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Search Results: 1 - 10 of 401293 matches for " M. Boglione "
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Which scalar meson is the glue-state ?
M. Boglione
Physics , 1996,
Abstract: Preliminary results of a work in collaboration with M.R. Pennington are presented. Extending a scheme introduced by Tornqvist, we investigate a dynamical model in which the spectrum of scalar mesons can be derived, with the aim of locating the lightest glue-state. Adding hadronic interaction contributions to the bare propagator, to `dress' the bare quark-model $q \overline q$ states, we are able to write the amplitudes and the phase shifts in the approximation in which scalar resonances decay only into two pseudoscalar channels. The fit of these quantities to experimental data gives a satisfactory understanding of how hadronic interactions modify the underlying `bare' spectrum. In particular, we examine the case in which a glue-state is introduced into the model.
Semi-inclusive hadron-hadron transverse spin asymmetries and their implication for polarized DIS
M. Boglione,E. Leader
Physics , 2000,
Abstract: We discuss a possible explanation of the 25 year old mystery of the large transverse spin asymmetries found in many semi-inclusive hadron-hadron reactions. We obtain the first reliable information about the transverse polarized quark densities Delta_T q(x) and we find surprising implications for the usual, longitudinal, polarized DIS. The plan of the presentation is as follows: 1) A brief reminder about the internal structure of the nucleon. 2) The transverse asymmetries. 3) Why it is so difficult to explain the asymmetries. 4) Failure and then success using a new soft mechanism. 5) implications for polarized DIS.
Reassessment of the Collins Mechanism for Single-spin Asymmetries and the behavior of Delta d(x) at large x
M. Boglione,E. Leader
Physics , 1999, DOI: 10.1103/PhysRevD.61.114001
Abstract: It is shown that the Collins mechanism explanation of the transverse single-spin asymmetries in p^{\uparrow} p -> \pi X leads to a transversely polarized d quark density Delta_T d(x) which violates the Soffer bound when one uses several standard forms for the longitudinally polarized d quark density Delta d(x) obtained from polarized deep inelastic scattering. Imposition of the Soffer bound with these Delta d(x) yields results in hopeless disagreement with the data. Remarkably, imposition of the Soffer bound, but using parametrizations of Delta d(x) that respect the PQCD condition Delta q(x) / q(x) -> 1 as x -> 1, leads to an excellent fit to most of the data. The implications for the polarized DIS neutron longitudinal asymmetry A_1^n at large x are dramatic.
Chiral poles and zeros and the role of the left hand cut
M. Boglione,M. R. Pennington
Physics , 1996,
Abstract: It has been recently claimed that the Inverse Amplitude Method provides a reliable unitarisation of Chiral Perturbation Theory allowing resonance poles to be accurately uncovered. We illustrate the sensitivity of these claims to the treatment of the Adler zero and to assumptions about the left hand cut (and hence about the underlying exchange forces). Previously favoured methods are shown to mistreat the Adler zeros and violate crossing symmetry casting doubt on the precision of their phenomenology. A more reliable solution is proposed.
Unquenching the scalar glueball
M. Boglione,M. R. Pennington
Physics , 1997, DOI: 10.1103/PhysRevLett.79.1998
Abstract: Computations in the quenched approximation on the lattice predict the lightest glueball to be a scalar in the 1.5-1.8 GeV region. Here we calculate the dynamical effect the coupling to two pseudoscalars has on the mass, width and decay pattern of such a scalar glueball. These hadronic interactions allow mixing with the $q \overline q$ scalar nonet, which is largely fixed by the well-established K_0^*(1430). This non-perturbative mixing means that, if the pure gluestate has a width to two pseudoscalar channels of ~100 MeV as predicted on the lattice, the resulting hadron has a width to these channels of only ~30 MeV with a large eta-eta component. Experimental results need to be reanalyzed in the light of these predictions to decide if either the f_0(1500) or an f_0(1710) coincides with this dressed glueball.
Dressing the Scalar Glueball
M. Boglione,M. R. Pennington
Physics , 1997, DOI: 10.1063/1.55951
Abstract: The hadronic dressing of the ten lightest scalar mesons, the $q{\bar q}$ nonet and a glueball, is discussed.
Comment on the "Coupling Constant and Quark Loop Expansion for Corrections to the Valence Appeoximation" by Lee and Weingarten
M. Boglione,M. R. Pennington
Physics , 1999, DOI: 10.1103/PhysRevD.62.038501
Abstract: Lee and Weingarten have recently criticized our calculation of quarkonium and glueball scalars as being "incomplete" and "incorrect". Here we explain the relation of our calculations to full QCD.
Determination of Radiative Widths of Scalar Mesons from Experimental Results on $γγ\toππ$
M. Boglione,M. R. Pennington
Physics , 1998, DOI: 10.1007/s100520050509
Abstract: The scalar mesons in the 1 GeV region constitute the Higgs sector of the strong interactions. They are responsible for the masses of all light flavour hadrons. However, the composition of these scalar states is far from clear, despite decades of experimental effort. The two photon couplings of the $f_{0}$'s are a guide to their structure. Two photon results from Mark II, Crystal Ball and CELLO prompt a new Amplitude Analysis of $\gamma\gamma\to\pi^+\pi^-$, $\pi^0\pi^0$ cross-sections. Despite their currently limited angular coverage and lack of polarized photons, we use a methodology that provides the nearest one can presently achieve to a model-independent partial wave separation. We find two distinct classes of solutions. Both have very similar two photon couplings for the $f_0(980)$ and $f_0(400-1200)$. Hopefully these definitive results will be a spur to dynamical calculations that will bring us a better understanding of these important states.
Azimuthal Spin Asymmetries in Semi-Inclusive Production from Positron-Proton Scattering
M. Boglione,P. J. Mulders
Physics , 2000, DOI: 10.1016/S0370-2693(00)00285-9
Abstract: The recent measurements of azimuthal single spin asymmetries by the HERMES collaboration at DESY may shed some light on presently unknown fragmentation and distribution functions. We present a study of such functions and give some estimates of weighted integrals directly related to those measurements.
Perspectives in Polarized Leptoproduction
P. J. Mulders,M. Boglione
Physics , 1999, DOI: 10.1016/S0375-9474(00)00034-8
Abstract: We discuss specific observables that can be measured in deep inelastic leptoproduction in the case of 1-particle inclusive measurements, namely azimuthal asymmetries and power-suppressed (higher twist) corrections. These quantities contain information on the intrinsic transverse momentum of partons, with close connection to the gluon dynamics in hadrons.
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