Higlights
• Constraining the anisotropy of the Universe with the Pantheon supernovae sample
2019, 43(12): 125102. doi: 10.1088/1674-1137/43/12/125102
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 $1\sigma$ 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.
• QCD analysis of CMS W + charm measurements at LHC with ${\sqrt { s} = 7\; {\bf{TeV}}}$ and implications for strange PDF
2019, 43(12): 123101. doi: 10.1088/1674-1137/43/12/123101
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 $W+$ 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 $W+$ charm production data to the original CT14NNLO PDFs. By comparison of the $g(x,Q)$, $s(x,Q)$, $u(x,Q)$, $d(x,Q)$, $\bar u(x,Q)$, and $\bar d(x,Q)$ PDFs at $Q=1.3$ GeV and $Q = 100$ GeV for the CT14NNLO and CT14NNLO+Wc, we see that the error band of the $s(x,Q)$ PDF is reduced in the region $x<0.4$, and the error band of $g(x,Q)$ PDF is also slightly reduced at region $0.01 < x<0.1$.
• Microscopic study of electromagnetic properties and band spectra of neutron deficient 133,135,137Sm
2019, 43(12): 124108. doi: 10.1088/1674-1137/43/12/124108
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.
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• Mass spectra and wave functions of the doubly heavy baryons with JP=1+ heavy diquark cores
Published: 2019-12-13, doi: 10.1088/1674-1137/44/1/013102
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Mass spectra and wave functions of the doubly heavy baryons are computed assuming that the two heavy quarks inside a baryon form a compact heavy ‘diquark core’ in a color anti-triplet, and bind with the remaining light quark into a colorless baryon. The two reduced two-body problems are described by the relativistic Bethe-Salpeter equations (BSEs) with the relevant QCD inspired kernels. We focus on the doubly heavy baryons with $1^+$ heavy diquark cores. After solving BSEs in the instantaneous approximation, we present the mass spectra and the relativistic wave functions of the diquark cores, and of the low-lying baryon states $J^P=\frac{1}{2}^+$ and $\frac{3}{2}^+$ with flavors $(ccq)$, $(bcq)$ and $(bbq)$. A comparison with other approaches is also made.
• Isotopic cross-sections in proton induced spallation reactions based on the Bayesian neural network method
Published: 2019-12-11, doi: 10.1088/1674-1137/44/1/014104
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The Bayesian neural network (BNN) method is proposed to predict the isotopic cross-sections in proton induced spallation reactions. Learning from more than 4000 data sets of isotopic cross-sections from 19 experimental measurements and 5 theoretical predictions with the SPACS parametrization, in which the mass of the spallation system ranges from 36 to 238, and the incident energy from 200 MeV/u to 1500 MeV/u, it is demonstrated that the BNN method can provide good predictions of the residue fragment cross-sections in spallation reactions.
• Predictions of ${\Upsilon{(4S) }\to {h_b(1P,2P) \pi^+\pi^-}}$ transitions
Published: 2019-12-06, doi: 10.1088/1674-1137/44/2/023103
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We study the contributions of intermediate bottomonium-like $Z_b$ states and the bottom meson loops in the heavy quark spin flip transitions $\Upsilon(4S) \to h_b(1P,2P) \pi^+\pi^-$. Depending on the constructive or destructive interferences between the $Z_b$-exchange and the bottom meson loops mechanisms, we predict two possible branching ratios for each process: BR$_{\Upsilon(4S) \to h_b(1P)\pi^+\pi^-}\simeq\big(1.2^{+0.8}_{-0.4}\times10^{-6}\big)$ or $\big( 0.5^{+0.5}_{-0.2}\times10^{-6}\big)$, and ${{BR}}_{\Upsilon(4S) \to h_b(2P)\pi^+\pi^-}\simeq \big(7.1^{+1.7}_{-1.1}\times10^{-10}\big)$ or $\big( 2.4^{+0.2}_{-0.1}\times10^{-10}\big)$. The contribution of the bottom meson loops is found to be considerably larger than that of the $Z_b$-exchange in the $\Upsilon(4S) \to h_b(1P) \pi\pi$ transitions, while its decay rates are not comparable to those of heavy quark spin conserved $\Upsilon(4S) \to \Upsilon(1S,2S) \pi\pi$ processes. We also predict the contribution of the charm meson loops in the branch fractions of $\psi(3S,4S) \to h_c(1P)\pi\pi$.
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2019 Vol. 43, No. 12
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