Hadron production in C+C at 1 and 2 A GeV analysis of data from experiments NOV02 and AUG04 for high resolution tracking (Runge-Kutta tracks) Pavel Tlustý, NPI Řež HADES Coll. Meeting XVI Dresden, April 5, 2006 summary of charged pi meson production in C+C

Experimental and analysis details November 2002 C+C 2AGeV  200*10 6 events: 56% LVL1 trigger + 44% LVL2 trigger only 2 sectors with 4 chambers + RK tracking used in the analysis 20 M events (gen4 dst’s) used for analysis (days , 1st level trigger events) UrQMD simulations - 47 M events (gen4) used for parameter production 20 M events (gen4) used for analysis August 2004 C+C 2AGeV  650*10 6 events: 50% LVL1 trigger + 50% LVL2 trigger 20 M events (gen1 dst’s) used for analysis (days , 1st level trigger events) UrQMD simulations - 47 M events (gen1) used for parameter production 20 M events (gen1) used for analysis

Principle: for each track a probability that it is of a particle type h is calculated, for all possible particle types Bayes theorem implemented cut on the resulted probability set to decide on PID Input: for each track (track candidate) with a given momentum we have a set of independent measured variables in HADES: velocity, energy loss, RICH response, MDC hit, SHOWER response Output: - a probability, that a given track corresponds to the particle type h - efficiency and purity for a selected cut Particle Identification Method

Runge-Kutta tracks matched to META inner mdc segment  2 > -1, RK  2 < 1000, SplineAccepted=1 tracks with TOFINO paddle multiplicity =1 for NOV02 only sectors No. 0 and 3 Track selection

Results of hadron ID - NOV02

Efficiency and purity - NOV02

Spectrometer acceptance acceptance calculated from SIM data as ratio N rectracks /N primary for p,  +,  - in theta vs momentum

Corrected particle yields

Corrected yields - NOV02 - sector No.0 Momentum distribution Theta distribution

Corrected yields - NOV02 - sector No.3 Momentum distribution Theta distribution

NOV02 gen4 - negative tracks vs theta differences between sectors SEC 0 SEC 3

Corrected yields - NOV02 - selected region Momentum distribution Theta distribution

NOV02 particle distributions in c.m. mom_cm > 200 MeV/c

NOV02 - pi distributions in theta_cm

NOV02 - pi distributions in mom_cm - UrQMD

NOV02 - pi distributions in mom_cm - EXP

no d in UrQMD0.24 ± 0.02d 1.05 ± 0.11 * ± 0.24p 0.96 ± ± 0.08 –– 0.96 ± ± 0,07 ++ ratio N exp / N sim simulationexperiment (± bias error) NOV02 particle yields per event (acceptance corrected)  p+d) exp /p sim

NOV02 particle yields per event UrQMD yields to   event (1st level trigger) 0.82  event (no bias) N  = 0.83 ± 0.08   TAPS N  = 0.77 ± 0.07   KAOS

Corrected yields - AUG04 - sec. no.1 Momentum distribution Theta distribution

AUG04 gen1 - negative tracks vs theta differences between sectors, gaps in SHOWER+TOFINO region SEC 0 SEC 3

Corrected yields - AUG04 - sec. no.1 Comparison of 2 analyses

no d in UrQMD0.42 ± 0.04d 0.90 ± 0.11 * ± 0.25p 0.89 ± ± 0.03 –– 0.88 ± ± 0.03 ++ ratio N exp / N sim simulationexperiment (± bias error) AUG04 particle yields per event (acceptance corrected)  p+d) exp /p sim

AUG04 particle yields per event UrQMD yields to   event (1st level trigger) 0.36  event (no bias)

Summary comparison of low vs high resolution data - theta distributions plotting of EXP/SIM ratio of yields versus momentum comparison of yields

NOV02 - KICK vs RK Theta distribution sec no.0 Theta distribution sec. no.3

AUG04 - KICK vs RK Theta distribution sec no.1

AUG04 - EXP/SIM ratio of yields vs momentum low efficiency for mips?

NOV02 particle yields per event UrQMD yields to   event (1st level trigger) 0.82  event (no bias) N  = 0.83 ± 0.08   TAPS N  = 0.77 ± 0.07   KAOS

AUG04 particle yields per event UrQMD yields to   event (1st level trigger) 0.36  event (no bias) most probably >10% yields lost due to low efficiency

NOV02 - META and track multiplicity 8% of  „empty events“ in EXP Mean multiplicity  in EXP greater than in SIM - different centrality or fake tracks in EXP ?

AUG04 - META and track multiplicity 10% of  „empty events“ in EXP Mean multiplicity  in EXP same as in SIM - same centrality ?

Summary and outlook hadron PID analysis (beta vs momentum) performed using kick and runge-kutta tracks for Nov02 and Aug04 experiment problem with track reconstruction efficiency for particles with low energy loss observed  meson and baryon yields extracted to be done: further efficiency corrections needed

NOV02 gen3 and gen4 QA tracks yields per sector, theta and phi distributions of negative tracks (test of PID) momentum determination - protons, pi- ??

NOV02 gen3 - negative tracks vs phi large differences between sectors, for spline 15% difference between 2 sectors, kick even worse  yields copy distribution of negative tracks should be the same in electron distributions???? SIM EXP

NOV01 - negative tracks vs phi sec0 not used for analysis much better than Nov02 gen3 EXP SIM

NOV02 gen4 - negative tracks vs phi much better than Nov02 gen3 SYS 0 SYS 1

NOV02 gen3 - negative tracks vs theta Sec0 - Inefficiency in theta<30 and theta ~ 65 EXP SEC0 SIM EXP SEC3

NOV01 - negative tracks vs theta much better than Nov02! EXP SIM

NOV02 gen4 - negative tracks vs theta differences between sectors SEC 0 SEC 3

NOV02 gen4 protons: mom_track vs mom_beta (p track - p  )  vs p track  p  = M p *  *  SYS 1 SYS 0 KICK SPLINE RK