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

2. 2 KLOE integrated luminosity 1999 run: 2.5 pb -1 machine and detector studies 2000 run: 25 pb -1 7.5 x 10 7  published results 2001 run: 190 pb -1 5.7 x 10 8  2002 run: 300 pb -1 9 x 10 8   analysis in progress

3. 3 Published results: 2000 data Measurement of branching fraction for the decay K S ->  e (Phys. Lett. B 535 (2002) 37) BR( K S ->  e  ) = (6.91±0.37)x10 -4 Study of the decay  ->  0  0  with the KLOE detector (Phys. Lett. B537 (2002) 21) BR(  -> f 0  ) = (4.47±0.21)x10 -4 and f 0 shape Study of the decay  ->   0  with the KLOE detector (Phys. Lett. B536 (2002) 209) BR(  -> a 0  ) = (7.4 ±0.7) x 10 -5 and a 0 shape

4. 4 Published results: 2000 data Measurement of  ( K S ->  +  - (  )) /  ( K S ->  0  0 ) (Phys. Lett. B 538 (2002) 21-26)  ( K S ->  +  - (  )) /  ( K S ->  0  0 )=(2.236  0.003  0.015) Measurement of  (  ->  '  ) /  (  ->  ) and the pseudoscalar mixing angle ( Phys. Lett. B 541 (2002) 45-51 ) BR(  ->  '  ) = (6.10±0.61±0.43)x10 -5

5. 5 K S ->  e 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 N  e N  = BR(K S ->  e ) BR(K S ->     )   e   x  e boost KSKS KLKL ‘K crash ’ cluster Events tagged by a ‘K crash ’ cluster 2 tracks and 1 vertex close to the IP Reject events with invariant mass M  close to the K 0 mass Use time information from calorimeter clusters to perform PID for charged tracks

6. 6  /e identification Time of flight e/  identification (  t = 2 ns) :  t(m) = t cluster – t.o.f. calculated with mass hypothesis m Sign of the charge is determined -> semileptonic asymmetry accessible  t(m e2 )-  t(m  1 )  t(m e1 )-  t(m  2 ) ee ee A S,L =   S,L   S,L   S,L   S,L 6 ns

7. 7 N(   e     ±  N(   e    ±  Charge independent fit compatible with the sum: N(  e  ±  E miss  E S  E e  E  P miss  P S  p 1  p   E S,P S from K L direction and  momentum Charge identified yields 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 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

8. 8  Long distance contribution to the rare K L      decay  Relative uncertainty on BR(K L         )  1.3% Motivations: Common preselection, essentially: K L tag Neutral vertex Fiducial volume  preselection, essentially: E  > 100 MeV Photons angular separation in the plane transverse to K L momentum > 150 o BR(K L ->  )/BR(K L ->3   )

9. 9 M  after preselection Two discriminating variables exploiting the fixed kinematics in K L center of mass system : E*   K L ->  selection M  after E* cut M  after  cut

10. 10 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 N   Data quality and stability with different data taking conditions is very good KLOE:  L = 51.6 ± 0.8 ns PDG:  L = 51.7 ± 0.4 ns KLOE:  L = 51.6 ± 0.8 ns PDG:  L = 51.7 ± 0.4 ns ‘01 data K L ->   selection KLOE preliminary: R = (2.80 ± 0.03 stat ± 0.03 syst )10 -3 NA48 (2002): R = (2.81 ± 0.01 stat ± 0.02 syst )10 -3 KLOE preliminary: R = (2.80 ± 0.03 stat ± 0.03 syst )10 -3 NA48 (2002): R = (2.81 ± 0.01 stat ± 0.02 syst )10 -3 2001+2002 data (143 + 169) pb-1

11. 11 Neutral kaons produced in a pure quantum state (J PC = 1 - - ) : Time evolution for          No simultaneous events: same final state + antisymmetric initial state L ~ 280 pb -1 Peak position sensitive to  m value K L regeneration on the pipe  t|/  s A first glance at interference

12. 12 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 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 Charged kaons

13. 13  Good statistical power  few % accuracy with 1 pb -1  Exploits the K  0 TAG  K  counting  insensitive to Kaon BR’s and reconstruction efficiencies  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 K+K+ K+K+ ++ N 2 = number of ev with 2 triggering  0 tags N 1 = number of ev with 1 triggering  0 tag The number of K + K - events N kk is function of N 1, N 2 and geometrical acceptances (  or,  and ), but not of the Tag efficiency (  id ) !! N 2 = N kk  and (  id BR K  ) 2 N 1 = 2 N kk BR K   id [  or (1- BR K  ) + BR K   and (1-  id )]   measurement with K ±

14. 14 Before tagging  peak  peak AND tagged Or Tagged Shapes for the pion (muon) peak are obtained from data in K ± ->  ± tagged events. To count N 1 and N 2 look at the pion Momentum in the kaon rest frame p* Kl3 background MC   measurement with K ± (2)

15. 15 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±32 stat ±34 lumi ) nb (  Together with the other channels will allow the extraction of all  parameters. W dependence for the 2002 scan (± 2 MeV) Preliminary results

16. 16 Fit function The two main terms are : Y=(E  0 – M  0 ) X=(E  + - E  - )/  3  ->      0 dynamics

17. 17 a d = 0.093  0.011  0.015  d = 2.45  0.09  0.11 rad M(  0 ) = 775.86  0.57  0.67 MeV  M   -0.54  0.34  0.68 MeV  M  = 0.45  0.39  0.67 MeV   = 145.2  1.2  1.0 MeV a d = 0.093  0.011  0.015  d = 2.45  0.09  0.11 rad M(  0 ) = 775.86  0.57  0.67 MeV  M   -0.54  0.34  0.68 MeV  M  = 0.45  0.39  0.67 MeV   = 145.2  1.2  1.0 MeV The (not quite) preliminary results, on 20 pb -1 (2000 data) are:   /dof = 1947(1874-8)  ->      0 dynamics

18. 18 M  (MeV) Events 2001 data (140 pb -1 ) 2000 data Same selection as of 2000 Event number scales with luminosity 5  final state M  (MeV) Events     5  final state  ->    update

19. 19 Same selection as of 2000 Event number scales with luminosity M  (MeV) Events 2001 data 2000 data 5  final state  ->      update

20. 20 With the (almost) complete statistics of 2001-2002 we finally found evidence for the f 0 ->     decay The amount of events in the f 0 peak is already indicative of a destructive interference with FSR With the (almost) complete statistics of 2001-2002 we finally found evidence for the f 0 ->     decay The amount of events in the f 0 peak is already indicative of a destructive interference with FSR Preliminary M  (MeV) 2001+2002 data 980 f 0 ->    

21. 21  bands  region Sidebands for bkg shape evaluation 700 evts in the peak 100 pb -1 (2001)  ->    ->      update

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

23. 23 E  + +E  -  2/Ndgf  ->    ->      2000: 16 pb-1 2001: 118pb-1 2002: 223pb-1

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

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

26. 26 We measure the cross-section  ( e + e -  hadrons ) as function of the hadronic c.m.s energy M 2 hadrons by 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 errors from Luminosity,  s, … enter only once of FSR d  ( e + e -  hadrons +   ) d  hadrons Radiative Return

27. 27 55 0 <  < 125 0  < 15 0  > 165 0     Two fiducial volumes are currently studied: Pion tracks are measured at angles 40 o <   <140 o large angle: 55 o <   <125 o –Allows a tagging of the radiative photon small angle:   165 o –Photon cannot be detected efficiently with EmC, untagged measurement in which we cut on the missing momentum   The two kinematical regions differ for:  cross section (SA: 24 nb; LA: 3 nb) M 2  spectrum shape background contamination relative contribution of FSR Signal selection

28. 28 M  2 (GeV) N i /0.01GeV 2 Performed on 73 pb -1 of 2001 data set after selection: about 10 6 events statistical error/bin < 1% for M  2 >0.45 GeV 2 after selection: about 10 6 events statistical error/bin < 1% for M  2 >0.45 GeV 2 Background Signal Selection efficiency Luminosity 30000 20000 10000 Small angle analysis

29. 29 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: M 2  (GeV 2 ) d  /dM 2  (nb/GeV 2 ) MC DATA               Preliminary results

30. 30 Pion form factor (prelim.) Data points have been fitted with the Gounaris-Sakurai-Parametrization m ,   ,   are free parameters of the fit, while m    m    are fixed to CMD-2 values M  =775.14 MeV   = 147.05 MeV  =(-0.08) 10 -3  = 2.89310 -3    124.8 0 (Stat. Errors only) (G.J. Gounaris and J.J. Sakurai, Phys.Rev. Lett. 21 (1968), 244) |F  | 2 =CMD2 =KLOE M 2  +  - ( GeV 2 ) KLOE PRELIMINARY Pion form factor (prelim.):

31. 31 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 a . 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 d  (e + e - ->      )/dM 2  for SA cuts based on full 2001 statistics with a precision of 2 % a derivation of  (e + e - ->     ) obtained by dividing d  (e + e - ->      )/dM 2  for the radiation function a fit of the pion form factor  conclusions & outlook

32. 32 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…! Conclusions

33. 33

34. 34 Trackmass M 2             This background contamination is more significant at small M 2  values and affects mainly the LA region The signal is further selected by performing a cut in the so called trackmass variable in order to reduce       background           background (M track  104 MeV) rejected by a cut on M track =120 MeV Remaining contamination estimated from MC:below 1% for SA region Background

35. 35 N     N    A S = N     N    To get the asymmetry, one has to correct the e    and e    event yields using the charge dependent efficiencies… Efficiencies are determined on data using several control samples and currently read:   e   = (21.7 ± 0.5)%   e   = (21.0 ± 0.5)% Quoted errors depend mainly on the statistics of the K L ->  e  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. Charge asymmetry

36. 36 In the S.M., in a completely independent way from hadronic matrix elements and related uncertainties one has: with Currently: R x = (-1.8 ± 6.1)·10 -3 from CPLEAR (1998) With 2 fb -1 KLOE can improve the accuracy by a factor ten A L  A S  R   (CPT) A S,L =   S,L   S,L   S,L   S,L A S not yet measured. Need 20 fb -1 to measure with 30% accuracy  S  Q) K S   e : motivations

37. 37 Re x + can be extracted by measuring the ratio of semileptonic K S and K L decay widths summing up both charge final states BR (K S  p e n) t L BR (K L  p e n) t S 8  10 -3 1  10 -3 7  10 -3 CPLEAR measurement (-1.8  6.1)  10 -3 KLOE statistical error on Re x + KLOE 2000: Phys. Lett. B535 (2002) (assuming d=0) Re x +  Re c * /a   e + p - n  H WK  K 0  Test of the D S= D Q rule. The relevant parameter is: Accuracy on Re x

38. 38 e+p-e-p+e+p-e-p+ e+p-e-p+e+p-e-p+ Data 89.6 pb -1 (2001) Signal distribution is approximately independent from the charge sign The charge dependence of the K S  p + p - background spectrum is relevant far away from the signal peak E miss - P miss (MeV) Background for K S  p e n

39. 39 Average e+p-e+p- e-p+e-p+ e( fiducial cuts )(31.00  0.07) % (30.9  0.1)% (31.0  0.1)% e( t.c.a. ) (92.4  0.1)% (92.3  0.2  0.1 )% (92.5  0.2  0.1 )% e( t 0 ) (99.74  0.03)% (99.74  0.04)% e( trigger ) (93.7  0.1)% (93.8  0.2)% (93.6  0.2)% e( t.o.f. ) (79.9  0.2)% (78.7  0.3)% (81.1  0.3)% e( t.c.a.  t 0  trig  t.o.f. ) (69.0  0.2)% (68.0  0.3)% (70.0  0.3)% e( overall )(21.4  0.4)% (21.0  0.5)% (21.7  0.5)% Quoted errors depend mainly on the statistics of the K L  p e n control sample and determine the overall systematic uncertainty (2%) Efficiencies

40. 40 K S  p + p - and K S  p 0 p 0 decays Both the isospin (I=0 and 2) amplitudes and the pp phase- shifts can be estimated from the measured K  pp branching ratios: A (K 0  p + p - ) = A 0 e i d 0 +  2A 2 e i d 2 A (K 0  p 0 p 0 ) = A 0 e i d 0 - A 2 e i d 2 /  2 A (K +  p + p 0 ) = 3/2 A 2 e i d 2 t + p +0 BR +- M K0 2 t S p +- BR +0 M K+ 2 1 + 1/ w 2 = (1+p +- / p 00 R) R p 00 /p +- = 1 + w 2 /2 + w  2 cos( d 0 -d 2 ) 1 + 2 w 2 - w 2  2 cos( d 0 -d 2 )

41. 41 K S  p + p - and K S  p 0 p 0 decays Measurement of both the absolute branching ratios With the KLOE published measurement of R = G(K S  p + p - )/G(K S  p 0 p 0 )=2.239 based on 17 pb -1 (R = 2.1857 PDG): d 0 -d 2  (48  3)  (while w is unchanged) Using the PDG values for the branching ratios, one gets: d 0 -d 2  (56.7  3.8)  (and w=0.045 ) This value is inconsistent with the prediction from O(p 2 ) c pT (45  6) , the measurement from pp scattering (45.2  1.3  1.5) , and the estimate from the K L decays In pipeline, planned for mid 2003: Measurement of R with an error of 10 -3

42. 42 Current best measurements: Gormley et al. (1970) : 30 kevts Layter et al. (1973): 80 kevts Crystal Barrel (1998): 3 kevts Current best measurements: Gormley et al. (1970) : 30 kevts Layter et al. (1973): 80 kevts Crystal Barrel (1998): 3 kevts Precise measurements of h  3p Dalitz plot slopes is a basic ingredient to extract quark mass ratios from the observed decay rate and offer a test ground for CHPT. At KLOE O(10 6 ) events collected with low background  precision measurement At KLOE O(10 6 ) events collected with low background  precision measurement Dynamics of h  p + p - p 0

43. 43 pp(g): likelihood estimator A particle ID estimation method based on a likelihood function has been worked out which allows an efficient separation of pions and electrons Method uses information from the EmC: - Time of Flight of Tracks - Signature of the energy deposit of Tracks Method uses information from the EmC: - Time of Flight of Tracks - Signature of the energy deposit of Tracks The main source of background are Radiative Bhabha events which enter our  selection.  +  -  0 and radiative bhabhas from data are used as control samples. -                    Log (relative Likelihood  -e) Bhabhas Pions

44. 44 pp(g): trackmass M track Effect of the Method becomes visible in the Trackmass distribution:      e e e e  before cutting on likelihood function after cutting on likelihood function Kinem. Variable Trackmass            mm This kinematical variable is the particle mass for the two tracks obtained by using the 4-momentum-conservation and the assumption that both particles have the same mass M trk :

45. 45 pp(g ): efficiency Trigger Reconstr. Filter Event Classification Particle ID method Trackmass blue = estimated from data red = estimated from MC The trigger efficiency for  +  - g  is  Trigger veto efficiency for single track (  - ) vs momentum Trigger veto efficiency  + vs momentum MeV  Efficiency ranges from 100% at M 2   GeV  to 75% at low M 2   big errors below 0.5GeV 2 due to low MC statistics (50000 events) Efficiency is very high ( > 99%) in the condition that at least 1 track satisfies the cut on the likelihood function Efficiency is  and flat in M 2  However the rejection of cosmics in the trigger rejects pion tracks with high momentum. Efficiency for 1 charged vertex near IP is ca. 90 %

46. 46 pp(g ): efficiency (2)  Total M  2 [GeV 2 ] Big errors at low M  2 due to low MC statistics for Trackmass Errors above 0.5 GeV 2 ca. 2% per bin Combining all the efficiencies:

47. 47 Luminosity Background ( ,...) Bhabha - Candidates (Systemat., Accept.) Track - Energy Track - Polar Angle * Data - BABAYAGA* - Berends(Drago/Venanzoni) Normalization : use KLOE itself for measurement : Large Angle Bhabhas (  eff = 425nb ) Theoret. Generators with rad. corrections 55° <  + - < 125 ° Acoll. < 9 ° E + -  400 MeV  Current estimate for luminosity precision is < 2% final precision is currently evaluated agreement with independent  -Counter < 0.5% (  eff,  ≈ 120 nb)  * C.M.C. Calame et.al. Nucl. Phys., B 584 (2000) BABAYAGA* Berends(Drago/Venanzoni) Current conservative estimate for luminosity precision is < 2% final precision is currently under evaluation agreement with independent  -Counter < 0.5% (  eff,  ≈ 120 nb) 

48. 48 Extraction of pion form factor We divide the      cross section by the cross section      for “pointlike” pions which is obtained from the MC generator Phokhara by setting F  = 1.   F  =(2.538  0.001) nb   =(24.43  0.01) nb MC   F  =1 spectrum   F  =1 was computed with 2*10 6 events of Monte Carlo (PHOKHARA) with F  =1, with the acceptance cuts of the analysis :              

49. 49 Comment on FSR Final State Radiation of pions should be included in the hadr. cross section for every bin in M hadrons However the LO FSR contribution at radiative return is dominated by FSR from pions produced at the collision energy: MfMf In the simultaneous occurrence of ISR and FSR, the FSR smears the “true” M 2  M 2  true M 2  meas.