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A new cosmological probe using super-massive black hole shadows
Jing-Zhao Qi, Xin Zhang
Published: , doi: 10.1088/1674-1137/44/5/055105
Abstract:
We study the prospects of using the low-redshift and high-redshift black hole shadows as new cosmological standard rulers for measuring cosmological parameters. We show that, using the low-redshift observation of the black hole shadow of ${\rm M87}^\star$, the Hubble constant can be independently determined with a precision of about 13% as $H_0=70\pm 9$ km ${\rm s}^{-1}$ ${\rm Mpc}^{-1}$. The high-redshift observations of super-massive black hole shadows may accurately determine a combination of parameters $H_0$ and ${\Omega_{m}}$, and we show by a simple simulation that combining them with the type Ia supernovae observations would give precise measurements of the cosmological parameters.
Ξbb and Ωbbb molecular states
J. M. Dias, Qi-Xin Yu, Wei-Hong Liang, Zhi-Feng Sun, Ju-Jun Xie, E. Oset
Published: , doi: 10.1088/1674-1137/44/6/064101
Abstract:
Using the vector exchange interaction in the local hidden gauge approach, which in the light quark sector generates the chiral Lagrangians and has produced realistic results for $\Omega_c, \Xi_c, \Xi_b$ and the hidden charm pentaquark states, we study the meson-baryon interactions in the coupled channels that lead to the $\Xi_{bb}$ and $\Omega_{bbb}$ excited states of the molecular type. We obtain seven states of the $\Xi_{bb}$ type with energies between $10408$ and $10869$ MeV, and one $\Omega_{bbb}$ state at $15212$ MeV.
Gyroscope precession frequency analysis of a five-dimensional charged rotating Kaluza-Klein black hole
Mustapha Azreg-Aïnou, Mubasher Jamil, Kai Lin
Published: , doi: 10.1088/1674-1137/44/6/065101
Abstract:
We study the spin precession frequency of a test gyroscope attached to a stationary observer in the five-dimensional rotating Kaluza-Klein black hole (RKKBH). We derive the conditions under which the test gyroscope moves along a timelike trajectory in this geometry, and the regions where the spin precession frequency diverges. The magnitude of the gyroscope precession frequency around the KK black hole diverges at two spatial locations outside the event horizon. However, in the static case, the behavior of the Lense-Thirring frequency of a gyroscope around the KK black hole is similar to the ordinary Schwarzschild black hole. Since a rotating Kaluza-Klein black hole is a generalization of the Kerr-Newman black hole, we present two mass-independent schemes to distinguish these two spacetimes.
Extraction of the CKM phase γ from the charmless two-body B meson decays
Si-Hong Zhou, Cai-Dian Lü
Published: , doi: 10.1088/1674-1137/44/6/063101
Abstract:
Using all experimentally measured charmless $B \to PP$, $PV$ decay modes, where $P(V)$ denotes a light pseudoscalar (vector) meson, we extract the CKM angle $\gamma$ by a global fit. All hadronic parameters are determined from the experimental data, such that the approach is least model dependent. The contributions of the various decay modes are classified by the topological weak Feynman diagram amplitudes, which are determined by the global fit. To improve the precision of the approach, we consider the flavor SU(3) breaking effects of the topological diagram amplitudes of the decay modes by including the form factors and decay constants. The fit result for the CKM angle $\gamma$ is $(69.8 \pm 2.1 \pm 0.9) ^{\circ }$. It is consistent with the current world average values but has a smaller uncertainty.
Microscopic study of 7Li-nucleus potential
Wen-Di Chen, Hai-Rui Guo, Wei-Li Sun, Tao Ye, Yang-Jun Ying, Yin-Lu Han, Qing-Biao Shen
Published: , doi: 10.1088/1674-1137/44/5/054109
Abstract:
A microscopic approach is employed to study the optical potential for the 7Li-nucleus interaction system without any free parameters. It is obtained by folding the microscopic optical potentials of the constituent nucleons of 7Li over their density distributions. We employ an isospin-dependent nucleon microscopic optical potential, which is based on the Skyrme nucleon-nucleon effective interaction and derived using the Green's function method, as the nucleon optical potential. The harmonic oscillator shell model is used to describe the internal wave function of 7Li and obtain the nucleon density distribution. The 7Li microscopic optical potential is used to predict the reaction cross-sections and elastic scattering angular distributions for the target range from 27Al to 208Pb and energy range below 450 MeV. Generally, the results can reproduce the measured data reasonably well. In addition, the microscopic optical potential is comparable to a global phenomenological optical potential by fitting the presently existing measured data.
Sea quark contributions to nucleon electromagnetic form factors with the nonlocal chiral effective Lagrangian
Ming-Yang Yang, Ping Wang
Published: , doi: 10.1088/1674-1137/44/5/053101
Abstract:
The sea quark contributions to the nucleon electromagnetic form factors of the up, down and strange quarks are studied with the nonlocal chiral effective Lagrangian. Both octet and decuplet intermediate states are included in the one loop calculations. Compared with the strange quark form factors, although their signs are the same, the absolute value of the light quark form factors are much larger. For both the electric and magnetic form factors, the contribution of the d quark is larger than of the u quark. The current lattice simulations of the light sea quark form factors are in between our results for the u and d quarks.
Constraints on neutron skin thickness and symmetry energy of 208Pb through Skyrme forces and cluster model
M. Moghaddari Amiri, O. N. Ghodsi
Published: , doi: 10.1088/1674-1137/44/5/054107
Abstract:
We used the cluster structure properties of the 212Po to estimate the neutron skin thickness of 208Pb. For this purpose, we considered two important components: (a) alpha decay is a low energy phenomenon; therefore, one can expect that the mean-field, which can explain the ground state properties of 212Po, does not change during the alpha decay process. (b) 212Po has a high alpha cluster-like structure, two protons and two neutrons outside its core nucleus with a double magic closed-shell, and the cluster model is a powerful formalism for the estimation of alpha decay preformation factor of such nuclei. The slope of the symmetry energy of 208Pb is estimated to be $75\pm25$ MeV within the selected same mean-fields and Skyrme forces, which can simultaneously satisfy the ground-state properties of parent and daughter nuclei, as their neutron skin thicknesses are consistent with experimental data.
First order QED processes in a spatially flat FLRW space-time with a Milne-type scale factor
Ion I. Cotăescu, Diana Popescu
Published: , doi: 10.1088/1674-1137/44/5/055104
Abstract:
The quantum electrodynamics (QED) in a spatially flat (1+3)-dimensional Friedmann-Lemaître-Robertson-Walker (FLRW) space-time with a Milne-type scale factor is outlined focusing on the amplitudes of the allowed processes in the first order perturbations. The definition of the transition rates is reconsidered such that an appropriate angular behavior of the probability for creation of an electron-positron pair from a photon is obtained, which has a similar rate as the creation of a photon and an electron-positron pair from vacuum. It is shown that these processes are allowed only in the first order perturbations, since the photon emission or absorption by an electron or positron are forbidden.
The spin-isospin decomposition of the nuclear symmetry energy from low to high density
Wenmei Guo, M. Colonna, V. Greco, U. Lombardo, H.-J. Schulze
Published: , doi: 10.1088/1674-1137/44/5/054110
Abstract:
The energy per particle BA in nuclear matter is calculated up to high baryon density in the whole isospin asymmetry range from symmetric matter to pure neutron matter. The results, obtained in the framework of the Brueckner-Hartree-Fock approximation with two- and three-body forces, confirm the well-known parabolic dependence on the asymmetry parameter β = (NZ)/A (β2 law) that is valid in a wide density range. To investigate the extent to which this behavior can be traced back to the properties of the underlying interaction, aside from the mean field approximation, the spin-isospin decomposition of BA is performed. Theoretical indications suggest that the β2 law could be violated at higher densities as a consequence of the three-body forces. This raises the problem that the symmetry energy, calculated according to the β2 law as a difference between BA in pure neutron matter and symmetric nuclear matter, cannot be applied to neutron stars. One should return to the proper definition of the nuclear symmetry energy as a response of the nuclear system to small isospin imbalance from the Z = N nuclei and pure neutron matter.
Shielding effects in fusion reactions with a proton-halo nucleus
Xue-ying He, Qin Dong, Li Ou
Published: , doi: 10.1088/1674-1137/44/5/054108
Abstract:
To explain the experimental observation that the fusion cross-section of a proton-halo nucleus with a heavy target nucleus is not enhanced as expected, the shielding hypothesis was proposed, where the proton-halo nucleus is polarized and the valence proton shielded by the core. In the frame of the improved quantum molecular dynamics model, the fusion reaction 17F on 208Pb around the Coulomb barrier is simulated. The existence of the shielding effect is verified by the microscopic dynamics simulations. Its influence on the effective interaction potential is also investigated.
Prediction of possible exotic states in the ${\eta \bar{K}K^*}$ system
Xu Zhang, Ju-Jun Xie
Published: , doi: 10.1088/1674-1137/44/5/054104
Abstract:
We investigate the $ \eta \bar{K}K^* $ three-body system in order to look for possible $ I^G(J^{PC}) = 0^+(1^{-+}) $ exotic states in the framework of the fixed-center approximation of the Faddeev equation. We assume the scattering of $ \eta $ on a clusterized system $ \bar{K}K^* $, which is known to generate $ f_1(1285) $, or a $ \bar{K} $ in a clusterized system $ \eta K^* $, which is shown to generate $ K_1(1270) $. In the case of $ \eta $-$ (\bar{K}K^*)_{f_1(1285)} $ scattering, we find evidence of a bound state $ I^G(J^{PC}) = 0^+(1^{-+}) $ below the $ \eta{f_1(1285)} $ threshold with a mass of around 1700 MeV and a width of about 180 MeV. Considering $ \bar{K} $-$ (\eta K^*)_{K_1(1270)} $ scattering, we obtain a bound state $ I(J^{P}) = 0(1^{-}) $ just below the $ \bar{K}{K_1(1270)} $ threshold with a mass of around 1680 MeV and a width of about 160 MeV.
The first excited single-proton resonance in 15F by complex-scaled Green's function method
Xin-Xing Shi, Quan Liu, Dong-Dong Ni, Jian-You Guo, Zhong-Zhou Ren
Published: , doi: 10.1088/1674-1137/44/5/054103
Abstract:
The complex-scaled Green's function (CGF) method is employed to explore the single-proton resonance in 15F. Special attention is paid to the first excited resonant state 5/2+, which has been widely studied in both theory and experiments. However, past studies generally overestimated the width of the 5/2+ state. The predicted energy and width of the first excited resonant state 5/2+ by the CGF method are both in good agreement with the experimental value and close to Fortune's new estimation. Furthermore, the influence of the potential parameters and quadruple deformation effects on the resonant states are investigated in detail, which is helpful to the study of the shell structure evolution.
Simple Woods-Saxon-type form for Ωα and Ξα interactions using folding model
Faisal Etminan, Mohammad Mehdi Firoozabadi
Published: , doi: 10.1088/1674-1137/44/5/054106
Abstract:
We derive a simple Woods-Saxon-type form for potentials between $Y=\Xi, \Omega$, and $\alpha$ using a single-folding potential method, based on a separable Y-nucleon potential. The potentials $\Xi+\alpha$ and $\Omega+\alpha$ are accordingly obtained using the ESC08c Nijmegens $\Xi N$ potential (in $^{3}S_{1}$ channel) and HAL QCD collaboration $\Omega N$ interactions (in lattice QCD), respectively. In deriving the potential between Y and $\alpha$, the same potential between Y and N is employed. The binding energy, scattering length, and effective range of the Y particle on the alpha particle are approximated by the resulting potentials. The depths of the potentials in $\Omega \alpha $ and $\Xi \alpha $ systems are obtained at $-61$ MeV and $-24.4$ MeV, respectively. In the case of the $\Xi \alpha$ potential, a fairly good agreement is observed between the single-folding potential method and the phenomenological potential of the Dover-Gal model. These potentials can be used in 3-,4- and 5-body cluster structures of $ \Omega$ and $\Xi$ hypernuclei.
Probe chiral magnetic effect with signed balance function
A. H. Tang
Published: , doi: 10.1088/1674-1137/44/5/054101
Abstract:
In this paper a pair of observables are proposed as alternative ways, by examining the fluctuation of net momentum-ordering of charged pairs, to study the charge separation induced by the Chiral Magnetic Effect (CME) in relativistic heavy ion collisions. They are, the out-of-plane to in-plane ratio of fluctuation of the difference between signed balance functions measured in pair’s rest frame, and the ratio of it to similar measurement made in the laboratory frame. Both observables have been studied with simulations including flow-related backgrounds, and for the first time, backgrounds that are related to resonance's global spin alignment. The two observables have similar positive responses to signal, and opposite, limited responses to identifiable backgrounds arising from resonance flow and spin alignment. Both observables have also been tested with two realistic models, namely, a multi-phase transport (AMPT) model and the anomalous-viscous fluid dynamics (AVFD) model. These two observables, when cross examined, will provide useful insights in the study of CME-induced charge separation.
Modification of the spectra of correlated charm-anticharm quark pairs in the quark-gluon plasma
Ismat Ullah, Min He
Published: , doi: 10.1088/1674-1137/44/5/054102
Abstract:
Heavy quarks play an important role in probing the properties of strongly interacting quark-gluon plasma (QGP) created in ultra-relativistic heavy-ion collisions. We study the interactions of single heavy (charm) quarks and correlated charm and anticharm ($c\bar c$) quark pairs with the medium constituents of QGP by performing fireball+Langevin simulations of the pertinent Brownian motion with elastic collisions. Besides studying the traditional observables, the nuclear modification factor and the elliptic flow of single heavy quarks in QGP for different thermal relaxation rates, we also study the broadening of the azimuthal correlations of charm and anticharm quark pairs in the QGP medium for different relaxation rates and transverse momenta classes. We quantified the smearing of $c\bar c$ pair azimuthal correlations with an increasing thermal relaxation rate: while the (nearly) back-to-back correlations among $c\bar c$ pairs are almost completely washed out at low transverse momentum (pT), these correlations at high pT largely survive the pair diffusion. This provides a novel observable for diagnosing the properties of QGP.
Quasinormal modes of charged black holes in Einstein-Maxwell-Weyl gravity
De-Cheng Zou, Chao Wu, Ming Zhang, Ruihong Yue
Published: , doi: 10.1088/1674-1137/44/5/055102
Abstract:
We study quasinormal modes (QNMs) of charged black holes in the Einstein-Maxwell-Weyl (EMW) gravity by adopting the test scalar field perturbation. We find that the imaginary part of QNM frequencies is consistently negative for different angular parameters l, indicating that these modes always decay and are therefore stable. We do not observe a linear relationship between the QNM frequency ω and parameter p for these black holes, as their charge Q causes a nonlinear effect. We evaluate the massive scalar field perturbation in charged black holes and find that random long lived modes (i.e., quasiresonances) could exist in this spectrum.