Stimulated by the recent LHCb observation of a new exotic charged structure $T^{+}_{cc}$, we propose to use the central diffractive mechanism existing in the $gamma{}pto{}D^{+}bar{T}^{-}_{cc}Lambda_c^{+}$ ($bar{T}_{cc}$ is antiparticle of $T^{+}_{cc}
$) reaction to produce $T^{+}_{cc}$. Our theoretical approach is based on the chiral unitary theory where the $T^{+}_{cc}$ resonance is dynamically generated. With the coupling constant of the $T^{+}_{cc}$ to $DD^{*}$ channel obtained from chiral unitary theory, the total cross sections of the $gamma{}pto{}D^{+}bar{T}^{-}_{cc}Lambda_c^{+}$ reaction are evaluated. Our study indicates that the cross section for $gamma{}pto{}D^{+}bar{T}^{-}_{cc}Lambda_c^{+}$ reaction are of the order of 1.0 pb, which is accessible at the proposed EicC~cite{Anderle:2021wcy} and US-EIC~cite{Accardi:2012qut} due to the higher luminosity. If measured in future experiments, the predicted total cross sections can be used to test the (molecular) nature of the $T^{+}_{cc}$.
Inspired by the discovery of a doubly charmed tetraquark state $T_{cc}^+$ by the LHCb Collaboration and based on the prediction of a doubly charmed $DD^{ast}$ molecule with $I(J^{P})=0(1^{+})$ in our recent works, [Phys.Rev.D 102 (2020), 091502] and
[Phys.Rev.D 99 (2019), 094018], we employ the effective Lagrangian approach to investigate the decay width of $T_{cc}to D Dpi$ and $T_{cc}to DDgamma$. We show that both the $T_{cc}to D Dpi$ and $T_{cc}to DDgamma$ modes contribute to the decay width of $T_{cc}$, with the former playing a more important role.However, within the $DD^*$ molecule picture, the obtained decay width is rather small compared with the experimental value of $Gamma=410pm175$ keV. We argue that the existence of a compact tetraquark component cannot lead to an appreciable increase of the decay width. As a result, the discrepancy may indicate that either $T_{cc}$ is more likely a near threshold $DD^*$ resonance or the decay width is close to the lower experimental boundary.
Ever since Yukawa proposed that the pion is responsible for mediating the nucleon-nucleon interaction, meson exchanges have been widely used in understanding hadron-hadron interactions. The most studied mesons are the $sigma$, $pi$, $rho$, and $omega
$, while other heavier mesons are often argued to be less relevant because they lead to short range interactions. However, the ranges of interactions should be compared with the size of the system under study but not in absolute terms. In this work, we propose that one charmoninium exchange is responsible for the formation of the $Omega_{ccc}Omega_{ccc}$ dibaryon, recently predicted by lattice QCD simulations. The same approach can be extended to the strangeness and bottom sectors, leading to the prediction on the existence of $OmegaOmega$ and $Omega_{bbb}Omega_{bbb}$ dibaryons, while the former is consistent with existing lattice QCD results, the latter remains to checked. In addition, we show that the Coulomb interaction may break up the $Omega_{ccc}Omega_{ccc}$ pair but not the $Omega_{bbb}Omega_{bbb}$ and $OmegaOmega$ dibaryons, particularly, the latter.
We apply the recently proposed RMF(BCS)* ansatz to study the charge radii of the potassium isotopic chain up to $^{52}$K. It is shown that the experimental data can be reproduced rather well, qualitatively similar to the Fayans nuclear density functi
onal theory, but with a slightly better description of the odd-even staggerings (OES). Nonetheless, both methods fail for $^{50}$K and to a lesser extent for $^{48,52}$K. It is shown that if these nuclei are deformed with a $beta_{20}approx-0.2$, then one can obtain results consistent with experiments for both charge radii and spin-parities. We argue that beyond mean field studies are needed to properly describe the charge radii of these three nuclei, particularly for $^{50}$K.
In recent years, more and more exotic hadronic states have been discovered successively. Many of them can be explained as hadronic molecules, such as $D_{s0}^*(2317)$, $X(3872)$, and $P_c$ pentaquark states. Analogous to the formation of nuclei, we s
tudy three-body hadronic molecules with the Gaussian expansion method and predict the existence of the $DDK$, $Xi_{cc}Xi_{cc}bar{K}$, and $BBbar{K}$ bound states, which are likely to be found in the current and updated facilities.
Motivated by renewed evidence for new physics in $b to sellell$ transitions in the form of LHCbs new measurements of theoretically clean lepton-universality ratios and the purely leptonic $B_stomu^+mu^-$ decay, we quantify the combined level of discr
epancy with the Standard Model and fit values of short-distance Wilson coefficients. A combination of the clean observables $R_K$, $R_{K^*}$, and $B_sto mumu$ alone results in a discrepancy with the Standard Model at $4.0sigma$, up from $3.5sigma$ in 2017. One-parameter scenarios with purely left-handed or with purely axial coupling to muons fit the data well and result in a $sim 5 sigma$ pull from the Standard Model. In a two-parameter fit of %$C_9$ and $C_{10}$, new-physics contributions with both vector and axial-vector couplings to muons the allowed region is much more restricted than in 2017, principally due to the much more precise result on $B_s to mu^+ mu^-$, which probes the axial coupling to muons.Including angular observables data restricts the allowed region further.A by-product of our analysis is an updated average of $text{BR}(B_s to mu^+ mu^-) = (2.8pm 0.3) times 10^{-9}$.
Inspired by the discovery of the spin-$frac{1}{2}$ doubly charmed baryon $Xi_{cc}^{++}$ and the subsequent theoretical studies of its magnetic moments, we study the magnetic moments of its spin-$frac{3}{2}$ heavy quark spin symmetry counterparts, up
to the next-to-leading order in covariant baryon chiral perturbation theory (BChPT) with the extended-on-mass-shell renormalization (EOMS) scheme. With the tree-level contributions fixed by the quark model while the two low energy constants (LECs) $C$ and $H$ controlling the loop contributions determined in two ways: the quark model (case 1) and lattice QCD simulations together with the quark model (case 2), we study the quark mass dependence of the magnetic moments and compare them with the predictions of the heavy baryon chiral perturbation theory (HB ChPT). It is shown that the difference is sizable in case 1, but not in case 2 due to the smaller LECs $C$ and $H$, similar to the case of spin-$frac{1}{2}$ doubly charmed baryons. Second, we predict the magnetic moments of the spin-$frac{3}{2}$ doubly charmed baryons and compare them with those of other approaches. The predicted magnetic moments in case 2 for the spin-$frac{3}{2}$ doubly charmed baryons are closer to those of other approaches. In addition, the large differences in case 1 and case 2 for the predicted magnetic moments may indicate the inconsistency between the quark model and the lattice QCD simulations, which should be checked by future experimental or more lattice QCD data.
The $D^{(ast)}Xi_{cc}^{(ast)}$ system and $bar{Xi}_{cc}^{(ast)}Xi_{cc}^{(ast)}$ system can be related to the $D^{(ast)}bar{D}^{(ast)}$ system via heavy anti-quark di-quark symmetry (HADS). In this work, we employ a contact-range effective field theor
y to systematically investigate the likely existence of molecules in these systems in terms of the hypothesis that X(3872) is a $1^{++}$~$Dbar{D}^{ast}$ bound state in the isospin symmetry limit, with some of the unknown low energy constants estimated using the light-meson saturation approximation. In the meson-meson system, a $J^{PC}=2^{++}$~$bar{D}^{ast}D^{ast}$ molecule commonly referred to as $X(4013)$ is reproduced, which is the heavy quark spin partner of $X(3872)$. In the meson-baryon system, we predict two triply charmed pentaquark molecules, $J^{P}=1/2^{-}$~$D^{ast}Xi_{cc}$ and $J^{P}=5/2^{-}$~$D^{ast}Xi_{cc}^{ast}$. In the baryon-baryon system, there exist seven di-baryon molecules, $J^{PC}=0^{-+}$~$bar{Xi}_{cc}Xi_{cc}$, $J^{PC}=1^{--}$~$bar{Xi}_{cc}Xi_{cc}$, $J^{PC}=1^{-+}$~$bar{Xi}_{cc}Xi_{cc}^{ast}$, $J^{PC}=1^{--}$~$bar{Xi}_{cc}Xi_{cc}^{ast}$, $J^{PC}=2^{-+}$~$bar{Xi}_{cc}Xi_{cc}^{ast}$, $J^{PC}=2^{-+}$~$bar{Xi}_{cc}^{ast}Xi_{cc}^{ast}$ and $J^{PC}=3^{--}$~$bar{Xi}_{cc}^{ast}Xi_{cc}^{ast}$. Among them, the $J^{PC}=0^{-+}$~$bar{Xi}_{cc}Xi_{cc}$ and/or $J^{PC}=1^{--}$~$bar{Xi}_{cc}Xi_{cc}$ molecules may contribute to the $X(7200)$ state recently observed by the LHCb Collaboration, which implies that $X(7200)$ can be related to $X(3872)$ via HADS. As a byproduct, with the heavy quark flavor symmetry we also study likely existence of molecular states in the $B^{(ast)}bar{B}^{(ast)}$, $bar{B}^{(ast)}Xi_{bb}^{(ast)}$, and $bar{Xi}_{bb}^{(ast)}Xi_{bb}^{(ast)}$ systems.
The $DDK$ 3-body system is supposed to be bound due to the strongly attractive interaction between the $D$ meson and the $K$ meson in the isospin zero channel. The minimum quark content of this 3-body bound state is $ccbar{q}bar{s}$ with $q=u,d$. It
will be an explicitly exotic tetraquark state once discovered. In order to confirm the phenomenological study of the $DDK$ system, we can refer to lattice QCD as a powerful theoretical tool parallel to the experiment measurement. In this paper, a 3-body quantization condition scheme is derived via the non-relativistic effective theory and the particle-dimer picture in finite volume. Lattice spectrum of this 3-body system is calculated within the existing model inputs. The spectrum shows various interesting properties of the $DDK$ system, and it may reveal the nature of the $D^*(2317)$. This predicated spectrum is expected to be tested in future lattice simulations.
Both unitary chiral theories and lattice QCD simulations show that the $DK$ interaction is attractive and can form a bound state, namely, $D^*_{s0}(2317)$. Assuming the validity of the heavy antiquark-diquark symmetry (HADS), the $Xi_{cc}bar{K}$ inte
raction is the same as the $DK$ interaction, which implies the existence of a $Xi_{cc}bar{K}$ bound state with a binding energy of $49-64$ MeV. In this work, we study whether a $Xi_{cc}Xi_{cc}bar{K}$ three-body system binds. The $Xi_{cc}Xi_{cc}$ interaction is described by exchanging $pi$, $sigma$, $rho$, and $omega$ mesons, with the corresponding couplings related to those of the $NN$ interaction via the quark model. We indeed find a $Xi_{cc}Xi_{cc}bar{K}$ bound state, with quantum numbers $J^P=0^-$, $I=frac{1}{2}$, $S=1$ and $C=4$, and a binding energy of $80-118$ MeV. It is interesting to note that this system is very similar to the well-known $NNbar{K}$ system, which has been studied extensively both theoretically and experimentally. Within the same framework, we show the existence of a $NNbar{K}$ state with a binding energy of $35-43$ MeV, consistent with the results of other theoretical works and experimental data, which serves as a consistency check on the predicted $Xi_{cc}Xi_{cc}bar{K}$ bound state.
