1. Accelerator Neutrino Oscillation Physics Lecture I Deborah Harris SUSSP St. Andrews, Scotland August 15, 2006

2. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I2 What have Accelerator-based Experiments told us so far? No  →  mixing at high  m 2 –CHORUS –NOMAD First Accelerator-based e appearance: LSND –Still remains to be confirmed or completely refuted Confirmation of “Atmospheric Neutrino Anomaly” and improved precision on  m atm 2 (or  m 13 2 ) –K2K: 1.4GeV, 250km –MINOS: 3.5GeV, 735km Confirmation of limits on  13 from CHOOZ –K2K

3. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I3 What do we want Accelerator Oscillations Experiments to tell us? –Are there sterile Neutrinos? –What is the larger mass splitting (  m 23 2 ) –  13 and CP violation: are they non-zero? –Neutrino Mass Hierarchy: are ’s like charged fermions?

4. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I4 Goals of Long Baseline Oscillation Measurements Measurements of “atmospheric neutrino oscillation parameters”,  m 23 and sin 2 2  23 :  disappearance as a function of neutrino energy P(  →  ) = 1-sin 2 2  23 sin 2 (  m 23 2 L/4E) Verify Oscillation Framework:  appearance P(  →  ) ≈ sin 2 2  23 sin 2 (  m 23 2 L/4E) Search for Sterile Neutrinos: Neutral Current disappearance, looking for three distinct  m 2 Searches for CP violation and understanding the neutrino mass hierarchy: P(  → e ) and P(  → e ) L=Baseline, E=Neutrino Energy

5. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I5 P(  → e ) on one slide (3 generations) P(  → e )=P 1 +P 2 +P 3 +P 4 Minakata & Nunokawa JHEP 2001 P(  → e )% The ± is or

6. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I6 Could you simplify please? Note: this is for  m 12 2 <<  m 23 2, and for L/E such that sin 2 (  m 23 2 L/4E)=1

7. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I7 Outline for the rest of this talk To reach all of the goals, we will need several accelerator- based experiments…. At this point, you could hear a sequence of mini-talks about the following experiments: –K2K –MINOS –MiniBooNE –OPERA –T2K –NOvA And I would have earned my trip to Scotland…but that’s not the way I think about these experiments…so I’ll talk about them all at once, step by step

8. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I8 Measuring Oscillation Probabilities with Accelerator-Based Beam   : Neutrino Flux (beamline design: lecture I)  x : Neutrino Cross Section (McFarland)  x M far : Signal efficiency  Detector Mass (detector design: lecture II) How well have we done/can we do? (Lecture III)

9. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I9 Neutrino Beam Fundamentals Atmospheric Neutrino Beam: –High energy protons strike atmosphere –Pions and kaons are produced –Pions decay before they interact –Muons also decay Conventional Neutrino Beam: very similar! Cosmic Ray , K  e  e μ

10. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I10 But we do more than just make pions… Major Components: Proton Beam Pion Production Target Focusing System Decay Region Absorber Shielding… Most  ’s from 2-body decays:   →    K + →    Most e ’s from 3-body decays:   →e  e  K + →   e  e energy is only function of  angle and  energy

11. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I11 Proton Beam Rules of Thumb –number of pions produced is roughly a function of “proton power” (or total number of protons on target x proton energy) –The higher energy beam you want, the higher energy protons you need… Proton SourceExperimentProton Energy (GeV) p/yrPower (MW) Neutrino Energy (GeV) KEKK2K12 1  10 20 /4 0.00521.4 FNAL BoosterMiniBooNE8 5  10 20 0.051 FNAL Main Injector MINOS and NOvA 120 2.5  10 20 0.253-17 CNGSOPERA4000.45  10 20 0.1225 J-PARCT2K40-50 11  10 20 0.750.77

12. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I12 Directing Protons is not trivial… Example from NuMI: extract beam from between two other beamlines, then make it point down at 3.5 o so it comes through the earth in Soudan Minnestota, 735km away: Example from T2K: Proton source on prime real estate, direction to K2K determined, need to bend HE protons in small space: “combined function” magnets (D and Q)

13. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I13 Integrated proton power vs time… First MINOS Restults (10 20 ) MINOS goal 2 flavors Discovery of NC’s LSND Nomad/ Chorus K2K MiniBooNE Plot courtesy Sacha Kopp CNGS goal

14. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I14 Neutrino Production Targets Have to balance many competing needs: –The longer the target, the higher the probability the protons will interact –The longer the target, the more the produced particles will scatter –The more the protons interact, the hotter the target will get—targeting above ~1MW not easy! –Rule of thumb: want target to be 3 times wider than +- 1 sigma of proton beam size Target Material ShapeSize (mm) Length (cm) Mini- BooNE Becylinder1070 K2KAlcylinder3066 MINOSgraphiteruler6.4x2090 NOvAgraphiteruler>6.490 CNGScarbonruler4mm wide 200 J-PARCgraphitecylinder12-15 mm 90

15. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I15 Target Photo Album CNGS Image courtesy of Bartoszek Engineering. NuMI MiniBooNE Shapes are similar, but cooling methods vary…some water cooled, some air cooled

16. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I16 Focusing Systems Want to focus as many particles as possible for highest neutrino flux Typical transverse momentum of secondaries: approximately  QCD, or about 200MeV Minimize material in the way of the pions you’ve just produced What kinds of magnets are there? –Dipoles—no, they won’t focus –Quadrupoles done with High Energy neutrino beams focus in vertical or horizontal, need pairs of them they will focus negative and positive pions simultaneously

17. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I17 What focusing would work best? Imagine particles flying out from a target: –When particle gets to front face of horn, it has transverse momentum proportional to radius at which it gets to horn B Field from line source of current is in the  direction but has a size proportional to 1/r How do you get around this? (hint:  pt  B   l )

18. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I18 What should the B-Field be? Make the particles at high radius go through a field for longer than the particles at low radius. (B  1/r, but make dl  r 2 ) Horn: a 2-layered sheet conductor No current inside inner conductor, no current outside outer conductor Between conductors, toroidal field proportional to 1/r There are also conical horns—what effect would conical horns have? FROM TO

19. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I19 Tuning the Neutrino Beam Energy The farther upstream the target is, the higher momentum pions the horns can “perfectly focus”..see this by considering As z gets larger, then p tune gets higher for the same R z 2R

20. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I20 Horn Photo Album Length (m) Diameter (m) # in beam K2K2.4,2.70.6,1.52 MBooNE~1.7~0.51 NuMI3,30.3,0.72 CNGS6.5m0.72 T2K1.4,2,2.5.47,.9,1.43 MiniBooNE CNGS K2K T2K Horn 1 NUMI Horn World Record (so far): MiniBooNE horn pulsed for 100M pulses before failing

21. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I21 Horn Question: Given two horns that are each 3m long and 16cm diameter, what kind of current would you need to give a 200MeV kick to produced secondary particles? For MINOS, for example: (2 horns) r=0.08m, l=3mx2: so for a 200MeV p t kick, I=180kAmps! For pion going through “sweet spot”, assume r/r max =1/2 1) 2000 Amps 2) 20,000 Amps 3) 200,000 Amps

22. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I22 Designing what provides the 180kA is almost as important as designing the horn itself!

23. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I23 What happens if you have 2 Horns? Can predict components of spectra from apertures of horns.   ~ p T /p = r neck / z horn. Overfocused by Horn 1 Underfocused by Horn 1 Focused by Horn 1, through 2 Hits only Horn 2 Goes through Horns 1, 2 p  R neck (cm) Z horn (meters) Max pion momentum focused (GeV)   Energy (GeV) Horn 10.9~1.0~166 Horn 24.0103815

24. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I24 How do these pions (and Kaons) decay? In the center of mass of the pion: 2 body means isotropic decay, neutrino only has one energy Now boost to the lab frame: you can show (easily) that And furthermore, you can show (slightly less easily) that the flux of neutrinos at a given location is simply  = boost of pion in lab  = angle between pion and Thought question: What about 3-body decays? Energy Flux versus Angle

25. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I25 Besides target location, how else can you lower the neutrino energy? Reduce Current in the horns –No, this just gives you fewer neutrinos in the peak  B   (in tail)  + (in peak) p MINOS Far Detector Spectra For 3 different Horn Currents Energy (GeV) Events (arb)

26. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I26 Thought Question How much does peak  rate on axis change when you input half as much current? I=200kA, 100kA, 0kA At MINOS (735km) Energy (GeV) Events (arb) (Note: 2.5 3 =16, 1.5 3 =3.4)

27. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I27 Off Axis Strategy Trick used by T2K, NOvA (first proposed by BNL) –Fewer total number of neutrino events –More at one narrow region of energy –For  to e oscillation searches, backgrounds spread over broad energies Only a consequence of 2-body decay!

28. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I28 Decay Regions How long a decay region you need (and how wide) depends on what the energy of the pions you’re trying to focus. The longer the decay region, the more muon decays you’ll get (per pion decay) and the larger e contamination you’ll have Again, tradeoffs between evacuating the decay volume and needing thicker vacuum windows to hold the vacuum versus filling the decay volume with Helium and thin windows, or with air and no windows… LengthDiameter MBoone50m1.8m K2K200mUp to 3m MINOS675m2m CNGS1000m2.45m T2K130mUp to 5.4m T2K Decay Region: Can accommodate off axis Angles from 2 to 3 degrees

29. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I29 Decay Pipe Photo Album CNGS T2K NUMI (downstream) NUMI (upstream)NUMI

30. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I30 Decay Pipe Cooling Slide courtesy C.K.Jung

31. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I31 Beamline Decay Pipe Comparison LengthE  (GeV)yy yy  e    (theoretical) MiniBooNE50m2.50.360.3%0.15% K2K200m3.51.00.9%0.5% MINOS675m91.31.2%0.8% CNGS1000m500.360.3%0.15% T2K130m90.470.2%0.10% y  =the number of pion lifetimes in one decay pipe… You can all show that neglecting things hitting the side of the decay pipe…

32. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I32 Neutrino Beam Divergence For a perfectly focused monochromatic pion beam, how wide is the neutrino beam? At what  is Φ(  )= Φ(0)/4?Where is Φ(  )= Φ(0)x0.99?

33. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I33 Follow Up Question: How much additional divergence is added due to multiple scattering? –Filling the decay pipe with air? –a 1mm Aluminum window? x=  c  =  (7.8m) X 0 =304m x=1mm X 0 =89mm

34. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I34 Additional Question How does the loss of neutrinos from divergence compare to the loss of neutrinos due to pion interactions? Filling the decay pipe with Air: 1mm Aluminum Window x=  c  =  (7.8m) int =692m/0.66 Lose 0.007  x=  mm int =390mm/0.66 Lose 0.002

35. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I35 Decay Pipe Effect Summary Additional RMS (  rms ) Loss from Interactions Filling Decay Pipe with Air: 0.006/sqrt(  )0.007  1mm Aluminum Window: 0.01/  0.002 Where are they =?  Remember, for a Flux ratio of 0.99, E  (GeV)    (peak) choice MiniBooNE2.518air K2K3.526He MINOS966vacuum CNGS50370vacuum T2K967He Moral of this story: Different p energies imply very different decay pipe choices

36. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I36 Absorbing Hadrons As proton power gets higher and higher, have to think more and more about what will collect all the un- interacted protons! MINOS Absorber (1kton): –Water-cooled Al core –Surround with Steel –Surround with concrete CNGS Absorber –Graphite core + Al cooling modules –Surround with cast iron –Surrounded by rock Note: for 10 20 protons on target per year, roughly 10 19 per year hit the absorber… CNGS MINOS

37. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I37 How can you measure the beam performance? Remnant Proton Measurements –Tales from the front line: NuMI and the target leak Muon Measurements –7 o muon spectrometer (MiniBooNE) –“Range stack” Muon Monitor system (MINOS) protons Pions+… Muons+… Neutrinos

38. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I38 Neutrino Beamline Instrumentation Proton Beam –Number of Protons on Target –Position and angle –Spot size of beam on target –Proton Losses before target Target –Position and angle –Is it intact? –Temperature Horns –Position and angle –Current –Is it intact? –Temperature Absorber –Temperature

39. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I39 What about seeing the Protons at the end of the decay pipe? Proton spot size at end of pipe is large: cannot just put in a new secondary position monitor Proton rates are now very intense: can use ionization chambers, but they must be very resistant to radiation damage, and can be low gain Question: what else makes it down to the end of the decay pipe? –Muons from pion decay –Undecayed pions –Secondary shower particles

40. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I40 Seeing protons at end of pipe No target in the way Target in the way For most beamlines, this “hadron monitor” is really a proton monitor: it tells you about the protons and the target, but not about how well you are making neutrinos

41. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I41 Lesson Learned: be prepared for disasters… Leaky Target at NuMI –the target has pipes around it that carry water to cool it –March 2005, discovered a leak: speculate the target surrounded by water… –Use Hadron Monitor to verify that water was there, and to check that it hasn’t reappeared since we solved the problem… Look at what is between target and baffle by shooting protons there!

42. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I42    p      Monitors to Study Beam (MINOS) Hadron Monitor: sees uninteracted protons after decay pipe Muon Monitors: 3 different depths means three different muon momentum spectra

43. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I43 Getting to Neutrino Spectrum from Muon Spectrum (MINOS) As you get to higher muon energies, you are looking at higher pion energies…which in turn mean higher neutrino energies…

44. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I44 Muon Monitors in Different Energy Neutrino Beams By looking at the rates in the three different muon detectors, can see how the energy distributions of the muons changes Can study neutrino fluxes by moving the target and seeing how you make more high energy neutrinos the farther back you move the target Can study fluxes by changing the horn current and see how you make more low energy neutrinos as you increaste the horn current. Graphs courtesy S. Kopp

45. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I45 Oscillation Experiments: Beams past, present, and near future… Exp’t Energy (GeV) MiniBooNE1.2 K2K1.4 MINOS2-6 OPERA15-25 T2K0.7 NOvA2 K2K T2K OPERA MINOS NOvA MiniBooNE

46. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I46 Conventional Neutrino Beam Summary Major Components: Proton Beam Production Target Focusing System Decay Region Shielding Monitoring Ways to Understand Flux: Hadron Production Proton Beam measurements Pion Measurements Muon Measurements at angles vs momentum at 0 o versus shielding

47. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I47 What else you can do with muons: Measure K/  ratio in Beam  e ’s from muon decay constrained by  spectrum (since they are part of the same channel) Kaons have no such constraint Remember problem set: to get the e   Ratio you would also need to know the K/  production ratio (and focusing differences) Any way this can be measured in the beam? Beam too hot to add Cerenkov counters to get track/track information Think 2-body decay kinematics: Center of MassLab Frame DecayMaximum p t  + →    30MeV K + →    236MeV K L →   216MeV

48. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I48 Example from MiniBooNE By adding collimator and spectrometer at 7 o, they will measure   /K ratio from difference in peaks  K/K L ratio from  + versus  - Backgrounds from muons that scatter in the dirt/collimator

49. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I49 Measuring  angular distribution in real beamline K2K Gas Cerenkov counter: measures angular distribution of Pions as function of momentum Located right after horns Works for pions above 2GeV

50. 15 August 2006Deborah Harris, Accelerator Neutrino Oscillation Physics Lecture I50 Measuring  angular distribution in real beamline