scholarly journals The low-energy effective theory of axions and ALPs

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Martin Bauer ◽  
Matthias Neubert ◽  
Sophie Renner ◽  
Marvin Schnubel ◽  
Andrea Thamm
Keyword(s):  
High Energy ◽  
New Physics ◽  
Mass Scale ◽  
Low Energy ◽  
Effective Theory ◽  
Loop Order ◽  
Flavor Changing ◽  
Effective Lagrangian ◽  
Anomalous Dimensions ◽  
Pseudoscalar Mesons

Abstract Axions and axion-like particles (ALPs) are well-motivated low-energy relics of high-energy extensions of the Standard Model, which interact with the known particles through higher-dimensional operators suppressed by the mass scale Λ of the new-physics sector. Starting from the most general dimension-5 interactions, we discuss in detail the evolution of the ALP couplings from the new-physics scale to energies at and below the scale of electroweak symmetry breaking. We derive the relevant anomalous dimensions at two-loop order in gauge couplings and one-loop order in Yukawa interactions, carefully considering the treatment of a redundant operator involving an ALP coupling to the Higgs current. We account for one-loop (and partially two-loop) matching contributions at the weak scale, including in particular flavor-changing effects. The relations between different equivalent forms of the effective Lagrangian are discussed in detail. We also construct the effective chiral Lagrangian for an ALP interacting with photons and light pseudoscalar mesons, pointing out important differences with the corresponding Lagrangian for the QCD axion.

scholarly journals Semileptonic τ decays: powerful probes of non-standard charged current weak interactions

2019 ◽  
Vol 212 ◽  
pp. 08002 ◽  
Author(s):  
Pablo Roig
Keyword(s):  
Weak Interactions ◽  
High Energy ◽  
New Physics ◽  
Effective Field ◽  
Low Energy ◽  
Effective Theory ◽  
Tau Decays ◽  
The Standard Model ◽  
Precision Observables ◽  
Hadronic Tau

When looking for heavy (O(few TeV)) New Physics, the most efficient way to bene?t from both high and low-energy measurements simultaneously is the use of the Standard Model Effective Field Theory (SMEFT). In this talk I highlight the importance of semileptonic τ decays in complementing, in this respect, the traditional low-energy precision observables and high-energy measurements. This is yet another reason for considering hadronic tau decays as golden channels at Belle-II beyond the unquestionable interest of the CP violation anomaly in τ → KS πντ decays, that I also discuss within the effective theory. A couple of new results for τ−→ K− ντ decays are also included.

scholarly journals Flavour Anomalies in a U(1) SUSY Extension of the SM

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 191
Author(s):  
Alexander Bednyakov ◽  
Alfiia Mukhaeva
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Gauge Boson ◽  
New Physics ◽  
Low Energy ◽  
Effective Theory ◽  
The Standard Model ◽  
Meson Mixing ◽  
Additional Anomaly ◽  
Lepton Flavour

Flavour anomalies have attracted a lot of attention over recent years as they provide unique hints for possible New Physics. Here, we consider a supersymmetric (SUSY) extension of the Standard Model (SM) with an additional anomaly-free gauge U(1) group. The key feature of our model is the particular choice of non-universal charges to the gauge boson Z′, which not only allows a relaxation of the flavour discrepancies but, contrary to previous studies, can reproduce the SM mixing matrices both in the quark and lepton sectors. We pay special attention to the latter and explicitly enumerate all parameters relevant for our calculation in the low-energy effective theory. We find regions in the parameter space that satisfy experimental constraints on meson mixing and LHC Z′ searches and can alleviate the flavour anomalies. In addition, we also discuss the predictions for lepton-flavour violating decays B+→K+μτ and B+→K+eτ.

scholarly journals INFINITE STATISTICS, SYMMETRY BREAKING AND COMBINATORIAL HIERARCHY

2009 ◽  
Vol 24 (18) ◽  
pp. 1425-1435 ◽  
Author(s):  
VLADIMIR SHEVCHENKO
Keyword(s):  
Symmetry Breaking ◽  
Mechanical Model ◽  
Degrees Of Freedom ◽  
High Energy ◽  
Low Energy ◽  
Effective Theory ◽  
Quantum Mechanical ◽  
Hierarchy Problem ◽  
Induced Gravity ◽  
Large Numbers

The physics of symmetry breaking in theories with strongly interacting quanta obeying infinite (quantum Boltzmann) statistics known as quons is discussed. The picture of Bose/Fermi particles as low energy excitations over nontrivial quon condensate is advocated. Using induced gravity arguments, it is demonstrated that the Planck mass in such low energy effective theory can be factorially (in number of degrees of freedom) larger than its true ultraviolet cutoff. Thus, the assumption that statistics of relevant high energy excitations is neither Bose nor Fermi but infinite can remove the hierarchy problem without necessity to introduce any artificially large numbers. Quantum mechanical model illustrating this scenario is presented.

scholarly journals Partition Function in One, Two, and Three Spatial Dimensions from Effective Lagrangian Field Theory

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Christoph P. Hofmann
Keyword(s):  
Partition Function ◽  
Degrees Of Freedom ◽  
Spatial Dimension ◽  
Lagrangian Method ◽  
Point Of View ◽  
Low Energy ◽  
Effective Theory ◽  
Goldstone Bosons ◽  
Effective Lagrangian ◽  
Spatial Dimensions

The systematic effective Lagrangian method was first formulated in the context of the strong interaction; chiral perturbation theory (CHPT) is the effective theory of quantum chromodynamics (QCD). It was then pointed out that the method can be transferred to the nonrelativistic domain—in particular, to describe the low-energy properties of ferromagnets. Interestingly, whereas for Lorentz-invariant systems the effective Lagrangian method fails in one spatial dimension (ds=1), it perfectly works for nonrelativistic systems in ds=1. In the present brief review, we give an outline of the method and then focus on the partition function for ferromagnetic spin chains, ferromagnetic films, and ferromagnetic crystals up to three loops in the perturbative expansion—an accuracy never achieved by conventional condensed matter methods. We then compare ferromagnets in ds=1, 2, 3 with the behavior of QCD at low temperatures by considering the pressure and the order parameter. The two apparently very different systems (ferromagnets and QCD) are related from a universal point of view based on the spontaneously broken symmetry. In either case, the low-energy dynamics is described by an effective theory containing Goldstone bosons as basic degrees of freedom.

scholarly journals The Dual QCD @ Work: 2018

2018 ◽  
Vol 192 ◽  
pp. 00048
Author(s):  
Andrzej J. Buras
Keyword(s):  
Lattice Qcd ◽  
New Physics ◽  
Low Energy ◽  
Effective Theory ◽  
Matrix Elements ◽  
General Study ◽  
The Road ◽  
The Past ◽  
Recent Developments ◽  
Energy Approximation

The Dual QCD (DQCD) framework, based on the ideas of ’t Hooft and Witten, and developed by Bill Bardeen, Jean-Marc Gérard and myself in the 1980s is not QCD, a theory of quarks and gluons, but a successful low energy approximation of it when applied to K → ππ decays and K¯0 - K0 mixing. After years of silence, starting with 2014, this framework has been further developed in order to improve the SM prediction for the ratio ε'/ε, the ΔI = 1/2 rule and B^K. Most importantly, this year it has been used for the calculation of all K → ππ hadronic matrix elements of BSM operators which opened the road for the general study of ε'/ε in the context of the SM effective theory (SMEFT). This talk summarizes briefly the past successes of this framework and discusses recent developments which lead to a master formula for ε'/ε valid in any extension of the SM. This formula should facilitate the search for new physics responsible for the ε'/ε anomaly hinted by 2015 results from lattice QCD and DQCD.

Skyrmions and effective Lagrangians

1989 ◽  
Vol 67 (12) ◽  
pp. 1168-1179
Author(s):  
B. Loiseau
Keyword(s):  
Inner Core ◽  
High Energy ◽  
Low Energy ◽  
Symmetric Model ◽  
Two Phase ◽  
Effective Lagrangian ◽  
Large N ◽  
Topological Current ◽  
Low Mass ◽  
Baryon Current

The need to model quantum chromodynamics (QCD) at low energy is emphasized. An outline of the1/NC expansion of QCD, for large NC, shows the deep link between the Skyrme effective Lagrangian and QCD. The Skyrme model, built from the nonlinear σ model plus a stabilizer term related to vector dominance, is briefly described. The model satisfies like QCD chiral symmetry. We illustrate how the gauged Wess–Zumino action demonstrates that the topological current can be identified with the baryon current. We recall how one can show that the topological soliton is a fermion for odd NC. An example of an effective Lagrangian, built from π and low-mass vector mesons, ω, ρ, and A1 fields, is given. It describes rather well low-energy meson and baryon physics. Predictions of effective Lagrangians of the Skyrme type on meson–meson, meson–baryon, and baryon–baryon scatterings at low energy are depicted. A two-phase chiral symmetric model, the chiral bag, is introduced. It contains an inner core of confined quarks and gluons surrounded by meson fields in the topological configuration of a Skyrmion. It can describe nuclei from the low- to the high-energy range.

scholarly journals Presymmetry in the Standard Model with adulterated Dirac neutrinos

2015 ◽  
Vol 30 (31) ◽  
pp. 1550160 ◽  
Author(s):  
Ernesto A. Matute
Keyword(s):  
Standard Model ◽  
High Energy ◽  
New Physics ◽  
Boson Mass ◽  
Effective Theory ◽  
Type I ◽  
Electroweak Symmetry ◽  
Seesaw Mechanism ◽  
Left Handed ◽  
The Standard Model

Recently we proposed a model for light Dirac neutrinos in which two right-handed (RH) neutrinos per generation are added to the particles of the Standard Model (SM), implemented with the symmetry of fermionic contents. The ordinary one is decoupled via the high scale type-I seesaw mechanism, while the extra pairs off with its left-handed (LH) partner. The symmetry of lepton and quark contents was merely used as a guideline to the choice of parameters because it is not a proper symmetry. Here we argue that the underlying symmetry to take for this correspondence is presymmetry, the hidden electroweak symmetry of the SM extended with RH neutrinos defined by transformations which exchange lepton and quark bare states with the same electroweak charges and no Majorana mass terms in the underlying Lagrangian. It gives a topological character to fractional charges, relates the number of families to the number of quark colors, and now guarantees the great disparity between the couplings of the two RH neutrinos. Thus, Dirac neutrinos with extremely small masses appear as natural predictions of presymmetry, satisfying the ’t Hooft’s naturalness conditions in the extended seesaw where the extra RH neutrinos serve to adulterate the mass properties in the low scale effective theory, which retains without extensions the gauge and Higgs sectors of the SM. However, the high energy threshold for the seesaw implies new physics to stabilize the quantum corrections to the Higgs boson mass in agreement with the naturalness requirement.

scholarly journals Effective Field Theory with Nambu–Goldstone Modes

2020 ◽  
pp. 137-219 ◽  
Author(s):  
Antonio Pich
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Dynamical Symmetry ◽  
New Physics ◽  
Effective Field ◽  
Low Energy ◽  
Effective Theory ◽  
Current Status ◽  
Symmetry Properties ◽  
Effective Theories

These lectures provide an introduction to the low-energy dynamics of Nambu–Goldstone fields, which associated with some spontaneous (or dynamical) symmetry breaking, using the powerful methods of effective field theory. The generic symmetry properties of these massless modes are described in detail and two very relevant phenomenological applications are worked out: chiral perturbation theory, the low-energy effective theory of QCD, and the (non-linear) electroweak effective theory. The similarities and differences between these two effective theories are emphasized, and their current status is reviewed. Special attention is given to the short-distance dynamical information encoded in the low-energy couplings of the effective Lagrangians. The successful methods developed in QCD could help us to uncover fingerprints of new physics scales from future measurements of the electroweak effective theory couplings.

scholarly journals Structure Functions of Hadrons in the QCD Effective Theory

1997 ◽  
Vol 50 (1) ◽  
pp. 139
Author(s):  
Takayuki Shigetani ◽  
Katsuhiko Suzuki ◽  
Hiroshi Toki
Keyword(s):  
Quark Distribution ◽  
High Energy ◽  
Structure Functions ◽  
Distribution Functions ◽  
Low Energy ◽  
Effective Theory ◽  
Spin Distribution ◽  
Diquark Model ◽  
Model Calculations ◽  
Diquark Correlation

We study the structure functions of hadrons with the low energy effective theory of QCD. We try to clarify a link between the low energy effective theory, where non-perturbative dynamics is essential, and the high energy deep inelastic scattering experiment. We calculate the leading twist matrix elements of the structure function at the low energy model scale within the effective theory. Calculated structure functions are taken to the high momentum scale with the help of the perturbative QCD, and compared with the experimental data. Through a comparison of the model calculations with the experiment, we discuss how the non-perturbative dynamics of the effective theory is reflected in the deep inelastic phenomena. We first evaluate the structure functions of the pseudoscalar mesons using the NJL model. The resulting structure functions show reasonable agreement with experiments. We then study the quark distribution functions of the nucleon using a covariant quark–diquark model. We calculate three leading twist distribution functions, the spin-independent f1(x), the longitudinal spin distribution g1(x), and the chiral-odd transversity spin distribution h1(x). The results for f1(x) and g1(x) turn out to be consistent with available experiments because of the strong spin-0 diquark correlation.

scholarly journals QUARK STRUCTURE OF PSEUDOSCALAR MESONS

2000 ◽  
Vol 15 (02) ◽  
pp. 159-207 ◽  
Author(s):  
THORSTEN FELDMANN
Keyword(s):  
High Energy ◽  
Wave Functions ◽  
Low Energy ◽  
Mixing Process ◽  
Chiral Perturbation ◽  
Fock States ◽  
Mixing Parameters ◽  
Pseudoscalar Mesons ◽  
Energy Application ◽  
Quark Structure

I review to which extent the properties of pseudoscalar mesons can be understood in terms of the underlying quark (and eventually gluon) structure. Special emphasis is put on the progress in our understanding of η–η′ mixing. Process-independent mixing parameters are defined, and relations between different bases and conventions are studied. Both, the low-energy description in the framework of chiral perturbation theory and the high-energy application in terms of light-cone wave functions for partonic Fock states, are considered. A thorough discussion of theoretical and phenomenological consequences of the mixing approach will be given. Finally, I will discuss mixing with other states (π0, ηc, …).

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