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Mapping the strong potential

Final Activity Report Summary - STRONG POTENTIAL (Mapping the Strong Potential)

The project dealt with the development of a procedure to analyse data from the ATLAS experiment at the large hadron collider (LHC) to extract information in the form of strong potential. Among the four fundamental forces in nature, the strong force binds the constituents of atomic nuclei and other fundamental particles together. The nature of the strong force, including the form of the strong potential, determines to a large extent what bound particle states can exist in our Universe. The exact form of the strong potential remains, however, not known. Measurements are needed in order to give support to the proposed potential models and to improve their predictive power.

One particle type that will be produced at the LHC is the Bc, a bound state of the two heaviest quarks, c and anti-b, able to form a stable state. We expected that excited states of the Bc, the Bc* resonances, would be produced as well. The aim of the project was to measure the masses of several of the Bc* states and their mass differences relative to the Bc. These values were determined by the form of the strong potential, so information on the shape of that potential could be extracted from this information.

Due to delays in the LHC schedule, since the start-up of the accelerator was shifted from 2007 to 2008, there was unfortunately no possibility to test the methods against real data. Nevertheless, the main research goal of the project, i.e. the development of an analysis procedure for extracting the Bc signal from the background using a computer-based simulation of the data that would be produced in the ATLAS detector, was met. Concerning Bc* states, a feasibility study showed that the hadronic decay modes of the Bc* should be used instead of the decay chain Bc* greater than Bc gamma, anticipated in the proposal.

The work was documented through presentations in scientific meetings and conferences. Work was in progress, by the time of the project completion, to document the analysis scenario in an ATLAS collaboration scientific note. One Master thesis was completed in Lund, and, by the time of this report, there were three graduate students, two in New Mexico and one in Lund, and one undergraduate student, in Lund, working on this topic.