# Presentation: 616401

## First MINOS Results from the NuMI Beam

- Alfons Weber (Oxford/RAL)
- for the MINOS collaboration

- Neutrino Factory Scoping Study, RAL April 2006

## Introduction to the MINOS experiment			
Overview of MINOS Physics Goals
The NuMI facility and the MINOS detectors
Near Detector and beam measurements
Selecting CC muon neutrino events
Near detector distributions and comparison with Monte Carlo 
Far detector analysis
Selecting Beam neutrino candidates
Near-Far extrapolation of the neutrino flux
Oscillation Analysis with 0.931020 POT

**Overview of MINOS Physics Goals**
**The NuMI facility and the MINOS detectors**
**Near Detector and beam measurements**
**Selecting CC muon neutrino events**
**Near detector distributions and comparison with Monte Carlo **
**Far detector analysis**
**Selecting Beam neutrino candidates**
**Near-Far extrapolation of the neutrino flux**
**Oscillation Analysis with 0.93********1020 POT**

**Overview**

## Current knowledge of atmospheric neutrino oscillations

- Current best measurements of  *Δ**m*2 and sin22*θ* from**Super-Kamiokande** (atmospheric neutrinos) and**K2K** (9x1019 POT)
- The limits (at 90% C.L.) are:
- sin22*θ* > 0.9
- 1.9 < *Δ**m*2 < 3.0 10-3eV2
- This analysis is for 9.3 1019 POT, and should provide a competitive measurement of the mixing parameters

**Allowed regions from Super-K and K2K**

## The MINOS Collaboration

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

## The MINOS Experiment

- (12 km)

**MINOS (Main Injector Neutrino Oscillation Search)**
- a long-baseline neutrino oscillation experiment:
- Neutrino beam provided by 120 GeV protons from the Fermilab Main Injector.
- Near Detector at Fermilab to measure the beam composition and energy spectrum
- Far Detector deep underground in the Soudan Mine, Minnesota, to search for evidence of oscillations

## MINOS Methodology

- Look for a deficit of νμ events at Soudan

**Unoscillated**

**Oscillated**

**ν****μ**** spectrum**

**Monte Carlo**

**Monte Carlo**

**Spectrum ratio**

## To perform the oscillation analysis, we need to predict the neutrino spectrum seen by the Far Detector in the absence of oscillations.

Want to minimise uncertainties related to beam modeling and cross-sections (nominal values are built-in to our Monte Carlo.)

Use the Near Detector data to correct the nominal Monte Carlo
beam spectrum
neutrino cross-sections

- Want to minimise uncertainties related to beam modeling and cross-sections (nominal values are built-in to our Monte Carlo.)
- Use the Near Detector data to correct the nominal Monte Carlo
- beam spectrum
- neutrino cross-sections

- Overview of the Oscillation Measurement

## Producing the neutrino beam

- 9μs spill of 120GeV protons every 2s
- 0.2 MW average beam power
- 20 1012 protons per pulse (ppp)

## The NuMI neutrino beam

| Beam | Target z position (cm) | FD Events per 1e20 pot |
| --- | --- | --- |
| LE-10 | -10 | 390 |
| pME | -100 | 970 |
| pHE | -250 | 1340 |

- LE
- pME
- pHE

- Events expected in fiducial volume

**Currently running in the LE-10 configuration**
- ~1.5 1019 POT in pME and pHE configurations early in the run for commissioning and systematics studies

## First Year of running

**Dataset used for the oscillation analysis**

**Observation of neutrinos in Near Detector!**

**Start of LE running**

**10****20**** pot!**

## The MINOS Detectors

- Detectors magnetised to 1.2 TGPS time-stamping to synch FD data to ND/Beam Flexible software triggering in DAQ PCs:    FD triggers from FNAL over IP

**Coil**

**Veto Shield**

******Far**
**Near******

**Plane installation fully completed on Aug 11, 2004**

- 5.4 kt mass,   8830m 484 steel/scintillator planes
- Divided into 2 super modules
- M64 multi-anode PMTs

- 1 kt mass,   3.84.815m282 steel and 153 scintillator plane
- Front 120 planes  Calorimeter
- Remaining planes  Spectrometer
- M16 multi-anode PMTs

## Detector Technology

**Scintillator strip**

**M64**

**M16**

**MINOS Near and Far Detectors are functionally identical: **
- 2.54cm thick magnetised steel plates
- co-extruded scintillator strips
- orthogonal orientation on alternate planes – U,V
- optical fibre readout to multi-anode PMTs

## Reconstruction of a MINOS event

## Reconstruction of a MINOS event

## Event topologies

**ν****μ**** CC Event**

**NC Event**

**ν****e** **CC Event**

**UZ**

**VZ**

**long ****μ**** track & hadronic activity at vertex**

**short, with typical EM shower profile**

**short event, often diffuse**

**3.5m**

**1.8m**

**2.3m**

**Monte Carlo**

**E****μ**** = E****shower ****+ p****μ**

**55%/********E****/GeV****      6% range, 10% curvature**

## Event selection cuts

-   CC-like events are selected in the following way:
- Event must contain at least one good reconstructed track
- The reconstructed track vertex should be within the fiducial volume of the detector:

- The fitted track should have negative charge (selects )
- Cut on likelihood-based Particle ID parameter which is used to separate CC and NC events.

- ν

**Calorimeter**

**Spectrometer**

- NEAR:1m < z < 5m (from detector front),R < 1m   from beam centre.
- FAR:z > 50cm from front face,    z > 2m from rear face, R < 3.7m from detector centre.

## Selecting CC events

**Input variables for PDF based event selection**

**Monte Carlo**

- Events selected by likelihood-based procedure, with 3 input Probability Density Functions (PDFs)
**event length in planes**
**fraction of event pulse height in the reconstructed track**
**average track pulse height per plane**** **
- Define Pμ (PNC) as the product of the three CC (NC) PDFs, at the values of these variables taken by the event

## CC selection efficiencies

- Particle ID (PID) parameter is defined:
- CC-like events are defined by *PID *> −0.2 in the FD (> −0.1 in the ND)
- NC contamination limited to low energy bins (below 1.5 GeV)
- Selection efficiency is quite flat as a function of visible energy

**CC-like**

**(87%)**

**(97%)**

**Monte****Carlo**

**PDF PID parameter distribution**

**PDF PID parameter distribution**

## Near Detector distributions

- We observe very large event rates in the Near detector (~107 events in the fiducial volume for 1020 POT)
- This provides a high statistics dataset with which we can study how well we understand the performance of the Near Detector and check the level to which our data agrees with our Monte Carlo predictions

**Reconstructed x vertex (m)**

**Reconstructed y vertex (m)**

**Coil hole**

**Detector outline**

**Fiducial region**

**Partially instrumented planes**

**Area normalised**

**Beam points down 3 degrees to reach Soudan**

**Reconstructed track angle with respect to vertical**

**Distribution of reconstructed event vertices in the x-y plane**

## Particle ID variables (LE-10 Beam)

- Calorimeter/ spectrometer boundary

**Event length**

**Track PH per plane**

**Track PH fraction**

- Particle ID variables (LE-10 Beam)

## PID parameter

- PID cut  to select CC-like events is at –0.1

**LE-10**

**pME**

**pHE**

## Energy spectra & ratios (CC-like events)

**LE-10**

**pME**

**pHE**

**LE-10**

**pME**

**pHE**

***Error envelopes shown on the plots reflect uncertainties due to cross-section modelling, beam modelling and calibration uncertainties ***

- Reconstructed Energy (GeV)

- Ratios of Data/MC

- Energy spectra & ratios (CC-like events)

## Hadron production tuning

- Agreement between data and Fluka05 Beam MC is pretty good, but by tuning the MC by fitting to hadronic xF and pT, improved agreement can be obtained.

**LE-10/185kA**

**pME/200kA**

**pHE/200kA**

- Weights applied as a function of hadronic xF and pT.

**LE-10/****Horns off**

**LE-10  events**

- Not used in the fit

## Reconstructed energy  distributions agree to within statistical uncertainties (~1-3%) 
Beam is very stable and there are no significant intensity dependent biases in event reconstruction.

- Beam is very stable and there are no significant intensity dependent biases in event reconstruction.

**Typical proton intensity ranges from 10****13**** ppp - 2.8times10****13**** ppp**

**Energy spectrum by batch**

**Energy spectrum by Month**

- Stability of the energy spectrum & reconstruction with intensity

## The agreement between low level quantities indicates that there are no obvious pathologies introduced by detector modeling and/or reconstruction.

Agreement between high level quantities is within the expected systematic uncertainties from cross-section modeling, beam modeling and calibration uncertainties (initial agreement improved after applying beam reweighting on the xF and pT of parent hadrons in the Monte Carlo)

- Agreement between high level quantities is within the expected systematic uncertainties from cross-section modeling, beam modeling and calibration uncertainties (initial agreement improved after applying beam reweighting on the xF and pT of parent hadrons in the Monte Carlo)

- Summary of ND Data/MC agreement

## Far Detector Beam Analysis

- Oscillation analysis performed using data taken in the LE-10 configuration from May 20th 2005 – December 6th 2005
- Total integrated POT: 0.931020
- Excluded periods of “bad data” – coil and HV trips, periods without accurate GPS timestamps. The effect of these cuts are small (~0.7% of our total POT)
- POT-weighted live-time of the Far detector: 98.9%

## Performing a blind analysis

- The MINOS collaboration decided to pursue a blind analysis policy for the first accelerator neutrino results
**The blinding procedure hides an unknown fraction of FarDet events based on their length and total energy deposition**.

- No blinding was applied to NearDet data
- Unknown fraction of Far Detector data was open
**performed extensive data quality checks.**

- Unblinding criteria were:
**no problems with the FarDet beam dataset (missing events, reconstruction problems,  etc.)**
**Oscillation analysis (cuts and fitting procedures) pre-defined and validated on MC; no re-tuning of cuts allowed after box opening**** **

## Selecting beam induced events

- Time stamping of the neutrino events is provided by two GPS units (located at Near and Far detector sites).
- FD Spill Trigger reads out 100μs of activity around beam spills
- Far detector neutrino events easily separated from cosmic muons (0.5 Hz) using topology

- Backgrounds estimated by applying selection algorithm on “fake” triggers taken in anti-coincidence with beam spills
**In 2.6 million “fake” triggers, 0 events survived the selection cuts (upper limit on background in open sample is 1.7 events at 90% C.L. )**

**Neutrino candidates are in 10****μ****s window**

**Time difference of neutrino interactions from beam spill**

## Vertex distributions of selected events

- Distributions consistent with neutrino interactions – no evidence of background contamination.

**Open dataset**

## Predicting the unoscillated FD spectrum

- directly use Near Detector data to perform extrapolation between Near and Far
- use Monte Carlo to provide necessary corrections due to 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
- This method is known as the **Beam Matrix** method.

## Beam Matrix Method : Near to Far extrapolation

-  Beam Matrix encapsulates the knowledge of pion 2-body decay kinematics & geometry.
-  Beam Matrix provides a very good representation of how the Far Detector spectrum relates to the near one.

## Predicted true FD spectrum

- higher than nominal FD MC in high energy tail
**	**
- expected, given that the ND  visible energy spectrum is also higher than the nominal MC in this region

**Predicted spectrum**

**Nominal MC**

**0.93********10****20**** POT**

- Predicted FD true spectrum from the Matrix Method

## Vertex distributions of selected events

- 296 selected events with a track – no evidence of background contamination.
- Distribution of selected events consistent with neutrino interactions

**Full dataset**

**Area normalised**

## Track quantities & PID parameter

**Track Length **

**Track Pulse Height per Plane**

**Particle Identification****Parameter **

**CC-like**

## Physics distributions

**y = E****shw****/(E****shw****+P****m****)**

**Muon Momentum (GeV/c)**

**Shower Energy (GeV)**

## We observe a 33% deficit of events between 0 and 30 GeV with respect to the no oscillations expectation.
Numbers are consistent for  sample and for the -only sample
The statistical significance of this effect is 5 standard deviations

- Numbers are consistent for  sample and for the -only sample
**The statistical significance of this effect is 5 standard deviations**

| Data sample | observed | expected | ratio | significance |
| --- | --- | --- | --- | --- |
| All CC-like events ( | 204 | 29815 | 0.69 | 4.1 |
|  only (<30 GeV) | 166 | 24914 | 0.67 | 4.0 |
|  only (<10 GeV) | 92 | 17711 | 0.52 | 5.0 |

- Numbers of observed and expected events

## Best-fit spectrum

## Ratio of Data/MC

## Allowed regions

## Systematic errors

- Systematic shifts in the fitted parameters have been computed with MC “fake data” samples for *Δ**m*2=0.003 eV2, sin22*θ*=0.9 for the following uncertainties:

| Uncertainty | m2 shift (eV2) | Sin22 shift |
| --- | --- | --- |
| Normalization +/- 4% | 0.63e-4 | 0.025 |
| Muon energy scale +/- 2% | 0.14e-4 | 0.020 |
| Relative Shower energy scale +/- 3% | 0.27e-4 | 0.020 |
| NC contamination +/- 30% | 0.77e-4 | 0.035 |
| CC cross-section uncertainties | 0.50e-4 | 0.016 |
| Beam uncertainty | 0.13e-4 | 0.012 |
| Intranuclear re-scattering | 0.27e-4 | 0.030 |
| Total (sum in quadrature) | 1.19e-4 | 0.063 |
| Statistical error (data) | 6.4e-4 | 0.15 |

## Summary and Conclusions

- In this talk we have presented the first accelerator neutrino oscillation results from a 0.931020 pot exposure of the MINOS far detector.
**Our result ****disfavours**** no disappearance at 5******** and is consistent with ********  oscillations with the following parameters:**

- The systematic uncertainties on this measurement are well under control and we should be able to make significant improvements in precision with a larger dataset.
- Our total exposure to date is 1.41020 pot.

## Outlook

***Δ******m*****2**** = 0.003 eV****2**

- Study neutrino/anti-neutrino oscillations
- Search for/rule out exotic phenomena:
- Sterile neutrinos,   Neutrino decay

**Improve this measurement:**
- Sensitivity at 1016 POT

**Search for sub-dominant ****ν****μ******** ****ν****e**** oscillations**

## Back-up slides

## The NUMI facility

**Design parameters:**
- 120 GeV protons from the Main Injector
- Main Injector can accept up to 6 Booster batches/cycle,
- Either 5 or 6 batches for NuMI
- 1.867 second cycle time
- 4x1013 protons/pulse
- 0.4 MW
- Single turn extraction (10ms)

## The NuMI beamline

**Primary proton line**

**Target hall **

**Decay pipe**

## Monitoring the NuMI beam

- Intensity
- Beam position
- Beam profile at the target
- Hadron and muon profiles at the end of the decay volume
- This information is then used offline to select good beam quality spills

## The MINOS Calibration Detector

-                           Eν = pμ + Ehad
-  Measured in a CERN test beam with a “mini-Minos”
** **operated in both Near and Far configurations
-  Study e/μ/hadron response of detector
-  Test MC simulation of low energy interactions
-  **Provides absolute energy scale for calibration**

**Single particle energy resolution**

**beam**

## Calibration of ND and FD response using:
Light Injection system (PMT gain)
Cosmic ray muons (strip to strip and detector to detector)
Calibration detector (overall energy scale)

Energy scale calibration:
1.9% absolute error in ND
3.5% absolute error in FD
3% relative

- Light Injection system (PMT gain)
- Cosmic ray muons (strip to strip and detector to detector)
- Calibration detector (overall energy scale)
- Energy scale calibration:
- 1.9% absolute error in ND
- 3.5% absolute error in FD
- 3% relative

- MINOS Calibration system

## Breakdown of selected events

| Cut | Events | efficiency |
| --- | --- | --- |
| All events in fiducial volume | 331 | - |
| Events with a track | 296 | 89.1% |
| Track quality cuts | 281 | 95.3% |
| PID cut (CC-like) | 204 | 72.9% |
| Track charge sign cut (negative muons only) | 186 | 91.2% |
| Reconstructed energy < 30 GeV | 166 | 89.2% |

## High rate in Near Detector results in multiple neutrino interactions per MI spill

Events are separated by topology and timing 

- Events are separated by topology and timing

**Time (us)**

**One near detector spill**

**Individual events**

**Batch structure clearly seen!**

- First Year of MINOS running

## Selected events as a function of time

- Neutrino events per P.O.T are flat as a function of time.

**Open dataset**

## Systematics

- Normalisation: 4%
-  POT counting, Near/Far selection efficiency
- Relative shower energy scale: 3%
- Inter-Detector calibration uncertainty
- Muon energy scale: 2%
- Uncertainty in dE/dX in MC
- NC contamination of CC-like sample: 30%
- From shape and normalisation of ND PID distribution
- CC cross-section uncertainties:
- MA (qel) and MA (res) -  5%
- KNO RES-DIS scaling factors - 20%
- Intranuclear rescattering: 10% shower energy scale uncertainty
- Beam uncertainty: difference between fits with weighted/unweighted MC

## Systematics : 1E22 p.o.t “Mock Data Set” 

**Mock Data**
**Nominal MC**

- To test the robustness of the method, a “fake dataset” was generated with tweaked beam/generator parameters and unknown oscillation parameters.

**True point**

**Best-fit point**

- 68,90% C.L. contours

- Beam Matrix Method yields an accurate estimation of the oscillation parameters despite the large differences between “Mock Data” and Monte Carlo (even for 1E22 protons on target!)

- Systematics : 1E22 p.o.t “Mock Data Set”

## Systematics : Test on 1E22 p.o.t Mock Data Set -  STEP A

-  MC used to correct for efficiency, purity and unsmearing quite different than the “data”.
- Since corrections are relatively small, STEP A accurately predicts the true Near Detector Spectrum.

**Nominal MC ( Black dotted line)**
**True               ( Black Line)**
**Predicted       (Black points)**

**Ratio of True/ Nominal  ( Black line)**
**Ratio of Predicted /True (Black dotted Line)**

## Systematics: Different Beam Matrix used

-     The different LE010 200 kA matrix corresponds to different beam.
-      **The Predicted Far spectrum is within 5% to the “actual” one. **
**     ****Beam Matrix Method quite robust to beam related uncertainties as well.**

- Method: Use instead of LE010 185 kA GNUMI matrix the LE010 200kA GNUMI matrix.

- NOTE: **Red dotted bands are ****± 5%.**

## Systematics : DIS cross sections changed by ±  20% fit on fake data

- Systematics : DIS cross sections changed by** **±  20% fit on fake data

## Systematics :Different Beam Matrix used, fit on fake data.

## We have investigated three other methods of deriving the FD spectrum from the ND data:

Extrapolation using the Far/Near ratio from the MC
Two independent methods of fitting to the ND data in order to derive systematic parameters that are used to reweight the FD Monte Carlo

These methods have quite different sensitivities to systematic errors, therefore comparing the results obtained with all four checks the robustness of our oscillation measurement

- Extrapolation using the Far/Near ratio from the MC
- Two independent methods of fitting to the ND data in order to derive systematic parameters that are used to reweight the FD Monte Carlo
- These methods have quite different sensitivities to systematic errors, therefore comparing the results obtained with all four checks the robustness of our oscillation measurement

**Predicted FD unoscillated spectra**

- Alternative methods for predicting the FD spectrum

## Notice that beam is pointing 3 degrees up at Soudan!

**X**

**Y**

**Z**

- Track angles

## Event generator

- (H. Gallagher, Nucl.Phys.Proc.Suppl. **112**: 188-194, 2002)
- Quasi-Elastic: dipole parametrization
- of form factors with ma=1.032 GeV/c2.
- Resonance Production:
- Rein-Seghal model for W<1.7 GeV/c2.
- (Annals Phys. **133**: 79, 1981)
- DIS: Bodek-Yang modified LO  model.
- For W<1.7 GeV tuned to electron and neutrino data in the resonance / DIS overlap region.
- (Bodek-Yang, Nucl. Phys. Proc. Suppl. **139**: 113-118, 2005 and H. Gallagher, NuINT05 Proceedings)
- Coherent Production:
- Rein-Seghal (Nucl. Phys. B **223**: 29, 1983*)*

## Shower profiles – LE-10 beam

- Fairly good agreement between data and MC
- Data showers tend to be slightly shorter and more “dense” than MC showers

## Numbers of tracks and showers

## Allowed region – primary analysis

## Allowed region – extended scale

## Systematics : DIS-Resonance region cross section factors changed by ±  20%

- Using the Beam matrix method  cross sections cancel out to a large extent.

**NEAR dis_factors +-20%**

**FAR dis_factors +-20%**

- Near Detector  Ratio of  MC to “Data” : changes are of the order of 5-6%

- Far  Detector  Ratio of  Predicted to “Data”  : changes are of the order of < 1%

## Energy spectra & Y (CC-like events) 

**These distributions shown after x****F****, p****T**** reweighting**

**Reconstructed Neutrino Energy (GeV)**

**Reconstructed Y =E****shw****/(E****shw****+E****m****)**

**LE-10**

**pME**

**pHE**

**LE-10**

**pME**

**pHE**

- Energy spectra & Y (CC-like events)

## The Beam Matrix Method

**step A)**

**step B)**

**step C)**

- NC background subtraction
- correct for selection efficiency and purity
- correct for detector response

**measured E (ND)          true E (ND)**

- Maps true E from ND to FD using
- pion decay kinematics
- beamline geometry

**true E (FD)         predicted visible E (FD)**

- add detector response
- efficiency
- background
- oscillations

## Step A, Beam Matrix Method

**1**

**2**

- Correction for purity

-  Reconstructed =>True and  Correction for efficiency