共查询到20条相似文献,搜索用时 15 毫秒
1.
The \begin{document}$ \alpha $\end{document} ![]()
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-particle preformation factors of nuclei above doubly magic nuclei \begin{document}$ ^{100} $\end{document} ![]()
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Sn and \begin{document}$ ^{208} $\end{document} ![]()
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Pb are investigated within the generalized liquid drop model. The results show that the \begin{document}$ \alpha $\end{document} ![]()
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-particle preformation factors of nuclei near self-conjugate doubly magic \begin{document}$ ^{100} $\end{document} ![]()
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Sn are significantly larger than those of analogous nuclei just above \begin{document}$ ^{208} $\end{document} ![]()
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Pb, and they will be enhanced as the nuclei move towards the \begin{document}$ N = Z $\end{document} ![]()
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line. The proton–neutron correlation energy \begin{document}$ E_{p-n} $\end{document} ![]()
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and two protons–two neutrons correlation energy \begin{document}$ E_{2p-2n} $\end{document} ![]()
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of nuclei near \begin{document}$ ^{100} $\end{document} ![]()
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Sn also exhibit a similar situation, indicating that the interactions between protons and neutrons occupying similar single-particle orbitals could enhance the \begin{document}$ \alpha $\end{document} ![]()
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-particle preformation factors and result in superallowed \begin{document}$ \alpha $\end{document} ![]()
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decay. This also provides evidence of the significant role of the proton–neutron interaction on \begin{document}$ \alpha $\end{document} ![]()
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-particle preformation. Also, the linear relationship between \begin{document}$ \alpha $\end{document} ![]()
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-particle preformation factors and the product of valence protons and valence neutrons for nuclei around \begin{document}$ ^{208} $\end{document} ![]()
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Pb is broken in the \begin{document}$ ^{100} $\end{document} ![]()
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Sn region because the \begin{document}$ \alpha $\end{document} ![]()
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-particle preformation factor is enhanced when a nucleus near \begin{document}$ ^{100} $\end{document} ![]()
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Sn moves towards the \begin{document}$ N = Z $\end{document} ![]()
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line. Furthermore, the calculated \begin{document}$ \alpha $\end{document} ![]()
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decay half-lives fit well with the experimental data, including the recent observed self-conjugate nuclei \begin{document}$ ^{104} $\end{document} ![]()
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Te and \begin{document}$ ^{108} $\end{document} ![]()
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Xe [Phys. Rev. Lett. 121, 182501 (2018)]. 相似文献
2.
Muyang Chen 《中国物理C(英文版)》2021,45(12):123104-123104-6
In this study, the first radial excited heavy pseudoscalar and vector mesons (\begin{document}$\eta_c(2S)$\end{document} ![]()
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, \begin{document}$\psi(2S)$\end{document} ![]()
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, \begin{document}$B_c(2S)$\end{document} ![]()
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, \begin{document}$B^*_c(2S)$\end{document} ![]()
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, \begin{document}$\eta_b(2S)$\end{document} ![]()
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, and \begin{document}$\varUpsilon(2S)$\end{document} ![]()
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) are investigated using the Dyson-Schwinger equation and Bethe-Salpeter equation approach. It is shown that the effective interactions of the radial excited states are harder than those of the ground states. With the interaction well determined by fitting the masses and leptonic decay constants of \begin{document}$\psi(2S)$\end{document} ![]()
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and \begin{document}$\varUpsilon(2S)$\end{document} ![]()
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, the first radial excited heavy mesons could be quantitatively described in the rainbow ladder approximation. The masses and leptonic decay constants of \begin{document}$\eta_c(2S)$\end{document} ![]()
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, \begin{document}$B_c(2S)$\end{document} ![]()
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, \begin{document}$B^*_c(2S)$\end{document} ![]()
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, and \begin{document}$\eta_b(2S)$\end{document} ![]()
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are predicted. 相似文献
3.
In this study, we investigate the \begin{document}$\bar{D}\Sigma_c$\end{document} ![]()
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, \begin{document}$\bar{D}\Xi^\prime_c$\end{document} ![]()
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, \begin{document}$\bar{D}\Sigma_c^*$\end{document} ![]()
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, \begin{document}$\bar{D}\Xi_c^*$\end{document} ![]()
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, \begin{document}$\bar{D}^{*}\Sigma_c$\end{document} ![]()
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, \begin{document}$\bar{D}^{*}\Xi^\prime_c$\end{document} ![]()
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, \begin{document}$\bar{D}^{*}\Sigma_c^*$\end{document} ![]()
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, and \begin{document}$\bar{D}^{*}\Xi_c^*$\end{document} ![]()
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pentaquark molecular states with and without strangeness via the QCD sum rules in detail, focusing on the light flavor, \begin{document}$SU(3)$\end{document} ![]()
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, breaking effects, and make predictions for new pentaquark molecular states besides assigning \begin{document}$P_c(4312)$\end{document} ![]()
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, \begin{document}$P_c(4380)$\end{document} ![]()
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, \begin{document}$P_c(4440)$\end{document} ![]()
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, \begin{document}$P_c(4457)$\end{document} ![]()
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, and \begin{document}$P_{cs}(4459)$\end{document} ![]()
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self-consistently. In the future, we can search for these pentaquark molecular states in the decay of \begin{document}$\Lambda_b^0$\end{document} ![]()
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, \begin{document}$\Xi_b^0$\end{document} ![]()
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, and \begin{document}$\Xi_b^-$\end{document} ![]()
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. Furthermore, we discuss high-dimensional vacuum condensates in detail. 相似文献
4.
Yueling Yang Junliang Lu Mingfei Duan Jinshu Huang Junfeng Sun 《中国物理C(英文版)》2021,45(8):083104-083104-9
Although J/ψ weak decays are rare,they are possible within the standard model of elementary particles.Inspired by the potential prospects of the future intensity frontier,the C parity violating J/ψ→πη~((')),ηη' decays and the strangeness changing J/ψ→πK,Kη~((')) decays are studied via the perturbative QCD approach.It is determined that the J/ψ→ηη' decays have relatively large branching ratios,approximately on the order of 10~(-11),which might be within the measurement capability and sensitivity of the future STCF experiment. 相似文献
5.
Impact of lepton p_T threshold on charge asymmetry predictions for inclusive W boson production in pp collisions at 13 TeV
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Kadir Ocalan 《中国物理C(英文版)》2021,45(8):083103-083103-9
This paper presents the impact of the lepton transverse momentum p_T~l threshold on the W boson charge asymmetry predictions in perturbative QCD for the inclusive W~++X→l~±v+X production in proton-proton(pp)collisions.The predictions are obtained at various low-p_T~l thresholds p_T~l 20,25,30,and 40 GeV in a fiducial region encompassing both the central and forward detector acceptances in terms of the lepton pseudorapidity0 ≤η_l≤4.5.The predicted distributions for the lepton charge asymmetry,which is defined by η_l(A_(η_l)),at the nextto-next-to-leading order(NNLO) accuracy are compared with the CMS and LHCb data at 8 TeV center-of-mass collision energy.The 8 TeV predictions reproduce the data fairly well within the quoted uncertainties.The predictions from the CT14 parton distribution function(PDF) model are in a slightly better agreement with the data over the other PDF sets that are tested.The 13 TeV predictions using various p_T~l thresholds are reported for A_(η_l) and the charge asymmetries that are defined in terms of the differential cross sections in bins of the W boson rapidity yw(A_(y_w)) and transverse momentum p_T~W(A_(p_T~W)).The NNLO predictions for the A_(η_l),A_(y_w).and A_(p_T~W) distributions are assessed to be in close correlation with the p_T~l value.The A_(η_l) and A_(y_w) distributions are particularly shown to be more correlated at a higher p_T~l threshold.The A_(p_T~W) distributions are also reported from the merged predictions with improved accuracy by the inclusion of the next-to-next-to-next-to-leading logarithm(N'LL) corrections,i.e.,at NNLO+N~3 LL.The predicted distributions from various p_T~l thresholds represent a finer probe in terms of the capability to provide more constraints on the ratio of u and d quark distribution functions in the parton momentum fraction range 10~(-4) x1. 相似文献
6.
In this study, by combining the equal spacing rule with recent observations of \begin{document}$ \Omega_c(X) $\end{document} ![]()
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and \begin{document}$ \Xi_c(X) $\end{document} ![]()
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baryons, we predict the spectrum of the low-lying \begin{document}$ \lambda $\end{document} ![]()
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-mode \begin{document}$ 1P $\end{document} ![]()
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-wave excited \begin{document}$ \Sigma_c $\end{document} ![]()
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states. Furthermore, their strong decay properties are predicted using the chiral quark model and the nature of \begin{document}$ \Sigma_c(2800) $\end{document} ![]()
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is investigated by analyzing the \begin{document}$ \Lambda_c\pi $\end{document} ![]()
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invariant mass spectrum. The \begin{document}$ \Sigma_c(2800) $\end{document} ![]()
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structure observed in the \begin{document}$ \Lambda_c \pi $\end{document} ![]()
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mass spectrum was found to potentially arise from two overlapping \begin{document}$ P $\end{document} ![]()
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-wave \begin{document}$ \Sigma_c $\end{document} ![]()
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resonances, \begin{document}$ \Sigma_c(2813)3/2^- $\end{document} ![]()
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and \begin{document}$ \Sigma_c(2840)5/2^- $\end{document} ![]()
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. These resonances have similar decay widths of \begin{document}$ \Gamma\sim 40 $\end{document} ![]()
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MeV and predominantly decay into the \begin{document}$ \Lambda_c \pi $\end{document} ![]()
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channel. The \begin{document}$ \Sigma_c(2755)1/2^- $\end{document} ![]()
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state is likely to be a very narrow state with a width of \begin{document}$ \Gamma\sim 15 $\end{document} ![]()
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MeV, with its decays almost saturated by the \begin{document}$ \Lambda_c \pi $\end{document} ![]()
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channel. Additionally, evidence of the \begin{document}$\Sigma_c(2755) {1}/{2}^-$\end{document} ![]()
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resonance as a very narrow peak may be seen in the \begin{document}$ \Lambda_c\pi $\end{document} ![]()
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invariant mass spectrum. The other two \begin{document}$ P $\end{document} ![]()
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-wave states, \begin{document}$\Sigma_c(2746) {1}/{2}^-$\end{document} ![]()
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and \begin{document}$\Sigma_c(2796) {3}/{2}^-$\end{document} ![]()
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, are relatively narrow states with similar widths of \begin{document}$ \Gamma\sim 30 $\end{document} ![]()
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MeV and predominantly decay into \begin{document}$ \Sigma_c\pi $\end{document} ![]()
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and \begin{document}$ \Sigma^{*}_c\pi $\end{document} ![]()
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, respectively. This study can provide useful references for discovering these low-lying \begin{document}$ P $\end{document} ![]()
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-wave states in forthcoming experiments. 相似文献
7.
The same-sign tetralepton signature via the mixing of neutral Higgs bosons and their cascade decays to charged Higgs bosons is a unique signal in the type-Ⅱ seesaw model with the mass spectrum MA0≈MH0>MH+>MH±±.In this study,we investigate this signature at future lepton colliders,such as the ILC,CLIC,and MuC.Direct searches for doubly charged scalar H±±at the LHC have excluded MHg+t<350(870) GeV in the H±±+W±W(±)(l±±)decay mode.Therefore,we choose MA0=400,600,1000,1500 GeV as our benchmark scenarios.Constrained by direct search,H±±+W±W(±)(l±±)d=is the only viable decay mode for Mρ=400 GeV at the √s=1 TeV ILC.With an integrated luminosity L=8 ab-1,the promising region,with approximately 150 signal events,corresponds to a narrow band in the range of 10-4 GeV≤v△≤10-2GeV.Meanwhile,for Mpo=600 GeV at the √s=1.5 TeV CLIC,approximately 10 signal events can be produced with L=2.5 ab-1.For heavier triplet scalars MA0■870 GeV,although the H±± decay mode is allowed,the cascade decays are suppressed.A maximum event number~16 can be obtained at approximately v△~4×104GeV and λ14~0.26 for MA0=1000 GeV with L=5 ab-1 at the √s=3 TeV CLIC.Finally,we find that this signature is not promising for MA0= 1500 GeV at the √s=6 TeV MuC.Based on the benchmark scenarios,we also study the observability of this signature.In the H±±+W±W(±)(l±±)d mode,one can probe MρS 800(1160) GeV at future lepton colliders. 相似文献
8.
In this study, we investigate the discovery potential of double-charm tetraquarks \begin{document}$ T^{\{cc\}}_{[\bar{q}\bar{q}']} $\end{document} ![]()
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. We find that their production cross sections at the LHCb with \begin{document}$ \sqrt{s} = 13 $\end{document} ![]()
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TeV reach \begin{document}$ \mathcal{O}(10^4) $\end{document} ![]()
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pb, which indicates that the LHCb has collected \begin{document}$ \mathcal{O}(10^8) $\end{document} ![]()
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such particles. Through the decay channels of \begin{document}$ T^{\{cc\}}_{[\bar{u}\bar{d}]}\to D^{+}K^{-}\pi^{+} $\end{document} ![]()
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or \begin{document}$ D^0D^+\gamma $\end{document} ![]()
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(if stable) or \begin{document}$ T^{\{cc\}}_{[\bar{u}\bar{d}]}\to D^0D^{*+}\to D^0D^0\pi^+ $\end{document} ![]()
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(if unstable), it is highly expected that they get discovered at the LHCb in the near future. We also discuss the productions and decays of the double-charm tetraquarks at future Tera-\begin{document}$ Z $\end{document} ![]()
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factories. 相似文献
9.
Ze-Sheng Chen Zhuo-Ran Huang Hong-Ying Jin T.G. Steele Zhu-Feng Zhang 《中国物理C(英文版)》2022,46(6):063102-063102-14
We study \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} ![]()
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and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} ![]()
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states as mixed states in QCD sum rules. By calculating the two-point correlation functions of pure states of their corresponding currents, we review the mass and coupling constant predictions of \begin{document}$ J^{PC} = 1^{++} $\end{document} ![]()
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, \begin{document}$1^{--}$\end{document} ![]()
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, and \begin{document}$ 1^{-+} $\end{document} ![]()
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states. By calculating the two-point mixed correlation functions of \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} ![]()
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and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} ![]()
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currents, we estimate the mass and coupling constants of the corresponding "physical state" that couples to both \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} ![]()
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and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} ![]()
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currents. Our results suggest that for \begin{document}$ 1^{++} $\end{document} ![]()
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states, the \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} ![]()
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and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} ![]()
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components are more likely to mix, while for \begin{document}$ 1^{--} $\end{document} ![]()
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and \begin{document}$ 1^{-+} $\end{document} ![]()
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states, there is less mixing between \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} ![]()
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and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} ![]()
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. Our results suggest the Y series of states have more complicated components. 相似文献
10.
Renqiang Zhang Wei Sun Feiyu Chen Ying Chen Ming Gong Xiangyu Jiang Zhaofeng Liu 《中国物理C(英文版)》2022,46(4):043102-043102-13
In this work, we generate gauge configurations with \begin{document}$ N_f = 2 $\end{document} ![]()
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dynamical charm quarks on anisotropic lattices. The mass shift of \begin{document}$ 1S $\end{document} ![]()
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and \begin{document}$ 1P $\end{document} ![]()
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charmonia due to the charm quark annihilation effect can be investigated directly in a manner of unitary theory. The distillation method is adopted to treat the charm quark annihilation diagrams at a very precise level. For \begin{document}$ 1S $\end{document} ![]()
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charmonia, the charm quark annihilation effect barely changes the \begin{document}$ J/\psi $\end{document} ![]()
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mass, but lifts the \begin{document}$ \eta_c $\end{document} ![]()
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mass by approximately 3–4 MeV. For \begin{document}$ 1P $\end{document} ![]()
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charmonia, this effect results in positive mass shifts of approximately 1 MeV for \begin{document}$ \chi_{c1} $\end{document} ![]()
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and \begin{document}$ h_c $\end{document} ![]()
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, but decreases the \begin{document}$ \chi_{c2} $\end{document} ![]()
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mass by approximately 3 MeV. We did not obtain a reliable result for the mass shift of \begin{document}$ \chi_{c0} $\end{document} ![]()
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. In addition, we observed that the spin averaged mass of the spin-triplet \begin{document}$ 1P $\end{document} ![]()
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charmonia is in good agreement with \begin{document}$ h_c $\end{document} ![]()
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, as expected by the non-relativistic quark model and measured by experiments. 相似文献
11.
Combining the b→sμ~+μ~-anomaly and dark matter observables,we study the capability of the LHC to test dark matter,Z',and a vector-like quark.We focus on a local U(1)_(L_μ-L_τ) model with a vector-like SU(2)_L doublet quark Q and a complex singlet scalar whose lightest component X_I is a candidate of dark matter.After imposing relevant constraints,we find that the b→sμ~+μ~-anomaly and the relic abundance of dark matter favor m_(X_I) 350 GeV and m_(Z') 450 GeV for m_Q 2 TeV and m_(X_R) 2 TeV(the heavy partner of m_(X_I)).Current searches for jets and missing transverse momentum at the LHC sizably reduce the mass ranges of the vector-like quark,and m_Q is required to be larger than 1.7 TeV.Finally,we discuss the possibility of probing these new particles at the high luminosity LHC via the QCD process pp→DD followed byD→s(b)X_I,D→s(b)Z'X_I,and then Z'→μ~+μ~-.Taking a benchmark point of m_Q=1.93 TeV,m_(Z')=170 GeV,and m_(X_I)=145 GeV,we perform a detailed Monte Carlo simulation and find that this benchmark point can be accessed at the 14 TeV LHC with an integrated luminosity of 3000 fb~(-1). 相似文献
12.
Spin alignments of vector mesons and hyperons in relativistic heavy-ion collisions have been proposed as signals of global polarization.The STAR experiment first observed the ∧ polarization.Recently,the ALICE collaboration measured the transverse momentum {PT) and the collision centrality dependence of K*,and Φ spin alignments during Pb-Pb collisions at ~(1/2)sNN=2.76 TeV.A large signal is observed in the low pT region of mid-central collisions for K~*,while the signal is much smaller for Φ,and these have not been understood yet.Since vector mesons have different lifetimes and their decay products have different scattering cross sections,they suffer from different hadronic effects.In this paper,we study the effect of hadronic interactions on the spin alignment of K~*,Φ,and p mesons in relativistic heavy-ion collisions with a multi-phase transport model.We find that hadronic scatterings lead to a deviation of the observed spin alignment matrix element p00 away from the true value for p and K*mesons(with a bigger effect on p) while the effect is negligible for the Φ meson.The effect depends on the kinematic acceptance:the observed p00 value is lower than the true value when the pseudorapidity(η) coverage is small,while there is little effect when the η coverage is large.Hence,this study provides valuable information to understand the vector meson spin alignment signals observed during the experiments. 相似文献
13.
Inspired by the newly observed X_0(2900) and X_1(2900) states at LHCb,the K~*■ and K■ interactions are studied in the quasipotential Bethe-Salpeter equation approach combined with the one-bo son-exchange model.The bound and virtual states from the interactions are searched for as poles in the complex energy plane of scattering amplitude.A bound state with I(J~P)=0(0~+) and a virtual state with 0(1~-) are produced from the K~*■ interaction and K■ interaction,and can be related to the X_0(2900) and X_1(2900) observed at LHCb,respectively.A bound state with I(J~P)=0(1~+) and a virtual state with I(J~P)=0(2~+) are also predicted from the K~*■ interaction,with the same α value,to reproduce the X_(0,1)(2900),which can be searched for in future experiments. 相似文献
14.
Xiao Pan You-Tian Zou Hong-Ming Liu Biao He Xiao-Hua Li Xi-Jun Wu Zhen Zhang 《中国物理C(英文版)》2021,45(12):124104-124104-7
In this work, we systematically study the two-proton (\begin{document}$2p$\end{document} ![]()
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) radioactivity half-lives using the two-potential approach, and the nuclear potential is obtained using the Skyrme-Hartree-Fock approach and the Skyrme effective interaction of SLy8. For true \begin{document}$2p$\end{document} ![]()
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radioactivity (\begin{document}$Q_{2p}$\end{document} ![]()
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\begin{document}$>$\end{document} ![]()
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0 and \begin{document}$Q_p$\end{document} ![]()
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\begin{document}$< $\end{document} ![]()
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0, where \begin{document}$Q_p$\end{document} ![]()
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and \begin{document}$Q_{2p}$\end{document} ![]()
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are the released energies of the one-proton and two-proton radioactivity, respectively), the standard deviation between the experimental half-lives and our theoretical calculations is 0.701. In addition, we extend this model to predict the half-lives of 15 possible \begin{document}$2p$\end{document} ![]()
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radioactivity candidates with \begin{document}$Q_{2p}$\end{document} ![]()
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\begin{document}$>$\end{document} ![]()
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0 obtained from the evaluated atomic mass table AME2016. The calculated results indicate a clear linear relationship between the logarithmic \begin{document}$2p$\end{document} ![]()
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radioactivity half-lives (\begin{document}${\log}_{10}T_{1/2}$\end{document} ![]()
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) and coulomb parameters [(\begin{document}$Z_{d}^{0.8}$\end{document} ![]()
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+\begin{document}${l}^{\,0.25}$\end{document} ![]()
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)\begin{document}$Q_{2p}^{-1/2}$\end{document} ![]()
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] considering the effect of orbital angular momentum proposed by Liu \begin{document}$et$\end{document} ![]()
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\begin{document}$al.$\end{document} ![]()
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[Chin. Phys. C 45, 024108 (2021)]. For comparison, the generalized liquid drop model (GLDM), effective liquid drop model (ELDM), and Gamow-like model are also used. Our predicted results are consistent with those obtained using other relevant models. 相似文献
15.
徐书生 《中国物理C(英文版)》2022,46(1):014105-014105-8
In the contact interaction model,the quark propagator has only one solution,namely,the chiral symmetry breaking solution,at vanishing temperature and density in the case of physical quark mass.We generalize the condensate feedback onto the coupling strength from the 2 flavor case to the 2+1 flavor case,and find the Wigner solution appears in some regions,which enables us to tackle chiral phase transition as two-phase coexistences.At finite chemical potential,we analyze the chiral phase transition in the conditions of electric charge neutrality andβequilibrium.The four chemical potentials,μu,μd,μs and He,are constrained by three conditions,so that one inde-pendent variable remains:we choose the average quark chemical potential as the free variable.All quark masses and number densities suffer discontinuities at the phase transition point.The strange quarks appear after the phase trans-ition since the system needg more energy to produce a d.-quark than an s-quark.Taking the EOS as an input,the TOV equations are solved numerically,and we show that the mass--radius relation is sensitive to the EOS.The max-imum mass of strange quark stars is not susceptible to the parameter Aq we introduced. 相似文献
16.
Han-zhou Yu Jing Li Yan-Lin Ye Biao Yang Cheng-Jian Lin Hui-Ming Jia Jian-Ling Lou Xiao-Fei Yang T. Baba Qi-Te Li Yu-Cheng Ge Zhi-Huan Li Hui Hua Jin-Yan Xu Zai-Hong Yang Jun Feng Hong-Liang Zang Qiang Liu Wei Jiang Yang Liu Jing-Jing Li Wei Liu Shi-Wei Bai Jie Chen Jia-Xing Han Jia-Hao Chen Kai Ma Dong-Xi Wang Lei Yang Nan-Ru Ma LI-Jie Sun 《中国物理C(英文版)》2021,45(8):084002-084002-5
17.
From a Bayesian analysis of the electric dipole polarizability,the constrained energy of isovector giant dipole resonance,the peak energy of isocalar giant quadrupole resonance,and the constrained energy of isocalar giant monopole resonance in ~(208)Pb,we extract the iso scalar and isovector effective masses in nuclear matter at saturation density p_0 as m_(s,0)~*/m=0.87_(-0.04)~(+0.04) and m_(v,0)~*/m=0.78_(-0.05)~(+0.06),respectively,at 90% confidence level.The constraints obtained on m_(s,0)~* and m_(v,0)~* lead to a positive iso spin splitting of nucleon effective mass in asymmetric nuclear matter of iso spin asymmetry δ at p_0 as m_(n-p)~*/m=(0.20_(-0.14)~(+0.15))δ.In addition,the symmetry energy at the subsaturation density p~*=0.05 fm~(-3) is determined to be E_(sym)(p~*)=16.7±1.3 MeV at 90% confidence level. 相似文献
18.
The XENON1T excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with an MeV mass and high speed. We consider a tangible model composed of two scalar MeV dark matter (DM) particles, \begin{document}$ S_A $\end{document} ![]()
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and \begin{document}$ S_B $\end{document} ![]()
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, to interpret the XENON1T keV excess via boosted \begin{document}$ S_B $\end{document} ![]()
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. A small mass splitting \begin{document}$ m_{S_A}-m_{S_B}>0 $\end{document} ![]()
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is introduced, and the boosted \begin{document}$ S_B $\end{document} ![]()
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can be produced using the dark annihilation process of \begin{document}$ S_A S_A^\dagger \to \phi \to S_B S_B^\dagger $\end{document} ![]()
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via a resonant scalar ?. \begin{document}$ S_B- $\end{document} ![]()
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electron scattering is intermediated by a vector boson X. Although the constraints from Big Bang nucleosynthesis, cosmic microwave background (CMB), and low-energy experiments set the \begin{document}$ X- $\end{document} ![]()
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mediated \begin{document}$ S_B- $\end{document} ![]()
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electron scattering cross section to be \begin{document}$ \lesssim 10^{-35} \mathrm{cm}^2 $\end{document} ![]()
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, the MeV scale DM with a resonance enhanced dark annihilation today can still provide sufficient boosted \begin{document}$ S_B $\end{document} ![]()
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and induce the XENON1T keV excess. The relic density of \begin{document}$ S_B $\end{document} ![]()
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is significantly reduced by the s-wave process \begin{document}$ S_B S_B^\dagger \to X X $\end{document} ![]()
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, which is permitted by the constraints from CMB and 21-cm absorption. A very small relic fraction of \begin{document}$ S_B $\end{document} ![]()
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is compatible with the stringent bounds on un-boosted \begin{document}$ S_B $\end{document} ![]()
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-electron scattering in DM direct detection, and the \begin{document}$ S_A $\end{document} ![]()
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-electron scattering is also allowed. 相似文献
19.
Cross-sections for the 27Al(γ, x)22Na multichannel reaction with the 28.3 MeV difference of reaction thresholds
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O.S. Deiev I.S. Timchenko S.N. Olejnik V.A. Kushnir V.V. Mytrochenko S.A. Perezhogin 《中国物理C(英文版)》2022,46(6):064002-064002-9
The bremsstrahlung flux-averaged cross-sections \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})}\rangle$\end{document} ![]()
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and the cross-sections per equivalent photon \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})_{Q}}\rangle$\end{document} ![]()
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were first measured for the photonuclear multichannel reaction \begin{document}${^{27}{\rm{Al}}}(\gamma,\textit{x})^{22}{\rm{Na}}$\end{document} ![]()
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at end-point bremsstrahlung gamma energies ranging from 35 MeV to 95 MeV. The experiments were performed with the beam from the NSC KIPT electron linear accelerator LUE-40 using the γ-activation technique. The bremsstrahlung quantum flux was calculated with the GEANT4.9.2 program and was also monitored via the \begin{document}$^{100}{\rm{Mo}}(\gamma,{n})^{99}{\rm{Mo}}$\end{document} ![]()
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reaction. The flux-averaged cross-sections were calculated using the partial cross-section \begin{document}$\sigma(E)$\end{document} ![]()
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values computed with the TALYS1.95 code for different level density models. Consideration is given to special features of calculating the cross-sections \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})}\rangle$\end{document} ![]()
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and \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})_{Q}}\rangle$\end{document} ![]()
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for the case of the final nucleus \begin{document}$^{22}{\rm{Na}}$\end{document} ![]()
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via several partial channels \begin{document}$\textit{x}$\end{document} ![]()
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: \begin{document}${n}\alpha + {dt} + {npt} + 2{n}{^{3}\text{He}} + {n2d} + {2npd} + {2p3n}$\end{document} ![]()
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. 相似文献
20.
V. V. Vien 《中国物理C(英文版)》2021,45(12):123103-123103-14
We construct a non-renormalizable gauge \begin{document}$ B-L $\end{document} ![]()
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model based on \begin{document}$ Q_4\times Z_4\times Z_2 $\end{document} ![]()
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symmetry that successfully explains the cobimaximal lepton mixing scheme. Small active neutrino masses and both neutrino mass hierarchies are produced via the type-I seesaw mechanism at the tree-level. The model is predictive; hence, it reproduces the cobimaximal lepton mixing scheme, and the reactor neutrino mixing angle \begin{document}$ \theta_{13} $\end{document} ![]()
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and the solar neutrino mixing angle \begin{document}$ \theta_{12} $\end{document} ![]()
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can obtain best-fit values from recent experimental data. Our model also predicts the effective neutrino mass parameters of \begin{document}$ m_{\beta }\in (8.80, 9.05)\, \mathrm{meV} $\end{document} ![]()
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and \begin{document}$ \langle m_{ee}\rangle \in (3.65, 3.95)\, \mathrm{meV} $\end{document} ![]()
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for normal ordering (NO) and \begin{document}$ m_{\beta }\in (49.16, 49.21)\, \mathrm{meV} $\end{document} ![]()
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and \begin{document}$ \langle m_{ee}\rangle \in (48.59, 48.67)\, \mathrm{meV} $\end{document} ![]()
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for inverted ordering (IO), which are highly consistent with recent experimental constraints. 相似文献