Isotopic and velocity distributions of Bi produced

Isotopicandvelocitydistributionsof83Biproducedincharge-pickupreactionsofat1AGeVPb20882A.Kelića,K.-H.Schmidta,T.Enqvista,#,A.Boudardb,P.Armbrustera,J.Benlliurec,M.Bernasd,S.Czajkowskie,R.Legraine,§,S.Lerayb,B.Mustaphad,&,M.Pravikoffe,F.Rejmundd,C.Stéphand,J.Taïebb,L.Tassan-Gotd,C.Volantb,W.Wlazłob,faGSI,Planckstraße1,D-64291Darmstadt,GermanybDAPNIA/SPhNCEA/Saclay,F-91191Gif-sur-Yvette,FrancecUniversityofSantiagodeCompostela,E-15706SantiagodeCompostela,SpaindIPNOrsay,IN2P3,F-91406Orsay,FranceeCENBG,IN2P3,F-33175Gradignan,FrancefJagiellonianUniversity,InstituteofPhysics,ul.Reymonta4,P-30-059Kraków,PolandAbstract:Isotopicallyresolvedcrosssectionsandvelocitydistributionshavebeenmeasuredincharge-pickupreactionsof1AGeV208Pbwithproton,deuteriumandtitaniumtarget.Thetotalandpartialcharge-pickupcrosssectionsinthereactions208Pb+1Hand208Pb+2Haremeasuredtobethesameinthelimitsoftheerrorbars.Aweakincreaseinthetotalcharge-pickupcrosssectionisseeninthereactionof208Pbwiththetitaniumtarget.Themeasuredvelocitydistributionsshowdifferentcontributions–quasi-elasticscatteringand∆-resonanceexcitation-tothecharge-pickupproduction.Dataontotalandpartialcharge-pickupcrosssectionsfromthesethreereactionsarecomparedwithotherexistingdataandalsowithmodelcalculationsbasedonthecouplingofdifferentintra-nuclearcascadecodesandanevaporationcode.Keywords:NUCLEARREACTIONS:208Pb+1H,2H,Ti,Ebeam=1AGeV;nuclideidentificationbyhigh-resolutionmagneticspectrometer;productionyieldsandvelocitydistributionsofcharge-pickupresidues.MODELDESCRIPTION:intra-nuclearcascadecodesandevaporationmodel.PACS:24.10.-i,25.40.-h,25.45.-z,27.80.+w,29.30.-h1.IntroductionInnuclearcharge-pickupreactionsatprojectileenergieswellabovetheFermienergytherearetwoprocessesmostlyresponsiblefortheincreaseofthenuclearchargeoftheprojectile[1]:Oneisaquasi-elasticcollisionbetweenatargetprotonandaprojectileneutronwheretheprotontakesoverthetotalkineticenergyoftheneutronendingupinthephasevolumeoftheprojectile-likefragment.Theothermechanismistheexcitationofatargetoraprojectilenucleonintothe∆(1232)-resonancestateanditssubsequentdecay.Typicaltransferreactionsobservedatlowerenergies[2]whereaprotonistransferredthroughthenuclearoverlapzoneareexcludedatrelativisticenergiesbecauseofthenon-overlappingFermispheresofprojectileandtarget.Thisisalsoconfirmedbythenon-observationoffragmentswithmasseshigherthanthemassoftheprojectile[3].Inpreviousworksspecialattentionwasdevotedtothecharge-exchangereactions,wherethenuclearchargeoftheprojectileincreasesordecreasesbyoneunitbutwherenomasslossoccurs.Asatrelativisticenergiescharge-exchangereactionsinvolvetheformationof∆−particlesandpions,theycanbeusedasatoolforstudyingthein-mediumbehaviourof#Presentaddress:UniversityofJyväskylä,FIN-40351Jyväskylä,Finland.§Deceased.&Presentaddress:ArgonneNationalLaboratory,9700SouthCassAvenue,Building203,Argonne,IL60439,USA.theseparticles[4].Thesereactionscanalsogivesomeinsightintotheneutrondensitydistributioninthenucleus[5].Themostcomprehensivestudyofcharge-exchangereactionsinvolvingrelativisticheavyions(upto40Ar)hasbeenperformedattheacceleratorSATURNEatSaclayasapartofaresearchprogramdedicatedtotheinvestigationofthenuclearresponsetospin-isospinexcitations;foranoverviewseereference[1].Aninterestingfindingfromthemeasuredinclusivemomentumspectraofthereactionproductswasashiftofthepositionandofthestrengthofthe∆-resonancepeakinheaviertargetsascomparedtotheprotontarget[1].HalfofthisshiftisexplainedbytheFermimotionofthe∆−particlesandthenucleonsinthenuclearmeanfield[6,7],whileeffectssuchasthestronglyattractiveinteractionbetween∆-particlenucleon-holestatesinthespin-longitudinalchannel[4]andtheinterplaybetween∆-excitationinthetargetandintheprojectile[8]couldcontributetoanotherhalf.Forprojectilesheavierthan40Ar,mostofthepublisheddataconcernonlytotalcharge-pickupcrosssections;see[9,10,11]andreferencestherein.Guoxiaoetal.triedtoestablishthesystematicdependenceofthetotalcharge-pickupcrosssectiononprojectileandtargetsize[12].Usingthedatameasuredforawiderangeofprojectilemasses,from12Cto197Au,theyfoundevidenceforasquaredependenceofthetotalcharge-pickupcrosssectionontheprojectilemass.Toexplainthissteepdependence,theysuggestedthepresenceofcoherentprocessesinthecharge-pickupreactions.Later,usingcompletemeasuredisotopicdistributionsofcharge-pickupproducts,Sümmereretal.[13,14]showedthatthescalingofthetotalcharge-pickupcrosssectionwiththesquareoftheprojectilemassismostlyduetotheevaporationofchargedparticlesfromtheprefragments.Therefore,theyconcludedthatthetotalcharge-pickupcrosssectionsarenotasensitivetoolforstudyingthebasicnucleon-nucleonprocessesinvolvedincharge-pickupreactions.Inthepresentwork,wereportontheisotopicallyresolvedcharge-pickupcrosssectionsfortheproductionof83Biintheinteractionsofrelativistic,1AGeV,projectileswithproton,deuteriumandtitaniumtarget.ThemeasurementswereperformedatGSI-Darmstadtusingthefulladvantageofrelativisticcollisionsininversekinematics.Thesedatarepresentapartofacomprehensivestudyoffragmentformationinaneutron-generatingtargetfora