Lauren Hsu

Fermi National Accelerator Laboratory

MIAMIDecember 2007

The MINOS

Experiment

Neutrino Oscillations with

MINOS

Goal of MINOS is to measure disappearance of !µ :

P(!!"!!) = 1 - sin22#sin2( )

Beam of !µ created by NuMI (Neutrinos at the Main Injector),

detected in Minnesota 735 km away.

1.27$m2*735km

E (GeV)

A 2-Detector Measurement

Neutrinos at the Main Injector

NuMI commissioning:

Early 2005

120 GeV proton beam

2-3!1013 protons per spill

cycle period: 2.2 s

beam power ~0.17 MW

10!s spill time

3.7e20 POT delivered to date

Creating neutrinos with the Tevatron

Main Injector

Neutrino Beamline

Horns focus parent "

and K

104m

Target to Near Detector = 1 km

Flexible Beam Energy

Flu

ka20

05

MINOS horn

Adjustable distance between target and focusing hornsselects #! of varying energies

Most data taken in the Low Energy (LE) configuration to maximize sensitivity

to oscillations.

MINOS target

Total NuMI Delivered Protons3.7e20 POT delivered to date

beam and detectors currently up and running

20

06

sh

utd

ow

n

200

7 s

hu

tdo

wn

data analyzed to

date

MINOS Detectors

8m

Far Detector

Soudan Mine

Two nearly identical detectors monitor #! flux at “near” and “far” locations

5.4kT, 705m underground, 484 fully

instrumented planes, commissioned 2003

~6m

Near Detector

Fermilab

0.98kT, 103m underground, 282

fully/partially instrumented planes,

105x data rate of far detector,

commissioned 2005

• 2.54 cm thick steel planes alternating with 1X4.1cm scintillator strips

• scintillator strips embedded w/ WLS fibers, read out by multi-anode Hamamatsu PMTs • 1.2-1.3T toroidal Bfield distinguishes #

! from #

!

person

(for

scale)

Simple, Robust Technology

•Scint. planes alternate in “u”

and “v” directions

• 2.54cm steel = 1.4 rad. length

• 6-7 p.e. per M.I.P. per strip

Similar technologies incorporated intocomponents of NO#A, MINER#A, Double Chooz…

uv

Near Detector

underside

Scintillator

Strip w/ WLS

fiberMulti-anode PMT

Near Detector:

Scintillator Plane

Calibration

CalDet

minature copy of

MINOS detectors

$E/E = 21.4%/ %E(GeV) & 4.1%

(measured with caldet)

EM Shower Resolution:

$E/E = 6-13% (range and curvature)

Muon Momentum Resolution:

$E/E = 56%/ %E(GeV) & 2%

6% uncertainty in absolute Energy

(measured with caldet)

Hadronic Shower Resolution:

Light injection system &

cosmic rays correct for non-

uniformity and time variation

in strip response

Signal Reconstruction#! CC interaction #x NC interaction #e CC interaction

U vs Z

V vs Z

Q vs Z

U vs Z

V vs Z

Q vs Z

U vs Z

V vs Z

Q vs Z

WZ W

!µ!x !e!x e-µ-

N NNHadrons

Hadrons Hadrons

clean channel for #!disappearance

search for !e appearancebg to !! CC,

search for sterile oscillations

!! Disappearancepreliminary results on 2.5e20 POT

Event SelectionSignature of a #! CC interaction is:

muon track + hadronic shower

Well reconstructed (muon) track

q < 0

track vertex inside fiducial volume

likelihood-based event topology discrimination

(NC/CC event separation)

(NC)

(NC)

(NC)

(NC)

Near Detector: NC/CC Separation Far Detector: NC/CC Separation

fiducial volume

near detector

far detector

This Result

2006 Result

Flux Predictions

Ideal Scenario: Near and Far detectors measure identical neutrino

fluxes, no need to know ! cross sections or hadron production.

Real Scenario: Angular acceptance & decay kinematics cause

Near and Far detectors to measure slightly different spectra

Construct a method to extrapolate near spectrum to obtain expected

far spectrum.

Probability toproduce #’s with

Etrue in Near Det.corresponds to #’s

with range of Etrue

in Far Det.

Beam Matrix Extrapolation

for each # of energy E# detected in Near Detector…

…p

robabili

ty to

dete

ct # o

f E#’ i

n

Far

Dete

cto

r

Elements determined by simulation of target

and beamline (Fluka05/GEANT3 )Cross-section, and flux uncertainties largely cancel!

Beam Modeling

Low

Energy

Med

Energy

High

Energy

Simultaneous fit to 8 different beam configurations (3 shown here)

constrains flux uncertainties

Remember: Many uncertainties in beam modeling cancel in construction of Beam Matrix!

Far Spectrum Cross-Checks3 additional extrapolation methods cross check the

Beam Matrix Prediction

Far/Near (F/N): Use Near data and ratio of fluxes to extrapolate to Far Detector

ND & 2DFit: Use output of Far MC after fitting Near spectrum to constrain beam

modeling, cross sections, and energy scale parameters

Far Spectrum Predictions

Disappearance Results

2.5e20 POT unblinded for this result

(cumulative with 1.27e20 POT from 2006 result)

310 events expected in [0,10]GeV, 496±20 observed

(significance of disappearance > 5$)

Improvements: 2X more data, upgrades to reconstruction, event selection

criteria, neutrino event generator…

<0.0050.041All other systematic uncertainties

0.0080.11Total systematic (summed in quadrature)

0.0080.010NC contamination ±50%

0.0800.17Statistical error (data)

<0.0050.075Absolute hadronic energy scale ±10%

<0.0050.065Near/Far normalization ±4%

Shift in

sin2(2#)

Shift in $m2

(10-3 eV2)Uncertainty

Results: Far Spectrum

Oscillation Hypothesis best fit

No Disappearance Hypothesis

P('2,n.d.f) = 0.18'2 /n.d.f = 41.2/34 = 1.2

P('2,n.d.f) is negligible'2 /n.d.f = 139.2/36

=3.9

Oscillation Contours

!

|"m32

2

|= 0.00238#0.00016+0.00020

08023

2 00.1)2(sin.!="

This Result, Best Fit:

(constrained to physical region)

eV2

Consistent with previous result within

statistical and systematic uncertainties

Fit to unconstrained physical region givesbest-fit sin2(2%) slightly > 1, Feldman-

Cousins analysis coming soon

Future MINOS Oscillation

Measurements

Sterile Oscillations

Signature of sterile oscillations:

deficit of NC events in Far Detector

!e, !!, !( interact via NC interaction.

A representative model for

interpreting MINOS NC data(Fogli et. al. PRD 63)

Looking for disappearance of standard model #’s in NC mode

Constraining #13: !e Appearance

Sensitivity Estimate:

To be updated soon!

Signature: Look for excess !e events

over expected background in Far

Detector

Data-driven techniques use Near

Detector Data to constrain backgrounds

Background

components

MIN

OS p

relim

inar

y

Summary

Future Measurements:

• Increased precision on atmospheric mixing parameters

• search for sterile oscillations

• search for nue appearance

2-detector experiment, designed to measure disappearance of #!

probes atmospheric oscillation parameters with man-made source

MINOS observes energy-dependent deficits consistent with oscillations

Preliminary Results on 2.5e20POT:

$m2 = 0.00238 eV2

sin2(2#23) = 1.00

significance of disappearance > 5)

Improvements over 2006: 2X more data + reconstruction, event selection

and event generator improvements

+0.00020*0.00016

*0.08