Invariant Mass Calculation J Rosi Reed 103107 Outline

Invariant Mass Calculation J/ψ Rosi Reed 10/31/07

Outline • • Introduction Summer ‘ 07 Activities Fall Progress Future Work

Introduction • J/ψ is the first excited state of charmonium • Rest mass 3. 1 Gev/c 2 • One decay channel is: e+e-

Summer Activities • J/ ψ Triggers 117705 and 137705 – Run # > 7132061 for full CTB coverage – pp 2006 • First cuts were – primary track (DCA = 3 cm) – 15 hits TPC for momentum resolution • Total of 2, 538, 988 Events

Summer Activities

Summer Activities • Gaussian fits used on momentum slices to determine – Efficiency – Purety • 2 more cuts introduced – log(d. E/dx) > 1. 2 – p > 1. 2 Ge. V/c

Summer Activities • Invariant mass calculation done by comparing e+e+, e-e- and e+e– e+e+, e-e- are the combinatoric background – e+e- contains signal for particles with p>2. 4 Gev with decay channel e+e-

e- width vs. p question

Fall Activities • I can now log into RCF! • Scheduler xml file is written – and it appears to work • Will submit job to run over all Full CTB Jpsi triggered events • Invariant Mass calculation will be: – Signal - Background – Signal = e+e- TH 1 D – Background ~2½((e+e+)*(e-e-))½

J/ψ triggered event Thanks Manuel!

Future Work • Improve cuts – DCA (3 cm is large) – TPC Hits (momentum resolution) – Towers seperated by >60 degrees phi • Look at the CTB – Extrapolate track to tower in the EMC – Photons will not leave a signal in the CTB • Cutting on no hit in the CTB cause the J/ψ signal to disappear