The differential cross section of Delbr\"{u}ck scattering is measured on a bismuth germanate $Bi_4Ge_3O_{12}$ target at photon energies $140 - 450 MeV$ and scattering angles $2.6 - 16.6 mrad$. A good agreement with the theoretical results, obtained exactly in a Coulomb field, is found.
Axis error includes +- 1.5/1.5 contribution (Error of measurement of the initial photons intensity).
None
Axis error includes +- 2/2 contribution (Error in counter efficiency determination).
Electron momentum distribution.
Electron-positron pairs mass distribution.
A high precision measurement of the υ-meson mass has been performed at the storage ring VEPP-4 using the MD-1 detector. The resonance depolarization method has been used for the absolute calibration of the beam energy that allowed to improve the accuracy of υ-mass measurement by a factor of ten. The following mass value has been obtained: M = 9459.7 ± 0.6 MeV.
No description provided.
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).
No description provided.
No description provided.
The process γγ→π+π− was measured using the detector MD-1 at VEPP-4. The two-photon reactionse+e−, μ+ μ− and π+ π− pair production were separated using scintillation counters, Cherenkov counters and shower-range chambers. A radiation widthГγγ(f2(1270))=3.1±0.35±0.35 keV was obtained.
Data read from graph.
The results of a search for narrow resonances ine+e− annihilation at centre-of-mass energies between 7.23 and 10.34 GeV are presented. The experiment was performed using the MD-1 detector at the VEPP-4 storage ring. The total luminosity integral of 16 pb−1 was taken. There is no evidence that new states exist. The upper limits on the leptonic widthΓee of possible resonances are less, by a factor of 10–80, than theΓee for the ϒ(1S) meson.
Average R value (excluding upsilon region).
Using the MD-1 detector at the VEPP-4e+e− strorage ring we have measured the inclusive Λ and370-1 production rates in direct Γ(1S) decays
Lambda x spectrum in direct upsilon(1S) decay.
Lambda multiplicity in direct upsilon(1S) decays.
Lambda multiplicity in surrounding continuum.
The total cross section of the processe+e− →hadrons has been measured in the center-of-mass energy range between 7.25 and 10.34 GeV using the MD-1 detector at the VEPP-4 collider. The ratioR=σ(e+e− →hadrons)/σ(e+e− →μ+μ−) was found to be constant in this energy range with the average value of 3.58±0.02±0.14.
Statistical errors only.
Mean value of R in the range 7.25 to 10.34 GeV.
Bose-Einstein correlations between identical particles are measured in samples of proton-proton collisions at 0.9 and 7 TeV centre-of-mass energies, recorded by the CMS experiment at the LHC. The signal is observed in the form of an enhancement of number of pairs of same-sign charged particles with small relative momentum. The dependence of this enhancement on kinematic and topological features of the event is studied.
The double ratio R_double at 900 and 7000 GeV.
The double ratio R_double at 7000 GeV in different bins of charged particle multiplicity and kT.
The double ratio R_double at 7000 GeV in different bins of charged particle multiplicity and kT.
The differential cross section for the inclusive production of isolated prompt photons has been measured as a function of the photon transverse energy E_T-gamma in pp collisions at sqrt(s)=7 TeV using data recorded by the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.9 inverse picobarns. Photons are required to have a pseudorapidity |eta_gamma|<1.45 and E_T-gamma > 21 GeV, covering the kinematic region 0.006 < x_T < 0.086. The measured cross section is found to be in agreement with next-to-leading-order perturbative QCD calculations.
Measured isolated prompt photon differential cross section.