A
bstract
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.
Flavor probes of axion-like particles Bauer, Martin; Neubert, Matthias; Renner, Sophie ...
The journal of high energy physics,
09/2022, Letnik:
2022, Številka:
9
Journal Article
Recenzirano
Odprti dostop
A
bstract
Axions and axion-like particles (ALPs) are well-motivated low-energy relics of high-energy extensions of the Standard Model (SM). We investigate the phenomenology of an ALP with ...flavor-changing couplings, and present a comprehensive analysis of quark and lepton flavor-changing observables within a general ALP effective field theory. Observables studied include rare meson decays, flavor oscillations of neutral mesons, rare lepton decays, and dipole moments. We derive bounds on the general ALP couplings as a function of its mass, consistently taking into account the ALP lifetime and branching ratios. We further calculate quark flavor-changing effects that are unavoidably induced by running and matching between the new physics scale and the scale of the measurements. This allows us to derive bounds on benchmark ALP models in which only a single (flavorless or flavor-universal) ALP coupling to SM particles is present at the new physics scale, and in this context we highlight the complementarity and competitiveness of flavor bounds with constraints derived from collider, beam dump and astrophysical measurements. We find that searches for ALPs produced in meson decays provide some of the strongest constraints in the MeV-GeV mass range, even for the most flavorless of ALP models. Likewise, we discuss the interplay of flavor-conserving and flavor-violating couplings of the ALP to leptons, finding that constraints from lepton flavor-violating observables generally depend strongly on both. Additionally, we analyze whether an ALP can provide an explanation for various experimental anomalies including those observed in rare
B
-meson decays, measurements at the ATOMKI and KTeV experiments, and in the anomalous magnetic moments of the muon and the electron.
We present a consistent implementation of weak decays involving an axion or axionlike particle in the context of an effective chiral Lagrangian. We argue that previous treatments of such processes ...have used an incorrect representation of the flavor-changing quark currents in the chiral theory. As an application, we derive model-independent results for the decays K−→ π−a and π−→ e−¯ νea at leading order in the chiral expansion and for arbitrary axion couplings and mass. In particular, we find that the K−→ π−a branching ratio is almost 40 times larger than previously estimated.
Axions and axion-like particles emerge in many models for physics beyond the Standard Model. Thus, they have gained increasing research interest in both experimental and theoretical physics apart ...from their original proposition as a solution to the strong
CP
-problem. Among other aspects it has recently been shown that ALPs can potentially provide a solution to the long-lasting discrepancy between theory and experiment of the anomalous magnetic moment of the muon. Provided that the ALP has flavor-violating couplings to leptons, they can also mediate flavor-violating decays like
μ
→
e
γ
. Both processes are mediated through related form factors that we compute to two-loop order. We further show numerical implications of our calculations and how they might affect constraints on ALP couplings derived from experiments.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The Higgs-boson production channel
gg\to h
g
g
→
h
mediated by light-quark loops receives large logarithmic corrections in
QCD, which can be resummed using factorization formulae derived in
...soft-collinear effective theory. In these factorization formulae the
radiative gluon jet function appears, which is a central object in the
study of factorization beyond the leading order in scale ratios. We
calculate this function at two-loop order for the first time and present
the subtleties that come along with this.
A
bstract
Factorization theorems in soft-collinear effective theory at subleading order in power counting involve “radiative jet functions”, defined in terms of matrix elements of hard-collinear ...fields with a soft momentum emitted from inside the jet. Of particular importance are the radiative quark jet functions with an external photon or gluon, which arise e.g. in the factorization theorems for the Higgs-boson amplitudes
h
→
γγ
,
h
→
gg
and
gg
→
h
induced by light-quark loops. While the photon case has been studied extensively in previous work, we present here a detailed study of the radiative jet function with an external gluon. We calculate this jet function at one- and two-loop order, derive its one-loop anomalous dimension and study its renormalization-group evolution.
A
bstract
We derive a factorization theorem for the Higgs-boson production amplitude in gluon-gluon fusion induced by a light-quark loop, working at next-to-leading power in soft-collinear effective ...theory. The factorization is structurally similar to that obtained for the
h
→
γγ
decay amplitude induced by a light-quark loop, but additional complications arise because of external color charges. We show how the refactorization-based subtraction scheme developed in previous work leads to a factorization theorem free of endpoint divergences. We use renormalization-group techniques to predict the logarithmically enhanced terms in the three-loop
gg → h
form factor of order
α
s
3
ln
k
−
M
h
2
/
m
b
2
with
k
= 6, 5, 4, 3. We also resum the first three towers of leading logarithms,
α
s
n
ln
2
n
−
k
−
M
h
2
/
m
b
2
with
k
= 0, 1, 2, to all orders of perturbation theory.
Axionlike particles (ALPs) with lepton-flavor-violating couplings can be probed in exotic muon and tau decays. The sensitivity of different experiments depends strongly on the ALP mass and its ...couplings to leptons and photons. For ALPs that can be resonantly produced, the sensitivity of three-body decays such as μ → 3e and τ → 3μ exceeds by many orders of magnitude that of radiative decays like μ → eγ and τ → μγ . Searches for these two types of processes are therefore highly complementary. We discuss experimental constraints on ALPs with a single dominant lepton-flavor-violating coupling. Allowing for one or more such couplings offers qualitatively new ways to explain the anomalies related to the magnetic moments of the muon or the electron. The explanation of both anomalies requires lepton-flavor-nonuniversal or lepton-flavor-violating ALP couplings.
Heavy neutral gauge bosons arise in many motivated models of beyond the Standard Model Physics. Experimental searches require that such gauge bosons are above the TeV scale in most models which means ...that the tools of effective field theories, in particular the Standard Model effective field theory (SMEFT), are useful. We match the SMEFT to models with heavy Z ′ bosons, including effects of dimension-8 operators, and consider the restrictions on model parameters from electroweak precision measurements and from Drell Yan invariant mass distributions and forward-backward asymmetry, A FB , measurements at the LHC. The results demonstrate the model dependence of the resulting limits on SMEFT coefficients and the relatively small impact of including dimension-8 matching. In all cases, the limits from invariant mass distributions are stronger than from A FB measurements in the Z ′ models we consider. Published by the American Physical Society 2024
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