Search Results (12 total)

The performance of over 2000 students in introductory calculus-based electromagnetism (E&M) courses at four large research universities was measured using the Brief Electricity and Magnetism Assessment (BEMA). Two different curricula were used at these universities: a traditional E&M curriculum and the Matter & Interactions (M&I) curriculum. At each university, postinstruction BEMA test averages were significantly higher for the M&I curriculum than for the traditional curriculum. The differences in post-test averages cannot be explained by differences in variables such as preinstruction BEMA scores, grade point average, or SAT Reasoning Test (SAT) scores. BEMA performance on categories of items organized by subtopic was also compared at one of the universities; M&I averages were significantly higher in each topic. The results suggest that the M&I curriculum is more effective than the traditional curriculum at teaching E&M concepts to students, possibly because the learning progression in M&I reorganizes and augments the traditional sequence of topics, for example, by increasing early emphasis on the vector field concept and by emphasizing the effects of fields on matter at the microscopic level.

The Brief Electricity and Magnetism Assessment (BEMA), developed by Chabay and Sherwood, was designed to assess student understanding of basic electricity and magnetism concepts covered in college-level calculus-based introductory physics courses. To evaluate the reliability and discriminatory power of this assessment tool, we performed statistical tests focusing both on item analyses (item difficulty index, item discrimination index, and item point biserial coefficient) and on the entire test (test reliability and Ferguson’s delta). The results indicate that BEMA is a reliable assessment tool.

Differential cross sections for π⁰ and ρ⁰ photoproduction from protons have been measured at photon energies 6, 12, and 18 GeV and momentum transfers 0.5 to 3 (GeV / c)².

We have measured the time distributions of the π⁺e^-ν̅ , π^-e⁺ν, and π⁺π^-π⁰ modes from initially pure K⁰'s in a spark-chamber experiment performed at the Bevatron. From 1079 K_e3 events between 0.2 and 7 K_S lifetimes, we find ReX=-0.070±0.036, ImX=0.107_-0.074^+0.092. This result is consistent with X=0 (relative probability = 0.25). From 148 K→π⁺π^-π⁰ events in the same fiducial volume, we get ReW=-0.05±0.17 and ImW=0.39_-0.37^+0.35. ("W" is variously known as η^+-0 and x+iy.) Our results are consistent with W=0 (relative probability = 0.30).

We have measured the time distribution of the π⁺e^-ν and π^-e⁺ν modes from initial K⁰'s in a spark-chamber experiment performed at the Bevatron. From 1079 events between 0.2 and 7 K_S⁰ lifetime, we find ReX=-0.069±0.036, ImX=+0.108_-0.074^+0.092. This result is consistent with X=0 (relative probability = 0.25), but more than 4 standard deviations from the existing world average, +0.14 -0.13i.

Experiments are reported which remove the discrepancies between the earlier observed K and L x-ray yields from low-Z muonic atoms and those calculated from theory. We have made direct measurements of the K / L yield ratios for targets of 4≤Z≤8 and a determination of the absolute K x-ray yield for Z=3. They agree excellently with the calculated values.

The momentum spectrum of muon-decay positrons has been investigated, in the region above 25 MeV, with a homogeneous magnet containing wire spark chambers with magnetic-core readout. At a given field, this spectrometer accepts, with essentially constant probability and a momentum resolution of ±1%, a 30% momentum range. On the basis of 2.8×10⁵ events we find for the Michel parameter the value ρ=0.760±0.009 (in agreement with V-A) provided we constrain, as has been customary, the low-energy parameter η to be zero. Since the two-component neutrino hypothesis (V+εA) predicts ρ=3 / 4 while leaving η free, it is more sensible to impose the constraint ρ=3 / 4 and fit for η; doing this, we obtain η=-0.7±0.6, again in agreement with V-A, which predicts η=0.

A precision measurement of the energy dependence of the asymmetry of the decay of the positive muon has been made with a wire spark-chamber spectrometer of large momentum acceptance. We find, as an average of runs at different fields and with different targets, δ=0.758±0.010, in agreement with the two-component neutrino theory.