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2023 No.3 2023 No.2
2023, 47(3): 035104. doi: 10.1088/1674-1137/aca95d
Abstract:
We show that the study of the hidden conformal symmetry that is associated with the Kerr/CFT correspondence can also apply to the cosmological horizon in the Kerr-Newman-Taub-NUT-de Sitter spacetime. This symmetry allows employing some two dimensional conformal field theory methods to understand the properties of the cosmological horizon. The entropy can be understood by using the Cardy formula, and the equation for the scattering process in the near region is in agreement with that obtained from a two point function in the two-dimensional conformal field theory. We also show that pair production can occur near the cosmological horizon in Kerr-Newman-Taub-NUT-de Sitter for near extremal conditions.
2023, 47(3): 035105. doi: 10.1088/1674-1137/aca95e
Abstract:
We study a charged Taub-NUT spacetime solution in the Dvali-Gabadadze-Porrati (DGP) brane. We show that the Reissner-Nordstrom-Taub-NUT-de Sitter solution of Einstein-Maxwell gravity solves the corresponding equations of motion, where the cosmological constant is related to the cross-over scale in the DGP model. Following the approach by Teitelboim in discussing the thermodynamics of de Sitter spacetime and the proposal by Wu et al. for a conserved charge associated with the NUT parameter, we obtain the generalized Smarr mass formula and the first law of thermodynamics of the spacetime.
2023, 47(3): 035103. doi: 10.1088/1674-1137/aca8f3
Abstract:
In this study, we used electromagnetic wave data (H0LiCOW, $H(z)$, SNe) and gravitational wave data (Tianqin) to constrain the interacting dark energy (IDE) model and investigate the Hubble tension and coincidence problems. By combining these four types of data (Tianqin+H0LiCOW+SNe+$H(z)$), we obtained the following parameter values with a confidence interval of $1\sigma$: $\Omega_m=0.36\pm0.18$, $\omega_x=-1.29^{+0.61}_{-0.23}$, $\xi=3.15^{+0.36}_{-1.1}$, and $H_0=70.04\pm $$0.42~ {\rm kms}^{-1}{\rm Mpc}^{-1}. According to our results, the best value of H_0 shows that the Hubble tension problem can be alleviated to some extent. In addition, the center value of \xi+3\omega_x = -0.72^{+2.19}_{-1.19}(1\sigma) indicates that the coincidence problem is slightly alleviated. However, \xi+3\omega_x = 0 is still within the 1\sigma error range, which indicates that the ΛCDM model is still the model in best agreement with the observational data at present. Finally, we compared the constraint results of the electromagnetic and gravitational waves on the model parameters and found that the constraint effect of electromagnetic wave data on model parameters is better than that of simulated Tianqin gravitational wave data. 2023, 47(3): 034003. doi: 10.1088/1674-1137/aca7e2 Abstract: The dissipative dynamics of nuclear fission is a well confirmed phenomenon that can be either described by a Kramers-modified statistical model or by a dynamical model employing the Langevin equation. Although dynamical models as well as statistical models incorporating fission delays have been found to explain the measured fission observables in several studies, they present conflicting results for shell closed nuclei in the mass region of 200. Notably, an analysis of the recent data on neutron shell closed nuclei in the excitation energy range of 40 - 80 MeV failed to provide a satisfactory description of the data, which was attributed to a mismatch with shell effects and/or entrance channel effects, without reaching a definite conclusion. In the present study, we demonstrate that a well established stochastic dynamical code can simultaneously reproduce the available data for pre-scission neutron multiplicities and fission and evaporation residue excitation functions for the following neutron shell closed nuclei ^{210} Po and ^{212} Rn and their isotopes ^{206} Po and ^{214,216} Rn without the need for including any extra shell or entrance channel effects. The relevant calculations are performed by using a phenomenological universal friction form factor with no ad-hoc adjustment of the model parameters. However, we note a significant deviation, beyond experimental errors, for some Fr isotopes. 2023, 47(3): 033001. doi: 10.1088/1674-1137/acac69 Abstract: We report a search for a heavier partner of the recently observed Z_{cs}(3985)^{-} state, denoted as Z_{cs}^{\prime -} , in the process e^{+} e^{-}\rightarrow K^{+}D_{s}^{*-}D^{* 0}+c.c. , based on e^+e^- collision data collected at the center-of-mass energies of \sqrt{s}=4.661 , 4.682 and 4.699 GeV with the BESIII detector. The Z_{cs}^{\prime -} is of interest as it is expected to be a candidate for a hidden-charm and open-strange tetraquark. A partial-reconstruction technique is used to isolate K^+ recoil-mass spectra, which are probed for a potential contribution from Z_{cs}^{\prime -}\to D_{s}^{*-}D^{* 0} ( c.c. ). We find an excess of Z_{cs}^{\prime -}\rightarrow D_{s}^{*-}D^{*0} ( c.c. ) candidates with a significance of 2.1\sigma , after considering systematic uncertainties, at a mass of (4123.5\pm0.7_\mathrm{stat.}\pm4.7_\mathrm{syst.}) \,\mathrm{MeV}/c^2 . As the data set is limited in size, the upper limits are evaluated at the 90% confidence level on the product of the Born cross sections ( \sigma^{\mathrm{Born}} ) and the branching fraction ( \mathcal{B} ) of Z_{cs}^{\prime-}\rightarrow D_{s}^{*-}D^{* 0} , under different assumptions of the Z_{cs}^{\prime -} mass from 4.120 to 4.140 MeV and of the width from 10 to 50 MeV at the three center-of-mass energies. The upper limits of \sigma^{\rm Born}\cdot\mathcal{B} are found to be at the level of \mathcal{O}(1) pb at each energy. Larger data samples are needed to confirm the Z_{cs}^{\prime -} state and clarify its nature in the coming years. 2023, 47(3): 033103. doi: 10.1088/1674-1137/aca1aa Abstract: Within the NRQCD factorization framework, we compute the next-to-leading-order QCD corrections to the gluon fragmentation into the {}^1S_0^{(1,8)} Fock components of a quarkonium, at the lowest order in velocity expansion. We follow the operator definition of the fragmentation function advanced by Collins and Soper. The key technique underpinning our calculation is the sector decomposition method widely used in the area of multi-loop computation. It is found that the NLO QCD corrections have significant effects, and qualitatively modify the profiles of the corresponding leading-order fragmentation functions. 2023, 47(3): 034103. doi: 10.1088/1674-1137/aca467 Abstract: The renormalization of the iterated one-pion exchange (OPE) has been studied in chiral effective field theory (χEFT) for the antinucleon-nucleon ( \overline{N} N ) scattering in some partial waves (Phys. Rev. C 105, 054005 (2022)). In this paper, we go further for the other higher partial waves but with total angular momenta J\leq 3 . Contact interactions are represented by a complex spherical well in the coordinate space. Changing the radius of the spherical well means changing the cutoff. We check the cutoff dependence of the phase shifts, inelasticities, and mixing angles for the partial waves and show that contact interactions are needed at leading order in channels where the singular tensor potentials of OPE are attractive. The results are compared with the energy-dependent partial-wave analysis of \overline{N} N scattering data. Comparisons between our conclusions and applications of χEFT to the nucleon-nucleon system are also discussed. 2023, 47(3): 034104. doi: 10.1088/1674-1137/acac6a Abstract: Using a (3+1)-D hydrodynamic model, CLVisc, we study the directed flow ( v_{1} ) of light hadrons produced in Au+Au, Ru+Ru, and Zr+Zr collisions at \sqrt{s_{NN}}= 200 GeV. The evolution of tilted energy density, pressure gradient, and radial flow along the x-direction is systematically investigated. The counter-clockwise tilt of the initial fireball is shown to be a vital source of directed flow for final light hadrons. A good description of directed flow is provided for light hadrons in central and mid-central Au+Au and isobar collisions at the RHIC. Our numerical results show a clear system size dependence for light hadron v_{1} across different collision systems. We further study the effect of nuclear structure on the directed flow and find that v_{1} for light hadrons is insensitive to nuclei with quadrupole deformation. 2023, 47(3): 034002. doi: 10.1088/1674-1137/aca584 Abstract: The cross sections for neutron-induced nuclear reactions on natural zinc, yttrium, and molybdenum targets were measured at a neutron energy of 14.77 ± 0.17 MeV using the activation technique, offline gamma-ray spectrometry, and a detailed covariance analysis. The uncertainty in the statistical model calculations of cross sections for the (n, 2n), (n, p), (n, α), and (n, γ) reactions with natural zinc, yttrium, and molybdenum at neutron energies from 13 to 17 MeV was calculated using the TALYS-1.96 nuclear code. The measured cross sections of the present study were compared with the experimental cross sections reported in the EXFOR database, the cross sections were calculated with the TALYS-1.96 and EMPIRE-3.2.3 nuclear codes and the evaluated nuclear data from the TENDL-2019, JENDL-5, and ENDF/B-VIII.0 libraries. 2023, 47(3): 033102. doi: 10.1088/1674-1137/aca888 Abstract: Updated measurements from the LHCb and SH0ES collaborations have respectively strengthened the deviations of the ratio R_{K} in rare semi-leptonic B-meson decays and the present-day Hubble parameter H_0 in the Universe, implying tantalizing hints of new physics beyond the standard model. In this paper, we consider a simple flavor-specific two-Higgs-doublet model, where long-standing R_{K^{(*)}} anomalies can be addressed by a one-flavor right-handed neutrino. An intriguing prediction resulting from the parameter space for the R_{K^{(*)}} resolution under flavor- and collider-physics constraints points toward a shift in the effective neutrino number, \Delta N_{\rm eff}=N_{\rm eff}-N_{\rm eff}^{\rm SM}, as a favored way to ease the H_0 tension. Depending on whether the neutrino is of the Dirac or Majorana type, we show that the resulting shift is \Delta N_{\rm eff}\simeq 1.0 for the former case and \Delta N_{\rm eff}\simeq 0.5 for the latter case. While the Dirac case is disfavored by the CMB polarization measurements, the Majorana solution is consistent with recent studies using a combined dataset from various sources. Consequently, such a simple flavor-specific two-Higgs-doublet model provides a link between R_{K^{(*)}} anomalies and H_0 tension, which in turn can be readily verified or disproved by upcoming measurements. 2023, 47(3): 034102. doi: 10.1088/1674-1137/aca8f2 Abstract: We explore the deuteron under strong magnetic fields in Skyrme models. The effects of the derivative dependent sextic term in the Skyrme Lagrangian are investigated, and the rational map approximation is used to describe the deuteron. The influences of strong magnetic fields on the electric charge distribution and mass of the deuteron are discussed. 2023, 47(3): 033101. doi: 10.1088/1674-1137/aca8f6 Abstract: As one of the key properties of the Higgs boson, the Higgs total width is sensitive to the global profile of the Higgs boson couplings, and thus new physics would modify the Higgs width. We investigate the total width in various new physics models, including various scalar extensions, composite Higgs models, and the fraternal twin Higgs model. Typically, the Higgs width is smaller than the standard model value due to mixture with other scalars if the Higgs is elementary, or curved Higgs field space for the composite Higgs. On the other hand, except for the possible invisible decay mode, the enhanced Yukawa coupling in the two Higgs doublet model or the exotic fermion embeddings in the composite Higgs could enhance the Higgs width greatly. The precision measurement of the Higgs total width at the high-luminosity LHC can be used to discriminate certain new physics models. 2023, 47(3): 034101. doi: 10.1088/1674-1137/aca5f5 Abstract: Exploration of the QCD phase diagram and critical point is one of the main goals in current relativistic heavy-ion collisions. The QCD critical point is expected to belong to a three-dimensional (3D) Ising universality class. Machine learning techniques are found to be powerful in distinguishing different phases of matter and provide a new way to study the phase diagram. We investigate phase transitions in the 3D cubic Ising model using supervised learning methods. It is found that a 3D convolutional neural network can be trained to effectively predict physical quantities in different spin configurations. With a uniform neural network architecture, it can encode phases of matter and identify both second- and first-order phase transitions. The important features that discriminate different phases in the classification processes are investigated. These findings can help study and understand QCD phase transitions in relativistic heavy-ion collisions. 2023, 47(3): 035101. doi: 10.1088/1674-1137/aca468 Abstract: Following the holographic principle, which suggests that the energy density of dark energy may be inversely proportional to the area of the event horizon of the Universe, we propose a new energy density of dark energy through the acceleration of the particle horizon scaled by the length of this parameter. The proposed model depends only on one free parameter: \beta \approx 0-1.99 . For values of \beta near zero, the deviation between the proposed model and the \mathrm{\Lambda } CDM model is significant, while for \beta \to 1.99 , the suggested model has no conflict with the \mathrm{\Lambda } CDM theory. Regardless of the value of \beta , the model considers dark energy to behave as matter with positive pressure in high redshifts, {\omega }_{X}\approx 0.33 , while for present and near-future Universe, it is considered to behave similar to that in the cosmological constant model and phantom field. Comparing the model with the Ricci dark energy model, we show that our model reduces the errors of the Ricci dark energy model concerning the calculation of the age of old supernovae and evolution of different cosmic components in high redshifts. Moreover, we calculated matter structure formation parameters such as the CMB temperature and matter power spectrum of the model to consider the effects of matter-like dark energy during the matter-dominated era. 2023, 47(2): 024107. doi: 10.1088/1674-1137/aca64f Abstract: Heavy quark observables are applied to probe the initial energy density distribution with violation of longitudinal boost invariance produced in relativistic heavy-ion collisions. Using an improved Langevin model coupled to a (3+1)-dimensional viscous hydrodynamic model, we study the nuclear modification factor (R_{AA}) and directed flow ( v_1 ) and elliptic flow ( v_2 ) coefficients of heavy mesons and their decayed electrons at an RHIC energy. We find that the counter-clockwise tilt of nuclear matter in the reaction plane results in a positive (negative) heavy flavor v_1 in the backward (forward) rapidity region, whose magnitude increases with the heavy quark transverse momentum. The difference in the heavy flavor R_{AA} between different angular regions is also proposed as a complementary tool to characterize the asymmetry of the medium profile. Our model results are consistent with currently available data at the RHIC and provide predictions that can be tested by future measurements. 2023, 47(2): 023109. doi: 10.1088/1674-1137/aca465 Abstract: Dimuon events induced by charm-quark productions from neutrino deep inelastic scattering (DIS) processes have been studied in traditional DIS experiments for decades. The recent progress in neutrino telescopes makes it possible to search for such dimuon events at energies far beyond the laboratory scale. In this study, we construct a simulation framework to calculate yields and distributions of dimuon signals in an IceCube-like km3 scale neutrino telescope. Owing to the experimental limitation in the resolution of double-track lateral distance, only dimuons produced outside the detector volume are considered. Detailed information about simulation results for a 10-year exposure is presented. As an earlier paper[Physical Review D 105, 093005 (2022)] and ours report on a similar situation, we use that paper as a baseline to conduct comparisons. We then estimate the impacts of different calculation methods of muon energy losses. Finally, we study the experimental potential of dimuon searches under the hypothesis of single-muon background only. Our results based on a simplified double-track reconstruction indicate a moderate sensitivity, especially with the ORCA configuration. Further developments on both the reconstruction algorithm and possible detector designs are thus required and are under investigation. 2023, 47(2): 024106. doi: 10.1088/1674-1137/aca4c1 Abstract: Jet quenching has successfully served as a hard probe to study the properties of Quark-Gluon Plasma (QGP). As a multi-particle system, jets require time to develop from a highly virtual parton to a group of partons close to mass shells. In this study, we present a systematical analysis on the effects of this formation time on jet quenching in relativistic nuclear collisions. Jets from initial hard scatterings were simulated with Pythia, and their interactions with QGP were described using a Linear Boltzmann Transport (LBT) model that incorporates both elastic and inelastic scatterings between jet partons and the thermal medium. Three different estimations of the jet formation time were implemented and compared, including instantaneous formation, formation from single splitting, and formation from sequential splittings, before which no jet-medium interaction was assumed. We found that deferring the jet-medium interaction with a longer formation time not only affects the overall magnitude of the nuclear modification factor of jets but also its dependence on the jet transverse momentum. 2023, 47(2): 024108. doi: 10.1088/1674-1137/ac988a Abstract: We study the baryon-baryon interactions with strangeness S = -2 and corresponding momentum correlation functions in leading order covariant chiral effective field theory. The relevant low energy constants are determined by fitting to the latest HAL QCD simulations, taking into account all the coupled channels. Extrapolating the so-obtained strong interactions to the physical point and considering both quantum statistical effects and the Coulomb interaction, we calculate the \Lambda\Lambda and \Xi^-p correlation functions with a spherical Gaussian source and compare them with recent experimental data. We find a good agreement between our predictions and the experimental measurements by using the source radius determined in proton-proton correlations, which demonstrates the consistency between theory, experiment, and lattice QCD simulations. Moreover, we predict the \Sigma^+\Sigma^+ , \Sigma^+\Lambda , and \Sigma^+\Sigma^- interactions and corresponding momentum correlation functions. We further investigate the influence of the source shape and size of the hadron pair on the correlation functions studied and show that the current data are not very sensitive to the source shape. Future experimental measurements of the predicted momentum correlation functions will provide a non-trivial test of not only SU(3) flavor symmetry and its breaking but also the baryon-baryon interactions derived in covariant chiral effective field theory. 2023, 47(2): 023108. doi: 10.1088/1674-1137/aca4c2 Abstract: A measurement of the Z production cross-section in \gamma e^{-} collisions at the Large Hadron-electron Collider (LHeC) is presented for comparison to that at the International Linear Collider (ILC). The total cross-section depends strongly on the polarization of the initial and final e^{-} beams and the electron beam energy E_{e} ; the energy of the proton beam was set to E_{p} = 7 TeV. The results show that the total cross-section in \gamma e^{-} \rightarrow Z e^{-} \rightarrow l^{-}l^{+}e^{-} at the LHeC is much larger than that at the ILC. 2023, 47(2): 023107. doi: 10.1088/1674-1137/aca585 Abstract: The W boson mass recently reported by the CDF collaboration shows a deviation from the standard model prediction with an excess at the 7\sigma level. We investigate two simple extensions of the standard model with an extra U(1) dark sector. One is the U(1)_x extension, where the U(1)_x gauge field mixes with the standard model through gauge kinetic terms. The other is a general U(1)_{\mathbf{A} Y+\mathbf{B} q} extension of the standard model. Fitting various experimental constraints, we find that the U(1)_x extension with only kinetic mixing can enhance the W boson mass by 10 MeV at most. The U(1)_{\mathbf{A} Y+\mathbf{B} q} extension can easily generate a 77 MeV enhancement of the W boson mass and also offer a viable dark matter candidate with a mass ranging from several hundred GeV to TeV, which may be detected by future dark matter direct detection experiments with improved sensitivities. 2023, 47(2): 024002. doi: 10.1088/1674-1137/ac9e9b Abstract: The reaction cross-sections of 238U (n, γ)239U have been experimentally determined at neutron energies of 6.117 ± 0.119 MeV, 4.626 ± 0.086 MeV, and 3.622 ± 0.348 MeV employing the relative activation approach along with the off-line γ-ray spectroscopy method. The D (d, n)3He reaction was utilized to obtain monoenergetic neutrons of the required energy, and the 197Au (n, γ)198Au reaction cross-sections were adopted as the referential standard to ascertain the neutron capture cross-sections of 238U. Furthermore, the effects of low-energy scattered neutrons, neutron fluence fluctuations, counting of geometric corrections when measuring γ-rays, and neutron and γ-ray self-absorption caused by the sample thickness have been considered and revised in the present work. For a comparison with experimental results, the cross-sections of the 238U (n, γ)239U reaction were calculated theoretically with the original parametric TALYS-1.9 program. The experimental measurements were in contrast to previous experimental results and the evaluation data available for ROSFOND-2010, CENDL-3.2 and ENDF/B-VIII.0. 2023, 47(2): 024104. doi: 10.1088/1674-1137/ac9e4b Abstract: An analysis of the breakup of the ^{31}{\rm Ne} weakly-bound neutron-halo system on a lead target is presented, considering the 2p_{3/2} and 1f_{7/2} ground-state configurations. It is shown that a high centrifugal barrier almost wipes out the breakup channel, thus assimilating the breakup of a weakly-bound system to that of a tightly-bound system, and also reduces the range of the monopole nuclear potential. Consequently, a high centrifugal barrier prevents the suppression of the Coulomb-nuclear interference (CNI) peak by weakening couplings to the breakup channel and reducing the range of the monopole nuclear potential, two main factors that would otherwise suppress such a peak. The present study also identifies couplings to the breakup channel and a long-ranged monopole nuclear potential as the main factors that lead to the suppression of the CNI peak. A low centrifugal barrier together with a Coulomb barrier would also effectively prevent the suppression of the CNI peak in proton-halos as reported in the case of the ^8{\rm B} proton-halo. 2023, 47(2): 025105. doi: 10.1088/1674-1137/ac9fba Abstract: In this study, we investigate the effect of nonlinear electrodynamics on the shadows of charged, slowly rotating black holes with the presence of a cosmological constant. Rather than the null geodesic of the background black hole spacetime, the trajectory of a photon, as a perturbation of the nonlinear electrodynamic field, is governed by an effective metric. The latter can be derived by analyzing the propagation of a discontinuity of the electromagnetic waveform. Subsequently, the image of the black hole and its shadow can be evaluated using the backward ray-tracing technique. We explore the properties of the resultant black hole shadows of two different scenarios of nonlinear electrodynamics, namely, the logarithmic and exponential forms. In particular, the effects of nonlinear electrodynamics on the optical image are investigated, as well as the image's dependence on other metric parameters, such as the black hole spin and charge. The resulting black hole image and shadow display rich features that potentially lead to observational implications. 2023, 47(2): 024105. doi: 10.1088/1674-1137/ac9fb8 Abstract: In relativistic heavy ion collisions, the fluctuations of initial entropy density convert to the correlations of final state hadrons in momentum space through the collective expansion of strongly interacting QCD matter. Using a (3+1)D viscous hydrodynamic program, CLVisc, we consider whether the nuclear structure, which provides initial state fluctuations as well as correlations, can affect the final state of heavy ion collisions, and whether one can find signals of α cluster structures in oxygen using final state observables in ^{16}\text{O}+{}^{16}\text{O} collisions at the CERN Large Hadron Collider. For the initial nucleon distributions in oxygen nuclei, we compare three different configurations, a tetrahedral structure with four-α clusters, the deformed Woods-Saxon distribution, and a spherical symmetric Woods-Saxon distribution. Our results show that the charged multiplicity as a function of centrality and the elliptic flow at the most central collisions using the four-α structure differs from those with the Woods-Saxon and deformed Woods-Saxon distributions, which may help to identify α clustering structures in oxygen nuclei. 2023, 47(2): 023106. doi: 10.1088/1674-1137/aca466 Abstract: The nonlocal chiral effective theory is applied to investigate the electromagnetic and strange form factors of nucleons. The bubble and tadpole diagrams are included in the calculation. With the contributions from bubble and tadpole diagrams, the obtained electromagnetic form factors are close to the results without these contributions as long as the low energy constants c_1 and c_2 are properly chosen, while the magnitudes of strange form factors become larger. The electromagnetic form factors are in good agreement with the experimental results, while the magnitudes of strange form factors are larger than the lattice data. 2023, 47(2): 025102. doi: 10.1088/1674-1137/ac9fbb Abstract: In this study, the gravitational deflection angle of photons in the weak field limit (or the weak deflection angle) and shadow cast by the electrically charged and spherically symmetric static Kiselev black hole (BH) in the string cloud background are investigated. The influences of the BH charge Q, quintessence parameter γ, and string cloud parameter a on the weak deflection angle are studied using the Gauss-Bonnet theorem, in addition to studying the influences on the radius of photon spheres and size of the BH shadow in the spacetime geometry of the charged-Kiselev BH in string clouds. Moreover, we study the effects of plasma (uniform and non-uniform) on the weak deflection angle and shadow cast by the charged-Kiselev BH surrounded by the clouds of strings. In the presence of a uniform/nonuniform plasma medium, an increase in the string cloud parameter a increases the deflection angle α. In contrast, a decrease in the BH charge Q decreases the deflection angle. Further, we observe that an increase in the BH charge Q causes a decrease in the size of the shadow of the BH. We notice that, with an increase in the values of the parameters γ and a, the size of the BH shadow increases, and therefore, the intensity of the gravitational field around the charged-Kiselev BH in string clouds increases. Thus, the gravitational field of the charged-Kiselev BH in the string cloud background is stronger than the field produced by the pure Reissner-Nordstrom BH. Moreover, we use the data released by the Event Horizon Telescope (EHT) collaboration, for the supermassive BHs M87* and Sgr A*, to obtain constraints on the values of the parameters γ and a. 2023, 47(2): 025103. doi: 10.1088/1674-1137/aca07c Abstract: We use the monodromy method to investigate the asymptotic quasinormal modes of regular black holes based on the explicit Stokes portraits. We find that, for regular black holes with spherical symmetry and a single shape function, the analytical forms of the asymptotic frequency spectrum are not universal and do not depend on the multipole number but on the presence of complex singularities and the trajectory of asymptotic solutions along the Stokes lines. 2023, 47(2): 025104. doi: 10.1088/1674-1137/aca4bc Abstract: By analyzing the propagation of discontinuity in nonlinear electrodynamics, we numerically investigate the related black hole shadows of recently derived rotating black hole solutions in f(R) gravity. In this context, the geodesic motion of the relevant perturbations is governed by an effective geometry, which is closely related to the underlying spacetime metric. We derive the effective geometry, and the latter is used to determine the trajectory of the propagation vector of an arbitrary finite discontinuity in the electrodynamic perturbations, namely, the photon. Subsequently, the image of the black hole is evaluated using the ray-tracing technique. Moreover, we discuss the physical relevance of metric parameters, such as the nonlinear coupling, spin, and charge, by studying their impact on the resultant black hole shadows. 2023, 47(2): 024103. doi: 10.1088/1674-1137/aca38d Abstract: In this study, we perform Tsallis Blast-Wave analysis on the transverse momentum spectra of identified hadrons produced in a wide range of collision systems at the Large Hadron Collider (LHC) including pp, pPb, XeXe, and PbPb collisions. The kinetic freeze-out properties varying with event multiplicity are investigated across these systems. We find that the extracted kinetic freeze-out temperature, radial flow velocity, and non-extensive parameter exhibit a universal scaling behavior for these systems with very different geometric sizes, especially when the independent baryon Tsallis non-extensive parameter is considered. This universality may indicate the existence of a unified partonic evolution stage in different collision systems at the LHC energies. 2023, 47(2): 024102. doi: 10.1088/1674-1137/aca38e Abstract: The charge exchange spin-dipole (SD) excitations of ^{90} Zr are studied using the Skyrme Hartee-Fock plus proton-neutron random phase approximation with SAMi-J interactions. The experimental value of the model-independent sum rule obtained from the SD strength distributions of ^{90} Zr(p, n) ^{90} Nb and ^{90} Zr(n, p) ^{90} Y is used to deduce the neutron skin thickness. The neutron skin thickness \Delta r_{np} of ^{90} Zr is extracted as 0.083\pm0.032 fm, which is similar to the results of other studies. Based on the correlation analysis of the neutron skin thickness \Delta r_{np} and the nuclear symmetry energy J as well as its slope parameter L, a constraint from the extracted \Delta r_{np} leads to the limitation of J to 29.2 \pm 2.6 MeV and L to 53.3 \pm 28.2 MeV. 2023, 47(2): 023105. doi: 10.1088/1674-1137/aca200 Abstract: We present a general method of constructing unfactorizable on-shell amplitudes (amplitude basis) and build up their one-to-one correspondence to the independent and complete operator basis in effective field theory (EFT). We apply our method to the Standard Model EFT and identify the amplitude basis in dimensions 5 and 6, which correspond to the Weinberg operator and operators in the Warsaw basis, except for some linear combinations. 2023, 47(2): 023001. doi: 10.1088/1674-1137/ac9d29 Abstract: Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb ^{-1} , collected by the BESIII detector in the energy region between 4599.53\; \,{\rm{MeV}} and 4698.82\; \,{\rm{MeV}} , we report the first observations of the Cabibbo-suppressed decays \Lambda_c^+\to n\pi^+\pi^0 , \Lambda_c^+\to n\pi^+\pi^-\pi^+ , and the Cabibbo-favored decay \Lambda_c^+\to nK^-\pi^+\pi^+ with statistical significances of 7.9\sigma , 7.8\sigma , and >10\sigma , respectively. The branching fractions of these decays are measured to be \mathcal{B}(\Lambda_{c}^{+}\rightarrow n\pi^{+}\pi^{0})=(0.64\pm0.09\pm0.02)%, \mathcal{B}(\Lambda_{c}^{+}\rightarrow n\pi^{+}\pi^{-}\pi^{+})=(0.45\pm 0.07\pm$$ 0.03)$%, and $\mathcal{B}(\Lambda_{c}^{+}\rightarrow nK^{-}\pi^{+}\pi^{+})=(1.90\pm0.08\pm0.09)$%, where the first uncertainties are statistical and the second are systematic. We find that the branching fraction of the decay $\Lambda_{c}^{+}\rightarrow n\pi^{+}\pi^{0}$ is about one order of magnitude higher than that of $\Lambda_{c}^{+}\rightarrow n\pi^{+}$.
2023, 47(2): 024101. doi: 10.1088/1674-1137/ac9f0a
Abstract:
This study considers a principal possibility of creating a nuclear light source of the vacuum ultra violet (VUV) range based on the $^{229}$Th nucleus. This nuclear light source can help solve two main problems — excitation of the low-lying $^{229m}$Th isomer and precision measurement of the nuclear isomeric transition energy. The thorium nuclear light source is based on the nuclei implanted in a thin dielectric film with a large bandgap. While passing an electric current through the sample, the $^{229}$Th nuclei are excited to the low energy isomeric state $3/2^+(8.19\pm0.12$ eV) through the process of inelastic scattering of conduction electrons. The subsequent spontaneous decay of $^{229m}$Th is followed by the emission of γ quanta in the VUV range. The luminosity of the thorium nuclear light source is approximately $10^5$ photons/s per 1 A of current, per 1 ng of $^{229}$Th. The suggested scheme to obtain γ radiation from the $^{229m}$Th isomer can be considered as a type of nuclear analogue of the optical radiation from the usual metal-insulator-semiconductor (MIS) junction.
2023, 47(2): 023104. doi: 10.1088/1674-1137/aca38f
Abstract:
Using the perturbative QCD approach, we studied the effects of the hadronic structure of photons on the pure annihilation rediative decays $B\to\phi\gamma$ and $B_s\to(\rho^0,\omega)\gamma$. These decays have small branching fractions due to the power suppression by $\Lambda/m_B$, which makes them very sensitive to next-leading power corrections. The quark components and the related two-particle distribution amplitudes of a final state photon are introduced. The branching fractions can be enhanced remarkably by factorizable and nonfactorizable emission diagrams. The branching fraction of $B\to \phi\gamma$ increases by approximately 40 times, and those of $B_s \to \rho^0\gamma$ and $B_s \to \omega\gamma$ are on the order of ${\cal O}(10^{-10})$. We also note that the ratio of branching fractions of $B_s \to \rho^0\gamma$ and $B_s \to \omega\gamma$ is very sensitive to the effects of the hadronic structure of photons. All these results can be tested in future.
2023, 47(2): 023101. doi: 10.1088/1674-1137/ac9dea
Abstract:
The decay constants of the low lying S-wave $B_c$ mesons, i.e. $B_c(nS)$ and $B^*_c(nS)$ with $n\leq 3$, are calculated in the nonrelativistic quark model. The running coupling of the strong interaction is taken into account, and the uncertainties due to varying parameters and losing Lorentz covariance are considered carefully. As a byproduct, the decay constants of the low lying S-wave charmonium and bottomium states are given in the appendixes.
2023, 47(2): 024001. doi: 10.1088/1674-1137/aca1ab
Abstract:
The fission yield data in the 14 MeV energy neutron induced fission of 238U play an important role in decay heat calculations and generation-IV reactor designs. In order to accurately measure fission product yields (FPYs) of 238U induced by 14 MeV neutrons, the cumulative yields of fission products ranging from 92Sr to 147Nd in the 238U(n, f) reaction with a 14.7 MeV neutron were determined using an off-line γ-ray spectrometric technique. The 14.7 MeV quasi-monoenergetic neutron beam was provided by the K-400 D-T neutron generator at China Academy of Engineering Physics (CAEP). Fission products were measured by a low background high purity germanium gamma spectrometer. The neutron flux was obtained from the 93Nb (n, 2n)92mNb reaction, and the mean neutron energy was calculated using the cross-section ratios for the 90Zr(n, 2n)89Zr and 93Nb(n, 2n)92mNb reactions. With a series of corrections, high precision cumulative yields of 20 fission products were obtained. Our FPYs for the 238U(n, f) reaction at 14.7 MeV were compared with the existing experimental nuclear reaction data and evaluated nuclear data, respectively. The results will be helpful in the design of a generation-IV reactor and the construction of evaluated fission yield databases.
2023, 47(2): 025101. doi: 10.1088/1674-1137/ac9fbe
Abstract:
The objective of this work is to generate a general formalism of $f(\bar{R}, L(X))-$gravity in the context of dark energy under the framework of K-essence emergent geometry with the Dirac-Born-Infeld (DBI) variety of action, where $\bar{R}$ is the familiar Ricci scalar, $L(X)$ is the DBI type non-canonical Lagrangian with $X={1\over 2}g^{\mu\nu}\nabla_{\mu}\phi\nabla_{\nu}\phi$, and ϕ is the K-essence scalar field. The emergent gravity metric (${\bar{G}}_{\mu\nu}$) and the well known gravitational metric ($g_{\mu\nu}$) are not conformally equivalent. We have constructed a modified field equation using the metric formalism in $f(\bar{R}, L(X))$-gravity incorporating the corresponding Friedmann equations into the framework of the background gravitational metric, which is of Friedmann-Lemaître-Robertson-Walker (FLRW) type. The solution of the modified Friedmann equations have been deduced for the specific choice of $f(\bar{R}, L(X))$, which is of Starobinsky-type, using the power law expansion method. The consistency of the model with the accelerating phase of the universe has been shown when we restrict ourselves to consider the value of the dark energy density as $\dot\phi^{2}=8/9=0.888 < 1$, which indicates that the present universe is dark-energy dominated. Graphical plots for the energy density (ρ), pressure (p), and equation of state parameter (${\omega}$) with respect to (w.r.t.) time (t) based on parametric values are interestingly consistent with the dark energy domination theory, and hence the accelerating features. We also highlight the corresponding energy conditions and constraints of the $f(\bar{R}, L(X))$ theory with a basic example.
2023, 47(2): 023103. doi: 10.1088/1674-1137/ac9fbd
Abstract:
By solving two body Dirac equations with potentials at finite temperature, we calculate the dissociation temperature $T_d$ of $B_c$ mesons in quark-gluon plasma. It is found that $T_d$ becomes higher with the relativistic correction than the $T_d$ from the Schrödinger equation. Both the short range interaction and the constant term of the potential at the long-range scale have a contribution to the shift of $T_d$, while the spin interaction is negligible.
2023, 47(2): 023102. doi: 10.1088/1674-1137/ac9de9
Abstract:
Recently, some progress has been made in the experiments on double-heavy tetraquarks, such as $T_{cc}$ reported by the LHCb Collaboration and $X_{cc\bar{s}\bar{s}}$ reported by the Belle Collaboration. Coming on the heels of our previous work about $T_{cc}$ and $T_{bb}$, we present a study on the bound and resonance states of their companions, $QQ\bar{q}\bar{s}$ ($Q=c,b; q=u, s$) tetraquarks with strange flavor in the chiral quark model. Two pictures, meson-meson and diquark-antidiquark ones, and their couplings were considered in our calculations. Isospin violation was neglected herein. Our numerical analysis indicated that the states $cc\bar{u}\bar{s}$ with $\dfrac{1}{2}(1^+)$ and $bb\bar{u}\bar{s}$ with $\dfrac{1}{2}(1^+)$ are the most promising stable states against strong interactions. Besides, we found several resonance states for the double-heavy strange tetraquarks with the real scaling method.