Investigation of the Hadronic Decay + 0 with CLAS 01.02.2017 - PowerPoint PPT Presentation

Mitglied der Helmholtz-Gemeinschaft Investigation of the Hadronic Decay η → π + π − π 0 with CLAS 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Institute for Nuclear Physics - J¨ ulich Research Center

One Meson, many Opportunities η Properties of the η -meson m η [ GeV / c 2 ] 0 . 5478 (Semi-)Leptonic Hadronic R a Γ η [ keV ] ( 1 . 31 ± 0 . 05 ) d i a t i 5 · 10 − 19 v τ [ s ] ¯ e J PC 0 − + π π π γ γ γ l + l - γ The η -meson is a C -, P -, G - and CP - eigenstate (π + π - ) (π + π - ) (π + π - ) All strong and electromagnetic decays are forbidden ( l + l - ) to first order →Quark mass ratio →QCD anomalies →Transition Form Factor Access to rare decay processes →Isospin violation →FSI →CP-violation 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 2

One Meson, many Opportunities η Properties of the η -meson m η [ GeV / c 2 ] 0 . 5478 (Semi-)Leptonic Hadronic R a Γ η [ keV ] ( 1 . 31 ± 0 . 05 ) d i a t i v 5 · 10 − 19 τ [ s ] ¯ e J PC 0 − + π π π γ γ γ l + l - γ The η -meson is a C -, P -, G - and CP - eigenstate (π + π - ) (π + π - ) (π + π - ) All strong and electromagnetic decays are forbidden ( l + l - ) to first order →Quark mass ratio →QCD anomalies →Transition Form Factor Access to rare decay processes →Isospin violation →FSI →CP-violation π + triangle anomaly box anomaly γ π η η η η 0 , , ' , ' γ L = + + ... WZW γ π - 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 2

One Meson, many Opportunities η Properties of the η -meson m η [ GeV / c 2 ] 0 . 5478 (Semi-)Leptonic Hadronic R a Γ η [ keV ] ( 1 . 31 ± 0 . 05 ) d i a t i v 5 · 10 − 19 τ [ s ] ¯ e J PC 0 − + π π π γ γ γ l + l - γ The η -meson is a C -, P -, G - and CP - eigenstate (π + π - ) (π + π - ) (π + π - ) All strong and electromagnetic decays are forbidden ( l + l - ) to first order →Quark mass ratio →QCD anomalies →Transition Form Factor Access to rare decay processes →Isospin violation →FSI →CP-violation π + π + ρ π - π η η η η 0 , , ' , ' γ L = + + ... WZW γ π - 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 2

One Meson, many Opportunities η Properties of the η -meson m η [ GeV / c 2 ] 0 . 5478 (Semi-)Leptonic Hadronic R a Γ η [ keV ] ( 1 . 31 ± 0 . 05 ) d i a t i v 5 · 10 − 19 τ [ s ] ¯ e J PC 0 − + π π π γ γ γ l + l - γ The η -meson is a C -, P -, G - and CP - eigenstate (π + π - ) (π + π - ) (π + π - ) All strong and electromagnetic decays are forbidden ( l + l - ) to first order →Quark mass ratio →QCD anomalies →Transition Form Factor Access to rare decay processes →Isospin violation →FSI →CP-violation 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 2

One Meson, many Opportunities η Properties of the η -meson m η [ GeV / c 2 ] 0 . 5478 (Semi-)Leptonic Hadronic R a Γ η [ keV ] ( 1 . 31 ± 0 . 05 ) d i a t i v 5 · 10 − 19 τ [ s ] ¯ e J PC 0 − + π π π γ γ γ l + l - γ The η -meson is a C -, P -, G - and CP - eigenstate (π + π - ) (π + π - ) (π + π - ) All strong and electromagnetic decays are forbidden ( l + l - ) to first order →Quark mass ratio →QCD anomalies →Transition Form Factor Access to rare decay processes →Isospin violation →FSI →CP-violation 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 2

One Meson, many Opportunities η Properties of the η -meson m η [ GeV / c 2 ] 0 . 5478 (Semi-)Leptonic Hadronic R a Γ η [ keV ] ( 1 . 31 ± 0 . 05 ) d i a t i v 5 · 10 − 19 τ [ s ] ¯ e J PC 0 − + π π π γ γ γ l + l - γ The η -meson is a C -, P -, G - and CP - eigenstate (π + π - ) (π + π - ) (π + π - ) All strong and electromagnetic decays are forbidden ( l + l - ) to first order →Quark mass ratio →QCD anomalies →Transition Form Factor Access to rare decay processes →Isospin violation →FSI →CP-violation Focus of this Talk 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 2

Decay Dynamics of η → π + π − π 0 System Isospin State | I , I z � C-Eigenvalue G-Eigenvalue η | 0 , 0 � + 1 + 1 ( π + π − π 0 ) | 0 , 0 � − 1 − 1 ( π + π − π 0 ) | 1 , 0 � + 1 − 1 Decay η → π + π − π 0 is G-violating ⇒ Forbidden to first order m s Decay is driven by isospin breaking part of strong interaction m d ⇒ C is conserved 25 Decay width: Γ ∝ Q − 4 20 � m s � 2 × � m u with: Q 2 = � 2 � − 1 15 � 1 − m d m d 10 ⇒ Determine decay width Γ ⇒ Access to quark mass ratio 5 m u ⇓ 0.2 0.4 0.6 0.8 1.0 m d Measure Γ( η → π + π − π 0 ) , e.g. via Γ( η → π + π − π 0 ) a) Γ( η → γγ ) b) Dalitz Plot Analysis 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 3

Dalitz Plot Analysis of η → π + π − π 0 Dimensionless Dalitz Plot Variables: √ T π + − T π − X = 3 T π + + T π − + T π 0 T π 0 Y = 3 T π + + T π − + T π 0 − 1 (a) KLOE coll., JHEP , 05, (2008) Describe three body decay by two variables (here: X and Y) Complete information about decay dynamics Parameterise decay width Γ : dXdY ∝ ( 1 + aY + bY 2 + cX + dX 2 + eXY + fY 3 + gX 2 Y + ... ) d 2 Γ c � = 0 and e � = 0: i) Imply C-violation ii) Cause asymmetries within the Dalitz Plot Compare Dalitz Plot parameters a,b,d,f from experiment and theory 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 4

Recent Measurements I 1 Y 25000 0.8 25000 0.6 20000 0.4 20000 0.2 15000 0 15000 N i 0.2 10000 − 0.4 − 10000 0.6 5000 − 0.8 − 5000 1 0 − 1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1 − − − − − X 1 0.5 0 0.5 1 − − X Most recent result from the KLOE-Collaboration: ( f ) η -Mesons produced via: e + e − → Φ → ηγ ≈ 4 . 7 · 10 6 η → π + π − π 0 events in the final data sample Fit function: Norm × ( 1 + aY + bY + cX + dX 2 + eXY + fY 3 ) Determined asymmetries of the Dalitz Plot ⇒ Consistent with zero ⇒ No C-violation (f) KLOE coll., JHEP , 019, (2016) 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 5

Recent Measurements II 3 10 × 0.07 100 i 1 N (a) 90 57 58 59 0.06 80 50 51 52 53 54 55 56 0.5 0.05 70 41 42 43 44 45 46 47 48 49 32 33 34 35 36 37 38 39 40 60 0.04 0 Y 23 24 25 26 27 28 29 30 31 50 0.03 16 17 18 19 20 21 22 40 9 10 11 12 13 14 15 -0.5 0.02 30 4 5 6 7 8 20 0.01 1 2 3 10 -1 0 0 -1 -0.5 0 0.5 1 0 10 20 30 40 50 60 X bin Result from the WASA-at-COSY Collaboration: ( d ) η -Mesons produced via: pd → 3 He η ≈ 120 k η → π + π − π 0 events in the final data sample Translate each pair (X,Y) into a global bin i ( X , Y ) → Obtain one dimensional Dalitz Plot Fit function: Norm × ( 1 + aY + bY + cX + dX 2 + eXY + fY 3 ) (d) WASA-at-COSY coll., Phys. Rev. , C90(045207), 2014 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 6

Recent Measurements and Theoretical Predictions Parameter: − a b d f 1 . 090 ( 5 )( + 8 0 . 057 ( 6 )( + 7 KLOE (08) ( a ) Exp. − 19 ) 0 . 124 ( 6 )( 10 ) − 16 ) 0 . 14 ( 1 )( 2 ) WASA ( d ) 1 . 144 ( 18 ) 0 . 219 ( 19 )( 47 ) 0 . 086 ( 18 )( 15 ) 0 . 115 ( 37 ) 0 . 073 ( 3 )( + 4 0 . 154 ( 6 )( + 4 0 . 142 ( 3 )( 5 KLOE (16) ( f ) 1 . 104 ( 3 )( 2 ) − 4 ) − 3 ) − 5 ) Theor. ChPT (NNLO) ( b ) 1 . 271 ( 75 ) 0 . 394 ( 102 ) 0 . 055 ( 57 ) 0 . 025 ( 160 ) NREFT ( c ) 1 . 213 ( 14 ) 0 . 308 ( 23 ) 0 . 050 ( 3 ) 0 . 083 ( 19 ) PWA ( e ) 1 . 116 ( 32 ) 0 . 188 ( 12 ) 0 . 063 ( 4 ) 0 . 091 ( 3 ) (a) KLOE coll., JHEP , 05, (2008) (b) J. Bijnens and K. Ghorbani., JHEP , 11, (2007) (c) S- P . Schneider et al., JHEP , 028, (2011) (d) WASA-at-COSY coll., Phys. Rev. , C90(045207), 2014 (e) Peng Guo et al., Phys. Rev. , D92(05016), (2015) (f) KLOE coll., JHEP , 019, (2016) WASA-at-COSY results used for Partial Wave Analysis (PWA) from JPAC ⋆ group ⇒ Direct calculation of: Q = 21 . 4 ± 0 . 4 stat ( e ) Dalitz Plot Analysis and determination of Q for γ p → p η [ η → π + π − π 0 ] with CLAS ⋆ See plenary talk ”Hadron Spectroscopy at JPAC“ by Alessandro Pilloni at 4.40 p.m. 01.02.2017 7th Workshop of the APS Topical Group Hadronic Physics 2017 Slide 7