First Search for the EMC Effect and Nuclear Shadowing in Neutrino Nuclear Deep Inelastic Scattering at MINERvA PDF
Preview First Search for the EMC Effect and Nuclear Shadowing in Neutrino Nuclear Deep Inelastic Scattering at MINERvA
Springer Theses Recognizing Outstanding Ph.D. Research Joel Allen Mousseau First Search for the EMC Eff ect and Nuclear Shadowing in Neutrino Nuclear Deep Inelastic Scattering at MINERvA Springer Theses Recognizing Outstanding Ph.D. Research Moreinformationaboutthisseriesathttp://www.springer.com/series/8790 AimsandScope The series “Springer Theses” brings together a selection of the very best Ph.D. theses from around the world and across the physical sciences. 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Joel Allen Mousseau First Search for the EMC Effect and Nuclear Shadowing in Neutrino Nuclear Deep Inelastic Scattering at MINERvA Doctoral Thesis accepted by University of Florida, Gainesville, Florida 123 JoelAllenMousseau UniversityofMichigan AnnArbor,Michigan,USA Additionalmaterialtothisbookcanbedownloadedfromhttp://extras.springer.com. ISSN2190-5053 ISSN2190-5061 (electronic) SpringerTheses ISBN978-3-319-44840-4 ISBN978-3-319-44841-1 (eBook) DOI10.1007/978-3-319-44841-1 LibraryofCongressControlNumber:2016952251 ©SpringerInternationalPublishingSwitzerland2017 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof thematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation, broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformation storageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilarmethodology nowknownorhereafterdeveloped. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant protectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthisbook arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsor theeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinorforany errorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper ThisSpringerimprintispublishedbySpringerNature TheregisteredcompanyisSpringerInternationalPublishingAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland Toallmyteachers Foreword Asaholisticscience,inphysicsweneedtoconsidernotonlytheindividualpieces of a system but also how these pieces combine to form larger structures. Just as cells group together to form complex life forms, protons and neutrons combine to form complicated atomic nuclei. We know from many decades of research that nucleons,anothernameforprotonsandneutrons,behaveslightlydifferentlywhen theycombinetoformatomicnuclei.Justasthecellswhichmakeupahumanliveror heartdiffer,thenucleonswhichmakeupacarbonatomaresubtlydifferentthanthe nucleonsboundinsideanargonnucleus.Innuclearphysics,thedifferencesbetween nucleonsindifferentnucleiarereferredtoas“nucleareffects.” Inthepast,nuclearphysicistsdetectednucleareffectswithbeamsofhigh-energy electrons.High-energybeamsallowelectronstointeractwiththequarkscontained insidenucleonsandnuclei,atypeofinteractioncalleddeepinelasticscattering,or DIS.Advancesinmodernphysicsnowallowphysiciststocreatehigh-intensityand high-energy beams of neutrinos. While neutrinos interact very rarely with nuclei, theirinteractionscanteachusmuchaboutthenatureoftheuniverse. Usingabeamofneutrinos,thisdissertationanalyzesneutrinoDISintheenergy rangeof5–50GeVwiththeMINER(cid:2)Adetector.Intheory,DISinteractionsbetween neutrinos and nuclei will be different from the interactions between electrons and nuclei. This is due to the differences in the weak nuclear force that governs the interactions between electrons, neutrinos, and quarks inside nuclei. If the weak nuclear forces behaves the way we believe it does, then we should see differences inourdataandthetheoryofelectronnucleiDIS. Neutrino DIS interactions are studied by measuring the cross section, or prob- ability, of a neutrino interacting with quarks inside bound nucleons as a function of a property called Bjorken-x. Bjorken-x is proportional to the momentum of the quark that was stuck inside the nucleon. Nuclear effects are defined depending on the region of Bjorken-x where they appear. At low Bjorken-x, nuclear shadowing suppressesthecrosssectionofboundnucleonsrelativetothecrosssectionoffree nucleon. At large Bjorken-x, the EMC effect likewise suppresses the bound cross sectionrelativetothefreecrosssection.Whilethetheoryofnuclearshadowingis vii viii Foreword fairly well established for electron DIS, the mechanism behind the EMC effect is virtuallyunknownforbothelectronsandneutrinos. The data are presented in this dissertation as ratios of carbon, iron, and lead crosssectionstothecrosssectionofplasticscintillator.Theratioobservedindatais comparedtoatheoreticalmodelthatassumesthenucleareffectsarethesameforall nuclei.Wefindthereisadisagreementbetweenthedataandthisassumptioninthe lowest Bjorken-x region for lead where shadowing is the dominate nuclear effect. Astheratioshowsalargerdeviationfromunityinthexrange0.1–0.2thancarbon oriron,wesaythatshadowingisenhancedinthatforlead. As the energy and intensity of neutrino beams used in experiments increase, theneedforprecisemeasurementsofneutrinopropertiessuchastheseintensifies. Futureneutrinoexperimentswilluselargenucleisuchasargon,iron,andcarbonas targetmaterialswhichhaveconsiderablenucleareffects.Iftheseexperimentsareto meettheirgoalsanddiscovernewphysics,theymustpreciselyunderstandneutrino interactionsanddynamicsofthoseinteractionswithinthenuclei.Thedatapresented inthisdissertationwillbeusedtotuneandvalidatethesimulationsofthesefuture experimentsandenablefuturephysiciststoaccuratelyanalyzetheirdata. Likewise, these data are very valuable in validating new models of nuclear effects. This dissertation contains the world’s only data set of neutrino DIS on multiplenucleartargetsinthesameneutrinobeam.Thenuclearphysicscommunity asawholewillbenefitfromhavingthisdatareadilyavailable.Itwillallowfurther development of the EMC effect and nuclear shadowing and possibly assist in answeringoneofthelargestquestionsinnuclearphysics. None of this work would have been possible without the determination and guidanceofthemembersoftheMINER(cid:2)Acollaboration.Ioweatremendousdebt to all the men and women who worked to make MINER(cid:2)A a reality behind the scenes, as well as those who helped tirelessly develop the neutrino reconstruction andanalysis.Icouldnotaskforagreatergroupofcolleaguesandpeersthanthose at Fermilab. Completing my graduate work at a national laboratory was the best decisionIhaveevermadeprofessionally.Iencourageallstudentstoseekoutactive researchcommunitieslikethosebasedatnationallabs.Theeducationandexpertise youwillreceivewillbeinvaluable. Supervisor’s Foreword The analysis presented in this thesis is the world’s first and highly anticipated measurementofthemuonneutrinocharged-currentdeepinelasticscattering(DIS) cross section using neutrinos with energy from 5 to 50GeV. While neutrino cross sections have been studied for many years, our current picture of neutrino and antineutrino charged-current (CC) interactions is cloudy. There exists tension between existing CC exclusive measurements from different experiments, and between measurements and theory. It is suspected that nuclear effects and inter- actionsarekeytounderstandingthesediscrepancies. OnesuchareaofintrigueisfoundintheCCDISevents.NucleareffectsinDIS havebeenthoroughlystudiedusingbeamsofchargedleptons(muonsandelectrons) as a function of Bjorken-x, the fractional momentum carried by the struck quark. Chargedleptonnucleareffectshavebeenextensivelycharacterizedforthepast50 years. However, nuclear effects in neutrino scattering have not yet been directly measured and are not well constrained by global fits to scattering data. We expect nuclear effects presentinneutrino DISmaydifferfromthosefound inleptonDIS duetotheadditionalpresenceoftheaxial-vectorcurrentinneutrinoscattering,and because neutral neutrinos probe the quarks in a way that charged leptons do not; differentnucleareffectsmayarisefromneutrinointeractionswiththevalenceand seaquarks. TheMINER(cid:2)AexperimentisuniqueinthatitwillproduceDIScrosssectionand structure function measurements across a wide range of nuclear material within a single data set and with a single neutrino beam. All previous measurements have been performed with a single nuclear target within a detector. This will allow MINER(cid:2)AtocompletelydescribeDISinlowZmaterialtohighZmaterial,without thedifficultiesassociatedwithcombiningmultipledatasetsacrossdifferentexperi- ments.Theworkpresentedinthispublicationisthefirstanalysistomeasureratios ofdifferentialcrosssectionsandabsolutecrosssectionsoncarbon,scintillator,iron, andleadasafunctionofneutrinoenergyandBjorken-x. ix x Supervisor’sForeword AbstractofDissertationPresentedtotheGraduateSchool oftheUniversityofFloridainPartialFulfillmentofthe RequirementsfortheDegreeofDoctorofPhilosophy FirstSearchfortheEMCEffectandNuclearShadowinginNeutrinoNucleusDeep InelasticScatteringatMINER(cid:2)A By JoelA.Mousseau August2015 Chair:HeatherRay Major:Physics Decades of research in electron-nucleus deep inelastic scattering (DIS) have providedaclearpictureofnuclearphysicsathighmomentumtransfer.Whilethese effects have been clearly demonstrated by experiment, the theoretical explanation oftheirorigininsomekinematicregionshasbeenlacking.Particularly,theeffects in the intermediate regions of Bjorken-x, anti-shadowing, and the EMC effect have no universally accepted quantum mechanical explanation. In addition, these effectshavenotbeenmeasuredsystematicallywithneutrino-nucleusdeepinelastic scattering,duetoexperimentslackingmultipleheavytargets. The MINER(cid:2)A (Main Injector Experiment (cid:2)-A) experiment, located in the Neutrinos at the Main Injector (NuMI) facility at Fermilab, is designed explicitly to measure these kind of effects with neutrinos. MINER(cid:2)A is equipped with solid targets of graphite, iron, lead, and plastic scintillator. The plastic scintillator region provides excellent particle-tracking capabilities, and the MINOS (Main Injector Neutrino Oscillation Search) near detector is used as a downstream muon spectrometer.Theexposureofmultiplenucleartargetstoanidenticalneutrinobeam allowsforasystematicstudyofthesenucleareffects. An analysis of the MINER(cid:2)A DIS data on carbon, iron, lead, and plastic scintillator has been conducted in the energy region 5 (cid:2) E(cid:2) < 50GeV and (cid:3)(cid:4) < 17ı. The data are presented as ratios of the total cross section ((cid:5).E(cid:2)/) as well as the differential cross section with respect to Bjorken-x (d(cid:5) ) of carbon, dxbj iron, and lead to scintillator. The total cross section data is useful for deciphering gross nuclear effects which effect neutrino energy reconstruction. No significant differences between simulation and MINER(cid:2)A DIS data are observed in the total cross section. The ratios of the x differential ratios, however, may provide clues bj for decoding long-standing questions about the EMC effect. The MINER(cid:2)A data tendtosupportnodifferenceinthestrengthoftheEMCeffectfromchargedlepton scattering.Thereisasuggestionofadditionalnuclearshadowing,notpredictedby simulation,intheratioofleadtoscintillator.
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