mea surement of p 0 – induced single leptons in the hades rich
DESCRIPTION
Mea surement of p 0 – induced single leptons in the HADES RICH. T. Eberl, T. Christ, L. Fabbietti, J. Friese, R. Gernhäuser, J. Homolka, H.-J. Körner, M. Münch, B. Sailer, and S. Winkler for the HADES collaboration. Motivation: Study of close e + e - - pairs RICH ring properties - PowerPoint PPT PresentationTRANSCRIPT
Measurement of – induced single leptons in the HADES RICH
T. Eberl, TU München
T. Eberl, T. Christ, L. Fabbietti, J. Friese, R. Gernhäuser, J. Homolka, H.-J. Körner, M. Münch, B. Sailer, and S. Winklerfor the HADES collaboration
Motivation:• Study of close e+e- - pairs• RICH ring properties• Comb. backgr. in e+e- - spectroscopy
Exp. SetupHADES with low B-Field
Results• Opening angle distributions of identified close e+e- - pairs
• Properties of Cherenkov Rings !!!
Dilepton Spectroscopy
T. Eberl, TU München
Comb. Backgr.Suppression
Close pair recognition !!!! & rejection
2 close rings in RICH
2 close tracks in MDC
HADES : Low mass e+e- pairs from , p, A + A collisions
full scale HGEANT simulation
Sources of Close Rings & Tracks
T. Eberl, TU München
Possible combinations P1 P2 RICH MDC e+ e- 1 1e+ e- 1 2e+ e- 2 2e+ e- 2 1 fake ? e+ e- 2 3 ??...........
e+/- 1 1p 1 1 fake !+/- 1 1 fake !...........
rare cases :p e+/- 1 2 +/- e+/- 1 2...........
e+
e-
< > ~ 2 0
Conversionin
Target & Radiator
e+
e-
0
< > ~ 13 0
Dalitz
interestingpair ???
Physics processes :0 - Dalitz , conversion, compt. scatt.
e-
Experimental Setup @ GSI, Darmstadt
T. Eberl, TU München
HADES with RICH, MDC 1 / 2 , META , low B – field
optimized for e+/- with low p full reconstr. of low mass pairs
Deflection in B - fieldMDC–META
~ 1 / P
standard
Acceptance for -Dalitz leptons
T. Eberl, TU München
Simulation: -Dalitz decay
3-threshold of RICH
HADES acceptance
C + C @ E = 1A GeV
T. Eberl, TU München
Numerical Experiment(Simulation)UrQMD + HGEANTSetup as in exp.Trig: MMeta > 3; included
NNsimsim = = 77 * 10 * 1066 evts. evts.
Experiment @ SIS - GSI
Ibeam = 106 / s, Targ: tot = 5% Trig: MMeta > 3; /tot ~ 0,7
NNexpexp = = 99 * 10 * 1066 evts. evts.
Analysis conditions:Event selection:• MDC I/II : multiplicity Mtrack > 3• RICH : min. 1 Ring corr. with MDC & META
Hit matching conditions:• before B- field : MDC-RICHMDC-RICH• after B- field : MDC-META noMDC-META• no TOF cut !!
e+/e- cand. for C + C @ 1A GeV
T. Eberl, TU München
Rings in RICH
Defl. angles MDC–META
of reconstructed tracks in RICH & MDC & META
Single ??
Doublee+e-
-10 -8 -6 -4 -2 02 46 81 0
200
600
1000
1400
1800
2200 SIM
EXP
N = 89205
- [°]MDC META
Measured RICH Rings
T. Eberl, TU München
C + CE = 1A GeV
-Dalitz decay leptons ?!
Ring recognition:
Pattern Matrix
Hough-Transf.
e+ e- pairs
T. Eberl, TU München
Opening angle distr. in MDC (before B – field)Reasonable agreement !!!
C + CE = 1A GeV
Sim. normalised to Exp.
0 – Dalitz
Opening angle [deg]
Co
un
ts [
a.u
. ]
Sim (total)
Exp
Conversion
Ring selection for single electrons
T. Eberl, TU München
opening angle [°]
0
20
40
60
80
100
120
140
160
180EXP
SIM
0 8642 10
e+e- pairs with 1 track / ring
2 RICH rings2 RICH rings
2 MDC tracks2 MDC tracks
ee++
ee--
Opening angle distr.In MDC (before B - field)
Single rings !
Rings for close tracks
T. Eberl, TU München
opening angle [°]
0
50
100
150
200
250
300
350
400
EXP
SIM
0 8642 10
Opening angle distr.in MDC (before B - field) e+e- pairs with 2 tracks / ring
ee++ ee--
ee++ ee--
1 RICH 1 RICH ringring
2 MDC 2 MDC trackstracks
1 MDC 1 MDC tracktrack
Double rings !
Ring properties: charge & pads
T. Eberl, TU München
Charge/ring [a.u.] Pads/ring
Co
un
ts [
a.u
.]
Co
un
t s [
a.u
.]C
ou
nt s
[a
.u.]
Co
un
t s [
a.u
.]
SimExp
Charge per ring Pads per ring
single
double
C + CE = 1A GeV
single
double
ee++ee--
ee++ ee--
Ring properties: cluster & quality
T. Eberl, TU München
clusters/ring matrix sum [a.u.]
Co
un
ts [
a.u
.]
Co
un
t s [
a.u
.]C
ou
nt s
[a
.u.]
Co
un
t s [
a.u
.]
SimExp
Clusters per ring Pattern Matrix sum
C + CE = 1A GeV
single single
double double
ee++ee--
ee++ ee--
Lepton recognition
T. Eberl, TU München
HADES reconstruction probability for a -Dalitz decay lepton
C+C, E=1AGeV, low field setup, cons. param. set Momentum [MeV/c]
Po
lar
ang
le [
deg
]
GEANT Simulation:
-Dalitz decay
ee--
RICHRICHMDCMDC
METAMETA
ee++
RICHRICH
MDCMDCMETAMETA
min 1 lepton required !
Pair recognition
T. Eberl, TU München
Po
lar
ang
le [
deg
]
Momentum [MeV/c]
GEANT Simulation:
-Dalitz decay
HADES reconstruction probability for a lepton from an identified -Dalitz lepton pair
C+C, E=1AGeV, low field setup
ee--
RICHRICHMDCMDC
METAMETA
ee++
RICHRICH
MDCMDCMETAMETA
2 leptons required !
Summary
Dilepton spectroscopy with HADES :• Measurement of close pairs for low momentum e+e- • Good statistics of 0 – Dalitz and conversion leptons• Experimental data for comb. backgr. and eff. studies
Results from prel. analysis• Ident. of rings from fully reconstr. single leptons in RICH• Full scale simulation vs. experiment : ok• Simulation: single lepton reconstr. prob. for 0 – Dalitz • Meas. of key ring prop. for singles and doubles (for each sector)Outlook:• Quantitative comb. backgr. studies• Efficiencies for single lepton identification
T. Eberl, TU München