Non-perturbative QCD Dynamics (NOP)

In this document, the production of Xibar+Xi- pairs is simulated in the pbarp -> Xibar+Xi- reaction channel at beam momenta of p_beam=7.0 GeV/c and p_beam=4.6 GeV/c. The first beam momentum is chosen at the energy corresponding to the formation of the X(3872), where a large data taking campaign is foreseen when PANDA is operational. The second beam momentum is chosen around 100 MeV/c2 above the production threshold of Xibar(1820)+Xi- + c.c. The feasibility to measure polarisations and spin correlations in the reaction channel is studied for the sequential process Xi- -> Lambda pi-, Lambda -> p pi- + c.c.

The PANDA experiment is one of the main pillars of the FAIR facility, currently under construction in Darmstadt, Germany. The PANDA will be a fixed target experiment designed for the study of non-perturbative phenomena of the strong interaction. Strange hyperon production is governed by the mass of the strange quark, m(s) ∼ 100 MeV, which corresponds to the confinement domain. Thus, hyperons are suitable probes in this energy region. This work is a simulation study focused on the feasibility of studying the production of the Sigmabar and Lambda hyperons in the pbar p ->Sigmabar Lambda reaction with the PANDA detector. A 10^4 events sample simulated at pbeam = 1.771 GeV/c is used to perform a single-tag (inclusive) and a double-tag (exclusive) event selection. From the former, it is concluded that the single-tag method does not provide with the clean signal required for spin observables extraction. In contrast, exclusive event selection provides with a signal reasonably clean from combinatorial background and completely clean from generic hadronic background events. A signal ( Sigmabar Lambda) reconstruction efficiency of e = 5.3 ± 0.2 % is obtained for exclusive event selection. The corresponding signal to background ratio is S/B Total ∼ 6 and the significance value
is ∼ 21.
In addition, an exclusive event selection is performed on a 10^4 events sample simulated at pbeam = 6 GeV/c. Almost all the generic hadronic background events are removed by the applied selection criteria. At this beam momentum, the obtained signal efficiency is e = 6.1 ± 0.3%, the signal to total background ratio is S/B Total ∼ 4 and the significance is ∼ 22. Both efficiencies are smaller compared to a previous simulation study on this channel, but are large enough to enable a study of the exclusive production of the pbar p -> Sigmabar Lambda reaction at PANDA. The difference between the results of this work and the previous work is attributed to the more realistic implementation of the signal production mechanism, as well as the detector and reconstruction algorithms.

The energy scale of hyperon production in pbarp -> YbarY reactions is given by the strange quark mass, which is close to the QCD cut-off region. In this energy scale, it is not clear whether quarks and gluons or hadrons act as the relevant degrees of freedom. Studying spin observables in these reactions could give new insight in QCD in the intermediate energy region.

In this feasibility study, the measurement of polarisation and spin correlation, the two accessible spin observables in PANDA, are studied. Expected observed production rates of antihyperon hyperon pairs are also presented. This study is an extension of previous similar work performed with a different software package.