Decays and transition form factors of π 0 , and η' mesons: status at KLOE/KLOE-2 and other experiments Andrzej Kupsc Uppsala University for the KLOE/KLOE-2 and for the WASA-at-COSY Collaborations Amherst, March 7th, 2014
Outline ● η,η' factories/data samples (pd, pp, e+e-) ● Selected results KLOE/WASA: Transition Form Factors /Anomalous processes (Γγγ) → ● γ ∗ γ η ● e + e - → ηγ ● η → e + e - e + e - / e + e - 0 e + e - (TFF) → → φ η/π → + π − γ ● η π Even P processes → + π − π 0 ● η π
Juliet Lee-Franzini KLOE Saclay Sven Kullander pd CBall WASA π-p, γp Ben Nefkens pd, pp
CELSIUS <2005 WASA Proposal 1987: key experiments: π 0 ,η e + e - → COSY 2007 – 2014
Meson tagging pd→ 3 He η >5x10 8 10 10 pp pp π 0 → pp→pp η
e+e- colliders BEPC II DAΦNE VEPP 2000 BESIII BEPCII L=6x10 32 cm -2 s -1 at J/Ψ DAΦNE L= 10 32 cm -2 s -1 at φ KLOE/KLOE-2 CMD-3,SND VEPP2000 L= 10 32 cm -2 s -1 at 2GeV
γ * →( φ ) → Hadrons (KLOE) 0 - 1 - 0 + 0 - 1 - 0 + φ (1020) KK a 0 (980) √s BR = 83% f 0 (980) η ' (960) π BR ~ O (10 −4 ) BR = 6.2 × 10 −5 ρ(770) γ η(550) BR = 15% 1x10 8 η BR = 1.3% π 0 0.5x10 6 η′ BR = 1.3 × 10 −3 σ T (1GeV) 80 nb + scan ±20 MeV ∼ Ο(10 pb −1 ) KLOE 2001-2005 data
ISR γγ √s W<√s s r e g g a T KLOE: Fv(W) in e + e - → π + π - (γ) y t i s o n i m u L
DAΦNE luminosity upgrade Frascati φ-factory Novel interaction scheme: e + e - collider √s = Mφ large angle beam crossing + crabbed waist sextupoles PRL104 (2010) 174801 Luminosity vs currents product KLOE-2 IP collisions: L NEW =3xL OLD from 2010 Commissioning for KLOE-2 Status:L=1.5 x 10 32 cm -2 s -1 with 1.3 A + 700/800 mA, 7pb -1 /day KLOE-2: Extension of the KLOE physics program at upgraded DAΦNE
KLOE KLOE-2 → Upgrades EM Calorimeter δE/E=5.7/√E % Inner Tracker: cyl. GEM δt=57/√E ⊕ 100 ps Drift Chamber δp T ~0.4% (θ<45 o ) Small angle EMC 2+2 taggers for: e + e − → e + e − γ ∗ γ ∗ → e + e − X y l u J t s a l y d a e R
Low Energy QCD processes Even # pseudoscalars PPPP u-d quark masses π-π,π-η scattering Anomalous: odd # pseudoscalars: PVV(Pγγ), PPPV Vector Meson Dominance: V PV → V 0 ↔ γ
Pseudoscalar Transition Form Factors (TFF) Structure of light mesons L/H energy QDC LAB l + l - spectra in HIon η: Γγγ m u /m d Fπ 0 q 2 → ∞ puzzle P l+l- → Dark photon g-2 LbL MesonNet(HP3) Workshop on Meson Transition Form Factors May 29-30,2012 Kraków
Radiative widths of η,π 0 η, π 0 : narrow and short lived => Гtot=Гγγ/BRγγ Two exp. techniques: γ Z → η,π 0 Primakoff ~ 5% → δΓ(η γγ) ~ 2.8% → δΓ(π 0 γγ) PrimEx PRL 106,162303(2011) e + e - : γγ → 0 η,π KLOE-2 Taggers 5fb -1 => δГ (π 0 ~ 1% → γγ) Γγγ=520±20 stat ±13 syst eV [KLOE JHEP1301 (2013) 119]
TFF kinematic regions: π 0 ,η π 0 η * γ P → * γ γ*→Pγ* γ*→Pγ* γ*→Pγ* γ*γ*→P γ*γ*→P P→γ*γ*
η,π 0 single off shell TFF ISR ISR ● BESIII ● Belle ● KLOE-2 ● GlueX γγ*→ π 0 γ*→Pγ VEPP 2000 0.3-2GeV KLOE-2 ISR, BESIII P→γ*γ Dalitz decays: KLOE, WASA,CBall,BESIII CLAS,NA48 Data:CELLO,NA60,CB-MAMI,CMD-2,SND
Dalitz decays η → e + e - γ FF=1 η → e + e - γ π 0 → e + e - γ
Analysis: π 0 → γe + e - Vertex r 20 mm + PID MC MC Vertex r (cyl) Data
σ(e+e- → π 0 γ,ηγ) Data: CMD-2,SND
e+e- → ηγ at 1 GeV KLOE JHEP1301 (2013) 119
V P γ * and e+e- PV processes → → slopes bπ, bη γ *→ φ → π 0 γ * γ *→ φ → ηγ * ω → π 0 γ * e + e - → π 0 ω γ * γ * →η γ * γ * →π 0 Naive VMD: Black: b π Red: b η KLOE prel result b η (m 2 φ ) φ → ηγ * BR 10 -4 φ ) φ → π 0 γ * BR 10 -5 b π 0 (m 2 TH: Bastian talk → Relation to ω/φ → π + π - π 0
Double off shell TFF η L=1.7 fb -1 γ *→ φ → ηγ * First observation!
η meson radiative decay width → 0 π 0 π 0 η π L=240 pb -1 I nsensitive to TFF Γγγ=520±20±13 eV 32.0±1.5 ±0.9 pb → η π + π − π 0 34.5±2.5 ±1.0 pb
φ e + e - η → → 0 π 0 π 0 η π 31k events → + π − π 0 η π 13k events Form factor/BR: PRL107 PRL106 U boson limits
φ e + e - π 0 → efficiency: Analysis in progress: 9k events Background 15% 2% background radiative Bhabha → low high q subtraction + andφ π0γ → → global efficiency
e+ π 0 /η HADES WASA CBall e- Decay NA48/NA62 3 σ diff Dorokhov,PLB667,145 e+ η'/η c Searches using formation: e+e- → η' , L=0.5pb -1 e- Formation => B< 2.1·10 -7 90% CL Vorobev SJNP 48(1988)273
→ → + π − γ/η + π − π 0 η π π → + π − γ η π ● No kin fit:use DC resolution ● Not use EMC Energy Φ ηγ L = 558 pb -1 → 205 k events eff=21% S/B=10 Consistent with CLEO Normalization → + π − π 0 η π
→ + π − γ η π PLB707 (2012) 184 e + e - → π + π - Fit data 2 χ 83 = Ndf 67 Mππ=√s α=1.89±0.25 stat ±0.59 syst GeV -2 α=1.31±0.08 stat ±0.40 systv GeV -2 [WASA PLB707 (2012) 243] [KLOE PLB718 (2013) 910]
From η + π − γ to η → e + e − γ → π sππ [GeV 2 ] η' π + π - γ → BESIII CLAS Mππ=√s WASA,KLOE: A+ α => b η(0)=2.05 +0.22 GeV -2 -0.10 EPJC73(13)2668 DATA: C Barrel PLB 402,195 ('97); KLOE PL B718, 910 ('13)
BESIII data sample on η' → + π − γ π BESIII PRD87, 092001('13) 158916±425
→ 0 γγ η/η′ π BRx10 4 VMD Exp η π 0 γγ 2.1 2.7 ± 0.5 PDG → η′ → ω[π 0 γ]γ 52 η′ π 0 γγ 3 <8 (90% CL) GAMS(87) → η′ ηγγ 2.5 — → η′ π 0 γγ 80% ω 4.6% ρ (+15% ρω interf? and φ) → Escribano (arXiv:1207.5400) Dominant VMD contribution
ω+ρ ρ
Three body decays, Dalitz plot 3 body decay: 0 1 + 2 + 3 → s i ( p 0 − p i ) 2 = (m 0 −m i ) 2 -2T i m 0 ≡ |A(X,Y)| 2 =N(1+aY+bY 2 +dX 2 +fY 3 +gX 2 Y) η´ π+π-η → BESIII PRD83, 012003('11) EXP: CBall, KLOE,WASA, VES, BESIII
KLOE new prel. DP η → + π − π 0 π KLOE2008 analysis (JHEP 0805,006) 0.45 fb -1 1.34·10 6 events in DP ⇒ large syst. uncertainty due to Event classification New analysis: 1.7 fb -1 4.48·10 6 events in DP ⇒ new analysis scheme improved MC new cross checks a b d f JHEP0805,006 1.090(5)( +8 ) 0.124(6)(10) 0.057(6)( +7 ) 0.140(10)(20) ‐ ‐ 19 ‐ 16 preliminary, 1.103(3)(?) 0.142(3)(?) 0.073(3)(?) 0.154( 6)(?) ‐ 2013 New analysis PRELIMINARY (no syst. ): f≠0 confirmed |A(X,Y)| 2 =N(1+aY+bY 2 +dX 2 +fY 3 +gX 2 Y) fits with g...
WASA-at-COSY new prel. DP η → + π − π 0 π 1.5·10 5 events a b d f preliminary, 1.144(18) 0.219(19)(37) 0.086(18)(18) 0.115(37) ‐ 2013
η´ πππ → U(3) CHPT, Borasoy, Nißler 2005: BR(η π + π − π 0 ) ≈ 1.8% large ρ ± π 0 →
η´ πππ → Z=x 2 +y 2 The data 20±5 ev. Z=x 2 +y 2 BR= 3.7±1.0 10 -3 GAMS PAN71,2124('08) 235 ± 45 (1.8 ± 0.4) × 10 −3 CLEO: PRL 102, 061801 (2009)
BESIII η´ πππ → BESIII, PRL 108,182001 (2012) η´ π+π-π 0 η´ π 0 π 0 π 0 → → 309±19 1014±39 BR= (3.56± 0.22± 0.34)x10 -3 BR=(3.83± 0.15± 0.39)x10 -3
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