The Lambda (3 rd installment) Lbar+random observations Richard Seto Ppg016 meeting Jan 2, 2003

Procedure CNT ntuples to pair ntuples from munir ppi- and pbarpi+ TOF-TOF, EMCE-EMCE, TOF-EMCE, all east Cuts done for me by munir No additional cuts for now Normalization is still just between 1.13 –1.2 GeV –Note- mass of lambda is Gaussian fit, convoluted with gausian of 1.3 GeV (from resolution?)- extracted “width” is plotted from (30 MeV, 2 MeV bins, 15-3=12 degrees of freedom –Chisq tends to be ~ 25 (10-45) for 13 DOF Centrality bins 0-10, 10-20, 20-40, 40-60, Pt bins.3-1.8, or.3,.8,1.3,1.8,2.3,2.8 Still problems with background – working on ++ and – (no results yet)

For the record (from munir) List of runs –run2_v03_burn1/CNT files. The complete list at /phenix/u/munir/FileList/UCR_CNT_file.lis We do 3-types of combinations: –Both pbar and pion are identified in tof (TOF-TOF) –Both pbar and pion are identified in PbSc (East-East) –One member of the pair in TOF and the other in PbSc (TOF-East) –Only pi+ in TOF and pbar in PbSc contributes for the third kind of mixing. –RKS has a question about this

Single particle Cuts EMCal (East): –|bbcz| < 30. –|zed|<75 –quality==31 || 63 –0.3<mom<1.2 for both protons and pions –emcsdphi*emcsdphi + emcsdz*emcsdz < 9. –isPi ans isK calculated using EMCal resolution of 480ps (followed HadPid in CVS) |isP|<2 |isPi|<2 Tof –|bbcz| < 30. –|zed|<75 –quality==31 || 63 –etof>0.002 –|tofsdphi|<2.5 && |tofsdz|<2.5 –|isP|<2.5 –|isPi|<2.5 –0.5<mom<3.0 for proton –0.25<mom<1.8 for pion

Pair acceptace criteria ghost track rejection : applied ONLY to same sign pairs –|delta_zed|<0.02 –|delta_phi|<0.03 –one member of the pair is randomly rejected intruder rejection : In same arm and same sector –TOF : delta_ttof=0 && delta_etof=0 –PbSc: delta_temc=0 && delta_ecore=0 –both members of pair are rejected. For actual pair +-, ++ and -- : –0<centclock<93 For mixed pair +-, ++ and -- : –18 centrality bins from 0% in an increment of 5%, the last bin is 85%-92% –15 bbcz bins from -30 cm in an increment of 4 cm –tracks from same centrality and vertex bins are mixed

Cut (TOF+)(EMC-) Typical cut requires for tof-emc combo + in TOF, and – in emce for phi – use same cut for lambda IS this OK? seems like a mass cut to me (looking at lbar) Without Pt<1.8 With cut Pt<1.8

Widths Consistent with flat lambda lambdabar

Masses Reasonable value Pdg= lambdabar lambda

Pt dependence “all”

To do Do a more careful study of these plots –See munirs stuff Look at ++, -- and study subtraction problems