ENTRY A0379 20021217 0000A037900000001 SUBENT A0379001 20021217 0000A037900100001 BIB 13 57 A037900100002 TITLE First measurement of the 3-He(3-HE,2P)4-He cross A037900100003 section down to the lower edge of the solar Gamow peak A037900100004 REFERENCE (J,PRL,82,5205,1999) A037900100005 REL-REF (N,,U.GREIFE+,J,NIM/A,350,327,1994) A037900100006 Techical details of LUNA system A037900100007 AUTHOR (R.Bonetti, C.Broggini, L.Campajola, P.Corvisiero, A037900100008 A.D'Alessandro, M.Dessalvi, A.D'Onofrio, A.Fubini, A037900100009 G.Gervino, L.Gialanella, U.Greife, A.Guglielmetti, A037900100010 C.Gustavino, G.Imbriani, M.Junker, P.Prati, V.Roca, A037900100011 C.Rolfs, M.Romano, F.Schuemann, F.Strieder, F.Terrasi, A037900100012 H.P.Trautvetter, S.Zavatarelli) A037900100013 INSTITUTE (2ITYMIL) Dipartimento di fisica and INFN A037900100014 (2ITYITY) INFN, padova A037900100015 (2ITYLGS) A037900100016 (2ITYNAP) Dipartimento di science fisiche and INFN A037900100017 (2ITYFSN) Dipartimento di science ambientali A037900100018 (2ITYGVA) Dipartimento di fisica and INFN A037900100019 (2ITYFRA) Frascati and INFN, ENEA A037900100020 (2ITYTUR) Dipartimento di fisica sperimentale and INFN A037900100021 (2GERBOC) Institut fuer experimentalphysik III A037900100022 COMMENT Abstract: we give the LUNA results on the cross A037900100023 section measurement of a key reaction of the proton- A037900100024 proton chain strongly affecting the calculated neutrinoA037900100025 luminosity from the sun: 3-He(3-HE,2P)4-He . Because A037900100026 of the cosmic ray suppression provided by the Gran A037900100027 Sasso underground laboratory, it has been possible to A037900100028 measure cross section throughout the energy range in A037900100029 which this reaction occurs in the sun, I.E., Down to A037900100030 16.5 KeV center of mass energy. The data clearly show A037900100031 the cross section increase due to the electron A037900100032 screening effect but they do not exhibit any evidence A037900100033 for a narrow resonance suggested to explain the 8-B andA037900100034 7-Be solar neutrino flux reduction. A037900100035 SAMPLE 3-He gas target A037900100036 DETECTOR (SIBAR) Eight thick (1 millimeter) detectors of 5*5 A037900100037 cm**2 area placed around the beam A037900100038 FACILITY (ACCEL,2ITYLGS) A037900100039 METHOD (SITA) A037900100040 (EXTB) A037900100041 (BCINT) Beam current was measured by calorimeter. A037900100042 (COINC) Selected events must fulfill the following A037900100043 conditions: A037900100044 1. There is a coincidence, within 1 microsecond, A037900100045 between the signal of two silicon detectors. A037900100046 2. Each proton deposits more than 2 MeV in the detectorA037900100047 and the sum of the two proton energies is within the A037900100048 constraints given by the Q-Value, 12.86 MeV, of the A037900100049 reaction. A037900100050 3. The coincidence occurs between two, and only two, A037900100051 detectors. A037900100052 Detection efficiency was determined by Monte Carlo A037900100053 programm as 5.3% +/- 0.2% A037900100054 HISTORY (20020709C) A037900100055 (20021217U) Last checking has been done. A037900100056 ERR-ANALYS (ERR-2) Maximal value of gas pressure uncertainty A037900100057 ADD-RES Electron screening potential energy was detemined as A037900100058 247+/-47 eV A037900100059 ENDBIB 57 0 A037900100060 COMMON 1 3 A037900100061 ERR-2 A037900100062 PER-CENT A037900100063 1. A037900100064 ENDCOMMON 3 0 A037900100065 ENDSUBENT 64 0 A037900199999 SUBENT A0379002 20021217 0000A037900200001 BIB 4 15 A037900200002 REACTION (2-HE-3(HE3,2P)2-HE-4,,SIG,,SFC) A037900200003 MISC-COL (MISC1) Centre of mass energy derived from the absoluteA037900200004 energy of the ion beam and the Monte Carlo simulation, A037900200005 including the energy loss of the beam inside the targetA037900200006 gas and the effects of the extended gas-target and A037900200007 detector geometry. A037900200008 (MISC2) Total charge (in coulombs) of 3-He ions ran A037900200009 across gas target A037900200010 (MISC3) Number of detected reactions. A037900200011 ERR-ANALYS (ERR-S) Statistical error, one standard deviation A037900200012 (ERR-1) Systematical error, one standard deviation A037900200013 the systematical error arising mainly from the 10% A037900200014 uncertaintly in the beam energy loss inside the target.A037900200015 COMMENT - By compiler. Effective beam particle energy was A037900200016 calculated by compiler. A037900200017 ENDBIB 15 0 A037900200018 NOCOMMON 0 0 A037900200019 DATA 8 11 A037900200020 EN DATA DATA-MAX ERR-S ERR-1 MISC1 A037900200021 MISC2 MISC3 A037900200022 KEV B*MEV B*MEV B*MEV B*MEV KEV A037900200023 SEE TEXT NO-DIM A037900200024 33. 7.7 7.7 0.49 16.5A037900200025 349. 1. A037900200026 33.98 13.15 4.98 0.83 16.99A037900200027 827. 7. A037900200028 34.92 5.26 5.26 0.33 17.46A037900200029 189. 1. A037900200030 35.94 14. 17.97A037900200031 272. 0. A037900200032 36.92 7.86 2.97 0.47 18.46A037900200033 337. 7. A037900200034 37.96 8.25 2.29 0.48 18.98A037900200035 387. 13. A037900200036 38.92 7.67 2.22 0.44 19.46A037900200037 242. 12. A037900200038 39.86 5.1 1.7 0.29 19.93A037900200039 190. 9. A037900200040 42.86 4.72 0.65 0.26 21.43A037900200041 365. 53. A037900200042 46.74 7.31 0.63 0.39 23.37A037900200043 167. 141. A037900200044 48.72 5.44 0.34 0.28 24.36A037900200045 298. 278. A037900200046 ENDDATA 26 0 A037900200047 ENDSUBENT 46 0 A037900299999 ENDENTRY 2 0 A037999999999