Search

The spin dynamics of a hydrogen atom during the passage of a periodic magnetic structure is discussed. The occupation numbers of the components of the hyperfine structure are considered as a function of time. The characteristic low-frequency oscillations are visible, which have a direct analogue in the effect of nuclear magnetic resonance. An envelope forms of these oscillations are found using the Krylov-Bogolyubov-Mitropol'skii method. The dependence of spin dynamics on the parameters of the magnetic structure is investigated. It is shown that this dependence is very sensitive to the structure of the magnetic field., Comment: 8 pages, 4 figures

We propose an experiment to search for a new gauge boson A' in $e^+e^-$ annihilation by means of a positron beam incident on a gas hydrogen target internal to the bypass at the VEPP-3 storage ring. The search method is based on a missing mass spectra in the reaction $e^+e^-\rightarrow \gamma$ A'. It allows observation of the A' signal independently of its decay modes and life time. The projected result of this experiment corresponds to an upper limit on the square of the coupling constant $\varepsilon^2=3\cdot 10^{-8}$ with a signal-to-noise ratio of two to one at an A' mass of 5-20 MeV., Comment: 20 pages, 17 figures

The ratio of the elastic $e^+ p$ to $e^- p$ scattering cross sections has been measured precisely, allowing the determination of the two-photon exchange contribution to these processes. This neglected contribution is believed to be the cause of the discrepancy between the Rosenbluth and polarization transfer methods of measuring the proton electromagnetic form factors. The experiment was performed at the VEPP-3 storage ring at beam energies of 1.6 and 1.0 GeV and at lepton scattering angles between $15^\circ$ and $105^\circ$. The data obtained show evidence of a significant two-photon exchange effect. The results are compared with several theoretical predictions., Comment: 5 pages, 2 figures, 3 tables

A precise comparison of the cross sections for the elastic scattering of electrons and positrons on protons was performed recently at the VEPP-3 storage ring in Novosibirsk, Russia. To provide the proposed accuracy, the energies of the electron and positron beams used during the experiment needed to be carefully maintained. This paper describes a special beam energy measurement system used in this experiment. This system is based on measuring the maximum energy of laser photons backscattered from electron and positron beams. It provides continuous beam energy measurements with a total relative uncertainty of less than $4.4 \cdot 10^{-5}$., Comment: 13 pages, 10 figures

This paper describes a new multipurpose event generator, ESEPP, which has been developed for the Monte Carlo simulation of unpolarized elastic scattering of charged leptons on protons. The generator takes into account the lowest-order QED radiative corrections to the Rosenbluth cross section including first-order bremsstrahlung without using the soft-photon or ultrarelativistic approximations. ESEPP can be useful for several significant ongoing and planned experiments., Comment: 28 pages, 5 figures, 2 tables

We report on the status of the Novosibirsk experiment on a precision measurement of the ratio $R$ of the elastic $e^+ p$ and $e^- p$ scattering cross sections. Such measurements determine the two-photon exchange effect in elastic electron-proton scattering. The experiment is conducted at the VEPP-3 storage ring using a hydrogen internal gas target. The ratio $R$ is measured with a beam energy of 1.6 GeV (electron/positron scattering angles are $\theta = 55 \div 75^{\circ}$ and $\theta = 15 \div 25^{\circ}$) and 1 GeV ($\theta = 65 \div 105^{\circ}$). We briefly describe the experimental method, paying special attention to the radiative corrections. Some preliminary results are presented., Comment: 5 pages, 6 figures and 1 table; contribution to the Proceedings of the PHIPSI11 Workshop (Novosibirsk, Russia, 19-22 September 2011)

PROZA-M experiment results as well the proposal of a new spin program with the use of a polarized proton beam are presented. Significant asymmetries were observed in inclusive $\pi^0$ production. The new program proposes to study a wealth of single- and double-spin observables in various reactions using longitudinally and transversely polarized proton beams at U70. The main goal is to define gluon contribution to nucleon spin by measuring double-spin asymmetry in charmonium production., Comment: 18 pages, 20 figures, Talk given at Advanced Study Institute Symmetries and Spin (July 19 - 26, Prague, Czech Republic)

New accurate measurement of tensor analyzing powers T20, T21 and T22 in deuteron photodisintegration has been performed. Wide-aperture non-magnetic detectors allowed to cover broad kinematic ranges in a single setup: photon energy = 25 to 600 MeV, proton emission angle in CM = 24 to 48 deg. and 70 to 102 deg. New data provide a significant improvement of a few existing measurements. The angular dependency of the tensor asymmetries in deuteron photodisintegration is extracted for the first time., Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett

A possibility to accelerate a high intensity polarized proton beam up to 70 GeV at the IHEP accelerator, extract it from the main ring and deliver to several experimental setups is being studied now. We propose to study a wealth of single- and double-spin observables in various reactions using longitudinally and transverserly polarized proton beams at U70. The proposed measurements can be done at the existing detectors as well as require to create a few new experimental setups at U70., Comment: 11 pages, 4 figures, To appear in the proceedings of 11th International Workshop On High Energy Spin Physics (DUBNA-SPIN-05), 27 Sep.-1 Oct. 2005, Dubna, Russia

It has been suggested that two-photon exchange corrections could explain the discrepancy between Rosenbluth extractions of the proton form factors and recent polarization transfer measurements. We propose a precise comparison of electron-proton and positron-proton scattering at Q^2=1.6 GeV^2 to determine if two-photon exchange at moderate Q^2 values is in fact able to explain the discrepancy., Comment: 13 pages, 10 figures. Proposal for a comparison of electron-proton and positron-proton scattering at VEPP-3

The differential cross section and target asymmetry components of the reaction D(e,pp)e'pi- on polarized deuteron were measured. The kinetic energies of the protons were measured within 55-180 MeV and 46-265 MeV. The polar acceptance angles in laboratory frame for the both protons are (64 - 82) degrees and the azimuthal angles are (-16 +16), (164 - 196) degrees. The sharp peak of the tensor a(20)-component of the target asymmetry is found near the invariant mass of the pppi-system M(pppi) = 2300 MeV/c**2. The performed calculations of the differential yield and the tensor target asymmetry do not describe the obtained experimental results., Comment: 4 pages, 2 Postscript figures

Recently, we have performed the experiment on studying the pion electroproduction at photon point on the internal polarized deuterium target at the VEPP-3 storage ring. For the more complete treatment of the reaction d(e,pp)X we investigate the reaction channel with an additional neutral pion production as background to the leading reaction of the single negative pion production. To study this background process we considered the nucleon pole mechanism and the two-body mechanism. In the latter mechanism a Delta(1232) and the pion are produced in one nucleon then the pion is absorbed by other nucleon producing just one more Delta (1232). The final proton-pion systems come from the decay of the both Deltas. In this work we have estimated the contribution of the reaction with additional neutral pion production into the whole yield for the different polarization states of the deuteron in the kinematic conditions of the VEPP-3 d(e,pp)X - experiment., Comment: 6 pages, 4 Postscript figures