Momentum correlations of charmed pairs produced in π−-Cu interactions at 230 GeV/c

Abstract

We study the production characteristics of 557 pairs of charmed hadrons produced in π − − Cu interactions at 230 GeV/c using a momentum estimator for charmed hadrons with missing decay products. We find, the mean value of the transverse momentum squared of the charmed pairs is <p 2 T,sum >= (1.98 ± 0.11 ± 0.09) GeV 2 /c 2 , the mean rapidity difference is < |y dif f | >= 0.54 ± 0.02 ± 0.24, and the mean effective mass is <M ef f >= (4.45 ± 0.03 ± 0.13) GeV/c 2 . Comparing these results with the next-to-leading order QCD predictions we find an agreement for the y dif f and M ef f , whilst the measured mean value of p 2 T,sum is significantly larger than the predicted value.

Correlations between D and $${\overline D}$$ mesons produced in 500 GeV/cπ−-nucleon interactions

“…16). These features have been observed by several other experiments [8,9,10,11,12,13,14,15,16]. Using the default parameters, the three models yield the same trend in correlations as we find in data.…”

“…In this section, we compare all the acceptance-corrected distributions discussed in the previous two sections (Figs. [7][8][9][10][11][12][13][14][15][16] to three sets of theoretical predictions: the distributions of cc pairs from a next-to-leading-order (NLO) perturbative QCD calculation by Mangano, Nason and Ridolfi (MNR) [3,4]; the distributions of cc pairs from the Pythia/Jetset Monte Carlo event generator [5] which uses a parton-shower model to include higher-order perturbative effects [6]; and the distributions of DD pairs from the Pythia (Version 5.7)/Jetset (Version 7.4) Monte Carlo event generator [5] which uses the Lund string model to transform cc pairs to DD pairs [7]. For all theoretical predictions, we use the default parameters suggested by the respective authors, which are discussed in the Appendix.…”

“…If p t,D and p t,D were completely uncorrelated, then the single-charm predictions (Figs. [10][11][12] would provide good estimates for these three distributions. At the opposite extreme, if p t,D and p t,D were completely anticorrelated -as in the leading-order perturbative QCD prediction -then the ∆p 2 t distribution would be a delta function at ∆p 2 t = 0 GeV 2 ; the p 2 t,DD distribution a delta function at p 2 t,DD = 0 GeV 2 ; and the ∆φ distribution a delta function at ∆φ = 180 • .…”

“…Some studies have been conducted with partially-reconstructed charm hadrons, in which the direction but not necessarily the magnitude of the charm particle momentum is determined directly. NA32 partially reconstructed 642 such charm pairs [11]. In photoproduction experiments, the largest sample of charm pairs reconstructed is from the E687 data [15], with 325 fully-reconstructed and 4534 partially-reconstructed charm pairs.…”