Multi-Pion Systems in Lattice QCD and the Three-Pion Interaction PDF Download

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Languages : en
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Author:
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Category :
Languages : en
Pages : 14507

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The ground-state energies of systems containing up to 12 pi+'s in a spatial volume V~(2.5 fm)3 are computed in dynamical, mixed-action lattice QCD at a lattice spacing of ~0.125 fm for four different values of the light-quark masses. Clean signals are seen for each ground-state, allowing for a precise extraction of both the pi+pi+ scattering length and pi+pi+pi+ interaction from a correlated analysis of systems containing different numbers of pi+'s. This extraction of the pi+pi+ scattering length is consistent with that from the pi+pi+ system alone. The large number of systems studied here significantly strengthens the arguments presented in our earlier work and unambiguously demonstrates the presence of a low energy pi+pi+pi+ interaction. The equation of state of a pi+ gas is investigated using our numerical results and the density dependence of the isospin chemical potential for these systems agrees well with the theoretical expectations of leading order chiral perturbation theory.

Author: Huey-Wen Lin
Publisher: Springer
ISBN: 3319080229
Category : Science
Languages : en
Pages : 255

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With ever increasing computational resources and improvements in algorithms, new opportunities are emerging for lattice gauge theory to address key questions in strongly interacting systems, such as nuclear matter. Calculations today use dynamical gauge-field ensembles with degenerate light up/down quarks and the strange quark and it is possible now to consider including charm-quark degrees of freedom in the QCD vacuum. Pion masses and other sources of systematic error, such as finite-volume and discretization effects, are beginning to be quantified systematically. Altogether, an era of precision calculation has begun and many new observables will be calculated at the new computational facilities. The aim of this set of lectures is to provide graduate students with a grounding in the application of lattice gauge theory methods to strongly interacting systems and in particular to nuclear physics. A wide variety of topics are covered, including continuum field theory, lattice discretizations, hadron spectroscopy and structure, many-body systems, together with more topical lectures in nuclear physics aimed a providing a broad phenomenological background. Exercises to encourage hands-on experience with parallel computing and data analysis are included.

Author: Kristina D Launey
Publisher: #N/A
ISBN: 9813146060
Category : Science
Languages : en
Pages : 393

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This book is a unique collection of reviews that share a common topic, emergent phenomena in atomic nuclei, while revealing the multifaceted nature of the subject, from quarks to heavy nuclei. It tells an amazing story of a decades-long journey of trials and successes, up to present days, with the aim to understand the vast array of experimental data and the fundamentals of strongly interacting fermions. The emphasis is on discovering emergent orderly patterns amidst the overarching complexity of many-particle quantum-mechanical systems. Recent findings are discussed within an interesting framework: a combination of nuclear theory and experiment, of group theory and computational science, and of pivotal models of astonishing simplicity and state-of-the-art models empowered by supercomputers.A special theme resonates throughout the book: the important role of symmetries, exact and approximate, in exposing emergent features and guiding large-scale nuclear modeling. World-renowned experts offer their unique perspective on symmetries in the world of quarks and gluons, and that of protons and neutrons — from chiral symmetry, through spin-isospin and quasi-spin symmetries, to symplectic symmetry, — as well as on the emergent nature of nuclear collectivity, clustering, and pairing, viewed from spectroscopy, microscopic considerations, and first principles. The book provides an excellent foundation that allows researchers and graduate students in physics and applied mathematics to review the current status of the subject, and to further explore the research literature through exhaustive sets of references that also point to studies underpinned by similar techniques in condensed matter and atomic physics along with quantum information.

Author: Thibaut Métivet
Publisher:
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Category :
Languages : en
Pages : 0

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The formalism of Quantum Chromodynamics on the lattice (or Lattice QCD) allows to perform ab-initio non-perturbative studies of strong-interaction driven processes, as it provides both a covariant regularisation of the theory of QCD and a natural framework for numerical computations. In this work, after a review of the main features of QCD and a step-by-step presentation of our discretization of QCD on a lattice, we undertake detailed studies of two problems of hadronic physics: the phenomenon of resonant scattering and the structure of the nucleon. The lattice calculations are performed with the Budapest-Marseille-Wuppertal Collaboration's 2+1-flavour gauge configurations, which give access to a wide range of lattice spacings, volumes and quarks masses, thereby allowing to study the sensibility of our results on these parameters, and to perform a complete continuum extrapolation. These configurations include dynamical quarks, and use a clover-improved Wilson QCD action. To investigate the scattering of particles on the lattice, we set up a Lüscher analysis for the emblematic case of pion-pion scattering in the channel of the rho meson resonance. We analyse our data with a variational generalized eigenvalue method, and give an in-depth calculation of the scattering phase-shifts and the corresponding resonance parameters, with a full control of the systematic errors. Our results provide an important step for lattice studies of scattering states, as they are the first to be performed at the physical pion mass, where one can see the actual decay of the rho into two pions. The obtained rho meson parameters are in good agreement with the experimental values, and consistent with a weak pion mass dependence of the coupling between the rho and two pions. As for our probe of the structure of the nucleon, we present a complete extraction of the electroweak isovector form factors, with a comprehensive study of the electric charge squared radius and of the axial charge. Our analysis also feature data at the physical pion mass, which turns out to be crucial in order to perform safe extrapolations to the physical point, as the chiral perturbation theory predicts violent variations of these quantities near the massless-quarks point. Our calculation includes source and sink projections onto the nucleon state, as well as a combined fit method between the two-point and three-point correlation functions to control the contamination of our data by excited states. Although one would need more data to perform a high-accuracy determination of the nucleon radius and axial charge at the physical point with a relevant estimation of the systematic errors, the results we obtain are in good agreement with the experiment and suggest that the excited-state effects are under control. Our analysis also highlights that gauge configurations ensembles near the physical pion mass and with large volumes must be used in order to extract accurate information about the nucleon structure from lattice calculations.

Author: Martin Ueding
Publisher:
ISBN:
Category : Isobaric spin
Languages : en
Pages :

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Category :
Languages : en
Pages : 15

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The O(100) different ground state energies of N-pion and M-kaon systems for N+M

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Languages : en
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Lattice QCD is currently entering the stage when it can usefully be applied to systems of multiple hadrons. I briefly review the status of recent calculations of scattering parameters in the two hadron sector and discuss recent calculations of systems composed of many mesons or baryons. In the mesonic case, the NPLQCD collaboration has continued its study of systems of up to twelve pions or kaons and have computed the effect of such a hadronic medium on the static quark potential. High statistics calculations on anisotropic lattices have allowed for precision extraction of the energies and scattering phase shifts of various two baryon systems and, for the first time, the energies of certain three baryon systems have been computed.

Author: Brian Foster
Publisher:
ISBN:
Category : Bubble chambers
Languages : en
Pages : 332

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Category :
Languages : en
Pages : 54514

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Doi: http://dx.doi.org/10.1103/PhysRevD.78.054514 Kaon condensation may play an important role in the structure of hadronic matter at densities greater than that of nuclear matter, as exist in the interior of neutron stars. We present the results of the first lattice QCD calculation of kaon condensation obtained by studying systems containing up to twelve charged kaons. Surprisingly, the equation of state of the condensate is remarkably well reproduced by leading order chiral perturbation theory. We determine the three-kaon interaction from the multi-kaon systems and update our results for pion condensates.