Transcript Cuts Study
Light vector mesons continued Radoslaw Karabowicz, Zbigniew Majka, Pawel Staszel, Pawel Szostak Jagiellonian University, Krakow Tools used for the simulation UrQMD event generator (13k central Au+Au collisions @ 25 AGeV) PLUTO event generator (1M light vector mesons decays) G4CBM transport code + simulation of the detector CAT (CBM Analysis Tools) - background reduction cuts - combining PLUTO and UrQMD events - combinatorial analysis >cvs –d [email protected]:/home3/cvs/CBM_CVS checkout cat 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 2 Pluto and UrQMD • Light vector mesons: particle particles/event e+e- br. ratio w 10 7.15·10-5 r 10 4.48·10-5 f 1 3.00·10-4 and wp0 e+e– Dalitz decay channel: 5.90·10-4 rapidity distributions – nearly Gaussian, s ~ 1.1 inverse slope from mt spectra T ~ 150 MeV average probability of one decay per event is 1/140 • Background: particle multiplicities NALL = 1582, NCH = 944, main background sources pi0, eta 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 3 100% Cuts Study 10% ackground Signal 1% 06.10.2004 0.1% R. Karabowicz, CBM Coll. Meet., GSI 4 100% 10% - ackground Signal 1%- BEFORE Single particle cuts (d>250microns, p_t<100MeV) Non-restrictive particle cuts (ang<10deg, vz>150microns, vt>1mm, D>250microns) Restrictive particle cuts (ang<10deg, vz>150microns, vt>1mm, D>250microns) 06.10.2004 0.1% Cuts Study Cut off the particles with: -distance between the track and the collision vertex greater than 250 microns -transverse momenta smaller than 100 MeV R. Karabowicz, CBM Coll. Meet., GSI 5 100% 10% - ackground Signal 1%- BEFORE Single particle cuts (d>250microns, p_t<100MeV) Non-restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) Restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) 06.10.2004 0.1% Cuts Study e+(e-) is checked against all other unlike sign particles. This particle is removed only if there is no partner fulfilling all conditions: -angle – opening angle -vt(z) – distance of the 2 particle vertex to the collision vertex in transverse (longitudinal) direction -DColl. – distance between two R. Karabowicz, CBM Meet., 6 GSItracks 100% 10% - ackground Signal 1%- BEFORE Single particle cuts (d>250microns, p_t<100MeV) Non-restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) Restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) 06.10.2004 0.1% Cuts Study Pair is removed if does not fulfill any of the given conditions: -angle – opening angle -vt(z) – distance of the 2 particle vertex to the collision vertex in transverse (longitudinal) direction -D – distance between two tracks R. Karabowicz, CBM Coll. Meet., 7 GSI 10% - ackground Signal 1%- BEFORE Single particle cuts(d>250microns, p_t<100MeV) Non-restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) Restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) 06.10.2004 0.1% Cuts Study 100% NOW Pair recognition cuts: (D>250um && 10% vt>1mm) (invMass<100 MeV from the smallest) Single particle cuts Non-restrictive particle cuts 1% Restrictive particle cuts R. Karabowicz, CBM Coll. Meet., GSI 8 0.1% ackground Signal 100% 10% - ackground Signal 1%- BEFORE Single particle cuts(d>250microns, p_t<100MeV) Non-restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) Restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) 06.10.2004 0.1% Cuts Study 100% NOW Pair recognition cuts: (D>250um && 10% vt>1mm) (invMass<100 MeV from the smallest) Single particle cuts Non-restrictive particle cuts 1% Restrictive particle cuts R. Karabowicz, CBM Coll. Meet., GSI 9 0.1% ackground Signal 100% 10% - ackground Signal 1%- BEFORE Single particle cuts(d>250microns, p_t<100MeV) Non-restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) Restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) 06.10.2004 0.1% Cuts Study 100% NOW Pair recognition cuts: (D>250um && 10% vt>1mm) (invMass<100 MeV from the smallest) Single particle cuts Non-restrictive particle cuts 1% Restrictive particle cuts R. Karabowicz, CBM Coll. Meet., GSI 10 0.1% ackground Signal 100% 10% - ackground Signal 1%- BEFORE Single particle cuts(d>250microns, p_t<100MeV) Non-restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) Restrictive particle cuts (ang<10deg, vt>150microns, vz>1mm, D>250microns) 06.10.2004 0.1% Cuts Study 100% NOW Pair recognition cuts: (D>250um && 10% vt>1mm) (invMass<100 MeV from the smallest) Single particle cuts Non-restrictive particle cuts 1% Restrictive particle cuts R. Karabowicz, CBM Coll. Meet., GSI 11 0.1% ackground Signal 100% Invariant mass spectrum S/B w 95.0 f 250.1 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 12 Studying magnetic field effect We compare the particle momentum with minimum momentum needed to fit into acceptance (less than 45 degrees) 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 13 Invariant mass spectra with magnetic field 0 kG 2 kG S/B S/B w 95.0 w 23.0 f 250.1 f 80.1 0 kG 2 4 4 kG S/B w 3.9 f 9.8 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 14 Invariant mass spectra with magnetic field – cont. 0 kG 6 kG S/B S/B w 95.0 w 2.1 f 250.1 f 4.1 8 kG 10 kG S/B S/B w 1.6 w 1.5 f 2.8 f 2.3 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 15 Pion misidentification Efficiency 90% -4 10 p mis S/B S/B w 95.0 w 60.3 f 250.1 f 148.2 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 16 Pion misidentification Efficiency 90% -4 10 S/B w 95.0 f 250.1 eff S/B w 21.7 f 70.3 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 17 Pion misidentification Efficiency 90% -4 10 p mis S/B S/B w 95.0 w 60.3 f 250.1 f 148.2 eff p mis, eff S/B S/B w 21.7 w 14.5 f 70.3 f 37.5 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 18 Summary We need more realistic transport code and track reconstruction + PID: - non-zero magnetic field (acceptance), - track reconstruction in STS (efficiency), - PID using RICH (efficiency+pion misidentification). We need better statistics from UrQMD and modified output from Pluto (eta, shifted rho). We are also considering using more sophisticated variables to cut on, like: - sum of polar angles, - opening angle in transverse plane. 06.10.2004 R. Karabowicz, CBM Coll. Meet., GSI 19