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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Simple arguments based on unitarity indicate that meson loops diagrams, induced by an underlying qq pair creation process, should badly disturb the phenomenologically successful spectroscopy and dynamics of the valence quark model, including such simple but mysterious regularities as the OZI rule. The author discusses some recent progress in adding pair creation to the valence quark model in a way which provides rationale for the quark model's success.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Simple arguments based on unitarity indicate that meson loops diagrams, induced by an underlying qq pair creation process, should badly disturb the phenomenologically successful spectroscopy and dynamics of the valence quark model, including such simple but mysterious regularities as the OZI rule. The author discusses some recent progress in adding pair creation to the valence quark model in a way which provides rationale for the quark model's success.
Author: Phiala Elisabeth Shanahan Publisher: Springer ISBN: 3319314386 Category : Science Languages : en Pages : 224
Book Description
This thesis discusses two key topics: strangeness and charge symmetry violation (CSV) in the nucleon. It also provides a pedagogical introduction to chiral effective field theory tailored to the high-precision era of lattice quantum chromodynamics (QCD). Because the nucleon has zero net strangeness, strange observables give tremendous insight into the nature of the vacuum; they can only arise through quantum fluctuations in which strange–antistrange quark pairs are generated. As a result, the precise values of these quantities within QCD are important in physics arenas as diverse as precision tests of QCD, searches for physics beyond the Standard Model, and the interpretation of dark matter direct-detection experiments. Similarly, the precise knowledge of CSV observables has, with increasing experimental precision, become essential to the interpretation of many searches for physics beyond the Standard Model. In this thesis, the numerical lattice gauge theory approach to QCD is combined with the chiral perturbation theory formalism to determine strange and CSV quantities in a diverse range of observables including the octet baryon masses, sigma terms, electromagnetic form factors, and parton distribution functions. This thesis builds a comprehensive and coherent picture of the current status of understanding of strangeness and charge symmetry violation in the nucleon.
Author: Publisher: ISBN: Category : Languages : en Pages : 55203
Book Description
We present an introduction to accurate measurements of the weak neutral current in the elastic scattering of longitudinally polarized electrons off hadronic targets, and show how they can provide new and stringent limits on the contribution of strange quarks to the nucleon form factors. Such a contribution is of particular interest for the study of nucleon structure, since strange quarks do not contribute to the valence state and give us a direct insight into the dynamics of quarkâ antiquark fluctuations. We discuss the latest published results of Happex and G0 experiments as well as the perspectives of high precision measurements of parity violating asymmetries.
Author: Herbert Weigel Publisher: Springer Science & Business Media ISBN: 3540754350 Category : Science Languages : en Pages : 279
Book Description
This concise research monograph introduces and reviews the concept of chiral soliton models for baryons. In these models, baryons emerge as (topological) defects of the chiral field. The many applications shed light on a number of bayron properties, ranging from static properties via nuclear resonances to even heavy ion collisions. This volume also features a number of appendices to help nonspecialist readers to follow in more detail some of the calculations in the main text.
Author: National Research Council Publisher: National Academies Press ISBN: 0309173663 Category : Science Languages : en Pages : 222
Book Description
Dramatic progress has been made in all branches of physics since the National Research Council's 1986 decadal survey of the field. The Physics in a New Era series explores these advances and looks ahead to future goals. The series includes assessments of the major subfields and reports on several smaller subfields, and preparation has begun on an overview volume on the unity of physics, its relationships to other fields, and its contributions to national needs. Nuclear Physics is the latest volume of the series. The book describes current activity in understanding nuclear structure and symmetries, the behavior of matter at extreme densities, the role of nuclear physics in astrophysics and cosmology, and the instrumentation and facilities used by the field. It makes recommendations on the resources needed for experimental and theoretical advances in the coming decade.
Author: Peter John Ehlers Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Entanglement between valence quarks and the sea in hadrons is shown to be deeply connectedto important features of QCD, namely chiral symmetry breaking and confinement. The sea degrees of freedom can be traced over to give a reduced density matrix, and it is shown that the resulting entanglement entropy acts as an order parameter of chiral symmetry breaking and potentially confinement in the nucleon. A general decomposition of the nucleon state in components labeled by definite chiral transformation properties is considered. In particular, the most general expression of the nucleon state in the chiral basis with three valence quarks is constructed, consistent with known QCD constraints, and its properties are studied. In the chiral basis, the nucleon state is naturally a bipartite system where all non-valence spin can be traced over to give a reduced density matrix for the valence spin. It is shown that the resulting entanglement entropy acts as an order parameter of chiral symmetry breaking on the null-plane. In the large-Nc limit, the entanglement entropy is minimized and the valence spin accounts for all of the nucleon spin, while in the limit of maximal entanglement entropy, the nucleon loses all memory of the valence spin and is therefore entirely accounted for by the non-valence spin. This suggests that the small observed valence content of the proton spin is a signature of strong entanglement in the nucleon between the valence quarks and the sea. The nucleon state vector in the chiral basis, fit to low-energy data, gives a valence spin content consistent with experiment and lattice QCD determinations, and has large entanglement entropy. Entanglement between valence and sea quarks in 1+1d QCD is also considered. While predecessors to QCD such as the parton model had a clear distinction between valence and sea particles, the Fock state expansion of a hadron gives no unambiguous definition of which quarks are valence quarks and which belong to the parton sea aside from their flavor. A rigorous definition of valence-sea (VS) entanglement in QCD is developed, which is consistent with the observation that it vanishes in the large-Nc limit and will remain low when finite-Nc states resemble their large-Nc counterparts. We perform a numerical study of VS entanglement in 1+1 dimensional discrete light-cone quantized QCD, and in the process develop a method for building the color-singlet basis of 1+1d QCD that is manifestly complete and orthogonal by construction. We find that the VS entanglement entropy for the first few excited states of both mesons and baryons is relatively low compared to all other states in the spectrum, with the VS entropy of ground state hadrons providing a minimum. We also see that for ground state mesons the entropy is well described in the 1/Nc approximation. These results suggest that low energy hadrons may be the only QCD bound states for which the large-Nc expansion, and perhaps the parton model, provide an accurate description. This work also provides evidence that the VS entanglement entropy of QCD in 3+1d, which would likely serve as an order parameter for the QCD phase transition, may be perturbatively accessible through a large-Nc expansion, and we develop a qualitative picture of what the VS entanglement entropy of nucleons in real QCD may look like.
Author: Nour Makke Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Understanding the nucleon structure is currently one of the main challenges encountered in nuclear physics. The present work represents a contribution to the study of the nucleon structure and deals, in particular, with the study of the role of strange quarks in the nucleon. The latter can be investigated by determing the strange quark distribution in the nucleon as well as the contribution of the spins of strange quarks to the nucleon spin (∆s). This work first presents a measurement of ∆s performed via Deeply Inelastic Scattering of a muon beam off polarized proton and deuterium targets. The result is found to be strongly dependent on the quark fragmentation functions into hadrons (FFs), which define the probability that a quark of a given flavour fragments into a final state hadron. The FFs are poorly known, in particular, the FF of strange quark into kaons, which play an important role in the determination of ∆s. In deep inelastic scattering process, the access to the FFs is provided by the hadron multiplicities which, in turn, define the average number of hadrons produced per DIS event. Pion and kaon multiplicities have been extracted versus different kinematic variables, using DIS data collected by deeply inelastic scattering of a 160 GeV muons off a deuterium target. A first LO extraction of the fragmentation functions has then been performed using the measured pion and kaon multiplicities.
Author: Alberto Reis Publisher: American Institute of Physics ISBN: Category : Science Languages : en Pages : 790
Book Description
The purpose of Hadron 05 was to discuss recent developments in hadron spectroscopy. New hadrons have been discovered in the past few years. These states do not quite fit into the traditional quark model classification scheme of hadrons. There has also been a remarkable improvement in the understanding of heavy quark bound systems, or heavy quarkonia, as well as the so-called scalar mesons. Topics covered include baryons, exotics, and hadron structure.
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Author: Phiala Elisabeth Shanahan
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Author: Herbert Weigel
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Author: National Research Council
Author: Peter John Ehlers
Author: Nour Makke
Author: Alberto Reis
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