# Presentation: 088994

## The Fermilab Neutrino Program – Status and Challenges Ahead

- Eric Prebys*
- Fermilab Accelerator Division/MiniBooNE

- *with acknowledgements to everyone who leaves talks where I can find them

## Preface

- The turn-on of the LHC in ~2007 will mark the end of the Fermilab Tevatron’s unprecedented 20+ year reign as the world’s highest energy collider.
- With the cancellation of the BTeV (B physics) project, the collider program is scheduled to be terminated in 2009, possibly sooner.
- The lab has a strong commitment to the International Linear Collider, but physics results are at least 15 years away.
- -> Neutrino physics will be the centerpiece of Fermilab science for at least a decade.

## Luckily, neutrinos are very interesting

- Many unanswered questions
- Type: Dirac vs. Majorana
- Generations: 3 active, but possibly sterile
- Masses and mass differences
- Mixing angles
- CP and possibly even CPT violation
- Multi-disciplinary
- Study
- Solar
- Atmospheric
- Reactor
- Lab based (beta-decay)
- Accelerator Based
- Application
- Particle physics
- Astrophysics
- Cosmology
- Trying to coordinate the effort and priorities
- See “APS Multidivisional Neutrino Study”
- http://www.aps.org/neutrino/

## Slide 4

## This Talk

**A Brief History of Neutrinos**
- Background
- Neutrino “problem”
- Neutrino oscillations
**Some Key Experimental Results**
- SuperKamiokande
- SNO
- Reactor Summary
- K2K
- LSND (????)
- Where do we stand?
**Major Fermilab Experiments**
- MiniBooNE
- NuMI/Minos
- Nova
**Meeting the Needs of these Experiments**
- Existing Complex
- Post-Collider
- Longer Term

## Neutrinos in the Standard Model

- Each Generation lepton has an associated neutrino, just as each “up-type” quark has a “down-type” partner

- A charged weak interaction causes a “flip” between partners

- Initially massless by definition

## 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”  (more about this shortly)

- Solar Problem

- Atmospheric Problem

## Theory of 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 squares of the masses.

## Three Generation Mixing

- General Mixing Parameterization

- CP violating phase

- Almost diagonal
- Third generation weakly coupled to first two
- “Wolfenstein Parameterization”

- Mixing large
- No easy simplification
- Think of mass and weak eigenstates as totally separate

## Large mixing makes it complicated!

- Where:

- Oscillatory behavior

- Jarlskog invariant (measure of CP violation)

- =sin13

- =changes sign for CP conjugate

- In *vacuum:*

- Problem: need a heck of a lot of neutrinos to study this

## Sources of a Heck 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

## 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.

- Also probe with “long baseline” accelerator and reactor experiments

## 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.

- Outer detector

- Inner detector

## 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.

## K2K

- First “long baseline” accelerator experiment
- Beam from KEK PS to Kamiokande, 250 km away
- Look for  disappearance (atmospheric “problem”)
- Results consistent with mixing

- Best fit

- No mixing

- Allowed Mixing Region

## LSND Experiment (odd man out)

- 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.
- Doesn’t fit “nicely” with the other results!

## Where we stand (w/o LSND)

## Incorporating LSND

**Only 3 active ******

**- not a good fit to data**

**3 active+1 or more 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...

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

## Big Questions in Neutrino Physics

- Size of the mixing angles*
- Particularly 13
- Mass heirarchy*
- Normal or Inverted
- Absolute masses
- Is neutrino Dirac or Majorana
- i.e. is the neutrino its own antiparticle
- CP violation parameters**
- Is the LSND result correct?*
- Are there sterile neutrinos?
- CPT violation?

- *Addressed by currently planned FNAL physics program
- **Possibly addressed by future program

## 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.

## Producing Neutrinos At an Accelerator

- Proton beam

*Mostly *pions

- Target

- Mostly lower energy

- We will look for these to oscillate

- Pion sign determined whether it’s a neutrino or anti-neutrino

- Beam needs:
- Lots of beam!!!
- Short spills
- to distinguish from cosmic background
- Bucket structure
- Use TOF to distinguish subrelativistic particles (mostly kaons)

## 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

- Horn current selects + ->  or  -> 

## MiniBooNE Experiment

- Proton flux ~ 6E16 p/hr (goal 9E16 p/hr)
- ~ 1 detected neutrino/minute
- L/E ~ 1
- Directly address LSND result

**FNAL****Booster**

**Be Target****and Horn**

**“****Little Muon Counter” (LMC): to understand K flux**

**50 m Decay Region**

**500m dirt**

**Detector**

- 8 GeV protons

## The MiniBooNE Detector

- Oscillation!!!

- Our beam will produce primarily muon neutrinos at high energy

- This is what we’re looking for

- 807 tons of mineral oil

## Detector

- 950,000 l of pure mineral oil
- 1280 PMT’s in inner region
- 240 PMT’s outer veto region
- Light produced by Cerenkov radiation and scintillation

- Light barrier

- Trigger:
- All beam spills
- Cosmic ray triggers
- Laser/pulser triggers
- Supernova trigger

## Neutrino Detection/Particle ID

- Important Background!!!

## Experimental Sensitivity (1E21 POT)

- No signal
- Can exclude most of LSND at 5

- Signal
- Can achieve good m2 separation

## Beam to MiniBooNE

- 6.6E20 to date
- Plan for ~2E20/year during NuMI running
- First oscillation results in 2006

- NuMI

## 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: Soudan Mine in Minnesota (735 km away)

## NuMI beams

- Two horns (second moveable) -> adjustable beam energy

## Near – 1040 m away

- Near – 1040 m away

** ****1 kton of steel plates**
** ****Detect neutrinos through appearance of charged particles**
** ****Magnetic field in plates determines sign**
** ****Range of particles separates particle types.**

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

## Far Detector – 735.3 km away

** ****Located in Soudan mine**
** ****5.4 kton**
** ****Operation as similar as possible to near detector **
** ****Two detectors used to reduce systematic effects**

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

- MINOS

- Soudan 2/CDMS II

**shaft**

## Minos Status

- Test Beam in December 2004
- Startup in March, 2005
- Collecting data steadily
- Detectors working well

- Near detector (different target positions)

- Far detector (fully contained event)

## Beam to NuMI/MINOS

- Accumulating data at ~2-2.5E20/yr
- Can do initial oscillation (disappearance) result with 1E20 (~end of year, not counting analysis)

- Target water leak problems

- Horn ground fault problems

## MINOS Ultimate Sensitivity

- ~3 years

- ~7 years

## Beyond Minos – an Off-Axis experiment

- Putting a Detector Off the NuMI Axis probes a narrower neutrino energy distribution than an on-axis experiment (albeit at a lower total intensity)
- By constraining L/E, one is able to resolve different contributions to the signal by comparing neutrino and anti-neutrino events
- sin(13)
- Si*gn* of m2
- Neutrinos and antineutrinossee different matter effects,which depend on mass
- resolve hierarchy question
- Next step to measuring CP violation

## Noa Proposal

- Place a 30 kT fully active liquid scintillator detector about 14 mr off the NuMI beam axis

## Nova dependence on 

- Nova dependence on 

- Nova results will have an inherent dependence on the CP violation parameter 
- Future experiments will measure and energy dependent asymmetry between andto measure

## Noa Sensitivity

- Noa Sensitivity

- Fraction of  covered

## Noa Status and Schedule

- Stage I approval: April, 2005
- Project Start: October, 2006
- First kton operational: October, 2009
- All 30 ktons operations: July, 2011
- Problems:
- Would really like a LOT of protons

## Proton Demands

- Highest number I could find on a plot

## The Fermilab Accelerator Complex

- = ProtonSystem

- =Proton Customer

- Mostly 35 years old

## Limits to Proton Intensity

- Total proton rate from Proton Source (Linac+Booster):
- Booster batch size
- Typical ~5E12 protons/batch
- Booster repetition rate
- 15 Hz instantaneous, lower average due to power limits and component heating
- Beam loss
- Damage and/or activation of Booster components
- Above ground radiation
- Total protons accelerated in Main Injector:
- Maximum main injector load
- ~5-6E13 presently
- Cycle time:
- 1.4s + loading time (1/15s per booster batch)

- Present Operational Limit

## Staged Approach to Neutrino Program

- Stage 0 (now):
- Goal: deliver 2.5E13 protons per 2 second MI cycle to NuMI (~2E20 p/yr)
- Deliver 1-2E20 protons per year to Booster Neutrino Beam (currently MiniBooNE)
- Stage 1 (~2007):
- A combination of Main Injector RF improvements and operational loading initiatives will increase the NuMI intensity to ~5E13 protons per 2.2 second cycle (~3.5E20 p/yr)
- It is hoped we can continue to operate BNB at the 2E20 p/yr level during this period.
- Stage 2 (post-collider):
- Proton to NuMI will immediately increase by 20%
- Consider (for example) using the Recycler as a preloader to the Main Injector and reducing the Main Injector cycle time (~6.5E20 p/yr)
- The exact scope and potential of these improvements are under study
- Stage 3 (proton driver or equiv.)
- Main Injector must accommodate 1.5E14 protons every 1.5 seconds
- 2MW @ 120 GeV
- NuMI beamline and target must also be compatible with these intensities.

- “Proton Plan”

## Re-tasking the Recycler

- At present, the Main Injector must remain at the injection energy while Booster “batches” are loaded.
- Booster batches are loaded at 15 Hz
- When we slip stack to load more batches, this will waste > 1/3 of the Main Injector duty factor.

- After the collider, we have the option of “preloading” protons into the Recycler while the Main Injector is ramping, thereby eliminating dead time.
- Small invenstment
- New beamline directly from Booster to Recycler
- Some new RF
- Big payoff
- At least 50% increase in protons to NuMI

## Thinking Big: A Proton Driver

## The Benefits of an 8 GeV Linac Proton Driver (stolen slide)

- The Benefits of an 8 GeV Linac Proton Driver (stolen slide)

**Anti-**
**Proton**

## Possible “budget” Alternative to Proton Driver (D. McGinnis proposal)

- Less Expensive than the Linear Proton Driver
- Can get to 2 MW
- None of the side benefits
- No synergy with ILC

- Retire Booster
- Build new transfer line
- Replace pBar Debuncher with new Booster
- Prestack in Accumulator
- Transfer to recycler/Main Injector

## Evolution of Proton Delivery

## Evolution of 13 discovery limit

- Bands show dependence on CP violation parameter 

## Other Activities at the lab (some very big)

- Other Neutrino:
- FLARE: Same physics motivation as Noa, but with a liquid Argon detector
- Cross section and production experiments as input to neutrino physics
- MIPP
- Minera
- Finese
- SciBar
- Fixed Target
- Active 120 GeV program, mostly test beams
- LHC
- Big player in CMS
- Level 2 Physics Center
- LARP accelerator collaboration
- ILC
- Major Commitment ramping up over the next few years
- Major superconducting RF effort
- Non-HEP
- Sloan Digital Sky Survey
- Auger
- Computing Grid development

## Conclusions

- It’s a little disorienting to see the end of the Fermilab collider program
- We are disappointed at the cancellation of the BTeV project, nevertheless
- Fermilab is poised to hold a leading position in neutrino research for the next 10-15 years.