We study the $Υ(1S)$ meson photoproduction on protons and nuclei at the near-threshold center-of-mass energies below 11.4 GeV (or at the corresponding photon laboratory energies $E_γ$ below 68.8 GeV). We calculate the absolute excitation functions for the non-resonant and resonant photoproduction of $Υ(1S)$ mesons off protons at incident photon laboratory energies of 63--68 GeV by accounting for direct ($γp \to {Υ(1S)}p$) and two-step ($γp \to P^+_b(11080,11125,11130) \to {Υ(1S)}p$) $Υ(1S)$ production channels within different scenarios for the non-resonant total cross section of elementary reaction $γp \to {Υ(1S)}p$ and for branching ratios of the decays $P^+_b(11080,11125,11130) \to {Υ(1S)}p$. We also calculate an analogous functions for photoproduction of $Υ(1S)$ mesons on $^{12}$C and $^{208}$Pb target nuclei in the near-threshold center-of-mass beam energy region of 9.0--11.4 GeV by considering respective incoherent direct ($γN \to {Υ(1S)}N$) and two-step ($γp \to P^+_b(11080,11125,11130) \to {Υ(1S)}p$, $γn \to P^0_b(11080,11125,11130) \to {Υ(1S)}n$) $Υ(1S)$ production processes within a nuclear spectral function approach. We show that a detailed scan of the $Υ(1S)$ total photoproduction cross section on a 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 U.S. and China should give a definite result for or against the existence of the non-strange hidden-bottom pentaquark states $P_{bi}^+$ and $P_{bi}^0$ ($i=$1, 2, 3) as well as clarify their decay rates.
Photoproduction of $Θ^+$ and other pentaquark states
基于Close和Dudek在$γN \to K Θ^+$及其重子-介子耦合中得到的最小唯象，我们给出了正宇称五夸克态$Σ_5$、$Λ_5$和$N_5$的{ \it相对}光生截面的限制.讨论了$γp \to K^0_S (Θ^+;Σ_d^+)$中出现异常信号的可能性。我们强调的重要性比较$γN \to K Θ^+$与“传统”的国家，如$γN \to K Σ(1660)$。
We present results and suggestions on how to confirm the existence and resonant nature of the $Pc(4450)$ detected at LHCb through photoproduction experiments. We find that this narrow structure might have escaped detection in past experiments and use those to give a constraint for the upper limit of the branching ratio/coupling to the $J/ψp$ channel.
Due to the discovery of the hidden-charm pentaquark $P_c$ states by the LHCb collaboration, the interests on the candidates of hidden-bottom pentaquark $P_b$ states are increasing. They are anticipated to exist as the analogues of the $P_c$ states in the bottom sector and predicted by many models. We give an exploration of searching for a typical $P_b$ in the $γp \to Υp$ reaction, which shows a promising potential to observe it at an electron-ion collider. The possibility of searching for $P_b$ in open-bottom channels are also briefly discussed. Meanwhile, the $t$-channel non-resonant contribu…
We study the $J/ψ$ photoproduction from nuclei at near-threshold incident photon energies of 5--11 GeV within the nuclear spectral function approach by considering incoherent direct ($γN \to {J/ψ}N$) and two-step ($γp \to P^+_c(4450)$, $P^+_c(4450) \to {J/ψ}p$) photon--nucleon charmonium creation processes. We calculate the absolute and relative excitation functions within the different scenarios for in-medium modification of the directly photoproduced $J/ψ$ mesons. We show that the overall subthreshold $J/ψ$ production in $γA$ reactions reveals some sensitivity to adopted in-medium modificati…
Inclusive hadroproduction of $χ_{c1}(3872)$, $X_b$ and pentaquarks
Technical University of Munich（慕尼黑工业大学）；II. Institut für Theoretische Physik, Universität Hamburg（汉堡大学理论物理第二研究所）；Central China Normal University（华中师范大学）
We study the $J/ψ$ photoproduction from nuclei in the near-threshold beam energy region of $E_γ$=5--11 GeV within the nuclear spectral function approach by considering incoherent direct ($γN \to {J/ψ}N$) and two-step ($γp \to P^+_c(4312)$, $P^+_c(4312) \to {J/ψ}p$; $γp \to P^+_c(4440)$, $P^+_c(4440) \to {J/ψ}p$; $γp \to P^+_c(4457)$, $P^+_c(4457) \to {J/ψ}p$) $J/ψ$ production processes. We calculate the absolute excitation functions for the non-resonant and resonant production of $J/ψ$ mesons off $^{12}$C and $^{208}$Pb target nuclei within the different scenarios for in-medium modification of…
In this contribution, we discuss the electromagnetic couplings of pentaquark states with hidden charm. This work is motivated by recent experiments at CERN by the LHCb Collaboraton and current experiments at JLab to confirm the existence of hidden-charm pentaquarks in photoproduction experiments.
The photoproduction of bottomonium-like states $Z_{b}(10610)$ and $Z_{b}(10650)$ via $γp$ scattering is studied within an effectiv Lagrangian approach and the vector-meson-dominance model. The Regge model is employed to calculate the photoproduction of $Z_{b}$ states via $t$-channel with $π$ exchange.The numerical results show that the values of the total cross-sections of $Z_{b}(10610)$ and $Z_{b}(10650)$ can reach 0.09 nb and 0.02 nb, respectively, near the center of mass energy of 22 GeV. The experimental measurements and studies on the photoproduction of $Z_{b}$ states near energy region a…
Inspired by the observation of the pentaquark states $P_{c}(4312),P_{c}(4440)$ and $P_{c}(4457)$ at LHCb, photoproduction of these three $P_{c}$ states via the interaction $γp\rightarrow J/ψp$ is investigated in an effective Lagrangian approach. The $t$-channel Pomeron exchange diffractive process is considered as the main background for the $J/ψ$ photoproduction. The numerical results show that the theoretical cross section, which is calculated by assuming a branching ratio $Br[P_{c}\rightarrow J/ψp]\simeq 3\%$, is consistent with the existing experimental data of the $ γp\rightarrow J/ψp$ pr…
We develop an extension of the usual three flavor quark model to four flavors (u, d, s and c), and discuss the classification of pentaquark states with hidden charm. We fit our model to the known baryon spectrum and we predict the double and triple charm baryons, finding good agreement with the most recent lattice QCD calculations. We compute the the ground state of hidden charm pentaquarks and their associated magnetic moments and electromagnetic couplings, of interest to pentaquark photoproduction experiments.
In this work, we investigate the possibility of interpreting two nucleon resonances, the $N(1875)$ and the $N(2100)$, as hadronic molecular states from the $Σ^*K$ and $ΣK^*$ interactions, respectively. With the help of effective Lagrangians in which coupling constants are determined by the SU(3) symmetry, the $Σ^*K$ and $ΣK^*$ interactions are described by the vector-meson and pseudoscalar-meson exchanges. With the one-boson-exchange potential obtained, bound states from the $Σ^*K$ and $ΣK^*$ interactions are searched for in a quasipotential Bethe-Saltpeter equation approach. A bound state wit…
In the past decade many charmonium-like states were observed experimentally. Especially those charged charmonium-like $Z_c$ states and bottomonium-like $Z_b$ states can not be accommodated within the naive quark model. These charged $Z_c$ states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these …
Photoproduction of Theta^+(1540,1/2^+) reexamined with new theoretical information
考虑到手征夸克-孤子模型（chiQSM）给出的K-N-Theta和K*-N-Theta耦合强度的新理论信息，我们利用有效拉格朗日方法重新研究了γ N -> Kbar Theta^+反应过程中奇异五夸克态重子Theta^+（1540，1/2^+）的光生.我们还考虑了交叉对称强子形状因子，也满足在壳条件。由于矢量K介子、g_{K* N Theta}和f_{K* N Theta}具有相当大的矢量和张量耦合，与赝标K介子的矢量耦合g_{K N Theta} ~ 0.8几乎相同，因此K* 交换贡献在光子束不对称性中起关键作用。
Stimulated by the exciting progress in the observation of new bottomonium states, we study the bottomonium spectrum. To calculate the mass spectrum, we adopt a nonrelativistic screened potential model. The radial Schrödinger equation is solved with the three-point difference central method, where the spin-dependent potentials are dealt with non-perturbatively. With this treatment, the corrections of the spin-dependent potentials to the wave functions can be included successfully. Furthermore, we calculate the electromagnetic transitions of the $nS$ ($n\leq 4$), $nP$ ($n\leq 3$), and $nD$ ($n\l…
The near-threshold photoproduction of $J/ψ$ is regarded as one golden process to unveil the nucleon mass structure, pentaquark state involving the charm quarks, and the poorly constrained gluon distribution of the nucleon at large $x$ ($>0.1$). In this paper, we present an analysis of the current experimental data under a two-gluon exchange model, which shows a good consistency. Using a parameterized function form with three free parameters, we have determined the nucleonic gluon distribution at the $J/ψ$ mass scale. Moreover, we predict the differential cross section of the electroproduction …
We present a neat example of a meson--baryon system where the vicinity of two different thresholds enhances the binding of a hadronic resonance, a pentaquark. As a consequence the pattern of states may change when moving among different flavor sectors, what poses a warning on naive extrapolations to heavy flavor sectors based on systematic expansions. For this purpose we simultaneously analyze the $N\bar D$ and $NB$ two-hadron systems looking for possible bound states or resonances. When a resonance is controlled by a coupled-channel effect, going to a different flavor sector may enhance or di…
The photoproduction of the $J/ψ$ off the proton is believed to deepen our understanding of various physics issues. On the one hand, it is proposed to provide access to the origin of the proton mass, based on the QCD multipole expansion. On the other hand, it can be employed in a study of pentaquark states. The process is usually assumed to proceed through vector-meson dominance, that is the photon couples to a $J/ψ$ which rescatters with the proton to give the $J/ψp$ final state. In this Letter, we provide a compelling hint for and propose measurements necessary to confirm a novel production m…
Photoproduction of eta-mesons on the deuteron above S11(1535) in the presence of a narrow P11(1670) resonance
本文研究了氘核上η介子的非相干光生。主要的注意力是支付给上述的区域的S11（1535）共振，而狭窄的共振结构中提取的总截面的γ n -> η n已被报道。从唯象的观点分析了相应的实验结果，模型中包含一个质量约为1670 MeV，宽度小于30 MeV的重子P11。在最近的一些工作中，这种共振被认为是J^P=1/2^+的五夸克反十重态的非奇异成员。计算了$η$介子的极化和非极化角分布。此外，我们给出了我们对中性K介子和双π光生的截面的预测，其中假设相同的窄P11（1670）共振通过衰变到K^0 λ和π δ组态。
The production of hidden-bottom pentaquark $P_{b}$ states via $γp$ and $π^{-}p$ scatterings is studied within an effective Lagrangian approach and the vector-meson-dominance mechnism. For the $P_{b}$ production in the process $γp\rightarrow Υp$, the dipole Pomeron model is employed to calculate the background contribution, and the experimental data can be well described. For the process $π^{-}p\rightarrow Υn$, the Reggeized $t$-channel with $π$ exchange is considered as the main background for the $P_{b}$ production. Near the threshold, two-peak structure from the states $P_{b (11080)$ and $P_…
We investigate theoretically the $K^{0} p$ invariant mass spectrum of the $K^{+} d \to K^{0} p p$ reaction and scrutinize how the signal of the "$Θ^{+}$" pentaquark, if it exists, emerges in the $K^{0} p$ spectrum. The most prominent advantage of this reaction is that we can clearly judge whether the "$Θ^{+}$" exists or not as a direct-formation production without significant backgrounds, in contrast to other reactions such as photoproduction and $π$-induced productions. We show that while the impulse or single-step scattering process can cover the "$Θ^{+}$" energy region with an initial kaon …
Understanding the nature of the hidden charm pentaquark(like) signals in the LHCb data for $Λ_b^0\to J/ψp K^-$ is a central problem of hadron spectroscopy. We propose a scenario completely different from previous ones such as hadron molecules and compact pentaquarks. We identify relevant double triangle mechanisms with leading or lower-order singularities. The associated anomalous threshold cusps at the $Σ_c^{(*)}\bar{D}^{(*)}$ thresholds are significantly more singular than the ordinary ones. Then we demonstrate that the double triangle amplitudes reproduce the peak structures of $P_c(4312)^+…
Quantum Chromodynamics, the theory of strong interactions, predicts several types of bound states. Among them are mesons ($q\bar{q}$) and baryons ($qqq$), which have been the only states observed in experiments for years. However, in the last decade, many states that do not fit this picture have been observed at $B$-factories (BaBar, Belle and CLEO), at $τ$-charm facilities (CLEO-c, BESIII) and also at proton-proton colliders (CDF, D0, LHCb, ATLAS, CMS). There is growing evidence that at least some of the new charmonium- and bottomonium-like states, the so-called XYZ mesons, are new forms of m…
Exploring interference between $P_{c \bar c}$ resonances and background in the pion-induced reaction
Hunan Normal University（湖南师范大学）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；The George Washington University（乔治华盛顿大学）；Lanzhou University of Technology（兰州理工大学）
