Engineering topics
Nakagawa, I
Publications and source records attributed to Nakagawa, I.
Measurement of the partial cross sections {sigma}{sub TT}, {sigma}{sub LT}, and ({sigma}{sub T} + {epsilon}{sigma}{sub L}) of the {sup 1}H(e, e{sup '{pi}+})n reaction in the {Delta}(1232) resonance
We report precision {sup 1}H(e, e{sup '{pi}+})n measurements in the {Delta}(1232) resonance at Q{sup 2}=0.127(GeV/c){sup 2} obtained at the MIT-Bates out-of-plane scattering facility. These are the lowest, but nonzero, Q{sup 2} measurements in the {pi}{sup +} channel. The data offer tests of the theoretical calculations, particularly of the background amplitude contributions. The chiral effective field theory and Sato-Lee model calculations are not in agreement with this experiment.
New Measurement of the {pi}{sup 0} Radiative Decay Width
High precision measurements of the differential cross sections for {pi}{sup 0} photoproduction at forward angles for two nuclei, {sup 12}C and {sup 208}Pb, have been performed for incident photon energies of 4.9-5.5 GeV to extract the {pi}{sup 0}{yields}{gamma}{gamma} decay width. The experiment was done at Jefferson Lab using the Hall B photon tagger and a high-resolution multichannel calorimeter. The {pi}{sup 0}{yields}{gamma}{gamma} decay width was extracted by fitting the measured cross sections using recently updated theoretical models for the process. The resulting value for the decay width is {Gamma}({pi}{sup 0}{yields}{gamma}{gamma})=7.82{+-}0.14(stat){+-}0.17(syst) eV. With the 2.8% total uncertainty, this result is a factor of 2.5 more precise than the current Particle Data Group average of this fundamental quantity, and it is consistent with current theoretical predictions.
Measurements of the energy dependence of the analyzing power in pp elastic scattering in the CNI region
We present new measurements of the analyzing power A{sub N} in proton-proton elastic scattering in the Coulomb-Nuclear Interference region at {radical}s = 7.7 and 21.7 GeV obtained with the polarized atomic hydrogen jet target at RHIC. These measurements complement our earlier results at {radical}s = 6.8 and 13.7 GeV confirming the presence of a hadronic helicity flip amplitude contribution in proton-proton elastic scattering at lower energies ({radical}s <8 GeV) while higher energy data ({radical}s >13 GeV) are consistent with no hadronic helicity flip contribution.
Nuclear incoherent photoproduction of {pi}{sup 0} and {eta} from 4 to 12 GeV
The mechanism of incoherent {pi}{sup 0} and {eta} photoproduction from complex nuclei is investigated from 4 to 12 GeV with an extended version of the multicollisional Monte Carlo (MCMC) intranuclear cascade model. The calculations take into account the elementary photoproduction amplitudes via a Regge model and the nuclear effects of photon shadowing, Pauli blocking, and meson-nucleus final-state interactions. The results for {pi}{sup 0} photoproduction reproduced for the first time the magnitude and energy dependence of the measured rations {sigma}{sub {gamma}A}/{sigma}{sub {gamma}N} for several nuclei (Be, C, Al, Cu, Ag, and Pb) from a Cornell experiment. The results for {eta} photoproduction fitted the inelastic background in Cornell's yields remarkably well, which is clearly not isotropic as previously considered in Cornell's analysis. With this constraint for the background, the {eta}{yields}{gamma}{gamma} decay width was extracted using the Primakoff method, combining Be and Cu data [{Gamma}{sub {eta}{yields}{gamma}{gamma}=}0.476(62) keV] and using Be data only [{Gamma}{sub {eta}{yields}{gamma}{gamma}=}0.512(90) keV]; where the errors are only statistical. These results are in sharp contrast ({approx}50-60%) with the value reported by the Cornell group [{Gamma}{sub {eta}{yields}{gamma}{gamma}=}0.324(46) keV] and in line with the Particle Data Group average of 0.510(26) keV.
Run-09 pC polarimeter analysis
Analysis of PC polarimeter data at {radical}s = 200 and 500 GeV from Run9 is presented. Final polarization results, fill-by-fill, for blue and yellow beams, as to be used by RHIC experiments (in collisions) are released and collected in http://www4.rcf.bnl.gov/cnipol/pubdocs/Run09Offline/. Global relative systematic uncertainties {delta}P/P (to be considered as correlated from fill to fill) are 4.7% for 100 GeV beams, and 8.3% (12.1%) for blue (yellow) 250 GeV beams. For a product of two beam polarizations P{sub B} {center_dot} P{sub Y} (used in double spin asymmetry measurements) the relative uncertainty {delta}(P{sub B} {center_dot} P{sub Y})/(P{sub B} {center_dot} P{sub Y}) 8.8% for 100 GeV beams and 18.5% for 250 GeV beams. For the average between two beam polarization (P{sub B} + P{sub Y})/2 (used in single spin asymmetry measurements, when data from two polarized beams are combined) the relative uncertainty is 4.4% for 100 GeV beams and 9.2% for 250 GeV beams. Larger uncertainties for 250 GeV beams relate to significant rate related systematic effects experienced in the first part of Run9 (due to thicker targets used and smaller trans. beam size at higher beam energy).