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Status report on KLOE physics

Status report on KLOE physics. Outline : Published papers Neutral kaons Charged kaons f decays Hadronic cross section Conclusions. Camilla Di Donato. KLOE integrated luminosity. KLOE integrated luminosity. 1999 run: 2.5 pb -1 machine and detector studies 2000 run: 25 pb -1

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Status report on KLOE physics

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  1. Status report on KLOE physics • Outline: • Published papers • Neutral kaons • Charged kaons • f decays • Hadronic cross section • Conclusions Camilla Di Donato

  2. KLOE integrated luminosity KLOE integrated luminosity 1999 run:2.5 pb-1 machine and detector studies 2000 run:25 pb-1 7.5 x 107f published results 2001 run:190 pb-1 5.7 x 108f 2002 run:300 pb-1 9 x 108f analysis in progress

  3. Published results: 2000 data • Measurement of branching fraction for the decayKS->pen • (Phys. Lett. B 535 (2002) 37) • BR(KS->pen) = (6.91±0.37)x10-4 • Study of the decay f -> p0 p0gwith the KLOE detector • (Phys. Lett. B537 (2002) 21) • BR(f -> f0g) = (4.47±0.21)x10-4 and f0 shape • Study of the decayf -> hp0g with the KLOE detector • (Phys. Lett. B536 (2002) 209) • BR(f -> a0g) = (7.4 ±0.7) x 10-5 and a0shape

  4. Published results: 2000 data • Measurement ofG(KS -> p+p-(g))/G(KS->p0 p0) • (Phys. Lett. B 538 (2002) 21-26) • G(KS -> p+p-(g))/G(KS->p0 p0)=(2.236  0.003  0.015) • Measurement ofG(f -> h' g)/G(f ->h g)and the pseudoscalar • mixing angle (Phys. Lett. B 541 (2002) 45-51) • BR(f-> h'g) = (6.10±0.61±0.43)x10-5

  5. ‘Kcrash’ cluster Npen epen BR(KS ->pen) = x KL Npp epp BR(KS->p+p-) e boost p KS n KS->pen The method already used for 2000 data (PLB 535, 37(2002)) has been used to analyze 90 pb-1 out of the 2001 data set • Events tagged by a ‘Kcrash’ cluster • 2 tracks and 1 vertex close to the IP • Reject events with invariant mass Mppclose to the K0mass • Use time information from calorimeter clusters to perform PID for charged • tracks

  6. G+S,L - G-S,L AS,L = G+S,L+ G-S,L p/e identification • Time of flight e/p identification (Dt = 2 ns) : • dt(m) = tcluster – t.o.f.calculated with mass hypothesis m • Sign of the charge is determined • ->semileptonic asymmetry accessible e-p+ dt(me1)-dt(mp2) dt(me2)-dt(mp1) 6 ns e+p-

  7. Charge identified yields N(p+e-n) =1520± 70 N(p-e+n)=1450±70 Emiss=ES-Ee- Ep Preliminary result on the asimmetry has an overall error of 3% and is consistent with 0. We expect 1% error with full 500 pb-1 data set ES,PS from KL direction andfmomentum Pmiss= |PS-p1-p2| Charge independent fit compatible with the sum: N(pen)=2950±120

  8. BR(KL->gg)/BR(KL->3p0) Motivations:  Long distance contribution to the rare KLm+m-decay  Relative uncertainty on BR(KL p0p0p0) 1.3% • Commonpreselection, essentially: • KLtag • Neutral vertex • Fiducial volume • ggpreselection, essentially: • Eg> 100 MeV • Photons angular separation in the plane transverse to KL momentum > 150o

  9. KL->ggselection Mgg after E* cut E* Mggafter preselection Mgg after a cut a Two discriminating variables exploiting the fixed kinematics in KL center of mass system:

  10. KL->3p0selection 2001+2002 data (143 + 169) pb-1 The three pions sample is trivially selected with minimal requirements on photon energies. To limit systematics due to photon splitting/merging inclusive selection is done withNg3 KLOE: tL = 51.6 ± 0.8 ns PDG: tL = 51.7 ± 0.4 ns ‘01 data Data quality and stability with different data taking conditions is very good KLOE preliminary: R =(2.80 ± 0.03stat ± 0.03 syst)10-3 NA48 (2002): R = (2.81 ±0.01stat ±0.02 syst)10-3

  11. A first glance at interference Neutral kaons produced in a pure quantum state (JPC = 1- - ) : Time evolution for p+p-p+p- : L ~ 280 pb-1 No simultaneous events: same final state + antisymmetric initial state |Dt|/ts Peak position sensitive to Dm value KL regeneration on the pipe

  12. Charged kaons Many improvements have been introduced for charged kaons in the reconstruction – classification – analysis chain, in order to cope with the peculiar features of these events at KLOE: • Improved energy loss treatment in track fit • Refined treatment of multiple scattering correlation matrix • Improved merging of split kaon tracks • Realistic drift chamber noise simulation from data • T0 global finding • Kaon time of flight corrections • Single arm tagging method in event classification

  13. sfmeasurement withK± K+ K +  K+ + • Good statistical power few % accuracy with 1 pb-1 • Exploits theK0TAG • K countinginsensitive to Kaon BR’s and reconstruction efficiencies N2 = number of ev with 2 triggering pp0 tags N2 = Nkk eand (id BRK )2 N1 = 2 Nkk BRKid [eor (1- BRK) + BRKeand (1- id)] N1 = number of ev with 1 triggering pp0 tag The number of K+K- events Nkk is function of N1, N2 and geometrical acceptances (eor ,eand ), but not of the Tag efficiency (id) !!

  14. sfmeasurement withK± (2) MC p peak AND tagged m peak Or Tagged Before tagging To count N1 and N2 look at the pion Momentum in the kaon rest frame p* Kl3 background Shapes for the pion (muon) peak are obtained from data in K±->m±ntagged events.

  15. Preliminaryresults Analysis procedure used to extract the cross section e+eK+K- at the peak on a subsample of 2002 data set: 2002 (7.0 pb-1): (1713±32stat±34lumi) nb (e=10.2%) W dependence for the 2002 scan (± 2 MeV) Together with the other channels will allowtheextraction of all f parameters.

  16. f->p+p-p0dynamics Y=(E0– M0) X=(E+- E- )/3 Fit function The two main terms are :

  17. f->p+p-p0dynamics The (not quite) preliminary results, on 20 pb-1 (2000 data) are: ad = 0.093 0.011 0.015 fd= 2.45 0.09 0.11rad M(r0)= 775.86 0.57 0.67MeV DM0+ = -0.54 0.34 0.68MeV DM+-= 0.45 0.39 0.67MeV Gr = 145.2 1.2 1.0 MeV c2/dof = 1947(1874-8)

  18. f-> hp0gupdate • Same selection as of 2000 • Event number scales with • luminosity 5g final state 2001 data (140 pb-1) 2000 data Events p+p-5g final state Events M (MeV) M (MeV)

  19. f-> p0p0gupdate 2001 data 2000 data Events M (MeV) • Same selection as of 2000 • Event number scales with • luminosity 5g final state

  20. f0 ->p+p- 2001+2002 data With the (almost) complete statistics of 2001-2002 we finally found evidence for the f0 ->p+p-decay The amount of events in the f0 peak is already indicative of a destructive interference with FSR Preliminary 980 Mpp (MeV)

  21. f->h(h,)g->p+p-gggupdate Sidebands for bkg shape evaluation 100 pb-1 (2001) hg bands 700 evts in the peak hg region

  22. h-h, ratio The selected number of hgevents scales with luminosity within errors as expected. Events are very clean with background <1% 300 kevents Year 2000 (16.3 pb-1): Nh’g/Nhg = (2.4 ± 0.24 stat ± 0.1 bkg )·10-3 Year 2001 (preliminary) (100 pb-1): Nh’g/Nhg = (2.2 ± 0.09 stat ± 0.05 bkg )·10-3

  23. f->h,g->p+p-7g c2/Ndgf Ep++Ep- • 2000: • 16 pb-1 • 2001: • 118pb-1 • 2002: • 223pb-1

  24. h->ggg KLOE can improve the current PDG limit for this C violating decay Mggg (MeV) Mggg (MeV) 142 pb-1 BR(hggg) < 3.5 10-5 KLOE preliminary

  25. Hadronic cross section and am Davier, Eidelman, Höcker, Zhang: hep-ph/0208177 3.0 s 1.6 s FJ 02 (e+e- based) 2.8 s PRELIMINARY hep-ex/0208001 Disagreement between e+e- based and t based evaluations Experiment and Theory with almost identical errors ( ± 8·10-10 ):

  26. Radiative Return ds(e+ e- hadrons + g) dMhadrons We measure the cross-sections(e+ e- hadrons) as function of the hadronic c.m.s energyM 2hadronsby using the radiative return disadvantage advantage Requires precise calculations of ISR Data comes as by-product of standard program EVA +Phokhara MC Generator Requires good suppression (or knowledge) Systematic errorsfrom Luminosity, s, … enter only once of FSR

  27. Signal selection • small angle: < 15oand > 165o • Photon cannot be detected efficiently with EmC, untagged measurement in which we cut on the missing momentum pp 550< q < 1250 p p q< 150 q > 1650 • large angle: 55o<<125o • Allows a tagging of the radiative photon p p Two fiducial volumes are currently studied: Pion tracks are measured at angles 40o< p<140o • The two kinematical regions differ for: • ppg cross section (SA: 24 nb; LA: 3 nb) • M2pp spectrum shape • background contamination • relative contribution of FSR

  28. Small angle analysis Ni/0.01GeV2 Mpp2(GeV) Performed on 73 pb-1 of 2001 data set after selection: about 106 events statistical error/bin < 1% for M2>0.45 GeV2 30000 20000 10000 Signal Background Luminosity Selection efficiency

  29. Preliminary results DATA is compared with the MC generatorPHOKHARA (NLO) whose output is expected to be accurate at 0.5% level and has been interfaced with the detector simulation program (GEANFI). MC events are generated with the SA fiducial volume cuts: d/dM2(nb/GeV2) MC • DATA M2pp (GeV2) qg<15o (qg>165o), 40o<qp<140o

  30. Pion form factor (prelim.): Pion form factor (prelim.) |Fp|2 =CMD2 KLOE PRELIMINARY M2p+ p-(GeV2) =KLOE Data points have been fitted with the Gounaris-Sakurai-Parametrization (G.J. Gounaris and J.J. Sakurai, Phys.Rev. Lett. 21 (1968), 244) mr, Gr ,  , are free parameters of the fit, whilemw Gw mr Grare fixed to CMD-2 values • Mr =775.14 MeV • Gr = 147.05 MeV •  =(-0.08) •10-3 •  = 2.893•10-3 • 124.80 (Stat. Errors only)

  31. pp(g):conclusions & outlook • a measurement of ds(e+e-->p+ p-g)/dM2pp for SA cuts • based on full 2001 statistics with a precision of 2 % • a derivation of s(e+e-->p+ p-)obtained by dividing • ds(e+e-->p+ p-g)/dM2pp for the radiation function • a fit of the pion form factor • Experimental and Theoretical groups are in close contact to improve the measurement and to allow an interpretation for the evaluation of the hadronic contribution to am. • Work is in progress in order to refine the analysis with all the statistics of 2001 (~170 pb-1 ) • Short term goal: a paper in beginning 2003 with:

  32. Conclusions • The increased performances of DAFNE are giving us the chance to investigate deeper and deeper the unique KLOE physics program. • All previously performed analyses are obtaining significantly improved results, and many new ones are coming to a definitively sound status. Precision measurements are on arrival also for relatively rare processes… …we are ready for the fb-1 era…!

  33. Background Trackmass M2pp The signal is further selected by performing a cut in the so called trackmass variable in order to reducep+ p- p0 background p+ p- p0 This background contamination is more significant at small M2ppvaluesand affects mainly the LA region p+ p- g m+ m- gbackground (Mtrack104 MeV) rejected by a cut on Mtrack=120 MeV m+ m- g Remaining contamination estimated from MC:below 1% for SA region

  34. Charge asymmetry N+/e+-N-/e- AS = N+/e++N-/e- To get the asymmetry, one has to correct the e+p-and e-p+event yields using the charge dependent efficiencies… Efficiencies are determined on data using several control samples and currently read: e(p+e-) = (21.7 ± 0.5)% e(p-e+) = (21.0 ± 0.5)% Quoted errors depend mainly on the statistics of theKL->pen control sampleand determine the overall systematic uncertainty (2%) Preliminary result on the asimmetry has an overall error of 3% and is consistent with 0. We expect 1% error with full 500 pb-1 data set.

  35. KSpen : motivations G+S,L - G-S,L AS,L = G+S,L+ G-S,L In the S.M., in a completely independent way from hadronic matrix elements and related uncertainties one has: (DS=DQ) (CPT) with AL-AS =4Rd=0 Currently: Rx = (-1.8 ± 6.1)·10-3 from CPLEAR (1998) With 2 fb-1 KLOE can improve the accuracy by a factor ten AS not yet measured. Need 20 fb-1 to measure with 30% accuracy

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