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Ratio of a strange quark mass m_s to up or down quark mass m_(u,d) predicted by a quark propagator in the framework of the chiral perturbation theory

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Chinese Physics C 2013年第4期37卷 1-6页

作者：彭金松周丽娟蒙成举潘继环马维兴袁通全 Department of Physics and Electronic Engineering Hechi University Department of Information and Computing Science Guangxi University of Technology Institute of High Energy Physics Chinese Academy of Sciences

Based on the fully dressed quark propagator and chiral perturbation theory, we study the ratio of the strange quark mass ms to up or down quark mass mu,d . The ratio is related to the determination of quark masses which are fundamental input parameters of QCD Lagrangian in the Standard Model of particle physics and can not be directly measured since the quark is confined within a hadron. An accurate determination of these QCD free parameters is extremely important for both phenomenological and theoretical applications. We begin with a brief introduction to the non-perturbation QCD theory, and then study the mass ratio in the framework of the chiral perturbation theory （χPT） with a parameterized fully dressed quark propagator which describes confining fully dressed quark propagation and is analytic everywhere in the finite complex p2-plane and has no Lehmann representation so there are no quark production thresholds in any theoretical calculations of observable data. Our prediction for the ratio ms/mu,d is consistent with other model predictions such as Lattice QCD, instanton model, QCD sum rules and the empirical values used widely in the literature. As a by-product of this study, our theoretical results, together with other predictions of physical quantities that used this quark propagator in our previous publications, clearly show that the parameterized form of the fully dressed quark propagator is an applicable and reliable approximation to the solution of the Dyson-Schwinger Equation of quark propagator in the QCD.

关键词： light quark mass ratio chiral perturbation theory dressed quark propagator non-perturbative QCD

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Lowest-lying spin-1/2 and spin-3/2 baryon magnetic moments in chiral perturbation theory

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Chinese Physics C 2010年第9期34卷 1307-1311页

作者：耿立升 J.Martin-Camalich L.Alvarez-Ruso M.J.Vicente-Vacas Departamento de Física Teórica and IFIC Universidad de Valencia-CSIC Centro de Física Computacional Departamento de FísicaUniversidade de Coimbra

We review some recent progress in our understanding of the lowest-lying spin-1/2 and spin-3/2 baryon magnetic moments （MMs） in terms of chiral perturbation theory （ChPT）.In particular,we show that at next-to-leading-order ChPT can describe the MMs of the octet baryons quite *** also make predictions for the decuplet MMs at the same chiral *** them,the MMs of the Δ＋＋ and Δ ＋ are found to agree well with data within the experimental uncertainties.

关键词： magnetic moments octet baryons decuplet baryons chiral perturbation theory

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The Pionic Deuterium and the Pion Tetrahedron Vacuum Polarization

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Journal of High Energy Physics, Gravitation and Cosmology 2024年第1期10卷 329-345页

作者： Rami Rom Zikhron-Ya’akov Israel

A double-well potential model is proposed for the pionic deuterium that enables to calculate the energy split, the potential barrier height and estimate the pion tetrahedron edge length. We propose that pion tetrahedrons, πTd = ud~dũ, play a central role in the Yukawa interaction by enabling quark exchange reactions between protons and neutrons by tunneling through a potential barrier. A vacuum polarization Feynman diagram is proposed for the πTd having chains of fermion loops for the two valence quarks and anti-quarks connected by gluons. With a higher order vacuum polarization diagram, the d and u quark loops are interleaved and the chiral symmetry is broken dynamically. The proposed πTd vacuum polarization integral does not diverge in both the IR and UV limits and vanishes in the limit of an infinite pion tetrahedron condensate. We propose a new Delbruck scattering Feynman diagram that includes d and u quark and anti-quark interleaved loops. We further propose that conversion of gravitons to photons may occur via quark and anti-quark loops that describe the pion tetrahedrons dynamics in the vacuum and may also transfer gravitational waves.

关键词： Pionic Deuterium (πD) Yukawa Interaction QCD Vacuum Double-Well Potential chiral perturbation theory Vacuum Polarization Gravitational Waves

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Molecular states in D_(s)^(*)+=^_(c)^(′,*)systems^(*)

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Chinese Physics C 2023年第12期47卷 16-30页

作者：尼加提·亚力坤董相坤邹冰松 School of Physics Science and Technology Xinjiang UniversityUrumqi 830046China CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Southern Center for Nuclear-Science theory(SCNT) Institute of Modern PhysicsChinese Academy of SciencesHuizhou 516000China

The possible hadronic molecules in D_(S)^(∗)+Ξ_(c)(′,∗)systems with J^(P)=1/2−,3/2−,and 5/2−are investigated with interactions described by light meson *** varying the cutoff in a phenomenologically reasonable range of 1−2.5 GeV,we find ten near-threshold(bound or virtual)states in the single-channel *** introducing the coupled-channel dynamics of D_(+)^(s)Ξ_(c)-D_(s)^(+)Ξ′c-D_(s)^(∗+)Ξ_(c-)D_(s)^(+)Ξ_(c)^(*)-D_(s)^(∗)+sΞ′_(c)-D_(s)^(∗)Ξ_(c)^(∗)systems,these states,except those below the lowest channels in each JP sector,move into the complex energy plane and become resonances in the mass range 4.43−4.76 *** spin-parities and nearby thresholds are 1/2−(D_(s)^(+)Ξ′_(c)),1/2^(−)(D_(s)^(++)Ξ_(c)^(*)),1/2−(D_(s)^(∗+)Ξ_(c)),1/2−(D_(s)^(∗+)Ξ_(c)^(′)),1/2−(D_(s)^(∗+)Ξ_(c)^(∗)),3/2−(D_(s)^(∗+)(Ξc),3/2−(D_(s)^(+)Ξ_(c)),3/2−(D_(s)^(∗+)Ξ′c),3/2−(D_(+s)^(∗)Ξ_(c)^(∗)),and 5/2−(D_(s)^(∗+)Ξ_(c)^(∗)).The impact of theδ(r)-term in the one-boson-exchange model on these states is ***Λ=1.5 GeV as an illustrative value,it is found that 1/2−(D_(s)^(*+)Ξ_(c))is a stable bound state(becoming unstable if the coupling to lower channels is turned on),1/2−(D∗+sΞc)and 3/2−(D_(s)^(∗+)Ξ_(c))are physical resonances in cases where theδ(r)-term is included or excluded,and the other seven states are physical resonances or"virtual-state-like"poles near thresholds,depending on whether theδ(r)-term is *** addition,the partial decay widths of the physical resonances are *** double-charm hidden-strangeness pentaquark states,as the partners of the experimentally observed Pc and Pcs states,can be searched for in the D(∗)Λ_(c)final states in the future.

关键词： pentaquarks chiral perturbation theory resonance

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Effective field theory approach to lepton number violatingτdecays

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Chinese Physics C 2021年第7期45卷 31-42页

作者：廖益马小东王昊琳 School of Physics Nankai UniversityTianjin 300071 Department of Physics National Taiwan UniversityTaipei 10617China Center for High Energy Physics Peking UniversityBeijing 100871

We continue our endeavor to investigate lepton number violating(LNV)processes at low energies in the framework of effective field theory(EFT).In this work we study the LNV tau decaysτ^(+)→lP_(i)^(+)P_(J)^(+),where L=e.μand P_(i,j)^(+)denote the lowest-lying charged pseudoscalarsπ^(+),K^(+).We analyze the dominant contributions in a series of EFTs from high to low energy scales,namely the standard model EFT(SMEFT),the low-energy EFT(LEFT),and the chiral perturbation theory(χPT).The decay branching ratios are expressed in terms of the Wilson coefficients of dimension-five and-seven operators in SMEFT and the hadronic low-energy *** Wilson coefficients involve the first and second generations of quarks and all generations of leptons;thus,they cannot be explored in low-energy processes such as nuclear neutrinoless double beta decay or LNV kaon ***,the current experimental upper bounds on the branching ratios are too weak to set useful constraints on these ***,if we assume the new physics scale is larger than 1 TeV,the branching ratios are well below the current experimental *** also estimate the hadronic uncertainties incurred in applyingχPT toτdecays by computing one-loop chiral logarithms and attempt to improve the convergence of chiral perturbation by employing dispersion relations in the short-distance part of the decay amplitudes.

关键词： lepton number violation tau lepton effective field theory chiral perturbation theory beyond standard model

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Transport coefficients of a massive pion gas

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Chinese Physics C 2010年第9期34卷 1453-1455页

作者： D.Fernández-Fraile A.Gómez Nicola Institut für Theoretische Physik Johann Wolfgang Goethe-Universitt Departamento de Física Teórica II Universidad Complutense

We review our main results concerning the transport coefficients of a light meson gas,in particular we focus on the case of a massive pion *** order results according to the chiral power-counting are presented for the DC electrical conductivity,thermal conductivity,shear viscosity,and bulk *** also comment on the possible correlation between the bulk viscosity and the trace anomaly in QCD,as well as the relation between unitarity and a minimum of the quotient η/s near the phase transition.

关键词： transport coefficients heavy-ion collisions chiral perturbation theory

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Phase diagram of two-color QCD matter at finite baryon and axial isospin densities

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Chinese Physics C 2020年第3期44卷 129-136页

作者：巢静宜 Institute of Modern Physics Chinese Academy of Sciences

We study the two-color QCD matter with two fundamental quark flavors using the chiral perturbation theory and the Nambu-Jona-Lasinio(NJL)*** effective Lagrangian is derived in terms of mesons and baryons,*** low lying excitations lie in the extended SU(4)flavor symmetry *** compute the leading order terms of the Lagrangian as a function of the baryon and axial isospin *** numerically solving the gap equations in the two-color NJL model,the phase diagram is obtained in the μ−ν5 plane.

关键词： two-color QCD diquarks chiral perturbation theory axial isospin density NJL model

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