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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 Outline g-2 impact today How is g-2 measured? Gerry and g-2 The Future B u N c e 2 0 0 8

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Muon g 2 where have all the muons gone l.jpg
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


Outline l.jpg
Outline

  • g-2 impact today

  • How is g-2 measured?

  • Gerry and g-2

  • The Future

BuNce 2008


Slide3 l.jpg

g-2 impact today

Chapter I


Particle physicists ask l.jpg
Particle Physicists Ask

Why spin?

  • Why matter?

    • CP Violation

  • Why mass?

    • Higgs field

  • Why this standard model?

    • SUSY or other extensions


  • Indirect evidence for new physics from the precision frontier l.jpg
    Indirect evidence for New Physics from thePrecision Frontier

    Muon Storage Ring at BNL


    G 2 experiment theory comparison l.jpg

    Standard Model

    BNL Expt.

    g-2 experiment / theory comparison

    • Key points:

      • Theory: 0.48 ppm

      • Experimental 0.54 ppm (statistics limited!)

    • Dam(expt-thy) = (297±88) x 10-11 (3.4 s)

    deRafael, Glasgow MDM

    Arguably, strongest experimental evidence of Physics Beyond Standard Model


    In 2001 the muon was in the news l.jpg
    In 2001, the muon was in the news…

    Time called the muon “a winner !”


    Slide8 l.jpg

    Compare to Theory

    “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:


    G 2 because of virtual loops many of which can be calculated very precisely l.jpg

    p

    p

    g

    m

    Z

    m

    p

    p

    B

    Good shape

    Not so good shape

    Weak

    Had LbL

    Had VP

    Had VP

    QED

    2006 plot

    KEY REGION

    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 l.jpg

    g

    m

    Z

    m

    p

    p

    p

    p

    B

    Weak

    Had LbL

    Had LbL

    QED

    Had VP

    Had VP

    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 l.jpg
    New physics enters through loops … e.g., SUSY

    R-parity conserving Supersymmetry (vertices have pairs)

    And the diagrams are amplified by powers of tanb(here linearly)


    Slide12 l.jpg

    Typical CMSSM 2D space showing g-2 effectHere 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.

    Present:

    Dam = 297 ± 88 x 10-11

    Future

    Dam = 297 ± 39 x 10-11

    scalar mass

    2s

    1s

    Excluded for neutral dark matter

    gaugino mass

    With new experimental and theoretical precision and same Dam

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


    Slide13 l.jpg

    Expt

    The Snowmass Points and Slopes give reasonable benchmarks to test observables with model predictionsMuon g-2 is a powerful discriminatorno matter where the final value lands!!

    Future?

    Model Version


    Slide14 l.jpg
    Suppose the MSSM reference point SPS1a* is realized and parameters determined by global fit (from LHC results)

    • sgn(m) can’t be obtained from the collider

    • tanbcan’t be pinned down by collider

    Possible future “blue band” plot, where tan β is determined from aμ.

    D. Stockinger

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

    *Snowmass Points and Slopes:

    http://www.ippp.dur.ac.uk/~georg/sps/sps.html



    Muon g 2 is determined from 3 measurements l.jpg

    B

    Muon g-2 is determined from 3 measurements

    (1) Precession frequency

    (2) Muon distribution

    (3) Magnetic field map


    And 4 miracles make it happen l.jpg
    And, 4 miracles make it happen

    • Polarized muons

    n p+ m+


    Muons are created from in flight p decay and enter ring in a bunch l.jpg
    Muons are created from in-flight p decay and enter ring in a bunch


    1997 first evidence that muons are stored l.jpg
    1997: First evidence that muons are stored!

    Matthias has found the electrons !

    149 ns


    E821 used forward decay beam which permitted a large p component to enter ring l.jpg

    Far Side

    Near Side

    A tough reality and delicate balancing act

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

    DP ~ 1.7%

    Pions @ 3.115 GeV/c

    Decay muons @ 3.094 GeV/c


    And 4 miracles make it happen21 l.jpg
    And, 4 miracles make it happen

    • Polarized muons

    • Precession proportional to (g-2)

    n p+ m+

    µ


    Slide22 l.jpg

    e

    Momentum

    Spin

    amis proportional to the difference between the spin precession and the rotation rate


    And 4 miracles make it happen23 l.jpg
    And, 4 miracles make it happen

    • Polarized muons

    • Precession proportional to (g-2)

    • Pm The magic momentum

      E field doesn’t affect muon spin when g = 29.3

    n p+ m+

    µ


    Bnl storage ring l.jpg

    100

    kV

    KICK

    0 500 ns

    incoming muons

    Quads

    BNL Storage Ring

    Only a few percent get stored!


    Magnetic field l.jpg

    2001

    1 ppm contours

    0.05

    0.09

    0.05

    0.07

    0.10

    0.17

    Magnetic Field

    Measured in situ using an NMR trolley

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


    And 4 miracles make it happen26 l.jpg
    And, 4 miracles make it happen

    • Polarized muons

    • Precession proportional to (g-2)

    • Pm The magic momentum

      E field doesn’t affect muon spin when g = 29.3

    • Parity violation in the decay

    n p+ m+

    µ


    Measuring the difference frequency w a l.jpg

    2.5 ns samples

    Counts

    TIME

    Measuring the difference frequency “wa”

    e+

    < 20 ps shifts

    < 0.1% gain change


    1 st plot showing muon precession signal the money plot l.jpg
    1st Plot showing muon precession signal … the “money” plot

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

    Plot made by Prisca Cushman


    Slide29 l.jpg

    Components do

    not pull g-2

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

    N(t) = N0e-t/t[1+Acos(wat + f)]

    Few billion events

    Getting a good c2requires understanding beam motions


    A double blind analysis culture l.jpg
    A double-blind analysis culture

    Magnetic Field

    Secret Offsets

    Secret Offsets

    UIUC

    UIUC

    Data Production

    BU

    Yale

    (Each year had different divisions of labor)


    E821 complete and published l.jpg
    E821 Complete and Published

    14 Individual analyses independent and consistent

    Bennett et al, PRD 73, 072003 (2006)


    Where have all the muons gone l.jpg
    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 …

    The “Gang of Four”

    *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


    Slide33 l.jpg

    Gerry and g-2

    Chapter III


    Slide34 l.jpg

    S

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

    • The rings have great power

    • The rings can consume you

    • The rings will corrupt you


    Gerry a respected counting house leader l.jpg
    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)



    Lots of highly cited papers l.jpg
    Lots of highly cited papers

    Gerry got us all to sign this too



    Gerry s world l.jpg
    Gerry’s World

    Secret passage way into the castle

    g-2 Quiz: Name that part




    Slide42 l.jpg

    The Future

    g-2FiNALe

    Goal: 0.14 ppm; 21 x statistics

    Move ring to FNAL

    Chapter IV


    Slide43 l.jpg

    Then, to accept the higher rate, changes in the experiment are required; e.g.,

    4

    Segmented detectors

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

    Open inflector

    2

    1

    Beamline changes

    3

    Improve kicker


    The g 2 f i nal e next generation experiment aiming at 4x improved precision l.jpg

    Gives 18 Hz of ring fills are required; e.g.,

    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

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


    Use pbar complex as an 800 m long dogbone beamline l.jpg

    pbar target are required; e.g.,

    8 GeV/c protons

    not 120 GeV as is now

    s(p) & 3.1 GeV/c

    Not 24 GeV (~3 lower)

    Li lens

    Pion to muon decay line optics

    New building required for ring

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


    Slide46 l.jpg

    Who will be the new Gerry ? are required; e.g.,

    Key Question


    Slide47 l.jpg

    Final Thought from the Lord(s) of the Ring(s) are required; e.g.,

    • to store muons

    • to observe positrons

    • to connect muons to new physics quantum loops

    One Ring to rule them all,

    One Ring to find them,

    One Ring to bring them all and in the darkness bind them

    THANKS GERRY !!!!!


    The end l.jpg
    The End ! are required; e.g.,


    Slide49 l.jpg
    “Muon Anomalous Magnetic Moment—The Last Word” are required; e.g., Robert W. WilliamsNew Frontiers in High-Energy Physics, 1978

    “I conclude that a super effort might lead to a determination of am 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.”


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