MINOS Flux Determination Žarko Pavlović Pittsburgh, 12/07/12
Outline Introduction MINOS experiment and NuMI beam Calculating flux and systematic errors Fitting the ND data (Beam tuning) Conclusion 2
Past neutrino experiments Determining flux not easy Use MC simulation Measure in the detector using process with known xsection In past, experiments often applied corrections Large 10-30% uncertainty 3
Two detector experiments Measure flux at Near Detector to infer flux at Far Need to calculate corrections (on top of R-2) For MINOS 20-30% 4
MINOS Experiment Two neutrino detectors Fermilab s NuMI beamline Verify υμ υτ mixing hypothesis Measure precisely m223 Test if sin22θ 23 maximal 735 km 5
NuMI Neutrino Beamline Muon Monitors Horns Target 10 m Absorber Decay Pipe 30 m Hadron Monitor 675 m p 5m Rock 12 m 18 m π, K Target 120 GeV protons hit graphite target 6
NuMI Neutrino Beamline Muon Monitors πtarget Absorber Decay Pipe Horns π+ 10 m 30 m Hadron Monitor 675 m 5m Rock 12 m 18 m 2nd horn Two magnetic horns focus positive π & K 2π f p Parabolic Horn focal length: µ Ia 0 7
Neutrino Beamline Muon Monitors Target Horns νμ μ+ π+ 10 m Absorber Decay Pipe 30 m 675 m Hadron Monitor 5m Rock 12 m 18 m Mesons decay in flight in decay pipe Beam composition (LE10/185kA): 92.9% υμ 5.8% υμ 1.3% υe / υe 8
MINOS Detectors Near Detector: 1 km from target 1 kton 282 steel and 153 scintillator planes Magnetized B~1.3T Coil Far Detector Far Detector: 735 km from target 5.4 kton 484 steel/scintillator planes Magnetized B~1.3T 12/06/12 Near Detector
Variable energy beam tan(θ) <pt>/pz = rhorn / tgtl 5 GeV π + 20 GeV π + Low energy 12/06/12 Eν ~ pz ~ tgtl
Variable energy beam tgtl 5 GeV π + 20 GeV π + High energy 12/06/12 tan(θ) <pt>/pz = rhorn / tgtl Eν ~ pz ~ tgtl
Near and Far Spectra Flux at Near and Far detector not the same Neutrino energy depends on angle w.r.t parent momentum 0.43Eπ Eν = 1 + γ 2θ 2 p to Far Detector π (stiff) + target π (soft) + 2 1 1 Flux 2 2 2 L 1 Decay Pipe θf θn ND 12
Far/Near ratio 20-30% correction on top of R-2 for ND at 1km For ND at 7km corrections at 2% level 12/06/12
Study of Beam systematics Non-hadron production 1. Proton beam 2. Secondary focusing modelling 3. MC geometry Hadron Production NB: Much of the inputs backed up with beamline instrumentation 12/06/12
1. Proton Beam Beam position and width can change the neutrino flux: protons missing the target reinteractions in target Use profile monitor measurements to correct MC 12/06/12 figure courtesy M. Bishai Proton Batch Position (mm)
2. Modelling of Focusing Also studied: Horn current miscalibration, skin depth, horn transverse misalignment, horn angle 12/06/12
Focusing peak Focusing uncertainties Misalignments & miscalibrations Input from beamline instrumentation Affects falling edge of the peak 17
Hadron production Proton beam momentum Target material Thick target 18
Thick-Target Effects Hadron production data largely from thin targets. Particles are created from reinteractions in NuMI target. E Noo Bi ni M Approx 30% of yield at NuMI p0=120 GeV/c J-PARC CNGS NuMI Fluka 2005 19
Cascade models Variation in calculated flux depending on the cascade model Indicates ~8% uncertainty in peak and ~15% in high energy tail 20
Underlying Hadron Production Different beams access regions of π s (xf,pt) off the target. Models disagree on these distributions Use variable beam configurations to map this out. LE010/185kA 12/06/12 LE100/200kA LE250/200kA
Hadron Production LE010/185k A LE010/185kA LE100/200kA LE250/200kA 12/7/12 LE100/200k A Same pt-xf bin contributes differently to different beams LE250/200k A LE010/185kA LE100/200kA LE250/200kA
MC tuning LE010/185kA LE100/200kA LE250/200lA Adjust the yields of π± and K± Include focusing uncertainties Allow that some discrepancy is due to detector effects or neutrino cross sections 23
Hadron production parameterization Adjust yields as a function of pt-pz Parameterize fluka yields using 16 parameters 3/ 2 d 2N = { A( xf ) + [ B ( xf ) pt ]} e C ( xf ) pt dxf dpt 24
Tuning MC Fit ND data from all beam configurations Simultaneously fit νμ and νμ spectra LE010/185kA LE100/200kA LE250/200kA υμ LE010/185kA 25
Pion weights Re-weight MC based on pt-xf Include in fit: Horn focusing, beam misalignments, neutrino energy scale, cross section, NC background Weights applied vs pz & pt 26
π+/π- ratio Best fit to νμ and νμ changes the π+/π- ratio Good agreement with NA49 data and MIPP 27
Far/Near Ratio Fits to ND data constrain the F/N ratio Errors are at <2% level 28
MINOS Systematic Errors Systematic errors from 2011 analysis (7.25e20 POT) Beam uncertainty small Phys.Rev.Lett.106:181801,2011 29
Offaxis neutrino beam 2 stopped π + 1 stopped K+ π+ K+ E m 2, K 2 2 M E, K 1 MiniBooNE le! diagram not to sca 30
Two views of the same decays Decays of hadrons produce neutrinos that strike both MINOS and MiniBooNE Parent hadrons sculpted by the two detectors acceptances. Plotted are pt and p of hadrons which contribute neutrinos to MINOS (contours) or MiniBooNE (color scale) MiniBooNE MiniBooNE MINOS MINOS 31
NumiBooNE Good agreement between data and MC 32
NuMI μ monitors µmon 1 Eµ,π >4.2GeV Εν >1.8GeVc π s µmon 2 Eµ,π >11GeV Εν >4.7GeV µmon 3 Eµ,π >21GeV Εν >9GeV µ s ν s µmon 1 µmon 2 3 arrays of ionization chambers µmon 3 MC 33
Pion parents Parent pt (GeV/c) µmonitor 1 µmonitor 2 µmonitor 3 Parent pz (GeV/c) 34
Fit to muon monitors Consistent with ND fits L. Loiacono, thesis (2010) 35
Conclusion MINOS tunes hadron production to simultaneously fit all ND data Technique independent of particle production experiments Beam systematics well constrained 36
Backup 37
F/N focusing uncertainties F/N ratio affected at 2% level 38
Predicting far spectrum X Courtesy M. Messier Construct beam matrix using MC Use Near Detector data to predict the unoscillated spectrum at the Far detector = 12/06/12 Courtesy T. Vahle