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 and –Run # > 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

Gaussian fits used on momentum slices to determine –Efficiency –Purety 2 more cuts introduced –log(dE/dx) > 1.2 –p > 1.2 GeV/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- TH1D –Background ~2 ½ ((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