Physics Generators existing at BNL
Tobias Toll, BNLEIC R&D Simulation Workshop
BNL 10/8/12
Monday, October 8, 2012
https://wiki.bnl.gov/eic/index.php/Simulations
For information about generators,on how to use, references etc.
https://wiki.bnl.gov/eic/index.php/Computing
Information about how to get started and using the EIC computing at BNL:
EIC computing at BNL
If you don’t have an RCF accounthttps://www.racf.bnl.gov/docs/getstart/newuserform
‣ email John McCarthy & ElkeTo add EIC to existing RCF accoint:
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Monday, October 8, 2012
Why simulate?
Physics simulators crucial for IR design and predicting feasibility of making key EIC measurements.
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Monday, October 8, 2012
Why simulate?
Deliverables Obserables MC generator
Polarised gluon distribution Δg
Scaling violation in inclusive DIS
PEPSI+LEPTO
Polarised quark and antiquark densities
semi-incl. DIS for pions and kaons
PEPSI+LEPTO
Sivers and unpolarised TMDs for quarks and
gluon
SIDIS with transv. polarisation/ions; di-hadron
(di-jet) heavy flavoursgmc_trans
GPDs, 3D structure of quarks and gluon in
b-pL space
Exclusive DIS: vector mesons and DVCS
MILOU
EIC e+p Physics Programme,Key measurements
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Monday, October 8, 2012
Why simulate?
Deliverables ObservablesMC
generator
integrated gluon distributions
F2, L Pythia6+EPS09
kT dependent gluons; gluon correlations
di-hadron correlations
Pythia6/DPMJetIII hybrid
b-dependence of gluon
distribution and correlations
Diffractive VM production and DVCS, coherent and incoherent
parts
Sartre
EIC e+A Physics Programme, Key measurements
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What is an MC generator?
T. Toll MC@NLO 9
DokshitzerGribovLipatovAltarelliParisiTextText
Monday, October 8, 2012
What is an MC generator?Hard scattering pQCD or QED Matrix Element, at LO, NLO...
Initial state QCD radiations: collinear
(DGLAP), non-collinear (CCFM, RCBK) ...
Input distribution: PDF, uPDF, GPD, TMD...
Final State brems-strahlung PS,
vacuum/medium
Lund Strings, Clusters,
independent, medium
...
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Monday, October 8, 2012
What is an MC generator?Hard scattering pQCD or QED Matrix Element, at LO, NLO...
Initial state QCD radiations: collinear
(DGLAP), non-collinear (CCFM, RCBK) ...
Input distribution: PDF, uPDF, GPD, TMD...
Final State brems-strahlung PS,
vacuum/medium
Lund Strings, Clusters,
independent, medium
...
Radiative corrections(see Elke’s talk)
Hadronic remnant
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Monday, October 8, 2012
Pythia6
http://home.thep.lu.se/~torbjorn/Pythia.htmlSjostrand, Torbjorn et al. JHEP 0605 (2006) 026 hep-ph/0603175 FERMILAB-PUB-06-052-CD-T, LU-TP-06-13
by T. Sjöstrand
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Multi-purpose generator in ep, all sorts of collinear LO ME
Collinear factorisation (DGLAP) PS
Lund fragmentation (JETSET)
Can simulate non-collinear effects with initial Gaussian gluon and
quark kT distributions.
Code modified to include radiative corrections via RADGEN (by Elke).
Monday, October 8, 2012
Pythia6
xB
-510 -410 -310 -210 -110 1
)2 (G
eV2 Q
1
10
210
310
410
510
610
710
810
y = 0.
01
y = 0.
95 y = 0.
05
y = 0.
6
!Ldt = 10 fb-1 20 GeV on 250 GeV
http://home.thep.lu.se/~torbjorn/Pythia.htmlSjostrand, Torbjorn et al. JHEP 0605 (2006) 026 hep-ph/0603175 FERMILAB-PUB-06-052-CD-T, LU-TP-06-13
by T. Sjöstrand
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Multi-purpose generator in ep, all sorts of collinear LO ME
Collinear factorisation (DGLAP) PS
Lund fragmentation (JETSET)
Can simulate non-collinear effects with initial Gaussian gluon and
quark kT distributions.
Code modified to include radiative corrections via RADGEN (by Elke).
Monday, October 8, 2012
LEPTOMulti-purpose DIS generator. For ep: LO DIS, QCDC & PGF
Often used as part of other software packages, e.g.: PEPSI & DJANGO
Initial state radiation from either DGLAP, or dipoles (ARIADNE)
Fragmentation from Lund model (JETSET)
Rapidity gaps simulated with soft colour interactions
Uses LHAPDF for PDF
Ingelman, G. et al. Comput.Phys.Commun. 101 (1997) 108-134 hep-ph/9605286 DESY-96-057
by G. Ingelman et. al.
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Monday, October 8, 2012
PEPSI DIS generator with polarised proton, based on LEPTO 4.3.
Includes LO DIS, QCDC, PGF + electro-weak interactions
Polarised density functions are set in LEPTO
Code modified to include radiative corrections via
RADGEN (by Elke)
Various parametrisations of Δq(x, Q2) and Δg(x, Q2)
-0.04
-0.02
0
0.02
0.04
-0.04
-0.02
0
0.02
0.04
-0.04
-0.02
0
0.02
0.04
10 -2 10 -1 1
DSSVDSSV andEIC 5 GeV on 100 GeV& 5 GeV on 250 GeV
all uncertainties for !"2= 9x!u x!d
x!s
x
Q2 = 10 GeV2
x!g
x
-0.2
-0.1
-0
0.1
0.2
0.3
10 -2 10 -1 1
L. Mankiewicz, A. Schäfer and M. Veltri, Comp. Phys. Comm. 71, 305-318 (1992)
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Uncertainty bands on helicity parton distributions, presently (blue) andwith EIC data (red), using projected inclusive and semi-inclusive
EIC data sets
Monday, October 8, 2012
gmc_transSIDIS generator for ep with polarized
proton, with TMDs,
Choice of TMD parameterisations:Sivers, Collins, Boer-Mulders
Produces a single hadron, not a full event:e+p→e+h, h = π+, π-, π0, K+, K-
Polarized cross-section used to generate angular distribution of produced hadron
x-410 -310 -210 -110 1
UT
A
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
< 20, 0.8 < z < 1.0210 < Q < 20, 0.1 < z < 0.2210 < Q
< 2, 0.8 < z < 1.021 < Q < 2, 0.1 < z < 0.221 < Q
Written for the HERMES collaboration
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Sivers asymmetry as a function of x for different Q2 and z values and integrated over pT, at the positivity bound, showing the precision scaled for 10 fb-1
Monday, October 8, 2012
MILOUA DVCS generator: ep→eϒp, based on
GPDs at evolved at NLO: DVCS, Bethe-Heitler and interference
Optional: protons dissociation and initial-state QED radiative effects and radiative
corrections
t-dependence parametrised as an exponential:
A. Freund and M. McDermott [All ref.s in: http://durpdg.dur.ac.uk/hepdata/dvcs.html]
EIC pseudo data20 GeV on 250 GeV!Ldt = 100 fb-1
0 1 2 3 4 5 6
0.5
0.0
0.5
! (rad) ! (rad)0 1 2 3 4 5 6
0.5
0.0
0.5
A UTsin
(!"!
s)
A UTsin
(!"!
s)
Q2 = 4.4 GeV2xB = 8.2 10-4t = -0.25 GeV2
Q2 = 13.9 GeV2xB = 8.2 10-4t = -0.25 GeV2
#2 = +1.5#2 = 0#2 = -1.5
dσ
d|t| = e−B(Q2)·|t|
Perez, E. et al. hep-ph/0411389 DESY-04-228
Maintained at BNL by Salvatore Fazio
16DVCS polarised asymmetry AUT for T-polarised photonsMonday, October 8, 2012
DJANGOHUsed by EIC primarily to simulate the effects of radiative
corrections in both ep and eA
DIS generator with both QED and QCD radiative effects
Contains HERACLES MC for complete one-loop electroweak radiative corrections and scattering
For high hadronic mass HERACLES uses an interface to LEPTO,for low mass to SOPHIA
Fragments partons via the Lund model in JETSET.
Can be used with nuclear PDFs as well
by H. Spiesberger MZ–TH/05–15
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Sartre
Diffraction in e+A collisions with the EIC
The e+A Working Group(Dated: Draft: April 30, 2009)
Abstract to be added ...
Contents
I. Introduction 1
II. All-twist saturation picture of diffractionin nuclei 3A. Comparison to HERA data 6B. The nuclear diffractive structure function 7
III. Leading-twist nuclear shadowing andcoherent diffraction in DIS with nuclei 10
IV. Kinematics of Diffractive Events 12
V. Key Measurements 13
VI. Detection of Diffractive Events 14A. Overview of Methods 14B. Forward Spectroscopy 15
1. Angular Divergence of the Beam 152. Measuring Small Scattering Angles 163. Existing Forward Spectrometer of
Relevance for EIC 16C. Large Rapidity Gap (LRG) Method 18D. Nuclear Breakup and Implications for EIC 19
VII. Simulations 20A. Triggering on Diffractive Events 20B. Acceptance Coverage 21C. Reproducability of HERA Plots 22
VIII. Detector and Machine Requirements 23
IX. Summary 23
References 25
I. INTRODUCTION
The phenomenon of diffraction is familiar to us frommany areas of physics and is generally understood to arisefrom the constructive or destructive interference of waves.One such example, a plane wave impinging on a singleslit is shown in Fig. 1. In the strong interactions, diffrac-tive events have long been interpreted as resulting fromscattering of sub-atomic wave packets via the exchange ofan object called the Pomeron (named after the Russianphysicist Isaac Pomeranchuk) that carries the quantumnumbers of the vacuum. Indeed, much of the strong in-teraction phenomena of multi-particle production can beinterpreted in terms of these Pomeron exchanges.
FIG. 1:
In the modern strong interaction theory of Quan-tum ChromoDynamics (QCD), the simplest model ofPomeron exchange is that of a colorless combinationof two gluons, each of which individually carries colorcharge. In general, diffractive events probe the com-plex structure of the QCD vacuum that contains color-less gluon and quark condensates. Because the QCD vac-uum is non–perturbative and because much of previouslystudied strong interaction phenomenology dealt with softprocesses, a quantitative understanding of diffraction inQCD remains elusive.
Significant progress can be achieved throught the studyof hard diffractive events at collider energies. These al-low one to study hadron final states with invariant massesmuch larger that the fundamental QCD momentum scaleof ∼ 200 MeV. By the uncertainity principle of quantummechanics, these events therefore provide considerableinsight into the short distance structure of the QCD vac-uum.
A QCD diagram of a diffractive event is shown inFig. 2. It can be visualized in the proton rest frame asthe electron emitting a photon with virtuality Q2 andenergy ω, that subsequently splits into a quark–anti-quark+gluon dipole; other wave packet dipole configura-tions are also feasible. These dipoles interact coherentlywith the hadron target via a colorless exchange. Thefigure depicts this as a colorless gluon ladder, which asdiscussed previously, is a simple model of Pomeron ex-change.
Because the spread in rapidity between the dipole and
|t | (GeV2) |t | (GeV2)0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18
)2 /d
t (nb
/GeV
e’ +
Au’
+ J/!)
!(e
+ A
u "d
)2 /d
t (nb
/GeV
e’ +
Au’
+ #)
!(e
+ A
u "d
J/$ #
"Ldt = 10 fb-11 < Q2 < 10 GeV2x < 0.01|#(edecay)| < 4p(edecay) > 1 GeV/c%t/t = 5%
"Ldt = 10 fb-11 < Q2 < 10 GeV2x < 0.01|#(Kdecay)| < 4p(Kdecay) > 1 GeV/c%t/t = 5%
104
103
102
10
1
10-1
10-2
105
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10-2
coherent - no saturationincoherent - no saturationcoherent - saturation (bSat)incoherent - saturation (bSat)
coherent - no saturationincoherent - no saturationcoherent - saturation (bSat)incoherent - saturation (bSat)
New event generator for exclusive diffractive vector meson and DVCS production in ep and eA (and UPC)
Uses the dipole models bSat and bNonSat
DGLAP gluon evolution, with Gaussian proton shape and Woods-Saxon nuclear shape
Uses Gemini++ for nuclear break-up
Outlook: Coherent inclusive diffraction
T. Ullrich and TT
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Based on Dual Parton Model, with soft and perturbative pomeron exchanges and AGK cutting rules
In ee, ep, pp, pA, eA, and AA. From a few GeV to highest cosmic ray energies
Only applicable for photo-production!
Uses FLUKA for intra-nuclear cascade and evaporation
Uses Lund model (JETSET) for fragmentation
Uses a Glauber model based on Woods-Saxon for initial nucleus
DPM-JetIII
S. Roesler, R. Engel and J. Ranft, arXiv:hep-ph/0012252
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Monday, October 8, 2012
e-
e-
A
σ
A’
New Pythia-DPM-JetIII hybridUsed primarily by EIC to simulate
dihadron correlations
Uses ME and PS from Pythia6, with nPDF EPS09
Nuclear geometry (WS) from DPMJet, as well as Nuclear evaporation/nuclear
fission/fermi break-up
Energy loss effects to simulate fragmentation effects in cold nuclear
matter (Salgado & Wiedermann)
By Liang Zheng with Elke and J.H.
2 2.5 3 3.5 4 4.50
0.020.040.060.08
0.10.120.140.160.18
eAueAu - sat
eAu - nosateCa
pTtrigger > 2 GeV/c
1 < pTassoc < pT
trigger
|!|<4
ep Q2 = 1 GeV2
!"!"
C(!"
)
C eAu
(!"
)
2 2.5 3 3.5 4 4.50
0.05
0.1
0.15
0.2EIC stage-II# Ldt = 10 fb-1/A
20Rad. Corr. in progress
Monday, October 8, 2012
New Pythia-DPM-JetIII hybrid4 contributions to decorrelation:
1. Higher order effects, like (a) initial state PS and (b) NLO hard gluon+loop
2. Non-collinear effects, like (a) intrinsic kT of gluon. Also, (b) combination, with non-collinear initial state radiations and Matrix Elements.
3. Saturation vs. 4. Multiple scattering (not in eA)
Can turn on/off 1(a), and has (crude) mechanism for 1(b) & 2(a)
CASCADE contains 1(a) & 2(a), (b)Only for ep & pp
In progress: CASCADE for eA (H. Jung & TT)
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Monday, October 8, 2012
• CASCADE (H. Jung et. al.)Multi-purpose DIS. kT-factorised ME, CCFM evolution, uPDFs. Saturation included in initial state and by bound in evolution.Jung, H. et al. Eur.Phys.J. C70 (2010) 1237-1249 arXiv:1008.0152 [hep-ph] DESY-10-107
• MC@NLO (S. Frixione, TT)Only Heavy Quarks in photo-production for ep. Coll. ME calculated at NLO and matched with PS. LHAPDF.Toll, Tobias et.al. Phys.Lett. B703 (2011) 452-461 arXiv:1106.1614 [hep-ph] CERN-PH-TH-2011-128
• RAPGAP (H. Jung)Multipurpose. Simulates hard diffractive DIS. DGLAP.Jung, Hannes Comput.Phys.Commun. 86 (1995) 147-161
Other resources
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