Search results for "Particle physics"
showing 10 items of 6826 documents
Chiral SU(3) Bethe Salpeter Model: Extension to SU(6) and SU(8) Spin-Flavor Symmetries
2008
Consistent SU(6) and SU(8) spin-flavor extensions of the SU(3) flavor Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian are constructed, which incorporate vector meson degrees of freedom. In the charmless sector, the on-shell approximation to the Bethe-Salpeter (BS) approach successfully reproduces previous SU(3) WT results for the lowest-lying s--wave negative parity baryon resonances. It also provides some information on the dynamics of heavier ones and of the lightest d-wave negative parity resonances, as e.g. the Lambda(1520). For charmed baryons the scheme is consistent with heavy quark symmetry, and our preliminary results in the strangeness-less charm C=+1 sector describe the mai…
Open-charm meson spectroscopy
2006
We present a theoretical framework that accounts for the new $D_J$ and $D_{sJ}$ mesons measured in the open-charm sector. These resonances are properly described if considered as a mixture of conventional $P-$wave quark-antiquark states and four-quark components. The narrowest states are basically $P-$wave quark-antiquark mesons, while the dominantly four-quark states are shifted above the corresponding two-meson threshold, being broad resonances. We study the electromagnetic decay widths as basic tools to scrutiny their nature. The proposed explanation incorporates in a natural way the most recently discovered mesons in charmonium spectroscopy.
A Heavy Quark Symmetry Approach to Baryons
2005
We evaluate different properties of baryons with a heavy c or b quark. The use of Heavy Quark Symmetry (HQS) provides with an important simplification of the non relativistic three body problem which can be solved by means of a simple variational approach. This scheme is able to reproduce previous results obtained with more involved Faddeev calculations. The resulting wave functions are parametrized in a simple manner, and can be used to calculate further observables.
Proton Spin in Chiral Quark Models
1997
The spin and flavor fractions of constituent quarks in the proton are obtained from their chiral fluctuations involving Goldstone bosons. SU(3) flavor symmetry breaking suggested by the mass difference between the strange and up, down quarks is included, and this improves the agreement with the data markedly.
Semi-inclusive deep inelastic lepton scattering off complex nuclei
1999
It is shown that in semi-inclusive deep inelastic scattering (DIS) of electrons off a complex nucleus A, the detection, in coincidence with the scattered electron, of a nucleus (A-1) in the ground state, as well as of a nucleon and a nucleus (A-2), also in the ground state, may provide unique information on several long standing problems, such as : i) the nature and the relevance of the final state interaction in DIS; ii) validity of the spectator mechanism in DIS; iii) the medium induced modifications of the nucleon structure function; iv) the origin of the EMC effect.
Relativity and constituent quark structure in model calculations of parton distributions
2004
According to recent studies, Parton Distribution Functions (PDFs) and Generalized Parton Distributions (GPDs) can be evaluated in a Constituent Quark Model (CQM) scenario, considering the constituent quarks as composite objects. In here, a fully covariant model for a system of two particles, together with its non relativistic limit, are used to calculate PDFs and GPDs. The analysis permits to realize that by no means the effects of Relativity can be simulated taking into account the structure of the constituent particles, the two effects being independent and necessary for a proper description of available high energy data in terms of CQM.
STRANGE HADRONS BRIDGE BETWEEN QUARKS AND STARS
2007
Future experimental opportunities for the hypernuclear physics at GSI/FAIR are presented. The HYPHI experiment will investigate exotic hypernuclei which are produced by nuclear collision with stable heavy ion beams and rare isotope beams (RI-beams) at GSI. Thanks to the use of [Formula: see text] beams and the skilful combination of experimental techniques, copious production of double Λ hypernuclei is expected at the PANDA experiment which will enable high precision γ spectroscopy for the first time. Finally a novel method to explore the interaction of antibaryons in nuclei by baryon-antibaryon pair production in antiproton nucleus interactions is outlined.
Dimensionally regularized box and phase-space integrals involving gluons and massive quarks
1999
The basic box and phase space integrals needed to compute at second order the three-jet decay rate of the Z-boson into massive quarks are presented in this paper. Dimensional Regularization is used to regularize the infrared divergences that appear in intermediate steps. Finally, the cancellation of these divergences among the virtual and the real contributions is showed explicitly.
From RHIC to LHC
2007
Measurements of the nuclear modification factor of inclusive yields of $\pi^0$, $p\bar{p}$, non-phtonic electrons and prompt photon measured at RHIC are reviewed. Some of the difficulties arising from interpretation of these measurements such as similarity of the suppression pattern of light and heavy quarks, quarks and gluons, light quarks and prompt photon are discussed. The potential of two-particle and promt photon correlation technique to unravel some of these open questions is presented. An emphasis is given to the influence of partonic transverse momentum on the prompt-photon correlations. The smearing between the trigger photon and back-to-back jet at LHC energy is discussed.
Deeply virtual electroproduction of photons and mesons on the nucleon : leading order amplitudes and power corrections
1999
We estimate the leading order amplitudes for exclusive photon and meson electroproduction reactions at large Q^2 in the valence region in terms of skewed quark distributions. As experimental investigations can currently only be envisaged at moderate values of Q^2, we estimate power corrections due to the intrinsic transverse momentum of the partons in the meson wavefunction and in the nucleon. To this aim the skewed parton distribution formalism is generalized so as to include the parton intrinsic transverse momentum dependence. Furthermore, for the meson electroproduction reactions, we calculate the soft overlap type contributions and compare with the leading order amplitudes. We give firs…