Reanalyzing Pentaquark Θ^＋（1540） in Framework of QCD Sum Rules Approach with Direct Instantons

In this article, we study the pentaquark state Θ＋（1540） with a （scalar） diquark-（pseudoscalar） diquarkantiquark type interpolating current in the framework of the QCD sum rules approach by including the contributions from the direct instantons. The numerical results indicate that the contributions from the direct instantons are very small and can be safely neglected.

Masses and Sigma Terms of Pentaquarks in Chiral Perturbation Theory

Assuming that the recently θ＋ and other exotic resonances belong to the pentaquark i0 of SU（3）I with J^P = 1/2, we constructed a relativistic effective lagrangian in the frame work of baryon chiral perturbation theory. The masses of pentaquarks under isospin symmetry is determined by calculating the propagator to one loop, where the extended on-mass-shell renormalization scheme is applied. Using the experimental data for masses of θ＋, Ξ and N, we estimated the mass of Σ and the a terms.

Masses and decays of triply-heavy pentaquarks

In this study,we analyzed masses and decays of triply-heavy pentaquarks QQQnn(Q=b,c)in the unified MIT bag model.We construct the color-spin wave functions of the triply-heavy pentaquarks and use the numerical variational method to compute all the ground-state masses of these systems.By excluding the scattering states in configuration spsce,we computed the decay width ratios of each decay channel relative to the maximum width for the compact pentaquark states,obtaining the main decay modes of the triply-heavy pentaquark systems.

Production of charmonium pentaquarks from b-baryon and B-meson decays:SU(3)analysis

Here,we study the production of charmonium pentaquarks cc¯qqq from bottom baryon and B-meson decays under the flavor SU(3)symmetry.Decay amplitudes for various processes are parameterized in terms of SU(3)irreducible nonperturbative amplitudes.Numerous relations between decay widths are deduced.Moreover,the strong decays of pentaquarks are considered.Our results can be tested in future measurements at LHCb,Belle II,and CEPC.Once decay branching fractions are measured,this study will be useful for the exploration of new decay channels and pentaquark states.

QCD sum rule study for hidden-strange pentaquarks

Inspired by the LHCb observations of hidden-charm Pc(s)states,we study their hidden-strange analog Psstates in both the[udu][■s]and[uds][■u]configurations.We investigate Ps pentaquark states in the pη′,pφ,ΛK,ΣK,andΣ*K*structures with JP=1/2-andΣ*K andΣK*with JP=3/2-and calculate their masses in the framework of QCD sum rules.Our numerical results show that the extracted hadron masses for all the pη′,pφ,ΛK,ΣK,andΣ*K*structures are significantly higher than theΣK mass threshold,and the masses forΣ*K andΣK*are also higher than the threshold of the corresponding hadron;hence,no bound state exists in such channels,which is consistent with the current experimental status.

Analysis of Pcs(4338) and related pentaquark molecular states via QCD sum rules

In this study,we tentatively identify Pcs(4338)■Ξc molecular state and distinguish the isospins of current operators to explore in detail the■Ξc,■Λc,■sΞc,■sΛc,■*Ξc,■*Λc,■*sΞc,and■*sΛcmolecular states without strange,with strange,and with double strange in the framework of QCD sum rules.The present exploration favors identifying Pcs(4338)(Pcs(4459))as the■Ξc(■*Ξc)molecular state with the spin-parity JP=1/2-(3/2-)and(I,I3)=(0,0),and the observation of their cousins with the isospin(I,I3)=(1,0)J/ψΣ0/ηcΣ0in the invariant mass distributions would decipher their inner structures.

Pentaquark^+的介质效应

在密度相关的相对论平均场理论基础上,假定^+通过交换有效的同位旋标量介子σ和ω与其他重子发生相互作用,研究了强子在包含^+的奇异核物质中的性质改变。讨论并计算了介质中的^+和核子有效质量及其对重子密度的依赖关系,分析了^+在核物质中包含的成分大小以及核子的同位旋效应对奇异核物质性质的影响,进一步计算了不同重子组成比例下奇异核物质的标量密度ρ_S和矢量密度ρ_B的对应曲线。

Pentaquark■^+对核物质状态方程的影响

假定■^+通过交换有效的同位旋标量介子σ和ω与核子和它本身发生相互作用,在密度相关的相对论平均场理论基础上研究了{p,n,■^+}系统状态方程和可能形成的亚稳定态．讨论了在不同的重子密度下质子中子同位旋比值以及Pentaquark ■^+成分对系统单个重子能的影响．计算结果表明,在单个重子能取极小时,■^+有可能在核物质中束缚存在．

基于分子态构型研究单粲味五夸克态的产生

基于有效拉氏量方法,本文研究了自旋宇称为J^(P)=1/2-的单粲味五夸克态的产生.本文根据强子可能的分子态图像,分别以ND_(s)或ND_(s)^(*)不同的分子态构型,讨论了B_(s)介子产生单粲味五夸克态csuud和十重态重子Δ,以及该五夸克态的两体强衰变过程.通过复合粒子判据,计算出与单粲味五夸克态csuud相关的强耦合常数.借助于强子的有效拉氏量方法,最终得到了单粲味五夸克态的产生分支比.结果表明,在单粲味五夸克态csuud为ND_(s)的构型下,具有Cabibbo允许的产生过程:B_(s)→P_(cs)Δ的分支比可以达到10^(-5)量级,而在ND_(s)^(*)的构型下,该过程的分支比仅为10^(-8)量级.本文的研究结果可以为单粲味五夸克态的实验搜寻和深入研究提供参考,并期望在将来的实验探测诸如LHCb,BelleⅡ,BaBar等B工厂中得到验证.

The pentaquarks observed by the LHCb experiment

In 1964, Murray Gell-Mann [1], the Nobel Prize winner in Physics, and George Zweig [2] separately proposed the quark model.The model revealed for the first time that a class of particles, baryons including protons and neutrons, were not elementary, instead were formed by three quarks (qqq), and another class, mesons,were made of quark-antiquark pairs (qqà). The quark model can successfully describe all the baryons and mesons (collectively referred to as hadrons) observed in the last century, thereby helps to explain how the strong force binds the quarks to form a particle.

Possible strange hidden-charm pentaquarks from Σ_c^((*))_s~* and Ξ_c^((',*))~* interactions

Using the one-boson-exchange model, we investigate the Λcs^＊, Σcs^＊, Σc^＊s^＊, Ξc^＊, Ξ＇c^＊, and Ξc^＊^＊ interactions by considering the one-eta-exchange and/or one-pion-exchange contributions. We further predict the existence of hidden-charm molecular pentaquarks. Promising candidates for hidden-charm molecular pentaquarks include a Ξ＇cD^＊ state with 0（（1/2）^-） and the Ξc^＊D^＊ states with 0（1/2^-） and 0（3/2^-）. Experimental searches for these predicted hidden-charm molecular pentaquarks are an interesting future research topic for experiments like LHCb.

Possibility of observation of hidden-bottom pentaquark resonances in bottomonium photoproduction on protons and nuclei near threshold

We study theΥ(1S)meson photoproduction on protons and nuclei at near-threshold center-of-mass energies below 11.4 GeV(or at the corresponding photon laboratory energies Eγbelow 68.8 GeV).We calculate the absolute excitation functions for the nonresonant and resonant photoproduction ofΥ(1S)mesons off protons at incident photon laboratory energies of 63-68 GeV by considering direct(γp→Υ(1S)p)and two-step(γp→P^+b(11080)→Υ(1S)p,γp→P^+b(11125)→Υ(1S)p,γp→P^+b(11130)→Υ(1S)p)Υ(1S)production channels within different scenarios for the nonresonant total cross section of the elementary reactionγp→Υ(1S)p and for branching ratios of the decays P^+b(11080)→Υ(1S)p,P^+b(11125)→Υ(1S)p,and P^+b(11130)→Υ(1S)p.We also calculate an analogous function for the photoproduction ofΥ(1S)mesons on the 12C and 208Pb target nuclei in the near-threshold center-of-mass beam energy region of 9.0-11.4 GeV by considering the respective incoherent direct(γN→Υ(1S)N)and two-step(γp→P^+b(11080)→Υ(1S)p,γp→P^+b(11125)→Υ(1S)p,γp→P^+b(11130)→Υ(1S)p andγn→P^0b(11080)→Υ(1S)n,γn→P^0b(11125)→Υ(1S)n,γn→P^0b(11130)→Υ(1S)n)Υ(1S))production processes using a nuclear spectral function approach.We demonstrate that a detailed scan of theΥ(1S)total photoproduction cross section on proton and nuclear targets in the near-threshold energy region in future high-precision experiments at the proposed high-luminosity electron-ion colliders EIC and EicC in the US and China should provide a definite result for or against the existence of the nonstrange hidden-bottom pentaquark statesP^+bi and P^0bi(i=1,2,3)as well as clarify their decay rates.

Revisiting hidden-charm pentaquarks from QCD sum rules

We revisit hidden-charm pentaquark states P_c(4380) and P_c(4450) using the method of QCD sum rules by requiring the pole contribution to be greater than or equal to 30% in order to better that the one-pole parametrization is valid. We find two mixing currents, and our results suggest that P_c(4380) and P_c(4450) can be identified as hiddencharm pentaquark states having J^P= 3/2^-and 5/2^+, respectively. However, there still exist other possible spin-parity assignments, such as J^P = 3/2^+ and J^P = 5/2^-, which must be clarified in further theoretical and experimental studies.

Neural network study of hidden-charm pentaquark resonances

Recently,the LHCb experiment announced the observation of hidden-charm pentaquark states Pc(4312),Pc(4440),and Pc(4457)nearΣcDandΣcD*thresholds.In this present work,we studied these pentaquarks in the framework of the nonrelativistic quark model with four types of potential.We solved five-body Schrodinger equation by using the artificial neural network method and made predictions of parities for these states,which are not yet determined by experiment.The mass of another possible pentaquark state near the D*Σc*with JP=5/2-is also calculated.

Low-lying 1/2- hidden strange pentaquark states in the constituent quark model

We investigate the spectrum of the low-lying 1/2- hidden strange pentaquark states, employing the constituent quark model, and looking at two ways within that model of mediating the hyperfine interaction between quarks – Goldstone boson exchange and one gluon exchange. Numerical results show that the lowest 1/2- hidden strange pentaquark state in the Goldstone boson exchange model lies at～1570 MeV, so this pentaquark configuration may form a notable component in S11（1535） if the Goldstone boson exchange model is applied. This is consistent with the prediction that S11（1535） couples very strongly to strangeness channels.

Magnetic moments of hidden-charm strange pentaquark states

In this study,the magnetic moments of hidden-charm strange pentaquark states with quantum numbers J^(P)=1^(±)/2,3^(±)/2,5^(±)/2,and 7^(+)/2 are calculated in the molecular,diquark-diquark-antiquark,and diquark-triquark models.The numerical results demonstrate that the magnetic moments change for different spin-orbit couplings within the same model and when involving different models with the same angular momentum.

Identifying hidden charm pentaquark signal from non-resonant background in electron–proton scattering

In this study,we analyze the electroproduction of the LHCb pentaquark states with the assumption that they are resonant states.Our main concern is to investigate the final state distribution in the phase space to extract a feeble pentaquark signal from a large non-resonant background.The results indicate that the signal to background ratio will increase significantly with a proper kinematic cut,which will be beneficial for future experimental analysis.

Quantum numbers of the pentaquark states Pc+ via symmetry analysis

We investigate the quantum numbers of the pentaquark states Pc+,which are composed of 4(three flavors)quarks and an antiquark,by analyzing their inherent nodal structure in this paper.Assuming that the four quarks form a tetrahedron or a square,and the antiquark is at the ground state,we determine the nodeless structure of the states with orbital angular moment L≤3,and in turn,the accessible low-lying states.Since the inherent nodal structure depends only on the inherent geometric symmetry,we propose the quantum numbers JPof the low-lying pentaquark states P_c^+may be■,■,■and■,independent of dynamical models.

Electromagnetic properties of the Pc(4312) pentaquark state

Using the light-cone QCD sum rules,we evaluate the magnetic moment of the P_c(4312) pentaquark state by considering both the \bar D\Sigma_c molecular and diquark-diquark-antiquark state,with quantum numbers J^P=2/1^(-1).In the calculations,we use the diquark-diquark-antiquark and molecular form of the interpolating currents for the P_(c4312) pentaquark and the distribution amplitudes of the photon.The numerical results for the magnetic moment obtained using the two different pictures are quite different from each other,which can be used to pin down the underlying structure of P_(c4312) .Any experimental measurement of the magnetic moment in the near future will provide an understanding of the internal structure of this pentaquark state.

Hidden-charm pentaquark states through current algebra:from their production to decay

There may be sevenD^((*))Σ_(c)^((*))hadronic molecular states.We construct their corresponding interpolating currents and calculate their masses and decay constants using QCD sum rules.Based on these results,we calculate their relative production rates inΛ^(0)_(b)decays using current algebra,that is,B(Λ^(0)_(b)→P_(c)K^(-)):B(Λ^(0)_(b)→P′_(c)K^(-)),where P_(c)and P′_(c)are two different states.We also study their decay properties via Fierz rearrangement and further calculate these ratios in the J/ψp mass spectrum,that is,B(Λ^(0)_(b)→P_(c)K^(-)→J/ψpK^(-)):B(Λ^(0)_(b)→P′_(c)K^(-)→J/ψpK^(-)).Our results suggest that theD*Σ^(*)_(c)molecular states of JP=1/2^(-)and 3/2^(-)may be observed in future experiments.