Toward discovering low-lying P-wave excited Σc baryon states

In this study, by combining the equal spacing rule with recent observations of \begin{document}$ \Omega_c(X) $\end{document} and \begin{document}$ \Xi_c(X) $\end{document} baryons, we predict the spectrum of the low-lying \begin{document}$ \lambda $\end{document}-mode \begin{document}$ 1P $\end{document}-wave excited \begin{document}$ \Sigma_c $\end{document} states. Furthermore, their strong decay properties are predicted using the chiral quark model and the nature of \begin{document}$ \Sigma_c(2800) $\end{document} is investigated by analyzing the \begin{document}$ \Lambda_c\pi $\end{document} invariant mass spectrum. The \begin{document}$ \Sigma_c(2800) $\end{document} structure observed in the \begin{document}$ \Lambda_c \pi $\end{document} mass spectrum was found to potentially arise from two overlapping \begin{document}$ P $\end{document}-wave \begin{document}$ \Sigma_c $\end{document} resonances, \begin{document}$ \Sigma_c(2813)3/2^- $\end{document} and \begin{document}$ \Sigma_c(2840)5/2^- $\end{document}. These resonances have similar decay widths of \begin{document}$ \Gamma\sim 40 $\end{document} MeV and predominantly decay into the \begin{document}$ \Lambda_c \pi $\end{document} channel. The \begin{document}$ \Sigma_c(2755)1/2^- $\end{document} state is likely to be a very narrow state with a width of \begin{document}$ \Gamma\sim 15 $\end{document} MeV, with its decays almost saturated by the \begin{document}$ \Lambda_c \pi $\end{document} channel. Additionally, evidence of the \begin{document}$\Sigma_c(2755) {1}/{2}^-$\end{document} resonance as a very narrow peak may be seen in the \begin{document}$ \Lambda_c\pi $\end{document} invariant mass spectrum. The other two \begin{document}$ P $\end{document}-wave states, \begin{document}$\Sigma_c(2746) {1}/{2}^-$\end{document} and \begin{document}$\Sigma_c(2796) {3}/{2}^-$\end{document}, are relatively narrow states with similar widths of \begin{document}$ \Gamma\sim 30 $\end{document} MeV and predominantly decay into \begin{document}$ \Sigma_c\pi $\end{document} and \begin{document}$ \Sigma^{*}_c\pi $\end{document}, respectively. This study can provide useful references for discovering these low-lying \begin{document}$ P $\end{document}-wave states in forthcoming experiments.     

Radial excited heavy mesons

In this study, the first radial excited heavy pseudoscalar and vector mesons (\begin{document}$\eta_c(2S)$\end{document}, \begin{document}$\psi(2S)$\end{document}, \begin{document}$B_c(2S)$\end{document}, \begin{document}$B^*_c(2S)$\end{document}, \begin{document}$\eta_b(2S)$\end{document}, and \begin{document}$\varUpsilon(2S)$\end{document}) 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} and \begin{document}$\varUpsilon(2S)$\end{document}, 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}, \begin{document}$B_c(2S)$\end{document}, \begin{document}$B^*_c(2S)$\end{document}, and \begin{document}$\eta_b(2S)$\end{document} are predicted.     

Impact of lepton p_T threshold on charge asymmetry predictions for inclusive W boson production in pp collisions at 13 TeV

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.     

The effect of hadronic scatterings on the measurement of vector meson spin alignments in heavy-ion collisions

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.     

Cross-sections for the 27Al(γ, x)22Na multichannel reaction with the 28.3 MeV difference of reaction thresholds

The bremsstrahlung flux-averaged cross-sections \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})}\rangle$\end{document} and the cross-sections per equivalent photon \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})_{Q}}\rangle$\end{document} were first measured for the photonuclear multichannel reaction \begin{document}${^{27}{\rm{Al}}}(\gamma,\textit{x})^{22}{\rm{Na}}$\end{document} 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} reaction. The flux-averaged cross-sections were calculated using the partial cross-section \begin{document}$\sigma(E)$\end{document} 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} and \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})_{Q}}\rangle$\end{document} for the case of the final nucleus \begin{document}$^{22}{\rm{Na}}$\end{document} via several partial channels \begin{document}$\textit{x}$\end{document}: \begin{document}${n}\alpha + {dt} + {npt} + 2{n}{^{3}\text{He}} + {n2d} + {2npd} + {2p3n}$\end{document}.     

Annihilation diagram contribution to charmonium masses

In this work, we generate gauge configurations with \begin{document}$ N_f = 2 $\end{document} dynamical charm quarks on anisotropic lattices. The mass shift of \begin{document}$ 1S $\end{document} and \begin{document}$ 1P $\end{document} charmonia due to the charm quark annihilation effect can be investigated directly in a manner of unitary theory. The distillation method is adopted to treat the charm quark annihilation diagrams at a very precise level. For \begin{document}$ 1S $\end{document} charmonia, the charm quark annihilation effect barely changes the \begin{document}$ J/\psi $\end{document} mass, but lifts the \begin{document}$ \eta_c $\end{document} mass by approximately 3–4 MeV. For \begin{document}$ 1P $\end{document} charmonia, this effect results in positive mass shifts of approximately 1 MeV for \begin{document}$ \chi_{c1} $\end{document} and \begin{document}$ h_c $\end{document}, but decreases the \begin{document}$ \chi_{c2} $\end{document} mass by approximately 3 MeV. We did not obtain a reliable result for the mass shift of \begin{document}$ \chi_{c0} $\end{document}. In addition, we observed that the spin averaged mass of the spin-triplet \begin{document}$ 1P $\end{document} charmonia is in good agreement with \begin{document}$ h_c $\end{document}, as expected by the non-relativistic quark model and measured by experiments.     

Double-heavy tetraquarks with strangeness in the chiral quark model

Recently, some progress has been made in the experiments on double-heavy tetraquarks, such as \begin{document}$ T_{cc} $\end{document} reported by the LHCb Collaboration and \begin{document}$ X_{cc\bar{s}\bar{s}} $\end{document} reported by the Belle Collaboration. Coming on the heels of our previous work about \begin{document}$ T_{cc} $\end{document} and \begin{document}$ T_{bb} $\end{document}, we present a study on the bound and resonance states of their companions, \begin{document}$ QQ\bar{q}\bar{s} $\end{document} (\begin{document}$ Q=c,b; q=u, s $\end{document}) tetraquarks with strange flavor in the chiral quark model. Two pictures, meson-meson and diquark-antidiquark ones, and their couplings were considered in our calculations. Isospin violation was neglected herein. Our numerical analysis indicated that the states \begin{document}$ cc\bar{u}\bar{s} $\end{document} with \begin{document}$ \dfrac{1}{2}(1^+) $\end{document} and \begin{document}$ bb\bar{u}\bar{s} $\end{document} with \begin{document}$ \dfrac{1}{2}(1^+) $\end{document} are the most promising stable states against strong interactions. Besides, we found several resonance states for the double-heavy strange tetraquarks with the real scaling method.     

Z0 boson associated b-jet production in high-energy nuclear collisions

The production of vector boson tagged heavy quark jets potentially provides new tools to probe the jet quenching effect. In this paper, we present the first theoretical study on the angular correlations (\begin{document}$ \Delta\phi_{bZ} $\end{document}), transverse momentum imbalance (\begin{document}$ x_{bZ} $\end{document}), and nuclear modification factor (\begin{document}$ I_{AA} $\end{document}) of \begin{document}$ Z^0 $\end{document} boson tagged b-jets in heavy-ion collisions, which was performed using a Monte Carlo transport model. We find that the medium modification of the \begin{document}$ \Delta\phi_{bZ} $\end{document} for \begin{document}$ Z^0$\end{document} + b-jet has a weaker dependence on \begin{document}$ \Delta\phi_{bZ} $\end{document} than that for \begin{document}$ Z^0$\end{document} + jet, and the modification patterns are sensitive to the initial jet \begin{document}$ p_T $\end{document} distribution. Additionally, with the high purity of the quark jet in \begin{document}$ Z^0$\end{document} + (b-) jet production, we calculate the momentum imbalance \begin{document}$ x_{bZ} $\end{document} and the nuclear modification factor \begin{document}$ I_{AA} $\end{document} of \begin{document}$ Z^0$\end{document} + b-jet in Pb+Pb collisions. We observe a smaller \begin{document}$ \Delta \langle x_{jZ} \rangle $\end{document} and larger \begin{document}$ I_{AA} $\end{document} of \begin{document}$ Z^0$\end{document} + b-jet in Pb+Pb collisions relative to those of \begin{document}$ Z^0$\end{document} + jet, which may be an indication of the mass effect of jet quenching and can be tested in future measurements.     

Molecular picture for X_0(2900) and X_1(2900)

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.     

A non-renormalizable B-L model with Q4 × Z4 × Z2 flavor symmetry for cobimaximal neutrino mixing

We construct a non-renormalizable gauge \begin{document}$ B-L $\end{document} model based on \begin{document}$ Q_4\times Z_4\times Z_2 $\end{document} symmetry that successfully explains the cobimaximal lepton mixing scheme. Small active neutrino masses and both neutrino mass hierarchies are produced via the type-I seesaw mechanism at the tree-level. The model is predictive; hence, it reproduces the cobimaximal lepton mixing scheme, and the reactor neutrino mixing angle \begin{document}$ \theta_{13} $\end{document} and the solar neutrino mixing angle \begin{document}$ \theta_{12} $\end{document} can obtain best-fit values from recent experimental data. Our model also predicts the effective neutrino mass parameters of \begin{document}$ m_{\beta }\in (8.80, 9.05)\, \mathrm{meV} $\end{document} and \begin{document}$ \langle m_{ee}\rangle \in (3.65, 3.95)\, \mathrm{meV} $\end{document} for normal ordering (NO) and \begin{document}$ m_{\beta }\in (49.16, 49.21)\, \mathrm{meV} $\end{document} and \begin{document}$ \langle m_{ee}\rangle \in (48.59, 48.67)\, \mathrm{meV} $\end{document} for inverted ordering (IO), which are highly consistent with recent experimental constraints.     

Microscopic study of higher-order deformation effects on the ground states of superheavy nuclei around 270Hs

We investigate the effects of higher-order deformations \begin{document}$\beta_\lambda$\end{document} (\begin{document}$\lambda=4,6,8,$\end{document} and 10) on the ground state properties of superheavy nuclei (SHN) near the doubly magic deformed nucleus \begin{document}$^{270}{\rm{Hs}}$\end{document} using the multidimensionally-constrained relativistic mean-field (MDC-RMF) model with five effective interactions: PC-PK1, PK1, NL3^*, DD-ME2, and PKDD. The doubly magic properties of \begin{document}$^{270}{\rm{Hs}}$\end{document} include large energy gaps at \begin{document}$N=162$\end{document} and \begin{document}$Z=108$\end{document} in the single-particle spectra. By investigating the binding energies and single-particle levels of \begin{document}$^{270}{\rm{Hs}}$\end{document} in the multidimensional deformation space, we find that, among these higher-order deformations, the deformation \begin{document}$\beta_6$\end{document} has the greatest impact on the binding energy and influences the shell gaps considerably. Similar conclusions hold for other SHN near \begin{document}$^{270}{\rm{Hs}}$\end{document}. Our calculations demonstrate that the deformation \begin{document}$\beta_6$\end{document} must be considered when studying SHN using MDC-RMF.     

Mixing of X and Y states from QCD sum rules analysis

We study \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} states as mixed states in QCD sum rules. By calculating the two-point correlation functions of pure states of their corresponding currents, we review the mass and coupling constant predictions of \begin{document}$ J^{PC} = 1^{++} $\end{document}, \begin{document}$1^{--}$\end{document}, and \begin{document}$ 1^{-+} $\end{document} states. By calculating the two-point mixed correlation functions of \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} currents, we estimate the mass and coupling constants of the corresponding "physical state" that couples to both \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} currents. Our results suggest that for \begin{document}$ 1^{++} $\end{document} states, the \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document} components are more likely to mix, while for \begin{document}$ 1^{--} $\end{document} and \begin{document}$ 1^{-+} $\end{document} states, there is less mixing between \begin{document}$ \bar{Q}Q\bar{q}q $\end{document} and \begin{document}$ \bar{Q}qQ\bar{q} $\end{document}. Our results suggest the Y series of states have more complicated components.     

New behaviors of α-particle preformation factors near doubly magic 100Sn

The \begin{document}$ \alpha $\end{document}-particle preformation factors of nuclei above doubly magic nuclei \begin{document}$ ^{100} $\end{document}Sn and \begin{document}$ ^{208} $\end{document}Pb are investigated within the generalized liquid drop model. The results show that the \begin{document}$ \alpha $\end{document}-particle preformation factors of nuclei near self-conjugate doubly magic \begin{document}$ ^{100} $\end{document}Sn are significantly larger than those of analogous nuclei just above \begin{document}$ ^{208} $\end{document}Pb, and they will be enhanced as the nuclei move towards the \begin{document}$ N = Z $\end{document} line. The proton–neutron correlation energy \begin{document}$ E_{p-n} $\end{document} and two protons–two neutrons correlation energy \begin{document}$ E_{2p-2n} $\end{document} of nuclei near \begin{document}$ ^{100} $\end{document}Sn also exhibit a similar situation, indicating that the interactions between protons and neutrons occupying similar single-particle orbitals could enhance the \begin{document}$ \alpha $\end{document}-particle preformation factors and result in superallowed \begin{document}$ \alpha $\end{document} decay. This also provides evidence of the significant role of the proton–neutron interaction on \begin{document}$ \alpha $\end{document}-particle preformation. Also, the linear relationship between \begin{document}$ \alpha $\end{document}-particle preformation factors and the product of valence protons and valence neutrons for nuclei around \begin{document}$ ^{208} $\end{document}Pb is broken in the \begin{document}$ ^{100} $\end{document}Sn region because the \begin{document}$ \alpha $\end{document}-particle preformation factor is enhanced when a nucleus near \begin{document}$ ^{100} $\end{document}Sn moves towards the \begin{document}$ N = Z $\end{document} line. Furthermore, the calculated \begin{document}$ \alpha $\end{document} decay half-lives fit well with the experimental data, including the recent observed self-conjugate nuclei \begin{document}$ ^{104} $\end{document}Te and \begin{document}$ ^{108} $\end{document}Xe [Phys. Rev. Lett. 121, 182501 (2018)].     

Analysis of hidden-charm pentaquark molecular states with and without strangeness via the QCD sum rules

In this study, we investigate the \begin{document}$\bar{D}\Sigma_c$\end{document}, \begin{document}$\bar{D}\Xi^\prime_c$\end{document}, \begin{document}$\bar{D}\Sigma_c^*$\end{document}, \begin{document}$\bar{D}\Xi_c^*$\end{document}, \begin{document}$\bar{D}^{*}\Sigma_c$\end{document}, \begin{document}$\bar{D}^{*}\Xi^\prime_c$\end{document}, \begin{document}$\bar{D}^{*}\Sigma_c^*$\end{document}, and \begin{document}$\bar{D}^{*}\Xi_c^*$\end{document} 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} , breaking effects, and make predictions for new pentaquark molecular states besides assigning \begin{document}$P_c(4312)$\end{document}, \begin{document}$P_c(4380)$\end{document}, \begin{document}$P_c(4440)$\end{document}, \begin{document}$P_c(4457)$\end{document} , and \begin{document}$P_{cs}(4459)$\end{document} self-consistently. In the future, we can search for these pentaquark molecular states in the decay of \begin{document}$\Lambda_b^0$\end{document}, \begin{document}$\Xi_b^0$\end{document} , and \begin{document}$\Xi_b^-$\end{document} . Furthermore, we discuss high-dimensional vacuum condensates in detail.     

Doubly heavy tetraquarks in an extended chromomagnetic model

Using an extended chromomagnetic model,we perform a systematic study of the masses of doubly heavy tetraquarks.We find that the ground states of the doubly heavy tetraquarks are dominated by the color-triplet ■configuration,which is opposite to that of fully heavy tetraquarks.The combined results suggest that the color-triplet configuration becomes more important when the mass difference between the quarks and antiquarks increases.We find three stable states that lie below the thresholds of two pseudoscalar mesons.They are the I^P=01⁺nnbb tetraquark,I^P=1⁺nncb tetraquark,and J^P=1⁺nsbb tetraquark.     

Same-sign tetralepton signature in type-Ⅱ seesaw at lepton colliders

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 M_A⁰≈M_H⁰>M_H⁺>M_H^±±.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 M_A⁰=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 M_A⁰■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 M_A⁰=1000 GeV with L=5 ab^-1 at the √s=3 TeV CLIC.Finally,we find that this signature is not promising for M_A⁰= 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.     

Atomic mass,Bjorken variable,and scale dependence of quark transport coefficient in Drell-Yan process for proton incident on nucleus

By means of the nuclear parton distributions determined without the fixed-target Drell-Yan experimental data and the analytic expression of quenching weight based on the BDMPS formalism, next-to-leading order analyses were performed on the Drell-Yan differential cross section ratios from the Fermilab E906 and E866 collaborations. It was found that the results calculated only with the nuclear effects of the parton distribution were not in agreement with the E866 and E906 experimental data. The incoming parton energy loss effect cannot be ignored in the nuclear Drell-Yan reactions. The predicted results indicate that, with the quark transport coefficient as a constant, the suppression due to the target nuclear geometry effect is approximately\begin{document}$ 16.85\ $\end{document}% for the quark transport coefficient. It was shown that we should consider the target nuclear geometry effect in studying the Drell-Yan reaction on nuclear targets. On the basis of the Bjorken variable and scale dependence of the quark transport coefficient, the atomic mass dependence was incorporated. The quark transport coefficient was determined as a function of the atomic mass, Bjorken variable\begin{document}$ x_2 $\end{document}, and scale \begin{document}$ Q^2 $\end{document} by the global fit of the experimental data. The determined constant factor \begin{document}$ \hat{q}_0 $\end{document} of the quark transport coefficient is \begin{document}$ 0.062\pm0.006 $\end{document} GeV\begin{document}$ ^2 $\end{document}/fm. It was found that the atomic mass dependence has a significant impact on the constant factor \begin{document}$ \hat{q}_0 $\end{document} in the quark transport coefficient in cold nuclear matter.     

Interpretation of XENON1T excess with MeV boosted dark matter

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 $\end{document} and \begin{document}$ S_B $\end{document}, to interpret the XENON1T keV excess via boosted \begin{document}$ S_B $\end{document}. A small mass splitting \begin{document}$ m_{S_A}-m_{S_B}>0 $\end{document} is introduced, and the boosted \begin{document}$ S_B $\end{document} can be produced using the dark annihilation process of \begin{document}$ S_A S_A^\dagger \to \phi \to S_B S_B^\dagger $\end{document} via a resonant scalar ?. \begin{document}$ S_B- $\end{document}electron scattering is intermediated by a vector boson X. Although the constraints from Big Bang nucleosynthesis, cosmic microwave background (CMB), and low-energy experiments set the \begin{document}$ X- $\end{document}mediated \begin{document}$ S_B- $\end{document}electron scattering cross section to be \begin{document}$ \lesssim 10^{-35} \mathrm{cm}^2 $\end{document}, the MeV scale DM with a resonance enhanced dark annihilation today can still provide sufficient boosted \begin{document}$ S_B $\end{document} and induce the XENON1T keV excess. The relic density of \begin{document}$ S_B $\end{document} is significantly reduced by the s-wave process \begin{document}$ S_B S_B^\dagger \to X X $\end{document}, which is permitted by the constraints from CMB and 21-cm absorption. A very small relic fraction of \begin{document}$ S_B $\end{document} is compatible with the stringent bounds on un-boosted \begin{document}$ S_B $\end{document}-electron scattering in DM direct detection, and the \begin{document}$ S_A $\end{document}-electron scattering is also allowed.     

Study of C parity violating and strangeness changing J/ψ→PP weak decays

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.     

Production of bottomonium-like Z_b states in e-h and ultraperipheral h-h collisions

The photoproduction of the bottomonium-like states Z_b(10610) and Z_b(10650) via γ p scattering is studied within an effective Lagrangian approach and the vector-meson-dominance model. The Regge model is employed to calculate the photoproduction of Z_b states via the t-channel with π exchange. The numerical results show that the values of the total cross-sections of Z_b(10610) and Z_b(10650) can reach 0.09 nb and 0.02 nb, respectively,near the center-of-mass energy of 22 GeV. Experimental measurements and studies of the photoproduction of Z_b states near the energy region around W ■ 22 GeV are suggested. Moreover, with the help of eSTARlight and STARlight programs, we have obtained the cross-sections and numbers of events for Z_b(10610) production in electron-ion collisions(EIC) and ultraperipheral collisions(UPCs). The results show that a considerable number of Z_b(10610)events can be produced in the relevant experiments on EICs and UPCs. We have also calculated the rates and kinematic distributions for γp → Z_bn in ep and pA collisions via EICs and UPCs. The results will provide an important reference for the RHIC, LHC, EIC-US, LHeC, and FCC experiments in searching for bottomonium-like Z_b states.