We study the bottom $Λ_b(6146)^0$ baryon, newly discovered by the LHCb Collaboration. By adopting an interpolating current of $(L_ρ, L_λ)=(0,2)$ type and $D$-wave nature with spin-parity quantum numbers $J^P=\frac{3}{2}^+$ for this heavy bottom baryon, we calculate its mass and residue. Using these spectroscopic parameters, we also investigate its dominant decays $Λ_b(6146)^0\rightarrowΣ_bπ$ and $Λ_b(6146)^0\rightarrowΣ^*_bπ$ and estimate the width of $Λ_b(6146)^0$ obtained via these channels. The obtained mass, $m_{Λ_b}=(6144\pm 68)$~MeV is in accord nicely with the experimental data. The width obtained via the dominant channels is also consistent with the experimental data of LHCb collaboration. We calculate the spectroscopic parameters and the same decay channels for the $c$-partner of $Λ_b(6146)^0$ state, namely $Λ_c(2860)^+$, as well. We compare the obtained results with the existing theoretical predictions as well as experimental data. The results indicate that the state $Λ_b(6146)^0$ and its charmed-partner $Λ_c(2860)^+$ can be considered as $1D$-wave baryons with $J^P=\frac{3}{2}^+$.
The newly reported exotic signal $Z_c(4100)$ by the LHCb Collaboration in the invariant mass spectrum of $η_cπ^-$ in $B^0\to η_c K^+ π^-$ has been a new experimental evidence for an exotic meson containing four constituent quarks. Although the present experimental information is very limited, we show that its correlations with some existing exotic candidates can be recognized. This signal can be either caused by final state interaction effects or a $P$-wave resonance state arising from the $D^*\bar{D}^*$ interaction. For the latter option its neutral partner will have exotic quantum numbers of…
We describe a heavy and exotic tetraquark state as a holographic molecule, by binding the lightest heavy-light meson $(0^-, 1^-)$ multiplet to a flavored sphaleron, in the bulk of the Witten-Sakai-Sugimoto model. Bound tetraquark states emerge as Efimov states in the heavy quark limit, with a binding energy for charm tetraquark comparable to the $T_{cc}^+$ recently reported by the LHCb, but a substantially smaller width, for a large but finite $^\prime$t Hooft coupling. Fixing the parameters of the model at the empirical mass of $T_{cc}^+$ allows us to predict the bindings of the undiscovered …
New resonance $Λ_c(2860)^+$, reported by LHCb, is a key to establish \emph{D}-wave charmed and charmed-strange baryon families. In this work, we first carry out an analysis of mass spectra of the $λ$-mode excited charmed and charmed-strange baryon states, which may reveal the relation of $Λ_c(2860)^+$, $Λ_c(2880)^+$, $Ξ_c(3055)^+$ and $Ξ_c(3080)^+$, $i.e.$, $Λ_c(2860)^+$ and $Λ_c(2880)^+$ can form a \emph{D}-wave doublet $[3/2^+,5/2^+]$ while $Ξ_c(3055)^+$ and $Ξ_c(3080)^+$ are the strange partners of $Λ_c(2860)^+$ and $Λ_c(2880)^+$, respectively. Further study of their two-body Okubo-Zweig-Ii…
The masses and residues of the radially excited heavy $Ω_c^{0}$ and $ Ω_b^{-}$ baryons with spin-parity $J^{P}=\frac{1}{2}^{+}$ and $J^{P}= \frac{3}{2}^{+}$ are calculated by means of QCD two-point sum rule method using the general form of their interpolating currents. In calculations the quark, gluon and mixed vacuum condensates up to ten dimensions are taken into account. In $Ω_c^{0}$ channel a comparison is made with the narrow excited states recently observed by the LHCb Collaboration.
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 $P_c$.
Selecting the newly observed $Ξ_b(6227)^-$ by LHCb as a study example, we decode its inner structure by giving the mass spectrum analysis and the investigation of its two-body strong decay behaviors. Our result indicates that the $Ξ_b(6227)^-$ is a good candidate of the $P$-wave $Ξ_b^{\prime}$ state with $J^P=3/2^-$ or $5/2^-$. In addition, we further provide the information of the properties of the partners of the $Ξ_b(6227)^-$. These predicted states include three $2S$ states and the remaining $1P$ states in the bottom-strange baryon family. The calculated sizable Okubo-Zweig-Iizuka$-$allowe…
Stimulated by the newly observed $Λ_b(6146)^0$ and $Λ_b(6152)^0$ resonances, we investigate the strong decays of the low-lying singly bottom baryons within the quark pair creation model. Considering their masses and decay modes, we tentatively assign these states as the $λ-$ mode $Λ_b(2S)$, $Λ_b(1D)$, $Σ_b(2S)$, and $Σ_b(1P)$ states, and then estimate their strong decay widths. Compared with the experimental total widths and decay modes measured by the LHCb Collaboration, the $Λ_b(6146)^0$ and $Λ_b(6152)^0$ can be reasonably clarified into the $J^P=5/2^+$ and $J^P=3/2^+$ $Λ_b(1D)$ sates respec…
Two bottom $Σ_b(6097)^\pm$ baryons were observed in the final states $Λ_b^0π^-$ and $Λ_b^0π^+$ in $pp$ collision by LHCb collaboration, whose masses and widths were measured. In a $^{3}P_{0}$ model, the strong decay widths of two ground $S$-wave and seven excited $P$-wave $Σ_b$ baryons have been systematically computed. Numerical results indicate that the newly observed $Σ_b(6097)^\pm$ are very possibly $Σ_{b2}^1({3\over 2}^-)$ with $J^P={3\over 2}^-$ or $Σ_{b2}^1({5\over 2}^-)$ with $J^P={5\over 2}^-$. The predicted decay widths of $Σ_b(6097)^\pm$ are consistent with experimental measurement …
We systematically study mass spectra and decay properties of $P$-wave $Ξ_c^\prime$ baryons of the $SU(3)$ flavor $\mathbf{6}_F$, using the methods of QCD sum rules and light-cone sum rules within the framework of heavy quark effective theory. Our results suggest that the three excited $Ξ_c^0$ baryons recently observed by LHCb can be well explained as $P$-wave $Ξ_c^\prime$ baryons: the $Ξ_c(2923)^0$ and $Ξ_c(2939)^0$ are partner states of $J^P = 1/2^-$ and $3/2^-$ respectively, both of which contain one $λ$-mode orbital excitation; the $Ξ_c(2965)^0$ has $J^P = 3/2^-$, and also contains one $λ$-…
In this work, we study strong and radiative decays of S-wave DΞmolecular state, which is related to the Ω^*_c states newly observed at LHCb. The coupling between the DΞmolecular state and its constituents D and Ξis calculated by using the compositeness condition. With the obtained coupling, the partial decay widths of the DΞmolecular state into the Ξ_c^{+}K^{-}, Ξ^{'+}_cK^{-} and Ω^{*}_c(2695)γfinal states through hadronic loop are calculated with the help of the effective Lagrangians. By comparison with the LHCb observation, the current results of total decay width support the Ω^{*}_c(3119) o…
Inspired by the newly observed $Ξ_c^0$ states by the LHCb Collaboration, we investigate the OZI-allowed two-body strong decays of the $λ$-mode $1P$ wave $Ξ'_c$ states within the chiral quark model. Our results indicate that: (i) the newly observed states $Ξ_c(2923)^0$ and $Ξ_c(2939)^0$ are good candidates of the $λ$-mode $1P$ wave $Ξ'_c$ states with the spin-parity $J^P=3/2^-$, namely $|^4P_λ3/2^-\rangle$ and $|^2P_λ3/2^-\rangle$, respectively. (ii) The another newly observed state $Ξ_c(2965)^0$ mostly corresponds to the $λ$-mode $1P$-wave $Ξ'_c$ state with the spin-parity $J^P=5/2^-$, namely …
The strong decays of the $P$-wave $Σ_b$, $Ξ_b'$ and $Ω_b$ baryons are investigated with a constituent quark model in the $j$-$j$ coupling scheme. The results show that the newly observed $Σ_b(6097)$ and $Ξ_b(6227)$ states by the LHCb collaboration can be assigned as the $λ$-mode $P$-wave singly bottom baryons. Given the heavy quark symmetry, both the $Σ_b(6097)$ and $Ξ_b(6227)$ states favor the light spin $j=2$ states with spin-parity numbers $J^P=3/2^-$ or $J^P=5/2^-$. More $P$-wave singly bottom baryons are most likely to be observed in future experiments for their relatively narrow width.
The LHCb Collaboration recently reported the observation of a new excited bottom baryon $Ξ_b(6227)^0$ and announced an improvement in the measurements related to the previously observed $Ξ_b(6227)^-$ state. We conduct an analysis for $Ξ_b(6227)^0$ state considering it as isospin partner of the $Ξ_b(6227)^-$ resonance and possibly $1P$ or $2S$ excited state with spin $J=\frac{3}{2}$. The corresponding masses for both possibilities have consistent results with the experimental data, indicating that only with the mass sum rules, one can not make exact decision on the nature and quantum numbers of…
It is interesting to search for new physics beyond the standard model at LHCb. We suggest that weak decays of doubly charmed baryon such as $Ξ_{cc}(3520)^+, Ξ_{cc}^{++}$ to charmless final states would be a possible signal for new physics. In this work, we consider two models, i.e. the unparticle and $Z'$ as examples to study such possibilities. We also discuss the cases for $Ξ^0_{bb}, Ξ_{bb}^-$ which have not been observed yet, but one can expect to find them when LHCb begins running. Our numerical results show that these two models cannot result in sufficiently large decay widths, therefore …
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…
Inspired by the newly observed $Ω_c^0$ states at LHCb, we decode their properties by performing an analysis of mass spectrum and decay behavior. Our studies show that the five narrow states, i.e., $Ω_c(3000)^0$, $Ω_c(3050)^0$, $Ω_c(3066)^0$, $Ω_c(3090)^0$, and $Ω_c(3119)^0$, could be grouped into the $1P$ states with negative parity. Among them, the $Ω_c(3000)^0$ and $Ω_c(3090)^0$ states could be the $J^P=1/2^-$ candidates, while $Ω_c(3050)^0$ and $Ω_c(3119)^0$ are suggested as the $J^P=3/2^-$ states. $Ω_c(3066)^0$ could be regarded as a $J^P=5/2^-$ state. Since the the spin-parity, the electr…
In this work, we treat the newly observed doubly charmed four-quark state $ T_{cc}^{+}$ as an axial-vector tetraquark with content $cc\overline{u} \overline{d}$, and calculate its spectroscopic parameters and width. The mass and current coupling of the tetraquark $T_{cc}^{+}$ are found by means of the QCD two-point sum rule method by taking into account quark, gluon and mixed condensates up to dimension $10$. The width of the $T_{cc}^{+}$ is evaluated using partial widths of decay processes $T_{cc}^{+} \to \widetilde{ T}π^{0}$ and $T_{cc}^{+} \to T_{cc;\overline{u}\overline{u}}^{0}π^{+}$ , whe…
Very recently, the LHCb Collaboration at the Large Hadron Collider at CERN observed new resonance $X(4630)$. The $X(4630)$ is decoded as a charmoniumlike molecule with hidden-strange quantum number well in the one boson exchange mechanism. Especially, the study of its hidden-charmed decays explicitly shows the dominant role of $J/ψϕ$ among all allowed hidden-charmed decays of $X(4630)$, which enforces the conclusion of $X(4630)$ as a charmoniumlike molecule. The discovery of the $X(4630)$ is a crucial step of constructing charmoniumlike molecule zoo.
LHCb collaboration measured CPV at the level of one percent in the difference of assymetries in $D^0(\bar D^0)\to π^+ π^-, K^+ K^-$ decays. If confirmed on a larger statistics and final systematics this would mean New Physics manifestation. The fourth quark-lepton generation can be responsible for the observed effect.
Very recently, three new structures $Ξ_c(2923)^0$, $Ξ(2938)^0$, and $Ξ(2964)^0$ at the invariant mass spectrum of $Λ_c^{+}K^{-}$ observed by the LHCb Collaboration triggers a hot discussion about their inner structure. In this work, we study the strong decay mode of the newly observed $Ξ_c$ assuming that the $Ξ_c$ is a $\bar{D}Λ-\bar{D}Σ$ molecular state. With the possible quantum numbers $J^p=1/2^{\pm}$ and $3/2^{\pm}$, the partial decay widths of the $\bar{D}Λ-\bar{D}Σ$ molecular state into the $Λ_c^{+}K^{-}$, $Σ_c^{+}K^{-}$,and $Ξ_c^{+}π^{-}$ final states through hadronic loop are calculate…
We suggest that the J/psi phi structures observed by LHCb can be fitted in two tetraquak multiplets, the S-wave ground state and the first radial excitation, with composition [cs][cbar sbar]. When compared to the previously identified [cq][cbar qbar] multiplet, the observed masses agree with what expected for a multiplet with q -->s. We propose the X(4274), fitted by LHCb with a single 1^++ resonance, to correspond rather to two, almost degenerate, unresolved lines with J^PC = 0^++, 2^++. Masses of missing particles in the 1S and 2S multiplets are predicted.
The newly observed $Σ_b(6097)$ provides us a good chance to further construct the high excited states of the bottom baryon family. In this work, we explain the $Σ_b(6097)$ to be a $1P$ state with $J^P=5/2^-$ or $3/2^-$ by giving the mass spectrum analysis and the strong decay calculation, and predict the existence of $1P$ and $2S$ partners of the $Σ_b(6097)$, where their masses and the corresponding decay behaviors are presented. Because of the success of describing the $Σ_b(6097)$ and the former observed $Ξ_b(6227)$ under the quasi-two-body treatment to the bottom baryons, we continue to pred…
Comparing the expected spectroscopy in the relativistic quark model and the predicted strong decays in the $^3P_0$ model employing the realistic wave functions from the relativistic quark model with the measured properties of the LHCb and BaBar charmed states, we find that the masses and strong decays of these charmed states can be reasonably explained in the conventional $q\bar{q}$ picture, and therefore suggest that the $D(2550)$/$D_J(2580)$, $D^*(2600)$/$D^*_J(2650)$, $D(2750)$/$D_J(2740)$, $D^*(2760)$/$D^*_J(2760)$, $D_J(3000)$, and $D^*_J(3000)$ can be identified as the $D(2^1S_0)$, $D(2^…
The LHCb collaboration recently announced preliminary evidence for CP violation in D meson decays. We discuss this result in the context of the standard model (SM), as well as its extensions. In the absence of reliable methods to evaluate the hadronic matrix elements involved, we can only estimate qualitatively the magnitude of the non-SM tree level operators required to generate the observed central value. In the context of an effective theory, we list the operators that can give rise to the measured CP violation and investigate constraints on them from other processes.
A search for the rare decays $B^0_s\rightarrow μ^+μ^-$ and $B^0\rightarrow μ^+μ^-$ is performed with the LHCb experiment using 1.1\,fb$^{-1}$ of data collected at $\sqrt s=8$\,TeV$ and 1.0\,fb$^{-1}$ of data collected at $\sqrt s=7$\,TeV. An excess of $B^0_s\rightarrow μ^+μ^-$ candidates with respect to the background expectations is observed with a statistical significance of 3.5 standard deviations. A branching fraction of ${\cal BR}(B^0_s\rightarrow μ^+μ^-) =(3.2^{+1.5}_{-1.2}) \times 10^{-9}$ is measured with an unbinned maximum likelihood fit. The measured branching fraction is in agreeme…
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.
Motivated by the newly observed resonance $X(2600)$ by BESIII Collaboration, we examine the trigluon glueball interpretation for it in the framework of QCD sum rules. We evaluate the mass spectra of the trigluon glueballs with quantum numbers $0^{-+}$ and $2^{-+}$ up to dimension 8 condensate in the operator product expansion. Our numerical results indicate that the mass of the $2^{-+}$ trigluon glueball is about $2.66\pm 0.06$ GeV, which is consistent with the mass of the X(2600) within the uncertainties, while $0^{-+}$ has a mass of $2.01\pm0.14$ GeV. The possible decay channels of the $2^{-…
We study the charmed and bottomed doubly strange baryons within the heavy-quark-light-diquark framework. The two strange quarks are assumed to lie in $S$ wave and thus their total spin is 1. We calculate the mass spectra of the $S$ and $P$ wave orbitally excited states and find the $Ω_c^0 (2695)$ and $Ω_c^0 (2770)$ fit well as the $S$ wave states of charmed doubly strange baryons. The five newly $Ω_c^0(X)$ resonances observed by the LHCb Collaboration, i.e. $Ω_c^0(3000)$, $Ω_c^0(3050)$, $Ω_c^0(3066)$, $Ω_c^0(3090)$, and $Ω_c^0(3119)$, can be interpreted as the $P$ wave orbitally excited states…
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…
Lately, the LHCb Collaboration reported the discovery of two new states in the $B^+\rightarrow D^+D^- K^+$ decay, i.e., $X_0(2866)$ and $X_1(2904)$. In the present work, we study whether these states can be understood as $D^*\bar{K}^*$ molecules from the perspective of their two-body strong decays into $D^-K^+$ via triangle diagrams and three-body decays into $D^*\bar{K}π$. The coupling of the two states to $D^*\bar{K}^*$ are determined from the Weinberg compositeness condition, while the other relevant couplings are well known. The obtained strong decay width for the $X_0(2866)$, in marginal …
Observation in astronomy suggests that our Universe contains an abundance of matter over antimatter, which can only be explained if the combined CP symmetry is violated. Studies of CP violation have driven the flavor physics with the aim of testing the Standard Model of particle physics and searching for physics beyond. CP violation is discovered in strange, beauty and charm meson systems, however no conclusive sign of CP violation in baryon decays has been observed yet. This review summarizes CP violation studies performed by the LHCb experiment in charmless decays and rare decays of beauty b…
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. …
The mass and decay constant of the $X(5568)$ state newly observed by D0 Collaboration are computed within the two-point sum rule method using the diquark-antidiquark interpolating current. In calculations, the vacuum condensates up to eight dimensions are taken into account. The obtained result for the mass of the $X(5568)$ state is in a nice agreement with the experimental data.
In this article, we tentatively identify the charmed mesons $D_J(2580)$, $D_J^*(2650)$, $D_J(2740)$, $D^*_J(2760)$, $D_J(3000)$, $D_J^*(3000)$ observed by the LHCb collaboration according to their spin, parity and masses, then study their strong decays to the ground state charmed mesons plus light pseudoscalar mesons with the heavy meson effective theory in the leading order approximation, and obtain explicit expressions of the decay widths. The ratios among the decay widths can be used to confirm or reject the assignments of the newly observed charmed mesons. The strong coupling constants in …
Stimulated by the recent observation of the $D_2^\ast(3000)$, we study the decay behaviors of the $3P$ and $2F$ charmed mesons in the present work. By comparing the masses and decay properties of the $3^3P_2$ and $2^3F_2$ charmed mesons with the observation of the $D_2^\ast(3000)$, we conclude that the most possible assignment of the $D_2^\ast(3000)$ is the $3^3P_2$ charmed meson, while the assignment of the $2^3F_2$ charmed meson could not be fully exclude. The results of the unobserved $3P$ and $2F$ charmed mesons in this work could provide some fundamental information of searching for these…
Focusing on recent measurement of $B^+ \to D_s^+D_s^-K^+$ process given by the LHCb Collaboration, we propose that this newly observed near the $D_s^+D_s^-$ threshold enhancement can be due to the contribution of the $χ_{c0}(2P)$, which is a $P$-wave charmonium below the $D_s^+D_s^-$ threshold. By performing a combined fit to the measured $D_s^+D_s^-$, $D_s^+K^+$, and $D_s^-K^+$ invariant mass spectra, introducing the $χ_{c0}(2P)$ can well reproduce the near threshold enhancement in the $D_s^+D_s^-$ invariant mass spectrum. When depicting the whole $D_s^+D_s^-$ invariant mass spectrum, the con…
We explore the sensitivity of displaced vertex searches at LHCb for testing sterile neutrino extensions of the Standard Model towards explaining the observed neutrino masses. We derive estimates for the constraints on sterile neutrino parameters from a recently published displaced vertex search at LHCb based on run 1 data. They yield the currently most stringent limit on active-sterile neutrino mixing in the sterile neutrino mass range between 4.5 GeV and 10 GeV. Furthermore, we present forecasts for the sensitivities that could be obtained from the run 2 data and also for the high-luminosity …
The CP violation of the neutral $B$ meson is the important phenomenon to search for the new physics. The like-sign dimuon charge asymmetry observed by the D$Ø$ Collaboration indicates the CP-violating new physics in the $B_s-\bar B_s$ mixing. On the other hand, LHCb observed the CP-violating asymmetry in $B_s^0\to J/ψϕ$ and $B_s^0\to J/ψf_0(980)$, which is consistent with the SM prediction. However, there is still room for new physics of the CP violation. The CKMfitter has presented the allowed region of the new physics parameters taking account of the LHCb data. Based on these results, we dis…
Inspired by the newly observed $Ω_b$ states by the LHCb Collaboration, we investigate the two-body strong decays of the low-lying $λ$-mode $Ω_b$ baryons up to $N=2$ shell using the chiral quark model within the $j$-$j$ coupling scheme. Our results indicate that: (i) the newly observed states $Ω_b(6316)^-$ and $Ω_b(6330)^-$ are good candidates of the light spin $j=1$ states, while the spin-parity $J^P=1/2^-$ and $J^P=3/2^-$ cannot be distinguished. The other two states, $Ω_b(6340)$ and $Ω_b(6350)$ mostly correspond to the light spin $j=2$ states, while the spin-parity $J^P=3/2^-$ and $J^P=5/2^-…
The new LHCb beauty-strange state as the bottom partner of the $D_{s0}^*(2317)$: a LQCD constrained coupled-channel chiral analysis
Instituto de Física Corpuscular, Centro Mixto Universidad de Valencia-CSIC（瓦伦西亚大学-西班牙国家研究委员会联合物理粒子研究所）；Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia-CSIC（瓦伦西亚大学-西班牙国家研究委员会联合理论物理系及IFIC）
The LHCb collaboration newly measured the decay rate of doubly charmed baryon $Ξ^{++}_{cc}\toΞ^{'+}π^+$ and a ratio of its branching fraction with respect to that of the decay $Ξ^{++}_{cc}\toΞ^{+}π^+$ is reported as $1.41\pm 0.17\pm 0.10$. This result conflicts with the theoretical predictions made by several groups. In our previous work, following the prescription given in early literature where the $us$ diquark in $Ξ^{+}_{c}$ is assumed to be a scalar whereas in $Ξ^{'+}_{c}$ is a vector i.e. the spin-flavor structure of $Ξ^{+}_{c}$ is $[us]_0 c$ and that of $Ξ^{'+}_{c}$ is $[us]_1 c$, we stu…
Stimulated by the $P_{cs}(4459)$ reported by the LHCb Collaboration, we perform a single $Ξ_c\bar{D}^*$ channel and a coupled $Ξ_c\bar{D}^*/Ξ_c^*\bar{D}/Ξ_c^{\prime}\bar{D}^*/Ξ_c^*\bar{D}^*$ channel analysis by using a one-boson-exchange model. Our results indicate that the newly $P_{cs}(4459)$ cannot be a pure $Ξ_c\bar{D}^*$ molecular state, but a coupled $Ξ_c\bar{D}^*/Ξ_c^*\bar{D}/Ξ_c^{\prime}\bar{D}^*/Ξ_c^*\bar{D}^*$ bound state with $I(J^P)=0(3/2^-)$, where the $Ξ_c\bar{D}^*$ and $Ξ_c^*\bar{D}$ components are dominant. Meanwhile, we find the interactions from the $Ξ_c^{\prime}\bar{D}^*$ sy…
Stimulated by the newly reported doubly-charmed tetraquark state $T_{cc}^+$ by LHCb, we carry out a systematic investigation of the $S$-wave interactions between the charmed meson ($D,\,D^{*}$) in $H$-doublet and the charmed meson ($D_{1},\,D_{2}^{*}$) in $T$-doublet by adopting the one-boson-exchange model. Both the $S$-$D$ wave mixing effect and the coupled channel effect are taken into account. By performing a quantitative calculation, we suggest that the $S$-wave $D^{*} D_{1}$ states with $I(J^{P})=0(0^{-},\,1^{-})$ and the $S$-wave $D^{*}D_{2}^{*}$ state with $I(J^{P})=0(1^{-})$ should be…
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）
In this paper we show that the intrinsic heavy-quark QCD mechanism for the hadroproduction of heavy hadrons at large $x_F$ can resolve the apparent conflict between measurements of double-charm baryons by the SELEX fixed-target experiment and the LHCb experiment at the LHC collider. We show that both experiments are compatible, and that both results can be correct. The observed spectroscopy of double-charm hadrons is in agreement with the predictions of supersymmetric light front holographic QCD.
The strong decays of the low-lying $λ$-mode $Λ_b(1D,2S)$ and $Σ_b(2S)$ states are studied in a chiral quark model. We find that: (i) the newly observed $Λ_b(6146/6152)$ resonances in the $Λ_bπ^+π^-$ spectrum by the LHCb Collaboration might be explained with the $λ$-mode $Λ_b(1D)$ states in the quark model. It should be emphasized that whether the structure in the $Λ_bπ^+π^-$ spectrum correspond to two states or one state should be further clarified with more observations in future experiments. (ii) The $Λ_b(2S)$ $|J^P = \frac{1}{2}^+,0\rangle$ state mainly decays into $Σ_b^*π$ channel, which m…
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 the newly reported hidden-charm pentaquark candidates $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ from the LHCb Collaboration, in the framework of the effective-range expansion and resonance compositeness relations. The scattering lengths and effective ranges from the $S$-wave $Σ_c\bar{D}$ and $Σ_c\bar{D}^*$ scattering are calculated by using the experimental results of the masses and widths of the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$. Then we calculate the couplings between the $J/ψp,\,Σ_c\bar{D}$ channels and the pentaquark candidate $P_c(4312)$, with which we further estimate the …
We study the potential of the LHCb 13 TeV single $W^{\pm}$ and $Z$ boson pseudo-data for constraining the parton distribution functions (PDFs) of the proton. As an example, we demonstrate the sensitivity of the LHCb 13 TeV data, collected with integrated luminosities of 5 fb$^{-1}$ and 300 fb$^{-1}$, to reducing the PDF uncertainty bands of the CT14HERA2 PDFs, using the error PDF updating package {\sc ePump}. The sensitivities of various experimental observables are compared. Generally, sizable reductions in PDF uncertainties can be observed in the 300 fb$^{-1}$ data sample, particularly in th…
We present a model for the $J/ψΛ$ spectrum in $B^-\to J/ψΛ\bar{p}$ decays, including the $P_{ψs}^Λ(4338)$ baryon recently observed by the LHCb collaboration. We assume production via triangle diagrams which couple to the final state via non-perturbative interactions which are constrained by heavy-quark and $SU_3$-flavor symmetry. The bulk of the distribution is described by a triangle diagram with a color-favored electroweak vertex, while the sharp $P_{ψs}^Λ(4338)$ enhancement is due to the triangle singularity in another diagram featuring a $1/2^-$ baryon consistent with $Σ_c(2800)$. We predi…
The low $x$ behaviour of the gluon density $xg(x,μ^2)$ at scale $μ^2=2.4$ GeV$^2$ is determined using exclusive $J/ψ$ production data from HERA and LHCb within the framework of collinear factorisation at next-to-leading order (NLO). It is shown that in the interval $3\times 10^{-6} < x <10^{-3}$ the gluon distribution function grows as $xg(x,μ^2)\propto x^{-λ}$ with $λ=0.135\pm 0.006 $. The impact this experimental data will have for the global parton distribution function (PDF) analyses in this low $x$ domain is quantified. No indication in favour of parton density saturation is observed.
The strong and radiative decay properties of the low-lying $Ω_c$ states are studied in a constituent quark model. We find that the newly observed $Ω_c$ states by the LHCb Collaboration can fit in well the decay patterns. Thus, their spin-parity can be possibly assigned as the following: (i) The $Ω_c(3000)$ has $J^P=1/2^-$ and corresponds to the narrow $1P$ mixed state $|1^2P_λ\frac{1}{2}^-\rangle_1$, its partner $|1^2P_λ\frac{1}{2}^-\rangle_2$ should be a broad state with a width of $\sim 100$ MeV. (ii) The $Ω_c(3050)$ and $Ω_c(3066)$ can be assigned to be two $J^P=3/2^-$ states, $|1^4P_λ\frac…
Three neutral resonances $Ξ_c(2923)^0$, $Ξ_c(2939)^0$ and $Ξ_c(2965)^0$ have been observed in the $Λ_c^+ K^-$ mass spectrum by the LHCb Collaboration. Given the $Ξ_c$ and $Ξ_c^\prime$ mass spectra predicted by the constituent quark models, these three resonances are tentatively treated as the $λ-$mode $Ξ_c(2S)$, $Ξ_c^\prime(2S)$, $Ξ_c^{\prime *}(2S)$, and $Ξ_c^\prime(1P)$ states, and their strong decay behaviors are calculated within the $^3P_0$ model. Our results indicate that the $Ξ_c(2923)^0$ and $Ξ_c(2939)^0$ can be clarified into the $J^P=3/2^-$ and $5/2^-$ $Ξ_c^\prime(1P)$ states respect…
Inspired by the newly observed $X_{0}(2900)$ and $X_1(2900)$ at LHCb, the $K^*\bar{D}^*$ and $K\bar{D}_1$ interactions are studied in the quasipotential Bethe-Salpeter equation approach combined with the one-boson-exchange model. The bound and virtual states from the interactions are searched for as the poles in the complex energy plane of scattering amplitude. A bound state with $I(J^P)=0(0^+)$ and a virtual state with $0(1^-)$ are produced from the $K^*\bar{D}^*$ interaction and $K\bar{D}_1$ interaction, and can be related to the $X_{0}(2900)$ and $X_1(2900)$ observed at LHCb, respectively. …
