121193004
Study of nuclear medium effects on polarization in (p, 2p) scattering at 1 GeV
We report on experimental investigation of the (p, 2p) reactions on nuclei 6Li, 7Li, 12C and 40Ca. In this experiment, polarizations of the secondary protons from the (p, 2p) reactions are measured using 1 GeV proton beam of the PNPI synchrocyclotron. Two final protons from the reaction are detected in coincidence by means of a two-arm magnetic spectrometer at non-symmetric scattering angles. The resolution of the spectrometer on separation energy of 4.5 MeV (FWHM) is enough to distinguish reliably the shell structure of the investigated nuclei. In order to measure polarization of the two secondary protons, both spectrometer arms are equipped with multiwire proportional chamber polarimeters.Strong reduction of polarizations (large depolarization factor) relatively to free pp scattering is observed in the experiment. The 6Li, 7Li P-shell data are interpreted in terms of this reduction being combined with classical phenomenon of the effective polarization calculated with the help of DWIA.For the S-shell protons the depolarization factors are apparently seen not being obscured by the spin-orbit coupling. In case of the 7Li S-shell data the depolarization factors calculated by deviation from IA are found to be ΔP/P=0.31±0.07 and 0.39±0.04 for the scattered and recoil proton polarization, respectively. As estimations show, significant and roughly equal polarization reduction of the two secondary protons with essentially different energies (≈-200 and 800 MeV) can hardly be explained by a trivial nuclear distortion effect like depolarization due to rescatterings in nuclear matter. Measurements with heavier nucleus targets (12C, 40Ca) show that magnitude of the depolarization is a decreasing function of the nuclear density in the part of the nucleus volume which effectively contributes to the pp scattering in a nucleus. An explanation of the observed depolarization might be done in terms of modification of the pp-scattering amplitude in the nuclear meidum.
102408955
THE INVESTIGATION OF THE DRIFT CHAMBER EFFICIENCY OPERATING IN PURE HYDROGEN AND HELIUM FOR PRESSURES UP TO 9-ATM
204171619
Total two photon hadronic cross-section and charm production cross-section measurement with the L3 detector
197518814
Heavy flavor production in gamma gamma collisions
121308441
B-quark production at 7 TeV with the CMS experiment
Measurements performed by the CMS experiment of the cross section for inclusive b-quark production in protonproton collisions at s = 7 TeV are presented. The measurements are based on data collected in 2010. The measurements are performed using different methods, such as inclusive jet measurements with secondary vertex tagging or selecting a sample of events containing jets and at least one muon, where the transverse momentum of the muon with respect to the closest jet axis discriminates b events from the background. The measurements of the total and single differential cross sections for B+, B0 and Bs mesons are also presented. The results are compared with predictions based on perturbative QCD calculations at leading and next-to-leading order.
121028786
Total cross-section for real and virtual photons
Results are presented for measurements of the total cross section γγ → hadrons process by the L3 and the OPAL collaborations at LEP. The QCD predictions are tested with the L3 measurement of total hadronic cross section for virtual γ∗γ∗ collisions and of total cross section for cc and bb production by quasi-real photons.