KEY TOPICS AND OBJECTIVES:

Physics:

THEORETICAL Methods:
  Objectives:

to Clarify:


QUARKONIUM  SYSTEM

The discovery of the J/psi dates back to 1974. The top threshold production ('toponium') will be eventually measured at next linear colliders, hopefully in the next decade. During all these yearsthe heavy quarkonia will remain a challenging objective for QCD. These systems open a privileged window into the QCD world: being multiscale systems they probe all the energy regimes, from the hard region, where an expansion in the coupling constant at the hard scale is legitimate, to the low energy region, where such an expansion is no longer viable and nonperturbative effects dominate. On the other side, the  multiscale-nature of the bound state together with the nonperturbative nature of the low energy region, made extremely ambitious the task to relate  the properties of these systems to QCD.


THEORETICAL DEVELOPMENTS

The  success of the early phenomenological potential models was at that time overwhelming and hinted to the confining properties of infrared QCD.

By exploiting the nonrelativistic nature of these systems a great degree of simplification may be achieved. In the last decade QCD nonrelativistic effective field theories have been quite successful in providing the appropriate tools to relate quarkonium physics to the fundamental parameters of QCD and to unveil the QCD dynamics. NRQCD predictions of heavy quarkonium production and decays made a relevant step forward on this way. The lattice implementation of such effective theories has been partially carried out and many further results are soon expected.

Looking back at the two past decades, we see that phenomenological models were successful, as they were compared to a limited set of data, with experimental errors in many cases ranging from 15% to 30%. Various potential models were able to fit all psi and upsilon radial excitations, while residual problems remained at the level of spin splittings,  decays and transition rates.

An increase of coordination between theoretical and experimental efforts would speed up  the progress in this field in the near future.


EXPERIMENTS:

Many experiments  have been completed, many data are available to be analysed, new experiments are currently in consideration or in construction.

In the 90's:

In this decade: At the end of this decade:



QUARKONIUM WORKING GROUP PROGRAM

We feel that it is the right time to intensify the exchange of ideas and information between experimentalists and theorists in quarkonium physics. We see a new opportunity in the field. We have new and more sophisticated theoretical tools that may allow us  to relate our measurements more directly to QCD.
Thus we propose to start a "Quarkonium working group".


AIMS:

The quarkonium working group is meant to:

An exhaustive list of STANDING PUZZLES and OPEN ISSUES and CONCRETE OBJECTIVES will be discussed and established at the first working group meeting via an open discussion between theoreticians and experimentalists. (At the end in appendix we just list some preliminary suggestions, we warmly invite the participants to add appropriate items).


PRACTICALITIES

On an adequate response to this proposal, we plan to create a web page with all the appropriate information, a discussion forum and organize a first meeting in which aims and priorities, as well as the working line will be carefully discussed between experimentalists and theoreticians.
An intermediate step may entail asking for (national or international) funds in support of the working group. Output of the work will be  the production of scientific reports summarizing the achieved results.


TENTATIVE LIST OF EXPERIMENTAL GROUPS TO BE CONTACTED:
 



APPENDIX (preliminary list of open issues and objectives)


OPEN ISSUES and OBJECTIVES

There are currently many open issues and puzzles, on which we would
like to focus, among them: