International Journal of Modern Physics A

We present a retrospective on the foundation, evolution, contributions and future prospects of the TEXONO Collaboration and its research programs on neutrino physics and dark matter searches at the Kuo-Sheng Reactor Neutrino Laboratory in Taiwan and, as a founding partner of the CDEX program, at the China Jinping Underground Laboratory in China.

We present new compact integrated expressions of SU3 breaking corrections to QCD spectral functions of heavy–light molecules and four-quark $XYZ$-like states at lowest order (LO) of perturbative (PT) QCD and up to $d=8$ condensates of the Operator Product Expansion (OPE). Including next-to-next-to-leading order (N2LO) PT corrections in the chiral limit and next-to-leading order (NLO) SU3 PT corrections, which we have estimated by assuming the factorization of the four-quark spectral functions, we improve previous LO results for the $XYZ$-like masses and decay constants from QCD spectral sum rules (QSSR). Systematic errors are estimated from a geometric growth of the higher order PT corrections and from some partially known $d=8$ nonperturbative contributions. Our optimal results, based on stability criteria, are summarized in Tables 18–21 while the $0^{++}$ and $1^{++}$ channels are compared with some existing LO results in Table 22. One can note that, in most channels, the SU3 corrections on the meson masses are tiny: $\le 10\%$ (respectively $\le 3\%$) for the $c$ (respectively $b$)-quark channel but can be large for the couplings ($\le 20\%$). Within the lowest dimension currents, most of the $0^{++}$ and $1^{++}$ states are below the physical thresholds while our predictions cannot discriminate a molecule from a four-quark state. A comparison with the masses of some experimental candidates indicates that the $0^{++}$ $X(4500)$ might have a large ${\bar{D}}_{s0}^{\ast }{D}_{s0}^{\ast }$ molecule component while an interpretation of the $0^{++}$ candidates as four-quark ground states is not supported by our findings. The $1^{++}$ $X(4147)$ and $X(4273)$ are compatible with the ${\bar{D}}_s^{\ast }{D}_s$, ${\bar{D}}_{s0}^{\ast }{D}_{s1}$ molecules and/or with the axial-vector $A_c$ four-quark ground state. Our results for the $0^{-\pm }$, $1^{-\pm }$ and for different beauty states can be tested in the future data. Finally, we revisit our previous estimates¹ for the ${\bar{D}}_0^{\ast }{D}_0^{\ast }$ and ${\bar{D}}_0^{\ast }{D}_1$ and present new results for the ${\bar{D}}_1{D}_1$.

We examine a suggested relation between stochastic quantization and the holographic Wilsonian renormalization group in the massive fermion case on Euclidean AdS space. The original suggestion about the general relation between the two theories is posted in arXiv:1209.2242. In the previous researches, it is already verified that scalar fields, U(1) gauge fields, and massless fermions are consistent with the relation. In this paper, we examine the relation in the massive fermion case. Contrary to the other case, in the massive fermion case, the action needs particular boundary terms to satisfy boundary conditions. We finally confirm that the proposed suggestion is also valid in the massive fermion case.

Studies of $J/\psi$ $v_2$ at RHIC and LHC energies have provided important elements toward the understanding on the production mechanisms and thermalization of charm quarks. Bottomonia has an advantage since it is a cleaner probe. A brief discussion has been provided for $\mathrm{{\rm Y}}(1S)$ $v_2$, which can become the new probe for QGP, including the necessity of studies for small systems.

We study the charged and spin currents on a coordinate dependent noncommutative space. Starting from the noncommutative extended relativistic equation of motion, the nonrelativistic approximation is obtained by using the Foldy–Wouthuysen transformation, and then the charged and spin currents are derived by using the extended Drude model. We find that the charged current is twisted by modifying the off-diagonal elements of the Hall conductivity, however, the spin current is not affected up to leading order of the noncommutative parameter.

We consider $SU(2)\times U(1)$ gauge theory coupled to matter field in adjoints and study RG group flow. We constructed Callan–Symanzik equation and subsequent $\beta$ functions and study the fixed points. We find there are two fixed points, showing metallic and antiferromagnetic behavior. We have shown that metallic phase develops an instability if certain parametric conditions are satisfied.

The Einstein–Cartan–Kibble–Sciama (ECKS) theory of gravity naturally extends Einstein’s general relativity (GR) to include intrinsic angular momentum (spin) of matter. The main feature of this theory consists of an algebraic relation between space–time torsion and spin of matter, which indeed deprives the torsion of its dynamical content. The Lagrangian of ECKS gravity is proportional to the Ricci curvature scalar constructed out of a general affine connection so that owing to the influence of matter energy–momentum and spin, curvature and torsion are produced and interact only through the space–time metric. In the absence of spin, the space–time torsion vanishes and the theory reduces to GR. It is however possible to have torsion propagation in vacuum by resorting to a model endowed with a nonminimal coupling between curvature and torsion. In the present work we try to investigate possible effects of the higher order terms that can be constructed from space–time curvature and torsion, as the two basic constituents of Riemann–Cartan geometry. We consider Lagrangians that include fourth-order scalar invariants from curvature and torsion and then investigate the resulting field equations. The solutions that we find show that there could exist, even in vacuum, nontrivial static space–times that admit both black holes and naked singularities.

We study the spectra of the doubly charmed tetraquark states in a diquark–antidiquark model. The doubly charmed tetraquark states form an antitriplet and sextet configurations according to flavor SU(3) symmetry. For the tetraquark state $[q{q}^{\prime }][\bar{c}\bar{c}]$, we show the mass for both bound and excited states. The two-body decays of tetraquark states $T^{cc}[0^{+}]$ and $T^{cc}[1^{--}]$ to charmed mesons have also been studied. In the end, the doubly charmed tetraquarks decays to a charmed baryon and a light baryon have been studied in the SU(3) flavor symmetry.

We derive the partition function of a nonrelativistic quantum string whose ends are allowed to freely move along the two-angled straight solid rods. We first derive the classical solution of the model and then use it to derive the partition function utilizing the path integral method. We show that the vacuum energy is the sum of the Lüscher potential plus a term which depends on the relative angle between the rods.

We investigate the geodesic motion of massless test particles in the background of a noncommutative geometry-inspired Schwarzschild black hole. The behavior of effective potential is analyzed in the equatorial plane and the possible motions of massless particles (i.e. photons) for different values of impact parameter are discussed accordingly. We have also calculated the frequency shift of photons in this space–time. Further, the mass parameter of a noncommutative inspired Schwarzschild black hole is computed in terms of the measurable redshift of photons emitted by massive particles moving along circular geodesics in equatorial plane. The strength of gravitational fields of noncommutative geometry-inspired Schwarzschild black hole and usual Schwarzschild black hole in General Relativity is also compared.