E.C. Aschenauer for the group arXiv: &

E.C. Aschenauer EIC R&D Meeting July 2014  Optimize the IR design to be able to integrate  the luminosity monitor  the lepton polarimeter  the low Q 2 -tagger  Develop a Monte Carlo code for Bremsstrahlung (wide and collinear emission) taking into account the polarization dependence of the bremsstrahlungs cross section  study impact on relative luminosity and how accurate polarization needs to be known  Determine the detector performance requirements based on physics and machine backgrounds  Integrate a first layout in the EICRoot simulation package  develop a dedicated e-polarimeter simulation package  Follow up with targeted detector R&D, which fulfills the determined requirements Request: Money for one PostDoc for 2 years  PostDoc starts 11 th of August 2

E.C. Aschenauer EIC R&D Meeting July arXiv: relativeluminosity 2009: Relative Luminosity uncertainty same size as physics asymmetry R=1.18x x10 -3 A LL = 0.4 – 4 x 10 -3

EIC R&D Meeting July 2014 E.C. Aschenauer 4 5 x 250 starts here 5 x 100 starts here hep-ph: (M.Stratmann, R. Sassot, ECA) cross section: pQCD scaling violations world data current data w/ eRHIC data

E.C. Aschenauer EIC R&D Meeting July Need systematics ≤ 2% arXiv: Dominant systematics: Luminosity Measurement  Relative Luminosity  needs to be controlled better then A LL  ~10 -4 at low x Absolut polarization measurements: electron P e and hadron P p relativeluminosity

E.C. Aschenauer EIC R&D Meeting July Polarisation: Hadrons in a storage ring: source instabilities Beam-Beam effects bunch-to-bunch emittance variation, Characteristic scale can be seen from AGS RHIC polarization profile variation for different bunches after acceleration leptons in a storage ring: Beam-Beam effects source instabilities leptons in eRHIC  What is the expected fluctuation in polarisation from cathode to cathode in the gatling gun in the gatling gun  from Jlab experience 3-5%  Is there the possibility for a polarization profile for the lepton bunches  if then in the longitudinal direction can be circumvented with 352 MHz RF Current: Hadrons & leptons in a storage ring: Variations in transfer efficiency from pre-accelerator to main ring  beam-beam interaction is important, it affects the bunch lifetime during the store leptons in eRHIC  What fluctuation in bunch current for the electron do we expect  limited by Surface Charge, need to see what we obtain from prototype gun Requirement: measure polarisation with enough statistical precision in sufficiently short time units to monitor polarisation as function of time and parameters influencing polarisation  hadron and lepton polarimetry are critical

E.C. Aschenauer EIC R&D Meeting July Fill in 2013: Beginning Fill in 2013: End P↑P↑P↑P↑ P↓P↓P↓P↓

E.C. Aschenauer EIC R&D Meeting July Fill in 2013: Beginning Fill in 2013: End P↑P↑P↑P↑ P↓P↓P↓P↓

E.C. Aschenauer EIC R&D Meeting July Account for beam polarization decay through fill  P(t)=P 0 exp(-t/  p ) growth of beam polarization profile R through fill pCarbonpolarimeter x=x0x=x0x=x0x=x0 ColliderExperiments correlation of dP/dt to dR/dt for all 2012 fills at 250 GeV Polarization lifetime has consequences for physics analysis  different physics triggers mix over fill  different  different RHIC-Result: Have achieved 6.5% systematical uncertainty for DSA and 3.4% for SSA will be challenging to reduce to 1-2% HERA-Result: Have achieved 1.4% systematical uncertainty at HERA for Lpol

E.C. Aschenauer 10  Technology: Compton Back scattering  measure photon and lepton  complementary & redundancy  e-Polarimeter location  at IP  overlap of bremsstrahlungs and compton photons  only possible if we have number of empty p-bunches = # cathods in gatling gun  luminosity loss  before/after IP  need to measure at location spin is fully longitudinal or transverse  1/6 turn should rotate spin by integer number of π  segmented Calorimeter  longitudinal polarization  Energy asymmetry  transverse polarization component  position asymmetry  After IP:  does collision reduce polarization  problem at ILC  for eRHIC very small  need to measure at location, where bremsstrahlung contribution is small  Before IP:  need to find room for photon calorimeter  Introduce dog-leg for polarimeter  minimizes bremsstrahlungs photon impact  creates synchroton radiation  Other considerations:  # of cathods in gatling gun: golden number is 20  This guarantees that a hadron bunch collides always with electrons produced from one particular cathode, avoiding/reducing significantly harmful beam-beam effect of particular cathode, avoiding/reducing significantly harmful beam-beam effect of electron beam parameter variations on the hadrons electron beam parameter variations on the hadrons EIC R&D Meeting July 2014

E.C. Aschenauer EIC R&D Meeting July Electron Direction (Rear Side) Hadron Direction (Forward Side) Synrad Fan Cryostat Cryostat Cryostat Cryostat CryostatCryostat CentralDetectorRegion IP Cold Magnet Apertures Crab Cavity Apertures WarmQuad WarmQuad ForwardDetectors Zero Degree Neutral Detector (ZDC) 10 mrad CrossingAngle Design follows requirements from physics as detailed here

Energy loss compensation schemes :  2 nd harmonic (788 MHz) cavities; or  main linac RF phase offset + high harmonic cavities Energy loss compensation schemes :  2 nd harmonic (788 MHz) cavities; or  main linac RF phase offset + high harmonic cavities Total SR power limit to 12 MW: operation at 15.9 GeV top energy -> 50 mA operation at 21.2 GeV top energy -> 18 mA SR power loss per recirculation pass Accumulated energy spread Transverse emittance growth © S. Brooks, F. Meot, V. Ptitsyn I e =50 mA I e =18 mA E.C. Aschenauer EIC R&D Meeting July

E.C. Aschenauer EIC R&D Meeting July Higher energy photons have smaller radiation cone – more concentrated. Flux decays exponentially with amplitude. However, it’s not negligible at large amplitude (>4 mm). Collimators and possible secondary emission need to be calculated further using GEANT4 or FLUKA. Line power density is estimated to be ~ 50 mW/mm, much less than in the ARC’s. Power dissipation is not a big problem. © Y.Jing, O. Tchubar

E.C. Aschenauer EIC R&D Meeting July Total power is about 40 W and practically all photons will propagate through IR without hitting the walls of vacuum chamber. It should be absorbed as far as possible from the detector to reduce the back-scattered photons and neutrons. Detailed design of the detector and SR absorbers are needed for GEANT4 simulations. © Y.Jing, O. Tchubar

by Stephen Brooks E.C. Aschenauer 15 EIC R&D Meeting July 2014  space constraints need to be taken into account in detector, e- polarimeter, lumi-monitor and tagger design design IR-8 hall IP FFAG lattice  The bypass is 2.40m outside the current RHIC IP.  The detector centre line is 2.10m inside the current RHIC IP. RHIC IP.  Relative spacing is 4.5m.

E.C. Aschenauer EIC R&D Meeting July 2014  Directly import CAD files  Import magnetic field maps  Implement Roman Pots, ZDC, Lumi Monitor, Electron Polarimeter -> work in continous progress … Goals: 16 ROOT event display hadron-going side beam line elements

E.C. Aschenauer EIC R&D Meeting July MC code for collinear emission is getting real

 Optimize the IR design to be able to integrate  the luminosity monitor  the lepton polarimeter  the low Q 2 -tagger  Develop a Monte Carlo code for Bremsstrahlung (wide and collinear emission) taking into account the polarization dependence of the bremsstrahlungs cross section  study impact on relative luminosity and how accurate polarization needs to be known  Integrate a first layout in the EICRoot simulation package  develop a dedicated e-polarimeter simulation package  Determine the detector performance requirements based on physics and machine backgrounds  Follow up with targeted detector R&D, which fulfills the determined requirements E.C. Aschenauer EIC R&D Meeting July

E.C. Aschenauer EIC R&D Meeting July BACKUP

E.C. Aschenauer 20 Summarized at: Hadron Beam: 1.the detection of neutrons of nuclear break up in the outgoing hadron beam direction  location/acceptance of ZDC 2.the detection of the scattered protons from exclusive and diffractive reaction in the outgoing proton beam direction the detection of the spectator protons from 3 He and Deuterium the detection of the spectator protons from 3 He and Deuterium  location/acceptance of RP;  potential impact of crab-cavities on forward scattered protons 3.local hadron polarimeter  CNI polarimeter Lepton Beam: 4.the beam element free region around the IR 5.minimize impact of detector magnetic field on lepton beam  synchrotron radiation  synchrotron radiation 5.space for low Q 2 scattered lepton detection 6.space for the luminosity monitor in the outgoing lepton beam direction 7.space for lepton polarimetry Important EIC is a high luminosity machine > cm -2 s -1 such controlling systematics becomes crucial  luminosity measurement  lepton and hadron polarization measurement  control of polarization direction EIC R&D Meeting July 2014

E.C. Aschenauer EIC R&D Meeting July “ZDC” MDI Treaty 4.5 m Q0 Q1 B1 Q2 Neutrons p = p o p = 80%p o p = 50%p o protons from Au decay IR design integrated in Detector MC framework: Direct import of CAD files Direct import of CAD files Geometry Geometry Material tags Material tags Direct import of.madx field info files Direct import of.madx field info files Detectors: Roman pots, ZDC, Lumi monitor, Detectors: Roman pots, ZDC, Lumi monitor, e-Polarimeter e-Polarimeter

detector acceptance:  >4.5 E.C. Aschenauer EIC R&D Meeting July x250 Generated + Quad aperture RP (at 20m) accepted  t (~p t 2 ) reach influences b T uncertainty t min ~ GeV 2  300 GeV 2  f/f > 50% t min ~ GeV 2  300 GeV 2  f/f > 50%  beam cooling critical to achieve high low t (p t ) acceptance with Roman Pots low t (p t ) acceptance with Roman Pots  add cerenkov counters to identify heavy products with same A/Z  LHCf products with same A/Z  LHCf simulated simulated + Quad-acceptance Quad-acceptance + 10  BC clearance RP performance:  RP performance assumptions very conservative following STAR RP   P/P 1% & angular resolution < 100  rad

E.C. Aschenauer 23   Momentum smearing mainly due to Fermi motion + Lorentz boost   Angle 99.9%) after IR magnets at 20m  after IR magnets  RP acceptance +10  beam clearance +10  beam clearance  90% tagging efficiency EIC R&D Meeting July 2014

E.C. Aschenauer 24 Results from GEMINI++ for 50 GeV Au +/-5mrad acceptance seems sufficient EIC R&D Meeting July 2014 Important: For coherent VM-production rejection power For coherent VM-production rejection power of incoherent needed up to 10 4 of incoherent needed up to 10 4  ZDC detection efficiency is critical  ZDC detection efficiency is critical Can we reconstruct the eA collision geometry: details: talk by L. Zheng

E.C. Aschenauer EIC R&D Meeting July E crit < 35 keV for 21.2 GeV electrons 2.3mrad 3.1mrad 4.6 mrad photonbeamline

E.C. Aschenauer 26 EIC R&D Meeting July 2014 Bremsstrahlung ep  e  p: Bethe-Heitler (collinear emission):  very high rate of ‘zero angle’ photons and electrons, but  sensitive to the details of beam optics at IP requires precise knowledge of geometrical acceptance requires precise knowledge of geometrical acceptance  suffers from synchrotron radiation  sperature limitation  pile-up QED Compton (wide angle bremsstrahlung):  lower rate, but  stable and well known acceptance of central detector  Methods are complementary, different systematics NC DIS:  in (x,Q 2 ) range where F 2 is known to O(1%)  for relative normalization and mid-term yield control BeAST HERA Concept:  normally only  is measured  Hera: reached 1-2% systematic uncertainty

EIC R&D Meeting July 2014  Concept: Use Bremsstrahlung ep  ep  as reference cross section  different methods: Bethe Heitler, QED Compton, Pair Production  eRHIC BUTs:  with cm -2 s -1 one gets on average of 23 bremsstrahlungs photons/bunch for proton beam  A-beam Z 2 -dependence  this will challenge single photon measurement under 0 o  coupling between polarization measurement uncertainty and uncertainty achievable for lumi-measurement  no experience no polarized ep collider jet  have started to calculate a with the help of Vladimir Makarenk  hopefully a is small E.C. Aschenauer 27 Goals for Luminosity Measurement:  Integrated luminosity with precision δL< 1%  Measurement of relative luminosity: physics-asymmetry/10  Fast beam monitoring for optimization of ep-collisions and control of mid-term variations of instantaneous luminosity Impact on method of luminosity measurement Impact on method of luminosity measurement requires ‘alternative’ methods for different goals requires ‘alternative’ methods for different goals

 zero degree calorimeter  high rate  measured energy proportional to # photons  subject to synchrotron radiation  alternative pair spectrometer 28 VacuumChamber L3L3L3L3  e + /e -  e-e-e-e- e+e+e+e+ Dipole Magnet very thin Converter L2L2L2L2 L1L1L1L1 SegmentedECal   The calorimeters are outside of the primary synchrotron radiation fan   The exit window conversion fraction reduces the overall rate   The spectrometer geometry imposes a low energy cutoff in the photon spectrum, which depends on the magnitude of the dipole field and the transverse location of the calorimeters E.C. Aschenauer EIC R&D Meeting July 2014

 Task: detect low Q 2 scattered electrons  quasi-real photoproduction physics E.C. Aschenauer 29 e’-detector EIC R&D Meeting July 2014   need a separate device designed similar to the JLab Hall D tagger (finely spaced scintillator array):  scattered lepton energy   at nominal energy can not register scattered electrons with Q 2 <0.1 in main spectrometer! DIS electron kinematics