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

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

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.

Summary of the event reconstruction with OPERA (see Nakamura and De Lellis talks at the previous ISS meetings) High precision tracking (  x<1mm  <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

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

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

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; Electrons 6 GeV

Slopes resolution (Tmicro-Tbase) Tx-Tx 1  =0.013 Ty-Ty 2  =0.007 Ty-Ty 1  =0.008 Tx-Tx 2  =0.014 Tx-Tx 1  =0.014 Tx-Tx 2  =0.014 Ty-Ty 2  =0.008 Ty-Ty 2  =0.008 MCdata

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) bg rejected MCData

MC vs data comparison Selected tracks characteristics: The track starts in the 1 st plate; Number of segments [3,15] ; The track is in a box with a surface of 1.8x1.8cm 2 ; The first segment of the track is in a cone around the beam direction with open angle defined by the beam width; Yes NO

Base Track angle resolution Bin(i-1)=T(i)-T(1), i>1 MCData

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

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

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

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

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.

TRIGGER MC Tx  = MC Ty  = data Tx  = data Tx  =0.0022

Slopes resolution (Tmicro-Tbase) Tx-Tx 1  =0.01 Ty-Ty 2  =0.01 Ty-Ty 1  =0.01 Tx-Tx 2  =0.01 Tx-Tx 1  =0.009 Tx-Tx 2  =0.01 Ty-Ty 2  =0.009 Ty-Ty 2  =0.009 MCdata

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 MCData

Base Track angle resolution Bin(i-1)=T(i)-T(1), i>1 MCData 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

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

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)

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

“MECC” structure Stainless steel or LeadFilmRohacell DONUT/OPERA type target + Emulsion spectrometer + TT + Electron/pi discriminator B Assumption: accuracy of film by film alignment = 10 micron (conservative) 13 lead plates (~2.5 X 0 ) + 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 3 cm Electronic detectors/ECC

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

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

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 X 0, 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

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 events NC and CC for neutrinos with energy 15 and 40 GeV

#evts per brick as a function of TT segmentation

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

Momentum measurement Momentum and charge for mips Momentum and charge for electrons

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)

Momentum resolution

(1/p)(true –rec)/true

Charge misidentification

A better alignment

Electron studies (very preliminary) Single electron with energies 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

True momentum at the target exit

Estimate of showering electrons

Momentum resolution vs z vertex

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

The silver channel

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

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?

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 δ CP =90° (0°) rather than 1 or even less !

What about  → e ? NB there are not yet detailed studies available Just to give an idea (L=3000 km, θ 13 =5°, δ CP =90°): anti- e with the wrong electron charge: ~10 4 e from oscillation: ~10 2 We have to search for a few% effect, but the S/B ratio may be improved by kinematical cuts

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/  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/  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

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

A realistic emulsion simulation (1/2) 1. The events are generated with Geant3/OpRoot with a 1 brick detector. 1. 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] 2. The object microtrack is defined in the class Micro_Track (look at 2. The emulsion digitalization 1. accept as input a root Ttree file filled with microtracks as defined in the class Micro_Tracks; 2. 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) ; 3. At this step is performed the digitalization of the emulsions; 4. The output of this step is a root Ttree filled with digitalized microtracks called TreeMS (same structure of the TreeM);

A realistic emulsion simulation (2/2) 3.Analysis tools: 1.A tool to perform the link up-down to take into account the linking efficiency, this tool accept as input the TreeMS and produce as output a root Ttree (TreeMSE) filled with the digitalized microtracks that survive to the linking up-down; 2.A tool to convert the micro tracks Ttree (TreeM/TreeMS/TreeMSE) in x.x.cp.root files; TAKE CARE: since at generator level there is no cut on the minimum energy of the microtrack, to make a realistic analysis it is fundamental to apply the link up-down algorithm that has low efficiency for very low energy base track (<5MeV) 4.Some tools to add background are included in the package (it is possible to merge real bg data or simulated bg with simulated events at cp-files level). Of course for people not using cp files it is also possible to merge simulated bg with simulated events by using standard root commands.

2 points simulation of a micro-track 10. GeV muons y2y2  x=  x 1 +  x 2 -  y=  y 1 +  y 2 -  z=  z 1 +  z 2 y1y1 z1z1 x2x2 z2z2 x1x1 zz By taking into account that dx and dy are statistical errors gaussian distributed and dz is a maximal error with a flat distribution, these assumptions automatically give the expected dependences on  : “Since the base-tracks are constructed by using the 2 points at base, the same results are obtained for free for base-tracks too”

Transversal and longitudinal resolution for simulated 10.GeV pions at  =0.7 mrad SlopLong1  =0.037 SlopLong2  =0.037 SlopTr1  =0.008 SlopTr1  =0.008 Smearing parameters are: Sx=0.25 micron, Sy=0.25 micron, Sz=2.5 micron.

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