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Neutrino-nucleus measurements

Neutrino-nucleus measurements. this is a topic that has gotten a lot more interesting over the past year will focus on results from the MiniBooNE experiment (… from an experimentalists point of view). Sam Zeller Fermilab Hadrons in the Nuclear Medium Workshop at ECT*, Trento

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Neutrino-nucleus measurements

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  1. Neutrino-nucleusmeasurements • this is a topic that has gotten a lot more interesting over the past year • will focus on results from the MiniBooNE experiment • (… from an experimentalists point of view) Sam Zeller Fermilab Hadrons in the Nuclear Medium Workshop at ECT*, Trento May 15, 2012

  2. Neutrino Physics • there are some big questions we will be trying to answer; • forthcoming experiments will largely be focused on: 3 m2ATM • measuring the neutrino masses • determining whether or not neutrinos are their own anti-particles • measuring n oscillation parameters more-precisely • - determining the n mass ordering • discovering whether n’s violate CP 2 m2SOL 1 long-baseline neutrino oscillation experiments enabled now that we know q13 is non-zero • correct interpretation of the outcome of n oscillation experiments • requires a precise understanding of n and n interaction cross sections

  3. Long-Baseline n Oscillation Experiments • in order to be sensitive to the MH and CP, experiments will be looking • for the conversion of nm to ne (and nm to ne) over large distances: distance between source and detector (known) incoming neutrino energy (unknown; need to infer) • neutrino energy is a crucial quantity • we typically fit distributions as a function of En (or L/En) to extract • information on neutrino oscillations (important to keep in mind)

  4. In Practice, this is Complex • in reality, the n oscillation formula looks like this: q13 is the “gate-keeper” CP violating phase, d matter effects neutrino mass ordering

  5. Where We are Headed • measure the neutrino energy • spectrum to disentangle • MH and CP violating effects • to get at this physics, need • to probe a range of n energies • means that we are studying • n interactions from 100’s MeV • to few-GeV (depends on baseline) • processes that we care about • are the same as what we study • in e- scattering … appearance of ne over a distance of 1300km P( e) (S. Parke)

  6. Electrons vs. Neutrinos (O. Benhar) • electron scattering: • - beam energy is known • - monochromatic (fixed Ee,qe) • - think in terms of w QE DIS D p p • neutrino scattering: • - beam energy is not known • - not monochromatic (spectrum of En) • - plus axial current contribution • - think in terms of En • (infer En from Elep,qlep or Elep+Ehad)

  7. Some of the Challenges (accel-based n experiments all use broad band beams, so contain contribs from all of these reaction mechanisms) • n beams not mono-energetic • (broad flux of neutrinos illuminating • the detector) • multiple contributions • sn’s are not particularly • well-constrained in this region • (most of the existing n data is low • statistics, collected on H2, D2 targets) • experiments nowadays • use nuclear targets • (nuclear effects alter what we see) T2K CNGS NOvA LBNE

  8. Modern Experiments • modern experiments are making improved sn measurements • advantages of new data: • - higher statistics • - intense, well-known •  beams • - nuclear targets (crucial!) • - also studying antineutrinos • (important for CP studies) K2K, MiniBooNE, MicroBooNE, SciBooNE, T2K ArgoNeuT, ICARUS, MINERA, MINOS, NOMAD, NOvA

  9. MiniBooNE Experiment • MiniBooNE designed and built to study neutrino oscillations • (nmne at large Dm2 to address LSND) • have been running for ~10 yrs now • have multiple n oscillation publications • over a million neutrino & • antineutrino interactions! • (world’s largest data set in this E range; we quickly realized • there were some useful measurements to be made here) • sn are a big part of our program • have since measured s’s for ~90% of n events in MiniBooNE • (high statistics, high quality data … will summarize some of our findings) ~74 physicists, 18 institutions

  10. MiniBooNE Detector Aguilar-Arevaloet al., NIM A599, 28 (2009) (inside view of MiniBooNE tank) • 800 tons of mineral oil •  interactions on CH2 • Cerenkov detector  ring imaging for event reconstruction and PID v

  11. MiniBooNE Detector muon candidate Aguilar-Arevaloet al., NIM A599, 28 (2009) v based on C ring topology, can differentiate different particle types • 4p coverage • scintillation light (enables NC elastic) • use particle decays for event ID • (m e, p+m e decays) • 800 tons of mineral oil •  interactions on CH2 • Cerenkov detector  ring imaging for event reconstruction and PID v

  12. Neutrino Beam 99% of flux flux of neutrinos seen by the detector: (for contained events, 98% from p decays in beam) predicted  energy spectrum • both n and n modes • <En> = 0.8 GeV • perfect for studying QE • and D production regions En (GeV)

  13. Flux Prediction • need to know your n flux to make n cross section measurements • (spent 5+ years on this on MiniBooNE) • made dedicated hadro-production • meas at CERN specifically for MB • M. Catanesi et al., Eur. Phys. J. C52, 29 (2007) • - same beam energy • - exact replica target • also analyzed data from BNL E910 • comprehensive  flux paper • Aguilar-Arevalo et al., PRD 79, 072002 (2009) (D. Schmitz, Columbia, Ph.D. thesis) • there was no tuning of the n flux based on MiniBooNE n data • flux known to ~11% at the peak (larger errors at lower and higher En)

  14. Neutrino Interactions • now want to start talking about some specific interaction measurements • let’s start on the left and • work our way up in energy … • what have we learned in exploring this region again 30+ years later?

  15.  W+ n Neutrino Quasi-Elastic Scattering Why important? • important for  oscillation experiments • - typically gives largest contribution to • signal samples in many osc exps (typically thought of as a process with a single knock-out nucleon) • examples: • e (e appearance) • X ( disappearance) signal events • biggest piece of the s at ~1 GeV • (lepton kinematics are used to infer En ) (heavily studied in 1970’s and 80’s, one of the 1stn interactions measured)

  16. Historical Data Kitagaki, PRD 28, 436 (1983) Baker, PRD 23, 2499 (1981) FNAL, D2 MA=1.05 ± 0.16 GeV 362 events BNL, D2 MA=1.07 ± 0.06 GeV 1,236 events Miller, PRD 26, 537 (1982) goal: make more accurate predictions for NC, so measured the axial FF in CC scattering ANL, D2 MA=1.00 ± 0.05 GeV 1,737 events Q2 (GeV2) • focus of many early bubble chamber exps (D2) MA~1.0 GeV

  17. QE Cross Section • conventional wisdom has always • been that thiss is well-known • - it’s a simple 2-body process • - predictions rely on impulse approx: • n interacts with one nucleon at time • e- scattering tells us vector piece • n fits tell us axial piece • this description has been • quite successful • - at least in describing bulk • of historical data (D2) • - can predict size, shape of s • MA=1.0 GeV these same exps also measured s(En) free nucleon prediction (MA=1.0 GeV) with these ingredients, it looked straightforward to extend this to describe n QE scattering on nuclei

  18. Repeated 30yrs Later on Carbon • two experiments: different E ranges, different detectors (T. Katori, Indiana U, Ph.D. thesis) • MiniBooNE 30% • * NOMAD Fermi Gas (MA=1.35 GeV) Fermi Gas (MA=1.03 GeV) MiniBooNE 2002-2012 detects m & not knock-out nucleon(s) NOMAD 1995-1998 sees both m and proton PRD 81, 092005 (2010) EPJ C63, 355 (2009)

  19. QE Cross Section on Carbon (T. Katori, Indiana U, Ph.D. thesis) • MiniBooNE 30% * NOMAD • * NOMAD Fermi Gas (MA=1.35 GeV) Fermi Gas (MA=1.35 GeV) Fermi Gas (MA=1.03 GeV) Fermi Gas (MA=1.03 GeV) • MiniBooNE data is well above • “standard” QE prediction • (increasing MA can reproduce s) • NOMAD data consistent with • “standard” QE prediction • (with MA=1.0 GeV) cannot consistently describe the data with a single prediction

  20. QE Cross Section on Carbon (T. Katori, Indiana U, Ph.D. thesis) • MiniBooNE 30% NOvA, LBNE CNGS * NOMAD * NOMAD • * NOMAD T2K Fermi Gas (MA=1.35 GeV) Fermi Gas (MA=1.35 GeV) Fermi Gas (MA=1.35 GeV) Fermi Gas (MA=1.03 GeV) Fermi Gas (MA=1.03 GeV) Fermi Gas (MA=1.03 GeV) MINERnA, MINOS, ArgoNeuT weighing in here • the difference is not many s, but can leave one in a quandary if want • to predict how many QE signal events you should see in your n osc exp • this is the situation we’ve been in for some time now

  21. QE Cross Section at Low Energy • MiniBooNE data is the 1st time have measured the n QE s on a nuclear • target at these low energies (< 2 GeV) • - naturally, these results garnered • a lot of attention, largely • because they were unexpected • (increased QE rates also seen in • K2K, MINOS, SciBooNE) • s’s are appreciably higher • than any conventional approach • (discrepancy is not 30%, • but really 40-45%) • community has been trying • to reconcile these results 40-45% (L. Alvarez-Ruso, NuFact11)

  22. Nuclear Effects to the Rescue? • a possible explanation has recently emerged … • while traditional nuclear effects decrease the sn, there are processes • that can increase the total yield (has been well-known in e- scattering) • there are add’l nuclear • dynamics present • (i.e., effects not included in the • independent particle approaches • we have been using for decades) • enhancement caused by • the interaction of incoming • n with more than 1 nucleon • in the target nucleus (an example for illustration) with extra piece, can replicate s without increasing MA Martini et al., PRC 80, 065001 (2009)

  23. Nuclear Effects to the Rescue? • idea is that there are two contributions present when we talk • about n QE scattering off of a nuclear target: (an example for illustration) “true QE” prediction we saw earlier (m+p) +p (single-nucleon knock-out; same as you would get for free nucleon scattering) Martini et al., PRC 80, 065001 (2009)

  24. Nuclear Effects to the Rescue? • idea is that there are two contributions present when we talk • about n QE scattering off of a nuclear target: n scattering off of a correlated nucleon state contributes more s at these energies and produces a multi-nucleon final state(+p+p) (an example for illustration) +p+p +p (would not have seen this large an effect in D2 so this would have been missed in early n experiments) Martini et al., PRC 80, 065001 (2009)

  25. Nuclear Effects to the Rescue? • idea is that there are two contributions present when we talk • about n QE scattering off of a nuclear target: • it has been suggested that • together account for MB (an example for illustration) +p+p these two final states are indistinguishable in MB and in Cerenkov detectors in general +p Martini et al., PRC 80, 065001 (2009)

  26. Nuclear Effects to the Rescue? • idea is that there are two contributions present when we talk • about n QE scattering off of a nuclear target: • could this explain the • difference between • MiniBooNE & NOMAD? (an example for illustration) +p+p jury is still out on this need to be clear what we mean by n “QE” when scattering off nuclear targets! +p Martini et al., PRC 80, 065001 (2009)

  27. Electron Scattering • while this is new to n scattering, have known for over 2 decades from • e-nucleus scattering that more complicated processes can take place • longitudinal part of sQE can be • described in terms of scattering • off independent nucleons • in contrast, there is a large • enhancement in transverse part • in both QE peak and dip region • (can be explained by SRC and 2-body currents) • likely also play a role in neutrinos! fT fL Carlson et al., PRC 65, 024002 (2002) • took us awhile to realize that we may be seeing the same thing in n scattering

  28. Has Been a Focus in the Past Year • 50+ theoretical papers on the topic of QE n-nucleus scattering • Butkevich, arXiv:1204.3160 • Lalakulich et al., arXiv:1203.2935 • Mosel, arXiv:1204.2269, 1111.1732 • Barbaro et al., arXiv:1110.4739 • Giusti et al., arXiv:1110.4005 • Meloni et al., arXiv:1203.3335, 1110.1004 • Martini et al., arXiv:1202.4745, 1110.0221, • 1110.5895, Phys. Rev C81, 045502 (2010) • Paz, arXiv:1109.5708 • Sobczyk, arXiv:1201.3673, 1109.1081, 1201.3673 • Nieves et al., arXiv:1204.5404, 1106.5374, • 1110.1200, Phys. Rev. C83, 045501 (2011) • Bodek et al., arXiv:1106.0340 • Amaro, et al., arXiv:1112.2123, 1104.5446, • 1012.4265, Phys. Lett B696, 151 (2011) • Antonov, et al., arXiv:1104.0125 • Benhar, et al., arXiv:1012.2032, 1103.0987, 1110.1835 • Meucci et al., arXiv:1202.4312, Phys. Rev. C83, 064614 (2011) • Ankowski et al., Phys. Rev. C83, 054616 (2011) • Alvarez-Ruso, arXiv:1012.3871 • Martinez et al., Phys. Lett B697, 477 (2011) • (disclaimer: this is not a complete list!) • need to do more than • describe behavior of s • as a function of En • (model-dependent)

  29. Moving Forward • preference is for differential distributions • (may not seem fancy but is fancy for n physics) • because of high statistics • (MB data sample is 146,000 events) • can measure double diff’l s’s • for the first time! (like Ee, qe) • d2s/dTmdqm • historically, never had • enough statistics to do this (T. Katori, Indiana U, Ph.D. thesis) Aguilar-Arevaloet al., PRD 81, 092005 (2010) • much less model-dependent (both Tm, qm are directly measured quantities) • and provides much richer information than s(En)

  30. Some Examples: 2D Comparisons • this is the 1st time we’ve had this • sort of information available MiniBooNE QE data Lalakulich, Gallmeister, Mosel arXiv:1203.2935 • we need measurements at other • En, A and the outgoing proton(s)! Nieves, Simo, Vacas, PL B707, 72 (2012)

  31. What Does This All Mean? • something as simple as QE scattering is not so simple • - nuclear effects can significantly increase the cross section • - idea that could be missing ~40% of s in our simulations is a big deal • good news: expect larger event yields • bad news: need to understand the • underlying physics • (1) impacts En determination • (2) effects will be different for n vs. n • (at worse, could produce a spurious CP effect) ex: Mosel/Lalakulich 1204.2269, Martini et al. 1202.4745, Lalakulich et al. 1203.2935, Leitner/Mosel PRC81, 064614 (2010) Lalakulich, Gallmeister, Mosel,1203.2935

  32. Neutrino/Antineutrino Ratio (J. Grange) • models give different • predictions for n/n • the situation is unclear • and will need to get • resolved … • large q13 means n/n • CP asymmetry we’re • trying to detect is small • so will need a detailed • understanding of these • n,n differences! larger effect for neutrinos independent particle model new model calculations independent particle model larger effect for antineutrinos new calc we are currently working on a n/ ns ratio measurement in MiniBooNE (J. Grange)

  33. Neutrino/Antineutrino Ratio (J. Grange) • models give different • predictions for n/n • the situation is unclear • and will need to get • resolved … • large q13 means n/n • CP asymmetry we’re • trying to detect is small • so will need a detailed • understanding of these • n,n differences! larger effect for neutrinos in the past year, have gone from a general complacency that we know the QE sn to having uncovered a host of rich nuclear effects … story will continue to evolve independent particle model new model calculations independent particle model larger effect for antineutrinos new calc we are currently working on a n/ ns ratio measurement in MiniBooNE (J. Grange)

  34.  0 + W+ n,p n,p n,p n,p Pion Production • NC 0 production • (background for ne appearance) • CC +, p0 production • (a complication for nm disappearance) • p production also has important • connections to n osc measurements

  35. Final State Effects Can Change the Picture • a new appreciation for nuclear effects in this region as well • “final state interactions (FSI)” • - before they leave the nucleus, • pions & nucleons can re-interact • - picture can be quite different from • what happens at the primary vertex • have to worry about these effects • (need descrip of initial n-nucleus s + produced f.s. particles) • for n, is a subject that needs more attention (U. Mosel,1108.1692 [nucl-th])

  36. Final State Effects are Important • and the predictions of their • effects can vary • the distortions are large (>20%) (T. Leitner) http://regie2.phys.uregina.ca/neutrino/ x2! momentum of p’s produced in MiniBooNE • area where n generators differ the most • need p kinematic measurements! • (has never been carefully studied in n scattering) • leave a big imprint on what • you see in your n detector

  37. Pion Production in MiniBooNE • trying to forge a new path here also • extensive program to measure final state particle kinematics • (measure “observable” single ps • p in final state regardless of • what was produced in initial state) Phys. Rev. D81, 013005 (2010) Phys. Rev. D83, 052009 (2011) Phys. Rev. D83, 052007 (2011) measurement NC p0 CC p0 CC p+ s(En) X X X ds/dQ2 X X ds/dpp X X X ds/dcosqp X X X ds/dTm X X ds/dcosqm X X d2s/dTmdcosqm X d2s/dTpdcosqp X • 3 channels, • 14 diff’l s’s “standard” cross section • data has immediate • implications for • nosc measurements • (including MB) the rest is new!

  38.  0 n,p n,p NC 0 Production • Why important? • important for neutrino oscillation experiments • - very important background for experiments looking for  e (13, MH, CP) • final state can mimic a e interaction if 0  NC p0 can be a sizable background also D Ng goal: 5-10% level or better T2K LBNE

  39. NC p0 Production (p0g g) • coming back to this 30 years later … Gargamelle MiniBooNE • 240 NC 0 events • propane-freon • 21,542 NC 0 events • CH2 • 4p detector does • a superb job (J. Link) M M(GeV) 1st time we’ve had a high statistics measurement of this process in n scattering Krenzet al., Nucl. Phys. B135, 45 (1978)

  40. NC 0 at MiniBooNE  • different philosophy than historical measurements 0 (CH2, flux-averaged) • total s for a NC n interaction • to produce a p0 exiting the • target nucleus, “observed s” • (this is what we care about) • measures initial n interaction s, • nuclear effects, & FSI effects • have not corrected any of • these effects out of the data • (this is something new) one of our flagship measurements Aguilar-Arevaloet al., PRD 81, 013005 (2010)

  41. NC 0 at MiniBooNE  Aguilar-Arevaloet al., PRD 81, 013005 (2010) 0   • this is the 1st time differential • ’s have been provided for • such neutrino interactions • this kinematic information was • crucial for nmne search in • MiniBooNE (En dependence of bkgs) cos p(GeV)   (C. Anderson, Yale, Ph.D. thesis) cos p(GeV) (CH2, flux-averaged)

  42. NC p0 Constraints • need measurements on other • targets and at other energies • - MINERnA • - ArgoNeuT • - ICARUS • - MicroBooNE • important for understanding: • - initial n-nucleus interaction • - p transport (abs, cex) • - role of axial-vector contrib • - effect of 2p2h on 1p prod (G. Karagiorgi, MIT) (if we had just measured the flux-integrated s would not have captured this energy dependence)

  43.   W+ n p CC 0 at MiniBooNE • as a cross-check, also studied the CC equivalent of this process • main difference is that get m in addition to p0 • these events have 3 Cerenkov rings, • so developed a custom 3-ring fitter v (B. Nelson, UC Boulder, Ph.D. thesis)   • most complex final • state that we attempt • to reconstruct in MB + • 5,800 events • (3 times all previous • n data sets combined)

  44.   W+ n p Historic CC 0 Measurements • this is what we’ve known on this reaction … this is our starting point most on D2, H2 • again, most of the historical • focus was on measuring s(En) • models tended to underpredict • the cross section at low E • x2 difference between • some of the measurements  

  45. CC 0 at MiniBooNE • have measured a variety of kinematics • for this process: • most comprehensive study of CC p0 • to date • - excess of data/model also present in • this channel too • - similar effects seen by K2K (higher En) • C. Mariani et al., Phys. Rev. D83, 054023 (2011) (E), d/dQ2 d/dT, d/d d/dp, d/d reduced model-dependence Aguilar-Arevalo, PRD 83, 052009 (2011) (B. Nelson, UC Boulder, Ph.D. thesis)

  46.  + W+ n,p n,p CC  at MiniBooNE • important background for • disappearance experiments • - if p absorbed, impacts En determination • - introduces a systematic on Dm223, q23 • long-standing discrepancy • between ANL & BNL (D2) nm nm s(En) again (didn’t want to live with this for MB disappearance search)

  47. - + CC  at MiniBooNE v • but p+ reconstruction in a C detector, m/p+ separation are challenging • (had never been done before) • 's frequently interact • hadronically, losing energy • & changing direction sharply • kinked track produces two • rings  kinked track fitter • plus detect e- from m, p+ decays • algorithm separately reconstructs muon & charged pion (M. Wilking, UC Boulder, Ph.D. thesis) v • really pushing C capabilities (but get correct identification 88% of the time)

  48. + CC  at MiniBooNE • highest purity sample (90% CC p+) Aguilar-Arevalo et al., PRD 83, 052007 (2011) s units • again, measuring what comes out • of nucleus = “observed s” • & complete final state kinematics (same as what we measured for QE) (E), d/dQ2, d2/dTd, d/dT, d/d, d/dT, d/dd2/dTd 8 dists (many firsts!)

  49. + CC  at MiniBooNE • highest purity sample (90% CC p+) Aguilar-Arevalo et al., PRD 83, 052007 (2011) s units • again, measuring what comes out • of nucleus = “observed s” • & complete final state kinematics (and the same for the pion too!) (E), d/dQ2, d2/dTd, d/dT, d/d, d/dT, d/dd2/dTd 8 dists (many firsts!)

  50. Future Prospects for MiniBooNE • MiniBooNE has provided a new wealth of • n-nucleus scattering data over past 2 years • in this process, we have thought about how to • provide the most useful information possible • coming soon: • - CC inclusive diff’l cross sections (M. Tzanov) • - n QE diff’l cross sections (J. Grange) • - n NC elastic diff’l cross sections (R. Dharmapalan) • - m+p QE analysis (A. Wickremasinghe)

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