pion multiplicities for ArKCl 1.75 A GeV, status 12.02.08

pi analysis was done using the SEP05 gen2 dst's, for details see Jehad's presentation in Cyprus meeting.
We use only 4 sectors with 4 chambers. Track selection - RK with not negative chi2_mdc_in and with cut on META quality (<2.5)

Since that time there were several changes which influenced the resulted yields, the shape of distributions (m_t, cos(theta_cm), rapidity remain unchanged. The changes are

1) most important -efficiency based on "new: simulations (Dec.07) is by 13% higher for pi mesons that that used for Jehad's (Cyprus) analysis based on gen2 UrQMD dst's (produced by M. Jurkovic in Aug.07), see http://forum.gsi.de/index.php?t=tree&th=1684&start=0&rid=312&S=128e242df07000655b2ddc75ba0ba3fe
The new efficiency matrix was not produced yet (we need more statistic in sim dst), so results shown below use old efficency matrix multiplied by 1.13
2) removed bug in normalization to one LVL1 event (normalization factor by 10% off)
3) track cleaning implemented - removing one of two tracks if they share one hit in MDC or META

This figure shows that after full analysis (digitization, hit reconstruction, tracking, PID) and efficciency/purity corrections we reconstruct the original UrQMD (LVL1) distribution:

  • selfconsistency check:
    selfconsistency check

The agreement is not perfect, but after production of new efficiency matrix it will improve.

Next figure shows theta distribution of pi+ and pi-:

  • pi theta distribution:
    pi theta distribution

pi multiplicities (LVL1) to HADES acceptance and to full solid angle. Extrapolation to full solid angle based on UrQMD

  LVL1 HADES LVL1 4pi LVL1 HADES LVL1 4pi min.bias 4pi
pi+ 1.90 3.15 2.12 3.51 1.74
pi- 2.30 3.72 2.57 4.16 2.05
pi0       4.07 2.07

LVL1 HADES: full tracking and pid, efficiency corrected, for both exp. data and UrQMD

LVL1 4pi exp : taken as LVL1 HADES multiplied by ratio from UrQMD:LVL1 4pi/LVL1 HADES

Estimate of number of participants: For min. bias 19.7 for ArK and 18.8 for ArCl (average 19.25). The enhancement of N_part between min. bias and LVL1 we estimate from enhancement of pi multiplicities (to 4pi), using UrQMD. The enhancement factor is 2.0. So estimated N_part for LVL1 is 2.0*(19.7+18.8)/2 = 38.5.
The pi multiplicity per participant (pi+ and pi- averaged) is then 3.44/38.5 = 0.089

*To be done:*
1) new efficiency matrix
2) new analysis - efficiency correction
3) extrapolation to full solid angle via extrapolation of p_t distributions
4) systematic errors estimate .....

-- PavelTlusty - 12 Feb 2008

Topic revision: r1 - 2008-02-12, PavelTlusty
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