Status Report on the performances of a magnetized ECC (“MECC”) detector L.S.Esposito LNGS on behalf of the ECC WG ( WG/ISSMainPage.html)

Physics at Neutrino Factory To exploit all the oscillation channels that are available thanks to the well know neutrino flux composition: e → μ (golden channel) e →  (silver channel) anti- μ → anti- e anti- μ → anti-  their CP conjugates in the case of a  -

What we want to measure Identification, momentum and charge of the leptons (muons and in particular electrons) Identify the different decay topologies of the  lepton:  h and  e Perform a complete and accurate kinematical reconstruction of neutrino events

The tools we propose to use Emulsion sheets: large-scale production by automatic coating Data taking: high speed automated track selector Magnetic field: to distinguish neutrino/ anti-neutrino interaction

OPERA experience Emulsion analysis  Primary vertex topology  Any decay topology  e/  separation  e/   separation  multiple scattering & shower reconstruction  end-of-range dE/dx (  -  separation) 8.3kg 10 X 0 supermodule 8 m Target Trackers Pb/Em. target Extract selected brick Pb/Em. brick 8 cm Pb 1 mm Basic “cell” Emulsion 1 brick: 10.2x12.7x7.5 cm 57 Em. Plates + 2CS 56 Pb (1 mm) Topological and kinematical analysis event by event

Summary of the event reconstruction with OPERA High precision tracking (  x<1  m,  <1mrad) Kink decay topology Electron and  /  0 identification Energy measurement Multiple Coulomb Scattering Track counting (calorimetric measurement) Ionization (dE/dx measurement)  separation e/  0 separation Topological and kinematical analysis event by event

MECC structure We focused on the “target + spectrometer” optimization Electronic det: e/  separator & “Time stamp” Rohacell® plate emulsion film stainless steel plate spectrometertargetshower absorber

MECC structure optimization Muon energy from 1 GeV to 10 GeV Spacer thickness from 2 cm to 5 cm Magnetic field: 0.25 T, 0.5 T, 1.0 T

Momentum measurement methods Different methods have been used in the past talk: Slope measurement 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 N.B. For all methods, but the Kalman, the momentum is compared at the exit of the target region (beginning of the spectrometer)

First example: 4 GeV muon momentum resolution

Second example: 4 GeV muon charge mis-identification

Performance of MECC: muon momentum resolution 3 cm gap 0.5 T

Performance of MECC: electron momentum resolution Only hits associated to the primary electrons are used in the parabolic fit. No Kalman procedure used. Given the non negligible energy loss in the target the electron energy at the exit is considered 3 cm gap 0.5 T

Performance of MECC: muon charge mis-identification 3 cm gap 0.5 T

Performance of MECC: electron charge mis-identification 3 cm gap 0.5 T

Study of compact emulsion spectrometer for identification of neutrino/anti-neutrino interaction Chika Fukushima Satoru Ogawa, Mitsuhiro Kimura, Hiroshi Shibuya, Koichi Kodama, Toshio Hara

Magnetic ECC used in the exposure Compact ECC structure

Beam exposure Dec. 7, 2005 KEK-PS T1 line Different stack were exposed: Different support used (40 μm polystyrene or 200 μm acrylic plate) 2 GeV  + [no magnet] 3000/cm 2 as reference beam 1 T magnetic field Different beams: 0.5 GeV, 1. GeV and 2. GeV, each with 1000/cm 2  + (  -)

The sagitta method L = 3 cm in this study

Spatial distribution

Results (preliminary) The relative error is roughly ds/s = 0.20  p [GeV/c] ds/s should be about 0.35 in the case of p = 10 GeV/c Assuming a Gaussian distribution, probability of the charge mis-identification for a 10 GeV lepton would be around 0.2% N.B. Multiple Coulomb scattering has larger tails than a Gaussian distribution. The probability of the charge mis-identification should be somewhat larger than the above value

Comments on the measurement Although not with the final geometry, this measurement is an example of how (in an easy and fast way) the MECC performances can be studied Advantages wrt the proposed setup Better plate to plate alignment (few  m instead of 10  m) Disadvantages wrt the proposed setup Only 2 gaps instead of 3 Gap width 1.5 cm instead of 3 cm

Possible design far detector Let us assume transverse dimension of a plane equal to 15.7x15.7 m 2 (as in the case of Nova) A brick contains 35 stainless steel plates 1 mm thick: it corresponds to about 2 X 0 A brick weigh 3.5 kg The spectrometer part consists of 3 gaps (3 cm each) and 4 emulsion films A wall contains bricks  weight 68 tons If I consider 60 walls  bricks  4.1 kton In terms of emulsion films the target is: 47,328,000 pieces (in OPERA we have 12,000,000) If I consider as electronic detector 35 Nova planes (corresponding to 5.3 X 0 ) after each MECC wall  2100 planes The total length of the detector is: about 150 m

Comments to the present design A highly segmented (with micrometric tracking) target followed by a high resolution spectrometer can be built up to a total mass of about 4 kton An electronic detector based on a technique à la Nova fulfils the requirements  synergy with other detectors The magnetization issue is common to the magnetized liquid scintillator detector  synergy with other detectors Finally, we are proposing a detector that combines the capability of the liquid scintillator technique in studying the golden channel, with the MECC technique capability in studying the silver and the platinum channels  interesting synergy among different techniques!

Caveat on the following slides The numbers quoted in the following are an educated guess driven by the OPERA calculations and the MECC performances quoted before The numbers are very preliminary, but are useful for a first evaluation of the impact of this detector on the NuFact sensitivity N.B. The topological decay selection is “identical” to the one studied in OPERA (target material is 1 mm thick)

 →  channel Expected signal and background

Signal and background: 5yrs, 5 kton The performances of this channel cannot be much better than in the OPERA case: the muon measurement is similar in both detectors; the main backgrounds comes from anti-neutrinos charm production  very important the identification of the primary lepton. It was 97% in the old silver paper: is there room for improvement? If lepton ID ⇑ by 1% background ⇓ by 30% !!! hadron decay in flight (20% of the total background) background from scattering, although not dominant, much smaller than in the OPERA case (a factor 40) D. Autiero et al., Eu.Phys.J C 33,243

 →e channel Expected signal and background

Comments This channel was not exploited in the past due to the impossibility to measure the electron charge With the MECC the study of this channel becomes possible and it is similar to the muonic one Main background: anti-neutrino charm production as in the muonic case, but not the hadron decay in flight (20% less background) Possible drawback: the electron ID is worse than the muon one (to be studied) Possible improvement: the pt cut at the 2ry vtx can be lowered from 250 MeV to 100 MeV (meson decays are not an issue) The MECC momentum resolution is better than the ECC one (~ 20% → ~10%): better kinematical analysis We assume the same signal and background (reduced by 20%) as in the muonic case

 →nh+nπ 0 channel (it contains more than 50% of the  signal) Expected signal and background

Comments This channel was not exploited in the past due to the impossibility to measure the hadron charge Main background: anti-neutrino charm production (50%) and hadron interactions (50%) The MECC momentum resolution is better than the ECC one (~ 20% → ~10%): better kinematical analysis Possible improvements: The kinematical analysis both at the 1ry and 2ry vtx can be improved given the better momentum measurement: in OPERA kinematical analysis has poor efficiency Only negative hadrons may contribute to the background → the hadron interaction back. decreases by a factor 2

Summary of the silver channel Take it with care, very preliminary!!! Signal (θ 13 =2°,δ=0°)Signal (θ 13 = 2°, δ=90°)Background L=732km old L=3000km old L=732km new L=3000km new

Conclusion and outlook Detailed study of the performance of a magnetized stainless steel target A proposal of a possible design of far detector A first test at KEK gave good results Basic performances of the detector can be easily studied with a single brick: no need for large R&D and prototype construction, but an extensive test beam program is mandatory A preliminary estimate based on the OPERA experience and taking into account the MECC features indicates that the number of silver events can be increased by about a factor 3 The way how to magnetize large volumes is a common task If no field only the muonic decay is left to study the silver channel The choice of the electronic detector could bring interesting synergies Finalize the electron analysis: the e/  separation and the charge reconstruction Study the muon identification with the electronic detector 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