Neutrino interaction systematic errors in MINOS and NOvA Mayly Sanchez Iowa State University Argonne National Laboratory Nufact 2012 - Williamsburg, VA July 24, 2012
MINOS and NOvA in a nutshell • Produce a high intensity beam of muon neutrinos at Fermilab. NO ! A Far Detector MINOS Far Detector • Measure background at the 810 km 735 km Near Detector and use it to predict the Far Detector spectrum. • Many uncertainties are expected to cancel. • Similar detectors ensure that neutrino interaction related uncertainties largely cancel. • If neutrinos oscillate we will 1st/2nd generation observe a distortion in the data ← long baseline → at the Far Detector at either site. See more general MINOS and NOvA talks on Friday Mayly Sanchez - ISU/ANL 2 NuFact 2012 - 07/24/12
The MINOS detectors • Functionally identical: Near and Far detectors • Octogonal steel planes ( 2.54cm thick ~1.44X 0 ) • Alternating with planes of scintillator strips ( 4.12cm wide, Moliere rad ~3.7cm) . • Near (ND) : ~ 1kton, 282 steel squashed octagons. Partially instrumented. • Far (FD) : 5.4 kton, 486 (8m/octagon) fully instrumented planes. Near Far Mayly Sanchez - ISU/ANL 3 NuFact 2012 - 07/24/12
Neutrino event topologies in MINOS To select ν e CC we focus on finding compact showers. MC events ! e CC Event NC Event “Irreducible” e - Signal Background ! 0 ! µ CC Event NC Event ! Reducible Background µ - Mayly Sanchez - ISU/ANL 4 NuFact 2012 - 07/24/12
MINOS Monte Carlo • MC tuned to external bubble chamber data for hadronization models. • Tuning focused in the following quantities: • Charged/neutral pion multiplicity and dispersion. • Forward/backward fragments. • Fragmentation functions. • Transverse momentum. • Transverse momentum still too low in forward hemisphere. • Model at lower W 2 is an extrapolation. Region of interest: 1 - 15 GeV 2 in W 2 T. Yang et al., Eur. Phys. Jour. C 63:1-10 (2009) Neutrino data taken with the Near Detector was used to correct the Far Detector expectation. Mayly Sanchez - ISU/ANL 5 NuFact 2012 - 07/24/12
MINOS electron neutrino selection • Initially the ND predicted Near Detector MINOS PRELIMINARY 5000 the early days backgrounds were 20% higher 4000 than observed in data. Total Data Total MC Events 3000 • Hadronization and final state 2000 interactions uncertainties give rise to large uncertainties in 1000 ND prediction. 0 0.2 0.4 0.6 0.8 1 ANN • External data is sparse in our region of interest. • Strong background suppression, since we select tails of BG distributions. 2009 • Improvements to nuclear rescattering model in MC reduced data/MC discrepancies in current analyses. Mayly Sanchez - ISU/ANL 6 NuFact 2012 - 07/24/12
MINOS electron neutrino selection • Initially the ND predicted Near Detector MINOS PRELIMINARY 5000 backgrounds were 20% higher 4000 than observed in data. Total Data Total MC Events 3000 • Hadronization and final state 2000 interactions uncertainties give rise to large uncertainties in 1000 ND prediction. 0 0.2 0.4 0.6 0.8 1 ANN • External data is sparse in our region of interest. Near Detector MINOS PRELIMINARY • Strong background ANN-selected POT suppression, since we select Total Data 2000 19 Events/GeV/10 Total MC tails of BG distributions. 2010 • Improvements to nuclear 1000 rescattering model in MC reduced data/MC discrepancies 0 1 2 3 4 5 6 7 8 9 in current analyses. Reconstructed Energy (GeV) Mayly Sanchez - ISU/ANL 7 NuFact 2012 - 07/24/12
Predicting the FD background MINOS PRELIMINARY • The Near Detector ν e selected NC and 3.5 ) CC � -4 3.0 Far/Near Ratio (x10 ! ν μ CC background components are 2.5 2.0 corrected by the Far/Near MC ratio. 1.5 1.0 0.5 0.0 1 2 3 4 5 6 7 8 Reconstructed Energy (GeV) Monte Carlo 3.5 ~10 -4 expected from geometry ) NC � -4 3.0 Far/Near Ratio (x10 and fiducial volume ratio alone � 2.5 2.0 • Far/Near ratio accounts for geometry, 1.5 fiducial volume ratio, intensity, 1.0 0.5 detector differences and oscillations. 0.0 1 2 3 4 5 6 7 8 Reconstructed Energy (GeV) • Data-driven background decomposition techniques allow us to 3.5 ) beam CC � -4 3.0 Far/Near Ratio (x10 e treat each component separately. 2.5 2.0 • The signal ν e and the ν τ CC from ν μ 1.5 1.0 oscillations are corrected using the 0.5 0.0 extrapolation of the ν μ CC spectrum. 1 2 3 4 5 6 7 8 Reconstructed Energy (GeV) Mayly Sanchez - ISU/ANL 8 NuFact 2012 - 07/24/12
MINOS systematic errors • To study the systematic errors, we generate special MC with the modified parameter in ND and FD. Using this modified MC for extrapolation and calculate the difference with the standard results. MINOS 2010 • For the main background components the hadronization model systematic is corrected to about 4%, while intranuclear and cross sections are down to 1% or less. • More recent analyses have these below 2.5%. Mayly Sanchez - ISU/ANL 9 NuFact 2012 - 07/24/12
The NOvA detectors • 14 kton Far Detector (~3x MINOS). -.1'"2$0&345 • >70% active detector. !"#$%&'("%) &*%+,&-.&/$00) • 360,000 detector cells read by APDs. • 0.3 kton Near Detector ),(;!<(='">,?+ • 18,000 cells/channels. • Each plane just 0.15 X 0 . Great for e - vs ! 0 . .%/0$&&"$,0(1/23+ !"#$%&'&()*+(,'--.(/--'&(01#2( 334(-1#'$.(56(.,178--9#5$ 17.#$%:'7#'&(01#2 ! ;.21<17=(/>'$(97&(?)@. Far Detector !"#"$ 14 kton 928 layers $ ) % !"#$%&'()#"*'%+,#- # " ! 4"5'&'02+3(63/7/02 Near Detector 8/9'#(1,,: 0.3 kton 206 layers Prototype installed on the surface %#%&$ '#(&$ and taking data! Mayly Sanchez - ISU/ANL 10 NuFact 2012 - 07/24/12
Neutrino event topologies in NOvA Monte Carlo events. !)$101A " (A( ' =A>0>4 !)$101A $->4 @,&61.) ' B Background $ (A( ' Signal ?@)+6>51A # B (A( ' </= Background *+,$-./012)13140+)5,06)7)819)3,+,:.1; NOvA uses GENIE for neutrino interactions, same tuning as MINOS. Mayly Sanchez - ISU/ANL 11 NuFact 2012 - 07/24/12
NOvA electron neutrino selection 21 2 • Several electron neutrino 1.8 10 POT FHC, sin 2 =0.1 ! � 13 Events identification techniques are 15 being developed. • Performance already 10 comparable to the NOvA TDR. • PID re-optimized for large θ 13 . 5 • Method used for this study is based on library matching algorithm (a la MINOS). 0 0 0.5 1 PID • Current implementation is promising and has room for Signal Signal:Bkg improvement. • An alternate method based on 100:40 PID>0.7 m a transverse/longitudinal likelihoods e b CC 70:15 of the shower energy profile will PID>0.9 be shown in the poster session. C N Mayly Sanchez - ISU/ANL 12 NuFact 2012 - 07/24/12
NOvA electron neutrino selection 21 2 • Several electron neutrino 1.8 10 POT FHC, sin 2 =0.1 ! � 13 Events identification techniques are 15 being developed. • Performance already 10 comparable to the NOvA TDR. • PID re-optimized for large θ 13 . 5 • Method used for this study is based on library matching algorithm (a la MINOS). 0 0 0.5 1 PID • Current implementation is promising and has room for Signal:Bkg improvement. Signal • An alternate method based on 100:40 PID>0.7 C C transverse/longitudinal likelihoods beam 70:15 of the shower energy profile will PID>0.9 NC be shown in the poster session. Mayly Sanchez - ISU/ANL 13 NuFact 2012 - 07/24/12
NOvA electron neutrino selection 21 2 • Several electron neutrino 1.8 10 POT FHC, sin 2 =0.1 ! � 13 Events identification techniques are 15 being developed. • Performance already 10 comparable to the NOvA TDR. • PID re-optimized for large θ 13 . 5 • Method used for this study is based on library matching algorithm (a la MINOS). 0 0 0.5 1 PID • Current implementation is promising and has room for Signal:Bkg improvement. Signal • An alternate method based on 100:40 PID>0.7 C C transverse/longitudinal likelihoods beam 70:15 of the shower energy profile will PID>0.9 NC be shown in the poster session. Mayly Sanchez - ISU/ANL 14 NuFact 2012 - 07/24/12
NOvA electron neutrino selection � signal signal � • The electron neutrino selection e e Selection Efficiency (%) prefers low hadronic y ν e signal 60 events and high hadronic y ν μ CC background events. 40 • For neutral current events the 20 main background arises from events with one or more ! 0 . 0 0 0.2 0.4 0.6 0.8 1 Hadronic y CC CC ! � � Neutral currents Neutral currents ! 2.5 Selection Efficiency (%) Selection Efficiency (%) PID>0.7 3 2 PID>0.9 1.5 2 1 1 0.5 0 0 0 0.2 0.4 0.6 0.8 1 0 1 2 3 4 5 Hadronic y 0 Number of s � Mayly Sanchez - ISU/ANL 15 NuFact 2012 - 07/24/12
Recommend
More recommend
