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                                       ELECTRonA
                                            -
                                  A detector simulation
                              and reconstruction framework
                                       for eRHIC
                                  Jurgis Pasukonis and Bernd Surrow




                                   5-10 GeV static electron
                                                              e RHIC   Recirculating
                                                                       linac injector
                                   ring


                                                               RHIC

                              Polarized     EBIS
                                                    BOOSTER                    e-
                              proton
                                                                               cooling
                              source
                                                              AGS
                                          LINAC
eA workshop BNL, 05/07/2005                                                              Bernd Surrow
Upton, NY
                                                          Outline                               2




                                                                        A
         Tutorial - ELECTRonA                                              e




                    eRHIC - Detector design aspects
                             General considerations                        e               A
                             Design 1: Forward physics
                              (unpolarized eA MPI-Munich group)
                             Design 2: General purpose
                              (unpolarized/polarized ELECTRon-A)




                                                              Summary and Outlook
eA workshop BNL, 05/07/2005                                                          Bernd Surrow
Upton, NY
                                        ELECTRA tutorial                     3



           WWW-page: http://starmac.lns.mit.edu/~erhic/electra/

           CVS repository

           Directory structure

           Documentation-folder: readme and ntuple.txt

           Build executables: electra.install

           Source code: Example geometry/rear and user

           Steering file: cardsfile

           Input files

           Example: Single particle generator and Lepto

           Reconstruction



eA workshop BNL, 05/07/2005                                        Bernd Surrow
Upton, NY
                                          eRHIC - Machine design aspects                 4


     IR design (1)
           Beam separation
              •   Cross-angle could in principle be used:

                       Required angle: 5mrad

                       Use crab-crossing scheme (Rotate ion bunch into
                        direction of electron beam): Required deflecting RF
                        voltage: V=14.4MV  Factor 10 larger then for
                        KEKB crab cavities

                       Therefore: Design IR region with zero crossing angle

              •   S over C shaped bending preferred

              •   Initial design: Dipole winding in the superconducting
                  electron low- quadrupoles

                       Problem: 1m machine element free region




eA workshop BNL, 05/07/2005                                                    Bernd Surrow
Upton, NY
                                       eRHIC - Machine design aspects                        5


     IR design (2)
           Beam separation cont.
              •   Recent idea: Dipole coils superimposed on C. Montag, B. Parker
                  detector solenoid
              •   Advantage: 3m machine element free
                  region
              •   Preliminary estimate of luminosity
                  reduction: Factor 2
           Accomodation of synchrotron radiation
            generated by beam separation
           Beam focusing
              •   Electron beam: Superconducting
                  quadrupole triplet configuration around IR
                  (ZDR0 design: 1m - Recent idea: 3m)

              •   Hadron beam: Normal conducting septum-
                  quadrupole triplet configuration (ZDR0
                  design: 5m - Recent idea: 7.2m)




eA workshop BNL, 05/07/2005                                                        Bernd Surrow
Upton, NY
                               eRHIC - Detector design aspects                         6


     General considerations (1)




    Lines of constant                                            Lines of constant
    electron energy                                              electron angle (e)




    Lines of constant                                            Lines of constant
    hadron energy                                                hadron angle ()




eA workshop BNL, 05/07/2005                                                 Bernd Surrow
Upton, NY
                                                                                                                      7
                                           Kinematics - Reconstruction
     Reconstruction of kinematic variables (1)


            Electron method: “scattered electron”

                           'e 
                              '   2
           2
                    E cos  
                              e
         Q                  2 
     xe  e 
         sy e      E '             
                                ' 
                              2 e
              E p 
                   1   e
                          sin    
                    Ee        2 
                                     
                                                            Jacquet-Blondel method: “hadronic final state”
                '
               Ee                   E e 2 'e 
                                      '
     y e  1
              2E e
                   1 cos e  1 E sin  2 
                           '

                                                                2
                                      e                           QJB
                                                         x JB                                    2            2
                                                                  sy JB                                 
                                                                                2
                                                                               pT ,h                  
                                                                                         px,h    py,h 
                                      'e  pT ,e
                                                2                                         h      h      
     Q  2E e E  cos  4 E e E cos  
         2
                1 '              '    '     2
         e         e              e   e
                                       2  1 y e     y JB 
                                                                  E  pz h
                                                                     2Ee       E  pz h   E h  pz,h 
                                                                                                h

                                                                     2
                                                                    pT ,h
                                                        Q  2
                                                           JB   
                                                                  1  y JB
                                                                          
eA workshop BNL, 05/07/2005                                                                                 Bernd Surrow
Upton, NY
                                                                                                                                                                8
                                                          Kinematics - Resolution
         Reconstruction of kinematic variables (2)


            Electron method: “scattered electron”
          x e   1 E e  x e
                                '               ' 
              '                               
                                             1tan e  'e
           x e  y e  E e  E e / E p   2 

          y e   1 E e  1  'e  '
                                 '

                                           
                     1  '   1c ot   e
           y e   y e  E e  y e   2 

         Qe2  E e
                      '  'e  '                                   Jacquet-Blondel method: “hadronic final state”
                                
          2  '  tan   e
          Qe  E e     2 

                                                                      x JB   1 F             2y 1     
                                                                                       2cot    JB c ot 
                                                                                                                         
                                                                                  1
                                                                       x JB   y JB  F           1 y JB  2 
                                                                                                                            
                                                                                                                                           pT ,h  E  pz h
                                                                                                                                            2               2

                                                                                                                                    F
                                                                      y JB  F                                                     2E  pz h
                                                                                         
                                                                                     cot  
                                                                                         2                                             pT ,h  E  pz h
                                                                                                                                                            2
                                                                       y JB  F                                                          2

                                                                                                                                 cot  
                                                                                                                                           pT ,h  E  pz h
                                                                                                                                            2               2


                                                                  QJB  2  y JB F 
                                                                       2                                y     
                                                                   2                 2cot    JB c ot 
                                                                                                                    
                                                                   QJB  1 y JB  F            y JB  2 
                                                                                                        1             
                                                                                                                     
    eA workshop BNL, 05/07/2005                                                                                                                       Bernd Surrow
    Upton, NY
                                                                                  9
                                 eRHIC kinematics - Resolution
     Reconstruction of kinematic variable (Resolution): Small angles




eA workshop BNL, 05/07/2005                                             Bernd Surrow
Upton, NY
                                                                                                         10
                                eRHIC kinematics - Resolution
     Reconstruction of kinematic variable (Resolution)

        Q2 resolution                                       y resolution




                                                          With “electron method” only:
                                                          Require:

                                                          • At low y : good energy resolution
                                                          • At low Q2: good position resolution


eA workshop BNL, 05/07/2005                                                                     Bernd Surrow
Upton, NY
                                                                                   11
                                     eRHIC kinematics - Resolution

         Reconstruction of kinematic variable: Bias in y and Q2

       y bias                                                 Q2 bias




eA workshop BNL, 05/07/2005                                               Bernd Surrow
Upton, NY
                                    eRHIC - Detector design aspects                                          12


     General considerations (2)
           Measure precisely scattered electron over large polar angle region (Kinematics of DIS
            reaction)

           Tag electrons under small angles (Study of transition region: DIS and photoproduction)

           Measure hadronic final state (Kinematics, jet studies, flavor tagging, fragmentation
            studies, particle ID)

           Missing ET for events with neutrinos in the final state (W decays) and Physics beyond the
            SM (Hermetic detector)

           Zero-degree photon detector to control radiative corrections

           Tagging of forward particles (Diffraction and nuclear fragments) such as…:
              •   Proton remnant tagger
              •   Zero degree neutron detector

           Challenge to incorporate above in one detector: Focus on two specific detector ideas!




eA workshop BNL, 05/07/2005                                                                         Bernd Surrow
Upton, NY
                                      eRHIC - Detector design aspects                                            13

                                                                                                I. Abt,     A.
     Design 1: Forward physics (unpolarized eA MPI-Munich group) (1)                           Caldwell, X.
                                                                                                Liu,     J.
           Detector concept                                                                    Sutiak, MPP-
                                                                                                2004-90, hep-
              •   Compact detector with tracking and central EM calorimetry inside a magnetic   ex 0407053
                  dipole field and calorimetric end-walls outside:

                       Bend forward charged particles into detector volume

                       Extend rapidity compared to existing detectors

              •   Tracking focuses on forward and backward tracks
              •   No tracking in central region




eA workshop BNL, 05/07/2005                                                                           Bernd Surrow
Upton, NY
                                      eRHIC - Detector design aspects                    14

                                                                        I. Abt,     A.
     Design 1: Forward physics (unpolarized eA MPI-Munich group) (2)   Caldwell, X.
                                                                        Liu,     J.
                                                                        Sutiak, MPP-
           Tracking system:                                            2004-90, hep-
              •   High-precision tracking
                                                                        ex 0407053

                  with pT/pT ~ 2%

              •   Angular coverage down to
                    6 over the full energy
                  range

              •   Concept: 14 Si-strip
                  tracking stations       (40
                  X 40 cm)

              •   Assumed hit resolution:
                  20m

              •   Momentum resolution
                  from simulations: Few
                  percent!




eA workshop BNL, 05/07/2005                                                   Bernd Surrow
Upton, NY
                                    eRHIC - Detector design aspects                                       15

                                                                                         I. Abt,     A.
     Design 1: Forward physics (unpolarized eA MPI-Munich group) (3)                    Caldwell, X.
                                                                                         Liu,     J.
                                                                                         Sutiak, MPP-
           Calorimeter system:                                                          2004-90, hep-
              •   Compact EM calorimeter systems: Si-Tungsten
                                                                                         ex 0407053

              •   Forward hadron calorimeter: Design follows existing ZEUS calorimeter




eA workshop BNL, 05/07/2005                                                                    Bernd Surrow
Upton, NY
                                      eRHIC - Detector design aspects                                                    16

                                                                                                        I. Abt,     A.
     Design 1: Forward physics (unpolarized eA MPI-Munich group) (4)                                   Caldwell, X.
                                                                                                        Liu,     J.
           Acceptance:                                                                                 Sutiak, MPP-
              •   Full tracking acceptance for || > 0.75 - No acceptance in central region || < 0.5
                                                                                                        2004-90, hep-
                                                                                                        ex 0407053
              •   Q2 acceptance down to 0.05GeV2 (Full W range) - Full acceptance down Q2=0GeV2
                  for W>80GeV
              •   High x: Electron (Q2) and Jet (x) to determine event kinematics




    Track efficiency:
    • Full efficiency below 6GeV for  < -8
    • For larger energies, full efficiency for  < -5
eA workshop BNL, 05/07/2005                                                                                   Bernd Surrow
Upton, NY
                                      eRHIC - Detector design aspects                      17

                                                                           J. Pasukonis,
       Design 2: General purpose (unpolarized/polarized ELECTRon-A) (1)   B.S.




                                                         e                        A
       Detector concept:
         •   Hermetic detector system inside ±3m
             machine element free region
         •   Starting point:

                 Barrel and rear EM system: e.g. Si-
                  Tungsten

                 Forward EM/hadron calorimeter: e.g.
                  Pb-scintillator

                 Tracking system and barrel EM inside
                  solenoid magnetic field

                 Tracking system based in high-
                  precision Si (inner) and micro-
                  pattern technology (Triple-GEM)
                  (outer)




eA workshop BNL, 05/07/2005                                                       Bernd Surrow
Upton, NY
                               eRHIC - Detector design aspects                                   18

                                                                               J. Pasukonis,
     Design 2: General purpose (unpolarized/polarized ELECTRon-A) (2)         B.S.

           Simulated ep event (LEPTO)

                                                                         Lower Q2
                                                                         acceptance  0.1GeV2




                                                                         DIS generators
                                                                         used so far:
                                                                          LEPTO
                                                                          DJANGO

eA workshop BNL, 05/07/2005                                                             Bernd Surrow
Upton, NY
                                  eRHIC - Detector design aspects                                19

                                                                               J. Pasukonis,
     Design 2: General purpose (unpolarized/polarized ELECTRon-A) (2)         B.S.

           Simulated ep event (LEPTO)

                                                                         Lower Q2
                                                                         acceptance  0.1GeV2




                                                                         DIS generators
                                                                         used so far:
                                                                          LEPTO
                                                                          DJANGO

eA workshop BNL, 05/07/2005                                                             Bernd Surrow
Upton, NY
                                  eRHIC - Detector design aspects                                20

                                                                               J. Pasukonis,
     Design 2: General purpose (unpolarized/polarized ELECTRon-A) (2)         B.S.

           Simulated ep event (LEPTO)

                                                                         Lower Q2
                                                                         acceptance  0.1GeV2




                                                                         DIS generators
                                                                         used so far:
                                                                          LEPTO
                                                                          DJANGO

eA workshop BNL, 05/07/2005                                                             Bernd Surrow
Upton, NY
                               eRHIC - Detector design aspects                           21

                                                                         J. Pasukonis,
     Design 2: General purpose (unpolarized/polarized ELECTRon-A) (3)   B.S.

           Simulated eCa event (VNI)




eA workshop BNL, 05/07/2005                                                     Bernd Surrow
Upton, NY
                                      eRHIC - Detector design aspects                    22

                                                                         J. Pasukonis,
     Design 2: General purpose (unpolarized/polarized ELECTRon-A) (4)   B.S.

           ELECTRA detector simulation and
            reconstruction framework:
              •   GEANT simulation of the central detector part
                  (tracking/calorimetry) available: Starting point
              •   Calorimeter cluster and track reconstruction
                  implemented
              •   Code available through CVS repository:
                  http://starmac.lns.mit.edu/~erhic/electra/
              •   Help welcome on:
                       Evaluate and optimize detector configuration

                       Design of forward tagging system and needed
                        particle ID systems for various exclusive
                        processes

                       In particular for eA events: Optimize forward
                        detector system for high-multiplicity
                        environment




eA workshop BNL, 05/07/2005                                                     Bernd Surrow
Upton, NY
                                   eRHIC - Machine design aspects                                       23


     Ring-ring design (3): ep beam parameters

                                               High energy setup       Low energy setup

                                                  p             e         p             e
                Energy (GeV)                     250            10        50            5
                Bunch intensity (1011)            1             1          1            1
                Ion normalized emittance
                 mm  mrad, x/y                15/15                    5/5

                Rms emittance, nm, x/y         9.5/9.5        53/9.5   16.1/16.1      85/38
                *, cm, x/y                    108/27         19/27    186/46         35/20
                Beam-beam parameters, x/y
                                               0.0065/        0.029/   0.019/         0.036/
                                               0.00325         0.08    0.0095          0.04
                k = y/x                         1            0.18        1           0.45
                Luminosity (1032cm-2s-1)                4.4                     1.5


                                                No cooling              Cooling needed
                                                2 p-p IPs assumed       No p-p IPs allowed
eA workshop BNL, 05/07/2005                                                                    Bernd Surrow
Upton, NY
                                    eRHIC - Machine design aspects                                          24


     Ring-ring design (4): eAu beam parameters
                                                   High energy setup        Low energy setup
                                                     Au              e        Au           e
                Energy (GeV/u)                       100            10       100           5
                Bunch intensity (1011)               0.01            1      0.0045          1
                Ion normalized emittance  mm        6/6                     6/6
                 mrad, x/y

                Rms emittance, nm, x/y             9.5/9.5        54/7.5    9.5/9.5      54/13.5

                *, cm, x/y                        108/27         19/34     108/27       19/19
                Beam-beam parameters, x/y          0.0065/        0.0224/   0.0065/       0.02/
                                                   0.0035           0.08    0.0035        0.04


                k = y/x                             1            0.14        1          0.25
                Luminosity (1030, cm-2s-1)                  4.4                    2.0

                 Electron cooling of Au beam is required to achieve and maintain Au emittance values!

eA workshop BNL, 05/07/2005                                                                        Bernd Surrow
Upton, NY

				
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