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The Neutrino SceneBoris KayserFermilabJune 3, 20041Evidence For Flavor ChangeNeutrinosSolar Reactor(L 180 km)AtmosphericAccelerator(L = 250 km)Stopped m+ Decay LSND L 30 mEvidence of Flavor ChangeCompellingVery StrongCompellingInterestingUnconfirmed()2Solar NeutrinosNuclear reactions in the core of the sun produce ne. Only ne. Sudbury Neutrino Observatory (SNO) measures, for the high-energy part of the solar neutrino flux: nsol d e p p fne nsol d n n p fne + fnm + fntFrom the two reactions,Clearly, fnm + fnt 0 . Neutrinos do change flavor.fnefne + fnm + fnt = 0.306 0.026 (stat) 0.024 (syst)3There is some spectrum of 3 or more neutrino mass eigenstates ni:(Mass)2n1n2n3n4Mass (ni) mine, nm, and nt are mixtures of these mass eigenstates.4nila (le e, lm m, lt t)DetectorUaiU is the Leptonic Mixing Matrix.5What Have We Learned?If LSND is confirmed, there are at least 4 neutrino species.If LSND is not confirmed, nature may contain only 3 neutrinos.Then, from the existing data, the neutrino spectrum looks like 6Dm2atmne |Uei|2nm |Umi|2nt |Uti|2n1n2n3(Mass)2Dm2sol n3nm+nt2sin2 q13Bounded by reactor exps. with L 1 kmFrom max. atm. mixing, From nm(Up) oscillate but nm(Down) dontIn LMAMSW, Psol(nene) = ne fraction of n2From max. atm. mixing, n1+n2 includes (nmnt)/2 From distortion of ne(solar) and ne(reactor) spectra7The Mixing MatrixThe flavor content picture shows the |Uai|2, but not the signs or phases of the Uai. U 1000c23s230s23c23 c130s13ei010s13ei0c13 c12s120s12c120001 eia1/2000eia2/20001 q12 qsol 32, q23 qatm 35-55, q13 15 would lead to P(na nb) P(na nb). CPBut note the crucial role of s13 sin q13.cij cos qijsij sin qijAtmosphericCross-MixingSolarMajorana CP phases8 The Future What We Would Like to Find OutwHow many different kinds of neutrinos are there?wWhat are the masses of the neutrinos?wWhat implications do neutrinos and solar-physics/astrophysics/cosmology have for each other?wAre neutrinos their own antiparticles?9w How extensive is the mixing of different types of neutrinos?w Do neutrino interactions violate CP?w Are there surprises, such as large electromagnetic interactions from extra dimensions?w What can neutrinos tell us about physics at the grand unification scale?w Are neutrinos responsible for the matter-antimatter asymmetry of the universe?10The American Physical Society Divisions of Particles and Fields Nuclear Physics Astrophysics Physics of Beamsare sponsoring a year-long study, aimed at laying the groundwork for a sensible future program to answer the open questions.To quote the Charge“The Study will lay scientific groundwork for the choices that must be made during the next few years.”11Working Groups The Central ElementEach working group is defined by an experimental approach.The groups and their leaders Solar and Atmospheric Neutrino ExperimentsJohn Bahcall , Josh Klein Reactor Neutrino ExperimentsGabriela Barenboim , Ed Blucher Superbeam Experiments and DevelopmentBill Marciano , Doug Michael 12Neutrino Factory and Beta Beam Experiments and DevelopmentStephen Geer , Michael Zisman Neutrinoless Double Beta Decay and Direct Searches for Neutrino MassSteve Elliott , Petr Vogel What Cosmology/Astrophysics and Neutrino Physics can Teach Each OtherSteve Barwick , John Beacom Theory Discussion GroupRabi Mohapatra 13Conclusions and recommendations in a report to be completed by end of August.Final General Meeting Snowmass, June 28-30See www.interactions.org/neutrinostudyAll are welcome!14Methods and PayoffsEmphasis on questions whose answers will come from accelerator and reactor experiments.Assume first that there are only 3 neutrino mass eigenstates.XWhat is the neutrino mass spectral pattern?Today: 1.9 10-3 Dm2atm 3.0 10-3 eV2 (90% SuperK)Tomorrow:? Dm2atm Several hundred km.20Accelerator LBL measurements depend on q13, qatm, Sign (Dm2atm), and .They can probe all of these quantities.Reactor experiments depend only on q13. Thus, they can measure q13 cleanly.21Sensitivity:Experimentsin2 2q13Present CHOOZ bound 0.2Double CHOOZ 0.03Future US experiment 0.01(Detectors at 200 m and 1.5 km)Sensitivity needed as part of the overall program: 0.01Other measurements: Neutrino magnetic moment, the anomalous Weinberg angle22XDo neutrino interactions violate CP?Look for P(nm ne) P(nm ne)(Superbeam)orP(ne nm) P(ne nm)( n Factory)Must separate CP violation from matter effects.Can establish CP if Facilitysin2 2q13 exceedsSuperbeam from proton driver10-2 n factory10-423We can exist only because Matter antimatterin the universe.CP in n oscillation would be evidence that the Matter antimatter asymmetry arose fromLeptonic not Quark or Squark CP in the early universe.24XAre there more than 3 neutrino mass eigenstates?MiniBooNE can confirm or refute LSND.If MiniBooNE running with n sees no signal, it will not have tested LSND unless it runs with n.If MiniBooNE (n and/or n) sees a signal tHow many additional neutrinos are there?tWhat are the splittings Dm2?tHow should reactor and LBL experiments be interpreted?tAre there new, Short-Base-Line CP effects?An additional detector would be called for.25ConclusionNeutrino physics presents us with exciting opportunities.Fermilab could play a leading role in the neutrino program of the future.
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