KEY TOPICS AND OBJECTIVES:
Quarkonium suppression in quark gluon plasma
QCD Effective field theories
Models and Approximations (Phenomenological models of all types, flux tube
and strings, QCD vacuum models,.....)
The present status of experiments (ongoing and planned);
The state of art of the QCD knowledge of the field;
The experimental data and/or the theoretical predictions still missing
which may be a clue to the underlying picture.
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.
The success of the early phenomenological potential models was
at that time overwhelming and hinted to the confining properties of infrared
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
An increase of coordination between theoretical and experimental efforts
would speed up the progress in this field in the near future.
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:
CLEO and LEP produced C=+ charmonia in photon-photon scattering (the search
for eta_b by ALEPH and L3 looks promissing, but further is needed to establish
BES formed new largest samples of J/psi and Psi' in e+ e- annihilation
(and keep going)
E760/E835 formed large samples of ALL charmonia in ppbar annihilations
(but the etac' and h_c candidates found by Crystal Ball and E760 still
lack stronger confirmations)
CDF/D0 studied prompt charmonium and bottomonium production in gluon-gluon
fusion: the unexpected result of these measures has initiated a
effort to put our understanding of QCD on a firmer basis.
NA50 investigated J/psi production in heavy ion collisions , finding signatures
of quark-gluon plasma formation
At the end of this decade:
BaBar and Belle produce large samples of B-->K+charmonium, golden channel
for the study of CP violation, but also viable for searches of etac' and
h_c (photon-photon collisions will also provide information on charmonia)
CDF/D0 will continue the study of polarization vs Pt in charmonium production
Cleo-III will run at upsilons below b threshold, producing new record samples.
Will hopefully search for eta_b and its radial excitations.
Cleo-C and BES will produce new large samples of psi and psi'. Cleo-C will
exploit the excellent performance of its crystal calorimetry, and in the
next years the calorimeter upgrade will improve BES performance.
HERA experiments will study charmonium formation in photon-gluon
HERA-B is studying quarkonia production, including chi_c, in
p-A collisions (of 920 GeV).
RHIC experiments STAR and PHENIX and CERN experiment NA60;
will study the production mechanisms
of heavy quarkonia in heavy ion collisions.
At LHC, experiments Atlas and CMS will challenge the understanding of heavy
quarkonia production in the central region.
LHC-b at CERN and BTeV at Fermilab will allow to test and study the above
mechanisms in the forward region, as well as providing record samples of
B mesons, who frequently decay to ccbar bound states.
ALICE experiment at LHC will further investigate the production mechanisms
of heavy quarkonia in heavy ion collisions.
If GSI antiproton ring is built, a new ppbar charmonium experiment will
produce new high statistic data samples of charmonia.
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".
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).
provide an opportunity for an intense and effective exchange of results
and needs between experimentalists and theorists;
to assess our present QCD knowledge of these systems;
to use these systems to improve the determination of the fundamental parameters
of the standard model;
to define an agenda of future measurements to test our theoretical predictions;
to indicate which experimental data could be a clue to our understanding
of QCD or which theoretical predictions are key to future and ongoing experiments;
to make these information useful and available to groups working at the
boundary of this physics.
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:
Past experiments: LEP, CLEO,E760/835 (e+e- annihilations, ppbar
annihilations, photon-photon fusion, charm photoproduction)
Present: BES, BABAR, BELLE, CDF, D0, CLEO-III, ZEUS, H1, HERMES, Hera-B,
NA50/NA60 (e+e- annihilations,
gluon-gluon, photon-photon fusion, photon-gluon fusion)
Future: CLEO-C,BTEV,LHC experiments, RHIC experiments, + somebody from
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:
Factorization in quarkonium production
Polarization in J/psi and Psi' polarization vs Pt in gluon-gluon fusion.
The role of the color-octet contributions in the light of J/Psi production
in photon-gluon fusion at HERA.
Psi vs Psi' decay dynamics: the '15%' rule.
Charmonium formation in ppbar annihilation: the large ppbar-ccbar coupling
and its helicity structure lacks a theoretical explanation.
Resummation issues at the endpoint in decays pr for small p_t in production.
Color octet role in exclusive decays.
Spectrum of heavy quarkonia (bbbar,ccbar,B_c)
versus heavy hybrids and glueballs.
J/psi in nuclear matter , color transparency , and so on.
Multipolarity of radiative decays between charmonia: this needs a consistent
review of theory predictions.(Inside the Nonrelativistic Effective Field
work out a better accuracy between lattice and continuum
operator matrix elements, make available the needed set of matching coefficients
in the various regularization schemes.
reduce to the minimal number the
nonperturbative operators (or matrix elements) involved in quarkonium phenomenology
and fix it via combined lattice and data determination (e.g.
passing from NRQCD to pNRQCD). Quantify the error/indetermination of the
present lattice results.
Perform all the allowed renormalon subtractions (in the spectra, decays)
in order to constrain the size of the remaining nonperturbative contributions
and be able to study the convergence properties of the perturbative series.
A '<5%' Mark on both theory predictions and experimental data on Onia
decay widths and branching ratios.
Robust theory tools to calculate alpha_s(q^2) in the charmonium system.
Device theoretical analyses and/or golden measurements to:
the average velocity of the valence quark in every onia;
b) quantify the
impact of light quark pairs on onia dynamics.
Precise determination of m_b, m_c and m_t after the appropriate renormalon
subtraction has been done.