# Presentation: 802784

## MiniBooNE : Current Status

- Heather Ray
- _[hray@fnal.gov](mailto:hray@fnal.gov)_
- Los Alamos National Lab

## Outline

-  Motivation
-  MiniBooNE
-  Beamline, Horn, Target, Tank
-  Steps to Analysis
-  Event Rate / Flux Predictions
-  Calibrations
-  PID
-  MiniBooNE Physics
-   CCQE
-  CC+
-  NC 0
-  NC Elastic

-    See Janet’s talk
-   Tuesday!

- H. Ray

- 5/23/05

## Current Oscillation Status

- Solar 
- Deficit of e from 
- m2 ~ 8x10-5 eV2
- Atmospheric 
- Zenith angle deficit of 
- m2 ~ 2x10-3 eV2
- LSND Accelerator Result
- Excess of anti-e in anti- beam
- m2 ~ 0.1 to 10 eV2

- P = Sin22 Sin2(1.27 m2 L/E)

- Need ~same L/E, different systematics

- H. Ray

- 5/23/05

## Beam, Horn, Target

- 8 GeV proton beam
-  1.6 s pulse, 5 Hz rate from Booster
-  p + Be  mesons
-  Mesons focused by magnetic horn
-  focusing increases  flux by factor of 6
- allow , anti- running
-  Mesons  DIF 
- E ~ 700 MeV, L ~ 541 m (L/E ~ 0.77 m/MeV)

**Primary (protons)**

**Secondary (mesons)**

**Tertiary (neutrinos)**

- H. Ray

- 5/23/05

## MiniBooNE Detector

- 800 Ton, 12 m diameter sphere
- Non-scintillating mineral oil
- Two regions
- Inner light-tight region, 1280 pmts (10% coverage)
- Optically isolated outer veto-region, 240 pmts
- Signature
- Cerenkov and Scintillation
- MiniBooNE vs LSND
- Energy of beam : 8 GeV vs 800 MeV
-  : DIF vs DAR
- Oil : non-scint, vs scint
- Backgrounds : mis-ID vs cosmics

- H. Ray

- 5/23/05

## Event Rate/Flux Predictions

-   flux
-  +-> + 
- Intrinsic e flux
- From +, K+, K0L
- ~0.4% of  flux
- comparable to osc signal!
- E910
- , K production @ 6, 12, 18 GeV
- w/thin Be target
- HARP
- , K production @ 8 GeV w/ 5, 50, 100%  thick Be target
- LMC spectrometer
- K decays produce wider angle    than  decays
-  scintillating fiber tracker

- From  decay
- From K decay

- Momentum of  at 7 degrees

- LMC 
- candidate event

- H. Ray

- 5/23/05

## Calibrations

- Laser Flasks (4)
- Measure tube Q, timing response
- Change I = study PMT, oil
- Muon tracker
- Track dir + entry point = test track reconstruction in tank
- Cube System (7)
- Optically isolated scint. cubes
- + tracker = identify cosmic , michel ele of known position for E calibration
- Energy Calibrations
- Michel Electrons : fix detector E scale, 14.8% E reconstruction @ 50 MeV
- 0 : mass peak, E scale and resolution at medium E

- Electron samples

- H. Ray

- 5/23/05

## PID

- 0 candidate

-  candidate

- Michel e from  decay

- Identify events using hit topology
- Use a “boosted tree” algorithm to separate e, mu, pi, delta
- More stable than ANN in performance and sensitivity to MC optical model
- PID Vars
- Reconstructed physical observables
- Track length, particle production angle relative to beam direction
- Auxiliary quantities
- Timing, charge related : early/prompt/late hit fractions, charge likelihood
- Geometric quantities
- Distance to wall

- Nuc. Inst and Meth A, Vol 543/2-3

- H. Ray

- 5/23/05

## Physics Intro

- >570K neutrino events to date, > 1 million expected
- ~222K CCQE
- ~141K CC +

- ~90K NC Elastic
- ~39K NC 0

- (CCQE)

- (NCE)

- (CC +)

- (NC 0)

- H. Ray

- 5/23/05

##  CCQE Events

- Relevance
- Largest class of evts; use to validate flux,  predictions
- Similar kin and cross section as e signal in appearance
- Intrinsic e bgd due to  decay can be constrained
- Sensitive to  disappearance for m2 ~0.1 - 10 eV2
- Event Selection
- Use Fisher discriminant to isolate events with -like Cerenkov ring in final state
- 80% purity, 55% efficiency
- Use of PID outputs provide 94% pure sample (in progress)
- Preliminary comparisons between measured distributions and MC expectations
- Ex: Q2 (sensitive to nuclear effects such as Pauli blocking, nuclear shadowing)

- H. Ray

- 5/23/05

##  CCQE Events

- Red error bands
- Flux errors
- + production, will be measured to 5% with HARP
- Cross section errors
- CCQE from axial mass uncertainty, threshold effects, Pauli blocking
- Yellow variation bands
- Flux, Cross section, Optical Model variation
- Optical model NOT 1 sigma, reflect current uncertainty on optical model parameters
- Data points
- ~ 50% of pot to date

- H. Ray

- 5/23/05

## Relevance
Primary background to CCQE evts/analysis
All previous measurements at bubble                            chambers, 7000 total evts, all on light                            targets, few measurements at low E
Use for sep osc measurement
Event Selection
At least 2 Michels, 
parent neutrino event in beam spill
Separate into near and far 
Michels based on distance to 
muon track
Close Michels from -
- capture on C
 = 20261.5 ns
Far michels from +
 = 21970.04 ns

- e-

- Relevance
- Primary background to CCQE evts/analysis
- All previous measurements at bubble                            chambers, 7000 total evts, all on light                            targets, few measurements at low E
- Use for sep osc measurement
- Event Selection
- At least 2 Michels,
- parent neutrino event in beam spill
- Separate into near and far
- Michels based on distance to
- muon track
- Close Michels from -
- - capture on C
-  = 20261.5 ns
- Far michels from +
-  = 21970.04 ns

- CC+ Events ..

- 

- +

- -

- +

- e+

- 2218±15 ns

- 2057±14 ns

- H. Ray

- 5/23/05

## CC+ Events

- Simple reconstruction (for now)
- Assume events are QE with Delta, instead of having recoil nucelon
- Don’t use pion information in reconstruction

- W

- W

- 

- 

- 

- 

- N

- N

- N

- 

- 

- H. Ray

- 5/23/05

## NC 0

- Relevance
- Background to e appearance (dominant mis-ID)
-  : crucial for distinguishing ->, ->s in atm.
- + angular distribution constrain mechanisms for                 NC 0 production
- Event Selection
- No decay ele, 2 Cerenkov rings > 40 MeV each
- signal yield extracted from fit with bgd MC : fit assuming 2 rings
- Reconstruction : 55% sample purity with 42% efficiency
- Examine mass spectrum, kinematics
- Bin data in kin. quantities : 0 momentum, E asymmetry, angle of 0 relative to beam, extract binned yields
- Compare distributions to MC expectations

- H. Ray

- 5/23/05

## NC 0 

- Errors are shape errors
- Dark grey :    flux errors
- Light grey : optical model

- 0 momentum = good data/mc agreement.  Falloff at high p = due to flux falloff
- Cos 0 sensitive to production mechanism (coherent = forward, resonant = not so forward)

- H. Ray

- 5/23/05

**Notes:**

Mass distribution : background peak near mpi0 expected due to final state interactions and multi pion events

## NC Elastic

- Study scint. properties of oil, low E response of detector
- Reconstruct p energy from scint. light
- Measure  (p+->p+)
- Help understand scint. light for e osc analysis
-  (NCE) /  (CCQE)
- Measure s (component of proton spin carried by strange quarks)

- Tank Hits = 150

- Tank hits < 150, veto < 6, 1 sub-event :  = 70%, purity = 80%

- H. Ray

- 5/23/05

**Notes:**
Plot shows expected purity and thits shape of nc elestic sample.  
High purity and efficiency sample id-ed and reconstructed

## Conclusions

- Accumulated >50% of 1021 pot needed for 4-5  coverage of LSND
- Already have worlds largest  dataset in 1 GeV range
- Reconstruction and analysis algos are working well :
-  CCQE : compare with flux predictions, disappearance analysis
-  CC + : measure cross section, oscillation search
-  NC 0 : measure cross section, analyze coherent contribution
-  NC Elastic : measure ratio of cross sections vs Q2
-  e appearance analysis well under way; plan on opening box in late 2005/early 2006

- H. Ray

- 5/23/05

## Backup Slides

## LSND

- 800 MeV proton beam -> water target
- 167 ton, liquid scintillator, 25% PMT coverage
- E ~ 20-53 MeV, L ~ 25 - 35 m (L/E ~ 1m/MeV)
- Measure   e osc. from DAR
-  P = 2.640.670.45 x 10-3, see 4 sigma excess

- H. Ray

- 5/23/05

## Exotic Searches

- Muon magnetic moment search
- Massive R, expect non-zero muon mag moment
- Need full dataset
- Rare particle searches
- Take advantage of beam structure
- Proton dribble monitor (if p between buckets, no search!)
- Astrophysics
- Supernova searches
- Gamma Ray bursts (GRB 030329)
- Solar flare emission searches
- Gamma Ray bursts

- H. Ray

- 5/23/05

## MiniBooNE ParticleID

**Start here**

**variable = i**
**Cut = ****c****i**

**1. Boosting: how to split node ?**
** – ****choose variable and cut **

**variable(i)<****c****i**

**Variable = k**
**Cut = ****c****k**

**variable(i)>=****c****i**

**variable(k)<****c****k**

**variable(k)>=****c****k**

**2. Boosting: how to generate tree?**
** – ****choose node to split **

**3. Boosting: how to boost tree ?**
** – ****choose algorithm to change event weight**

**Define Gini Index = P (1 - P) and P =∑****ω****S****/ ∑****ω****(S+B)****  here, *****ω***** is event weight**
**For a given node, determine which variable and cut value maximizes:**

**G ****= GiniIndex****Father**** – ( ****GiniIndex****LeftSon****  + GiniIndex****RightSon**** )**

**Among the existing leaves, find the one which gives the biggest ****G**
**and split it. Repeat this process to generate a tree of the chosen size. **

**Take ALL the events in a leaf as signal events if there are more signal **
**events than background events in that leaf. Otherwise, take all the events **
**as background events. Mark down those events which are misidentified. **
**Reduce the weight of those correctly identified events while increase the **
**weight of those misidentified evens. Then, generate the next tree.**

**4. Boosting: output value**
** – ****sum over**** ****(****polarity **X** tree weight) in all trees**

**See**** B. Roe et al. NIM A543 (2005) 577 ****and**** references therein**

- H. Ray

- 5/23/05