New possibility for further measurements of nucleon form factors at large momentum transfer in time-like region: $\bar{p}+{p}\to \ell^+ +\ell^-$, $\ell=e$ or $μ$
We briefly summarize the status with electromagnetic nucleon form factors, and give in this framework, arguments to study the angular dependence of the differential cross section and single-spin polarization phenomena (polarized target or polarized beam) in $\bar{p}+{p}\to \ell^++\ell^-$, in view of the availability of future antiproton beams.
Testing axial and electromagnetic nucleon form factors in time-like regions in the processes $\bar p + n\to π^- +\ell^-+\ell^+$ and $\bar p+ p\to π^0 +\ell^- + \ell^+$, $\ell=e$, $μ$
We study charged lepton flavor violation (CLFV) associated with heavy quark pair production in lepton-nucleon deep-inelastic scattering $\ell_i N \to \ell_j q\bar{q} X$. Here $\ell_i$ and $\ell_j$ denote the initial and final leptons; $N$ and $X$ are respectively the initial nucleon and arbitrary final hadronic system. We employ a model Lagrangian in which a scalar and pseudoscalar mediator generates the CLFV. We derive heavy quark structure functions for scalar and pseudoscalar currents and compute momentum distributions of the final lepton for the process. Our focus is on the heavy quark mas…
We study the helicity distributions of light flavor quark-antiquark ($q \bar{q}$) pairs in the nucleon sea. The valence quarks are handled by adopting the light-cone SU(6) quark-spectator-diquark model and the sea $q \bar{q}$ pairs are treated from statistical consideration by introducing the helicity suppression factors $l_q(x)$ and $\bar l_q(x)$ to parametrize the helicity distributions of q-flavor sea quark and antiquark respectively, while $Δl_q(x)=l_q(x)-\bar l_q(x)$ represents a combined effect of helicity contribution due to sea $q \bar{q}$ pairs. From fitting the nucleon polarization a…
Dielectron production in reactions $π^- p \rightarrow n e^+e^-$ and $π^- p \rightarrow n e^+e^- γ$ at energies less than 1 GeV is studied assuming electron-positron pair production to occur in the virtual time-like photon splitting process. Theoretical predictions of the effective mass distribution of dielectrons and their angular dependence are presented. Extraction of the electromagnetic form factor of baryon transition in the time-like region from future experiments of the HADES Collaboration is discussed.
We study baryon-number-violating processes, including proton and bound neutron decays and $n-\bar n$ oscillations, in a left-right-symmetric (LRS) model in which quarks and leptons have localized wavefunctions in extra dimensions. In this model we show that, while one can easily suppress baryon-number-violating nucleon decays well below experimental bounds, this does not suppress $n-\bar n$ transitions, which may occur at levels comparable to current limits. This is qualitatively similar to what was found in an extra-dimensional model with a Standard-Model low-energy effective field theory (SM…
We have previously calculated the pion-nucleon $Σ_{πN}$ term in the chiral mixing approach with $u,d$ flavors only, and found the lower bound $Σ_{πN} \geq \left(1 + \frac{16}{3} \sin^2 θ\right){3 \over 2} \left(m_{u}^{0} + m_{d}^{0}\right)$. The mixing angle $θ$ can be calculated as $\sin^2θ= \frac{3}{8}\left(g_A^{(0)} + g_A^{(3)}\right)$. With presently accepted values of current quark masses, this leads to $Σ_{πN} \geq 58.0 \pm 4.5 \begin{array}{l} +11.4 \\ -6.5 \end{array}$ MeV, which is in agreement with the values extracted from experiments, and substantially higher than most previous two…
Chiral matching of dimension-7 baryon-number-violating operators and application to $ΔI=3/2$ nucleon decays
State Key Laboratory of Nuclear Physics and Technology, Institute of Quantum Matter, South China Normal University（华南师范大学量子物质研究院核物理与技术国家重点实验室）；Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Nuclear Science（广东省基础与应用基础研究基金委物质结构与基本相互作用卓越中心广东省核科学重点实验室）
Intrinsic charm content of the nucleon and charmness-nucleon sigma term
在推广的手征组分夸克模型中，研究了核子的内禀$c \bar{c}$含量。将核子看作是三夸克和五夸克的混合物，相应的跃迁用$^{3}$ P \it机制处理，计算了核子波函数中夸克-反夸克分量的几率.给出了在核子波函数和粲-核子σ项中的$c \bar{c}$几率的预言。我们的数值计算结果与文献中报道的各种其他方法的预测是一致的。
In the framework of a baryon-number-violating effective Lagrangian, we calculate improved lower bounds on partial lifetimes for proton and bound neutron decays, including $p \to \ell^+ \ell'^+ \ell'^-$, $n \to \barν\ell^+ \ell'^-$, $p \to \ell^+ ν\barν$, and $n \to \barν\barνν$, where $\ell$ and $\ell'$ denote $e$ or $μ$, with both $\ell = \ell'$ and $\ell \ne \ell'$ cases. Our lower bounds are substantially stronger than the corresponding lower bounds from direct experimental searches. We also present lower bounds on $(τ/B)_{p \to \ell^+γ}$, $(τ/B)_{n \to \barνγ}$, $(τ/B)_{p \to \ell^+ γγ}$, …
We study the semi-inclusive production of real, high-$p_T$, isolated photons in unpolarized and polarized lepton-proton collisions, $\ell p\to \ellγX$. In particular we analyze the transverse nucleon single-spin asymmetry within the collinear twist-3 formalism in perturbative QCD to leading order (LO) accuracy. We find that this spin asymmetry is generated by twist-3 dynamical quark-gluon-quark ($qgq$) correlations in the nucleon through the so-called soft-fermion and hard pole contributions. Hence, this process unprecedentedly allows for a point-by-point scan of the support of the dynamical $…
Flavor Asymmetry of the Nucleon Sea and the Five-Quark Components of the Nucleons
核子中的内禀粲夸克存在五夸克Fock态，这一观点曾被提出过，但至今仍缺乏确凿的证据。我们推广了以前的理论方法的轻夸克部门和研究可能的实验签名，这样的五夸克态。特别地，我们比较了$\bar d - \bar u$和$\bar u + \bar d - s -\bar s$的数据与基于五夸克Fock态的计算。数据和计算之间的定性协议被解释为证据的存在的内禀轻夸克海的核子。还提取了$|uudu\bar{u}>$和$|uudd\bar{d}>$ Fock状态的概率。
我们推广了Brodsky { \it et al.}从核子中的内禀粲夸克分布到包含内禀$\bar u, \bar d, s$和$\bar s$海夸克的轻夸克扇区。我们将计算结果与现有的$\bar d - \bar u$、$s + \bar s$和$\bar u + \bar d - s -\bar s$数据进行比较。理论和实验数据之间的良好一致性被解释为核子中存在内禀轻夸克海的证据。还提取了$|uudu\bar{u}>$、$|uudd\bar{d}>$和$|uuds\bar{s}>$ Fock状态的概率。
We perform a systematical investigation of the possible deuteron-like bound states with configuration $Ξ_{cc}N (\bar{N})$, where $N(\bar{N})$ denotes the nucleon (anti-nucleon), in the framework of the one-boson-exchange-potential model. In the spin-triplet sector we take into account both the ${}^3S_1$ and ${}^3D_1$ channels due to non-vanishing tensor force. There exist several candidates of the loosely bound molecular states for the $Ξ_{cc}N$ and $Ξ_{cc}\bar{N}$ systems, which lie below the threshold of $Λ_cΛ_c$ or $Λ_c{\barΛ}_c$. We also investigate the possible loosely bound states with c…
Within the effective Lagrangian approach, we study the $p\bar{p} \rightarrow ψη$ [$ψ\equivψ(3686)$, $J/ψ$] reaction at the low energy where the contributions from nucleon pole and low-lying nucleon resonances, $N(1520)$, $N(1535)$ and $N(1650)$ are considered. All the model parameters are determined with the help of current experimental data on the decay of $ψ\to p \bar{p} η$. Within the model parameters, the total and differential cross sections of the $p\bar{p} \rightarrow ψη$ reaction are predicted. We show that the relative phases between different amplitudes of different nucleon resonance…
Extraction of Various Five-Quark Components of the Nucleons
我们推广了Brodsky { \it et al.}从核子中的内禀粲夸克分布到包含内禀$\bar u, \bar d, s$和$\bar s$海夸克的轻夸克扇区。我们将计算结果与现有的$\bar d - \bar u$、$s + \bar s$和$\bar u + \bar d - s -\bar s$数据进行比较。理论与实验数据的良好吻合使得我们可以提取质子中$|uudu\bar{u}>$、$|uudd\bar{d}>$和$|uuds\bar{s}>$五夸克Fock态的几率。在考虑了内禀夸克分布的QCD演化后，我们还计算了内禀粲的$x$依赖性。
We consider the chiral Lagrangian with nucleon, isobar, and pion degrees of freedom. The baryon masses and the axial-vector form factor of the nucleon are derived at the one-loop level. We explore the impact of using on-shell baryon masses in the loop expressions. As compared to results from conventional chiral perturbation theory we find significant differences. An application to QCD lattice data is presented. We perform a global fit to the available lattice data sets for the baryon masses and the nucleon axial-vector form factor, and determine the low-energy constants relevant at N$^3$LO for…
We investigate the strong force fields and stabilities of the nucleon and the singly heavy baryon $Σ_c$ within the framework of the chiral quark-soliton model. Having constructed the pion mean fields in the presence of the $N_c-1$ level quarks self-consistently, we are able to examine the gravitational form factors of $Σ_c$. We mainly focus in the present work on the stability conditions for both the nucleon and $Σ_c$ and discuss the strong force fields and their physical implications. We also present the results for the gravitational form factors and relevant observables, emphasising the diff…
We present a detailed analysis of the beam energy dependence of the mechanisms for the generation of directed and elliptic flows in Au+Au collisions focusing on the role of hadronic rescattering and spectator shadowing within a microscopic transport model JAM with different equation of state. A systematic study of the beam energy dependence is performed for Au+Au collisions at $\sqrt{s_{NN}} =2.3 - 62.4$ GeV. The transition of the dynamical origin of the directed flow is observed. We find that the initial Glauber type nucleon-nucleon collisions generate negative $v_1$ for nucleons at midrapidi…
We carry out an ab initio calculation of the neutrino flux-folded inclusive cross sections, measured on $^{12}$C by the MiniBooNE and T2K collaborations in the charged-current quasielastic (CCQE) regime. The calculation is based on realistic two- and three-nucleon interactions, and on a realistic nuclear electroweak current with one-and two-nucleon terms that are constructed consistently with these interactions and reproduce low-energy electroweak transitions. Numerically exact quantum Monte Carlo methods are utilized to compute the nuclear weak response functions, by fully retaining many-body…
