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CP violation and mass hierarchy searches with Neutrino Factories and Beta Beams

CP violation and mass hierarchy searches with Neutrino Factories and Beta Beams. NuGoa – Aspects of Neutrinos Goa, India April 10, 2009 Walter Winter Universität Würzburg. TexPoint fonts used in EMF: A A A A A A A A. Contents. Motivation from theory: CPV CPV Phenomenology

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CP violation and mass hierarchy searches with Neutrino Factories and Beta Beams

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  1. CP violation and mass hierarchy searches with Neutrino Factories and Beta Beams NuGoa – Aspects of Neutrinos Goa, India April 10, 2009Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAAAAA

  2. Contents • Motivation from theory: CPV • CPV Phenomenology • The experiments • Optimization for CPV • CP precision measurement • CPV from non-standard physics • Mass hierarchy measurement • Summary

  3. Motivation from theory

  4. Where does CPV enter? • Example: Type I seesaw (heavy SM singlets Nc) Could also be type-II, III seesaw,radiative generation of neutrino mass, etc. Block-diag. Primary source of CPV(depends BSM theory) Charged leptonmass terms Eff. neutrinomass terms Effective source of CPV(only sectorial origin relevant) Observable CPV(completely model-indep.) CC

  5. Connection to measurement • From the measurement point of view:It makes sense to discuss only observable CPV(because anything else is model-dependent!) • At high E (type I-seesaw): 9 (MR)+18 (MD)+18 (Ml) = 45 parameters • At low E: 6 (masses) + 3 (mixing angles) + 3 (phases) = 12 parameters LBL accessible CPV: dIf  UPMNS real CP conserved CPV in 0nbb decay Extremely difficult! (Pascoli, Petcov, Rodejohann, hep-ph/0209059) There is no specific connectionbetween low- and high-E CPV! But: that‘s not true for special (restrictive) assumptions!

  6. Why is CPV interesting? • Leptogenesis:CPV from Ncdecays • If special assumptions(such as hier. MR,NH light neutrinos, …)it is possible that dCPis the only source ofCPV for leptogensis! (Nc)i (Nc)i ~ MD(in basis where Ml and MR diagonal) Different curves:different assumptions for q13, … (Pascoli, Petcov, Riotto, hep-ph/0611338)

  7. How well do we need to measure? • We need generic argumentsExample: Parameter space scan for eff. 3x3 case (QLC-type assumptions, arbitrary phases, arbitrary Ml)The QLC-type assumptions lead to deviations O(qC) ~ 13 • Can also be seen in sum rules for certain assumptions, such as(F: model parameter) • This talk: Want Cabibbo-angle order precision for dCP! (arXiv:0709.2163) (Niehage, Winter, arXiv:0804.1546)

  8. CPV phenomenology

  9. Terminology • Any value of dCP(except for 0 and p)violates CP • Sensitivity to CPV:Exclude CP-conservingsolutions 0 and pfor any choiceof the other oscillationparameters in their allowed ranges

  10. Measurement of CPV • Antineutrinos: • Magic baseline: • Silver: • Platinum, Superb.: (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004)

  11. Degeneracies Iso-probability curves • CP asymmetry(vacuum) suggests the use of neutrinos and antineutrinos • One discrete deg.remains in (q13,d)-plane(Burguet-Castell et al, 2001) • Additional degeneracies: (Barger, Marfatia, Whisnant, 2001) • Sign-degeneracy (Minakata, Nunokawa, 2001) • Octant degeneracy (Fogli, Lisi, 1996) Neutrinos Antineutrinos Best-fit

  12. Intrinsic vs. extrinsic CPV • The dilemma: Strong matter effects (high E, long L), but Earth matter violates CP • Intrinsic CPV (dCP) has to be disentangled from extrinsicCPV (from matter effects) • Example: p-transitFake sign-solutioncrosses CP conservingsolution • Typical ways out: • T-inverted channel?(e.g. beta beam+superbeam,platinum channel at NF, NF+SB) • Second (magic) baseline Critical range True dCP (violates CP maximally) NuFact, L=3000 km Degeneracy above 2s(excluded) Fit True (Huber, Lindner, Winter, hep-ph/0204352)

  13. The magic baseline

  14. CPV discovery reach … in (true) sin22q13 and dCP Best performanceclose to max. CPV (dCP = p/2 or 3p/2) Sensitive region as a function of trueq13 anddCP dCP values now stacked for each q13 No CPV discovery ifdCP too close to 0 or p No CPV discovery forall values of dCP 3s ~ Cabibbo-angleprecision at 2sBENCHMARK! Read: If sin22q13=10-3, we expect a discovery for 80% of all values of dCP

  15. The experiments

  16. Beta beam concept… originally proposed for CERN (CERN layout; Bouchez, Lindroos, Mezzetto, 2003; Lindroos, 2003; Mezzetto, 2003; Autin et al, 2003) (Zucchelli, 2002) • Key figures (any beta beam): g, useful ion decays/year? • Often used “standard values”:3 10186He decays/year1 101818Ne decays/year • Typical g ~ 100 – 150 (for CERN SPS) g More recent modifications: • Higher g(Burguet-Castell et al, hep-ph/0312068) • Different isotope pairs leading to higher neutrino energies (same g) (http://ie.lbl.gov/toi) (C. Rubbia, et al, 2006)

  17. Current status: A variety of ideas “Classical” beta beams: • “Medium” gamma options (150 < g < ~350) • Alternative to superbeam! Possible at SPS (+ upgrades) • Usually: Water Cherenkov detector (for Ne/He) (Burguet-Castell et al, 2003+2005; Huber et al, 2005; Donini, Fernandez-Martinez, 2006; Coloma et al, 2007; Winter, 2008) • “High” gamma options (g >> 350) • Require large accelerator (Tevatron or LHC-size) • Water Cherenkov detector or TASD or MID? (dep. on g, isotopes) (Burguet-Castell et al, 2003; Huber et al, 2005; Agarwalla et al, 2005, 2006, 2007, 2008, 2008; Donini et al, 2006; Meloni et al, 2008) • Hybrids: • Beta beam + superbeam(CERN-Frejus; Fermilab: see Jansson et al, 2007) • “Isotope cocktail” beta beams (alternating ions)(Donini, Fernandez-Martinez, 2006) • Classical beta beam + Electron capture beam(Bernabeu et al, 2009) • … • The CPV performance depends very much on the choice from this list! Often: baseline Europe-India

  18. Neutrino factory:International design study (Geer, 1997; de Rujula, Gavela, Hernandez, 1998; Cervera et al, 2000) IDS-NF: • Initiative from ~ 2007-2012 to present a design report, schedule, cost estimate, risk assessment for a neutrino factory • In Europe: Close connection to „Euronus“ proposal within the FP 07 • In the US: „Muon collider task force“ Signal prop. sin22q13 Contamination Muons decay in straight sections of a storage ring ISS

  19. IDS-NF baseline setup 1.0 • Two decay rings • Em=25 GeV • 5x1020 useful muon decays per baseline(both polarities!) • Two baselines:~4000 + 7500 km • Two MIND, 50kt each • Currently: MECC at shorter baseline (https://www.ids-nf.org/)

  20. NF physics potential • Excellent q13, MH, CPV discovery reaches (IDS-NF, 2007) • Robust optimum for ~ 4000 + 7500 km • Optimization even robust under non-standard physics(dashed curves) (Kopp, Ota, Winter, arXiv:0804.2261; see also: Gandhi, Winter, 2007)

  21. Optimization for CPV

  22. Optimization for CPV • Small q13:Optimize discovery reach in q13 direction • Large q13:Optimize discovery reach in (true) dCPdirection~ Precision! • What defines “small” vs “large q13”? A Double Chooz, Day Bay, T2K, … discovery? Optimization for large q13 Optimization for small q13

  23. Large q13 strategy • Assume e.g. that Double Chooz discovers q13 • Minimum wish listeasy to define: • 5s independent confirmation of q13 > 0 • 3s mass hierarchy determination for any (true) dCP • 3s CP violation determination for 80% (true) dCP(~ 2s sensitvity to a Cabibbo angle-size CP violation) For any (true) q13 in 90% CL D-Chooz allowed range! • What is the minimal effort for that? • NB: Such a minimum wish list is non-trivial for small q13 (arXiv:0804.4000; Sim. from hep-ph/0601266; 1.5 yr far det. + 1.5 yr both det.)

  24. Example: Minimal beta beam (arXiv:0804.4000) • Minimal effort = • One baseline only • Minimal g • Minimal luminosity • Any L (green-field!) • Example: Optimize L-g for fixed Lumi: • CPV constrains minimal g • g as large as 350 may not even be necessary!(see hep-ph/0503021) • CERN-SPS good enough? Sensitivity for entire Double Chooz allowed range! 5yr x 1.1 1018 Ne and 5yr x 2.9 1018 He useful decays

  25. Small q13 strategyExample: Beta beams • Assume that Double Chooz … do not find q13 • Example: Beta beam in q13-direction (for max. CPV) • „Minimal effort“ is a matter of cost! LSF ~ 2 50 kt MIDL=400 km (LSF) (Huber et al, hep-ph/0506237) (Agarwalla et al, arXiv:0802.3621)

  26. Experiment comparison • The sensitivities are expected to lie somewhere between the limiting curves • Example: IDS-NF baseline(~ dashed curve) (ISS physics WG report, arXiv:0810.4947, Fig. 105)

  27. CP precision measurement

  28. Why is that interesting? • Theoretical exampleLarge mixingsfrom CL and n sectors?Example: q23l = q12n = p/4, perturbations from CL sector(can be connected with textures)(Niehage, Winter, arXiv:0804.1546; see also Masina, 2005; Antusch, King 2005 for similar sum rules) • The value of dCP is interesting (even if there is no CPV) • Phenomenological exampleStaging scenarios: Build one baseline first, and then decide depending on the outcome • Is dCP in the „good“ (0 < dCP < p) or „evil“ (p < dCP < 2p) range?(signal for neutrinos ~ +sin dCP) dCPandoctantdiscriminatethese examples!

  29. Performance indicator: CP coverage • Problem: dCP is a phase (cyclic) • Define CP coverage (CPC):Allowed range for dCP which fits a chosen true value • Depends on true q13 and true dCP • Range:0 < CPC <= 360 • Small CPC limit:Precision of dCP • Large CPC limit:360 - CPCis excluded range

  30. CP pattern • Performance as a function of dCP (true) • Example: Staging.If 3000-4000 km baseline operates first, one can use this information to determine if a second baseline is needed Precision limit Exclusion limit (Huber, Lindner, Winter, hep-ph/0412199)

  31. CPV from non-standard physics?

  32. CPV from non-standard interactions • Example: non-standard interactions (NSI) in matter from effective four-fermion interactions: • Discovery potential for NSI-CPV in neutrino propagation at the NFEven if there is no CPV instandard oscillations, we mayfind CPV!But what are the requirements for a model to predict such large NSI? ~ current bound IDS-NF baseline 1.0 (arXiv:0808.3583) 3s

  33. CPV discovery for large NSI • If both q13 and |eetm| large, the change to discover any CPV will be even larger: For > 95% of arbitrary choices of the phases • NB: NSI-CPV can also affect the production/detection of neutrinos, e.g. in MUV(Gonzalez-Garcia et al, hep-ph/0105159; Fernandez-Martinez et al, hep-ph/0703098; Altarelli, Meloni, 0809.1041; Antusch et al, 0903.3986) IDS-NF baseline 1.0 (arXiv:0808.3583)

  34. Models for large NSI? • Effective operator picture:Describes additions to the SM in a gauge-inv. way! • Example: NSI for TeV-scale new physicsd=6: ~ (100 GeV/1 TeV)2 ~ 10-2 compared to the SMd=8: ~ (100 GeV/1 TeV)4 ~ 10-4 compared to the SM • Current bounds, such as from CLFV: difficult to construct large (= observable) leptonic matter NSI with d=6 operators (except for ettm, maybe)(Bergmann, Grossman, Pierce, hep-ph/9909390; Antusch, Baumann, Fernandez-Martinez, arXiv:0807.1003; Gavela, Hernandez, Ota, Winter,arXiv:0809.3451) • Need d=8 effective operators! • Finding a model with large NSI is not trivial! n mass d=6, 8, 10, ...: NSI

  35. Systematic analysis for d=8 Feynman diagrams Basis (Berezhiani, Rossi, 2001) • Decompose all d=8 leptonic operators systematically • The bounds on individual operators from non-unitarity, EWPD, lepton universality are very strong! (Antusch, Baumann, Fernandez-Martinez, arXiv:0807.1003) • Need at least two mediator fields plus a number of cancellation conditions(Gavela, Hernandez, Ota, Winter, arXiv:0809.3451) Avoid CLFVat d=8:C1LEH=C3LEH Combinedifferentbasis elements C1LEH, C3LEH Canceld=8CLFV But these mediators cause d=6 effects Additional cancellation condition(Buchmüller/Wyler – basis)

  36. Mass hierarchy (MH)

  37. Motivation • Specific models typically come together with specific MH prediction (e.g. textures are very different) • Good model discriminator (Albright, Chen, hep-h/0608137) 8 8 Normal Inverted

  38. Matter effects • Magic baseline: • Removes all degeneracy issues (and is long!) • Resonance: 1-A  0 (NH: n, IH: anti-n)Damping: sign(A)=-1 (NH: anti-n, IH: n) • Energy close to resonance energy helps (~ 8 GeV) • To first approximation: Pem ~ L2 (e.g. at resonance) • Baseline length helps (compensates 1/L2 flux drop) (Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004)

  39. Baseline dependence Event rates (A.U.) • Comparison matter (solid) and vacuum (dashed) • Matter effects (hierarchy dependent) increasewith L • Event rate (n, NH) hardly drops with L • Go to long L! (Dm212  0) NH matter effect Vacuum, NH or IH NH matter effect (Freund, Lindner, Petcov, Romanino, 1999)

  40. Mass hierarchy sensitivity • For a given set of true q13 and dCP: Find the sgn-deg.solution • Repeat that for all true true q13 and dCP (for this plot)

  41. Small q13 optimization: NF Em-L (single baseline) L1-L2 (two baselines) • Magic baseline good choice for MH • Em ~ 15 GeV sufficient (peaks at 8 GeV) (Kopp, Ota, Winter, 2008) (Huber, Lindner, Rolinec, Winter, 2006)

  42. Small q13 optimization: BB (Agarwalla, Choubey, Raychaudhuri, Winter, 2008) • Only B-Li offers high enough energies for „moderately high“ g • Magic baseline global optimum if g>=350 (B-Li) • Recently two-baseline setups discussed(Coloma, Donini, Fernandez-Martinez, Lopez-Pavon, 2007; Agarwalla, Choubey, Raychaudhuri, 2008)

  43. Optimization for large q13 (arXiv:0804.4000) • Performance as defined before (incl. 3s MH) • L > 500 km necessary • Large enough luminosity needed • High enough g necessary • Ne-He: limited to g > 120 • B-Li: in principle, smaller g possible • High g = high E = stronger matter effects!

  44. Physics case for CERN-India?(neutrino factory) • MH measurement if q13 small (see before; also de Gouvea, Winter, 2006) • Degeneracy resolution for 10-4≤ sin22q13≤ 10-2(Huber, Winter, 2003) • Risk minimization (e.g., q13 precision measurement) (Gandhi, Winter, 2007) • Compementary measurement(e.g. in presence of NSI)(Ribeiro et al, 2007) • MSW effect verification (even for q13=0) (Winter, 2005) • Fancy stuff (e.g. matter density measurement) (Gandhi, Winter, 2007)

  45. Summary • The Dirac phase dCP is probably the only realistically observable CP phase in the lepton sector • Maybe the only observable CPV evidence for leptogenesis • This and f1, f2: the only completely model-inpendent parameterization of CPV • What precision do we want for it? Cabibbo-angle precision?  Relates to fraction of „dCP“ ~ 80-85% • For a BB or NF, the experiment optimization/choice depends on q13 large or small • Other interesting aspects in connection with CPV: CP precision measurement, NSI-CPV • MH for small q13 requires magic baseline

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