1. /18 N eutrino E xperiment with S pectrometer S i n E urope Search for sterile neutrinos at CERN G. Sirri INFN Bologna on behalf of the NESSiE Collaboration IFAE, Ferrara 13 Aprile 2012

2. /18 Neutrino Oscillations: A Solved Problem? IFAE, Ferrara 13/04/2012G.Sirri - INFN Bologna2 Neutrino oscillations have established a picture through a large number of experiments consistent with the mixing of three physical neutrino e,  and  with mass eigenstates 1, 2 and 3. A number of anomalies (at the level of 2-3 sigmas discrepancies) appeared recently in neutrino data in the region of Δm 2 ~ 1 eV 2 Predominantly from single detector experiments… Are they experimental errors or due to unaccounted oscillations between “sterile” neutrinos and active neutrinos? The possible presence of oscillations into sterile neutrinos has been proposed by B. Pontecorvo in 1967, but so far without conclusion… BUT

3. /18 IFAE, Ferrara 13/04/2012G.Sirri - INFN Bologna3 Two distinct classes of anomalies have been observed: apparent disappearance signals: (1) from the anti-ν e events detected from near-by nuclear reactors (2) from Mega-Curie k-capture calibration sources used by the Gallium experiments to detect solar ν e observation for excess signals of anti-ν e originated by initial anti-ν μ (BUT lack of ν μ  ν e oscillations) (LNSD/MiniBooNE) These experiments may all point out to the possible existence of at least one fourth non standard neutrino state driving oscillations at a small distances, with typically Δm 2 new ≥ 1 eV 2 and relatively large mixing angles. The existence of additional neutrino states may be also hinted — or at least not excluded — by cosmological data.

4. /18 28 a Short-Base-Line Neutrino Beam   AND   in Appearance ( e ) Measure at L/E corresponding to  m 2 ∼ 1 eV 2 in Disappearance (  ) AND with ≥ 2 sites Measure Electrons Measure Muons in a wide momentum range (0.2 – 10 GeV) Measure Charge-Id Low systematics High rate capability (for both beams and detectors) 2 3 combs L.Stanco © How to disentangle the observed anomalies? IFAE, Ferrara 13/04/20124G.Sirri - INFN Bologna

5. /18 A new approach to sterile oscillations at CERN/SPS IFAE, Ferrara 13/04/2012G.Sirri - INFN Bologna5 The experiment is based on two LAr-TPC’s followed by magnetized spectrometers, observing the electron and muon neutrino events at the ”Far” and “Near” positions 1600 and 300 m from the proton target, respectively. ICARUS “Imaging” detector capable to identify unambiguously all reaction channels with a LAr-TPC This project will exploit the ICARUS T600, moved from Gran Sasso to the CERN “Far” position. An additional 1/4 of the T600 detector (T150) will be constructed and located in the “Near” position. NESSiE Magnetic spectrometers to determine muon charge and p Two spectrometers will be placed downstream of the two LAr-TPC detectors to greatly complement the physics capabilities.

6. /18 arXiv:1203.3432 see also arXiv:1111.2242 Bari Bologna Frascati Lecce Padova Roma 1 Salerno IFAE, Ferrara 13/04/20126G.Sirri - INFN Bologna

7. /18 New Neutrino Facility in the CERN North Area 100 GeV primary beam fast-extracted from SPS; target station next to TCC2; decay pipe L=100m, ø = 3m; beam dump: 15m of Fe with graphite core, followed by μ stations. Neutrino beam angle: pointing upwards; at -3m in the far detector ~5mrad slope. IFAE, Ferrara 13/04/20127G.Sirri - INFN Bologna

8. /18 Charge and momentum measurements in Neutrino Interactions for the Charge Current mode: important and challenging Important : increase the active target mass by measuring the muon momentum increase the range of Δm 2 (at higher values, especially in the eV 2 range) calibration of the beam with a clean muon measurement at high p normalization point for the NC/CC rates clean separation of ν and anti-ν interactions disentangle the ν and anti-ν reverse contaminations in the beams Challenging : find best compromise between passive and active materials  NESSiE Muon Spectrometers IFAE, Ferrara 13/04/20128G.Sirri - INFN Bologna

9. /18 TWO Spectrometers “à la OPERA” PLUS Air-Magnet Coils 875 cm 410 cm 586 cm FAR NEAR Coils B detector layers 1800 + 700 m 2 of RPC 20,000+12,000 digital channels B B = 1.5 T IFAE, Ferrara 13/04/20129G.Sirri - INFN Bologna

10. /18 AIR-Magnets B = 0.25 T IFAE, Ferrara 13/04/201210G.Sirri - INFN Bologna

11. /18 Magnetic Fields Air-MagnetIron-Magnet (First Arm) IFAE, Ferrara 13/04/201211G.Sirri - INFN Bologna

12. /18 Installation at CERN Slide 12 occupancy IFAE, Ferrara 13/04/2012G.Sirri - INFN Bologna

13. /18 Magnetic Field in Iron and in Air) Air-Magnet Iron Magnet (two arms) Iron Magnet (one arm) Charge mis-identification percentage including selection, efficiency and reconstruction procedures. IFAE, Ferrara 13/04/201213G.Sirri - INFN Bologna

14. /18 Expected signals (Example for LSND/MiniBooNE anomalies ) Event rates for the near and far detectors given for 4.5 10 19 p.o.t. The oscillated signals are clustered below 3 GeV of visible energy Values for Δm 2 around 2 eV 2 are reported as examples. IFAE, Ferrara 13/04/201214G.Sirri - INFN Bologna

15. /18 Measured muon momenta in Far detector for anti-  CC and  CC with oscillation (red) compared to the non-oscillated distribution. Event rates are for 4.5x10 19 p.o.t. at 100 GeV, negative polarity reconstructed in the fiducial volumes of the Spectrometer alone Expected signals (2) IFAE, Ferrara 13/04/201215G.Sirri - INFN Bologna

16. /18 Sensitivity for ν µ disappearance IFAE, Ferrara 13/04/201216G.Sirri - INFN Bologna

17. /18 Conclusions SPECTROMETERS capable of precise momentum measurements would complement the LAr experiment by allowing to: Measure ν μ disappearance in a wide energy range. This is a key information for rejecting/observing the existing anomalies over the whole parameter space of sterile neutrino oscillations Measure the neutrino flux at the Near detector in the full muon momentum range, relevant to keep the systematic errors at the lowest possible values. the measurement of the muon charge would enable to: separate ν μ from anti-ν μ in the anti-neutrino beam (where the ν μ contamination is large). This is a critical issue to fully exploit the experimental capability of observing any difference between ν μ → ν e and anti-ν μ → anti-ν e (CP violation signature). reduce the data taking period by collecting both ν μ and anti-ν μ IFAE, Ferrara 13/04/201217G.Sirri - INFN Bologna