In a previous publication [T. Abbott et al., E802 Collaboration, Phys. Rev. C 63, 064602 (2001); 64, 029901(E) (2001)], measurements of the A dependence and pseudorapidity interval (δη) dependence of midrapidity E T distributions in a half-azimuth (Δ=π) electromagnetic calorimeter were presented for p + Be, p + Au, O+Cu, Si+Au, and Au+Au collisions at the BNL-AGS. The validity of the "nuclear geometry" characterization versus δη was illustrated by plots of the E T(δη) distribution in each δη interval in units of the measured 〈ET(δη)〉p+Au in the same δη interval for p + Au collisions. These plots, with aperture corrected scale in the physically meaningful units of number of average observed p + Au collisions, were nearly universal as a function of δη, confirming that the reaction dynamics for ET production at midrapidity at AGS energies is governed by the number of projectile participants and can be well characterized by measurements in apertures as small as Δ=π, δη=0.3. A key ingredient in these analyses is the probability P0 for no signal to be detected in a given aperture δη for the fundamental p + Au collision. In fact the measured 〈ET(δη)〉1p+Au is biased and the true 〈ET(δη)〉p+Autrue for the detector aperture is the measured value times 1-p0. The issues and merits of measuring the ET(δη) distribution in units of 〈ET(δη)〉p+Au or 〈E T(δη)〈p-Autrue in the same δη interval are presented and discussed. This method has application at RHIC, where p-p data could be used as the reference distribution for two participants. The ET distributions for B+A collisions, with E T(δη) scale normalized by 〈E T(δη)〉p-ptruein the same aperture for p-p collisions, would then be given directly in the popular unit "per participant-pair" [K. Adcox et al., PHENIX Collaboration, Phys. Rev. Lett. 86, 3500 (2001); I. G. Bearden et al., BRAHMS Collaboration, Phys. Lett. B523, 227 (2001); B. B. Back et al., PHOBOS Collaboration, Phys. Rev. C 65, 031901 (R) (2002); C. Adler et al., STAR Collaboration, Phys. Rev. Lett. 89, 202301 (2002)].
|Original language||English (US)|
|Number of pages||6|
|Journal||Physical Review C - Nuclear Physics|
|State||Published - Sep 2003|
ASJC Scopus subject areas
- Nuclear and High Energy Physics