Measurement of the $e^+e^- \to \eta\pi^+\pi^-$ cross section in the center-of-mass energy range 1.22-2.00 GeV with the SND detector at the VEPP-2000 collider

The SND collaboration Aulchenko, V.M. ; Achasov, M.N. ; Barnyakov, A.Yu. ; et al.
Phys.Rev. D91 (2015) 052013, 2015.
Inspire Record 1332929 DOI 10.17182/hepdata.73176

<p>In the experiment with the SND detector at the VEPP-2000 <inline-formula><mml:math display="inline"><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>-</mml:mo></mml:msup></mml:math></inline-formula> collider the cross section for the process <inline-formula><mml:math display="inline"><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>-</mml:mo></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:mi>η</mml:mi><mml:msup><mml:mi>π</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mo>-</mml:mo></mml:msup></mml:math></inline-formula> has been measured in the center-of-mass energy range from 1.22 to 2.00 GeV. Obtained results are in agreement with previous measurements and have better accuracy. The energy dependence of the <inline-formula><mml:math display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msup><mml:mo stretchy="false">→</mml:mo><mml:mi>η</mml:mi><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> cross section has been fitted with the vector-meson dominance model. From this fit the product of the branching fractions <inline-formula><mml:math display="inline"><mml:mrow><mml:mi>B</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mi>ρ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>1450</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">→</mml:mo><mml:mi>η</mml:mi><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msup><mml:mo stretchy="false">)</mml:mo><mml:mi>B</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mi>ρ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>1450</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>e</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msup><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math></inline-formula> has been extracted and compared with the same products for <inline-formula><mml:math display="inline"><mml:mrow><mml:mi>ρ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>1450</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">→</mml:mo><mml:mi>ω</mml:mi><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> and <inline-formula><mml:math display="inline"><mml:mrow><mml:mi>ρ</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>1450</mml:mn><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math></inline-formula> decays. The obtained cross section data have been also used to test the conservation of vector current hypothesis.</p>

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Study of $e^+e^- \to \omega\pi^0 \to \pi^0\pi^0\gamma$ in the energy range $1.05-2.00$ GeV with SND

Achasov, M.N. ; Aulchenko, V.M. ; Barnyakov, A.Yu. ; et al.
Phys.Rev. D88 (2013) 054013, 2013.
Inspire Record 1224801 DOI 10.17182/hepdata.62287

The cross section for the process e+e- --> omega pi0 --> pi0 pi0 gamma has been measured in the energy range 1.05--2.00 GeV. The experiment has been performed at the e+e- collider VEPP-2000 with the SND detector. The measured e+e- --> omega pi0 cross section above 1.4 GeV is the most accurate to date. Below 1.4 GeV our data are in good agreement with the previous SND and CMD-2 measurements. Data on the e+e- --> omega pi0 cross section are well described by the VMD model with two excited rho-like states. From the measured cross section we have extracted the gamma^* --> omega pi0 transition form factor. It has been found that the VDM model cannot describe simultaneously our data and data obtained from the omega --> pi0 mu+ mu- decay. We have also tested CVC hypothesis comparing our results on the e+e- --> omega pi0 cross section with data on the tau- --> omega pi- nu_{tau} decay.

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