J/ψ-pair resonances by LHCb: a new revolution?

Studies of the resonance components in the $B_s$ decays into charmonia plus kaon pair

In this work, the decays of $B_s$ mesons to a charmonium state and a $K^+K^-$ pair are carefully investigated in the perturbative QCD approach. Following the latest fit from the LHCb experiment, we restrict ourselves to the case where the produced $K^+K^-$ pair interact in isospin zero $S$, $P$, and $D$ wave resonances in the kinematically allowed mass window. Besides the dominant contributions of the $ϕ(1020)$ resonance in the $P$-wave and $f_2'(1525)$ in the $D$-wave, other resonant structures in the high mass region as well as the $S$-wave components are also included. The invariant mass sp…

On a possibility of exotic heavy baryons

Triggered by a recent announcement by the LHCb Collaboration of five excited $Ω^0_c$ resonances of small widths we propose an interpretation based on the Chiral Quark Soliton Model. We argue that three of the LHCb resonances are parity ($-$) excitations of the ground state SU(3) sextets, while the other two with the smallest widths are exotic pentaquarks that belong to the SU(3) $\overline{\mathbf{15}}$. We first briefly review the model and discuss the status of the putative $Θ^+(1540)$. Next we show how to generalize the model to the case of heavy baryons. We test this approach against the g…

Investigation of the bottom analog of the Zcs(3985) state

Motivated by the recent discovery of the hidden charm exotic state with strangeness by the BESIII and LHCb Collaborations, we study the $S$ wave strange hidden bottom tetraquark in two kinds of quark models. Both meson-meson and diquark-antidiquark configurations are taken into account. The numerical results indicate that there is no bound state in both quark models. However, several resonance states have been predicted. Three resonance states with $I(J^{P})=\frac{1}{2}(0^{+})$ are found, the energy ranges of which are $10479\sim 10550$, $10528\sim 10632$, and $10597\sim 10681$ MeV, respective…

Nucleon resonances $N(1875)$ and $N(2100)$ as strange partners of LHCb pentaquarks

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…

From $J/ψ$ to LHCb pentaquark

The original charmonium two-body problem, like the $c\bar c$ structure of the $J/ψ$ meson, has become more involved in the last few years with the discovery of new resonances such as the tentative molecular state $X(3872)$ or the possible pentaquark one $P_{c}(4380)^{+}$. We discuss herein how these exotic states (and others) can be described in a unified way adding higher Fock state components to the naive quark model picture. In particular, we present our theoretical results on the pentaquark states $P_{c}(4380)^{+}$ and $P_{c}(4450)^{+}$, and on the new charmonium-like resonances $X(4140)$,…

The ccbar Pentaquarks by a Quark Model

Recent LHCb experiments have shown us that there are two resonances in the $J/ψp$ channel in the $Λ_b$ decay, whose spin and parity are most probably (3/2$^-$ 5/2$^+$). In this work, we investigate the $I(J^P)=1/2(1/2^-)$, $1/2(3/2^-)$, and $1/2(5/2^-)$ $uudc{\bar c}$ pentaquark states by employing the quark cluster model. It is found that the color-octet isospin-1/2 spin-3/2 $uud$ configuration gives an attraction to such five-quark systems. This configuration together with the color-octet $c{\bar c}$ pair gives structures around the $Σ_c^{(*)}{\bar D}{}^{(*)}$ thresholds: one bound state, tw…

Enhancement of charm CP violation due to nearby resonances

Quantitative understanding of CP violation is extremely important as naturalness reasoning strongly suggests that new physics should be accompanied by beyond the Standard Model CP-odd phases. In 2019 LHCb made the first $5 σ$ discovery of CP violation in the charm system, leading to the new world average $Δa_{CP}^{\mathrm{dir}} = -0.00161 \pm 0.00028$. While some calculations have found this observation as requiring new physics, we suggest that scalar resonances nearby to $m_{D^0}$, in particular, $f_0(1710)$ and/or $f_0(1790)$ cause enhancements for CP violation within the SM. Thereby, our ca…

A possible interpretation for $X(6900)$ observed in four-muon final state by LHCb -- A light Higgs-like boson?

A peak structure of $J/ψ$ pair production around $6.9~{\rm GeV}$ was observed and analyzed by the LHCb collaboration using the Run I and II data of LHC. How to understand this peak arouses enthusiastic discussions among both theorists and experimentalists of high energy physics, because this discovery might hint something new. Overwhelming works on this topic tend to attribute the peak as a four-quark state: tetraquark or molecule. Instead, we suggest that this peak is corresponding to a fundamental Higgs-like boson with mass about $6.9~{\rm GeV}$ which is advocated by a BSM effective theory. …

LHCb的$P_c(4312)^+$在GlueX $γp\to J/ψp$总截面中是否合理？

Is the LHCb $P_c(4312)^+$ plausible in the GlueX $γp\to J/ψp$ total cross sections ?

本文通过拟合GlueX实验的$γp\to J/ψp$总截面数据寻找LHCb观测到的奇特$P_c(4312)^+$态，发现$S$波共振与非共振背景的相消干涉能解释数据中的凹陷结构，并讨论了模型局限与统计量需求。

Dalitz-plot dependence of CP asymmetry in B+- --> K+- K+ K- decays

A large CP asymmetry predicted recently in the framework of the QCD factorization model for the B+- --> K+- K+ K- decays in the range of the K+ K- invariant masses above the phi(1020) resonance has been confirmed by the LHCb Collaboration. We discuss the emergence and size of this asymmetry in an extended model involving S- and P-waves together with the contribution from the D-wave f2(1270) resonance and compare our model with the experimental data of the LHCb and BABAR Collaborations.

From $J/ψ$ to LHCb pentaquarks

The two exotic $P_c^+(4380)$ and $P_c^+(4450)$ discovered in $2015$ by the LHCb Collaboration, together with the four resonances $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$, reported in $2016$ by the same collaboration, are described in a constituent quark model which has been able to explain the properties of charmonium states from the $J/ψ$ to the $X(3872)$. Using this model we found a $\bar DΣ_c^*$ bound state with $J^P=\frac{3}{2}^-$ that may be identified with the $P_c^+(4380)$. In the $\bar D^*Σ_c$ channel we found three possible candidates for the $P_c^+(4450)$ with $J^P=\frac{1}{2}^-…

Light Resonances and the Low-$q^2$ Bin of $R_{K^*}$

LHCb has reported hints of lepton-flavor universality violation in the rare decays $B \to K^{(*)} \ell^+\ell^-$, both in high- and low-$q^2$ bins. Although the high-$q^2$ hint may be explained by new short-ranged interactions, the low-$q^2$ one cannot. We thus explore the possibility that the latter is explained by a new light resonance. We find that LHCb's central value of $R_{K^*}$ in the low-$q^2$ bin is achievable in a restricted parameter space of new-physics scenarios in which the new, light resonance decays preferentially to electrons and has a mass within approximately $10$ MeV of the …

The new resonances Z_{cs}(3985) and Z_{cs}(4003) (almost) fill two tetraquark nonets of broken SU(3)_f

New data from BESIII and LHCb show the existence of resonances with strangeness filling multiplets of the broken SU(3)_f symmetry, with the pattern predicted by the quark model. This is the case of the newly discovered Z_{cs} (3985) and Z_{cs}(4003), which have a natural accommodation in the tetraquark picture, as shown in this note. The quasi-degeneracy between Z_{cs} (3985) and Z_{cs}(4003) reproduces, in the strange sector, the situation observed with X(3872) and Z_c(3900). This represents a significative score in favor of the tetraquark scheme.

Neural Network Study of Hidden-Charm Pentaquark Resonances

Very recently, LHCb experiment announced the observation of hidden-charm pentaquark states $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ near the $ Σ_c \bar{D}$ and $ Σ_c \bar{D}^\ast$ thresholds, respectively. In this present work, we studied thesepentaquarks in the framework of the nonrelativistic quark model with four types of potential. We solved 5-body Schrödinger equation by using artificial neural network method and made predictions of parities for these states which are not determined in the experiment yet. The mass of another possible pentaquark state near the $\bar{D}^\ast Σ_c^\ast$ with…

On LHCb pentaquarks as a baryon-psi(2S) bound state -- prediction of isospin 3/2 pentaquarks with hidden charm

The pentaquark $P_c^+(4450)$ recently discovered by LHCb has been interpreted as a bound state of $Ψ(2S)$ and nucleon. The charmonium-nucleon interaction which provides the binding mechanism is given, in the heavy quark limit, in terms of charmonium chromoelectric polarizabilities and densities of the nucleon energy-momentum tensor (EMT). In this work we show in model-independent way, by exploring general properties of the effective interaction, that $Ψ(2S)$ can form bound states with nucleon and $Δ$. Using the Skyrme model to evaluate the effective interaction in the large-$N_c$ limit and est…

Vector resonance $X_1(2900)$ and its structure

The new vector resonance $X_1(2900)$ observed recently by LHCb in the $ D^{-}K^{+}$ invariant mass distribution in the decay $B^{+} \to D^{+}D^{-}K^{+}$ is studied to uncover internal structure of this state, and calculate its physical parameters. In the present paper, the resonance $ X_1(2900)$ is modeled as an exotic vector state, $ J^P=1^- $, built of the light diquark $u^{T}Cγ_5d$ and heavy antidiquark $\overline{c} γ_μγ_5C\overline{s}^{T}$. The mass and current coupling of $ X_1(2900)$ are computed using the QCD two-point sum rule approach by taking into account various vacuum condensates…

Resonance $X(4630)$

We investigate the structure $X(4630)$ discovered by the LHCb collaboration in the process $B^{+}\rightarrow J/ψϕK^{+}$ as a resonance in the $ J/ψϕ$ mass distribution. We explore this resonance as a diquark-antidiquark state $X=[cs][\overline{c}\overline{s}]$ with spin-parities $J^{\mathrm{PC}}=1^{-+}$. Its mass and current coupling are calculated using the QCD two-point sum rule method by taking into account vacuum condensates up to dimension $10$. We also study decays of this tetraquark to mesons $J/ψϕ$, $η_{c}η^{(\prime )}$, and $χ_{c1}η^{(\prime )}$, and compute partial widths of these ch…

Resonances gone topsy turvy - the charm of QCD or new physics in $b \to s \ell^+ \ell^-$?

We investigate the interference pattern of the charm-resonances $Ψ(3370,4040,4160,4415)$ with the electroweak penguin operator $O_9$ in the branching fraction of $B^+\to K^+μμ$. For this purpose we extract the charm vacuum polarisation via a standard dispersion relation from BESII-data on $e^+e^-\to hadrons$. In the factorisation approximation (FA) the vacuum polarisation describes the interference fully non-perturbatively. The observed interference pattern by the LHCb collaboration is opposite in sign and and significantly enhanced as compared to the FA. A change of the FA-result by a factor …

Vector Leptoquarks and the 750 GeV Diphoton Resonance at the LHC

The ATLAS and CMS collaborations recently presented evidence of a resonance decaying to pairs of photons around 750 GeV. In addition, the BaBar, Belle, and LHCb collaborations have evidence of lepton non-universality in the semileptonic decays of $B$ mesons. In this work, we make a first step towards a unified explanation of these anomalies. Specifically, we extend the Standard Model by including vector leptoquarks and a scalar singlet that couples linearly to pairs of the leptoquarks. We find there is parameter space that gives the correct cross section for a putative 750 GeV resonance decayi…

因子化辅助拓扑振幅方法下三体衰变 $B \ o D (V \ o ) PP $ 的分析

Analysis of three-body decays $B \to D (V \to ) PP $ under the factorization-assisted topological-amplitude approach

本文系统分析了 $B_{(s)} \ o D_{(s)} (V \ o) P_1 P_2$ 三体衰变，采用 FAT 方法计算中间过程并结合 Breit-Wigner 分布处理共振态衰变，预测了多个分支比并验证了与实验数据的一致性。

Exploring the resonances $X(4140)$ and $X(4274)$ through their decay channels

Investigation of the resonances $X(4140)$ and $X(4274)$, which were recently confirmed by the LHCb Collaboration [1], is carried out by treating them as the color triplet and sextet $[cs][\bar{c}\bar {s}]$ diquark-antidiquark states with the spin-parity $J^{P}=1^{+}$, respectively. We calculate the masses and meson-current couplings of these tetraquarks in the context of QCD two-point sum rule method by taking into account the quark, gluon and mixed vacuum condensates up to eight dimensions. We also study the vertices $X(4140)J/ψϕ$ and $X(4274)J/ψϕ$, and evaluate corresponding strong couplings…

利用重夸克对称性检验 $P_{Ψs}^Λ(4459)$ 的双峰假设

An examination of the two-peak hypothesis of $P_{Ψs}^Λ(4459)$ using heavy quark symmetries

本文利用重夸克对称性检验LHCb发现的$P_{Ψs}^Λ(4459)$是否由两个共振峰组成，并与已知双峰态$P_c(4450)$关联，其中一个峰对应$\ar{D}^*Ξ_c$分子态。

The $B^+ \to J/ψωK^+ $ reaction and $D^*\bar{D}^*$ molecular states

We study the $B^+ \to J/ψωK^+ $ reaction, measured by the LHCb collaboration, and show that it is driven by the presence of two resonances, the $X(3940)$ and $X(3930)$, that are of molecular nature and couple most strongly to $D^* \bar{D}^*$, but also to $J/ψω$. Because of that, in the $J/ψω$ mass distribution we find a peak related to the excitation of the resonances and a cusp with large strength at the $D^* \bar{D}^*$ threshold.

New Axion Searches at Flavor Factories

We assess the impact of searches at flavor factories for new neutral resonances that couple to both photons and gluons. These are well motivated by "heavy axion" solutions of the strong CP problem and by frameworks addressing both Dark Matter and the Higgs hierarchy problem. We use LHCb public diphoton data around the Bs mass to derive the current best limit on these resonances for masses between 4.9 and 6.3 GeV. We estimate that a future LHCb dedicated search would test an axion decay constant of O(TeV) for axion masses in the few-to-tens of GeV, being fully complementary to the low mass ATLA…

$R_K$ anomalies and simplified limits on $Z'$ models at the LHC

The LHCb collaboration has recently reported a 2.5 $σ$ discrepancy with respect to the predicted value in a test of lepton universality in the ratio $R_{K^*}= \hbox{BR}(B \to K^* μ^+ μ^-) / \hbox{BR}(B \to K^* e^+ e^-)$. Coupled with an earlier observation of a similar anomaly in $R_{K}$, this has generated significant excitement. A number of new physics scenarios have been proposed to explain the anomaly. In this work we consider simplified limits on $Z'$ models from ATLAS and CMS searches for new resonances in dilepton and dijet modes, and we use the simplified limits variable $ζ$ to correla…

Studying the Pc(4450) resonance in J/psi photoproduction off protons

The LHCb has reported the observation of a resonancelike structure, the Pc(4450), in the J/psi p invariant masses. In our work, we discuss the feasibility of detecting this structure in J/psi photoproduction, e.g. in the measurements that have been approved for the experiments in Hall A/C and in Hall B with CLAS12 at JLab. Also the GlueX Collaboration has already reported preliminary results. We take into account the experimental resolution effects, and perform a global fit to world J/psi photoproduction data in order to study the possibility of observing the Pc(4450) signal in future JLab dat…

Do the $P_c^+$ Pentaquarks Have Strange Siblings?

The recent LHCb discovery of states $P_c^+(4380)$, $P_c^+(4450)$, believed to be $c\bar c uud$ pentaquark resonances, begs the question of whether equivalent states with $c\bar c \to s\bar s$ exist, and how they might be produced. The precise analogue to the $P_c^+$ discovery channel $Λ_b \to J/ψ\, K^- \! p$, namely, $Λ_c \to ϕπ^0 \! p$, is feasible for this study and indeed is less Cabibbo-suppressed, although its limited phase space suggests that evidence of a $s\bar s uud$ resonance $P_s^+$ would be confined to the kinematic endpoint region.

Multiquark Hadrons

A number of candidate multiquark hadrons, i.e., particle resonances with substructures that are more complex than the quark-antiquark mesons and three-quark baryons that are prescribed in the textbooks, have recently been observed. In this talk I present: some recent preliminary BESIII results on the near-threshold behavior of sigma(e+e- --> Lambda Lambda-bar) that may or may not be related to multiquark mesons in the light- and strange-quark sectors; results from Belle and LHCb on the electrically charged, charmoniumlike Z(4430)^+ --> pi^+ psi ' resonance that necessarily has a four-quark sub…

Searching for fully-heavy tetraquark states in QCD moment sum rules

In this talk, we briefly report the investigations of the mass spectra for the $cc\bar c\bar c, bb\bar b\bar b$, $bc\bar b\bar c$ and $cc\bar b\bar b$ tetraquark states by using the QCD moment sum rule method. The calculations for the fully-charm $cc\bar c\bar c$ tetraquarks have been successfully predicted the existence of di-$J/ψ$ resonances including $X(6900)$ in LHCb's observation. The quantum numbers for these resonance structures are also suggested. More efforts are still needed in both theoretical and experimental aspects to study the properties of these fully-heavy tetraquark states. T…

Contribution of vector resonances to the {\bar B}_d^0 -> {\bar K}^{*0} mu^+ mu^- decay

The fully differential angular distribution for the rare flavor-changing neutral current decay \bar{B}_d^0 -> \bar{K}^{*0} (-> K- pi+) mu+ mu- is studied. The emphasis is placed on accurate treatment of the contribution from the processes \bar{B}_d^0 -> \bar{K}^{*0} (-> K- pi+) V with intermediate vector resonances V = rho(770), omega(782), phi(1020), J/psi, psi(2S), ... decaying into the mu+ mu- pair. The dilepton invariant-mass dependence of the branching ratio, longitudinal polarization fraction f_L of the \bar{K}^{*0} meson, and forward-backward asymmetry A_{FB} is calculated and compared …

非零温度下共振态 X(4630) 的分析

Analysis of the resonance X(4630) at non-zero temperature

本文利用热QCD求和规则方法计算非零温度下共振态X(4630)的质量与衰变常数，发现其在退禁闭温度附近显著下降，且零温时结果与LHCb实验高度一致。

强子共振对 $B o K^{(*)}τ^+τ^-$ 衰变的影响

Impact of Hadronic Resonances on $B\to K^{(*)}τ^+τ^-$ Decays

本文研究强子共振对 $B o K^{(*)}τ^+τ^-$ 衰变的影响，采用数据驱动方法结合 LHCb 的测量结果，预测不同初始动量点下的衰变分支比，并探讨共振效应在标准模型预测和新物理影响下的作用。

Canonical interpretation of the $D_{s0}(2590)^{+}$ resonance

The $D_{s0}(2590)^{+}$ resonance observed by LHCb Collaboration is a strong candidate of the $D_{s}(2^1S_0)$ state according to its spin parity and strong decay mode. However, the measured mass seems relatively lower than the previous theoretical predictions, which interests the coupled channel interpretations in the literature. In this work, we adopt an alternate approach, taking into account the screening effects in the potential model, to describe the $D_{s0}(2590)^{+}$ resonance. The mass spectrum and strong decays of the excited charmed-strange mesons are investigated within the modified …

Studying the P_c(4450) resonance in J/psi photoproduction off protons

A resonance-like structure, the P_c(4450), has recently been observed in the J/psi p spectrum by the LHCb collaboration. We discuss the feasibility of detecting this structure in J/psi photoproduction in the CLAS12 experiment at JLab. We present a first estimate of the upper limit for the branching ratio of the P_c(4450) to J/psi p. Our estimates, which take into account the experimental resolution effects, predict that it will be possible to observe a sizable cross section close to the J/psi production threshold and shed light on the P_c(4450) resonance in the future photoproduction measureme…

Is $f_X(1500)$ observed in the $B\to π(K)KK$ decays $ρ^0(1450)$?

We suggest that the uncertain state $f_X(1500)$ observed by Belle and BaBar more than a decade ago, which has been viewed as a single scalar or a combination of several even spin resonances, is the vector $ρ^0(1450)$ reported recently by LHCb. Adopting the perturbative QCD approach, we determine the di-kaon distribution amplitudes with the $ρ^0(1450)$ resonance from the LHCb data for the quasi-two-body decays $B^{\pm}\to π^{\pm}ρ^0(1450)\toπ^{\pm}K^+K^-$. It is then shown that the $B^+ \to K^+K^+K^-$ decay spectrum around the invariant mass $M(K^+K^-)\sim 1.5~\rm GeV$ measured by BaBar can be …

The S-wave resonance contributions in the $B^0_s$ decays into $ ψ(2S,3S)$ plus pion pair

The three-body decays $B^0_s \rightarrow ψ(2S,3S) π^+ π^-$ are studied based on the perturbative QCD approach. With the help of the nonperturbative two-pion distribution amplitudes, the analysis is simplified into the quasi-two-body processes. Besides the traditional factorizable and nonfactorizable diagrams at the leading order, the next-to-leading order vertex corrections are also included to cancel the scale dependence. The $f_0(980)$, $f_0(1500)$ resonance contributions as well as the nonresonant contributions are taken into account using the presently known $ππ$ time-like scalar form fact…

探测Λ_c^+ → n ar{K}^0 π^+衰变中的异ospin结构和低能共振

Probing the isospin structure and low-lying resonances in $Λ_c^+ \to n\bar{K}^0 π^+$ decays

通过研究Λ_c^+ → n ar{K}^0 π^+衰变，探索低能重子光谱中的未解之谜和ar{K}N系统的异ospin动力学，利用耦合通道的chiral单元ary方法分析该衰变过程，揭示N(1535)和Λ(1670)的动态生成，并发现N(1535)的窄峰和Λ(1670)的深凹结构，支持其分子解释。

The double thresholds distort the lineshapes of the $P_{ψs}^Λ(4338)^0$ resonance

Very recently, the LHCb Collaboration reported the first observation of the hidden charm pentaquark with strangeness, $P_{ψs}^Λ(4338)^0$. Considering this state is very close to the $Ξ_c^0\bar{D}^0$ and $Ξ_c^+D^-$ thresholds, we explore the possible bias of the Breit-Wigner parameterization, with emphasis on the effect of its coupling to the double thresholds $Ξ_c^0\bar{D}^0$ and $Ξ_c^+D^-$. We first use a qualitative picture based on the ``uniformization" of the Riemann surface of the two-channel system to understand the positions of the enhancement. Then we use the Lippmann-Schwinger equatio…

关于在质子和原子核上的近阈反K介子诱导粲偶素产生中检验LHCb隐粲奇异五夸克$P_{cs}(4459)^0$双峰结构的可能性

On the possibility of testing the two-peak structure of the LHCb hidden-charm strange pentaquark $P_{cs}(4459)^0$ in near-threshold antikaon-induced charmonium production on protons and nuclei

本研究在LHCb隐粲奇异五夸克$P_{cs}(4459)^0$的双峰场景下，通过计算反K介子诱导质子与核产生近阈$J/ψ$的各类分布，验证了相关可观测量对该共振态双峰结构及$P_{cs}(4338)^0$的敏感性，为其存在提供新的探测途径。

CP violation in $B^{\pm} \rightarrow π^{\pm}π^{+}π^{-}$ in the region with low invariant mass of one $π^{+}π^{-}$ pair

Recently, the large CP asymmetries in $B^\pm\toπ^\pmπ^+π^-$ decays were found by the LHCb Collaboration to localize in the region $m_{π^+π^-}^2<0.4 \text{GeV}^2$. We find such large localized CP asymmetries may be due to the interference between a light scalar and $ρ^0(770)$ intermediate resonances. Consequently, we argue that the distribution of CP asymmetries in the Dalitz plots of three-body B decays could be very helpful for identifying the presence of the scalar resonance.

X_1(2900)作为P波D̄*K*共振的双极点结构

Double pole structures of $X_1(2900)$ as the $P$-wave $\bar{D}^*K^*$ resonances

本文揭示X_1(2900)在P波D̄*K*双介子图像中具有双极点结构，通过道耦合计算验证其与X_0(2900)、X_1(2900)的一致性，并预言四个新的粲-奇异四夸克态。

Is pentaquark doublet a hadronic molecule?

A recently announced discovery by LHCb of a doublet of overlapping pentaquark resonances poses a question of what can be the origin of this doublet structure. We attract attention to the fact that such degeneracy could naturally arise if constituent "baryon" and "meson" were in the colored rather than colorless states. This is an appealing possibility, also because in such a case the pentaquark state would be no less "elementary" than the other hadrons, and would provide a chance for essentially new non-Abelian chemistry.

Search for Hidden-Charm Pentaquark with CLAS12

LHCb recently announced the discovery of two exotic structures in the $J/ψ+ p$ decay channel, which have been referred to as charmonium-pentaquark states. Resolving between the models and clarifying the nature of the discovered hidden-charm pentaquark peaks, and possibly searching for similar peaks with other quantum numbers, requires further experimental studies. The states were observed in the decay mode $J/ψ+p$. Thus, it is natural to expect that these pentaquarks can be produced in the photoproduction process $γ+p\to P_c\to J/ψ+p$ where these states will appear as s-channel resonances at p…