arXiv subjects

Cai-Dian Lü

Publications and source records attributed to Cai-Dian Lü.

At least 73 records · Page 4Linked to original sources

arXiv2012

Determination of $f_0-σ$ mixing angle through $B_s^0 \to J/Ψ~f_0(980)(σ)$ decays

We study $B_s^0 \to J/ψf_0(980)$ decays, the quark content of $f_0(980)$ and the mixing angle of $f_0(980)$ and $σ(600)$. We calculate not only the factorizable contribution in QCD facorization scheme but also the nonfactorizable hard spectator corrections in QCDF and pQCD approach. We get consistent result with the experimental data of $B_s^0 \to J/ψf_0(980)$ and predict the branching ratio of $B_s^0 \to J/ψσ$. We suggest two ways to determine $f_0-σ$ mixing angle $θ$. Using the experimental measured branching ratio of $B_s^0 \to J/ψf_0(980) $, we can get the $f_0-σ$ mixing angle $θ$ with some theoretical uncertainties. We suggest another way to determine $f_0-σ$ mixing angle $θ$ using both of experimental measured decay branching ratios $B_s^0 \to J/ψf_0(980) (σ)$ to avoid theoretical uncertainties.

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arXiv2012

Analysis of $B\to K^*_J (\to K π) μ^+μ^-$ in the higher kaon resonance region

We study the resonant contributions in the process $\bar{B}^0\to K^- π^+μ^+μ^-$ with the $K^-π^+$ invariant mass square $m_{Kπ}^2\in [1, 5] {\rm GeV}^2$. Width effects of the involved strange mesons, $K^*(1410), K_0^*(1430), K_2^*(1430), K^*(1680), K_3^*(1780)$ and $K_4^*(2045)$, are incorporated. In terms of the helicity amplitudes, we derive a compact form for the full angular distributions, through which the branching ratios, forward-backward asymmetries and polarizations are attained. We propose that the uncertainties in the $B\to K^*_J$ form factors can be pinned down by the measurements of a set of SU(3)-related processes. Using results from the large energy limit, we derive the dependence of branching fractions on the $m_{Kπ}$, and find that the $K^*_2(1430)$ resonance has a clear signature, in particular, in the transverse polarizations.

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arXiv2011

Gluon Fusion induced Zg and Zgg Productions in the Standard Model at the LHC

We report calculations of the gluon induced Zg and Zgg productions in the Standard Model at the LHC operating at both 7 TeV and 14 TeV collision energy. We present total cross sections and differential distributions of the processes and compare them with the leading and next-to-leading order QCD pp -> Z+1 jet, Z+2 jets results. Our results show that the gluon induced Zg and Zgg productions contribute to pp -> Z+1 jet, Z+2 jets at 1% level.

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arXiv2011

Nonleptonic two-body decays of charmed mesons

Nonleptonic decays of charmed mesons into two pseudoscalar mesons or one pseudoscalar meson and one vector meson are studied on the basis of a generalized factorization method considering the resonance effects in the pole model for the annihilation contributions. Large strong phases between different topological diagrams are considered in this work, simply taking the phase in the coefficients $a_i$. We find that the annihilation-type contributions calculated in the pole model are large in both of the $PP$ and $PV$ modes, which make our numerical results agree with the experimental data better than those previous calculations.

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arXiv2011

Study of $B\to K^{(*)} \ell^+\ell^-$ Decays in the Family Non-universal $Z'$ Models

In a combined investigation of the $B\to K^{(*)}\ell^+\ell^-$ decays, constraints on the related couplings in family non-universal $Z^{\prime}$ models are derived. We find that within the allowed parameter space, the recently observed forward-backward asymmetry in the $B\to K^*\ell^+\ell^-$ decay can be explained, by flipping the signs of the Wilson coefficients $C_9^{\rm eff}$ and $C_{10}$. With the obtained constraints, we also calculate the branching ratio of the $B_s\toμ^+μ^-$ decay. The upper bound of our prediction is near the upper bound given by CDF Collaboration recently.

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arXiv2011

Two body hadronic $D$ decays

We analyze the decay modes of $D/D_s\to PP,PV$ on the basis of a hybrid method with the generalized factorization approach for emission diagrams and the pole dominance model for the annihilation type contributions. Our results of PV final states are better than the previous method, while the results of PP final states are comparable with previous diagrammatic approach.

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arXiv2011

Branching ratios, forward-backward asymmetries and angular distributions of $B\to K_2^*l^+l^-$ in the standard model and new physics scenarios

We analyze the $B\to K_2^*(\to Kπ)l^+l^-$ (with $l=e,μ,τ$) decay in the standard model and two new physics scenarios: vector-like quark model and family non-universal $Z'$ model. We derive its differential angular distributions, using the recently calculated form factors in the perturbative QCD approach. Branching ratios, polarizations, forward-backward asymmetries and transversity amplitudes are predicted, from which we find a promising prospective to observe this channel on the future experiment. We also update the constraints on effective Wilson coefficients and/or free parameters in these two new physics scenarios by making use of the experimental data of $B\to K^*l^+l^-$ and $b\to sl^+l^-$. Their impact on $B\to K_2^*l^+l^-$ is subsequently explored and in particular the zero-crossing point for the forward-backward asymmetry in these new physics scenarios can sizably deviate from the SM scenario. In addition we also generalize the analysis to a similar mode $B_s\to f_2'(1525)(\to K^+K^-) l^+l^-$.

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arXiv2010

Distinguishing two kinds of scalar mesons from heavy meson decays

In the SU(3) symmetry limit, semileptonic $D^+\to Sl^+ν$ and $B^-\to Sl^-\barν$ decays, with $S=a_0(980)$, $f_0(980)$ and $f_0(600)$, are found to obey different sum rules in the $\bar qq$ and the tetra-quark descriptions for scalar mesons. Thus these sum rules can distinguish the two scenarios for light scalar mesons model-independently. This method also applies to the $\bar B^0\to J/ψ(η_c) S$ decays. Two kinds of SU(3) symmetry breaking effects are found to be under control, which will not spoil our method. The branching fractions of the $D^+\to Sl^+ν$, $B^-\to Sl^-\barν$ and $\bar B^0\to J/ψ(η_c) S$ decays roughly have the order $10^{-4}$, $10^{-5}$ and $10^{-6}$, respectively. The ongoing BES-III and the forthcoming Super B experiments are able to measure these channels and accordingly to provide detailed information of the scalar meson inner structure.

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arXiv2010

Decays of $B$ meson to two charmed mesons

The factorization theorem in Decays of $B_{(s)}$ mesons to two charmed mesons (both pseudoscalar and vector) can still be proved in the leading order in $m_D/m_B$ and $Λ_{\rm{QCD}}/m_D$ expansion. Working in the perturbative QCD approach, we find that the factorizable emission diagrams are dominant. Most of branching ratios we compute agree with the experimental data well, which means that the factorization theorem seems to be reliable in predicting branching ratios for these decays. In the decays of a $B$ meson to two vector charmed mesons, the transverse polarization states contribute $40%-50%$ both in the processes with an external W emission and in the pure annihilation decays. This is in agreement with the present experimental data. We also calculate the CP asymmetry parameters. The results show that the direct CP asymmetries are very small. Thus observation of any large direct CP asymmetry will be a signal for new physics. The mixing induced CP asymmetry in the neutral modes is large. This is also in agreement with the current experimental measurements. They can give a cross check of the $\sin 2β$ measurement from other channels.

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arXiv2009

$B_c$ to P-Wave Charmonia Transitions in Covariant Light-Front Approach

In the covariant light-front quark model, we investigate the $B_c\to h_c, χ_{c0,1,2}$ form factors. The form factors are evaluated in space-like kinematic region and are recasted to the physical region by adopting the exponential parametrization. We also study the semileptonic $B_c$ decays and find that branching fractions for the $B_c\to (h_c,χ_{c0,1,2})l\barν(l=e,μ)$ decays have the order $10^{-3}$ while branching fractions for $B_c\to (h_c,χ_{c0,1,2})τ\barν_τ$ are suppressed by one order. These predictions will be tested at the forthcoming hadron colliders.

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arXiv2009

Branching Ratios, Forward-backward Asymmetry and Angular Distributions of $B\to K_1l^+l^-$ Decays

Using the $B\to K_1$ form factors evaluated in the perturbative QCD approach, we study semileptonic $B\to K_1(1270)l^+l^-$ and $B\to K_1(1400)l^+l^-$ decays, where $K_1(1270)$ and $K_1(1400)$ are mixtures of $K_{1A}$ and $K_{1B}$ which are $^3P_1$ and $^1P_1$ states, respectively. Using the technique of helicity amplitudes, we express the decay amplitudes in terms of several independent and Lorentz invariant pieces. We study the dilepton invariant mass distributions, branching ratios, polarizations and forward-backward asymmetries of $ B\to K_1l^+l^-$ decays. The ambiguity in the sign of the mixing angle will induce much large differences to branching ratios of semileptonic B decays: branching ratios without resonant contributions either have the order of $10^{-6}$ or $10^{-8}$. But the polarizations and the forward-backward asymmetries are not sensitive to the mixing angles. We find that the resonant contributions will dramatically change the dilepton invariant mass distributions in the resonant region. We also provide the angular distributions of $ B\to K_1l^+l^-\to (Kππ)l^+l^-$ decays.

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arXiv2009

Covariant Light-Front Approach for $B_c$ transition form factors

In the covariant light-front quark model, we investigate the form factors of $B_c$ decays into $D, D^*, D_s, D_s^*, η_c, J/ψ, B, B^*, B_s, B_s^*$ mesons. The form factors in the spacelike region $q^2<0$ are directly evaluated. To extrapolate the form factors to the full kinematic region, we fit the form factors by adopting a three-parameter form from the spacelike region. $b\to u,d,s$ transition form factors at maximally recoiling point ($q^2=0$) are smaller than $b\to c$ and $c\to d,s$ transition form factors, while the $b\to d,s,c$ form factors at zero recoiling point are close to each other. In the fitting procedure, we find the parameters for the form factors $A_2(B_c\to B^*)$ and $A_2(B_c\to B^*_s)$ strongly depend on the decay constants of $B^*$ and $B_s^*$ mesons. Fortunately, the semileptonic and nonleptonic $B_c$ decays are not sensitive to these form factors. With the form factors, we also investigate the branching fractions, polarizations of the semileptonic $B_c\to Mlν$ decays. Semileptonic $B_c\to (η_c,J/ψ)lν$ and $B_c\to (B_s,B_s^*)lν$ decays have much larger branching fractions than $B_c\to (D,D^*,B,B^*)lν$. In the three kinds of $B_c\to Vlν$ decays, contributions from the longitudinal polarized vector is comparable with those from the transversely polarized vector. These predictions will be tested at the ongoing and forthcoming hadron colliders.

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arXiv2009

Transition form factors of B decays into p-wave axial-vector mesons in the perturbative QCD approach

The $B_{u,d,s}\to V,A$ form factors are studied in perturbative QCD approach ($V,A$ denote a vector meson and two kinds of p-wave axial-vector mesons: $^3P_1$ and $^1P_1$ states, respectively.). The form factors are directly studied in the large recoiling region and extrapolated to the whole kinematic region within the dipole parametrization. Adopting decay constants with different signs for the two kinds of axial-vectors, we find that the two kinds of $B\to A$ form factors have the same sign. The two strange mesons $K_{1A}$ and $K_{1B}$ mix with each other via the SU(3) symmetry breaking effect. In order to reduce the ambiguities in the mixing angle between $K_{1A}$ and $K_{1B}$, we propose a model-independent way that utilizes the B decay data. Most of the branching fractions of the semilteptonic $B\to Al\bar ν_l$ decays are of the order $10^{-4}$, which still need experimental tests in the on-going and forthcoming experiments.

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arXiv2008

$B\to S$ Transition Form Factors in the PQCD approach

Under two different scenarios for the light scalar mesons, we investigate the transition form factors of $B(B_s)$ mesons decay into a scalar meson in the perturbative QCD approach. In the large recoiling region, the form factors are dominated by the short-distance dynamics and can be calculated using perturbation theory. We adopt the dipole parametrization to recast the $q^2$ dependence of the form factors. Since the decay constants defined by the scalar current are large, our predictions on the $B\to S$ form factors are much larger than the $B\to P$ transitions, especially in the second scenario. Contributions from various light-cone distribution amplitudes (LCDAs) are elaborated and we find that the twist-3 LCDAs provide more than a half contributions to the form factors. The two terms of the twist-2 LCDAs give destructive contributions in the first scenario while they give constructive contributions in the second scenario. With the form factors, we also predict the decay width and branching ratios of the semileptonic $B\to Sl\barν$ and $B\to Sl^+l^-$ decays. The branching ratios of $B\to Sl\barν$ channels are found to have the order of $10^{-4}$ while those of $B\to Sl^+l^-$ have the order of $10^{-7}$. These predictions can be tested by the future experiments.

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arXiv2008

What can we learn from $B\to a_1(1260)(b_1(1235))π(K)$ decays?

We investigate the $B\to a_1(1260)(b_1(1235))π(K)$ decays under the factorization scheme and find many discrepancies between theoretical predictions and the experimental data. In the tree dominated processes, large contributions from color-suppressed tree diagrams are required in order to accommodate with the large decay rates of $B^-\to a_1^0π^-$ and $B^-\to a_1^-π^0$. For $\bar B^0\to (a_1^+, b_1^+)K^-$ decays which are both induced by $b\to s$ transition, theoretical predictions on their decay rates are larger than the data by a factor of 2.8 and 5.5, respectively. Large electro-weak penguins or some new mechanism are expected to explain the branching ratios of $B^-\to b_1^0K^-$ and $B^-\to a_1^-\bar K^0$. The soft-collinear-effective-theory has the potential to explain large decay rates of $B^-\to a_1^0π^-$ and $B^-\to a_1^-π^0$ via a large hard-scattering form factor $ζ_J^{B\to a_1}$. We will also show that, with proper charming penguins, predictions on the branching ratios of $\bar B^0\to (a_1^+, b_1^+)K^-$ can also be consistent with the data.

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arXiv2008

The $B(B_s)\to D_{(s)} P$, $D_{(s)} V$, $D_{(s)}^{}P$ and $D_{(s)}^{}V$ decays in the perturbative QCD approach

Two-body non-leptonic charmed decays $B_{(s)} \to D_{(s)}P$, $D_{(s)}^*P$, $D_{(s)}V$ and $D_{(s)}^*V$ are analyzed in perturbative QCD approach, where $P$ and $V$ denote the light pseudoscalar meson and vector meson, respectively. We test the $D$ meson wave function by a $χ^2$ fit with experimental data of six $B\to DP$ channels. We give the branching ratios of all the charmed B decay channels, most of which agree with experiments amazingly well. The predicted $B_s$ decays can be confronted with the future experimental data. By straightforward calculations, our pQCD approach gives the right relative strong phase of $a_2/a_1$ with experiments. We also predict the percentage of transverse polarizations in $B_{(s)} \to D^* V$ decay channels.

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arXiv2008

Partners of Z(4430) and Productions in B Decays

Recently, Belle Collaboration has reported a resonant state produced in $B\to K πψ'$, which is called Z(4430). This state is charged, so it can not be interpreted as an ordinary charmonium state. In this paper, we analyze the octet to which this particle belongs and predict the masses of mesons in this octet. Utilizing flavor SU(3) symmetry, we study production rates in several kinds of B decays. The $\bar B^0\to Z_s^-π^+\to K^-ψ'π^+$ and $B^-\to \bar Z_s^0 π^-\to K_Sψ'π^-$ decay channels, favored by Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, can have branching ratios of ${\cal O}(10^{-5})$. This large branching ratio could be observed at the running $B$ factories to detect $Z_s$ particles containing a strange quark. We also predict large branching ratios of the $Z$ and $Z_c$ ($\bar cc\bar c D, D=u,d,s$) particle production rates in non-leptonic $B_c$ decays and radiative B decays. Measurements of these decays at the ongoing $B$ factories and the forthcoming Large Hadron Collider (LHC)-b experiments are helpful to clarify the mysterious $Z$ particles.

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arXiv2007

The transition form factors for semi-leptonic weak decays of $J/ψ$ in QCD sum rules

Within the Standard Model, we investigate the semi-leptonic weak decays of $J/ψ$. The various form factors of $J/ψ$ transiting to a single charmed meson ($D^{(*)}_{(d,s)}$) are studied in the framework of the QCD sum rules. These form factors fully determine the rates of the weak semi-leptonic decays of $J/ψ$ and provide valuable information about the non-perturbative QCD effects. Our results indicate that the decay rate of the semi-leptonic weak decay mode $J/ψ\to D^{(*)-}_{s}+e^{+}+ν_{e}$ is at order of $10^{-10}$.

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