hades coll. meeting, oct. 31, 2007 charged pion production in c+c at 1 and 2 a gev results of data...

HADES coll. meeting, Oct. 31, 2007

Charged pion production in C+C

at 1 and 2 A GeV

• results of data analysis from experiments NOV02 and AUG04

Jehad Mousa and Pavel Tlustý

• study of charged meson production in C+C

• new: more detailed efficiency study of real data

new method of extrapolation of particle yields to full solid angle

better control of systematic errors

• report on C+C charged meson analysis http://hades-wiki.gsi.de/cgibin/view/Physics/HadronProduction

HADES coll. meeting, Oct. 31, 2007

• two tracking methods: Kick and Runge-Kutta

• Kick+RK : inner mdc segment 2 > -1,

• RK: 2 < 1000, RKAccepted=1, MetaHit matched

• tracks with TOFINO paddle multiplicity =1

• PID - velocity and momentum

Track selection and PIDTrack selection and PID

HADES coll. meeting, Oct. 31, 2007

PID efficiency and purityPID efficiency and purity

- performance checked using UrQMD

- pions identified for momenta 150 < p < 1000 MeV/c

HADES coll. meeting, Oct. 31, 2007

Acceptance and efficiencyAcceptance and efficiency efficiency calculated using UrQMD as

ratio

Nrectracks/Nprimary

for p, +,- in theta vs momentum

averaged over phi

HADES coll. meeting, Oct. 31, 2007

““Selfconsistency check” - NOV02 - Selfconsistency check” - NOV02 -

UrQMDUrQMD

),( ),(

),( ),(),(

pEp

pPpNpN identified

corr

UrQMD input (emitted) and its reconstruction by analysis

HADES coll. meeting, Oct. 31, 2007

““Selfconsistency check” - NOV02 - Selfconsistency check” - NOV02 -

UrQMDUrQMD UrQMD input (emitted) and its reconstruction by analysis

HADES coll. meeting, Oct. 31, 2007

Reconstruction efficiency checkReconstruction efficiency check

-

-

HADES coll. meeting, Oct. 31, 2007

Reconstruction efficiency checkReconstruction efficiency check

Errors of individual data points from

sectorwise analysis:

1 GeV 2 GeV

RMS 3-5% 2-3%

maximum up to 20% up to 20%

Error of integral yield from

sectorwise analysis:

1 GeV 2 GeV

RMS 2% 1.5%

maximum 7% 4%

HADES coll. meeting, Oct. 31, 2007

Results

HADES coll. meeting, Oct. 31, 2007

dN/d cos(cm) ~ 1. + A2 ∙ cos2(cm)

Center of mass polar distributions

HADES coll. meeting, Oct. 31, 2007

H

h

h

Center of mass polar distributions

HADES coll. meeting, Oct. 31, 2007

Center of mass polar distributions

A2 EXP A2 UrQMD

mom_cm > 200 MeV/c 1.05 ± 0.20 1.08

all momenta 0.70

exp. data in agreement with UrQMD => A2 = 0.7 used for PLUTO simulation of dileptons

2 A GeV

1 A GeV

A2 EXP A2 UrQMD

mom_cm > 200 MeV/c 0.88 ± 0.12 1.45

all momenta 0.56

exp. A2 lower by ~ 40% than UrQMD => A2 = 0.34 recommended for PLUTO simulation of dileptons

HADES coll. meeting, Oct. 31, 2007

Brockman et al. Ar+KCl 1.8 AGeV

central collisions:

Brockman: similar A2 = 0.52 but different A2 dependence on momentum

FOPI NPA 781 (2007) shows the same anisotropy for Ca+Ca 1.93 A GeV

HADES 2 A GeV

Center of mass polar distributions

HADES coll. meeting, Oct. 31, 2007

mmTT distributions distributions

21 /2

/12

1 TmTm

TT

TT eCeCdm

d

m

Fitting of mT spectra measured at midrapidity by a Bolzmann distribution with one or two slope function

Inverse slope shows temperature of thermal source

HADES coll. meeting, Oct. 31, 2007

mmTT distributions C+C 1 A GeV distributions C+C 1 A GeV

HADES coll. meeting, Oct. 31, 2007

mmTT distributions C+C 2 A GeV distributions C+C 2 A GeV

HADES coll. meeting, Oct. 31, 2007

mmTT distributions at midrapidity distributions at midrapidity

1 A GeV

2 A GeV

1 A GeV

2 A GeV

H

H

HADES coll. meeting, Oct. 31, 2007

Fits of pFits of ptt by 1 or 2 slopes by 1 or 2 slopes

HADES coll. meeting, Oct. 31, 2007

mmTT distributions distributions

HADES coll. meeting, Oct. 31, 2007

mmTT distributions distributions

1 A GeV 2 A GeV

HADEST+ = 58 ± 1

T- = 58 ± 1

T+ = 50 ± 10; 89.5 ± 2.1

T- = 49 ± 5; 86 ± 3

KaosT- = 45 ± 3; 62 ± 3 T- = 40 ± 3; 86 ± 3

Taps T0 = 54 ± 3 T0 = 83 ± 2 (one slope!)

HADES coll. meeting, Oct. 31, 2007

Rapidity distributionsRapidity distributions

HADES coll. meeting, Oct. 31, 2007

Extrapolation in pExtrapolation in ptt

HADES coll. meeting, Oct. 31, 2007

Extrapolation in pExtrapolation in ptt

HADES coll. meeting, Oct. 31, 2007

Rapidity distributionsRapidity distributions

symmetrized

HADES coll. meeting, Oct. 31, 2007

Rapidity distributionsRapidity distributions

HADES coll. meeting, Oct. 31, 2007

Rapidity distributionsRapidity distributions

symmetrized

HADES coll. meeting, Oct. 31, 2007

LVL1 trigger events - efficiency corrected

within HADES acceptance and extrapolated to full solid angle

Pion multiplicities IPion multiplicities I

Extrapolation to all rapidities

A – based on UrQMD

B – based on PLUTO

HADES coll. meeting, Oct. 31, 2007

PLUTO simulationsPLUTO simulations

Variations of extrapolation factor within 3% for both 1 and 2 A GeV data

HADES coll. meeting, Oct. 31, 2007

LVL1 trigger events - efficiency corrected, within HADES acceptance

Systematic errors from reconstruction efficiency?

1) N(p+d)exp/N(p)UrQMD same within 6%

2) track multiplicity distributions Exp vs UrQMD

reasonably agree

3) sectorwise analysis - error within 5%

Pion multiplicities IIPion multiplicities II

LVL1 trigger events extrapolation from HADES acceptance to 4 and all momenta - using UrQMD and measured anisotropy =>M = 0.53 for 1 A GeV and 1.29 for 2 A GeV - used for normalization of di-lepton spectra

Systematic errors ? - possibly small, extrapolation factor only ~ 1.5,

study using PLUTO show small deviations, still 10% difference between UrQMD and PLUTO

HADES coll. meeting, Oct. 31, 2007

Pion multiplicities IIIPion multiplicities IIIcentrality selection

by the LVL1 trigger:

estimate of Npart :

8.6 and 8.4 for 1 and 2 A GeV

HADES coll. meeting, Oct. 31, 2007

Pion multiplicities per participantPion multiplicities per participant

1 A GeV 2 A GeV

HADES 0.061 ± 0.007 0.153 ± 0.016

Kaos0.061 ± 0.009 ± ??

Taps ( 0 )0.056 ± 0.004 + 11% 0.138 ± 0.014 + 23%

HADES coll. meeting, Oct. 31, 2007

Summary

• charged meson production from C+C at 1 and 2 A GeV studied

• new results:

multiplicities - in large acceptance

polar anisotropies - momentum dependence

mT fits - one vs two slopes

rapidity distributions - rapidity width

HADES coll. meeting, Oct. 31, 2007

Backup slides

HADES coll. meeting, Oct. 31, 2007

Principle:for each track a probability that it is of a particle type h is calculated, for all possible particle types Bayes theorem implementedcut 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 variablesin 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 MethodParticle Identification Method

HADES coll. meeting, Oct. 31, 2007

Experimental and analysis Experimental and analysis

detailsdetails November 2002 C+C 2 AGeV 200*106 events: 56% LVL1 trigger + 44% LVL2 trigger only 2 sectors with 4 chambers

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: 75% LVL1 trigger + 25% LVL2 trigger

20 M events (gen2 dst’s) used for analysis (day 250, 1st level trigger events)

UrQMD simulations - 47 M events (gen2) used for parameter production 20 M events (gen2) used for analysis

HADES coll. meeting, Oct. 31, 2007

Theta_cm distributions - Kick vs RKTheta_cm distributions - Kick vs RK

dN/d cos(cm) ~ 1. + A2 ∙ cos2(cm)

HADES coll. meeting, Oct. 31, 2007

Kick track multiplicities - exp vs UrQMD

HADES coll. meeting, Oct. 31, 2007

pt distributions - exp vs UrQMD vs PLUTOmidrapidity

midrapidity