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(Accelerator-based) Long baseline neutrino experiments

120711 ICHEP2012 @Melbourne. (Accelerator-based) Long baseline neutrino experiments. Takashi Kobayashi KEK. Contents. Introduction Players and their status Important issues in LBL experiments Results n e appearance n m disappearance n t appearance Speed of neutrino Future

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(Accelerator-based) Long baseline neutrino experiments

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  1. 120711 ICHEP2012 @Melbourne (Accelerator-based)Long baseline neutrino experiments Takashi Kobayashi KEK

  2. Contents • Introduction • Players and their status • Important issues in LBL experiments • Results • ne appearance • nm disappearance • nt appearance • Speed of neutrino • Future • Summary

  3. Neutrino physics • Great progress in last decade • Exhibit first violation of standard “SM”: Non-zero mass • Surprisingly large mixing unlike quarks • Yet unknowns & puzzles (>40yrs behind quark) • Flavor mixing • Standard 3 x 3 PMNS mixing picture is correct? • All three flavors participate mixing? (q13?) • Why so different from quark mixing? • CP is violated? • Mass • Absolute mass • “Unexplained lightness of the existence” • Mass ordering (hierarchy) • Any additional neutrino?? • Unraveling mysteries of neutrino is expected to shed light on fundamental questions in particle physics • High energy scale physics • Matter dominated universe

  4. 3 flavor mixing & oscillation mi: 3 masses, Weak Mass eigenstates 3 mixing angles and 1 CPV phase: q12, q23, q23, d Pontecorvo-Maki-Nakagawa-SakataMatrix Sol, Reactor (LB) Acc. LBL Reactor (SB) Flavor transition (oscillation) sij=sinqij, cij=cosqij Flavor transition = Dmij2 and off-diag. elements are non-zero Frequency is characterized by Dmij2=mi2-mj2: 2 differences

  5. Only upper bound on q13 No measurement of Dm13 q23 maximal? Mass hierarchy (sign of Dm312) No hint on CPV (Absolute mass) Knowledge before Summer 2011 T.Schwetz,M.Tortola,J.Valle, hep-ph:1103.0734v2 ~2.5x10-3eV2

  6. Long baseline oscillation experiments • Optimized for Dm2 = 4En/L=2~3x10-3eV2 • nm beam of 1~10GeV from pion decay •  Baseline ~ several 100km • Physics • nm disappearance (q23, Dm23): q23 really maximal (45deg)?? • nt appearance (q23, Dm23): Definite check. Consistent w/ disappearance? • ne appearance (q13, Dm13):Last key to realize CPV search • Sterile neutrino search • Something new! • Players • Confirmation of SK atmn results (90s, 2000s-) • K2K(1999~2004), MINOS(2005~2012), CNGS(2008~) • Discovery of nue appearance (Starting ~2010s) • T2K(2009~), NOvA (2013~) • CPV and mass hierary (20XX~)

  7. Importance of nmne appearance • Sensitive to • CPV • sign of Dm13 (Mass hierarchy) thru Matter effect CPV Sol term • Existence of ne appearance • Non-zero (reasonable size) q13 • CPV term can exist Chance to detect CPV in the future!

  8. LBLPlayers

  9. MINOS (2005~2012) ~3GeV nm beam from FNAL 120GeV MI ~350kW operation achieved (magnetized)Iron-scintillator tracker at 735km (5.4kt) and near (980t) Physics goals (Anti-)nm disappearance ne appearance Also measure atmospheric neutrino Finished data taking on Apr.30, 2012 10.7x1020POT for nm 3.4x1020POT for anti-nm Far detector 735km 16 10 10 Total POT (1020) #p/week(1018) May2012 May2005 4 10 En (GeV)

  10. CERN neutrino to Gran Sasso (CNGS) • Wide band nm beam of 10~30GeV from CERN 400GeV SPS • Detectors at Gran Sasso • 732km from CERN • ntappearance (+ ne appearance) • First beam May 2006 OPERA (2008~) • t ID by decay topology (kink) • Emulsion-Counter Hybrid • 150k ECC blocks ~1.25kt • Accumulated 1.4x1020pot by 2011 (~1.8e20, 84% of requested in 2012) ICARUS(Oct.2010~): • 600ton LiqAr TPC (T600) • 5.8x1019pot accumulated ICARUS detector in LNGS hall B

  11. T2K experiment • Started data taking in Jan 2010 • First physics results w/ full data bfr the EQ (1.43x1020pot) in June 2011 • Resumed data taking in Mar. 2012 • New results w/ data until June 9, 2012 (3.01x1020pot) released (18% increase from Nu2012) • Off-axis nm beam @ ~600MeV from J-PARC 30GeV MR • 200kW achieved (>100T p/pulse) • Super-Kamiokande @ 295km • Main physics goals • ne appearance • nm disappearance K.Sakashita

  12. Important issues in LBL experiments Typical basic principle of experiment Measure neutrino at near site Fnear・snear・enear • (Integrated) Beam power (& detector mass) • Understanding of • Beam • Neutrino interaction • Detector (efficiency) for better syst. precision Can measure only product Extrapolate (Not just 1/L2!) Predict far detector observation Nfar(E)=Posc・Ffar・sfar・efar Near to Far Flux extrapolation (T2K case) compare Far observations R.Snider@ICHEP

  13. Understanding beam • Flux & Near to far flux extrapolation are govened by • parent hadron (p/K..) production (p&q dist.) • Beam line geometry (controllable) • Hadron production measurements have played critical role • HARP @ CERN-PS (K2K, MiniBooNE) • MIPP @ FNAL (MINOS) • NA49/NA61 @ CERN-SPS (T2K, US program) • Etc.. B.Popov@Nu2012 30GeV p+C results from NA61 for T2K NA61 (S.d.Luise@ICHEP)

  14. Understanding cross sections MINERnA: s dedicated expt @FNAL-NuMI T2K-ND CC (M.R.Salzgeber@ICHEP) Anti-nmCCqe Completed LE mode Nu: 4.0e20pot Anti-Nu:1.7e20pot ME run start in 2013 See Parallel talk by R.Snider Poster by H.Ray • Many efforts:T2K-ND, SciBooNE, MiniBooNE, MINERnA, … T2K-ND(p0d) NCp0 (G.Lopez@ICHEP) CCqe tent ion btw MiniBooNE & high energy data

  15. New Results

  16. T2K ne appearance results • T2K reported the first indication of ne appearance (=non-zero q13) on June 15th, 2011 w/ all data, 1.43x1020POT taken before the earthquake • PRL107,041801,2011 • At Nu2012, updated results w/ data taken in 2012 • Here, further updated results w/ full data taken so far, 3.01x1020POT presented (18% increase from Nu2012) • See K.Sakashita’s parallel talk for detail

  17. Measurements by T2K Near detectors F・sCC measurement Constraint on Far detector prediction Consistency checks of BG predictions Measurements of NCp0 production Measurements of intrinsic necontami. Eve nt rate is stable See poster by

  18. K.Sakashita T2K analysis and results • Signal:neCCqe ne+np+e- • Selection • 1 e-like ring (>100MeV) • No decay-e • Inv. mass of 1st ring and forced-found 2nd ring <105MeV (remove remaining p0) • Rec. En <1250MeV e-like (showering) ring m-like ring MC MC Good rejection of nm events

  19. K.Sakashita T2K: 11 candidate events

  20. T2K ne appearance results K.Sakashita

  21. Attempts for detecting ne appearance OPERA (talk by Marilisa De Serio) MINOS (talk by Giles Barr) Both experiments are not optimized for ne appearance search • Rule out q13=0 at 2s level • Consistent w/ T2K Consistent w/ background Excluded high Dm2 region

  22. T2K nm disappearance • Data bfr EQ: 1.43e20pot (2% of approved amount) • Signal: nmCCQE: nm+nm+p • 1ring m-like, 0 or 1 decay-e, pm>200MeV/c • 31 events remain Best fit: (sin22q23,Dm232) =(0.98, 2.65 x10-3 eV2) 90%CL region sin22q23 > 0.84 Dm232 = 2.2~3.1x10-3eV2

  23. MINOS nm disappearance Giles Barr nm beam Anti-nm Atmn

  24. Constraint on osc. params Giles Barr • Best Dm2 determination from MINOS • All results from SK, MINOS, T2K are consistent MINOS results

  25. Parallel talk by Marilisa De Serio OPERA nt appearance First cand. (t1had kink) reported in 2010 • Status of the analysis • 2 candidate events so far ( expected 2.1 with 0.2 background events) • A few more events are under study. • Progress in estimating detection efficiency and BG. 2ndCand (t3h) reported in June 2012

  26. nt appearance from SK atmn Y.Hayato

  27. Speed of neutrino S.Bertolucci @ Nu2012 MINOS measurement (Giles Barr) S.Bertolucci @ Nu2012 All consistent w/ c

  28. Near future T2K expected stat error at 750kW x 5x107s Stat err only! • Improve significance of ne appearance is of urgent importance • Precision measurements of BOTH appearance & disappearanceare important • Experimental determination of Dm13 is also very important • Also, first trial of mass hierarchy determination G.Fogli@Nu2012 sin22q23=1 fixed Could give hint on dCP Stat err only! Acc ne appearance measurement  Pme=f(s12s23s13sd) nm disappearance measurement  Precise q23 Reactor ne disappearance measurement  Precise q13 Already similar precision! Unofficial plot (Okumura/TK) Players T2K, NOnA, MINOS+(MINOS det + 700kW NOnA optimized higher energy beam), (SK), etc See G.Barr’ s talk

  29. Optimized experiment for ne appearance FNAL NuMI off-axis beam Power upgrade 320kW700kW Recycler: anti-proton  proton Rep cycle 2.2s  1.33s New 14kton liquid scintillator fine grained detector @810km Construction for power upgrade and detector on-going Plan to start meas. from May 2013 First trial of hierarchy determination NOvA (2013~) See Parallel talk by Jonathan M. Paley 2 5 (GeV) 29

  30. Toward CPV&Mass hierarchy • Large q13 opened possibility of CPV search (& mass hierarchy determination) • BUT, not necessarily means EASY (Relative CPV effect ∝1/sin q13) • Expected CP effect ~ 20% at sin22 q13 &sind=1 (~2% @ sind=0.1) at 1stosc. max. • Order of magnitude higher statistics from present generation experiments • High intensity beam (~MW or higher) • High sensitivity huge detector • Should also capable for proton decay detection • Requirement on systematic uncertainty becomes severe • Hadronprodcution • Xsec meas. • Good near detector as far as possible • Matter effect is larger at larger L (E) •  Experiment to determine Mass hierarchy could be realized earlier w/ very long baseline (>1000km) Asym by matter effect Genuine CPV Asymmetry btw app. prob. for n and anti-n 295km 2300km Example of size of effects

  31. World efforts to formulate future direction • US: LBNE • Reconfigured to phased approach:10kt on surface first  DOE CD-1 review in fall 2012 • Go underground if enough additional fund become available • EU • EoI of LBNO, CERN-SPSC-2012-021 (SPSC-EOI-007), is submitted to/received by CERN SPSC (June 2012) • Excellent sensitivity on hierarchy • Japan: Two options w/ J-PARC T.Nakadaira@Nu2012 US Y.K.Kim LBNE @Homestake Project X (8GeV LINAC +MI)

  32. Summary • ne appearance • Evidence obtained by T2K • P-value 0.7%(2.5s)(2011)  0.08%(3.2s) (2012) • Opened possibility of CPV/Hierarchy meas. • 2s level from MINOS • nt appearance • 2 signal candidates w/ 0.2 BG in OPERA • 3.8s level excess in SK atmnt enhanced analysis • nm disappearance • q23 most constrained by SK atmn: sin22q23 > 0.93~0.95 (@90%CL) • Dm232 by MINOS (2.39+0.09-0.11)x10-3eV2 (4% meas) • Speed of neutrino consistent w/ light • Future • Near: Improve ne appearance significance  precision measurements of ne appearance & nm disappearance • Hint on CPV and/or Mass hierarchy • Future experiments for CPV&Mass hierarchy are being discussed & proposed (LoI, EoI, ..)

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