Measurements of bottom-antibottom azimuthal production correlations in proton-antiproton collisions at root s=1.8 TeV

We have measured the azimuthal angular correlation of b (b) over bar production, using 86.5 pb(-1) of data collected by Collider Detector at Fermilab (CDF) in p (p) over bar collisions at root s = 1.8 TeV during 1994-1995. In high-energy p (p) over bar collisions, such as at the Tevatron, b (b) over bar production can be schematically categorized into three mechanisms. The leading-order (LO) process is "flavor creation," where both b and (b) over bar quarks substantially participate in the hard scattering and result in a distinct back-to-back signal in final state. The "flavor excitation" and the "gluon splitting" processes, which appear at next-leading-order (NLO), are known to make a comparable contribution to total b (b) over bar cross section, while providing very different opening angle distributions from the LO process. An azimuthal opening angle between bottom and antibottom, Delta phi, has been used for the correlation measurement to probe the interaction creating b (b) over bar pairs. The Delta phi distribution has been obtained from two different methods. One method measures the Delta phi between bottom hadrons using events with two reconstructed secondary vertex tags. The other method uses b (b) over bar -> (J/psi X)(lX(')) events, where the charged lepton (l) is an electron (e) or a muon (mu), to measure Delta phi between bottom quarks. The b (b) over bar purity is determined as a function of Delta phi by fitting the decay length of the J/psi and the impact parameter of the center dot. Both methods quantify the contribution from higher-order production mechanisms by the fraction of the b (b) over bar pairs produced in the same azimuthal hemisphere, f(toward). The measured f(toward) values are consistent with both parton shower Monte Carlo and NLO QCD predictions.