2023 Vol. 47, No. 4

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2023-4 Contents
2023, 47(4): 1-2.
Sequential single pion production explaining the dibaryon "d*(2380)" peak
R. Molina, Natsumi Ikeno, Eulogio Oset
2023, 47(4): 041001. doi: 10.1088/1674-1137/acb0b7
In this study, we investigate the two step sequential one pion production mechanism, that is, \begin{document}$ np(I=0)\to $\end{document}\begin{document}$ \pi^-pp $\end{document} followed by the fusion reaction \begin{document}$ pp\to \pi^+d $\end{document}, to describe the \begin{document}$ np\to \pi^+\pi^-d $\end{document} reaction with \begin{document}$ \pi^+\pi^- $\end{document} in state \begin{document}$ I=0 $\end{document}. In this reaction, a narrow peak identified with a "\begin{document}$ d(2380) $\end{document}" dibaryon has been previously observed. We discover that the second reaction step \begin{document}$ pp\to \pi^+d $\end{document} is driven by a triangle singularity that determines the position of the peak of the reaction and the high strength of the cross section. The combined cross section of these two mechanisms produces a narrow peak with a position, width, and strength, that are compatible with experimental observations within the applied approximations made. This novel interpretation of the peak accomplished without invoking a dibaryon explains why this peak has remained undetected in other reactions.
Binding energy produced within the framework of the accretion of millisecond pulsars
Ali Taani
2023, 47(4): 041002. doi: 10.1088/1674-1137/acb346
The role and implication of binding energy through the accretion-induced collapse (AIC) of accreting white dwarfs (WDs) for the production of millisecond pulsars (MSPs) are investigated. The binding energy model is examined due to the dynamic process in closed binary systems, and the possible mass of the companion sufficient to induce their orbital parameters is investigated. The deterministic nature of this interaction has a strong sensitivity to the equation of state of the binary systems (where the compactness of a neutron star is proportional to the amount of binding energy) associated with their initial conditions. This behavior mimics the commonly assumed mass and amount of accreted matter under the instantaneous mass loss (\begin{document}$\Delta M \sim 0.18M_{\odot}$\end{document}). As a result, this indicates an increase in the MSP's gravitational mass due to angular momentum losses. The outcome of such a system is then a circular binary MSP in which the companion is a low-mass WD, thus distinguishing the binary formation scenarios. In addition, the results of this work could provide constraints on the expected mass and binding energy of a neutron star based on the accretion rate.
Observation of ${ {\boldsymbol e^+\boldsymbol e^- \to\boldsymbol p\boldsymbol p \bar{\boldsymbol p} \bar{\boldsymbol n} \boldsymbol\pi^{-} + \boldsymbol c.\boldsymbol c. }}$
M. Ablikim, M. N. Achasov, P. Adlarson, M. Albrecht, R. Aliberti, A. Amoroso, M. R. An, Q. An, X. H. Bai, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, V. Batozskaya, D. Becker, K. Begzsuren, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, J. F. Chang, W. L. Chang, G. Chelkov, C. Chen, Chao Chen, G. Chen, H. S. Chen, M. L. Chen, S. J. Chen, S. M. Chen, T. Chen, X. R. Chen, X. T. Chen, Y. B. Chen, Z. J. Chen, W. S. Cheng, X. Chu, G. Cibinetto, F. Cossio, J. J. Cui, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, Y. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, S. X. Du, P. Egorov, Y. L. Fan, J. Fang, S. S. Fang, W. X. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, K Fischer, M. Fritsch, C. Fritzsch, C. D. Fu, H. Gao, Y. N. Gao, Yang Gao, S. Garbolino, I. Ga
2023, 47(4): 043001. doi: 10.1088/1674-1137/acb6eb
Using data taken at 29 center-of-mass energies between 4.16 and 4.70 GeV with the BESIII detector at the Beijing Electron Positron Collider corresponding to a total integrated luminosity of approximately 18.8 \begin{document}$ \rm fb^{-1} $\end{document}, the process \begin{document}$ e^+e^- \to p p \bar{p} \bar{n} \pi^{-} + c.c. $\end{document} is observed for the first time with a statistical significance of \begin{document}$ 11.5\sigma $\end{document}. The average Born cross sections in the energy ranges of (4.160, 4.380) GeV, (4.400, 4.600) GeV and (4.610, 4.700) GeV are measured to be \begin{document}$ (21.5\pm5.7\pm1.2) $\end{document} fb, \begin{document}$ (46.3\pm10.6\pm2.5) $\end{document} fb and \begin{document}$ (59.0\pm9.4\pm3.2) $\end{document} fb, respectively, where the first uncertainties are statistical and the second are systematic. The line shapes of the \begin{document}$ \bar{p}\bar{n} $\end{document} and \begin{document}$ pp\pi^- $\end{document} invariant mass spectra are consistent with phase space distributions, indicating that no hexaquark or di-baryon state is observed.
Expected measurement precision of the branching ratio of the Higgs boson decaying to the di-photon at the CEPC
Fangyi Guo, Yaquan Fang, Gang Li, Xinchou Lou
2023, 47(4): 043002. doi: 10.1088/1674-1137/acaa22
This paper presents the prospects of measuring \begin{document}$\sigma(e^{+} e^{-} \to ZH)\times {\rm Br}(H \to \gamma \gamma)$\end{document} in three Z decay channels \begin{document}$ Z \to q \bar{q}/ {\mu ^ + }{\mu ^ - }/ \nu \bar \nu $\end{document} using the baseline detector with \begin{document}$\sqrt{s} = 240$\end{document}GeV at the Circular Electron Positron Collider (CEPC). Simulated Monte Carlo events were generated and scaled to an integrated luminosity of 5.6 ab–1 to mimic the data. Extrapolated results to 20 ab–1 are also reported. The expected statistical precision of these measurements after combining three channels of Z boson decay was 7.7%. With some preliminary estimation on the systematical uncertainties, the total precision is 7.9%. The performance of the CEPC electro-magnetic calorimeter (ECAL) was studied by smearing the photon energy resolution in simulated events in the \begin{document}$e^{+} e^{-} \to ZH \to q\bar q\gamma \gamma $\end{document} channel. In the present ECAL design, the stochastic term in resolution plays the dominant role in the precision of Higgs measurements in the \begin{document}$H \to \gamma \gamma $\end{document} channel. The impact of the resolution on the measured precision of \begin{document}$\sigma(ZH)\times {\rm Br}(ZH \to q\bar q\gamma \gamma)$\end{document} as well as the optimization of the ECAL constant and stochastic terms were studied for further detector design.
Role of the scalar ${{\boldsymbol f}_{\bf 0}\boldsymbol{(980)} }$ in the process ${ {\boldsymbol D}_{\boldsymbol s}^{\bf +}\bf \to \boldsymbol\pi^{\bf +} \boldsymbol\pi^{\bf 0} \boldsymbol\pi^{\bf 0}} $
Han Zhang, Yun-He Lyu, Li-Juan Liu, En Wang
2023, 47(4): 043101. doi: 10.1088/1674-1137/acb3b3
Based on BESIII measurements of the reaction \begin{document}$ D_s^+\to \pi^+\pi^0\pi^0 $\end{document}, we investigate this process by considering the S-wave pseudoscalar-pseudoscalar interaction within the unitary chiral approach and the contributions from the intermediate resonances \begin{document}$ f_0(1370) $\end{document} and \begin{document}$ f_2(1270) $\end{document}. Our calculation can reasonably reproduce the experimental data, and our results imply that \begin{document}$ f_0(980) $\end{document}, which is dynamically generated from the S-wave pseudoscalar-pseudoscalar interaction, plays an important role in this process, and the contributions from the intermediate resonances \begin{document}$ f_0(1370) $\end{document} and \begin{document}$ f_2(1270) $\end{document} are also necessary. More precise measurements of this process in future can shed light on the nature of \begin{document}$ f_0(1370) $\end{document} and \begin{document}$ f_2(1270) $\end{document}.
Leptoquark and vector-like quark extended model for simultaneousexplanation of W boson mass and muon g–2 anomalies
Shi-Ping He
2023, 47(4): 043102. doi: 10.1088/1674-1137/ac9e4c
The CDF collaboration recently announced a new measurement result for the W boson mass, and it is in tension with the standard model prediction. In this paper, we explain this anomaly in the vector-like quark (VLQ) \begin{document}$ (X,T,B)_{L,R} $\end{document} and leptoquark (LQ) \begin{document}$ S_3 $\end{document} extended model. In this model, both the VLQ and LQ have positive corrections to the W boson mass. Moreover, it may be a solution to the \begin{document}$ (g-2)_{\mu} $\end{document} anomaly because of the chiral enhancements from top, T, and B quarks.
Is the magic texture of Majorana neutrinos immanent in Dirac nature?
Yuta Hyodo, Teruyuki Kitabayashi
2023, 47(4): 043103. doi: 10.1088/1674-1137/aca95a
Magic textures are successful candidates of the correct texture for Majorana neutrinos. In this study, we demonstrate that several types of magic textures of Majorana neutrinos are approximately immanent in the flavor mass matrix of Dirac neutrinos. In addition, the normal mass ordering of Dirac neutrino masses is slightly preferable to inverted mass ordering in the context of magic textures.
Stellar energy loss rates associated with photoneutrino processes in the minimal extension of the standard model
C. Aydın
2023, 47(4): 043104. doi: 10.1088/1674-1137/acb48c
Using the minimal extension of the standard model and considering the charge radius and the anapole moments of a neutrino, we derive analytical expressions for the stellar energy loss rates associated with the production of a neutrino pair \begin{document}$ e^- + \gamma \rightarrow e^- + \nu_e +\overline{\nu_e} $\end{document} in hot plasma under three limiting regimes (nondegenerate, intermediate, and degenerate electrons) of the temperature, electron chemical potential, and plasma energy. The obtained results reveal the presence of an extra contribution of approximately \begin{document}$10$\end{document}% based on the considered calculations.
R-Symmetric NMSSM
Shuai Xu, Sibo Zheng
2023, 47(4): 043105. doi: 10.1088/1674-1137/aca95c
It is well known that the observed Higgs mass is more naturally explained in the next-to-minimal supersymmetric standard model (NMSSM) than in the minimal supersymmetric standard model. Without any violation of this success, there are variants of the NMSSM that can lead to new phenomenologies. In this study, we propose a new variant of the NMSSM by imposing an unbroken R symmetry. We first identify the minimal structure of such a scenario from the perspective of both simplicity and viability, then compare the model predictions to current experimental limits, and finally highlight the main features that differ from those of well-known scenarios.
Note on rare Z-boson decays to double heavy quarkonia
Dao-Neng Gao, Xi Gong
2023, 47(4): 043106. doi: 10.1088/1674-1137/acb7d1
Within the standard model, we have investigated rare Z-boson decays into double heavy quarkonia, \begin{document}$ Z\to VV $\end{document} and \begin{document}$ Z\to VP $\end{document}, with V and P denoting vector and pseudoscalar quarkonia, respectively. It is assumed that the leading-order QCD diagrams would give the dominant contributions to these processes, and the corresponding branching fractions, for instance, \begin{document}$ {\cal B}(Z\to J/\Psi J/\Psi) $\end{document}, have been estimated to be approximately\begin{document}$ 10^{-13} $\end{document} in literature. However, these decays could also happen through electromagnetic transitions \begin{document}$ Z\to V\gamma^* $\end{document} and \begin{document}$ Z\to P\gamma^* $\end{document}, with the virtual photon transforming into V. Interestingly, the smallness of the vector quarkonium mass can give rise to a large factor \begin{document}$ m_Z^2/m_V^2 $\end{document} relative to the QCD contributions, which thus counteracts the suppression from the electromagnetic coupling. We systematically include these two types of contributions in our calculation to predict branching fractions for these decays. Particularly, owing to the virtual photon effects, it is found that \begin{document}$ {\cal B}(Z\to J/\Psi J/\Psi) $\end{document} will be significantly enhanced, up to \begin{document}$ 10^{-10} $\end{document}.
Search for heavy Majorana neutrinos at future lepton colliders
Peng-Cheng Lu, Zong-Guo Si, Zhe Wang, Xing-Hua Yang, Xin-Yi Zhang
2023, 47(4): 043107. doi: 10.1088/1674-1137/acb997
A nonzero neutrino mass may be a sign of new physics beyond the standard model (SM). To explain the small neutrino mass, we can extend the SM using right-handed Majorana neutrinos in a low-scale seesaw mechanism, and the CP violation effect can be induced due to the CP phase in the interference of heavy Majorana neutrinos. The existence of heavy Majorana neutrinos may lead to lepton number violation processes, which can be used to search for the signals of heavy Majorana neutrinos. In this paper, we focus on the CP violation effect related to two generations of heavy Majorana neutrinos at \begin{document}$ 15 $\end{document} GeV \begin{document}$ <m_{N_1}< 70 $\end{document} GeV in the pair production of W bosons and rare decays. It is valuable to investigate Majorana neutrino production signals and the related CP violation effects in rare W boson decays at future lepton colliders.
Search for the singlet vector-like top quark in the $ {\boldsymbol T\boldsymbol\to{\boldsymbol {tZ}}} $ channel with $ {{\boldsymbol Z}{\bf\to} \boldsymbol\nu\bar{\boldsymbol\nu}} $ at hadron colliders
Lin Han, Shiyu Wang, Liangliang Shang, Bingfang Yang
2023, 47(4): 043108. doi: 10.1088/1674-1137/acb994
Based on a simplified model including a singlet vector-like top quark T with charge |Q|=\begin{document}$ 2/3 $\end{document}, we analyze the prospects of observing T via the single T production in the \begin{document}$ tZ $\end{document} channel with Z decaying to neutrinos at the hadron-hadron colliders. This simplified model only includes two free parameters, the coupling constant \begin{document}$ g^* $\end{document} and the T quark mass \begin{document}$ m_T $\end{document}. To investigate the observability of the single T production, we perform a detailed background analysis and detector simulation for the collision energies 14 TeV, 27 TeV, and 100 TeV. We scan the \begin{document}$ g^*-m_T $\end{document} parameter space and show the exclusion and discovery capabilities on the T quark with the highest integrated luminosity designed at these colliders. Moreover, the limits from the narrow-width approximation and electroweak precision observables are considered.
Cosmological imprints of Dirac neutrinos in a keV-vacuum 2HDM
Shao-Ping Li, Xin-Qiang Li, Xin-Shuai Yan, Ya-Dong Yang
2023, 47(4): 043109. doi: 10.1088/1674-1137/acb6de
The Dirac neutrino masses could be simply generated by a neutrinophilic scalar doublet with a vacuum being dramatically different from the electroweak one. While the case with an eV-scale vacuum has been widely explored previously, we exploit in this work the desert where the scalar vacuum is of \begin{document}$\mathcal{O}(\mathrm{keV})$\end{document} scale. In this regime, there would be rare hope to probe the keV-vacuum neutrinophilic scalar model via the lepton-flavor-violating processes, which makes it distinguishable from the widely considered eV-scale vacuum. Although such a keV-vacuum scenario is inert in the low-energy flavor physics, we show that the baryogenesis realized via the lightest Dirac neutrino can be a natural candidate in explaining the baryon asymmetry of the Universe. Furthermore, the Dirac neutrinos with a keV-vacuum scalar can generate a shift of the effective neutrino number within the range \begin{document}$0.097\leqslant \Delta N_{\rm eff}\leqslant 0.112$\end{document}, which can be probed by the future Simons Observatory experiments. In particular, the model with a minimal value \begin{document}$\Delta N_{\rm eff}=0.097$\end{document} can already be falsified by the future CMB Stage-IV and Large Scale Structure surveys, providing consequently striking exploratory avenues in the cosmological regime for such a keV-vacuum scenario.
Charged-current non-standard neutrino interactions at the LHC and HL-LHC
Chong-Xing Yue, Xue-Jia Cheng, Ji-Chong Yang
2023, 47(4): 043111. doi: 10.1088/1674-1137/acb993
A series of new physics scenarios predict the existence of the extra charged gauge boson \begin{document}$ W' $\end{document}, which can induce charged-current (CC) non-standard neutrino interactions (NSIs). The theoretical constraints on the simplified \begin{document}$ W' $\end{document} model and further on the CC NSI parameters \begin{document}$ \widetilde{\epsilon}^{ qq'Y}_{\alpha\beta} $\end{document} from partial wave unitarity and \begin{document}$ W' $\end{document} decays are considered. The sensitivity of the process \begin{document}$ p p \rightarrow W'\rightarrow \ell\nu $\end{document} to the \begin{document}$ W' $\end{document} model at the LHC and high-luminosity (HL) LHC experiments is investigated by estimating the expected constraints on \begin{document}$ \widetilde{\epsilon}^{qq'Y}_{\alpha\beta} $\end{document} (\begin{document}$ \alpha = \beta = e $\end{document} or μ) using a Monte-Carlo (MC) simulation. We find that the interference effect plays an important role, and the LHC can strongly constrain \begin{document}$ \widetilde{\epsilon}^{qq'L}_{\alpha\beta} $\end{document}. Compared with those at the \begin{document}$ 13 \;{\rm TeV} $\end{document} LHC with \begin{document}$ {\cal{L}}=139\;{\rm fb}^{-1} $\end{document}, the expected constraints at the \begin{document}$ 14 \;{\rm TeV} $\end{document} LHC with \begin{document}$ {\cal{L}}=3\;{\rm ab}^{-1} $\end{document} can be strengthened to approximately one order of magnitude.
Resonance contributions from χc0 in charmless three-body hadronic B meson decays
Ya-Lan Zhang, Chao Wang, Yi Lin, Zhen-Jun Xiao
2023, 47(4): 043112. doi: 10.1088/1674-1137/acbaea
Within the framework of perturbative QCD factorization, we investigate the nonfactorizable contributions to the factorization-forbidden quasi-two-body decays \begin{document}$ B_{(s)}\rightarrow h\chi_{c0}\rightarrow h\pi^+\pi^-(K^+K^-) $\end{document} with \begin{document}$ h=\pi, K $\end{document}. We compare our predicted branching ratios for the \begin{document}$ B_{(s)}\rightarrow K\chi_{c0}\rightarrow K\pi^+\pi^-(K^+K^-) $\end{document} decay with available experiment data as well as predictions by other theoretical studies. The branching ratios of these decays are consistent with data and other theoretical predictions. However, in the Cabibbo-suppressed decays \begin{document}$ B_{(s)}\rightarrow h\chi_{c0}\rightarrow h\pi^+\pi^-(K^+K^-) $\end{document} with \begin{document}$ h=\bar{K}^0,\pi $\end{document}, the values of the branching ratios are of the order of \begin{document}$ 10^{-7} $\end{document} and \begin{document}$ 10^{-8} $\end{document}. The ratio \begin{document}$ R_{\chi_{c0}} $\end{document} between the decays \begin{document}$B^+\rightarrow $\end{document}\begin{document}$ \pi^+\chi_{c0}\rightarrow \pi^+\pi^+\pi^-$\end{document} and \begin{document}$ B^+\rightarrow K^+\chi_{c0}\rightarrow K^+\pi^+\pi^- $\end{document} and the distribution of branching ratios for different decay modes in invariant mass are considered in this study.
Searching for the axion-like particle at the EIC
Yandong Liu, Bin Yan
2023, 47(4): 043113. doi: 10.1088/1674-1137/acbbc0
The axion-like particle (ALP) is a well motivated new particle candidate for beyond the standard model. In this study, we propose to probe the ALP via photon fusion scattering at the upcoming Electron-Ion Collider (EIC) with electron and proton energies of \begin{document}$ E_e=20\; {\rm GeV} $\end{document} and \begin{document}$ E_p=250\; {\rm GeV} $\end{document}, respectively. We can constrain the effective coupling strength between the ALP and photons to be \begin{document}$ 0.2\; {\rm TeV}^{-1} $\end{document} at the \begin{document}$ 2\sigma $\end{document} confidence level with an integrated luminosity of \begin{document}$ 300\; {\rm fb}^{-1} $\end{document} for the mass range \begin{document}$ m_a\in [5,40]\; {\rm GeV} $\end{document}. Such bounds may be significantly improved if we consider the nucleus beam at the EIC. We also demonstrate that the limits from the EIC can be stronger than the off Z-pole measurement at the LEP and light-by-light scattering with pp collisions at the LHC.
Atomic mass, Bjorken variable, and scale dependence of quark transport coefficient in Drell-Yan process for proton incident on nucleus
Wei-Jie Xu, Tian-Xing Bai, Chun-Gui Duan
2023, 47(4): 043110. doi: 10.1088/1674-1137/acb8a4
By means of the nuclear parton distributions determined without the fixed-target Drell-Yan experimental data and the analytic expression of quenching weight based on the BDMPS formalism, next-to-leading order analyses were performed on the Drell-Yan differential cross section ratios from the Fermilab E906 and E866 collaborations. It was found that the results calculated only with the nuclear effects of the parton distribution were not in agreement with the E866 and E906 experimental data. The incoming parton energy loss effect cannot be ignored in the nuclear Drell-Yan reactions. The predicted results indicate that, with the quark transport coefficient as a constant, the suppression due to the target nuclear geometry effect is approximately\begin{document}$ 16.85\ $\end{document}% for the quark transport coefficient. It was shown that we should consider the target nuclear geometry effect in studying the Drell-Yan reaction on nuclear targets. On the basis of the Bjorken variable and scale dependence of the quark transport coefficient, the atomic mass dependence was incorporated. The quark transport coefficient was determined as a function of the atomic mass, Bjorken variable\begin{document}$ x_2 $\end{document}, and scale \begin{document}$ Q^2 $\end{document} by the global fit of the experimental data. The determined constant factor \begin{document}$ \hat{q}_0 $\end{document} of the quark transport coefficient is \begin{document}$ 0.062\pm0.006 $\end{document} GeV\begin{document}$ ^2 $\end{document}/fm. It was found that the atomic mass dependence has a significant impact on the constant factor \begin{document}$ \hat{q}_0 $\end{document} in the quark transport coefficient in cold nuclear matter.
Pre-neutron fragment mass yields for 235U(n, f ) and 239Pu(n, f ) reactions at incident energies from thermal up to 20 MeV
Fanglei Zou, Xiaojun Sun, Kai Zhang, Hongfei Chen, Jie Yan, Junlong Tian, Yunyi Cui
2023, 47(4): 044101. doi: 10.1088/1674-1137/acb910
Pre-neutron fragment mass yields in the vicinity of the thermal neutron energy are highly important for applications because of the larger fission cross sections of the \begin{document}$ ^{235} $\end{document}U(n, f) and \begin{document}$ ^{239} $\end{document}Pu(n, f) reactions. In this paper, pre-neutron fragment mass yields at incident energies from thermal up to 20 MeV are systematically studied using an empirical fission potential (EFP) model, the potential parameters of which are obtained from the measured data. The energy dependences of the peaks and valleys of the pre-neutron fragment mass yields are described by exponential and linear functions for the \begin{document}$ ^{235} $\end{document}U(n, f) and \begin{document}$ ^{239} $\end{document}Pu(n, f) reactions, respectively. The energy dependences of the evaporation neutrons, which play a crucial role in the reasonable description of pre-neutron fragment mass yields, are also obtained from the fission cross sections. The pre-neutron fragment mass yields in this study are not only consistent with the results of previous studies in regions of several MeVs but also agree well with existing measured data at incident energies from thermal up to 20 MeV. The results show that the feasibility of this EFP model is verified in this extended energy region.
Unified mechanism behind the even-parity ground state and neutron halo of 11Be
Jing Geng, Yi-Fei Niu, Wen-Hui Long
2023, 47(4): 044102. doi: 10.1088/1674-1137/acb7cd
Using the axially deformed relativistic Hartree-Fock-Bogoliubov (D-RHFB) model, we explore the mechanism behind the parity inversion and halo occurrence in 11Be, which are well reproduced by the RHF Lagrangian PKA1. It is illustrated that evidently enhanced deformation effects by the π-pseudo-vector and ρ-tensor couplings in PKA1 are crucial for correctly describing both the even-parity ground state (GS) and the neutron halo of 11Be. Coupling with the deformation, the intrude \begin{document}$ 1d_{5/2} $\end{document} component largely enhances the couplings between the even-parity orbit \begin{document}$ 1/2_2^+ $\end{document} and the nuclear core to ensure an even-parity GS, whereas the \begin{document}$ 2s_{1/2} $\end{document} component therein dominates the halo formation in 11Be. Moreover, the deformed halo in 11Be is found to be stabilized by the attractive inherent correlations between the \begin{document}$ 1d_{5/2} $\end{document} and \begin{document}$ 2s_{1/2} $\end{document} components of the halo orbit \begin{document}$ 1/2_2^+ $\end{document}, instead of pairing correlations, which paves a new way for understanding the halo pictures in deformed unstable nuclei.
The European Muon Collaboration effect from short-range correlated nucleons in a x-rescaling model
Rong Wang, Na-Na Ma, Tao-Feng Wang
2023, 47(4): 044103. doi: 10.1088/1674-1137/acb7d0
In this paper, we examine the hypothesis that the nuclear EMC effect arises merely from the N-N SRC pairs inside the nucleus and that the properties of the N-N SRC pair are universal among the various nuclei, using the conventional x-rescaling model for the EMC effect. With the previously determined effective mass of the short-range correlated nucleon and the number of N-N SRC pairs estimated, we calculated the EMC effect of various nuclei within the x-rescaling approach. According to our calculations, the nuclear EMC effect due to the mass deficits of the SRC nucleons is not sufficient to reproduce the observed EMC effect in experiments. We speculate that the internal structure of the mean-field single nucleon is also clearly modified. Alternatively, there can be more origins of the EMC effect beyond the N-N SRC configuration (such as the α cluster), or the universality of N-N SRC pair is significantly violated from light to heavy nuclei.
Extending the VDPC+BCS formalism by including three-body forces
Zi-Yu Xia
2023, 47(4): 044104. doi: 10.1088/1674-1137/acb14a
Recently, Jia proposed a formalism to apply the variational principle to a coherent-pair condensate for a two-body Hamiltonian. The present study extends this formalism by including three-body forces. The result is the same as the so-called variation after particle-number projection in the BCS case, but now, the particle number is always conserved, and the time-consuming projection is avoided. Specifically, analytical formulas of the average energy are derived along with its gradient for a three-body Hamiltonian in terms of the coherent-pair structure. Gradient vanishment is required to obtain analytical expressions for the pair structure at the energy minimum. The new algorithm iterates on these pair-structure expressions to minimize energy for a three-body Hamiltonian. The new code is numerically demonstrated when applied to realistic two-body forces and random three-body forces in large model spaces. The average energy can be minimized to practically any arbitrary precision.
Systematic study of global optical model potentials in (d, p) transfer reactions
Yonghao Gao, Zhongzhou Ren, Lei Jin
2023, 47(4): 044105. doi: 10.1088/1674-1137/acb2bc
In the T-matrix form of the transfer reaction, the optical model potentials (OMPs) are used to compute the scattering wave function and transition operator. For most cases, the elastic scattering cross sections, normally used to generate the OMPs, are not directly given in the same experiment. Then, the global OMPs, which fit the experimental data over a broad mass and energy range, are widely used in the theoretical calculations. Different sets of global OMPs with different parameter sets can reproduce the scattering cross section equally well within the uncertainty. Here, we apply different global OMPs to calculate the (differential) cross sections of \begin{document}$ (d,p) $\end{document} transfer reactions on the target nuclei \begin{document}$ ^{12}{\rm{C}} $\end{document}, \begin{document}$ ^{48}{\rm{Ca}} $\end{document}, \begin{document}$ ^{124}{\rm{Sn}} $\end{document} , and \begin{document}$ ^{208}{\rm{Pb}} $\end{document} at different energies. The results demonstrate that the effects of deuteron and nucleon global OMPs on transfer (differential) cross sections vary with energy and target mass. Furthermore, the influences of the spin-orbit coupling term of deuteron and nucleon global OMPs on the transfer cross sections are not negligible.
Estimation of transport coefficients of dense hadronic and quark matter
Debashree Sen, Naosad Alam, Sabyasachi Ghosh
2023, 47(4): 044106. doi: 10.1088/1674-1137/acb992
In this study, we calculated transport coefficients including the shear viscosity and electrical conductivity relative to the density of dense hadronic and quark matter. By considering the simple massless limit for the quark matter and two different effective models for the hadronic matter, we estimated the transport coefficients of the two phases separately. Accordingly, density profiles of the transport coefficients were depicted in two parts: the phase-space part and the relaxation time part. From calculating the shear viscosity to density ratio, we also explored the nearly perfect fluid domain of the quark and hadronic matter.
Joule-Thomson expansion of charged dilatonic black holes
Meng-Yao Zhang, Hao Chen, Hassan Hassanabadi, Zheng-Wen Long, Hui Yang
2023, 47(4): 045101. doi: 10.1088/1674-1137/aca958
Based on the Einstein-Maxwell theory, the Joule-Thomson (J-T) expansion of charged dilatonic black holes (the solutions are neither flat nor AdS) in \begin{document}$ (n+1) $\end{document}-dimensional spacetime is studied herein. To this end, we analyze the effects of the dimension n and dilaton field α on J-T expansion. An explicit expression for the J-T coefficient is derived, and consequently, a negative heat capacity is found to lead to a cooling process. In contrast to its effect on the dimension, the inversion curve decreases with charge Q at low pressures, whereas the opposite effect is observed at high pressures. We can observe that with an increase in the dimension n or parameter α, both the pressure cut-off point and the minimum inversion temperature \begin{document}$T_{\rm min}$\end{document} change. Moreover, we analyze the ratio \begin{document}$T_{\rm min}/T_{\rm c}$\end{document} numerically and discover that the ratio is independent of charge; however, it depends on the dilaton field and dimension: for \begin{document}$ n=3 $\end{document} and \begin{document}$ \alpha=0 $\end{document}, the ratio is 1/2. The dilaton field is found to enhance the ratio. In addition, we identify the cooling-heating regions by investigating the inversion and isenthalpic curves, and the behavior of the minimum inversion mass \begin{document}$M_{\rm min}$\end{document} indicates that this cooling-heating transition may not occur under certain special conditions.
High dimensional AdS-like black hole and phase transition in Einstein-bumblebee gravity
Chikun Ding, Yu Shi, Jun Chen, Yuebing Zhou, Changqing Liu
2023, 47(4): 045102. doi: 10.1088/1674-1137/aca8f4
In this study, we obtained an exact high dimensional anti-de Sitter (AdS) black hole solution in Einstein-bumblebee gravity theory. This AdS-like black hole can only exist with a linear functional potential of the bumblebee field. We found that the Smarr formula and the first law of black hole thermodynamics can still be constructed in this Lorentz symmetry breaking black hole spacetime, but the conceptions of the black hole horizon area/entropy and the volume inside the horizon should be renewed due to its anisotropy. We also found that two types of phase transition exist: small-large black hole phase transition and Hawking-Page phase transition, like those of the Schwarzschild AdS black hole. After Lorentz symmetry breaking, the black hole mass at the divergent point of heat capacity becomes small, and the Gibbs free energy of the meta-stable large black hole is also smaller, showing that the large stable black hole can be more easily formed.