steve geer ids meeting cern march 2009 1 neutral currents and tests of 3-neutrino unitarity in...
TRANSCRIPT
![Page 1: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/1.jpg)
Steve Geer IDS Meeting CERN March 2009 1
Neutral Currents and Tests of 3-neutrino Unitarity in
Long-Baseline Exeriments
Steve Geer
Barger, Geer, Whisnant, New J. Phys. 6 (2004) 135.
![Page 2: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/2.jpg)
Steve Geer IDS Meeting CERN March 2009 2
Introduction
• In addition to measureing oscillation parameters, it is important to test the 3-flavor mixing framework.
• The NC event rate measures the total flux of active neutrinos. Hence the anticipated far detector NC event sample will be depleted if there are transitions to sterile neutrinos
• To understand prospects observing/limiting the sterile neutrino transition probability Ps using NC measurements we must account for:– statistics– normalization uncertainties (Flux, spectrum & cross-
section)– detector efficiencies– event-type mis-identification
![Page 3: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/3.jpg)
Steve Geer IDS Meeting CERN March 2009 3
Current Example: MINOS
arXiv:0807.24243 Oct 2008
Measured NC Spectrum in Far
Dectector
•Far detector NC prediction based on near detector measurements look for deficit
![Page 4: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/4.jpg)
Steve Geer IDS Meeting CERN March 2009 4
Observations
Present sensitivity based on O(100) NC events is limited by statistics, and is sensitive to Ps > few 10%
NC events selected with 90% efficiency & 60% purity.
In the future expect superbeam experiments will provide very large NC event samples, and it seems likely that the systematic uncertainties will limit the ultimate sensitivity to Ps.
![Page 5: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/5.jpg)
Steve Geer IDS Meeting CERN March 2009 5
In a Perfect World
• Pure beam with well known flux and spectrum, perfect detector, no cross-section uncertainties.
• Use NC & CC event rates integrated over spectra (NNC, N, Ne, N) oscillation probabilities
0N
/10 NCsNC PNN
PNN 0
/0eee PNN
/0PNN
DEFINE
Predicted number of CCinteractions with no oscillations
yxxy PP
NC
xNC cross-section
CC cross-sections
![Page 6: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/6.jpg)
Steve Geer IDS Meeting CERN March 2009 6
With a Less Perfect Detector
,,
,,
0
1ex
NCxxxNCNCNCsNC PPN
N
,,
,,
0
1ex
exxxeNCNCse PPN
N
,,,,
0
1ex
xxxNCNCs PPN
N
,,,,
0
1ex
xxxNCNCs PPN
N
• Define:
• Solutions for Ps , including a statistical analysis to obtain significance Ps/(Ps), given in New J. Phys. 6 (2004) 135 for some
limiting cases.
xx ,
yx ,
Probability that event of type x correctly identified
Probability event of type x mis-identifiedas event of type y
![Page 7: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/7.jpg)
Steve Geer IDS Meeting CERN March 2009 7
A few definitions
– Normalized mis-id factor
– Normalized NC rate
– Normalized CC rate
– Systematic uncertaintyon fluxes & NC
yyyxxyxyf /(= no. wrong / no. right)
0, NCNCNC
NCNC N
NR
0,
N
NR
No. observeddivided by No. expectedif nothinginteresting is happening
00 / NCNCNC NN
![Page 8: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/8.jpg)
Steve Geer IDS Meeting CERN March 2009 8
Aside: Analytical expressions for Ps / Ps
Consider simplest case: Below CC threshold, & ignore e CC interactions (for other cases New J. Phys 6
(2004)135):
• If the fij are small we can ignore terms O(f2), and obtain:
• In the limiting case where normalization uncertainties dominate (over event mis-identification):
NC
NCNC
s
s
R
RfR
P
P
,1
Significance of deviation of Ps
from zero
220, )1()/()1( NCsNCNCNCs
s
s
s
PNP
P
P
P
![Page 9: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/9.jpg)
Steve Geer IDS Meeting CERN March 2009 9
Detector Simulations
• Need efficiency and mis-id factors:
– Consider several “toy experiments” integrate over parametrized beam spectra use parametrized detector responses
– Use NEUGEN to simulate neutrino interactions
– Define NC & CC event samples using various simple selection criteria matched to candidate detector technologies (e.g. water cherenkov, iron-scintillator)
![Page 10: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/10.jpg)
Steve Geer IDS Meeting CERN March 2009 10
Toy Results for ξxx and yyyxxyxyf /
![Page 11: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/11.jpg)
Steve Geer IDS Meeting CERN March 2009 11
Observations
• K2K-Like experiment:– All fi,j < 0.1, hence impact of mis-id small
compared to statistical uncertainties
• T2K-Like experiment:– fNCNC ~ 0.5
– fNC ~ 0.25 suggests cannot neglect mis-id
• MINOS-Like experiment:– fNCNC ~ 1 good NC event efficiency
– fNC ~ 1 cannot neglect if stats large
– Simulated f’s consistent with present MINOS analysis (better than we have a right to expect)
![Page 12: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/12.jpg)
Steve Geer IDS Meeting CERN March 2009 12
NC Cross-Section Uncertainty
N0 = Predicted No. CC Events (no Oscillations)
NC
PERFECT DETECTOR efficiencies ξxx = 1mis-ID factors ξxy = 0
Up
per
Bo
und
on
Ps
(90
% C
L)
0.12
0.06
0
Sensitivity of the next generation of experiments will be limited by normalization uncertainties unlessthey can be reduced below a few % Additional motivation for experiments like Minerva
![Page 13: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/13.jpg)
Steve Geer IDS Meeting CERN March 2009 13
Efficiencies & Mis-ID: T2K-Like
N0 = Predicted No. CC Events (no Oscillations)
NC
Up
per
Bo
und
on
Ps
(90
% C
L)
NC
0.12
0.06
0
The impact of CC background in the NC sample seems also likely to limit the precision of the NC test.
Worthwhile understanding how to minimize NCf ,
![Page 14: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/14.jpg)
Steve Geer IDS Meeting CERN March 2009 14
Efficiencies & Mis-ID: MINOS-like
MINOS-like detectordoes better at low statistics (higher efficiency) but worse at high statistics (larger mis-id).
N0 = Predicted No. CC Events (no Oscillations)
NC
PerfectMINOS-likeK2K-like
Up
per
Bo
und
on
Ps
(90
% C
L)
![Page 15: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/15.jpg)
Steve Geer IDS Meeting CERN March 2009 15
3 Discovery Sensitivity
![Page 16: Steve Geer IDS Meeting CERN March 2009 1 Neutral Currents and Tests of 3-neutrino Unitarity in Long-Baseline Exeriments Steve Geer Barger, Geer, Whisnant,](https://reader035.vdocuments.mx/reader035/viewer/2022062518/5697bf701a28abf838c7da2f/html5/thumbnails/16.jpg)
Steve Geer IDS Meeting CERN March 2009 16
Summary
• Sensitivity to Ps below O(0.1) will require progress on background suppression & knowledge of normal-izations (cross-sections & fluxes) motivation for experiments like Minerva.
• If the sensitivity is ultimately limited by normalization-type uncertainties NC the sensitivity to Ps can be understood analytically. For example, at 3, sensitivity 3NC/(1+3NC).
• To achieve few-percent-level 3 sensitivity on Ps is likely to require (i) percent-level knowledge of fluxes and cross-sections, (ii) minimizing NCf ,