Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 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
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Search for Spin Exotic Resonances Status of the π 1 ( 1600 ) Diffractive Dissociation Photoproduction Highly Excited Non-strange Mesons Light Meson Resonances from Radiative J /ψ Decays News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays f 0 ( 980 ) and a 0 ( 980 ) in Charmonium Decays f 1 ( 1285 ) → π + π − π 0 Beyond Resonances Sebastian Neubert — Light Meson Spectroscopy 2/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Perspectives beyond the Quark Model Chiral Symmetry Breaking, Gluonic DoF ... Octet: Goldstone-Bosons of Chiral Symmetry breaking Sebastian Neubert — Light Meson Spectroscopy 3/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Perspectives beyond the Quark Model Chiral Symmetry Breaking, Gluonic DoF ... Octet: Goldstone-Bosons of Chiral Symmetry breaking Exited States: Flux Tube Model Isgur, Paton Phys. Rev. D31(1985)2910 Sebastian Neubert — Light Meson Spectroscopy 3/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Perspectives beyond the Quark Model Chiral Symmetry Breaking, Gluonic DoF ... Octet: Goldstone-Bosons QCD-allowed contributions to meson of Chiral Symmetry breaking spectrum: Exited States: Flux Tube Model HYBRIDS Isgur, Paton Phys. Rev. D31(1985)2910 GLUEBALLS Sebastian Neubert — Light Meson Spectroscopy 3/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Search for States beyond the Constituent Quark Model Status of the Spin Exotic π 1 ( 1600 ) Sebastian Neubert — Light Meson Spectroscopy 4/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Search for States beyond the Quark Model Status of the spin exotic π 1 ( 1600 ) Exotic Signatures Over-filled multiplets (too many states) Isospin exotics: “forbidden” decays Spin exotics: J PC = 0 −− , 0 + − , 1 − + , 2 + − ... forbidden in q ¯ q COMPASS (2004): π − Pb → π − π + π − Pb ∼ 400 000 events -50 ) Phase (degrees) 2 -+ + 800 1 1 ρ π P (d) (a) Intensity / (40 MeV/c -100 700 600 -150 500 -200 400 -250 300 -300 200 -350 -+ + ++ + ∆ φ (1 1 ρ π P - 1 0 ρ π S) 100 0 -400 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Mass of π - π - π + System (GeV/c 2 ) Mass of π - π - π + System (GeV/c 2 ) [PRL 104 (2010) 241803] Sebastian Neubert — Light Meson Spectroscopy 5/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Search for States beyond the Quark Model Status of the spin exotic π 1 ( 1600 ) Exotic Signatures Over-filled multiplets (too many states) Isospin exotics: “forbidden” decays Spin exotics: J PC = 0 −− , 0 + − , 1 − + , 2 + − ... forbidden in q ¯ q COMPASS (2004): π − Pb → π − π + π − Pb ∼ 400 000 events Spin Exotic π 1 ( 1600 ) -50 ) Phase (degrees) 2 -+ + 800 1 1 ρ π P (d) (a) Intensity / (40 MeV/c -100 Significant 1 − + amplitude consistent 700 600 -150 with resonance at ∼ 1 . 7 GeV / c 2 500 -200 400 No leakage observed ( < 5 % ) -250 300 BW for π 1 ( 1600 ) + background: -300 200 M = ( 1 . 660 ± 0 . 010 + 0 . 000 − 0 . 064 ) GeV / c 2 -350 -+ + ++ + ∆ φ (1 1 ρ π P - 1 0 ρ π S) 100 0 -400 Γ = ( 0 . 269 ± 0 . 021 + 0 . 042 − 0 . 064 ) GeV / c 2 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Mass of π - π - π + System (GeV/c 2 ) Mass of π - π - π + System (GeV/c 2 ) [PRL 104 (2010) 241803] Sebastian Neubert — Light Meson Spectroscopy 5/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be The COMPASS Experiment Spectrometer and Hadron Beam Overview CO mmon M uon and P roton A pparatus for S tructure and S pectroscopy 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) Sebastian Neubert — Light Meson Spectroscopy 6/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Pion Diffraction at COMPASS 1 − + in π − π + π − 2008 run: 190 GeV π − beam on ℓ H 2 target 100M events π − + p → π − π + π − + p a 2 ( 1320 ) mass region π 2 ( 1670 ) mass region Sebastian Neubert — Light Meson Spectroscopy 7/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Pion Diffraction at COMPASS 1 − + in π − π + π − 2008 run: 190 GeV π − beam on ℓ H 2 target 100M events π − + p → π − π + π − + p The spin exotic J PC = 1 − + ρπ P -wave: Phase motion vs Intensity (statistical errors only) 1 ++ ρπ S -wave 3 × 10 ) 2 1 -+ 1 + P COMPASS 2008 25 ρ π Events /(20 MeV/c π - p → π - π - π + p ) -+ 2 ∆ Φ (1 1 + ρ π P - 1 ++ 0 + ρ π S) COMPASS 2008 Events /(20 MeV/c 150 π - p → π - π - π + p 2 2 2 2 0.1 GeV /c < t' < 1.0 Gev /c 20 2 2 2 2 0.1 GeV /c < t' < 1.0 Gev /c 100 15 50 0 10 preliminary -50 preliminary 5 -100 0 -150 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Mass of - - + System (GeV/c 2 ) π π π 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Mass of - - + System (GeV/c 2 ) π π π Sebastian Neubert — Light Meson Spectroscopy 7/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be Pion Diffraction at COMPASS 1 − + in π − π + π − Parallel Session 2008 run: 190 GeV π − beam on ℓ H 2 target F . Haas, Fri. 17th, 9:20h, 100M events π − + p → π − π + π − + p Light Mesons 6 The spin exotic J PC = 1 − + ρπ P -wave: Phase motion vs Intensity (statistical errors only) 1 ++ ρπ S -wave 3 × 10 ) 2 1 -+ 1 + P COMPASS 2008 25 ρ π Events /(20 MeV/c π - p → π - π - π + p ) -+ 2 ∆ Φ (1 1 + ρ π P - 1 ++ 0 + ρ π S) COMPASS 2008 Events /(20 MeV/c 150 π - p → π - π - π + p 2 2 2 2 0.1 GeV /c < t' < 1.0 Gev /c 20 2 2 2 2 0.1 GeV /c < t' < 1.0 Gev /c 100 15 50 0 10 preliminary -50 preliminary 5 -100 0 -150 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Mass of - - + System (GeV/c 2 ) π π π 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Mass of - - + System (GeV/c 2 ) π π π Sebastian Neubert — Light Meson Spectroscopy 7/28
Search for Spin Exotic Resonances Highly Excited Non-strange Mesons News on Strange Mesons f 0 ( 980 ) - a 0 ( 980 ) Mixing in Isospin Violating Decays Be COMPASS: π − + p → η ′ π + p The spin exotic J PC = 1 − + η ′ π P -wave Strong 1 − + η ′ π P -wave reported by E852 and VES - resonant? 8000 2 2 events / 40 MeV/c COMPASS 2008 events / 40 MeV/c COMPASS 2008 - - - - p ’p p ’p 6000 π → π η 7000 π → π η PC PC ++ -+ D (J = 2 ) intensity P (J = 1 ) intensity 2 ++ + + 6000 5000 5000 1 − + 4000 4000 3000 3000 preliminary preliminary 2000 2000 1000 1000 0 0 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 m [GeV] m [GeV] Strong 1 − + signal ) [deg] 20 COMPASS 2008 - - 0 π p → π η ’p phase D - P + -20 + / P + Similar to BNL / VES -40 + arg(D -60 -80 Extendend mass range -100 preliminary -120 ∆ φ ( 2 ++ − 1 − + ) No fit to spin-density -140 -160 matrix yet -180 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 m [GeV] Production mechanism? Sebastian Neubert — Light Meson Spectroscopy 8/28
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