ENTRY L0258 20200713 L044L025800000001 SUBENT L0258001 20200713 L044L025800100001 BIB 10 34 L025800100002 TITLE Stringent upper limit on the direct 3alpha decay of L025800100003 the Hoyle state in 12C L025800100004 AUTHOR (R.Smith,M.Gai,M.W.Ahmed,M.Freer,H.O.U.Fynbo, L025800100005 D.Schweitzer,S.R.Stern) L025800100006 INSTITUTE (1USAUCO,1USADKE,1USANCC,2UK BIR,2DENAAU) L025800100007 (2UK UK) Sheffield Hallam University, Sheffield L025800100008 REFERENCE (J,PR/C,101,021302,2020) Present paper is a new L025800100009 independent analysis of experimental data published L025800100010 in REL-REF. L025800100011 REL-REF (O,L0180001,W.R.Zimmerman+,J,PRL,110,152502,2013) L025800100012 FACILITY (ESTRG,1USATNL) Experiment performed at the HIgS L025800100013 facility at TUNL L025800100014 SAMPLE Gas mixture of CO2 (80%) + N2 (20%) at pressure of L025800100015 100 torr in sensitive volume of the optical time L025800100016 projection chamber with dimensions of 30 x 30 x 21 cm3.L025800100017 DETECTOR Time projection chamber with working gas mixture L025800100018 serving at the same time as reaction target. L025800100019 Ionization electrons drift towards a double L025800100020 parallel-grid avalanche multiplier, yielding charge L025800100021 multiplication and light emission. Avalanche-induced L025800100022 photons from N2 emission are collected, intensified L025800100023 and recorded with a Charge Coupled Device (CCD) L025800100024 camera, providing two-dimensional track images. The L025800100025 event's time projection (third coordinate) and the L025800100026 deposited energy are recorded by photomultipliers and L025800100027 by the TPC charge-signal, respectively. Detector has L025800100028 nearly 100 % efficiency and negligible background. L025800100029 INC-SOURCE (LCS) Nearly monoenergetic gamma-rays were produced L025800100030 by Compton backscattering of photons of the L025800100031 free-electron laser. Beams of circularly polarized L025800100032 gamma rays with energies between 9.1 and 10.7 MeV L025800100033 were used with energy spreads of 300-350 keV and L025800100034 on-target intensities of 2E+8 photons/sec. L025800100035 HISTORY (20200713C) Compiled by S.H. L025800100036 ENDBIB 34 0 L025800100037 NOCOMMON 0 0 L025800100038 ENDSUBENT 37 0 L025800199999 SUBENT L0258002 20200713 L044L025800200001 BIB 3 9 L025800200002 REACTION ((6-C-12(G,2A),,WID)/(6-C-12(G,TOT),,WID)) L025800200003 ANALYSIS From measured total width of 10.025 MeV state and L025800200004 3 alpha particle decay width ratio, an upper limit on L025800200005 3 alpha decay of Hoyle state was determined from L025800200006 R-matrix theory, which gives relation of width and L025800200007 penetrability of a state. Three alpha penetrability L025800200008 ratios were calculated using Monte Carlo code with L025800200009 WKB approximation. L025800200010 STATUS (TABLE) Data taken from text p.3 of the reference L025800200011 ENDBIB 9 0 L025800200012 NOCOMMON 0 0 L025800200013 DATA 2 1 L025800200014 EN-RES DATA-MAX L025800200015 MEV NO-DIM L025800200016 10.025 5.7E-6 L025800200017 ENDDATA 3 0 L025800200018 ENDSUBENT 17 0 L025800299999 ENDENTRY 2 0 L025899999999