J/&psi → μ μ Yields for the Summer 2004 dataset

Here are some basic PR plots from just running over the whole 293 pb^-1 in the 5.3.1 reprocessing of the CDF Run II data, in the J/ψ stream. i.e. jpmm0d. Default CDF Tracks (defTracks) are refit potentially including L00 and ISL, using the standard mass calibration procedures, and then matched with track stubs in the Muon chambers (I use TrackAssoc to do the Muon association). In the plots, I attempt to model the ΔΓ/Γ analysis cuts (see Section II) namely:

p_T > 1.5 GeV both μ
n_{Si Hits} ≥ 3 both μ
χ²_CMU < 9 for μ with CMU stub
J/ψ vertex z coordinate ∈ (-50.0,-18.0) ∪ (-14.0,14.5) ∪ (18.5,50.0) cm
Vertex fit converges

Here's a J/ψ mass plot with the above cuts, which corresponds to ≈ 260 pb^-1. To get the yield and width, the plot is fit with two guassians, plus an 1st order polynomial. I get ≈ 2 million J/ψs and the σ ≈ 14 MeV/c².The fit isn't great, but varying the fit function to make it beautiful does not actually change the yield much, and we don't need to know this number, but rather just want to give a feel for how many J/ψ there are. Your milage may vary.

Here is the L_xy distribution for entries above where

the red plot is for dimuon masses in a window of m_&muμ &isin m_J/ψ ± 80 MeV
the blue plot is for dimuon masses in a range of m_&muμ ∈ (m_J/ψ- 160 MeV, m_J/ψ- 80 MeV) ∪ (m_J/ψ+ 80 MeV, m_J/ψ+ 160 MeV).

The idea is to show that most J/ψs are prompt.

Steven Nahn

Last modified: Thu Aug 12 13:49:39 CDT 2004