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Light flavor at e + e colliders: Impact of hadronic cross sections on g 2 Andreas Hafner (hafner@slac.stanford.edu) Mainz University On behalf of the B A B A R Collaboration FPCP May 23, 2013 Andreas Hafner (Mainz University) ISR at

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SLIDE 1

Light flavor at e+e−colliders: Impact of hadronic cross sections on gµ − 2

Andreas Hafner (hafner@slac.stanford.edu)

Mainz University On behalf of the BABA

R Collaboration

FPCP May 23, 2013

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 1 / 24

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SLIDE 2

Outline

1

Motivation: muon-anomaly (g − 2)µ

2

Initial State Radiation (ISR) analyses at BABA

R

3

Status of Hadronic Cross Section Measurements e+e− → p¯ p e+e− → π+π−π+π− e+e− → K +K −

4

Summary

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 2 / 24

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SLIDE 3

Motivation: muon-anomaly (g − 2)µ Introduction and direct measurement

The anomalous magnetic moment of the muon (g − 2)µ

gyromagnetic ratio: g

  • µ = g e

2mc ·

S spin 1

2 → Dirac theory: g = 2

QFT: g = 2

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 3 / 24

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SLIDE 4

Motivation: muon-anomaly (g − 2)µ Introduction and direct measurement

The anomalous magnetic moment of the muon (g − 2)µ

gyromagnetic ratio: g

  • µ = g e

2mc ·

S spin 1

2 → Dirac theory: g = 2

QFT: g = 2 muon anomaly: aµ = (g − 2)µ/2 atheory

µ

= aQED

µ

+aweak

µ

+ahad

µ

BNL E821 11 659 208.9 ±6.4

Brookhaven National Laboratory (BNL) [G.W. Bennett et al., PRD73, 072003 (2006)] aµ units in 10−10

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 3 / 24

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SLIDE 5

Motivation: muon-anomaly (g − 2)µ Introduction and direct measurement

The anomalous magnetic moment of the muon (g − 2)µ

gyromagnetic ratio: g

  • µ = g e

2mc ·

S spin 1

2 → Dirac theory: g = 2

QFT: g = 2 muon anomaly: aµ = (g − 2)µ/2 atheory

µ

= aQED

µ

+aweak

µ

+ahad

µ

BNL E821 11 659 208.9 ±6.4 QED 11 658 471.809±0.015 weak 15.4 ±0.2

γ µ+ µ+ γ µ+ µ+ QED weak Z 0 γ

[T.Kinoshita et al., PRD73, 013003 (2006)] [A.Czarnecki et al., PRD67, 073006 (2003) Erratum-ibid. D73, 119901 (2006)] [M.Knecht et al., JHEP 0211, 003 (2002)] aµ units in 10−10

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 3 / 24

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SLIDE 6

Motivation: muon-anomaly (g − 2)µ Introduction and direct measurement

The anomalous magnetic moment of the muon (g − 2)µ

gyromagnetic ratio: g

  • µ = g e

2mc ·

S spin 1

2 → Dirac theory: g = 2

QFT: g = 2 muon anomaly: aµ = (g − 2)µ/2 atheory

µ

= aQED

µ

+aweak

µ

+ahad

µ

BNL E821 11 659 208.9 ±6.4 QED 11 658 471.809±0.015 weak 15.4 ±0.2 had 693.0 ± 4.9

hadro

  • had. vacuum polarisation
  • had. cross section

αQCD ≈ O(1) αQCD

q ¯ q

q ¯ q

hadronic

  • ptical theorem

e− e+ hadrons

γ µ+ µ+

aµ units in 10−10

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 3 / 24

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SLIDE 7

Motivation: muon-anomaly (g − 2)µ Introduction and direct measurement

The anomalous magnetic moment of the muon (g − 2)µ

gyromagnetic ratio: g

  • µ = g e

2mc ·

S spin 1

2 → Dirac theory: g = 2

QFT: g = 2 muon anomaly: aµ = (g − 2)µ/2 atheory

µ

= aQED

µ

+aweak

µ

+ahad

µ

BNL E821 11 659 208.9 ±6.4 QED 11 658 471.809±0.015 weak 15.4 ±0.2 had 693.0 ± 4.9 BNL−SM 28.7 ±8.0

hadro

  • had. cross section

e− e+ hadrons

  • exp. input

dispersion relation: ahad

µ,LO = 1 4π3

∞

m2

π0 ds K(s) σhad(s)

K(s) ∼ 1/s & σhad(s) ∼ 1/s →∼ 1/s2 (low energies important!)

⇓ 3.6σ [M. Davier et al., EPJ C71, 1515 (2011)]

aµ units in 10−10

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 3 / 24

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SLIDE 8

ISR at BABA R

PEP-II and the BABA

R detector at SLAC

asymmetric e+e−-collider: 9 GeV (e−) and 3.1 GeV (e+) √s = 10.58 GeV ⇒ Υ(4S) ⇒ above BB-threshold main purpose: B-physics multi purpose detector data taken from 1999 – 2008 integrated luminosity: 531 fb−1

  • n Υ(4S): 454 fb−1

≈ 600 · 106 BB-pairs

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 4 / 24

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SLIDE 9

ISR at BABA R

Initial State Radiation (ISR) events at BABA

R

ISR selection Detected high energy photon: Eγ > 3 GeV → defines ECM & provides strong background rejection Event topology: γISR back-to-back to hadrons → high acceptance Kinematic fit including γISR → very good energy resolution (4 – 15 MeV) e+e−-boost into the laboratory reference frame → high efficiency at production threshold of hadronic system Continuous measurement from threshold to ∼4.5 GeV → provides common, consistent systematic uncertainties

hadrons γ e−(9 GeV) e+(3 GeV) √ s′ = ECM γ

hadrons Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 5 / 24

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SLIDE 10

ISR at BABA R

ISR analyses at BABA

R

published e+e− → π+π−

PRD 86 (2012) 032013, PRL 103 (2009) 231801

e+e− → φf0(980)

PRD 74 (2006) 091103, PRD 76 (2007) 012008

e+e− → π+π−π0

PRD 70 (2004) 072004

e+e− → K +K −η, K +K −π0, K 0

S K ±π∓

PRD 77 (2008) 092002, PRD 71 (2005) 052001

e+e− → 2(π+π−)

PRD 85 (2012) 112009, PRD 76 (2007) 012008

e+e− → K +K −π0π0, K +K −π+π−, 2(K +K −)

PRD 86 (2012) 012008, PRD 76 (2007) 012008

e+e− → 2(π+π−)π0, 2(π+π−)η, K +K −π+π−π0, K +K −π+π−η

PRD 76 (2007) 092005

e+e− → 3(π+π−), 2(π+π−π0), 2(π+π−)K +K −

PRD 73 (2006) 052003

e+e− → p¯ p

PRD 87 (2013) 092005, PRD 73 (2006) 012005

e+e− → Λ ¯ Λ, Λ ¯ Σ0, Σ0 ¯ Σ0

PRD 76 (2007) 092006

e+e− → c¯ c → . . . . . . . . . about to be submitted for publication to PRD e+e− → K +K −

  • ngoing analyses

e+e− → K 0

S K 0 L , π+π−π0π0, K 0 S K ±π∓π0/η

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 6 / 24

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SLIDE 11

Recent results e+e− → p¯ p

e+e− → p¯ p

Based on 469 fb−1: PRD 87 (2013) 092005 Update of PRD 73 (2006) 012005 based on 232 fb−1 Efficiency obtained from simulation [K¨

uhn et al., EPJC 18 (2001),497]

Measure Cross Section σ Extract effective form factor: σ = 4πα2βC

3m2

p¯ p |FF|2, |FF| =

  • |GM|2 + 1

2τ |GE|2

Measure the ratio |GE/GM| from angular distributions

dσ dcosθ ∼ (1 + cos2θ) + τ| GE GM |2sin2θ

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 7 / 24

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SLIDE 12

Recent results e+e− → p¯ p

Form factor in comparison to other experiments

FENICE DM2 DM1 BES PS170 E835 E760 BABAR

Mpp

– (GeV/c2)

Proton form factor

0.2 0.4 0.6 2 2.25 2.5 2.75 3

(a)

BES CLEO NU E835 E760 BABAR

Mpp

– (GeV/c2)

Proton form factor

0.02 0.04 0.06 0.08 3 3.5 4 4.5

(b)

Steep rise at threshold seen by PS170 confirmed → tail of a resonance below threshold? FF exhibits sharp drops at Mp¯

p =2.2 GeV and 3 GeV

Good fit to pQCD prediction: Brodsky-Lepage [PRL 43 (1979) 545]: FF ∼ α2

S(Mp¯ p)

M4

p¯ p

(Mp¯

p > 3 GeV

/c2)

FENICE DM2 DM1 BES CLEO NU PS170 E835 E760 BABAR

Mpp

– (GeV/c2)

Proton form factor

10

  • 2

10

  • 1

2 3 4 Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 8 / 24

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SLIDE 13

Recent results e+e− → p¯ p

Time-like |GE/GM| measurements

BABA

R measurement:

Angular distributions from threshold up to 3 GeV Observe maximum at Mp¯

p ≈ 2 GeV

/c2 Inconsistent with PS170 measurement at LEAR ISR method → weak angular dependence of detection efficiency

dσ(GM) dcosθ

∼ 1 + cos2θp

dσ(GE ) dcosθ ∼ sin2θp

BABAR PS170

Mpp

– (GeV/c2)

|GE/GM|

0.5 1 1.5 2 2.25 2.5 2.75 3 Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 9 / 24

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SLIDE 14

Recent results e+e− → p¯ p

Contributions of Exclusive Final States to gµ − 2

Contributions of different energy regions to the dispersion integral

0.0 GeV, ∞ ρ, ω 1.0 GeV φ, . . . 2.0 GeV 3.1 GeV

ψ

9.5 GeV

Υ

1

→ E < 1 GeV region dominates → π+π− channel needed!

ahad

µ

Integral

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 10 / 24

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SLIDE 15

Recent results e+e− → p¯ p

π+π− Cross Section

[GeV] s 0.5 1 1.5 2 2.5

  • 1

10 1 10

2

10

3

10

TOF OLYA CMD CMD2 KLOE08 KLOE10 SND DM1 DM2 BABAR Average

  • π

+

π →

  • e

+

e

[GeV] s 0.5 1 1.5 2 2.5

  • 1

10 1 10

2

10

3

10 [GeV] s 0.7 0.72 0.74 0.76 0.78 0.8 0.82 0.84 400 600 800 1000 1200 1400

OLYA CMD CMD2 KLOE08 KLOE10 SND DM1 BABAR Average

[GeV] s 0.7 0.72 0.74 0.76 0.78 0.8 0.82 0.84 400 600 800 1000 1200 1400

ρ peak ρ − ω interference Dip at 1.6 GeV: excited ρ states Dip at 2.2 GeV Contribution to ahad

µ : 75%!

Systematic Uncertainties BABA

R:

CMD-2: SND: KLOE: 0.5% 0.8% 1.5% 0.8%

σπ+π−[ nb] σπ+π−[ nb]

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 11 / 24

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SLIDE 16

Recent results e+e− → p¯ p

π+π− Cross Section

[GeV] s 0.5 0.6 0.7 0.8 0.9 1 Cross section(exp) / Average - 1

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 Average BABAR

  • π

+

π →

  • e

+

e [GeV] s 0.5 0.6 0.7 0.8 0.9 1 Cross section(exp) / Average - 1

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 [GeV] s 0.5 0.6 0.7 0.8 0.9 1

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 Average KLOE08 KLOE10

  • π

+

π →

  • e

+

e

[GeV] s 0.5 0.6 0.7 0.8 0.9 1

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2

KLOE and BABA

R dominate the world average

Uncertainty of both measurements smaller than 1% Systematic difference, especially above ρ peak Difference → relatively large uncertainty for ahad

µ

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 12 / 24

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SLIDE 17

Recent results e+e− → p¯ p

π+π− Cross Section

[GeV] s 0.5 0.6 0.7 0.8 0.9 1 Cross section(exp) / Average - 1

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 Average BABAR

  • π

+

π →

  • e

+

e [GeV] s 0.5 0.6 0.7 0.8 0.9 1 Cross section(exp) / Average - 1

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 [GeV] s 0.5 0.6 0.7 0.8 0.9 1

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 Average KLOE08 KLOE10

  • π

+

π →

  • e

+

e

[GeV] s 0.5 0.6 0.7 0.8 0.9 1

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2

KLOE and BABA

R dominate the world average

Uncertainty of both measurements smaller than 1% Systematic difference, especially above ρ peak Difference → relatively large uncertainty for ahad

µ

Need to solve this discrepancy!

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 12 / 24

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SLIDE 18

Recent results e+e− → p¯ p

Contributions of Exclusive Final States

Contributions of different energy regions to the dispersion integral

0.0 GeV, ∞ ρ, ω 1.0 GeV φ, . . . 2.0 GeV 3.1 GeV

ψ

9.5 GeV

Υ

0.0 GeV, ∞ ρ, ω 1.0 GeV φ, . . . 2.0 GeV 3.1 GeV

Precise measurements 1 GeV < E < 2 GeV needed! High multiplicity channels! Why new analyses? Improve Statistics Improve Systematics Use existing data for bkg subtraction

σ[ nb]

⇒ ⇒

Integral ahad

µ π+π−

Uncertainty δahad

µ Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 13 / 24

slide-19
SLIDE 19

Recent results e+e− → π+π−π+π−

e+e− → π+π−π+π−

  • Phys. Rev. D85, 112009 (2012), based on 454 fb−1

supersedes our previous publication, based on 89 fb−1 of the data:

  • Phys. Rev. D71, 052001 (2005).

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 14 / 24

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SLIDE 20

Recent results e+e− → π+π−π+π−

Internal structure in various ECM energy slices

5000 1 2 3 4 10000 1 2 3 4 10000 20000 2000 4000 1 2 3 4 500 1000 1 2 3 4 200 1 2 3 4 Entries / 25 MeV/c2 1.0 - 1.4 GeV/c2 1.4 - 1.8 GeV/c2 1.8 - 2.3 GeV/c2 2.3 - 3.0 GeV/c2 M3π (GeV/c2) 3.0 - 4.5 GeV/c2

a1(1260) DATA MC

(EPJ C18, 497 (2001))

First column (4 entries/event): a1(1260)

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 15 / 24

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SLIDE 21

Recent results e+e− → π+π−π+π−

Internal structure in various ECM energy slices

5000 1 2 3 4 5000 0.5 1 1.5 2 2.5 10000 1 2 3 4 10000 20000 0.5 1 1.5 2 2.5 2000 4000 1 2 3 4 5000 0.5 1 1.5 2 2.5 500 1000 1 2 3 4 1000 2000 0.5 1 1.5 2 2.5 200 1 2 3 4 500 0.5 1 1.5 2 2.5 Entries / 25 MeV/c2 1.0 - 1.4 GeV/c2 1.4 - 1.8 GeV/c2 1.8 - 2.3 GeV/c2 2.3 - 3.0 GeV/c2 M3π (GeV/c2) 3.0 - 4.5 GeV/c2 M2π (GeV/c2)

a1(1260) ρ0 DATA MC

(EPJ C18, 497 (2001))

First column (4 entries/event): a1(1260) Second column (4 entries/event): strong ρ0 contribution e.g. for M4π > 1.4 GeV /c2: 1/4th of entries in ρ0 peak ρ0ρ0 is forbidden → ρ0 in each event!

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 15 / 24

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SLIDE 22

Recent results e+e− → π+π−π+π−

Internal structure in various ECM energy slices

5000 1 2 3 4 5000 0.5 1 1.5 2 2.5 1000 0.5 1 1.5 2 2.5 10000 1 2 3 4 10000 20000 0.5 1 1.5 2 2.5 1000 2000 0.5 1 1.5 2 2.5 2000 4000 1 2 3 4 5000 0.5 1 1.5 2 2.5 250 500 0.5 1 1.5 2 2.5 500 1000 1 2 3 4 1000 2000 0.5 1 1.5 2 2.5 100 0.5 1 1.5 2 2.5 200 1 2 3 4 500 0.5 1 1.5 2 2.5 Entries / 25 MeV/c2 1.0 - 1.4 GeV/c2 1.4 - 1.8 GeV/c2 1.8 - 2.3 GeV/c2 2.3 - 3.0 GeV/c2 M3π (GeV/c2) 3.0 - 4.5 GeV/c2 M2π (GeV/c2) M2π (GeV/c2) 20 0.5 1 1.5 2 2.5

a1(1260) f0(980) ρ0 f2(1270) DATA MC

|Mother

2π

  • Mρ| < 25 MeV

/c2 (EPJ C18, 497 (2001))

First column (4 entries/event): a1(1260) Second column (4 entries/event): strong ρ0 contribution e.g. for M4π > 1.4 GeV /c2: 1/4th of entries in ρ0 peak ρ0ρ0 is forbidden → ρ0 in each event! Third column (1 entry/event): 2π lie within ρ0 mass → other π+π−’s mass plotted f2(1270), a1(1260), f0(980) . . .? → Partial Wave Analysis needed

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 15 / 24

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SLIDE 23

Recent results e+e− → π+π−π+π−

Cross section for e+e− → π+π−π+π−

5 10 15 20 25 30 35 0.5 1 1.5 2 2.5 3 3.5 4 4.5 ECM (GeV) σ(e+e- → π+π-π+π-) (nb)

J/ψ

Systematic uncertainties

2.4% in peak region (1.1-2.8 GeV) 11% (0.6-1.1 GeV) 4% (2.8-4.0 GeV)

J/ψ visible

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 16 / 24

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SLIDE 24

Recent results e+e− → π+π−π+π−

Cross section for e+e− → π+π−π+π−

5 10 15 20 25 30 35 0.5 1 1.5 2 2.5 3 3.5 4 4.5 ECM (GeV) σ(e+e- → π+π-π+π-) (nb)

J/ψ

Systematic uncertainties

2.4% in peak region (1.1-2.8 GeV) 11% (0.6-1.1 GeV) 4% (2.8-4.0 GeV)

J/ψ visible

5 10 15 20 25 30 35 40 1000 1500 2000 2500 3000 3500

ECM (MeV) σ(e+e- → π+π-π+π-) (nb)

ND OLYA CMD SND M3N DM1 GG2 DM2 CMD2 BaBar 2005 BaBar 2012 1 2 3 4 600 800 1000

< 1.4 GeV: agreement with previous BABA

R results, SND and CMD-2 data

> 1.4 GeV: highest precision (DM2, 20%)

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 16 / 24

slide-25
SLIDE 25

Recent results e+e− → K+K−

e+e− → K +K −

PRELIMINARY

→ about to be submitted to PRD, based on 232 fb−1 Efficiency obtained from simulation [K¨

uhn et al., EPJC 18 (2001),497]

→ data/MC corrections of utmost importance: trigger, tracking, K-ID and mis-ID Unfolding bkg-subtracted and data/MC corrected mass spectrum PHOKHARA [Czy˙

z et al., EPJC35 (2004) 527; EPJC39 (2005), 411]

→ Geometrical acceptance → 2ndorder ISR corrections ISR effective luminosity from µµγ(γ): KK/µµ ratio

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 17 / 24

slide-26
SLIDE 26

Recent results e+e− → K+K−

Cross section σ(e+e− → K +K −)

PRELIMINARY Bare cross section including FSR Φ(1020) BABA

R

Uncertainty of 0.8% near φ peak!

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 18 / 24

slide-27
SLIDE 27

Recent results e+e− → K+K−

A phenomenological fit to the form factor

BABA

R

BABA

R PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 19 / 24

slide-28
SLIDE 28

Recent results e+e− → K+K−

Comparison to other experiments

PRELIMINARY PRELIMINARY PRELIMINARY

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 20 / 24

slide-29
SLIDE 29

Recent results e+e− → K+K−

The Φ parameters

mΦ and ΓΦ obtained from the fit of the form factor BABA

R

mΦ = 1019.51 ± 0.02 ± 0.05sys MeV ΓΦ = 4.29 ± 0.04 ± 0.06sys MeV PDG mΦ = 1019.455 ± 0.020 MeV ΓΦ = 4.26 ± 0.04 MeV → good agreement From integrated Φ peak: Γee

Φ × B(Φ → K +K −) = α2β3(s,mK ) 324 m2

Φ

ΓΦ a2 ΦCFS

BABA

R:

Γee

Φ ×B(Φ → K +K −) = 0.6344±0.0059exp±0.0028fit±0.0015cal keV(1.1%)

CMD2: Γee

Φ × B(Φ → K +K −) = 0.605 ± 0.002 ± 0.013 keV(2.1%)

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 21 / 24

slide-30
SLIDE 30

Recent results e+e− → K+K−

Charged kaon form factor at large Q2

Predictions based on QCD in asymptotic regime (Chernyak, Brodsky-Lepage, Farrar-Jackson) Power law: FK ∼ αS(Q2)Q−n with n=2 →in good agreement with the data (2.5-5 GeV n = 2.10 ± 0.23) HOWEVER: data on |FK|2 factor ∼ 20 above prediction! No trend in data up to 25 GeV2 for approaching the asymp. QCD prediction

PRELIMINARY

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 22 / 24

slide-31
SLIDE 31

Recent results e+e− → K+K−

Impact on gµ − 2

0.0 GeV, ∞ ρ, ω 1.0 GeV φ, . . . 2.0 GeV 3.1 GeV

ψ

9.5 GeV

Υ

0.0 GeV, ∞ ρ, ω 1.0 GeV φ, . . . 2.0 GeV 3.1 GeV

[PR 477, 1 (2009).]

ahad

µ

δahad

µ (all aµ units in 10−11)

ahad

µ (K +K −) = 216.3 ± 2.7 ± 6.8

↓ ahad

µ (K +K −) = 229.5 ± 1.4 ± 2.2

calculation only based on BABA

R 2013 data!

ahad

µ (π+π−π+π−) = 133.5 ± 1.0 ± 5.2

↓ ahad

µ (π+π−π+π−) = 136.4 ± 0.3 ± 3.6

calculation only based on BABA

R 2012 data! Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 23 / 24

slide-32
SLIDE 32

Recent results e+e− → K+K−

Impact on gµ − 2

0.0 GeV, ∞ ρ, ω 1.0 GeV φ, . . . 2.0 GeV 3.1 GeV

ψ

9.5 GeV

Υ

0.0 GeV, ∞ ρ, ω 1.0 GeV φ, . . . 2.0 GeV 3.1 GeV

[PR 477, 1 (2009).]

ahad

µ

δahad

µ (all aµ units in 10−11)

ahad

µ (K +K −) = 216.3 ± 2.7 ± 6.8

↓ ahad

µ (K +K −) = 229.5 ± 1.4 ± 2.2

calculation only based on BABA

R 2013 data!

ahad

µ (π+π−π+π−) = 133.5 ± 1.0 ± 5.2

↓ ahad

µ (π+π−π+π−) = 136.4 ± 0.3 ± 3.6

calculation only based on BABA

R 2012 data! E [MeV]

cm

s Æp p pp (e e )[nb]

+

  • +
  • 1000

1200 1400 1600 1800 2000 5 10 15 20 25 30 35 40 45

PRELIMINARY

dominant contribution to δahad

µ :

ahad

µ (π+π−π0π0) = 180.1 ± 0.3 ± 12.4

⇓ BABA

R analysis in progress

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 23 / 24

slide-33
SLIDE 33

Summary

Summary

Measurement of hadronic cross sections via ISR is a very productive field in addition to B-physics at BABA

R

Most accurate measurements of σ(e+e− → p¯ p/K +K −/π+π−π+π−) From threshold of the invariant mass up to ∼ 4.5 GeV /c2 e+e− → p¯ p Enhancement at threshold of the FF confirmed |GE/GM| measured via angular distributions for mp¯

p < 3 GeV

e+e− → K +K −/π+π−π+π− Important for theoretical predictions of (gµ − 2) → Hint for new physics? → In combination with other measurements: aexp

µ

− atheory

µ

≈ 3 − 4σ

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 24 / 24

slide-34
SLIDE 34

Summary

backup slides

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 25 / 24

slide-35
SLIDE 35

Summary

PEP-II and the BABA

R detector at SLAC

asymmetric e+e−-collider: 9 GeV (e−) and 3.1 GeV (e+) √s = 10.58 GeV ⇒ Υ(4S) ⇒ above BB-threshold main purpose: B-physics multi purpose detector data taken from 1999 – 2008 integrated luminosity: 531 fb−1

  • n Υ(4S): 454 fb−1

≈ 600 · 106 BB-pairs

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 26 / 24

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SLIDE 36

Summary

Coherent K ∗K ∗ contribution in e+e− → K +K −ππ

K +K −π+π−

1000 2000 0.75 1 1.25 1.5

m(K

  • π

+) (GeV/c 2)

N(K

*0)/0.04 GeV/c 2

200 400 600 800 0.75 1 1.25 1.5

m(K

  • π

+) (GeV/c 2)

N(K2

*0)/0.04 GeV/c 2

Extract number of K ∗(892)0 and K ∗

2 (1430)0 by fitting K +π− mass

in every 40 MeV /c2 bin of K − π+ mass → less than 1%K ∗(892)0K ∗(892)0

K +K −π0π0

250 500 750 1000 0.75 1 1.25 1.5 m(K+π0) (GeV/c2) N(K*-)/0.04 GeV/c2 20 40 60 80 0.75 1 1.25 1.5 m(K+π0) (GeV/c2) N(K2*-)/0.04 GeV/c2

Extract number of K ∗(892)+ and K ∗

2 (1430)+ by fitting 40 MeV

/c2 bins of K −π0 mass → 30% K ∗(892)±K ∗(892)∓

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 27 / 24

slide-37
SLIDE 37

Summary

e+e− → φππ → K +K −ππ

0.25 0.5 0.75 1 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3

Ec.m. (GeV) σ(φππ) (nb)

e+e− → Φππ → K +K −ππ

50 100 150 200 0.4 0.6 0.8 1 1.2 1.4

m(π+π-) (GeV/c2) Events/0.015 GeV/c2

f0(600) f0(980)

minimum 2 peaks! resonance confirmed: JPC = 1−− M=2176 ± 14 ± 4 MeV /c2; Γ = 90 ± 22 ± 10 MeV

500 1000 1500 0.98 1 1.02 1.04 1.06 m(K+K-) (GeV/c2) Events/0.0025 GeV/c2

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 28 / 24

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SLIDE 38

Summary

e+e− → φπ+π− → K +K −π+π−

50 100 150

  • 1
  • 0.5

0.5 1

cos Θφ Events/0.2

50 100 150

  • 1
  • 0.5

0.5 1

cos Θπ+ Events/0.2

50 100 150

  • 1
  • 0.5

0.5 1

cos ΘK+ Events/0.2

φ and π+π− system are in S-wave pions in π+π− system are in S-wave kaons from φ are in P-wave (as expected)

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 29 / 24

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SLIDE 39

Summary

charmonium branching ratios

1 2 3 3 3.1 3.2 3.3

M4π (GeV/c2) σ (nb) (a) BJ

/ ψ →2(π+π−) · σJ / ψ int

= N(J/ψ → 2(π+π−)) dL/dE · ǫMC = (48.9 ± 2.1stat ± 1.0syst) MeV /c2 nb BJ

/ ψ →2(π+π−)

= (3.67 ± 0.16stat ± 0.08syst ± 0.09ext) · 10−3 BPDG

J / ψ →2(π+π−)

= (3.55 ± 0.23) · 10−3

→ agrees with PDG, higher in precision

1 2 3 4 3.6 3.7 3.8

M4π (GeV/c2) σ (nb) (b) Bψ(2S)→J

/ ψ π+π− · BJ / ψ →µ+µ− · σψ(2S) int

= N(ψ(2S) → π+π−µ+µ−) dL/dE · ǫMC = (84.7 ± 2.2stat ± 1.8syst) MeV /c2 nb Bψ(2S)→J

/ ψ π+π−

= 0.354 ± 0.009stat ± 0.007syst ± 0.007ext BPDG

ψ(2S)→J / ψ π+π−

= 0.336 ± 0.004 BCLEO

ψ(2S)→J / ψ π+π−

= 0.3504 ± 0.0007syst ± 0.0077ext

→ agrees with recent CLEO result (PRD 78, 011102 (2008))

Andreas Hafner (Mainz University) ISR at BABA R FPCP 2013 30 / 24