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Measurement of Muon (g-2) and Future Prospects

Measurement of Muon (g-2) and Future Prospects. David Hertzog University of Illinois at Urbana-Champaign. Motivation The theory situation The basic experimental requirements Specifics. Our piece of the PhiPsi08 poster. UED. Here is an example, related to g-2. SUSY.

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Measurement of Muon (g-2) and Future Prospects

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  1. Measurement of Muon (g-2) and Future Prospects David Hertzog University of Illinois at Urbana-Champaign • Motivation • The theory situation • The basic experimental requirements • Specifics Our piece of the PhiPsi08 poster

  2. UED Here is an example, related to g-2 SUSY SUSY Extra Dimensions The future am measurement will separate the two models by more than 7 standard deviations and thus allow for a clear decision in favor of one of them The quest for new physics understanding requires different tools • LHC: direct search for new particles • But, what new physics will they reveal? • Precision measurements: • Lepton flavor violation (m, t) • EDMs of e, n, atoms, etc. • Rare decays • 0nbb • Unitarity tests • Muon g-2 Consider a post-LHC world with many new mass states found

  3. TIME Compare K. Hagiwara, A.D. Martin, Daisuke Nomura, T. Teubner Arguably, strongest experimental evidence of Physics Beyond Standard Model The Standard Model theory has improved. Hopefully at this Workshop we will learn even more • Key points: • Theory: 0.48 ppm • Experimental 0.54 ppm (0.46 ppm stat; 0.31 ppm syst.) • Dam(expt-thy) = (297±88) x 10-11 (3.4 s) deRafael, Glasgow MDM

  4. p p g m Z m p p B 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 key discussion point at this Workshop, so I will defer to the experts

  5. g m Z m p p p p B Weak Had LbL Had LbL QED Had VP Had VP g ≠ 2 because of virtual loops, many of which can be calculated very precisely • Hadronic Light by Light has a 36% relative uncertainty !! ~ 0.34 ppm • Leading contribution must be positive • But, then we need a hadronic model • Many constraints, but can we achieve 15% relative error ? • At Glasgow, we learned of several new efforts • A Dyson-Schwinger calculation (C. Fischer) • Two independent lattice efforts (Hayakawa et al; Rakow for QCDSF) THIS IS THE QUESTION WE GET ASKED ALL THE TIME BY FUNDING COMMITTEES

  6. 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)

  7. Typical CMSSM 2D space showing g-2 effect(note: NOT an exclusion plot) Present: Dam = 297 ± 88 x 10-11 Future Dam = 297 ± 39 x 10-11 Here, neutralino accounts for the WMAP implied dark matter density 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 Topical Review: D. Stöckinger hep-ph/0609168v1

  8. Sidebar: There are LOTs of “SUSYs” • General MSSM has > 100 free parameters. • Advantage: Well, we don’t know them  open minded. • Disadvantage: Not predictive, but experiments can “restrict” parts of this multi-dimensional space • Beware of claims of “Ruling Out SUSY” ! • CMSSM – “constrained” and, related but even more constrained, MSUGRA, … and others • These models assume many degeneracies in masses and couplings in order to restrict parameters. • Typically: m0, m1/2, sgn(m), tanb, A (or even fewer) • Then there is R parity – is sparticle number conserved? • And, many ways to describe EW symmetry breaking

  9. 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 SPS Definitions

  10. 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 With these SUSY parameters, LHC gets tan b of 10.22 ± 9.1. Tan b “blue band” plot based on present aμ. Possible future “blue band” plot, where tan β is determined from aμ to < 20% or better D. Stockinger sexp = 25 x 10-11 * SPS1a is a ``Typical '' mSUGRA point with intermediate tanb = 10 *Snowmass Points and Slopes: http://www.ippp.dur.ac.uk/~georg/sps/sps.html

  11. Dam improvement requires both experimental and theoretical progress units: x 10-11 This would get to ~9s Combined Error Experimental Error Actual path ? Theory Error

  12. e Momentum Spin Final report: Bennett et al, PRD 73, 072003 (2006) Considerations to aim at ~15 x 10-11 experimental precision

  13. The BNL storage ring will remain the central element

  14. wa 1 ppm contours Muon g-2 is determined by a ratio of two precision measurements:waand B(and some knowledge of the muon orbit) Improving here requires greater statistics … x 25 (to be discussed) And, reducing background and controlling fit parameters from beam motions B Improving here requires more uniform field – shimming, and in the delicate procedure to calibrate and measure the field – using pNMR

  15. NA2 2.5 ns samples N A <A>=0.4 An “event” is an isolated electron above a threshold. Higher rate exacerbates pileup & gain stability issues e+ Lab Frame N, A and NA2

  16. Then, to accept the higher rate, changes in the experiment are required; e.g., 4 Segmented detectors More muons are available, even in the existing experimental setup. Open inflector 2 1 Quad doubling 3 Improve kicker

  17. It is instructive to understand the muon production, first with the standard “forward-decay” beam The FLASH is a limiting factor to just “turning up the rate” for any new expt. Survive momentum selection Pions @ 3.15 GeV/c Decay muons @ 3.094 GeV/c The hadronic flash background limits fit start time Far side Near inflector Pedestal vs. Time

  18. p m Muon Accumulator Ring MAR How to get more muons AND avoid the flash • Take the 0-degree forward muons • High polarization, highest yield • Long beamline to remove flash by pion decay • “Recycle” by muon accumulator ring (MAR) • Very long beamline • Take 180-degree “backward” muons • High polarization (reversed), slightly smaller yield • Intrinsically, no flash because of p/m momentum difference

  19. Catch most muons in first 2 turns. Although spin precesses, it’s okay Rest of turns just reduce pions by decay time Figure of Merit NP2 increased by factor of ~12 or more Fast “Switcher” magnet required to flick beam straight (default is stay in ring to avoid background) p/m Fluxes and Figure of Merit p/m m p 0 1 2 3 4 5 6 7 8 Number of turns in racetrack MAR: Muon Accumulator Ring

  20. Alternatively, consider a single long beamline Removed pions Got muons Ideal…

  21. Ideal conditions at FNAL using 8 GeV p • Long beamline possible; more m, less flash • High repetition rate of muon fills in ring • 84 fills / 1.4 sec (x 14.5 compared to BNL)  x 25 stats in ~1 year m->e g-2 Rare Kaon Decays m Test Facility or along TeV ring g-2

  22. 3.15 GeV/c pions 5.4 GeV/c pions 3.094 GeV/c muons For JPARC, high-intensity, 30 GeV p beam, and tight space suggests backward decay beam

  23. Can inject wider DP/P pions beam into decay channel to increase flux 2nd-order achromat to inject pions into channel

  24. Both Sides Expected No hadron-induced prompt flash In the backward decay beam, large difference in p/m momentum eliminates pion flash. Lorentz boos limits yield. Pions @ 5.32 GeV/c Decay muons @ 3.094 GeV/c DP/P opened up here to catch more flux

  25. Geant simulation using new detector schemes Event Method Same GEANT simulation Energy Method A complementary method of determining wa is to plot Energy versus Time

  26. I did not discuss the equally important issue of systematic error improvements … • Magnetic field • Make it more uniform • Keep muons better centered • Improve precision of the calibration probe interpolation, which implies position precision • Precession signal • Detector gain stability monitoring improvements • Pileup reduction • Muon loss reduction (better kicker) • Alternative methods of analysis (Q and T)

  27. Conclusions • A next-generation experiment is likely to happen. • My remarks: • Motivation sharp with respect to LHC era physics search • A few theory clarifications will go a long way to give the project higher priority • Resolution of tau vs ee problem in HVP • Confirmation of VEPP-2M ee result from KLOE and BaBar • Progress (or at least a believable path) toward improved HLbL hertzog@uiuc.edu

  28. SPS points and slopes • SPS 1a: ``Typical '' mSUGRA point with intermediate value of tan_beta. • SPS 1b: ``Typical '' mSUGRA point with relatively high tan_beta; tau-rich neutralino and chargino decays. • SPS 2: ``Focus point '' scenario in mSUGRA; relatively heavy squarks and sleptons, charginos and neutralinos are fairly light; the gluino is lighter than the squarks • SPS 3: mSUGRA scenario with model line into ``co-annihilation region''; very small slepton-neutralino mass difference • SPS 4: mSUGRA scenario with large tan_beta; the couplings of A, H to b quarks and taus as well as the coupling of the charged Higgs to top and bottom are significantly enhanced in this scenario, resulting in particular in large associated production cross sections for the heavy Higgs bosons • SPS 5: mSUGRA scenario with relatively light scalar top quark; relatively low tan_beta • SPS 6: mSUGRA-like scenario with non-unified gaugino masses • SPS 7: GMSB scenario with stau NLSP • SPS 8: GMSB scenario with neutralino NLSP • SPS 9: AMSB scenario SPS PLOT www.ippp.dur.ac.uk/~georg/sps/sps.html

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