Search for Anomalons Using Plastic Nuclear Track Detectors

We exposed a stack of CR39 track detectors containing Ag foils to a 1.7 GeV/nucleon 56Fe'beam and investigated the anomalous mean free path effect. Neither the whole set of 7517 nor a subset of 2542 interacting fragments produced probably in the Ag target show an effect. By combining the data of this and an earlier experiment we can also exclude an effect for 3219 interacting fragments produced in AZ=I oollisi0ns. INTRODUCTION The situation of mean-free-path (mfp) measurements for relativistic projectile fragments (PF's) under different experimental conditions is still not clear. The results of emulsion experiments /I-3,11/ showing an anomalously large interaction cross section of PF's within the first few centimeters from their point of emission are contradicted by some other experiments using different techniques like Cherenkov detectors /4,5/, plastic nuclear track detectors /6,7/ or even by experiments using nuclear emulsions /8-10/. There are some indications that the effect is preferentially observed for fragments produced in collisions with heavy target nuclei and for fragments produced in extremely peripheral collisions: In nuclear emulsion a large number of collisions occurs with silver target nuclei whereas the experiments using Cherenkov or plastic nuclear track detectors provide targets not heavier than oxygen. If anomalons would be produced only in collisions with heavy targets this would explain all the negative results in these experiments. Furthermore some observations are supporting the idea, that anomalons are sproduced in extremely peripheral collisions. The most striking hint come_ifrom a bubble chamber experiment /12/, where collision products of a 3.7 GeV/nucleon 12C beam were analyzed. No anomalous behavior was observed for all types of analyzed interaction products except _2C projectiles that had undergone a collision, but did not loose charge. If we follow the hypothesis, that anomalons are produced preferably in peripheral interactions, all experiments having a low sensitivity in detecting these interactions should see a reduced or no effect of anomalous mfp's. Experiments of this type are our first plastic track detector experiment /6/ and the nuclear emulsion experiment of the BCJJL collaboration /9/. THE EXPERIMENTAL METHOD We performed a new experiment which meets the requirements of both heavy target and high efficiency for the detection of AZ=I interactions. For this purpose 200um thick silver foils were stacked between the CR39 foils (C_2HI_0 _) of 600um thickness. A stack of each 150 silver and plastic foils with a size of 10cm * 8cm was exposed at the Bevalac to a 1.7 GeV/nucleon Fe beam with 103 particles per cm2. The beam nuclei were https://ntrs.nasa.gov/search.jsp?R=19850027835 2017-09-12T19:27:56+00:00Z