Nuclear Theory·nucl-th

Thursday·February 24, 2022

12 papers—3 primary·9 cross-listed

04
Standard Model prediction for paramagnetic EDMs
Yohei Ema🇺🇸 · Ting Gao🇺🇸 · Maxim Pospelov🇺🇸
Standard Model $C P$ violation associated with the phase of the Cabibbo-Kobayashi-Maskawa quark mixing matrix is known to give small answers for the EDM observables. Moreover, predictions for the EDMs of neutrons and diamagnetic atoms suffer from considerable uncertainties. We point out that the $C P$ -violating observables associated with the electron spin (paramagnetic EDMs) are dominated by the combination of the electroweak penguin diagrams and $Δ I = 1/2$ weak transitions in the baryon sector, and are calculable within chiral perturbation theory. The predicted size of the semileptonic operator $C_{S}$ is $7 \times 1 0^{- 16}$ which corresponds to the equivalent electron EDM $d_{e}^{eq} = 1.0 \times 1 0^{- 35} e cm$ . While still far from the current observational limits, this result is three orders of magnitude larger than previously believed.
↳ hep-phhep-exnucl-thPRL(2022)·76 citations
05
Magnetic field induced corrections to the NJL model coupling constant from vacuum polarization
Thiago H. Moreira🇧🇷 · Fabio L. Braghin🇧🇷
Magnetic field dependent corrections for the coupling constant of the Nambu-Jona-Lasinio model are calculated by considering the one-loop background field method. These coupling constants turn out to break chiral and flavor symmetries and they lead to a slight improvement of the numerical values of the up and down quark condensates when compared to results from lattice QCD. The corresponding magnetic field dependencies of the neutral pion and kaon masses are also presented and compared with available lattice QCD calculations. The resulting magnetic field correction to the $η - η^{'}$ mixing angle is also estimated.
↳ hep-phnucl-thPRD(2022)·16 citations
06
Implications of the first evidence for coherent elastic scattering of reactor neutrinos
Jiajun Liao🇨🇳 · Hongkai Liu🇮🇱 · Danny Marfatia🇺🇸
The recent evidence for coherent elastic neutrino-nucleus scattering (CE $ν$ NS) in the NCC-1701 germanium detector using antineutrinos from the Dresden-II nuclear reactor is in good agreement with standard model expectations. However, we show that a $2 σ$ improvement in the fit to the data can be achieved if the quenching factor is described by a modified Lindhard model. We also place constraints on the parameter space of a light vector or scalar mediator that couples to neutrinos and quarks, and on a neutrino magnetic moment. We demonstrate that the constraints are quite sensitive to the quenching factor at low recoil energies by comparing constraints for the standard Lindhard model with those by marginalizing over the two parameters of the modified Lindhard model.
↳ hep-phhep-exnucl-exnucl-thPRD(2022)·30 citations
07
Pion model with the Nakanishi Integral Representations
R. M. Moita (ITA)🇧🇷 · J. P.B. C.de Melo (LFTC-UCS/UNICID)🇧🇷 · T. Frederico (ITA)🇧🇷 · W. de Paula (ITA)🇧🇷
In the present work, we describe a model for the pion based on an analytic expression for the Bethe-Salpeter (BSA) amplitude, combined with some ingredients from Lattice QCD calculations. The running quark mass function $M (p^{2})$ , used here, reproduces well the results of Lattice QCD calculations. The analytical form of the running quark mass function contains a single time-like pole, which implies in time-like poles of the dressed quark propagator. Such a form allows to build the weight functions, $G_{i} (γ, z)$ , for the Nakanishi integral representation of each scalar function, $χ_{i} (k, p)$ , appearing in the decomposition of the Bethe-Salpeter amplitude in terms of Dirac operators, Such scalar amplitudes can also be used to obtain the pion valence light-front wave function.
↳ hep-phnucl-thRev.Mex.Fis.Suppl.(2022)·1 citation
08
Kaon electromagnetic form factors in dispersion theory
Dominik Stamen🇩🇪 · Deepti Hariharan🇩🇪 · Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪 · Peter Stoffer🇨🇭
The electromagnetic form factors of charged and neutral kaons are strongly constrained by their low-energy singularities, in the isovector part from two-pion intermediate states and in the isoscalar contribution in terms of $ω$ and $ϕ$ residues. The former can be predicted using the respective $π π \to K ˉ K$ partial-wave amplitude and the pion electromagnetic form factor, while the latter parameters need to be determined from electromagnetic reactions involving kaons. We present a global analysis of time- and spacelike data that implements all of these constraints. The results enable manifold applications: kaon charge radii, elastic contributions to the kaon electromagnetic self energies and corrections to Dashen's theorem, kaon boxes in hadronic light-by-light (HLbL) scattering, and the $ϕ$ region in hadronic vacuum polarization (HVP). Our main results are: $⟨ r^{2} ⟩_{c} = 0.359 (3) fm^{2}$ , $⟨ r^{2} ⟩_{n} = - 0.060 (4) fm^{2}$ for the charged and neutral radii, $ϵ = 0.63 (40)$ for the elastic contribution to the violation of Dashen's theorem, $a_{μ}^{K -box} = - 0.48 (1) \times 1 0^{- 11}$ for the charged kaon box in HLbL scattering, and $a_{μ}^{HVP} [K^{+} K^{-}, \leq 1.05 GeV] = 184.5 (2.0) \times 1 0^{- 11}$ , $a_{μ}^{HVP} [K_{S} K_{L}, \leq 1.05 GeV] = 118.3 (1.5) \times 1 0^{- 11}$ for the HVP integrals around the $ϕ$ resonance. The global fit to $K ˉ K$ gives $M ˉ_{ϕ} = 1019.479 (5) MeV$ , $Γ ˉ_{ϕ} = 4.207 (8) MeV$ for the $ϕ$ resonance parameters including vacuum-polarization effects.
↳ hep-phhep-exhep-latnucl-thEPJC(2022)·122 citations
09
Twist-three cross-sections in deeply virtual Compton scattering
Yuxun Guo🇺🇸 · Xiangdong Ji🇺🇸 · Brandon Kriesten🇺🇸 · Kyle Shiells🇺🇸
We study the deeply virtual Compton scattering process with both twist-two and twist-three Compton form factors and present our cross-sections formulas with all polarization configurations. While the twist-three contributions are generally assumed to be negligible in the literature due to the kinematical suppression, we compare them with the twist-two ones at typical JLab 6 GeV and 12 GeV kinematics as well as EIC kinematics and show their kinematical suppression explicitly, justifying the leading-twist approximation made in the literature. In addition, we also estimate the twist-three Compton form factors using Wandzura-Wilczek relations and inputs of twist-two generalized parton distributions based on a reggeized spectator model. With those estimated Compton form factors, we analyze the kinematical behavior of twist-two and twist-three cross-sections in a wide range of kinematics, and discuss the optimal regions for separating the leading-twist effects from the higher-twist ones.
↳ hep-phnucl-exnucl-thJHEP(2022)·17 citations
10
Relativistic hydrodynamics with spin in the presence of electromagnetic fields
Rajeev Singh🇵🇱 · Masoud Shokri🇩🇪 · S. M. A. Tabatabaee Mehr🇮🇷
We extend the classical phase-space distribution function to include the spin and electromagnetic fields coupling and derive the modified constitutive relations for charge current, energy-momentum tensor, and spin tensor. Because of the coupling, the new tensors receive corrections to their perfect fluid counterparts and make the background and spin fluid equations of motion communicate with each other. We investigate special cases which are relevant in high-energy heavy-ion collisions, including baryon free matter and large mass limit. Using Bjorken symmetries, we find that spin polarization increases with increasing magnetic field for an initially positive baryon chemical potential. The corrections derived in this framework may help to explain the splitting observed in Lambda hyperons spin polarization measurements.
↳ hep-phnucl-thNPA(2023)·45 citations
11
Unphysical Discontinuities, Intruder States and Regularization in $G W$ Methods
Enzo Monino🇫🇷 · Pierre-François Loos🇫🇷
By recasting the non-linear frequency-dependent $G W$ quasiparticle equation into a linear eigenvalue problem, we explain the appearance of multiple solutions and unphysical discontinuities in various physical quantities computed within the $G W$ approximation. Considering the $G W$ self-energy as an effective Hamiltonian, it is shown that these issues are key signatures of strong correlation in the $(N \pm 1)$ -electron states and can be directly related to the intruder state problem. A simple and efficient regularization procedure inspired by the similarity renormalization group is proposed to avoid such issues and speed up convergence of partially self-consistent $G W$ calculations.
↳ physics.chem-phcond-mat.mtrl-scicond-mat.str-elnucl-thJ.Chem.Phys.(2022)·11 citations
12
Production of $P_{c}$ (4312) state in electron-proton collisions
In Woo Park🇰🇷 · Su Houng Lee🇰🇷 · Sungtae Cho🇰🇷 · Yongsun Kim🇰🇷
We study the cross sections for the electro-production of $P_{c} (4312)$ particle, a recently discovered pentaquark state, in electron-proton collisions assuming possible quantum numbers to be $J^{P} = \frac{1}{2}^{\pm}, \frac{3}{2}^{\pm}$ . $s$ is set to the energy of the future Electron Ion Collider at Brookhaven National Laboratory, in order to asses the possibility of the measurement in this facility. One can discriminate the spin of $P_{c} (4312)$ by comparing the pseudorapidity distribution in two different polarization configurations for proton and electron beams. Furthermore, the parity of $P_{c} (4312)$ can be discerned by analyzing the decay angle in the $P_{c} \to p + J / ψ$ channel. As the multiplicity of $P_{c}$ production in our calculation is large, the EIC can be considered as a future facility for precision measurement of heavy pentaquarks.
↳ hep-phnucl-exnucl-thPRD(2022)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE