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Latest on muon g-2 from experiment

Latest on muon g-2 from experiment. G.Venanzoni LNF/INFN. Meson production at Intermediate and High Energies - Messina 10/11/11. Muon anomaly as precision test of the SM. Hagiwara et al. arxiv:1105.3149 .

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Latest on muon g-2 from experiment

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  1. Latest on muon g-2 from experiment G.Venanzoni LNF/INFN Meson production at Intermediate and High Energies - Messina 10/11/11

  2. Muonanomalyasprecisiontestofthe SM Hagiwara et al. arxiv:1105.3149 • Long establisheddiscrepancy (>3) between SM prediction and BNL E821 exp. • A twofoldimprovement on a TH-EXPfrom 2001 (thanks to BNL and new e+e-measurements)! • TheoreticalerroraSM(56x10-10) dominated by HLO VP (45x10-10) and HLbL(2.54x10-10). • ExperimentalerroraEXP=6.3 x10-10 (0.54 ppm), E821. Plan to reduce it to 1.6 10-10 (0.14 ppm) by thenew g-2 experimentsat FNAL (E989) and J-PARC. T.Teubner, PHIPSI08 In 2001 aEXP-aTH=(2316)•10-10 HLO VP H LbL aHLO = (692.34.2)10-10 [A.Hoecker, LP11] aHLbL =(10.52.6)10-10[P. dR&V. 08] (11 4)10-10 (J.N.) aHLbL~25-40% aHLO~0.6%

  3. aHLO: L.O. Hadronic contribution to amcan be estimated by means of a dispersion integral: H 1 / s2 makes low energy contributions especially important: in the range < 1 GeV contributes to 70% ! - K(s) = analytic kernel-function - above sufficiently high energy value, typically 2…5 GeV, use pQCD Input: a) hadronic electron-positron cross section data b) hadronict- decays, which can be used with the help of the CVC-theorem and an isospin rotation (plus isospin breaking corrections) (G.dR 69, E.J.95, A.D.H.’97,….) (A., D., H. ’97)

  4. Cross section data: Two approaches: Energy scan (CMD2, SND, BES,CLEO): • energy of colliding beams is changed to the desired value • “direct” measurement of cross sections • needs dedicated accelerator/physics program • needs to measure luminosity and beam energy for every data point Radiative return (KLOE, BABAR, BELLE, BESIII?): • runs at fixed-energy machines (meson factories) • use initial state radiation process to access lower energies or resonances • data come as by-product of standard physics program • requires precise theoretical calculation of the radiator function • luminosity and beam energy enter only once for all energy points • needs larger integrated luminosity

  5. 5 ISR: Initial State Radiation Particle factories (DAFNE, PEP-II, KEK-B) can measure hadronic cross sectionsas a function of the hadronic c.m. energy using initial state radiation (radiative returnto energies below the collider energy √s). hard photon radiated in initial state incoming e+ and e- with M2ee= s hadrons virtual photon g* with M2g*< s The emissionof a hardg in thebremsstrahlungprocess in theinitialstatereducestheenergyavailabletoproducethehadronicsystem in thee+e-collision.

  6. e+e- data: current and future/activities SuperB(?) DAFNE-2(?) HAD ~3-5% ~7-15% ~6% ~1%

  7. Measuredcrosssectionfore+e-→p+ p- (2010)( data: different experiments Measured Cross section for e+e-→p+ p- 08 B. Lee Roberts for the New Muon (g-2) Collaboration – DPF 10 August 2011

  8. Situation ofTwo-pion channel Davieret al., EPJ C 71, 1515 (2011) Most data points dominated by systematic uncertainties that are correlated between data points A. Hoecker LP11

  9. New KLOE result on e+e-→p+ p- by ppg/mmgratio (ISR) An alternative way to obtain |Fp|2is the bin-by-bin ratioofpion overmuonyields(asdonebyBaBar). meas. quantities preliminary • Many radiative corrections drop out: • radiator function • int. luminosity from Bhabhas • Vacuum polarization See Mandaglio’s talk Good agreement with previous measurement!

  10. Multihadronchannelsbetween 1 and 2.5 GeV Davieret al., EPJ C 71, 1515 (2011) BABAR measured (almost) all the exclusive e+e–® hadrons modes Many inconsistencies resolved Huge impact on hadronic vacuum polarisation calculation A.Hoecker LP 11

  11. T. Teubner 08 Exclusive vs inclusive measurements? • Mostrecent inclusive measurements: MEA and B antiB, withtotalintegratedluminosity of 200 nb-1 (one hour of data takingat 1032 cm-2 sec-1).10% stat.+ 15% syst. Errors • 2) New BaBar data isimproving a lotthisregion. Howeverstill the question on the completeness of exclusive data vs systematics of old inclusive measurements s (GeV) E. Solodov, unpublished s (GeV)

  12. New dataatthehorizon: First data from VEPP-2000 @Novosibirsk (L~ 1031 cm-2 sec-1) L~30 pb-1 SND e+e-→2p+2p0 CMD3 e+e-→3p+3p- Additional results also from BaBar, Belle(BES) with ISR, and possibly with DAFNE upgraded in energy (DAFNE-2, see arXiv:1007.521)

  13. Two-pion e+e-vst spectral functions Missing isospin corrections and/or problems with data? Additional data are needed. Meanwhile…

  14. Jegerlehner and Szafron claim that the e+e-vst is solved if an additional correction (r-g mix.) is included F. Jegerlehner and R. Szafron, Eur. Phys. J. C71 (2011) 1632 JS 11 DHMZ 11

  15. What about the lattice? • A new 2-3% lattice result for the lowest-orderhadronic (u,d quarks only) contribution: Very promising results! Prospects for HLBL? Experimental value: Excellent agreement Feng, Jansen, Petschlies, Renner, arXiv:1103.4818v1 [hep-lat]

  16. KLOE-2 to measure gg* → p0,h to constrain amHLBL • Constrain the on-shell amplitudes and remove a significant portion of the theoretical uncertainty on the HLBL • A reasonable improvement on amp0 See Moricciani and Mascolo talks

  17. The SM Value for amfrom e+e-→ hadrons significant work ongoing well known M. Davier, et al., Eur. Phys. J. C (2011) 71: 1515

  18. We need a new (possibly more) (g-2)m experiment(s)! Current discrepancy limited by experimental uncertainty. Twoproposals to improve it x4: • New experiment at FNAL (E989) at magic momentum, consolidated method. 20 x mw.r.t. E821. Relocate the BNL storage ring (12 T) to FNAL. Has got a Stage-1 Approval! • Alternative proposal at J-PARC w/out magic momentum and no E field, requiring ultra-slow muons generated from laser-ionisedmuonium atoms Precision target ~ 16 10-11 . If the central value remains the same  ~7s from SM!

  19. We need a new (possibly more) (g-2)m experiment(s)! Current discrepancy limited by experimental uncertainty. Twoproposals to improve it x4: • New experiment at FNAL (E989) at magic momentum, consolidated method. 20 xmw.r.t. E821. Relocate the BNL storage ring (12 T) to FNAL. Has got a Stage-1 Approval! • Alternative proposal at J-PARC w/out magic momentum and no E field, requiring ultra-slow muons generated from laser-ionisedmuonium atoms Precision target ~ 16 10-11 . If the central value remains the same  ~7s from SM!

  20. Fermilab(g-2)Experiment: • E821 at Brookhaven • E989 at Fermilab • move the storage ring to Fermilab, improved shimming, new detectors, electronics, DAQ • new beam structure that takes advantage of the multiple rings available at Fermilab, more muons per hour, less per fill of the ring

  21. Experimental Technique 25ns bunch of ≥ 1 X 1012 protons Pions p=3.1GeV/c Target Central orbit Kicker Modules R=711.2cm d=9cm R b R Electric Quadrupoles xc xc ≈ 77 mm b ≈ 10 mrad B·dl ≈ 0.1 Tm Inflector (1.45T) Injection orbit • Muon polarization • Muon storage ring • injection & kicking Storage ring • focus with Electric Quadrupoles • 24 electron calorimeters B. Lee Roberts, University of Sussex – 8 July 2011 - p. 21/68 B. L. Roberts, Fermilab , 3 September 2008

  22. Picture of a Lead-Scifi Calorimeter from E821 In E989 we plan to us W-SciFi Calorimeters Waveform digitizer gives t, E

  23. The arrival time spectrum of high-energy e- gt Ee ≥ 1.8 GeV gtm = 64.4 ms; (g-2): ta = 4.37 ms; Cyclotron: tC = 149 ns ms Systematic uncertainty on wa expected to be reduced by 1/3 at E989 (compared to E821) thanks to reduced pion contamination, segmented detectors, and an improved storage ring kick of the muons onto orbit.

  24. wp= Larmor frequency of the freep We measure wa and wpindependently Use l = mm /mp as the “fundamental constant” The magnetic field is measured and controlled using pulsed NMR and the free-induction decay. wp Blind analysis Systematic uncertainty on wp expected to be reduced by a factor ~2 thanks to better shimming (uniformity of B), relocations of critical NMR probes, and other incremental changes

  25. Why Fermilab? • The existence of many storage rings that are interlinked permits us to make the “ideal” beam structure. • proton bunch structure: • BNL 4 X 1012 p/fill: repetition rate 4.4 Hz • FNAL 1012 p/fill: repetition rate 15 Hz • using antiproton rings as an 900m pion decay line • 20 times less pion flash at injection than BNL • 0o muons • ~5-10x increase m/p over BNL • Can run parasitic to main injector experiments (e.g. to NOVA) or take all the booster cycles

  26. Uses 6/20 batches* parasitic to n program Proton plan up to AP0 target is almostthe same as for Mu2e Modified AP2 line (+ quads) New beam stub into ring Fermilab beam complex for (g-2) Polarized muons delivered and stored in the ring at the magic momentum, 3.094 GeV/c beam rebunched in Recycler 4 x (1 x 1012) p *Can use all 20 if MI program is off

  27. The 900-m long decay beam reduces the pion “flash” by x20 and leads to 6 – 12 times more stored muons per proton (compared to BNL) Flash compared to BNL Stored Muons / POT B. Lee Roberts for the New Muon (g-2) Collaboration – DPF 10

  28. Upgrades at Fermilab • New segmented detectors to reduce pileup • W-scifi prototype under study X0 = 0.7 cm • NIM A602 :396-402 (2009). • New electronics • 500 MHz 12-bit WFDs, with deep memories • Improvements in the magnetic field calibration, measurement and monitoring.

  29. Muon (g-2) storage ring to be relocated to FNAL Sikorsky S64F 12.5 T hook weight (Outer coil 8T)

  30. Timeschedule Goal is to be ready for data in 2016 • Total project cost ~$4XM • CD0 expected this year • Conceptual Design Report being prepared • FY2011 Funding began this June • FY12 and beyond is being discussed between DOE and Fermilab

  31. Conclusion • The muon (g-2) has served in the last 10 years as one of the strongest test of the SM • Impressive accuracy of BNL experiment: damEXP = 0.54 ppm • Theoretical prediction has steadily improved thanks to precise e+e- data (uncertainty of ~1%, worldwide effort) damTH= 0.43 ppm • Still a discrepancy of more than 3 “standard deviations” between SM and Experiment; error dominated by experiment • New (g-2)m experiments are foreseen at Fermilab and J-Parc damEXP= 0.14 ppm • Theoretical uncertainty will improve thanks to current and planned experimental activities (as well as theoretical ones) Stay Tuned!

  32. SPARE

  33. Latest on g-2 from experiment G. Venanzoni LNF/INFN LC11: understanding QCD at Linear Colliders in searching for old and new physics - Trento 12 - 16 September 2011

  34. Impact of DAFNE-2 on exclusivechannels in the range [1-2.5] GeV with a scan (Statisticsonly) arXiv:1007.521 e+e-3p • Published BaBar results:89 fb-1(ISR) • “BaBar”  10 (890 fb-1) • KLOE-2 energy scan: 20 pb-1/point • @ L= 1032 cm-2 s-1, 25 MeV bin •  1 year data-taking e+e-2p DAFNE-2 e+e-4p 34 DAFNE-2 is statistically equivalent to 510 ab-1 (Super)B-factory

  35. Impact of DAFNE-2 on (g-2)m arXiv:1007.521 aexp- atheo,SM= (27.7 8.4)10-10 (3.3) [Eidelman, TAU08] 8.4= ~5HLO~3HLbL6BNL 4 2.6DAFNE-2 2.5 1.6NEW G-2 DAFNE-2 7-8 if 27.7 will remain the same) aHLO=5.3=3.3(s<1GeV) 3.9(1< s<2GeV) 1.2(s>2GeV) This means: HAD ~ 0.4% s<1GeV (instead of 0.7% as now) HAD ~ 2% 1<s<2GeV (instead of 6% as now) aHLO2.6=1.9 (s<1GeV) 1.3 (s<1GeV)1.2(s>2GeV) With ISR at 1 GeV With Energy Scan 1-2 GeV Possibleat DAFNE-2! However the project is not yet approved… Precise measurement of HADatlowenergiesveryimportantalso for em(MZ) (necessary for ILC) !!!

  36. The error budget for a new experiment represents a continuation of improvements already made during E821 B. Lee Roberts, University of Sussex – 8 July 2011

  37. The am Experiments: • Place polarized muons in a B field • spin precession frequency (q = ± e) • cyclotron frequency Since g > 2, the spin gets ahead of the momentum

  38. 0 Spin Motion: Use Electric Field for Vertical Focusing Electrostatic quadrupoles cover 43% of ring Small (< 1ppm) correction for muons not at the magic g. G. Venanzoni for the New Muon (g-2) Collaboration – PHIPSI11, September 2011

  39. G. Venanzoni for the New Muon (g-2) Collaboration – PHIPSI11, September 2011

  40. Dispersion Integral: K(s)~1/s • Contribution of different energy regions to the dispersion integral and the error to aHLO ~75% (mostly 2) ~40% ~55% Very important also the region 1-2 GeV error2 contributions aexp 1.5 10-10 = 0.2% onaHLO New g-2 exp.

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