118636693
Polarization effects in the quasielastic (p, 2p) reaction with the nuclear S-Shell Protons at 1 GeV
The polarization of the secondary protons in the (p, 2p) reaction with the S-shell protons of nuclei 4He, 6Li, 12C, 28Si, 40Ca was measured at 1 GeV unpolarized proton beam. The spin correlation parameters Cij for the 4He and 12C targets also were for the first time obtained as well. The polarization measurements were performed by means of a two-arm magnetic spectrometer, each arm of which was equipped with the multiwire-proportional chamber polarimeter. This experiment was aimed to study a modification of the proton-proton scattering matrix in the nuclear medium.
122971502
Design principles of the end cap drift chambers in the L3 experiment
Abstract The end cap detector based on multimodule construction has been designed and produced for the L3 experiment. The purpose of this article is to present a fruitful approach for solving the complex problem of selecting a set of strongly interrelated design parameters to satisfy performance criteria in the face of severe environmental and space constraints. The design principle of the end cap drift chamber affected by a complex of external problems caused by the layout is reviewed. It is shown that in the framework of detailed consideration of each parameter, a good space–time linearity, spatial and angular resolution is obtainable. The results of experimental tests are presented.
125946313
SPATIAL FOCUSING OF 1-GeV PROTONS BY A BENT MONOCRYSTAL
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.
53583095
High Precision Measurements of the Pion Proton Differential Cross Section
Study of the elastic scattering can produce a rich information on the dynamics of the strong interaction. The EPECUR collaboration is aimed at the research of baryon resonances in the second resonance region via pion-proton elastic scattering and kaon-lambda production. The experiment features high statistics and better than 1 MeV resolution in the invariant mass thus allowing searches for narrow resonances with the coupling to the pi p channel as low as 5%. The experiment is of "formation" type, i.e. the resonances are produced in s-channel and the scan over the invariant mass is done by the variation of the incident pion momentum which is measured with the accuracy of 0.1% with a set of 1 mm pitch proportional chambers located in the first focus of the beam line. The reaction is identified by a magnetless spectrometer based on wire drift chambers with a hexagonal structure. Background suppression in this case depends on the angular resolution, so the amount of matter in the chambers and the setup was minimized to reduce multiple scattering. 
The measurements started in 2009 with the setup optimized for elastic pion-proton scattering. With 3 billions of triggers already recorded the differential cross section of the elastic pi p-scattering on a liquid hydrogen target in the region of the diffraction minimum is measured with statistical accuracy about 1% in 1 MeV steps in terms of the invariant mass. The paper covers the experimental setup, current status and some preliminary results.
120690144
Polarization in quasielastic (p,2p) scattering on a 4He nucleus at 1 GeV
The polarization of secondary protons from the (p, 2p) reaction induced by 1-GeV protons incident to a 4He nucleus was measured in a kinematically complete experiment. By using a two-arm magnetic spectrometer, two secondary protons from this reaction were recorded in coincidence at unequal scattering angles of Θ1 = 18°−24.21° and Θ2 = 53.22° over a broad range of the recoil-nucleus momentum KB between 0 and 150 MeV/c. It was found that the measured polarization of either secondary proton is less than that observed in free elastic proton-proton scattering. The magnitude of this difference is determined by the mean binding energy of s-shell protons rather than by the effective nuclear density. The polarizations measured in inclusive quasielastic and elastic scattering of 1-GeV protons on 4He nuclei are presented for scattering angles in the range Θ1 = 18° − 24.21°.
123930049
Heavy Quark Production at CMS and ATLAS
measured with the new data against the framework of quantum chromodynamics (QCD). Two general-purpose detectors, ATLAS [1] and CMS [2], designed to explore the physics at the TeV scale, have an extensive research program for heavy-flavour studies. The two experiments are very different in the layout chosen for the magnet system. In ATLAS, a solenoid provides the magnetic ﬁeld for the Inner Tracker, while a system of air-core toroids outside the calorimeters provides the ﬁeld for the Muon Spectrometer. The magnetic ﬁeld in CMS is provided by a single very large solenoid which contains both the Inner Tracker and the calorimeters. The muon chambers are embedded in the iron of the solenoid return yoke. The magnet layout determines the weight (ATLAS is larger but lighter) of the two detectors. The potential of ATLAS and CMS for heavy-flavour measurements is presented for the LHC start-up luminosities (10 pb
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.
118088627
Resonance production in two-photon collisions at LEP with the L3 detector
The ee→eeKS0K±π∓, ee→eeηπ+π− and e+e−→e+e−π+π−π+π− final states are studied with the L3 detector at LEP using data collected at center-of-mass energies from 160 GeV up to 202 GeV. The mass spectrum of the KS0K±π∓ final state shows an enhancement around 1470 MeV, which is identified with the pseudoscalar meson η(1440). This state is observed in γγ collisions for the first time and its two-photon width is measured. Clear evidence is also obtained for the formation of the axial vector mesons f1(1420) and f1(1285). In the ηπ+π− channel the f1(1285) is observed, and upper limits for the formation of η(1440) and η(1295) are obtained. The process e+e−→e+e−π+π−π+π− is dominated by ρ0ρ0 production. A spin-parity analysis of the ρ0ρ0 system for Wγγ 3GeV the f2(1270) meson is observed.
204171619
Total two photon hadronic cross-section and charm production cross-section measurement with the L3 detector
122913826
On flavour production in CMS
The LHC provides new opportunities to improve our understanding of the b quark using high statistics data samples and the 14 TeV center-of-mass energy. The prospects to measure the cross section for inclusive b production in events containing jets and at least one muon are presented. Studies of detector systematic effects and theoretical uncertainties are included. QCD aspects of the beauty production are discussed. An outline of the basic vertex reconstruction algorithms used in CMS is given.