Achim Denig Experimental Summary Experimental Summary Achim Denig University of Mainz Institute for Nuclear Physics MITP Workshop on the Hadronic Contribution to (g-2) µ Schloss Waldthausen, Mainz April 5, 2013 Simon Eidelman: VEPP-2000 Andreas Hafner: ISR Results Andrzej Kupsc:γγ-physics (I) Simon Eidelman: γγ-physics (II) Input for HVP Input for HLbL

Achim Denig Experimental Summary Anomalous Magnetic Moment of the Muon 2 New (g-2) µ ring arrived at FNAL, also JPARC measurement Factor 4 improvement! Let's speculate assume new exptl. measurement will be 1 sigma higher than today's value  without change in theoretical value Δa μ = a μ exp – a μ SM = 4.3 sigma  reduction of theoretical uncertainty of factor 2: Δa μ = 7.7 sigma

Achim Denig Experimental Summary Electroweak Precision Physics α em (M Z 2 ) limiting electroweak precision fits  Test overall consistency of the electroweak Standard Model  Since the discovery of the Higgs boson more timely than ever 3 SM running sin 2 Θ W (M Higgs ) limited by α em New data from JLAB, Mainz, LHC

Achim Denig Experimental Summary Exp. Input relevant for HVP 4 22  < 2 GeV 2-5GeV >5GeV  Jegerlehner (2010)

Achim Denig Experimental Summary 5  s [GeV]  had [mbarn] Hadronic Cross Section via Energy Scan 1 st Generation R < 11 GeV  60's, 70's, 80's, 90's measurements from Orsay, Frascati, SLAC, Novosibirsk BES Beijing 2 -5 GeV. Novosibirsk < 1.4 GeV Excl. channels 2 nd Generation Expts.  new millenium VEPP-2M Novosibirsk BEPC Beijing Energy Scan = systematic variation of collider’s √s Inclusive R meas.

Achim Denig Experimental Summary Overview Novosibirsk Results CMD-2: π + π - <1%, higher multiplicities few % accuracy SND measurement of π + π - with 1.2% accuracy CMD-2 6

Achim Denig Experimental Summary 7 VEPP-2000: Upgrade E max =2.0 GeV VEPP-2000 (since 2010): Upgrade towards E max =2.0 GeV, concept of round beams L max = cm -2 s -1 at 2 GeV, presently 20% reached Upgrade of detectors CMD-3, SND Statistics already now competitive with BABAR

Achim Denig Experimental Summary 8 New Results VEPP-2000 BaBar CMD-3 pbarp threshold e + e - -> 3(     ) PLB 723, 82 e + e - -> ωπ 0 ->π 0 π 0 γ PRD D88, SND, preliminary Precision goals: 2π: ~0.3% multi-hadronic: ~ few % Many many other final states under investigation …. e + e - -> π + π - π + π - γ

Achim Denig Experimental Summary 9  s [GeV]  had [mbarn] Hadronic Cross Section via Radiative Return e-e- e+e+  ISR Hadrons M hadr Initial State Radiation (ISR) aka Radiative Return Possible at modern particle factories Needs no systematic variation of beam energy High statistics thanks to high integrated luminosities  Entire E range <√s accessible Rev. Mod. Phys. 83, 1545–1588 (2011) BABAR & BELLE √s=10.6 GeV DA  NE KLOE √s=1.02 GeV

Achim Denig Experimental Summary Tagged analysis: ISR photon measured in KLOE-Calorimeter Increased amount of Final State Radiation (FSR) Untagged analysis: No ISR detection; cut on missing momentum Threshold mass region not accessible PublicationModeNormalizationInt. Luminosity* Phys.Lett. B606 (2005) 12untaggedRadiator141 pb -1 Phys.Lett. B670 (2009) 285untaggedRadiator240 pb -1 Phys.Lett. B700 (2011) 102taggedRadiator232 pb -1 Phys.Lett. B720 (2013) 336untagged  240 pb -1 *full KLOE statistics 2,500 pb -1 KLOE: ISR at 1.02 GeV (DA  NE) 10

Achim Denig Experimental Summary BABAR: Pion Form Factor Normalization to muon yield! BABAR, PRL 103, (2009) < 1% systematic. uncertainty 11

Achim Denig Experimental Summary Comparison BABAR vs. KLOE: e + e       Although both KLOE and BABAR claim < 1% accuracy, large deviations seen ?! Reason unknown CMD-2, SND with larger statistical errors  inbetween KLOE / BABAR

Achim Denig Experimental Summary Summary of ISR Results Accuracy: 2π: < 1% 3π: ~10% 4π: ~ 3% ≥ 5π: 10% and higher 13

Achim Denig Experimental Summary Summary of ISR Results 14

Achim Denig Experimental Summary 15 ρ resonance Flagship analysis: e + e -  π + π - tagged γ ISR Pion form factor < 3 GeV ISR Programme Future

Achim Denig Experimental Summary BES: 3-5% stat. accuracy BESIII: <<1% BESIII online spectrum 2013/14 energy scan New R scan New R Scan 16 R measurement foreseen in 3 phases R in range 2 – 4.5 GeV ~1% statistical, 3% systematic accuracy  improve α QED (m Z 2 ) by factor 2 R in range 2 – 3 GeV, high statistics  Improve nucleon IG E I/IG M I ratio Fine binning R ratio in charmonium region  charmonium spectroscopy NEW

Achim Denig Experimental Summary Summary I: HVP 17 Dominating 2π channel measured with < ~1% accuracy  most precise ISR measurements (KLOE, BABAR) in conflict with each other  cross check by BESIII - ISR  VEPP-2000 aims for unprecedented accuracy 0.3% Higher multiplicities dominated by BABAR ISR measurements  cross check and improvement expected by VEPP-2000, BESIIII BELLE-II in intermediate future ?! Issues: - Radiative corrections - Precise formfactor models in MC - FSR modelling

Achim Denig Experimental Summary Exp. Input relevant for HLbL 18 hopefully

Achim Denig Experimental Summary 19 General: Transition Formfactors F(Q 1 2, Q 2 2 )

Achim Denig Experimental Summary 20  , ,  Selection criteria –1 electron (positron) detected –1 positron (electron) along beam axis –Meson fully reconstructed –Measured electron-meson system with low p t –Missing mass close to 0 Momentum transfer –tagged: Q 2 = -q 1 2 = -(p - p’) 2  Highly virtual photon –untagged: q 2 = -q 2 2 ~ 0 GeV 2  Quasi-real photon F(Q 2,0) SL Meson Transition Formfactors F(Q 2,0) Single Tag Method

Achim Denig Experimental Summary 21 ~7 % difference low Q 2 ~10…15% high Q 2 Difference BABAR – BELLE ~2σ syst  puzzling situation ? Predictions for various distribution amplitudes (including QCD corrections) World's Knowledge of

Achim Denig Experimental Summary 22 World's Knowledge of  Timelike and spacelike data seem to be equal  Slope at high Q 2 much less pronounced Include timelike transition FF data from BaBar taken at Q 2 = s  (4S) = 112 GeV 2 Additional CLEO point at Q 2 =14.2 GeV 2   , 

Achim Denig Experimental Summary 23 Relevance for HLbL courtesy: V. Pauk, JGU Weighting functions dominate at low Q < 2 GeV ! Pseudoscalar Mesons Axial Vector Mesons

Achim Denig Experimental Summary 24 Impact of KLOE-II Future Installation of dedicated tagging detectors close to beam pipe

Achim Denig Experimental Summary 25 Impact of BESIII 10fb √s=3.77 GeV Presently available: 2.9 √s=3.77 GeV ~ 4 √s> 4 GeV  Close gap in Q 2 btw. future KLOE-II and existing CLEO data MonteCarlo π0π0 η

Achim Denig Experimental Summary 26 Impact of BESIII no tag double tag single tag courtesy: N. Asmussen, JGU Single tag analysis: Q 2 range above 0.3 GeV 2 accessible M ππ mass spectrum down to threshold Background from di-muon and radiative Bhabha evts. Improved vs. of EKHARA needed Goal: 5 … 10% accuaracy

Achim Denig Experimental Summary 27 Timelike (TL) FFs  JLAB photo prod.  LNF/Frascati DA  NE  factory  BES-III ‘  -c Factory’  MAMI Crystal Ball photo prod.  Jülich WASA/pp Achim Denig Experimental Summary Meson Factories

Achim Denig Experimental Summary A2 / MAMI: TL FF Accepted by Phys. Rev. C: S. Prakhov, M. Unverzagt et al. (A2 collab.) Vector Meson Dominance model: Λ -2 =(1.95 ± 0.15 stat ± 0.10 syst ) GeV -2 TL calculation: S. Leupold, C. Terschlüsen Padé calculation: R. Escribano, P. Masjuan, P. Sanches-Puertas

Achim Denig Experimental Summary Summary II: HLbL 29 Huge experimental progress in all kinematic ranges KLOE-II and BESIII will measure pseudoscalar TFF in low Q 2 range Hadronic models need to be validated by data  exptl. accuracy in most cases not yet precise enough Dispersion relations for HLbL calculation  nice interplay btw. theory and experiment

Achim Denig Experimental Summary Conclusions 30 Further reduction of factor 2 of uncertainties of hadronic corrections of (g-2) µ does not seem to be impossible !

Achim Denig Experimental Summary 31 Additional slides

Achim Denig Experimental Summary TL FF Future New precision data expected from: - VEPP KLOE-ISR - BESIII-ISR ?

Achim Denig Experimental Summary Novosibirsk VEPP-2M: √s < 1.4 GeV VEPP-2M collider: GeV in c.m., L  2 * cm -2 s -1 at 1 GeV Detectors CMD-2 (solenoidal B field) and SND (w/o B field) Integrated Luminosity collected by CMD-2 and SND: 70 pb -1 to be compared to 6 pb -1 in Orsay and Frascati at higher energies 33

Achim Denig Experimental Summary KLOE: Pion Form Factor Achim Denig Review of R measurements Features Approx. 1% systematic. uncertainties Coverage from threshold to 1 GeV Agreement btw. KLOE data sets within systematic uncertainties  Cross check for Radiator and Luminosity 34

Achim Denig Experimental Summary BEPC:  incl ( e + e   Hadrons ) 35 Results 3-5 % statistical accuracy per scan point Systematic uncertainty: ~5 …8% Major improvement of R Best measurement to date Important QCD test Of utmost importance for α em (m Z 2 ) arXiv:hep-ex/ arXiv:hep-ex/

Achim Denig Experimental Summary Summary of ISR Results 36 Published results: Data set: fully available 450 fb -1 older results based on 245 (90) fb -1

Achim Denig Experimental Summary ISR-channel e + e           Typical features: Systematic uncertainty: 3% (precision results up to 1.4 GeV also from VEPP-2M) Above 1.4 GeV: BABAR improves significantly over old expts. from Extraction of J/ψ BR‘s with competitive precision to charm factories J/ψ         PDG12 37

Achim Denig Experimental Summary 38 Impact of BESIII Future 10fb √s=3.77 GeV Presently available: 2.9 √s=3.77 GeV ~ 4 √s> 4 GeV  Close gap in Q 2 btw. future KLOE-II and existing CLEO data Data 2.9 fb √s=3.77 GeV π < Q 2 < 0.5 GeV 2

Achim Denig Experimental Summary 39 ISR-channel e + e       Precision on  peak: 0.8% Extract Mass and Width of  (1020) in good agreement with PDG12; similar in precision as PDG Huge deviation from Brodsky-Lepage pQCD prediction: F K 2 = 8π f K 2 α S (Q 2 )/Q 2 preliminary NEW

Achim Denig Experimental Summary BABAR: Nucleon Form Factors 40 Cross section parametrized by magnetic and electric form factors G M and G E Conflicting results ?! Ratio ΙG E Ι/ΙG M Ι Effektive FF  IFI 2 NEW arXiv: : Analysis on full data set

Achim Denig Experimental Summary 41 Radiative Return at BELLE BELLE ISR programme lead to important results on charmonium spectroscopy So far no publication on light hadron systems below 3 … 4 GeV (prelimary result on e+e-  π + π - π 0 ) No clear indication of e.g. Y(4260) resonance seen in J/ψ ππ D 0 D 0 bar D + D*  D* + D*  D0Dπ+D0Dπ+ D 0 D*  π + PRL 98 (2007) e+e-  D*+D*-, D+-D*-+ PRL 99 (2007) e+e-  π+π- J/ψ PRL 99 (2007) e+e-  π+π- ψ(3685) PRD 77(2008) e+e-  D 0 +D 0 bar-, D+-D- PRL 100 (2008) e+e-  D 0 +D-π+ PRL 101 (2008) e+e-  Λ c + Λ c -, Λ c 0 Λ c 0 bar

Achim Denig Experimental Summary CMD-2 Measurement  (e + e    +    0.7%0.6% (95)/ 0.8% (98) % ~ 9  10 5  +  - events 4 running campaigns, overall fair agreement Radiative corrections with 0.3% uncertainty systematic uncertainty 42 Phys.Lett.B578(2003)285 JETP.Lett.82(2005)743 JETP.Lett.84(2006)413 PLB648(2007)78

Achim Denig Experimental Summary BABAR and BELLE Scan Bottominium 43 Scan of R b = σ(e+e-  bbar)/σ(e+e-  μ+μ-) in Bottomonium region Identify bbar by event shape Asymmetric Υ(5S) peak oberserved Difficult interpretation (many channels) Υ(5S) peak obsesved as in BABAR Anomalous decay patterns of decays from Υ(5S) in lower lying Υ resonances arXiv: arXiv:

Achim Denig Experimental Summary Rely on tagged (=measured) photon for identifying ISR-events High fiducial efficiency : wide-angle ISR-g forces hadronic system into detector fiducial region at large polar angles Harder momentum spectrum due to boost - fewer problems with soft particles; - allows to go down to threshold Can access a very wide mass range in one single experiment: from threshold to GeV Features : BABAR: ISR at 10.6 GeV  ISR Hadrons 44

Achim Denig Experimental Summary 45 Radiative Return at BELLE ISR programme lead to important results on charmonium spectroscopy So far no publication on light hadron systems below 3 … 4 GeV (prelimary result on e+e-  π + π - π 0 ) Y(4360) Y(4660) Y(4260) PRL 98 (2007) e+e-  D*+D*-, D+-D*-+ PRL 99 (2007) e+e-  π+π- J/ψ PRL 99 (2007) e+e-  π+π- ψ(3685) PRD 77(2008) e+e-  D 0 +D 0 bar-, D+-D- PRL 100 (2008) e+e-  D 0 +D-π+ PRL 101 (2008) e+e-  Λ c + Λ c -, Λ c 0 Λ c 0 bar

Achim Denig Experimental Summary 46 ISR-channel e + e           BaBar preliminary  (1700)  (1450) BaBar preliminary  (2050) E c.m. [GeV]  ( e + e            nb  E c.m. [GeV] Typical features: Second most important contribution for (g-2)  Precision (preliminary result): 8% Analysis on full data (454 fb -1 ) sample almost ready: ~4% systematic uncertainty preliminary

Achim Denig Experimental Summary 47 Running Fine Structure Constant  QED (0) = 1 / 137  QED (M Z 2 ) = 1 / 129 {    (s) q q  had (5) Contribution to is the hadronic vacuum polarization contribution of the five lightest quarks u,d,s,c,b Low energy contributions are less  weighted in dispersion integral  from which energy range on  use pQCD?  had (5) ** **  lept (M Z 2 )=  had (M Z 2 )= ± (5) [ F. Jegerlehner ArXiv: ]