h, h’ studies with the KLOE detector at DaFne A. Farilla – I.N.F.N. Rome III for the KLOE Collaboration Ada Farilla Uppsala, October 2001

* * The DAFNE complex Design philosophy: DEAR DAFNE is an Electron - Positron Collider at s = 1.02 GeV F resonance ( F – Factory ) Design philosophy: Moderate Single Bunch Luminosity * Large Number of Bunches 4·1030(VEPP-2M) * 120 Bunches Design Luminosity  5 ·1032 Two interaction points for detectors: KLOE (CP(T) violation and K Physics) DEAR / FINUDA (Kaon-Nucleon Interaction and Hypernuclear Physics) Ada Farilla Uppsala, October 2001

Beam trajectory length ~ 98 m Beam crossing frequency 368.25 MHz Beam-beam scattering @ 5A/beam requires two independent lines Beam trajectory length ~ 98 m Beam crossing frequency 368.25 MHz Nbunch/ring = 120 (max) Bunch spacing : 2.7 ns Bunch sizes @ I.P.: length = 30 mm (sz) transv.(x) = 2 mm (sx) transv.(y) = 20 mm (sy) Ada Farilla Uppsala, October 2001

The KLOE physics program e/e to O(10-4) via double ratio Semileptonic asymmetry (CPT test) Interferometry 2 pb-1 20 pb-1 200 pb-1 2 fb-1 Close out KS and f physics KS  3p0, other rare KS decays KL  2p, KL gg, form factors s(e+e-  hadrons) to 1% (stat) 1999 2000 Today End 2001 KS physics BR(KS  p+p-)/BR(KS p0p0) BR(KS pen) f radiative decays f  f0g, a0g f  hg, hg Ada Farilla Uppsala, October 2001

DAFNE performance L dt2001 = 108 pb-1 So far in 2001… KLOE integrated luminosity 4 Oct So far in 2001… L dt2001 = 108 pb-1 Peak luminosity exceeded 3.5 1031 cm-2s-1 (average > 2 1031 ) Integrated luminosity exceeded 2.0 pb-1/day (average > 0.8) Expected total integrated luminosity in 2001: 200 pb-1 -> ~650 Millions F’s corresponding to ~ 7.4 Millions h produced ( BR f->hg = (1.297+0.033)% ) Ada Farilla Uppsala, October 2001

The KLOE Detector Superconducting Coil B=0.6 T Be beam pipe (0.5 mm thickness) permanent + Quad’s instrumentation Iron Yoke Cylindrical Drift Chamber 4 m Diameter, 3.3 m Length 90% Helium, 10% Isobutane 12582 / 52140 sense / total wires all stereo wires Electromagnetic Calorimeter Pb / Scintillating Fibres (4880 PMTs) Endcap - Barrel - Modules Ada Farilla Uppsala, October 2001

The Electromagnetic Calorimeter Pb - Sc.Fibres - Matrix Efficient Detection of Photons > 20 MeV  Barrel + Endcap = 98% Hermetic Coverage  Discriminate KL  p0p0 against KL  p0p0 p0 Reconstruct KL  p0 p0 decay vertex with a precision < 1 cm  Serve as a 1st level Trigger <r> = 5 g/cm3 <l0> = 1.6 cm sampl. frac.~15% (m.i.p.) Lead 1.2 mm 1.0 mm 1.35 mm Design: sE /E = 5% /E(GeV) s t = 70 ps /E (GeV) Measured : sE /E = 5.7% /E(GeV) s t= 54 ps /E (GeV)  50 ps 450 cm 15X0 52.5 cm Ada Farilla Uppsala, October 2001

EmC: time and energy performances ) GeV ( ps 54 E = s(t)  50 ps Time resolution Energy residuals e+e-e+e-g Eg from DC Energy resolution e+e-g effects due to the beam (spread and bunch to bunch fluctuation) and to EMC cell to cell variation have been subctracted from the constant term Ada Farilla Uppsala, October 2001

EmC resolution on full neutral channels f  p0g  ggg, f  hg  ggg p0  gg h  gg mp0 = 135.0 MeV sm = 13.0 MeV mh = 546.4 MeV sm = 40.3 MeV Ada Farilla Uppsala, October 2001

permanent magnet quadrupoles Quadrupole Calorimeter (QCAL) 45 cm 0.5 mm Al-Be 9° permanent magnet quadrupoles 10 cm Acceptance increased thanks to Quadrupole Instrumentation : Lead-Scintillator-Tile Sampling Calorimeter QCal Spherical Beam Pipe QCAL Ada Farilla Uppsala, October 2001

The Drift Chamber ~52000 stereo wires  High and uniform track reconstruction efficiency  Determine the KL,S vertex with an accuracy of ~ 1mm  Good momentum resolution (dp/p  0.3% ) for Kl3 rej.  Transparent to low energy g (down to 20 MeV) and KL,S regeneration -> ~52000 stereo wires cell structure: 3:1 field:sense ratio 3 × 3 cm2 in the 46 outer layers 2 × 2 cm2 in the 12 inner layers [90% He, 10% iC4H10 ( X0=900m ) mec. str. in C-Fibre (<0.1 X0)] Ada Farilla Uppsala, October 2001

DC resolution and stability sp/p < 0.3% 45°<<135° Residuals Resolution Well below 200 mm spatial resolution in most of the impact parameter range Drift distance (cm) e+e-e+e- sp (MeV/c) Polar angle mpp = 497.7 MeV/c2 sm = 1 MeV/c2 KS  p+p- Polar angle Ada Farilla Uppsala, October 2001

Pseudoscalars: f   g ,  g With the decay   ’ we can probe the gluonic content of the ’: theoretical predictions for BR(  ’) range from 2x10-4 down to ~10-6 in case of significant gluonic content. [N.Deshapande and G. Eilam., Phys. Rev. D25 (1980) 270, J. L. Rosner, Phys. Rev. D27 (1983) 1101, F.E.Close, The DAFNE Physics Handbook Vol. II, Frascati 1992] The mass eigenstates (547), ’(958) can be related to the SU(3) octet-singlet states 8, 0 through the mixing angle p , whose value has been discussed many times in the last 30 years: both from theoretical predictions and from phenomenological analyses it varies from -23° to -10°. [A. Bramon et al., Eur. J. C7 (1999) , A. Bramon et al., Phys. Lett. B503 (2001 ) 571 ] [ F.J. Gilman, R. Kauffman, Phys. Rev. D 36 (1987) 2761] Recent developments in ChPTand phenomenological analyses suggest the need to use two mixing parameters 8 and0 in the octet-singlet basis. [H. Leutwyler, Nucl. Phys. Proc. Suppl. 64 (1998) 223, R. Kaiser and H. Leutwyler, hep-ph/9806336, P. Ball, J. M. Frere and M. Tytgat, Phys. Lett. B365 (1996) 367] P 8 and0 are related to the mixing angle FP that can be extracted from the ratio of the amplitudes of   ’ and    [T. Feldmann,P. Kroll and B. Stech, Phys.Lett.B449 (1999) 339, T. Feldmann Int. J. Mod. Phys. A15(2000)] Ada Farilla Uppsala, October 2001

f   g ,  g f   g  p+ p- p0 g  p+ p- 3 g BR 3 · 10 - 3 f   g  p+ p-  g  p+ p- 3 g BR  2 · 10 - 5 The main background comes from:f  KS KL , f  p + p- p0 Event selection: 3 g from the IP ( T – R/c  5•st ) 1 charged vertex in cylindrical region around IP ( r  4 cm ; z 8 cm ) Ep+ + Ep_  430 MeV for f -> h g Ep+ + Ep_  550 MeV for f -> h g Kinematic fit From MC simulation Ep+ + Ep_ (MeV) f->p pp0 f -> h g f -> h g Ada Farilla Uppsala, October 2001

f   g ,  g f -> h g f -> h g p0 h h h Invariant mass before and after kinematic fit p0 h h h Ada Farilla Uppsala, October 2001

f   g ,  g -> h g control sample: Monte Carlo-Data comparison Radiative g energy p momentum -> h g control sample: Monte Carlo-Data comparison Charged vertex r p + p- opening angle Ada Farilla Uppsala, October 2001

E1 vs E2 (after kin. fit) (MeV) f   g ,  g The photon energy spectrum of    and   ’ events allows a very clear identification of the photons in the two cases. This can be used to exploit correlations between the energies of two hardest photons in the   ’ events. MC MC ’ MC  MeV   ’ events are inside the ellipse    events are in the two bands at ~363 MeV E1 vs E2 (after kin. fit) (MeV) Ada Farilla Uppsala, October 2001

f   g ,  g In a data sample of 16.6pb-1, after background subtraction we find: N’ = 124  12stat  5syst , N = (502.1  2.2stat )x102 (Final efficiency : e ’ = 23% , e  = 37.6% ) For the ratio of the two BRs we find: R = ( Nh eh / Nh eh )•RBR= (5.3 ± 0.5(stat) ± 0.4(sys))•10-3 Using the PDG2000 value for BR(f ->h g) we get: BR(f ->h g) = (6.8 ± 0.6(stat) ± 0.5(sys))•10-5 hep-ex 0107022, Kloe collaboration Contributed paper to Lepton Photon 2001 Ada Farilla Uppsala, October 2001

f   g Invariant mass of p+ p- g g Recent measuremets of f   g Ada Farilla Uppsala, October 2001

f   g From the ratio R we have extracted the mixing angle FP both in the approach suggested by Bramon et al. (Eur. Phys. J. C7 (99)) [ using ms/m= 1.45 ] and in the approach suggested by Feldmann (Int. J. Mod. Phys. A15 (2000)) [using fs=1.34 fp, fq=1.07 fp]. We find the same result with the two methods: FP=(40.0 )o hep-ex 0107022, Kloe collaboration Contributed paper to Lepton Photon 2001 +1.7 - 1.5 Ada Farilla Uppsala, October 2001

 h p0 p0  h p p  p0 p p f  h g f  h g  p0 p0 p0 f   g  p+ p- 7 g We measure BR(f ->h‘g) also in the channels: f  h g  h p0 p0  p0 p p f  h g  h p p  p0 p0 p0 No attempt to distinguish the two channels Main background comes from: f -> KS KL ( + “spurious” e.m. clusters) Ada Farilla Uppsala, October 2001

7 g from the IP ( T – R/c  5•st ) f   g  p+ p- 7 g 7 g from the IP ( T – R/c  5•st ) 1 charged vertex in cylindrical region around IP ( r  4 cm ; z 8 cm ) KSKL rejection: veto on KS  p+ p- Ep+ + Ep_ < 440 MeV cut on -0.9 <cosqp+ p-< 0.84 Ep+ + Ep_ before K-rej. MeV Ep+ + Ep_ afterK-rej. MeV Ada Farilla Uppsala, October 2001

Nh = 150  12(stat.) f   g  p+ p- 7 g Ep+ + Ep_ events after background subtraction 1 s agreement with the value of BR(f   gg ) found in the final state p+ p- 3 g Ep+ + Ep_ MeV Ada Farilla Uppsala, October 2001

f   g  g g g , f  p0 g  g g g Event selection: 3 g from the IP ( T – R/c  5•st ) 21o < cosqg < 159o Etot > 800MeV Kinematic fit with 4-momentum conservation Photon assignment: minimization of c2 (p0 g) c2 (h g) Final efficiency : e = 63% Main background comes from e+e- -> gg(g) Ada Farilla Uppsala, October 2001

gg invariant mass (MeV) Signal selection gg invariant mass distribution p0g gg invariant mass (MeV) cosqgg and DEgg define the two signal bands vs QED background cosqgg hg DEgg MeV Ada Farilla Uppsala, October 2001

mass distribution after background subtraction f   g  g g g , f  p0 g  g g g gg invariant mass distribution after background subtraction p0 h G(f  h g  g g g) G(f  p0g  g g g) = (3.75 ± 0.02 ± 0.09) KLOE 2000 * (16.6 pb-1) Preliminary KLOE* : BR(f  p0g) = (1.377 ± 0.007± 0.05) • 10-3 PDG’00 : BR(f  p0g) = (1.26 ± 0.10) • 10-3 * Kloe internal note 234 Ada Farilla Uppsala, October 2001

Work in progress 1) BR(h  p0p0p0 )/BR(h  gg) 2) BR(h  p0p0p0 )/BR(h  p+p-p0) 3) Fit the Dalitz plot of h  p+p-p0 4) Limit on BR(h  g g g) (C-violating decay) 5) BR(h  p0 g g) 6) Study of h  p+p-g 7) Study of h’  p+p-g Ada Farilla Uppsala, October 2001

DAFNE is increasing the Luminosity delivered Conclusions The KLOE detector performs as expected DAFNE is increasing the Luminosity delivered With only ~12% of the collected statistics we have already the most precise measurement of BR(f ->h g) and of the pseudoscalar mixing angle fP Many other interesting h decays are under study Ada Farilla Uppsala, October 2001