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Neural network study of hidden-charm pentaquark resonances
Halil Mutuk
Published:   , doi: 10.1088/1674-1137/43/9/093103
Abstract:
Very recently, LHCb experiment announced the observation of hidden-charm pentaquark states \begin{document}$P_c(4312)$\end{document}, \begin{document}$P_c(4440)$\end{document}, and \begin{document}$P_c(4457)$\end{document} near the \begin{document}$ \Sigma_c \bar{D}$\end{document} and \begin{document}$ \Sigma_c \bar{D}^\ast$\end{document} thresholds, respectively. In this present work, we studied thesepentaquarks in the framework of the nonrelativistic quark model with four types of potential. We solved 5-body Schrödinger equation by using artificial neural network method and made predictions of parities for these states which are not determined in the experiment yet. The mass of another possible pentaquark state near the \begin{document}$\bar{D}^\ast \Sigma_c^\ast$\end{document} with \begin{document}$J^P=5/2^-$\end{document} is also calculated.
Properties of the decay $ H\to\gamma\gamma $ using the approximate $ \alpha_s^4 $-corrections and the principle of maximum conformality
Qing Yu, Xing-Gang Wu, Sheng-Quan Wang, Xu-Dong Huang, Jian-Ming Shen, Jun Zeng
Published:   , doi: 10.1088/1674-1137/43/9/093102
Abstract:
The Higgs boson decay channel, \begin{document}$ H\to\gamma\gamma $\end{document}, is an important channel for probing the properties of the Higgs boson. In the paper, we analyze its decay width by using the perturbative QCD corrections up to \begin{document}$ \alpha_s^4 $\end{document}-order level with the help of the principle of maximum conformality (PMC). The PMC has been suggested in the literature to eliminate the conventional renormalization scheme-and-scale ambiguities. After applying the PMC, we observe that an accurate renormalization scale-independent decay width \begin{document}$ \Gamma(H\to\gamma\gamma) $\end{document} up to N4LO level can be achieved. Taking the Higgs mass, \begin{document}$ M_{\rm H} = 125.09\pm0.21\pm0.11 $\end{document} GeV, given by the ATLAS and CMS collaborations, we obtain \begin{document}$ \Gamma(H\to \gamma\gamma)|_{\rm LHC} = 9.364^{+0.076}_{-0.075} $\end{document} KeV.
Energy staggering parameters in nuclear magnetic rotational bands
Wu-Ji Sun, Jian Li
Published:   , doi: 10.1088/1674-1137/43/9/094104
Abstract:
The systematics of energy staggering for the magnetic rotational bands with \begin{document}$ M1 $\end{document} and \begin{document}$ E2 $\end{document} transition properties strictly consistent with the features of good candidates of magnetic rotational bands in the \begin{document}$ A\sim80 $\end{document}, 110, 130 and 190 mass regions are presented. The regularities exhibited by these bands concerning the staggering parameter which increases with increasing spin are in agreement with the semiclassical description of shears mechanism. In addition, the abnormal behaviours in the backbend regions or close to band termination have also been discussed. Taking the magnetic dipole bands with same configuration in three \begin{document}$ N = 58 $\end{document} isotones, i.e., \begin{document}$ ^{103} {\rm Rh}$\end{document}, \begin{document}$ ^{105} {\rm Ag}$\end{document}, and \begin{document}$ ^{107} {\rm In}$\end{document}, as examples, the transition from chiral rotation to magnetic rotation with the proton number approaching \begin{document}$ Z = 50 $\end{document} is presented. Moreover, the self-consistent tilted axis cranking and principle axis cranking relativistic mean-field theories are applied to investigate the rotational mechanism in dipole band of \begin{document}$ ^{105} {\rm Ag}$\end{document}.
Response functions of hot and dense matter in the Nambu-Jona-Lasino model
Chengfu Mu, Ziyue Wang, Lianyi He
Published:   , doi: 10.1088/1674-1137/43/9/094103
Abstract:
We investigate the current-current correlation functions or the so-called response functions of a two-flavor Nambu-Jona-Lasino model at finite temperature and density. We study the linear response by using the functional path integral approach and introducing the conjugated gauge fields as external sources. The response functions can be obtained by expanding the generational functional in powers of the external sources. We derive the response functions parallel to two well-established approximations for the equilibrium thermodynamics: the mean-field theory and a beyond-mean-field theory taking into account the mesonic contributions. The response functions based on the mean-field theory recover the so-called quasiparticle random phase approximation. We calculate the dynamical structure factors for the density responses in various channels within the random phase approximation. We show that the dynamical structure factors in the baryon axial vector and isospin axial vector channels can be used reveal the quark mass gap and the Mott dissociation of mesons, respectively. Noting that the mesonic contributions are not taken into account in the random phase approximation, we also derive the response functions parallel to the beyond-mean-field theory. We show that the mesonic fluctuations naturally give rise to three kinds of famous diagrammatic contributions: the Aslamazov-Lakin contribution, the Self-Energy or Density-of-State contribution, and the Maki-Thompson contribution. Unlike the equilibrium case, in evaluating the fluctuation contributions, we need to treat carefully the linear terms in the external sources and the induced perturbations. In the chiral symmetry breaking phase, we find an additional chiral order parameter induced contribution, which ensures that the temporal component of the response functions in the static and long-wavelength limit recovers the correct charge susceptibility defined by using the equilibrium thermodynamic quantities. These contributions from the mesonic fluctuations are expected to have significant effects on the transport properties of hot and dense matter around the chiral phase transition or crossover, where the mesonic degrees of freedom are still important.
An alternative approach to thermodynamic phase transitions
Seyed Hossein Hendi, Shahram Panahiyan, Behzad Eslam Panah, Mubasher Jamil
Published:   , doi: 10.1088/1674-1137/43/7/073104
Abstract:
One of the major open problems in theoretical physics is a consistent quantum gravity theory. Recent developments in thermodynamic phase transitions of black holes and their van der Waals-like behavior may provide an interesting quantum interpretation of classical gravity. Studying different methods of investigating phase transitions can extend our insight into the nature of quantum gravity. In this paper, we present an alternative theoretical approach for finding thermodynamic phase transitions in the extended phase space. Unlike the standard methods based on the usual equation of state involving temperature, our approach uses a new quasi-equation of state, constructed from the slope of temperature versus entropy. This approach addresses some of the shortcomings of the other methods, and provides a simple and powerful way of studying the critical behavior of a thermodynamical system. Among the applications of this approach, we emphasize the analytical demonstration of possible phase transition points, and the identification of the non-physical range of horizon radii for black holes.