Do you want to publish a course? Click here

Form factor of pi^0-->gammagamma^*

52   0   0.0 ( 0 )
 Added by Bing An Li
 Publication date 2001
  fields
and research's language is English
 Authors Bing An Li




Ask ChatGPT about the research

An intrinsic form factor has benn found and the slope of the form factor has been predicted.



rate research

Read More

The gamma(*) pi(0) -> gamma form factor is obtained within the Lagrangian quark model with separable interaction known to provide a good description of the pion observables at low energies. The pion-quarks vertex is chosen in a Gaussian form. The form factor obtained is close to the available experimental data and reaches smoothly the Brodsky-Lepage limit at Q2 = 10 GeV2.
Recent experimental data for the differential decay distribution of the decay $tau^-to u_tau K_Spi^-$ by the Belle collaboration are described by a theoretical model which is composed of the contributing vector and scalar form factors $F_+^{Kpi}(s)$ and $F_0^{Kpi}(s)$. Both form factors are constructed such that they fulfil constraints posed by analyticity and unitarity. A good description of the experimental measurement is achieved by incorporating two vector resonances and working with a three-times subtracted dispersion relation in order to suppress higher-energy contributions. The resonance parameters of the charged $K^*(892)$ meson, defined as the pole of $F_+^{Kpi}(s)$ in the complex $s$-plane, can be extracted, with the result $M_{K^*}=892.0 pm 0.9 $MeV and $Gamma_{K^*}=46.2 pm 0.4 $MeV. Finally, employing the three-subtracted dispersion relation allows to determine the slope and curvature parameters $lambda_+^{}=(24.7pm 0.8)cdot 10^{-3}$ and $lambda_+^{}=(12.0pm 0.2)cdot 10^{-4}$ of the vector form factor $F_+^{Kpi}(s)$ directly from the data.
A measurement of the vector to pseudoscalar conversion decay $phi to pi^0 e^+e^-$ with the KLOE experiment is presented. A sample of $sim 9500$ signal events was selected from a data set of 1.7 fb$^{-1}$ of $e^+e^-$ collisions at $sqrt{s} sim m_{phi}$ collected at the DA$Phi$NE $e^+e^-$ collider. These events were used to obtain the first measurement of the transition form factor $| F_{phi pi^0}(q^2) |$ and a new measurement of the branching ratio of the decay: $rm{BR},(phi to pi^0 e^+e^-) = (,1.35 pm 0.05^{,,+0.05}_{,,-0.10},) times 10 ^{-5}$. The result improves significantly on previous measurements and is in agreement with theoretical predictions.
In light of recent experimental results, we revisit the dispersive analysis of the $omega to 3pi$ decay amplitude and of the $omegapi^0$ transition form factor. Within the framework of the Khuri-Treiman equations, we show that the $omega to 3pi$ Dalitz-plot parameters obtained with a once-subtracted amplitude are in agreement with the latest experimental determination by BESIII. Furthermore, we show that at low energies the $omegapi^0$ transition form factor obtained from our determination of the $omega to 3pi$ amplitude is consistent with the data from MAMI and NA60 experiments.
161 - D. R. Boito , R. Escribano , 2010
Dispersive representations of the Kpi vector and scalar form factors are used to fit the spectrum of tau ---> K pi nu_tau obtained by the Belle collaboration incorporating constraints from results for K_l3 decays. The slope and curvature of the vector form factor are obtained directly from the data through the use of a three-times-subtracted dispersion relation. We find $lambda_+=(25.49 pm 0.31) times 10^{-3}$ and $lambda_+= (12.22 pm 0.14) times 10^{-4}$. From the pole position on the second Riemann sheet the mass and width of the $K^*(892)^{pm}$ are found to be $m_{K^*(892)^pm}=892.0pm 0.5$~MeV and $Gamma_{K^*(892)^pm}=46.5pm 1.1$~MeV. The phase-space integrals needed for K_l3 decays are calculated as well. Furthermore, the Kpi isospin-1/2 P-wave threshold parameters are derived from the phase of the vector form factor. For the scattering length and the effective range we find respectively $a_{1}^{1/2},= ( 0.166pm 0.004),m_pi^{-3}$ and $b_{1}^{1/2},=( 0.258pm 0.009),m_pi^{-5}$.
comments
Fetching comments Fetching comments
Sign in to be able to follow your search criteria
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا