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

http://hades-wiki.gsi.de/cgibin/view/Physics/HadronProduction















• 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


PID efficiency and purityPID efficiency and purity

- performance checked using UrQMD

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


Acceptance and efficiencyAcceptance and efficiency efficiency calculated using UrQMD as

ratio

Nrectracks/Nprimary

for p, +,- in theta vs momentum

averaged over phi


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

UrQMDUrQMD

),( ),(

),( ),(),(

pEp

pPpNpN identified

corr

UrQMD input (emitted) and its reconstruction by analysis


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

UrQMDUrQMD UrQMD input (emitted) and its reconstruction by analysis


Reconstruction efficiency checkReconstruction efficiency check

-

-


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%


Results


dN/d cos(cm) ~ 1. + A2 ∙ cos2(cm)

Center of mass polar distributions


H

h

h




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


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



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


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


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


mmTT distributions at midrapidity distributions at midrapidity

1 A GeV

2 A GeV

1 A GeV

2 A GeV

H

H


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



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!)


Rapidity distributionsRapidity distributions


Extrapolation in pExtrapolation in ptt



symmetrized


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


PLUTO simulationsPLUTO simulations

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


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


Pion multiplicities IIIPion multiplicities IIIcentrality selection

by the LVL1 trigger:

estimate of Npart :

8.6 and 8.4 for 1 and 2 A GeV


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%


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


Backup slides


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


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


Theta_cm distributions - Kick vs RKTheta_cm distributions - Kick vs RK

dN/d cos(cm) ~ 1. + A2 ∙ cos2(cm)


Kick track multiplicities - exp vs UrQMD


pt distributions - exp vs UrQMD vs PLUTOmidrapidity

midrapidity

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

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