P. Lukin

High-statistics measurement of the pion form factor in the ρ-meson energy range with the CMD-2 detector

We present a measurement of the pion form factor based on e+e- annihilation data from the CMD-2 detector in the energy range 0.6<sqrt(s)<1.0 GeV with a systematic uncertainty of 0.8%. A data sample is five times larger than that used in our previous measurement.

Study of the process e+e−→KS0KL0 in the center-of-mass energy range 1004–1060 MeV with the CMD-3 detector at the VEPP-2000 e+e− collider

This work is supported in part by the Russian Education and by the Russian Foundation for Basic RFBR 14-02-00580-a, RFBR 14-02-91332, RFBR 15-02-05674-a and RFBR 16-02-00160-a.

Study of the process e+e−→pp¯ in the c.m. energy range from threshold to 2 GeV with the CMD-3 detector

Abstract Using a data sample of 7.7 pb − 1 collected with the CMD-3 detector at the VEPP-2000 e + e − collider we select about 2900 events of the process e + e − → p p ¯ and measure its cross section at 12 energy points with about 6% systematic uncertainty. From the angular distribution of produced nucleons we obtain the ratio G E / G M .

Measurement of the e + e − → K + K − π + π − cross section with the CMD-3 detector at the VEPP-2000 collider

The process e + e − →K + K − π + π − e + e − → K + K − π + π − has been studied in the center-of-mass energy range from 1500 to 2000 MeV using a data sample of 23 pb −1 collected with the CMD-3 detector at the VEPP-2000 e + e − e + e − collider. Using about 24u2009000 selected events, the e + e − →K + K − π + π − e + e − → K + K − π + π − cross section has been measured with a systematic uncertainty decreasing from 11.7% at 1500–1600 MeV to 6.1% above 1800 MeV. A preliminary study of K + K − π + π − K + K − π + π − production dynamics has been performed.

Measurement of the running of the fine structure constant below 1 GeV with the KLOE detector

Abstract We have measured the running of the effective QED coupling constant α ( s ) in the time-like region 0.6 s 0.975 GeV with the KLOE detector at DAΦNE using the Initial-State Radiation process e + e − → μ + μ − γ . It represents the first measurement of the running of α ( s ) in this energy region. Our results show a more than 5 σ significance of the hadronic contribution to the running of α ( s ) , which is the strongest direct evidence both in time- and space-like regions achieved in a single measurement. By using the e + e − → π + π − cross section measured by KLOE, the real and imaginary parts of the shift Δ α ( s ) have been extracted. From a fit of the real part of Δ α ( s ) and assuming the lepton universality the branching ratio B R ( ω → μ + μ − ) = ( 6.6 ± 1.4 s t a t ± 1.7 s y s t ) ⋅ 10 − 5 has been determined.

Study of the process e+e− → π+π−π+π− in the c.m. energy range 920–1060 MeV with the CMD-3 detector

The cross section of the process ee → πππη has been measured using a data sample of 21.8 pb collected with the CMD-3 detector at the Corresponding author: solodov@inp.nsk.su Preprint submitted to Elsevier May 6, 2018 VEPP-2000 ee collider. 2769±95 signal events have been selected in the center-of-mass energy range 1394–2005 MeV. The production dynamics is dominated by the ω(782)η and φ(1020)η intermediate states in the lower energy range, and by the a0(980)ρ(770) intermediate state at higher energies.

Current status of luminosity measurement with the CMD-3 detector at the VEPP-2000

Since December 2010 the CMD-3 detector has taken data at the electron-positron collider VEPP-2000. The collected data sample corresponds to an integrated luminosity of 60 pb−1 in the c.m. energy from 0.32 up to 2 GeV. The preliminary results of the luminosity measurement are presented in various energy ranges. The current accuracy for integrated luminosity is estimated to be 1%.

e^+e^-

Abstract We searched for the μ + μ − decay of a light vector gauge boson, also known as dark photon, in the e + e − → μ + μ − γ ISR process by means of the Initial State Radiation (ISR) method. We used 1.93 fb−1 of data collected by the KLOE experiment at the DAΦNE ϕ-factory. No structures have been observed over the irreducible μ + μ − background. A 90% CL limit on the ratio e 2 = α ′ / α between the dark coupling constant and the fine structure constant of 3 × 10 − 6 – 2 × 10 − 7 has been set in the dark photon mass region between 519 MeV and 973 MeV. This new limit has been combined with the published result obtained investigating the hypothesis of the dark photon decaying into hadrons in e + e − → π + π − γ ISR events. The combined 90% CL limit increases the sensitivity especially in the ρ–ω interference region and excludes e 2 greater than ( 13 − 2 ) × 10 − 7 . For dark photon masses greater than 600 MeV the combined limit is lower than 8 × 10 − 7 resulting more stringent than present constraints from other experiments.

collider

The three precision measurements of the cross section

Combined limit on the production of a light gauge boson decaying into μ+μ− and π+π−

sigmabig(e^+e^-rightarrowpi^+pi^-gamma(gamma)big)