1. EIC SOFTWARE TOOLS AND NEEDS
Franco Bradamante, A. B., Anna Martin, Giulio Sbrizzai

2. Starting model detector layout
-4<h<4: Tracking & e/m Calorimetry (hermetic coverage)
hadronic calorimeters
e/m calorimeters
RICH detectors
SBS
CBM
EIC R&D
(UCLA, BNL)
EIC R&D
(UCLA, BNL)
ALICE
silicon trackers
TPC
GEM trackers
3T solenoid coils
7/23/2019
A. Bressan

3. Wish list for EIC Reach in kinematic variables
Reliable electron identification
Good hadron PID
High spatial resolution of primary vertex
Low material budget
The more close to 4p acceptance the better
Luminosity and polarization measurement
Close-to-beam-line acceptance add-on detectors to register
recoil protons
low Q2 electrons
neutrons in hadron beam direction
And all this at affordable price!
7/23/2019
A. Bressan

4. COMPUTING TOOLS
The software runs on the BNL (RHIC and ATLAS Computing Facility) where the EIC group has its own nodes, where I do have an account.
7/23/2019
A. Bressan

5. EIC Root based on FairRoot
Slide from Florian Uhlig (ROOT 2015 Workshop)
7/23/2019
A. Bressan

6. EicRoot framework building blocks
Interface to GEANT, ROOT, …
FairBase
PandaRoot
FopiRoot
Track finder,
TPC R&D stuff, …
Presently we are
focused on this part
EicRoot
CbmRoot
GENERATOS
(eic-smear)
RICH stuff
solenoid
modeling
IR design
configuration
7/23/2019
A. Bressan

7. IR v2.1: implementation in EicRoot
photon transport line with Al exit window
Roman Pots
+18 m
electrons
+4.5 m
0 m
-4.5 m
dipole magnet for pair spectrometer
-15 m
low Q2 tagger
-31 m
Legend:
beam pipe
hadron magnet apertures
electron magnet apertures
emcals for lumi monitor
-33m
-45 m
7/23/2019
A. Bressan

8. Our experience from COMPASS
Generators (from good-old Lepto to Pythia 6…BTW EIC plans to bring ℓ𝑁 in Pythia 8)
RC tools
Radgen
Djangoh/HERACLES
GEANT
Moreover we plan to use the comparison with the COMPASS data to validate the new tools developed.
i.e. relevant synergies with COMPASS that remains our primary activity
7/23/2019
A. Bressan

9. Present Activities for EIC
Insert spin effects into the Monte Carlo event generators (presently focused on FFs):
Account for radiative effects at Monte Carlo level
Run EIC ROOT to give inputs for hardware design
RICH dedicated simulations
7/23/2019
A. Bressan

10. Radiative Corrections (DJANGOH/HERACLES)
𝑄 2 =− ℓ− ℓ ′ −𝑘 2
𝑥 = 𝑄 2 2𝑃∙ ℓ− ℓ ′ −𝑘
Photon radiation from the leptons modify the one boson cross-section and change the DIS kinematics on the event by event basis
The direction of the virtual photon is different from the one reconstructed from the leptons, giving rise to:
False asymmetries in the azimuthal distribution of hadrons calculated with respect to the virtual photon direction
Smearing of the kinematic distributions (e.g. 𝑧 and 𝑃 ℎ𝑇 )
To take into account correctly this effect in the SIDIS cross-section we need both the correct weights for every event and an unfolding procedure for the smearing. THIS can ONLY be done by using a Monte Carlo code for RC

11. Radiative Corrections : Deliverables
Deliverables achieved at the end of the project:
Calculate radiative corrections for transverse polarized observables to measure TMDs and polarized exclusive observables.
Provide proof that the MC phase space constrains on the hadronic final state is equal to calculating radiative corrections for each polarized and unpolarized semi-inclusive hadronic final state independently.
Define a software framework and develop a library based on this framework, which integrates the radiative corrections depending on polarization and other determining factors in a wrapper-software.

12. Synergies in RD_FA Study of Universality and Scaling:
SIDIS: JLAB (6 and 12 GeV 𝑒 − ), HERMES (27 GeV 𝑒 − /completed), COMPASS (160 GeV 𝜇)….EIC ( GeV cms).
𝑒 + 𝑒 − : BesIII (4 GeV cms), Babar (10 GeV cms), Belle e BelleII (10 GeV cms)
𝑝𝑝: RHIC ( GeV cms)
all involved in the study of transverse spin and momentum effects (what about LHC? Only After?)
Test the portability simulation codes based on different FF models such as the cluster model of HERWIG ⟶ℓ𝑁
Comparison of tuning for Pythia/Jetset
Development of common simulation codes?
7/23/2019
A. Bressan

13. Backup
7/23/2019
A. Bressan

14. EIC Root based on FairRoot
Active project, officially supported by GSI
Large experiment and user base
Regular releases, active forums, long-term developer support
Several software building blocks readily available
Designed with flexibility in mind
Simulation and reconstruction in the same environment
ROOT-based I/O
Virtual geometry concept (several formats supported)
Virtual Monte-Carlo concept (easy switching between GEANT 3 & 4 transport engines in particular)
7/23/2019
A. Bressan

15. Geometry description Input formats: Output format:
ROOT TGeo (required for tracking detectors)
GEANT GDML
Old HADES .geo files
CAD design drawings (.stp, .stl, .slp)
Output format:
ROOT TGeo
7/23/2019
A. Bressan

16. Example: basic vertex+barrel tracker
Vertex tracker + TPC in 3T field; 10 GeV/c pions at q=75o; momentum resolution?
-> see examples/tracking/config.2 directory for details
7/23/2019
A. Bressan

17. Tracking: momentum resolutionp+
p+; h=3
High resolution up to (at least) |h|~3
High redundancy
(Reasonably) low cost
Low material budget (see next slides)
EIC R&D
(Temple, Saclay)
Variations: MuMegas barrels, smaller TPC radius, …
7/23/2019
A. Bressan

18. Tracking: smearing in kinematic variables
{PYTHIA 20x250 GeV, NO bremsstrahlung} -> {GEANT} -> {Kalman filter track fit}
same procedure; simulation WITH bremsstrahlung
-> looks good despite poor resolution at low Y and long bremsstrahlung tails
7/23/2019
A. Bressan

19. Tracking: “purity” in (x,Q2) kinematic bins
Describes migration between kinematic bins
Important to keep it close to 1.0 for successful unfolding
bremsstrahlung OFF
bremsstrahlung ON
Bremsstrahlung matters even for detector with ~5% X/X 0
“Straightforward” tracking can hardly help at Y<0.1
Other options:
Tracking: try gaussian sum filter; account for kinks; etc …
… or use e/m calorimeter?
7/23/2019
A. Bressan

20. Lepton Kinematics and (x,Q2) coverage
Increasing lepton beam
energy: scattered lepton
is boosted to negative h
Q2 > 1.0 GeV2: rapidity coverage -4 < h < 1 is sufficient
Q2 < 0.1 GeV2: a dedicated low-Q2 tagger is required
high y-coverage limited by
radiative corrections
-> can be suppressed by
requiring hadronic activity
low y-coverage limited by
E’e resolution
-> use hadron or double angle
method to reconstruct event
kinematics
7/23/2019
A. Bressan

21. SIDIS: Pion Kinematics
Cuts: Q2>1 GeV2, 0.01<y<0.95, z>0.1
Increasing lepton beam energy boosts hadrons
more to negative rapidity
Increasing hadron beam energy influences max. hadron energy at fixed h (and p±, K±, p± look the same)
-3<h<3 covers entire pt & z region important for physics
7/23/2019
A. Bressan

22. Interaction Region design
7/23/2019
A. Bressan

23. IR v2.1: design schematics
Electron Direction (Rear Side)
Hadron Direction (Forward Side)
Cryostat
Cryostat
Forward
Detectors
Cryostat
Synrad Fan
Cryostat
Central
Detector
Region
Cryostat
Cryostat
Warm
Quad IP
Warm
Quad
10 mrad
Crossing
Angle
Zero Degree Neutral Detector (ZDC)
Crab Cavity Apertures
Cold Magnet Apertures
space & ~1mrad acceptance for Lumi Monitor
space & ~20mrad acceptance for low Q2 tagger
space & ~8mrad acceptance for ZDC
space & ~10mrad acceptance for Roman Pots
7/23/2019
A. Bressan

24. IR v2.1: implementation in EicRoot
Hadron beam line
Roman Pots location
FFAG bypass
Main detector
Ecal
tracking
layers
20 cm
30cm
Electron beam line
Low Q2 tagger location
-> field maps and magnet aperture sizes imported automatically
-> Roman Pots, Low Q2 tagger & Lumi Monitor partly implemented
7/23/2019
A. Bressan

25. Low Q2 tagger {PYTHIA, 20x250 GeV}
Compact detector system comprising of:
2 tracking layers -> reconstruct q
EmCal -> reconstruct energy
electrons
Tuning phase:
Check magnet bore locations & apertures
Make sure magnetic field maps are correct
Adjust scattering angle reconstruction code …
Y-coordinate, [cm]
X-coordinate, [cm]
7/23/2019
A. Bressan