Highlights
  • Charged pion condensation in anti-parallel electromagnetic fields and nonzero isospin density
    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.
  • Hunting potassium geoneutrinos with liquid scintillator Cherenkov neutrino detectors
    The research on geoneutrinos is a new interdisciplinary subject involving particle experiments and geo-science. Potassium-40 (40K) decays contribute roughly to 1/3 of the radiogenic heat of the Earth, which is not yet accounted for by experimental observation. Solar neutrino experiments with liquid scintillators have observed uranium and thorium geoneutrinos and are the most promising experiments with regard to low-background neutrino detection. In this study, we present the new concept of using liquid-scintillator Cherenkov detectors to detect the neutrino-electron elastic scattering process of 40K geoneutrinos. Liquid-scintillator Cherenkov detectors using a slow liquid scintillator achieve this goal with both energy and direction measurements for charged particles. Given the directionality, we can significantly suppress the dominant intrinsic background originating from solar neutrinos in conventional liquid-scintillator detectors. We simulated the solar- and geo-neutrino scatterings in the slow liquid scintillator detector, and implemented energy and directional reconstructions for the recoiling electrons. We found that 40K geoneutrinos can be detected with three-standard-deviation accuracy in a kiloton-scale detector.
  • High-K multi-particle bands and pairing reduction in 254No
    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.
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  • Semileptonic decays $ {{B/B_s \to (D^{(*)},D_s^{(*)}) l \nu_l}} $ in the PQCD approach with the lattice QCD input
    Published: 2020-04-08, doi: 10.1088/1674-1137/44/5/053102
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    We study the semileptonic $ B/B_s \to (D^{(*)},D_s^{(*)}) l\nu_l $ decays in the framework of the Standard Model (SM), by employing the perturbative QCD (PQCD) factorization formalism combined with the lattice QCD input for the relevant transition form factors. We calculate the branching ratios $ {\cal B}(B_{(s)} \to D_{(s)}^{(*)} l \nu_l ) $ with $ l = (e,\mu,\tau) $, the ratios of the branching fractions $ R(D^{(*)}) $ and $ R(D_s^{(*)} ) $, and the physical observables $ P_\tau(D_{(s)}^{(*)}) $, $ F_L(D^*_{(s)}) $ and $ A_{FB}(\tau) $. The “PQCD+Lattice” predictions for $ {\cal B}(B \to D^{(*)} l\nu_l) $ and $ R(D^{(*)}) $ agree with the available experimental measurements within errors. For the ratios $ R(D_s) $ and $ R(D_s^*) $, the "PQCD+Lattice" predictions agree with the other predictions. For $ P_\tau(D^*) $ and $ F_L(D^*) $, our theoretical predictions agree with the measured values within errors. Our theoretical predictions of the semileptonic $ B/B_s $ decays considered could be tested in the near future by the LHCb and Belle II experiments.
  • A new cosmological probe using super-massive black hole shadows
    Published: 2020-04-07, doi: 10.1088/1674-1137/44/5/055105
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    We study the prospects of using the low-redshift and high-redshift black hole shadows as new cosmological standard rulers for measuring cosmological parameters. We show that, using the low-redshift observation of the black hole shadow of ${\rm M87}^\star$, the Hubble constant can be independently determined with a precision of about 13% as $H_0=70\pm 9$ km ${\rm s}^{-1}$ ${\rm Mpc}^{-1}$. The high-redshift observations of super-massive black hole shadows may accurately determine a combination of parameters $H_0$ and ${\Omega_{m}}$, and we show by a simple simulation that combining them with the type Ia supernovae observations would give precise measurements of the cosmological parameters.
  • Ξbb and Ωbbb molecular states
    Published: 2020-04-03, doi: 10.1088/1674-1137/44/6/064101
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    Using the vector exchange interaction in the local hidden gauge approach, which in the light quark sector generates the chiral Lagrangians and has produced realistic results for $\Omega_c, \Xi_c, \Xi_b$ and the hidden charm pentaquark states, we study the meson-baryon interactions in the coupled channels that lead to the $\Xi_{bb}$ and $\Omega_{bbb}$ excited states of the molecular type. We obtain seven states of the $\Xi_{bb}$ type with energies between $10408$ and $10869$ MeV, and one $\Omega_{bbb}$ state at $15212$ MeV.
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