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The effect of hadronic scatterings on the measurement of vector meson spin alignments in heavy-ion collisions
Diyu Shen, Jinhui Chen, Zi-Wei Lin
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Spin alignments of vector mesons and hyperons in relativistic heavy-ion collisions have been proposed as signals of the global polarization. The STAR experiment first observed the \begin{document}$ \Lambda$\end{document} polarization. Recently, the ALICE collaboration measured the transverse momentum (\begin{document}$p_T$\end{document}) and the collision centrality dependence of \begin{document}$K^*$\end{document} and \begin{document}$\phi$\end{document} spin alignments in Pb-Pb collisions at \begin{document}$\sqrt {{{\rm{s}}_{{\rm{NN}}}}} $\end{document} = 2.76 TeV. A large signal is observed in the low \begin{document}$p_T$\end{document} region of mid-central collisions for \begin{document}$K^*$\end{document} while the signal is much smaller for \begin{document}$\phi$\end{document}, and these have not been understood yet. Since vector mesons have different lifetimes and their decay products have different scattering cross sections, they suffer from different hadronic effects. In this paper, we study the effect of hadronic interactions on the spin alignment of \begin{document}$K^*$\end{document}, \begin{document}$\phi$\end{document} and \begin{document}$\rho$\end{document} mesons in relativistic heavy-ion collisions with a multi-phase transport model. We find that hadronic scatterings lead to a deviation of the observed spin alignment matrix element \begin{document}$\rho_{00}$\end{document} away from the true value for \begin{document}$\rho$\end{document} and \begin{document}$K^*$\end{document} mesons (with a bigger effect on \begin{document}$\rho$\end{document}) while the effect is negligible for the \begin{document}$\phi$\end{document} meson. The effect depends on the kinematic acceptance: the observed \begin{document}$\rho_{00}$\end{document} value is lower than the true value when the pseudorapidity (\begin{document}$\eta$\end{document}) coverage is small while there is little effect when the \begin{document}$\eta$\end{document} coverage is big. Our study thus provides valuable information to understand the vector meson spin alignment signals observed in the experiments.
Categorization of two-loop Feynman diagrams in the $ {\cal O}(\alpha^2) $ correction to $ e^+e^- \rightarrow ZH $
Zhao Li, Yefan Wang, Quan-feng Wu
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The \begin{document}$ e^+e^- \rightarrow ZH $\end{document} process is the dominant process for the Higgs boson production at the future Higgs factory. In order to match the analysis on the Higgs properties with the highly precise experiment data, it will be crucial to include the theoretical prediction to the full next-to-next-to-leading order electroweak effect in the production rate \begin{document}$ \sigma(e^+e^-\rightarrow ZH) $\end{document}. In this inspiring work, we categorize the two-loop Feynman diagrams of the \begin{document}$ {\cal O}(\alpha^2) $\end{document} correction to \begin{document}$ e^+e^- \rightarrow ZH $\end{document} into 6 categories according to the relevant topological structures. Although 25377 diagrams contribute to the \begin{document}$ {\cal O}(\alpha^2) $\end{document} correction in total, the number of the most challenging diagrams with seven denominators is 2250, which contain only 312 non-planar diagrams with 155 independent types. This categorization could be a valuable reference for the complete calculation in the future.
Properties of Pc(4312) pentaquark and its bottom partner
K. Azizi, Y. Sarac, H. Sundu
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We present an analysis of the newly observed pentaquark \begin{document}$P_c(4312)^+$\end{document} to enlighten its quantum numbers. To do that, the QCD sum rule approach is used. The measured mass of this particle is close to \begin{document}$\Sigma_c^{++}\bar{D}^-$\end{document} threshold and has a small width, and this supports its possibility of being a molecular state. We consider an interpolating current in a molecular form and analyze both the positive and negative parity states with spin- \begin{document}$\dfrac{1}{2}$\end{document} . We also consider the bottom counterpart of the state with similar molecular form. Our mass result for the charm pentaquark state supports that, the quantum numbers of the observed state is consistent with \begin{document}$J^P=\dfrac{1}{2}^{-}$\end{document} .
Bardeen black hole surrounded by perfect fluid dark matter
He-Xu Zhang, Yuan Chen, Tian-Chi Ma, Peng-Zhang He, Jian-Bo Deng
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We derive an exact solution of the spherically symmetric Bardeen black hole surrounded by perfect fluid dark matter (PFDM). By treating the magnetic charge g and dark matter parameter \begin{document}$\alpha$\end{document} as thermodynamic variables, we find that the thermodynamic first law and the corresponding Smarr formula are satisfied. The thermodynamic stability of the black hole is also studied. The result show that, there exists a critical radius \begin{document}$r_{+}^{C}$\end{document}, where the heat capacity diverges, suggesting that the black hole is thermodynamically stable in the range \begin{document}$0<r_{+}<r_{+}^{C}$\end{document}. In addition, the critical radius \begin{document}$r_{+}^{C}$\end{document} increases with the magnetic charge g and decreases with the dark matter parameter \begin{document}$\alpha$\end{document}. Applying the Newman-Janis algorithm, we generalize the spherically symmetric solution to the corresponding rotating black hole. With the metric at hand, the horizons and ergospheres are studied. It turns out that for a fixed dark matter parameter \begin{document}$\alpha$\end{document}, in a certain range, with the increase of the rotation parameter a and magnetic charge g, the Cauchy horizon radius increases while the event horizon radius decreases. Finally, we investigate the energy extraction by the Penrose process in rotating Bardeen black hole surrounded by PFDM.
Simulation of the neutron-tagged deep inelastic scattering at EicC
Gang Xie, Meng-Yang Li, Cheng-Dong Han, Rong Wang, Xu-Rong CHEN
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Measuring the pionic structure function is of high interests as it provides a new area for understanding the strong interaction among quarks and testing the QCD predictions. To this purpose, we investigate the feasibility and the expected impacts of a possible experiment on EicC. We show the simulation results on the statistical precision of an EicC measurement, based on the model of leading neutron tagged DIS process and the parton distribution functions of the pion from JAM18 global analysis. The simulation shows that at EicC, the kinematics cover \begin{document}$x_{\pi}$\end{document} range from 0.01 to 1, and \begin{document}$Q^2$\end{document} range from 1 GeV\begin{document}$^2$\end{document} to 50 GeV\begin{document}$^2$\end{document}, within the acceptable statistical uncertainty. Assuming an integrated luminosity of 50 fb\begin{document}$^{-1}$\end{document}, in the low-\begin{document}$Q^{2}$\end{document} region (\begin{document}$<10$\end{document} GeV\begin{document}$^2$\end{document}), the MC data show that the suggested measurement in the whole \begin{document}$x_{\rm{\pi}}$\end{document} range reaches very high precision (\begin{document}$<3$\end{document}%). To perform such an experiment, only the addition of a far-forward neutron calorimeter is needed.
Renormalizability of leading order covariant chiral nucleon-nucleon interaction
Chun-Xuan Wang, Li-Sheng Geng, Bingwei Long
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In this work, we study renormalization group invariance of the recently proposed covariant power counting in the case of nucleon-nucleon scattering [Chin.Phys. C42 (2018) 014103] at leading order. We show that unlike the Weinberg scheme, renormalizaion group invariance is satisfied in the \begin{document}$^3P_{0}$\end{document} channel. Another interesting feature is that the \begin{document}$^1S_{0}$\end{document} and \begin{document}$^3P_{1}$\end{document} channels are correlated. Fixing the relevant low energy constants by fitting to the \begin{document}$^1S_{0}$\end{document} phase shifts at \begin{document}$T_\mathrm{lab.}=10$\end{document} and 25 MeV with cutoff values \begin{document}$\Lambda = 400-650$\end{document} MeV, one can describe the \begin{document}$^3P_{1}$\end{document} phase shifts relatively well. In the limit of \begin{document}$\Lambda\rightarrow \infty$\end{document}, the \begin{document}$^1S_0$\end{document} phase shifts become cutoff independent, whereas the \begin{document}$^3P_{1}$\end{document} phase shifts do not. This is consistent with the Wigner bound and previous observations that the \begin{document}$^{3}P_1$\end{document} channel better be treated perturbatively. As for the \begin{document}$^1P_{1}$\end{document} and \begin{document}$^3S_{1}$\end{document}-\begin{document}$^3D_{1}$\end{document} channels, renormalization group invariance is satisfied.
The collisional Penrose process of 4D rotational Einstein-Gauss-Bonnet black holes
Yunlong Liu, Xiangdong Zhang
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The collisional Penrose process of massive spinning particles in the rotational Einstein-Gauss-Bonnet (EGB) black hole background is studied. By numerically solving the equations of motion for spinning particles, we find that the energy extraction efficiency increase with the decrease of the EGB coupling parameter \begin{document}$ \alpha$\end{document} monotonically. Moreover, the efficiency \begin{document}$ \eta$\end{document} increases as the particle's spin s growing. Besides, we also find that the energy extraction efficiency increases with the decreases of the EGB coupling parameter \begin{document}$ \alpha$\end{document}. When the EGB coupling constant \begin{document}$ \alpha=0$\end{document}, our results reduce to the Kerr case which has been investigated previously.
Nucleon-pair approximation with uncoupled representation
Y. Lei, Y. Lu, Y. M. Zhao
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In this paper, we propose an approach of the nucleon-pair approximation (NPA) with m-scheme basis, in which the collective nucleon pairs are represented in terms of antisymmetric matrices, and commutations between nucleon pairs are given by using matrix multiplication that avoids angular-momentum couplings and recouplings. Therefore the present approach significantly simplifies the NPA computation. Furthermore, it is formulated on the same footing with and without isospin.
Temporal and spatial chaos in the Kerr-AdS black hole in an extended phase space
Bing Tang
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Based on the Melnikov method, we investigate chaotic behaviors in the extended thermodynamic phase space for a slowly rotating Kerr-AdS black hole under temporal and spatial perturbations. Our results show that the temporal perturbation coming from a thermal quench of the spinodal region in the phase diagram may cause the temporal chaos only when the perturbation amplitude is above a critical value, which involves the angular momentum J. Under the spatial perturbation, however, it is found that the spatial chaos always occurs, which is independent of the perturbation amplitude.
Production of the bottomonium-like Zb states in e-h and ultraperipheral h-h collisions
Xiao-Yun Wang, Wei Kou, Qing-Yong Lin, Ya-Ping Xie, Xurong Chen, Alexey Guskov
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The photoproduction of bottomonium-like states \begin{document}$ Z_{b}(10610) $\end{document} and \begin{document}$ Z_{b}(10650) $\end{document} via \begin{document}$ \gamma p $\end{document} scattering is studied within an effective Lagrangian approach and the vector-meson-dominance model. The Regge model is employed to calculate the photoproduction of \begin{document}$ Z_{b} $\end{document} states via t-channel with \begin{document}$ \pi $\end{document} exchange. The numerical results show that the values of the total cross-sections of \begin{document}$ Z_{b}(10610) $\end{document} and \begin{document}$ Z_{b}(10650) $\end{document} can reach 0.09 nb and 0.02 nb, respectively, near the center of mass energy of 22 GeV. The experimental measurements and studies on the photoproduction of \begin{document}$ Z_{b} $\end{document} states near energy region around \begin{document}$ W\simeq 22 $\end{document} GeV is suggested. Moreover, with the help of eSTARlight and STARlight programs, one obtains the cross-sections and event numbers of \begin{document}$ Z_{b}(10610) $\end{document} production in electron-ion collision (EIC) and Ultraperipheral collisions (UPCs). The results show that a considerable number of events from \begin{document}$ Z_{b}(10610) $\end{document} can be produced on the relevant experiments of EICs and UPCs. Also, one calculates the rates and kinematic distributions for \begin{document}$ \gamma p\rightarrow Z_{b}n $\end{document} in \begin{document}$ ep $\end{document} and \begin{document}$ pA $\end{document} collisions via EICs and UPCs, and the relevant results will provide an important reference for the RHIC, LHC, EIC-US, LHeC, and FCC experiments to search for the bottomonium-like \begin{document}$ Z_{b} $\end{document} states.
$ { \bar{ B}\to{ {X_s \gamma }}}$ in BLMSSM
Jian-Bin Chen, Meng Zhang, Li-Li Xing, Tai-Fu Feng, Shu-Min Zhao, Ke-Sheng Sun
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Applying the effective Lagrangian method, we study the Flavor Changing Neutral Current \begin{document}$b\to s\gamma$\end{document} within the minimal supersymmetric extension of the standard model where baryon and lepton numbers are local gauge symmetries. Constraints on the parameters are investigated numerically with the experimental data on branching ratio of \begin{document}$\bar{B}\to X_s\gamma$\end{document}. Additionally, we present the corrections to direct CP-violation in \begin{document}$\bar{B}\rightarrow X_s\gamma$\end{document} and time-dependent CP-asymmetry in \begin{document}$B\rightarrow K^*\gamma$\end{document}. With appropriate assumptions on parameters, we find the direct CP-violation \begin{document}$A_{CP}$\end{document} is very small, while one-loop contributions to \begin{document}$S_{K^*\gamma}$\end{document} can be significant.
Reduction of PDF uncertainty in the measurement of the weak mixing angle at the ATLAS experiment
Yao Fu, Siqi Yang, Minghui Liu, Liang Han, Tie-Jiun Hou, Carl Schmidt, Chen Wang, C.–P. Yuan
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We investigate the parton distribution function (PDF) uncertainty in the measurement of the effective weak mixing angle \begin{document}$\sin^2 \theta _{{\rm{eff}}}^{\ell}$\end{document} at the CERN Large Hadron Collider (LHC). The PDF-induced uncertainty is large in the proton-proton collisions at the LHC due to the dilution effect. The measurement of the Drell-Yan forward-backward asymmetry (\begin{document}$A_{\rm FB}$\end{document}) at the LHC can be used to reduce the PDF uncertainty in the \begin{document}$\sin^2 \theta _{{\rm{eff}}}^{\ell}$\end{document} measurement. However, when including the full mass range of lepton pairs in the \begin{document}$A_{\rm FB}$\end{document} data analysis, the correlation between the PDF updating procedure and the \begin{document}$\sin^2 \theta _{{\rm{eff}}}^{\ell}$\end{document} extraction leads to a sizable bias in the obtained \begin{document}$\sin^2 \theta _{{\rm{eff}}}^{\ell}$\end{document} value. From our studies, we find that the bias can be significantly reduced by removing Drell-Yan events with invariant mass around the Z pole region, while most of the sensitivity in reducing the PDF uncertainty remains. Furthermore, the lepton charge asymmetry in the W boson events as a function of the rapidity of the charged leptons, \begin{document}$A_\pm(\eta_\ell)$\end{document}, is known to be another observable which can be used to reduce the PDF uncertainty in the \begin{document}$\sin^2 \theta _{{\rm{eff}}}^{\ell}$\end{document} measurement. The constraint from \begin{document}$A_\pm(\eta_\ell)$\end{document} is complementary to that from the \begin{document}$A_{\rm FB}$\end{document}, thus no bias affects the \begin{document}$\sin^2 \theta _{{\rm{eff}}}^{\ell}$\end{document} extraction. The studies are performed using the Error PDF Updating Method Package (EPUMP), which is based on the Hessian updating methods. In this article, the CT14HERA2 PDF set is used as an example.
Thermodynamics of warped anti-de Sitter black holes under scattering of scalar field
Bogeun Gwak
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We investigate the thermodynamics and stability of the horizons in warped anti-de Sitter black holes of the new massive gravity under the scattering of a massive scalar field. Under scattering, conserved quantities can be transferred from the scalar field to the black hole, which change the state of the black hole. We determine that the changes in the black hole are well coincident with the laws of thermodynamics. In particular, the Hawking temperature of the black hole cannot be zero in the process as per the third law of thermodynamics. Furthermore, the black hole cannot be overspun beyond the extremal condition under the scattering of any mode of the scalar field.