Study of Fundamental Interactions in e ⁺e ^– and Hadronic Collisions

Participating countries and international organizations:

Belarus, CERN, China, Germany, Italy, Poland, Russia, Sweden.

Issues addressed and main goals of research:

The Standard Model (SM) provides the most accurate and universal description of the physics phenomena on a microscale nowadays. However, it is not free from a number of shortcomings. Some predictions of the Standard Model still have not been observed experimentally. In many cases the accuracy of the predictions is limited by the experimental knowledge of the key free parameters of the theory. At the same time, the search for New Physics beyond the Standard Model may show the way to further develop the theory and to get rid of its shortcomings. The main tool for these studies is the collider experiments using both proton-proton (LHC) and electron-positron collisions. The latter are most suitable for precision studies of elementary particles with obvious advantages from well-defined kinematics of the initial state and the absence of the large QCD background typical of hadronic colliders.

The precision test of SM predictions and search for new phenomena beyond the SM in charmonium and tau lepton decays are fulfilled in the scope of this theme using the world best facility in this energy domain - the unique electron-positron collider BEPC-II and the BES-III detector. At the same time, preparation for experiments at the future electron-positron colliders (ILC, CLIC, CEPC, FCC-ee) is under way.

An important complement to the studies in e+e- collisions are the planned measurements at the AMBER experiment to address fundamental issues of Quantum Chromodynamics, which are expected to lead to significant improvements in the understanding of QCD as the present theory of strong interactions. AMBER (Apparatus for Meson and Baryon Experimental Research) is a new fixed-target experimental facility at the M2 beam line of the CERN SPS. The proposed measurements cover the range from lowest-Q2 physics as the determination of the proton radius by elastic muon-proton scattering, over average-Q2 reactions to study hadron spectroscopy, to high-Q2 hadron-structure investigations using the Drell-Yan, charmonia and prompt-photon production hard processes. 

Expected results in the current year:

• BES-III data analysis.

• Development of offline software and analysis tools.

• Development of a multipurpose MC event generator to describe the main processes of e ⁺e ^- annihilation including radiative corrections at a level of more than one loop. The generator will take into account the particle polarization for both initial and final states.

• Development of standard program codes to calculate radiation corrections at a level of 2 (for EW interactions) and 3 (for strong interactions) loops.

• Study of the research potential of the experiments at the CLIC, FCC, CEPC colliders in the domain of precision measurements and search for new physics on the basis of full detector simulation.

• Development of proposals for the physics research program of the Super c-t Factory.

• Test run to determine the proton radius by elastic muon-proton scattering.

• R&D to develop a prototype of the Micromegas chamber of 50 cm х 50 cm followed by the test-beam studies.

Collaboration