We investigate the observed pentaquark candidates $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ from the latest LHCb measurement, as well as four possible spin partners in the $\bar{D}^{(*)}Σ_c^*$ system predicted from the heavy quark spin symmetry with the hadronic molecule scenarios. Similar to the previous calculation on $P_c(4380)$ and $P_c(4450)$, the partial widths of all the allowed decay channels for these $P_c$ states are estimated with the effective Lagrangian method. The cutoff dependence of our numerical results are also presented. Comparing with the experimental widths, our results show that $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ can be described well with the spin-parity-$1/2^-$-$\bar{D}Σ_c$, $1/2^-$-$\bar{D}^*Σ_c$ and $3/2^-$-$\bar{D}^*Σ_c$ molecule pictures, respectively.
The antiquark-diquark-diquark model describes pentaquark states both in terms of quarks and hadrons. We discuss pentaquark states with hidden charm $P(\bar c cuud)$ discovered in the $J/Ψp$ spectrum by the LHCb collaboration. We consider three pentaquark states as members of the lowest ($S$-wave) multiplet and discuss the mass splitting scheme. The latest LHCb data for pentaquarks with hidden charm provide an opportunity to make an assumption about the diquark content of the pentaquark states. We give a classification for the LHCb pentaquarks and define recombination channels for these states.
In this article, a possible interpretation of the pentaquark candidates recently observed at LHCb is given. We show that the reaction dynamics and the peculare kinematics situation can produce the peak in the spectrum and the sharp phase motion. The mechanism called triangle singularity likely causes the appearance of the new pentaquarks candidates.
The relativistic five-quark equations are found in the framework of the dispersion relation technique. The solutions of these equations using the method based on the extraction of the leading singularities of the amplitudes are obtained. The five-quark amplitudes for the hidden-charm pentaquarks including the u, d, c - quarks are calculated. The poles of these amplitudes determine the masses of pentaquarks. The masses of pentaquarks with JP=3/2-, 5/2+ are calculated.
The newly measurement of production fractions of $P_c$ states by LHCb collaboration have put restriction on their branching ratios of $J/ψp$ decay, thus constraining their photoproduction in $γp\to J/ψp$ reaction. We show the tension between LHCb results and the current experiments in search of $P_c$ photoproduction. We also find that the present information of branching ratios of $P_c\to J/ψp$ has already confronted sharply with the models which study the nature of $P_c$.
New LHCb Collaboration results on pentaquarks with hidden charm [1] are discussed. These results fit nicely in the hadrocharmonium pentaquark scenario [2,3]. In the new data the old LHCb pentaquark $P_c(4450)$ splits into two states $P_c(4440)$ and $P_c(4457)$. We interpret these two almost degenerate hadrocharmonium states with $J^P=1/2^-$ and $J^P=3/2^-$ as a result of hyperfine splitting between hadrocharmonium states predicted in [2]. It arises due to QCD multipole interaction between color-singlet hadrocharmonium constituents. We improve the theoretical estimate of hyperfine splitting [2,…
The LHCb has discovered two new states with preferred $J^P$ quantum numbers $3/2^-$ and $5/2^+$ from $Λ_b$ decays. These new states can be interpreted as hidden charm pentaquarks. It has been argued that the main features of these pentaquarks can be described by diquark model. The diquark model predicts that the $3/2^-$ and $5/2^+$ are in two separate octet multiplets of flavor $SU(3)$ and there is also an additional decuplet pentaquark multiplet. Finding the states in these multiplets can provide crucial evidence for this model. The weak decays of b-baryon to a light meson and a pentaquark ca…
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 $X(4140)$,…
On March 26th, 2019, at the Rencontres de Moriond QCD conference, the LHCb Collaboration reported the observation of three new pentaquarks, namely $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, which are consistent with the loosely bound molecular hidden-charm pentaquark states composed of an S-wave charmed baryon $Σ_c$ and an S-wave anti-charmed meson ($\bar{D}, \bar{D}^*$). In this work, we present a direct calculation by the one-boson-exchange (OBE) model and demonstrate explicitly that the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ do correspond to the loosely bound $Σ_c\bar{D}$ with $(I=1/2,J^P=…
Recently, LHCb collaboration reported the observation of two hidden-charmed resonances $P_c(4380)$ and $P_c(4450)$ consistent with hidden-charmed pentaquarks. We perform a dynamical investigation about the $\bar{D}Σ_c^*(2520)$ and $\bar{D}^*Σ_c(2455)$ interactions which are described by the meson exchanges in a quasipotential Bethe-Salpeter equation approach. Two poles around $4450$ and $4390$ MeV are produced from the $\bar{D}^*Σ_c(2455)$ interaction with spin parities $3/2^-$ and $5/2^+$, respectively. The peak for $5/2^+$ state has a comparable hight as that of $3/2^-$ state in the $J/ψp$ i…
The discovery of three pentaquark peaks -- the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ -- by the LHCb collaboration has a series of interesting consequences for hadron spectroscopy. If these hidden-charm objects are indeed hadronic molecules, as suspected, they will be constrained by heavy-flavor and SU(3)-flavor symmetries. The combination of these two symmetries will imply the existence of a series of five-flavor pentaquarks with quark content $\bar{b} c s d u$ and $b \bar{c} s d u$, that is, pentaquarks that contain each of the five quark flavors that hadronize. In addition, from SU(3)-fla…
Exotic resonant structures found in $Λ^0_b$ and $\overline{B}^0$ decays into charmonium in the LHCb experiment are discussed. Examination of the $J/ψp$ system in $Λ^0_b\to J/ψK^- p$ decays shows two states each of which must be composed of $uudc\overline{c}$ quarks, and thus are called charmonium pentaquarks. Their masses are $4380\pm 8\pm 29$~MeV and $4449.8\pm 1.7\pm 2.5$~MeV, and their corresponding widths ($Γ$) are $205\pm 18\pm 86$ MeV, and $39\pm 5\pm 19$ MeV. The preferred $J^P$ assignments are of opposite parity, with one state having spin 3/2 and the other 5/2. Models of internal bind…
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…
The recently discovered $P_c(4380)^+$ and $P_c(4450)^+$ states at LHCb have masses close to the $\bar DΣ_c^*$ and $\bar D^*Σ_c$ thresholds, respectively, which suggest that they may have significant meson-baryon molecular components. We analyze these states in the framework of a constituent quark model which has been applied to a wide range of hadronic observables, being the model parameters, therefore, completely constrained. The $P_c(4380)^+$ and $P_c(4450)^+$ are studied as molecular states composed by charmed baryons and open charm mesons. Several bound states with the proper binding energ…
The diquark-diquark-antiquark model describes pentaquark states both in terms of quarks and hadrons. The latest LHCb data for pentaquarks with open charm emphasize the importance of hadron components in the structure of pentaquarks. We discuss pentaquark states with hidden charm $P(\bar c cuud)$ and those with open charm $P(\bar uussc)$ which were discovered recently in LHCb data ($J/Ψp$ and $Ξ_c^+ K^-$ spectra correspondingly). Considering the observed states as members of the lowest (s-wave) multiplet we discuss the mass splitting of states and the dumping of their widths.
We interpret the newly discovered pentaquark $P_c(4450)$ as a bound state of charmonium $ψ(2S)$ and the nucleon. The binding potential is due to charmonium-nucleon interaction that in the heavy quark approximation is proportional to the product of the charmonium chromoelectric polarizability and the nucleon energy-momentum distribution. We use the large $N_c$ expansion to estimate the quarkonium polarizability and calculate the nucleon properties in the framework of the mean-field picture of light baryons. Two almost degenerate states $J^P=(1/2)^-$ and $J^P=(3/2)^-$ are predicted at the positi…
Very recently, two hidden-charmed resonances $P_c(4380)$ and $P_c(4450)$ consistent with pentaquark states were observed at the LHCb detector. The two $P_c$ states locate just below the $\bar{D}Σ^*_c$ and $\bar{D}^*Σ_c$ thresholds with mass of gaps about 5 and 15 MeV, respectively. Inspired by this fact we perform a dynamical investigation about the $\bar{D}Σ_c^*(2520)$ and $\bar{D}^*Σ_c(2455)$ interactions which are described by the meson exchanges. A bound state which carries spin-parity $J^P=3/2^-$ is produced from the $\bar{D}Σ^*_c(2520)$ interaction, which is consistent with the $P_c(4380…
Recently the LHCb collaboration has observed a new pentaquark state, the $P_c(4337)^+$. Owing to its proximity to the $χ_{c0}(1S) p$, $\bar{D}^* Λ_c$, $\bar{D} Σ_c$ and $\bar{D} Σ_c^*$ thresholds, this new pentaquark might very well be a meson-baryon bound state. However its spin and parity have not been determined yet and none of the previous possibilities can be ruled out. We briefly explore a few of these options and the consequences they entail in the present manuscript: (i) the $P_c(4337)^+$ might be a $χ_{c0}(1S) p$ bound state, (ii) the $P_c(4312)^+$ and $P_c(4337)^+$ might be $\bar{D}^…
A coupled-channel approach including the $Λ_c\bar{D}^{(*)}$ and $η_c p$ channels in addition to the $Σ_c^{(*)}\bar{D}^{(*)}$ and $J/ψp$ channels, as required by unitarity and heavy quark spin symmetry (HQSS), is applied to the hidden-charm pentaquark $P_c$ states, i.e., $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, discovered by LHCb Collaboration. It is demonstrated that to obtain cutoff independent results, the one-pion exchange potential in the multichannel systems is to be supplemented with next-leading order counter terms responsible for the $S$-wave-to-$D$-wave transitions. We show that the …
The field of exotic spectroscopy is extremely rich and productive. Several observations and searches for pentaquark states have been performed in the last 4 years, starting from the LHCb observation in 2015. This is still quite a recent discovery, and possibly the beginning of a new era in both observation of new states and understanding of the QCD binding mechanisms. The most recent results from LHCb and Belle are presented regarding measurements and searches for charm, strange and beauty pentaquarks, along with an introduction on phenomenology of multiquark states.
A recent analysis by the LHCb collaboration suggests the existence of three narrow pentaquark-like states --- the $P_c(4312)$,$P_c(4440)$ and $P_c(4457)$ --- instead of just one in the previous analysis (the $P_c(4450)$). The closeness of the $P_c(4312)$ to the $\bar{D} Σ_c$ threshold and the $P_c(4440)$/$P_c(4457)$ to the $\bar{D}^* Σ_c$ one suggests a molecular interpretation of these resonances. We show that these three pentaquark-like resonances can be naturally accommodated in a contact-range effective field theory description that incorporates heavy-quark spin symmetry. This description …
The LHCb collaboration have recently updated their analysis of the resonant $J/ψ\, p$ mass spectrum in the decay $Λ_b^0 \to J/ψ\, p\, K^-$, making use of their combined Run~1 and Run~2 data. In the updated analysis, three narrow states, $P_c (4312)^+$, $P_c (4440)^+$, and $P_c (4457)^+$, are observed. The spin-parity assignments of these states are not yet known. We interpret these narrow resonances as compact hidden-charm diquark-diquark-antiquark pentaquarks. Using an effective Hamiltonian, based on constituent quarks and diquarks, we calculate the pentaquark mass spectrum for the complete $…
We study the near-threshold $J/ψ$ meson production on protons and nuclei by considering incoherent direct non-resonant $K^-p \to {J/ψ}Λ$ and two-step resonant ${K^-}p \to P_{cs}(4459)^0 \to {J/ψ}Λ$ charmonium production processes. We calculate the absolute excitation functions, energy and momentum distributions for the non-resonant, resonant and for the combined (non-resonant plus resonant) production of $J/ψ$ mesons off protons as well as off carbon and tungsten target nuclei at near-threshold incident antikaon energies by considering these elementary production channels as well as by assumin…
We consider the ${\bar D}^{(*)}Σ_c^{(*)}$ states, together with $J/ψN$ and other coupled channels, and take an interaction consistent with heavy quark spin symmetry, with the dynamical input obtained from an extension of the local hidden gauge approach. By fitting only one parameter to the recent three pentaquark states reported by the LHCb collaboration, we can reproduce the three of them in base to the mass and the width, providing for them the quantum numbers and approximate molecular structure as $1/2^-$ $\bar{D} Σ_c$, $1/2^-$ $\bar{D}^* Σ_c$, and $3/2^-$ $\bar{D}^* Σ_c$, and isospin $I=1/…
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…
We study baryo-charmonium [$η_{\rm c}$- and $J/ψ$-$N^*$, $η_{\rm c}(2S)$-, $ψ(2S)$- and $χ_{\rm c}(1P)$-$N$] and baryo-bottomonium [$η_{\rm b}(2S)$-, $Υ(2S)$- and $χ_{\rm b}(1P)$-$N$] bound states, where $N$ is the nucleon and $N^*$ a nucleon resonance. In the baryo-quarkonium model, the five $qqq Q \bar Q$ quarks are arranged in terms of a heavy quarkonium core, $Q \bar Q$, embedded in light baryonic matter, $qqq$, with $q = u$ or $d$. The interaction between the $Q \bar Q$ core and the light baryon can be written in terms of the QCD multipole expansion. The spectrum of baryo-charmonium state…
I give a brief comment on the LHCb's discovery of $P_c$ and $P_{cs}$ pentaquark states. These pentaquark states not only reveal a new kind of hadronic molecules, but also shed new light on the possible structure of pentaquark components in baryons, hence may play very important role for understanding un-quenching dynamics and the whole baryon spectroscopy.
We perform a theoretical analysis of the $Λ_b \to J/ψK^- p$ reaction from where a recent LHCb experiment extracts a $Λ(1405)$ contribution in the $K^- p$ spectrum close to threshold and two baryon states of hidden charm in the $J/ψ\,p$ spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and $J^P$ of the experiment, concretely some states built up from the $J/ψ\, N$, $\bar D^* Λ_c$, $\bar D^* Σ_c$, $\bar D Σ^*_c$ and $\bar D^* Σ^*_c$ coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are ab…
The recent abundant observations of pentaquarks and tetraquarks by high-energy accelerator facilities indicate the realization of the conjecture by Gell-Mann and Zweig, and by De Rujula, Georgi and Glashow [1-3]. We construct a coupled-channel model for the hidden-charm pentaquarks with strangeness whose quark content is $udsc \bar c$, $P_{cs}$, described as $ Λ_c \bar{D}_s^{(*)}, Ξ_c^{('*)} \bar{D}^{(*)}$ molecules coupled to the five-quark states. These molecules are formed by the suitable cooperation of heavy quark and chiral symmetries. We reproduce the experimental mass and quantum number…
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}^-…
We consider decays of the hidden charm LHCb pentaquarks in the hadrocharmonium and molecular scenarios. In both pictures the LHCb pentaquarks are essentially nonrelativistic bound states. We develop a semirelativistic framework for calculation of the partial decay widths that allows the final particles to be relativistic. Using this approach we calculate the decay widths in the hadrocharmonium and molecular pictures. Molecular hidden charm pentaquarks are constructed as loosely bound states of charmed and anticharmed hadrons. Calculations show that molecular pentaquarks decay predominantly int…
We study the possibility that at least one of the two pentaquark structures recently reported by LHCb can be described as a compact pentaquark state, and we give predictions for new channels that can be studied by the experimentalists if this hypothesis is correct. We use very general arguments dictated by symmetry considerations, in order to describe the pentaquark states within a group theory approach. A complete classification of all possible states and quantum numbers, that can be useful both to the experimentalists, for new finding, or to theoretical model builders, are given, without the…
Inspired by $P_c(4380)$ and $P_c(4450)$ recently observed by LHCb, a QCD sum rule investigation is performed, by which they can be identified as exotic hidden-charm pentaquarks composed of an anti-charmed meson and a charmed baryon. Our results suggest that $P_c(4380)$ and $P_c(4450)$ have quantum numbers $J^P=3/2^-$ and $5/2^+$, respectively. Furthermore, two extra hidden-charm pentaqurks with configurations $\bar{D}Σ_c^*$ and $\bar{D}^*Σ_c^*$ are predicted, which have spin-parity quantum numbers $J^P=3/2^-$ and $J^P=5/2^+$, respectively. As an important extension, the mass predictions of hid…
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…
Inspired by the LHCb's discovery of hidden-charm pentaquarks, the anticharmed strange pentaquarks $P_{\bar c s}$ in a favor of the hadronic molecule picture are investigated from the one-boson-exchange model. Similar to the hidden-charm pentaquarks, three molecular bound states, one with spin parity $J^P=1/2^-$ below the $\bar DΣ$ threshold and another two with $J^P=\{1/2^-,3/2^-\}$ below the $\bar D^*Σ$ threshold, are predicted at $3-3.2$ GeV mass region. The mass ordering of the later two states can be interchanged by different reductions of the $δ(r)$ term. Furthermore, resonances associate…
We study the electroproduction of the LHCb pentaquark states with the assumption that they are resonant states. The main concern here is to investigate the final state distribution in the phase space in order to extract the feeble pentaquark signal from the large non-resonant background. Our results show that the ratio of the signal to background would increase significantly with proper kinematic cut, which would be very helpful for future experimental analysis.
As a hot issue, exploring exotic pentaquarks is full of challenges and opportunities for both theorist and experimentalist. In this work, we focus on a type of pentaquark with the $QQqq\bar{q}$ ($Q=b,c$; $q=u,d,s$) configuration, where their mass spectrum is estimated systematically. Especially, our result indicates that there may exist some stable or narrow exotic pentaquark states. Obviously, our study may provides valuable information for further experimental search for the $QQqq\bar{q}$ pentaquarks. With the running of LHCb and forthcoming Belle II, we have a reason to believe that these p…
We study the $P_{cs}(4459)^0$ recently observed by LHCb using the method of QCD sum rules. Our results support its interpretation as the $\bar D^* Ξ_c$ hadronic molecular state of either $J^P=1/2^-$ or $3/2^-$. Within the hadronic molecular picture, the three LHCb experiments observing $P_c$ and $P_{cs}$ states \cite{lhcb,Aaij:2015tga,Aaij:2019vzc} can be well understood as a whole. This strongly supports the existence of hadronic molecules, whose studies can significantly improve our understanding on the construction of the subatomic world. To verify this picture, we propose to further invest…
We comment on the recent evidence by the LHCb Collaboration for a structure in the $J/ψΛ$ final state produced in the decay $Ξ^-_b \to J/ψΛK^-$, with minimal quark content $c \bar c u d s$.
In the framework of the color-magnetic interaction, we have systematically studied the mass splittings of the possible hidden-charm pentaquarks $qqqc\bar{c}$ ($q=u,d,s$) where the three light quarks are in a color-octet state. We find that i) the LHCb $P_c$ states fall in the mass region of the studied system; ii) most pentaquarks should be broad states since their $S$-wave open-charm decays are allowed while the lowest state is the $J^P=\frac12^-$ $Λ$-like pentaquark with probably the suppressed $η_cΛ$ decay mode only; and iii) the $J^P=\frac52^-$ states do not decay through $S$-wave and thei…
In a previous work we have studied the isospin 1/2 lowest positive and negative parity states of the pentaquark $uudc\overline{c}$, in a constituent quark model with a linear confinement and an SU(4) flavor-spin hyperfine interaction and we compared the results with the $P^+_c(4312)$, $P^+_c(4440)$ and $P^+_c(4457)$ pentaquarks observed at LHCb in 2019. Here we extend the previous work by calculating ratios of decay rates of the $P_c$ pentaquarks to $J/Ψ$ and $η_c$ and similarly the ratio of decay rates to $Λ_c {\bar D}^*$ and $Λ_c \bar D$. Our predictions are based on the SU(4)$\times$SU(2) s…
Using the bound state version of the topological soliton model for the baryons we show that the existence of a bound (or quasi-bound) $\bar D$-soliton state leads to the possibility of having hidden charm pentaquarks with quantum numbers and masses, which are compatible with those of the candidates recently reported by the LHCb experiment. The implications of heavy quark symmetry are elaborated.
The LHCb collaboration reported a fully charmed tetraquark state X(6900) in the invariant mass spectrum of $J/ψ$ pairs in 2020. This discovery inspires us to further study the fully heavy pentaquark system. In this work, we investigate systematically all possible configurations for ground fully heavy pentaquark system via the variational method in the constituent quark model. According to our calculations, we further analyze the relative lengths between quarks and the contributions to the pentaquark masses from different terms of the Hamiltonian. We think no stable states exist in fully heavy …
Inspired by the recent evidence of $P_{cs}(4459)$ reported by LHCb, we continue to perform the investigation of hidden-charm molecular pentaquarks with double strangeness, which are composed of an $S$-wave charmed baryon $Ξ_c^{(\prime,*)}$ and an $S$-wave anti-charmed-strange meson $\bar{D}_s^{(*)}$. Both the $S$-$D$ wave mixing effect and the coupled channel effect are taken into account in realistic calculation. A dynamics calculation shows that there may exist two types of hidden-charm molecular pentaquark with double strangeness, i.e., the $Ξ_{c}^{*}\bar D_s^*$ molecular state with $J^P={5…
We analyze the decay modes of the three $[\frac 12\frac 12^-]_{S=0,1}$ and $[\frac 12\frac 32^-]_{S=1}$ non-strange pentaquarks with hidden charm and bottom, predicted by holographic QCD in the heavy quark limit. In leading order, the pentaquarks %are composed of heavy-light mesons in bulk bound to an instanton core. They are degenerate and stable by heavy quark symmetry. At next to leading order, the spin interactions lift the degeneracy and cause the pentaquarks to decay. We show that the open charm (bottom) decay modes dwarf the hidden charm (bottom) ones, with total widths that are consist…
In present work, we investigate the spectrum of several low-lying $sscq\bar{q}$ pentaquark configurations employing the constituent quark model, within which the hyperfine interaction between quarks is taken to be mediated by Goldstone boson exchange. Our numerical results show that four $sscq\bar{q}$ configurations with $J^{P}=1/2^{-}$ or $J^{P}=3/2^{-}$ lie at energies very close to the recently observed five $Ω_{c}^{0}$ states by LHCb collaboration, this indicates that the $sscq\bar{q}$ pentaquark configurations may form sizable components of the observed $Ω_{c}^{0}$ resonances.
We derive the consequences of the MFV hypothesis for $ΔF =1$ flavour observables based on the latest LHCb data. Any future measurements beyond the MFV bounds and relations unambiguously indicate the existence of new flavour structures next to the Yukawa couplings of the Standard Model.
The $J/ψp$ signals at 4380 MeV and 4450 MeV which were seen by the LHCb collaboration in the decay $Λ^0_b\to K^-J/ψp$ are discussed following the hypothesis of the existence of diquark-diquark-antiquark composite states. The discussed problems concern: (i) estimation of masses and mass splittings for low-lying states, (ii) determination of decay modes in the quark recombination scheme, (iii) unitarity and analyticity constrains for pentaquark propagators, (iv) hadronic deuteron-like components in the diquark-diquark-antiquark multiplet.
Hidden charm pentaquarks and the nature of $P_{c}$ states observed at LHCb
Hunan Normal University（湖南师范大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
$QQ^\prime qq\bar q$ pentaquarks are studied in a potential model, under the hypothesis that they are composite objects of two diquarks and one antiquark. The interaction between two colored objects includes two contributions, one based on the $q\bar q$ potential in QCD, computed in the gauge/string duality approach, and another describing the spin-spin interaction. The model has been extended to investigate pentaquarks with different quark content, as $Qqqq\bar q$ and $Qqqq\bar Q$, the latter including the states observed by LHCb, $P_c(4380)^+$ and $P_c(4450)^+$, later updated, with a new dat…
In this article, we study the scalar-diquark-scalar-diquark-antiquark type $udsc\bar{c}$ pentaquark state with the QCD sum rules, the predicted mass $M_P=4.47\pm0.11\,\rm{GeV}$ is in excellent agreement with the experimental data $ 4458.8 \pm 2.9 {}^{+4.7}_{-1.1} \mbox{ MeV}$ from the LHCb collaboration, and supports assigning the $P_{cs}(4459)$ to be the hidden-charm pentaquark state with the spin-parity $J^P={\frac{1}{2}}^-$. We take into account the flavor $SU(3)$ mass-breaking effect, and estimate the mass spectrum of the diquark-diquark-antiquark type $udsc\bar{c}$ pentaquark states with …
The recent experimental results of LHCb collaboration suggested the existence of pentaquark states with charmonium. To understand the structure of the states, a dynamical calculation of 5-quark systems with quantum numbers $IJ^P=\frac{1}{2}(\frac{1}{2})^\pm$, $\frac{1}{2}(\frac{3}{2})^\pm$ and $\frac{1}{2}(\frac{5}{2})^\pm$ is performed in the framework of chiral quark model with the help of gaussian expansion method. The results show that the negative parity states can be bound states while all of the positive parity states are the scattering states. The $P_c(4380)$ state is suggested to be t…
The past seventeen years have witnessed tremendous progress on the experimental and theoretical explorations of the multiquark states. The hidden-charm and hidden-bottom multiquark systems were reviewed extensively in [Phys. Rept. 639 (2016) 1-121]. In this article, we shall update the experimental and theoretical efforts on the hidden heavy flavor multiquark systems in the past three years. Especially the LHCb collaboration not only confirmed the existence of the hidden-charm pentaquarks but also provided strong evidence of the molecular picture. Besides the well-known $XYZ$ and $P_c$ states,…
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…
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.
Very recently, the LHCb Collaboration reported their new results about the pentaquarks at charm energy region. Based on the new experimental results, we recalculate the molecular states composed of a $Σ_c^{(*)}$ baryon and a $\bar{D}^{(*)}$ meson in a quasipotential Bethe-Salpeter equation approach. The two-peak structure around 4450 MeV can be interpreted as two $Σ_c \bar{D}^*$ bound states with spin parities $1/2^-$ and $3/2^-$. The newly observed pentaquark $P_c(4312)$ can be assigned as a $Σ_c\bar{D}$ bound state with spin parity $1/2^-$. The experimental determination of spin parities wil…
