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We discuss the possible existence of the fully-heavy tetraquarks. We calculate the ground-state energy of the \\[bb {\\bar{b}} {\\bar{b}}\\] bound state, where b stands for the bottom quark, in a nonrelativistic effective field theory framework with one-gluon-exchange (OGE) color Coulomb interaction, and in a relativized diquark model characterized by OGE plus a confining potential. Our analysis advocates the existence of uni-flavor heavy four-quark bound states. The ground state \\[bb{\\bar{b}}{\\bar{b}}\\] tetraquark mass is predicted to be \\[(18.72\\pm 0.02)\\] GeV. Mass inequality relations among the lowest \\[QQ\\bar{Q}\\bar{Q}\\] states, where \\[Q\\in \\{c, b\\}\\], and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state \\[QQ\\bar{Q}\\bar{Q}\\]. The possible decays of the lowest \\[bb\\bar{b}\\bar{b}\\] are highlighted, which might provide useful references in the search for them in ongoing LHC experiments, and its width is estimated to be a few tens of MeV.

We present new linear relations among the masses of S-wave tetraquarks with either one flavour (\\(QQ \\bar Q \\bar Q\\)) or two (\\(QQ\\bar q \\bar q\\)). Because the relations are sensitive to the hidden-colour, spin, and spatial degrees of freedom, comparison to experimental data can help to reveal the internal structure of tetraquarks, and discriminate among different theoretical models. Depending on the model, the relations are either exact, or valid in perturbation theory, and a thorough comparison with existing literature confirms their validity at the MeV level. Additionally, we explore the connections among tetraquark models, and show how those with effective (quark or diquark) masses are related to dynamical potential models. We also show how the spectrum of diquark models is effectively a limiting case of (more general) quark models, and in particular, that the diquark concept is most relevant in the particular combination \\(QQ\\bar q \\bar q\\), where \\(Q\\) is much heavier than \\(\\bar q\\).

We calculate the spectrum of \\(q\\bar q c \\bar c\\) and \\(s\\bar s c \\bar c\\) tetraquarks, where \\(q\\), \\(s\\) and \\(c\\) stand for light (\\(u,d\\)), strange and charm quarks, respectively, in a relativized diquark model, characterized by one-gluon-exchange (OGE) plus confining potential. In the diquark model, a \\(q\\bar q c \\bar c\\) (\\(s\\bar s c \\bar c\\)) tetraquark configuration is made up of a heavy-light diquark, \\(q c\\) (\\(sc\\)), and anti-diquark, \\(\\bar q \\bar c\\) (\\(\\bar s \\bar c\\)). According to our results, 13 charmonium-like observed states can be accommodated in the tetraquark picture, both in the hidden-charm (\\(q\\bar q c \\bar c\\)) and hidden-charm hidden-strange (\\(s\\bar s c \\bar c\\)) sectors.

We study the excited \\(B\\) mesons' contributions to the coupled-channel effects under the framework of \\({}^3P_0\\) model for the bottomonium. Contrary to what has been widely accepted, the contributions of \\(P\\) wave \\(B\\) mesons are generally the largest and this result is independent of the potential parameters to some extent. We also push the calculation beyond \\(B(1P)\\) and carefully analyze the contributions of \\(B(2S)\\). A form factor is a key ingredient to suppress the contributions of \\(B(2S)\\) for low lying bottomonia. However, this suppression mechanism is not efficient for highly excited bottomonia such as \\(\\Upsilon(5S)\\) and \\(\\Upsilon(6S)\\). We give explanations why this difficulty happens to \\({}^3P_0\\) model and suggest analyzing flux-tube breaking model for the full calculation of coupled-channel effects.

With Gaussian expansion method (GEM), realistic wave functions are used to calculate coupled-channel effects for the bottomonium under the framework of \\({}^3P_0\\) model. The simplicity and accuracy of GEM are explained. We calculate the mass shifts, probabilities of the \\(B\\) meson continuum, \\(S-D\\) mixing angles, strong and dielectric decay widths. Our calculation shows that both \\(S-D\\) mixing and the \\(B\\) meson continuum can contribute to the suppression of the vector meson's dielectric decay width. We suggest more precise measurements on the radiative decays of \\(\\Upsilon(10580)\\) and \\(\\Upsilon(11020)\\) to distinguish these two effects. The above quantities are also calculated with simple harmonic oscillator (SHO) wave function approximation for comparison. The deviation between GEM and SHO indicates that it is essential to treat the wave functions accurately for near threshold states.

At the large distances compared to the chiral symmetry breaking scale, a four-quark system \\(\\bar Q \\bar Q qq\\) (with \\(Q\\) as heavy and \\(q\\) as light quarks) can be treated as two asymptotic mesons interacting via strong residual forces. The static heavy quark assumption enables using the Born-Oppenheimer approximation, where one can compute the potential between two heavy antiquarks in the presence of two light quarks of finite mass -- a prescription utilized in several lattice QCD studies. To analyse the long-range strong force in a \\(\\bar Q \\bar Q qq\\) system, we study the interaction between two bottom mesons in the heavy quark limit using chiral effective field theory and dispersion theory with unphysical pion mass. We present methods to obtain two-pion-exchange potential between two static heavy mesons at non-physical pion mass and compare our preliminary results with the corresponding lattice QCD potentials.

Motivated by recent experimental evidence for apparent \\(cc c c\\) states at LHCb, CMS and ATLAS, we consider how the mass spectrum and decays of such states can be used to discriminate among their possible theoretical interpretations, with a particular focus on identifying whether quarks or diquarks are the most relevant degrees of freedom. Our preferred scenario is that \\(X(6600)\\) and its apparent partner state \\(X(6400)\\) are the tensor \\((2^++)\\) and scalar \\((0^++)\\) states of an S-wave multiplet of \\(cc c c\\) states. Using tetraquark mass relations which are independent of (or only weakly dependent on) model parameters, we give predictions for the masses of additional partner states with axial and scalar quantum numbers. Additionally, we give predictions for relations among decay branching fractions to \\(J/ J/\\), \\(J/ _c\\), \\(_c_c\\) and \\(D^(*) D^(*)\\) channels. The scenario we consider is consistent with existing experimental data on \\(J/ J/\\), and our predictions for partner states and their decays can be confronted with future experimental data, to discriminate between quark and diquark models.

The charmoniumlike state \\(Y(4260)\\) is described as predominantly a \\(D_1 \\bar{D}\\) molecule in a coupled-channel quark model [Phys.\\,Rev.\\,D\\,\\textbf{96},\\,114022\\,(2017)]. The heavy quark spin symmetry (HQSS) thus implies the possible emergence of its heavy quark spin partners with molecular configuration as \\(D_1 \\bar{D}^*\\) and \\(D_2^* \\bar{D}^*\\) below these charmed mesons' thresholds. We analyze the probabilities of various intermediate charmed meson loops for \\(J^{PC}=1^{--}\\) exotic state \\(Y(4360)\\) and find that the channel \\(D_1 \\bar{D}^*\\) couples more strongly around its mass regime, and the coupling behavior remains the same even if the mass of \\(Y(4360)\\) is pushed closer to \\(D_1 \\bar{D}^*\\) threshold. This enlightens that the most favorable molecular scenario for the \\(Y(4360)\\) could be \\(D_1 \\bar{D}^*\\), and hence it can be interpreted as HQSS partner of the \\(Y(4260)\\). We also find the strong coupling behavior of \\(D_2^* \\bar{D}^*\\) channel with the \\(\\psi(4415)\\), which makes it a good candidate for a dominant \\(D_2^* \\bar{D}^*\\) molecule. We discuss the important decay patterns of these resonances to disentangle their long- and short-distance structures.

Man is the best of the creations of the Almighty Allah Who reflects the perfect model of His creations. Allah’s showers His bounties, benediction and blessings on those who are inclined to extend favors to His creation. Incompetent people exploited the religious sentiments of the gullible to get their desired malicious designs, and for this very purpose they did not feel any reluctance to twist, distort and interpolate the divinely revealed teachings. The greedy and vested-interest groups exploited and capitalize the so-called religious seminaries for their personal gains and advantages. On account of wrongdoings and evil practices of all these religious mentors (Priests, Bhikshus, Pundits, Rabbis and Seminaries, etc.) common people have become fed-up with their religions. As a result of it, a society devoid of all high moral values is coming into existence. This social anxiety and precariousness has destroyed the peace and tranquility of mind of people. Ali Ibn Usman Al-hajveri, a great mystic, depicted the true picture of mysticism in his book Kashf al-Mahjoob. He emphasized that true mysticism is to follow the teachings of Quran and Sunnah in letter and spirit. He severely criticized those so-called scholars who misled the innocent people and led them to astray. He also criticized those scholars who twist and distort the teachings of religion and make them subservient to their vein desires.

Invoked by the recent CMS observation regarding candidates of the \\(\\chi_b(3P)\\) multiplet, we analyze the ultrafine and mass splittings among \\(3P\\) multiplet in our unquenched quark model (UQM) studies. The mass difference of \\(\\chi_{b2}\\) and \\(\\chi_{b1}\\) in \\(3P\\) multiplet measured by CMS collaboration (\\(10.6 \\pm 0.64 \\pm 0.17\\) MeV) is very close to our theoretical prediction (\\(12\\) MeV). Our corresponding mass splitting of \\(\\chi_{b1}\\) and \\(\\chi_{b0}\\) enables us to predict more precisely the mass of \\(\\chi_{b0}(3P)\\) to be (\\(10490\\pm 3\\)) MeV. Moreover, we predict ratios of the radiative decays of \\(\\chi_{bJ}(nP)\\) candidates, both in UQM and quark potential model. Our predicted relative branching fraction of \\(\\chi_{b0}(3P)\\to\\Upsilon(3S)\\gamma\\) is one order of magnitude smaller than \\(\\chi_{b2}(3P)\\), this naturally explains the non-observation of \\(\\chi_{b0}(3P)\\) in recent CMS search. We hope these results might provide useful references for forthcoming experimental searches.