Recommendations  Quark and Hadron Dynamics  Non-linear Low-x Effects

How to proceed

The investigation of hadron and quark dynamics at accelerators is carried out with three types of probes.

1.

Lepton probes of hadrons.

2.

Hadron probes of hadrons.

3.

Hadron production via e⁺e^- annihilation.

   

Table: European hadron facilities operating in 2000 and beyond. 

 

Facility	Projectile	Energy (GeV)	$\mathcal{L}$ (cm-2s-1
DA$\Phi$NE	$e^{+}e^{-}\rightarrow \phi \rightarrow K^{+}K^{-}$	0.016 (K)	1033
COSY	p	2.5	109p/s
CELSIUS	p	1.36	$2\times 10^{32}$

 

 

The advantages of leptons as a probe are well known. They involve electroweak processes that are to a good approximation single-step interactions. In lepton-hadron scattering the spatial resolution can be easily tuned. For momentum transfers of order 0.5 GeV one sees nucleons in nuclei, for transfers larger than 1 GeV one becomes sensitive to the quark constituents. To probe the scale of short distances, experiments require high momentum transfer and high energy. To explore correlations between quarks and gluons, one also needs polarisation and identification of the final states. High luminosity is an essential requirement for exclusive scattering. Hadron beams allow one to study hadron dynamics and spectroscopy. For example, one can study hadron excitations and their decays. Observation of particles with specific quantum numbers serves as a filter that allows investigation of the composition of hadrons, e.g. strangeness, charm, glue. Another possible filter is to look for final states sensitive to specific interactions, e.g. lepton pairs (e⁺e^-, $\mu ^{+}\mu ^{-}$) or photons. Finally, it is possible to use e⁺e^- colliders to study properties of the hadrons that are produced with opposite quantum numbers in collinear pairs, for example strangeness ( $e^{+}e^{-}\rightarrow K^{+}K^{-}$) or baryon number ( $e^{+}e^{-}\rightarrow p\overline{p}$). This is the case of the new e⁺e^- collider at the $\phi$ mass (DA$\Phi$NE) which will start operating in 1998 at Frascati, in Italy. A possible extension to 2 GeV and to a $\tau$ charm factory will be considered in the future. Other projects such as the RHIC$\;$spin programme in the United States, B factories in the United States and Japan will also yield important information on hadron and quark dynamics. Some research areas are not covered by European facilities: thus, several European groups participate in collaborations in the United States, for example at Jefferson Lab and SLAC. Some areas are not yet covered anywhere in the world, such as a high intensity proton facilities in the energy range 30-50 GeV. To cover this area, Japan has proposed to build at KEK a 50 GeV high intensity (10 $\mu$A) proton accelerator dedicated to hadron probes. This project with its variety of secondary beams is likely to become a world class hadron facility.