Studies on decays of light mesons 9th Workshop on Hadron Physics in China and Opportunities Worldwide Lena Heijkenskjöld Institut für Kernphysik, JGU Mainz 24-29 July 2017
Experiments Dalitz plot studies Transition Form Factors Introduction Light meson decays Three different but complementary experiments WASA-at-COSY KLOE/KLOE-2 A2 Dalitz plot studies Focus on: Transition form factor measurements L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 1/13
Experiments Dalitz plot studies Transition Form Factors WASA-at-COSY Wide Angle Shower Apparatus Operated at Cooler Synchrotron (COSY) 2006-2015. COSY — (un)polarised proton/deutron beam p = 600 - 3700 MeV/c. Frozen pellet target — hydrogen/deuterium. Designed for studies of light mesons. p + d → 3 ❍❡ + X p + p → p + p + X or H.-H. Adam et al arXiv:nucl-ex/0411038 Ex t rac t ion ANK E RF c avit y J ESSICA ooling JULIC PAX TOF icc hast Elec t ron c ooler oc St EDDA WASA Quadrupole Central Detector Forward Detector Barrier buc k et ∼ 4 π coverage of decay particles Clean tagging of recoil particles c avit y Mini drift chamber: 17 cylindrical layers Plastic scintillators Dipole Proportional chamber Calorimeter: 1012 CsI(Na) crystals Solenoid: B max =1.3T L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 2/13
Experiments Dalitz plot studies Transition Form Factors KLOE/KLOE-2 K LOng Experiment At DA Φ Ne — e + e − collider √ s = M Φ = 1019 . 4 MeV. e + + e − → Φ → X + Y + ... KLOE operated 2000-2006. collecting 2.5fb − 1 @ M Φ + 250 pb − 1 off-peak → Upgraded to KLOE-2, will collect > 5 fb − 1 2014-2018 F. Bossi, et al. , Nuovo Cimento, 30 (2008) 10 G. Amelino-Camelia et al., Eur. Phys. J. C, 68 (2010) 619 Improved vertex reconstruction and track parameters Drift Chamber For θγ down to 10 ◦ 4m diameter, 3.3 m long ∂ p ⊥ / p ⊥ < 0 . 4 % ( θ > 45 ◦ ) σ xy = 150 µ m, σ z =2mm Calorimeter Pb/scintillating fiber Quadropole coverage 98% coverage of solid angle for KL decays � σ T = 57 ps / E ( GeV ) ⊕ 140 ps e + e − taggers for γγ physics Magnetic field B=0.52 T Figure from E. Perez del Rio presentation at International Workshop on e + e − collisions from Phi to Psi 2017 L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 3/13
Experiments Dalitz plot studies Transition Form Factors A2 A2 At MAinzer MIkrotron (MAMI) — (un)polarised electron accelerator, E max = 1 . 6 GeV. Electrons + radiator → tagged bremsstrahlung photons (un/linearly/circularly polarised) γ + p → p + X A. Starostin, et al., Phys. Rev. C 64, 055205 (2001) R. Novotny, IEEE Trans. Nucl. Sci. 38, 379 (1991) J. C. McGeorge Eur. Phys. J. A (2008) 37: 129-137 The Glasgow photon tagger + The end point tagger The Crystal Ball + TAPS setup Photon beam E γ = 80 - 1401 MeV σ [µbarn] 10³ Bremsstrahlung Probability [a.u] Meson Photoproduction Cross Section Crystal Ball Resolution: 1-4 MeV total 9 8 672 NaI(TI) crystals 7 Prim a ry Be a m 10² π⁰ 6 5 4 10 η ω Target, PID & 3 Dump Foca l Pla ne η ' 2 MWPC - 1 1 e Ma gne t 0 0.5 1.5 E / [GeV] S pe ctrom e te r 1 T agger EPT Ele ctron La dde r End Point T agger Resolution: Glasgow Detector T agger Vetos (47 Channels) 384 plastic scintillators MAMI Be a m Electron C ollim a tor Beam Photon Beam Photon Beam E γ = E 0 – E Ta rge t Ra dia tor - e TAPS Correction Magnet Radiator 366 BaF , 72 PbWO crystals 2 4 L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 4/13
Experiments Dalitz plot studies Transition Form Factors What is a Dalitz plot? Kinematic variables 3-body decay: A given by two independent variables → 2D representation. Common choice of variables when m 1 = m 2 0.5 3 1 0.45 2 0.4 0.5 ] 0.35 T ∗ 1 − T ∗ √ 2 [GeV 1 2 Z = X 2 + Y 2 0.3 s ij = | P i + P j | 2 X = 3 Q 0.25 Y Φ 0 0 0.2 23 ( 2 m 1 + m 3 ) T ∗ Φ= tan − 1 X s -1 0.15 3 -0.5 Y = − 1 Y ( m 1 Q ) 0.1 -2 0.05 -1 -3 0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 -1 -0.5 0 0.5 1 0 0.2 0.4 0.6 0.8 1 2 s [GeV ] X Z 12 Parametrisation To compare experimental/theory results — only for smooth distributions. |A ( X , Y ) | 2 ∝ N ( 1 + aY + bY 2 + cX + dX 2 + eXY + fY 3 + gX 2 Y + ... ) |A ( Z , Φ) | 2 ∝ N ( 1 + 2 α Z + 2 β Z 3 / 2 sin ( 3 Φ) + 2 γ Z 2 + 2 δ Z 5 / 2 sin ( 3 Φ) + ... ) L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 5/13
− − − − − − − − − − Experiments Dalitz plot studies Transition Form Factors η → π + π − π 0 L. Caldeira Balkeståhl, Doctoral dissertation Uppsala U. 2016 25 Study ratio of light m q 20 15 m s m 2 d − m 2 ∼ Q − 2 = m d A χ PT u 10 LO m 2 s − m 2 ud Q D 5 NNLO χ PT calculated 1 — slow convergence We inbe rg 77 0 0 0.2 0.4 0.6 0.8 1 m u m d Dispersive calculations 2 , 3 — use χ PT constraints and exp. results → Q 1 J. Bijnens, et al., JHEP 11 (2007) 030, 2 G. Colangelo, et al.,Phys.Rev.Lett. 118, (2017) 022001, 3 P . Guo, et al., arXiv:1608.01447 [hep-ph] L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 6/13
Experiments Dalitz plot studies Transition Form Factors η → π + π − π 0 L. Caldeira Balkeståhl, Doctoral dissertation Uppsala U. 2016 25 Study ratio of light m q 20 15 m s m 2 d − m 2 ∼ Q − 2 = m d A χ PT u 10 LO m 2 s − m 2 ud Q D 5 NNLO χ PT calculated 1 — slow convergence We inbe rg 77 0 0 0.2 0.4 0.6 0.8 1 m u m d Dispersive calculations 2 , 3 — use χ PT constraints and exp. results → Q 1 J. Bijnens, et al., JHEP 11 (2007) 030, 2 G. Colangelo, et al.,Phys.Rev.Lett. 118, (2017) 022001, 3 P . Guo, et al., arXiv:1608.01447 [hep-ph] Experimental Dalitz plots KLOE WASA 0.07 1 1 Y 25000 0.8 57 58 59 0.06 0.6 20000 0.4 50 51 52 53 54 55 56 0.5 0.05 0.2 41 42 43 44 45 46 47 48 49 15000 0 e + e − → φ → γη 32 33 34 35 36 37 38 39 40 0.04 − 0.2 KLOE 10000 Y 0 − 0.4 23 24 25 26 27 28 29 30 31 − 0.6 0.03 5000 16 17 18 19 20 21 22 pd → 3 He η − 0.8 WASA 9 10 11 12 13 14 15 − 1 -0.5 0.02 0 − 1 − 0.8 − 0.6 − 0.4 − 0.2 0 0.2 0.4 0.6 0.8 1 4 5 6 7 8 X 0.01 1 2 3 A. Anastasi, et al., JHEP 1605 (2016) 019 -1 0 High statistics Dalitz plot density distribution. -1 -0.5 0 0.5 1 X Fit parametrisation → test of theory. P . Adlarson, et al., Phys.Rev. C90 (2014) no.4, 045207 Determination of theory parameters → Q L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 6/13
❍❡ Experiments Dalitz plot studies Transition Form Factors ω → π + π − π 0 Study decay dynamic × -6 10 Final state P-wave 0.1 0.08 0.06 π − π interactions — Previously unmeasured 0.04 0.02 Full predictions by lagrangian approaches 4 and dispersion 0 00.1 3 0.20.30.40.50.60.70.80.9 2 1 0 calculations 5 , 6 . Φ Z -1 -2 -3 1 4 [Uppsala]C. Terschlüsen, et al., Eur.Phys.J. A49 (2013) 116 5 [Bonn] S.P . Schneider, et al., Eur.Phys.J. C72 (2014) 2012 6 [JPAC] I. Danilkin et al., Phys. Rev. D91 (2015) 094029 π ω π ρ π L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 7/13
Experiments Dalitz plot studies Transition Form Factors ω → π + π − π 0 Study decay dynamic × -6 10 Final state P-wave 0.1 0.08 0.06 π − π interactions — Previously unmeasured 0.04 0.02 Full predictions by lagrangian approaches 4 and dispersion 0 00.1 3 0.20.30.40.50.60.70.80.9 2 1 0 calculations 5 , 6 . Φ Z -1 -2 -3 1 4 [Uppsala]C. Terschlüsen, et al., Eur.Phys.J. A49 (2013) 116 5 [Bonn] S.P . Schneider, et al., Eur.Phys.J. C72 (2014) 2012 6 [JPAC] I. Danilkin et al., Phys. Rev. D91 (2015) 094029 π ω π ρ π Experimental Dalitz plot pd → 3 ❍❡ ω and pp → pp ω WASA ( 4 . 408 ± 0 . 042 ) × 10 4 events 1 + 2 α Z + 2 β Z 3 / 2 sin 3 φ + O ( Z 2 ) � � A ∼ [ Pwave ] × − → First observation of intermediate ρ ∝ α parameter P . Adlarson, et al., Phys.Lett. B770 (2017) 418 L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 7/13
Experiments Dalitz plot studies Transition Form Factors η ′ → ηπ 0 π 0 η ′ → ηππ : Test for Resonance ChPT 7 , 9 , large-N C ChPT 8 , 9 and Dispersive approach 10 7 G. Ecker, et al., Phys. Lett. B 223 (1989) 425, 8 R. Kaiser et al., Eur. Phys. J. C 17 (2000) 623, 9 Escribano, et al. JHEP 1105 (2011) 094, 10 T. Isken et al., arXiv:1705.04339 η Cusp effect η ’ π + π 0 Not yet observed in this channel π − π 0 NREFT 11 → ( a 2 − a 0 ): ππ S-wave scat. lengths for I=0,2 11 Kubis, et al., Eur.Phys.J. C62 (2009) 511-523 L. Heijkenskjöld KPH, JGU Mainz 24-29 July 2017 8/13
Recommend
More recommend
