arXiv subjects

Ruilin Zhu

Publications and source records attributed to Ruilin Zhu.

At least 37 records · Page 2Linked to original sources

arXiv2024

Polarization and quantum entanglement effects in $B^\pm_c\to J/ψ+π^\pm +π^0$ process

Motivated by the very recent observation of the $B^+_c\to J/ψ+π^+ +π^0$ decay using proton-proton collision data by the LHCb collaboration, we study the four-body angular distributions and the quantum entanglement effects in the $B^+_c\to J/ψ+π^+ +π^0$ associated with $J/ψ\to μ^++μ^-$. The helicity angular distributions are given in the QCD effective theory and the von Neumann entropy is obtained in $B^\pm_c\to J/ψ(\to μ^+μ^-)+ρ^\pm(\to π^\pm π^0)$ decay process.

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arXiv2024

Beauty-charm Meson Family with Coupled Channel Effects and Their Strong Decays

We systematically study the mass spectra and their two-body hadronic decays of the beauty-charm meson family considering the coupled channel effects. Our results can good explain the observed $B_c$ meson spectrum and the prediction of the mass spectrum for unobserved beauty-charm mesons can be tested in future experiments. For the coupled channel components, we predicted the $1S$ state in beauty-charm meson family is about $4\%$, while the $2S$, $1P$, $2P$, $1D$, and $2D$ states are about $14\%$, $10\%$, $33\%$, and $17\%$ respectively. For the $3S$, $2P$ and $2D$ states, the strong decay is allowed, The two-body hadronic decay widths of the $3^1S_0$, $3^3S_1$, $2^3P_2$ states are about 110 MeV, 69 MeV, and 3 MeV, respectively. While the two-body decay widths of the $2^3D_1$, $2D$, $2D^\prime$, and $2^3D_2$ states are 60 MeV, 149 MeV, 65 MeV, and 72 MeV, respectively.

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arXiv2023

Convergent decay constants for beauty-charm mesons at N$^3$LO in QCD and phenomenological implications

We show the three-loop calculation of the matching coefficients $\mathcal{C}_J$ for the four heavy flavor-changing currents in nonrelativistic Quantum Chromodynamics effective theory and confirm the surprising observation of the nonconvergence behaviors of the matching coefficients for beauty-charm mesons. We demonstrate that the higher-order correction to the wave function at origin can solve the nonconvergence problem. By employing the scaling relation, we simultaneously obtain the decay constants for beauty-charm mesons up to the three-loop accuracy and the hyperfine mass splitting in agreement with the experimental data. The perturbative predictions for the leptonic decays of the beauty-charm mesons shall provide a guide in ongoing and future precision heavy flavor experiments.

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arXiv2023

Distinguishing Low-lying Vector Beauty-charm Meson via Polarization Analysis

To distinguish the low-lying vector beauty-charm meson, we systematically study the $B_c^*\to B_c+γ$, $B_c^*\to \ell+ν_{\ell}$ and $B_c^{(*)}\to J/ψ+nh$ processes within effective theory by the helicity decomposition method. The significant difference of polarization asymmetry in $B_c^{(*)}\to J/ψ+nh$ indicates a general law in vector-to-vector and pseudoscalar-to-vector transition processes, which can be tested in current and future LHC experiments. In the end, we discuss the experiment search and discovery potential for the low-lying vector beauty-charm meson.

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arXiv2023

Three-loop matching coefficients for heavy flavor-changing currents and the phenomenological applications

Within the framework of non-relativistic QCD (NRQCD) factorization, we compute the matching coefficients between full Quantum Chromodynamics (QCD) and NRQCD for the heavy flavor-changing vector, axial-vector, scalar and pseudo-scalar currents up to next-to-next-to-next-to-leading order (N$^3$LO). We accomplish the analytical expressions for the three-loop renormalization constants and the corresponding anomalous dimensions for all of the four NRQCD currents with two different heavy flavors. The three-loop QCD corrections to the matching coefficients turn out to be significantly larger than lower order corrections. By employing the scale relation, we obtain the N$^3$LO corrections to the wave functions at the origin for the vector $B_c^*$ meson and the pseudo-scalar $B_c$ meson from the known result for the equal-mass heavy quarkonium in potential NRQCD (pNRQCD). We find large cancellations at the third order between the matching coefficients and the wave functions at the origin, and obtain the convergent decay constants of $B^*_{c}$ and $B_{c}$ up to N$^3$LO. We present the complete perturbative QCD predictions for the decay constants, leptonic decay widths, and branching ratios of the beauty-charmed mesons.

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arXiv2023

Gluon Transverse-Momentum-Dependent Distributions from Large-Momentum Effective Theory

We demonstrate that gluon transverse-momentum-dependent parton distribution functions (TMDPDFs) can be extracted from lattice calculations of appropriate Euclidean correlations in large-momentum effective theory (LaMET). Based on perturbative calculations of gluon unpolarized and helicity TMDPDFs, we present a matching formula connecting them and their LaMET counterparts, where the latter are renormalized in a scheme facilitating lattice calculations and converted to the $\overline{\rm MS}$ scheme. The hard matching kernel is given up to one-loop level. We also show that the perturbative result is independent of the prescription used for the pinch-pole singularity in the relevant correlations. Our results offer a guidance for the extraction of gluon TMDPDFs from lattice simulations, and have the potential to greatly facilitate perturbative calculations of the hard matching kernel.

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arXiv2023

Three-loop QCD matching of the flavor-changing scalar current involving the heavy charm and bottom quark

We compute the matching coefficient between the quantum chromodynamics (QCD) and the non-relativistic QCD ( NRQCD) for the flavor-changing scalar current involving the heavy charm and bottom quark, up to the three-loop order within the NRQCD factorization. For the first time, we obtain the analytical expressions for the three-loop renormalization constant $\tilde{Z}_s(x,R_f)$ and the corresponding anomalous dimension $\tildeγ_s(x,R_f)$ for the NRQCD scalar current with the two heavy bottom and charm quark. We present the precise numerical results for those relevant coefficients $(C_{FF}(x_0), \cdots, C_{FBB}(x_0))$ with an accuracy of about thirty digits. The three-loop QCD correction turns out to be significantly large. The obtained matching coefficient $C_s(μ_f,μ,m_b,m_c)$ is helpful to analyze the threshold behaviours when two different heavy quarks are close to each other and form the double heavy $B_c$ mesons.

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arXiv2022

Next-to-next-to-leading order matching of beauty-charmed meson $B_{c}$ and $B^*_{c}$ decay constants

We present the next-to-next-to-leading order (NNLO) QCD corrections to the decay constants for both the pseudoscalar and vector beauty-charmed mesons $B_{c}$ and $B^*_{c}$ in nonrelativistic QCD effective theory. Explicit NNLO calculation verified that the $B_c$ decay constant from pseudoscalar current is identical with the $B_c$ decay constant from axial-vector current. The NNLO result for the vector decay constant of $B^*_{c}$ meson is novel. Combined with the latest extraction of nonrelativistic QCD long-distance matrix elements of $B_c$ meson, we give the branching ratios of leptonic decays of $B_{c}$ and $B^*_{c}$ mesons. In addition, the novel anomalous dimension for the flavor-changing heavy quark vector current in nonrelativistic QCD effective theory are helpful to investigate the threshold behaviours of two different heavy quarks.

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arXiv2022

Scrutinizing New Physics in Semi-leptonic $B_{c}\rightarrow J/ψτν$ Decay

We perform a global analysis of the $b\to cτν$ data using the recent lattice results on the $B_c\to J/ψ$ vector and axial-vector form factors. To explore the effects from the tensor operator of new physics beyond the standard model, we determine the tensor form factors by using the non-relativistic QCD (NRQCD) relations between tensor and (axial-)vector form factors. Based on the lattice+NRQCD form factors, we fit the Wilson coefficients and the new physics couplings in $R_2$, $S_1$ and $U_1$ leptoquark models by including the recently measured $R(Λ_c)$ and imposing the relaxed constraint $\mathcal B(B_c\to J/ψ)<30\%$ in light of the recent studies on LEP1 data and $B_c$ lifetime. We give predictions for the experimental observables including $R(J/ψ)$, $P_τ(J/ψ)$, $F_L(J/ψ)$ and $\mathcal A_{FB}(J/ψ)$ as well as their $q^2$ distribution in new physics scenarios/models. Our results suggest that the longitudinal $τ$ polarization fraction $P_τ(J/ψ)$ and the forward-backward asymmetry $\mathcal A_{FB}(J/ψ)$ are useful for testing the $R_2$ leptoquark model.

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arXiv2022

Next-to-leading order QCD calculation of $B_c$ to charmonium tensor form factors

We present a next-to-leading order (NLO) QCD corrections to $B_c\to η_c$ and $B_c\to J/ψ$ tensor form factors within nonrelativistic QCD (NRQCD) framework. The full analytical results for $B_c$ to S-wave charmonium tensor form factors are obtained. We also studied the asymptotic behaviours of tensor form factors in hierarchy heavy quark limit, i.e. $m_b\to\infty,~ m_c\to\infty, ~\mathrm{and }~m_c/m_b\to0$. A compact expression for tensor form factors are given analytically in the hierarchy heavy quark limit. The relation among different form factors is also analyzed especially at large momentum recoil point. The numerical results for the $B_c$ to charmonium tensor form factors in all the physical region are given in the end.

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arXiv2022

Inclusive approach to hunt for the beauty-charmed baryons $Ξ_{bc}$

With a distinctive internal structure from all established hadrons, the beauty-charmed baryons $Ξ_{bc}$ can provide us with new points of view to decipher the strong interaction. In this work, we point out that the inclusive $Ξ_{bc} \to Ξ_{cc}^{++}+X$ decay is a golden channel for the experimental discovery of $Ξ_{bc}$ at the LHC. A unique feature of this process is that the $Ξ_{cc}^{++}$ is displaced, which greatly reduces the combinatorial background. A feasibility analysis is performed on the $Ξ_{bc}^+$ search, which is expected to have a longer lifetime than $Ξ_{bc}^0$ and thus a better displacement resolution. The $Ξ_{bc}^+ \to Ξ_{cc}^{++}+X$ branching ratio is calculated within the heavy diquark effective theory. Combining the $Ξ_{bc}$ production rate and the $Ξ_{cc}^{++}$ detection efficiency, we anticipate that hundreds of signal events will be collected during LHCb Run 3.

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arXiv2022

Hadronic molecule interpretation of $T^+_{cc}$ and its beauty-partners

Motivated by the latest discovery of a new tetraquark $T_{cc}^+$ with two charm quarks and two light antiquarks by LHCb Collaboration, we investigated the $DD^*$ hadronic molecule interpretation of $T_{cc}^+$. By calculation, the mass and the decay width of this new structure $T_{cc}^+$ can be understood in one-meson exchange potential model. The binding energies for these $DD^*$ hadronic molecules with $J^P=1^+$ are around $1MeV$. Besides, we also studied the possible beauty-partners $T_{bb}(10598)$ of hadronic molecule $T^+_{cc}$, which may be feasible in future LHCb experiments.

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arXiv2021

Renormalization and Mixing of Staple-Shaped Wilson Line Operators on the Lattice Revisited

Transverse-momentum-dependent parton distribution functions and wave functions (TMDPDFs/TMDWFs) can be extracted from lattice calculations of appropriate Euclidean matrix elements of staple-shaped Wilson line operators. We investigate the mixing pattern of such operators under lattice renormalization using symmetry considerations. We perform an analysis for operators with all Dirac structures, which reveals mixings that are not present in one-loop lattice perturbation theory calculations. We also present the relevant one-loop matching in a renormalization scheme that does not introduce extra non-perturbative effects at large distances, both for the TMDPDFs and for the TMDWFs. Our results have the potential to greatly facilitate numerical calculations of TMDPDFs and TMDWFs on the lattice.

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arXiv2021

Soft Gluon Resummation in Double Heavy Quarkonium Production at LHC

In this paper, the soft gluon resummation effect in double heavy quarkonium production at the LHC is studied. By applying the transverse momentum dependent factorization formalism, the large logarithms introduced by the small total transverse momentum of heavy quarkonium pair final state system, are resummed to all orders in the expansion of the strong interaction coupling at the Next-to-Leading Logarithm accuracy. We also compare our result with the LHC data. We find that the distribution shape predicted by resummation calculation is consistent with experimental data very well. Since this process is mainly initiated by gluon fusion, it supplies us an important channel to study the gluon parton property in hadrons.

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arXiv2021

Fully-heavy tetraquark spectra and production at hadron colliders

Motivated by the observation of exotic structure around 6900MeV in the $J/ψ$-pair mass spectrum using proton-proton collision data by the LHCb collaboration, we study the spectra of fully-heavy tetraquarks within Bethe-Salpeter equation and Regge trajectory relation. The $X(6900)$ may be explained as a radially excited state with quark content $cc\bar{c}\bar{c}$ and spin-parity $0^{++}(3S)$ or $2^{++}(3S)$ or an orbitally excited $2P$ state. New $cc\bar{c}\bar{c}$ structures around 6.0GeV, 6.5GeV, and 7.1GeV are predicted together. Other $bb\bar{b}\bar{b}$ and $bc\bar{b}\bar{c}$ structures which may be experimentally prominent are discussed. On the other hand, the fully-heavy S-wave tetraquark productions at hadron colliders are investigated and their cross-sections are obtained.

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arXiv2021

Next-to-next-to-leading order corrections to quark Quasi parton distribution functions

We present the next-to-next-to-leading order (NNLO) calculation of quark quasi parton distribution functions (PDFs) in the large momentum effective theory. The nontrivial factorization at this order is established explicitly and the full analytic matching coefficients between the quasi distribution and the lightcone distribution are derived. We demonstrate that the NNLO numerical contributions can improve the behavior of the extracted PDFs sizably. With the unprecedented precision study of nucleon tomography at the planned electron-ion collider, high precision Lattice QCD simulations with our NNLO results implemented will enable to test the QCD theory and more precise results on the PDFs of nucleons will be obtained.

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arXiv2020

Complete Matching for Quasi-distribution Functions in Large Momentum Effective Theory

We complete the procedure of extracting parton distribution functions (PDFs) using large momentum effective theory (LaMET) at leading power accuracy in the hadron momentum. We derive a general factorization formula for the quasi PDFs in the presence of mixing, and give the corresponding hard matching kernel at $\mathcal O(α_s)$, both for the unpolarized and for the polarized quark and gluon quasi-PDFs. Our calculation is performed in a regularization-independent momentum subtraction scheme. The results allow us to match the nonperturbatively renormalized quasi-PDFs to normal PDFs in the presence of mixing, and therefore can be used to extract flavor-singlet quark PDFs as well as gluon PDFs from lattice simulations.

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arXiv2020

Radiative decays of Upsilon(nS) into S-wave and P-wave charmonium

Motivated by very recent measurement of the radiative decays of $Υ(1S)$ to $χ_{c1}$ at Belle, we use the nonrelativistic QCD factorization theory and calculate the branching fractions of the radiative decays of bottomonium into S-wave and P-wave charmonium, i.e. $Υ(nS) \to η_c(nS)+γ$ and $Υ(nS)\to χ_{cJ}+γ$. We systematically studied the branching fractions of the radiative decays of bottomonium into charmonium. Compared to the previous calculation, we obtained the analytical expression for the decay widths and considered the color-octet contributions. For $Υ(nS) \to η_c(nS)+γ$, the relativistic corrections are also obtained. Through the calculation, the theoretical prediction for $Υ(1S)\toχ_{c1}+γ$ is still smaller than the recent Belle measurement. Further theoretical work and experimental analysis are necessary to understand the $χ_{c1}$ production mechanism in upsilon decays.

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