COLLECTED PAPERS IN PHYSICS AND ENGINEERING

By C. CAZIA

1 OVERVIEW 1 2 SCIENCE QUESTIONS 22 3 SOCIETAL APPLICATIONS AND BENEFITS 146 4 GLOBAL NUCLEAR SCIENCE 178 5 NUCLEAR SCIENCE GOING FORWARD 203 6 RECOMMENDATIONS 221 CONTENTS CHAPTER 1 OVERVIEW INTRODUCTION THIS FOURTH DECADAL ASSESSMENT OF NUCLEAR PHYSICS BY THE NATIONAL RESEARCH COUNCIL COMES EXACTLY ONE CENTURY AFTER ERNEST RUTHERFORD S DISCOVERY OF THE ATOMIC NUCLEUS HIS VISIONARY INSIGHT MARKED THE BEGINNING OF NUCLEAR PHYSICS AT 100 YEARS NUCLEAR PHYSICS IS A ROBUST AND VITAL SCIENCE WITH TECHNOLOGICAL BREAKTHROUGHS ENABLING EXPERIMENTS AND COMPUTATIONS THAT IN TURN ARE OPENING DIVERSE NEW FRONTIERS OF EXPLORATION AND DISCOVERY AND ADDRESSING DEEP AND IMPORTANT QUESTIONS ABOUT THE PHYSICAL UNIVERSE NUCLEAR PHYSICISTS TODAY ARE ADVANCING THE FRONTIERS OF HUMAN KNOWLEDGE IN WAYS THAT ARE FORCING US TO REVISE OUR VIEW OF THE COSMOS ITS BEGINNINGS AND THE STRUCTURE OF MATTER WITHIN IT AT THE SAME TIME THESE ADVANCES IN NUCLEAR PHYSICS ARE YIELDING APPLICATIONS THAT ADDRESS SOME OF THE NATION S CHALLENGES IN SECURITY HEALTH ENERGY AND EDUCATION AS WELL AS CONTRIBUTING INNOVATIONS IN TECHNOLOGY AND MANUFACTURING THAT HELP DRIVE OUR ECONOMY THERE HAVE BEEN STUNNING ACCOMPLISHMENTS AND MAJOR DISCOVERIES IN NUCLEAR SCIENCE SINCE THE LAST DECADAL ASSESSMENT LIKE RUTHERFORD TODAY S NUCLEAR SCIENTISTS FIND THAT THE DATA FROM WELL CRAFTED EXPERIMENTS OFTEN CHALLENGE THEM TO REVISE THEIR IDEAS ABOUT THE STRUCTURE OF MATTER INDEED THE MATTER THAT MAKES UP ALL LIVING ORGANISMS AND ECOSYSTEMS PLANETS AND STARS THROUGHOUT EVERY GALAXY IN THE UNIVERSE IS MADE OF ATOMS AND 99 9 PERCENT OF THE MASS OF ALL THE ATOMS IN THE UNIVERSE COMES FROM THE NUCLEI AT THEIR CENTERS WHICH ARE OVER 10 000 TIMES SMALLER IN DIAMETER THAN THE ATOMS THEMSELVES THE PROTON S RADIUS IS ABOUT A FEMTOMETER OR 10 15 M A DISTANCE SCALE CALLED THE FEMTOSCALE ALTHOUGH NUCLEI ARE INCREDIBLY SMALL AND DENSE THEY ARE FAR FROM FEATURELESS THEY ARE COMPLEX STRUCTURES MADE OF PROTONS AND NEUTRONS WHICH THEMSELVES ARE COMPLEX STRUCTURES MADE OUT OF AS FAR AS IS KNOWN ELEMENTARY CONSTITUENTS KNOWN AS QUARKS AND GLUONS BEYOND WHAT RUTHERFORD COULD POSSIBLY HAVE IMAGINED NUCLEAR PHYSICS SPANS AN ENORMOUS RANGE OF DISTANCE SCALES FROM WELL BELOW THE FEMTOSCALE UPWARD TO THE SCALE OF THE UNIVERSE ITSELF THE UNITED STATES BECAME A POWERHOUSE IN NUCLEAR PHYSICS IN THE DECADES FOLLOWING THE 1 MANHATTAN PROJECT TODAY VIBRANT NUCLEAR PHYSICS PROGRAMS ARE FOUND ALONG WITH LARGE AND SOPHISTICATED NUCLEAR PHYSICS LABORATORIES IN MOST OF THE TECHNOLOGICALLY ADVANCED COUNTRIES AROUND THE WORLD U S NUCLEAR PHYSICISTS OFTEN INVOLVE THEMSELVES IN LARGE COLLABORATIVE EFFORTS WITH SCIENTISTS FROM MANY COUNTRIES CARRYING OUT EXPERIMENTS IN THE UNITED STATES OR ABROAD SUCH EFFORTS CREATE NEW OPPORTUNITIES AND OPTIMIZE THE DEPLOYMENT OF THE RESOURCES NEEDED TO GERMINATE AND SUSTAIN SCIENTIFIC PROGRESS AND MAINTAIN INTELLECTUAL LEADERSHIP IN NUCLEAR PHYSICS MANAGING THESE RESOURCES HAS BECOME ESSENTIAL TO THIS END THE U S NUCLEAR PHYSICS COMMUNITY HAS DEVELOPED PROCESSES THAT BUILD A COMMUNITY WIDE VISION IDENTIFYING WHICH PATHWAYS WILL BE THE MOST EFFECTIVE AND DIRECT TO SCIENTIFIC DISCOVERIES THAT OPEN NEW VISTAS AND DRIVE THE FIELD THE NATIONAL RESEARCH COUNCIL S DECADAL ASSESSMENTS OF NUCLEAR PHYSICS HAVE BECOME ONE OF THE TOOLS BY WHICH THE FIELD DEVELOPS ITS ROADMAP IN THIS REPORT THE COMMITTEE ON THE ASSESSMENT OF AND OUTLOOK FOR NUCLEAR PHYSICS ASSESSES THE STATE OF NUCLEAR PHYSICS AT A TIME WHEN IT IS RAPIDLY EVOLVING AND NEW FRONTIERS ARE OPENING UP THE COMMITTEE ASSESSES HERE U S NUCLEAR PHYSICS AND ITS PROSPECTS FOR THE FUTURE IN AN INTERNATIONAL CONTEXT NUCLEAR PHYSICS IS BROAD AND DIVERSE IN THE QUESTIONS IT IS ANSWERING AND THE CHALLENGES IT FACES ON ITS MANY FRONTIERS AS WELL AS IN ITS TECHNIQUES AND TECHNOLOGIES WE FRAME THIS INTRODUCTION WITH FOUR OVERARCHING QUESTIONS THAT SPAN SEVERAL OF THE TRADITIONAL SUBFIELDS OF NUCLEAR PHYSICS THAT ARE CENTRAL TO THE FIELD AS A WHOLE THAT REACH OUT TO OTHER AREAS OF SCIENCE AS WELL AND THAT TOGETHER ANIMATE NUCLEAR PHYSICS TODAY 1 HOW DID VISIBLE MATTER COME INTO BEING AND HOW DOES IT EVOLVE 2 HOW  DOES  SUBATOMIC  MATTER  ORGANIZE  ITSELF  AND  WHAT  PHENOMENA EMERGE 3 ARE THE FUNDAMENTAL INTERACTIONS THAT ARE BASIC TO THE STRUCTURE OF MATTER FULLY UNDERSTOOD 4 HOW CAN THE KNOWLEDGE AND TECHNOLOGICAL PROGRESS PROVIDED BY NUCLEAR PHYSICS BEST BE USED TO BENEFIT SOCIETY ACCOMPLISHMENTS SINCE THE LAST DECADAL ASSESSMENT HAVE BROUGHT US MUCH CLOSER TO ANSWERING EACH OF THESE FOUR QUESTIONS IN EACH CASE RECENT RESEARCH HAS REVEALED NEW PHYSICS DISCOVERIES AND OPENED NEW FRONTIERS FOR EXPLORATION THE QUESTIONS ARE MULTIFACETED BROAD AND DEEP AND THE CHALLENGES THEY POSE PROVOKE INTRIGUING OPPORTUNITIES FOR THE DECADE TO COME IN THE REMAINDER OF THIS INTRODUCTION THESE FOUR QUESTIONS ARE DISCUSSED IN SOME DETAIL AND ILLUSTRATED BY A FEW VIGNETTES IN CHAPTER 2 THE SCIENTIFIC RATIONALE AND OBJECTIVES OF NUCLEAR PHYSICS ARE ARTICULATED MORE FULLY CHAPTER 2 IS ORGANIZED ACCORDING TO THE MAIN SCIENCE AREAS WITHIN THE FIELD BUT THE FOUR OVERARCHING QUESTIONS CROSS THE BOUNDARIES BETWEEN THESE SUBFIELDS LINKING THE DISCIPLINE TOGETHER AS AN INTELLECTUAL WHOLE WHILE IT AT THE SAME TIME ADVANCES ON 2 VARIED FRONTIERS NUCLEAR PHYSICS HAS JANUS LIKE QUALITIES PROBING FUNDAMENTAL LAWS OF NATURE THAT LINK IT TO PARTICLE PHYSICS WHILE AT THE SAME TIME LOOKING TOWARD COMPLEX PHENOMENA THAT EMERGE FROM THE FUNDAMENTAL LAWS AS IN ATOMIC AND CONDENSED MATTER PHYSICS AND ASTROPHYSICS AND COSMOLOGY ZOOMING IN ON PHENOMENA HAPPENING AT THE SHORTEST DISTANCE SCALES THAT OUR BEST MICROSCOPES CAN SEE AND ZOOMING OUT TO THE STARS AND THE COSMOS BECAUSE IT SITS IN THIS LIMINAL POSITION BETWEEN THE FUNDAMENTAL AND THE EMERGENT BETWEEN THE MICROSCOPIC AND THE ASTRONOMICAL NUCLEAR PHYSICS NATURALLY ADDRESSES THESE CENTRAL QUESTIONS FROM VARIED ANGLES PROVIDING UNIQUE PERSPECTIVES HOW DID VISIBLE MATTER COME INTO BEING AND HOW DOES IT EVOLVE THE CHALLENGES POSED BY THIS QUESTION ARE SHARED BY COSMOLOGISTS ASTRONOMERS PARTICLE PHYSICISTS AND NUCLEAR PHYSICISTS ALIKE THE UNIVERSE IS NOT ENTIRELY MADE OF ATOMS AND LIGHT IT ALSO CONTAINS DARK MATTER AND DARK ENERGY COMPONENTS THAT ARE KNOWN TO EXIST BECAUSE THEIR GRAVITATIONAL INFLUENCE CAN BE SEEN ON ORDINARY MATTER BUT ALL THE MATTER THAT CAN BE SEEN VISIBLE MATTER IS MADE OF ATOMS CONSISTING OF A TINY COMPACT NUCLEUS AND ELECTRONS ORBITING AROUND IT ATOMIC NUCLEI COME IN A VERY BROAD RANGE OF MASSES AND ELECTRIC CHARGE WHEN THE CHARGES OF THE NEGATIVE ELECTRONIC CLOUD CANCEL OUT THE POSITIVE CHARGE OF THE NUCLEUS THE ATOM IS NEUTRAL INTERACTIONS OF THE ELECTRONIC CLOUDS AROUND NUCLEI ENABLE THE COMPLEX CHEMICAL PROCESSES THAT ARE ESSENTIAL FOR LIFE AND FORM THE BASIS OF OUR MODERN TECHNOLOGICAL WORLD ATOMIC INTERACTIONS ARE THUS DICTATED BY THE ATOMIC NUCLEI AS IT IS THEIR CHARGE THAT DETERMINES THE ELECTRONIC STRUCTURE UNDERSTANDING NUCLEAR PHYSICS AND WHAT GOES ON WITHIN THE NUCLEI AT THE CORE OF ALL VISIBLE MATTER STARTS WITH UNDERSTANDING THE ORIGINS OF THE NUCLEI LIGHT AND HEAVY AND OF THE PROTONS AND NEUTRONS OF WHICH THEY ARE MADE HOW WERE THE PROTONS AND NEUTRONS CREATED DURING THE BIG BANG AND HOW DID THESE PROTONS AND NEUTRONS ASSEMBLE INTO SUCH A BROAD RANGE OF NUCLEI THROUGH NUCLEAR TRANSFORMATIONS INSIDE STARS AND STELLAR EXPLOSIONS NUCLEAR SCIENCE IN CONCERT WITH ASTROPHYSICS ATTEMPTS TO ANSWER THESE QUESTIONS THE QUEST TO UNDERSTAND HOW PROTONS NEUTRONS AND NUCLEI FORM AND EVOLVE IS FUNDAMENTAL TO UNDERSTANDING OUR ORIGINS ONE EXAMPLE OF HOW NUCLEAR PHYSICS IS LEARNING HOW VISIBLE MATTER COMES INTO BEING IS PROVIDED BY EXPERIMENTS AT TWO ACCELERATORS THE RELATIVISTIC HEAVY ION COLLIDER IN BROOKHAVEN NEW YORK AND THE LARGE HADRON COLLIDER IN GENEVA SWITZERLAND BY COLLIDING NUCLEI AT ENORMOUS ENERGIES SCIENTISTS ARE USING THESE FACILITIES TO MAKE LITTLE DROPLETS OF BIG BANG MATTER THE SAME STUFF THAT FILLED THE WHOLE UNIVERSE A FEW MICROSECONDS AFTER THE BIG BANG USING POWERFUL DETECTORS THEY ARE SEEKING ANSWERS TO QUESTIONS ABOUT THE PROPERTIES OF THE MATTER THAT FILLED THE MICROSECONDS OLD UNIVERSE THAT CANNOT BE ASCERTAINED BY ANY CONCEIVABLE ASTRONOMICAL OBSERVATIONS MADE WITH TELESCOPES AND SATELLITES SINCE THE LAST DECADAL ASSESSMENT OF NUCLEAR PHYSICS RESEARCH HAS SHOWN THAT DURING THE MICROSECOND EPOCH WHEN THE TEMPERATURE 3