Highlights
• What can we learn from the total width of the Higgs boson?
2023, 47(3): 033101. doi: 10.1088/1674-1137/aca8f6
As one of the key properties of the Higgs boson, the Higgs total width is sensitive to the global profile of the Higgs boson couplings, and thus new physics would modify the Higgs width. We investigate the total width in various new physics models, including various scalar extensions, composite Higgs models, and the fraternal twin Higgs model. Typically, the Higgs width is smaller than the standard model value due to mixture with other scalars if the Higgs is elementary, or curved Higgs field space for the composite Higgs. On the other hand, except for the possible invisible decay mode, the enhanced Yukawa coupling in the two Higgs doublet model or the exotic fermion embeddings in the composite Higgs could enhance the Higgs width greatly. The precision measurement of the Higgs total width at the high-luminosity LHC can be used to discriminate certain new physics models.
• Explanation of Y(4630) as a hadronic resonant state
2023, 47(3): 033104. doi: 10.1088/1674-1137/aca959
Theorists have given various explanations for the discovery of Y(4630). We find that if Y(4630) is interpreted as the D-wave resonant state of the $\Lambda_c \bar {\Lambda}_c$ system, the particle mass, decay width, and all quantum numbers are consistent with experimental observations. We use the Bonn approximation to obtain the interaction potential of the one boson exchange model. Then, we extend the complex scaling method to calculate the bound and resonant states. The results indicate that the $\Lambda_c \bar{\Lambda}_c$ system can form not only the bound state of the S wave but also the resonant state of the high angular momentum, and the $^3D_1$ wave resonant state can explain the structure of Y(4630) very well.
• Axial chiral vortical effect in a sphere with finite size effect
2023, 47(3): 034106. doi: 10.1088/1674-1137/acac6d
We investigate the axial vortical effect in a uniformly rotating sphere subject to finite size. We use the MIT boundary condition to limit the boundary of the sphere. For massless fermions inside the sphere, we obtain the exact axial vector current far from the boundary that matches the expression obtained in cylindrical coordinates in literature. On the spherical boundary, we find both the longitudinal and transverse (with respect to the rotation axis) components with magnitude depending on the colatitude angle. For massive fermions, we derive an expansion of the axial conductivity far from the boundary to all orders of mass, whose leading order term agrees with the mass correction reported in literature. We also obtain the leading order mass correction on the boundary, which is linear and stronger than the quadratic dependence far from the boundary. The qualitative implications on the phenomenology of heavy ion collisions are speculated.
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• Nonextensive effects on QCD chiral phase diagram and baryon-number fluctuations within Polyakov-Nambu-Jona-Lasinio model
2023, 47(5): 053103-053103-7. doi: 10.1088/1674-1137/acbf2a
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In this paper, a version of the Polyakov-Nambu-Jona-Lasinio (PNJL) model based on nonextensive statistical mechanics is presented. This new statistics summarizes all possible factors that violate the assumptions of the Boltzmann-Gibbs (BG) statistics to a dimensionless nonextensivity parameter q. Thus, when q tends to 1, it returns to the BG case. Within the nonextensive PNJL model, we found that as q increases, the location of the critical end point (CEP) exhibits non-monotonic behavior. That is, for $q<1.15$, CEP moves in the direction of lower temperature and larger quark chemical potential. However, for $q>1.15$, CEP turns to move in the direction of lower temperature and lower quark chemical potential. In addition, we studied the moments of the net-baryon number distribution, that is, variance ($\sigma^{2}$), skewness (S), and kurtosis (κ). Our results are generally consistent with the latest experimental data reported, especially for $\sqrt{S_{NN}}>19.6\ \mathrm{GeV}$, when q is set to $1.07$.
• Anisotropic strange quark star in Finch-Skea geometry and its maximum mass for non-zero strange quark mass (ms ≠ 0)
2023, 47(5): 055101-055101-16. doi: 10.1088/1674-1137/acb90f
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A class of relativistic astrophysical compact objects is analyzed in the modified Finch-Skea geometry described by the MIT bag model equation of state of interior matter, $p=\dfrac{1}{3}\left(\rho-4B\right)$, where B is known as the bag constant. B plays an important role in determining the physical features and structure of strange stars. We consider the finite mass of the strange quark ($m_{s} \neq 0$) and study its effects on the stability of quark matter inside a star. We note that the inclusion of strange quark mass affects the gross properties of the stellar configuration, such as maximum mass, surface red-shift, and the radius of strange quark stars. To apply our model physically, we consider three compact objects, namely, (i) VELA X-1, (ii) 4U 1820-30, and (iii) PSR J 1903+327, which are thought to be strange stars. The range of B is restricted from 57.55 to $B_{\rm stable}$ ($\rm MeV/fm^{3}$), for which strange matter might be stable relative to iron ($^{56}{\rm Fe}$). However, we also observe that metastable and unstable strange matter depend on B and $m_{s}$. All energy conditions hold well in this approach. Stability in terms of the Lagrangian perturbation of radial pressure is studied in this paper.
• Determining the nuclear temperature dependence on source neutron-proton asymmetry in heavy-ion reactions at intermediate energy
2023, 47(5): 054002-054002-8. doi: 10.1088/1674-1137/acbd91
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In this article, we investigate the dependence of nuclear temperature on emitting source neutron-proton ($N/Z$) asymmetry with light charged particles (LCPs) and intermediate mass fragments (IMFs) generated from intermediate-velocity sources in thirteen reaction systems with different $N/Z$ asymmetries, $^{64} \rm{Zn}$ on $^{112} \rm{Sn}$, and $^{70} \rm{Zn}$, $^{64} \rm{Ni}$ on $^{112,124} \rm{Sn}$, $^{58,64} \rm{Ni}$, $^{197} \rm{Au}$, and $^{232} \rm{Th}$ at 40 MeV/nucleon. The apparent temperature values of LCPs and IMFs from different systems are deduced from the measured yields using two helium-related and eight carbon-related double isotope ratio thermometers, respectively. Then, the sequential decay effect on the experimental apparent temperature deduction with the double isotope ratio thermometers is quantitatively corrected explicitly with the aid of the quantum statistical model. The present treatment is an improvement compared to our previous studies in which an indirect method was adopted to qualitatively consider the sequential decay effect. A negligible $N/Z$ asymmetry dependence of the real temperature after the correction is quantitatively addressed in heavy-ion reactions at the present intermediate energy, where a change of 0.1 units in source $N/Z$ asymmetry corresponds to an absolute change in temperature of an order of 0.03 to 0.29 MeV on average for LCPs and IMFs. This conclusion is in close agreement with that inferred qualitatively via the indirect method in our previous studies.
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2023 Vol. 47, No. 3
Published: 01 March 2023
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