17 research outputs found
The role of teachers in same-/cross-ethnic friendship preferences in elementary school classrooms
No full textThe aims of the present study were to: (1) examine changes in friendship preferences for same- over cross-ethnic peers across the school year among 1st, 3rd, and 5th grade European American and African American children, (2) test the extent to which shifts in these preferences and mean levels of preferences are explained by teacher observed emotional support and self-reported desegregation grouping strategies, (3) examine grade and ethnic differences in the relations between teacher emotional support and desegregation grouping strategies and children’s preferences for same- over cross-ethnic friendships, and (4) test whether friendship preferences for same- over cross-ethnic peers vary as a function of student grade, ethnicity, and numerical ethnic minority status in the classroom.
The results revealed that, on average, European American and African American children’s preferences for same- over cross-ethnic friendships remained stable over the school year. Teacher emotional support was negatively associated with mean levels of same-ethnic friendship preferences among fifth graders only. Teacher desegregation grouping strategies were positively associated with mean levels of same-ethnic friendship preferences among 5th grade European American‒but not African American‒students. No significant grade differences were evident in children’s preferences for same- over cross-ethnic friendships. However, there was a descriptive indication that first grade African American children displayed lower same-ethnic friendship preferences than third or fifth grade African American students. Further, African American first graders reported lower same-ethnic friendship preferences than European American first graders. Student numerical ethnic minority status in the classroom was unrelated to same-ethnic friendship preferences among both European and African American students.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2019-08-01The student, Marina Serdiouk, accepted the attached license on 2017-06-21 at 15:03.The student, Marina Serdiouk, submitted this Dissertation for approval on 2017-06-21 at 15:18.This Dissertation was approved for publication on 2017-06-30 at 14:42.DSpace SAF Submission Ingestion Package generated from Vireo submission #11245 on 2017-09-29 at 10:45:59Made available in DSpace on 2017-09-29T17:45:24Z (GMT). No. of bitstreams: 2
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Previous issue date: 2017-06-30Embargo set by: Colleen Fallaw for item 103465
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Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103465
Lift date: 2020-03-02T19:56:41Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103465
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Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 103465
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Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 103465 on 2020-03-03T10:15:35Z
Photostructured coating on a voltage degrader for a Time Projection Chamber (TPC)
No full textFibreglass-reinforced epoxy (Stesalit) tubes and rods were coated with a photostructured metal layer system of copper, nickel and gold for a voltage degrader built in a particle detector at CERN, Geneva. The metal layers were applied with galvanotechnical processes involving an original photolithographic exposure in three dimensions to produce a complex electrical circuit design able to provide the correct potential to 420 different conductors. The Stesalit substrate material, even after a first layer of electroless copper, is electrically quite resistive, creating problems for the electrodeposition of the subsequent nickel layer. A mathematical simulation of the plating thickness distribution showed that the electrolytic nickel deposition was suitable for short rods but electroless nickel was needed for the long rods. The functional properties of the metallized Stesalit components are satisfactory: no degradation of the gas quality within the Time Projection Chamber is observed; the potential distribution along the field cage is precise and, under electric fields exceeding 10 kV/cm, the leakages are below 10 nA, indicating very low microdischarge and corona effects
Measurement of the production cross-section of positive pions in p-Al collisions at 12.9 GeV/c
No full textA precision measurement of the double-differential production cross-section, , for pions of positive charge, performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV/c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 GeV/c to 6.5 GeV/c, and within an angular range from 30 mrad to 210 mrad. The absolute normalization was performed using prescaled beam triggers counting protons on target. The overall scale of the cross-section is known to better than 6%, while the average point-to-point error is 8.2%.A precision measurement of the double-differential production cross-section, d 2 σ π + / d p d Ω , for pions of positive charge, performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV / c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210 000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 to 6.5 GeV/ c , and within an angular range from 30 mrad to 210 mrad. The absolute normalization was performed using prescaled beam triggers counting protons on target. The overall scale of the cross-section is known to better than 6%, while the average point-to-point error is 8.2%.A precision measurement of the double-differential production cross-section, , for pions of positive charge, performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV/c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 GeV/c to 6.5 GeV/c, and within an angular range from 30 mrad to 210 mrad. The absolute normalization was performed using prescaled beam triggers counting protons on target. The overall scale of the cross-section is known to better than 6%, while the average point-to-point error is 8.2%
Measurement of the production of charged pions by protons on a tantalum target
No full textA measurement of the double-differential cross-section for the production of charged pions in proton-tantalum collisions emitted at large angles from the incoming beam direction is presented. The data were taken in 2002 with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a tantalum target with a thickness of 5% of a nuclear interaction length. The angular and momentum range covered by the experiment (100 MeV/c ≤ p< 800 MeV/c and 0.35 rad ≤ θ< 2.15 rad) is of particular importance for the design of a neutrino factory. The produced particles were detected using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. Track recognition, momentum determination and particle identification were all performed based on the measurements made with the TPC. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections d 2σ/dpdθ at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c). In addition, the pion yields within the acceptance of typical neutrino factory designs are shown as a function of beam momentum. The measurement of these yields within a single experiment eliminates most systematic errors in the comparison between rates at different beam momenta and between positive and negative pion production. © 2007 Springer-Verlag / Società Italiana di Fisica
Absolute momentum calibration of the HARP TPC
No full textIn the HARP experiment the large-angle spectrometer is using a cylindrical TPC as main tracking and particle identification detector. The momentum scale of reconstructed tracks in the TPC is the most important systematic error for the majority of kinematic bins used for the HARP measurements of the double-differential production cross-section of charged pions in proton interactions on nuclear targets at large angle. The HARP TPC operated with a number of hardware shortfalls and operational mistakes. Thus it was important to control and characterize its momentum calibration. While it was not possible to enter a direct particle beam into the sensitive volume of the TPC to calibrate the detector, a set of physical processes and detector properties were exploited to achieve a precise calibration of the apparatus. In the following we recall the main issues concerning the momentum measurement in the HARP TPC, and describe the cross-checks made to validate the momentum scale. As a conclusion, this analysis demonstrates that the measurement of momentum is correct within the published precision of 3
Large-angle production of charged pions by 3 GeV/c-12 GeV/c protons on carbon, copper and tin targets
No full textA measurement of the double-differential π± production cross-section in proton–carbon, proton–copper and proton–tin collisions in the range of pion momentum 100 MeV/c≤p<800 MeV/c and angle 0.35 rad≤θ<2.15 rad is presented. The data were taken with the HARP detector in the T9 beam line of the CERN PS. The pions were produced by proton beams in a momentum range from 3 GeV/c to 12 GeV/c hitting a target with a thickness of 5% of a nuclear interaction length. The tracking and identification of the produced particles was done using a small-radius cylindrical time projection chamber (TPC) placed in a solenoidal magnet. An elaborate system of detectors in the beam line ensured the identification of the incident particles. Results are shown for the double-differential cross-sections d2σ/dpdθ at four incident proton beam momenta (3 GeV/c, 5 GeV/c, 8 GeV/c and 12 GeV/c)
The HARP detector at the CERN PS
No full textHARP is a high-statistics, large solid angle experiment to measure hadron production using proton and pion beams with momenta between 1.5 and 15 GeV/c impinging on many different solid and liquid targets from low to high Z. The experiment, located in the T9 beam of the CERN PS, took data in 2001 and 2002. For the measurement of momenta of produced particles and for the identification of particle types, the experiment includes a large-angle spectrometer, based on a Time Projection Chamber and a system of Resistive Plate Chambers, and a forward spectrometer equipped with a set of large drift chambers, a threshold Cherenkov detector, a time-of-flight wall and an electromagnetic calorimeter. The large angle system uses a solenoidal magnet, while the forward spectrometer is based on a dipole magnet. Redundancy in particle identification has been sought, to enable the cross-calibration of efficiencies and to obtain a few percent overall accuracy in the cross-section measurements. Detector construction, operation and initial physics performances are reported. In addition, the full chain for data recording and analysis, from trigger to the software framework, is described
Forward production of charged pions with incident protons on nuclear targets at the CERN Proton Synchrotron
No full textMeasurements of the double-differential π± production cross section in the range of momentum 0.5⩽p⩽8.0 GeV/c and angle 0.025⩽θ⩽0.25 rad in collisions of protons on beryllium, carbon, nitrogen, oxygen, aluminum, copper, tin, tantalum, and lead are presented. The data were taken with the large-acceptance HAdRon Production (HARP) detector in the T9 beamline of the CERN Proton Synchrotron. Incident particles were identified by an elaborate system of beam detectors. Thin targets of 5% of a nuclear interaction length were used. The tracking and identification of the produced particles were performed using the forward system of the HARP experiment. Results are obtained for the double-differential cross sections d2σ/dp dΩ mainly at four incident proton beam momenta (3, 5, 8, and 12 GeV/c). Measurements are compared with the GEANT4 and MARS Monte Carlo generators. A global parametrization is provided as an approximation of all the collected datasets, which can serve as a tool for quick yield estimate
Measurement of the production cross-section of positive pions in the collision of 8.9 GeV/c protons on beryllium
No full textThe double-differential production cross-section of positive pions, d 2σπ+/d pdΩ, measured in the HARP experiment is presented. The incident particles are 8.9 GeV/c protons directed onto a beryllium target with a thickness of 5% of a nuclear interaction length. The measured cross-section has a direct impact on the prediction of neutrino fluxes for the MiniBooNE and SciBooNE experiments at Fermilab. After cuts, 13 million protons on target produced about 96000 reconstructed secondary tracks which were used in this analysis. Cross-section results are presented in the kinematic range 0.75∈GeV/c≤pπ≤ 6.5∈GeV/c and 30∈mrad≤θπ≤ 210∈mrad in the laboratory frame. © 2007 Springer-Verlag / Società Italiana di Fisica
Particle identification algorithms for the HARP forward spectrometer
No full textThe particle identification (PID) methods used for the calculation of secondary pion yields with the HARP forward spectrometer are presented. Information from time of flight and Cherenkov detectors is combined using likelihood techniques. The efficiencies and purities associated with the different PID selection criteria are obtained from the data. For the proton–aluminium interactions at 12.9 GeV/c incident momentum, the PID efficiencies for positive pions are 86% in the momentum range below 2 GeV/c, 92% between 2 and 3 GeV/c and 98% in the momentum range above 3 GeV/c. The purity of the selection is better than 92% for all momenta. Special emphasis has been put on understanding the main error sources. The final PID uncertainty on the pion yield is 3.3%
