# Presentation: 802931

## The Case for Muons at a Fermilab Proton Driver Facility

- Unique Features of the Proton Driver
- The Physics Case
-  Lepton Flavor Violation (LFV)
-  A  eA
-    e
-    eee
- Muon Electric Dipole Moment (EDM)
- Muon Anomalous Dipole Moment (g-2)
- The Experiments

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Unique Features of the Proton Driver

-   Only a small fraction of the beam from a new 8 GeV PD needed
-     fill MI.  The remainder could be used for a low energy 
-    program that runs simultaneous with a 120 GeV  program.
-  The Recycler Ring could be used to repackage the proton beam
-     to the desired bunch structure
-  Fill Recycler with 1.5 x 1014 protons every 100 ms
- (one missing pulse every 1.5 s for MI)
- ~1.4 x 1022 protons/yr at 8 GeV
-  Gradually empty in 100 ms intervals between PD pulses
-  Extraction could be DC or in bursts
-  Recycler can chop 1.5 x 1014 protons into 588 bunches of
-    0.25 x 1012 protons and a pulse width of 3 ns.
-  Extract one bunch at a time with a fast kicker

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Muon Source

-  Detailed  source design does not exist
-     Straw man design worked out for the front end of a  factory
-     supported by extensive MARS simulations

-  1.4 x 1022 protons/year at 8 GeV yields ~3 x 1021 muons/year.

- Charged particle
- spectra at end of
- decay channel

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Muon Source (cont.)

-    An interface between the decay channel and experiments is required
-  A PRISM-like FFAG ring downstream of the decay channel can reduce
-    the momentum spread and make efficient use of the muon flux
-  Detailed design work required, particularly to develop a cost estimate
-  Could be the first step towards a  factory based on a  storage ring

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## General Statements

- We have learned many important things from 
- The  is a clean laboratory for new physics
- We know that  oscillate and have mass
- Neutral lepton flavor violation
- LFV in  decays that result directly from  mass/mixings are suppressed by small  mass.
- Implies charged LFV at high mass scales
- Enhanced by new dynamics at TeV scale (SUSY?)

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## General Statements (cont.)

- We expect CP violation in the lepton sector
- Manifested in EDMs as well as  oscillations
- _Possible connection with cosmology (leptogenesis)_
- Muon g-2 is a very precise test of SM
- Sensitive to any new particles that couple to muons
- 2.7 signal from BNL g-2 exp.  Hint of new physics?

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Scenario 1 - SUSY discovered at LHC

LFV muon decays, EDM and g-2 should all be enhanced by SUSY.

To understand the detailed nature of SUSY, measurements such as these will have to be made as 
    many of the model’s parameters are only accessible 
    from low-energy experiments.

- LFV muon decays, EDM and g-2 should all be enhanced by SUSY.
- To understand the detailed nature of SUSY, measurements such as these will have to be made as
-     many of the model’s parameters are only accessible
-     from low-energy experiments.

- The Physics Case

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Lepton Flavor Violation 

- No LFV in the SM
- Non-zero masses of  can be explained via the seesaw
-      mechanism with massive right-handed 
- LFV in charged lepton processes is negligibly small for a simple seesaw neutrino model.
- The SUSY seesaw extension to the SM can produce
-      LFV at significant rates

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## SUSY and LFV

- g-2: the diagonal term
- EDM: complex phases
- LFV: the off-diagonal term

- SUSY contains new sources of flavor
- mixing in the mass matrices of
- sleptons and squarks.  LFV processes
- are induced by the off-diagonal
- terms in the slepton mass matrixes

- Off-diagonal terms depend on how SUSY breaking is generated  and
- what kinds of LFV interactions exist at the GUT scale.

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## LFV

- The flavor off-diagonal terms in the slepton mass matrix are induced by  renormalization effects
- due to GUT and/or
- neutrino interactions.

- @ M_Planck

- GUT Yukawa
-  interaction

- Neutrino Yukawa
- interaction

- CKM matrix

- Neutrino oscillation

- L.J.Hall,V.Kostelecky,S.Raby,1986;A.Masiero, F.Borzumati, 1986

- SUSY GUT and SUSY Seesaw model

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## ebranching ratio

- Phys. Lett. **B391** (1997) 341

- Small (<10) tan  values are
- highly disfavoured by combined
- LEP data.
- (ALEPH, DELPHI, L3 & OPAL
- Collaborations, hep-ex/0107030)

- ebranching ratio

- The branching ratio can be large.  The SO(10) SUSY GUT model is ~10-100x larger

- SU(5) SUSY GUT

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## SUSY predictions of A  e-A 

- From Barbieri,
- Hall,
- Hisano ...

**MECO single event sensitivity**

**PRIME single event**
**sensitivity**

-   e & A  eA Branching
- Ratios are linearly correlated** **

-         100                   200                   300  100                   200                   300

- Complementary measurements** **(discrimination between SUSY models)

**R********e**

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Muon g-2

- aexp = 116592080(58) x 10-11  (BNL,  combined)
- aSM = aQED + ahad + aweak = 116591829(73) x 10-11
- aexp - aSM = 251(93) x 10-11 (2.7 )
- Big effect!  Larger than EW contribution.
- Depending on the details of SUSY breaking, amSUSY can be larger than the EW contribution

- A very precise test of the SM

- 215 x 10-11  <  aNP <  637 x 10-11

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## 

- SUSY and g-2

- Chargino and neutralinos
- contribute to g-2 and EDM
- at the one loop level

- For tan  between 4 - 40

- Large tan  limit

- This is right where SUSY particles are generally expected!

- If sparticle masses are measured at the LHC, aNP can be used to
- extract tan  and constrain SUSY mixing.

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Muon EDM

- SM contribution is heavily suppressed.  Observation is
-    unambiguous evidence for new physics.
- Current bound is O(10-19) e cm
- Conventional scaling arguments from better measured e EDM:
- 	d = (m/me)de < 3.3 x 10-25 e cm (90% CL)
- EDM is CPV (assuming CPT).  Sensitive to new physics.  Possible
-    connection to leptogenesis.
- EDM arises from operators similar to g-2, so possible
-    observation of aNP also motivates search for EDM.

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## SUSY and EDMs

- Deviations from lepton mass scaling occur naturally in SUSY
- For SUSY + seesaw, same mechanism responsible for R mass can enhance
- d to the level of 5 x 10-23 e cm, even for small tan  (hep-ph/0006329)

-  EDM greatly enhanced for non-
- degenerate heavy neutrinos
- Leptogenesis requires non-degenerate
- heavy neutrino masses

- A measurement of d = 10-24 probes
- |tan CP| > 3 x 10-3

- aNP  0 can induce an EDM:

-  Magnitude increases with 
- Yukawa couplings and tan 

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## The Physics Case

-     LHC finds SM Higgs at a reasonable mass and nothing else.  g-2 discrepancy is the only indication of new physics beyond non-zero neutrino masses.
- Precision measurements come to the forefront since they are sensitive to heavier virtual physics.
- -e conversion and g-2 are particularly sensitive to a range of new physics beyond SUSY

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Sensitivity to Different Muon Conversion Mechanisms

- Compositeness

- Second Higgs doublet

- Heavy Z’,        Anomalous Z    coupling

- Predictions at 10-15

- Supersymmetry

- Heavy Neutrinos

- Leptoquarks

- After W. Marciano

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Limits on Muon Number Violating Processes

- -e conversion has the greatest mass reach and is more sensitive to nearly all new physics contributions that are not mediated by a photon.
-   e is ~ 300 times more sensitive to processes mediated by a photon.
- Relative rates for eg and -Ne-N give information on underlying physics
- A significant rate for eg with polarized  could give additional information on mechanism

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## g-2 is sensitive to a wide range of new physics 

- besides SUSY

- Muon substructure
- Anomalous             couplings
- Extra Higgs bosons
- Leptoquarks
- Many other things (extra dimensions, etc.)

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## The Experiments - LFV

-   e

-  Continuous beam required.
-  Present upper limit (1.2 x 10-11) expected to be reduced to 10-13
-     (or observed) by MEG - start data taking in 2006
-  Exploiting higher intensities a nontrivial challenge, limited by accidentals.
-  Advances in detector design required for further advance.

-   eee

-  Continuous beam required
-  Improved sensitivity beyond current bound of 1 x 10-12 an easier task
-  High rate tracking required
-  Sensitivity of ~10-16 possible (hep-ph/0109217)

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

##   e

-  Requires pulsed beam with small extinction and small p/p
-  Current limit of 6.1 x 10-13 should be pushed to 10-17 by MECO and 10-19
-     by PRIME.
-  Sensitivity dominated by performance of pulsed beam.
-  Measurement can continue to benefit from increased beam intensity.

- e  e

-  Further progress requires a pulsed beam
-  Current limit of 8 x 10-11 could be extended to 10-13  (hep-ph/0109217)
-  Detector requirements closely resemble those for   3e

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Future Progress in g-2

-  E969 at BNL: 	0.5 ppm accuracy (0.27 ppm sys, 0.46 ppm stat)
-  Plans for upgrade (not yet funded):  0.5  0.20 ppm
-  Reduce sys. error by x2
-  Increase statistical sample by x9
-  + near-term improvement in theory  Significant confrontation with SM

-  A new dedicated g-2 experiment
-     could improve precision by 4x
-  Reduce sys. error by x7
-  Increase stat. sample by x200
-  Substantial R&D required
-  New ring or improve present ring?

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## New Approach to  EDM

**side**
**view**

- New Approach to  EDM

- Precession
- of  in
- storage ring

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

##  EDM

-  Current sensitivity of 3.4 x 10-19 e cm expected to be improved to 10-24
-     using new method at JPARC.
-  SUSY calculations range from 10-22 to 10-32 e cm, so more muons needed
-  Measurement is rate limited.  Need many short pulses separated
-     by > 500 ns

-  EDM

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Desirable Beam Characteristics

| Experiment |  | I0/Im  | T
[ns]  | T
[s]  | p
[MeV]  | p/p
  |
| --- | --- | --- | --- | --- | --- | --- |
| A  eA
  e
  eee
e e  | 1021
1017
1017
1016  | < 10-10
n/a
n/a
< 10-4  | < 100
n/a
n/a
< 1000  | > 1
n/a
n/a
> 20  | < 80
< 30
< 30
< 30  | < 5
< 10
< 10
1...2  |
|   | 1014 | < 10-4  | 100  | > 20  | 30 | < 10 |
| g-2
EDM  | 1015
1016  | < 10-7
< 10-6  | < 50
< 50  | > 103
> 103  | 3100
<1000  | < 2
< 2  |

- hep-ph/0109217

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Summary

-  Important  physics experiments can be executed at a PD facility
-  LFV
-  g-2
-  muon EDM
-  The physics case for these measurements is solid
-  These measurements are complementary to other methods
-     that explore the frontier beyond the Standard Model
-  Depending on what is found at the LHC, they may be the only
-    way to get at this information.
-  In either case, they will provide essential information in our
-    attempt to discover and understand physics beyond the
-    Standard Model

- R. Ray for the muon working group, Fermilab Proton Driver Workshop

## Summary (cont.)

-  The combination of a new PD and the existing Recycler can
-    provide a unique facility with unmatched intensity and flexibility
-  An 8 GeV  program could run simultaneous with a 120 GeV
-    MI program
-  Some effort needs to be put into the design of a muon source
-     to understand cost and feasibility issues.
-  This could be the first step towards a  factory

- R. Ray for the muon working group, Fermilab Proton Driver Workshop