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					      Hadron production in C+C
         at 1 and 2 A GeV
                     Pavel Tlustý, NPI Řež


  • analysis of data from experiments NOV02 and AUG04
  for high resolution tracking (Runge-Kutta tracks)


  • summary of charged p meson production in C+C




HADES Coll. Meeting XVI                      Dresden, April 5, 2006
          Experimental and analysis details

November 2002 C+C 2 AGeV
                200*106 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 348-350, 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 1 AGeV
               650*106 events: 50% LVL1 trigger + 50% LVL2 trigger

                    20 M events (gen1 dst’s) used for analysis
                       (days 251+253, 1st level trigger events)
UrQMD simulations - 47 M events (gen1) used for parameter production
                    20 M events (gen1) used for analysis
                Particle Identification Method
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
                   Track selection



• Runge-Kutta tracks matched to META
• inner mdc segment c2 > -1, RK c2 < 1000, SplineAccepted=1
• tracks with TOFINO paddle multiplicity =1
• for NOV02 only sectors No. 0 and 3
Results of hadron ID - NOV02
   Efficiency and purity - NOV02




good up to 1000 MeV/c
Spectrometer acceptance
             Acceptance+efficiency calculated
               from UrQMD data as ratio
                     Nrectracks/Nprimary
             for p, p+,p- in theta vs momentum


             averaged over phi
Corrected particle yields - NOV02 - UrQMD
    UrQMD input (emitted) and its reconstruction by analysis
                          N identified( , p) P( , p)
         N corr ( , p) 
                               A( , p) E ( , p)
      Particle yields - NOV02 sec. No.0


                            Momentum distribution




Theta distribution
     Particle yields - NOV02 sec. No.3


                           Momentum distribution




Theta distribution
Negative tracks - NOV02
             theta distributions:


     SEC 0   differences between sectors and
             gaps already in tracks distribution


             - effect of subdetectors efficiency



     SEC 3
Particle yields - NOV02 - selected region


                           momentum distribution




theta distribution
NOV02 particle distributions in c.m.
                     UrQMD input (emitted)
                     and reconstruction by analysis


                        mom_cm > 200 MeV/c
NOV02 - p distributions in theta_cm
NOV02 - p distribution in mom_cm - UrQMD
NOV02 - p distributions in p_cm - EXP
NOV02 particle yields per event - RK

efficiency corrected, within HADES acceptance
1st level trigger events
             experiment      UrQMD           ratio
            (± bias error)                 Nexp / Nsim
 p+          0.74 ± 0,07      0.77         0.96 ± 0.10
 p–          0.77 ± 0.08      0.80         0.96 ± 0.10
 p           2.37 ± 0.24      2.48         1.05 ± 0.11 *
 d           0.24 ± 0.02        no d in UrQMD

      * (p+d)exp/psim
NOV02 particle yields per event - RK
                                 Nov02        Nov01
      yield/event                 0.77         0.79
                                          HADES acc - 1st level trigger
      correction to 4p 1.46              1.61
      yield corr. to 4p           1.12    4p - 1st1.27 trigger
                                                   level
      correction       to 0.71           0.76
      trigger
      norm. to baryons ?                 0.92
      min bias yield              0.80    4p min.0.89
                                                  bias



• UrQMD yields to 4p - 1.15 p / event (1st level trigger)
•                      0.82 p / event (no bias)

• Np = 0.83 ± 0.08        p0     TAPS
• Np = 0.77 ± 0.07        p+     KAOS
Corrected particle yields - AUG04 sec. No.1


                            Momentum distribution




 Theta distribution
Negative tracks - AUG04
             theta distributions


     SEC 0   differences between sectors,


             gaps in SHOWER+TOFINO
             region



     SEC 3
 Particle yields - AUG04 sec. No.1
analysis check - comparison of 2 RK analyses
AUG04 particle yields per event - RK

efficiency corrected, within HADES acceptance
1st level trigger events
             experiment      simulation        ratio
            (± bias error)                   Nexp / Nsim
 p+          0.30 ± 0.03        0.34         0.88 ± 0.10
 p–          0.32 ± 0.03        0.36         0.89 ± 0.10
 p           2.47 ± 0.25        3.21         0.90 ± 0.11 *
 d           0.42 ± 0.04          no d in UrQMD

      * (p+d)exp/psim
AUG04 particle yields per event - RK
                                 Aug04        Nov01
      yield/event                 0.31         0.79
                                         HADES acc - 1st level trigger
      correction to 4p 1.49              1.61
      yield corr. to 4p           0.46   4p - 1st1.27 trigger
                                                  level
      correction       to 0.69           0.76
      trigger
      norm. to baryons ?                 0.92
      min bias yield              0.32   4p min.0.89
                                                 bias



• UrQMD yields to 4p - 0.52 p / event (1st level trigger)
•                      0.36 p / event (no bias)

• Np = 0.34 ± 0.02        p0     TAPS
• Np = 0.48 ± 0.02        p-     M. Gadzicki et al. (N+N1AGeV)
          Summary of “p” results

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


• comparison of yields
• check of centrality selection of the 1st level trigger - multiplicity
spectra, number of charged baryons per event….
                 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 mom




                           low efficiency for
                                 mips?
NOV02 particle yields per event - kick+RK
                                  RK             kick
       yield/event                 0.77           0.79
       correction to 4p 1.46              1.44
       yield corr. to 4p           1.12           1.14
       correction       to 0.71           0.71
       trigger
       norm. to baryons ?                 ?
       min bias yield              0.80           0.81



 • UrQMD yields to 4p - 1.15 p / event (1st level trigger)
 •                      0.82 p / event (no bias)

 • Np = 0.83 ± 0.08        p0     TAPS
 • Np = 0.77 ± 0.07        p+     KAOS
AUG04 particle yields per event - kick+RK
                                  RK             kick
       yield/event                 0.31           0.31
       correction to 4p 1.49              1.41
       yield corr. to 4p           0.46           0.44
       correction       to 0.69           0.69
       trigger
       norm. to baryons ?                 ?
       min bias yield              0.32           0.30

 • UrQMD yields to 4p - 0.52 p / event (1st level trigger)
 •                      0.36 p / event (no bias)

 • most probably >10% yields lost due to low efficiency

 • Np = 0.34 ± 0.02        p0     TAPS
 • Np = 0.48 ± 0.02        p-     M. Gadzicki et al. (N+N1AGeV)
     NOV02 - META and track multiplicity
Mean multiplicity in EXP greater
than in UrQMD -
different centrality or fake tracks
in EXP ?




8% of „empty events“ in EXP
     AUG04 - META and track multiplicity

Mean multiplicity in EXP same
as in UrQMD -
same centrality ?




10% of „empty events“ in EXP
               Summary and outlook
• hadron PID analysis (beta vs momentum) performed using kick
and runge-kutta tracks for NOV02 and AUG04 experiment
• p meson and baryon yields extracted


•to be done:
•problem with track reconstruction efficiency for particles with low
energy loss observed, further efficiency corrections needed
• new dst‘s for AUG04?
   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
EXP                      sectors, for spline 15% difference
                         between 2 sectors, kick even
                         worse


                         p yields copy distribution of
                         negative tracks
SIM

                         should be the same in electron
                         distributions????
      NOV01 - negative tracks vs phi

                        sec0 not used for analysis
EXP

                        much better than Nov02 gen3




SIM
        NOV02 gen4 - negative tracks vs phi

SYS 0
                            much better than Nov02 gen3




SYS 1
NOV02 gen3 - negative tracks vs theta


          EXP SEC0   Sec0 - Inefficiency in theta<30
                     and theta ~ 65




          EXP SEC3




             SIM
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
     (ptrack - pb ) vs ptrack     pb = Mp * b * g
  SYS 1                   SYS 0          SYS 1      SYS 0
KICK




SPLINE




RK

				
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posted:5/17/2013
language:English
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