Beyond-Standard-Model Tensor Interaction and Hadron Phenomenology

Abstract

We evaluate the impact of recent developments in hadron phenomenology on extracting possible fundamental tensor interactions beyond the standard model. We show that a novel class of observables, including the chiral-odd generalized parton distributions, and the transversity parton distribution function can contribute to the constraints on this quantity. Experimental extractions of the tensor hadronic matrix elements, if sufficiently precise, will provide a, so far, absent testing ground for lattice QCD calculations. DOI: 10.1103/PhysRevLett.115.162001 PACS numbers: 13.60.Hb, 13.40.Gp, 24.85.+p High precision measurements of beta decay observables play an important role in beyond the standard model (BSM) physics searches, as they allow us to probe couplings other than of the V − A type, which could appear at the low energy scale. Experiments using cold and ultracold neutrons [1][2][3][4], nuclei [5][6][7][8], and meson rare decays [9] are being performed, or have been planned, that can reach the per-mil level or even higher precision. Effective field theory (EFT) allows one to connect these measurements and BSM effects generated at TeV scales. In this approach that complements collider searches, the new interactions are introduced in an effective Lagrangian describing semileptonic transitions at the GeV scale including four-fermion terms, or operators up to dimension six for the scalar, tensor, pseudoscalar, and V þ A interactions (for a review of the various EFT approaches, see Ref.[10]). Because the strength of the new interactions is defined with respect to the strength of the known SM interaction, the coefficients of the various terms, ϵ i , (i ¼ S; T; P; L; R) depend on the ratio m 2 W =Λ 2 i , where Λ i is the new physics scale relevant for these nonstandard interactions, and mW Þ. Therefore, the precision with which ϵ i ∝ m 2 W =Λ 2 i , is known determines a lower limit for Λ i . The scalar (S) and tensor (T) operators, in particular, contribute linearly to the beta decay parameters through their interference with the SM amplitude, and they are, therefore, more easily detectable. The matrix elements or transition amplitudes between neutron and proton states of all quark bilinear Lorentz structures in the effective Lagrangian which are relevant for beta decay observables, involve products of the BSM couplings, ϵ i , and the corresponding hadronic charges, g i , i.e., considering only terms with left-handed neutrinos,whereSðTÞ , characterize nucleon structure; however, at variance with the electroweak currents, there exists no fundamental coupling to these charges in the standard model. Therefore, they cannot be measured directly in elastic scattering processes. This Letter is concerned with an alternative approach aimed at extracting the hadronic charges from experimental data obtained in electron scattering. In previous work, various approaches have been developed to calculate these quantities including lattice QCD [11][12][13][14][15], and most recently, Dyson-Schwinger equations [16,17]. Lattice QCD ...

Electric dipole moment of C13

“…The first reason is because the effect of the quark EDM to the nucleon EDM is suppressed by the nucleon tensor charge. The nucleon tensor charge is the linear coefficient which relates the quark EDM to the nucleon EDM, and the extraction from experimental data shows values smaller than one [131][132][133][134]. Recent lattice QCD analyses give also consistent data [135][136][137][138][139][140][141][142][143].…”

The Tensor and the Scalar Charges of the Nucleon from Hadron Phenomenology

“…The development expected from such a measurement and statistical analysis will qualitatively improve the present estimates for a number of processes, e.g. we expect about 10% improvement in the errorbars with CLAS12 and SoLID data [9]. We would like to restate that DiFFs are universal and can, as such, be transported to, e.g., SIDIS or proton-proton asymmetries.…”

“…The impact of data based determinations of the tensor charge has been studied in Ref. [9]. Given the sensitivity bounds on the Fierz term b, an error of about 10 − 15% on the tensor charge is estimated to be sufficient.…”

“…The grey band gives the error assuming Δg T = 0, and the average g T of the three hadronic analyses considered in Ref. [9]. The lattice evaluations from Refs.…”

Nucleon tensor form factors in a relativistic confined quark model

“…[18,19] the u and d quark valence contributions to the tensor charges have been evaluated using experimental data on di-hadron production from the the HERMES, COMPASS, and BELLE Collaborations. The impact of recent developments in hadron phenomenology on extracting possible fundamental tensor interactions beyond the Standard Model has been studied in a recent paper [20].…”