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1. Executive Summary using slow anti-protons), medical physics and biology, and space science (APPA collaborations). At SPIRAL2, an alternative approach to producing radioactive beams will be used. Rather than fragmenting high-energy projectiles directly, the Isotope Separation On-Line, ISOL, method will be applied, where radioactive species are produced by bombarding uranium with high-energy neutrons and post-accelerating the fission fragments. Both methods, the in-flight fragmentation and the ISOL production of radioactive beams, are complementary with respect to their capabilities of producing different highly unstable nuclei, and both need similar types of highly sophisticated detectors such as the travelling gammaray spectrometer. Major upgrades of two existing heavy ion accelerators are planned at CERN and INFN Legnaro. Both HIE-ISOLDE at CERN and SPES at Legnaro will be advanced ISOL radioactive beam facilities. Together with SPIRAL2, they will pave the way for the ultimate high power ISOL facility EURISOL, whose conceptual design was supported via a Design Study in the EU Framework Programme 6, and should be included in the next edition of the ESFRI list. Since radioactive beam intensities are small, long beamtimes are needed. With the anticipated approval of the Accelerator Driven subcritical Reactor, ADS, project MYRRHA in Mol and its inclusion in the ESFRI list, there will be an opportunity to install the ISOL@MYRRHA experiment, which could provide ample beamtime during the scheduled downtimes of the ADS. There are two other multi-purpose ESFRI projects that offer opportunities for nuclear structure research, the Extreme Light Infrastructure, ELI, and the European Spallation Source, ESS. Whilst the plans for nuclear physics installations at the ELI branch in Bucharest are in an advanced state, the use of ESS for nuclear physics purposes still needs to be explored in more detail. Concerning hadron physics, there are three collider projects in Europe that point further into the future. The Polarized Antiproton eXperiment, PAX, and the Electron Nucleon Collider, ENC, are potential future upgrades of FAIR. Both would use the High Energy Storage Ring, HESR. ENC would in addition make use of the PANDA detector and hence could be set up at a very reasonable cost. The PAX experiment aims at unravelling the nucleon’s structure by colliding polarised antiprotons with polarised protons. The ENC would scatter polarised electrons on polarised protons or light ions to measure exclusive reactions at much higher centre-of-mass energies than were available at DESY. The physics programme aims at determining Generalised Parton Distributions, which will provide a three-dimensional picture of the nucleon. The Large Hadron electron Collider project, LHeC, at CERN is driven by the European particle physics community, but has important implications for high-energy nuclear physics as well. High-energy electrons colliding with high-energy heavy ions will probe the gluon density at extremely small momentum fractions, where theory predicts gluon saturation effects. Since matter essentially consists of glue, a detailed understanding of its distribution is of prime importance. 1.3.3 Collaboration at European and Global Level The ambitious experimental and theoretical programme in Nuclear Physics, briefly outlined above and described in more detail in subsequent sections, would not be possible without close collaboration at European and international level. There are several types of collaboration common in the field. Since nearly all nuclear physics facilities apply an open access policy that is only controlled by Programme Advisory Committees who assess the quality and feasibility of the proposed experiment, funding is one of the main issues. In this context, the EU’s Framework Programmes supporting transnational access to European large-scale nuclear physics laboratories for groups from less well off countries are very instrumental. Big projects need elaborate planning, strong support of the whole community, coordination with cognate fields and, most importantly, the support of research councils and science ministries. In this context, NuPECC has been active as an expert committee of the European Science Foundation (research councils) by focusing the views of the nuclear physics community in Europe (ca. 6 000 scientists and engineers) onto Long Range Plans, submitting roadmaps to ESFRI (science ministries) and initiating EU Framework Programme projects (Integrating Infrastructure Initiatives, Integrating Activities and an ERA-net). There are cross memberships with sister organisations in Europe (Nuclear Physics Board, NPB, of the European Physical Society, EPS), the USA (NSAC) and Asia (ANPhA) to coordinate regional large-scale nuclear physics projects. At a global level, NuPECC represents Europe on the Working Group WG.9 on International Cooperation in Nuclear Physics of the International Union of Pure and Applied Physics, IUPAP, and contributes to the OECD Global Science Forum working group’s reports on Nuclear Physics. 10 | Perspectives of Nuclear Physics in Europe – NuPECC Long Range Plan 2010
1.4 Scientific Themes In the following sub-sections, we introduce each of the main scientific topics and the major directions within them. We refer the interested reader to a more comprehensive treatment in the subsequent chapters. 1.4.1 Hadron Physics Hadrons are strongly interacting, composite particles made from so-called “current quarks” and gluons, the point-like elementary building blocks of QCD. Neither quarks nor gluons have ever been seen in isolation. Instead, they are confined inside hadrons in special ‘colour neutral’ combinations. Baryons such as the familiar nucleons of nuclei, the proton and the neutron, each consist of three so-called “constituent quarks”. Other hadrons consisting of a quark and an anti-quark form mesons. The lightest meson, the pion, is responsible for the long-range part of the interaction between nucleons and plays a major role in the binding of the nucleons inside the nucleus. Open key questions in hadron physics are: • How does the strong interaction confine quarks and gluons into hadrons • What precisely is the internal structure of hadrons in terms of fundamental quarks and gluon degrees of freedom • What is the role of quarks and self-interacting gluons in nuclei The constituent quark picture provides a simple classification scheme for organising the various hadronic species. In spite of its deceptive simplicity, this picture is however far from complete. The mass of the current quarks that comprise the nucleon is very small (about one percent of the proton mass). This gives rise to an (approximate) symmetry in QCD, known as chiral symmetry. Due to the very strong interaction between quarks and gluons at small energy scales, chiral symmetry is spontaneously broken (much like the breaking of rotational symmetry in a magnet). Via this mechanism, constituent quarks receive their mass of several hundred MeV and the pion emerges as a (nearly) massless excitation of the non-trivial QCD vacuum. These ‘Goldstone bosons’ form the basic building blocks of a low-energy theory for QCD, which is widely used in the description of the large-distance properties of hadrons, their mutual low-momentum interactions, and more recently also nuclear structure physics. We now know that the internal structure of hadrons is far richer than previously thought. Indeed, their description depends on the resolution scale of the experimental probes. Whilst at low resolution, baryons and mesons emerge as objects governed by the dynamics of broken chiral symmetry, high-resolution experiments reveal a structure containing a multitude of pairs of quarks and anti-quarks of different types (flavours) and a host of gluons, revealing the elementary degrees of freedom of QCD. QCD describes the strong-interaction sector of the Standard Model of elementary particles. In contrast to electro-magnetism, the force carriers (gluons) self-interact, which renders the theory intrinsically non-linear. In the high-energy regime, the interaction between quarks and gluons can be described by perturbation theory, much like the interaction between electrons and photons in Quantum Electrodynamics. This is because the interaction strength weakens with increasing energy (or shorter distances) due to a mechanism called ‘asymptotic freedom’. The perturbative treatment of the interaction processes, however, starts to fail when the distance between quarks becomes comparable to the size of the nucleon. In this case, the interaction becomes so strong that very complex phenomena emerge, which are for instance being investigated in electron/positron/ muon-scattering experiments on nucleons at MAMI in Mainz, ELSA in Bonn, HERMES at DESY, COMPASS at CERN and Jefferson Lab (JLab) in the US. From such experiments, one can obtain ‘snapshots’ of the internal structure. Depending on the energy of the projectile, such snapshots provide position or momentum distributions of the quarks inside a hadron. However, a consistent description of hadron properties, such as their spin, has still to be achieved from the measured photon or particle distributions. This will be studied in future experiments at the upgraded COMPASS and Jefferson Lab facilities, or new lepton scattering research infrastructures such as the proposed Electron-Nucleon- Collider, ENC, at FAIR or the Electron-Ion-Collider, EIC, at either Brookhaven National Laboratory, BNL, or JLab. In addition, it is realistic to expect that new theoretical approaches, in the framework of Generalised Parton Distributions for example, will lead to a real ‘hadron tomography’. In responding to the first two key questions above, hadron spectroscopy has played a prominent role at DAΦNE at LNF, COSY, MAMI, ELSA and JLab. Whilst the large set of excited hadrons discovered in spectroscopy experiments is clear evidence for quark degrees of freedom, unexpected spectroscopic results at e.g. BELLE have recently challenged the picture of hadrons being composed of quark-antiquarks or three quarks only. They indicate a much more complex structure of perhaps multiquark or quark molecule character. One of the most promising experiments to search for these exotic hadrons in the future will be PANDA at FAIR. Perspectives of Nuclear Physics in Europe – NuPECC Long Range Plan 2010 | 11
Page 1 and 2: Forward Look Perspectives of Nuclea
Page 3 and 4: Contents Foreword 3 1. Executive Su
Page 5: Foreword The goal of this European
Page 8 and 9: 1. Executive Summary 1.1.3 Objectiv
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Page 14 and 15: 1. Executive Summary The role of gl
Page 16 and 17: 1. Executive Summary from the few-b
Page 18 and 19: 1. Executive Summary Advances in nu
Page 20 and 21: 1. Executive Summary and AMS or hig
Page 22 and 23: 2. Recommendations and Roadmap EURI
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4.1.2 Basic Properties of Quantum C
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coupling can be applied. A key tool
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opportunity to determine the moduli
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A broad experimental programme has
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4.1.4 Hadron Spectroscopy Recent Ac
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Physics Perspectives There is a mul
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Global Perspective and Efforts In t
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The longest-range parts of these fo
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concentrate their efforts and conti
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4. Scientific Themes 4.2 Phases of
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tion of state would therefore deter
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an increase at the deconfinement te
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can be described with statistical h
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Box 3. Heavy ion fragmentation and
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Figure 7. Isotopic dependence of th
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energies so far did not find indica
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4.2.5 The High-Energy Frontier The
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Figure 10. Elliptic flow parameter
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elevant experimental and analysis r
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the same time being able to precise
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technology), a three-dimensional ar
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4. Scientific Themes 4.3 Nuclear St
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4.3.2 Theoretical Aspects Ab Initio
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the continuum, as done, e.g., in th
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Each of these extensions will open
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Halos, clusters and few-body correl
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Figure 3. Mirror Energy Differences
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Superheavy elements The existence o
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Figure 5. Gamma-ray spectrum of the
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The experimental evidence for the e
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4.3.7 Ground-State Properties Figur
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For nuclear astrophysics applicatio
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A detector array for high-energy ph
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and rejection power of separators.
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4. Scientific Themes 4.4 Nuclear As
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powers many of the objects we obser
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Hydrostatic burning Stars spend the
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Significant uncertainties remain fo
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nova ejecta (a few seconds). In thi
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have to be calculated. Current micr
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An improvement in the precision of
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a neutron. Application of the detai
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urning can be treated in such a sta
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Currently, all stellar models study
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determination of abundance patterns
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4. Scientific Themes 4.5 Fundamenta
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This could be achieved at upgraded
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experiment that is currently being
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ut also scintillating bolometers as
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highest experimental sensitivities
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New time reversal invariant scalar
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due to the interference of photon a
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muon intensities. These could be ac
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4.5.4 Properties of Known Basic Int
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Highly-charged ions The fourth dire
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sponding force acts and α is a str
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ackground, call for upgrades of the
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4.6 Nuclear Physics Tools and Appli
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5.1 Contributors Hartmut Abele (Wie
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5.3 Acronyms and Abbreviations ADS
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