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.
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.
125946313
SPATIAL FOCUSING OF 1-GeV PROTONS BY A BENT MONOCRYSTAL
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°.
119049564
Focusing of a 1-GeV proton beam as it is brought into the channeling regime by a curved single crystal
The possibility of focusing high-energy particles by means of bulk capture of particles in the channeling regime is demonstrated experimentally. Protons with energies of 1 GeV, as they were bulk captured by the (111) plane of a curved silicon crystal from an angular interval with FWHM = 7.2 mrad at the exit from the crystal, had an angular divergence with FWHM = 1.6 mrad. The phase space of the beam of channeling particles in this case decreased slightly (by a factor of 1.8).
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.
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
115852037
Beauty in gamma gamma at LEP and determination of the b quark mass
197518814
Heavy flavor production in gamma gamma collisions
29354690
The CMS Magnetic Field Map Performance
The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field values. The value of the field at a given point of a volume is obtained by interpolation from a regular grid of values resulting from a TOSCA calculation or, when available, from a parameterization. The results of the measurements and calculations are presented, compared and discussed.
2455980
Design and Performance of the Alignment System for the CMS Muon Endcaps
The alignment system for the CMS muon endcap detector employs several hundred sensors such as optical 1-D CCD sensors illuminated by lasers and analog distance- and tilt-sensors to monitor the positions of one sixth of 468 large cathode strip chambers. The chambers mounted on the endcap yoke disks undergo substantial deformation on the order of centimeters when the 4 T field is switched on and off. The muon endcap alignment system is required to monitor chamber positions with 75-200 mum accuracy in the Rphi plane, ~400 mum in the radial direction, and ~1 mm in the z-direction along the beam axis. The complete alignment hardware for one of the two endcaps has been installed at CERN. A major system test was performed when the 4 T solenoid magnet was ramped up to full field for the first time in August 2006. We present the overall system design and first results on disk deformations, which indicate that the measurements agree with expectations.