# Presentation: 396160

## Muon g-2:Where have all the muons gone? 

**David Hertzog**

***Bunce Symposium***

**Gerry**

**Collaboration:**
***	******Boston, BNL, Budker, Cornell, Heidelberg, Illinois, ***
***	******KVI, KEK, Minnesota, Tokyo, Yale***

## g-2 impact today 

**g-2 impact today **

**B****u****N****c****e ****2****0****0****8**

**Outline**

**How is g-2 measured?**

**Gerry and g-2**

**The Future**

## g-2 impact today

**g-2 impact today**

## Particle Physicists Ask

**Why matter? **
**CP Violation**
**Why mass?**** **
**Higgs field**
**Why this standard model?****	**
**SUSY or other extensions**

**Why spin?**

## Indirect evidence for New Physics from thePrecision Frontier

**Muon Storage Ring at BNL**

## g-2 experiment / theory comparison  

**Key points: **
**Theory: **_**0.48 ppm**_
**Experimental 0.54 ppm  ****(statistics limited!)**
******a********(expt-thy) = (297±88) x 10****-11**** (3.4 ******** **

**deRafael, Glasgow MDM**

**Arguably, strongest experimental evidence of Physics Beyond Standard Model**

## In 2001,  the muon was in the news...

**In 2001,  the muon was in the news...**

**Time called the muon “a winner !”**

## “I will spare you the long, checkered, sometimes amusing history of the theory here, with it’s sign flips, and “gotcha” corrections, and them there radiative corrections, and hard-to-figure-out loops with those pions and other stuff that goes on kinda’ quick when you aren’t really looking to see if it’s so and such ...” (S.P.)

**“****I will spare you the long, ****checkered****, sometimes ****amusing**** history of the theory here, with it’s sign flips, and “****gotcha****” corrections, and them there radiative corrections, and hard-to-figure-out loops with those pions and other stuff that goes on kinda’ quick when you aren’t really looking to see if it’s so and such ...” (S.P.)**

**“****Look you guys, put the damn number on the table !”**
**T. Kirk (BNL) New York Times, August, 2002**

**Just tell the theorists:**

**Compare to Theory**

## g ≠ 2 because of virtual loops, many of which can be calculated very precisely

**A significant amount has happened in 2008 ... some confirming ... some unnerving**

## Hadronic light-by-light is settling down (finally)

**This is new, based on combined work by three leading groups**

## New physics enters through loops ... e.g., SUSY

**R-parity conserving Supersymmetry (vertices have pairs)**

**And the diagrams are ****amplified by *****powers***** of tan******** ****(here linearly)**

## Typical CMSSM 2D space showing g-2 effectHere and in next slides, we also project a reduced uncertainty on expt/thy from 88 to 39 in 10-11 units based on a next-generation expt.

**Typical CMSSM 2D space showing g-2 effect****Here and in next slides, we also project a reduced uncertainty on expt/thy from 88 to 39 in 10****-11**** units based on a next-generation expt.**

**This CMSSM calculation: Ellis, Olive, Santoso, Spanos.  Plot update: K. Olive**

**gaugino mass**

**scalar mass**

**Excluded for neutral dark matter**

**1******

**2******

**With new experimental and theoretical precision and same ********a******

**Present:**
******a****** = 297 ± 88 x 10-11

**Future**
******a****** = 297 ± 39 x 10-11

## The Snowmass Points and Slopes give reasonable benchmarks to test observables with model predictionsMuon g-2 is a powerful discriminator no matter where the final value lands!!

**Model Version**

**Future?**

## Suppose the MSSM reference point SPS1a* is realized and parameters determined by global fit (from LHC results)

**sgn(********)****  can’t be obtained from the collider**
**tan******** ****can’t be pinned down by collider**

**Possible future “****blue band****” plot, where tan *****β *****is determined from *****a******μ*****.**
**D. Stockinger**

*******Snowmass Points and Slopes:**
**http://www.ippp.dur.ac.uk/~georg/sps/sps.html**

******* SPS1a is a ``Typical '' mSUGRA point with intermediate tan******** = 10**

## How is g-2 measured ?

**How is g-2 measured ?**

## (1)  Precession frequency

(2)  Muon distribution

(3)  Magnetic field map

**(1)  Precession frequency**
**(2)  Muon distribution**
**(3)  Magnetic field map**

**Muon g-2 is determined from 3 measurements**

## And, 4 miracles make it happen

**And, 4 miracles make it happen**

**P****olarized muons**
**	**** **

**************************

## Muons are created from in-flight  decay and enter ring in a bunch

## 1997: First evidence that muons are stored!

**Matthias has found the electrons !**

**149 ns**

## E821 used forward decay beam, which permitted a large  component to enter ring

**Pions @ 3.115 GeV/c**

**Decay muons @ 3.094 GeV/c**

******P ~ 1.7%**

## And, 4 miracles make it happen

**And, 4 miracles make it happen**

**P****olarized muons**
**	**** **
**P****recession proportional to (*****g*****-2) **
**	**

**************************

**μ**

## a is proportional to the difference between the spin precession and the rotation rate

***a********* ****is proportional to the difference between the spin precession and the rotation rate**

## And, 4 miracles make it happen

**And, 4 miracles make it happen**

**P****olarized muons**
**	**** **
**P****recession proportional to (*****g*****-2) **
**	**
**P******** The magic momentum**
***E***** field doesn’t affect muon spin when ******** = 29.3**

**************************

**μ**

## BNL Storage Ring

**BNL Storage Ring**

**Only a few percent get stored!**

## Magnetic Field

**Continuously monitored using 150 fixed probes mounted above and below the storage region**

**Measured *****in situ***** using an NMR trolley**

## And, 4 miracles make it happen

**And, 4 miracles make it happen**

**P****olarized muons**
**	**** **
**P****recession proportional to (*****g*****-2) **
**	**
**P******** The magic momentum**
***E***** field doesn’t affect muon spin when ******** = 29.3**
**P****arity violation in the decay**

**************************

**μ**

## Measuring the difference frequency  “a”

**Measuring the difference frequency  ****“********a****”**

**e****+**

**< 20 ps shifts**
**< 0.1% gain change**

## 1st Plot showing muon precession signal ... the “money” plot

**Plot made by Prisca Cushman**

**But, Gerry got all of us who were awake then to sign it too**

## Data can “almost” be fit using a simple 5-parameter function

**Few billion events**
**Getting a good ********2**** ****requires understanding beam motions**** **

**Data can “almost” be fit using a simple 5-parameter function**

***N(t)*****  =  *****N******0***** ****e****-*****t*****/************[1+*****A******cos*****(***********a******t***** + **********)]**

## A double-blind analysis culture

**Data Production**

**Secret Offsets**

**Secret Offsets**** **

**Magnetic Field**

**Yale**

**UIUC**

**UIUC**

**BU**

**(Each year had different divisions of labor)**

## E821 Complete and Published

**14 Individual analyses independent and consistent**

**Bennett et al, PRD **_**73**_**, 072003 (2006)**

## Where have all the muons gone?*

**Where have all the protons gone?**
**Gone to pions, every one ...**
**Where have all the pions gone?**
**Gone to muons, every one ...**
**Where have all the muons gone?**
**Gone to electrons, every one ...**
**Where have all the spokesmen gone?**
**Gone to coffee, every one ...**

***Apologies to Pete Seeger. **
**The complete set of our lyrics, ****once sung on Gerry’s deck**** at a pool party, remain locked unto the year 2050**

**The “Gang of Four”**

## Gerry and g-2

**Gerry and g-2**

## S

**The rings have great power**
**The rings can consume you**
**The rings will corrupt you**

**Gerry Bunce, Bill Morse, Vernon Hughes, Gordon Danby + hosts of others **

**S**

## Gerry, a respected counting house leader ...

**Gerry, like MacArthur, has returned !!**
**Now we will stabilize our beam and**
**Gotham will be safe once again ...  (Ofer, 1997)**

## A Proud Papa

## Lots of highly cited papers

**Gerry got us all to sign this too**

## Toys’ for Grown Boys

## Gerry’s World

**Secret passage way into the castle**

**g-2 Quiz:  Name that part**

## Gerry: Casting the Golden Ring

## ...while building the ring ...

**...****while building the ring ...**

## The Future
g-2FiNALe
Goal:  0.14 ppm;  21 x statistics
Move ring to FNAL

**The Future**
**g-2****F****i****NAL****e**
**Goal:  0.14 ppm;  21 x statistics**
**Move ring to FNAL**

## For BNL E969, we identified some obvious places to improve the muon transmission and to prepare for higher rate  

**Improve kicker**

**Open inflector**

**Beamline changes**

**For BNL E969, we identified some obvious places to improve the muon transmission and to prepare for higher rate****  **

**1**

**2**

**3**

## The g-2FiNALe “next-generation” experiment aiming at >4x improved precision

**The g-2****F****i****NAL****e “next-generation” experiment aiming at >4x improved precision**

**Gives 18 Hz of ring fills**
**BNL was 4.4 Hz**
**Intensity being studied, but expect 1year run will achieve the x21 statistics goal**
**Most items are costed**
**Including moving the ring**
**Goal is < $20 M **
**Target area least understood**

## Use pbar complex as an 800 m long “dogbone” beamline

**Use pbar complex as an ****800 m**** long “dogbone” beamline**

**pbar target **
**8 GeV/c protons **
**not 120 GeV as is now**
** ********(********) & 3.1 GeV/c**
**Not 24 GeV (~3 lower)**
**Li lens**
**Pion to muon decay line optics**
**New building required for ring**

## Who will be the new Gerry ?

**Who will be the new Gerry ?**

## One Ring to rule them all,    
One Ring to find them, 	
One Ring to bring them all and in the darkness bind them

**One Ring to rule them all,    **
**One Ring to find them, ****	**
**One Ring to bring them all and in the darkness bind them**

**Final Thought from the Lord(s) of the Ring(s)**

**to store muons**
**to observe positrons**
**to connect muons to new physics quantum loops**

**THANKS GERRY !!!!!**

## The End !

## “Muon Anomalous Magnetic Moment—The Last Word”Robert W. WilliamsNew Frontiers in High-Energy Physics, 1978

**“****I conclude that a super effort might lead to a determination of ****a******** to between 1 and 2 parts per million ...”**
**“****It is the end of an era; the muon g-2 worker is no longer a Kit Carson blazing a trail in the wilderness, but more like a**** J. Edgar Hoover**** keeping a watchful eye on the imaginative excesses of theorists.”**