Higlights
• A non-relativistic model for the [cc] [cc] tetraquark
2019, 43(1): 013105. doi: 10.1088/1674-1137/43/1/013105
We use a non-relativistic model to study the spectroscopy of a tetraquark composed of [cc] [cc] in a diquark-antidiquark configuration. By numerically solving the Schrödinger equation with a Cornell-inspired potential, we separate the four-body problem into three two-body problems. Spin-dependent terms (spin-spin, spin-orbit and tensor) are used to describe the splitting structure of the cc spectrum and are also extended to the interaction between diquarks. Recent experimental data on charmonium states are used to fix the parameters of the model and a satisfactory description of the spectrum is obtained. We find that the spin-dependent interaction is sizable in the diquark-antidiquark system, despite the heavy diquark mass, and also that the diquark has a finite size if treated in the same way as the cc systems. We find that the lowest S-wave T4c tetraquarks might be below their thresholds of spontaneous dissociation into low-lying charmonium pairs, while orbital and radial excitations would be mostly above the corresponding charmonium pair thresholds. Finally, we repeat the calculations without the confining part of the potential and obtain bound diquarks and bound tetraquarks. This might be relevant to the study of exotic charmonium in the quark-gluon plasma. The T4c states could be investigated in the forthcoming experiments at the LHC and Belle Ⅱ.
• Mixed electroweak-QCD corrections to e+e-μ+μ-H at CEPC with finite-width effect
2019, 43(1): 013108. doi: 10.1088/1674-1137/43/1/013108
The associated production of Higgs boson with a muon pair, e+e-μ+μ-H, is one of the golden channels to pin down the properties of the Higgs boson in the prospective Higgs factories exemplified by CEPC. The projected accuracy of the corresponding cross section measurement is about per cent level at CEPC. In this work, we investigate both O(α) weak correction and the O(ααs) mixed electroweak-QCD corrections for this channel, appropriately taking into account the effect of finite Z0 width. The μ+μ- invariant mass spectrum is also predicted. The mixed electroweak-QCD correction turns out to reach 1.5% of the Born-order result, and thereby must be included in future confrontation with the data. We also observe that, after including higher-order corrections, the simplified prediction for the integrated cross section employing the narrow-width-approximation may deviate from our full result by a few per cents.
• Alternative methods for measurement of the global polarization of Λ hyperons
2019, 43(1): 014103. doi: 10.1088/1674-1137/43/1/014103
We propose alternative methods for measurement of the global polarization of Λ hyperons. These methods involve event averages of proton and Λ momenta in the laboratory frame. We carry out simulations using these methods and show that all of them work equally well in obtaining the global polarization of Λ hyperons.
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• Observation of ${{e^+e^- \rightarrow D_s^+} \overline{ D}^{\bf (*)0} {K^-}}$ and study of the P-wave ${{D_s}}$ mesons
Published: 2019-01-18, doi: 10.1088/1674-1137/43/3/031001
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Studies of $e^+e^- \to D^+_s \overline{D}{}^{(*)0}K^-$ and the $P$ -wave charmed-strange mesons are performed based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567 pb−1 collected with the BESIII detector at $\sqrt{s}= 4.600$ GeV. The processes of $e^+e^-\to D^+_s \overline{D}{}^{*0} K^-$ and $D^+_s \overline{D}{}^{0} K^-$ are observed for the first time and are found to be dominated by the modes $D_s^+ D_{s1}(2536)^-$ and $D_s^+ D^*_{s2}(2573)^-$ , respectively. The Born cross sections are measured to be $\sigma^{B}(e^+e^-\to D^+_s \overline{D}{}^{*0} K^-) = (10.1\pm2.3\pm0.8)$ pb and $\sigma^{B}(e^+e^-\to D^+_s \overline{D}{}^{0} K^-) = (19.4\pm2.3\pm1.6)$ pb, and the products of Born cross section and the decay branching fraction are measured to be $\sigma^{B}(e^+e^-\to D^+_s D_{s1}(2536)^- + c.c.)\cdot$ ${\cal{B}}( D_{s1}(2536)^- \to \overline{D}{}^{*0} K^-) = (7.5 \pm 1.8 \pm 0.7)$ pb and $\sigma^{B}(e^+e^-\to D^+_s D^*_{s2}(2573)^- + c.c.)\cdot {\cal{B}}( D^*_{s2}(2573)^- \to \overline{D}{}^{0} K^-) =$ $(19.7 \pm 2.9 \pm 2.0)$ pb. For the $D_{s1}(2536)^-$ and $D^*_{s2}(2573)^-$ mesons, the masses and widths are measured to be $M( D_{s1}(2536)^- ) = (2537.7 \pm 0.5 \pm 3.1)\; {\rm{MeV}}/c^2$ , $\Gamma( D_{s1}(2536)^- ) = (1.7\pm 1.2 \pm 0.6)$ MeV, and $M( D^*_{s2}(2573)^- ) =$ $(2570.7\pm 2.0 \pm 1.7)\; {\rm{MeV}}/c^2,$ $\Gamma( D^*_{s2}(2573)^- ) = (17.2 \pm 3.6 \pm 1.1)$ MeV. The spin-parity of the $D^*_{s2}(2573)^-$ meson is determined to be $J^P=2^{+}$ . In addition, the processes $e^+e^-\to D^+_s \overline{D}{}^{(*)0} K^-$ are searched for using the data samples taken at four (two) center-of-mass energies between 4.416 (4.527) and 4.575 GeV, and upper limits at the 90% confidence level on the cross sections are determined.
• Spectroscopy of light ${{N^*}}$ baryons
Published: 2019-01-18, doi: 10.1088/1674-1137/43/3/034106
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We present the masses of N baryons upto 3300 MeV. The radial and orbital excited states are determined using hypercentral constituent quark model with the first-order correction. The obtained masses are compared with the experimental results and other theoretical predictions. The Regge trajectories are also determined in (n, $M^2$ ) and (J, $M^2$ ) planes. Moreover, the magnetic moments with $J^{P}= \displaystyle\frac{1}{2}^{+}, \displaystyle\frac{1}{2}^{-}$ are calculated. We also calculates the $N\pi$ decay width of excited nucleons.
• In-medium NN→NΔ cross section and its dependence on effective Lagrange parameters in isospin-asymmetric nuclear matter
Published: 2019-01-14, doi: 10.1088/1674-1137/43/2/024105
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The in-medium $NN\rightarrow N\Delta$ cross sections and its differential cross sections in isospin asymmetric nuclear medium are investigated in the framework of the one-boson exchange model by including isovector mesons, i.e., $\delta$ and $\rho$ mesons. Our results show that the in-medium $NN\rightarrow N\Delta$ cross sections are suppressed when the density increases, and the differential cross sections become isotropic with an increase in the density around the $\Delta$ threshold energy. The isospin splitting on the medium correction factor, $R=\sigma_{ NN\rightarrow N\Delta}^*/\sigma_{NN\rightarrow N\Delta}^{\rm{free}}$ is observed for different channels of $NN\to N\Delta$ , especially around the threshold energy for all the effective Lagrangian parameters. By analyzing the selected effective Lagrangian parameters, our results show that the larger effective mass is, the weaker medium correction $R$ is.
Current Issued
2019 Vol. 43, No. 1
Published: 05 January 2019
Archive
IF: 3.298

Monthly founded in 1977

ISSN 1674-1137 CN 11-5641/O4

Original research articles, Ietters and reviews Covering theory and experiments in the fieids of

• Particle physics
• Nuclear physics
• Particle and nuclear astrophysics
• Cosmology
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