Search results for "Quark"
showing 10 items of 2905 documents
Prediction of hidden charm strange molecular baryon states with heavy quark spin symmetry
2019
We have studied the meson-baryon $S-$wave interaction, using coupled channels, in the isoscalar hidden-charm strange sector and $J^P = 1/2^-,3/2^-$ and $5/2^-$. We impose constraints of heavy quark spin symmetry in the interaction and obtain the non vanishing matrix elements from an extension of the local hidden gauge approach to the charm sector. The ultraviolet divergences are renormalized using the same meson-baryon-loops regulator previously employed in the non-strange hidden charm sector, where a good reproduction of the properties of the newly discovered pentaquark states is obtained. We obtain five states of $1/2^-$, four of $3/2^-$ and one of $5/2^-$, which could be compared in the …
A Closer Study of the Framed Standard Model Yielding Testable New Physics plus a Hidden Sector with Dark Matter Candidates
2018
This closer study of the FSM: [I] retains the earlier results in offering explanation for the existence of three fermion generations, as well as the hierarchical mass and mixing patterns of leptons and quarks; [II] predicts a vector boson $G$ with mass of order TeV which mixes with $\gamma$ and $Z$ of the standard model. The subsequent deviations from the standard mixing scheme are calculable in terms of the $G$ mass. While these deviations for (i) $m_Z - m_W$, (ii) $\Gamma(Z \rightarrow \ell^+ \ell^-)$, and (iii) $\Gamma(Z \rightarrow {\rm hadrons})$ are all within present experimental errors so long as $m_G > 1$ TeV, they should soon be detectable if the $G$ mass is not too much bigger; […
The Hunt for New Physics in the Flavour Sector with up vector-like quarks
2012
We analyse the possible presence of New Physics (NP) in the Flavour Sector and evaluate its potential for solving the tension between the experimental values of $\AJPKs$ and $\BTNu$ with respect to the Standard Model (SM) expectations. Updated model independent analyses, where NP contributions are allowed in Bd - anti-Bd and Bs - anti-Bs transitions, suggest the need of New Physics in the $bd$ sector. A detailed analysis of recent Flavour data is then presented in the framework of a simple extension of the SM, where a $Q=2/3$ vector-like isosinglet quark is added to the spectrum of the SM. Special emphasis is given to the implications of this model for correlations among various measurable …
Resummed jet rates for $e^+e^-$ annihilation into massive quarks
2003
Expressions for Sudakov form factors for heavy quarks are presented. They are used to construct resummed jet rates for up to four jets in $e^+e^-$ annihilation. The coefficients of leading and next-to-leading logarithmic corrections, mandatory for a combination with higher order matrix elements, are evaluated up to second order in $\alpha_s$.
Strangeness production inp�p annihilation at rest and the quark ? diquark structure of nucleons
1988
The importance of approximate isospin selection rules observed inN¯ N annihilation at rest into two strange mesons is emphasized. The selection rules are traced back to a symmetry between amplitudes describing annihilation by the flux of quarks. Presumably the symmetry reflects the symmetry of ¯qq annihilation vertices. The relation of the symmetry to a quark — diquark substructure of the nucleon is discussed.
Long Range Structure of the Nucleon
2010
The long range structure of the nucleon is discussed starting from the old model of a quark bag with a pion cloud (``cloudy bag'') carrying on to the more recent ideas of the parton model of the nucleon. On the basis of the most recent measurements of the form factors at MAMI, JLab and MIT quantitative results for nucleon charge densities are presented within both non-relativistic and relativistic frameworks.
General analysis of weak decay form factors in heavy to heavy and heavy to light baryon transitions
1992
We present a complete analysis of the heavy to heavy and heavy to light baryon semi-leptonic decays in the heavy quark effective theory within the framework of a Bethe-Salpeter (BS) approach and demonstrate the equivalence of this approach to other work in the field. We present in a compact form the baryon BS amplitudes which incorporate the symmetries manifest in the heavy quark limit and which also show clearly the light quark dynamics. A similar form of the BS amplitude is presented for light baryons. Using the BS amplitudes, the heavy to heavy and heavy to light semi-leptonic baryon decays are considered. As expected there is a dramatic reduction in the number of form factors. An advant…
Charm and bottom baryon decays in the Bethe-Salpeter approach: Heavy to heavy semileptonic transitions
1998
Charm and bottom baryons and mesons are studied within the framework of a relativistically covariant 3D reduction of the Bethe-Salpeter equation. We carry out an analysis of semileptonic decays of heavy hadrons within this framework using explicit oscillator-type wave functions where we calculate Isgur-Wise functions, decay rates and asymmetry parameters. Within this model we also study the effect of interactions between the light quarks inside the heavy baryon and how they affect the values of the computed heavy baryon observables. We also elaborate on the role of relativistic effects in the calculation of the heavy baryon Isgur-Wise function.
Low-energy interactions of Nambu-Goldstone bosons with D mesons in covariant chiral perturbation theory
2010
We calculate the scattering lengths of Nambu-Goldstone bosons interacting with D mesons in a covariant formulation of chiral perturbation theory, which satisfies heavy-quark spin symmetry and analytical properties of loop amplitudes. We compare our results with previous studies performed using heavy-meson chiral perturbation theory and show that recoil corrections are sizable in most cases.
Magnetic moments of heavy baryons
2000
6 páginas, 2 figuras, 4 tablas.-- PACS number(s): 12.39.Fe, 12.39.Hg, 14.20.Lq, 14.20.Mr