Masses and decay constants of the η and η′ mesons from lattice QCD

We determine the masses, the singlet and octet decay constants as well as the anomalous matrix elements of the η and η′ mesons in Nf = 2 + 1 QCD. The results are obtained using twenty-one CLS ensembles of non-perturbatively improved Wilson fermions that span four lattice spacings ranging from a ≈ 0.086 fm down to a ≈ 0.050 fm. The pion masses vary from Mπ = 420 MeV to 126 MeV and the spatial lattice extents Ls are such that LsMπ ≳ 4, avoiding significant finite volume effects. The quark mass dependence of the data is tightly constrained by employing two trajectories in the quark mass plane, enabling a thorough investigation of U(3) large-Nc chiral perturbation theory (ChPT). The continuum limit extrapolated data turn out to be reasonably well described by the next-to-leading order ChPT parametrization and the respective low energy constants are determined. The data are shown to be consistent with the singlet axial Ward identity and, for the first time, also the matrix elements with the topological charge density are computed. We also derive the corresponding next-to-leading order large-Nc ChPT formulae. We find F8 = 115.0(2.8) MeV, θ8 = −25.8(2.3)°, θ0 = −8.1(1.8)° and, in the $$ \overline{\mathrm{MS}} $$ MS ¯ scheme for Nf = 3, F0(μ = 2 GeV) = 100.1(3.0) MeV, where the decay constants read $$ {F}_{\eta}^8 $$ F η 8 = F8 cos θ8, $$ {F}_{\eta \prime}^8 $$ F η ′ 8 = F8 sin θ8, $$ {F}_{\eta}^0 $$ F η 0 = −F0 sin θ0 and $$ {F}_{\eta \prime}^0 $$ F η ′ 0 = F0 cos θ0. For the gluonic matrix elements, we obtain aη(μ = 2 GeV) = 0.0170(10) GeV3 and aη′(μ = 2 GeV) = 0.0381(84) GeV3, where statistical and all systematic errors are added in quadrature.

Topology change, emergent symmetries and compact star matter

Topology effects have being extensively studied and confirmed in strongly correlated condensed matter physics. In the limit of large number of colors, baryons can be regarded as topological objects—skyrmions—and the baryonic matter can be regarded as a skyrmion matter. We review in this paper the generalized effective field theory for dense compact-star matter constructed with the robust inputs obtained from the skyrmion approach to dense nuclear matter, relying on possible “emergent” scale and local flavor symmetries at high density. All nuclear matter properties from the saturation density n0 up to several times n0 can be fairly well described. A uniquely novel—and unorthdox—feature of this theory is the precocious appearance of the pseudo-conformal sound velocity $v^{2}_{s}/c^{2} \approx 1/3$ v s 2 / c 2 ≈ 1 / 3 , with the non-vanishing trace of the energy momentum tensor of the system. The topology change encoded in the density scaling of low energy constants is interpreted as the quark-hadron continuity in the sense of Cheshire Cat Principle (CCP) at density $\gtrsim 2n_{0}$ ≳ 2 n 0 in accessing massive compact stars. We confront the approach with the data from GW170817 and GW190425.

S-matrix bootstrap for effective field theories: massless pions

We use the numerical S-matrix bootstrap method to obtain bounds on the two leading Wilson coefficients (or low energy constants) of the chiral lagrangian controlling the low-energy dynamics of massless pions. This provides a proof of concept that the numerical S-matrix bootstrap can be used to derive non-perturbative bounds on massless EFTs in more than two spacetime dimensions.

An EFT toolbox for baryon and lepton number violating dinucleon to dilepton decays

In this paper we systematically consider the baryon (B) and lepton (L) number violating dinucleon to dilepton decays (pp → ℓ+ℓ′+, pn → $$ {\mathrm{\ell}}^{+}\overline{\nu}^{\prime } $$ ℓ + ν ¯ ′ , nn → $$ \overline{\nu}\overline{\nu}^{\prime } $$ ν ¯ ν ¯ ′ ) with ∆B = ∆L = −2 in the framework of effective field theory. We start by constructing a basis of dimension-12 (dim-12) operators mediating such processes in the low energy effective field theory (LEFT) below the electroweak scale. Then we consider their standard model effective field theory (SMEFT) completions upwards and their chiral realizations in baryon chiral perturbation theory (BχPT) downwards. We work to the first nontrivial orders in each effective field theory, collect along the way the matching conditions, and express the decay rates in terms of the Wilson coefficients associated with the dim-12 operators in the SMEFT and the low energy constants pertinent to BχPT. We find the current experimental limits push the associated new physics scale larger than 1 − 3 TeV, which is still accessible to the future collider searches. Through weak isospin symmetry, we find the current experimental limits on the partial lifetime of transitions pp → ℓ+ℓ′+, pn → $$ {\mathrm{\ell}}^{+}\overline{\nu}^{\prime } $$ ℓ + ν ¯ ′ imply stronger limits on nn → $$ \overline{\nu}\overline{\nu}^{\prime } $$ ν ¯ ν ¯ ′ than their existing lower bounds, which are improved by 2−3 orders of magnitude. Furthermore, assuming charged mode transitions are also dominantly generated by the similar dim-12 SMEFT interactions, the experimental limits on pp → e+e+, e+μ+, μ+μ+ lead to stronger limits on pn → $$ {\mathrm{\ell}}_{\alpha}^{+}{\overline{\nu}}_{\beta } $$ ℓ α + ν ¯ β with α, β = e, μ than their existing bounds. Conversely, the same assumptions help us to set a lower bound on the lifetime of the experimentally unsearched mode pp → e+τ+ from that of pn → $$ {e}^{+}{\overline{\nu}}_{\tau } $$ e + ν ¯ τ , i.e., $$ {\Gamma}_{pp\to {e}^{+}{\tau}^{+}}^{-1}\gtrsim 2\times {10}^{34} $$ Γ pp → e + τ + − 1 ≳ 2 × 10 34 yr.

Asymptotic Properties of Discrete Minimal s,logt-Energy Constants and Configurations

We investigated the energy of N points on an infinite compact metric space (A,d) of a diameter less than 1 that interact through the potential (1/ds)(log1/d)t, where s,t≥0 and d is the metric distance. With Elogts(A,N) denoting the minimal energy for such N-point configurations, we studied certain continuity and differentiability properties of Elogts(A,N) in the variable s. Then, we showed that in the limits, as s→∞ and as s→s0>0,N-point configurations that minimize the s,logt-energy tends to an N-point best-packing configuration and an N-point configuration that minimizes the s0,logt-energy, respectively. Furthermore, we considered when A are circles in the Euclidean space R2. In particular, we proved the minimality of N distinct equally spaced points on circles in R2 for some certain s and t. The study on circles shows a possibility for the utilization of N points generated through such new potential to uniformly discretize on objects with very high symmetry.

Relativistic N-particle energy shift in finite volume

We present a general method for deriving the energy shift of an interacting system of N spinless particles in a finite volume. To this end, we use the nonrelativistic effective field theory (NREFT), and match the pertinent low-energy constants to the scattering amplitudes. Relativistic corrections are explicitly included up to a given order in the 1/L expansion. We apply this method to obtain the ground state of N particles, and the first excited state of two and three particles to order L−6 in terms of the threshold parameters of the two- and three-particle relativistic scattering amplitudes. We use these expressions to analyze the N-particle ground state energy shift in the complex φ4 theory.

New method for calculating electromagnetic effects in semileptonic beta-decays of mesons

We construct several classes of hadronic matrix elements and relate them to the low-energy constants in Chiral Perturbation Theory that describe the electromagnetic effects in the semileptonic beta decay of the pion and the kaon. We propose to calculate them using lattice QCD, and argue that such a calculation will make an immediate impact to a number of interesting topics at the precision frontier, including the outstanding anomalies in |Vus| and the top-row Cabibbo-Kobayashi-Maskawa matrix unitarity.

Particular kinetic patterns of heavy oil feedstock hydroconversion in the presence of dispersed nanosize MoS2

A kinetic model of the heavy oil feedstock hydroconversion performed in continuous flow reactor in the presence of in-situ synthesized dispersed nanosize catalyst Molybdenum disulfide (MoS2) has been proposed. The kinetic parameters of heavy oil feedstock with different properties have been determined for the two process versions: with coke formation and without appreciable coke formation. It has been stated that hydroconversion in the presence of in-situ synthesized dispersed MoS2 (C(Mo) = 0.05% wt. (per feed)) corresponds to a first-order reaction for all studied feedstock samples. The rate and activation energy constants have been determined. It has been shown that the conditions of polycondensation products (coke) formation result in increasing process rate and decreasing activation energy.