81 research outputs found
Scintillation Counters for the D0 Muon Upgrade
We present the results of an upgrade to the D0 muon system. Scintillating
counters have been added to the existing central D0 muon system to provide
rejection for cosmic ray muons and out-of-time background, and to provide
additional fast timing information for muons in an upgraded Tevatron.
Performance and results from the 1994-1996 Tevatron run are presented.Comment: 30 pages, 25 postscript figure
Isolation and characterisation of human gingival margin-derived STRO-1/MACS+ and MACS− cell populations
Recently, gingival margin-derived stem/progenitor cells isolated via
STRO-1/magnetic activated cell sorting (MACS) showed remarkable periodontal
regenerative potential in vivo. As a second-stage investigation, the present
study's aim was to perform in vitro characterisation and comparison of the
stem/progenitor cell characteristics of sorted STRO-1-positive (MACS+) and
STRO-1-negative (MACS−) cell populations from the human free gingival margin.
Cells were isolated from the free gingiva using a minimally invasive technique
and were magnetically sorted using anti-STRO-1 antibodies. Subsequently, the
MACS+ and MACS− cell fractions were characterized by flow cytometry for
expression of CD14, CD34, CD45, CD73, CD90, CD105, CD146/MUC18 and STRO-1.
Colony-forming unit (CFU) and multilineage differentiation potential were
assayed for both cell fractions. Mineralisation marker expression was examined
using real-time polymerase chain reaction (PCR). MACS+ and MACS− cell
fractions showed plastic adherence. MACS+ cells, in contrast to MACS− cells,
showed all of the predefined mesenchymal stem/progenitor cell characteristics
and a significantly higher number of CFUs (P<0.01). More than 95% of MACS+
cells expressed CD105, CD90 and CD73; lacked the haematopoietic markers CD45,
CD34 and CD14, and expressed STRO-1 and CD146/MUC18. MACS− cells showed a
different surface marker expression profile, with almost no expression of CD14
or STRO-1, and more than 95% of these cells expressed CD73, CD90 and
CD146/MUC18, as well as the haematopoietic markers CD34 and CD45 and CD105.
MACS+ cells could be differentiated along osteoblastic, adipocytic and
chondroblastic lineages. In contrast, MACS− cells demonstrated slight
osteogenic potential. Unstimulated MACS+ cells showed significantly higher
expression of collagen I (P<0.05) and collagen III (P<0.01), whereas MACS−
cells demonstrated higher expression of osteonectin (P<0.05; Mann–Whitney).
The present study is the first to compare gingival MACS+ and MACS− cell
populations demonstrating that MACS+ cells, in contrast to MACS− cells,
harbour stem/progenitor cell characteristics. This study also validates the
effectiveness of the STRO-1/MACS+ technique for the isolation of gingival
stem/progenitor cells. Human free gingival margin-derived STRO-1/MACS+ cells
are a unique renewable source of multipotent stem/progenitor cells
Design, Performance and Calibration of the CMS Forward Calorimeter Wedges
We report on the test beam results and calibration methods using charged particles of the CMS Forward Calorimeter (HF). The HF calorimeter covers a large pseudorapidity region (3\l |\eta| \le 5), and is essential for large number of physics channels with missing transverse energy. It is also expected to play a prominent role in the measurement of forward tagging jets in weak boson fusion channels. The HF calorimeter is based on steel absorber with embedded fused-silica-core optical fibers where Cherenkov radiation forms the basis of signal generation. Thus, the detector is essentially sensitive only to the electromagnetic shower core and is highly non-compensating (e/h \approx 5). This feature is also manifest in narrow and relatively short showers compared to similar calorimeters based on ionization. The choice of fused-silica optical fibers as active material is dictated by its exceptional radiation hardness. The electromagnetic energy resolution is dominated by photoelectron statistics and can be expressed in the customary form as a/\sqrt{E} + b. The stochastic term a is 198% and the constant term b is 9%. The hadronic energy resolution is largely determined by the fluctuations in the neutral pion production in showers, and when it is expressed as in the electromagnetic case, a = 280% and b = 11%
Synchronization and Timing in CMS HCAL
The synchronization and timing of the hadron calorimeter (HCAL) for the Compact Muon Solenoid has been extensively studied with test beams at CERN during the period 2003-4, including runs with 40 MHz structured beam. The relative phases of the signals from different calorimeter segments are timed to 1 ns accuracy using a laser and equalized using programmable delay settings in the front-end electronics. The beam was used to verify the timing and to map out the entire range of pulse shapes over the 25 ns interval between beam crossings. These data were used to make detailed measurements of energy-dependent time slewing effects and to tune the electronics for optimal performance
Energy Response and Longitudinal Shower Profiles Measured in CMS HCAL and Comparison With Geant4
The response of the CMS combined electromagnetic and hadron calorimeter to beams of pions with momenta in the range 5-300 GeV/c has been measured in the H2 test beam at CERN. The raw response with the electromagnetic compartment calibrated to electrons and the hadron compartment calibrated to 300 GeV pions may be represented by sigma = (1.2) sqrt{E} oplus (0.095) E. The fraction of energy visible in the calorimeter ranges from 0.72 at 5 GeV to 0.95 at 300 GeV, indicating a substantial nonlinearity. The intrinsic electron to hadron ratios are fit as a function of energy and found to be in the range 1.3-2.7 for the electromagnetic compartment and 1.4-1.8 for the hadronic compartment. The fits are used to correct the non-linearity of the e pi response to 5% over the entire measured range resulting in a substantially improved resolution at low energy. Longitudinal shower profile have been measured in detail and compared to Geant4 models, LHEP-3.7 and QGSP-2.8. At energies below 30 GeV, the data, LHEP and QGSP are in agreement. Above 30 GeV, LHEP gives a more accurate simulation of the longitudinal shower profile
Design, Performance, and Calibration of CMS Hadron-Barrel Calorimeter Wedges
Extensive measurements have been made with pions, electrons and muons on four production wedges of the Compact Muon Solenoid (CMS) hadron barrel (HB) calorimeter in the H2 beam line at CERN with particle momenta varying from 20 to 300 GeV/c. Data were taken both with and without a prototype electromagnetic lead tungstate crystal calorimeter (EB) in front of the hadron calorimeter. The time structure of the events was measured with the full chain of preproduction front-end electronics running at 34 MHz. Moving-wire radioactive source data were also collected for all scintillator layers in the HB. These measurements set the absolute calibration of the HB prior to first pp collisions to approximately 4%
Design, Performance, and Calibration of CMS Hadron Endcap Calorimeters
Detailed measurements have been made with the CMS hadron calorimeter endcaps (HE) in response to beams of muons, electrons, and pions. Readout of HE with custom electronics and hybrid photodiodes (HPDs) shows no change of performance compared to readout with commercial electronics and photomultipliers. When combined with lead-tungstenate crystals, an energy resolution of 8\% is achieved with 300 GeV/c pions. A laser calibration system is used to set the timing and monitor operation of the complete electronics chain. Data taken with radioactive sources in comparison with test beam pions provides an absolute initial calibration of HE to approximately 4\% to 5\%
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