Study of correlations between photoproduced pairs of charmed particles at Experiment E831/FOCUS (in Portuguese)
- Brazilian Center for Physics Research, Rio de Janeiro (Brazil)
The authors present the study of the charm-pair correlations produced in photon-nucleon interactions at $$\langle$$Eγ$$\rangle$$ = 175 GeV/c, by the Fermilab fixed target experiment E831/FOCUS. The E831/FOCUS experiment produced and reconstructed over one million charm particles. This high statistics allows the reconstruction of more than 7000 charm-pair mesons D$$\bar{D}$$, 10 times the statistic of former experiments, and also allows to get, for the first time, about 600 totally reconstructed charm-pairs in the DDs and DΛc channels. They were able to study, with some detail, the kinematical correlations between the charm and anticharm particle forming a pair, in the square transverse momentum (pT2), azimuthal angle difference (ΔΦ), rapidity difference (Δy) and the charm-pair mass variables. They observe some correlation for the longitudinal momenta, and a significant correlation for the transverse momenta of the charm and anticharm particles. They compare the experimental distributions with theoretical predictions based on the photon-gluon fusion model (PGF), for the production of c$$\bar{c}$$ quarks, and the standard Lund hadronization model. These models are implemented by the PYTHIA Monte Carlo event generator. The PYTHIA program allows the inclusion, in the simulation, of non-perturbative effects that have been shown to be important for charm production. In order to compare data and simulation, they have generated two Monte Carlo samples, the first one set to favor the production of D$$\bar{D}$$ pairs (MCDD2), and the second one set to favor the production of DDsand DΛc pairs, where each one uses different functions and parameters values for the theoretical models in the simulation. They observe, for the correlation distributions, that the set of parameters used by the MCDD2 model together with the intrinsic transverse momentum (k$$\perp$$) of the partons inside the nucleons, has a better agreement with data distributions than the one used by the MCDSLC model. Finally, the relative pair/anti-pair yield production ratio is calculated for five sets of charm-pairs, D+D0, D+Ds-, D0Ds-, D+Λc- e D0Λc-, both for data as well as for the two Monte Carlo samples. They observe that the MCDSLC model predicts charm-pair yield production ratios closer to the yield ratios data than the MCDD2 model.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 964429
- Report Number(s):
- FERMILAB-THESIS-2008-88; TRN: US0903482
- Country of Publication:
- United States
- Language:
- Portuguese
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