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Hanqing Zheng

Publications and source records attributed to Hanqing Zheng.

At least 19 recordsLinked to original sources
arXiv2025

Quantum Weak Measurement Amplifies Dispersion Signal of Rydberg Atomic System

Rydberg atoms, with their long coherence time and large electric dipole moment, are pivotal in quantum precision measurement. In the process of approaching the standard quantum limit, higher demands are placed on detection schemes. This paper presents a scheme to amplify dispersion signal of Rydberg atomic microwave detection system, using a quantum weak measurement technique together with improved dimensionless pointer. The scheme effectively mitigates the impact of technical noise and can be used to achieve a measurement precision close to the limit set by atomic shot noise in theory. Compared with the superheterodyne method based on transmission detection, our scheme has been experimentally proved to have a sensitivity increase of 5$\sim$6 dB. In this work, the Rydberg dispersion signal amplification mechanism offers a approach to enhance microwave detection sensitivity, which also facilitates deeper investigations into its dynamic processes and further applications of this mechanism in quantum communication and quantum control.

quant-ph↗
arXiv2017

A New Medical Diagnosis Method Based on Z-Numbers

How to handle uncertainty in medical diagnosis is an open issue. In this paper, a new decision making methodology based on Z-numbers is presented. Firstly, the experts' opinions are represented by Z-numbers. Z-number is an ordered pair of fuzzy numbers denoted as Z = (A, B). Then, a new method for ranking fuzzy numbers is proposed. And based on the proposed fuzzy number ranking method, a novel method is presented to transform the Z-numbers into Basic Probability Assignment (BPA). As a result, the information from different sources is combined by the Dempster' combination rule. The final decision making is more reasonable due to the advantage of information fusion. Finally, two experiments, risk analysis and medical diagnosis, are illustrated to show the efficiency of the proposed methodology.

cs.AI↗
arXiv2008

Low Lying Scalar Resonances and Chiral Symmetry

Current theoretical studies on the $σ$ and $κ$ resonances are reviewed. It is emphasized that all evidences accumulated so far are consistent with the picture that the $σ$ meson is the chiral partner of the Nambu--Goldstone bosons in a linear realization of chiral symmetry.

hep-ph↗
arXiv2004

Some Remarks on Exotic Resonances

Using large $N_c$ counting rule, it is argued that tetra-quark resonances do not exist. Also it is pointed out that there exists the violation of exchange degeneracy in the exotic $KN$ scattering channel. It implies either the failure of resonance saturation assumption or it suggests the existence of exotic baryon resonances in such a channel.

hep-ph↗
arXiv2003

How to parameterize a light and broad resonance (the $σ$ meson)

We point out that a commonly used parameterization form to describe the $σ$ resonance is problematic by introducing a spurious singularity below two particle threshold, on the second sheet. The spurious singularity violates chiral symmetry and leads to sizable contribution when the resonance is light and broad -- as what happens to the $σ$ resonance, hence must be removed.

hep-ph↗
arXiv2003

Further remarks on $ππ$ scattering dispersion relations

The naive use of higher order perturbation theory leads the left--hand cut integrals in $ππ$ dispersion relations~\cite{hjy,Xiao01} divergent. This problem is discussed and solved. Also we point out that the Adler zero condition imposes three constraints on the dispersion relations. The $σ$ pole position is determined using the improved method, $M_σ= 483\pm 13 {\rm MeV}$,$Γ_σ= 705 \pm 50{\rm MeV}$. The scattering length parameter is found to be in excellent agreement with the experimental result.

hep-ph↗
arXiv2001

The Use of Dispersion Relations in the $ππ$ and $K\bar K$ Coupled-Channel System

Systematic and careful studies are made on the properties of the IJ=00 $ππ$ and $K\bar K$ coupled-channel system, using newly derived dispersion relations between the phase shifts and poles and cuts. The effects of nearby branch point singularities to the determination of the $f_0(980)$ resonance are estimated and and discussed.

hep-ph↗
arXiv2001

The Use of Analyticity in the $ππ$ and $K\bar K$ Coupled Channel System

Studies on the IJ=00 $ππ$ and $K\bar K$ coupled--channel system are made using newly derived dispersion relations between the phase shifts and poles and cuts. It is found that the $σ$ resonance must be introduced to explain the experimental phase shifts, after evaluating the cut contribution. The effects of nearby branch point singularities to the determination of the $f_0(980)$ resonance are also carefully clarified.

hep-ph↗
arXiv2000

A Numerical Analysis to the {$π$} and {K} Coupled--Channel Scalar Form-factor

A numerical analysis to the scalar form-factor in the $ππ$ and KK coupled--channel system is made by solving the coupled-channel dispersive integral equations, using the iteration method. The solutions are found not unique. Physical application to the $ππ$ central production in the $pp\to ppππ$ process is discussed based upon the numerical solutions we found.

hep-ph↗
arXiv2000

Top quark, heavy fermions and the composite Higgs boson

We study the properties of heavy fermions in the vector-like representation of the electro-weak gauge group $SU(2)_W\times U(1)_Y$ with Yukawa couplings to the standard model Higgs boson. Applying the renormalization group analysis, we discuss the effects of heavy fermions to the vacuum stability bound and the triviality bound on the mass of the Higgs boson. We also discuss the interesting possibility that the Higgs particle is composed of the top quark and heavy fermions. The bound on the composite Higgs mass is estimated using the method of Bardeen, Hill and Lindner, 150GeV$\leq m_H\leq$ 450GeV.

hep-ph↗
arXiv1999

Some Remarks on the Final State Interactions in $B\to πK$ Decays

Careful discussions are made on some points which are met in studying B decay final state interactions, taking the $B^0\to π^+ K^-$ process as an example. We point out that $π$--exchange rescatterings are not important, whereas for $D^*$ and $D^{**}$ exchanges, since the $B^0\to D^+D_s^-$ decay has a large branching ratio their contributions may be large enough to enhance the $B\to πK$ branching ratio significantly. However our estimates fail to predict a large enhancement.

hep-ph↗
arXiv1999

Studying High Energy Final State Interactions by N/D Method

We discuss the final state interaction effects at high energies via a multi-channel N/D method. We find that the 2 by 2 charge--exchange final state interactions typically contribute an enhancement factor of a few times $10^{-2}$ in the $B$ meson decay amplitudes, both for the real and the imaginary part. We also make some discussions on the elastic rescattering effects.

hep-ph↗
arXiv1996

A Renormalization Group Analysis of the Higgs Boson with Heavy Fermions and Compositeness

We study the properties of heavy fermions in the vector-like representation of the electro-weak gauge group $SU(2)_W\times U(1)_Y$ with Yukawa couplings to the standard model (SM) Higgs boson. Using the renormalization group analysis, we discuss their effects on the vacuum stability and the triviality bound on the Higgs self-coupling, within the context of the standard model (i.e., the Higgs particle is elementary). Contrary to the low energy case where the decoupling theorem dictates their behavior, the inclusion of heavy fermions drastically change the SM structure at high scale. We also discuss the interesting possibility of compositeness, i.e., the Higgs particle is composed of the heavy fermions using the method of Bardeen, Hill and Lindner~\cite{BHL91}. Finally we briefly comment on their possible role in explaining $R_b$ and $R_c$.

hep-ph↗
arXiv1995

A comment on the anomalous $Zt\bar t$ couplings and the $Z\to b\bar b$ decay

By reanalyzing the influence of the anomalous $Z\bar t t$ couplings on the $Z\rightarrow b\bar b$ decay process, we pointed out the ambiguity in the conventional treatment of the effective Lagrangian approach, because of the possible existence of large contributions given by constant terms beyond the leading cutoff dependent term.

hep-ph↗
arXiv1995

FINAL STATE INTERACTIONS OF $B\to DK$ DECAYS

We study the final state strong interactions of the $B\rightarrow DK$ decay processes, using the Regge model. We conclude that the final state interaction phases are very small, typically a few degrees. Neglecting final state interactions in obtaining the weak decay amplitudes is a good approximation.

hep-ph↗
arXiv1995

Spontaneous breaking of vector symmetries and the non-decoupling light Higgs particle

Using a four fermion interaction Lagrangian, we demonstrate that the spontaneous breaking of vector symmetries requires the existence of a light (comparing with the heavy fermion mass) scalar particle and the low energy effective theory (the $σ$ model) obtained after integrating out heavy fermion degrees of freedom is asymptotically a renormalizable one. When applying the idea to the electroweak symmetry breaking sector of the standard model, the Higgs particle's mass is of the order of the electroweak scale: $185 GeV /\sqrt{N_c} < m_H < 720 GeV /\sqrt{N_c}$ where $N_c$ is the color degrees of freedom of the heavy fermion fields.

hep-ph↗