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High-K multi-particle bands and pairing reduction in 254No
Xiao-Tao He, Shu-Yong Zhao, Zhen-Hua Zhang, Zhong-Zhou Ren
Published: , doi: 10.1088/1674-1137/44/3/034106
The multi-particle states and rotational properties of the two-particle bands in $^{254}{\rm{No}}$ are investigated by the cranked shell model with pairing correlations treated by the particle number conserving method. The rotational bands on top of the two-particle $K^{\pi}=3^+, \;8^-$ and $10^+$ states and the pairing reduction are studied theoretically in $^{254}{\rm{No}}$ for the first time. The experimental excitation energies and moments of inertia of the multi-particle states are reproduced well by the calculations. Better agreement with the data is achieved by including the high-order deformation $\varepsilon_{6}$, which leads to enlarged $Z=100$ and $N=152$ deformed shell gaps. An increase of $J^{(1)}$ in these two-particle bands compared with the ground state band is attributed to the pairing reduction due to the Pauli blocking effect.
Drawing insights from pion parton distributions
Minghui Ding, Khépani Raya, Daniele Binosi, Lei Chang, C. D. Roberts, S. M. Schmidt
Published: , doi: 10.1088/1674-1137/44/3/031001
A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale $\zeta_2:=2\,{\rm{GeV:}}\langle x_{\rm valence} \rangle = 0.48(3)$, $\langle x_{\rm glue} \rangle = 0.41(2)$, $\langle x_{\rm sea} \rangle = 0.11(2)$; and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, $q^\pi(x)$, exhibits the $x\simeq 1$ behaviour predicted by quantum chromodynamics (QCD). After evolution to $\zeta=5.2\,{\rm{GeV}}$, the prediction for $q^\pi(x)$ matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.
Comparative study of the forward and backward methods for calculating jet properties in pp collisions at ${\sqrt{ s}}$=7 TeV
Yu-Liang Yan, Ayut Limphirat, Dai-Mei Zhou, Pornrad Srisawad, Yupeng Yan, Chunbin Yang, Xu Cai, Ben-Hao Sa
Published: , doi: 10.1088/1674-1137/44/3/034104
We propose a forward method based on PYTHIA6.4 to study the jet properties in ultra-relativistic pp collisions. In the forward method, the partonic initial states are first generated with PYTHIA6.4 and then hadronized in the Lund string fragmentation model, and finally the hadronic jets are constructed from the created hadrons. Jet properties calculated with the forward method for pp collisions at $\sqrt{s}$=7 TeV are comparable to those calculated with the usual anti-$k_t$ algorithm (backward method) in PYTHIA6.4. The comparison between the backward and forward methods may contribute to the understanding of the partonic origin of jets in the backward method.
Nuclear chart in covariant density functional theory with dynamic correlations: From oxygen to tin
Yi-Long Yang, Ya-Kun Wang
Published: , doi: 10.1088/1674-1137/44/3/034102
Nuclear masses of even-even nuclei with the proton number $8\leqslant Z\leqslant 50$ (O to Sn isotopes) from the proton drip line to neutron drip line are investigated using the triaxial relativistic Hartree-Bogoliubov theory with the relativistic density functional PC-PK1. Further, the dynamical correlation energies (DCEs) associated with the rotational motion and quadrupole-shaped vibrational motion are taken into account by the five-dimensional collective Hamiltonian (5DCH) method. The root-mean-square deviation with respect to the experimental masses reduces from 2.50 to 1.59 MeV after the consideration of DCEs. The inclusion of DCEs has little influence on the position of drip lines, and the predicted numbers of bound even-even nuclei between proton and neutron drip lines from O to Sn isotopes are 569 and 564 with and without DCEs, respectively.
Charged pion condensation in anti-parallel electromagnetic fields and nonzero isospin density
Jingyi Chao, Mei Huang, Andrey Radzhabov
Published: , doi: 10.1088/1674-1137/44/3/034105
The formation of charged pion condensate in anti-parallel electromagnetic fields and in the presence of the isospin chemical potential is studied in the two-flavor Nambu–Jona-Lasinio model. The method of Schwinger proper time is extended to explore the quantities in the off-diagonal flavor space, i.e. the charged pion. In this framework, $\pi^{\pm}$ are treated as bound states of quarks and not as point-like charged particles. The isospin chemical potential plays the role of a trigger for charged pion condensation. We obtain the associated effective potential as a function of the strength of the electromagnetic fields and find that it contains a sextic term which possibly induces a weak first order phase transition. The dependence of pion condensation on model parameters is investigated.
Neutron-antineutron oscillations in the deuteron studied with NN and ${{\bar NN}}$ interactions based on chiral effective field theory
Johann Haidenbauer, Ulf-G. Meißner
Published: , doi: 10.1088/1674-1137/44/3/033101
Neutron-antineutron ($ n-\bar n $) oscillations in the deuteron are considered. Specifically, the deuteron lifetime is calculated in terms of the free-space $ n-\bar n $ oscillation time $ \tau_{n-\bar n} $ based on $ NN $ and $ \bar NN $ interactions derived within chiral effective field theory (EFT). This results in $ (2.6\pm 0.1) \times 10^{22}\,\tau^2_{n-\bar n} $ s, which is close to the value obtained by Dover and collaborators more than three decades ago, but disagrees with recent EFT calculations that were performed within the perturbative scheme proposed by Kaplan, Savage, and Wise. Possible reasons for the difference are discussed.
Applicability of 9Be global optical potential to description of 8,10,11B elastic scattering
Yong-Li Xu, Yin-Lu Han, Hai-Ying Liang, Zhen-Dong Wu, Hai-Rui Guo, Chong-Hai Cai
Published: , doi: 10.1088/1674-1137/44/3/034101
We achieved a set of 9Be global phenomenological optical model potentials by fitting a large experimental dataset of the elastic scattering observable for target mass numbers from 24 to 209. The obtained 9Be global optical model potential was applied to predict elastic-scattering angular distributions and total reaction cross-sections of 8,10,11B projectiles. The predictions are made by performing a detailed analysis comparing with the available experimental data. Furthermore, these elastic scattering observables are also predicted for some lighter targets outside of the given mass number range, and reasonable results are obtained. Possible physical explanations for the observed differences are also discussed.