1 event generator: electron and electron-pair simulations for phenix using exodus and pythia ralf...
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Event Generator:Electron and electron-pair simulations for
PHENIX using EXODUS and PYTHIA
Ralf Averbeck,State University of New York at Stony Brook,
PHENIX Upgrade Workshop, Montauk 3/21 - 3/23 2001
PHENIX Upgrade Workshop, Montauk, 3/21/01 2 R. Averbeck, SUNY SB
Outline
Motivation The heart of the simulation package: EXODUS
event generator decay machine acceptance filter
Proof of principle: CERES cocktail Electrons in PHENIX (Au+Au @ 130 GeV): part I Electrons from open charm
Can PYTHIA describe existing open-charm data? PYTHIA extrapolated to RHIC
Electrons in PHENIX (Au+Au @ 130 GeV): part II Summary
PHENIX Upgrade Workshop, Montauk, 3/21/01 3 R. Averbeck, SUNY SB
MotivationSimulation of
phase-space distributions of “all relevant” sources of electrons & electron pairs (or whatever particle species you prefer)
decays acceptance resolution
Valuable for: acceptance studies (e.g. detector upgrades) development of analysis strategies “reference” for data (“cocktail” plots)
THE example: ”GENESIS” generator (CERES)
G. Agakichiev at al.: Eur.Phys.Jour. C4(98)231
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EXODUS: a “new” cocktail generator
EventBuilder
cc bb DY0 p
Decay Machine
ExperimentFilter
NtuplesASCII
Events
PYTHIA Particle generator
NtuplesASCII
NtuplesASCII
standalone C++ package using ROOT classes
complete separation of particle generator, decay machine, acceptance filter, detector resolution => extremely flexible!
PHENIX Upgrade Workshop, Montauk, 3/21/01 5 R. Averbeck, SUNY SB
EXODUS: particle generator
particle: PID, (E;p), weightstandalone phenomenological generator:
’J/ (, K, p)
needed as input: weight factor (relative to 0): measurement (or model) phase space distributions (pt, y): measurement (or model) mass distributions ()
input distributions provided using “standard” parameterizations (ROOT histograms)
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Resonance mass distributions ()
2222 )()(
2141
cMmMdm
dN
2)(m
m )(22
22
4
4log5.1exp
e
ec mM
mm
m
M
G.J. Gounaris, J.J. Sakurai:(Phys.Rev.Lett. 21(1968)244
With:
PHENIX Upgrade Workshop, Montauk, 3/21/01 7 R. Averbeck, SUNY SB
Phase space distributions and relative particle weights (Au+Au @ 130 GeV)
Transverse momentum:
)mm96.1
96.1logx13exp(p
dp
dN22
t
tt
UA1 parametrization + mt-scaling
Rapidity:
.constdy
dN 5.0y5.0
relative particle weights from thermal model (J.Stachel QM99): ’ Alternative pt distributions: flat, exponential
Alternative y distribution: 2))()(()(
)(75.0exp
)(
)(75.0exp
m
yy
m
yy
dy
dN
PHENIX Upgrade Workshop, Montauk, 3/21/01 8 R. Averbeck, SUNY SB
Decay machine
Task: first generation => full history (for each event)
Generic decay algorithms: Dalitz, 2- and 3-body decays
Individual decay channels can be activated/deactivated
Propagation of weight factors! Only non-trivial decay: Dalitz
PHENIX Upgrade Workshop, Montauk, 3/21/01 9 R. Averbeck, SUNY SB
Dalitz Decays
Parent -> X + l+l- (masses: M, mx, ml)Lepton pair mass:
)()/(
)/(21
)/(
)/(41
2 22
2
2
22/3 )( mF
Mm
Mm
Mm
MmB
mdm
dN ll 22
22
2
2
))/(1(
)/(4
)/(1
)/(1 )(
Mm
Mm
Mm
MmB
xx
with
(N. Kroll, W.Wada: Phys. Rev. 98(1955)1355)
Electromagnetic form factors from exp. data: Lepton-G
(L.G. Landsberg et al. Phys. Rep. 128(85)301)
Angular distr. of leptons in the virtual photon’s restframe:
2cos1d
dN
PHENIX Upgrade Workshop, Montauk, 3/21/01 10 R. Averbeck, SUNY SB
Proof of principle: p+Be @ 450 GeV/c (CERES)
22 041.0)053.0( ppp mrad6.0 mrad3
GeV/c2.0tp 65.210.2 mrad35ee
Take resolution into account: Take acceptance into account: Generation and decay of 10M primary particles/species:
Reasonable description of data (as did GENESIS)
EXODUS technically OK!
PHENIX Upgrade Workshop, Montauk, 3/21/01 11 R. Averbeck, SUNY SB
momentum resolution: (nominal: )
PHENIX acceptance filter (available from J.Jia)
PHENIX: resolution and acceptance
22p 006.0)p036.0(p 22
p 006.0)p003.0(p
PHENIX Upgrade Workshop, Montauk, 3/21/01 12 R. Averbeck, SUNY SB
Electrons in PHENIX (Au+Au @ 130 GeV): part I
Relative weights from thermal model (except J/ transverse momentum distribution from data (+ mt scaling)
flat rapidity distributions Run1 momentum resolution + full PHENIX acceptance
But what about the contribution from open charm?
PHENIX Upgrade Workshop, Montauk, 3/21/01 13 R. Averbeck, SUNY SB
Open charm production in PYTHIA
Goal: tune PYTHIA to describe existing open-charm data (following P. Braun-Munzinger et al. Eur.Phys.J. C 1(98)123) and extrapolate to RHIC
the surprising truth: data exist only from SPS and FNAL fixed target experiments (srqt(s) < 40 GeV)
parameters available in PYTHIA: parton-distribution function (pdf): MRS(G) mass of charm quark: mc = 1.35 GeV/c2
average intrinsic transverse momentum of partons: <kt
2> = 1.0 (GeV/c)2
K (“fudge” cross section scaling factor): K = 5.2
PHENIX Upgrade Workshop, Montauk, 3/21/01 14 R. Averbeck, SUNY SB
PYTHIA tuning: total D cross sections
PYTHIA describes sqrt(s) dependence
different K factors for charged and neutral Ds!
different PDFs do equally well
different <kt2> work
too
PHENIX Upgrade Workshop, Montauk, 3/21/01 15 R. Averbeck, SUNY SB
PYTHIA tuning: D kinematics
Data: D+, D-, D0, D0, Ds+, Ds
+ (E769 PRL 77(96)2392) Common K factor: 5.2
Different PDFs: different <kt2>:
PHENIX Upgrade Workshop, Montauk, 3/21/01 16 R. Averbeck, SUNY SB
PYTHIA tuning: D-meson correlations
Data: D+, D-, D0, D0, Ds+,
Ds+ (WA92 CERN
PPE/36-180)
PHENIX Upgrade Workshop, Montauk, 3/21/01 17 R. Averbeck, SUNY SB
PYTHIA extrapolation to RHIC
extrapolation to RHIC: reasonably small uncertainty cc cross sections (pp):
380 b (130 GeV)730 b (200 GeV)
PHENIX Upgrade Workshop, Montauk, 3/21/01 18 R. Averbeck, SUNY SB
Electrons in PHENIX (Au+Au @ 130 GeV): part II
Add semi-leptonic decay contributions from open charm to cocktail from light-meson decays:
PHENIX Upgrade Workshop, Montauk, 3/21/01 19 R. Averbeck, SUNY SB
Electrons in PHENIX (Au+Au @ 130 GeV): part II
Expected pair spectrum with nominal resolution:
PHENIX Upgrade Workshop, Montauk, 3/21/01 20 R. Averbeck, SUNY SB
Summary
(Simple) simulation tools are available phenomenological event generator decay machine detector resolution parameterization acceptance filter
and can easily be extended! PYTHIA:
describes existing open-charm data has been extrapolated to RHIC energies has been coupled with EXODUS
In case you want to use the package: GO AHEAD!