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The energy loss of protons and deuterons in D2O ice has been measured over the energy range Ep=18-541 kev using the double focusing magnetic spectrometer to measure the energy of the particles after they have traversed a known thickness of the ice target. One method of measurement is used to determine relative values of the stopping cross section as a function of energy, another method measures the absolute values. The results are in very good agreement with the values calculated from Bethe's semi-empirical formula. Possible sources of error are considered and the accuracy of these measurements is estimated to be ±4 percent.
The D(d,p)T reaction cross section has been measured by two methods using D2O ice targets. For Ed from 206 to 516 kev, a double-focusing magnetic spectrometer was used to obtain the momentum spectrum of the protons and tritons, from which the reaction cross section can be determined. For Ed from 35 to 550 kev, the proton yield from a thick target was differentiated to obtain the cross section. Both thin and thick target methods were used to measure the angular distribution over the energy range Ed from 35 to 550 kev. The angular distribution is expressed in terms of a Legendre polynomial expansion. Various sources of experimental error are considered and the probable error of the total cross section is found to be ±5 percent.
The stopping cross section of H2, He, O2, air, N2, Ne, A, Kr, Xe, H2O, NH3, NO, N2O, CH4, C2H2, C2H4, and C6H6 for protons has been measured over the energy range Ep=30-600 kev. An electrostatic analyzer measures the energy of protons incident on a gas cell, and the transmitted beam energy is measured with a magnetic spectrometer. The gas cell is closed off with thin aluminum windows. Comparison of the molecular stopping cross section of the compounds with the values obtained by summing the constituent atomic cross sections shows that Bragg's rule does not hold for any of these compounds below Ep=150 kev; for NO the additive rule does not hold at any energy studied. Above 150 kev the stopping cross section of carbon is obtained by subtracting the hydrogen contribution from the values measured for the hydrocarbons. Average ionization po...
Magnetic analysis of the alpha-particle spectrum from N14(d, α)C12 covering the excitation energy range from 4.4 to 9.2 Mev in C12 shows a level at 7.68±0.03 Mev. At Ed=620 kev, θlab=90°, transitions to this state are only 6 percent of those to the level at 4.43 Mev.
We present constraints on the angle gamma of the unitarity triangle with a Dalitz analysis of neutral D decays to K_Sπ^+π^- from the processes B^0-->[overline D]^0K^(*0) ([overline B]^0-->D^0[overline K]^(*0)) and B^0-->D^0K^(*0) ([overline B]^0-->[overline D]^0[overline K]^(*0)) with K^(*0)-->K^+π^- ([overline K]^(*0)-->K-π^+). Using a sample of 371×10^6 B[overline B] pairs collected with the BABAR detector at PEP-II, we constrain the angle gamma as a function of r_S, the magnitude of the average ratio between b-->u and b-->c amplitudes.
We use a sample of 384×106 B[overline B] events collected with the BABAR detector at the PEP-II e+e- collider to study angular distributions in the rare decays B-->K*[script-l]+[script-l]-, where [script-l]+[script-l]- is either e+e- or µ+µ-. For low dilepton invariant masses, m[script-l][script-l]<2.5 GeV/c2, we measure a lepton forward-backward asymmetry [script A]FB=0.24-0.23+0.18±0.05 and K* longitudinal polarization FL=0.35±0.16±0.04. For m[script-l][script-l]>3.2 GeV/c2, we measure [script A]FB=0.76-0.32+0.52±0.07 and FL=0.71-0.22+0.20±0.04.
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