## 2019 Vol. 43, No. 12

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2019, 43(12): 123101. doi: 10.1088/1674-1137/43/12/123101
Abstract:
We calculate cross-sections and cross-section ratios of a charm quark production in association with a W gauge boson at next-to-leading order QCD using MadGraph and CT10NNLO, CT14NNLO, and MSTW2008NNLO PDFs. We compare the results with measurements from the CMS detector at the LHC at a center-of-mass energy of 7 TeV. Moreover, we calculate absolute and normalized differential cross-sections as well as differential cross-section ratios as a function of the lepton pseudorapidity from the W boson decay. The correlation between the CT14NNLO PDFs and predictions for \begin{document}$W+$\end{document} charm data are studied as well. Furthermore, by employing the error PDF updating method proposed by the CTEQ-TEA group, we update CT14NNLO PDFs, and analyze the impact of CMS 7 TeV \begin{document}$W+$\end{document} charm production data to the original CT14NNLO PDFs. By comparison of the \begin{document}$g(x,Q)$\end{document}, \begin{document}$s(x,Q)$\end{document}, \begin{document}$u(x,Q)$\end{document}, \begin{document}$d(x,Q)$\end{document}, \begin{document}$\bar u(x,Q)$\end{document}, and \begin{document}$\bar d(x,Q)$\end{document} PDFs at \begin{document}$Q=1.3$\end{document} GeV and \begin{document}$Q = 100$\end{document} GeV for the CT14NNLO and CT14NNLO+Wc, we see that the error band of the \begin{document}$s(x,Q)$\end{document} PDF is reduced in the region \begin{document}$x<0.4$\end{document}, and the error band of \begin{document}$g(x,Q)$\end{document} PDF is also slightly reduced at region \begin{document}$0.01 < x<0.1$\end{document}.
2019, 43(12): 123102. doi: 10.1088/1674-1137/43/12/123102
Abstract:
In this article, we take the scalar diquark and antidiquark operators as the basic constituents, and construct the \begin{document}$C\gamma_5\otimes\stackrel{\leftrightarrow}{\partial}_\mu\otimes \gamma_5C$\end{document} type tetraquark current to study Y(10750) with the QCD sum rules. The predicted mass \begin{document}$M_{Y}=10.75\pm0.10\,\rm{GeV}$\end{document} and width \begin{document}$\Gamma_Y= 33.60^{+16.64}_{-9.45}\,{\rm{MeV}}$\end{document} support the assignment of Y(10750) as the diquark-antidiquark type vector hidden-bottom tetraquark state, with a relative P-wave between the diquark and antidiquark constituents.
2019, 43(12): 123103. doi: 10.1088/1674-1137/43/12/123103
Abstract:
The precision study of \begin{document}$W^-W^+H$\end{document} production with subsequent \begin{document}$W^{\pm} \rightarrow l^{\pm} \overset{ _{(-)}}{\nu_{l}}$\end{document} and \begin{document}$H \rightarrow b\bar{b}$\end{document} decays at the Large Hadron Collider (LHC) aids in the investigation of Higgs gauge couplings and the search for new physics beyond the standard model. In this study, we calculate the shower-matched next-to-leading order QCD and electroweak (EW) corrections from the \begin{document}$q\bar{q}$\end{document} annihilation and photon-induced channels to the \begin{document}$W^-W^+H$\end{document} production at the \begin{document}$14~ {\rm TeV}$\end{document} LHC. We deal with the subsequent decays of Higgs and \begin{document}$W^{\pm}$\end{document} bosons by adopting the MADSPIN method. Both the integrated cross section and some kinematic distributions of \begin{document}$W^{\pm}$\end{document}, H, and their decay products are provided. We find that the QCD correction significantly enhances the leading-order differential cross section, while the EW correction from the \begin{document}$q\bar{q}$\end{document} annihilation channel obviously suppresses it, especially in the high energy phase-space region, due to the Sudakov effect. The \begin{document}$q\gamma$\end{document}- and \begin{document}$\gamma\gamma$\end{document}-induced relative corrections are positive and insensitive to the transverse momenta of \begin{document}$W^{\pm}$\end{document}, H, and their decay products. These photon-induced corrections compensate the negative \begin{document}$q\bar{q}$\end{document}-initiated EW correction, and become the dominant EW contribution as the increment of the \begin{document}$pp$\end{document} colliding energy. The parton shower (PS) effects on kinematic distributions are not negligible. The relative PS correction to the b-jet transverse momentum distribution can exceed 100% in the high \begin{document}$p_{T, b}$\end{document} region. Moreover, we investigate the scale and PDF uncertainties, and find that the theoretical error of the \begin{document}${\rm QCD}+{\rm EW}+q\gamma+\gamma\gamma$\end{document}-corrected integrated cross section mainly originates from the renormalization scale dependence of the QCD correction.
2019, 43(12): 124001. doi: 10.1088/1674-1137/43/12/124001
Abstract:
The \begin{document}$\Lambda$\end{document} separation energy for \begin{document}$\Lambda$\end{document} hypernuclei, denoted \begin{document}$B_\Lambda$\end{document}, measured in 1967, 1968, and 1973 are recalibrated using the current best estimates of the mass of particles and nuclei. The recalibrated \begin{document}$B_\Lambda$\end{document} are systematically larger (except in the case of \begin{document}$^6_\Lambda$\end{document}He) than the originally published values by about 100 keV. The effect of this level of recalibration is very important for light hypernuclei, especially for the hypertriton. The early \begin{document}$B_\Lambda$\end{document} values measured in 1967, 1968, and 1973 are widely used in theoretical research, and the new results provide better constraints for the conclusions of such studies.
2019, 43(12): 124002. doi: 10.1088/1674-1137/43/12/124002
Abstract:
Differential and angle-integrated cross sections for the 10B(n, α)7Li, 10B(n, α0) 7Li and 10B(n, α1) 7Li* reactions have been measured at CSNS Back-n white neutron source. Two enriched (90%) 10B samples 5.0 cm in diameter and ~85.0 μg/cm2 in thickness each with an aluminum backing were prepared, and back-to-back mounted at the sample holder. The charged particles were detected using the silicon-detector array of the Light-charged Particle Detector Array (LPDA) system. The neutron energy En was determined by TOF (time-of-flight) method, and the valid α events were extracted from the En-Amplitude two-dimensional spectrum. With 15 silicon detectors, the differential cross sections of α-particles were measured from 19.2° to 160.8°. Fitted with the Legendre polynomial series, the (n, α) cross sections were obtained through integration. The absolute cross sections were normalized using the standard cross sections of the 10B(n, α)7Li reaction in the 0.3 − 0.5 MeV neutron energy region. The measurement neutron energy range for the 10B(n, α)7Li reaction is 1.0 eV≤En < 2.5 MeV (67 energy points), and that for the 10B(n, α0) 7Li and 10B(n, α1) 7Li* reactions is 1.0 eV ≤ En < 1.0 MeV (59 energy points). The present results have been analyzed by the resonance reaction mechanism and the level structure of the 11B compound system, and compared with existing measurements and evaluations.
2019, 43(12): 124101. doi: 10.1088/1674-1137/43/12/124101
Abstract:
This work uses the Boltzmann transport model to study the thermal production of \begin{document}$J/\psi$\end{document} and \begin{document}$\psi(2S)$\end{document} in the quark gluon plasma (QGP) produced by \begin{document}$\sqrt{s_{\rm NN}}=5.02$\end{document} TeV Pb-Pb collisions. The \begin{document}$J/\psi$\end{document} nuclear modification factors are studied in detail alongside the mechanisms of primordial production and the recombination of charm and anti-charm quarks in the thermal medium. The \begin{document}$\psi(2S)$\end{document} binding energy is much smaller in the hot medium compared to the ground state; thus, \begin{document}$\psi(2S)$\end{document} with middle to low \begin{document}$p_{\rm T}$\end{document} can be thermally regenerated in the later stages of QGP expansions, enabling \begin{document}$\psi(2S)$\end{document} to inherit larger collective flows from the bulk medium. We quantitatively study the nuclear modification factors of both \begin{document}$J/\psi$\end{document} and \begin{document}$\psi(2S)$\end{document} in different centralities and transverse momentum bins for \begin{document}$\sqrt{s_{\rm NN}}=5.02$\end{document} TeV Pb-Pb collisions.
2019, 43(12): 124102. doi: 10.1088/1674-1137/43/12/124102
Abstract:
In order to describe charge exchange reactions at intermediate energies, we implemented as a first step the formulation of the normal eikonal approach. The calculated differential cross-sections based on this approach deviated significantly from the conventional DWBA calculations for CE reactions at 140 MeV/nucleon. Thereafter, improvements were made in the application of the eikonal approximation so as to keep a strict three-dimensional form factor. The results obtained with the improved eikonal approach are in good agreement with the DWBA calculations and with the experimental data. Since the improved eikonal approach can be formulated in a microscopic way, it is easy to apply to CE reactions at higher energies, where the phenomenological DWBA is a priori difficult to use due to the lack, in most cases, of the required phenomenological potentials.
2019, 43(12): 124103. doi: 10.1088/1674-1137/43/12/124103
Abstract:
The multinucleon transfer (MNT) process has been proposed as a promising approach to produce neutron-rich superheavy nuclei (SHN). MNT reactions based on the radioactive targets 249Cf, 254Es, and 257Fm are investigated within the framework of the improved version of a dinuclear system (DNS-sysu) model. The MNT reaction 238U + 238U was studied extensively as a promising candidate for producing SHN. However, based on the calculated cross-sections, it was found that there is little possibility to produce SHN in the reaction 238U + 238U. In turn, the production of SHN in reactions with radioactive targets is likely.
2019, 43(12): 124104. doi: 10.1088/1674-1137/43/12/124104
Abstract:
We propose a method for extracting the properties of the isobaric mass parabola based on the total double \begin{document}$\beta$\end{document}-decay energies of isobaric nuclei. Two important parameters of the mass parabola, the location of the most \begin{document}$\beta$\end{document}-stable nuclei \begin{document}$Z_{A}$\end{document} and the curvature parameter \begin{document}$b_{A}$\end{document}, are obtained for 251 A values, based on the total double \begin{document}$\beta$\end{document}-decay energies of nuclei compiled in the AME2016 database. The advantage of this approach is that the pairing energy term \begin{document}$P_{A}$\end{document} caused by the odd-even variation can be removed in the process, as well as the mass excess \begin{document}$M(A,Z_{A})$\end{document} of the most stable nuclide for the mass number A, which are employed in the mass parabolic fitting method. The Coulomb energy coefficient \begin{document}$a_{c} = 0.6910$\end{document} MeV is determined by the mass difference relation for mirror nuclei, and the symmetry energy coefficient is also studied by the relation \begin{document}$a_{\rm sym}(A) = 0.25b_{A}Z_{A}$\end{document}.
2019, 43(12): 124105. doi: 10.1088/1674-1137/43/12/124105
Abstract:
In this study, we compared the effect of the isospin asymmetry of proton and neutron density distributions in the neutron skin-type (NST) case and in the Hartree-Fock formalism (HF) on the half-life of alpha emitters with the atomic number in the range of \begin{document}$82\leqslant Z\leqslant 92$\end{document}. The NST case and HF formalism based on the Skyrme-SLy4 effective interaction reveal different isospin asymmetries for selected alpha emitters. Furthermore, the obtained results reveal an increase in the α-decay widths of about 30% for the NST case in comparison with the equivalent values obtained by HF formalism. The standard deviations for calculated half-lives within the NST case and HF formalism are about 0.438 and 0.391, respectively.
2019, 43(12): 124106. doi: 10.1088/1674-1137/43/12/124106
Abstract:
We study the structure of neutron-rich calcium isotopes in the shell model with realistic interactions. The CD-Bonn and Kuo-Brown (KB) interactions are used. As these interactions do not include the three-body force, their direct use leads to poor results. We tested whether the adjustment of the single particle energies (SPEs) would be sufficient to include the three-body correlations empirically. It turns out that the CD-Bonn interaction, after the adjustment of SPEs, gives good agreement with the experimental data for the energies and spectroscopy. For the KB interaction, both the SPEs and monopole terms require adjustments. Thus, the monopole problem is less serious for modern realistic interactions which include perturbations up to the third order. We also tested the effect of the non-central force on the shell structure. It is found that the effect of the tensor force in the CD-Bonn interaction is weaker than in the KB interaction.
2019, 43(12): 124107. doi: 10.1088/1674-1137/43/12/124107
Abstract:
All existing experimental evidence for the bound state nature of \begin{document}$X(3872)$ \end{document} relies on observing its decay products, which are measured with a finite experimental mass resolution that is typically \begin{document}$\Delta m \geqslant 2$ \end{document} MeV , and much larger than its alleged binding energy, \begin{document}$B_X=0.00\,(18)$ \end{document} MeV. On the other hand, we have found recently that there is a clear cancellation in the \begin{document}$1^{++}$ \end{document} channel of the invariant \begin{document}$D {\bar D}^*$ \end{document} mass around the threshold between continuum and the bound state. This is very much like a similar cancellation in the proton-neutron continuum with the deuteron in the \begin{document}$1^{++}$ \end{document} channel. Based on comparative fits with a common Tsallis distribution of the experimental cross-sections for prompt production of deuterons and \begin{document}$X(3872)$ \end{document} in pp collisions with a finite \begin{document}$p_T$ \end{document}, we find a strong argument for questioning the bound state nature of this state, which also suggests that the large observed production rate could be consistent with a half-bound state.
2019, 43(12): 124108. doi: 10.1088/1674-1137/43/12/124108
Abstract:
A microscopic high spin study of neutron deficient and normally deformed 133,135,137Sm has been carried out in projected shell model framework. The theoretical results have been obtained for the spins, parities and energy values of yrast and excited bands. Besides this, the band spectra, band head energies, moment of inertia and electromagnetic transition strengths are also predicted in these isotopes. The calculations successfully give a deeper understanding of the mechanism of the formation of yrast and excited bands from the single and multi-quasi particle configurations. The results on moment of inertia predict an alignment of a pair of protons in the proton (1h11/2)2 orbitals in the yrast ground state bands of 133-137Sm due to the crossing of one quasiparticle bands by multi-quasiparticle bands at higher spins. The discussion in the present work is based on the deformed single particle scheme. Any future experimental confirmation or refutation of our predictions will be a valuable information which can help to understand the deformed single particle structure in these odd mass neutron deficient 133-137Sm.
2019, 43(12): 124109. doi: 10.1088/1674-1137/43/12/124109
Abstract:
We investigate the mass-shift of P-wave charmonium (\begin{document}${\chi_c}_0$\end{document}, \begin{document}${\chi_c}_1$\end{document}), and S and P-wave bottomonium (\begin{document}$\eta_b$\end{document}, \begin{document}$\Upsilon$\end{document}, \begin{document}${\chi_b}_0$\end{document}, and \begin{document}${\chi_b}_1$\end{document}) states in magnetized hot asymmetric nuclear matter using the unification of QCD sum rules (QCDSR) and the chiral \begin{document}$SU(3)$\end{document} model. Within QCDSR, we use two approaches, i.e., the moment sum rule and the Borel sum rule. The magnetic field induced scalar gluon condensate \begin{document}$\left\langle \frac{\alpha_{s}}{\pi} G^a_{\mu\nu} {G^a}^{\mu\nu} \right\rangle$\end{document} and the twist-2 gluon operator \begin{document}$\left\langle \frac{\alpha_{s}}{\pi} G^a_{\mu\sigma} {{G^a}_\nu}^{\sigma} \right\rangle$\end{document} calculated in the chiral \begin{document}$SU(3$\end{document}) model are utilised in QCD sum rules to calculate the in-medium mass-shift of the above mesons. The attractive mass-shift of these mesons is observed, which is more sensitive to magnetic field in the high density regime for charmonium, however less so for bottomonium. These results may be helpful to understand the decay of higher quarkonium states to the lower quarkonium states in asymmetric heavy ion collision experiments.
2019, 43(12): 124110. doi: 10.1088/1674-1137/43/12/124110
Abstract:
The electric quadrupole moment \begin{document}$Q$\end{document} and the magnetic moment \begin{document}$\mu$\end{document} (or the \begin{document}$g$\end{document} factor) of low-lying states in even-even nuclei 72-80Ge and odd-mass nuclei 75-79Ge are studied in the framework of the nucleon pair approximation (NPA) of the shell model, assuming the monopole and quadrupole pairing plus quadrupole-quadrupole interaction. Our calculations reproduce well the experimental values of \begin{document}$Q(2_1^{+})$\end{document} and \begin{document}$g(2_1^+)$\end{document} for 72,74,76Ge, as well as the yrast energy levels of these isotopes. The structure of the \begin{document}$2_1^+$\end{document} states and the contributions of the proton and neutron components in \begin{document}$Q(2_1^{+})$\end{document} and \begin{document}$g(2_1^+)$\end{document} are discussed in the \begin{document}$SD$\end{document}-pair truncated shell-model subspace. The overall trend of \begin{document}$Q(2_1^{+})$\end{document} and \begin{document}$g(2_1^+)$\end{document} as a function of the mass number \begin{document}$A$\end{document}, as well as their signs, are found to originate essentially from the proton contribution. The negative value of \begin{document}$Q(2^+_1)$\end{document} in 72,74Ge is suggested to be due to the enhanced quadrupole-quadrupole correlation and configuration mixing.
2019, 43(12): 125101. doi: 10.1088/1674-1137/43/12/125101
Abstract:
Considering the cosmological constant as the pressure, this study addresses the laws of thermodynamics and weak cosmic censorship conjecture in the Reissner-Nordström-AdS black hole surrounded by quintessence dark energy under charged particle absorption. The first law of thermodynamics is found to be valid as a particle is absorbed by the black hole. The second law, however, is violated for the extremal and near-extremal black holes, because the entropy of these black hole decrease. Moreover, we find that the extremal black hole does not change its configuration in the extended phase space, implying that the weak cosmic censorship conjecture is valid. Remarkably, the near-extremal black hole can be overcharged beyond the extremal condition under charged particle absorption. Hence, the cosmic censorship conjecture could be violated for the near-extremal black hole in the extended phase space. For comparison, we also discuss the first law, second law, and the weak cosmic censorship conjecture in normal phase space, and find that all of them are valid in this case.
2019, 43(12): 125102. doi: 10.1088/1674-1137/43/12/125102
Abstract:
We test the possible dipole anisotropy of the Finslerian cosmological model and the other three dipole-modulated cosmological models, i.e. the dipole-modulated ΛCDM, wCDM and Chevallier–Polarski–Linder (CPL) models, by using the recently released Pantheon sample of SNe Ia. The Markov chain Monte Carlo (MCMC) method is used to explore the whole parameter space. We find that the dipole anisotropy is very weak in all cosmological models used. Although the dipole amplitudes of four cosmological models are consistent with zero within the \begin{document}$1\sigma$\end{document} uncertainty, the dipole directions are close to the axial direction of the plane of the SDSS subsample in Pantheon. This may imply that the weak dipole anisotropy in the Pantheon sample originates from the inhomogeneous distribution of the SDSS subsample. A more homogeneous distribution of SNe Ia is necessary to constrain the cosmic anisotropy.
2019, 43(12): 129101. doi: 10.1088/1674-1137/43/12/129101
Abstract:
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