ENTRY C2608 20210504 C204C260800000001 SUBENT C2608001 20210504 C204C260800100001 BIB 12 66 C260800100002 TITLE Total Cross Section of Negative Pions in Hydrogen C260800100003 AUTHOR (H.L.Anderson,E.Fermi,E.A.Long,R.Martin,D.E.Nagle) C260800100004 REFERENCE (J,PR,85,934,1952) C260800100005 #doi:10.1103/PhysRev.85.934.2 C260800100006 INSTITUTE (1USACHI) C260800100007 FACILITY (SYNCY,1USACHI) The large Chicago cyclotron. C260800100008 INC-SPECT The negative pions are produced in the large Chicago C260800100009 cyclotron by protons of 450 MeV striking a target C260800100010 which in some of the experiments was copper and in C260800100011 others beryllium. A sharply collimated beam C260800100012 containing pions with energy defined within ~3 C260800100013 percent. In addition to the pions this beam contains C260800100014 some muons and electrons of the same momentum. Their C260800100015 number has been determined from a range curve. The C260800100016 muons amount to between 5 percent and 10 percent. The C260800100017 electrons are present in negligible numbers for beams C260800100018 above 100 MeV. Below this energy the electron C260800100019 contamination increases rapidly. For this reason low C260800100020 energy measurements have been taken by reducing with C260800100021 a beryllium absorber the energy of the 122-MeV beam. C260800100022 SAMPLE A glass cylinder 3 inches in diameter and 7.5 inches C260800100023 long, closed by 0.005-inch copper windows. This C260800100024 chamber can be alternately filled with and emptied of C260800100025 liquid hydrogen. C260800100026 DETECTOR (SCIN) Two scintillation crystals of 1-inch-square C260800100027 cross section separated by a distance of about one C260800100028 meter. A pair of liquid scintillation counters. C260800100029 METHOD (COINC) The coincidences of these two scintillation C260800100030 counters indicate the number of particles entering C260800100031 the equipment. Beyond the second crystal the pions C260800100032 enter the scattering chamber. The particles which are C260800100033 not scattered out of the beam are recorded by the C260800100034 coincidences which they give in a pair of liquid C260800100035 scintillation counters. The double coincidence rate C260800100036 of the first two scintillators is recorded and at the C260800100037 same time the quadruple coincidence rate of all four C260800100038 scintillators. The attenuation of the beam is C260800100039 obtained from a comparison of the ratio of the C260800100040 quadruple to double coincidence counts with and C260800100041 without the hydrogen and is computed as a cross C260800100042 section. C260800100043 ERR-ANALYS (DATA-ERR) No details on sources of uncertainties. C260800100044 CORRECTION A number of corrections have been applied to the C260800100045 results on account of the following effects: C260800100046 (1) Background due to accidentals (usually 1 percent C260800100047 or less). C260800100048 (2) Angular spread of the beam due to geometry, C260800100049 diffraction scattering, and pi-mu decay. In some C260800100050 experiments the multiple scattering was compensated C260800100051 by means of an equivalent aluminum foil; in others it C260800100052 was computed. This correction is important only at C260800100053 low energies. C260800100054 (3) Muon and electron component in the original beam. C260800100055 It is assumed that muons and electrons suer only C260800100056 Coulomb scattering and have no specific nuclear C260800100057 interaction. C260800100058 (4) Correction for scattered particles C260800100059 recorded by the end counters. This correction was C260800100060 computed on the assumption of isotropic scattering in C260800100061 the center-of-mass system. It amounted to between 4 C260800100062 percent and 2 percent depending on whether the recoil C260800100063 protons are or are not recorded. The correction would C260800100064 be larger if the scattering were predominately C260800100065 forward but smaller if charge exchange scattering C260800100066 were important. C260800100067 HISTORY (20210504C) BP C260800100068 ENDBIB 66 0 C260800100069 NOCOMMON 0 0 C260800100070 ENDSUBENT 69 0 C260800199999 SUBENT C2608002 20210504 C204C260800200001 BIB 2 2 C260800200002 REACTION (1-H-1(PIN,NON),,SIG) C260800200003 STATUS (TABLE) Table I, page 935. C260800200004 ENDBIB 2 0 C260800200005 NOCOMMON 0 0 C260800200006 DATA 4 5 C260800200007 EN EN-RSL DATA DATA-ERR C260800200008 MEV MEV MB MB C260800200009 89.0 8.0 21.0 8.0 C260800200010 112.0 6.0 31.0 9.0 C260800200011 135.0 6.0 52.0 6.0 C260800200012 176.0 6.0 66.0 6.0 C260800200013 217.0 6.0 60.0 6.0 C260800200014 ENDDATA 7 0 C260800200015 ENDSUBENT 14 0 C260800299999 ENDENTRY 2 0 C260899999999