# Presentation: 555972

## Zelimir Djurcic
Physics Department
Columbia University

***Physics Department***
***Columbia University***

***  ******Status of MiniBooNE***
***Experiment***

***   ******WIN07, Calcutta***
***January 15-20,2007***

## MiniBooNE 

**MiniBooNE consists of about 70 scientists from 16 institutions. **

-    Y. Liu, D.Perevalov, I. Stancu   *Alabama*
-    S. Koutsoliotas   *Bucknell*
-    R.A. Johnson, J.L. Raaf   *Cincinnati*
-    T. Hart, R.H. Nelson, M.Tzanov, E.D. Zimmerman,
-     M.Wilking  *Colorado*
-    A. Aguilar-Arevalo, L.Bugel, L. Coney,
-   **J.M. Conrad**, Z. Djurcic, J. Monroe,
-    K. Mahn, D. Schmitz, M.H. Shaevitz, M. Sorel,
-    G.P. Zeller   *Columbia*
-    D. Smith   *Embry Riddle*

-    L.Bartoszek, C. Bhat, S J. Brice, B.C. Brown,
-    D.A. Finley, R. Ford, F.G.Garcia,
-    P. Kasper, T. Kobilarcik, I. Kourbanis,
-    A. Malensek, W. Marsh, P. Martin, F. Mills,
-    C. Moore, E. Prebys,
-    A.D. Russell, P. Spentzouris, R. Stefanski,
-    T. Williams   *Fermilab*
-     D. C. Cox, A. Green, T.Katori, H.-O. Meyer, C. Polly,
-     R. Tayloe   *Indiana*
-    G.T. Garvey, C. Green, **W.C. Louis**, G.McGregor,
-    S.McKenney, G.B. Mills, H. Ray, V. Sandberg,
-    B. Sapp, R. Schirato, R. Van de Water,
-    D.H. White  *Los Alamos*
-    R. Imlay, W. Metcalf, S. Ouedraogo, M. Sung,
-    M.O. Wascko *Louisiana State *
-    J. Cao, Y. Liu, B.P. Roe, H. Yang   *Michigan*
-    A.O. Bazarko, P.D. Meyers, R.B. Patterson,
-    F.C. Shoemaker, H.A.Tanaka   *Princeton*
-    A. Currioni, B.T. Fleming *Yale*
*   *P. Nienaber St. *Mary’s U. of Minnesota*
*   *E. Hawker *Western Illinois U.*
-    J.Link *Virginia State U.*

**MiniBooNE **
**Collaboration**

## Before MiniBooNE

- Zelimir Djurcic-WIN2007

## Before MiniBooNE: The LSND Experiment

- LSND took data from 1993-98  - 49,000 Coulombs of protons  - L = 30m and 20 < E< 53 MeV

**Saw an excess of********e**** :****87.9 ****± 22.4 ± 6.0 events.**
**With an oscillation probability of ****(0.264 ± 0.067 ± 0.045)%.**
**3.8 ******** significance for excess.**

***Oscillations?***

**Before MiniBooNE: The LSND Experiment**

- Signal:    p  e+ n
- 			 n p  d (2.2MeV)

- Zelimir Djurcic-WIN2007

## Current Oscillation Status

- m2 = 2.510-3 eV2

- Homestake, Sage, Gallex, Super-K
- SNO, KamLAND
- m2 = 8.210-5 eV2

- This signal looks very different
- from the others...

-  Much higher m2 = 0.1 – 10 eV2
-  Much smaller mixing angle
-  Only one experiment!

**Current Oscillation Status**

- In SM there are
- only 3 neutrinos

- Zelimir Djurcic-WIN2007

**Notes:**
needs allowed region plot

## Want the same L/E

- Want higher statistics
- Want different systematics
- Want different signal signature and backgrounds

- Fit to oscillation hypothesis

- Backgrounds

**Confirming or Refuting LSND**

**Need definitive study of ****************e**** at high ********m****2**** ...  MiniBooNE **

- Zelimir Djurcic-WIN2007

## MiniBooNE

***(******Boo******ster****** N******eutrino****** E******xperiment)***

- Zelimir Djurcic-WIN2007

## Search for e appearance in  beam

**magnetic horn: ****meson focusing**

**decay region: **
****** ******** ************ ****,  K ******** **********

**absorber: ****stops undecayed mesons**

**“****little muon **
**      ****counters:” **
**         ****measure K flux **
**         ****in-situ**

********** →********e****?**

- 50 m decay pipe

- magnetic focusing horn

- FNAL 8 GeV Beamline

**Search for ********e**** appearance in ************ beam**

**************e ****???**

- Use protons from the 8 GeV booster  Neutrino Beam      <E>~ 1 GeV

**MiniBooNE Detector:**
**12m diameter sphere**
**950000 liters of oil ****(CH****2****)**
**1280 inner PMTs**
**240 veto PMTs**

- Zelimir Djurcic-WIN2007

## Few words on:

***-Neutrino Flux***
***-Cross-section***
***-Detector Modeling***

- Zelimir Djurcic-WIN2007

## Flux at MiniBooNE Detector

********
** ****mainly from**** ************ ******** ******************
-  **<E********> ~ 700 MeV**

- predicted flux

**********Flux at MiniBooNE Detector**

- Flux simulation uses Geant4 Monte Carlo
- Meson production is based on Sanford-Wang parameterization of p-Be interaction cross-section.

- E910: , K production @ 6, 12, 18 GeV
-      w/thin Be target
- HARP: , K production @ 8 GeV
-      w/ 5, 50, 100%  thick Be target

## Low Energy  Cross Sections

**MINOS, NuMI**

**K2K, NOvA**

**MiniBooNE, T2K**

**Super-K atmospheric ******

**Low Energy ******** Cross Sections**

- Imperative is to precisely
- predict signal & bkgd rates
- for future oscillation experiments
- We need data on nuclear targets!
- (most past data on H2, D2)

**Current cross-section studies devoted to understanding of the backgrounds in the MiniBooNE appearance signal.**

## Neutrino Interactions in the Detector

**Neutrino Interactions in the Detector**

******e**** ****n ******** e****-**** ****p**

**We are looking for ****************e ****:**

- Current Collected data:
- 700k neutrino candidates (before analysis
- cuts) for 7 x 1020 protons on target (p.o.t.)

**If LSND is correct, we expect several hundred ********e**** (after analysis cuts) from  for ****************e ****oscillations.**

-   **48% QE**
** ****31% CC ********+**
** ****1% NC elastic**
-  **8% NC ********0**
-  **5% CC ********0**
-  4**% NC ********+/-**
-  **4% multi-******

**NUANCE MC generator converts the flux into event rates in MiniBooNE detector**

- Zelimir Djurcic-WIN2007

## Detector Modeling

- Detector (optical) model defines how light of generated event is propagated and detected in MiniBooNE detector

- Sources of light: Cerenkov (prompt, directional cone),and scintillation+fluorescence of oil (delayed, isotropic)

- Propagation of light: absorption, scattering (Rayleigh and Raman) and reflection at walls, PMT faces, etc.

**Strategy to verify model:**
- External Measurements: emission, absorption of oil, PMT properties.
- Calibration samples: Laser flasks, Michel electrons, NC elastic events.
- Validation samples: Cosmic muons (tracker and cubes).

- Zelimir Djurcic-WIN2007

## Energy Calibration

** ****Michel electrons  from ******** decay**:
- provide E calibration at low energy **(52.8 MeV),**
- good monitor of light transmission, electron PID

******0**** mass peak**: energy scale & resolution
- at medium energy **(135 MeV),** reconstruction

- We have calibration sources spanning wide range of energies and all event types !

- 12%
- E res
-  at
- 52.8 MeV

**Energy Calibration**

**      ****cosmic ray ******** + tracker + cubes**:
-     energy scale & resolution at high energy
**(100-800 MeV),** cross-checks track reconstruction

- provides  tracks of
-  known length → E

**PRELIMINARY**

## How to Detect and Reconstruct

***Neutrino Events***

- Zelimir Djurcic-WIN2007

## Detector Operation

- Main trigger is an accelerator signal indicating a beam spill.
- Information is read out in 19.2 s interval covering arrival of beam
- and requests of various triggers (laser, random strobe, cosmic...).

**Detector Operation**

- The rate of neutrino
- candidates was constant:
- 1.089 7 x 10-15 /P.O.T.

- Zelimir Djurcic-WIN2007

## Detector Operation and Event reconstruction

- To reconstruct an event:
- -Separate hits in beam window by time into sub-events of related hits
- -Reconstruction package maximizes likelihood of observed charge and time distribution of PMT hits to find track position, direction and energy (from the charge in the cone) for each sub-event

- No high level analysis needed to see neutrino events

- Backgrounds: cosmic muons and decay electrons

- ->Simple cuts reduce non-beam backgrounds to ~10-3

- Electronics continuously record charges and times of PMT hits.

- Zelimir Djurcic-WIN2007

## Particle Identification

******0**** ****→**** ******

**Michel e****-**
**candidate**

**beam ******
**candidate**

**beam ********0**
**candidate**

- Čerenkov rings provide primary means of identifying
-       products of  interactions in the detector

********** ****n ******** ********-**** p**

******e**** ****n ******** e****-**** ****p**

********** ****p ******** ************ p**** ********0**

**n          n**

**Particle Identification**

- Zelimir Djurcic-WIN2007

## Particle Identification II

**Search for oscillation**** **
******e**** ****n ******** e****-**** ****p**
**events is by detection of single electron like-rings, based on Čerenkov**** ****ring profile.**

**muon**

**Angular distributions of PMT **
**hits relative to track direction:**

**electron**

**PRELIMINARY**

## Signal Separation from Background

**Reducible**
**NC ********0 ****(1 or 2 e-like rings)**
******N******** decay (1 e-like ring)**
**Single ring ******** events**

**Irreducible**
**Intrinsic ********e**** events in **
**beam from K/******** decay**

- 0→

- Signal

- N

**Search for O(****10****2****) ********e**** oscillation events in O(****10****5****) ************ unoscillated events **

**Backgrounds**

## Background Rejection and Blind Analysis

**for reducible background**

**“****Simple” cuts+Likelihood****: easy to understand**

**Boosted decision trees****: maximize sensitivity**

**Background Rejection and Blind Analysis**

**MiniBooNE is performing a blind analysis:**

- We do not look into the data region where the oscillation candidates
- are expected (“closed box”).
- We are allowed to use:
- Some of the info in all of the data
- All of the info in some of the data
- (But NOT all of the info in all of the data)

- Zelimir Djurcic-WIN2007

## Boosting PID Algorithm 

- Go through all PID variables and find best
-      variable and value to split events.
- For each of the two subsets repeat
-      the process
- Proceeding in this way a tree is built.
- Ending nodes are called leaves.
- After the tree is built, additional trees
-      are built with the leaves re-weighted.
- The process is repeated until best S/B
-       separation is achieved.
-  PID output is a sum of event scores from
-       all trees (score=1 for S leaf, -1 for B leaf).

**Boosting PID Algorithm**** **

**Boosted Decision Trees at MiniBooNE:**
**Use about 200 input variables to train the trees**
**-target specific backgrounds**
**-target all backgrounds generically**

- Boosting Decision Tree

**Muons**

**Electrons**

**PRELIMINARY**

**Reference NIM A 543 (2005) 577.**

- Zelimir Djurcic-WIN2007

## Likelihood Approach

**Apply likelihood fits to three hypotheses:**
**-single electron track**
**-single muon track**
**-two electron-like rings (********0 ****event hypothesis )**

**Form likelihood differences using minimized –logL**
**quantities:      **log(Le/L) and log(Le/L)

**Compare observed light distribution to fit prediction:**
**Does the track actually look like an electron?**

**log(L****e****/L********)**

- log(Le/L)<0** ********-like events**

- log(Le/L)>0** e-like events**

**PRELIMINARY**

- Zelimir Djurcic-WIN2007

## CCQE and 0 Analysis

- Zelimir Djurcic-WIN2007

## MiniBooNE Quasi-Elastic Data

*l*

- CCQE events are used because one can use CCQE kinematics to reconstruct the neutrino energy** **– one can look at **neutrino energy spectra**
**We are looking for an oscillation signal in an *****E************QE***** distribution of electron       events**
**One can use an *****E************QE****** *****distribution of muon events to understand our             models**

****

-   measure visible E
-   and  from mostly
-  Čerenkov () + some
-   scintillation light (*p*)

- 90% purity sample
- Main bkgd: CC+
- (+ absorbed)

**p**

****

**n**

- Scintillation

- Cerenkov **1**

- 12C

- Cerenkov **2**

**e**

- 

**Compare data **
**to the Smith Moniz **
**model implemented **
**in NUANCE for **** **
**CCQE events**

-  n → - p

## MiniBooNE Quasi-Elastic Data

- of the momentum transfer, Q2
- Similar effects have been seen in other
- channels and by other experiments
- Given the Fermi gas model approximation
- used one can imagine deficiencies –            particularly in the low  Q2 (very forward)      kinematic region
- Use  data sample to adjust available
- parameters in present model to reproduce data: only  – e differences are due to lepton mass effects,  vs. e
- With the high statistics and         resolutions attainable at MiniBooNE, the      MiniBooNE data will be used in the future
- to carefully study this and other models
- of CCQE interactions

**MiniBooNE Quasi-Elastic Data**

- Zelimir Djurcic-WIN2007

## 0 ’s Background Determination

- e appearance: ****0 production important because background to →e

- 0→

- Signal

- N

- Reconstruction of  π0  results in excellent Data/MC agreement.
- We use Data to reweight (i.e. tune) NUANCE rate prediction as a function of  π0 momentum.

**PRELIMINARY**

- We measure rate of π0 in the data sample out of the oscillation region
- and extrapolate it into the oscillation region.

## Data Un-smearing and efficiency correction

- MC is used to unsmear the data:

- In bins of true momentum vs. reconstructed momentum, count MC events, over BG, in the signal window.
- Divide by the total number of π0 events generated in that true momentum bin.
- Invert the matrix.
- Perform a BG subtraction on the data in each reconstructed momentum bins.
- Multiply the data vector by the MC unsmearing Matrix

- Monte Carlo Events Passing Analysis Cuts

- All events

- Events with no π0

**Data Un-smearing and efficiency correction**

## The Corrected Data Distribution

- The corrected π0 momentum distribution is softer than the default Monte Carlo.  The normalization discrepancy is across all interaction channels in MiniBooNE.

- From this distribution we derive a reweighting function for Monte Carlo events.

- Ratio of  data and MC points scaled to equal numbers of events.

- MC: Generated distribution.
- Data: Corrected to true
-          momentum and
-          100% efficiency.

- Zelimir Djurcic-WIN2007

## Reweighting improves data/MC agreement.

- The plots are:
-  Decay opening angle
-  Energy of high energy γ
-  Energy of low energy γ
-  π angle wrt the beam
- The disagreement cos θπ may be due to coherent π0 production which we fit for.

**Reweighting MC to Data**

- Zelimir Djurcic-WIN2007

## The Resulting π0 MisID Distribution

- The resulting misID distribution is softer in *E*ν QE.
- Also there  are less misID events per produced π0 than in the default Monte Carlo.
- The error on misID yield is well below the 10% target.
- This is not the final PID cut set!

**PRELIMINARY**

- Zelimir Djurcic-WIN2007

## Cross-Checks

- Zelimir Djurcic-WIN2007

## Important Cross-check... 

- ... comes from NuMI events detected in MiniBooNE detector!

- MiniBooNE

**D**e**cay Pipe**

**Beam Absorber**

- We get e ,  , 0 , +/- ,   ,etc. events
- from NuMI in MiniBooNE detector, all
- mixed together           **Use them to check**
**our ********e**** reconstruction and PID separation!**

- Remember that MiniBooNE
- conducts a blind data
- analysis! We do not look in
- MiniBooNE data region
-  where the osc. e are
- expected...

- The beam at MiniBooNE from NuMI is significantly enhanced in e from K decay because of the off-axis position.

- NuMI events cover whole energy region relevant to e osc. analysis at MiniBooNE.

****

## Example of use of the events from NuMI beam 

**Boosted Decision Tree**

**Likelihood Ratios**

- e/

- e/

**PRELIMINARY**

**PRELIMINARY**

**Data/MC agree through background and signal regions**

**PRELIMINARY**

## Appearance Signal 

***and Backgrounds***

- Zelimir Djurcic-WIN2007

## Oscillation e

- Arbitrary Units

- Oscillation e
- Example (fake)
- oscillation signal
-  m2 = 1 eV2
- sin22 = 0.004
- Fit for excess as
- function of
- reconstructed e
- energy

**Appearance Signal and Backgrounds**

**PRELIMINARY**

- Zelimir Djurcic-WIN2007

## MisID 

- Arbitrary Units

**Appearance Signal and Backgrounds**

- MisID 
- of these......
- ~83% 0
- Only ~1% of 0s are misIDed
- Determined by clean 0 measurement
- ~7%   decay
- Use clean 0 measurement to estimate  production
- ~10% other
- Use  CCQE rate to normalize and MC for shape

**PRELIMINARY**

- Zelimir Djurcic-WIN2007

## e from +

- Arbitrary Units

**Appearance Signal and Backgrounds**

- e from +
- Measured with  CCQE sample
- Same parent + kinematics
- Most important low E background
- Very highly constrained (a few percent)

**PRELIMINARY**

- Zelimir Djurcic-WIN2007

## e from K+

- Arbitrary Units

**Appearance Signal and Backgrounds**

- e from K+
- Use High energy e and  to normalize
- Use kaon production data for shape

**PRELIMINARY**

- Zelimir Djurcic-WIN2007

## High energy e 

- Arbitrary Units

**Appearance Signal and Backgrounds**

- High energy e
- data
- Events below 1.5 GeV still in closed box (blind analysis)

**PRELIMINARY**

- Zelimir Djurcic-WIN2007

##       

**Combined fit constrains uncertainties common to ************ ****and ********e**

- 2=I,J(OI-PI)(CIJ)-1(OJ-PJ)

- Systematic error matrix
- CIJ includes estimated
- systematic uncertainties

-       

- CIJ =

********

**************e**

**************e**

******e**

**PRELIMINARY**

- PI =PI (sin2(2),m2)

- Scan sin2(2)e,m2,with
- sin2(2)x=0; calculate
- 2 value over ande
- bins:

- Zelimir Djurcic-WIN2007

## Evaluating Systematics

- Reconstructed visible muon energy (left) muon neutrino energy (right)  using CCQE data.

- Error bands show both statistical
- and systematic errors

**Evaluating Systematics**

**PRELIMINARY**

- Zelimir Djurcic-WIN2007

## MiniBooNE Oscillation Sensitivity

- LSND best fit sin22 = 0.003 m2 = 1.2 eV2

**MiniBooNE Oscillation Sensitivity**

- 

- MiniBooNE aims to cover
- LSND region.
- We are currently
- finalizing work on systematic
- error (i.e. error matrix)
- that combines the error sources
- (flux,  or measured rate, detector
- modeling) of signal and
- the background components
- to predict sensitivity to
- oscillation signal

- Zelimir Djurcic-WIN2007

## Total accumulated dataset 7.5 x 1020 POT, 

- world’s largest dataset in this energy range.
- Jan 2006: Started running with antineutrinos.
- Detected NuMI neutrinos – using in analysis.
- Oscillation Analysis progress: we are preparing
- to open the closed “oscillation box”.

**Summary**

- Zelimir Djurcic-WIN2007

## Backup Slides

- Zelimir Djurcic-WIN2007

## Explaining the LSND result

- RH neutrinos that don’t interact (Weak == LH only)
- CPT Violation
- 3 neutrino model,  manti-2 > m2
- Run in neutrino, anti-neutrino mode, compare measured oscillation probability
- Mass Varying Neutrinos
- Mass of neutrinos depends on medium through which it travels
- Lorentz Violation
- Oscillations depend on direction of propagation
- Oscillations explained by small Lorentz violation
- Don’t need to introduce neutrino mass for oscillations!
- Look for sidereal variations in oscillation probability

**Explaining the LSND result**

- Zelimir Djurcic-WIN2007

## World p+Be Measurements

**World p+Be Measurements**

- E910: , K production @ 6, 12, 18 GeV w/thin Be     	   target
- HARP: , K production @ 8 GeV w/ 5, 50, 100%  thick Be target

- Zelimir Djurcic-WIN2007

## HARP Results

- kinematic boundary
- of HARP measurement
- at exactly 8.9 GeV/c

-  black boxes are the distribution of + which decay to a  that **passes through the MiniBooNE detector**

**HARP Results**

-  HARP (CERN)
- Data taken with MiniBooNE target slugs      using 8 GeV beam
- Results on thin target just added (Apr06).

- Further improvement in flux prediction expected soon with HARP thick target and K data

## About NUANCE

- Total cross-sections are then the sum of all relevant exclusive channels
- Nuclear effects of hadrons propagating through the nucleus are considered to give you an expected final state condition
- The most critical exclusive channel for the MiniBooNE oscillation search is the
**charged-current quasi-elastic** interaction
- NUANCE models CCQE events using the relativistic Fermi gas model of Smith and Moniz as a framework
- The next most critical exclusive channels are the **NC production of ****NC ********0****'s **
- NUANCE uses the resonant and coherent p0 production models of Rein and Sehgal

**About NUANCE**

- Zelimir Djurcic-WIN2007

## NuMI events at MiniBooNE 

- NuMI ’s sprayed in all directions.
*K* and  decays at off-axis angle:

**Decay Pipe**

*p* beam

- , *K*

**MiniBooNE**

- Opportunity to check the /*K* ratio of yields off the target.

- 

- ~110mrad to MiniBooNE

**NuMI events at MiniBooNE **

- Zelimir Djurcic-WIN2007

## Production of the 0 ’s

- Resonant 0 production
-  N              N=(p,n)
-                     0 N’

- Coherent 0 production
-  A   A 0

- 0→

**In addition to its primary decay ********N****, **
**the ******** resonance has a branching fraction **
**of 0.56% to ****N******** final state.**

- e appearance: ****0 production important because background to →e

- 0→

- Signal

- N

- Zelimir Djurcic-WIN2007

## Coherent Fit Effect

- Reweighted

- Unweighted

- The fit coherent fraction is higher after reweighting.
- This was expected based on the additional peaking in the reweighted cos θ distribution.
- The reweighted fit does much better in the important forward region.

- Fit coherent, resonant, and background components to the data

**Coherent Fit Effect**

- Zelimir Djurcic-WIN2007