newest results from minos - university of miami · 17.12.2008 jeff dejong , iit minos, 1 newest...

17.12.2008 Jeff deJong, IIT 1MINOS,

Newest Results From MINOSNewest Results From MINOSJeff de JongJeff de Jong

(on behalf of the MINOS Collaboration)(on behalf of the MINOS Collaboration)

Illinois Institute of TechnologyIllinois Institute of TechnologyMiami 2008, Dec 16-20Miami 2008, Dec 16-20


Talk Outline Introduction to MINOS/NuMI Recent Results from MINOS

Charge Current:

dissappearance results

Neutral Current: s Sterile search results

Charge Current: e appearance sensitivity studies

Other ongoing MINOS studies(not discussed here)●

vs

ie CPT

● atmospheric neutrinos● Cosmic rays● neutrino flux/crosssection measurements using ND


MINOS Collaboration

Argonne – Athens – Benedictine – Brookhaven – Caltech – Cambridge-Campinas Diderot – Fermilab – Harvard -IIT – Indiana – ITEP - Lebedev – LLNL Minnesota – Twin Cities –

Minnesota/Duluth – Oxford - Pittsburgh Rutherford Sao Paulo – South Carolina – Stanford Sussex - Texas A&M – Texas/Austin Tufts – UCL -Warsaw- Western Washington – William & Mary

172 Physicists from 31 Institutions


MINOS Overview• Main Injector Neutrino

Oscillation Search• Neutrinos at the Main Injector

(NuMI) beam at Fermilab Two detectors Near detector at Fermilab

measure beam composition

energy spectrum Far detector in Minnesota

search for evidence of oscillations


NuMI / Neutrino Production

● Low Energy Beam composition(%)92.9

5.8

,1.3 ee

●Neutrino beam energy is tunable by modifying the target position wrt the horn.● Run in LE configuration as peak is closer to expected oscillation minimum.

● two magnetic focusing horns guide positive mesons down the decay pipe

Beam Stats.~ 275 kW,1018 POT/day,3x1013POT/10 s spill


Integrated Protons on Target

Shut

down

1st Results Dataset (1.27x1020 POTs LE10)

Additional 1.98x1020 POTs LE10

High Energy Runs

Run I Run II

Shut

down

Run III

Ongoing LE10 Running (>1.5×1020 POTs)

1st Results Dataset (1.27x1020 POTs LE10)

Additional 1.98x1020 POTs LE10

High Energy Runs

Ongoing LE10 Running (>2.5×1020 POTs)

●Jan 21,2005 First interaction in ND. CC

NC


MINOS Detectors

Near DetectorNear Detector

Far DetectorFar Detector

Detector Near FarDepth ~100m ~700mFrom Target ~ 1 km ~735 km

0.98 5.4Mass (kTon)

Two functionally identical detectors ● iron/scintillator tracking calorimeter● magnetized 1” steel planes <B>~1.3T● Scintillating strips 1.0cm x 4.1 cm● multianode PMT readout● GPS time stamping to synchronize FD to ND

●two detectors minimizes systematics due to flux/coss section uncertainties


Neutrino Interactions

ν ν

γγ

Z

π0

N(+X)

νµ µ

W

N X

νe e

W

N X

νµ CC Event NC Event ν e CC Event


Neutrino Interactions

long µ track+ hadronic activity at vertex

νµ CC EventUZ

VZ

3.5m

short event, often diffuse

NC Event

1.8m

short, with typical EM shower profile

ν e CC Event

2.3m


Charged Current Analysis of 3.36×1020 POT of MINOS Data

Precision measurement of |∆m322| and sin22θ

23

Phys Rev Lett 101 131802 (2008)

CC Analysis


Particle ID

CC/NC separation using a nearest neighbour algorithm (kNN) with 4 inputs

Track Length(# of planes)●For Hits on Track

Mean Pulse Height Fluxuation in Pulse Height Transverse Track Profile

●Neutral Current contamination increases at low energy/short tracks


Near Far ExtrapolationDue to different solid angles Far Detector Spectrum != Near Detector SpectrumUse MonteCarlo to provide corrections to the observed ND spectrum

FD

Decay Pipe

π+Target

NDp

Encode the pion decay kinematics and angular acceptance into a beam transfer matrix

● convert ND spectrum to FD


Systematic Uncertainties

● Relative (ND to FD) normalisation (4%)● Absolute hadronic energy scale (10%)● NC background (50%)

Effects of uncertainties estimated by fitting systematically shifted MC in place of data.

Note: analysis is still statistically limited!

Three largest uncertainties included as penalty terms in fit to data :

€

χ2= (2(ei−oi)+2nbins

∑ oiln(oi/ei))+∆sj

2

σsj

2nsys

∑


Far Detector CC spectrum

● Significant energydependent suppression of

CC events observed

Best Fit (constrained) parameters :

2flavor oscillations

|∆m2| = (2.43±0.13) x 103 eV2 (68% C.L.)sin2(2θ) > 0.90 (90% C.L.)2/ndof=90/97

Best Fit (unconstrained) parameters

|∆m2| = (2.33) x 103 eV2

sin2(2θ) =1.07 2/ndof=0.6

Observed 848/ Expect 1065±60 (syst).

P=sin2 2sin2

1.27m2LE


Other Interpretations

Decay

Decoherence

V. Barger et al., PRL82:2640(1999)

2/ndof=104/97 2=14Disfavored at 3.7

2/ndof=123/97 2=33Disfacvored at 5.7

G.L. Fogli et al, PRD 67:093006(2003)

P=sin2cos2 e−L2E 2

P=1−sin22

21−e

−2L2E


NC Analysis

Neutral Current Analysis of 2.46×1020 POT of MINOS Data

Looking for sterile neutrino mixing Phys Rev Lett 101 221804 (2008)


NC Motivation● Given the standard 3flavor oscilllation model, the extrapolated near detector neutral current rate at the FD should match the total observed Neutral Current (NC) rate.

● An observed deficit of NC events at the Far Detector could indicate oscillation to sterile neutrinos.(which don't interact at all)

●Compare the NC energy spectrum with the expectation of standard 3flavor oscillations●Fix the oscillation parameters at :

Reminder: For NC events we expect showers and no tracks, or very short tracks.(e events will fall into NC sample)

sin2(223)=1.0 and m232=2.43x103eV2 ⟵ MINOS 2008 CC Result

=0.61 and m221=7.59x105eV2 ⟵ KAMLAND+SNO

=0 or 0.21 and NMH) ⟵ From Chooz Limit


NC Event Selection

Main background: inelastic (highy)νμ CC events

Excluded

Excluded

Excluded

Cleaned Near Detector Data Set

FD Same cuts as ND: < 60 planes; no track or no track

beyond 5 planes from shower


NC ResultsNC Far Detector SpectrumNC Far Detector SpectrumShown for Shown for 1313=0 and the Chooz Limit=0 and the Chooz Limit

● Assume 1 sterile neutrino and that mixing occurs at one value of m2

● Far detector background predictions depends on oscillation parameters.●Survival and oscillation probabilities

●Fraction of all dissappearing events going to a sterile neutrino

)/27.1(sin)(

)/27.1(sin1)(22

22

ELmP

ELmP

ss ∆α=ν−ν

∆α−=ν−ν

µ

µµµ

f s=P s

1−P

w/o e appearance with e appearancef s=0.28−0.28

0.25statsyst f s0.68 90%C.L.

f s=0.43−0.270.23statsyst

f s0.80 90%C.L. Results Consistent with no deficit in NC rate !!


e CC appearance Analysis

e CC appearance SensititiesResults expected in a few months


e CC appearanceWorking toward a measurement of sin2(213)

selection is a neural network based on characteristics of EM showers.

e spectrum is background dominatedDominant backgrounds are short CC/NC

events

Data driven systematic uncertainty currently at ~ 10% :

Pe=sin2213sin

2223sin21.27m13

2 L /E

hope is to reduce this to 5% in near future

With 3.25x1020 protons (ie current exposure) at the Chooz limit we expect 12 signal and 42 background events.

MINOS can improve CHOOZ limit by a factor of 2


Summary Slide

● Updated results for CC dissappearance have been presented

|∆m2| = (2.43±0.13) x 103 eV2 (68% C.L.)sin2(2θ) > 0.90 (90% C.L.)

● First results for NC dissappearance/sterile searches: (w/o ne appearance)f s=0.28−0.28

0.25statsyst f s0.68 90%C.L.

● MINOS is on the verge of having its first e appearance measurement


Backup Slides


PID parameters

newest results from minos - university of miami · 17.12.2008 jeff dejong , iit minos, 1 newest...

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