Motivated by the successes of relativistic theories in studies of atomic/molecular and nuclear systems and the need for a relativistic chiral force in relativistic nuclear structure studies, we explore a new relativistic scheme to construct the nucleon-nucleon interaction in the framework of covariant chiral effective field theory. The chiral interaction is formulated up to leading order with covariant power counting and a Lorentz invariant chiral Lagrangian.We find that the relativistic scheme induces all six spin operators needed to describe the nuclear force. A detailed investigation of the partial wave potentials shows a better description of the;S——0 and;P;phase shifts than the leading order Weinberg approach, and similar to that of the next-to-leading order Weinberg approach. For the other partial waves with angular momenta J≥1, the relativistic results are almost the same as their leading order non-relativistic counterparts.
In a recent measurement LHCb reported pronounced structures in the J/ψJ/ψspectrum.One of the various possible explanations of those is that they emerge from non-perturbative interactions of vector charmonia.It is thus important to understand whether it is possible to form a bound state of two charmonia interacting through the exchange of gluons,which hadronise into two pions at the longest distance.In this paper,we demonstrate that,given our current understanding of hadron-hadron interactions,the exchange of correlated light mesons(pions and kaons)is able to provide sizeable attraction to the di-J/ψsystem,and it is possible for two J/ψmesons to form a bound state.As a side result we find from an analysis of the data for theψ/(2 S)J/ψππtransition including bothππand KK final state interactions an improved value for theψ(2 S)→J/ψtransition chromo-electric polarisability:|αψ(2 S)J/ψ|=(1.8±0.1)GeV-3,where the uncertainty also includes the one induced by the final state interactions.
Xiang-Kun DongVadim BaruFeng-Kun GuoChristoph HanhartAlexey NefedievBing-Song Zou
After summarizing the experimental results and present status of the d^＊（2380） observed at WASA@COSY,two “extreme” models for explaining its structure, a compact hexaquark dominated model and a loose △△＇-D_（12）π model, are briefly discussed, especially the former. By comparing their results with the corresponding data, the differences of the two models are addressed. As a remedy for the latter model, a mixing model and its result are also quoted for a comparison. It is shown that the compact hexaquark dominated structure might be more promising.However, the mixing model is also a possible structure, and more accurate Γ_（d^＊）→NN_π data are needed for confirmation.
The Wilsonian renormalization group approach to the Lippmann-Schwinger equation with a multitude of cutoff parameters is introduced.A system of integro-differential equations for the cutoff-dependent potential is obtained.As an illustration,a perturbative solution of these equations with two cutoff parameters for a simple case of an S-wave low-energy potential in the form of a Taylor series in momenta is obtained.The relevance of the obtained results for the effective field theory approach to nucleon-nucleon scattering is discussed.
Recently,a relativistic chiral nucleon-nucleon interaction was formulated up to leading order,which provides a good description of the phase shifts of J≤1 partial waves[Chin.Phys.C 42(2018)014103].Nevertheless,a separable regulator function that is not manifestly covariant was used in solving the relativistic scattering equation.In the present work,we first explore a covariant and separable form factor to regularize the kernel potential and then apply it to study the simplest but most challenging ^(1)S_(0) channel which features several lowenergy scales.In addition to being self-consistent,we show that the resulting relativistic potential can describe quite well the unique features of the ^(1)S_(0) channel at leading order,in particular the pole position of the virtual bound state and the zero amplitude at the scattering momentum ~340 MeV,indicating that the relativistic formulation may be more natural from the viewpoint of effective field theories.
The production of the X（3872） as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103（2009） 162001, that the production of the X（3872） at high pT implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.
Miguel Albaladejo郭奉坤Christoph HanhartUlf-G.Mei?nerJuan NievesAndreas Nogga杨智
The proton charge radius rP is a fundamental quantity in particle physics,as it challenges our understanding of the so successful Standard Model in the non-perturbative regime of the strong interactions.It is defined by the slope of the proton charge form factor GE p etT at zero momentum transfer,with t the invariant four-momentum transfer squared.The proton charge radius was first indirectly measured in the Nobel prize winning electron scattering experiments by Hofstadter et al.[1,2],who fitted the form factor data with a dipole form and extracted the radius from the slope of the dipole.
We adopt the quark pair creation model to investigate the light meson emissions of several charmoniumlike states.The quark pair creation model is applied to four-body systems,and we calculate the pion/kaon emissions of X(4700),Z_(c)(4430),Y(4230),Y(4360),Y(4390),and Y(4660)within compact tetraquark configurations.We find that the pion/kaon decay widths of X(4700)and Z_(c)(4430)the resonances Y(4230),Y(4360),Y(4390),and Y(4660)cay behaviors will provide useful information for future experimental searches and theoretical interpretations.
In order to confirm the existence of the dibaryon state d^(*)(2380)observed at WASA@COSY,we estimate the cross section for production of the possible dibaryon and anti-dibaryon pair d^(*)d^(*)in the energy region of the upcoming experiments at Panda.Based on some qualitative properties of d^(*)extracted from the analyses in the non-relativistic quark model,the production cross section for this spin-3 particle pair are calculated with the help of a phenomenological effective relativistic and covariant Lagrangian approach.
based on our analysis of the contributions from the connected and disconnected contraction diagrams to the pion-kaon scattering amplitude,we provide the first determination of the only free low-energy constant at O(p^(4)),known as L_(0)^(r),in SU(4|1)Partially-Quenched Chiral Perturbation theory using the data from the Extended Twisted Mass collaboration,L_(0)^(r)(μ=M_(ρ))=0.77(20)(25)(7)(7)(2)·10^(-3).The theory uncertainties originate from the unphysical scattering length,the physical low-energy constants,the higher-order chiral corrections,the(lattice)meson masses and the pion decay constant,respectively.
Chaitra Kalmahalli GuruswamyUlf-G MeißnerChien-Yeah Seng
