Search results for "baryon"
showing 10 items of 759 documents
ElectromagneticN→N*(1535)transition in the relativistic constituent-quark model
1990
We study a light-cone model of the nucleon and the ${S}_{11}(1535)$ resonance which provides a relativistic generalization of the constituent-quark model in the nonperturbative low-${Q}^{2}$ regime. The two parameters of the model, namely, the size parameter $\ensuremath{\alpha}$ and the constituent-quark mass ${m}_{q}\ensuremath{\approx}300$ MeV, are fixed by the axial form factor. We find good agreement for the electromagnetic form factors of the nucleon up to ${Q}^{2}\ensuremath{\approx}1\ensuremath{-}2$ Ge${\mathrm{V}}^{2}$. All static properties of the nucleon, except for the neutron charge radius, are reproduced within 10%. In addition, we show that the electromagnetic current of the …
Low energy structure of the nucleon from chiral effective field theory
2014
We present some updated results regarding the scalar and electromagnetic structure of the nucleon obtained by the relativistic formulation of chiral effective field theory with baryons. We compare them with previous determinations available in the literature, and show their relevance for searches of physics beyond the standard model in the low energy frontier. An accurate knowledge of the structure of the nucleon is important to improve our understanding of the funda- mental interactions and provide theoretical estimations of some important quantities with a small uncertainty. This is specially relevant for experiential searches of physics be- yond the standard model in the low energy front…
Inelastic photoproduction
1995
Abstract Inelastic photoproduction of J Ψ particles at high energies is one of the processes to determine the gluon distribution in the nucleon. We have calculated the QCD radiative corrections to the color-singlet model of this reaction. They are large at moderate photon energies, but decrease with increasing energies. The cross section and the J Ψ energy spectrum are compared with the available fixed-target photoproduction data and predictions are given for the HERA energy range.
Transverse spectra of hadrons at RHIC
2002
We present results on spectra of pions, kaons and (anti)protons from a study of heavy ion collisions using the perturbative QCD + saturation model to calculate the production of initial (transverse) energy and baryon number followed by a hydrodynamic description of the expansion of produced matter. In particular, we study how the hadron spectra and multiplicities depend on the decoupling temperature $\Tdec$ when the low temperature phase contains all hadrons and and hadron resonances with mass below 2 GeV. We show that the spectra and multiplicities of pions, kaons and (anti)protons measured at RHIC in central Au+Au collisions with $\sqrt s=130$ GeV can be obtained with a single decoupling …
Measurement of the relative branching fractions ofB¯→D/D*/D**l−ν¯ldecays in events with a fully reconstructedBmeson
2007
We determine the relative branching fractions of semileptonic B decays to charmed final states. The measurement is performed on the recoil from a fully reconstructed B meson in a sample of 362×106 BB pairs collected at the Υ(4S) resonance with the BABAR detector. A simultaneous fit to a set of discriminating variables is performed on a sample of B→DX-ν decays to determine the contributions from the different channels. We measure Γ(B-→D-ν)/Γ(B-→DX-ν)=0.227±0. 014±0.016, Γ(B-→D*-ν)/Γ(B-→DX- ν)=0.582±0.018±0.030, and Γ(B-→D **-ν)/Γ(B-→DX-ν)=0.191±0. 013±0.019 for the charged B sample, and Γ(B0→D- ν)/Γ(B0→DX-ν)=0.215±0.016±0. 013, Γ(B0→D*-ν)/Γ(B0→DX- ν)=0.537±0.031±0.036, and Γ(B0→ D**-ν)/Γ(B0→…
Nucleon andΔ(1232)form factors at low momentum transfer and small pion masses
2012
An expansion of the electromagnetic form factors of the nucleon and $\ensuremath{\Delta}(1232)$ in small momentum transfer and pion mass is performed in a manifestly covariant EFT framework consistent with chiral symmetry and analyticity. We present the expressions for the nucleon and $\ensuremath{\Delta}(1232)$ electromagnetic form factors, charge radii, and electromagnetic moments in the framework of $SU(2)$ baryon chiral perturbation theory, with nucleon and $\ensuremath{\Delta}$-isobar degrees of freedom, to next-to-leading order. Motivated by the results for the proton electric radius obtained from the muonic-hydrogen atom and electron-scattering process, we extract values for the seco…
Two-loop Anomalous Dimensions of Heavy Baryon Currents in Heavy Quark Effective Theory
1996
We present results on the two-loop anomalous dimensions of the heavy baryon HQET currents $J=(q^TC\Gamma\tau q)\Gamma'Q$ with arbitrary Dirac matrices $\Gamma$ and $\Gamma'$. From our general result we obtain the two-loop anomalous dimensions for currents with quantum numbers of the ground state heavy baryons $\Lambda_Q$, $\Sigma_Q$ and $\Sigma_Q^*$. As a by-product of our calculation and as an additional check we rederive the known two-loop anomalous dimensions of mesonic scalar, pseudoscalar, vector, axial vector and tensor currents $(J=\bar q\Gamma q)$ in massless QCD as well as in HQET.
Constituent-quark model description of triply heavy-baryon nonperturbative lattice QCD data
2015
This paper provides results for the spectra of triply charmed and bottom baryons based on a constituent quark model approach. We take advantage of the assumption that potential models are expected to describe triply heavy baryons to a similar degree of accuracy as the successful results obtained in the charmonium and bottomonium sectors. The high precision calculation of the ground state and positive and negative parity excited states recently reported by nonperturbative lattice QCD provides us with a unique opportunity to confront model predictions with data. This comparison may also help to build a bridge between two difficult to reconcile lattice QCD results, namely, the lattice SU(3) QC…
On the Delta-nucleon and rho-pi splittings: A QCD-inspired look in free hadrons versus nuclei
1997
Relationships between mass intervals for free hadrons and in nuclei are studied in two theoretical approaches inspired by QCD: naive quark model and skyrmion model, taking one example each from mesons and baryons, that of pi-rho splitting in mesons, and nucleon-Delta splitting in baryons. Possible deconfinement effects in nuclei are examined.
Heavy-hadron interactions from Lattice QCD
2018
I review recent progress in heavy hadron spectroscopy and from ab-initio Lattice QCD calculations.After motivating lattice calculations for heavy-hadrons by contrasting recent LHCb results charmed and doubly-charmed baryons with lattice predictions, selected resultsfrom scattering calculations for heavy-light mesons and for charmonia are presented.I close with a discussion of recent Lattice QCD predictions of explicitlyexotic doubly-heavy states.