hadron production in hard scattering event generatorgeant
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Hadron production in hard scattering
Event Generator GEANT
JETSET:Single particle production in hard scattering
High probability to detect leading hadron in the forward detector
The primary hadrons produced in string fragmentation come from the string as a whole, rather than from an individual parton.
- Before- After quarkTarget remnant
DIS:Q2>1GeV2
W2>4 GeV2 (10)y<0.85
LUND Fragmentation Functions
LUND Fragmentation Functions
HERMES
low PT
high PT
PDF side: gaussian <kT2>
212 2212 2 0
10 2 2
0
( , )( , )1 ( , )( , )
( , )
hf ff
h
hf f fDIS
f ff
fD ze dxq x QdN z Qe dxq x Q D
dzN e dxq x Q
Q
z
MC:MC:PYTHIA in combination with JETSET; PDF:CTEQ-6PYTHIA in combination with JETSET; PDF:CTEQ-6
DATA:DATA:unpolarised p-targetunpolarised p-target
QQ2 2 > 1GeV> 1GeV22, W, W22>10 GeV>10 GeV22, z>0.2, 2<p, z>0.2, 2<phh<15GeV<15GeV
HERMES: Fragmentation and Multiplicities
Tuning of JETSET FF parameters to multiplicities in acceptanceTuning of JETSET FF parameters to multiplicities in acceptance
PT
+
-
+
-
-
+
-
+
Mu
ltip
lici
ties
z PT
HERMESHERMES-MCTune-2Tune-3JETSET-std
CLAS data vs LUND-MC
CLAS data (4.3GeV) and LUND-MC comparison
0.5<z<0.8
LUND-MC tuned at higher energies
QQ2 2 > 1GeV> 1GeV22, W, W22>4 GeV>4 GeV22, z>0.5,y<0.85, z>0.5,y<0.85
LUND event-II
Lund ID
ep -> e’+ -> e’ pK→
Particle number in the event
Parent and first daughter line numbers
p
K*+
charge and status
px py pz
Momentum in GeV, E m Vx Vy Vz,
Vertex in cm
K
Exclusive + at 6 GeV
PYTIA-6
+ 2
Exclusive production background from PYTHIA
Pions from string (direct) present the lower limit for current fragmentation events
Filled (open) symbols represent pions from exclusive (all) vector mesons.
electron
0 sample “clean” at large z (non-string pions are mainly from semi-inclusive +, )
GEANT simulation
Angular acceptance for charged tracks for CLAS+IC configuration
Maximum angle ~50o
Minimum angle ~14o
13o
50o
Background studies for CLAS with IC
CLAS data
GEANT+backgroundtarget
IC edgeshielding
Background accounting procedure tested with e1dvcs
CLAS GEANT-MC + background consistent with data
Acceptance moments from MC
generatedreconstructed
Extract acceptance moments from MC
CLASHERMES
3 methods to analize the azimuthal moments
fit
I
II
III
Different methods have different sensitivity to acceptance corrections
LUND MC with Long. Pol. Target: SSA for +
sin and sin2 moments arising from the Collins effect added in MC using predictions from Efremov et al.Phys.Rev.D67:063511,2003
Simulated and reconstructedSSA moments consistent
distributions from MC vs 5.7 CLAS data.Fiducial cuts on e,+ and smearing applied.
CLAS-Data
Summary
Monte-Carlo generators have become an essential tool for feasibility studies, simulation of anticipated physics and background rates, acceptance and other corrections.
Detailed simulation of processes of interest is crucial to keep under control systematic errors due to, both detector and physics background contributions
LUND-MC combined with GEANT-simulation of detector response provide test of procedures for global analysis and extraction of physics observables.
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