arXiv subjects

Liang-Liang Liu

Publications and source records attributed to Liang-Liang Liu.

9 recordsLinked to original sources

arXiv2025

The asymmetry $A_{LL}^{\cos2ϕ}$ in the polarized proton-proton Drell-Yan process within TMD factorization

We study the $\cos2ϕ$ azimuthal asymmetry in doubly longitudinally polarized proton-proton Drell-Yan collisions within the transverse momentum dependent factorization framework. The asymmetry arises from the convolution of the longitudinal transversity distribution $h_{1L}^{\perp}$ for both protons. Using the Bacchetta-Delcarro-Pisano-Radici-Signori parametrization for the nonperturbative Sudakov form factor and the Wandzura-Wilczek approximation for the collinear $h_{1L}^{\perp}$, we predict the double spin asymmetry $A_{LL}^{\cos2ϕ}$ at RHIC and NICA kinematics. Our results demonstrate sensitivity to sea quark distributions, with the asymmetry reaching up to $25\%$ for maximal sea quark contributions. These predictions highlight the potential of polarized Drell-Yan measurements to probe sea quark dynamics and advance our understanding of nucleon structure.

hep-ph↗

arXiv2022

Forward-backward asymmetries in $Λ_b \rightarrow Λl^+ l^-$ in Bethe-Salpeter equation approach

Using the Bethe-Salpeter equation (BSE) we investigate the forward-backward asymmetries $( A_{FB}) $ in $Λ_b \rightarrow Λl^+ l^-(l=e,μ,τ)$ in the quark-diquark model. This approach provides precise form factors that are different from those of QCD sum rules. We calculate the rare decay form factors for $Λ_b \rightarrow Λl^+ l^-$ and investigate the (integrated) forward-backward asymmetries in these decay channels. We find that the integrated $A^l_{FB}$, $\bar{A}^l_{FB}(Λ_b \rightarrow Λe^+ e^-) \simeq -0.1371 $, $\bar{A}^l_{FB}(Λ_b \rightarrow Λμ^+ μ^- ) \simeq -0.1376 $, $\bar{A}^l_{FB}(Λ_b \rightarrow Λτ^+ τ^-) \simeq -0.1053 $, the hadron side asymmetries $\bar{A}^h_{FB}(Λ_b \rightarrow Λμ^+ μ^-)\simeq -0.2315$, the lepton-hadron side asymmetries $\bar{A}^{lh}_{FB}(Λ_b \rightarrow Λμ^+ μ^-)\simeq 0.0827$, the longitudinal polarization fractions $\bar{F}_L(Λ_b \rightarrow Λμ^+ μ^-)\simeq 0.5681$.

hep-ph↗

arXiv2020

FCNC transitions of $Λ_b$ to neutron in Bethe-Salpeter equation approach

In a covariant quark-diquark model, we investigate the rare decay of $Λ_b \rightarrow n l^+ l^-$ and $Λ_b \rightarrow n γ$ in the Bethe-Salpeter equation approach. In this model the baryons are treated as bound states of a constituent quark and a diquark interacting via a gluon exchange and the linear confinement. We find that the ratio of form factors $R$ is varies from $-0.90$ to $-0.25$ and the branching ratios $Br(Λ_b \rightarrow n l^+ l^-)\times 10^{8}$ are $6.79(l=e),~4.08 ~ (l=μ),~2.9 ~(l=τ) $ and the branching ratio $Br(Λ_b \rightarrow γ)\times 10^{7} )=3.69$ in central values of parameters.

hep-ph↗

arXiv2019

Rare $Λ_b \rightarrow Λl^+ l^- $ decay in the Bethe-Salpeter equation approach

We study the rare decays $Λ_b \rightarrow Λl^+ l^-~(l=e,μ, τ)$ in the Bethe-Salpeter equation approach. We find that depending on the values of parameters in our model the branching ratio $Br(Λ_b \rightarrow Λμ^+ μ^-)\times 10^{6}$ varies from $0.812$ to $1.445$ when $κ= 0.050 \sim 0.060$ GeV$^3$ and the binding energy $E_0=-0.14$ GeV while $Br(Λ_b \rightarrow Λμ^+ μ^-)\times 10^{6}$ varies from $1.051$ to $1.098$ when $κ= 0.055$ Gev$^3$ and the binding energy $E_0$ changes from $-0.19$ to $-0.09$ GeV. These results agree with the experimental data. In the same parameter regions, we find that the branching ratio $Br(Λ_b \rightarrow Λe^+ e^-(τ^+ τ^-) )\times 10^{6}$ varies in the range $0.660-1.028$ ($0.252-0.392$) and $0.749-1.098$ ($0.286-0.489$), respectively.

hep-ph↗

arXiv2018

Electromagnetic form factors of $Λ_c$ in the Bethe-Salpeter equation approach

We study the electromagnetic form factors (EMFFs) of $Λ_c$ and the quark and diquark current contributes to the EMFFs of $Λ_c$ in the space-like (SL) region in the Bethe-Salpeter equation approach. In this picture, the heavy baryon $Λ_c $ is regarded as composed of a heavy quark and a scalar diquark. We find that for different values of parameters the quark and diquark current contribute to the EMFFs of $Λ_c$ is very different, but the total contribute to the EMFFs of $Λ_c$ is similarly. The EMFFs of $Λ_c$ are similar to those of other baryons (proton, $Ξ^-$, $Σ^+$) with a peak at $ω=1$ ($ω=v^\prime \cdot v $ is the velocity transfer between the initial state (with velocity $v$) and the final state (with velocity $v^\prime$) of $Λ_c$).

hep-ph↗

arXiv2018

Possible open-charmed pentaquark molecule $Ω_c(3188)$ --- the $D Ξ$ bound state --- in the Bethe-Salpeter formalism

We study the $S$-wave $DΞ$ bound state in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. With the kernel generated by the hadronic effective Lagrangian, two open-charmed bound states, which quantum numbers are $I=0$, $J^P=(\frac{1}{2})^-$ and $I=1$, $J^P=(\frac{1}{2})^-$, respectively, are predicted as new candidates of hadronic pentaquark molecules in our formalism. If existing, they could contribute to the broad 3188 eV structure near the five new narrow $Ω_c$ states observed recently by the LHCb Collaboration.

hep-ph↗

arXiv2017

Non-leptonic two-body weak decays of $Λ_c(2286)$

We study the non-leptonic two-body weak decays of $Λ_c^+(2286)\to {\bf B}_n M$ with ${\bf B}_n$ ($M$) representing as the baryon (meson) states. Based on the $SU(3)$ flavor symmetry, we can describe most of the data reexamined by the BESIII Collaboration with higher precisions. However, our result of ${\cal B}(Λ_c^+ \to pπ^0)=(5.6\pm 1.5)\times 10^{-4}$ is larger than the current experimental limit of $3\times10^{-4}$ (90\% C.L.) by BESIII. In addition, we find that ${\cal B}(Λ_c^+ \to Σ^+ K^0)=(8.0\pm 1.6)\times 10^{-4}$, ${\cal B}(Λ_c^+ \to Σ^+ η^\prime)=(1.0^{+1.6}_{-0.8})\times 10^{-2}$, and ${\cal B}(Λ_c^+ \to p η^\prime)=(12.2^{+14.3}_{-\,\,\,8.7})\times 10^{-4}$, which are accessible to the BESIII experiments.

hep-ph↗

arXiv2016

Electromagnetic form factors of $Λ_b$ in the Bethe-Salpeter equation approach

The heavy baryon $Λ_b $ is regarded as composed of a heavy quark and a scalar diquark which has good spin and isospin quantum numbers. In this picture, we calculate the electromagnetic (EM) form factors of $Λ_b$ in the Bethe-Salpeter equation approach. We find that the shapes of the EM form factors of $Λ_b$ are similar to those of $Λ$, which have a peak at about $ω=1$, but the amplitudes are much smaller than those of $Λ$.

hep-ph↗

arXiv2015

Influence of oxygen on thermal stability of nanocrystalline aluminum studied by positron annihilation spectroscopy

The thermal stability of nanocrystalline (nc) Al has been studied by means of positron lifetime spectroscopy and X-ray diffraction (XRD), prepared by compacting nanoparticles under high pressures. Those nanoparticles were produced by the flow-levitation (FL) method [1] and the arc-discharge (DC) method. Effect of oxide at nanoparticle surface on structure stability was investigated especially in this experiment. The positron lifetime results reveal that vacancy clusters in grain boundaries are dominant positron traps according to the high relative intensity of the positron lifetime τ2 in both samples. The mean grain size of the sample consisting of nanoparticles with partially oxidized surfaces is almost unchanged after aging at 150 for 84 h, with that of the sample consisting of pure nc Al increasing. The partially oxidized surfaces of nanoparticles hinder the growth of grain when aging at 150, vacancy clusters related to Al2O3 need longer aging time to decompose, which implies that the oxide stabilizes the microstructure of the nanomaterials. The effect is beneficial for nc materials to keep excellent properties.

cond-mat.mtrl-sci↗