PARAMETER $\beta $ IN ${{\boldsymbol \phi}}$ $\rightarrow$ ${{\boldsymbol P}}{{\boldsymbol e}^{+}}{{\boldsymbol e}^{-}}$ DECAYS
In the one-pole approximation the electromagnetic transition form factor for ${{\mathit \phi}}$ $\rightarrow$ ${{\mathit P}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ (${{\mathit P}}$ = ${{\mathit \pi}},{{\mathit \eta}}$) is given as a function of the ${{\mathit e}^{+}}{{\mathit e}^{-}}$ invariant mass squared, ${{\mathit q}^{2}}$, by the expression: $\vert \mathit F({{\mathit q}^{2}})\vert ^2$ = (1 $−$ ${{\mathit q}^{2}}/{{\mathit \Lambda}^{2}}){}^{-2}$, where vector meson dominance predicts parameter $\Lambda \approx{}$0.770 GeV ($\Lambda {}^{-2}\approx{}$1.687 GeV${}^{-2}$). The slope of this form factor, $\beta $ = d$\mathit F$/d${{\mathit q}^{2}}({{\mathit q}^{2}}$=0), equals $\Lambda {}^{-2}$ in this approximation.
The measurements below obtain $\beta $ in the one-pole approximation.
PARAMETER $\beta $ IN ${{\boldsymbol \phi}}$ $\rightarrow$ ${{\boldsymbol \eta}}{{\boldsymbol e}^{+}}{{\boldsymbol e}^{-}}$ DECAY
INSPIRE search
| $\bf{
1.29 \pm0.13}$
|
OUR AVERAGE
|
| $1.28$ $\pm0.10$ ${}^{+0.09}_{-0.08}$ |
30k |
|
|
KLOE |
| $3.8$ $\pm1.8$ |
213 |
1 |
|
SND |
|
1
The uncertainty is statistical only. The systematic one is negligible, in comparison.
|
|
| References: |
|
| PL B742 1 |
Study of the Dalitz Decay ${{\mathit \phi}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ with the KLOE Detector |
|
| PL B504 275 |
Study of Conversion Decay ${{\mathit \phi}}$ $\rightarrow$ ${{\mathit \eta}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ and ${{\mathit \eta}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit e}^{+}}{{\mathit e}^{-}}$ in the Experiment with SND Detector at the VEPP-2M Collider |
|
