Hadronic Cross Section Measurements with ISR and the Implications on g µ 2

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Hadronic Cross Section Measurements with ISR and the Implications on g µ 2 Konrad Griessinger on behalf of the BABAR Collaboration Institut for Nuclear

1 Hadronic Cross Section Measurements with ISR and the Implications on g µ 2 Konrad Griessinger on behalf of the BABAR Collaboration Institut for Nuclear Physics Mainz University Determination of Fundamental QCD Parameters, 09 March 2016 K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

2 Outline 1 Introduction Theoretical relation a µ σ had Experimental setup at BABAR 2 Recent Results e + e K + K e + e K 0 S K 0 L e + e K 0 K 0 π + π and e + e K 0 S K 0 S K + K 3 Summary K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

3 Introduction The contributions to a µ and its uncertainty µ = g e 2m s (g µ 2)/2 =: a µ = 0 (Dirac) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

4 Introduction The contributions to a µ and its uncertainty µ = g e 2m s (g µ 2)/2 =: aµ SM = aµ QED + aµ weak + aµ hadronic K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

5 Introduction The contributions to a µ and its uncertainty µ = g e 2m s (g µ 2)/2 =: aµ SM = aµ QED + aµ weak + aµ hadronic γ µ + µ QED K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

6 Introduction The contributions to a µ and its uncertainty µ = g e 2m s (g µ 2)/2 =: aµ SM = aµ QED + aµ weak + aµ hadronic γ γ µ + µ µ + µ QED weak K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

7 Introduction The contributions to a µ and its uncertainty µ = g e 2m s (g µ 2)/2 =: aµ SM = aµ QED + aµ weak + aµ hadronic γ γ γ µ + µ µ + µ µ + µ q QED weak q hadronic K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

8 Introduction The contributions to a µ and its uncertainty µ = g e 2m s (g µ 2)/2 =: aµ SM = aµ QED + aµ weak + aµ hadronic Interaction Contribution [ 11 ] Uncertainty [ 11 ] QED [1] EW [5] hadronic VP [4, 9] hadronic LbL [8, 3] total theory E821 experiment [13] deviation exp-theo K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

9 Introduction Discrepancy between SM prediction and direct measurement from Eur.Phys.J., C71:1515, 2011 [4]. HMNT 07 (e + e -based) 285 ± 51 JN 09 (e + e ) 299 ± 65 Davier et al. 09/1 (τ-based) 157 ± 52 Davier et al. 09/1 (e + e ) 312 ± 51 Davier et al. 09/2 (e + e w/ BABAR) 255 ± 49 HLMNT (e + e w/ BABAR) 259 ± 48 DHMZ (τ newest) 195 ± 54 DHMZ (e + e newest) 287 ± 49 BNL-E821 (world average) 0 ± 63 BNL-E a µ a µ exp 11 Just a fluctuation? 3σ effect, thus reduction of uncertainties necessary! K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

10 Introduction Theoretical relation a µ σ had Connection between a µ and σ had a had µ 1 4π 3 m 2 π K µ (s) σ e + e had(s)ds Kernel function cross section K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

11 Introduction Theoretical relation a µ σ had Connection between a µ and σ had a had µ 1 4π 3 m 2 π K µ (s) σ e + e had(s)ds 1.0 GeV ρ, ω 0.0 GeV, Υ ψ 9.5 GeV 3.1 GeV φ, GeV φ, GeV σ had (left) from Nuovo Cim., C034S1:31-40, 2011 [7] and relative contributions to a had µ (right). K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

0 GeV, E e + 3.1 GeV), Luminosity: L 454 fb 1 (Υ (4S)) K.

12 Introduction Experimental setup at BABAR The BABAR Experiment Experimental specifications Energy: s.58 GeV (E e 9.0 GeV, E e GeV), Luminosity: L 454 fb 1 (Υ (4S)) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

13 Introduction Experimental setup at BABAR Initial State Radiation (ISR) events at BABAR e (9GeV) γ s = E CM hadrons γ hadrons e + (3GeV) ISR selection: large angle analyses Detected high energy photon: E γ > 3GeV defines E CM & provides strong background rejection Event topology: γ ISR back-to-back to hadrons high acceptance Kinematic fit including γ ISR very good energy resolution (4 15MeV) e + e -boost into the laboratory reference frame high efficiency at production threshold of hadronic system Continuous measurement from threshold to 5GeV provides common, consistent systematic uncertainties K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

Introduction Experimental setup at BABAR Initial State Radiation (ISR) events at BABAR e (9GeV) γ s = E CM hadrons γ hadrons e + (3GeV) ISR selection: small angle analyses ISR photon γ ISR not

14 Introduction Experimental setup at BABAR Initial State Radiation (ISR) events at BABAR e (9GeV) γ s = E CM hadrons γ hadrons e + (3GeV) ISR selection: small angle analyses ISR photon γ ISR not detected more statistics at high energies Event topology: γ ISR back-to-back to hadrons high acceptance Kinematic fit not including γ ISR energy resolution 15MeV e + e -boost into the laboratory reference frame high efficiency at production threshold of hadronic system Continuous measurement from threshold to 8GeV provides common, consistent systematic uncertainties K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

15 Introduction Experimental setup at BABAR Most important channels Cross Sections of the single channels measured at BABAR (from Nucl.Phys.Proc.Suppl., : , 20 [6]). K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

16 Introduction Experimental setup at BABAR Most important channels ρ, ω 1.0 GeV 0.0 GeV, Υ ψ 9.5 GeV 3.1 GeV φ, GeV φ,... ρ, ω 0.0 GeV, 3.1 GeV 2.0 GeV 1.0 GeV Right panel: Cross Sect. of single channels (from Nucl.Phys.Proc.Suppl., : , 20 [6]). Left panel: Relative contributions to a had µ (from Nuovo Cim., C034S1:31-40, 2011 [7]). K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

17 Introduction Experimental setup at BABAR Most important channels 1.0 GeV ρ, ω, 0.0 GeV, 3.1 GeV 2.0 GeV φ,... Right panel: Cross Sect. of single channels (from Nucl.Phys.Proc.Suppl., : , 20 [6]). Left panel: Relative contributions to δa had µ (from Nuovo Cim., C034S1:31-40, 2011 [7]). K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

18 Recent Results e + e K + K e + e K + K Phys.Rev. D88 (2013) 3, [] Phys.Rev. D92 (2015) 7, [12] K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March 2016 / 25

19 Recent Results e + e K + K Cross section σ(e + e K + K ) Cross section (nb) 3 2 φ(20) Phys.Rev. D88 (2013) 3, BABAR 1 J/ψ and ψ(2s) subtracted Uncertainty of 0.8% near φ peak! s s (GeV) ( luminosity from µµγ and K-ID K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

20 Recent Results e + e K + K Cross section σ(e + e K + K ) Cross section (nb) 3 2 φ(20) Phys.Rev. D88 (2013) 3, BABAR 1 J/ψ and ψ(2s) subtracted s s (GeV) ( a had µ (K + K ) = (229.5 ± 1.4 ± 2.2) 11 improvement by factor 2.8 over previous world data K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

21 2 K 2 2 K Recent Results 2 e + e K + K 2 K A phenomenological fit to the form factor F K BABAR F K 4 3 BABAR 2 / fit - 1 F 1-1 Phys.Rev. D88 (2013) 3, Phys.Rev. D88 (2013) 3, s s (GeV) ( GeV) s s (GeV) ( GeV) BABAR Fit BABAR s (GeV) / fit - 1 F 0.8 BABAR Fit BABAR s (GeV) / fit - 1 F BABAR Fit 0.2 BABAR s (GeV) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

22 Recent Results e + e K + K The Φ parameters m Φ and Γ Φ obtained from the fit of the form factor BABAR m Φ = ± 0.02(±0.11) MeV Γ Φ = 4.29 ± 0.04(±0.07) MeV PDG m Φ = ± MeV Γ Φ = 4.26 ± 0.04 MeV good agreement From integrated Φ peak: Γ ee Φ B(Φ K + K ) = α2 β 3 (s,m K ) mφ Γ Φ aφ 2 C FS BABAR: Γ ee Φ B(Φ K + K ) = ± exp ± fit ± cal kev(1.1%) CMD2: Γ ee Φ B(Φ K + K ) = ± ± kev(2.1%) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

23 Recent Results e + e K + K Charged kaon form factor at large Q 2 Predictions based on QCD in asymptotic regime (Chernyak, Brodsky-Lepage, Farrar-Jackson) Power law: F K α S (Q 2 )Q n with n=2 in good agreement with the data (2.5-5 GeV n = 2. ± 0.23) HOWEVER: data on F K 2 factor 20 above prediction! No trend in data up to 5 GeV for approaching the asymp. QCD prediction F K Phys.Rev. D88 (2013) 3, CLEO BABAR Fit asymptotic QCD prediction s s (GeV) ( K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

24 Recent Results e + e K + K Small angle analysis even larger Q 2 Cross section (pb) Phys.Rev. D92 (2015) 7, M K + K (GeV/c2 ) Small angle measurement reaches energies above 5 GeV Smooth decrease over full energy range K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

25 Recent Results e + e K + K Comparison between small and large angle analysis F K BABAR (LA ISR) CLEO Seth et al. BABAR (SA ISR) Phys.Rev. D92 (2015) 7, M + - K K (GeV/c 2 ) Good agreement between measurements in overlapping region K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

26 Recent Results e + e K + K Asymptotic behavior of the form factor at largest Q 2? M 2 K + K - F K (GeV2 /c 4 ) BABAR (SA ISR) CLEO 0.9 Seth et al CZ (NLO) Asy (NLO) Asy (LO) Phys.Rev. D92 (2015) 7, M + - K K (GeV/c 2 ) At large energies, data tends to agree better with predictions K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

27 Recent Results e + e K 0 S K 0 L e + e K 0 S K 0 L Phys.Rev. D89 (2014) 9, [11] K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

28 Recent Results e + e K 0 S K 0 L Detection of K 0 S K 0 L K 0 S π + π and K 0 L selected via recoil mass Events/ GeV/c Phys.Rev. D89 (2014) 9, Events/ GeV/c Phys.Rev. D89 (2014) 9, m(π + π - ) GeV/c m c rec GeV/c 2 K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

29 Recent Results e + e K 0 S K 0 L K 0 S K 0 L mass spectrum Events/0.001 GeV/c Phys.Rev. D89 (2014) 9, Fit results σ φ = 1409 ± 33 ± 42 ± 15 nb m φ = ± ± ± MeV/c 2 Γ φ = ± 0.3 ± ± MeV Γ ee Φ B(Φ K S 0K L 0) = ±0.0033±0.0122± kev m(k S K L ) GeV/c 2 consistent with world data K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

30 Recent Results e + e K 0 S K 0 L Cross section of e + e K 0 S K 0 L σ (nb) Phys.Rev. D89 (2014) 9, E c.m. (GeV) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

31 Recent Results e + e K 0 S K 0 L Cross section of e + e K 0 S K 0 L σ (nb) σ(k σ S K ( L ) nb) (nb) σ(k 0 S K 0 L ) + σ(k + K ) Phys.Rev. D89 (2014) 9, E c.m. (GeV) -3 Phys.Rev. D89 (2014) 9, E c.m. (GeV) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

32 Recent Results e + e K 0 K 0 π + π and e + e K 0 S K 0 S K + K e + e K 0 S K 0 L π+ π e + e K 0 S K 0 S π+ π e + e K 0 S K 0 S K + K Phys.Rev. D89 (2014) 9, [11] K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

33 Recent Results e + e K 0 K 0 π + π and e + e K 0 S K 0 S K + K Cross sections of e + e K 0 S K 0 L π+ π and K 0 S K 0 S π+ π σ(k S K L π + π - ) (nb) 1 Phys.Rev. D89 (2014) 9, σ(k S K S π + π - ) (nb) Phys.Rev. D89 (2014) 9, J/ψ 0.2 J/ψ E c.m. (GeV) E c.m. (GeV) First cross section measurements Clear J/ψ peaks K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

34 Recent Results e + e K 0 K 0 π + π and e + e K 0 S K 0 S K + K Cross section of e + e K 0 S K 0 S K + K σ(k S K S K+K - ) (nb) Phys.Rev. D89 (2014) 9, J/ψ removed E c.m. (GeV) First cross section measurement J/ψ observed in mass distribution K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

35 Summary Summary ISR physics has proven to be a very productive field even years after the end of data taking at the B-factories Precision measurements of hadronic cross sections have greatly improved aµ SM & more hadronic final states in preparation g µ 2 puzzle needs to be solved Data from new experiments (e.g. BES-III) Light-By-Light scattering needs to be studied E989 at Fermilab and J-PARC g-2/edm QCD predictions on form factors are tested experimentally K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

36 The End Thank you! Any questions? K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

37 Backup slides K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

38 References I [1] T. Aoyama, M. Hayakawa, T. Kinoshita, and M. Nio. Complete tenth-order qed contribution to the muon g 2. Phys. Rev. Lett., 9:111808, Sep [2] G. Bennett et al. Final Report of the Muon E821 Anomalous Magnetic Moment Measurement at BNL. Phys.Rev., D73:072003, [3] G. Colangelo, M. Hoferichter, A. Nyffeler, M. Passera, and P. Stoffer. Remarks on higher-order hadronic corrections to the muon g 2. Phys.Lett., B735:90 91, K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

39 References II [4] M. Davier, A. Hoecker, B. Malaescu, and Z. Zhang. Reevaluation of the Hadronic Contributions to the Muon g 2 and to α(m Z ). Eur.Phys.J., C71:1515, [5] C. Gnendiger, D. Stöckinger, and H. Stöckinger-Kim. The electroweak contributions to (g 2) µ after the Higgs boson mass measurement. Phys.Rev., D88(5):053005, [6] A. Hafner. Exclusive hadronic cross sections measured via ISR from BaBar. Nucl.Phys.Proc.Suppl., : , 20. K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

40 References III [7] F. Jegerlehner. Electroweak effective couplings for future precision experiments. Nuovo Cim., C034S1:31 40, [8] F. Jegerlehner and A. Nyffeler. The Muon g-2. Phys.Rept., 477:1 1, [9] A. Kurz, T. Liu, P. Marquard, and M. Steinhauser. Hadronic contribution to the muon anomalous magnetic moment to next-to-next-to-leading order. Phys.Lett., B734: , K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

41 References IV [] J. P. Lees et al. Precision measurement of the e + e K + K (γ) cross section with the initial-state radiation method at BABAR. Phys. Rev., D88(3):032013, [11] J. P. Lees et al. Cross sections for the reactions e + e K 0 S K 0 L, K 0 S K 0 L π+ π, K 0 S K 0 S π+ π, and K 0 S K 0 S K + K from events with initial-state radiation. Phys. Rev., D89(9):092002, [12] J. P. Lees et al. Study of the e + e K + K reaction in the energy range from 2.6 to 8.0 GeV. Phys. Rev., D92(7):072008, K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

42 References V [13] K. Olive et al. Review of Particle Physics. Chin.Phys., C38:090001, [14] N. Saito. A novel precision measurement of muon g-2 and EDM at J-PARC. AIP Conf.Proc., 1467:45 56, K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

43 2 Breit-Wigner fit function F K 4 3 BABAR Phys.Rev. D88 (2013) 3, s s (GeV) ( GeV) F K (s) = (a φ BW φ (s) + a φ BW φ (s) + a φ BW φ (s))/3 + (a ρ BW ρ (s) + a ρ BW ρ (s) + a ρ BW ρ (s) + a ρ BW ρ (s))/2 + (a ω BW ω (s) + a ω BW ω (s) + a ω BW ω (s) + a ω BW ω (s))/6 with a φ + a φ + a φ = 1 a ρ + a ρ + a ρ + a ρ = 1 a ω + a ω + a ω + a ω = 1 K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

44 K S K S K + K mass spectrum Events/0.05 GeV/c Phys.Rev. D89 (2014) 9, m(k S K S K + K - ) (GeV/c 2 ) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

45 Basic method Definition of g: µ = g e 2m s. Motion in magnetic field: µ Storage Ring ω c = e B mγ, ω l = e B mγ + ae B m, ω a = a e B m. (a = (g 2)/2) spin momentum ω a = a µ eb m µ actual precession 2 Spin precession. [7] K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

46 Direct Measurement Concept ω a is independent of E for γ = 29.3 E µ = γm µ = 3.1 GeV. K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25 Realization in detail Protons from AGS Pions p=3.1 GeV Polarized Muons Inflector Injection Point Target π + µ + νµ Injection Orbit Storage Ring Orbit In Pion Rest Frame π + spin momentum νµ µ + Forward Decay Muons are highly polarized Storage Ring Kicker Modules From π + production to µ + decay. [7] Electric field necessary for focussing: BMT equation ω a = e [ (a µ B a µ 1 ] ) γ 2 v E 1 m µ.

47 Direct Measurement Result Direct Measurement of (g µ 2) Experiment E821 at Brookhaven National Laboratory The result [2]: a µ = ( ± 54 stat ± 33 syst ) 11 K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

48 Direct Measurement Result New Direct Measurement of (g µ 2) Experiment E989 at Fermilab The goal: Reduce uncertainty by factor 4 (!) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

49 Direct Measurement Result New Direct Measurement of (g µ 2) Experiment E989 at Fermilab K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

50 Direct Measurement Result Ultra-cold muon experiment at J-PARC MLF from [14] The goal: Uncertainty of 11 (!) K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

51 Direct Measurement Result Ultra-cold muon experiment at J-PARC MLF from [14] New Method: Produce muons from ionization of muonium, store them and track decay. K. Griessinger (U Mainz) Hadronic Cross Section Measurements 09 March / 25

Review of ISR physics at BABAR

Review of ISR physics at BABAR Konrad Griessinger on behalf of the BABAR Collaboration Institute for Nuclear Physics Mainz University Hadronic Physics with Lepton and Hadron Beams, Jefferson Lab, September