View
221
Download
0
Category
Tags:
Preview:
Citation preview
NuMI
MINOS
Neutrinos Change FlavorUnder Wisconsin
Current NuMI/MINOS Oscillation ResultsAlec Habig, for the MINOS Collaboration
XLIII Rencontres de Moriond EW 2008
27 institutions147 physicists
Argonne • Arkansas Tech • Athens Benedictine • Brookhaven • Caltech Cambridge • Campinas • Fermilab
Harvard • IIT • Indiana Minnesota-Twin Cities • Minnesota-
Duluth Oxford • Pittsburgh • RutherfordSao Paulo • South Carolina • Stanford Sussex • Texas A&M • Texas-Austin
Tufts • UCL • Warsaw • William & Mary
NuMI
MINOS
Neutrinos Change FlavorUnder Wisconsin
Current NuMI/MINOS Oscillation ResultsAlec Habig, for the MINOS Collaboration
XLIII Rencontres de Moriond EW 2008
27 institutions147 physicists
Argonne • Arkansas Tech • Athens Benedictine • Brookhaven • Caltech Cambridge • Campinas • Fermilab
Harvard • IIT • Indiana Minnesota-Twin Cities • Minnesota-
Duluth Oxford • Pittsburgh • RutherfordSao Paulo • South Carolina • Stanford Sussex • Texas A&M • Texas-Austin
Tufts • UCL • Warsaw • William & Mary
NuMI
MINOS
MINOSMain Injector Neutrino Oscillation Search
• Investigate atmospheric sector oscillations using intense, well-understood NuMI beam
• Two similar magnetized iron-scintillator calorimeters– Near Detector
• 980 tons, 1 km from target, 90 m deep
– Far Detector• 5400 tons, 735 km away, 700 m deep
735 km
NuMI
MINOS
Physics Goals
• Precise (~10%) measurement of m223
• Confirm ↔ flavor oscillations– Provide high statistics discrimination against alternatives
such as sterile , decoherence, decay, etc
• Search for subdominant ↔e oscillations – a shot at measuring 13
• Directly compare vs oscillations (a test of CPT)– MINOS is first large underground detector with a magnetic
field for +/- tagging
• Study interactions and cross sections using the very high statistics Near Detector data set
• Cosmic Ray Physics
This talk Published Coming later this year
Atmospherics Beam
NuMI
MINOS
Disappearance Sensitivity
• Measure flux at Near Det, see what’s left at Far Det• Simulated results plotted as F/N ratio
– Position of dip gives m2
– Depth of dip gives sin22• Spectral ratio shapes would differ in alternative models
Unoscillated
Oscillated
spectrum
Monte Carlo Monte Carlo
ν ν
2
2 21 sn isi nL
PEm
θΔ
μ μ
Spectrum ratio
NuMI
MINOS
Far Detector
M16 PMT
16 mm
A module of 20 strips
…on a plane
8 fibers ona pixel
• 486 planes, 5400 tons total– Each 1” steel + 1 cm plastic
scintillator thick – 8 m diameter with torodial
~1.5 T B-field– 31 m long total, in two 15 m
sections– 192 scintillator strips across
• Alternating planes orthogonal for stereo readout
– Scint. CR veto shield on top/sides
• Light extracted from scint. strips by wavelength shifting optical fiber– Both strip ends read out with
Hamamatsu M16 PMTs– 8x multiplexed
NuMI
MINOS
3D Reconstruction
• Take all the “U” view lit-up strips– Cross with all the “V”
view lit-up strips– X marks the spot(s)
See live events athttp://www.soudan.umn.edu
NuMI
MINOS
3D Reconstruction
• This is a real interaction from the beam– appears inside
detector,– cruises along through
many planes,– curving in the
magnetic field,• Curvature tells us
momentum…
– stops.• …so does range
See live events athttp://www.soudan.umn.edu
NuMI
MINOS
Near Detector
• 282 planes, 980 tons total– Same 1” steel,1 cm plastic scintillator planar construction, B-field– 3.8x4.5 m, some planes partially instrumented, some fully, some steel only– 16.6 m long total
• Light extracted from scint. strips by wavelength shifting optical fiber– One strip ended read out with Hamamatsu M64 PMTs, fast QIE electronics– No multiplexing upstream, 4x multiplexed in spectrometer region
3.8 m
4.8 m
NuMI
MINOS
Hadronic: 56±2%/E
EM: 21±4%/ E
• 60-plane ‘micro-MINOS’– has taken data at T7 & T11 test beam lines
at CERN during 2001, 2002, 2003• Instrumented with both Near and
Far Detector electronics– To provide cross-calibrations– Energy uncertainties: 3% relative, and
1.9% (ND) & 3.5% (FD) absolute
Caldet
NuMI
MINOS
NuMI Spectrum
• Three standard beam configurations– Obtained by changing target and
horn 2 locations– Target easy to move, used to
approximate ME, HE with “pME”, “pHE” beams
– Horn 2 harder to move, has not yet been adjusted
– Can also adjust horn currents for more variations
• At L of 735 km and m2 indicated by Super-K, the “Low” energy beam is closest to the first oscillation minima– Unfortunately, also the least
intense (still 107 per 1020 pot at the Near Detector!)
BeamTarget z
position (cm)FD Events
per 1e20 pot
LE-10 -10 390
pME -100 970
pHE -250 134098.7% (5.8% )
1.3% e e
NuMI
MINOS
Beam Data Analyzed
• up to 3x1013 protons every 2.2 seconds (~250 kW) (104 events/day in ND!)
RUN I - 1.27x1020 POT(published in PRL)
Higher energy beam
RUN IIa1.23x1020 POT
(NEW)
RUN IIb~0.75x1020
POT(in can)
This talk: Run I + Run IIa - 2.497x1020 POT
RUN III>0.63x1020
POT(current)Far Det
>99% live!
NuMI
MINOS
Near Detector Data
• How do data look in the Near Detector, where we have ~unlimited statistics?
• If we understand things there, we can then look at the Far Detector data where the physics is happening, so:– Examine ND closely– Compare ND data/MC– “Blind” analysis done ?
? ?
NuMI
MINOS
Lots of in the Near Detector
• A mean of 3 interactions per spill (in 8 or 10 s), up to 10
• Near Detector Electronics gates for 19 s during the entire spill
– Digitizes continuously every 19 ns, no dead time
• Separate events using timing and topology• Below: ~35 x 106 events for 1.27 x 1020 POT
image the ND’s internal structure with !
A typical 6-event spill,colored by time
NuMI
MINOS
Z
N(+X)
W
N X
e e
W
N X
What sort of Interaction?
CC Event NC Event e CC Event
Long track + hadronic activity at vertex
3.5m
Short event, often diffuse
1.8m
Monte Carlo
E = Eshower+E
55%/E 5% range, 10% curvature(hadronic)
22%/E
(leptonic)
E = Eshower
Short, with typical EM shower profile
2.3m
7 variable log-likelihood PID formed, improves over PRL analysis
NuMI
MINOS
Reconstructed Beam Spectrum
LE-10 pME pHE
LE-10 events
Weights applied as a function of hadronic xF and pT.
MIPP data on MINOS target will be used to refine this in the future, NA49 and Harp results also used
Discrepancies between data and Fluka05 Beam MC vary with beam setting: so source is due to beam modeling uncertainties rather than cross-section uncertainties
MC tuned by fitting to hadronic xF and pT over 7 beam configurations (3 shown here)
NuMI
MINOS
What is Expected in Soudan?
• Measure Near Detector E spectrum• To first order the beam spectra at Soudan is the
same as at Fermilab, but: – Small but systematic differences between Near and Far– Use Monte Carlo to correct for energy smearing and
acceptance– Use our knowledge of pion decay kinematics and the
geometry of our beamline to predict the FD energy spectrum from the measured ND spectrum
f
to farDetector
Decay Pipe
(soft)
(stiff)
n
target
ND2
222 1
11
L
Flux221
43.0
EE
NuMI
MINOS
On to the Far Detector…
• “Blind” analysis– Only after understanding the
Near Detector, reconstruction, selected non-oscillation Far Detector parameters, and early pHE (ie, non-oscillating) beam data did we “open the box”
– Data “re-blinded” when developing analysis improvements and adding new data
NuMI
MINOS
Spectrum
expected
observed
i
i
e
o|m2
32| = 2.38 +0.20 (stat + syst) x 10-3 eV2
sin2223 = 1.00 -0.08 (stat + syst)
2/ndf=41.2/34 (18 bins x 2 spectra (Run I, Run IIa) – 2)
−0.16Measurement errors are 1σ, 1 DOF
2 2 2 2
1 1
( ,sin 2 , ,...) 2( ) 2 ln( / ) /j
nsystnbins
j i i i i i ji j
m e o o o e
NuMI
MINOS
Allowed Region
• Fit includes systematic penalty terms
• Fit is constrained to physical region: sin2(223)≤1
• Consistent with previous experiments
• Already best measurement of |m2
32|
NuMI
MINOS
MC MINOSMC
The Future
• disappearance– more data, looser cuts
as systematics are better understood
– add rock muons
• Anti-neutrino oscillations– in neutrino beam– anti-neutrino running?
• Search for/rule out exotics– Sterile neutrinos– Neutrino decay– Neutrino de-coherence
• e appearance– New sensitivities!
Simulated data based onm2=2.7x10-3 eV2 and sin22=1.0 (Old values! For Comparison Purposes Only,m2 really does = 2.38x10-3 eV2 these days, but this plot has not been remade)
NuMI
MINOS
Progress Towards the Future
• This year should see the first looks at:– A NC analysis to directly test for participation of s
in the disappearance
– A e analysis to search for 13 via e appearance
• As with the disappearance analysis, the Near Detector data and backgrounds must be well understood before the Far Detector data (and its potential new physics) is examined
• Here follow two important steps towards this goal:
NuMI
MINOS
Selecting Neutral Current Events
• Simple NC event selection:– < 60 planes;– no track or– no track beyond
5 planes from shower
NuMI
MINOS
NC Spectrum
• NC events can be used to search for sterile neutrino component in FD– via disappearance of NC events at FD– FD data coming soon
Real ND NC Data Projected s Limitswhen FD box is opened
NuMI
MINOS
e Appearance Sensitivity
• Working towards a 13 measurement by using Near Detector data-driven methods to estimate e appearance backgrounds– At Near Detector, all e events are background rather than due to e
appearance. – Apply the NN-based e selection to the ND data to get an all-
background sample.– Find what fraction of those background events are NC showers,
mis-ID’d CC events, or real e from the beam
• Use these new background estimates to correct Far Detector sensitivity projections for unknowns in hadronic shower modeling etc.
• Two independent methods agree• Estimated systematic errors based on these Near Detector
studies are 10%– Far Detector sideband studies are next
NuMI
MINOS
Muon Removal
• “MRCC” sample: – shower only events
obtained by removing the muon from CC selected events and reconstructing the shower remnant.
• Comes from a well understood spectra, with well known efficiency and purity.
• Apply the e selection to these non-e events– Results in a background
sample of electromagnetic dominated hadronic showers.
NuMI
MINOS
Muon Removal
• >20% Data/MC discrepancy in both the standard e and the muon removed CC samples
• Comparisons of standard Data and MC shower topological distributions disagree in the same way as does MRCC data with MRCC MC– So MC hadronic shower
production/modeling is a major contribution to the disagreement.
– Kinematic phase space of MRCC and selected NC events matches well, but MRCC and selected CC events do not.
• The MRCC sample is thus used to make and ad-hoc correction to the model to NC events per bin– Beam e from MC, CC events are
the remainder
NuMI
MINOS
Horn on/off Method
• After applying e selection cuts to Near Detector data, the composition of the selected events is quite different with the NuMI focusing horns on or off.
• Get horn on/off ratios from MC, then solve for NC and CCbackgrounds in bins of energy, get beam e from the beam MC (a well understood number)– Independent of hadronic modeling
Non = NNC + NCC + Ne (1)Noff = rNC*NNC + rCC*NCC + re*Ne (2)
from MC:rNC(CC,e) = NNC(CC,e)
off/NNC(CC,e)on
NuMI
MINOS
Horn on/off Method
rCC
rNC
Solve eqs.(1), (2)
• On/off ratios match well between data and MC (after fiducial volume cuts).
• Apply these fractions to the total data to deconvolute it into its components.
• The MC predicts 24% too much CC and 28% too much NC background!
• Also checked using 3rd beam spectrum, pHE
Agrees with Muon Removal method!
NuMI
MINOS
Projected 13 Limits
• Extrapolating these data-driven backgrounds to the Far Detector, e appearance limit projections are calculated using the horn on/off method
• Shown as a function of CP-violating phase , since over the MINOS allowed m2 range the limits vary little
• This plot is for our current exposure, with estimated 10% systematics
• Blind analysis in progress
NuMI
MINOS
Projected 13 Limits
• Projected limits shown for expected MINOS exposures
• Data-driven systematics are hoped to drop to 5% with more work plus more horn off data in future years
• Inverted hierarchy shown only for lowest exposure for simplicity, but mostly marches along behind the normal limits
NuMI
MINOS
• The first 2.51020 POT of NuMI beam data have been analyzed for disappearance oscillations and are consistent with standard neutrino oscillations with the following parameters:
• A Neutral Current data spectrum has been measured at the Near Detector. When extrapolated to the Far Detector and compared to data, direct limits on sterile neutrino participation will be set
• Studies of Near Detector data are used to establish data-drive backgrounds to e appearance at the Far Detector. The current MINOS exposure will be sensitive to 13 at the Chooz limit
Summary
This work was supported by the U.S. Department of Energy, the U..K. Science and Technology Facilities Council, and the State and University of Minnesota. We gratefully acknowledge the Minnesota Department of Natural Resources for allowing us to use the facilities of the Soudan Underground Mine State Park. This researcher was directly supported by NSF RUI grant #0653016.
2 0.20 3 232 0.16
223 0.08
2.38 10 eV
sin 2 1.00
m
NuMI
MINOS
Extra Slides
NuMI
MINOS
New Improved Analysis
• Several improvements over previous analysis– better reconstruction
– improved event separation
– improved shower modelling
– new intra-nuclear modelling
• CC event identification based on– track properties
– event length
– event kinematics
• Derive PID based on PDFs of the above
NuMI
MINOS
Improvements
• Larger fiducial volume (3%)• improved reconstruction (4%)• improved PID
– higher efficiency– higher purity
NuMI
MINOS
Unconstrained Fit
07.12sin
eV10 26.22
2-32
Δm
NuMI
MINOS
Parameter Spaces
04/19/23 Alec Habig, HE xyz Neutrino-induced muons observed with MINOS
NuMI
MINOS
What Changed?
04/19/23 Alec Habig, HE xyz Neutrino-induced muons observed with MINOS
NuMI
MINOS
What Changed?
Improvements:•reco & selection•shower modelling
04/19/23 Alec Habig, HE xyz Neutrino-induced muons observed with MINOS
NuMI
MINOS
What Changed?
Data sets:•Pre-shutdown•Post-shutdown
Improvements:•reco & selection•shower modelling
04/19/23 Alec Habig, HE xyz Neutrino-induced muons observed with MINOS
NuMI
MINOS
What Changed?
Data sets:•Pre-shutdown•Post-shutdown
Improvements:•reco & selection•shower modelling
Recommended