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Neutrino Oscillation Studies with the Fermilab NuMI beam: Episode III

Neutrino Oscillation Studies with the Fermilab NuMI beam: Episode III. Historical Introduction: Pre-history, Episodes I and II Physics Motivation Off-axis Beams Backgrounds and Detector Issues Sensitivity of NuMI Off-axis Experiments. Pre-history. Stage: Japan, early 1960’s

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Neutrino Oscillation Studies with the Fermilab NuMI beam: Episode III

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  1. Neutrino Oscillation Studies with the Fermilab NuMI beam: Episode III • Historical Introduction: Pre-history, Episodes I and II • Physics Motivation • Off-axis Beams • Backgrounds and Detector Issues • Sensitivity of NuMI Off-axis Experiments 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  2. Pre-history Stage: Japan, early 1960’s Progress in Theoretical Physics: many papers by Nagoya group (Sakata and Co.), Kyoto group and others addressing issues: • Fundamental symmetries of Nature • Conserved quantum numbers • Leptons-hadrons symmetry • Bold predictions Examples of important cultural values [Prof. Yamada] Not enough experimental input/feedback, Second neutrino just barely discovered MNS: 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  3. Neutrino Mixing Leads to Interference Effects (Oscillations) Components of the initial state have different time evolution => Y(t)  Y(0) Amplitude Amplitude 3-slit interference Experiment: mass difference  difference in optical path length 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  4. Young Experiment Three slit interference experiment detector source I(x) – interference pattern is a result of phase differences due to optical path differences 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  5. Neutrino Oscillations Primer • if all masses are equal i.e. Neutrino oscillations are sensitive to mass differences only. • oscillates as a function of L/E • for Appearance experiment. • : disappearance experiment • :total number of neutrinos is conserved • If Uai is complex then hence T (or CP) violation • Possible Majorana phases do not contribute to oscillations 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  6. Episode I: Before the “New Era” Theory: • Neutrino mass differences 1-100 eV2 • Neutrino mixingmatrix similar to quarks (small or very small mixing angles) Experiment: • No evidence for neutrino oscillations in accelerator (BEBC, CDHS, CHARM, CCFR) or reactor (Bugey, Gosgen) experiments • Confusing ‘solar neutrino problem’ New Era started by “SuperK revolution”: • Neutrinos have mass, mass differences are very small • Neutrino mixing angles are very large 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  7. Episode II: elucidation Two frequencies of oscillations, large mixing angles, at least two of them: • Dm122 ~ 7(?), 12(?) x 10-5 eV2 • q12 ~ 35o • Super K, SNO, KamLand • Dm132 ~ 1.5 - 4x10-3 eV2 • q12 ~ 45o • SuperK, K2K, MINOS, OPERA, ICARUS Dawn of physics beyond the Standard Model Interference of these two amplitudes may lead to relatively large CP-violating effects 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  8. Neutrinos vs Standard Model Whereas • There is a major effort to complete the Standard Model (Higgs search) • There is a broad front of experiments looking for possible deviations from the Standard Model (SUSY searches, B-physics experiments, g-2, EDM, …) The first evidence for physics beyond the standard model is here: • Neutrino mass and oscillations Where does it lead us? • Just an extension (additional 9? 7? Parameters) ? • First glimpse at physics at the unification scale ? (see-saw??) • Extra dimensions? • Unexpected? (CPT violation ???) 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  9. Surprising pattern of mixing angles: WWSS? • We have large mixing angles. How very interesting… I thought that mixing angles tend to be small… Hmm.. sin22q23 is very close to 1 . Maximal mixing  symmetry. What is this new symmetry of Nature? • We have sin22q12 and sin22q23 large, yet sin22q13 rather small. How very interesting… How small is it, really? What makes it so small? Protected by some new symmetry?? What symmetry? 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  10. Three outstanding questionsAD 2003 ne nm nt • Neutrino mass pattern: This ? Or that? n3 n2 n1 • Electron component of n3 (sin22q13) Dm2atm mass n2 n1 n3 Dm2sun “Inverted” mass hierarchy “Normal” mass hierarchy • Complex phase of s  CP violation in a neutrino sector  (?) baryon number of the universe 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  11. b and 0nbb decay experiments and mass hierarchy Dm2atm Dm2sun n2 n3 • Coupling primarily to n1 and n2 • In case of inverted hierarchy m ~ 50 meV required. Challenging.. • In case of normal hierarchy required mass sensitivity in a few meV range. Tough! • Want to know the mass pattern n1 Dm2atm n2 n3 n1 Dm2sun 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  12. The key: nm ne oscillation experiment 3 unknowns, 2 parameters under control L, E, neutrino/antineutrinoNeed several independent measurements to learn about underlying physics parameters 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  13. Observations • First 2 terms are independent of the CP violating parameter d • The last term changes sign between n and n • If q13 is very small (≤ 1o) the second term (subdominant oscillation) competes with 1st • For small q13, the CP terms are proportional to q13; the first (non-CP term) to q132 • The CP violating terms grow with decreasing En (for a given L) • CP violation is observable only if all angles ≠ 0 • Two observables dependent on several physics parameters: need measurements at different L and E 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  14. Telling the Mass Hierarchy: Neutrino Propagation in Matter • Matter effects reduce mass of ne and increase mass of ne • Matter effects increase Dm223 for normal hierarchy and reduce Dm223 for inverted hierarchy for neutrinos, opposite for antineutrinos 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  15. Anatomy of Bi-probability ellipses d Minakata and Nunokawa, hep-ph/0108085 ~cosd • Observables are: • P • P • Interpretation in terms of sin22q13, d and sign of Dm223 depends on the value of these parameters and on the conditions of the experiment: L and E ~sind sin22q13 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  16. Varying the mixing angle.. • Parameter correlation: even very precise determination of Pn leads to a large allowed range of sin22q23  antineutrino beam is more important than improved statistics • CP violation effects (size of the ellipse) ~ sin2q13, overall probability ~ sin22q13 relative effect very large 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  17. Receipe for an ne Appearance Experiment • Large neutrino flux in a signal region • Reduce background (neutral currents, intrinsic ne) • Efficient detector with good rejection against NC background • Large detector • Lucky coincidences: • distance to Soudan = 735 km, Dm2=0.025-0.035 eV2 • => ‘large’ cross section • Below the t threshold! (BR(t->e)=17%) 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  18. ne Appearance Counting Experiment: a Primer This determines sensitivity of the experiment • Systematics: • Know your expected flux • Know the beam contamination • Know the NC background*rejection power (Note: need to beat it down below the level of ne component of the beam only) • Know the electron ID efficiency 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  19. Off-axis NuMI Beams: unavoidable byproduct of MINOS experiment • Beam energy defined by the detector position (off-axis, Beavis et al) • Narrow energy range (minimize NC-induced background) • Simultaneous operation (with MINOS and/or other detectors) • ~ 2 GeV energy : • Below t threshold • Relatively high rates per proton, especially for antineutrinos • Matter effects to amplify to differentiate mass hierarchies • Baselines 700 – 1000 km 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  20. NuMI Challenge: “have” beam, need a new detecor • Surface (or light overburden) • High rate of cosmic m’s • Cosmic-induced neutrons • But: • Duty cycle 0.5x10-5 • Known direction • Observed energy > 1 GeV • Principal focus: electron neutrinos identification • Good sampling (in terms of radiation/Moliere length) • Large mass: • maximize mass/radiation length • cheap • Off-axis collaboration: Letter of Intent 2002, • Proposal in preparation (October 2003), forthcoming workshops at Fermilab: July 10-12, September 11-13 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  21. NuMI Off-axis Detector Low Z imaging calorimeter: • Glass RPC or • Liquid or solid scintillator Electron ID efficiency ~ 40% while keeping NC background below intrinsic ne level Well known and understood detector technologies Primarily the engineering challenge of (cheaply) constructing a very massive detector How massive?? 50 kton detector, 5 years run => • 10% measurement if sin22q13 at the CHOOZ limit, or • 3s evidence if sin22q13 factor 10 below the CHOOZ limit (normal hierarchy, d=0), or • Factor 20 improvement of the limit 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  22. Backgrounds Summary • ne component of the beam • Constrained by nm interactions observed in the near MINOS detector (p) • Constrained by nm interactions observed in the near MINOS detector (m) • Constrained by pion production data (MIPP) • NC events passing the final analysis cuts (p0?) • Constrained by neutrino data from K2K near detector • Constrained by the measurement of EM ‘objects’ as a function of Ehad in the dedicated near detector • Cosmics • Cosmic muon induced ‘stuff’ overlapped with the beam-induced neutrino event • (undetected) cosmic muon induced which mimics the 2 GeV electron neutrino interaction in the direction from Fermilab within 10 msec beam gate • Expected to be very small • Measured in a dedicated setup (under construction) 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  23. Beam-Detector Interactions • Optimizing beam can improve signal • Optimizing beam can reduce NC backgrounds • Optimizing beam can reduce intrinsic ne background • Easier experimental challenge, simpler detectors • # of events ~ proton intensity x detector mass • Allocate the re$ources to maximize the product, rather than individual components 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  24. NuMI and JHF experiments in numbers 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  25. Two phase program Phase I (~ $100-200 M, running 2007 – 2014) • 50 kton (fiducial) detector with e~35-40% • 4x1020 protons per year • 1.5 years neutrino (6000 nm CC, 70-80% ‘oscillated’) • 5 years antineutrino (6500 nm CC, 70-80% ‘oscillated’) Phase II ( running 2014-2020) • 200 kton (fiducial) detector with e~35-40% • 20x1020 protons per year (new proton source?) • 1.5 years neutrino (120000 nm CC, 70-80% ‘oscillated’) • 5 years antineutrino (130000 nm CC, 70-80% ‘oscillated’) 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  26. Determination of mass hierarchy: complementarity of JHF and NuMI Combination of different baselines: NuMI + JHF extends the range of hierarchy discrimination to much lower angles mixing angles Minakata,Nunokawa, Parke 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  27. Physics related to neutrino masses A quest for a neutrino mass spectrum  mass generation mechanisms: • Neutrinos have non-zero mass • 0.05 < m3< 0.23 eV • Mass differences too small to be detectable by direct measurements  interference experiments [ remember DmK=m(K0S)-m(KOL) ] A search for fundamental symmetries: • Conserved ‘family lepton’ number • Conserved lepton number • CP conservation in a lepton sector  leptogenesis  baryon number of the Universe our existence • CPT conservation • New, hereto unknown symmetries of Nature? 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  28. Conclusions • Neutrino Physics is an exciting field for many years to come • Most likely several experiments with different running conditions will be required to unravel the underlying physics. Healthy complementary program is shaping up (see Ichikawa-san). • Fermilab/NuMI beam is uniquely matched to this physics in terms of beam intensity, flexibility, beam energy, and potential source-to-detector distances that could be available • Important element of the HEP program in the US for the next 20 years 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  29. NuMI Of-axis Sensitivity for Phases I and II We take the Phase II to have 25 times higher POT x Detector mass Neutrino energy and detector distance remain the same 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  30. Two body decay kinematics At this angle, 15 mrad, energy of produced neutrinos is 1.5-2 GeV for all pion energies  very intense, narrow band beam ‘On axis’: En=0.43Ep 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  31. Signal and background Fuzzy track = electron Clean track = muon (pion) 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  32. Background examples nmCC - withp0 - muon NC -p0 - 2 tracks 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  33. Sources of the ne background At low energies the dominant background is from m+e++ne+nm decay, hence • K production spectrum is not a major source of systematics • ne background directly related to the nmspectrum at the near detector ne/nm ~0.5% All K decays 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab

  34. Mass Textures and q13 Predictions, Examples 1st Yamada Symposium, NDM 2003 Adam Para, Fermilab Altarelli,Feruglio, hep-ph/0206077

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