Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Neutron-antineutron ( <jats:inline-formula> <jats:tex-math><?CDATA $ n-\bar n $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033101_M2.jpg" xlink:type="simple" /> </jats:inline-formula>) oscillations in the deuteron are considered. Specifically, the deuteron lifetime is calculated in terms of the free-space <jats:inline-formula> <jats:tex-math><?CDATA $ n-\bar n $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033101_M3.jpg" xlink:type="simple" /> </jats:inline-formula> oscillation time <jats:inline-formula> <jats:tex-math><?CDATA $ \tau_{n-\bar n} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033101_M4.jpg" xlink:type="simple" /> </jats:inline-formula> based on <jats:inline-formula> <jats:tex-math><?CDATA $ NN $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033101_M5.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ \bar NN $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033101_M6.jpg" xlink:type="simple" /> </jats:inline-formula> interactions derived within chiral effective field theory (EFT). This results in <jats:inline-formula> <jats:tex-math><?CDATA $ (2.6\pm 0.1) \times 10^{22}\,\tau^2_{n-\bar n} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033101_M7.jpg" xlink:type="simple" /> </jats:inline-formula> 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. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Tensor reduction is of considerable importance in calculations of multi-loop amplitudes, and the projection method is one of the most popular approaches for tensor reduction. However, the projection method can be problematic when applied to amplitudes with massive fermions, due to the inconsistency between helicity and chirality. We propose an extended projection method for reducing the loop amplitude which contains a fermion chain with two massive spinors. The extension is achieved by decomposing one of the massive spinors into two massless spinors, the “null spinor” and the “reference spinor”. The extended projection method can be effectively applied in all processes, including the production of massive fermions. We present the tensor reduction for a virtual <jats:italic>Z</jats:italic> boson decaying into a top-quark pair as a demonstration of our approach. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>In order to make a further confirmation of the assignments of the excited bottom and bottom-strange mesons <jats:inline-formula> <jats:tex-math><?CDATA $ B_{1}(5721) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M7.jpg" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math><?CDATA $ B_{2}^{*}(5747) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M8.jpg" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math><?CDATA $ B_{s1}(5830) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M9.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ B_{s2}^{*}(5840) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M10.jpg" xlink:type="simple" /> </jats:inline-formula> and identify possible assignments of <jats:inline-formula> <jats:tex-math><?CDATA $ B_{J}(5840) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M11.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ B_{J}(5970) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M12.jpg" xlink:type="simple" /> </jats:inline-formula>, we study the strong decay of these states with the <jats:inline-formula> <jats:tex-math><?CDATA $ ^{3}P_{0} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M13.jpg" xlink:type="simple" /> </jats:inline-formula> decay model. Our analysis supports the assignments of <jats:inline-formula> <jats:tex-math><?CDATA $ B_{1}(5721) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M14.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ B_{2}^{*}(5747) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M15.jpg" xlink:type="simple" /> </jats:inline-formula> as the <jats:inline-formula> <jats:tex-math><?CDATA $ 1P_{1}' $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M16.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ 1^{3}P_{2} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M17.jpg" xlink:type="simple" /> </jats:inline-formula> states, and <jats:inline-formula> <jats:tex-math><?CDATA $ B_{s1}(5830) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M18.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ B_{s2}^{*}(5840) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M19.jpg" xlink:type="simple" /> </jats:inline-formula> as the strange partners of <jats:inline-formula> <jats:tex-math><?CDATA $ B_{1}(5721) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M20.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ B_{2}^{*}(5747) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M21.jpg" xlink:type="simple" /> </jats:inline-formula>. Besides, we tentatively identify the recently observed <jats:inline-formula> <jats:tex-math><?CDATA $ B_{J}(5840) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M22.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ B_{J}(5970) $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M23.jpg" xlink:type="simple" /> </jats:inline-formula> as the <jats:inline-formula> <jats:tex-math><?CDATA $ 2^{3}S_{1} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M24.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ 1^{3}D_{3} $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M25.jpg" xlink:type="simple" /> </jats:inline-formula> states. It is noted that these conclusions need further confirmation by measurements of the decay channels <jats:inline-formula> <jats:tex-math><?CDATA $ B_{J}(5840)\rightarrow B\pi $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M26.jpg" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math><?CDATA $ B_{J}(5970)\rightarrow B\pi $?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033103_M27.jpg" xlink:type="simple" /> </jats:inline-formula> . </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Calculation of disconnected quark loops in lattice QCD is very time consuming. Stochastic noise methods are generally used to estimate these loops. However, stochastic estimation gives large errors in the calculations of disconnected diagrams. We use the symmetric multi-probing source (SMP) method to estimate the disconnected quark loops, and compare the results with the <jats:inline-formula> <jats:tex-math><?CDATA $Z(2)$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033104_M1.jpg" xlink:type="simple" /> </jats:inline-formula> noise method and the spin-color explicit (SCE) method on a quenched lattice QCD ensemble with lattice volume <jats:inline-formula> <jats:tex-math><?CDATA $12^{3}\times24$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033104_M3.jpg" xlink:type="simple" /> </jats:inline-formula> and lattice spacing <jats:inline-formula> <jats:tex-math><?CDATA $a\approx0.1$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033104_M4.jpg" xlink:type="simple" /> </jats:inline-formula> fm. The results show that the SMP method is very suitable for the calculation of pseudoscalar disconnected quark loops. However, the SMP and SCE methods do not have an obvious advantage over the <jats:inline-formula> <jats:tex-math><?CDATA $Z(2)$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_033104_M5.jpg" xlink:type="simple" /> </jats:inline-formula> noise method in the evaluation of the scalar disconnected loops. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>The cross-section data of the <jats:sup>85</jats:sup>Rb(<jats:italic>n</jats:italic>, 2<jats:italic>n</jats:italic>)<jats:sup>84</jats:sup>Rb reaction have been measured with the neutron energies of 12 MeV to 19.8 MeV using the activation technique and the relative method. The <jats:sup>85</jats:sup>Rb samples were irradiated on the surface of a two-ring orientation assembly with neutrons produced from the <jats:sup>3</jats:sup>H(<jats:italic>d</jats:italic>, <jats:italic>n</jats:italic>)<jats:sup>4</jats:sup>He reaction at the 5SDH-2 1.7-MV Tandem accelerator in China. Theoretical model calculations were performed with the TALYS-1.9 code. The present data were compared with previously obtained experimental data and the available evaluated data. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>We achieved a set of <jats:sup>9</jats:sup>Be 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 <jats:sup>9</jats:sup>Be global optical model potential was applied to predict elastic-scattering angular distributions and total reaction cross-sections of <jats:sup>8,10,11</jats:sup>B 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. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Nuclear masses of even-even nuclei with the proton number <jats:inline-formula> <jats:tex-math><?CDATA $8\leqslant Z\leqslant 50$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_034102_M1.jpg" xlink:type="simple" /> </jats:inline-formula> (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. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a new method for solving the probability distribution for baryons, antibaryons, and mesons at the hadronization of the constituent quark and antiquark system. The hadronization is governed by the quark combination rule in the quark combination model developed by the Shandong Group. We employ the method of the generating function to derive the outcome of the quark combination rule, which is significantly simpler and easier to generalize than the original method. Furthermore, we use the formula of the quark combination rule and its generalization to study the property of the multiplicity distribution of net-protons. Taking a naive case of quark number fluctuations and correlations at hadronization, we calculate ratios of multiplicity cumulants of final-state net-protons and discuss the potential applicability of the quark combination model by studying hadronic multiplicity fluctuations and the underlying phase transition property in relativistic heavy-ion collisions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We propose a forward method based on PYTHIA6.4 to study the jet properties in ultra-relativistic <jats:italic>pp</jats:italic> 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 <jats:italic>pp</jats:italic> collisions at <jats:inline-formula> <jats:tex-math><?CDATA $\sqrt{s}$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_034104_M2.jpg" xlink:type="simple" /> </jats:inline-formula>=7 TeV are comparable to those calculated with the usual anti- <jats:inline-formula> <jats:tex-math><?CDATA $k_t$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_034104_M3.jpg" xlink:type="simple" /> </jats:inline-formula> 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. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>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, <jats:inline-formula> <jats:tex-math><?CDATA $\pi^{\pm}$?></jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpc_44_3_034105_M1.jpg" xlink:type="simple" /> </jats:inline-formula> 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. </jats:p>