Searches for Neutrino Mass in the NuTeV/CCFR Experiments

1. Searches for Neutrino Mass in the NuTeV/CCFR Experiments Michael H. Shaevitz Columbia University (Win99 Conference, Cape Town, South Africa) • Neutrino Oscillations • Neutral/Charged Current Ratio mneandmnt • ne Appearance Search e tand e sterile • Neutral Heavy Lepton Search • Search in new instrumented decay channel • Sensitivity in mass region 0.02 < ML0< 2.0 GeV

2. NuTeV Collaboration R. A. Johnson, M. Vakili, V. Wu University of Cincinnati, Cincinnati, OH 45221 J. Conrad, S.Koutsoliotas1, J. H. Kim, C. McNulty, A.Romosan2, M. H. Shaevitz, E. G. Stern, A. Vaitaitis Columbia University, New York, NY 10027 R. H. Bernstein, L. Bugel, M. J. Lamm, W. Marsh, P. Nienaber, P. Spentzouris, J. Yu Fermi National Accelerator Laboratory, Batavia, IL 60510 T. Adams, A. Alton, T. Bolton, J. Goldman, M. Goncharov, D. Naples Kansas State University, Manhattan, KS 66506 L. de Barbaro, D. Buchholz, H. Schellman, G. P. ZellerNorthwestern University, Evanston, IL 60208 J. Brau, R. B. Drucker, R. Frey, D. Mason University of Oregon, Eugene, OR 97403 S. Avvakumov, P. de Barbaro, A. Bodek, H. Budd, D. A. Harris, K. S. McFarland, W. K. Sakumoto, U. K. Yang University of Rochester, Rochester, NY 14627 1Current address: Bucknell University 2Current address: Lawrence Berkeley National Laboratory

3. NuTeV Collaboration R. A. Johnson, M. Vakili, V. Wu University of Cincinnati J. Conrad, S.Koutsoliotas1, J. H. Kim, C. McNulty, A. Romosan2, M. H. Shaevitz, E. G. Stern, A. Vaitaitis Columbia University R. H. Bernstein, L. Bugel, M. J. Lamm, W. Marsh, P. Nienaber, P. Spentzouris, J. Yu Fermi National Accelerator Laboratory T. Adams, A. Alton, T. Bolton, J. Goldman, M. Goncharov, D. Naples Kansas State University L. de Barbaro, D. Buchholz, H. Schellman, G. P. ZellerNorthwestern University J. Brau, R. B. Drucker, R. Frey, D. Mason University of Oregon S. Avvakumov, P. de Barbaro, A. Bodek, H. Budd, D. A. Harris, K. S. McFarland, W. K. Sakumoto, U. K. Yang University of Rochester 1Current address: Bucknell University 2Current address: Lawrence Berkeley National Laboratory

4. Neutrino Oscillations - Current Situtation Signals: • LSND: • Atmospheric: • Solar: Limits: • Chorus, Nomad, E531,CCFR,CDHS: • Karmen: • CCFR and Nomad: • Bugey and CHOOZ

5. CP violation leads to different oscillation probabilities for: Most experiments have information on only one sign of neutrino or sometimes a combination of both signs Future experiments investigating current hints should look for particle/antiparticle oscillation differences Lepton sector may be the place to study CP violation mechanisms with no messy hadron uncertainties. In 3 generation mixing, there can be a non-trivial phase between mixing-matrix elements Interference between amplitudes can then lead to CP violation Possible CP Violation with 3  Mixing

6.  or e - Neutral Current  Short Event ,e  - Charged Current  Long Event  e - Charged Current  Short with extra EM energy at start Lab E -Detector at Fermilab • Identify event type by length in the detector and energy deposition distribution.

7. NuTeV Sign-Selected Quad-triplet Beam Separate running. Wrong-sign rate: 1-2  10-3 ne contamination 1.2% (syst. uncertainty 2%) CCFR Quad-triplet Beam Mixed beam of (mainly nm with 5:1 ratio) ne contamination 2.2% (systematic uncertainty 4%)  Beams

8. If nmne then interaction of ne will always look short If nmnt then interaction of nt will mostly look short Neutral/Charged Current Ratio Osc. Search • Effect of Oscillations: • Increase the observed • Increase the visible energy of the shower • Method • Input external electroweak data to predict the no-oscillation value of RnExp . • Compare with this measured value and attribute any difference to oscillations

9. Previous CCFR Result • sin2qW = 0.2236 ± 0.0041  MW = 80.2 ± 0.2 GeV • Error dominated by systematic uncertainties • ne contamination • CC charm production off s and d quarks • charm mass uncertainty: mc = 1.31  0.24GeV • Results agreed  Limits set on n-oscillation • Limits now superseded by Chorus and Nomad

10. NuTeV Electroweak Measurements: n Osc. • Separate data allow the use of the Paschos-Wolfenstein relations. • Much smaller systematic uncertainties • “Sea”quark contributions cancel  reduced mc dep. • ne content reduced  no KL contribution NuTeV Weak Mixing Angle Measurement (See talk by Randy Johnson in electroweak section) • R- is insensitive to CP-conserving oscillations with • But is sensitive to CP-violating modes • Single mode results: or • and other combinations sin2qW = 0.2253 ± 0.0021  MW = 80.26 ± 0.11 GeV

11. R-Measurement compared to Standard Model Prediction • Use world average sin2qW excluding n results • Most of uncertainty is in charm mass • Using CCFR: mc= 1.32 ± 0.24 GeV  No systematic deviation from Standard Model Prediction.

12. What would oscillation look like? • Oscillations of nmto ntor ne will change R-Exp as a function of visible shower energy

13. NuTeV Limits on nmnt,e • Results for single-mode oscillations • First look at oscillations

14. ne Appearance Oscillation Search • Identify ne events statistically using the longitudinal energy deposition pattern: • Electrons add energy at the beginning of the shower • Use variable that compares hadronic energy in 1st three counters to total:

15. CCFR 3 Distributions • Fit distributions to an electron and hadron shower shape component • Hadron shower shape found from CC events • Electron shower shape from testbeam/Geant MC  Fits yield number of ne events in visible energy bins

16. Comparison of ne Events to Expectation • Compare measured ne flux to prediction of detailed beamline simulation tied to the observed nm flux. • e sterile oscillations decrease number of e events • e t oscillations decrease number of e events • Only 12% of  events look like CC ne events (Curves are the prediction for e t oscillations with sin2 2q =1 and dm2 =150 (1000) eV2 for the dashed (dotted) curves.)

17. Disappearance Limitsne  ntand ne  nsterile • ne  ntless sensitive than preliminary NOMAD limit but ne  nsterile channel added • Extends Bugey reactor disappearance limits in 30-300 eV2 region

18. NuTeV Searches for Neutral Heavy Leptons • Evidence for neutrino mass is mounting • But why are masses so small? • Various extensions to the Standard Model that incorporate small neutrino masses suggest • Heavy isosinglet partner (R) : Le , Lm , Lt • Possibly other weak isosinglet particles beyond these n partners • May also be candidate for hot dark matter NuTeV search range: 0.02 < ML0< 2.0 GeV Current Preliminary Results: 0.3 < MLm< 2.0 GeV

19. L0 Production and Decay • L0 Production From meson decays through mixing with standard neutrinos. (Mixing parameter U2) • K and p decays in the normal decay pipe • D meson production in primary target and dumps p, K, D • L0 Decays Also through mixing with standard neutrinos with both neutral- and charged-current decays possible

20. NuTeV Decay Channel • 30mlong decay region filled with helium in 4.6m diameter bags to reduce n interaction background  Less than 100 n events in helium • Interspersed with drift chambers at three locations • 5m  5m veto located upstream of channel • Lab E calorimeter used to measure energies of electrons, hadrons, and muons Decay channel layout with simulated L0mp event

21. Observed Multi-track n Events • Multi-track neutrino interactions in the chamber material and helium demonstrate reconstruction performance and efficiency

22. NHL Kinematics and Event Selection • Cuts used to isolate L0 decay topology • Two charged tracks in decay channel chambers • from common vertex in helium region • away from chambers and other material • project to tracks or energy clusters in calorimeter • No veto-wall hits • Em > 2.2 GeV Ep,e> 10 GeV • Track slopes: • Transverse Mass < 5.0 GeV • xbj< 0.1 and Wdis< 2.0 GeV

23. Backgrounds • Backgrounds are very small • predicted from full simulations of neutrino interactions in the material in the decay channel • Close to one-event sensitivity in most channels • Background sources • n events in channel helium (mainly background for mp channel)  0.4 events • n quasi-elastic and resonance production events   5  10-2 events • K0’s that decay in the channel that are produced in n interactions outside channel   4  10-3 events • Expect <1 event background

24. L0 Monte Carlo • Use model of Gronau, Leung, and Rosner (Phys.Rev.D29,1984) • Beamline simulation with meson production and ray-tracing and L0 production from meson decay. • Decay of L0 in channel with polarization effects.(J. Formaggio, et al., Phys.Rev.D57,1998) • Full detector simulation with noise and extra cosmic-ray tracks.

25. Results of L Search • No candidate events observed • Present result for L with decays to at least one muon • Modes , e, and . (U2 is mixing parameter for L0 with  )

26. Summary • Neutrino Oscillations • New NuTeV single mode limits • or • e  ,sterile oscillation limits • Future: • R+ oscillation search for    • NuTeV shower shape analysis •   e • e  ,sterile • Neutral Heavy Lepton Search • Limits set on L  X • for 0.3 < MLm< 2.0 GeV • about 2-10 more sensitive than previous • Future • Include ee and e decay modes • Extend mass region: 0.02 < ML0< 2.0 GeV • Search for Le type heavy leptons

27. Some Questions for Panel Discussion • Suppose that atmospheric and solar really are oscillations to a sterile partner. What experiment or series of experiments could establish this beyond doubt? • What are the weak points of the Super-Kamiokande analysis? • How could this be improved? What can future experiments add? What is the estimate of CP violation? Can one get a result on ne disappearance from Super-K and from future experiments? • Is there a next step in reactor experiments at very small delta Dm2 ? If so what is it ? • What are the appropriate goals and requirements for a follow-up experiment that is designed to investigate one of the current possible oscillation hints? • Statistical significance, observed oscillatory behavior, oscillation parameter measurements, CP violation effects ...

28. 5-Sigma Coverage of Various Exps.

29. Longbaseline Emulsion Detector Sensitivities • 1kton emulsion detector at 730km for 2 yrs.

30. Long Baseline Sensitivities