Sterile neutrinos in Icarus and Borexino Paola Sala (Icarus) - PowerPoint PPT Presentation

Sterile neutrinos in Icarus and Borexino Paola Sala (Icarus) Gioacchino Ranucci (Borexino) INFN Milano Milano 4-4- 2013 1

Outline  Neutrino oscillations and hints of sterile neutrinos .  The ICARUS-NESSIE Proposal at the CERN- SPS short baseline neutrino facility  Short Distance Neutrino Oscillations with BoreXino - SOX Milano 4-4- 2013 Slide# : 2

The new physics frontier  The discovery of a Higgs boson at CERN/LHC has crowned the success of the Standard Model (SM).  Neutrino masses and oscillations represent today a main experimental evidence of a potentially unknown physics beyond the A candidate event in the Standard Model. search for the Higgs boson, showing two  Being the only elementary fermions whose electrons and two muons (Image: CMS/CERN) basic properties are still largely unknown, neutrinos must naturally be one of the main priorities to complete our knowledge of the SM. The first CNGS neutrino event in ICARUS Milano 4-4- 2013 Slide# : 3

Neutrinos: a golden field for astro-particle physics  Neutrinos have been the origin of an impressive number of “ Surprises ” :  Masses, once zero “ by ignorance ” , are actually important  Oscillations extend and complete the C+KM quark mixing  Oscillations due to matter exist  But this is not all ! Important discoveries may be ahead:  CP violation in the lepton sector  Majorana or Dirac  ’ s;  -less  -decay,   -masses  Sterile neutrino and other “ surprises ”  Right handed neutrinos and see-saw mechanisms  The cosmological importance of neutrinos is immense Milano 4-4- 2013 Slide# : 4

Neutrino flavors and oscillations  So far, 3 neutrino flavors  e      Combination of 3 mass eigenstates  3 mixing angles  2 mass differences  1 CP phase neutrino Oscillations In 2 flavors approximation: P (     ) = sin 2 (2  ) sin 2 (1.27 D m 2 L (m) /E (MeV) )   <->  e   <->   INFN-CTS_march 2013 Slide# : 5

Known oscillation parameters Solar and reactor  e ,  e disappearance : Davis, KamLand, SNO, Borexino …  D m 2 12 = D m 2 solar = O (MeV) / O (100 km) ≈ 8 x 10 -5 eV 2  sin 2  12 ≈0.3 Atmospheric and accelerator   disappearance,      : SuperKamiokande, Minos, Opera and Icarus @ CNGS, T2K  D m 2 23 = D m 2 atm = O (GeV) / O (1000 km) ≈ 2.4 x 10 -3 eV 2  sin 2  23 ≈ 0.39 Accelerator     e , reactor  e disapp. : DayaBay, Reno, T2K  sin 2  23 ≈0.024  Mass Hierarchy and mass values are unknown   CP is unknown  From Z 0 width : only 3 active neutrinos However: Milano 4-4- 2013 Slide# : 6

Some unexplained   ->  e events: The LNSD Anomaly L/E ≈1 Milano 4-4- 2013 Slide# : 7

The MiniBooNE experiment at FNAL (1998-today) L/E ≈1 Primary beam : 8 GeV/c protons Neutino beam ≈ 1 GeV   or    . Distance ≈ 500 m An event excess of 78.4 ± 28.5 events (2.8σ) is observed for anti-   . Low energy excess of 162.0 ± 47.8 events (3.4σ) in neutrino mode INFN-CTS_march 2013 Slide: 8

LSND-like exclusion from the present ICARUS experiment allowed MiniBooNE Eur. Phys. J. C 73 (2013) allowed LSND 90% allowed LSND 99% limit of KARMEN present ICARUS exclusion area ICARUS result strongly limits the window of parameters for a possible LSND anomaly to a very narrow region ( D m 2 ≈ 0.5 eV 2 and sin 2 2  ≈ 0.005) where there is an overall agreement (90% CL) of ● the present ICARUS limit ● the limits of KARMEN ● the positive signals of LSND and MiniBooNE Slide# : 9 Milano 4-4- 2013

The Gallium and reactor disappearance anomaly  Recent re-evaluation of reactor antineutrino spectra  The ratio R between the observed and predicted rates of previous experiments is decreased to R = 0.927 ± 0.023 , 3.0  from unity.  SAGE and GALLEX experiments recorded the calibration signal produced by intense artificial k- capture sources of 51 Cr and 37 Ar. The ratio R between the detected and predicted neutrino rates are Can be fitted with consistent : R = (0.86 ± 0.05), about neutrino oscillations 2.7  from R=1 around D m 2 new ≈ 2 eV 2 and sin 2 (2  new ) ≈ 0.3. Milano 4-4- 2013 Slide# : 10

Over- all evidence is mounting…. Planck ? Combined evidence for some possible anomaly at ≈ 1 eV 2 : Could be the hint for the existence of one – or more- additional neutrino? Milano 4-4- 2013 Slide# : 11

What are “sterile” neutrinos ?  Sterile neutrinos are a hypothetical type of neutrinos that do not interact via any of the fundamental interactions of the Standard Model except gravity.  The name was coined in 1957 by Bruno Pontecorvo.  If they are heavy enough, they may also contribute to cold dark matter or warm dark matter. Bruno Pontecorvo  Sterile neutrinos may mix with ordinary neutrinos  Oscillations into sterile neutrinos are detected as disappearance of ordinary neutrinos (reactors, Gallex anomalies)  Oscillations     sterile    detected as appearance (LSND) Milano 4-4- 2013 Slide# : 12

A search for sterile neutrino :ICARUS-NESSIE at CERN  A new neutrino beam for a short base-line (L/E ≈ 1) experiment  The experimental set-up will include a FAR and a NEAR detectors, identical except for dimensions  In absence of oscillations, apart some beam related small spatial corrections, the two spectra at different distances should a precise copy of each other,  The ICARUS Liquid Argon Time Projection chamber technology will allow for high precision, low background oscillation study  Magnetic spectrometers (NESSIE collab.) will be installed in far and near position for  μ disappearance searches  This will presumably permit a definitive clarification of the “LNSD anomaly” in all the available oscillation channels in the same experiment.  ICARUS-NESSIE proposal, SPSC-P-347 , arXiv:1208.0862 Slide# : 13

New CERN SPS 2 GeV neutrino facility in North Area 100 GeV primary proton beam fast extracted from CERN-SPS in North Area: C-target station + two magnetic horns, ~110 m decay pipe, beam dump followed by  stations. Interchangeable  and  focussing . Far position (1600 m) ICARUS-T600 detector + magnetic spectrometer Near position (460 m) 150t LAr-TPC detector to be build anew + magnetic spectrometer Slide# : 14

ICARUS LAr-TPC detection technique  2D projection for each of 3 wire planes per TPC  3D spatial reconstruction from stereoscopic 2D projections  charge measurement from Collection plane signals Collection (top view) Induction 2 (top view) Induction 1 (frontal view) CNGS   charge current interaction, one of TPC ’ s shown Neutrino Telescopes, 11-15 March 2013 15

ICARUS @ LNGS: the first LARGE LAr-TPC Hall B cathode LN 2 vessels 1.5m cryogenics readout electronics (behind) T300 T300 E E readout wire arrays T300 module: two TPCs with the common cathode  Two identical T300 modules  3 readout wire planes at 0 ° , ± 60 ° , 3mm (2 TPC chambers per module) plane spacing (for each TPC chamber):   53000 wires, 3 mm pitch  LAr active mass 476 t:  2 Induction planes, 1 Collection  (17.9 x 3.1 x 1.5 for each TPC) m 3 ;  drift length = 1.5 m;  PMT for scintillation light (128 nm):  E drift = 0.5 kV/cm; v drift = 1.6 mm/ms  (20+54) PMTs  trigger and t 0 Total energy reconstruction of events from charge integration.  Full sampling, homogeneous calorimeter; excellent accuracy for contained  events. Neutrino Telescopes, 11-15 March 2013 16

T600 in hall B (CNGS2-2009) INFN-CTS_march 2013 Slide: 17