Bc Lifetime in Bc± → J/ψ+l±+X

This web page summarizes the results for the measurement the Bc± lifetime using the decay modes Bc± → J/ψ+l±+X, where l± is an electron or muon and X are unmeasured particles. The measurement is done with in 1 fb-1 of exclusive J/ψ data.

The results have been approved as of March 27, 2008.
We measure:

## A more detailed summary of the results can be found here: pdf.

Top: ct* projection for Bc lifetime fit in the J/ψ+μ channel. Middle: ct* projection for Bc lifetime fit in the J/ψ+e channel. Bottom: Combined -2log(L) for J/ψ+μ and J/ψ+e channels.

Below are the eps and jpeg versions of figures meant for download that are in the above note.

• Figure 1: J/ψ mass (.eps)(.jpg)
• Figure 2: J/ψ+μ mass - Monte Carlo of J/ψ+μ mass from Bc decays (.eps)(.jpg)
• Figure 3a: Particle fractions - J/ψ+track sample for muon channel, ct*<0 μm, third track Q=+1 (.eps)(.jpg)
• Figure 3b: Particle fractions - J/ψ+track sample for muon channel, ct*<0 μm, third track Q=-1 (.eps)(.jpg)
• Figure 3c: Particle fractions - J/ψ+track sample for muon channel, 0<ct*<150 μm, third track Q=+1 (.eps)(.jpg)
• Figure 3d: Particle fractions - J/ψ+track sample for muon channel, 0<ct*<150 μm, third track Q=-1 (.eps)(.jpg)
• Figure 3e: Particle fractions - J/ψ+track sample for muon channel, ct*>150 μm, third track Q=+1 (.eps)(.jpg)
• Figure 3f: Particle fractions - J/ψ+track sample for muon channel, ct*>150 μm, third track Q=-1 (.eps)(.jpg)
• Figure 4a: Particle fractions - J/ψ+track sample for electron channel, ct*<0 μm, third track Q=+1 (.eps)(.jpg)
• Figure 4b: Particle fractions - J/ψ+track sample for electron channel, ct*<0 μm, third track Q=-1 (.eps)(.jpg)
• Figure 4c: Particle fractions - J/ψ+track sample for electron channel, 0<ct*<150 μm, third track Q=+1 (.eps)(.jpg)
• Figure 4d: Particle fractions - J/ψ+track sample for electron channel, 0<ct*<150 μm, third track Q=-1 (.eps)(.jpg)
• Figure 4e: Particle fractions - J/ψ+track sample for electron channel, ct*>150 μm, third track Q=+1 (.eps)(.jpg)
• Figure 4f: Particle fractions - J/ψ+track sample for electron channel, ct*>150 μm, third track Q=-1 (.eps)(.jpg)
• Figure 5a: D0 Mass - Fitted for event where π leg passes track cuts, 3<pT<4 GeV/c2 (.eps)(.jpg)
• Figure 5b: Λ - Fitted for event where p- leg passes track cuts, 2<pT<3 GeV/c2 (.eps)(.jpg)
• Figure 5c: D0 Mass - Fitted for event where π leg passes track cuts and muon ID, 3<pT<4 GeV/c2 (.eps)(.jpg)
• Figure 5d: Λ - Fitted for event where p- leg passes track cuts and electron ID, 2<pT<3 GeV/c2 (.eps)(.jpg)
• Figure 6: Hadron faking muon probabilities (.eps)(.jpg)
• Figure 7a: Hadron faking e+ probabilities (.eps)(.jpg)
• Figure 7b: Hadron faking e- probabilities (.eps)(.jpg)
• Figure 8a: Fitted J/ψ+fake μ ct* (.eps)(.jpg)
• Figure 8b: Fitted J/ψ+fake e ct* (.eps)(.jpg)
• Figure 9a: Fitted fake J/ψ+μ ct* (.eps)(.jpg)
• Figure 9b: Fitted fake J/ψ+e ct* (.eps)(.jpg)
• Figure 10: J/ψμ Δφ - Fitted azimuthal angle distribution between J/ψ and μ for data with no vertex probability cut.(.eps)(.jpg)
• Figure 11a: Impact parameter of third μ with respect to the J/ψ vertex for data with no vertex probability cut (expect signal excess in lowest 2 bins).(.eps)(.jpg)
• Figure 11b: Impact parameter of electron with respect to the J/ψ vertex for data with no vertex probability cut (expect signal excess in lowest 2 bins).(.eps)(.jpg)
• Figure 12a: Fitted bb(bar) J/ψ+μ ct* (.eps)(.jpg)
• Figure 12b: Fitted bb(bar) J/ψ+e ct* (.eps)(.jpg)
• Figure 13: e+e- veto efficiency - From Pythia MC (.eps)(.jpg)
• Figure 14: Fitted residual e+e- J/ψ+e ct* (.eps)(.jpg)
• Figure 15a: K Factor for Bc± → J/ψ+μ±+X decays (.eps)(.jpg)
• Figure 15b: K Factor for Bc± → J/ψ+e±+X decays (.eps)(.jpg)
• Figure 16a: Fitted J/ψ+μ ct* - Fit to measure Bc lifetime (.eps)(.jpg)
• Figure 16b: Fitted J/ψ+μ ct* - Fit to measure Bc lifetime (backgrounds drawn as one function)(.eps)(.jpg)
• Figure 17a: Fitted J/ψ+e ct* - Fit to measure Bc lifetime (.eps)(.jpg)
• Figure 17b: Fitted J/ψ+e ct* - Fit to measure Bc lifetime (backgrounds drawn as one function)(.eps)(.jpg)
• Figure 18a: -2Log(L) for J/ψ+μ and J/ψ+e lifetime fits(.eps)(.jpg)
• Figure 18b: -2Log(Le)-2Log(Lμ) - Combined for lifetime in J/ψ+l decays(.eps)(.jpg)

Below are the eps and jpeg versions of figures meant for download that are not in the above note.

• Figure 1: Fitted J/ψ+fake μ σct* (.eps)(.jpg)
• Figure 2: Fitted J/ψ+fake e σct* (.eps)(.jpg)
• Figure 3: Fitted fake J/ψ+μ σct* (.eps)(.jpg)
• Figure 4: Fitted fake J/ψ+e σct* (.eps)(.jpg)
• Figure 5: Fitted bb(bar) J/ψ+μ σct* (.eps)(.jpg)
• Figure 6: Fitted bb(bar) J/ψ+e σct* (.eps)(.jpg)
• Figure 7: Fitted residual e+e- J/ψ+e σct* (.eps)(.jpg)
• Figure 8: Fitted J/ψ+track σct* for ct*<0 μm - prompt model for muon channel (.eps)(.jpg)
• Figure 9: Fitted J/ψ+track σct* for ct*<0 μm - prompt model for electron channel (.eps)(.jpg)
• Figure 10: σct* projection from Bc lifetime fit in J/ψ+μ channel (.eps)(.jpg)
• Figure 11: σct* projection from Bc lifetime fit in J/ψ+μ channel (backgrounds drawn as one function)(.eps)(.jpg)
• Figure 12: σct* projection from Bc lifetime fit in J/ψ+e channel (.eps)(.jpg)
• Figure 13: σct* projection from Bc lifetime fit in J/ψ+e channel (backgrounds drawn as one function)(.eps)(.jpg)
• Figure 14: J/ψ mass with trigger confirmation for J/ψ muon legs (.eps)(.jpg)
• Figure 15: TOF Projection - TOF+dE/dx fit to third track in J/ψ+track (electron channel), 0<ct*<150 μm, 2.0<p<2.5, Q=-1 (.eps)(.jpg)
• Figure 16: dE/dx Projection - TOF+dE/dx fit to third track in J/ψ+track (electron channel), 0<ct*<150 μm, 2.0<p<2.5, Q=-1 (.eps)(.jpg)
• Figure 17: dE/dx Fit - to third track in J/ψ+track (muon channel), ct*<0 μm, 4.5<p<5.0, Q=-1 (.eps)(.jpg)
• Figure 18: Signed Impact Parameter - for electrons in J/ψ+e events with no vertex probability cut (.eps)(.jpg)
• Figure 19: Cross check of conversion veto efficiency using signed impact parameter(.eps)(.jpg)
• Figure 20: Radius of origin for e+e- pairs in data J/ψ+e events with no vertex probability cut (.eps)(.jpg)
• Figure 21: Radius of origin for e+e- pairs in Pythia J/ψ+e events with no vertex probability cut (.eps)(.jpg)
• Figure 22: J/ψ+μ mass for events with ct*>120 μm - Normalization of predicted components comes from Bc lifetime fit (.eps)(.jpg)
• Figure 23: J/ψ+e mass for events with ct*>120 μm - Normalization of predicted components comes from Bc lifetime fit (.eps)(.jpg)
• Figure 24: Comparison of Bc cτ with most precise D0 and CDF Run I measurements. Includes unofficial world average. (.eps)(.jpg)
• Figure 25: Electron likelihood ratio for pure sample of electrons. (.eps)(.jpg)
• Figure 26: Optimized electron likelihood ratio cut for electron selection. (.eps)(.jpg)
• Figure 27: Efficiency for the electron likelihood ratio cut. (.eps)(.jpg)