# Presentation: 586449

## (Status of ) The search for  to e

- (Status of ) The search for  to e
- oscillations at MiniBooNE
- Andrew Bazarko – Princeton University
- 9 October 2003
- WIN03 – Weak Interactions and Neutrinos
- Lake Geneva, Wisconsin

## MiniBooNE status snapshot

-     MiniBooNE has been running for 1 year at Fermilab
-                acquired 15% of goal 1021 protons on target
-     At the moment (Sept – mid Nov) accelerator is shutdown
-          important accelerator improvements are underway

- MiniBooNE’s first event:
- beam-induced muon
- (Labor Day weekend 2002)

- Outline
-    Overview of the experiment
-          (preview of tomorrow’s tour)
-    First neutrino events and analysis
-    Outlook

## LSND:

- Evidence for

- (Bugey is e disappearance)

- 87.9+22.4+6.0 events

- m2~0.2-10 eV2

-  beam from + decay at rest
- energy 20-53 MeV
- baseline 30 m
- L/E ~ 1 m/MeV

## Where does LSND’s m2~0.2-10 eV2 

- 3 light neutrino flavors
- Solar (+KamLAND) neutrinos:
-  mostly
- Atmospheric (+K2K) neutrinos:
-  mostly** **

- Where does LSND’s *m*2~0.2-10 eV2
- fit in this picture??

##  Oscillation Scenarios: 

- With current results from solar, atmospheric, and LSND
- oscillation searches (3 m2s), we have an interesting situation:

**Only 3 active ******

**- not a good fit to data**

**3 active+1 sterile ******

**- possible(?)**

- OR...

**CPT violation:**

**- possible(?)**

- OR...

- OR...

- Need to definitively check the LSND result.

## MiniBooNE!

**?**

**Fermilab**

**detector**

******target ** ** **

**8 Gev Booster**

**Tevatron**

**Main Injector**

- Goal: test LSND with
- 5- sensitivity over
- whole allowed range
-  higher statistics
-  different signature
-  different backgrounds
-  different systematics

## BooNE: Fermilab Booster Neutrino Experiment

- S. Koutsoliotas   *Bucknell*
- E. Hawker, R.A. Johnson, J.L. Raaf   *Cincinnati*
- T. Hart, E.D. Zimmerman   *Colorado*
- Aguilar-Arevalo, L.Bugel, J.M. Conrad,
-    J. Formaggio, J. Link, J. Monroe, 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, B.T. Fleming, R. Ford, F.G.Garcia,
-    P. Kasper, T. Kobilarcik, I. Kourbanis,
-    A. Malensek, W. Marsh, P. Martin, F. Mills,
-    C. Moore, P. J. Nienaber, E. Prebys,
-    A.D. Russell, P. Spentzouris, R. Stefanski,
-    T. Williams   *Fermilab*
- D. C. Cox, A. Green, H.-O. Meyer, R. Tayloe
*         **Indiana*
- G.T. Garvey, C. Green, W.C. Louis, G.McGregor,
-    S.McKenney, G.B. Mills, V. Sandberg,
-    B. Sapp, R. Schirato, R. Van de Water,
-    D.H. White  *Los Alamos*
- R. Imlay, W. Metcalf, M. Sung, M.O. Wascko
*          **Louisiana State *
- J. Cao, Y. Liu, B.P. Roe   *Michigan*
- A.O. Bazarko, P.D. Meyers, R.B. Patterson,
-    F.C. Shoemaker, H.A.Tanaka   *Princeton*

- BooNE: Fermilab _Boo_ster _N_eutrino _E_xperiment

- First phase: “MiniBooNE”
-  Single detector, e                      	appearance
-  L/E=500 m/500 MeV =      .....30 m/30 MeV (LSND)

## MiniBooNE

**8GeV**

**Booster**

- ?

- K

- +

- magnetic horn

- and target

- decay pipe

- 25 or 50 m

- LMC

- 450 m dirt

- detector

- absorber

- 8-GeV protons on Be target 
- *K**+**,*..., focused by horn
-         decay in 50-m pipe, mostly to 
-           all but absorbed in steel and dirt
-                 ’s interact in 40-ft tank of mineral oil
-                       charged particles produce light
-                                  detected by phototube array

- Look for electrons produced by mostly-beam

- The Booster

- 8 GeV proton accelerator
- supplies beam to all Fermilab
- experiments

-       It must now run at record intensity

- MiniBooNE runs simultaneously
-    with the collider program;  goals:

- Booster

- MiniBooNE

- Main Injector

- antiproton source
- TeVatron
- NuMI
- 120 GeV fixed target

-  5x1020 p.o.t per year
- (1x1021 total)

- MiniBooNE: negligible
- impact on collider;
- improvements to
- Booster good
- for NuMI

## Booster performance

- red: Booster output (protons/minute)

- blue: energy loss per proton
-                                  (W-min/proton)

- July 2002  - Sept 2003

- goal
- intensity

- MiniBooNE
- startup

- We are pushing the
- Booster hard
- Must limit radiation damage
- and activation of Booster
- components:
-    increase protons
-    but decrease beam loss
- ~steady improvements
-      careful tuning
-      understanding optics
- need factor of 2-3 to reach
- goal 1021 p.o.t. by early 2005
- further improvements coming
-      collimator project (now)
-      large-aperture RF cavities

## Target and magnetic horn 

- 170 kA in 140 sec pulses @ 5 Hz

- Prior to run, tested to
-   11M pulses
- has performed flawlessly:
-   40M pulses in situ

- the horn

- the target

- the target

- Increases neutrino intensity by 7x

- World’s longest-lived horn

## Intrinsic e in the beam

- Intrinsic e in the beam

- 
-               *e*+e
*K**+**e*+e
*K**L*-*e*+e

- Monte Carlo

- important bkgd to osc search
- Tackle this background with
-    half-million  interactions in detector
-    HARP experiment (CERN)
-    E910 (Brookhaven)
-    “Little Muon Counter”
-    25 m / 50 m decay length option

## Little Muon Counter (LMC)

-  off-axis (7o) muon spectrometer
-  *K* decays produce higher-energy
-    wide-angle muons than  decays
-  clean separation of muon parentage
-  scintillating fiber tracker

- Monte Carlo

- temporary LMC detector (scintillator paddles)
-       commission data acquisition
-       53 MHz beam RF structure seen

## The MiniBooNE detector

## MiniBooNE detector 

- MiniBooNE detector

- Phototube support structure
- provides opaque barrier between
- veto and main volumes

- pure mineral oil  (Cherenkov:scint ~ 3:1)
- total volume:      800 tons (6 m radius)
- fiducial volume: 445 tons (5m radius)

## Slide 16

## Slide 17

## Pattern of hit tubes (with charge and time information)

- allows    reconstruction of track location and direction
- and        separation of different event types.

- e.g. candidate events:

- muon
- from  interaction

- Michel electron
- from stopped decay
- after  interaction

- 0  two photons
- from  interaction

- size = charge; red = early, blue = late

## Understanding the detector

- Laser flasks

-  four Ludox-filled flasks
-  fed by optical fiber from laser

- 397 nm laser
- (no scintillation!)
- modeling other
- sources of “late light”

## Stopping muon calibration system

- Scintillator tracker above the tank

- Optically isolated scintillator cubes
-    in tank:
-       six 2-inch (5 cm) cubes
-       one 3-inch cube

- stopping muons with known path length

- calibration sample
-      of muons up to 700 MeV

## Energy scale and resolution

- plentiful source from cosmics
-      and beam-induced muons

- at Michel endpoint (53 MeV)

- Michel electrons
-    (electrons from the decay of stopped muons)

- cosmic muon lifetime in oil
-  measured:   = 2.15 ± 0.02 s
-  expected:    = 2.13 s
-                   (8% - capture)

-  candidate lifetime (ns)

- Michel electron energy (MeV)

- Michel electrons throughout
- detector (r<500 cm)

- 15%
- E resolution
- at 53 MeV

- PRELIMINARY

- PRELIMINARY

## Neutrino events

- beam comes in spills @ up to 5 Hz
- each spill lasts 1.6 sec
- trigger on signal from Booster
- read out for 19.2 sec; beam at [4.6, 6.2] sec
- no high level analysis needed to see
- neutrino events
- backgrounds: cosmic muons
-                       decay electrons
- simple cuts reduce non-beam
-    backgrounds to ~10-3

- 160k neutrino candidates
-       in 1.5 x 1020 protons on target

## The road to   e appearance analysis

- The road to   e appearance analysis

- Blind e appearance analysis
-      you can see all of the info on some events
-      or
-      some of the info on all events
-      but
-      you cannot see all of the info on all of the events

- Early physics:  other analyses before   e appearance
-      interesting in their own right
-      relevant to other experiments
-      necessary for   e search
-             vets data-MC agreement (optical properties, etc.)
-                and reliability of reconstruction algorithms
-              progress in understanding backgrounds

## NC elastic

- abundance ~15%
- usually sub-C
- dominated by
-    scintillation

- low Ntank (pmt hits)
- high late light fraction

- understanding of
-     scintillation
- sensitive to nucleon
-   strange spin component

- CC quasi-elastic

- abundance ~40%
- simple topology
- one muon-like ring
- proton rarely above C

- select “sharp” events
- ~88% purity

- kinematics:
-     E,  E, Q2
- relatively well-known 
-    disappearance

- Early physics

## CC  quasi-elastic events

- CC  quasi-elastic events

- selection:  topology
-                     ring sharpness
-                     on- vs. off-ring hits
-                   timing
-                      single -like ring
-                      prompt vs. late light

- Evis

- cos 

- yellow band: Monte Carlo with current
- uncertainties from

-    variables combined
-       in a Fisher discriminant

- PRELIMINARY

- PRELIMINARY

-  flux prediction
-  CCQE
-  optical properties

- data and MC relatively normalized

## E

- E

- Q2

- Neutrino energy

- kinematic reconstruction:
-      assume  *n*  - *p*
*     *use E,  to get E

- Monte Carlo

- energy resolution

- <10% for E>800 MeV

- sensitive to  disappearance

- PRELIMINARY

- PRELIMINARY

## Preliminary  disappearance sensitivity

- Preliminary  disappearance sensitivity

- systematics
- dominated:
- from
- uncertainty in flux
- prediction

## NC 0 production

- NC 0 production

- NTANK>200, NVETO<6, no decay electron
- perform two ring fit on *all* events
- require ring energies E1, E2 > 40 MeV

- fit mass peak to extract signal yield
- including background shape from Monte Carlo

- note bkgd also peaking

- PRELIMINARY

## 0 production angle 

- 0 production angle

- sensitive to production mechanism

- coherent is highly forward peaked

- data and MC
- are relatively
- normalized
- MC shape
- assumes
- Rein-Sehgal
- cross sections

- cos 0

- PRELIMINARY

- cos CM

- 0 momentum

- 0 decay angle
- and
- 0 momentum

- CM frame

- lab frame

- 

- CM = /2

- cosCM= 

- small 
- opening
- angle

- CM = 

- cosCM= 

- 

- photon
- energies
- asymmetric

- PRELIMINARY

- PRELIMINARY

## NC elastic scattering

- Now select NTANK < 150
-                    NVETO< 6

- Background subtraction

- clear beam
- excess
- use random
- triggers to
- subtract
- non-beam
- background

- PRELIMINARY

- PRELIMINARY
- beam with unrelated
- background

- PRELIMINARY
- normalized strobe
-     data

- PRELIMINARY

- beam after
- strobe
- subtraction

##  NC elastics

-  NC elastics

- Consider NTANK spectrum

- MC and data shapes agree
-  qualitatively for NTANK>50

- Unknown component NTANK<30

- data and MC relatively normalized for NTANK>50

- Late light selection:

- fit event vertex for NTANK>50
- calculate fraction of late hits
- select events with significant late light

## e appearance sensitivity

- 1500 intrinsic e

- 500 mis-ID

- 5000 mis-ID

- 1000 LSND-based e

- e appearance sensitivity

- preliminary estimates,
- backgrounds and signal

- cover LSND allowed region at 5 

- updated estimates coming

- currently expect results in 2005

## Conclusions

- beam is working well, but still need higher intensity
-      improvements underway (shutdown) will be key

- steadily taking data
-      currently at 15% of 1021 p.o.t

- first sample of neutrino physics
-      detector and reconstruction algorithms are working well

## Slide 35