Framework Of Effective Field Theory Research Articles

Radiative proton capture on N15 within effective field theory

The astrophysical $S$ factor for the radiative proton capture process on the $^{15}\mathrm{N}$ nucleus, i.e., $^{15}\mathrm{N}(p, \gamma)^{16}\mathrm{O}$, at stellar energies are studied within the framework of the cluster effective field theory. The thermonuclear $^{15}\mathrm{N}(p, \gamma)^{16}\mathrm{O}$ reaction links the type-I to type-II cycles of the carbon-nitrogen-oxygen cycle and affects the abundances of elements in the univere. For investigating this reaction in the effective field theory formalism, we first construct an effective Lagrangian that is appropriate for this reaction at low-energies. Since the intermediate excited states of the $^{16}\mathrm{O}$ nucleus have a crucial role in this reaction, we include these resonances in the formalism. The corresponding radiative capture amplitudes and cross section are calculated, which lead to the astrophysical $S$ factor. The low energy constants introduced in the effective Lagrangian are determined by fitting the theoretical results to the observed $S$ factors in the range of $130~\mathrm{keV} < E_p < 2500~\mathrm{keV}$ using three different experimental data sets. Considering the recent data sets, we obtain $S(0) = 29.8\mbox{-}34.1~\mathrm{keV\ b}$, which is in a good agreement with the estimates from $R$-matrix approaches in the literature. The values of $S$ at the Gamow energy are found to be larger than $S(0)$ values by about $10\%$.

Neutrino specific spin-3/2 dark matter

In this paper we consider a spin-frac{3}{2} dark matter (DM) particle which couples to neutrinos, as a viable candidate to produce the observed DM relic density through the thermal freeze-out mechanism. The couplings of DM to neutrinos is considered first in a general dimension-6 effective field theory framework. We then consider two specific neutrino-portal models discussed in the literature. In the first model DM couples to the standard model neutrinos through mixing generated by a sterile pseudo-Dirac massive neutrino, and in the second model we consider the U(1)_{L_mu - L_tau } gauge symmetric model. For each of these models we explore the parameter space required to generate the observed relic density. The constraints on the parameters of these models from the existing and proposed neutrino experiments, as well as from existing cosmological and astrophysical bounds, are considered in the context of the relic density calculations.

Gravitational radiation from inspiralling compact objects: Spin effects to the fourth post-Newtonian order

The linear- and quadratic-in-spin contributions to the binding potential and gravitational-wave flux from binary systems are derived to next-to-next-to-leading order in the Post-Newtonian (PN) expansion of general relativity, including finite-size and tail effects. The calculation is carried out through the worldline effective field theory framework. We find agreement in the overlap with the available PN literature and test-body limit. As a direct application, we complete the knowledge of spin effects in the evolution of the orbital phase for aligned-spin circular orbits to fourth PN order. We estimate the impact of the new results in the number of accumulated gravitational-wave cycles. We find they will play an important role in providing reliable physical interpretation of gravitational-wave signals from spinning binaries with future detectors such as LISA and the Einstein Telescope.

Electromagnetic flavor-changing lepton decays from Lorentz and CPT violation

Lorentz- and $CPT$-violating effects initiating two-body electromagnetic flavor-changing decays of charged leptons are studied in the framework of Lorentz-violating effective field theory. An analysis of data from experiments at the Paul Scherrer Institute and at the Stanford Linear Accelerator measuring the branching ratios of these decays provides 576 constraints on independent flavor-changing effects in the charged-lepton sector, consistent with no Lorentz and $CPT$ violation at the level of parts in ${10}^{\ensuremath{-}13}--{10}^{\ensuremath{-}9}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$.

Light-cone sum rule analysis of semileptonic decays varLambda _b^0 rightarrow varLambda _c^+ ell ^- {overline{nu }}_ell

In this work, we analyze the semileptonic decay processes of varLambda _b rightarrow varLambda _c in the light-cone sum rule approach. In order to calculate the form factors of the varLambda _b baryon transition matrix element, we use the light-cone distribution amplitudes of varLambda _b obtained from the QCD sum rule in the heavy quark effective field theory framework. With the calculation of the six form factors of the varLambda _b rightarrow varLambda _c transition matrix element, the differential decay widths of varLambda _b^0 rightarrow varLambda _c^+ ell ^- {overline{nu }}_ell (ell = e, ~mu , ~tau ) and their absolute branching fractions are obtained. Additionally, the ratio of R(varLambda _c^+) equiv {mathcal {B}}r(varLambda _b^0 rightarrow varLambda _c^+ tau ^- {overline{nu }}_tau )/{mathcal {B}}r(varLambda _b^0 rightarrow varLambda _c^+ mu ^- {overline{nu }}_mu ) is also obtained in this work. Our results are in accord with the newest experimental result and other theoretical calculations and predictions.

Gravitational form factors of the delta resonance in chiral EFT

The leading one-loop corrections to the gravitational form factors of the delta resonance are calculated in the framework of chiral effective field theory. Various contributions to the energy–momentum tensor and the renormalization of the low-energy constants are worked out. Using the small scale expansion, expressions for static quantities are obtained and the real and imaginary parts of the gravitational form factors are calculated numerically.

Generic 3-point statistics with tensor modes in light of Swampland and Trans-Planckian Censorship Conjecture

Recently proposed Swampland Criteria (SC) and Trans-Planckian Censorship Conjecture (TCC) question the theoretical consistency of inflationary cosmology. While SC can be in tension with the recent observational bound on tensor-to-scalar ratio which is a consequence of single field consistency relation, the requirement of TCC translates to the fact that inflation can not produce a detectable signal for stochastic gravitational wave, raising a question on future prospects of detection of Primordial Gravitational Waves (PGW). But the constraint can be relaxed significantly by considering Non Bunch Davies (NBD) initial states, that in turn brings back the observational relevance of PGW via its 2-point function. Also with NBD states the tension between SC and observational bound on tensor-to-scalar ratio vanishes. Focusing on these theoretical importance of NBD states, in this article we develop consistent 3-point statistics with tensor modes for all possible correlators (auto and mixed) for NBD initial states in a generic, model independent framework of Effective Field Theory of inflation and analyze the properties of the correlators in the light of TCC. We also construct the templates of the corresponding nonlinearity parameters f_{NL} for different shapes of relevance and investigate if any of the 3-point correlators could be of interest for future CMB missions. Our analysis reveals that the prospects of detecting the tensor auto correlator are almost nil whereas the mixed correlators might be relevant for future CMB missions.

Monolepton production in SMEFT to mathcal{O} (1/Λ4) and beyond

We calculate pp → ℓ+ν, ℓ− overline{nu} to mathcal{O} (1/Λ4) within the Standard Model Effective Field Theory (SMEFT) framework. In particular, we calculate the four-fermion contribution from dimension six and eight operators, which dominates at large center of mass energy. We explore the relative size of the mathcal{O} (1/Λ4) and mathcal{O} (1/Λ2) results for various kinematic regimes and assumptions about the Wilson coefficients. Results for Drell-Yan production pp → ℓ+ℓ− at mathcal{O} (1/Λ4) are also provided. Additionally, we develop the form for four fermion contact term contributions to pp → ℓ+ν, ℓ− overline{nu} , pp → ℓ+ℓ− of arbitrary mass dimension. This allows us to estimate the effects from even higher dimensional (dimension > 8) terms in the SMEFT framework.

Weinberg’s Compositeness

Nearly 60 years ago, Weinberg suggested a criterion for particle “compositeness”, which has acquired a new life with the discovery of new, exotic hadrons. His idea resonates with model-based intuition. I discuss the role it plays in the context of another of Weinberg’s creations, the model-independent framework of effective field theories.

Mono-γ production of a dark vector at future e + e − colliders* *Supported by the Innovation Capability Support Program of Shaanxi Province (2021KJXX-47), the Double First Class start-up fund (WF220442604), the Shanghai Pujiang Program (20PJ1407800), National Natural Science Foundation of China (12090064), as well as Chinese Academy of Sciences Center for Excellence in Particle Physics (CCEPP)

The associated production of a dark particle and photon, represented as a mono-γ event, is a promising channel to probe particle content and dynamics in the dark sector. In this study, we investigate the properties of the mono-γ production of vector dark matter at future colliders. Photon-like and Pauli operators as well as triple gauge boson interactions involving dark matter are considered in the framework of effective field theory. We show that, in comparison with the Pauli operator, the triple gauge boson couplings are significantly more interesting in high energy colliders. Beam polarization effects are also analyzed, and we show that the experimental sensitivities cannot be significantly enhanced because of the smaller luminosity.

Two-loop power spectrum with full time- and scale-dependence and EFT corrections: impact of massive neutrinos and going beyond EdS

We compute the density and velocity power spectra at next-to-next-to-leading order taking into account the effect of time- and scale-dependent growth of massive neutrino perturbations as well as the departure from Einstein-de-Sitter (EdS) dynamics at late times non-linearly. We determine the impact of these effects by comparing to the commonly adopted approximate treatment where they are not included. For the bare cold dark matter (CDM)+baryon spectrum, we find percent deviations for k ≳ 0.17h Mpc-1, mainly due to the departure from EdS. For the velocity and cross power spectrum the main difference arises due to time- and scale-dependence in presence of massive neutrinos yielding percent deviation above k ≃ 0.08, 0.13, 0.16h Mpc-1 for ∑mν = 0.4, 0.2, 0.1 eV, respectively. We use an effective field theory (EFT) framework at two-loop valid for wavenumbers k ≫ k FS, where k FS is the neutrino free-streaming scale. Comparing to Quijote N-body simulations, we find that for the CDM+baryon density power spectrum the effect of neutrino perturbations and exact time-dependent dynamics at late times can be accounted for by a shift in the one-loop EFT counterterm, Δγ̅1 ≃ - 0.2 Mpc2/h 2. We find percent agreement between the perturbative and N-body results up to k ≲ 0.12h Mpc-1 and k ≲ 0.16h Mpc-1 at one- and two-loop order, respectively, for all considered neutrino masses ∑mν ≤ 0.4 eV.

Subleading contributions to N -boson systems inside the universal window

We study bosonic systems in the regime in which the two-body system has a shallow bound state or, equivalently, a large value of the two-body scattering length. Using the effective field theory framework as a guide, we construct a series of potential terms which have decreasing importance in the description of the binding energy of the systems. The leading order potential terms consist of a two-body term, usually attractive, plus a three-body term, usually repulsive; this last term is required to prevent the collapse of systems with more than two particles. At this order, the parametrization of the two-body potential is done to obtain a correct description of the scattering length, which governs the dynamics in this regime, whereas the three-body term fixes a three-body datum. We investigate the role of the cut-off in the leading order description and we extend the exploration beyond the leading order by including the next-to-leading order terms in both, the two- and three-body potentials. We use the requirement of the stability of the N-body system, whose energy is variationally estimated, to introduce the three-body forces. The potential parametrization, as a function of the cut-off, is fixed to describe the energy of 4 He clusters up to seven particles within the expected accuracy. Finally, we also explore the possibility to describe at the same time the atom-dimer scattering length.

Unraveling the 0νββ decay mechanisms

We discuss the possibilities of distinguishing among different mechanisms of neutrinoless double beta decay arising in the effective field theory framework. Following the review and detailed investigation of the particular ways of discrimination, we conclude that the 32 different low-energy effective operators can be split into multiple groups that are in principle distinguishable from each other by measurements of the phase-space observables and by comparison of the decay rates obtained using different isotopes. This would require not only a substantial experimental precision but necessarily also a considerable improvement of the current theoretical knowledge of the underlying nuclear physics. Specifically, the limiting aspect in our approach turns out to be the currently unknown or uncertain values of low-energy constants. Besides the study adopting the effective field theory language we also look into several typical UV models.

Results on photon-mediated dark-matter–nucleus interactions from the PICO-60 C3F8 bubble chamber

Many compelling models predict dark matter coupling to the electromagnetic current through higher multipole interactions, while remaining electrically neutral. Different multipole couplings have been studied, among them anapole moment, electric and magnetic dipole moments, and millicharge. This study sets limits on the couplings for these photon-mediated interactions using non-relativistic contact operators in an effective field theory framework. Using data from the PICO-60 bubble chamber leading limits for dark matter masses between 2.7 GeV/c$^2$ and 24 GeV/c$^2$ are reported for the coupling of these photon-mediated dark matter-nucleus interactions. The detector was filled with 52 kg of C$_3$F$_8$ operating at thermodynamic thresholds of 2.45 keV and 3.29 keV, reaching exposures of 1404 kg-day and 1167 kg-day, respectively.

Gravitational corrections to a non-Abelian gauge theory

This paper is part of a series of papers exploring the renormalization of field theories coupled to gravity using the effective field theory framework. In previous works, we studied the universality of the electric charge and the two-loops beta function in the Einstein-QED system. Now, we use this framework to study the non-Abelian gauge theory with fermions coupled to gravity. We show that even though some of the counterterms are dependent on the gravitational coupling, the renormalized coupling constant, and therefore the beta function, do not receive any gravitational correction at one-loop order. Also, we explicitly show that, at this order, the Slavnov-Taylor identities are respected. Finally, we end the paper by putting into perspective the results of the present and the past papers.

Measurements of the Higgs boson inclusive and differential fiducial cross-sections in the diphoton decay channel with pp collisions at sqrt{s} = 13 TeV with the ATLAS detector

A measurement of inclusive and differential fiducial cross-sections for the production of the Higgs boson decaying into two photons is performed using 139 fb−1 of proton-proton collision data recorded at sqrt{s} = 13 TeV by the ATLAS experiment at the Large Hadron Collider. The inclusive cross-section times branching ratio, in a fiducial region closely matching the experimental selection, is measured to be 67 ± 6 fb, which is in agreement with the state-of-the-art Standard Model prediction of 64 ± 4 fb. Extrapolating this result to the full phase space and correcting for the branching ratio, the total cross-section for Higgs boson production is estimated to be 58 ± 6 pb. In addition, the cross-sections in four fiducial regions sensitive to various Higgs boson production modes and differential cross-sections as a function of either one or two of several observables are measured. All the measurements are found to be in agreement with the Standard Model predictions. The measured transverse momentum distribution of the Higgs boson is used as an indirect probe of the Yukawa coupling of the Higgs boson to the bottom and charm quarks. In addition, five differential cross-section measurements are used to constrain anomalous Higgs boson couplings to vector bosons in the Standard Model effective field theory framework.

B¯→D(*)ℓX¯ decays in effective field theory with massive right-handed neutrinos

We calculate the complete differential decay distributions for the $B$ meson decays, $\bar B \to D^{(*)} \ell \bar{X}$, to a massive right-handed (RH) neutrino in the low-energy effective field theory (LEFT) framework. We find that a massive RH neutrino does not introduce any new angular structures compared to the massless case, but can cause significant distortions in angular observables. We study the phenomenology of low-energy four-fermion operators permitted by the standard model effective field theory (SMEFT) extended with RH neutrinos (SMNEFT). We show that to explain the positive value of the difference in forward-backward asymmetries, $\Delta A_{\text{FB}}\equiv A_{\text{FB}}^\mu-A_{\text{FB}}^e$, tentatively inferred from Belle data, the RH neutrino must be massive. We also make predictions for $q^2$ dependent angular observables to motivate future measurements.

AbInitio Prediction of the ^{4}He(d,γ)^{6}Li Big Bang Radiative Capture.

The rate at which helium (^{4}He) and deuterium (d) fuse together to produce lithium-6 (^{6}Li) and a γ ray, ^{4}He(d,γ)^{6}Li, is a critical puzzle piece in resolving the discrepancy between big bang predictions and astronomical observations for the primordial abundance of ^{6}Li. The accurate determination of this radiative capture rate requires the quantitative and predictive description of the fusion probability across the big bang energy window (30 keV≲E≲400 keV), where measurements are hindered by low counting rates. We present first-principle (or, abinitio) predictions of the ^{4}He(d,γ)^{6}Li astrophysical S factor using validated nucleon-nucleon and three-nucleon interactions derived within the framework of chiral effective field theory. By employing the abinitio no-core shell model with continuum to describe ^{4}He-d scattering dynamics and bound ^{6}Li product on an equal footing, we accurately and consistently determine the contributions of the main electromagnetic transitions driving the radiative capture process. Our results reveal an enhancement of the capture probability below 100keV owing to previously neglected magnetic dipole (M1) transitions and reduce by an average factor of 7 the uncertainty of the thermonuclear capture rate between 0.002 and 2GK.

Neutral-current electroweak physics and SMEFT studies at the EIC

We study the potential for precision electroweak (EW) measurements and beyond-the-Standard Model (BSM) searches using cross-section asymmetries in neutral-current deep inelastic scattering at the electron-ion collider (EIC). Our analysis uses a complete and realistic accounting of systematic errors from both theory and experiment and considers the potential of both proton and deuteron beams for a wide range of energies and luminosities. We also consider what can be learned from a possible future positron beam and a potential tenfold luminosity upgrade of the EIC beyond its initial decade of running. We use the SM effective field theory (SMEFT) framework to parametrize BSM effects and focus on semileptonic four-fermion operators, whereas for our precision EW study, we determine how well the EIC can measure the weak mixing angle. New features of our study include the use of an up-to-date detector design of the EIC Comprehensive Chromodynamics Experiment and accurate running conditions of the EIC, the simultaneous fitting of beam polarization uncertainties and Wilson coefficients to improve the sensitivity to SMEFT operators, and the inclusion of the weak mixing angle running in our fit template. We find that the EIC can probe BSM operators at scales competitive with and in many cases exceeding LHC Drell-Yan bounds while simultaneously not suffering from degeneracies between Wilson coefficients.

NNLO event generation for ppto Zhto {mathrm{ell}}^{+}{mathrm{ell}}^{-}boverline{b} production in the SM effective field theory

We consider associated Zh production with Z → ℓ+ℓ− and hto boverline{b} decays in hadronic collisions. In the framework of the Standard Model effective field theory (SMEFT) we calculate the QCD corrections to this process and achieve next-to-next-to-leading order plus parton shower (NNLO+PS) accuracy using the MiNNLOPS method. This precision is obtained for a subset of six SMEFT operators, including the corrections from effective Yukawa- and chromomagnetic dipole-type interactions. Missing higher-order QCD effects associated with the considered dimension-six operators are estimated to have a relative numerical impact of less than a percent on the total rate once existing experimental limits on the relevant Wilson coefficients are taken into account. We provide a dedicated Monte Carlo (MC) code that evaluates the NNLO SMEFT corrections on-the-fly in the event generation. This MC generator is used to study the numerical impact of NNLO+PS corrections on the kinematic distributions in ppto Zhto {mathrm{ell}}^{+}{mathrm{ell}}^{-}boverline{b} production employing simple SMEFT benchmark scenarios. We identify the invariant mass {m}_{boverline{b}} of the two b-tagged jets as well as the three-invariant jet mass {m}_{boverline{b}j} as particularly interesting observables to study SMEFT effects. These distributions receive contributions that change both their normalisation and shape with the latter modifications depending on the exact jet definition. To our knowledge SMEFT effects of this type have so far not been discussed in the literature. The presented MC generator can also serve as a starting point to obtain NNLO+PS accuracy for a suitable enlarged set of effective operators in the future.