Light Meson Spectroscopy News and Recent Developments Sebastian - - PowerPoint PPT Presentation

SLIDE 1

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Light Meson Spectroscopy

News and Recent Developments Sebastian Neubert

Technische Universit¨ at M¨ unchen

Hadron 2011

Sebastian Neubert — Light Meson Spectroscopy 1/28

SLIDE 2

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Search for Spin Exotic Resonances Status of the π1(1600)

Diffractive Dissociation Photoproduction

Highly Excited Non-strange Mesons Light Meson Resonances from Radiative J/ψ Decays News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays f0(980) and a0(980) in Charmonium Decays f1(1285) → π+π−π0 Beyond Resonances

Sebastian Neubert — Light Meson Spectroscopy 2/28

SLIDE 3

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Perspectives beyond the Quark Model

Chiral Symmetry Breaking, Gluonic DoF ...

Octet: Goldstone-Bosons

• f Chiral Symmetry breaking

Sebastian Neubert — Light Meson Spectroscopy 3/28

SLIDE 4

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Perspectives beyond the Quark Model

Chiral Symmetry Breaking, Gluonic DoF ...

Octet: Goldstone-Bosons

• f Chiral Symmetry breaking

Exited States: Flux Tube Model

Isgur, Paton Phys. Rev. D31(1985)2910

Sebastian Neubert — Light Meson Spectroscopy 3/28

SLIDE 5

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Perspectives beyond the Quark Model

Chiral Symmetry Breaking, Gluonic DoF ...

Octet: Goldstone-Bosons

• f Chiral Symmetry breaking

Exited States: Flux Tube Model

Isgur, Paton Phys. Rev. D31(1985)2910

QCD-allowed contributions to meson spectrum:

Sebastian Neubert — Light Meson Spectroscopy 3/28

HYBRIDS GLUEBALLS

SLIDE 6

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Search for States beyond the Constituent Quark Model Status of the Spin Exotic π1(1600)

Sebastian Neubert — Light Meson Spectroscopy 4/28

SLIDE 7

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Search for States beyond the Quark Model

Status of the spin exotic π1(1600)

Exotic Signatures

Over-filled multiplets (too many states) Isospin exotics: “forbidden” decays Spin exotics: JPC = 0−−, 0+−, 1−+, 2+−... forbidden in q¯ q COMPASS (2004): π−Pb→ π−π+π−Pb ∼ 400 000 events

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Intensity / (40 MeV/c 100 200 300 400 500 600 700 800 P π ρ

+

1

• +

1 (d) )

2

System (GeV/c

+

π

• π
• π

Mass of 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Phase (degrees)

• 400
• 350
• 300
• 250
• 200
• 150
• 100
• 50

S) π ρ

+ ++

P - 1 π ρ

+

1

• +

(1 φ ∆ (a)

[PRL 104 (2010) 241803]

Sebastian Neubert — Light Meson Spectroscopy 5/28

SLIDE 8

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Search for States beyond the Quark Model

Status of the spin exotic π1(1600)

Exotic Signatures

Over-filled multiplets (too many states) Isospin exotics: “forbidden” decays Spin exotics: JPC = 0−−, 0+−, 1−+, 2+−... forbidden in q¯ q COMPASS (2004): π−Pb→ π−π+π−Pb ∼ 400 000 events

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Intensity / (40 MeV/c 100 200 300 400 500 600 700 800 P π ρ

+

1

• +

1 (d) )

2

System (GeV/c

+

π

• π
• π

Mass of 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Phase (degrees)

• 400
• 350
• 300
• 250
• 200
• 150
• 100
• 50

S) π ρ

+ ++

P - 1 π ρ

+

1

• +

(1 φ ∆ (a)

[PRL 104 (2010) 241803]

Sebastian Neubert — Light Meson Spectroscopy 5/28

Spin Exotic π1(1600)

Significant 1−+ amplitude consistent with resonance at ∼ 1.7 GeV/c2 No leakage observed (< 5%) BW for π1(1600) + background: M = (1.660 ± 0.010 +0.000

−0.064) GeV/c2

Γ = (0.269 ± 0.021 +0.042

−0.064) GeV/c2

SLIDE 9

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

The COMPASS Experiment

Spectrometer and Hadron Beam

Sebastian Neubert — Light Meson Spectroscopy 6/28

Overview

COmmon Muon and Proton Apparatus for Structure and Spectroscopy Located at CERN’s SPS M2-beamline: high intensity π/p beam up to 280GeV/c

Apparatus

Two-stage magnetic spectrometer Large acceptance charged tracking Calorimetry (ECAL/HCAL) Kaon PID (CEDARs/RICH)

SLIDE 10

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Pion Diffraction at COMPASS

1−+ in π−π+π−

2008 run: 190 GeV π− beam on ℓH2 target 100M events π− + p → π−π+π− + p a2(1320) mass region π2(1670) mass region

Sebastian Neubert — Light Meson Spectroscopy 7/28

SLIDE 11

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Pion Diffraction at COMPASS

1−+ in π−π+π−

2008 run: 190 GeV π− beam on ℓH2 target 100M events π− + p → π−π+π− + p The spin exotic JPC = 1−+ρπ P-wave: Intensity (statistical errors only)

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events /(20 MeV/c 5 10 15 20 25

3

10 ×

P π ρ

+

1

• +

1

COMPASS 2008 p

+

π

• π
• π

→ p

• π

2

/c

2

< t' < 1.0 Gev

2

/c

2

0.1 GeV

preliminary

Phase motion vs 1++ρπ S-wave

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events /(20 MeV/c

• 150
• 100
• 50

50 100 150

S) π ρ

+ ++

P - 1 π ρ

+

1

• +

(1 Φ ∆

COMPASS 2008 p

+

π

• π
• π

→ p

• π

2

/c

2

< t' < 1.0 Gev

2

/c

2

0.1 GeV

preliminary

Sebastian Neubert — Light Meson Spectroscopy 7/28

SLIDE 12

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Pion Diffraction at COMPASS

1−+ in π−π+π−

2008 run: 190 GeV π− beam on ℓH2 target 100M events π− + p → π−π+π− + p The spin exotic JPC = 1−+ρπ P-wave: Intensity (statistical errors only)

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events /(20 MeV/c 5 10 15 20 25

3

10 ×

P π ρ

+

1

• +

1

COMPASS 2008 p

+

π

• π
• π

→ p

• π

2

/c

2

< t' < 1.0 Gev

2

/c

2

0.1 GeV

preliminary

Phase motion vs 1++ρπ S-wave

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events /(20 MeV/c

• 150
• 100
• 50

50 100 150

S) π ρ

+ ++

P - 1 π ρ

+

1

• +

(1 Φ ∆

COMPASS 2008 p

+

π

• π
• π

→ p

• π

2

/c

2

< t' < 1.0 Gev

2

/c

2

0.1 GeV

preliminary

Sebastian Neubert — Light Meson Spectroscopy 7/28

Parallel Session

F . Haas, Fri. 17th, 9:20h, Light Mesons 6

SLIDE 13

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

COMPASS: π− + p → η′π + p

The spin exotic JPC = 1−+η′π P-wave

Strong 1−+η′πP-wave reported by E852 and VES - resonant?

m [GeV] 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

2

events / 40 MeV/c 1000 2000 3000 4000 5000 6000

preliminary

COMPASS 2008 ’p η

• π

→ p

• π

) intensity

++

= 2

PC

(J

+

D m [GeV] 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

2

events / 40 MeV/c 1000 2000 3000 4000 5000 6000 7000 8000

preliminary

COMPASS 2008 ’p η

• π

→ p

• π

) intensity

• +

= 1

PC

(J

+

P

Strong 1−+ signal Similar to BNL / VES Extendend mass range No fit to spin-density matrix yet Production mechanism?

m [GeV] 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 ) [deg]

+

/ P

+

arg(D

• 180
• 160
• 140
• 120
• 100
• 80
• 60
• 40
• 20

20

preliminary

COMPASS 2008 ’p η

• π

→ p

• π

+

• P

+

phase D

Sebastian Neubert — Light Meson Spectroscopy 8/28

2++ 1−+

∆φ(2++ − 1−+)

SLIDE 14

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

COMPASS: π− + p → η′π + p

The spin exotic JPC = 1−+η′π P-wave

Strong 1−+η′πP-wave reported by E852 and VES - resonant?

m [GeV] 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

2

events / 40 MeV/c 1000 2000 3000 4000 5000 6000

preliminary

COMPASS 2008 ’p η

• π

→ p

• π

) intensity

++

= 2

PC

(J

+

D m [GeV] 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

2

events / 40 MeV/c 1000 2000 3000 4000 5000 6000 7000 8000

preliminary

COMPASS 2008 ’p η

• π

→ p

• π

) intensity

• +

= 1

PC

(J

+

P

Strong 1−+ signal Similar to BNL / VES Extendend mass range No fit to spin-density matrix yet Production mechanism?

m [GeV] 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 ) [deg]

+

/ P

+

arg(D

• 180
• 160
• 140
• 120
• 100
• 80
• 60
• 40
• 20

20

preliminary

COMPASS 2008 ’p η

• π

→ p

• π

+

• P

+

phase D

Sebastian Neubert — Light Meson Spectroscopy 8/28

2++ 1−+

∆φ(2++ − 1−+) Parallel Session

• T. Schl¨

uter, Thu. 16th, 17:10h, Light Mesons 5

SLIDE 15

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

COMPASS π−π+π− vs π−π0π0

Isospin Symmetry

Partial wave intensities/phases: π−π+π− vs π−π0π0 (normalized to a2)

)

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 5 10 15 20 25

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• = 1-(1++)0+ rho pi S

∈

M

PC

J

G

I

Comparison

π−π0π0 not acceptance corrected yet Channels probe different parts of spectrometer Qualitative agreement

)

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 2 4 6 8 10 12 14 16 18 20 22

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π
• 38% of 2008 data

acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π

= 1-(2++)1+ rho pi D

∈

M

PC

J

G

I )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 1 2 3 4 5 6 7

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• = 1-(2-+)0+ f2 pi S

∈

M

PC

J

G

I )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Relative Phase (deg)

• 150
• 100
• 50

50 100 150

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• ( 1-(2++)1+ rho pi D -- 1-(1++)0+ rho pi S )

Φ )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Relative Phase (deg)

• 150
• 100
• 50

50 100 150

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• ( 1-(2-+)0+ f2 pi S -- 1-(1++)0+ rho pi S )

Φ

Sebastian Neubert — Light Meson Spectroscopy 9/28

a1 a2

∆φ(a2 − a1)

π2

∆φ(π2 − a1)

SLIDE 16

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

COMPASS π−π+π− vs π−π0π0

Isospin Symmetry

Partial wave intensities/phases: π−π+π− vs π−π0π0 (normalized to a2)

)

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 5 10 15 20 25

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• = 1-(1++)0+ rho pi S

∈

M

PC

J

G

I

Comparison

π−π0π0 not acceptance corrected yet Channels probe different parts of spectrometer Qualitative agreement

)

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 2 4 6 8 10 12 14 16 18 20 22

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π
• 38% of 2008 data

acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π

= 1-(2++)1+ rho pi D

∈

M

PC

J

G

I )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 1 2 3 4 5 6 7

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• = 1-(2-+)0+ f2 pi S

∈

M

PC

J

G

I )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Relative Phase (deg)

• 150
• 100
• 50

50 100 150

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• ( 1-(2++)1+ rho pi D -- 1-(1++)0+ rho pi S )

Φ )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Relative Phase (deg)

• 150
• 100
• 50

50 100 150

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• ( 1-(2-+)0+ f2 pi S -- 1-(1++)0+ rho pi S )

Φ

Sebastian Neubert — Light Meson Spectroscopy 9/28

a1 a2

∆φ(a2 − a1)

π2

← difference expected by Isospin for f2π

∆φ(π2 − a1)

SLIDE 17

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

COMPASS π−π+π− vs π−π0π0

Isospin Symmetry

Partial wave intensities/phases: π−π+π− vs π−π0π0 (normalized to a2)

)

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 5 10 15 20 25

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• = 1-(1++)0+ rho pi S

∈

M

PC

J

G

I

Comparison

π−π0π0 not acceptance corrected yet Channels probe different parts of spectrometer Qualitative agreement

)

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 2 4 6 8 10 12 14 16 18 20 22

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π
• 38% of 2008 data

acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π

= 1-(2++)1+ rho pi D

∈

M

PC

J

G

I )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 )

2

Events / (40 MeV/c 1 2 3 4 5 6 7

3

10 ×

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• = 1-(2-+)0+ f2 pi S

∈

M

PC

J

G

I )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Relative Phase (deg)

• 150
• 100
• 50

50 100 150

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• ( 1-(2++)1+ rho pi D -- 1-(1++)0+ rho pi S )

Φ )

2

Mass (GeV/c 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Relative Phase (deg)

• 150
• 100
• 50

50 100 150

PRELIMINARY

COMPASS 2008

mass indep. PWA (53 waves)

not acceptance corrected

p π π

• π

→ p

• π
• π

+

π

• π

38% of 2008 data acceptance corrected 38% of 2008 data not acceptance corrected

π π

• π
• ( 1-(2-+)0+ f2 pi S -- 1-(1++)0+ rho pi S )

Φ

Sebastian Neubert — Light Meson Spectroscopy 9/28

a1 a2

∆φ(a2 − a1)

π2

← difference expected by Isospin for f2π

∆φ(π2 − a1) Parallel Session

F . Nerling, Fri. 17th, 9:40h Light Mesons 6

SLIDE 18

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

CLAS Experiment at JLAB Hall B

CEBAF Large Acceptance Spectrometer

Tagged photon beam (2001)

Ee− = 5.744 GeV 5 × 107 photons / s Liquid H2 target (18cm cell)

CLAS Detector

Toroidal B-Field Large acceptance TOF and DIRC for PID

Tagger e − Beam Radiator Target CLAS Detector

Sebastian Neubert — Light Meson Spectroscopy 10/28

SLIDE 19

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

CLAS Experiment at JLAB Hall B

CEBAF Large Acceptance Spectrometer

Tagged photon beam (2001)

Ee− = 5.744 GeV 5 × 107 photons / s Liquid H2 target (18cm cell)

CLAS Detector

Toroidal B-Field Large acceptance TOF and DIRC for PID

Tagger e − Beam Radiator Target CLAS Detector

Sebastian Neubert — Light Meson Spectroscopy 10/28

Parallel Session

• D. Weygand, Thu. 16th, 14:30h

Light Mesons 4

SLIDE 20

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Search for Photoproduction of JPC = 1−+

γ + p → π+π+π− + n at CLAS

83 000 events for PWA a2(1320) and π2(1670) resonances clearly seen in photoproduction No exotic 1−+ signal

[PRL 102 (2009) 102002]

Sebastian Neubert — Light Meson Spectroscopy 11/28

SLIDE 21

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Search for Photoproduction of JPC = 1−+

γ + p → π+π+π− + n at CLAS

83 000 events for PWA a2(1320) and π2(1670) resonances clearly seen in photoproduction No exotic 1−+ signal

[PRL 102 (2009) 102002]

Sebastian Neubert — Light Meson Spectroscopy 11/28

Parallel Session

• C. Bookwalter, Thu. 16th, 16:30h,

Light Mesons 5

SLIDE 22

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Search for Photoproduction of JPC = 1−+

γ + p → π+π+π− + n at CLAS

83 000 events for PWA a2(1320) and π2(1670) resonances clearly seen in photoproduction No exotic 1−+ signal → confirmed by COMPASS Primakoff (preliminary)

[PRL 102 (2009) 102002]

Sebastian Neubert — Light Meson Spectroscopy 11/28

Parallel Session

• C. Bookwalter, Thu. 16th, 16:30h,

Light Mesons 5

SLIDE 23

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Search for Photoproduction of JPC = 1−+

γ + p → π+π+π− + n at CLAS

83 000 events for PWA a2(1320) and π2(1670) resonances clearly seen in photoproduction No exotic 1−+ signal → confirmed by COMPASS Primakoff (preliminary)

[PRL 102 (2009) 102002]

Sebastian Neubert — Light Meson Spectroscopy 11/28

Parallel Session

• C. Bookwalter, Thu. 16th, 16:30h,

Light Mesons 5

Parallel Session

• D. Ryabchikov , Fri. 17th, 10:25h

Low Energy Processes 2

SLIDE 24

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

The 1−+ Hybrid on the Lattice

• C. A. Meyer and Y. Van Haarlem, Phys. Rev. C 82, 025208 (2010) (arXiv:1004.5516v2)

Sebastian Neubert — Light Meson Spectroscopy 12/28

SLIDE 25

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Highly Excited Non-strange Mesons

Sebastian Neubert — Light Meson Spectroscopy 13/28

SLIDE 26

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Excited Mesons in Parity Doublets?

[PRD 77 (2008) 034002]

plot from M. Shifman and A. Vainshtein [PRD 77 (2008) 034002] See also: R. F . Wagenbrunn and L. Ya. Glozman [PRD 75 (2007) 036007] and references therein

Sebastian Neubert — Light Meson Spectroscopy 14/28

SLIDE 27

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Excited Mesons in Parity Doublets?

[PRD 77 (2008) 034002]

plot from M. Shifman and A. Vainshtein [PRD 77 (2008) 034002] See also: R. F . Wagenbrunn and L. Ya. Glozman [PRD 75 (2007) 036007] and references therein

Sebastian Neubert — Light Meson Spectroscopy 14/28

Disputed Pattern

Non-q¯ q candidates have been

• mitted from plot

Most states above 2 GeV/c2 from

• nly ONE experiment (CB) in ¯

pp

SLIDE 28

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Excited Mesons in Parity Doublets?

[PRD 77 (2008) 034002]

plot from M. Shifman and A. Vainshtein [PRD 77 (2008) 034002] See also: R. F . Wagenbrunn and L. Ya. Glozman [PRD 75 (2007) 036007] and references therein

Sebastian Neubert — Light Meson Spectroscopy 14/28

Disputed Pattern

Non-q¯ q candidates have been

• mitted from plot

Most states above 2 GeV/c2 from

• nly ONE experiment (CB) in ¯

pp ... only ONE?

SLIDE 29

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

The BES III Experiment

at the Beijing Electron Positron Collider

BES III @ BEPCII

e+e− Collider √ s = 2 . . . 4.6 GeV Design luminosity: ∼ 1033 cm−2s−1(@ 2 × 1.89 GeV) Charm-factory:

2.25 · 108J/ψ events 1.06 · 108ψ′ events

Plenary Talk

Li, Hai-Bo on Wed. 15th, 12:00h “Highlights from BES III”

Sebastian Neubert — Light Meson Spectroscopy 15/28

SLIDE 30

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

X(1835) & Co, in J/ψ → γη′π+π−

at BES III [PRL 106 (2011) 072002] ηc

Sebastian Neubert — Light Meson Spectroscopy 16/28

SLIDE 31

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

X(1835) & Co, in J/ψ → γη′π+π−

at BES III [PRL 106 (2011) 072002]

X(1835) X(2120) X(2370) f1(1510)

Fitted mass spectrum: remarkably narrow peaks – interferences? No spin-parity assignments yet → amplitude analysis needed

Sebastian Neubert — Light Meson Spectroscopy 16/28

SLIDE 32

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

X(1835) & Co, in J/ψ → γη′π+π−

at BES III [PRL 106 (2011) 072002]

X(1835) X(2120) X(2370) f1(1510)

Fitted mass spectrum: remarkably narrow peaks – interferences? No spin-parity assignments yet → amplitude analysis needed Should consider possible η′ππ quantum numbers: IG = 0+ or 1− (JPC) = (0−+),(1−+), (1++), (2−+)....

Sebastian Neubert — Light Meson Spectroscopy 16/28

SLIDE 33

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

X(1835) & Co, in J/ψ → γη′π+π−

at BES III [PRL 106 (2011) 072002]

X(1835) X(2120) X(2370) f1(1510)

Fitted mass spectrum: remarkably narrow peaks – interferences? No spin-parity assignments yet → amplitude analysis needed Should consider possible η′ππ quantum numbers: IG = 0+ or 1− (JPC) = (0−+),(1−+), (1++), (2−+)....

Sebastian Neubert — Light Meson Spectroscopy 16/28

Parallel Session

Liu, Hongwei Fri. 17th, 10:40h Light Mesons 6

SLIDE 34

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

X(1870) in J/ψ → ωηπ+π−

at BES III

J/ψ → ωa±

0 (980)π → ωηπ+π−

f1(1285) (1405) η X(1870)

Sebastian Neubert — Light Meson Spectroscopy 17/28

SLIDE 35

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

News on Strange Mesons

Sebastian Neubert — Light Meson Spectroscopy 18/28

SLIDE 36

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Strangeness at COMPASS & BELLE

COMPASS: K − + p → K −π+π− + p ∼ 270 000 events

]

2

)[GeV/c

• π

+

π

• M (K

0.5 1 1.5 2 2.5 ]

2

Events / 10 [MeV/c 0.5 1 1.5 2 2.5 3 3.5

3

10 ×

preliminary

COMPASS 2008 negative hadron beam recoil

p

• π

+

π

• K

→ p

• K

not acceptance corrected

(1270)

1

K (1400)

1

K (1770)

2

K ]

2

)[GeV/c

+

π

• M (K

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 ]

2

Events / 20 [MeV/c 5 10 15 20 25 30

3

10 ×

preliminary

COMPASS 2008 negative hadron beam recoil

p

• π

+

π

• K

→ p

• K

not acceptance corrected

K*(892) (1430)

2

K*

BELLE @ Υ(4s): B+ → J/ψK +π+π− ∼ 10 000 events

[PRD 83 (2011) 032005]

Sebastian Neubert — Light Meson Spectroscopy 19/28

SLIDE 37

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Strangeness at COMPASS & BELLE

COMPASS: K − + p → K −π+π− + p ∼ 270 000 events

]

2

)[GeV/c

• π

+

π

• M (K

0.5 1 1.5 2 2.5 ]

2

Events / 10 [MeV/c 0.5 1 1.5 2 2.5 3 3.5

3

10 ×

preliminary

COMPASS 2008 negative hadron beam recoil

p

• π

+

π

• K

→ p

• K

not acceptance corrected

(1270)

1

K (1400)

1

K (1770)

2

K ]

2

)[GeV/c

+

π

• M (K

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 ]

2

Events / 20 [MeV/c 5 10 15 20 25 30

3

10 ×

preliminary

COMPASS 2008 negative hadron beam recoil

p

• π

+

π

• K

→ p

• K

not acceptance corrected

K*(892) (1430)

2

K*

BELLE @ Υ(4s): B+ → J/ψK +π+π− ∼ 10 000 events

[PRD 83 (2011) 032005]

Sebastian Neubert — Light Meson Spectroscopy 19/28

Parallel Session

P . Jasinski , Tue. 14th, 17:50h Light Mesons 3

SLIDE 38

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Isospin Violating Decays f0(980)-a0(980) Mixing

f0(980) a0

0(980)

K0 ¯ K0 f0(980) a0

0(980)

K+ K−

[PRD76 (2007) 074028]

Sebastian Neubert — Light Meson Spectroscopy 20/28

SLIDE 39

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Sources of f0 and a0 → Charmonium Decays

Isospin Conserving J/Ψ → φππ and χc1 → πηπ Decays

f0(980) → ππ IG = 0+ J/ψ → φ(ππ) @ BES a0(980) → ηπ IG = 1− ψ′ → γ + χc1 → γ + (ηπ0)π0 @ CLEO

Sebastian Neubert — Light Meson Spectroscopy 21/28

SLIDE 40

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

f0(980) - a0(980) Mixing Signals

Isospin Violating Decays J/ψ → φηπ0 and ψ′ → γπ0π+π−

(a0

0(980) → ηπ) recoiling against φ (and sideband)

J/ψ

• I=0

→ φ

• I=0

ηπ0

• a0

0(980)

(f0(980) → π+π−) in χc1 mass window (and sideband) χc1

• I=0

→ π0

• I=1

π+π−

f0(980) PRD 83 (2011) 032003

Sebastian Neubert — Light Meson Spectroscopy 22/28

SLIDE 41

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

f0(980) - a0(980) Mixing Intensities

BES III Charmonium Data Samples: 2.25 · 108J/ψ events 1.06 · 108ψ′ events

ξfa = Br(J/ψ → φa0(980)) Br(J/ψ → φf0(980)) = 0.60% ξaf = Br(χc1 → γπ0f0(980)) Br(χc1 → γπ0a0(980)) = 0.31% Errors given as red area [PRD 83 (2011) 032003]

Sebastian Neubert — Light Meson Spectroscopy 23/28

SLIDE 42

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

f0(980) - a0(980) Mixing Intensities

BES III Charmonium Data Samples: 2.25 · 108J/ψ events 1.06 · 108ψ′ events

ξfa = Br(J/ψ → φa0(980)) Br(J/ψ → φf0(980)) = 0.60% ξaf = Br(χc1 → γπ0f0(980)) Br(χc1 → γπ0a0(980)) = 0.31% Errors given as red area [PRD 83 (2011) 032003]

Sebastian Neubert — Light Meson Spectroscopy 23/28

Poster Session

Liu, Chuyan Tue. 14th, 18:20h

SLIDE 43

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Isospin Violating Decay f1(1285) → π+π−π0

VES: π− + A → f1π− + A → (π0π+π−)π− + A

Extracted f1(1285) → 3π signal: Br(a0(980) → π−π+) = 2.0 ± 0.6 ± 0.4%

[EPJ A47 (2011) 68]

Sebastian Neubert — Light Meson Spectroscopy 24/28

f1(1285)

SLIDE 44

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Pion - Nucleus Scattering at Small Momentum Transfer @ COMPASS

π π π π Pb Pb γ π π π π Pb Pb P

Sebastian Neubert — Light Meson Spectroscopy 25/28

SLIDE 45

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Coulomb and Strong Interaction

Disentangle both processes through Helicity structure (Partial wave analysis) Different t′-distributions (slope!) JPCM = 1++0

)

2

/c

2

Momentum Transfer t' (GeV 1 2 3 4 5 6 7 8 9 10

• 3

10 × Intensity 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

9

10 × S π ρ

+ ++

1 COMPASS 2004 Pb

+

π

• π
• π

→ Pb

• π

2

/c

2

t' < 0.01 GeV

2

< 1.38 GeV/c

π 3

1.26 < m

p r e l i m i n a r y

JPCM = 2++1

)

2

/c

2

Momentum Transfer t' (GeV 1 2 3 4 5 6 7 8 9 10

• 3

10 × Intensity 5 10 15 20 25 30 35 40 45

6

10 × 1 Spin Total

++

2 COMPASS 2004 Pb

+

π

• π
• π

→ Pb

• π

2

/c

2

t' < 0.01 GeV

2

< 1.38 GeV/c

π 3

1.26 < m

p r e l i m i n a r y

Sebastian Neubert — Light Meson Spectroscopy 26/28

SLIDE 46

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Coulomb and Strong Interaction

Disentangle both processes through Helicity structure (Partial wave analysis) Different t′-distributions (slope!) JPCM = 1++0

)

2

/c

2

Momentum Transfer t' (GeV 1 2 3 4 5 6 7 8 9 10

• 3

10 × Intensity 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

9

10 × S π ρ

+ ++

1 COMPASS 2004 Pb

+

π

• π
• π

→ Pb

• π

2

/c

2

t' < 0.01 GeV

2

< 1.38 GeV/c

π 3

1.26 < m

p r e l i m i n a r y

JPCM = 2++1

)

2

/c

2

Momentum Transfer t' (GeV 1 2 3 4 5 6 7 8 9 10

• 3

10 × Intensity 5 10 15 20 25 30 35 40 45

6

10 × 1 Spin Total

++

2 COMPASS 2004 Pb

+

π

• π
• π

→ Pb

• π

2

/c

2

t' < 0.01 GeV

2

< 1.38 GeV/c

π 3

1.26 < m

p r e l i m i n a r y

Allows to study interferences between both production mechanisms.

Sebastian Neubert — Light Meson Spectroscopy 26/28

Parallel Session

• D. Ryabchikov , Fri. 17th, 10:25h

Low Energy Processes 2

SLIDE 47

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Primakoff 3π Spectral Function from χPT

Absolute Cross Section Measurement @ COMPASS

Weizs¨ acker-Williams: heavy nucleus acts as a quasi-real photon source χPT amplitude included in PWA ⇒ γπ− → π−π+π− absolute cross section

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.5 1 1.5 2 2.5 3 )

2

Events / (5 MeV/c 5 10 15 20 25 30 35

3

10 × COMPASS 2004 Pb

+

π

• π
• π

→ Pb

• π

)

2

/c

2

Ranges in t’ (GeV all t’

• 3

t’ < 10

• 2

< t’ < 10

• 3

10

• 1

< t’ < 10

• 2

10 0.1 < t’ < 1 t’ > 1 [x5]

Resonance region

Chiral Regime

Sebastian Neubert — Light Meson Spectroscopy 27/28

SLIDE 48

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Primakoff 3π Spectral Function from χPT

Absolute Cross Section Measurement @ COMPASS

Weizs¨ acker-Williams: heavy nucleus acts as a quasi-real photon source χPT amplitude included in PWA ⇒ γπ− → π−π+π− absolute cross section

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.45 0.5 0.55 0.6 0.65 0.7 b) µ ) (

π 3

(m σ 0.2 0.4 0.6 0.8 1 1.2 COMPASS 2004

+

π

• π
• π

→ γ

• π

Pb

+

π

• π
• π

→ Pb

• π

from

ChPT Intensity Leading Order ChPT Prediction [EPJ A36 (2008) 181]

preliminary

Full Systematic Error Luminosity Uncertainty Sebastian Neubert — Light Meson Spectroscopy 27/28

SLIDE 49

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Primakoff 3π Spectral Function from χPT

Absolute Cross Section Measurement @ COMPASS

Weizs¨ acker-Williams: heavy nucleus acts as a quasi-real photon source χPT amplitude included in PWA ⇒ γπ− → π−π+π− absolute cross section

)

2

System (GeV/c

+

π

• π
• π

Mass of 0.45 0.5 0.55 0.6 0.65 0.7 b) µ ) (

π 3

(m σ 0.2 0.4 0.6 0.8 1 1.2 COMPASS 2004

+

π

• π
• π

→ γ

• π

Pb

+

π

• π
• π

→ Pb

• π

from

ChPT Intensity Leading Order ChPT Prediction [EPJ A36 (2008) 181]

preliminary

Full Systematic Error Luminosity Uncertainty Sebastian Neubert — Light Meson Spectroscopy 27/28

Parallel Session

• S. Grabm¨

uller , Fri. 17th, 10:05h Low Energy Processes 2

SLIDE 50

Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f0(980)-a0(980) Mixing in Isospin Violating Decays Be

Conclusion and Outlook

Conclusion

COMPASS 2008/2009: large data sets in diffractive π−/K −/p dissociation (up to 2 orders of magnitude improvement) Charmonium decays: valuable source of light mesons Clear evidence for spin-exotic π1(1600):

Diffraction vs. photoproduction ? Where is the I = 0 partner η1(1600)?

Outlook

Improvement of Amplitude Analysis Models BES III, COMPASS continue data taking GluEx @ JLab Hall-D: Dedicated photoproduction experiment Belle II: Charm/Beauty Factory PANDA: ¯ pp annihilation

Sebastian Neubert — Light Meson Spectroscopy 28/28