# Presentation: 375584

## The Fermilab Neutrino Oscillation Program – Status and Challenges Ahead

*Eric Prebys*
- FNAL Beams Division/MiniBooNE

*Much of talk shamelessly stolen from various public experimental websites*

## Outline

**A Brief History of Neutrinos**
- Background
- Neutrino “problem”
- Neutrino oscillations
**Some Key Experimental Results**
- SuperKamiokande
- SNO
- Reactor Summary
- LSND (????)
- Where do we stand?
**Major Fermilab Experiments**
- MiniBooNE
- NuMI/Minos
**Impact on the Accelerator Facility**
- Proton Source
- Main Injector

## A Brief History of Neutrinos: The Beginning

- Electron Energy

- Expected monoenergetic electrons

- Observed electron spectrum

- In “beta decay”, one element changes to another when the nucleus emits an electron (or positron)

**It was even postulated that maybe beta decay violated conservation of energy!**

- In1930, Wolfgang Pauli suggested a *“desperate remedy”,* in which an “invisible” particle was carrying away  the missing energy. He called this particle a “neutron”.

- Enrico Fermi changed the name to “neutrino” in 1933, and it became an integral part of his **extremely  successful** weak decay theory.
**In 1956, Reines and Cowen observe first direct evidence of neutrinos – 26 years after their prediction!**

## The Question of Mass, the Standard Model

- All observed kinematics of neutrino interactions are consistent with **zero mass** to within the limits of sensitivity.
- In Fermi model (and later standard model), neutrinos are massless *by definition**.*
- In 1956, Bruno Pontecorvo first shows that it might be possible for neutrinos to *oscillate *from one type to another if they have a small – **but nonzero** – mass*.*
**Other important developments:**
- 1962: Lederman, Steinberger, and Schwartz show that that there are at least two distinct “flavors” of neutrinos (e)
- 1970’s: “Standard Model” completed – with *massless* neutrinos.
- 1989: LEP experiments prove there are **only three flavors** of active neutrino (e ,, and )

## Neutrinos in the Standard Model

- Each Generation lepton has an associated neutrino

- The weak interaction causes a charged lepton to “flip” to a neutrino and vice versa

- The weak interaction conserves “lepton number”

## The “Neutrino Problem”

- 1968: Experiment in the Homestake Mine first observes neutrinos from the Sun, **but there are far fewer than predicted**.  Possibilities:
- Experiment wrong?
- Solar Model wrong? *(**** believed by most not involved)*
- Enough created, but maybe oscillated (or decayed to something else) along the way.
- ~1987: Also appeared to be too few atmospheric muon neutrinos.  Less uncertainty in prediction.  Similar explanation.
- Both results confirmed by numerous experiments over the years.
- 1998:  SuperKamiokande observes clear oscillatory behavior in signals from atmospheric neutrinos.  For most, this establishes neutrino oscillations “beyond a reasonable doubt”.

## Neutrino Oscillations

- Neutrinos are produced as *weak eigenstates* (e ,, or ).
- In general, these can be represented as *linear combination of mass eigenstates*.
- If the above matrix is not diagonal *and* the masses are not equal, then the net weak flavor content will *oscillate *as the neutrinos propagate.
**Example: **if there is mixing between the e and :then the probability that a e will be detected as a  after a distance *L* is:

- Distance in *km*

- Energy in GeV

- Mass eigenstates

- Flavor eigenstates

- Only measure *magnitude* of the *difference* of the square of the masses!

- Problem: need a hell of a lot of neutrinos to study this!

## Sources of a Hell of a Lot of Neutrinos

- The sun:
- Mechanism: nuclear reactions
- Pros: free
- Cons: only electron neutrinos, low energy, exact flux hard to calculate, can’t turn it on and off.
- Atmosphere:
- Mechanism: Cosmic rays make pions, which decay to muons, electrons, and neutrinos.
- Pros: free, muon and electron neutrinos, higher energy than solar neutrinos, flux easier to calculate.
- Cons: flux fairly low, can’t turn it on and off.
- Nuclear Reactors:
- Mechanism: nuclear reactions.
- Pros: “free”, they do go on and off.
- Cons: only electron neutrinos, low energy, little control of on and off cycles.
- Accelerators:
- Mechanism: beam dumps -> particle decays + shielding -> neutrinos
- Pros: Can get all flavors of neutrinos, higher energy, can control source.
- Cons: NOT free.

- Different experiments probe different ranges of

- Path length

- Energy

## Probing Neutrino Mass Differences

- & Reactors

- Accelerators use  decay to *directly* probe  e

- Reactors use use *disappearance* to probe  e  

- Cerenkov detectors directly measure  and e  content in atmospheric neutrinos. Fit to e mixing hypotheses

- Solar neutrino experiments typically measure the disappearance of e.

## SuperKamiokande Atmospheric Result

- Huge water Cerenkov detector can directly measure and  e  signals.
- Use azimuthal dependence to measure distance traveled (through the Earth)
- Positive result announced in 1998.
- Consistent with  mixing.

## SNO Solar Neutrino Result

- Looked for Cerenkov signals in a large detector filled with heavy water.
- Focus on 8B neutrinos
- Used 3 reactions:
* ****e*+*d**p+p+e**-*: only sensitive to ***e*
-  ***x*+*d**p+n+****x*: equally sensitive to ***e *,***** *,****
* ****x*+ *e**-* ***x*+ *e**-*: 6 times more sensitive to ***e *than ***** *,*****d*
- Consistent with initial full SSM flux of ***e*’s mixing to ***** *,******

- Just SNO

- SNO+others

## Reactor Experimental Results

- Single reactor experiments (Chooz, Bugey, etc).  Look for ***e* disappearance: all negative
- KamLAND (single scintillator detector looking at ALL Japanese reactors): ***e* disappearance consistent with mixing.

## LSND Experiment

- Looked for ****  ***e* and ****  ***e* in  decay from the 800 MeV LANSCE proton beam at Los Alamos
- Look for ***e* appearance via:
- Look for ***e* appearance via:
- Observe excess in both channels (higher significance in ***e*)
- Only exclusive *appearance* result to date.

## Where We Stand: Oscillation Scenarios

- We have 3 very different ***m**2*’s.  Very hard to fit with only three
- mass states...

**Only 3 active ******

**- not a good fit to data**

**3 active+1 sterile ******

**- possible(?)**

- OR...

**CPT violation******

**- possible(?)**

- OR...

- OR...

- Can fit three mass states quite well *without* LSND, but no a priori reason to throw it out.  Must check...

## Enter the Fermilab Neutrino Program

- MiniBooNE-neutrinos from 8 GeV   Booster proton beam (L/E~1): absolutely confirm or refute the LSND result

- NuMI/Minos – neutrinos from 120 GeV Main Injector proton beam (L/E~100):precision measurement  of  oscillations as seen in atmospheric neutrinos.

## The Fermilab Accelerator Complex

## MiniBooNE Beamline

- 8GeV Beam from Booster

## Producing Neutrinos for MiniBooNE

- 8 GeV Proton beam

- Mostly pions

- Berylium Target

- Mostly below our detection threshold

- We will look for these to oscillate to e

- Select positive pions with neutrino horn.

## Neutrino Horn – “Focusing” Neutrinos 

- Can’t focus neutrinos themselves, but they will go more or less where the parent particles go.

- Target

- Coaxial “horn” will focus particles of a particular sign in both planes

- p

- We select + -> 

## Neutrino Horn – Cont’d

-  Horn will pulse with 170 kA 150 usec pulse!
-  Horn heating limits the average rep rate to 5 Hz.
- Horn fatigue is an issue.
- Under nominal MiniBooNE running conditions, it will pulse about 100 million times per year.
- Highest rate neutrino horn ever built!

## MiniBooNE Secondary “Beamline”

- 25m

- 25m

- Detector

- “Teletubby Hill”

- Counting House

- 50m Muon absorber

- removable25m Muon absorber

- Target vault

- Proton Beam

- Decay region

- NOT to scale!!!!!!

- 500 m

## Predicted Neutrino Flux at the Detector

- The L/E ~1 m/MeV is similar to that at LSND.

**p********Be ****************K************K****0****L******

************
**K**K0L

****ee
**K****+**ee  , K0Lee

**-**8 GeV protons on Be:

- -yield a high flux of  :

- -with a low background of e :

- Flux estimate is important!

## The MiniBooNE Detector

- Oscillation!!!

- Beam will produce primarily muon neutrinos at high energy

- This is what we’re looking for

- 807 tons of mineral oil

- 1280 PMT’s

## Identifying Particles

- Oscillation Signature

- Of course it’s a bit more complicated than that...

## Expected Signal (1021 protons on target)

- Approximate number of electron neutrino-like events

- ~500k C charged current events

- Expected Signal (1021 protons on target)

## MiniBooNE Status: Running Since October

- Michel *e*
- candidate

- Beam 
- candidate

- Beam 0
- candidate

## Integrated Beam Flux (as of 3/18)

- All systems working well
- We're at 5% of 1021 protons on target.
- Currently at about 40% of MiniBooNE baseline

## Predicted MiniBooNE Sensitivity (1021 protons)

- Predicted MiniBooNE Sensitivity (1021 protons)

## MINOS: Main Injector Neutrino Oscillation Study

- _MINOS_: Main Injector Neutrino Oscillation S*tudy*

- 8 GeV Booster beam is injected into Main Injector.
- Accelerated to 120 GeV
- Transported to target
- Two detectors for understanding systematic
- Near detector: FNAL (L=1km)
- Far detector: Sudan Mine in Minesota (735 km away)

## NuMI beams

- Horn 2

- Horn 1

- No clear plan to achieve this yet

## Near – 1040 m away

- Near – 1040 m away

** ****veto - target - shower - ******** spectrometer**
** ****1 kT**
** ****3.8 x 4.8 “squeezed” octagon**
** ****12,300 scint.strips**
** ****1-end readout**
** ****no-multiplexing**
** ****220 M64s**
** ****QIE-based front-end**
**282 steel planes**
**153 scintillator planes**
** ****65 km WLS fiber**
** ****51 km clear fiber**

**Near detector will provide high event **
**statistics for “mundane” neutrino physics**

## Far Detector – 735.3 km away

** ****2 Supermodules**
** ****5.4 kT**
** ****484 scint. planes**
** ****92,928 strips (4.1 x 1.0 cm)**
** ****8-fold MUXed 2-ended readout**
** ****1452 M16s**
** ****722 km of WLS fiber**
** ****794 km of ****clear fiber**

** ****B ~ 1.5T (R=2m)**
** ****HAD ~ 55% / E ****1/2**
** ****EM ~ 23% / E ****1/2**

- MINOS

- Soudan 2/CDMS II

**shaft**

## MINOS Sensitivity to Oscillations

**Projections are for**
**2-3 years of running**

## NuMI/Minos Status

- Far detector nearing completion and taking cosmic data.
- Near detector components nearly complete and ready to be put in detector hall.
- Blasting finished and civil construction almost complete.
- Work beginning on beamline
- First beam planned for beginning of 2005.

## What’s so Hard About Neutrino Physics (from the Accelerator Standpoint)?

- Probability that a 150 GeV proton on the antiproton target will produce an accumulated pbar:  			.000015 (1.5E-5)
- Probability that a proton on the MiniBooNE target will result in a detected neutrino:		 .000000000000004 (4E-15)
- Probability that a proton on the NUMI target will result in a detected neutrino at the MINOS far detector: 	     .000000000000000025 (2.5E-17)
*** **Need more protons in a year than Fermilab has produced in its lifetime!!*

## Demand for 8 GeV Protons

- Fancy MI Loading schemes (or >5E12)

- Shortfall

## Fermilab Accelerators

- History
-  Early 1960’s – plans solidify for a high energy national accelerator laboratory.
-  1966 – The AEC chooses the Weston, IL site from amongst hundreds proposed.
-  1968 – Construction begins.
-  1972 – First 200 GeV beam in the Main Ring.
-  1983 – First (512 GeV) beam in the  Tevatron (“Energy Doubler”).  Old Main Ring serves as “injector”.
-  1985 – First proton-antiproton collisions observed at CDF (1.6 TeV CoM).
-  1995 – Top quark discovery. End of Run I.
-  1999 – Main Injector complete.
-  2001 – Run II begins.

## Preac(cellerator) and Linac

**“****Preac” - **Coolest looking thing at Fermilab.  Static Cockroft-Walton generator accelerates H- ions from 0 to 750 KeV.  (Actually, there are two of these, H- and I-)

**“****Old linac”-** 200 MHz “Alvarez tubes” accelerate H- ions from 750 keV to 116 MeV

**“****New linac”-** 800 MHz “ cavities” accelerate H- ions from 116 MeV to 400 MeV

- Preac/Linac can deliver about 45 mA of current for about 35 usec at a 15 Hz repetition rate

## Booster

-  400 MeV Linac H- beam is injected into booster over several (up to 15) “turns”.  The ion beam allows one to “cheat” Liouville’s theorem and inject (negative) beam on top of existing (positive) beam.
-  The main magnets of the Booster form a 15 Hz offset resonant circuit , so the Booster field is continuously “ramping”, whether there is beam in the machine or not. Ramped elements limit the average rep rate to somewhat lower.
- From the Booster, beam can be directed to
-  The Main Injector
-  MiniBooNE (switch occurs in the MI-8 transfer line).
-  The Radiation Damage Facility (RDF) – actually, this is the old main ring transfer line.
-  A dump.

-  One full booster “batch” sets a fundamental unit of protons throughout the accelerator complex (max 5E12).
- This is divided amongst 84 53 MHz RF buckets, which sets another fundamental sub-unit (max 6E10).

## Main Injector

-  The Main Injector can accept 8 GeV protons OR antiprotons from
-  Booster
-  The anti-proton accumulator
-  The Recycler (which shares the same tunnel)
-  It can accelerate protons to 120 GeV (in a minimum of 1.4 s) and deliver them to
-  The antiproton production target.
-  (soon) The fixed target area.
-  (soon) The NUMI beamline.
-  It can accelerate protons OR antiprotons to 150 GeV and inject them into the Tevatron.
-  The Main Injector can also accept 150 GeV antiprotons from the Tevatron and *decelerate* them to 8 GeV for transfer to the Recycler.

-  The Main Injector is exactly 7 times the circumference of the Booster.  Allowing one empty “slot” for switching, it can hold six booster batches, in the absence of exotic stacking schemes (slip stacking, RF barrier).
-  It’s envisioned that one batch will be used for stacking and the rest for NUMI and/or switchyard 120.

## What Limits Total Proton Intensity?

- Maximum number of Protons the Booster can stably accelerate: 5E12
- Maximum average Booster rep. Rate:  currently 7.5 Hz, may have to go to 10 Hz for NuMI+MiniBooNE
- (NUMI only) Maximum number of booster batches the Main Injector can hold: currently 6 *in principle*, possibly go to 11with fancy loading schemes in the future
- (NUMI only) Minimum Main Injector ramp cycle time (NUMI only): 1.4s+loading time (at least 1/15s**nbatches*)
- Losses in the Booster:
- Above ground radiation
- Damage and/or activation of tunnel components

*Our biggest worry at the moment!!!!*

## Booster Losses (Normalized to Trip Point)

- Present rate

- Maximum based on trip point

- Also limit total booster average power loss (B:BPL5MA) to 400W.

## Booster Tunnel Radiation Levels

-  On a December access
-  The people doing the radiation survey got about 20 mR.
-  Two technicians received 30 mR doing a minor HV cable repair.
-  We’re at (or past??) the absolute limit on our overall activation
-  Some limits lowered afterwards (450W -> 400W)

## How Have We Been Doing?

- Total Booster Output (protons/minute)

- Energy Lost per Proton  (W-min/proton)

- MiniBooNE

- Discovered dogleg problem: tune to reduce dogleg currents

- Test with one dogleg off (halfway to MiniBooNE goal!)

## Some Cold Hard Facts about the Future (improvements since 11/02 indicated)

- Running as we are now, the Booster can deliver a little  over 1E20 protons per year – this is about a factor of six over typical stacking operations, and gives MiniBooNE about 20% of their baseline.
- NuMI will come on line in 2005, initially wanting about half of MiniBooNE’s rate, but hoping to increase their capacity – through Main Injector Improvements – *until it is equal to MiniBooNE.*
- Whatever the lab’s official policy, there will be great pressure (and good physics arguments) for running MiniBooNE and NuMI *at the same time*.
- -> By 2006 or so, the Proton Source might be called upon to deliver 10  times what it is delivering now.
*At the moment, there is no plan for assuring this, short of a complete replacement*!
- So what are we going to try?...

- 2E20

- 12

- 40%

- 5

## Booster Collimator System

- Unshielded copper secondary collimators were installed in summer 2002, with a plan to shield them later.
- Due the the unexpected extent of the shielding and the difficulty of working in the area, the design was ultimately abandoned as unacceptable.
- Collimators were removed during the January shutdown.
- A new collimator system is being designed with steel secondary jaws fixed within a movable shielding body.
- Hope to have then ready before summer shutdown.

- Basic Idea...

- A scraping foil deflects the orbit of halo particles...

- ...and they are absorbed by thick collimators in the next periods.

## Dogleg Problem

-  Each of the two Booster extraction septa has a set of *vertical* dogleg magnets to steer the beam around it during acceleration.
- More powerful doglegs were installed in 1998 to reduce losses early in the cycle.
-  These magnets have an edge focusing effect which distorts the *horizontal* injection lattice:
-  50% increase in maximum 
-  100% increase in maximum dispersion.
-  Harmonic contributions.
-  Effect goes like I2.  Now tune to minimize.
- Recently got an unusual opportunity to explore potential improvements from fixing the problem.
- Working on schemes to reduce or remove problem.

- Septum

- Dogleg Magnets

## New RF System?

- The existing RF cavities form the primary aperture restriction (2 1⁄4” vs. 3 1⁄4”).
- They are high maintenance, so their activation is a worry.
- There is a plan for a new RF system with 5” cavities:
- Powered prototype built
- Building *two* vacuum prototypes for the summer shutdown with substantial machining done at universities.
- Evaluate these and procede (hopefully?) with full system

## Main Injector Improvements

- Beam Loading Compensation for high intensity multi-batch operation.
- Explore schemes to load more than 6 Booster batches:
- Slipstacking: change momentum of sequential batches so they “slip” together.
- RF barrier bucket: use RF manipulation to move batches around.
- Shorten Main Injector ramp time from 1.4s -> 1s?
- Expensive
- Potential gain must  be examined in the context of pbar production

## Conclusions

- We are in a very exciting time for the study of neutrinos.
- Fermilab will play a major role in these studies in the next few years.
- When the lab committed to supporting these experiments, we were *two orders* of magnitude away from being able to deliver the necessary protons.
- Now we believe that we have a chance to run MiniBooNE and NuMI/Minos sumultaneously.