SHORT-BASELINE NEUTRINO PHYSICS AT MiniBooNEweb.mit.edu/panic11/talks/monday/PARALLEL-1E/3-1410/zimmerma… · lots of single pion production. • High energies ( E > 5 GeV ) are

SHORT-BASELINE NEUTRINO PHYSICS AT MiniBooNE

E. D. ZimmermanUniversity of Colorado

PANIC 2011Cambridge, Mass.25 July 2011

Short-Baseline Neutrino Physics at MiniBooNE

• MiniBooNE

• Neutrino cross-sections

• Hadron production channels

• Oscillation physics

• Antineutrino Oscillations

• MiniBooNE-SciBooNE joint result

Motivating MiniBooNE: LSND

Liquid Scintillator Neutrino Detector

• Stopped π+ beam at Los Alamos LAMPF produces νe, νμ,

ν̅μ but no ν̅e (due to π－ capture).

• Look for delayed coincidence of positron and neutron capture.

• Major background non-beam (measured, subtracted)

• 3.8 standard dev. excess above background.

• Oscillation probability:

!̄e + p ! e+ + n

Search for ν̅e appearance via reaction:

P (!̄µ ! !̄e) = (2.5 ± 0.6stat ± 0.4syst) " 10!3

LSND oscillation signal

• LSND “allowed region” shown as band

• KARMEN2 is a similar experiment with a slightly smaller L/E; they see no evidence for oscillations. Excluded region is to right of curve.

99% CL

90% CL

The Overall Picture

• With only 3 masses, can’t construct 3 Δm2 values of different orders of magnitude!

• Current ideas out there:

• An experiment or two is wrong

• Sterile neutrino sector: extra masses and mixing angles

LSND !m2

> 0.1eV2

!̄µ ! !̄e

Atmos. !m2" 2 # 10!3eV

2!µ ! !?

Solar !m2" 10!4eV

2!e ! !?

MiniBooNE:E898 at Fermilab

• Purpose is to test LSND with:

• Higher energy• Different beam • Different oscillation signature • Different systematic effects

• L=500 meters, E=0.5−1 GeV: same L/E as LSND.

• Oscillation signature is charged-current quasielastic scattering:

• Dominant backgrounds to oscillation:

• Intrinsic νe in the beam

• Particle misidentification in detector

Oscillation Signature at MiniBooNE

!e + n ! e!

+ p

Neutral current resonance:∆→ π0 → γγ or ∆→ nγ, mis-ID as e

! ! µ ! "e in beam

K+! !0e!"e, K0

L! !0e±"e in beam

• 8 GeV primary protons come from Booster accelerator at Fermilab

• Booster provides about 5 pulses per second, 5×1012 protons per 1.6 μs pulse under optimum conditions

• Beryllium target, single 174 kA horn

• 50 m decay pipe, 91 cm radius, filled with stagnant air

MiniBooNE Beamline

.

MiniBooNE neutrino detector

• Pure mineral oil• 800 tons; 40 ft diameter• Inner volume: 1280 8” PMTs• Outer veto volume: 240 PMTs

MiniBooNE’s track-based reconstruction

• A detailed analytic model of extended-track light production and propagation in the tank predicts the probability distribution for charge and time on each PMT for individual muon or electron/photon tracks.

• Prediction based on seven track parameters: vertex (x,y,z), time, energy, and direction (θ,φ)⇔(Ux, Uy, Uz).

• Fitting routine varies parameters to determine 7-vector that best predicts the actual hits in a data event

• Particle identification comes from ratios of likelihoods from fits to different parent particle hypotheses

Beam/Detector Operation

• Fall 2002 - Jan 2006: Neutrino mode (first oscillation analysis).

• Jan 2006 - 201?: Antineutrino mode

• (Interrupted by short Fall 2007 - April 2008 neutrino running for SciBooNE)

• Present analyses use:• ≥5.7E20 protons on target for neutrino analyses• 5.66⇒8.58E20 protons on target for antineutrino analyses

(Updated on data collected up to May 2011)• Over one million neutrino interactions recorded: by far the

largest data set in this energy range

Neutrino scattering cross-sections

• To understand the flavor physics of neutrinos (i.e. oscillations), it is critical to understand the physics of neutrino interactions

• This is a real challenge for most neutrino experiments:

• Broadband beams

• Large backgrounds to most interaction channels

• Nuclear effects (which complicate even the definition of the scattering processes!)

Scattering cross-sectionsfor νμ

• Lowest energy ( E < 500 MeV ) is dominated by CCQE.

• Moderate energies( 500 MeV < E < 5 GeV ) have lots of single pion production.

• High energies ( E > 5 GeV ) are completely dominated by deep inelastic scattering (DIS).

• Most data over 20 years old, and on light targets (deuterium).

• Current and future experiments use nuclear targets from C to Pb; almost no data available. T2K

NOνA CNGSLBNE

BooNEs NuMI, MINOS,Minerνa

100 MeV

300 GeV

The state of knowledge of νμ interactions before the current

generation of experiments:

Dominant interaction channels at MiniBooNE

CCQE (44%)

DIS (0.4%)

(19%)+CC

(0.5%)-CC NCEL (17%)

(1%)NC multi-Others (4.1%)

(2%)+NC (5%)0NC

(3%)CC multi-

(4%)0CC

ν μ-

n p

W

Charged-currentquasielastic

ν μ-

W

n,p

π+

Δn,p+ coherent

Charged-current π+ production

ν ν

Δπ0

n,p n,p+ coherent

Z

Neutral-current π0 production

ν μ-

Δπ0

n p

W

Charged-current π0 production

ν ν

n,p n,p

ZNeutral-currentelastic

Dominant interaction channels at MiniBooNE

CCQE (44%)

DIS (0.4%)

(19%)+CC

(0.5%)-CC NCEL (17%)

(1%)NC multi-Others (4.1%)

(2%)+NC (5%)0NC

(3%)CC multi-

(4%)0CC

ν μ-

n p

W

Charged-currentquasielastic

ν μ-

W

n,p

π+

Δn,p+ coherent

Charged-current π+ production

ν ν

Δπ0

n,p n,p+ coherent

Z

Neutral-current π0 production

ν μ-

Δπ0

n p

W

Charged-current π0 production

ν ν

n,p n,p

ZNeutral-currentelastic

MiniBooNE has measured cross-sections for all of these exclusive

channels, which add up to 89% of the total event rate

MiniBooNE cross-section measurements

• NC π0

• CC π0

• CC π+

• CC Quasielastic

• NC Elastic

• CC Inclusive

Due to limited time, only

discussing a few topics here.

See plenary talk by G. Zeller

Measured observable CCπ0 cross-section

• The dominant error is π+ charge exchange and absorption in the detector.

• First-ever differential cross-sections on a nuclear target.

• The cross-section is larger than expectation for all energies.

• Phys.Rev.D83:052009,2011

]2 [GeV2Q0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

] 2 /

CH2

/ G

eV2

X)

[cm

0 -

µ Xµ

( 2 Q

0

2

4

6

8

10

12

14

16

18-3910×

Statistical error

Systematic error

NUANCE

[MeV]E600 800 1000 1200 1400 1600 1800 2000

] 2 /

CH2

X)

[cm

0 -

µ Xµ

(

0

5

10

15

20

25

-3910×

statistical absorption+ + 0+

beam unisims+beam

cross-sectionsDISCoptical model

QTcorr+beam K

production+CC-beam

hadronic0beam K

MC prediction

[GeV]E0.6 0.8 1 1.2 1.4 1.6 1.8 2

] 2 /

CH2

X)

[cm

0 -

µ Xµ

(

0

5

10

15

20

25

-3910×

Statistical error

Systematic error

NUANCE

Additionally, we measure differential cross-sections vs:

• θμ• θπ

• Eμ• Eπ

Measured observable charged-current π+ cross-sections

• Differential cross sections (flux averaged):

• dσ/dQ2, dσ/dEμ, dσ/dcosθμ, dσ/d(Eπ), dσ/dcosθπ:

• Double Differential Cross Sections

• d2σ/dEμdcosθμ, d2σ/dEπdcosθπ

• Data Q2 shape differs from the model

• Phys.Rev.D83:052007,2011.

16

Neutrino Energy (MeV)600 800 1000 1200 1400 1600 1800 2000

)2) (

cm!

(E"

0

0.02

0.04

0.06

0.08

0.1

0.12

-3610# Error Bands

MiniBooNE Measurement

Total Uncertainty

MC Prediction


Frac

tiona

l Unc

erta

inty

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5 Error Bands


Total Uncertainty

MC/Measurement

FIG. 20: The !(E!) measurement is shown with cumulativesystematic errors. The absolutely normalized Monte Carloprediction is shown for comparison. The bottom plot showsthe fractional uncertainties and the ratio of the Monte Carloprediction to the measurement.

)4/c2 (MeV2Q0 200 400 600 800 1000 1200 1400

310#

)2/M

eV4 c2

(cm

)2(Q$" $

0

10

20

30

40

50

60

-4510# Error Bands


Total Uncertainty

MC Prediction

)4/c2 (MeV2Q0 200 400 600 800 1000 1200 1400

310#

)2/M

eV4 c2

(cm

)2(Q$" $

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5 Error Bands


Total Uncertainty

MC/Measurement

FIG. 21: The "!/"(Q2) measurement is shown with cumu-lative systematic errors. The absolutely normalized MonteCarlo prediction is shown for comparison. The bottom plotshows the fractional uncertainties and the ratio of the MonteCarlo prediction to the measurement.

16


)2) (

cm!

(E"

0

0.02

0.04

0.06

0.08

0.1

0.12

-3610# Error Bands


Total Uncertainty

MC Prediction


Frac

tiona

l Unc

erta

inty

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5 Error Bands


Total Uncertainty

MC/Measurement

FIG. 20: The !(E!) measurement is shown with cumulativesystematic errors. The absolutely normalized Monte Carloprediction is shown for comparison. The bottom plot showsthe fractional uncertainties and the ratio of the Monte Carloprediction to the measurement.

)4/c2 (MeV2Q0 200 400 600 800 1000 1200 1400

310#

)2/M

eV4 c2

(cm

)2(Q$" $

0

10

20

30

40

50

60

-4510# Error Bands


Total Uncertainty

MC Prediction

)4/c2 (MeV2Q0 200 400 600 800 1000 1200 1400

310#

)2/M

eV4 c2

(cm

)2(Q$" $

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5 Error Bands


Total Uncertainty

MC/Measurement

FIG. 21: The "!/"(Q2) measurement is shown with cumu-lative systematic errors. The absolutely normalized MonteCarlo prediction is shown for comparison. The bottom plotshows the fractional uncertainties and the ratio of the MonteCarlo prediction to the measurement.

Neutrino Oscillations: 2007 result

• Search for νe appearance in the detector using quasielastic scattering candidates

• Sensitivity to LSND-type oscillations is strongest in 475 MeV < E < 1250 MeV range

• Data consistent with background in oscillation fit range

• Significant excess at lower energies: source unknown, consistent experimentally with either νe or single photon production

Oscillation analysis region

Oscillation search: Phys.Rev.Lett.98:231801 (2007)Low-E excess: Phys.Rev.Lett.102:101802 (2009)

Antineutrino Oscillations

• LSND was primarily an antineutrino oscillation search; need to verify with antineutrinos as well due to potential CP-violating explanations

• Published analysis has same number of protons on target in antineutrino vs. neutrino mode, but...

• Antineutrino oscillation search suffers from lower statistics than in neutrino mode due to lower production and interaction cross-sections

• Also, considerable neutrino contamination (22±5)% in antineutrino event sample (e-print 1102.1964 [hep-ex])

Oscillation Fit Method

• Simultaneous maximum likelihood fit to

• ν̅e CCQE sample

• High-statistics ν̅μ CCQE sample

• ν̅μ CCQE sample constrains many of the uncertainties:

• ν̅e and ν̅μ flux uncertainties:

• Cross section uncertainties (assume lepton universality)

πνμ

μνe

• Background modes -- estimate before constraint from ν̅μ data (constraint changes background by about 1%)

• Systematic error on background ≈10% (energy dependent)

Data in antineutrino oscillation search: published 5.66E20 POT

• 475 MeV < E < 1250 MeV:

• 99.1±9.8(syst) expected after fit constraints

• 120 observed; excess 20.9±13.9 (total)

• Raw “one-bin” counting excess significance is 1.5σ

• Also saw small excess at low energy, consistent with neutrino mode excess if attributed to neutrino contamination in ν̅ beam

New! 5.66E20 POT

475-1250 MeVoscillation-sensitive region

•Phys. Rev. Lett. 105, 181801 (2010)

Electron antineutrino appearance oscillation results

• Results for 5.66E20 POT

• Maximum likelihood fit for simple two-neutrino model

• Oscillation hypothesis preferred to background-only at 99.4% confidence level.

• E>475 avoids question of low-energy excess in neutrino mode.

• Signal bins only:

• Pχ2(null)= 0.5%

• Pχ2(best fit)= ~10%

•Phys. Rev. Lett. 105, 181801 (2010)

Oscillation fit for475<E<3000 MeV

BEST FIT POINT

Updated antineutrino data: 8.58E20 POT

• Analysis is very nearly unchanged; 52% more statistics

• Most significant change: new constraint on neutrino flux from K+ decays from SciBooNE result (e-print 1105.2871 [hep-ex], accepted by Phys. Rev. D., in press)

• Reduces this component of background by 3%; error by factor of 3

• Other systematic errors, constrained by MiniBooNE data, shrink slightly due to higher statistics in control samples:

• Pion-decay neutrino normalization factors

• Dirt neutrino background

• Neutral-current π0 production

Updated antineutrino data: 8.58E20 POT

• 475 MeV < E < 1250 MeV:

• 151.7±15.0(syst) expected after fit constraints

• 168 observed; excess 16.3±19.4 (total)

• Raw “one-bin” counting excess significance 0.84σ

• Excess in oscillation-sensitive region is reduced somewhat with new data; low-energy excess is more significant and resembles neutrino-mode data

(GeV)QE!E

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Eve

nts

/Me

V

0.0

0.2

0.4

0.6

0.8

1.0Data (stat err.)

+/-µ from e!+/- from Ke! 0 from Ke!

misid0"# N$ %

dirtotherConstr. Syst. Error

3.0

Figure 5: The !e data compared to the MC background prediction. The data corresponds

to 8.584e20 POT. Systematic errors are shown on the MC and statistical errors on data.

experiments was generated to determine the proper !"2 cut for the given confidence level

(CL).

Figures 10 and 11 show where the minimum of the "2 surface is and its minimum as a

function of !m2 for the E > 200 MeV and E > 475 MeV fits. The minimum for !m2 < 1

is not too di"erent than the high !m2, as can also be conclude from the 68%CL contour in

Figures 8 and 9. The di"erence is slightly bigger for E > 475 MeV, however it is still within

68% contour.

Table 8 summarizes all the fit results and compares them to the ones coming from 5.661e20

analysis.

V.2 Null probability

To find the null probability we looked at the constrained "2 in 200-1250MeV (475-1250MeV)

energy range and counted the number of fake experiments with higher constrained "2. The

two !e high energy bins (1250-1500MeV, 1500-3000MeV) were used along with the !µ CCQE

sample to constrain the data. Figure 12 shows the distribution of fake experiments. The

fake data follows a chi2 distribution, so we get the same probability using either counting

or e"ective NDF. The data has the constrained "2 equal to 14.46 (9.27) for 200-1250MeV

12

475-1250 MeVoscillation-sensitive region

PRELIMINARY JULY 2011

Updated electron antineutrino appearance oscillationresults




• Signal bins only:

• Pχ2(null)= 14.9%

• Pχ2(best fit)= 35.5%

• Still consistent with LSND, though evidence for LSND-like oscillations no longer as strong

)!(22sin

-310 -210 -110 1

)4/c2

| (eV

2m"|

-210

-110

1

10

21068% CL

90% CL

95% CL

99% CL

LSND 90% CL

LSND 99% CL

)!(22sin

-310 -210 -110 1

)4/c2

| (eV

2m"|

-210

-110

1

10

21068% CL

90% CL

95% CL

99% CL

LSND 90% CL

LSND 99% CL

Figure 8: The likelihood fit results for the E > 200 MeV (left) and E > 475 MeV (right).

These are the fake data corrected contours.

with assumed LSND BF signal and 34.1% of fake experiments below mean value. This plot

applies for the E > 475 MeV fits.

Table 9 gives the probabilities of observing the !!2 = 3.83 with 8.584e20 data (see

Table 8) given that we have observed !!2 = 8.83 with 5.661e20. The probability was

calculated by counting the fraction of fake experiments with !!2 < 3.83. The fake data was

generated at either MiniBooNE Best Fit point, LSND Best Fit point or Null point and it

was added to the real 5.661e20 data.

Figure 16 shows the projections starting from the existing 8.584e20POT data set.

17

Oscillation fit for475 < E < 3000 MeV

TextBEST FIT POINT


Primary test of LSND

The full energy range

• Low-energy excess is now more prominent; excess above background in 200<E<475 MeV is 38.6±18.5 events.

• Full energy range: excess is 57.7±28.5

(GeV)QE!E

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Eve

nts

/Me

V

0.0

0.2

0.4

0.6

0.8

1.0Data (stat err.)

+/-µ from e!+/- from Ke! 0 from Ke!

misid0"# N$ %

dirtotherConstr. Syst. Error

3.0

Figure 5: The !e data compared to the MC background prediction. The data corresponds

to 8.584e20 POT. Systematic errors are shown on the MC and statistical errors on data.

experiments was generated to determine the proper !"2 cut for the given confidence level

(CL).

Figures 10 and 11 show where the minimum of the "2 surface is and its minimum as a

function of !m2 for the E > 200 MeV and E > 475 MeV fits. The minimum for !m2 < 1

is not too di"erent than the high !m2, as can also be conclude from the 68%CL contour in

Figures 8 and 9. The di"erence is slightly bigger for E > 475 MeV, however it is still within

68% contour.

Table 8 summarizes all the fit results and compares them to the ones coming from 5.661e20

analysis.

V.2 Null probability

To find the null probability we looked at the constrained "2 in 200-1250MeV (475-1250MeV)

energy range and counted the number of fake experiments with higher constrained "2. The

two !e high energy bins (1250-1500MeV, 1500-3000MeV) were used along with the !µ CCQE

sample to constrain the data. Figure 12 shows the distribution of fake experiments. The

fake data follows a chi2 distribution, so we get the same probability using either counting

or e"ective NDF. The data has the constrained "2 equal to 14.46 (9.27) for 200-1250MeV

12


Oscillation fits: full energy range




• Fit over all bins:

• Pχ2(null)= 10.1%

• Pχ2(best fit)= 50.7%

• This is not our primary test of LSND, due to known low-energy excess: can’t be interpreted as a pure antineutrino fit

)!(22sin

-310 -210 -110 1

)4/c2

| (eV

2m

"|

-210

-110

1

10

210

LSND 90% CL

LSND 99% CL

68% CL90% CL95% CL99% CLKARMEN2 90% CLBUGEY 90% CL

)!(22sin

-310 -210 -110 1

)4/c2

| (eV

2m

"|

-210

-110

1

10

210

LSND 90% CL

LSND 99% CL

68% CL90% CL95% CL99% CLKARMEN2 90% CLBUGEY 90% CL

Figure 9: The likelihood fit results for the E > 200 MeV (left) and E > 475 MeV (right).

These are the fake data corrected contours. Also shown are the exclusion regions from

KARMEN and Bugey experiments.

!m2 sin22! Probability

MiniBooNE Best Fit 4.64 0.00377 1%

LSND Best Fit 1.2 0.003 2.5%

Null point 0.01 0.0003 16.6%

Table 9: Probability of observing !"2 = 3.83 with 8.584e20 data in a E > 475 MeV fit

given the observed !"2 = 8.83 with 5.661e20. The probability was calculated assuming

three di"erent hypothesis, MiniBooNE Best Fit point, LSND Best Fit point and Null point.

18


Low-energy excess: how does it scale?

• Excess above background in 200<E<475 MeV is 38.6±18.5 events. Scaling from what is observed in neutrino mode, can test various hypotheses.

• Expect if it scales with...

• Total background: 50

• Neutrino contamination only: 17

• Δ→Nγ decays: 39

• Dirt: 46

• Protons on target (neutrals in secondary beam): 165

• K+ in secondary beam: 67

• NC π0: 48

• Inclusive CC: 59

Another way to fit: subtract low-E excess expected from neutrinos

• In principle, we are trying to fit for ν̅ oscillations only, with expected contributions from ν subtracted as background

• However, neutrino contribution to low-energy excess isn’t in background simulation since its explanation is unknown

• We can assume it scales with total neutrino-induced event rate in each bin, and subtract it out when fitting for antineutrino oscillations.


• Fit over all bins: Pχ2(null)=28.3%; Pχ2(best fit)=76.5% )!(22sin

-310 -210 -110 1

)4/c2

| (eV

2m

"|

-210

-110

1

10

21068% CL

90% CL

95% CL

99% CL

LSND 90% CL

LSND 99% CL

Figure 18: The allowed region for the E > 200 MeV fit when 17 events have been removed

from low energy region.

comparing data to data 2. First we compare the number of events (all selected !e events

without any energy cuts) normalized to POT in di!erent data sets. We calculate the "2

between the normalized event rates and the probability assuming "2 distribution with 1 DF.

Table 13 shows the compatibility between di!erent data sets calculated this way. The second

test involved the data/mc ratio. Table 14 gives the number of data and predicted MC events

for 3 three di!erent periods. Note that jul07 now includes two absorber down run periods.

The MC used for prediction of background events is the old MC used for 5.661e20 analysis.

Since we are looking at the Data/MC ratio the changes to Npi+-, K+, and dirt that went

into the last iteration of MC are irrelevant. Looking at the "2 probability between between

2Some systematics like POT uncertainty do not cancel in these tests and including these systematics

would make the compatibility slightly higher.

29


Consistency of new and old data

• Statistical tests on data sets:

• K-S tests performed across all data sets; no anomalous results

• Beam/detector stability:

• Horn and target have been in use since 2004

• Monitoring of primary beam and neutrino events/POT shows no change over the data collection period except for known beam absorber failure in 2006

• No evidence for any significant change in either flux or detector

Anti-Neutrino/POT (Alexis) Nu/POT calculated using reprocessed data

02/Jul/06 01/Jan/07 02/Jul/07 01/Jan/08 02/Jul/08 31/Dec/08 02/Jul/09 31/Dec/09 02/Jul/10 01/Jan/11

-17

10

!/P

OT

0

5

10

15

20

25

30

35

40

-17 10! 0.1)"/POT = (20.7 /ndf = 675.15/6552

POT8.60e+20

27/Oct/10 26/Nov/10 26/Dec/10 25/Jan/11 24/Feb/11 26/Mar/11 25/Apr/11

-17

10

!/P

OT

0

5

10

15

20

25

30

35

40

-17 10! 0.1)"/POT = (20.8 /ndf = 99.39/842

POT1.76e+20

New data Runs 22780 thru 24169

POT systematic error about 2% Antineutrino candidates vs. protons on target

22

Future sensitivity in ν̅ data

MiniBooNE has requested a total of 1.5×1021 POT in antineutrino mode. Data collection will continue through spring 2012 (at least).

Sensitivity to LSND at 2-3 sigma for expected full data set: hashed region shows possible region (68% C.L.) of future results assuming LSND best-fit signal

Systematics limit approaches above 2×1021 POT

E>475MeV fit

Protons on TargetPOT

2 !"

0

2

4

6

8

10

12

14

16

18

20

22

POT

2010#

10PO

T20

10#12

POT

2010#

15

POT

2010#

20

POT data + LSND BF signal2010#8.58

POT

2010#

5.66

POT)2010#Fake data (BF 8.58

Fake data (null)

Real data

90%

95%

99%

$3

Figure 16: The projection of the MiniBooNE result with more POT under three di!erent

scenarios. The fake experiment dots represent the mean value from fake experiments. The

fake experiments were done at each POT by adding the fake data generated at either Mini-

BooNE Best Fit point, LSND Best Fit point or Null point to the real 8.584e20 data set.

The band around the points which assume LSND Best Fit signal contains 68.2% of fake

experiments.

25

Thisresult Goal

Muon neutrino disappearance with SciBooNE as near detector

• SciBooNE: Scintillating bar detector (originally from K2K) was in the BooNE beamline in 2007-08 to measure cross-sections

• Can also be used as a near detector for MiniBooNE

• New result this summer: νμ disappearance search using both detectors

• Mean baseline: 76m (SciBooNE), 520m (MiniBooNE): oscillation probabilities differ significantly for 0.5 < Δm2 < 30 eV2

Overview

15

50 m

100 m 440 m

MiniBooNE

Detector

Decay region

SciBooNE

DetectorTarget/Horn

Fermilab visual media service

SciBooNEMiniBooNE (2002-)

8GeV Booster

Target/Horn

SciBooNE constraint reduces error at MiniBooNE

• Flux errors become 1-2% level: negligible for this analysis• Cross-section errors reduced, but still significant due to

different kinematic acceptance.

MiniBooNE prediction

34

(GeV)Reconstructed E0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.80

2000

40006000

800010000

1200014000

1600018000

20000

2200024000

MiniBooNE EnuQE


5000

10000

15000

20000

25000

30000 Total err.

Flux + X-sec. err.

MiniBooNE det. err.

MiniBooNE only error Error for this joint analysis


5000

10000

15000

20000

25000

30000 Total err.

Flux + X-sec. err.

MiniBooNE det. err.

SciBooNE-MiniBooNE νμ disappearance result

• No evidence for oscillations

• Limit is better than other experiments in 10-30 eV2 region

• e-print 1106.5685 [hep-ex]

• Analysis of antineutrino mode is underway

90% CL limit

The observed limits from both analyses are within the ±1σ band.Another support for null oscillation signal.

World strongest limit at 10 < Δm2 < 30 eV2

48

2 2sin0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

]2 [

eV2

m

-110

1

10 90% CL limits from previous exp’s.

90% CL sensitivity (Sim. fit)

90% CL limit (Sim. fit)

90% CL limit (Spec. fit)

Conclusions• Cross-sections:

• MiniBooNE has most precise measurements of top five interaction modes on carbon; only differential and double-differential cross-sections in some modes

• Some disagreements with most common nuclear models

• Oscillation searches

• Significant νe and ν̅e excesses above background are emerging in both neutrino mode and antineutrino mode in MiniBooNE

• Newest data update: excess is mostly at low energy, as with neutrinos.

• Antineutrino data are still consistent with LSND; significance of oscillation signal is reduced

• Antineutrino results still heavily statistics-limited; MiniBooNE plans to accumulate more data until the goal of 1.5×1021 protons on target is reached.

Conclusions• Cross-sections:

• MiniBooNE has most precise measurements of top five interaction modes on carbon; only differential and double-differential cross-sections in some modes

• Some disagreements with most common nuclear models

• Oscillation searches

• Significant νe and ν̅e excesses above background are emerging in both neutrino mode and antineutrino mode in MiniBooNE

• Newest data update: excess is mostly at low energy, as with neutrinos.

• Antineutrino data are still consistent with LSND; significance of oscillation signal is reduced

• Antineutrino results still heavily statistics-limited; MiniBooNE plans to accumulate more data until the goal of 1.5×1021 protons on target is reached. See also: M. Shaevitz plenary talk tomorrow

Documents

SHORT-BASELINE NEUTRINO PHYSICS AT MiniBooNEweb.mit.edu/panic11/talks/monday/PARALLEL-1E/3-1410/zimmerma… · lots of single pion production. • High energies ( E > 5 GeV ) are