Quasi-Elastic Neutrino Scattering measured with MINERvA

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Quasi-Elastic Neutrino Scattering measured with
MINERvA
Ronald Ransome
Rutgers, The State University of New Jersey
Piscataway, NJ
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The MINERvA Collaboration

• D. Drakoulakos, P. Stamoulis, G. Tzanakos, M.
  ZoisUniversity of Athens, Athens, Greece
• C. Castromonte, H. da Motta, M. Vaz, J.L.
  Palomino Centro Brasileiro de Pesquisas Físicas,
  Rio de Janeiro, Brazil
• D. Casper, C. Simon, J. Tatar, B.
  ZiemerUniversity of California, Irvine,
  California
• E. PaschosUniversity of Dortmund, Dortmund,
  Germany
• M. Andrews, B. Baldin, D. Boehnlein, C. Gingu, N.
  Grossman, D. A. Harris, J. Kilmer, M. Kostin,
  J.G. Morfin, J. Olsen, A. Pla-Dalmau, P.
  Rubinov, P. Shanahan Fermi National Accelerator
  Laboratory, Batavia, Illinois
• J. Felix, G. Moreno, M. Reyes, G.
  ZavalaUniversidad de Guanajuato -- Instituto de
  Fisica, Guanajuato, Mexico
• I. Albayrak, M.E. Christy, C.E. Keppel, V.
  TvaskisHampton University, Hampton, Virginia
• A. Butkevich, S. KulaginInstitute for Nuclear
  Research, Moscow, Russia
• I. Niculescu. G. NiculescuJames Madison
  University, Harrisonburg, Virginia
• W.K. Brooks, A. Bruell, R. Ent, D. Gaskell, D.
  Meekins, W. Melnitchouk, S. WoodJefferson Lab,
  Newport News, Virginia
• E. MaherMassachusetts College of Liberal Arts,
  North Adams, Massachusetts

• R. Gran, C. RudeUniversity of Minnesota-Duluth,
  Duluth, Minnesota
• A. Jeffers, D. Buchholz, B. Gobbi, A. Loveridge,
  J. Hobbs, V. Kuznetsov, L. Patrick, H.
  SchellmanNorthwestern University, Evanston,
  Illinois
• L. Aliaga, J.L. Bazo, A. GagoPontificia
  Universidad Catolica del Peru, Lima, Peru
• S. Boyd, S. Dytman, I. Danko, D. Naples, V.
  PaoloneUniversity of Pittsburgh, Pittsburgh,
  Pennsylvania
• S. Avvakumov, A. Bodek, R. Bradford, H. Budd, J.
  Chvojka, M. Day, R. Flight, H. Lee, S. Manly, K.
  McFarland, A. McGowan, A. Mislevic, J. Park, G.
  PerdueUniversity of Rochester, Rochester, New
  York
• R. Gilman, G. Kumbartzki, R. Ransome, E.
  SchulteRutgers University, New Brunswick, New
  Jersey
• S. Kopp, L. Loiacono, M. ProgaUniversity of
  Texas, Austin, Texas
• H. Gallagher, T. Kafka, W.A. Mann, W.
  OliverTufts University, Medford, Massachusetts
• R. Ochoa, O. Pereyra, J. SolanaUniversidad
  Nacional de Ingenieria, Lima, Peru
• D.B. Beringer, M.A. Kordosky, A.G. Leister, J.K.
  NelsonThe College of William and Mary,
  Williamsburg, Virginia
• Co-Spokespersons Members of the MINERvA
  Executive Committee

A collaboration of 80 Particle, Nuclear, and
Theoretical physicists from 23 Institutions
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MINERvA Experiment

• Main INjector ExpeRiment ?-A (at Fermi-Lab)
• Placed upstream of MINOS near-detector in NuMI
  beam line
• Fully active detector designed to make high
  precision measurements of neutrino-nucleus
  interactions
• Built around central tracking volume of
  fine-grained scintillator
• Measure cross-sections
• Full event reconstruction
• Liquid 4He, C, Fe, and Pb nuclear targets

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NuMI Neutrino Flux
Intense neutrino beam with broad energy
range MINERvA will use mixture of LE, ME, HE beam
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Neutrino-Nucleon Cross section
NuMI flux range
1-20 GeV
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Event Rates 13 Million total CC events in a 4
year run
Assume 16.0x1020 in LE, ME, and HE configurations
in 4 years
Fiducial Volume 3 tons CH, 0.6 t C, .6 t
Fe and .6 t Pb Expected CC event samples 8.6
M n events in CH 1.4 M n events in C 1.4 M n
events in Fe 1.4 M n events in Pb

• Main CC Physics Topics with Expected Produced n
  Statistics in 3 tons of CH
• Quasi-elastic 0.8 M events
• Resonance Production 1.6 M total
• Transition Resonance to DIS 2 M events
• DIS and Structure Functions 4.1 M DIS events
• Coherent Pion Production 85 K CC / 37 K NC
• Strange and Charm Particle Production gt 230 K
  fully reconstructed events
• Generalized Parton Distributions order 10 K
  events
• Nuclear Effects C1.4 M, Fe 1.4 M and Pb 1.4
  M

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Detector Design

• Thin modules hang like file folders on a stand
• Attached together to form completed detector
• Different absorbers for different detector
  regions

108 Frames in total
Side HCAL (OD)
SideECAL
Fully Active Target
NuclearTargets
DownstreamHCAL
Downstream ECAL
Veto Wall
Fully Active Target 8.3 tons
Nuclear Targets 6.2 tons (40 scint.)
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Active Scintillator Target
Triangular scintillators are arranged into planes
Wave length shifting fiber is read out by
Multi-Anode PMT
1.7 cm
WLS fiber
Particle trajectory
3.3 cm
2.5 mm resolution with charge sharing Light yield
6.5 photo-electron/MeV
PMT
WLS
Clear Fiber
Scintillator
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Nuclear Target region
XUXVXUXV (4 tracking points) between each layer
Main detector
Beam
Carbon, Iron, Lead mixed elements in layers to
give same systematics
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Quasi-Elastic Neutrino Interactions (QE)
Charged current
?n ????p
scc c1GE2 c2GM2 c3FA2

• GE2 , GM2 extracted from electron-proton elastic
  scattering
• FA2 is the axial form factor (extracted from
  neutrino-neutron scattering cross section)
• c1, c2, c3 kinematic factors
• c3FA2 accounts for about half of cross section

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Experimental Challenges

• No free neutron targets, must use nuclei!
• Need to isolate QE events from other processes
• Use of nuclei introduces complications
• Non-zero total transverse momentum
• Fermi momentum
• Final state interactions (FSI)
• FSI
• Particle production
• Proton Loss
• Non-QE processes can mimic QE
• Possible modification of form factor
• Projected to be a few percent (theoretical)
• Thick targets cause
• Particle absorption

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Quasi-elastic scattering

• Signature is mp with no other final state
  particles and zero transverse momentum
• If reaction occurs in nucleus
• Fermi momentum gives non-zero transverse momentum
• FSI can give additional particles
• Resonance and DIS can produce proton unobserved
  neutrons, mimicking QE
• QE ranges from 30 of total cross section for 2
  GeV neutrinos to less than 5 of total cross
  section for 10 GeV neutrinos
• Requires good background rejection

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Quasi-elastic

• Question what is the nuclear dependence of
  extracted form factor due to contamination and
  losses, i.e. experimental effects?
• Question what is the effect due to nucleon
  being in nuclear medium, i.e. intrinsic
  modification?

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Anticipated statistics on Axial FF
800 K QE on C 150 K QE on Fe and Pb Comparisons
in low Q2 better than 1 statistical uncertainty
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Simulation

• Use GENIE
• Neutrino event generator
• Uses combination of theoretical models and world
  neutrino data to generate events
• Generates events on multiple nuclei
• For this simulation use fixed neutrino energies
• http//howto.genie-mc.org/
• Model Detector
• Check for track overlap (reduces observed
  multiplicity)
• Particles stopped in interaction target
• Count observed tracks
• For this simulation assume perfect particle ID

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Analysis

• Analysis Cuts
• Number of tracks
• mp ideal case for QE event, or single muon
• Also looked at higher multiplicities improves
  efficiency, decreases purity
• Particle ID Non-QE processes produce pions
• Vetoed charged and neutral pions
• Q2 (GeV/c)2
• 0-1.2 (GeV/c)2 bins of 0.3 (GeV/c)2
• 1.2 (GeV/c)2 and greater
• Total Transverse Momentum
• Less than 0.25 GeV/c cut
• No Transverse Momentum cut for this simulation
• Event type (supplied by event generator)
• Efficiency QE with cuts/Total QE
• Purity QE with cuts/(all processes with cuts)

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m or mp events
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Results

• Efficiency is high in low Q2 region (80-100)
• Nearly identical for C and Pb
• Little energy dependence
• Purity decreases with Q2 and neutrino energy
• Remains above 70, even for 10 GeV neutrino
• C and Pb have similar Q2 dependence, with Pb
  5-10 less than C

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Conclusions

• Corrections for C and Pb are not dramatically
  different
• Relatively small energy dependence
• Magnitude of correction 30 or less
• Will need to compare actual data with GENIE
  output to determine accuracy of GENIE
• Expect that we can compare extracted cross
  sections to better than 5 systematics
• Comparison to He still underway