0 in 0 0 on 0 First results results on in comparison - PowerPoint PPT Presentation

the ρπ ρπ decay Spin- -exotic exotic search search in in the decay channel channel: : Spin 0 in π − π 0 π 0 on π − π 0 π First results results on in comparison comparison First − final π − π + π − to π − π + π final states states to (diffractively diffractively produced produced on on proton proton) ) ( Frank Nerling Universität Freiburg, Physikalisches Institut for the COMPASS Collaboration Hadron 2011, XIV Intern. Conf. on Hadron Spectroscopy, Munich, Germany, 13-17 June 2011 Outline: Outline: • Introduction � Spin-exotic mesons & the COMPASS experiment � PWA method • First results on diffractive 3 π production (2008 proton target data) � 3 π final states neutral vs. charged mode � PWA results on main & small waves • Conclusions & outlook Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

Motivation: Search Search for for Spin Spin Exotic Exotic States States Motivation: Hybrid candidates (1.3 - 2.2 GeV/c²): Diffractive scattering lightest hybrid predicted: exotic J PC =1 −+ • study of J PC exotic mesons • π 1 (1400): VES, E852, Crystal Barrel −> ηπ • t-channel Reggeon exchange • π 1 (1600): E852, VES −> ρπ, η ‘ π, f 1 π , b 1 π • forward kinematics, target stays intact • π 1 (2000): E852 −> f 1 (1285) π , b 1 (1235) π …. still controversal � COMPASS Diffractive pion dissociation • incoming π − excited to resonance X - • X - decays into final state, e.g. (3 π) − • small momentum transfer Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

ρπ of ρπ Spin Exotic Exotic Search Search -- -- two two decay decay modes modes of Spin decay channel channel: Neutral Mode : Neutral Mode decay Hybrid candidates (1.3 - 2.2 GeV/c²): Diffractive scattering lightest hybrid predicted: exotic J PC =1 −+ • study of J PC exotic mesons • π 1 (1400): VES, E852, Crystal Barrel −> ηπ • t-channel Reggeon exchange • π 1 (1600): E852, VES −> ρπ, η ‘ π, f 1 π , b 1 π • forward kinematics, target stays intact • π 1 (2000): E852 −> f 1 (1285) π , b 1 (1235) π …. still controversal � COMPASS Diffractive pion dissociation • incoming π − excited to resonance X - • X - decays into final state, e.g. (3 π) − : π − p −−> π − π 0 π 0 p (neutral mode) • small momentum transfer Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

ρπ of ρπ Spin Exotic Exotic Search Search -- -- two two decay decay modes modes of Spin decay channel channel: : Charged Charged Mode Mode decay Hybrid candidates (1.3 - 2.2 GeV/c²): Diffractive scattering lightest hybrid predicted: exotic J PC =1 −+ • study of J PC exotic mesons • π 1 (1400): VES, E852, Crystal Barrel −> ηπ • t-channel Reggeon exchange • π 1 (1600): E852, VES −> ρπ, η ‘ π, f 1 π , b 1 π • forward kinematics, target stays intact • π 1 (2000): E852 −> f 1 (1285) π , b 1 (1235) π …. still controversal � COMPASS Diffractive pion dissociation • incoming π − excited to resonance X - • X - decays into final state, e.g. (3 π) − : π − p −−> π − π + π − p (charged mode) • small momentum transfer � cf. previous, talk by F. Haas Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

The COMPASS experiment The COMPASS experiment COmmon Muon Proton Apparatus for Structure and Spectroscopy (~250 physicists, 25 institutes, 10 countries) a) Nucleon spin structure: � polarised muon beam (160 GeV/c µ + ) polarised solid targets ( 6 LiD, NH 3 ) � see Talks, E. Kabuß, N.Makke, C.Höppner MuonWall SM2 E/HCAL E/HCAL ~50m SM1 Target b) Baryon & meson spectroscopy: MuonWall • Diffractive production (this talk) (different kind) • Central production • Primakoff RICH � hadron beams (190 GeV/c π - , K - ) Beam Hadron runs: (muon or hadron) • 2004 pilot run (4 days π − on Pb target: ~BNL statistics) • 2008/09 (large statistics (LH 2 ), π ± , Κ ± , p ± beam , plus nuclear targets ) Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

COMPASS spectrometer: Hadron Hadron setup 2008/09 setup 2008/09 COMPASS spectrometer: all COMPASS trackers: SciFi, Si, MM, GEM, DC, Straw, MWPC + Upgraded trackers close to beam: ColdSilicons, PixelGEMs 0.4m liquid H 2 target ECAL2 (0.4 ° ≤ θ γ ≤ 2°) Beam (muon or hadron) ECAL1 (2 ° ≤ θ γ ≤ 12°) Recoil detector (RPD) Electromagnetic calorimeters to trigger on reactions inside target (final states involving neutrals, e.g. π°, η, or η ’ ) Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

COMPASS spectrometer: Hadron Hadron setup 2008/09 setup 2008/09 COMPASS spectrometer: After final cuts on ∆Φ and exclusivity: all COMPASS trackers: SciFi, Si, MM, GEM, DC, Straw, MWPC + Upgraded trackers close to beam: ColdSilicons, PixelGEMs 0.4m σ ≈ 8 MeV liquid H 2 target ECAL2 (0.4 ° ≤ θ γ ≤ 2°) Beam (muon or hadron) ECAL1 (2 ° ≤ θ γ ≤ 12°) Recoil detector (RPD) Electromagnetic calorimeters to trigger on reactions inside target (final states involving neutrals, e.g. π°, η, or η ’ ) Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

π final 3 π Diffractive dissociation dissociation into into 3 final states states Diffractive (2008 data data, LH , LH 2 target) ) (2008 2 target Mass of outgoing 3 π system – neutral Mass of outgoing 3 π system – charged mode: π − p −−> π − π 0 π 0 p mode: π − p −−> π − π + π − p 38% of 2008 data PWA: ~ 1M events PWA: ~ 24M events (acceptance corr.) Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

PWA using using isobar isobar model model PWA X - decay described using isobar model: • Intermediate di-pion resonance (isobar) • Spin S and rel. orbital angular momentum L w.r.t bachelor π − • L+S couple to J • Partial waves (reflectivity basis): J PC M ε [ isobar ] L Partial wave analysis: • program: Illinois/Protvino/Munich (D.Ryabchikov) software (IHEP/VES, TUM/COMPASS) • Isobars : ( ππ) S [broad f 0 (600)+f 0 (1370)], f 0 (980), ρ (770), f 2 (1270), ρ 3 (1690) • Acceptance: corrections included (2004: ~60%, rather flat, 2008: similar for charged, neutral not yet) Step 1) Mass independent PWA: (40MeV/c² bins, 52+1 partial waves) Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

PWA using using isobar isobar model model PWA X - decay described using isobar model: • Intermediate di-pion resonance (isobar) • Spin S and rel. orbital angular momentum L w.r.t bachelor π − • L+S couple to J • Partial waves (reflectivity basis): J PC M ε [ isobar ] L Partial wave analysis: • program: Illinois/Protvino/Munich (D.Ryabchikov) software (IHEP/VES, TUM/COMPASS) • Isobars : ( ππ) S [broad f 0 (600)+f 0 (1370)], f 0 (980), ρ (770), f 2 (1270), ρ 3 (1690) • Acceptance: corrections included (2004: ~60%, rather flat, 2008: similar for charged ) Step 1) Mass independent PWA: (40MeV/c² bins, 52+1 partial waves) Step 2) Mass dependent χ 2 fit: (to mass independent result) • Main partial waves chosen, parameterised by Breit-Wigner • Coherent background for some waves Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

PWA using using isobar isobar model model PWA X - decay described using isobar model: • Intermediate di-pion resonance (isobar) • Spin S and rel. orbital angular momentum L w.r.t bachelor π − • L+S couple to J • Partial waves (reflectivity basis): J PC M ε [ isobar ] L Partial wave analysis: • program: Illinois/Protvino/Munich (D.Ryabchikov) software (IHEP/VES, TUM/COMPASS) • Isobars : ( ππ) S [broad f 0 (600)+f 0 (1370)], f 0 (980), ρ (770), f 2 (1270), ρ 3 (1690) • Acceptance: corrections included (2004: ~60%, rather flat, 2008: similar for charged ) Step 1) Mass independent PWA: (40MeV/c² bins, 52+1 partial waves) = following results Step 2) Mass dependent χ 2 fit: (to mass independent result) • Main partial waves chosen, parameterised by Breit-Wigner • Coherent background for some waves Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

First comparison comparison: Neutral vs. : Neutral vs. charged charged mode mode First Mass independent PWA independent PWA results results Mass -- normalisation normalisation -- -- -- 2 (1320) (1320) − −> > ρπ ρπ a 2 a Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

First comparison comparison: Neutral vs. : Neutral vs. charged charged mode mode First simple isospin simple isospin symmetry symmetry check check 2 (1320) (1320) − −> > ρπ ρπ a 2 a Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011

First comparison comparison: Neutral vs. : Neutral vs. charged charged mode mode First simple isospin simple isospin symmetry symmetry check check 2 (1320) (1320) − −> > ρπ ρπ 1 (1260) (1260) − −> > ρπ ρπ a 2 a 1 a a π 2 π 2 (1670) (1670) − −> > f 2 π π π 2 π 2 (1670) (1670) − −> > ρπ ρπ f 2 Diffractive dissociation into 3 π – neutral vs. charged mode Frank Nerling 17/06/2011