Towards the study of 2H(p, γ)3He reaction in the Big Bang Nucleosynthesis energy range in LUNA

摘要

TheBigBangNucleosynthesisbeganafewminutesaftertheBigBang,whentheUniversewassufficientlycoldtoallowdeuteriumnucleitosurvivephoto-disintegration.ThetotalamountofdeuteriumproducedintheUniverseduringthefirstminutesdependsonthecosmologicalparameters(liketheenergydensityinbaryons,Ωbh2,andtheeffectiveneutrinonumber,Neff)andonthenuclearcrosssectionsoftherelevantreactions.Themainsourceofuncertaintyinthedeuteriumestimationcomesfromthe2H(p,γ)3Hecrosssection.MeasurementsofCosmicMicrowaveBackground(CMB)anisotropiesobtainedbythePlancksatelliteareinverygoodagreementwiththetheoreticalpredictionsoftheminimalΛCDMcosmologicalmodel,significantlyreducingtheuncertaintyonitsparameters.ThePlanckdataallowstoindirectlydeducewithveryhighprecisiontheabundancesofprimodialnuclides,suchastheprimodialdeuteriumfraction2H/H=(2.65±0.07).10-5(68%C.L.).TheastrophysicalobservationsindampedLyman-asystemsathighredshiftsprovideasecondhighaccuracymeasurementoftheprimodialabundanceofdeuterium2H/H=(2.53±0.04)10-5(68%C.L.).ThepresentexperimentalstatusontheastrophysicalS-factorofthe2H(p,γ)3HereactionintheBBNenergyrange,givesasystematicuncertaintiesof9%.Alsothedifferencebetweenab-initiocalculationsandexperimentalvaluesofS12isatthelevelof10%.Inordertoclarifytheactualscenario,ameasurementof2H(p,γ)3Hecrosssectionwithaprecisionofafewpercentinthe70-400keVenergyrangeisplannedatLUNAin2016.AfeasibilitytestofthemeasurementhasbeenperformedinOctober2014,givingthepreliminaryresultsonthecrosssection.Theexperimentalsetupforthetestandfinalmeasurementcampaignwillbepresented...