VEPP-2M Collider Research Articles

Measurement of the e + e − → ηπ+π− cross section in the % MathType!MTEF!2!1!+- % feaagaart1ev2aaatCvAUfKttLearuqr1ngBPrgarmWu51MyVXgatC % vAUfeBSjuyZL2yd9gzLbvyNv2CaeHbd9wDYLwzYbItLDharyavP1wz % ZbItLDhis9wBH5garqqr1ngBPrgifHhDYfgasaacH8srps0lbbf9q8 % WrFfeuY-Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0-yr0RYxir-J % bba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dmeaabaqaciGacaGaae % qabaWaaqaafaaakeaadaGcaaqaaiabdohaZbWcbeaaaaa!3E0A! $$ \sqrt s $$ = 1.04–1.38-GeV energy range with a spherical neutral detector at the VEPP-2M collider

The e + e − → ηπ+π− cross section in the η → 2γ channel has been measured in the $$ \sqrt s $$ = 1.04- to 1.38-GeV energy range. The data with a total integrated luminosity of 9.05 pb−1 were collected on a spherical neutral detector at the VEPP-2M collider. The results are consistent with the BaBar and CMD2 data and have a higher statistical accuracy.

Use of the methods of accelerator physics in precision measurements of particle masses at the VEPP-4 complex with the KEDR detector

Based on precision measurements of the beam energy using the resonant depolarization and Compton backscattering methods, it is possible to conduct high-precision experiments in the field of high-energy physics at the VEPP4M electron-positron collider with the KEDR detector. The J/ψr- and ψ(2s)-meson masses measured at the VEPP4M collider ar e among the ten most precisely known masses of elementary particles measured over the whole physical history. The degree of accuracy that we attained in determining theτlepton mass by the threshold behavior of the e+e- τ+τ reaction cross section is the best in the world. Systems automatically controlling the temperature of the distillate that cools the magnets of the main accelerating structure and the RF accelerating cavities of the VEPP4M collider have been developed, produced, and placed in operation in order to increase the efficiency of the complex. Simultaneous measurements of the transverse displacement and the angle of inclination of the beam near the interaction point can be taken with the aid of a multipinhole X-ray camera.

Tau mass measurement at KEDR

The status of the experiment on the precise τ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ + τ − cross section behavior around the production threshold. The preliminary result based on 15.2 pb −1 of data is m τ = 1776.69 −0.19 +0.17 ± 0.15 MeV .

Results on [formula omitted] hadrons cross sections from VEPP-2M and BaBar

In 1992-2000, data on e + e − annihilation into hadrons were collected in the energy range 0.36 < s < 1.4 GeV with the CMD-2 and SND detectors at the VEPP-2M collider in Novosibirsk. The results of the R ( s ) measurements in these experiments are presented. The radiative return program at BaBar also allows to study low energy e + e − annihilation and overview of the results are presented in this paper.

New optical diagnostics of the VEPP-4M collider

The experiments in measuring the dynamic aperture and beam energy spread of the VEPP-4M collider [1] are described. The optical diagnostics of the accelerator were applied for these purposes.

Measurement of [formula omitted] cross section with CMD-2 detector at VEPP-2M collider

The process e+e−→ϕ→K+K− has been studied with the CMD-2 detector using about 542 000 events detected in the center-of-mass energy range from 1.01 to 1.034 GeV. The systematic error of the cross section is estimated to be 2.2%. The ϕ(1020) meson parameters in the ϕ→K+K− decay channel have been measured: σ0(ϕ→K+K−)=2016±8±44 nb, mϕ=1019.441±0.008±0.080 MeV/c2, Γϕ=4.24±0.02±0.03 MeV, Be+e−BK+K−=(14.27±0.05±0.31)×10−5.

Tau mass measurement at KEDR

The status of the experiment on the precise τ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ+τ− cross section behavior around the production threshold. The preliminary result based on 15.2 pb−1 of data is mτ=1776.69−0.19+0.17±0.15 MeV.

CMD-2 and SND results on [formula omitted] hadrons cross sections

In 1992-2000, data on e + e − annihilation into hadrons were collected in the energy range 0.36 s 1.4 GeV with the CMD-2 and SND detectors at the VEPP-2M collider in Novosibirsk. The results of the R ( s ) measurements in these experiments are presented.

Review of beam energy measurements at VEPP-4M collider: KEDR/VEPP-4M

An accurate knowledge of the colliding beam energies is essential for the current experiments with the KEDR detector at the VEPP-4M collider. Now the experimental activity is focused on the measurements of τ lepton mass and parameters of narrow resonances of the ψ -family in the c.m.energy range of 3.0–4.0 GeV. Two complementary approaches are used for the beam energy measurements. The resonant spin depolarization technique (RD) provides an accuracy about 1–3 keV for the instantaneous beam energy value, but requires a special regime of the collider. Between calibrations the interpolation procedure is used providing the accuracy of 6–10 keV for the J / ψ , ψ ( 2 s ) and 15–30 keV for the τ lepton mass determination experiments. Another approach allows to calculate beam energy via the maximum energy of backscattering laser photons. The Compton BackScattering (CBS) monitor allows continuous on-line monitoring of the beam energy with accuracy about 150 keV, which is critical during the τ lepton mass measurement. The statistical error for a 1 h period is about 100 keV, the present systematic error is 50–70 keV.

Electron–positron colliders, detectors and experiments at BINP

An overview of electron–positron colliders and experiments on them currently performed and prepared at the Budker Institute of Nuclear Physics is presented. They include a new collider VEPP-2000 (an upgrade of the VEPP-2M collider) with CMD-3 and SND experiments, the VEPP-4M collider with the KEDR detector and the electron/positron injection complex.

Measurement of cross sections for processes involving e + e − annihilation to hadrons at the VEPP-2M collider

Results obtained by measuring, in experiments at the VEPP-2M e + e − collider with the CMD-2 and SND detectors at the Novosibirsk Institute of Nuclear Physics, cross sections for e + e − → hadrons annihilation processes at energies in the range 360 ≤ √s ≤ 1380 MeV are surveyed. The measured cross sections and the vector-meson parameters deduced from an analysis of these cross sections are presented. The cross section for the process e + e − → π + π − is compared with the spectral function for the decay τ − → π − π 0 ν τ.

New precise determination of the τ lepton mass at KEDR detector

The status of the experiment on the precise τ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ + τ − cross section behaviour around the production threshold. The preliminary result based on 6.7 pb −1 of data is m τ = 1776.80 −0.23 +0.25 ± 0.15 MeV . Using 0.8 pb −1 of data collected at the ψ ′ peak the preliminary result is also obtained: Γ e e ⋅ B τ τ ( ψ ′ ) = 7.2 ± 2.1 eV .

Measurement of the τ lepton mass at the KEDR detector

A precise τ lepton mass measurement performed at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ+τ− cross section behavior around the production threshold. The result based on 6.7 pb−1 of data is mτ = 1776.81−0.23+0.25 ± 0.15 MeV. Using 0.8 pb−1 of data collected at the ψ′ peak, we have also determined that ΓeeBττ(ψ′) = 9.0 ± 2.6 eV.

Pion Form Factor at SND (new edition)

The update of the e^+e^-\to\pi^+\pi^- process cross section, measured in the energy region \sqrt{s}<1 GeV with SND detector at VEPP-2M collider is presented.

Study of ϕ→π+π−π0 with CMD-2 detector

The cross section of the process e+e−→π+π−π0 has been measured in the c.m. energy range 984–1060 MeV with the CMD-2 detector at the VEPP-2M collider. The obtained value of Br(ϕ→e+e−)Br(ϕ→π+π−π0)=(4.51±0.16±0.11)×10−5 is in good agreement with the previous measurements and has the best accuracy. Analysis of the Dalitz plot was performed. The contributions of the dominant ϕ→ρπ mechanism as well as of a small direct ϕ→3π amplitude were determined.

Development and validation of self-consistent 3D beam-beam modeling code within SciDAC

The calculation of beam-beam effects has been an ongoing activity within SciDAC. We report the first validation of a detailed beam-beam simulation with data measured at the VEPP-2M collider in Novosbirsk. The validation of the simulation gives us con.dence to apply it to understanding and improving the operation of existing colliders such as the Tevatron, RHIC and LHC, and the design of the International Linear Collider.

Monte-Carlo generator for e+e- annihilation into lepton and hadron pairs with precise radiative corrections

Recently, various cross sections of e+e- annihilation into hadrons were accurately measured in the energy range from 0.37 to 1.39 GeV with the CMD-2 detector at the VEPP-2M collider. In the pi+pi- channel a systematic uncertainty of 0.6% has been achieved. A Monte-Carlo Generator Photon Jets (MCGPJ) was developed to simulate events of the Bhabha scattering as well as production of two charged pions, kaons and muons. Based on the formalism of Structure Functions, the leading logarithmic contributions related to the emission of photon jets in the collinear region are incorporated into the MC generator. Radiative corrections (RC) in the first order of alpha are accounted for exactly. The theoretical precision of the cross sections with RC is estimated to be better than 0.2%. Numerous tests of the program as well as comparison with other MC generators and CMD-2 experimental data are presented.

Study of the process e + e − → π+π− in the energy region $$400 &lt; \sqrt s &lt; 1000 MeV^\P $$

The cross section of the process e^+e^-\to \pi^+\pi^- was measured in the SND experiment at the VEPP-2M collider in the energy region 400<\sqrt[]{s}<1000 MeV. This measurement was based on about 12.4 \times 10^6 selected collinear events, which include 7.4\times 10^6 e^+e^-\to e^+e^-, 4.5\times 10^6 e^+e^-\to\pi^+\pi^- and 0.5\times 10^6 e^+e^-\to\mu^+\mu^- selected events. The systematic uncertainty of the cross section determination is 1.3 %. The \rho-meson parameters were determined: m_\rho=774.9\pm 0.4\pm 0.5 MeV, \Gamma_\rho=146.5\pm 0.8\pm 1.5 MeV, \sigma(\rho\to\pi^+\pi^-)=1220\pm 7\pm 16 nb as well as the parameters of the G-parity suppressed decay \omega\to\pi^+\pi^-: \sigma(\omega\to\pi^+\pi^-)=29.9\pm 1.4\pm 1.0 nb and \phi_{\rho\omega} = 113.5\pm 1.3\pm 1.7 degree.

Tau threshold experiments: status and expectations

A study of the threshold behavior of the cross section of τ lepton production is the most promising way of the τ mass determination. The most precise measurement of this kind was performed by the BES collaboration in 1991. We critically analyze the results of this experiment and report the main features of the new one, planned with the KEDR detector at the VEPP-4M collider in Novosibirsk.

STUDY OF THE PROCESS e+e-→π+π-π0 IN THE ENERGY RANGE 1.04-1.38 GEV WITH CMD-2 DETECTOR

The data sample of 6 pb -1 collected by Cryogenic Magnetic Detector (CMD-2) at VEPP-2M collider in the c.m. energy range 1.04-1.38 GeV have been used to measure cross section of the process e+e-→π+π-π0 and to study its dynamics. It is shown that for description of the invariant mass spectra of π+π- pairs one should take into account the ωπ0 contribution arising due to ρ-ω - interference.