KLOE C. Di Donato: Fisica di KLOE (40’) T.Capussela: Dinamica del decadimento h p+p-p0 (15’) G. Saracino: R&D GEM / TPG (25’)

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

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

Published results: 2000 data Measurement of branching fraction for the decay KS -> pen (Phys. Lett. B 535 (2002) 37) BR(KS -> pen ) = (6.91±0.37)x10-4 Study of the decay f -> p0 p0 g with the KLOE detector (Phys. Lett. B537 (2002) 21) BR(f -> f0 g ) = (4.47±0.21)x10-4 and f0 shape Study of the decay f -> h p0 g with the KLOE detector (Phys. Lett. B536 (2002) 209) BR(f -> a0 g ) = (7.4 ±0.7) x 10-5 and a0 shape

Published results: 2000 data Measurement of G(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 of G(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

KS -> pen Npen BR(KS -> pen) epen = Npp BR(KS -> p+p-) epp KL 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 p e boost KS KL ‘Kcrash’ cluster n Npen Npp = BR(KS -> pen) BR(KS -> p+p-) epen epp x Events tagged by a ‘Kcrash’ cluster 2 tracks and 1 vertex close to the IP Reject events with invariant mass Mpp close to the K0 mass Use time information from calorimeter clusters to perform PID for charged tracks

p/e identification AS,L = e-p+ dt(me1)-dt(mp2) dt(me2)-dt(mp1) 6 ns 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 AS,L = G+S,L - G-S,L G+S,L + G-S,L e-p+ dt(me1)-dt(mp2) dt(me2)-dt(mp1) 6 ns e+p-

Charge identified yields N(p-e+n) = 1450±70 N(p+e-n) = 1520± 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 and f momentum Pmiss= |PS-p1-p2| Charge independent fit compatible with the sum: N(pen)=2950±120

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% Common preselection, essentially: KLtag Neutral vertex Fiducial volume gg preselection, essentially: Eg> 100 MeV Photons angular separation in the plane transverse to KL momentum > 150o

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

KL->3p0 selection 2001+2002 data ‘01 data 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 with Ng3 2001+2002 data (143 + 169) pb-1 KLOE: tL = 51.6 ± 0.8 ns PDG: tL = 51.7 ± 0.4 ns ‘01 data KLOE preliminary: R = (2.80 ± 0.03stat ± 0.03 syst)10-3 NA48 (2002): R = (2.81 ± 0.01stat ± 0.02 syst)10-3 Data quality and stability with different data taking conditions is very good

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

Charged kaons Improved energy loss treatment in track fit 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

sf measurement with K± Good statistical power few % accuracy with 1 pb-1 Exploits the K0 TAG K counting  insensitive to Kaon BR’s and reconstruction efficiencies  + K K+ 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)] K+ + 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 ) !!

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

Preliminary results 2002 (7.0 pb-1): (1713±32stat±34lumi) nb (e=10.2%) 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 allow the extraction of all f parameters.

f->p+p-p0 dynamics Fit function The two main terms are : Y=(E0– M0) X=(E+ - E- )/3 Fit function The two main terms are :

f->p+p-p0 dynamics ad = 0.093  0.011  0.015 The (not quite) preliminary results, on 20 pb-1 (2000 data) are: ad = 0.093  0.011  0.015 fd = 2.45  0.09  0.11 rad M(r0) = 775.86  0.57  0.67 MeV DM0+ = -0.54  0.34  0.68 MeV DM+- = 0.45  0.39  0.67 MeV Gr = 145.2  1.2  1.0 MeV c2/dof = 1947(1874-8)

f-> hp0g update 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)

f-> p0p0g update Same selection as of 2000 5g final state Events Event number scales with luminosity 5g final state M (MeV) Events 2001 data 2000 data

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)

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

h-h, ratio The selected number of hg events 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

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

h->ggg KLOE preliminary 142 pb-1 BR(hggg) < 3.5  10-5 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

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

Radiative Return We measure the cross-section s(e+ e-  hadrons ) as function of the hadronic c.m.s energy M 2hadrons by using the radiative return ds(e+ e-  hadrons + g ) dMhadrons 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 errors from Luminosity, s, … enter only once of FSR

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

Small angle analysis Performed on 73 pb-1 of 2001 data set Mpp2(GeV) Ni/0.01GeV2 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

Preliminary results MC DATA DATA is compared with the MC generator PHOKHARA (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

Pion form factor (prelim.): Data points have been fitted with the Gounaris-Sakurai-Parametrization |Fp|2 =CMD2 =KLOE M2p+ p- (GeV2) KLOE PRELIMINARY (G.J. Gounaris and J.J. Sakurai, Phys.Rev. Lett. 21 (1968), 244) mr, Gr ,  ,  are free parameters of the fit, while mw 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)

pp(g): conclusions & outlook 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: 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

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…!

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

Charge asymmetry AS = N+/e+ - N-/e- 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… N+/e+ - N-/e- AS = N+/e+ + N-/e- 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 the KL->pen control sample and 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.

KS pen : motivations AL -AS =4Rd =0 In the S.M., in a completely independent way from hadronic matrix elements and related uncertainties one has: (DS=DQ) (CPT) AS,L = G+S,L - G-S,L G+S,L + G-S,L AL -AS =4Rd =0 with 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