V. S. Panin

Experimental investigation of high-energy photon splitting in atomic fields

Data analysis of an experiment in which photon splitting in atomic fields was observed is presented. The experiment was performed at the tagged photon beam of the ROKK-1M facility at the VEPP-4M collider. In the energy region of 120-450 MeV, statistics of 1.6x10(9) photons incident on the BGO target was collected. About 400 candidate photon-splitting events were reconstructed. Within the attained experimental accuracy, the experimental results are consistent with the calculated exact atomic-field cross section. The predictions obtained in the Born approximation differ significantly from the experimental results.

Investigation of an electromagnetic calorimeter based on liquid krypton

Abstract Effects determining the energy and spatial resolution of a calorimeter based on liquid krypton have been studied. With cathode strips of 10 mm a spatial resolution of 0.4 mm has been obtained in a cosmic rays test. The energy resolution of the calorimeter (0.4 ton of krypton) has been measured with positrons, achieving a rms of 5.7% at E = 130 MeV and 1.7% at E = 1200 MeV. The measurements are compared to Monte Carlo simulations.

A high precision measurement of the ϒ, ϒ′ and ϒ″-meson masses

Abstract An experiment has been performed at the storage ring VEPP-4 using the MD-1 detector. The resonance depolarization method has been employed for the absolute calibration of the beam energy. This has allowed the accuracy of the mass measurement to be improved by a factor of ten. The following mass values of ϒ, ϒ′ and ϒ″ -mesons have been obtained: M ( ϒ )=9460.6±0.4 MeV, M ( ϒ ′)=10023.8±0.5 MeV, M ( ϒ ″)=10355.5±0.5 MeV.

Liquid krypton calorimeter for KEDR detector

Abstract A description of the liquid krypton calorimeter for the KEDR detector and experimental results on energy and position resolution obtained with prototypes are presented.

Experiments with the MD-1 detector at the e+e− collider VEPP-4 in the energy region of ϒ mesons

Abstract This paper reviews physical results obtained at the e+e− collider VEPP-4 with the MD-1 detector. The results of experiments on the ϒ meson physics and study of the hadron production in continuum in the energy region 7.2–10.3 GeV as well as the results of study of the two photon reactions are presented. Among results obtained in the upsilon physics: the precise measurement of the ϒ(1S), ϒ(2S), ϒ(3S) masses and the precise determination of the ϒ(1S) and ϒ(2S) electronic widths. In the experiments on study of the hadron production in continuum the precise measurement of the R was carried out. The peculiarity of the detector is the magnetic field transverse to the orbit plane which provided the possibility to study two photon reactions with tagging one or both scattered electrons even at zero emission angle. Among results on the γγ reactions is the measurement of the two photon total hadronic cross section performed in the double-tag mode. In the QED experiments a new QED effect — the impact parameter cut-off in single bremsstrahlung was discovered.

Liquid krypton calorimeter for KEDR detector and last prototype results

Abstract The liquid krypton calorimeter for the KEDR-VEPP-4M experiment is described. The experimental results with a prototype, obtained at the tagged photon beam of VEPP-4M in the photon energy region between 50 and 4500 MeV, are presented. The results on the energy resolution are in a good agreement with the Monte-Carlo expectations and are equal to 6% and 2% at 100 and 1000 MeV respectively. The spatial resolution is about 1–1.5 mm in a wide energy region and agrees with the expected spatial resolution.

Liquid krypton electromagnetic calorimeter

Abstract A calorimeter using 30 tons of liquid krypton for the KEDR detector is being constructed. The main effects which determine the energy and space resolution have been studied. An energy resolution of 1.7% at 1.2 GeV was obtained with the prototype. A space resolution of 0.4 mm for relativistic particles has been reached with the prototype.

Total cross section of two-photon production of hadrons

The total cross section for γγ→hadrons was measured as a function of the invariant massW of the system (1.25 to 4.25 GeV) at thee+e−-collider VEPP-4 with the detector MD-1. For the first time the data were obtained by detecting both scattered leptons with almost zero emission angles. The mean squared four momentum transfer 〈q2〉 is −0.005 GeV2, the rmsW resolution is 100–250 MeV. The data on the mean charged multiplicity 〈nC〉 are well described by the function 〈nC〉=(1.62 ±0.37)+(1.83±0.45)·ln(W(GeV)). TheW dependence of the total cross section is consistent with the theoretical prediction σ(nb)=240+270/W(GeV).

High precision mass measurements in Ψ and ϒ families revisited

Abstract High precision mass measurements in Ψ and ϒ families performed in 1980–1984 at the VEPP-4 collider with OLYA and MD-1 detectors are revisited. The corrections for the new value of the electron mass are presented. The effect of the updated radiative corrections has been calculated for the J / Ψ (1 S ) and Ψ (2 S ) mass measurements.

The test of the LKr calorimeter prototype at the tagged photon beam

Abstract The experiment with the prototype of liquid krypton electromagnetic calorimeter for the KEDR detector is described. The experiment was carried out at the VEPP-4M collider at the tagged photon beam. The tagged photons were obtained in the energy region 50–625 MeV using the ROKK-1M facility. The edges of the bremsstrahlung spectra were used for the energy resolution measurement in the high-energy region up to 4500 MeV. The energy resolution comparable with the resolution of the best crystal calorimeters and the excellent spatial resolution (∼1 mm) have been obtained. The results are in good agreement with the Monte-Carlo simulation.