# Presentation: 142724

## Low Energy Physics Potentialof a Proton Driver

- Peter Kasper
- 26-Sep-2003
- http://home.fnal.gov/~kasper/talks/LRPC.ppt

## Because it is Complementary!

- In an era where we will be producing events at 8 **TeV** CM Energy WHY would you ever want an 8 **GeV** program?
- There is physics that you cannot do at ultra-high energy scale proton machines
- e.g. Neutrino beams
- Low energy experiments can help unravel high energy experimental mysteries
- e.g. the high Q2 HERA events could not have been leptoquarks -- the Atomic Parity Violation data ruled it out!
- Stringent limits on “forbidden” low energy processes can probe energy scales not accessible to the colliders
- e.g. neutron electric dipole moment

## Topics Covered

- A physics program based on 8 GeV protons from the Booster or a Proton Driver (linear or circular) will likely fall into one or more of the following categories
- Neutrino Physics
- Fundamental Neutron Physics
- Muon Physics
- In all cases, high intensities will be required in order to create a state of the art facility.
- What might be achieved with the Booster?
- What more could be done with a Proton driver?

## What can we do with what we have?

- Enormous progress has been made recently on increasing the output from the Booster
- However the physics potential of NuMI and MiniBooNE make it worth the effort to push as high as we can.
- Even greater output is possible but we can only go so far
- These experiments represent a great starting point for high intensity programs at both high and low energies
- The Booster will hopefully be able to meet their needs in the short term
- A Proton Driver not only allows the programs to advance but opens up other interesting possibilities

## Proton Availability – Near Term

-  Booster Now
- ~5e16 p/hr (limited by tunnel activation)
- ~5e12 p/cycle maximum sustainable intensity
- 6.5 Hz maximum beam cycle rate @ 5e12 p/cycle = 1.2e17 p/hr
- 1.8e17 p/hr (Shielding Assessment limit) = 5e12 @ 10 Hz
-  Pbar Production + Full MiniBooNE (Booster limit → 1.2e17 p/hr)
- 5e12 @ (0.5+5.0) Hz = 1.0e17 p/hr
- 5e12 @ (1.0+5.0) Hz = 1.1e17 p/hr (with slip-stacking)
-  Pbar Production + NuMI
- 5e12 @ (1.0+2.5) Hz = 6.3e16 p/hr
- 5e12 @ 3.0 Hz = 5.4e16 p/hr available to MiniBooNE
- NuMI will want to increase protons to the MI
- MiniBooNE will want to increase rep rate

## Proton Availability – Medium Term

- Increase rep rate to 10 Hz (Booster limit → 1.5e17 p/hr)
- Full 9E16 p/hr rate for MiniBooNE/BooNE
- Introduce fast stacking in MI for NuMI and Pbar and raise Booster limit to SA value of 1.8e17 p/hr
- MI must handle 6E13 p/cycle
- Minimum MI Cycle time goes to 2.27 sec
- MI gets 5e12 @ 5.3 Hz = 9.5e16 p/hr
- 8 GeV users can get 8.5e16 p/hr (still OK for BooNE)
- Shorten MI acceleration cycle to 1 sec (few $10M’s)
- Minimum MI Cycle time goes to 1.8 sec
- MI gets 5e12 @ 6.7 Hz = 1.2e17 p/hr
- 8 GeV users can get 6.0e16 p/hr (probably adequate)

## Proton Availability – Far Term

- Eliminate MI fill time??
- Booster fills recycler while MI is accelerating
- Assumes the recycler is not being used for P-bar’s
- Recycler is used to do slip-stacking and to fill the MI
- Minimum MI cycle time is reduced to 1 sec.
- 12 x 5e12 Booster batches per second exceeds both the Booster SA limit and the assumed rep-rate limit
- Assume maximal Booster i.e. 5e12 @ 15 Hz = 2.7e17 p/hr
- MI gets 5e12 @ 12 Hz = 2.2e17 p/hr
- 8 GeV users can get 5.4e16 p/hr
- Is this even possible?
- Additional gains will require a new proton source

## Summary of Possible Booster Output

- Current Radiation Limit

- 6.5 Hz Rep Rate Limit

- Booster SA Limit

- 5e12 @ 15 Hz

- Is this possible??

- ?

## Recap

- The present facility can be made to meet the needs of MiniBooNE
- NuMI goals are challenging and may require significant MI and possibly Booster upgrades
- MiniBooNE and NuMI will be able to live together but as time goes on and demand goes up, there are significant issues that must be addressed.
- Upgrading to 10 Hz (if radiation can be controlled) will make a MiniBooNE successor possible.
- A fast slip-stacking scheme (if it can be done) will greatly benefit NuMI and leave sufficient protons for BooNE etc.
- Further increasing the MI’s output will significantly reduce protons to any 8 GeV users.
- In the long term the only solution is a new proton driver

## Proton Driver Machine Characteristics

|   | Energy | Pulse | P/pulse | Rep Rate | P/hr | Power |
| --- | --- | --- | --- | --- | --- | --- |
|   | (GeV) | (s) |   | (Hz) |   | (MW) |
| Booster (2005) | 8 | 1.6 | 5.00E+12 | 6.5 | 1.17E+17 | 0.04 |
| Booster (Max) | 8 | 1.6 | 5.00E+12 | 15 | 2.70E+17 | 0.10 |
| PD synchrotron | 8 | 1.6 | 2.50E+13 | 15 | 1.35E+18 | 0.48 |
| SC Linac | 8 | 1,000 | 1.50E+14 | 10 | 5.40E+18 | 1.92 |

|   | MI pulses | 8 GeV pulses | P/hr | Power |
| --- | --- | --- | --- | --- |
|   | (Hz) | (Hz) |   | (MW) |
| Booster (2005) | 3.5 | 3 | 5.40E+16 | 0.02 |
| Booster (Max) | 12 | 3 | 5.40E+16 | 0.02 |
| PD synchrotron | 6 | 9 | 8.10E+17 | 0.29 |
| SC Linac | 1 | 9 | 4.86E+18 | 1.73 |

- Protons available to 8 GeV programs running with the MI

- 15 - 90 times what we can get from the Booster!!

## Physics Potential with Low Energy Protons

- Can comfortably support any MiniBooNE follow on experiments together with MI operations.
- Provides sufficient additional beam power to produce a world class neutron source dedicated to experiments in particle physics
- Address fundamental questions in our field
- Are on the scale of small HEP experiments
- Provides sufficient additional  beam power to produce high intensity low energy muon beams
- Beyond the Standard Model searches
- Muon collider R&D
- These are just the examples that we have thought of now
- Great physics at relatively low cost and low risk

## Low Energy Neutrino Physics

- MiniBooNE hopes to complete its neutrino running some time in 2005 ( after NuMI start up ).
- If MiniBooNE sees a signal then precise measurements will be required (BooNE)
- An upgrade to two "MiniBooNE-type" detector sites
- There may be more than one "MiniBooNE-type" detector at the new location  (under discussion)
- The needs will be for about the same rates as MiniBooNE receives now (no significant upgrades to the beam)
- If the new proton driver "hooks in" at the same place as the present 8 GeV line, then the set-up is in place.

## What if MiniBooNE sees a signal? .. Exciting!
The present data cannot be fit with just 3 neutrinos
The favored extensions to the Standard Model assume sterile neutrinos 

- The present data cannot be fit with just 3 neutrinos
- The favored extensions to the Standard Model assume sterile neutrinos

- Allowed regions for 3+1 models given LSND and Null Short BaseLine experiments

## But multiple sterile neutrinos are likely to be involved
It will require much study to understand this new situation. Fermilab should position itself to be able to follow up.

- It will require much study to understand this new situation. Fermilab should position itself to be able to follow up.

## Other Interesting Neutrino Experiments

- FINeSE – Measuring the strange spin of the proton
- Proposal in progress: An example of “Build it and they will come”
- Cheap and simple 10 ton detector placed 100 m downstream of the BooNE decay pipe
- Neutrino running parasitic on MiniBooNE with comparable intensity requirements.
- Will help reduce MiniBooNE’s flux errors
- Provide useful information on NC x-section for NuMI
- Other proposals are likely assuming the low energy neutrino beam is still available late in the decade.

## Neutrino Magnetic Moment

- Non-zero neutrino magnetic moment, , is indicative of physics beyond the standard model.
- Theories with extra dimensions predict large ( ≲ 10-11 B ) magnetic moments
- Can be detected through an extra contribution to the neutrino-electron scattering x-section coming from a photon exchange as well as the normal Z exchange.

- (MeV)

## Neutrino Magnetic Moment (cont.)

- Current best measurement by LSND  < 6.8 × 10-10 B
- MiniBooNE hopes to make a modest improvement over the LSND result ( ≲ 4 × 10-10 B )
- To reach sensitivities of order 10-11 B will require
- a detector sensitive to electron recoil energies ≥ 1 MeV
- An order of magnitude more beam than is available with the current facility
- See thesis of Bonnie Fleming for details (http://home.fnal.gov/~bfleming/thesisprint.html)
- To take advantage of the extra intensity available with a PD the current 8 GeV target station and beamline will need to be upgraded

## A Neutron Source for Particle Physics

- Can address many fundamental questions such time-symmetry violation, baryon number conservation, parity violation in strong interactions, right-handed weak currents, and quantum mechanics at the macroscopic scale. [Nucl. Inst. & Meth. **A440** (2000) 471]
- Optimize source design for specific particle physics experiments unlike existing facilities dedicated to neutron scattering experiments.
- Make a long ( 400 s ) pulsed source
- Requires short, high intensity proton pulse
- Complementary to existing short (40 s) pulsed sources.
- Advantages:-
- High peak intensities
- Can use TOF techniques to measure neutron energies
- Reduced backgrounds due to low duty factor

## Existing and Proposed Neutron Sources

- * Projected to turn on in 2006

| Source | Beam Type | Power | Parameters | Time-Avg. Flux | Duty Factor |
| --- | --- | --- | --- | --- | --- |
|   |   | (MW) |   | (1014 n/cm2-s) |   |
| Existing |   |   |   |   |   |
| HIFR (ORNL) | Steady | 100 | Be Reflector | 13.0 | 1.0 |
| ILL (Grenoble) | Steady | 60 | D2O Reflector | 15.0 | 1.0 |
| SINQ (PSI) | Steady | 1.30 | 0.6GeV | 1.0 | 1.0 |
| LANCE (LANL) | Short-pulsed | 0.10 | 0.8GeV, 20Hz | 0.04 | 0.001 |
| ISIS (Rutherford) | Short-pulsed | 0.16 | 0.8GeV, 50Hz | 0.06 | 0.002 |
| SNS* (ORNL) | Short-pulsed | 2.00 | 1.0GeV, 60Hz | 0.7 | 0.0024 |
| Proposed |   |   |   |   |   |
| ESS (PSI) | Short-pulsed | 6.50 | 1.3GeV, 50Hz | 2.5 | 0.002 |
| JHF (JAERI) | Short-pulsed | 1.00 | 3.0GeV, 25Hz | 0.3 | 0.12 |
| FNAL |   |   |   |   |   |
| Booster | Long-pulsed | 0.04 | 8.0GeV, 15Hz | 0.07 | 0.0026 |
| PD synchrotron | Long-pulsed | 0.48 | 8.0GeV, 15Hz | 0.65 | 0.006 |

## Neutron Electric Dipole Moments

- CP violation in flavor-conserving channels would be clear indication of new physics
- Extensions to Standard Model such as extra Higgs, right-handed currents, or SUSY can give rise to EDM
- dn ~ 10-25 - 10-27 e-cm
- Best measurement to date
- P.G. Harris et al, Phys Rev Lett 82 (1999)
- ISIS at RAL
- |dn| < 6.3  10-26
- Probes energy scales beyond the reach of colliders
- Two methods used
- EDM coupled to an external electric field
- EDM coupled to atomic fields during Bragg scattering in crystals
- Magnetic resonance techniques used to detect precession of the EDM

## EDMs with External Fields

- Current best result is based on 1st method
- Can Improve sensitivity of by using trapped ultracold neutrons to maximize time spent in the electric field
- Need pulsed source and TOF to reject higher energy background neutrons
- With even 100 MeV TOF resolution orders of magnitude improvements could be obtained in S/N ratio

## EDMs from Bragg Scattering

- Atomic E-fields are much greater than those generated in the lab
- Time spent in the field is much shorter
- Increasing the sensitivity of the method depends on the use of multiple Bragg scatters
- Made possible by using perfect silicon crystals
- To isolate EDM compare results from both 1.92 Å  and 3.84 Å neutrons
- Both scatter in Si but respond differently to an EDM precession
- Use TOF to separate the two wavelengths

## Neutron Beta Decay

- Provides a  precision measurement of |Vud|
- Need to measure the neutron lifetime, , and the ratio of the vector and axial vector couplings  = gA/gV
- 1/ = 0.1897 |Vud|2 ( 1 + 32 ) ( 1 + 0.0739 ± 0.0008 )
- accurate at the 10-4 level

-  is determined by measuring the beta asymmetry from polarized neutrons
- The current experimental situation is unclear with measurements forming two separated clusters.
- Both  and  measurements are well suited to a long pulse source

## Physics with Low Energy Muon Beams

- Muon system is an excellent place to look for physics beyond the standard model
- There has been considerable interest in pushing the limits on LFV processes  → e decays and  → e conversion in nuclei
- Good examples of existing muon facilities are:-
- The AGS (24GeV, 0.06MW) provides a pulsed muon source of ~ 1011 stopped muons/sec
- Suitable for  → e decay searches
- The PSI cyclotron (590MeV, 1.0MW) produces a continuous beam of up to 108 stopped muons/sec
- Suitable for  → e conversion searches

## Lepton Flavor Violation

- New experiments are currently under construction to address both processes
- MECO at AGS for m → e conversion
- Current limit 10-12
- expect a sensitivity of 10-16
- SUSY predictions  ~10-15
- MEG at PSI for m → eg decay
- Current limit 10-11
- expect a sensitivity of 10-14
- SUSY predictions  ~10-13
- Both experiments are expecting to take data in the latter half of the decade

## Muon Source at FNAL?

- A Proton Driver of the types proposed would be capable of producing more intense beams than at existing facilities
- The physics case will depend strongly on what is learnt from MECO and MEG
- Will a new generation of experiments be necessary? They could discover something!
- If new generation experiments are called for ... will the needed advances be in the muon source or in the detectors themselves
- Future progress could be coupled to the development of a front-end to a neutrino factory based on muon decays.

## Concluding Remarks

- The Booster WILL max out
- A Proton Driver will provide a future for the lab’s growing neutrino program
- It will provide the lab with the flexibility to respond to possible discoveries in the current program
- It also opens up possibilities for other new facilities attracting new user communities
- A surprising amount of work has been done to produce the present level of physics and machine studies
**Further progress will depend on an indication from the lab that it is serious**