Using a 39.7 pb Run-II data sample collected from February to
October 2002, a new measurement of the inclusive
cross-section has been performed. The events were collected
using the CMU-CMU di-muon triggers, and the raw yields were corrected
by the geometric and kinematic acceptance, trigger efficiency and
reconstruction efficiency. A dependent differential cross
section has been calculated for events with rapidity |y|<0.6. The
total integrated cross section for inclusive production in
interactions at C.O.M. energy, GeV/c,
is measured to be:
Non-relativistic quarkonia bound states are best described by Non-Relativistic QCD ( NRQCD) theoretical models which are used to predict the hadroproduction cross-sections  . At large transverse momenta, fragmentation type production is expected to dominate and color-octet matrix elements dominate the color-singlet matrix element contribution . Using color-octet matrix elements extracted from data, the model can accomodate the Run I data at the Tevatron for GeV/c. At low transverse momenta, soft gluon effects and non-fragmentation effects from other octet matrix elements that are difficult to calculate theoretically become important and cause theory predictions and data to diverge. The Run-II CDF detector has an improved dimuon trigger with a lower threshold of > 1.4 GeV/c. This has extended the low transverse momentum range of triggered events down to GeV/c. A new measurement of the total inclusive cross-section using Run-II data has been carried out.
The sample used for this analysis was collected using the Level 1 and Level 3 Central Muon (CMU) di-muon triggers. The single muon trigger efficiency as a function of the muon transverse momentum is shown here. The data sample used was collected during the stable running period of February to October 2002 and corresponds to a total luminosity of .
decays were reconstructed from tracks reconstructed in the Central Outer Tracker (COT) drift chamber and matched to track-stubs in the Central Muon Chambers (CMU). The invariant mass was calculated from the sum of the four-momenta of the two muons. Figure 1 shows the invariant mass distribution for all the selected events in the range GeV/c with rapidity |y|<0.6. From a fit to a double Gaussian and a order polynomial background, the total number of reconstructed for this study is with an average width of GeV/c. The mass sideband subtracted transverse momentum distribution of reconstructed events in shown in Figure 2 .
The data sample is divided into thirty ranges of transverse momentum, covering the range 0-17 GeV/c. In each range, the total number of s reconstructed with rapidity |y|<0.6 is measured. To estimate the correct yield, the invariant mass signal distribution including the radiative tail from internal bremsstrahlung is fitted using mass template shapes obtained from a MC simulation of the COT. The fits to the COT invariant mass distributions in three of the transverse momentum ranges are shown in Figures 3 . 4 . and 5 .
The CMU muon detector covers the pseudo-rapidity range of . In this region the coverage of the central tracking chamber, COT is 100% and the CDF detector acceptance is driven by the muon detector geometry and kinematic reach. A full GEANT simulation of the CDF detector is used to estimate the acceptance correction.
The acceptance efficiency as a function of reconstructed
and rapidity, is defined as
where and y' are the generated true values of the momentum and rapidity including the radiated photon.
The acceptance as a function of and is shown in Figures 6. and 7.
The yield in each bin is corrected for the 2-D
acceptance, , Level 1 single muon
trigger efficiency, , and the muon
selection cuts, using an event by
The differential cross section is then calculated as follows:
where , is the correction factor for y smearing, is the combined L3, offline tracking and muon reconstruction efficiency, is the integrated luminosity, and is the bin size of the bin.
Table 1 summarizes the different contributions to the systematic uncertainties to be applied to the cross-section measurement.
Table 1: Source of systematic uncertainty in the cross-section measurement
The cross-section values are listed in Table 2.
Table 2: The differential crossection as a function of , for . The systematic uncertainties shown are the dependent uncertainties only. The correlated independent systematic uncertainty in each bin is +/- 6.7%.
The differential cross-section results are displayed in Figures 8. and 9. The invariant cross-section, with systematic uncertainties is shown in Figures 10. and 11.
The integrated cross section obtained from an integral of the
differential cross section is: