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Atsuko K. Ichikawa, Kyoto University

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Atsuko K. Ichikawa, Kyoto University EXPLORING PARTICLE-ANTIPARTICLE ASYMMETRY IN NEUTRINO OSCILLATION Atsuko K. Ichikawa, Kyoto University INTRODUCTION OF MYSELF • Got PhD by detecting doubly-strange nuclei using emulsion • After that, working on accelerator-based long- baseline neutrino oscillation experiments in Japan, especially on neutrino production, neutrino detector in accelerator-site and analysis. • Recently, started a high- pressure Xenon gas project for double-beta decay search 2 CONSTITUENTS OF THIS WORLD How can we distinguish btw. u, c and t Electric d, s and b charge e, and e, and Same spin, same charge… Only by mass! Except for ’s. + (Higgs, dark matter, dark energy…..?) Fig. from FNAL home page 3 HOW CAN WE DISTINGUISH NEUTRINOS? - IT IS TWO SIDES OF COINS- Neutrinos do interact with matter and 4 HOW CAN WE DISTINGUISH NEUTRINOS? - IT IS TWO SIDES OF COINS- Neutrinos do interact with matter and • An electron neutrino changes to an electron. We call this • A muon neutrino changes to a muon. categorization • A tau neutrino changes to atau. ‘flavor’. And it was believed that electron neutrino only changes to electron, never into muon nor tau before the neutrino oscillation was found. 5 NEUTRINOS DO INTERACT, BUT …. photon Concrete Wall X-ray ~1cm High Energy Mean Free path ~10cm of particles High Energy proton ~30cm ~1GeV muon ~200cm ~1GeV neutrino (atmospheric, accelerator) ~108 km≒distance btw. Solar and earth ~1MeV neutrino (solar, reactor) ~1014 km≒100 light-year 6 SUPER-KAMIOKANDE 7 SUPER-KAMIOKANDE • Since April 1996 • Water Cherenkov detector w/ fiducial volume 22.5kton • Detector performance is well- matched at sub GeV • Excellent performance for single particle event • Good e-like(shower ring) / μ-like separation (next page) ~11000 x 20inch PMTs (inner detector, ID) 8 SUPER-KAMIOKANDE 9 SUPER KAMIOKANDE DETECTOR 1,000 m underground 50kton water tank Detect Cherenkov photons with 11,146 20 inch photomultiplier tubes 42m C Scientific American 39m 10 SUPER KAMIOKANDE DETECTOR 1,000 m underground 50kton water tank Detect Cherenkov photons with 11,146 20 inch e photomultiplier tubes 42m C Scientific American 39m 11 SUPER KAMIOKANDE DETECTOR 1,000 m underground 50kton water tank Detect Cherenkov photons with 11,146 20 inch photomultiplier tubes 42m C Scientific American 39m 12 SUPER KAMIOKANDE DETECTOR 1,000 m underground 50kton water tank Detect Cherenkov photons with 11,146 20 inch photomultiplier tubes 42m C Scientific American 39m 13 THEY CAN BE DISTINGUISHED. electron muon - e e+ e+ e- e- e- e- - SK MC event display e e+ 14 TAU NEUTRINO…. tau is heavy. So the charged current interaction dose not occur unless energy > ~ 3.5 GeV. 42m C Scientific American 39m 15 MIXING BTW. FLAVOR AND MASS We know that there are three types of charged lepton (, , ), distinguishable only via mass. Then, we found that there are three types of neutrinos, distinguishable via interaction w/ matter. IF NEUTRINOS HAVE MASSES, there is no need for three types to be mass eigenstates. , 1,2,3 : mass eigenstates Same thing is happening for quarks. (e.g. Cabibbo angle) Partner of quark 16 Then, a neutrino is produced as an eigenstate of one flavor, but propagate with two different speed 1 2 =|1>cos+|2>sine Neutrino Oscillation! muon neutrino m2 m2 tau neutrino i 1 L i 2 L 2E 2E |1> e cos+|2> e sin flight length 2 2 2 2 L P( ) sin 2 sin (m ) 4E17 OSCILLATE ACROSS LOOOONG DISTANCE 2 2 2 2 L(km) P( ) sin 2 sin 1.27m (eV ) E(GeV ) Atmospheric Accelerator ~300 km @ Reactor ~2.4x10-3eV2 E=700 MeV ~50 km @ ~7.6x10-5eV2 E=3 MeV Solar However, in other words, nature allows oscillations corresponding to three m2’s happen in Earth Scale ≫ case 18 could be also possible AND WE FOUND, m3 electron neutrino muon neutrino tau neutrino m1 m1 m2 m3 m3 m1 m2 m2 s u quark partner c quark partner t quark partner d d s b 19 S. Stone, ICHEP2012 20 DO THEY MEAN SOMETHING? quark lepton 0.97 0.23 0.004 0.82 0.55 0.16 UCKM 0.23 1.01 0.04 U PMNS 0.49 0.52 0.55 0.008 0.04 0.89 0.20 0.65 0.70 Assuming some 2 / 3 1/ 3 0 symmetry among quarks and leptons, U MNS 1/ 6 1/ 3 1/ 2 some models predict 1/ 6 1/ 3 1/ 2 1 0 0 0.816 0.577 0 UCKM 0 1 0 0.408 0.577 0.707 0 0 1 0.408 0.577 0.707 21 MIXING BTW. FLAVOR AND MASS flavor flavor flavor Kobayashi-Maskawa theory Mixing with >= 3 types can have imaginary components. In case of 3 generations, one CP phase. 1 0 0 c 0 s ei c s 0 13 13 12 12 UPMNS 0 c23 s23 0 1 0 s12 c12 0 i 0 s23 c23 s13e 0 c13 0 0 1 (cij cosij , sij sinij ) 22 ANTI-PARTICLE • Reverse the rotation of the clock i.e.phase of wavefunction → particle behaves like oppositely-charged particle. · · vs. 23 MIXING BTW. FLAVOR AND MASS flavor flavor flavor Kobayashi-Maskawa theory CKM (quark sector) ~60° PMNS (lepton sector) ~? Mixing with > 3 generation can have imaginary components, which introduce different behavior between particle and anti-particle=CP violation. In case of 3 generations, one CP phase. 1 0 0 c 0 s ei c s 0 13 13 12 12 UPMNS 0 c23 s23 0 1 0 s12 c12 0 i 0 s23 c23 s13e 0 c13 0 0 1 (cij cosij , sij sinij ) 24 LEPTONIC CPV CAN BE MUCH LARGER THAN QUARK’S ~60°~70° looks large, but cannot explain matter-dominant universe. is dependent on definition. Jarlskog Invariant : independent of definition. show the size of CP violation effect. ≡ ∗ ∗ sin 2 sin 2 sin 2 cos sin 310 0.03sin PDG2015 “NEUTRINOMASS,MIXING, AND OSCILLATIONS” sin sin 0.09 → sin 0.58 If we find that sin 0.58, we can, at least, say that there exists CPV which is as large as to produce matter-dominant universe. 25 NEUTRINO OSCILLATION OF THREE STATES Two neutrinos case Three neutrinos case neutrino Depending on the value of , neutrino and antineutrino oscillate differently! antineutrino 26 OSCILLATIONS PECULIAR TO THE ACC.-BASED LONG BASELINE EXPERIMENT CP violation is accessible only via appearance, and can be large for appearance. disappearance ∼∝ sin 2 ~100% at right energy e ~∝sin sin 2~5% ~∝cos sin 2~95% Interference term ~∝sin for neutrino ~∝sin for antineutrino 27 27% effect on appearance World Acc.-based Long baseline oscillation experiments OPERA(2008-2012) ICARUS (2010-2012) 732km MINOS (2005- 2012) 735km MINOS+ (2013-) NOvA (2013-) 819km K2K (1999-2004) 250km T2K (2009-) 295km 28 COMPONENTS OF THE LONG BASELINE NEUTRINO Neutrino beamline EXPERIMENT Proton Beam Near Far Accelerator Decay Volume dump Detector Detector Target&Horns monitor A few 100m ~ a few km A few 100km Toroidal magnetic field by `horn’ focuses timing synchronized → beam using GPS or →̅ beam 29 Decay Volume 1st Horn & 2nd Horn 3rd Horn 30 World Acc.-based Long baseline oscillation experiments OPERA(2008-2012) ICARUS (2010-2012) 732km MINOS (2005- 2012) 735km MINOS+ (2013-) NOvA (2013-) 819km K2K (1999-2004) 250km T2K (2009-) 295km 31 APPEARANCE 3.8 appearance by Super-K atmospheric data (Abe et al., PRL 110, 181802 (2013)) from a sample of enhanced -like events. OPERA experiment, long baseline accelerator neutrino experiments. identifies production in event-by-event basis using nuclear emulsion. 5 events observed →confirmation by 5.1significance. 18 Phys. Rev. Lett. 115, 121802 (2015) World Acc.-based Long baseline oscillation experiments OPERA(2008-2012) ICARUS (2010-2012) 732km MINOS (2005- 2012) 735km MINOS+ (2013-) NOvA (2013-) 819km K2K (1999-2004) 250km T2K (2009-) 295km 33 e appearance 2011 T2K observed 6 events(1.5 bkgs). 2.5 significance. 2013 T2K observed 28 events over 4.9bkgs 7.3 significance. Also first confirmation of ‘appearance’ w/ >5 significance. Example of e candidate event 34 OSCILLATIONS PECULIAR TO THE LONG BASELINE EXPERIMENT disappearance ∼∝ sin 2 ~100% at right energy Since ,, are known from other e measurements, possibly ~∝sin sin 2can ~5%be determined ~∝cos→ measurement, sin 2 ~95% even w/o ̅ →̅ meas. Interference term ~∝sin for neutrino ~∝sin for antineutrino 35 27% effect on appearance World Acc.-based Long baseline oscillation experiments OPERA(2008-2012) ICARUS (2010-2012) 732km MINOS (2005- 2012) 735km MINOS+ (2013-) NOvA (2013-) 819km K2K (1999-2004) 250km T2K (2009-) 295km 36 candidate candidate 13 DEEP LEARNING! NOvA Based on neutrino data by 2016 NH= Now accumulating antineutrino data! IH= 39 T2K HAS STARTED ANTINEUTRINO DATA TAKING IN 2013 (best fit for other parameters) 40 AND SELECTED EVENT DISTRIBUTIONS (best fit for other parameters) 41 INDICATION OF CP VIOLATION??? ∆ v.s. Normal mass 171°, 27° ordering Inverted mass 84°, 73° 90% C.L. ordering allowed regions CP conserving case is disfavored Feldman-Cousins critical 2 values for 90 % C.L. by >90% C.L. Need more statistics! no CPV This year, we doubled neutrino- 90% Confidence Interval: beam data. Results coming soon. 42 PROSPECT IN 10 YEARS • T2K • beam power 350 kW → 900 kW by ~2021 • CP violation may be indicated with >90% C.L. if it is maximally violated. • NOvA • Mass ordering determination (~3) • CP violation may be indicated with >90% C.L. if it is maximally violated. • T2K-II • Target Beam power 1.3 MW, near detector upgrade • x 3 times T2K POT in total by ~2026 • CP violation can be observed with 3 C.L. if it is maximally violated • (new collaborators are welcomed) T2K-II Expected number of events (1:1 : ̅ running case) sample : 455 evts±20% change depending on ̅ sample : 129 evts±13% change depending on 43 SURPRISE? //// and LHC is searching TeV scale new physics.
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