e.c. aschenauer does matter respond to fast moving color charge passing through it ? is this...

E.C. Aschenauer

2 E.C. Aschenauer

Does this saturation produce matter of universal properties in the nucleon and all nuclei viewed at nearly the speed of light?

Where does the saturation of gluon densities set in? Is there a simple boundary that separates the region from the more dilute quark gluon matter? If so how do the distributions of quarks and gluons change as one crosses the boundary?

How are sea quarks and gluons and their spin distributed in space and momentum inside the nucleon? How are these quark and gluon distributions correlated with the over all nucleon properties, such as spin direction? What is the role of the motion of sea quarks and gluons in building the nucleon spin?

How does the nuclear environment affect the distribution of quarks and gluons and their interaction in nuclei?

How does matter respond to fast moving color charge passing through it? Is this response different for light and heavy quarks?

How does the transverse spatial distribution of gluons compare to that in the nucleon?

q h

γ* e’

e

E.C. Aschenauer EIC SOFTWARE MEETING @ JLAB, September 2015 3

ELECTRON- PROTON:


Based on: Frankfurt, Freund and Strikman (FFS) [Phys. Rev. D 67, 036001 (1998). Err. Ibid. D 59 119901 (1999)]

FFS

Old model: written before data came out! Used by H1 and ZEUS for their DVCS measurements The ALLM parametrization for F2 is used

The code MILOU contains two main different models for DVCS simulation:

Written by E. Perez, L Schoeffel, L. Favart [arXiv:hep-ph/0411389v1] maintained by S. Fazio BNL

The code MILOU is written in Fortran and was originally developed for HERA experiments. First, the differential cross sections are integrated by the numerical integration package BASES [S. Kawabata, Comp. Phys. Comm. 41, 127 (1986)] to yield probability distributions, which are used by the event generation package SPRING to generate events. MILOU allows to Use both non GPD and GPD-based models Simulate amplitudes for DVCS, BH and the interference term Choosing a proper |t|-dependence Include radiative corrections

https://wiki.bnl.gov/eic/index.php/MILOU#Ref2

https://wiki.bnl.gov/eic/index.php/MILOU#Ref2


GPDs-based Based on: A. Freund and M. McDermott All ref. in: http://durpdg.dur.ac.uk/hepdata/dvcs.html

GPDs, evolved at NLO by an indipendent code which provides tables of CFF at LO, the CFFs are just a convolution of GPDs:

provide the real and imaginary parts of Compton form factors (CFFs), used to calculate cross sections for DVCS and DVCS-BH interference.

q3

DVCS + ISR

The B slope is allowed to be costant or to vary with Q2

a logarithmic t-dependence can be also chosen

Proton dissociation (ep → eγY) can be included, with hadronisation of the

system Y performed by PYTHIA

The initial state radiative corrections can be set Possible Improvements: MILOU proves still to be a valid simulator, capable of reproducing HERA data.

Nevertheless, the tables of CFF used by the code are not under user’s control and

are taken from: http://durpdg.dur.ac.uk/hepdata/dvcs.html the page is not maintained and the authors of the code which generates the tables left physics.

As more data will be collected, if would be helpful to generate a new updated set of tables.

Stratmann & Spiesberger currently on a NLO rad-correction code for DVCS


http://durpdg.dur.ac.uk/hepdata/dvcs.html


Multi-purpose DIS generator. For ep: LO DIS, QCDC & PGF

Often used as part of other software packages, e.g.: PEPSI & DJANGO

Parton shower either ala DGLAP, or dipoles (ARIADNE)

Fragmentation from Lund model (JETSET)

Rapidity gaps simulated with soft colour interactions

Can use LHAPDF for PDF

Ingelman, G. et al. Comput.Phys.Commun. 101 (1997) 108-134 hep-ph/9605286


Based on M.D. Baker PhD Thesis (MIT, 1993) http://lss.fnal.gov/archive/thesis/1900/fermilab-thesis-1993-57.pdf Generalized Cahn effect to all orders of kT/Q for LO-DIS Generalized to include kT at O(s) (QCDC+PGF)

Joshipura & Kramer, JPG 8 (1982) 209 with errors fixed

M.D. Baker + E.C.A.

http://lss.fnal.gov/archive/thesis/1900/fermilab-thesis-1993-57.pdf









Σ Elab (GeV) ep 30x250 GeV

W2 (GeV2)

Now FIXED! Quark mass mixup

M.D. Baker See https://wiki.bnl.gov/eic/index.php/LEPTO for details

Also fixed: LFRAME=4 Lab w/ z along γ*

& PEPSI & DJANGOH

https://wiki.bnl.gov/eic/index.php/LEPTO


DIS generator with polarized proton, based on LEPTO 4.3. Includes LO DIS, QCDC, PGF + electro-weak interactions Polarised and unpolarised PDFs are set in LEPTO Code modified to include radiative corrections via RADGEN (by ECA) need to be finalized To be improved: - include most modern polarised PDFs - combine it with LHAPDF

L. Mankiewicz, A. Schäfer and M. Veltri, Comp. Phys. Comm. 71, 305-318 (1992)


Written for the HERMES collaboration

SIDIS generator for ep with polarized proton, with TMDs

Choice of several TMD parameterizations: 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

Need a new concept for a TMD MC

MPYTHIA see talk by Hrayr or cascade or ….


Hadron level Monte Carlo generator for ep and pp scattering applying kt-factorisation and unintegrated PDFs

H. Jung et al. The Monte Carlo program CASCADE generates a full hadron event record according to the HEP common standards. CASCADE is intended for small x processes. Until now, it uses only gluon chains in the initial state cascade. Different sets of un-integrated gluon densities are available, which all describe HERA F2 data equally well. 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


ELECTRON- PROTON &

ELECTRON – NUCLEUS (UN)-POLARISED


Multi-purpose generator in ep, all sorts of collinear LO ME

Collinear factorization (DGLAP) PS

Lund fragmentation (JETSET)

Can simulate non-collinear effects with initial Gaussian gluon and quark kT distributions. uses LHAPDF for ep/eA PDFs http://home.thep.lu.se/~torbjorn Pythia.html Sjostrand, Torbjorn et al. JHEP 0605 (2006) 026 hep-ph/0603175

several modifications see following pages

http://home.thep.lu.se/~torbjorn

http://home.thep.lu.se/~torbjorn


For PYTHIA & LEPTO & DJANGOH &... Consider clusters and multiparticle beam remnants (e.g. quark +

baryon w/ struck q-bar) The momentum is usually split according to some distribution P(χ). A

single value χ applies to both pL and pT. This keeps the split “soft”. BUT for PYTHIA 2-particle beam remnants, pL is split according to

P(χ) BUT pT (i.e. recoil kT) is arbitrarily split 50%-50%. Not Physical ! all fixed Changes to Model: nuclear parton distributions integrated VM model

t-dependence has been made Q2 dependent reproduce HERA data r005 has been implemented for exclusive rho production has been

implemented radiative corrections have been included eA still needs work

M.D. Baker, E. Aschenauer


Generator for (un)polarised (long.) NC and CC events in ep and eA ep and eA PDFs from LHAPDF

DIS generator with both QED and QCD radiative effects for all cases

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.

Still to do: implement Semi-inclusive CC


Based on Dual Parton Model, with soft and perturbative pomeron exchanges. EIC version modified by Nestor Armestoto take the nuclear fission effect into consideration through FLUKA

In ee, ep, pp, pA, eA, and AA. From a few GeV to highest cosmic ray energies Only applicable for photo-production !

The extension to nuclei is done through Glauber-Gribov theory. Furthermore, the

model employs FLUKA to simulate nuclear evaporation and intra-nuclear cascade.

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

Details: https://wiki.bnl.gov/eic/index.php/DPMJet


By L. Zheng with ECA and J.H. Lee

Used primarily by EIC to simulate dihadron correlations

Uses ME and PS from Pythia6, with nPDF 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)


4 contributions to de-correlation: 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

Can turn on/off 1(a), and has mechanism for 1(b) & 2(a)

CASCADE contains 1(a) & 2(a), (b)

Currently only for ep & pp


ELECTRON – NUCLEUS


“One thing to be mentioned for the case to run PYTHIA in DPMJET is that [typically] only one nucleon in the nucleus will be picked as a target nucleon in the collision.”

M.D. Baker, J.H. Lee, E.C. Aschenauer (PLANNED for 2016)

From: https://wiki.bnl.gov/eic/index.php/DpmjetHybrid

Not valid in the parton saturation / nuclear shadowing regime!


pzquark = Mxγ

ħ=c=1 r=0.88 fm 1/(2Mr) = 0.12 ∆pz∆z =1/2

∆z = 1/(2Mxγ)

∆z/r* = 1/(2Mxr) = 0.12/xBj

High xBj:

Low xBj:

Bauer, Spital, Yennie, Pipkin Rev. Mod. Phys. 50 (1978) 261

λh/r≈1/(2Mxr)=0.12/xBj

Nucleus Rest Frame

For xBj<<0.12, parton wavefunctions and/or interaction cannot be localized.


Most of the complications in saturation theory lie in predicting the dependence on x, Q2. With Glauber, we can make simple map:

F2A/F2

N(x,Q2) σdipole P(Ncoll,b)

Physics impact: Direct measurement of kT recoil

more challenging due to sharing.

Centrality measure to look for enhanced saturation at b=0 may be EASIER.


Th. Ullrich and T. Toll

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


several excellent MC generators are available for ep BUT

o need a MC generator for (un)-polarized kT dependent physics o many have radiative corrections not integrated

RadCor, physics and detector smearing don’t factorize

o need to have RadCor implemented in MC to unfold effects on physics & kinematics o unfolding in bins: Ntrue=Nmeas-Nbckg o Migration from bin to bin influences bin size

Situation for eA generators is significantly worse need a SIDIS generator w/o saturation need CASCADE like eA generator

events smeared into acceptance

MC generators will be the tool to extract the physics from EIC data need to invest work to make them able to do so

https://www.hepforge.org



https://wiki.bnl.gov/eic/index.php/Simulations

https://wiki.bnl.gov/eic/index.php/Simulations

27

BACKUP

E.C. Aschenauer EIC SOFTWARE MEETING @ JLAB, September 2015

e.c. aschenauer does matter respond to fast moving color charge passing through it ? is this...

Documents