arXiv subjects

Tao Huang

Publications and source records attributed to Tao Huang.

At least 307 records · Page 17Linked to original sources

arXiv2012

Form factors $f^{B\to π}_+(0)$ and $f^{D\to π}_+(0)$ in $QCD$ and determination of $|V_{ub}|$ and $|V_{cd}|$

We present a QCD study on $B, D\toπ$ semileptonic transitions at zero momentum transfer and an estimate of magnitudes of the associated CKM matrix elements. Light cone sum rules (LCSRs) with chiral correlator are applied to calculate the form factors $f^{B\to π}_+(0)$ and $f^{D\to π}_+(0)$. We show that there is no twist-3 and-5 component involved in the light-cone expansions such that the resulting sum rules have a good convergence and offer an understanding of these form factors at twist-5 level. A detailed $\mathcal{O}(α_s)$ computation is carried out in leading twist-2 approximation and the $\bar{MS}$ masses are employed for the underlying heavy quarks. With the updated inputs and experimental data, we have $f^{B\to π}_+(0)=0.28^{+0.05}_{-0.02}$ and $|V_{ub}|=(3.4^{+0.2}_{-0.6}\pm0.1\pm0.1)\times10^{-3}$; $f^{D\to π}_+(0)=0.62\pm0.03$ and $|V_{cd}|=0.244\pm0.005\pm0.003\pm0.008$. As a by-product, a numerical estimate for the decay constant $f_D$ is yielded as $f_{D}=190^{+12}_{-11}\mathrm{MeV}$.

hep-ph↗

arXiv2012

Photon-to-pion transition form factor and pion distribution amplitude from holographic QCD

We try to understand the recently observed anomalous behavior of the photon-to-pion transition form factor in the holographic QCD approach. First the holographic description of the anomalous γ^*γ^*π^0 form factor is reviewed and applied to various models. It is illustrated that in describing the anomalous form factor, the holographic approach is asymptotically dual to the perturbative QCD (pQCD) framework, with the pion mode π(z)\sim z corresponding to the asymptotic pion distribution amplitude. This indicates some inconsistency in light-front holography, since π(z)\sim z would be dual to φ(x)\sim \sqrt{x(1-x)} there. After clarifying these subtleties, we employ the relation between the holographic and the perturbative expressions to study possible asymptotic violation of the transition form factor. It is found that if one require that the asymptotic form factor possess a pQCD-like expression, the pion mode can only be ultraviolet-enhanced by logarithmic factors. The minimally deformed pion mode will then be of the form π(z)\sim z\ln (zΛ)^{-1}. We suppose that this deformation may be due to the coupling of the pion with a nontrivial open string tachyon field, and then the parameter $Λ$ will be related to the quark condensate. Interestingly, this pion mode leads immediately to Radyushkin's logarithmic model, which fitted very well the experimental data in the large-Q^2 region. On the other side, the pQCD interpretation with a flat-like pion distribution amplitude, proposed by Radyushkin and Polyakov, fails to possess a holographic expression.

hep-ph↗

arXiv2011

A Localization Method for the Internet of Things

Many localization algorithms and systems have been developed by means of wireless sensor networks for both indoor and outdoor environments. To achieve higher localization accuracy, extra hardware equipments are utilized by most of the existing localization solutions, which increase the cost and considerably limit the location-based applications. The Internet of Things (IOT) integrates many technologies, such as Internet, Zigbee, Bluetooth, infrared, WiFi, GPRS, 3G, etc, which can enable different ways to obtain the location information of various objects. Location-based service is a primary service of the IOT, while localization accuracy is a key issue. In this paper, a higher accuracy localization scheme is proposed which can effectively satisfy diverse requirements for many indoor and outdoor location services. The proposed scheme composes of two phases: 1) partition phase, in which the target region is split into small grids; 2) localization refinement phase, in which a higher accuracy of localization can be obtained by applying an algorithm designed in the paper. A trial system is set up to verify correctness of the proposed scheme and furthermore to illustrate its feasibility and availability. The experimental results show that the proposed scheme can improve the localization accuracy.

cs.NI↗

arXiv2011

Skyrmion properties from holographic instantons of large size

Based on the intanton approximation of Skyrmion and recent progresses on the holographic approach, we study baryon properties using Skyrmions generated from holographic instantons. First we employ Atiyah and Manton's early observation to show that the instanton approximation gives the correct infrared behavior for the Skyrmion solution, and thus those of the electromagnetic form factors of the nucleon. We then use Skyrmions generated from flat-space instanton solutions to study various baryon properties, treating the instanton size as an arbitrary variable. It is found that, a large instanton size is required to reproduce the physical axial coupling. From such an instanton configuration, the predictions for other baryon quantities in the Skyrme model improve the original results quite a lot. Some of the results reproduce those by quantizing the full instanton solution, while no fine-tuning of the mesonic parameters are needed. From these we conclude that the baryons in the low energy region can be effectively described by large instantons.

hep-ph↗

arXiv2011

Constraints on the Light Pseudoscalar Meson Distribution Amplitudes from Their Meson-Photon Transition Form Factors

The meson-photon transition form factors $γγ^*\to P$ ($P$ stands for $π$, $η$ and $η'$) provide strong constraints on the distribution amplitudes of the pseudoscalar mesons. In this paper, these transition form factors are calculated under the light-cone perturbative QCD approach, in which both the valence and non-valence quarks' contributions have been taken into consideration. To be consistent, an unified wavefunction model is adopted to analyze these form factors. It is shown that with proper charm component $f^{c}_{η'}\sim -30$ MeV and a moderate DA with $B\sim 0.30$, the experimental data on $Q^{2}F_{ηγ}(Q^2)$ and $Q^{2}F_{η'γ}(Q^2)$ in whole $Q^2$ region can be explained simultaneously. Further more, a detailed discussion on the form factors' uncertainties caused by the constituent quark masses $m_q$ and $m_s$, the parameter $B$, the mixing angle $ϕ$ and $f_{η'}^c$ are presented. It is found that by adjusting these parameters within their reasonable regions, one can improve the form factor to a certain degree but can not solve the puzzle for $Q^{2}F_{πγ}(Q^2)$, especially to explain the behavior of $π-γ$ form factor within the whole $Q^2$ region consistently. We hope further experimental data on these form factors in the large $Q^2$ region can clarify the present situation.

hep-ph↗

arXiv2011

In-medium mass modifications of the $D_0$ and $B_0$ mesons with the QCD sum rules

In this article, we calculate the in-medium mass modifications of the scalar mesons $D_0$ and $B_0$ using the QCD sum rules. In calculations, we observe that the $D_0N$ and $B_0N$ scattering lengths are about $1.1\,\rm{fm}$ and $4.1\,\rm{fm}$ respectively, the mass-shifts $δM_{D_0}=69\,\rm{MeV}$ and $δM_{B_0}=217\,\rm{MeV}$, and the $D_0N$ and $B_0N$ interactions are repulsive. The positive mass-shifts indicate that the decays of the higher charmonium states into the $D_0\bar{D}_0$ pair are suppressed.

hep-ph↗

arXiv2011

$B \to A$ transitions in the light-cone QCD sum rules with the chiral current

In this article, we calculate the form-factors of the transitions $B \to a_1(1260)$, $b_1(1235) $ in the leading-order approximation using the light-cone QCD sum rules. In calculations, we choose the chiral current to interpolate the $B$-meson, which has outstanding advantage that the twist-3 light-cone distribution amplitudes of the axial-vector mesons have no contributions, and the resulting sum rules for the form-factors suffer from much less uncertainties. Then we study the semi-leptonic decays $B \to a_1(1260) l\barν_l$, $b_1(1235) l\barν_l$ $(l=e,μ,τ)$, and make predictions for the differential decay widths and decay widths, which can be confronted with the experimental data in the coming future.

hep-ph↗

arXiv2011

Blow up criterion for nematic liquid crystal flows

In this paper, we establish a blow up criterion for the short time classical solution of the nematic liquid crystal ow, a simplified version of Ericksen-Leslie system modeling the hydrodynamic evolution of nematic liquid crystals, in dimensions two and three. More precisely, $0<T_*<+\infty$ is the maximal time interval iff (i) for $n=3$, $|ω|+|\nabla d|^2\notin L^1_tL^\infty_x(\mathbb R^3\times [0,T_*])$, and (ii) for $n=2$, $|\nabla|^2\notin L^1_tL^\infty_x(\mathbb R^2\times [0,T_*])$.

math.AP↗

arXiv2011

Strong solutions of the compressible nematic liquid crystal flow

We study strong solutions of the simplified Ericksen-Leslie system modeling compressible nematic liquid crystal flows in a domain $Ω\subset\mathbb R^3$. We first prove the local existence of unique strong solutions provided that the initial data $ρ_0, u_0, d_0$are sufficiently regular and satisfy a natural compatibility condition. The initial density function $ρ_0$ may vanish on an open subset (i.e., an initial vacuum may exist). We then prove a criterion for possible breakdown of such a local strong solution at finite time in terms of blow up of the quantities $\|ρ\|_{L^\infty_tL^\infty_x}$ and $\|\nabla d\|_{L^3_tL^\infty_x}$.

math.AP↗

arXiv2011

Blow up criterion for compressible nematic liquid crystal flows in dimension three

In this paper, we consider the short time strong solution to a simplified hydrodynamic flow modeling the compressible, nematic liquid crystal materials in dimension three. We establish a criterion for possible breakdown of such solutions at finite time in terms of the temporal integral of both the maximum norm of the deformation tensor of velocity gradient and the square of maximum norm of gradient of liquid crystal director field.

math.AP↗

arXiv2011

$B_{(s)}\to S$ transitions in the light cone sum rules with the chiral current

$B_{(s)}$ semi-leptonic decays to the light scalar meson, $B_{(s)}\to S l\barν_l, S l \bar{l}\,\,(l=e,μ,τ)$, are investigated in the QCD light-cone sum rules (LCSR) with chiral current correlator. Having little knowledge of ingredients of the scalar mesons, we confine ourself to the two quark picture for them and work with the two possible Scenarios. The resulting sum rules for the form factors receive no contributions from the twist-3 distribution amplitudes (DA's), in comparison with the calculation of the conventional LCSR approach where the twist-3 parts play usually an important role. We specify the range of the squared momentum transfer $q^2$, in which the operator product expansion (OPE) for the correlators remains valid approximately. It is found that the form factors satisfy a relation consistent with the prediction of soft collinear effective theory (SCET). In the effective range we investigate behaviors of the form factors and differential decay widthes and compare our calculations with the observations from other approaches. The present findings can be beneficial to experimentally identify physical properties of the scalar mesons.

hep-ph↗

arXiv2011

The cross section of the process $e^{+}+e^{-}\to J/ψ+η_c$ within the QCD light-cone sum rules

We calculate the cross section of the exclusive process $e^{+} +e^{-}\to J/ψ+η_c$ at the leading order approximation within the QCD light-cone sum rules (LCSR) approach. It is found that the form factor $F_{VP}(V=J/ψ,P=η_c)$ depends mainly on the behavior of the twist-2 distribution amplitude of the $η_c$-meson at the scale of this process. Thus in order to obtain a reliable estimation of the cross section, it is important to have a realistic distribution amplitude of the $η_c$ meson, and to deal with the evolution of the distribution amplitude to the effective energy scale of the process. Our results show that one can obtain a compatible prediction with the Belle and BarBar experimental data.

hep-ph↗

arXiv2010

A Practical Localization Algorithm Based on Wireless Sensor Networks

Many localization algorithms and systems have been developed by means of wireless sensor networks for both indoor and outdoor environments. To achieve higher localization accuracy, extra hardware equipments are utilized by most of the existing localization algorithms, which increase the cost and greatly limit the range of location-based applications. In this paper we present a method which can effectively meet different localization accuracy requirements of most indoor and outdoor location services in realistic applications. Our algorithm is composed of two phases: partition phase, in which the target region is split into small grids and localization refinement phase in which a higher accuracy location can be generated by applying a trick algorithm. A realistic demo system using our algorithm has been developed to illustrate its feasibility and availability. The results show that our algorithm can improve the localization accuracy.

cs.NI↗

arXiv2010

An Implication on the Pion Distribution Amplitude from the Pion-Photon Transition Form Factor with the New BABAR Data

The new BABAR data on the pion-photon transition form factor arouses people's new interests on the determination of pion distribution amplitude. To explain the data, we take both the leading valence quark state's and the non-valence quark states' contributions into consideration, where the valence quark part up to next-to-leading order is presented and the non-valence quark part is estimated by a phenomenological model based on its limiting behavior at both $Q^2\to 0$ and $Q^2\to\infty$. Our results show that to be consistent with the new BABAR data at large $Q^2$ region, a broader other than the asymptotic-like pion distribution amplitude should be adopted. The broadness of the pion distribution amplitude is controlled by a parameter $B$. It has been found that the new BABAR data at low and high energy regions can be explained simultaneously by setting $B$ to be around 0.60, in which the pion distribution amplitude is closed to the Chernyak-Zhitnitsky form.

hep-ph↗

arXiv2010

$γ^{*}ρ^0\toπ^0$ Transition Form Factor in Extended AdS/QCD Models

The $γ^{*}ρ^0\toπ^0$ transition form factor is extracted from recent result for the $γ^* γ^* π^0$ form factor obtained in the extended hard-wall AdS/QCD model with a Chern-Simons term. In the large momentum region, the form factor exhibits a $1/Q^4$ behavior, in accordance with the perturbative QCD analysis, and also with the Light-Cone Sum Rule (LCSR) result if the pion wave function exhibits the same endpoint behavior as the asymptotic one. The appearance of this power behavior from the AdS side and the LCSR approach seem to be rather similar: both of them come from the {"}soft" contributions. Comparing the expressions for the form factor in both sides, one can obtain the duality relation $z\propto \sqrt{u(1-u)}$, which is compatible with one of the most important relations of the Light-Front holography advocated by Brodsky and de Teramond. In the moderate $Q^2$ region, the comparison of the numerical results from both approaches also supports a asymptotic-like pion wave function, in accordance with previous studies for the $γ^* γ^* π^0$ form factor. The form factor at zero momentum transfer gives the $γ^{*}ρ^0π^0$ coupling constant, from which one can determine the partial width for the $ρ^0(ω)\to π^0 γ$ decay. We also calculate the form factor in the time-like region, and study the corresponding Dalitz decays $ρ^0(ω)\to π^0 e^+e^-, π^0μ^+μ^-$. Although all these results are obtained in the chiral limit, numerical calculations with finite quark masses show that the corrections are extremely small. Some of these calculations are repeated in the Hirn-Sanz model and similar results are obtained.

hep-ph↗

arXiv2009

Remarks on the two-dimensional power correction in the soft wall model

We present a direct derivation of the two-point correlation function of the vector current in the soft wall model by using the AdS/CFT dictionary. The resulting correlator is exactly the same as the one previously obtained from dispersion relation with the same spectral function as in this model. The coefficient $C_2$ of the two-dimensional power correction is found to be $C_2=-c/2$ with $c$ the slope of the Regge trajectory, rather than $C_2=-c/3$ derived from the strategy of first quantized string theory. Taking the slope of the $ρ$ trajectory $c\approx0.9{GeV}^2$ as input, we then get $C_2\approx-0.45{GeV}^2$. The gluon condensate is found to be $<α_sG^2>\approx0.064{GeV}^4$, which is almost identical to the QCD sum rule estimation. By comparing these two equivalent derivation of the correlator of scalar glueball operator, we demonstrate that the two-dimensional correction can't be eliminated by including the non-leading solution in the bulk-to-boundary propagator, as was done in \cite{Colangelo2}. In other words, the two-dimensional correction does exist in the scalar glueball case. Also it is manifest by using the dispersion relation that the minus sign of gluon condensate and violation of the low energy theorem are related to the subtraction scheme.

hep-ph↗

arXiv2009

Radiative Corrections on the $B\to P$ Form Factors with Chiral Current in the Light-Cone Sum Rules

Based on the approach of the vector form factor $F^{+}_{B\toπ, K}(q^2)$ in our previous papers, we extend the calculation of the radiative corrections to the $B\to P$ ($P$ stands $π$, $K$ and all light pseudoscalar mesons) scalar and tensor form factors $F^{0,T}_{B\to P}(q^2)$ with chiral current in the light-cone sum rules (LCSRs). The most uncertain twist-3 contributions to the $B\to P$ form factors can be naturally eliminated through a properly designed correlator. We present the next-leading-order formulae of $F^{+,0,T}_{B\to P}(q^2)$ with the $b$-quark pole mass that is universal. It has been shown that our results are simpler and less uncertain under the same parameter regions since we only need to calculate the next leading order on the twist-2 part from the obtained LCSR. Second, we obtain $f^{+,0}_{B\toπ}(0)=0.260^{+0.059}_{-0.040}$, $f^{T}_{B\toπ}(0)=0.276^{+0.052}_{-0.039}$, $f^{+,0}_{B\to K}(0)=0.334^{+0.094}_{-0.069}$ and $f^{T}_{B\to K}(0) =0.379^{+0.092}_{-0.077}$ at $q^2=0$ and the $SU_f(3)$-breaking effects are discussed too.

hep-ph↗

arXiv2008

Heavy-to-light transition form factors and their relations in light-cone QCD sum rules

The improved light-cone QCD sum rules by using chiral current correlator is systematically reviewed and applied to the calculation of all the heavy-to-light form factors, including all the semileptonic and penguin ones. By choosing suitable chiral currents, the light-cone sum rules for all the form factors are greatly simplified and depend mainly on one leading twist distribution amplitude of the light meson. As a result, relations between these form factors arise naturally. At the considered accuracy these relations reproduce the results obtained in the literature. Moreover, since the explicit dependence on the leading twist distribution amplitudes is preserved, these relations may be more useful to simulate the experimental data and extract the information on the distribution amplitude.

hep-ph↗