Search

Lepton scattering is an established ideal tool for studying inner structure of small particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High Intensity heavy-ion Accelerator Facility (HIAF) which is currently under construction, together with a new electron ring. The proposed collider will provide highly polarized electrons (with a polarization of $\sim$80%) and protons (with a polarization of $\sim$70%) with variable center of mass energies from 15 to 20 GeV and the luminosity of (2-3) $\times$ 10$^{33}$ cm$^{-2}$ s$^{-1}$. Polarized deuterons and Helium-3, as well as unpolarized ion beams from Carbon to Uranium, will be also available at the EicC. The main foci of the EicC will be precision measurements of the structure of the nucleon in the sea quark region, including 3D tomography of nucleon; the partonic structure of nuclei and the parton interaction with the nuclear environment; the exotic states, especially those with heavy flavor quark contents. In addition, issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC. In order to achieve the above-mentioned physics goals, a hermetical detector system will be constructed with cutting-edge technologies. This document is the result of collective contributions and valuable inputs from experts across the globe. The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States. The success of this project will also advance both nuclear and particle physics as well as accelerator and detector technology in China., EicC white paper, written by the whole EicC working group

Using an almost complete relativistic method based on the Bethe-Salpeter equation, we study the mixing angle $\theta$, the mass splitting $\bigtriangleup M$, the strong decay widths $\Gamma(D^{({\prime})}_1)$ and the weak production rates $Br(B\to D^{({\prime})}_1\ell\nu_{\ell})$ of the $D_1(2420)$ and $D_1^{\prime}(2430)$. We find there is the strong cancellation between the $^1P_1$ and $^3P_1$ partial waves in $D_1^{\prime}(2430)$ with $\theta \sim-35.3^{\circ}$, which leads to the `$1/2$ vs $3/2$' puzzle. The puzzle can not be overcome by adding only relativistic corrections since in a large parameter range where $\bigtriangleup M$ is linear varying and not small, the $\theta$, $\Gamma(D^{({\prime})}_1)$ and $Br(B\to D^{({\prime})}_1\ell\nu_{\ell})$ remain almost unchanged but conflict with data. While in a special range around the mass inverse point where $\bigtriangleup M=0$ and $\theta =\pm 90^{\circ}$, they change rapidly but we find the windows where $\bigtriangleup M$, $\Gamma(D^{({\prime})}_1)$ and $Br(B\to D^{({\prime})}_1\ell\nu_{\ell})$ are all consistent with data. The small $\bigtriangleup M$ confirmed by experiment, is crucial to solve the `$1/2$ vs $3/2$' puzzle., Comment: 18 pages, 5 figures

Mass spectra and wave functions of the $J^P=\frac{1}{2}^+$ $(bcq)$ baryons are calculated by the relativistic Bethe-Salpeter equation\,(BSE) with considering the mixing effects between the $1^+$ and $0^+$ $(bc)$-diquarks inside. Based on the diquark picture, the three-body problem of baryons is transformed into two two-body problems. The BSE and wave functions of the $0^+$ diquark are given, and then solved numerically to obtain the effective mass spectra and form factors. Also we present the wave functions at zero point for the $(bc)$-diquark. Considering the obtained diquark form factors, the $(bcq)$ baryons are then described by the BSE as the bound state of a diquark and a light quark, where the interaction kernel includes the inner transitions between the $0^+$ and $1^+$ diquarks. The general wave function of the $\frac{1}{2}^+$ $(bcq)$ baryons is constructed and solved to obtain the corresponding mass spectra. Especially, by using the obtained wave functions, the mixing effects between $\Xi_{bc}(\Omega_{bc})$ and $\Xi_{bc}'(\Omega'_{bc})$ in ground states are computed and determined to be small ($\sim \!1\%$). The numerical results indicate that it is a good choice to take $\Xi_{bc}$ and $\Xi'_{bc}$ as the baryon states with the inside $(bc)$-diquarks occupying the definite spin., Comment: 26 pages, 15 figures

In this paper we take B-L supersymmetric standard model (B-LSSM) and TeV scale left-right symmetric model (LRSM) as two representations of the two kinds of new physics models to study the nuclear neutrinoless double beta decays ($0\nu2\beta$) so as to see the senses onto these two kinds of models when the decays are taken into account additionally. Within the parameter spaces allowed by all the exist experimental data, the decay half-life of the nucleus $^{76}$Ge and $^{136}$Xe, $T^{0\nu}_{1/2}$($^{76}$Ge, $^{136}$Xe), is precisely calculated and the results are presented properly. Based on the numerical results, we conclude that the room of LRSM type models for the foreseeable future experimental observations on the decays is greater than that of B-LSSM type models., Comment: 37 pages, 9 figures

We calculate the two-body strong decays of the orbitally excited scalar mesons $$D_0^*(2400)$$ and $$D_J^*(3000)$$ by using the relativistic Bethe–Salpeter (BS) method. $$D_J^*(3000)$$ was observed recently by the LHCb Collaboration, the quantum number of which has not been determined yet. In this paper, we assume that it is the $$0^+(2P)$$ state and obtain the transition amplitude by using the PCAC relation, low-energy theorem and effective Lagrangian method. For the 1P state, the total widths of $$D_0^*(2400)^{0}$$ and $$ D_0^*(2400)^+$$ are 226 and 246 MeV, respectively. With the assumption of $$0^+(2P)$$ state, the widths of $$D_J^*(3000)^0$$ and $$D_J^*(3000)^+$$ are both about 131 MeV, which is close to the present experimental data. Therefore, $$D_J^*(3000)$$ is a strong candidate for the $$2^3P_0$$ state.

We present a detailed discussion on the doubly charmed baryon $\Xi_{cc}$ production at the RHIC and LHC via the proton-nucleus ($p$-N) and nucleus-nucleus (N-N) collision modes. The extrinsic charm mechanism via the subprocesses $g+c\to (cc)[n]+\bar{c}$ and $c+c\to (cc)[n]+g$ together with the gluon-gluon fusion mechanism via the subprocess $g+g\to(cc)[n]+\bar{c}+\bar{c}$ have been taken into consideration, where the intermediate diquark is in $[n]=[^1S_0]_{\bf 6}$-state or $[^3S_1]_{\bar{\bf 3}}$-state, respectively. Total and differential cross sections have been discussed under various collision energies. To compare with the $\Xi_{cc}$ production via proton-proton collision mode at the LHC, we observe that sizable $\Xi_{cc}$ events can also be generated via $p$-N and N-N collision modes at the RHIC and LHC. For examples, about $8.1\times10^7$ and $6.7\times10^7$ $\Xi_{cc}$ events can be accumulated in $p$-Pb and Pb-Pb collision modes at the LHC within one operation year., Comment: 10 pages, 6 figures

We take ($\mu^\pm e^\mp$) systems and consider the states with quantum number $J^P=0^-$ as examples, to explore the different contents of the instantaneous Bethe-Salpeter (BS) equation and its analog, Breit equation, by solving them exactly. The results show that the two equations are not equivalent, although they are analogous. Furthermore, we point out that the Breit equation contains extra un-physical solutions, so it should be abandoned if one wishes to have an accurate description of the bound states for the instantaneous interacting binding systems.

We try to apply a constituent quark model (a variety chiral constituent quark model) and the resonating group approach for the multi-quark problems to compute the effective potential between the $N\bar{N}$ in $S$-wave (the quarks in the nucleons $N$ and $\bar{N}$, and the two nucleons relatively as well, are in $S$ wave) so as to see the possibility if there may be a tight bound state of six quarks as indicated by a strong enhancement at threshold of $p\bar{p}$ in $J/\psi$ and B decays. The effective potential which we obtain in terms of the model and approach shows if the experimental enhancement is really caused by a tight $S$-wave bound state of six quarks, then the quantum number of the bound state is very likely to be $I=1, J^{PC}=0^{-+}$., Comment: 8 pages, 9 figures

We present an approach to solve a Bethe-Salpeter (BS) equation exactly without any approximation if the kernel of the BS equation exactly is instantaneous, and take positronium as an example to illustrate the general features of the solutions. As a middle stage, a set of coupled and self-consistent integration equations for a few scalar functions can be equivalently derived from the BS equation always, which are solvable accurately. For positronium, precise corrections to those of the Schr\"odinger equation in order $v$ (relative velocity) in eigenfunctions, in order $v^2$ in eigenvalues, and the possible mixing, such as that between $S$ ($P$) and $D$ ($F$) components in $J^{PC}=1^{--}$ ($J^{PC}=2^{++}$) states as well, are determined quantitatively. Moreover, we also point out that there is a problematic step in the classical derivation which was proposed first by E.E. Salpeter. Finally, we emphasize that for the effective theories (such as NRQED and NRQCD etc) we should pay great attention on the corrections indicated by the exact solutions., Comment: 4 pages, replace for shortening the manuscript

The uncertainties in estimating the hadronic production of the $B_c$ meson are studied under the framework of the complete $\alpha_s^4$ approach of the perturbative QCD and the gluon-gluon fusion mechanism. Quantitative comparisons on the production at TEVATRON and LHC are made. Considering the detectors at TEVATRON and LHC, we have also estimated the production with proper kinematic cuts. Based on the results, we conclude that the experimental studies of the $B_c$ meson at the two colliders will be complimentary and stimulative. We find that as c.m. energy is increasing from RUN-I to RUN-II at TEVATRON, the production cross-section increases about 20%.

Since long-lived light bottom squark (sbottom) and its anti-particle with a mass close to the bottom quark have not been excluded by experiments so far, we consider such a sbottom to combine with its anti-particle to form a color singlet meson-like bound state or to combine with a common anti-quark to form a fermion-like one, or accordingly their anti-particles to form an anti-particle bound system. Namely we calculate the low-lying spectrum of the systems based on QCD inspired potential model. To be as relativistic as possible, we start with the framework of Bethe-Salpeter (BS) equation even for non-relativistic binding systems. Finally, we obtain the requested spectrum by constructing general forms of the BS wave functions and solving the BS equations under instantaneous approximation.

We exhibit a method for obtaining the low chemical potential dependence of the dressed quark propagator from an effective quark-quark interaction model. Within this approach we explore the chemical potential dependence of the dressed-quark propagator, which provides a means of determining the behavior of the chiral and deconfinement order parameters. A comparison with the results of previous researches is given.

The production of the three normal neutrinos via $e^-e+$ collision at $Z$-boson peak (neutrino production in a Z-factory) is investigated thoroughly. The differences of $\nu_e$-pair production from $\nu_\mu$-pair and $\nu_\tau$-pair production are presented in various aspects. Namely the total cross sections, relevant differential cross sections and the forward-backward asymmetry etc for these neutrinos are presented in terms of figures as well as numerical tables. The restriction on the room for the mixing of the three species of light neutrinos with possible externals (heavy neutral leptons and/or stereos) from refined measurements of the invisible width of $Z$-boson is discussed., Comment: 5 pages, 6 figures

The semileptonic decays of meson $B_c$ to a P-wave charmonium state $\chi_c(^3P_J)$ or $h_c(^1P_1)$ are computed. The results show that the decays are sizable so they are accessible in Tevatron and in LHC, especially, with the detectors LHCB and BTeV in the foreseeable future, and of them, the one to the $^1P_1$ charmonium state potentially offers us a novel window to see the unconfirmed $h_c$ particle. In addition, it is pointed out that since the two charmonium radiative decays $\chi_c(^3P_{1,2}) \to J/\psi+\gamma$ have sizable branching ratios, the cascade decays of the concerned decays and the charmonium radiative decays may affect the result of the observing the $B_c$ meson through the semileptonic decays $B_{c}\to {J/\psi}+{l}+\nu_{l}$ substantially.

Based on a modification of the global color symmetry model, we have calculated the four-quark condensate [: (q) over bar gamma mu lambdaC degrees /2 q(q) over bar gamma mu lambdaC degrees /2 q :] beyond vacuum saturation approximation by including the contribution of pi and sigma masons. The numerical results show that there is a sizeable correction of the four-quark condensate in comparison with its factorized value using the vacuum saturation approximation.

The minimum supersymmetric standard model with bilinear R-parity violation is studied systematically. Considering low-energy supersymmetry, we examine the structure of the bilinear R-parity violating model carefully. We analyze the mixing such as Higgs bosons with sleptons, neutralinos with neutrinos and charginos with charged leptons in the model. Possible and some important physics results such as the lightest Higgs may heavy than the weak Z-boson at tree level etc are obtained. The Feynman rules for the model are derived in $'$t Hooft- Feynman gauge, which is convenient if perturbative calculations are needed beyond the tree level., 50 pages, includes 12 figs, revised some formulaes, accepted by EPJC

It is shown that the effective gluon propagator in the global color symmetry model can be calculated in the instanton dilute liquid approximation. The calculated effective gluon propagator is consistent with the general command on the qualitative features of the gluon propagator, i.e., (i) the gluon propagator is significantly enhanced at small space-like k(2), and (ii) for k(2) > 1.5 GeV2 the perturbative results are quantitatively reliable.

With the fresh experimental bounds of b → sγ issued by CLEO and the value of the top-quark mass by CDF and D0, the constraints on the two Higgs doublet models (2HDM) are re-examined. In the examination an effective Lagrangian is used, which contains all of the energy scale evolution not only from the W boson mass to the bottom-quark mass but also from the top-quark mass to W boson mass for the QCD corrections. As a result, it is implied that the constraint on the mass of the charged Higgs boson emerging in the concerned models turns to be more stringent than that achieved by the earlier analyses.

We study possible observational effects of the two Higgs doublets in the e(+)e(-), at the LEP II energy. We have found that the observational values can be obviously different from those predicted by the minimal standard model (MSM), but the results depend on the parameters of the extended model. The possibilities of the observation are discussed in some details.

The effects of CP asymmetry in top-pair production with polarized photon beam collisions, which may arise in two Higgs doublet extensions of the minimal standard model, are studied. Some of the advantages to observe the CP non-invariance in the production are pointed out. The CP asymmetry will be enhanced by polarized photon fusion greatly compared to the unpolarized one and the signal can reach so high up to a few percents.

In this work, the light JPC = 0++ mesons f0(975), a0(980) and S*(980) are interpreted as the usual states, their masses are investigated in the framework of the QCD sum rules.

We re-evaluated the decay up to one-loop order of electroweak corrections in standard model with the nowadays parameters, determined by the best measurements including the latest ones from LEP and SLC. Within error range of the CDF measurement of top-quark; mass, the electroweak correction reduces the decay width less than 0.7% and the correction value varies in the range of 0.5%.

In order to have a reliable calculation on a transition between two double heavy mesons and bearing a sizable recoil, a generalized "instantaneous approximation" is emphasized and the way how to make the approximation is described in this paper. The reliability and limitation of the approach are discussed. Prospect on its potential applications is outlined also.

Virtual effects of supersymmetry on the flavor changing process at LEPII are calculated in the minimal supersymmetric standard model (MSSM). We analyze the cross section of , and find that even for the most distinguishable mode , the effect is small compared with the SM expectation.

The hybrid components of a pro ton can give rise to direct contribution to Δg due to the gluon operator and Δs due to the axial current operator as well. We evaluate such contribution precisely within the framework of the bag model, but the result shows that the contribution is not significant.

We have applied the velocity superselection rule proposed by Georgi, Isgur and Wise to some transition matrix element calculations in an extended way. We have found that by the approach , is about which is consistent with the potential model calculations.

A method for universally treating the quark pair with a vacuum quantum number is proposed and it is applied to calculating some charm meson decays as examples. The smallness for W-exchange and annihilation mechanisms has new explanation and the result obtained by means of the proposed method on the decay fits the experimental data well.

In this work, we evaluate the lifetimes of the doubly charmed baryons $\Xi_{cc}^{+}$, $\Xi_{cc}^{++}$ and $\Omega_{cc}^{+}$. We carefully calculate the non-spectator contributions at the quark level where the Cabibbo-suppressed diagrams are also included. The hadronic matrix elements are evaluated in the simple non-relativistic harmonic oscillator model. Our numerical results are generally consistent with that obtained by other authors who used the diquark model. However, all the theoretical predictions on the lifetimes are one order larger than the upper limit set by the recent SELEX measurement. This discrepancy would be clarified by the future experiment, if more accurate experiment still confirms the value of the SELEX collaboration, there must be some unknown mechanism to be explored., Comment: 17 pages, 3 figures and 1 table

The light top-squark $\sto$ may be the lightest squark and its lifetime may be `long enough' in a kind of SUSY models which have not been ruled out yet experimentally, so colorless `supersymmetric hadrons (superhadrons)' $(\sto \bar{q})$ ($q$ is a quark except $t$-quark) may be formed as long as the light top-squark $\sto$ can be produced. Fragmentation function of $\sto$ to heavy `supersymmetric hadrons (superhadrons)' $(\sto \bar{Q})$ ($\bar{Q}=\bar{c}$ or $\bar{b}$) and the hadronic production of the superhadrons are investigated quantitatively. The fragmentation function is calculated precisely. Due to the difference in spin of the SUSY component, the asymptotic behavior of the fragmentation function is different from those of the existent ones. The fragmentation function is also applied to compute the production of heavy superhadrons at hadronic colliders Tevatron and LHC under the so-called fragmentation approach. The resultant cross-section for the heavy superhadrons is too small to observe at Tevatron, but great enough at LHC, even when all the relevant parameters in the SUSY models are taken within the favored region for the heavy superhadrons. The production of `light superhadrons' $(\sto \bar{q})$ ($q=u, d, s$) is also roughly estimated. It is pointed out that the production cross-sections of the light superhadrons $(\sto \bar{q})$ may be much greater than those of the heavy superhadrons, so that even at Tevatron the light superhadrons may be produced in great quantities., Comment: 20 pages, 9 figures

To further investigate the applicability of the projection scheme for eliminating the unphysical divergence $s/m_e^2$ due to U(1) gauge invariance violation, we study the process $e^-+W^+\to e^-+\bar t+b$ which possesses advantages of simplicity and clearness. Our study indicates that the projection scheme can indeed eliminate the unphysical divergence $s/m_e^2$ caused by the U(1) gauge invariance violation and the scheme can apply to very high energy region., Latex, 13 pages, 4 EPS fiures

A calculation on the rates and the branching ratios of two-body decay of proton and neutron is presented in detail in this paper. A relativistic formalism based on the B.S. wave functions is employed to consider the bound state effects of the quarks inside the nucleon automatically and completely. In order to solve the well-known Van Royen-Weisskopf's paradox occurring in nonrelativistic quark models, a B.S. wave function of mesons with a spin structure different from the Bargmann-Wigner's is accepted and as a result changes in the. branching ratios and the rates are made, e.g. the mode becomes the largest among the two-body modes for the proton decay and the rate for the neutron decay decreases, with the effective interaction induced from the minimum SU(5) model.

An approximate effective Lagrangian of composite operators in superfield formalism for the N=1 pure supersymmetric Yang-Mills model is obtained with the help of renormalization group equations for the generating functional. While the supersymmetry is always kept unbroken by this effective Lagrangian we find that the chiral symmetry may and may not be unbroken.

Some of the important W± and Z decay amplitudes, relating to the chiral anomalies of the quark sector in the Standard Model, are given by means of the interactions determined by the effective Lagrangian (action) of the nonlinear σ model for the pseudogoldstone bosons. The corresponding decay rates are calculated. It is shown that the decay rates are quite large, especially, the rate of the decay W →πγ and probably that of W → Dsγ are predicted being unexpectedly great (ΓW→πγ = 0.35 GeV). This indicates that the chiral anomalies and our approach should receive tests from SPPS and Tevantron experiments.

The compactification of the D = 10 E8 × E8' field theory limit of superstring to the D = 4 SU3×SU2×U1 standard model is investigated by means of the scheme developed by Manton, Forgacs and Chapline.

The exotic fermions occurred in some composite models (such as the family gauged composite model) and their oniums are examined systematically in this paper. It is emphasized that coloured oniums as well as colourless ones may be formed, if their constituents are coloured in high-dimensional representations. According to a rough estimate, the exotic fermions and their oniums should have masses of the order of 0.1 to 1 Tev, hence they may play some roles in the events at energies of SPPS and/or the next generation colliders, if they do exist.

The effective Hamiltonian for nonleptonic decays of strange, charm and beauty, involving the QCD corrections at short distances but with possible t-quark mass mt > mW and a correction of the initial value for the renormalization group equations, is computed in the framework of the operator product expansion (OPE). The numerical results show that our calculation gives corrections in right direction for approaching to the ΔI = 1/2 rule and if using the latest experimental measurements on e and e'/e for system as input, the KM parameter would be constrained in a reasonable region (2.5 ~ 22.5) × 10-3.