Invariant Mass Calculation J/ψ

Rosi Reed

3/5/08

Introduction

• J/ψ is the first excited state of charmonium

• Rest mass 3.096 Gev/c2

• Full Width 93.4 keV

• One decay channel is: e+e-

– BR 5.94%– Width 5.55 keV

• J/ ψ Triggers 117705 and 137705– Run # > 7132061 for full CTB coverage– pp 2006

First cuts on dE/dx

Gaussian Fits to log(dEdx)

TPC Hits 15

TPC Hits 30

Invariant Mass Calculation w/Errors

Cut log(dEdx>1.25)

Invariant Mass Calculation w/Errors

TPC Hits > 30

P >2.0, log(dEdx*1e6)>1.24P >2.5, log(dEdx*1e6)>1.26P >3.0, log(dEdx*1e6)>1.28P >4.0, log(dEdx*1e6)>1.31

TPC Hits – 30 is too tight

Invariant Mass Calculation w/Errors

TPC Hits > 23

P >2.0, log(dEdx*1e6)>1.24P >2.5, log(dEdx*1e6)>1.26P >3.0, log(dEdx*1e6)>1.28P >4.0, log(dEdx*1e6)>1.31

Invariant Mass Calculation w/Errors

TPC Hits > 23 P >1.5, log(dEdx*1e6)>1.2

Future Work + Questions• Extrapolate track to tower in the EMC

– Plot p/E per event

– Include cuts based on EMC signal• Towers separated by >60 degrees phi

• p/E for PID?

• Total E?

• Inv. Mass calculation has– B = 2*(N++N--)^2

• Why is this multiplied by 2?

• What was the measured number of J/ψ in the pp2006 data set?