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Phi Radiative decays at KLOE Camilla Di Donato* for the KLOE Collaboration *Sezione I.N.F.N. Napoli

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Outline Scalar mesons at -factory: f 0 (980) [PLB634 (2006) 148] f 0 (980) Pseudoscalar mesons at -factory: mass measurement BR( and mixing angle

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Scalar mesons at a -factory Scalar Mesons Spectroscopy: f 0 (980), (600) and a 0 (980) are accessible ( not accessible) through S ; Questions: 1. Is (600) needed to describe the mass spectra ? 2. “couplings”of f 0 (980) and a 0 (980) to |ss> and to KK, and . 4-quark vs. 2-quark states (1020) Mass (MeV/c 2 ) a 0 (980) I=0I=1/2I=1 f 0 (980) f 0 (600) “ ” K* 0 (800) “ ” How a -factory can contribute to the understanding of the scalar mesons

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Kaon-loop KL ( Achasov-Ivanchenko, NPB ): for each scalar meson S there are three free parameters of the fit: g S , g SKK, M S 2.No-Structure NS ( by G.Isidori and L.Maiani ): a modified BW + a polynomial continuum : g S , g S , g SKK, M S + pol. cont. parameters 3.Scattering Amplitudes SA ( M.E.Boglione, M.R.Pennington, Eur. Phys., J. C30 (2003) ) A (a 1 +b 1 m 2 +c 1 m 4 ) T( ) + (a 2 +b 2 m 2 +c 2 m 4 ) T( ) pole residual g The scalar amplitude description We use three different approaches in the description of the scalar amplitude: S g KK g SKK g SPP KK KK S V g V S g S e+e+ e-e-

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, large angle: looking for f e + e → events with the photon at large angle (45 < <135 ) Main contributions: – ISR (radiative return to , ) – FSR Search for the f 0 signal as a deviation of M spectrum from the expected ISR + FSR shape 676,000 events selected ( ) M( ) (MeV ) f 0 (980) region M( ) (MeV ) Events/1.2 MeV

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Fit to the m( ) spectrum: ( 491 bins, 1.2 MeV wide, m( ) = 420 to 1009 MeV) Fit : ISR + FSR + + scalar ± interf( SCAL+ FSR ) Kaon-Loop and No-Structure fits: Good description in both cases of signal and background (Kuhn-Santamaria); “negative” interference; The introduction of a (600) doesn’t improve the fit. KL fitNS fit

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Scattering Amplitude Fit g = 6.6 ×10 -4 BR ( f 0 ) × BR ( f 0 ) ~ 3 × [similar conclusion from Boglione Pennington analysis of data (KLOE + SND)] Summarizing: The peak at ~980 MeV is well interpreted in both KL and NS approaches as due to the decay f 0 (980) with a negative interference with FSR. The couplings suggest the f 0 (980) to be strongly coupled to kaons and to the . Scattering Amplitude gives a marginal agreement.

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Forward-Backward asymmetry Data Simulation FSR+ISR Simulation FSR+ISR+ scalar(KL) FB asymmetry vs. m ( ): Clear signal ~ 980MeV Interesting comparison with Phokara MC simulation A = (N( + >90 o ) – N( + 90 o ) + N( + <90 o )) + - system: A(ISR) C-odd A(FSR) & A( scalar ) C-even Cross-section:|A(tot)| 2 = |A(ISR) + A(FSR) + A( scalar )| 2 zoom

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, New analysis scheme: Allow for interference between e + e - 0 and S Bi-dimensional analysis of Dalitz-plot : m( ) vs m( ) final state: VMD vs scalar →S→→S→ e + e → → √s = MeV 450 pb from 2001 – 2002 data taking ~ 400k events Two main contributions to final M : KLOE preliminary

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, final state: VMD vs scalar Fit with No-Structure approach: in progress Fit Dalitz plot with improved Kaon loop parametrization: (Achasov Kiselev hep-ph/ ) Insertion of a KK scattering phase New parametrization of scattering phase Scalar contributions: f 0 (980) and (600) Combined fit to scattering data and to already published KLOE data on S gives six sets of parameters able to describe both distributions

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, K-Loop fit: f 0 + MeV KLOE preliminary Free parameters: M f 0, g_ f 0 + -, g_ f 0 K + K -, VMD description /KK phases and (600) fixed to Achasov’s results

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, KL fit results parameter values are from best fit The first error is statistical error from fit, the second one reflects the changes related to the other fit variants with acceptable KLOE preliminary

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Pseudoscalar mesons at -factory mass measurement; ● Br /Br with + - 7 final state; ● Pseudoscalar mixing angle.

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, mass measurement Large discrepancy between the two most precise measurements GEM measurement M = ( ± ± 0.032) MeV/c 2 Reaction used: p + d → 3 He + [ M. Abdel-Bary et al., Phys. Lett. B 619 (2005) ] NA48 measurement Using →3 from p → n : M = ( ± ± 0.041) MeV/c 2 [ A, Lai et al., Phys. Lett. B 533 (2002) 196]

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Measurement method E1E1 E2E2 E3E3 Using the decays: Px,Py,Pz,Etot t-r/c of clusters A kinematic fit is performed imposing: conservation compatible with light velocity As a consequence of the kinematic fit the mass measurement is almost independent from the energy of the clusters, it is dominated by the cluster positions. The momentum and the vertex position are precisely determined run by run from the study of the Bhabha scattering at large angle e + e - e + e – (90000 events for each run). Absolute scale determined buy line shape and mass cross checking purpose

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, KLOE Kinematic fit applied on → events and 0 selected by looking at different Dalitz plot regions M (MeV) = ( ) MeV = ( ) MeV = ( ) MeV = ( 1.66 ) MeV 2 /ndf = 304/257 00 2 /ndf = 146/161 E 1

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, KLOE data sample divided into 8 periods, each of 50 pb -1 M( 0 ) = ( 6 stat 30 syst ) keV M( 0 ) PDG = ( 0.6 ) keV Systematics mainly from √ s and vertex position EMC linearity in progress NA48 compatibility: 0.24 M (MeV) M (MeV) M( ) = ( 5 stat 69 syst ) keV KLOE preliminary

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, BR( )/ BR( ) Signal selection: charged vertex in a cylinder with a 4 cm radius and a 16 cm height around the interaction point 7 prompt photons |t – r/c| < 5 t and 21 < < 159 anti K S K L tag No way to separate radiative and from ' ' ' E (MeV)

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, ' ' wrong combination 427 pb √s = M N obs = 3750 observed N bkg = 345 estim. bkg N sig =(N obs - N bkg )=3405 ± 65 stat ± 28 syst Signal extraction: data Ks + - Kl 0 0 0 Ks 0 0 Kl + - 0 Ks + - Kl 0 0 0 Signal M (MeV) ' mass distribution after wrong mass combination subtraction KLOE preliminary

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Results SourceSyst. Err. Filfo-Evcl1% TRK1% VTX1% Back. Sub. 0.1% / ´ 0.4% 22 1.5% BR”3% KK 1% total4% Previous KLOE results: Phys. Lett. B541 (2002) Systematics dominated by knowledge of ’ branching ratios KLOE preliminary

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Mixing angle and ’ gluonic content Using the Bramon approach (A.Bramon et. al. Eur. Phys. J. C7, 271(1999)) we extract mixing angle: KLOE preliminary

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Extensive study of f 0 (980) properties with KLOE data: Clear evidence of f 0 both in invariant mass and in the forward-backward asymmetry. M fitted with three different theoretical approaches: [PLB634 (2006) 148] Preliminary results on S : fit to Dalitz plot with improved kaon loop model Perspectives with our new data sets: 2 M : search for f 0 a 0 KK Energy scan (4 points - 10 pb -1 each - in the MeV range): improved study of the √s-dependence of the cross-section Off-peak data (~200 pb MeV): search for Measurement of mass: KLOE preliminary result is in agreement with NA48 measurement in + final state, in agreement with the KLOE previous result in + final state; Pseudoscalar mixing angle Conclusions

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, KL fit results: f 0 + (the six variants), S term Fixed M,

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, KL fit results: VDM/S compositions

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Camilla Di DonatoNovosibirsk, Feb 27 - Mar 2, Fit function: the Achasov parametrization

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