ENTRY M0556 20190524 M100M055600000001 SUBENT M0556001 20190524 M100M055600100001 BIB 13 56 M055600100002 TITLE The 4He(gamma,2n) reaction measured with tagged M055600100003 photons. M055600100004 AUTHOR (S.M.Doran,I.J.D.MacGregor,J.R.M.Annand,I.Anthony, M055600100005 S.N.Dancer,S.J.Hall,J.D.Kellie,J.C.McGeorge, M055600100006 G.J.Miller,R.O.Owens,P.A.Wallace,B.Schoch, M055600100007 H.Schmieden,S.Klein) M055600100008 REFERENCE (J,NP/A,559,347,1993) M055600100009 INSTITUTE (2GERMNZ,2UK GLS,2GERTUE) M055600100010 FACILITY (MICRT,2GERMNZ) 180 MeV electron microtron MAMI-A at M055600100011 Mainz. M055600100012 INC-SOURCE (TAGD) M055600100013 METHOD (EDE) M055600100014 DETECTOR (TELES,SCIN,SCIN) M055600100015 SAMPLE The liquid-helium target-cell consisted of 6 mm thick M055600100016 elliptical aluminium frame with 125 micron thick M055600100017 Kapton windows and an internal aperture with major M055600100018 and minor axes of 109 and 500 mm, respectively. The M055600100019 effective number of target nuclei was to be M055600100020 4.27 (+-0.08) x 10**22/cm2. M055600100021 ERR-ANALYS (ERR-S) Statistical errors are given. M055600100022 (ERR-SYS) Systematic errors about 22.4 % (for Eg = M055600100023 = 80 - 131 MeV) were obtained by adding in quadrature M055600100024 the systematic uncertainties from the folowing M055600100025 sources: M055600100026 (ERR-1,10.5,35.4) Uncertainty in detector thresholds M055600100027 (Eg = 80- 97 MeV) 35.4 %; M055600100028 (Eg = 97 - 115 MeV) 18.8 %; M055600100029 (Eg = 115 - 131 MeV) 10.5 %; M055600100030 (ERR-2) Uncertainty in detector efficiencies 10.0 %; M055600100031 (ERR-3) Uncertainty in tagging efficiency 2.9 %; M055600100032 (ERR-4) Uncertainty in target thickness 1.9 %; M055600100033 (ERR-5) Uncertainty in tagger multiplicity correction M055600100034 (ERR-6) Uncertainty in T.O.F. multiplexing correction M055600100035 (ERR-7) Uncertainty in deadtime correction 0.2 %. M055600100036 ADD-RES The cross sections for 4He(gamma,pn)pn and M055600100037 4He(gamma,pp)nn reactions. M055600100038 COMMENT The results of tagged-photon measurements of the M055600100039 4He(gamma,pn)D, 4He(gamma,pn)pn and 4He(gamma,pp)nn M055600100040 reactions, carried our with photons of energies 80 - M055600100041 131 MeV, are presented. The (gamma,pn)D M055600100042 three-body-breakup cross section dominates the M055600100043 four-body-breakup cross section. M055600100044 The three-body-breakup cross section and the M055600100045 corresponding deuteron recoil-momentum spectrum are M055600100046 reasonably accounted for by a mechanism of photon M055600100047 absorption on correlated proton-neutron pairs. M055600100048 In contrast the four-body-breakup mechanism appears to M055600100049 have two components: absorption on correlated M055600100050 proton-neutron pairs and a more complex additional M055600100051 component which has a distribution similar to phase M055600100052 space. The data rule out substantial photon M055600100053 absorption on proton-proton pairs. M055600100054 HISTORY (19990305C) Data were compiled at the USA BNL NNDC by M055600100055 V.V.Varlamov. M055600100056 (20190524A) Corrected by SD and VV: TITLE, DETECTOR, M055600100057 ERR-ANALYS, STATUS, DATA, lowercase. M055600100058 ENDBIB 56 0 M055600100059 COMMON 7 6 M055600100060 ERR-SYS ERR-2 ERR-3 ERR-4 ERR-5 ERR-6 M055600100061 ERR-7 M055600100062 PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT PER-CENT M055600100063 PER-CENT M055600100064 22.4 10.0 2.9 1.9 0.9 0.9 M055600100065 0.2 M055600100066 ENDCOMMON 6 0 M055600100067 ENDSUBENT 66 0 M055600199999 SUBENT M0556002 20190524 M100M055600200001 BIB 3 4 M055600200002 REACTION (2-HE-4(G,N+P)1-H-2,,SIG) M055600200003 STATUS (TABLE) Table 1 from Nucl.Phys.,A559(1993)347. M055600200004 HISTORY (20190303U) Corrected by SD and VV: STATUS updated. M055600200005 DATA (DATA-ERR -> ERR-S). M055600200006 ENDBIB 4 0 M055600200007 NOCOMMON 0 0 M055600200008 DATA 4 3 M055600200009 EN-MIN EN-MAX DATA ERR-S M055600200010 MEV MEV MICRO-B MICRO-B M055600200011 80. 97. 58.6 4.2 M055600200012 97. 115. 84.6 3.4 M055600200013 115. 131. 91.9 3.0 M055600200014 ENDDATA 5 0 M055600200015 ENDSUBENT 14 0 M055600299999 ENDENTRY 2 0 M055699999999