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Excited Baryons In Lattice Qcd
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Book Synopsis Excited Baryons in Lattice QCD. by :
Download or read book Excited Baryons in Lattice QCD. written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present first results of calculations of masses of positive and negative parity excited baryons in lattice QCD using an O(a2) improved gluon action and a fat-link clover fermion action in which only the irrelevant operators are constructed with fat links. The results are in agreement with earlier calculations of N* resonances using improved actions and exhibit a clear mass splitting between the nucleon and its chiral partner. The results also indicate a splitting between the lowest J{sup P}=1/2− states for the two standard nucleon interpolating fields. The study of different Lambda interpolating fields suggests a similar splitting between the lowest two Lambda12−} octet states. However, the empirical mass suppression of the Lambda*(1405) is not evident in these quenched QCD simulations, suggesting an important role for the meson cloud of the Lambda*(1405) or a need for more exotic interpolating fields.
Book Synopsis Baryon Spectroscopy in Lattice QCD. by :
Download or read book Baryon Spectroscopy in Lattice QCD. written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We review recent developments in the study of excited baryon spectroscopy in lattice QCD. After introducing the basic methods used to extract masses from correlation functions, we discuss various interpolating fields and lattice actions commonly used in the literature. We present a survey of results of recent calculations of excited baryons in quenched QCD, and outline possible future directions in the study of baryon spectra.
Book Synopsis Excited Baryon Spectrum from Lattice QCD. by : Frank Lee
Download or read book Excited Baryon Spectrum from Lattice QCD. written by Frank Lee and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We report lattice calculations of the low-lying baryon mass spectrum, with an emphasis on the introduction of two new techniques. One is the constrained fitting method based on Bayesian statistics which allows reliable extraction of excited states. The other is the use of the overlap fermion action which preserves exact chiral symmetry of QCD on the lattice and allows us to reach deep down into the chiral regime (our pion mass is as low as 180 MeV) where interesting chiral dynamics are exposed. One example is the elusive Roper state N(1440)1/2+ which shows up naturally as the 1st-excited state of the nucleon from the standard interpolating field. Together with other baryons, our preliminary results indicate that the level-ordering of the low-lying baryon states on the lattice is largely consistent with experiment and with that expected from meson-exchange quark models.
Book Synopsis Lattice QCD Determination of Patterns of Excited Baryon States by :
Download or read book Lattice QCD Determination of Patterns of Excited Baryon States written by and published by . This book was released on 2007 with total page 74504 pages. Available in PDF, EPUB and Kindle. Book excerpt: Energies for excited isospin I = 1/2 and I = 3/2 states that include the nucleon and Delta families of baryons are computed using quenched, anisotropic lattices. Baryon interpolating field operators that are used include nonlocal operators that provide G2 irreducible representations of the octahedral group. The decomposition of spin 5/2 or higher spin states is realized for the first time in a lattice QCD calculation. We observe patterns of degenerate energies in the irreducible representations of the octahedral group that correspond to the subduction of the continuum spin 5/2 or higher. The overall pattern of low-lying excited states corresponds well to the pattern of physical states subduced to the irreducible representations of the octahedral group.
Book Synopsis Excited State Baryon Spectroscopy from Lattice QCD. by :
Download or read book Excited State Baryon Spectroscopy from Lattice QCD. written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Structure of Nucleon Excited States from Lattice QCD by : Finn M. Stokes
Download or read book Structure of Nucleon Excited States from Lattice QCD written by Finn M. Stokes and published by Springer Nature. This book was released on 2019-08-20 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum Chromodynamics (QCD) describes the interactions between elementary quarks and gluons as they compose the nucleons at the heart of atomic structure. The interactions give rise to complexity that can only be examined via numerical simulations on supercomputers. This work provides an introduction to the numerical simulations of lattice QCD and establishes new formalisms relevant to understanding the structure of nucleons and their excited states. The research opens with an examination of the non-trivial QCD vacuum and the emergence of “centre domains.” The focus then turns to establishing a novel Parity-Expanded Variational Analysis (PEVA) technique solving the important problem of isolating baryon states moving with finite momentum. This seminal work provides a foundation for future calculations of baryon properties. Implementation of the PEVA formalism discloses important systematic errors in conventional calculations and reveals the structure of nucleon excited states from the first principles of QCD for the first time.
Book Synopsis Excited Baryons and Chiral Symmetry Breaking of QCD. by :
Download or read book Excited Baryons and Chiral Symmetry Breaking of QCD. written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: N* masses in the spin-1/2 and spin-3/2 sectors are computed using two non-perturbative methods: lattice QCD and QCD sum rules. States with both positive and negative parity are isolated via parity projection methods. The basic pattern of the mass splittings is consistent with experiments. The mass splitting within the same parity pair is directly linked to the chiral symmetry breaking QCD.
Book Synopsis Baryon Resonances and Pentaquarks on the Lattice by :
Download or read book Baryon Resonances and Pentaquarks on the Lattice written by and published by . This book was released on 2005 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: We review recent progress in computing excited baryons and pentaquarks in lattice QCD.
Book Synopsis Baryon Spectroscopy and Resonances by :
Download or read book Baryon Spectroscopy and Resonances written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A short review of current efforts to determine the highly excited state spectrum of QCD, and in particular baryons, using lattice QCD techniques is presented. The determination of the highly excited spectrum of QCD is a major theoretical and experimental challenge. The experimental investigation of the excited baryon spectrum has been a long-standing element of the hadronic-physics program, an important component of which is the search for so-called 'missing resonances', baryonic states predicted by the quark model based on three constituent quarks but which have not yet been observed experimentally. Should such states not be found, it may indicate that the baryon spectrum can be modeled with fewer effective degrees of freedom, such as in quark-diquark models. In the past decade, there has been an extensive program to collect data on electromagnetic production of one and two mesons at Jefferson Lab, MIT-Bates, LEGS, MAMI, ELSA, and GRAAL. To analyze these data, and thereby refine our knowledge of the baryon spectrum, a variety of physics analysis models have been developed at Bonn, George Washington University, Jefferson Laboratory and Mainz. To provide a theoretical determination and interpretation of the spectrum, ab initio computations within lattice QCD have been used. Historically, the calculation of the masses of the lowest-lying states, for both baryons and mesons, has been a benchmark calculation of this discretized, finite-volume computational approach, where the aim is well-understood control over the various systematic errors that enter into a calculation; for a recent review. However, there is now increasing effort aimed at calculating the excited states of the theory, with several groups presenting investigations of the low-lying excited baryon spectrum, using a variety of discretizations, numbers of quark flavors, interpolating operators, and fitting methodologies. Some aspects of these calculations remain unresolved and are the subject of intense effort, notably the ordering of the Roper resonance in the low-lying Nucleon spectrum.
Book Synopsis Excited Baryons in Holographic QCD. by :
Download or read book Excited Baryons in Holographic QCD. written by and published by . This book was released on 2011 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The light-front holographic QCD approach is used to describe baryon spectroscopy and the systematics of nucleon transition form factors. Baryon spectroscopy and the excitation dynamics of nucleon resonances encoded in the nucleon transition form factors can provide fundamental insight into the strong-coupling dynamics of QCD. The transition from the hard-scattering perturbative domain to the non-perturbative region is sensitive to the detailed dynamics of confined quarks and gluons. Computations of such phenomena from first principles in QCD are clearly very challenging. The most successful theoretical approach thus far has been to quantize QCD on discrete lattices in Euclidean space-time; however, dynamical observables in Minkowski space-time, such as the time-like hadronic form factors are not amenable to Euclidean numerical lattice computations.
Book Synopsis Excited Baryons and Chiral Symmetry Breaking of QCD. by : F. X. Lee
Download or read book Excited Baryons and Chiral Symmetry Breaking of QCD. written by F. X. Lee and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: N* masses in the spin-1/2 and spin-3/2 sectors are computed using two non-perturbative methods: lattice QCD and QCD sum rules. States with both positive and negative parity are isolated via parity projection methods. The basic pattern of the mass splittings is consistent with experiments. The mass splitting within the same parity pair is directly linked to the chiral symmetry breaking QCD.
Book Synopsis Baryon Spin-flavor Structure from an Analysis of Lattice QCD Results of the Baryon Spectrum by :
Download or read book Baryon Spin-flavor Structure from an Analysis of Lattice QCD Results of the Baryon Spectrum written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The excited baryon masses are analyzed in the framework of the 1/Nc expansion using the available physical masses and also the masses obtained in lattice QCD for different quark masses. The baryon states are organized into irreducible representations of SU(6) x O(3), where the [56,lP=0] ground state and excited baryons, and the [56,2+] and [70}},1-] excited states are analyzed. The analyses are carried out to order O(1/Nc) and first order in the quark masses. The issue of state identifications is discussed. Numerous parameter independent mass relations result at those orders, among them the well known Gell-Mann-Okubo and Equal Spacing relations, as well as additional relations involving baryons with different spins. It is observed that such relations are satisfied at the expected level of precision. The main conclusion of the analysis is that qualitatively the dominant physical effects are similar for the physical and the lattice QCD baryons.
Book Synopsis Excited-state Spectroscopy of Triply-bottom Baryons from Lattice QCD. by :
Download or read book Excited-state Spectroscopy of Triply-bottom Baryons from Lattice QCD. written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The spectrum of baryons containing three b quarks is calculated in nonperturbative QCD, using the lattice regularization. The energies of ten excited bbb states with J{sup P} = 1/2, 3/2+, 5/2+, 7/2+, 1/2−, and 3/2− are determined with high precision. A domain-wall action is used for the up-, down- and strange quarks, and the bottom quarks are implemented with NRQCD. The computations are done at lattice spacings of a H"0.11 fm and a H"0.08 fm, and the results demonstrate the improvement of rotational symmetry as a is reduced. A large lattice volume of (2.7 fm)3 is used, and extrapolations of the bbb spectrum to realistic values of the light sea-quark masses are performed. All spin-dependent energy splittings are resolved with total uncertainties of order 1 MeV, and the dependence of these splittings on the couplings in the NRQCD action is analyzed.
Book Synopsis Excited Baryons from the FLIC Fermion Action by :
Download or read book Excited Baryons from the FLIC Fermion Action written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Masses of positive and negative parity excited nucleons and hyperons are calculated in quenched lattice QCD using an order (a2) improved gluon action and a fat-link clover fermion action in which only the irrelevant operators are constructed with fat links. The results are in agreement with earlier N* simulations with improved actions, and exhibit a clear mass splitting between the nucleon and its parity partner, as well as a small mass splitting between the low-lying J{sup P}=1/2−N* states. Study of different Lambda interpolating fields suggests a similar splitting between the lowest two 1/2−Lambda* states, although the empirical mass suppression of the Lambda*(1405) is not seen.
Book Synopsis Excited-state Spectroscopy of Singly, Doubly and Triply-charmed Baryons from Lattice QCD. by :
Download or read book Excited-state Spectroscopy of Singly, Doubly and Triply-charmed Baryons from Lattice QCD. written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Spectroscopy of Doubly Charmed Baryons from Lattice QCD. by :
Download or read book Spectroscopy of Doubly Charmed Baryons from Lattice QCD. written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This study presents the ground and excited state spectra of doubly charmed baryons from lattice QCD with dynamical quark fields. Calculations are performed on anisotropic lattices of size 163 × 128, with inverse spacing in temporal direction at−1=5.67(4) GeV and with a pion mass of about 390 MeV. A large set of baryonic operators that respect the symmetries of the lattice yet which retain a memory of their continuum analogues are used. These operators transform as irreducible representations of SU(3)F symmetry for flavor, SU(4) symmetry for Dirac spins of quarks and O(3) for spatial symmetry. The distillation method is utilized to generate baryon correlation functions which are analyzed using the variational fitting method to extract excited states. The lattice spectra obtained have baryonic states with well-defined total spins up to 7/2 and the pattern of low-lying states does not support the diquark picture for doubly charmed baryons. On the contrary the calculated spectra are remarkably similar to the expectations from models with an SU(6)×O(3) symmetry. Various spin-dependent energy splittings between the extracted states are also evaluated.
Book Synopsis Baryon Spectroscopy and Operator Construction in Lattice QCD. by : R. Edwards
Download or read book Baryon Spectroscopy and Operator Construction in Lattice QCD. written by R. Edwards and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This talk describes progress at understanding the properties of the nucleon and its excitations from lattice QCD. I begin with a review of recent lattice results for the lowest-lying states of the excited baryon spectrum. The need to approach physical values of the light quark masses is emphasized, enabling the effects of the pion cloud to be revealed. I then outline the development of techniques that will enable the extraction of the masses of the higher resonances. I will describe how such calculations provide insight into the structure of the hadrons, and enable comparison both with experiment, and with QCD-inspired pictures of hadron structure, such as calculations in the limit of large N{sub c}.
