Search results for "Quark"
showing 10 items of 2905 documents
Light flavor and heavy quark spin symmetry in heavy meson molecules
2012
We propose an effective field theory incorporating light SU(3)-flavor and heavy quark spin symmetry to describe charmed meson-antimeson bound states. At lowest order the effective field theory entails a remarkable simplification: it only involves contact range interactions among the heavy meson and antimeson fields. We show that the isospin violating decays of the X(3872) can be used to constrain the interaction between the D and a (D) over bar* mesons in the isovector channel. As a consequence, we can rule out the existence of an isovector partner of the X(3872). If we additionally assume that the X(3915) and Y(4140) are D*(D) over bar* and D*(s)(D) over bar*(s) molecular states, we can de…
Consequences of heavy-quark symmetries for hadronic molecules
2013
Among the newly observed structures in the heavy-quarkonium mass region, some have been proposed to be hadronic molecules. We investigate the consequences of heavy- quark flavor symmetry on these heavy meson hadronic molecules. The symmetry allows us to predict new hadronic molecules on one hand, and test the hadronic molecular assumption of the observed structures on the other hand. We explore the consequences of the flavor symmetry assuming the X(3872) and Z(b)(10 610) as an isoscalar D (D) over bar* and isovector B (B) over bar* hadronic molecule, respectively. A series of hadronic molecules composed of heavy mesons are predicted. In particular, there is an isoscalar 1(++) B (B) over bar…
Charmed and strange baryon resonances with heavy-quark spin symmetry
2012
We study charmed and strange baryon resonances that are generated dynamically by a unitary baryon-meson coupled-channel model which incorporates heavy-quark spin symmetry. This is accomplished by extending the SU(3) Weinberg-Tomozawa chiral Lagrangian to SU(8) spin-flavor symmetry plus a suitable symmetry breaking. The model produces resonances with negative parity from s-wave interaction of pseudoscalar and vector mesons with $1/2^+$ and $3/2^+$ baryons. Resonances in all the isospin, spin, and strange sectors with one, two, and three charm units are studied. Our results are compared with experimental data from several facilities, such as the CLEO, Belle or BaBar Collaborations, as well as…
Tensor charges and form factors of SU(3) baryons in the self-consistent SU(3) chiral quark-soliton model
2010
We investigate the tensor form factors of the baryon octet within the framework of the chiral quark-soliton model, emphasizing those of the nucleon, taking linear 1/N_c rotational as well as linear m_s corrections into account, and applying the symmetry-conserving quantization. We explicitly calculate the tensor form factors H_{T}^{q}(Q^{2}) corresponding to the generalized parton distributions H_{T}(x,\xi,t). The tensor form factors are obtained for the momentum transfer up to Q^{2}\leq1\,\mathrm{GeV}^{2} and at a renormalization scale of 0.36\,\mathrm{GeV}^{2}. We find for the tensor charges \delta u=1.08, \delta d=-0.32, \delta s=-0.01 and discuss their physical consequences, comparing t…
Triply heavy baryons and heavy quark spin symmetry
2011
We study the semileptonic $b\to c$ decays of the lowest-lying triply-heavy baryons made from $b$ and $c$ quarks in the limit $m_b, m_c \gg \Lambda_\mathrm{QCD}$ and close to the zero recoil point. The separate heavy quark spin symmetries strongly constrain the matrix elements, leading to single form factors for $ccb\to ccc$, $bbc\to ccb$, and $bbb\to bbc$ baryon decays. We also study the effects on these systems of using a $Y$-shaped confinement potential, as suggested by lattice QCD results for the interaction between three static quarks.
Nucleon structure from Lattice QCD using a nearly physical pion mass
2014
We report the first Lattice QCD calculation using the almost physical pion mass mpi=149 MeV that agrees with experiment for four fundamental isovector observables characterizing the gross structure of the nucleon: the Dirac and Pauli radii, the magnetic moment, and the quark momentum fraction. The key to this success is the combination of using a nearly physical pion mass and excluding the contributions of excited states. An analogous calculation of the nucleon axial charge governing beta decay has inconsistencies indicating a source of bias at low pion masses not present for the other observables and yields a result that disagrees with experiment.
Are there compact heavy four-quark bound states?
2007
6 pages, 1 figure.-- PACS nrs.: 12.39.Jh; 14.40.Lb.-- ISI Article Identifier: 000251327200050.-- ArXiv pre-print available at: http://arxiv.org/abs/0710.2516
Stability of multiquarks in a simple string model
2007
A simple string model inspired by the strong-coupling regime of Quantum ChromoDynamics is used as a potential for studying the spectrum of multiquark systems with two quarks and two antiquarks, with a careful treatment of the four-body problem. It is found that the ground state is stable, lying below the threshold for dissociation into two isolated mesons.
Electromagnetic structure of few-nucleon ground states
2015
Experimental form factors of the hydrogen and helium isotopes, extracted from an up-to-date global analysis of cross sections and polarization observables measured in elastic electron scattering from these systems, are compared to predictions obtained in three different theoretical approaches: the first is based on realistic interactions and currents, including relativistic corrections (labeled as the conventional approach); the second relies on a chiral effective field theory description of the strong and electromagnetic interactions in nuclei (labeled $\chi$EFT); the third utilizes a fully relativistic treatment of nuclear dynamics as implemented in the covariant spectator theory (labeled…
Spectroscopy of doubly charmed baryons
2004
We study the mass spectrum of baryons with two and three charmed quarks. For double charm baryons the spin splitting is found to be smaller than standard quark-model potential predictions. This splitting is not influenced either by the particular form of the confining potential or by the regularization taken for the contact term of the spin-spin potential. We consistently predict the spectra for triply charmed baryons.