arXiv subjects

Chuan-Qiang Song

Publications and source records attributed to Chuan-Qiang Song.

6 recordsLinked to original sources

arXiv2026

Matching from quark to hadronic operators: external source vs spurion methods

Various weak processes at the hadronic scale have been utilized to search for new physics at high energy scale, which can be described by the QCD chiral Lagrangian matched from the low-energy effective theory (LEFT). Utilizing the chiral symmetry $SU(2)_L\times SU(2)_R \to SU(2)_V$ at the quark and hadronic levels, we make a comprehensive comparison of various matching methods, including the external source method, conventional spurion method, and our systematic spurion method. Although different methods show agreements for dimension-6 LEFT operator matching, we find that for higher-dimensional operators, the external source method is quite limited or inapplicable, the conventional spurion methods needs to introduce more and more spurions, while our spurion method does not need to introduce any new spurions than the ones in the dimension-6 matching. Using minimal set of spurions, we thus establish an one-to-one correspondence between the LEFT and chiral operators, with several examples, such as derivative operators at dimensions 7 and 8 with a single bilinear, four-quark operators at the dimension-9 level with two quark bilinears, which can be applied to the study of neutrino/electron scatterings and neutrinoless double beta decay.

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arXiv2026

Comprehensive Effective Field Theory Analysis for Baryon Number Violating Processes

Baryon number-violating processes arise generically in many extensions of the Standard Model, with Grand Unified Theories providing the most compelling realizations. Ongoing experimental searches at JUNO, Hyper-K, and DUNE motivate a more precise and model-independent analysis utilizing the effective field theory (EFT) framework capable of connecting ultraviolet dynamics to low-energy hadronic observables. In this work, we perform a pipeline analysis that connects baryon number-violating (BNV) new physics to its low-energy description through the Standard Model EFT (SMEFT) up to dimension nine and the Low-Energy EFT (LEFT) up to dimension eight, and subsequently matches onto chiral perturbation theory using a systematic spurion method. We show that the complete set of dimension-eight LEFT operators enables the inclusion of the full set of chiral representations for three-quark operators with derivatives, which are also embedded in the chiral Lagrangian after quark-hadron matching. By contrast, the conventional dimension-six operators generate only the $(\bar{\mathbf{3}},\mathbf{3})$ and $(\mathbf{8},\mathbf{1})$ representations. The higher dimensional LEFT operators should be matched from higher order SMEFT operators, and thus a wider class of UV completions are allowed. We consider the complete tree-level UV resonances for dimension 6 and 7 SMEFT operators, and representative UVs for higher dimension operators.

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arXiv2026

A Comprehensive Effective Field Theory Framework for Coherent Elastic Neutrino-Nucleus Scattering

Coherent elastic neutrino-nucleus scattering (CE$ν$NS) stands out as a pivotal process for precision tests of the Standard Model electroweak sector, investigations of neutrino properties, and searches for new physics (NP). Recent experimental measurements by COHERENT, CONUS+, and ton-scale xenon detectors--including PandaX-4T and XENONnT--underscore the need for a systematic theoretical framework to bridge high-energy physics scenarios with low-energy observational data. In this work, we develop a comprehensive end-to-end effective field theory (EFT) framework for CE$ν$NS, encompassing the complete energy scale hierarchy spanning the ultraviolet (UV) regime down to the nuclear sector. We consider the low-energy EFT (LEFT) operators up to dimension 8, incorporating their QCD renormalization group running effects, and employ the systematic spurion method to achieve the matching between these operators and the chiral Lagrangian. A full power counting analysis is performed, extending to nuclear response functions, which evaluates contributions from LEFT operators up to dimension 8 while accounting for the nucleon number enhancement effect intrinsic to CE$ν$NS. Moreover, we match the relevant LEFT operators for CE$ν$NS onto operators up to dimension 8 within the Standard Model EFT. By also providing their complete tree-level ultraviolet completions, this procedure establishes a consistent top-down theoretical workflow. Leveraging a broad suite of CE$ν$NS experimental data, this framework enables a combined analysis to extract constraints on the scales of EFT operators and neutrino non-standard interaction parameters.

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arXiv2025

Constraints on neutrino non-standard interactions from COHERENT, PandaX-4T and XENONnT

We investigate constraints on neutrino non-standard interactions (NSIs) in the effective field theory framework, using data from the first measurement of solar $^8$B neutrinos via coherent elastic neutrino-nucleus scattering (CE$ν$NS) in the PandaX-4T and XENONnT experiments and data from the COHERENT experiment. The impacts of neutrino NSIs on the CE$ν$NS cross section and the matter effect in the propagation of solar neutrinos are included, while we obtain that the expected number of CE$ν$NS events is more sensitive to neutrino NSIs appearing in the cross section. Due to relatively large statistical uncertainties, the sensitivities of the PandaX-4T and XENONnT experiments to the neutrino NSIs are currently limited, compared to the COHERENT experiment. Besides, we find that since the central value of the measured CE$ν$NS counts significantly differs from the Standard Model prediction, the sensitivity of PandaX-4T experiment is even more restricted compared to XENONnT. However, the measurements of PandaX-4T and XENONnT are uniquely sensitive to the neutrino NSIs for the $τ$ flavor due to oscillation feature of the solar $^8$B neutrinos. We also assess how the experimental central value, exposure, and systematic uncertainties will affect the constraints on neutrino NSIs from various CE$ν$NS measurements in the future.

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arXiv2025

Systematic Spurion Matching between Low Energy EFT and Chiral Lagrangian

The hadronic chiral Lagrangian can be matched from the low energy effective field theory (LEFT) operators at the quark level. Traditionally, as the mass dimension of the LEFT operators increases, more and more external sources are necessarily introduced in the chiral perturbation theory (ChPT). In this work, we present a systematic matching procedure with the single spurion field $\mathbf{T}$ of the flavor $SU(3)_V$ octet, without the need of external sources. We present the complete sets of the LEFT operators, which have been reformulated using the flavor $SU(3)_V$ symmetry up to dimension 9. At the same time, the ChPT Lagrangian is also reformulated using the single spurion and lepton fields, instead of external sources. The spurion matching can be performed between LEFT and ChPT operators with the same flavor $SU(3)_V$ and $CP$ structures, and the same leptonic currents, using the naive dimensional analysis at the quark and hadronic levels.

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arXiv2024

Complete CP-eigen Bases of Meson-Baryon Chiral Lagrangian up to $p^5$-order

Chiral perturbation theory describes the low energy dynamics of mesons and baryons in terms of the nonlinear Goldstone boson and fermion degrees of freedom. Through the Young tensor technique, we construct the on-shell operator bases for the meson-baryon system up to $p^5$-order, using the chiral dimension power counting and heavy baryon expansion. For the Lorentz structure, additional treatments on off-shell external sources and operators with higher derivatives are necessarily considered, while for the internal structure, the invariant tensor basis is converted into the trace basis equivalently, and Cayley-Hamilton relations are utilized to classify different CP eigen-operators. Finally we present the complete operator set of $C$+$P$+, $C$+$P$-, $C$-$P$+, and $C$-$P$- eigen-operators at the $p^5$-order, and obtain the operator counting from the Hilbert series.

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