The Status of the MINOS Experiment

HEP Seminar

Sussex University

26th October 2005

Chris Smith

Sussex/UCL

Contents

Introduction to MINOS

MINOS Physics Goals

NuMI Beamline

MINOS Detectors

Atmospheric Neutrinos

Accelerator Neutrinos

Summary

Introduction

MINOS is a two-detector long baseline neutrino oscillation experiment

NuMI beam-line at FNAL produces nm

Near detector, on-site at FNAL, L~1km

Far detector, in Soudan mine, Northern	Minnesota, L=735km

Differences between Near/Far neutrino energy spectra provides information about “atmospheric” oscillations

Near Det: 980 tons

Far Det: 5400 tons

735 km

Analysis Concept

Compare ratio of neutrino energy spectrum in Far detector to that in Near detector

Allows partial cancellation of systematic errors

In practice this is done “via MC”

Fit to shape of event rate ratio for oscillation parameter measurement

P(nmnt) ≈ sin22q23sin2(1.27Dm232 L/E)

Position of minimum

 Dm2

Depth of minimum

 sin22q

Unoscillated (~Near)

Oscillated (Far)

The MINOS Collaboration

32 institutions

175 physicists

Argonne • Athens • Benedictine • Brookhaven • Caltech • Cambridge • Campinas • Fermilab
College de France • Harvard • IIT • Indiana • ITEP-Moscow • Lebedev • Livermore
Minnesota-Twin Cities • Minnesota-Duluth • Oxford • Pittsburgh • Protvino • Rutherford
Sao Paulo • South Carolina • Stanford • Sussex • Texas A&M
Texas-Austin • Tufts • UCL • Western Washington • William & Mary • Wisconsin

Brazil • France • Greece Russia • UK • USA

MINOS Physics Goals

Demonstrate oscillation behaviour:

Make precise measurement of charged current energy distributions in Near and Far detector to confirm oscillations

Discriminate against other models: decoherence, decay, ...

Precise measurement of oscillation parameters:

m223 to 10%

Search for sub-dominant nm ne oscillations

First measurement of q13?

First direct measurement of atmospheric n vs n oscillations:

MINOS Far detector is first large, deep underground detector with magnetic field

Muon Neutrino Disappearance

Oscillated/Unoscillated nm CC event rate rate ratio vs energy

Example contours for m232 = 0.0025 eV2, sin2 223 = 1.0

MINOS 90%

and 99% CL

allowed oscillation

parameter space.

Greatly improves existing measurement

Excellent test against alternative hypotheses

Continued improvement with additional protons

Electron Neutrino Appearance

Select electron events using EM shower shape pattern recognition

Backgrounds from NC, nm CC, intrinsic beam ne CC

m2 = 0.0025 eV2

MINOS 3 Discovery Limits

m2 = 0.0025 eV2

sin2 213= 0.067

25e20 POT

NuMI & Main Injector

Main Injector:

120 GeV protons

2.5 x 1013 ppp

1.9 sec rep rate (~8 s spill)

0.25 MW

NuMI Beam:

Graphite target

Two magnetic horns

675 m. vac. decay pipe

hadron absorber

designed for 4 x 1013 ppp

Beam Monitoring:

muon detectors

hadron detectors

Near Detector !

Wilson Hall

Extraction to NuMI

Target Building

Decay Tunnel

Absorber Hall

NuMI Building

Near Detector

NuMI Beam Layout

Protons

p, K

n

To Soudan

NuMI Beamline

120 GeV protons extracted from MI to NuMI tunnel

Pitched downwards @160mrad, then 58mrad toward Soudan

Incident on segmented graphite target

Focus charged hadrons with two magnetic horns pulsed with 200kA

675m long steel decay pipe (0.5 Torr, encased in 2-3m concrete)

Hadron absorber downstream of decay pipe

200m rock upstream of Near Detector for muon absorption

NuMI Target

47 2cm graphite segments

6.4 x 28 mm2 profile

Beam is 1mm radius

1.9 interaction lengths

Water cooled

4kW deposited beam power

Could survive 1MW if 2mm beam size

(Slide courtesy S. Kopp)

The Magnetic Horns

Toroidal magnet B ~ 1/r

pT kick of pT  Bdℓ  r  p E

i

i

i



B





(Slide courtesy S. Kopp)

Neutrino Spectra

Horn 2 and target can be moved to vary neutrino energy range:

LE, ME, HE

Target can be moved alone to produce pseudo-ME and pseudo-HE beams

MINOS initially running with LE beam

Move Target only

Move Target and Horn 2

Final Focus to NuMI Target Hall

Final BPM’s+ SEM’s

ToroidTGT

Shielding Wall to Target Hall

MI Q105

MI Q101

BPM

SEM

Toroid101

Installed in NuMI line

Slide courtesy

S. Kopp

Secondary Hadron and Muon Instrumentation

Parallel plate ionization chambers

Hadron Monitor under construction (U. Texas)

A muon monitor station

Nests in Hadron Absorber

3 Stations in excavated alcoves

Photo S. Kopp

Photo S. Kopp

Beam Extraction - After 12 Pulses!

Profile monitor output along the beamline (few pulses later)

December 3-4, 2004

Graphite protection ‘baffle’

Graphite target

Water cooling line

target

horn

baffle

Beam Scans with Target,

Hadron and Muon Monitors

p beam

Baffle, target, horn geometry

Horizontal scan

The MINOS Detectors

Three MINOS Detectors:

Near Detector	980 tons

MINOS building at FNAL

Far Detector	5400 tons

Soudan Underground Lab

Former Iron mine, now a state park

Calibration Detector	12 ton

3-year test-beam programme at CERN PS

Detector Technology

Detectors are steel + scintillator tracking-sampling calorimeters

5.94cm longitudinal spacing

Each scintillator layer is segmented and consists of 4.1cm wide strips

Consecutive planes are rotated by +/- 90o

Light collected by WLS fibres and detected using PMTS

8 m

Scintillator Module

WLS Fibers

WLS Fibers

Optical Connector

Optical Connector

Optical Connector

Optical Connector

Clear Fiber Ribbon Cable (2-6 m)

Clear Fiber Ribbon Cable (2-6 m)

Multiplex

Box

Multiplex

Box

PMTs

Connection to

electronics

Connection to

electronics

Special Thanks

M. Proga

Detector Technology

2.57cm steel layer

1cm scintillator layer

Air gap

Clear fibres connect scintillator modules to light tight box containing PMTs

Specially made “cookies” align fibres on PMT face

Detector Technology

4.1cm x 1cm polystyrene strips coextruded with TiO2 coating and groove for WLS fibre

Strips combined to form modules – made light tight with aluminium covering

Plastic manifolds guide fibres to connector

Hamamatsu multi-pixel PMTs detect light

Far Detector: Hamamatsu M16 PMT

Near Detector: Hamamatsu M64 PMT

The Far Detector Challenge

Far Detector

Shaft too narrow to bring down anything wider than ~2m ...

Bottom steel plane layer

Top steel plane layer

Scintillator plane

Orientations alternate 90o in successive planes

Steel layers welded together from plates

Then eight scintillator modules are attached

Far Detector Plane Assembly

Far Detector Design

8 m diameter octagonal tracking calorimeter

486 layers of 2.54cm magnetized steel plates (~1.5T)

2 sections each 15m long

Veto shield against entering cosmic ray muons

SM 2

Optical Fibre Read out

SM 1

Electronics Racks

Completed Far Detector

Detector as of July 2003, after energizing coil of SM2

Far Detector Live Time

Live time has been steadily increasing since completion

Taking cosmic ray and atmospheric neutrino data

Now averaging ~99.6% live time!

Near Detector Design

Equivalent to the Far detector in absorber, active planes, B-field

Structure:

Veto section

Target section

Shower section

Muon spectrometer

282 steel planes

153 scint. Planes

Every 5th plane is “fully” instrumented

In calorimeter, other planes are partially instrumented

3.8 m x 4.8 m	“squeezed” octagon

Coil hole

Instrumented area

Near Detector Assembly

Plane construction completed in August 2004

Commissioned and calibrated with cosmic ray muons and light injection system

Calibration Strategy

MINOS designed to achieve 2% relative and 5% absolute energy calibration:

Light Injection System

PMT/Electronics non-linearity

PMT gain drifts

Cosmic Ray Muons

Strip-to-strip Normalisation

Energy scale calibration across detector using stopping muons(Muon Energy Unit)

Calibration Detector

Characterize muon, electron and hadron responses

Relate MEU to GeV for MINOS

Calibration Detector

The 3rd MINOS detector!

60 plane mini-MINOS

Took e, , , p data at CERN PS for 0.1-10 GeV in T7, T11 beamlines

MC expectation

Energy Resolution

Hadrons: 55%/E

Electrons: 22%/E

Detector Performance

A cosmic ray muon in the Far Detector:

Two orthogonal spatial views, timing (2.3ns single hit res.) and charge

U vs Z

V vs Z

Time vs Z

Charge vs Z

u

plane (z)

v

plane (z)

Live Events: http://farweb.minos-soudan.org/events/LiveEvent.html

Moon Shadow

Have recorded in excess of 10M cosmic muons

Can observe shadow of moon

Angular resolution improved by selecting high momentum muons

P > 20 GeV/c

All tracks

Not to scale...

HE primary cosmic rays shadowed by moon

Atmospheric Neutrinos





Earth

MINOS

_

Neutrino Induced Up-going Muons

Data Collection

7/03 – 6/04 Normal B-field

2/05 – 4/05 Normal B-field

304 live days

6/04 – 1/05 Reverse B-field

160 live days

Data Analysis

Muon ID cut

Track quality

Fiducial (m enters detector)

Direction consistent with timing and tracking

1/b cut

Down-going

Up-going Muons:
1/b Distribution

Up-going: 91 events

464 live days

Up-going Muons:
Zenith Angle

28  3

37  4

30

Low Resolution

96  10

127  13

107

All Events

68  7

90  9

77

Good timing

Expected

m223=0.0024 eV2

Expected

No Oscilations

Data

Selection

107

Total

13

PC up

25

PC Down

69

FC

4.50.5

NC + e/e CC (Estimated)

4.40.5

CR Muons

(from data)

FC + PC Atmospheric Neutrinos:
Results

Vertex Distribution

Data Breakdown:

Backgrounds:

“Low resolution” => low energy events which are prone to mis-reconstruction of muon direction and therefore charge sign

“Good Timing” => 0.1% probability of mis-reconstruction, reduced from 4%

Energy

Zenith Angle

Upward-going/Downward-going Double Ratio:

Rdataup/down / Rmcup/down = 0.62  0.14 (stat)  0.02 (sys)

FC + PC Atmospheric Neutrinos:
Energy and Zenith Angle

FC + PC Atmospheric Neutrinos:
Oscillation Analysis

Oscillation Probability:

P(nmnt) ≈ sin22q23sin2(1.27Dm232 L/E)

L/E Distribution

L calculated using the zenith angle and assuming the muon was produced at a height of 20km in the Earth's atmosphere

FC + PC Atmospheric Neutrinos:
Oscillation Limits

Consistent with a wide range of oscillation parameters, including most recent results from Super-K, K2K

Data disfavour null hypothesis of no oscillations at 98% level

: 34 events

anti : 18 events

FC + PC Atmospheric Neutrinos:
Charge Ratio

Considering the 77 data events with good timing

Look at the Q/p value returned from the track fit:

FC + PC Atmospheric Neutrinos:
Charge Separated Up/Down

Define nm fraction to be:

f = N(nm) / N(nm + nm)

then

fdata = 0.35  0.07 (stat)  0.02 (sys)

and

fdata / fmc = 0.98  0.19 (stat)  0.06 (sys)

(valid for event rate comparisons with Bartol 3D and Neugen3)

FC + PC Atmospheric Neutrinos:
Charge Separated Up/Down

nm : 34 events

nm : 18 events

Data is consistent with nm and nm oscillating with the same parameters

However CPT violating scenarios with large Dm223 are not excluded with current data

Accelerator Neutrinos

Timeline

July 2003	Far Detector completed

December 2004	Near Detector completed

December 2004	First beam to NuMI

January 2005	First beam on target & ND events

March 2005	First FD event

NuMI has delivered ~7.0e19 POT so far

Expect 1e20 by FNAL shutdown in early 2006

Near Detector already has high statistics ~10k events/day!

MINOS is performing a blind oscillation analysis so we don't know how many events in Far Detector!

NuMI Beam Protons on Target

As of 13th October 2005:

Near Detector Neutrino Events

All data from a single spill (8 s) is written to the same “snarl”

Events are formed by time slicing + topological reconstruction

8 s spill of 5 (or 6) batches each ~1.6 s long

Events recorded within an 18 s window

Two views of each event

U vs Z and V vs Z  X,Y,Z

High energy beam spill with 8 events

Single Spill

5 distinct time slices -> 5 events

Event 1: Rock Muon

Hit Time distribution

Reconstructing a Snarl...

Single Spill

5 distinct time slices -> 5 events

Event 2: Rock Muon

Hit Time distribution

Reconstructing a Snarl...

Single Spill

5 distinct time slices -> 5 events

Event 3: Rock Muon

Hit Time distribution

Reconstructing a Snarl...

Single Spill

5 distinct time slices -> 5 events

Event 4: Contained Event

Hit Time distribution

Reconstructing a Snarl...

Single Spill

5 distinct time slices -> 5 events

Event 5: Rock Muon

Hit Time distribution

Reconstructing a Snarl...

Near Detector Energy Scan
Moving Target Only

Near Detector nm-CC events from Data

E (GeV)

Reconstructed Neutrino Energy Spectrum

MINOS preliminary

Low Energy

Pseudo-Medium

Energy

Pseudo-High

Energy

Far Detector Neutrino Events

Preliminary

pm = 2.5 GeV/c

Ehad = 4.8 GeV

U vs Z

U vs Z

X vs Y

High Energy Beam Events

May 2005 running

Not the “oscillation” data set

Far Detector Neutrino Events

Preliminary

pm = 23 GeV/c

Ehad = 6.1 GeV

U vs Z

U vs Z

X vs Y

High Energy Beam Events

May 2005 running

Not the “oscillation” data set

Far Detector Neutrino Events

Preliminary

pm = 0 GeV/c

Ehad = 2.4 GeV

U vs Z

U vs Z

X vs Y

High Energy Beam Events

May 2005 running

Not the “oscillation” data set

Far Detector Neutrino Event Distributions

Events from high energy beam

How do we know events are from NuMI beam?

Timing coincidence with spill signal

Muon angle with respect to FNAL

Cosmic muon events are well separated

Far Detector Neutrino Event Distributions

MINOS PRELIMINARY

XYZ vertex positions for reconstructed nm CC events

First NuMI Neutrino Analysis: Beam Energy Choice

Initial running is with LE beam

After ~1e20 POT perform oscillation analysis to verify we are running with the optimal beam energy

Summary

MINOS is taking beam data!

Both detectors and NuMI operating smoothly

~10k neutrinos/day in Near Detector

Beam neutrinos observed in Far Detector

NuMI beam intensity still increasing (reached 2.7e13 ppp)

First atmospheric results

Oscillation data consistent with Super-K

First test of CPT!

Initial oscillation analysis after ~1e20 POT

MINOS is performing a blind analysis

An unknown fraction of Far Detector events are hidden

Long baseline results in 2006!

The End

Backup Slides

10 cm Beam Port

Stepper Motor

& Linear Slide

Limit Switch

Beam-intercepting Ti foils (5m)

Limit Switch

Mechanical/Vacuum System

‘Bayonet’-style insertion is compact

Frame is never in the path of beam

Insertion accuracy/repeatability

Vacuum ~10-9 Torr on 30l/s ion pump

Proton

beam

Segmented Foil SEM’s

www.hep.utexas.edu/~kopp/minos/sem/

Foil Secondary Emission Monitors

Beam profile + halo measurement

Very low mass (5 m Ti)

Reduced Beam Heating problems

Ti signal lasts longer in the beam

Slide courtesy

S. Kopp

Atmospheric Neutrinos – SuperK

BEST FIT:

m2 = 2.4  10-3 eV2 (2.4)

sin2(2Θ) = 1.0 (1.02)

‘DIP’

Latest new development:

- selection of events w/ good resol’n in L/E

- provides better sensitivity to m2 !!

- can resolve characteristic dip in the

L/E distribution at the ~3 level.

Note use of linear scale!

68, 90, 99% CL intervals shown

K2K – the 1st Long-Baseline Accelerator-based Experiment

12GeV PS@KEK

beamline

39m

41.4m

Super-Kamiokande I

Outer detector

Inner detector

1885 8” PMTs

11146 20” PMTs

250km

Diagrams

courtesy

Y. Hayato

K2K – the 1st Long-Baseline Accelerator-based Experiment

107 Observed / 149.7 Expected

Based on 0.89 x 1020 p.o.t.

m2 = 2.8  10-3 eV2

sin2(2Θ) = 1.0

Plots courtesy C. Walter

Simulated Neutrino Interaction













‘u’ - view

‘v’ - view

ghost hits due to

optical summing

plane #

strip #

2005-10-21T11:09:56