E/sub T//sup 0/ and. pi. /sup 0/ spectra from. cap alpha cap alpha. , dd, and pp interactions at. sqrt. s/sub NN/ = 31 GeV at the CERN ISR [report]

M.J. Tannenbaum
1984 unpublished
Inclusive Single Particle Production Inclusive single particle production at large transverse momentum, p_, from heavy nuclear targets was first studied by Cronin and collabo-T .2 rators at Permilab in the period 1973-1977, basically because of the unavailability of liquid hydrogen targets. They measured the invariant cross section Ed a/dp , for inclusive ir~ K~ p,p production near 90°f rom the interaction of 200 to 400 GeV/c protons with an assortment of nuclear targets and found that the
more » ... found that the atomic weight dependence at fixed P-, 3 1 could be represented by a power law: (T pA (P T ) . The exponent a(P T ) varied with P T , the particle produced and the nucleonnucleon center-of-mass energy, ^s™, and reached values in excess of = 1. This was dubbed the "Anomalous Nuclear Enhancement." For irp roduction, a(P T ) increased with P , reaching a maximum value at P J-4.6 GeV/c which varied between a = 1.18 at Ss =19.4 GeV and a = 1.13 at The next step in the study of the collisions of nucleii at high energy occurred at the CERN ISR in 1980, with runs on act and pa interactions at nucleon-nucleon center-of-mass energies of /Sj-. = 31 GeV for aa and /s^j = 44 GeV for pa. Several experiments took data on inclusive single particle production. The conclusion was that the anomalous enhancement died away for pa collisions, a } 1 at /I = 44 GeV, but came on even stronger for aa collisions at /s^ = 31 GfeV. The ratio of the cross aection for inclusive production of a i" at a given P T in aa and pp collisions varied from a value of J>18 in the range of 3 <_ P < 4 GeV/c to J-24 to 30 in the range 4 < P" < 5 GeV/c to J-30 to 40 in the range 5 <_ P T <_ 7 GeV/c. The best quoted error on this ratio was J-20% at P J"6 GeV/c. It is expected that the error will be reduced by a uctor of 3 when results ?iom the 1983 ISR run become available. If the ratio of the cross sections is assumed to obey a power law {A^j) a T ,~~) then values of a as high as 1. ± O.J05 have been observed for inclusive pion production at P T -^6 GeV/c in an collisions. The present situation is more thoroughly described in Martin Faessler's review article. One conclusion that I draw from these results is that pA collisions are different from AA collisions. For a somewhat different point of view, see Sherman Frankel's presentation to this conference. Other Results Previous to 1984 In the period 1980 to 1983, some additional data became available. Among the most noteworthy were the results from the Multipartide Spectrometer Group at Fermilab who presented the first measurement of transverse energy, E T , emission in the central region of pA collisions. In this type measurement, the transverse energy, L = E.sinfl., is summed over all the particles emitted on an event into a fixed but large solid angle, typically Ai)> = 2ir, Ay = ±1, where y is the rapidity measured in the cm. system. A frequency distribution, or spectrum of E_ over all events is then computed. The E,_ spectrum covered the range 1 <_ E T _< 21 GeV for proton collisions on several nucleii from hydrogen to lead, at »'Ij_. = 27.4 GeV, and showed that the parameterization A a was still reasionable. However, the exponent a had risen to values as high a a = 2iO. "he A.F.S. Group at CERN also presented a charged E T spectrum, reconstructed from charged particles observed on minimum bias triggers from i:he 1980 aa and pa runs at the ISR. The spectrum falls 4 orders of magnitude over the charged E T range from 0 to 12 GeV. E£ Results from the 1983 CERN ISR Run This brings us to August 1983, when the second (and final) light ion run took place at the CERN ISR. This run was a considerable improvement over the 1980 run, with aa, pa, dd and pp collisions all studied at "i^, = 31 GeV. The aa luminosity achieved at the low-B intersection 30 -2 -1 1-1 was 1.0 x 10 cm s . The integrated luminosity was a factor of 16 higher than the 1980 run (Table I) .
doi:10.2172/6174559 fatcat:sfhyqmbndbdqzdnnw5ueyda3au