Monte Carlo simulations for the JEDI polarimeter at COSY

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1 Monte Carlo simulations for the JEDI polarimeter at COSY Paul Maanen on behalf of the JEDI Collaboration JEDI Collaboration Physics Institute III B, RWTH Aachen University DPG Frühjahrstagung 216

2 Outline Introduction Detector concept Simulation studies Summary & Outlook 2/18 Paul Maanen on behalf of the JEDI Collaboration

3 Motivation Where is the Antimatter in our Universe? One precondition for Baryogenesis: CP Standard Model prediction: n B n B n 1 18 WMAP and COBE (212): n B n B n 1 1 )Not enough CP in Standard Modell H = S ~E S P: H =+d ~ S ~E S T : H =+d ~ S ~E d ~ S d = EDM )Electric Dipole Moments violate CP (assuming CPT ) )Probe into the physics of the early universe 3/18 Paul Maanen on behalf of the JEDI Collaboration

4 Nuclear scattering polarimetry Nuclear scattering cross section for scattering of polarized particles: (, )= ( ) 1 + P y A y ( ) cos( ) Measure left-right asymmetries in cross section: P y = 1 A y L R L+R May need to also include up, down to account for tensor polarization Currently using elastic deuteron-carbon scattering 4/18 Paul Maanen on behalf of the JEDI Collaboration

5 Design goals for an EDM polarimeter EDM search in storage rings: Let EDM interact with fields, wait for polarization change: d ~ S dt / d ~ E ~ S Current candidate method for EDM search implicates a linear buildup of polarization with time at P = O(1 6 /1s) Design goals for polarimeter: Large FoM Minimal influence on beam High sensitivity to systematic effects Good long term stability and reproducibility 5/18 Paul Maanen on behalf of the JEDI Collaboration

6 Target choice Cross-Section 2 FOM = σ A y dσ/dω [mb/sr] MeV 2 MeV FOM [a.u.] MeV 2 MeV Θ [deg] Θ [deg] A y 1 Analyzing Power 2 MeV: T. Kawabata et al. Phys. Rev. C 7, MeV: Y. Satou et al. Phys. Let. B 549, MeV 2 MeV Θ [deg] Carbon was chosen as working choice Large analysing power, high elastic cross section FOM for Protons also concentrated in the forward region 6/18 Paul Maanen on behalf of the JEDI Collaboration

7 Detector concept Fast HCAL Target chamber PL Sci PMT Vacuum pipe COSY beam 7/18 Paul Maanen on behalf of the JEDI Collaboration

8 Signal generation E d Θ [deg] E p C(d,pn) 12 C E n Elastically scattered deuterons retain almost complete beam energy. Break-up has almost no analyzing power, so discard it Protons and neutrons from break-up are energetically well separated )Complete stop of particles provides good signal separation Inelastic reactions carry some analysing power, so maybe keep these 8/18 Paul Maanen on behalf of the JEDI Collaboration

9 Candidate Materials: LYSO/Plastic Scintillator Fe + Pl. LYSO LYSO Plastic Density [g/cm3] Decay [ns] L. Y. % NaI(Tl) S. Peak [nm] N ref Melt. [ C] Hygrosc. No No Radioact Yes No 9/18 Paul Maanen on behalf of the JEDI Collaboration

10 Simulation setup Geometry: Single detector element Generated 1k events each at T d = 27 MeV,5 < < 2, < <36 Signal: 12 C(d, d) 12 C Background: 12 C(d, pn) 12 C 2 Ay,el FOM / ( el el + bg bg ) el el + bg bg A y,bg ( el el + bg bg ) 1/18 Paul Maanen on behalf of the JEDI Collaboration

11 Lyso scintillators rel. freq deuteron range in lyso Constant.1976 ±.3159 Mean ±.66 Sigma.5184 ±.5261 rel. freq deuteron lateral displacement in lyso Constant.1856 ±.2761 Mean.823 ± Sigma 2.46 ± range [mm] lat. displacement x [mm] Chosen detector size of cm 3 as starting value 11/18 Paul Maanen on behalf of the JEDI Collaboration

12 Detector response - lyso Edep in lyso rel. freq. [%] 1 1 other neutron (breakup) escapes neutron (other) escapes γ escapes deuteron escapes no particle escape Breakup is main cause of efficiency loss 12/18 Paul Maanen on behalf of the JEDI Collaboration E dep

13 Detection efficiencies (lyso) dcelastic detection efficiency in lyso dcbreakup detection efficiency in lyso 1 % 1 %.8 5%.8 5%.6 1%.6 1%.4 2%.4 2% E cut relative fom in lyso E cut rel. fom [au] E cut % 2% 13/18 Paul Maanen on behalf of the JEDI Collaboration

14 Plastic scintillators 25 E vs z - deuterons in iron E kin rel. freq deuteron range in plastic Constant.3739 ±.537 Mean ±.39 Sigma.3565 ± z / mm range [mm] Use degrader to suppress photon background and reduce length of plastic detector. T d = 27 MeV Absorber thickness 4 mm Scintillator thickness 5 mm 14/18 Paul Maanen on behalf of the JEDI Collaboration

15 Detector response - plastic E dep in plastic rel. freq. [%] 1 1 other neutron (breakup) escapes neutron (other) escapes γ escapes deuteron escapes no particle escape E dep 15/18 Paul Maanen on behalf of the JEDI Collaboration

16 Detection efficiencies (plastic) dcelastic detection efficiency in plastic dcbreakup detection efficiency in plastic % 5% 1% % 5% 1%.4.3 2%.8.6 2% E cut relative fom in plastic E cut rel. fom [au] % 2% E cut 16/18 Paul Maanen on behalf of the JEDI Collaboration

17 Results Main cause of efficiency loss is breakup in detector Maximum relative FOM: % 2% Plastic LYSO LYSO and plastic scintillators provide comparable performance No strong dependence on energy resolution 17/18 Paul Maanen on behalf of the JEDI Collaboration

18 Summary & Outlook We have a candidate layout for JEDI polarimeter Simulations suggest promising performance Hardware tests with LYSO crystals are in progress Will include E E particle identification technique Will include inelastic scattering in simulation 18/18 Paul Maanen on behalf of the JEDI Collaboration