Status Report on the performances of a magnetized ECC (“MECC”) detector

1. Status Report on the performances of a magnetized ECC (“MECC”) detector Pasquale Migliozzi INFN – Napoli L.S.Esposito,A.Longhin,M.Komatsu, A.Marotta G.De Lellis, P.M., M.Nakamura, P.Strolin

2. Outline • The OPERA experience • Why a magnetized ECC detector? • Detector overview and performances • Preliminary evaluation of the impact on →, e→, e→, →e channels and the corresponding CP ones • Outlook

3. The OPERA experience The detector is being constructed at the Gran Sasso Laboratory. Meanwhile several tests with charged particles and neutrinos at FNAL are under way An ECC brick is a self-consistent object. The whole detector is just an ensemble of bricks.

4. Summary of the event reconstruction with OPERA(see Nakamura and De Lellis talks at the previous ISS meetings) • High precision tracking (dx<1mm dq<1mrad) • Kink decay topology • Electron and g/p0 identification • Energy measurement • Multiple Coulomb Scattering • Track counting (calorimetric measurement) • Ionization (dE/dx measurement) • p/m separation • e/p0 separation Topological and kinematical analysis event by event

5. Layer 1 Plastic base Layer 2 Base track microtrack A bit of nomenclature An emulsion plate

6. STEP 1 • Event generated with OpRoot/Geant3; STEP 2 • Angular and position smearing; • Eff. parametrization; • Pulse Height parametrization; STEP 3 • Linking up-down; • Conversion to x.x.cp.root files brick simulation step by step

7. Electrons 6 GeV • The events were generated with OpRoot • The smearing parameters are: • Sx=0.4 micron, • Sy=0.25 micron, • Sz=2.5 micron. (these value were obtained with a tuning on the data) • Eff. measured in the empty brick by using cosmic muons • Pulse Height parametrized by using the data in the empty brick;

8. Slopes resolution (Tmicro-Tbase) Tx-Tx1 s=0.014 Tx-Tx2 s=0.014 Tx-Tx1 s=0.013 Tx-Tx2 s=0.014 MC data Ty-Ty2 s=0.008 Ty-Ty2 s=0.008 Ty-Ty2 s=0.007 Ty-Ty1 s=0.008

9. eCHI2P vs PH This is the results of the micro track slopes resolution simulation (eCHI2P) and of the micro track pulse height parametrization (bt PH) MC Data bg rejected

10. MC vs data comparison Selected tracks characteristics: • The track starts in the 1st plate; • Number of segments [3,15] ; • The track is in a box with a surface of 1.8x1.8cm2; • The first segment of the track is in a cone around the beam direction with open angle defined by the beam width; Yes NO

11. Base Track angle resolution Bin(i-1)=T(i)-T(1), i>1 MC Data

12. Base Pulse and eCHI2P MC eCHI2P Mean=1.2 RMS=0.9 data eCHI2P Mean=1.1 RMS=1.0 MC PH Mean=26.4 RMS=3.0 data PH Mean=26.3 RMS=3.0

13. Brick not exposed to the e beam Eff no lead MC pions Eff lead MC pions about efficiencies… Reference brick eff.

14. Number of segments followed without propagation (strongly related to micro track efficiencies) Eff. As measured in Empty brick (only cosmics exposition) Data MC without Efficiencies micro track rejection MC+eff.

15. Pulse height vs plate number and energy loss MC: no correlation between Micro tracks momentum and pulse height by construction Data MC

16. Pions 4 GeV • The events were generated with OpRoot • The smearing parameters are: • Sx=0.25 micron, • Sy=0.25 micron, • Sz=2.5 micron. • these value are the same used for all the “official” productions • NO parameters optimization was made for this set of data.

17. TRIGGER data Tx s=0.0053 MC Tx s=0.0055 MC Ty s=0.0029 data Tx s=0.0022

18. Slopes resolution (Tmicro-Tbase) Tx-Tx1 s=0.009 Tx-Tx2 s=0.01 Tx-Tx1 s=0.01 Tx-Tx2 s=0.01 MC data Ty-Ty2 s=0.009 Ty-Ty2 s=0.009 Ty-Ty2 s=0.01 Ty-Ty1 s=0.01

19. eCHI2P vs PH This is the results of the micro slopes resolution simulation (eCHI2P) and of the micro pulse height parametrization (bt PH) bg rejected MC Data

20. Base Track angle resolution Bin(i-1)=T(i)-T(1), i>1 MC Data Tx Mean=11.5 RMS=5.3 Tx Mean=11.7 RMS=5.3 Tx Mean=11.2 RMS=5.3 Ty Mean=11.4 RMS=5.2

21. Base Pulse and eCHI2P MC eCHI2P Mean=0.7 RMS=0.5 data eCHI2P Mean=0.8 RMS=0.8 MC PH Mean=26.6 RMS=2.9 data PH Mean=26.6 RMS=3.0

22. Number of segments followed without propagation (strongly related to micro track efficiencies) Data MC+eff. Assuming eff.=84.% (84.% at theta<0.1mrad measured data)

23. An ideal detector exploiting a Neutrino Factory should: • Identify and measure the charge of the muon (“golden channel”) with high accuracy • Identify and measure the charge of the electron with high accuracy (“time reversal of the golden channel”) • Identify the  decays (“silver channel”) • Measure the complete kinematics of an event in order to increase the signal/back ratio

24. B “MECC” structure DONUT/OPERA type target + Emulsion spectrometer + TT + Electron/pi discriminator 3 cm Stainless steel or Lead Film Rohacell Electronic detectors/ECC Assumption: accuracy of film by film alignment = 10 micron (conservative) 13 lead plates (~2.5 X0) + 4 spacers (2 cm gap) (NB in the future we plan to study stainless steel as well. May be it will be the baseline solution: lighter target) The geometry of the MECC is being optimized

25. Electron/pion discriminator à la NOMAD(“our dream”) Having an electronic e/p discriminator would also allow for the golden channel search! A detailed study is needed in order to optimize the discriminator

26. How many evts per brick? Emulsions do not have time resolution How to disentangle events occurred at different time?

27. Key points • The MECC needs a time stamp: TT mandatory • CC/NC classification needs MECC-TT match • The event density depends on the TT resolution • The OPERA-like approach (thick target, 10 X0, and TT attached to the ECC) does not work • With the present set-up it works given the lightness of the target-spectrometer region • The scanning is not driven by the electronic detectors: the matching is done after event location

28. Method for time stamp • TT is placed downstream from the target region (see previous slide) • TT segmentation varied between 1 and 5 cm • 1 TT plane per projection • Only digital information is used: 2 tracks crossing one TT strip give 1 hit • Optimization performed by using 10000 events NC and CC for neutrinos with energy 15 and 40 GeV

29. #evts per brick as a function of TT segmentation

30. Results We assume for the time being 100 events per brick. Possible improvements: a higher granularity TT

31. Momentum measurement Momentum and charge for mips Momentum and charge for electrons

32. Methods • Different methods have been tried • Slope measurement (used in the past talk) • Sagitta measurement • Parabolic fit (also used for Kalman initialization) • Kalman reconstruction • All methods have been implemented in a single program in order to ease the comparison • NB for all methods, but the Kalman, the momentum is compared at the exit of the target region (beginning of the spectrometer)

33. Momentum resolution

34. (1/p)(true –rec)/true

35. Charge misidentification

36. A better alignment

37. Electron studies (very preliminary) • Single electron with energies 1-5-10 GeV have been generated uniformly in the target region • reconstruction done on hits coming from the primary electron (preselection at true level) • Method: parabolic fit (Kalman for electrons requires some more work) • Given the non negligible energy loss in the target the electron energy at the exit is considered

38. True momentum at the target exit

39. Estimate of showering electrons

40. Momentum resolution vs zvertex

41. q-mis vs zvertex Given the true-hit based reconstruction, the quoted charge misidentification can be seen as an lower limit. Anyhow it is a good starting point!

42. The silver channel

43. The old detector setup • We considered a detector with 4 kton mass (lead) • Only the muonic channel was considered (20% of the total decays) • We considered only one event per brick • Non-muonic decays discarded given the impossibility to measure the charge of the decay products

44. The detected number of silver events Below 3° the silver channel contributes very little in disentangling the intrinsic degeneracy What happens with the new setup based on the MECC technique?

45. How many silver events with MECC? • Let us assume a constant target mass: 4 kton • We can collect about 100 events in a brick: x100 gain • We can search for non muonic decays: x5 gain • NB the background for non-muonic events has to be carefully evaluated; rejection power due to the improved kinematical reconstruction wrt OPERA could be extremely useful • Overall gain: the silver statistics increases by a factor 500  significant contribution to the clone solution well below 3° (studies are in progress) • i.e. for L=3000km at 1° we expect more than 500 (100) silver events at δCP=90° (0°) rather than 1 or even less !

46. What about →e? • NB there are not yet detailed studies available • Just to give an idea (L=3000 km, θ13=5°, δCP=90°): • anti-e with the wrong electron charge: ~104 • e from oscillation: ~102 • We have to search for a few% effect, but the S/B ratio may be improved by kinematical cuts

47. Outlook • Study the performance of a stainless steel target • Detailed study of the way how to magnetize the detector • Define a realistic baseline for the e/p discriminator: its choice depends on the total target mass, the TT width (i.e. how many evts per brick), the costs, … • Finalize the electron analysis: the e/p separation and the charge reconstruction • Check the sensitivity to the “golden” (the muon threshold is at 3 GeV!) • A full simulation of neutrino events is mandatory in order to evaluate the oscillation sensitivity and provide the input for GLOBES • We plan to perform a first exposure of a MECC on a charged beam at CERN this year

49. ROOT OpGen (NEVGEN) OpROOT GEANT3 The simulation program Emulsion digitization is handled by this program FEDRA Off-line reconstruction program for emulsion data ORFEO

50. The events are generated with Geant3/OpRoot with a 1 brick detector. The output of this step is a root Ttree filled with generator level microtracks called TreeM (no smearing effects); - [ if a beamfile is used in the output file can be added a Ttree called TreeH with the beamfile informations] The object microtrack is defined in the class Micro_Track (look at http://web.na.infn.it/index.php?id=527); The emulsion digitalization accept as input a root Ttree file filled with microtracks as defined in the class Micro_Tracks; this step is decoupled from the event generation so, in principle, the events could be produced also with the OpSim package or with other generators (Geant4, FLUKA) ; At this step is performed the digitalization of the emulsions; The output of this step is a root Ttree filled with digitalized microtracks called TreeMS (same structure of the TreeM); A realistic emulsion simulation (1/2)