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Status and Physics opportunities at the F factory

Status and Physics opportunities at the F factory. C.Bloise. Laboratori Nazionali di Frascati dell’INFN. Overview KLOE at DA F NE Data Taking in Y2K and Y2001 F Radiative Decays F p + p - p 0 s (e + e - p + p - ) Ks semileptonic decays Direct CP violation Conclusions.

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Status and Physics opportunities at the F factory

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  1. Status and Physics opportunities at the F factory C.Bloise Laboratori Nazionali di Frascati dell’INFN • Overview • KLOE at DAFNE • Data Taking in Y2K and Y2001 • F Radiative Decays • Fp+p-p0 • s(e+e- p+p-) • Ks semileptonic decays • Direct CP violation • Conclusions Snowmass 2001 - 6 July

  2. Overview • DAFNE • Symmetric e+e- machine Ebeam=510 MeV • Desired Working Luminosity 5 1032 cm-2 s-1 • Working Luminosity now 2.5 1031 cm-2 s-1 • DEAR ( DAFNE Exotic Atoms Research) • Measurement of the Ka line shift in kaonic hydrogen and kaonic deuterium • FINUDA (Fisica Nucleare a Dafne) • L-hypernuclei spectroscopy and lifetime ; DI=1/2 rule • Search for S-hypernuclei • KLOE (KLOng Experiment) • F radiative decays (f0g, a0g, hg, h’g ) • Measurement of interest for ChPT (K Semileptonic Decays and Kl4, h/h’ mixing , K 3p… ) • Measurement of s(pp) at low energy : of interest to improve the knowledge of g-2 • Measurement to test CP and CPT violation with K ( Double Ratio, Interferometry)

  3. DAFNE Two independent machines intersection at  25 mrad Bunch length 3 cm Horizontal size 2 mm Vertical size 0.02 mm Working condition now : 800 mA stored into 50 e+/e- bunches Delivered Luminosity : 1.3 pb-1 per day (sustained)

  4. The KLOE Detector d=4m

  5. Time resolution (neutrals channel only) 54 ps  50 ps s(t) = E ( GeV ) EMC: time and energy performances Energy residuals e+e- e+e-g Eg from DC Energy resolution e+e-g

  6. Emc resolution on full neutral channels Mp0 = 135.0 MeV sM = 13.0 MeV Mh = 546.4 MeV sM = 40.3 MeV F  p0(h)g  ggg h  gg p0 gg PDG ‘00 KLOE 10.7 pb-1

  7. DC resolution and stability Stability vs Pressure Residuals • calibration performed when residuals > 40mm • each color represents a calibration point Resolution 1 month

  8. DC momentum resolution I sp (MeV/c) F K+K- e+e-e+e- sp/p < 0.3% 45° < q < 135° After correcting forK dE/dx : Mf = 1019.0 MeV s = 1.2 MeV Polar angle

  9. DC momentum resolution II KSp+p- Pc.o.m. = 110 MeV/c sp= 1.8 MeV/c Mpp = 497.7 MeV/c2 sM= 1 MeV/c2

  10. The Trigger System Requirements: • High ( > 99 % ) efficiency on all CP violating decays Trigger must reject/downscale: • Bhabhas ( q > 20) • cosmic rays • machine background Technical solution: • Two level system: • Fast ( ~ 200 ns ) L1 to start calorimeter’s FEE • Slower ( ~ 2 ms ) L2 to collect more event information and confirm L1 decision • L1 synchronised with machine RF/4 and distributed with 50 ps precision • Two independent chains: • EmC trigger: based on multiplicity of fired calorimeter’s sectors • DC trigger: based on multiplicity of hit drift chamber wires

  11. The KLOE physics program Luminosity arrow (pb-1) • CPT limits KSp+e-n / p-e+n vs KLp+e- n / p-e+n • CP violation studies (double ratio+interf.) • rare and not so rare KS decays (gg, p ee, pmm, ppp ) • kaon form factors (KLpln , Kp0 ln ) • K± decays (in particular p0e±n, ppp) • sHADfor (g-2)m • semileptonic KS decays (KSpln) • regeneration measurements at low momenta • f p+ p-p0 • radiative f decays (f hg , h’g , ƒ0g , a0g , …) 2000 1000 100 20

  12. Y2K Data • Data taking: 23 Sep—11 Dec • 5.61G triggers, 13.6 TB raw data • Ldt = 23.1 pb-1 • Total events collected: • 130M Bhabhas • 10.9M KL tags • 7.2M KL crash • 19.5M K+K-w/ vertex 415 nb-1 / day

  13. Data Taking - Y2001 e+/e- Machines much more symmetric Lower Wiggler Field Beam Decoupling @DEAR Easier Multibunch Operation Feedback system improved Max Luminosity Limited by Background Level @KLOE Single-bunch Luminosity - 1030 cm-2 s-1 reached @ 20 mA Peak Luminosity ~1.9 1031 cm-2 s-1 Average/Peak Luminosity ~ 0.55

  14. Data Taking -Y2001 • Data taking: 16 — 29 Apr • 2.16 G triggers, 5.3 TB raw data • Ldt = 11.3 pb-1 ~900 nb-1/day • Resumed in June • 1.3 pb-1 integrated per day

  15. Data Taking - Y2001 • Machine Development • Insertion of Octupoles to correct Non-linear Distortions in the Wigglers (September) • Background Reduction • Increase in the Luminosity • Upgrade of the control system of the Quads in the IRs in 2002 • Kloe Data Taking : • 15 weeks till the end of the year • Exp. Integrated Luminosity : ~200 pb-1 , assuming • No improvement in the Luminosity, • Stable running scenario

  16. Data Yield - 200 pb-1 • Ks 2 108 • Tagged Ks (Kl visible Interactions) 0.6 108 • Ks p+p-0.3 108 x BR ~ 2 107 • Ks p0p00.3 108 x BR ~ 1 107 • Ks p e n 0.9 107 x BR ~ 6700 • Ks gg3.3 107 x BR ~ 70 • Ks p0 e +e - Single Event Sensitivity 0.8-1.5 10-7 • Ks p0 p0p0 Single Event Sensitivity 3 10-8 • Kl 2 108 • Tagged Kl (Ks p+p- ) 0.9 108 • Kl Decay in FV (D.C.) 2.5 107 • . . . • Klp+p- ~ 2.7 104 • Kl p0p0 ~ 1.0 104 • Kl gg ~ 0.5 104 • K+/- 3 108 • Tagged K+ (K- ) 0.7 108 • Reconstructed K+ (K-) 5 10 7

  17. f h’g Branching Ratio and h’-h mixing angle Preliminary f  h’ g p+p-7g favourable S/B 223 events selected in ‘00 22 ± 7 background sidebands 196 ± 20 expected signal Mh’ = 958.0  0.6 MeV/c2 BR(f h’g) = (6.9 ± 0.6 ± 0.5)  10-5 (PDG2000: BR = (6.7 ± 1.5)  10-5 ) QP = (-14 ± 1.6)o

  18. Fit Procedure: First fit: (E,p) and TOF constraints applied Pairing: best g ’s pairing with 2po+Mp opo > 700 MeV Second fit: constraints on po masses also required f  f0g  popog decay Preliminary result: Excess of 1960  56events BR( f f0 g  p0 p0 g) = ( 0.79 ± 0.02 ± 0.08 ) · 10 -4

  19. f  p + p - p 0 ~0.3M events 3 contributions to Dalitz plot Preliminary f  r ,0p 0,  f  p+p-p0(direct) e+e-  wp0 E0 – mp0 GeV in the fit the mass and width of the r, the DM(r,r0) and the direct decay contribution are left free (E+-E-)/3 GeV A1 (x10-2) f1 (deg) M(r+,-) M(r0) GDM(+,-) KLOE 8.5  0.5 88  9 775.3 0.4 773.0 0.6 149.1  1.0 0.4  0.3 (*) PDG -15 11 (CMD-2) 776.0 0.9 (**) 150.2  0.8 - (*) CPT test at< 5 x 10-4 (**) mixed charges (t decay and e+e-) average: M(r0) - M(r+,-) = 0.4 0.8 Efficiency (X,Y) from Montecarlo: fine tuning in progress to reduce systematic effects on M(r0) (now at 2 MeV level)

  20. Measurement ofs(e+e-p+ p-) @ s 1 GeV • Hadronic cross section below the f threshold has been measured by CMD-2 at Novosibirsk Collider by the energy scan • At KLOE we are investigating the radiative return method (a photon radiated in the initial state ) to measure shad p p

  21. shad and am • the interest in the measurement of shad has increased recently with the new results of the BNL g-2 experiment • am is correlated to the hadronic cross section via the dispersion integral: • In the case of a radiative photon the cross section is related to shad via the radiator function H:

  22. KLOE contribution to the measurement The KLOE detector @DAFNE can study: • the r resonance, which contributes to ~65% of the dispersion integral • this measurement has been recently performed by the CMD-2 detector at Novosibirsk with a precision of ~1% • the hadronic cross section above threshold • this has become recently interesting after the fit of Jegerlehner et al. of the NA7 epepg data • the fit can be analitically extrapolated in the timelike region and used to test t data

  23. The fiducial volume Two fiducial volumes are currently studied: • small angle: qS<21oqS>169o • highest cross section; small bckd from ppp; no photon tagging available r resonance • large angle: 60o<qS<120o • large bckd from ppp, especially at low Q2; possibility of using the calorimeter to discriminate  mpp at threshold • the pions must be central (55o - 125o) to cut down the background

  24. The Event Generator : EVA • EVA generates the process eeppg(g) , with a hard photon (Eg>10MeV) emitted by ISR or by FSR (and a soft photon) • At present accurate simulation is limited to polar angles of the pp system: 5o<qS<21o 159o<qS<175o • This causes a reduction by a factor of ~6 in statistics • Kuehn et al. have published (hep-ph/0106132 , 13 Jun 2001) the NLO corrections to the process; the new version of EVA will be soon available

  25. The method - the acceptance eacc is evaluated from MC - the global selection efficiency esel is evaluated from DATA+MC - the trigger efficiencyetrig is evaluated from DATA • theBackgrounds come from: e+ e - e+ e -g(radiative Bhabha) e+ e -m+ m -g e+ e -fp+ p -p0 (BR = 15.5 %) e+ e -p+ p-g(Final State Radiation) • the Luminosity is measured using the Bhabha scattering at large angles

  26. Background suppression • Bhabha events are rejected with a likelihood function based on the TOF and on the shape of the energy deposit in the EMC • the likelihood function is built from data using ppp and eeg events • mmg and ppg(FSR) events are suppressed by the acceptance cuts and, anyhow, they populate the high Mpp region = efficiency on pions = (1-eff) for electrons Efficiency of likelihood function

  27. Before Likelihood ( Rad. Bhabhas ) After Likelihood Cutting on Mtrk • After the likelihood cut the signal peak is clearly visible in the Mtrk variable • The final background suppression is obtained by cutting 10MeV around the pion mass • For an inclusive analysis this cut must be released on the high Mtrk side mmg p+p-p0 Mtrkis defined by the following relation

  28. The error on the small angle points will decrease by ~3 once we can lower the angular cut The pion form factor |Fp(s)|2 small angle large angle Ldt = 16.5 pb-1 CMD-2 result : hep-ex/9904027 26 Apr 1999 G-S parametrization with fixed parameters (no fit) s = Mpp(MeV)

  29. Ks tagging Clean Ks selection by time of flight of KL interacting in calorimeter KS “KL” b* distribution Ecl  100 MeV |cos(qcl)|  0.7 b* = [0.195,0.245] eTAG ~ 30 %

  30. KLinteracting in EMC (KLCRASH) p- n e+ Analysis of KSpen (1) • Events selection summary • Kcrash tag • Kinematics preselection • Track to cluster association to apply time of flight p-e identification • Close kinematically the event to get pn Normalization to KS p+p-

  31. Analysis of KSpen (2) • 2 methods to estimate TCA, T0 and calorimeter trigger efficiencies: • Single particle efficiencies taken from data using KS p+p-subsamples and KL pen ,fp+p- p0control samples. Efficiencies for p+ ,p- ,m+,m-,e used to weight the Monte Carlo: • e1 = (82.1 ± 0.5) % • Efficiencies directly from data using KS p+p- , KL pencontrol samplee2 =(81.4 ± 0.6) % Emiss(ep)-Pmiss (MeV) eT =(81.7 ± 0.5) % Emiss(p e)-Pmiss (MeV)

  32. KS penandKS p+ p- MC FIT Data: 2000 11.5 pb-1 eTOT = (21.8 ±0.3)% N(KSpen)=283 ±19 events KSpen signal • The fit is performed in the variable Emiss-Pmiss • A fit is performed on data using MC spectra for background and signal • CMD2 : • BR(KSpen) = [7.2 ± 1.2]  10-4 • KLOE preliminary result: • BR(KS pen) = [7.47 ± 0.51(stat)]  10-4 • (systematics under evaluation) • In a 5MeV window: • signal 248  17 • background 9.0  1.4 Emiss-Pmiss

  33. Conclusions KLOE will integrate 200 pb-1 by the end of the year “Rare” Ks Decays SES 10-8-10 -7 Semileptonic and non-leptonic Kaon Decays Scalar and Pseudo-Scalar Mesons below 1 GeV shad near threshold / 1 GeV Machine Development continues Octupole installation Interaction Regions will be Upgraded in 2002 A Peak-Luminosity of 1032 cm-2 s-1 is needed to address CP/ CPT studies (Double Ratio – Interferometry )

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