Sergio Scopetta has been mainly working in inclusive
and semi - inclusive polarized and unpolarized deep inelastic lepton 
scattering off the nucleon. The aim is to study structure and fragmentation
functions relevant to the above processes and analyze the phenomenological
implications of the results.
A theoretical framework which relates the light cone description of 
the above processes to a laboratory description in terms of non relativistic 
and relativistic quark models of the nucleon has been developed. 
In order to establish the connection between the structure and 
fragmentation functions at the hadronic scale and the observations, 
a renormalization group evolution to real experimental conditions must 
be also developed.
This procedure allows an estimate of the structure functions 
and of the size of the cross sections which have been planned to be measured. 
As a first step, we have evaluated the quantities which appear at 
leading twist in the cross sections. We have used the well known
f_1 and g_1 parton distributions to estimate the validity of the model 
and thereafter predict the unmeasured ones. In particular
we have done a thorough quark model analysis of the physics of the 
chirality-odd structure function h_1 (using Jaffe's notation), not 
accessible in the usual inclusive experiments, investigating its difference 
from the longitudinal distribution g_1, mainly due to QCD evolution, 
which has been studied up to Next to Leading Order [1,2].
As a second step, we are planning to include gluon interactions in our
procedure, which should allow us to extend the technique to higher twist
contributions and to get a full investigation of the observables involved
in the process.
At the same time, an attempt of unifying the description of constituent
and current quarks is being developed. A very promising accord with the
DIS data of the F_2 structure functions has been obtained by 
considering the constituent quark as a composite object, and therefore
evaluating the parton distributions through a convolution between 
constituent quark momentum distributions and constituent quark 
structure functions [3].
Moreover, some older work relevant to the network has been completed [4,5]. 

References

[1] S. Scopetta and V. Vento, "A quark model analysis of the transversity
    distribution", hep-ph/9706413, submitted to Phys. Lett. B.
[2] S. Scopetta and V. Vento, "A quark model analysis of the transversity
    distribution: Next to leading order evolution", hep-ph/9707250.
[3] S. Scopetta, V. Vento and M. Traini, "Towards an unified picture of 
    constituent and current quarks", hep-ph/9708262, 
    submitted to Phys. Lett. B.
[4] A.I. L'vov, S. Scopetta, D. Drechsel and S. Scherer, "Polarization
    phenomena in small angle photoprduction of e+ e- Pairs and the 
    Gerasimov-Drell-Hearn Sum Rule", nucl-th/9707006, Phys. Rev. C,
    to appear.
[5] C. Ciofi degli Atti, S. Scopetta, A.Yu. Umnikov and L.P. Kaptari,
    "Spin structure functions of nucleons and nuclei", invited talk
    at the Conference "Perspectives in Hadron Physics", Trieste, May 1997,
    to appear in the Proceedings.





Rapport du group:



-S. Scopetta and V. Vento have started a collaboration regarding the 
measurability of transversity structure function in semi-inclusive and
Drell-Yan processes.

 Preprint: A quark model analysis of the transversity distribution
 IFIC97/29

-M. Rho and V. Vento have continued a collaboration regarding the structure
of proton in relation with the spin problem
 
 Preprint: Color anomaly and flavor singlet axial charge of the proton
 in the Chiral Bag: The Cheshire Cat Revisited. IFIC97/28

- F.Cano, P.Gonzalez, S.Noguera, Desplanques and Silvestre-Brac are looking for
the electromagnetic form factors of the nucleon in a non relativistic quark
model.

- F.Cano, P.Gonzalez,S.Noguera and B.Desplanques(Grenoble) are regarding 
relativistic improvements of the strong and electromagnetic transition 
operators for non relativistic quark models.

Publication: A (p/E) calculation of strong pionic decays of baryons.
F. Cano, P. Gonzalez, B. Desplanques and S. Noguera to be published in 
Z. Phys. A

-J. A. Pe\~narrocha and F.J. Botella, study of ambiguities in the 
determination of the polarization of  \Lambda_b in the cascade process:
\Lambda_b ---> \Lambda J/\Psi ---> N\pi J/\Psi

-J. A Pe\~narrocha, M. Tung and J. Bernabeu: strong corrections in 
polarized t- \bar{t} production starting from e^+-e^- anihilation.

Publication: Analytic O(\alpha_s) results for bottom and top quark
production in e^+-e^- collisions, Nucl. Phys. B470 (1996) 41.