1 / 42

DONUT - Observation of n t Interactions

DONUT - Observation of n t Interactions. Reinhard Schwienhorst University of Minnesota. The DONUT collaboration :

ouida
Download Presentation

DONUT - Observation of n t Interactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. DONUT -Observation of nt Interactions Reinhard Schwienhorst University of Minnesota The DONUT collaboration: Aichi University, Kobe University, Nagoya University, Science Education Institute of Osaka Prefecture, Toho University, Utsunomiya University, University of California at Davis, Fermilab, Kansas State University, University of Minnesota, University of Pittsburgh, University of South Carolina, Tufts University, University of Athens, Gyeongsang National University, Changwon National University, Chonnam National University, Kon-Kuk University, Korean National University of Education, Pusan National University, Wonkwang University

  2. Outline • Tau Neutrino • Experimental Apparatus • Emulsion Modules • Neutrino Beam • Data Set • Neutrino Interactions • Emulsion Analysis • Candidate Events • Tau Neutrino Magnetic Moment • Conclusions Reinhard Schwienhorst,7/2000

  3. Tau Neutrino • PDG: • Experimental goal: establish nt existence directly • also search for rare processes Reinhard Schwienhorst,7/2000

  4. Experimental Technique • Create nt beam: p + N  Ds + X, Ds  t + nt, t nt + X • 800GeV protons incident on • high-density tungsten target • long-lived particles interact (p, K) • only short-lived particles decay • Observe weak nt interactions: nt + N t + X • large mass, high resolution neutrino target • t decay length 1mm • primary decay channel: t  n’s + 1 charged particle • decay kink Reinhard Schwienhorst,7/2000

  5. Experimental Setup Reinhard Schwienhorst,7/2000

  6. Neutrino Beam • Production Cross Sections: • s(D±)=11mB/nucleon • s(D0)=27mB/nucleon • s(Ds)=5.2mB/nucleon • BR(Dsnt)=6.3% • Beam Composition: • 45% ne • 45% nm • 10% nt • 3.61017POT • expect 1100 n interactions Interacted energy spectrum n energy (GeV) Reinhard Schwienhorst,7/2000

  7. Spectrometer Reinhard Schwienhorst,7/2000

  8. Target Stand Reinhard Schwienhorst,7/2000

  9. Emulsion Target/Vertex Detector Reinhard Schwienhorst,7/2000

  10. Nuclear Emulsion Reinhard Schwienhorst,7/2000

  11. Emulsion Target Design Reinhard Schwienhorst,7/2000

  12. Data Set (nearly completed) Reinhard Schwienhorst,7/2000

  13. nm CC Interaction m n W N X n n n Reinhard Schwienhorst,7/2000

  14. Muon Spectrum Reinhard Schwienhorst,7/2000

  15. ne CC Interaction e n W N X n n Reinhard Schwienhorst,7/2000

  16. Electromagnetic Energy 84 ne CC interactions • events with >20GeV electromagnetic energy • EMCAL + estimate from target region • energy spectrum similar to muon spectrum • expect70 • small contributions from NC, nt CC ne CC Reinhard Schwienhorst,7/2000

  17. Emulsion Scanning Station • Scanning Table • microscope • CCD camera with frame grabber • X-Y precision moving table • digitizes one field of view ((200mm)2) at 16 depths • Track Recognition Hardware • combine 16 dots to track segments (position and angle) • 30 segments/second • Computer • control stage • record track segments • Current scanning speed: 8h/event((5mm)220mm) Reinhard Schwienhorst,7/2000

  18. Emulsion Spatial Resolution Reinhard Schwienhorst,7/2000

  19. Emulsion Data Analysis • Scan Back • project a single track from spectrometer into emulsion • follow the track upstream until it stops • locate other tracks coming from this vertex • difficult in events with many tracks • Net Scan • predict a vertex position with the spectrometer • scan the volume around this position • software vertex search • takes more time than scan back Reinhard Schwienhorst,7/2000

  20. Net Scan Step 0:Prepare Vertex Prediction Reinhard Schwienhorst,7/2000

  21. Net Scan Step 1:Record all Emulsion Track Segments recorded segments (106) reconstructed tracks (105) 4mm 15mm Reinhard Schwienhorst,7/2000

  22. Net Scan Step 2:Remove Penetrating Tracks • Only display tracks with at least two segments that start inside the scan volume (103) Reinhard Schwienhorst,7/2000

  23. Net Scan Step 3:Form Vertices • Find the distance-of-closest-approach for every track pair • Create a vertex if • DCA<20mm • location is upstream of both tracks • Yields 101 vertices Reinhard Schwienhorst,7/2000

  24. Net Scan Step 4:Select the Primary Vertex • Trivial for vertices with 3 or more tracks • Otherwise: • check track linking to spectrometer • search for missed upstream segments • lower efficiency Reinhard Schwienhorst,7/2000

  25. All Emulsion Tracks and Segments reconstructed vertex tracks 0.1 mm reconstructed tracks recorded segments 1 mm Reinhard Schwienhorst,7/2000

  26. t Decay Search decay products n t n n W N X Reinhard Schwienhorst,7/2000

  27. Charm e or m n W X charm decay products N charmparticle • Expect • (0.75) (0.07) (0.4) (203) = 4.3±0.8 D±CC/tot charm chgd N • 6.5±1.3 D0 • Found: • 3 charged charm (1 m+m-) • Control sample, kink signature • 3 neutral charm (V decay) • As background to t sample: • only if 1ry lepton is not identified • identification efficiency  85% • expect <0.3 events Reinhard Schwienhorst,7/2000

  28. nt CC Candidates • Expect: • 6.4±1.7 long decays (primary t reconstructed) • 2.1±0.5 short decays (primary t not reconstructed) • Found: • 3 long decays • 1 short decay • Expected background: • <0.3 charm events • <0.2 events with hadronic interaction Analysis not yet completed! Reinhard Schwienhorst,7/2000

  29. Event Parameters contours: — 50% — 90% log(ldecay (cm)) log(ldecay (cm)) — 98% — 99.5% log(pdaughter (GeV)) log(kink (rad)) log(lepton (rad)) lepton-hadrons (rad) Reinhard Schwienhorst,7/2000

  30. nt Magnetic Moment • mn0 in the Standard Model • mne could explain the solar neutrino problem • if mn0 then mn0 • Current PDG limits: • ne: mne< 1.8×10-10mB • nm: mnm< 7.4×10-10mB • nt: mnt< 5.4×10-7mB (BEBC, ?) • other limits: • Astrophysics: mn 10-11mB (Supernova 1987A) • Cosmology: mn 10-11mB (Nucleosynthesis) • Neutrino oscillations  • think in terms of mass eigenstates n1, n2, n3 • measure in terms of weak eigenstate: • measure mne , mnm , mnt (for initial neutrino flavor) • use mixing matrix to determine mn1 , mn2 , mn3 Reinhard Schwienhorst,7/2000

  31. Magnetic Moment Interaction nt nt g e e • Detection channel: nt-e scattering • electron from the atomic shell • dsm/dTe1/Te • stot = sm + sSM • signature: production of a single electron • forward direction (qe2 < 2me/ Ee) • typical electron energy <10GeV • no hadronic activity in the event • no interaction “vertex” Reinhard Schwienhorst,7/2000

  32. Monte Carlo Simulation • Neutrino flux based on well-established results • Neutrino interaction generation • LEPTO for n-N • calculation for n-e • Detector simulation • GEANT • include efficiencies, resolution • does not include non-neutrino background Neutrino target view of a simulated mnt event n Reinhard Schwienhorst,7/2000

  33. Event Selection • Analyze full data set • 6,000,000 triggers on tape • Select n-e magnetic moment scattering candidates • Reject non-n interactions • Reject n-N interactions • hadron/muon Id • Identify electrons with small forward angle (<0.03rad) • Compare data-MC with well-understood data events • verify cuts, control systematics • events with identified muons (mostly nm-N CC interactions) • electromagnetic showers from knock-on electrons • produced by high-momentum muons Reinhard Schwienhorst,7/2000

  34. ne-N CC Interaction Rejection ne-N CC scattering nt-e magnetic moment scattering • Dominant background • Reject if hadrons were reconstructed • Also reconstruct electrons: • In n-e scattering:Ee qe2 < 2me • for Ee>1GeV • qe < 0.03rad Reinhard Schwienhorst,7/2000

  35. Candidate Event 3273_10082 Spectrometer Neutrino Target Region Reinhard Schwienhorst,7/2000

  36. mnt Result • 1 event was selected in the data analysis • Expected rate from SM processes: 2.3 events • No evidence for magnetic moment interactions • 90% confidence limit for mnt: • mnt <3.910-7mB • preliminary (depends on the measured nt flux) • statistical analysis method: Feldman-Cousins • sensitivity 4.910-7mB • calculation: • s(Ds)=5.2mB/nucleon • BR(Dsnt)=6.3% Reinhard Schwienhorst,7/2000

  37. Conclusions • DONUT will achieve its goal • Preliminary results: • we have seen nt interaction candidates • we will see 6nt interactions • we will do parameter studies • mnt <3.910-7mB (90% CL) • Some work still remains • Goal: extend data set from 200 to 300 • Emulsion scanning takes time • Vertex location takes precision Reinhard Schwienhorst,7/2000

  38. Experimental Setup • Sub-micron grain size • Requires sub-micron scanning resolution • Yields sub-micron track resolution • Requires good (2mm) vertex prediction to minimize scanning time • Integrating particle detector • Requires shielding to remove charged particles from the beam • Requires emulsion-spectrometer track linking to identify events t p t nt nt Ds W beam dump Shielding Emulsion Target Spectrometer Photographic Emulsion Target: Reinhard Schwienhorst,7/2000

  39. Emulsion technique • Charged particles passing through emulsion • ionization • black silver grains after development • size1mm • plates must be aligned to 1mm • hardware: x-ray sources • software: penetrating muons • Scanning stage (microscope) must have resolution < 1mm Reinhard Schwienhorst,7/2000

  40. Typical non-neutrino background m target stand material Reinhard Schwienhorst,7/2000

  41. Knock-on Electron electromagnetic shower m Reinhard Schwienhorst,7/2000

  42. ne CC event n hadrons electromagnetic shower Reinhard Schwienhorst,7/2000

More Related