1. Status and Physics opportunities at the  factory  Overview  KLOE at DA  NE  Data Taking in Y2K and Y2001   Radiative Decays    +  -  0   (e + e -  +  - )  Ks semileptonic decays  Direct CP violation  Conclusions Snowmass 2001 - 6 July C.Bloise Laboratori Nazionali di Frascati dell’INFN

2. Overview  DA  NE  Symmetric e + e - machine E beam =510 MeV  Desired Working Luminosity 5 10 32 cm -2 s -1  Working Luminosity now 2.5 10 31 cm -2 s -1  DEAR ( DA  NE Exotic Atoms Research)  Measurement of the K  line shift in kaonic hydrogen and kaonic deuterium  FINUDA (Fisica Nucleare a Dafne)   -hypernuclei spectroscopy and lifetime ;  I=1/2 rule  Search for  -hypernuclei  KLOE (KLOng Experiment)   radiative decays (f0 , a0 , ,  ’  )  Measurement of interest for ChPT (K Semileptonic Decays and Kl4,  /  ’ mixing, K 3  … )  Measurement of  ) 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. DA  NE 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. )GeV( ps54 E   (t)  50 ps Time resolution (neutrals channel only) e+e- e+e- EMC: time and energy performances e + e   e + e    from DC Energy residuals Energy resolution

6. Emc resolution on full neutral channels        M  = 135.0 MeV  M = 13.0 MeV M  = 546.4 MeV  M = 40.3 MeV PDG ‘00 KLOE 10.7 pb -1

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

8. DC momentum resolution I After correcting for K  dE/dx : M  = 1019.0 MeV  = 1.2 MeV  K + K -  p /p < 0.3% 45° <  < 135° Polar angle  p (MeV/c) ee eeee eeee eeee ee ee eeee eeee eeee ee

9. DC momentum resolution II M  = 497.7 MeV/c 2  M = 1 MeV/c 2 M  = 497.7 MeV/c 2  M = 1 MeV/c 2 P c.o.m. = 110 MeV/c  p = 1.8 MeV/c P c.o.m. = 110 MeV/c  p = 1.8 MeV/c KS  KS  KS  KS  

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

11. The KLOE physics program  CPT limits K S  + e -  /  - e + vs K L  + e - /  - e +  CP violation studies (double ratio+interf.)  rare and not so rare K S decays (  ee,  )  kaon form factors (K L  l, K   0 l  )  K ± decays (in particular  0 e ±,  )   HAD for (g-2)   semileptonic K S decays (K S  l )  regeneration measurements at low momenta         radiative  decays (  ’ , ƒ 0 , a 0 , …)     Luminosity arrow (pb -1 )

12. Y2K Data Data taking: 23 Sep—11 Dec 5.61G triggers, 13.6 TB raw data L dt = 23.1 pb -1 Total events collected: 130M Bhabhas 10.9M K L tags 7.2M K L 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 - 10 30 cm -2 s -1 reached @ 20 mA Peak Luminosity ~1.9 10 31 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 L dt = 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 10 8 Tagged Ks (Kl visible Interactions) 0.6 10 8 Ks  +  - 0.3 10 8 x BR ~ 2 10 7 Ks  0  0 0.3 10 8 x BR ~ 1 10 7 Ks  e 0.9 10 7 x BR ~ 6700 Ks  3.3 10 7 x BR ~ 70 Ks  0 e + e - Single Event Sensitivity 0.8-1.5 10 -7 Ks  0  0  0 Single Event Sensitivity 3 10 -8 Kl 2 10 8 Tagged Kl (Ks  +  - ) 0.9 10 8 Kl Decay in FV (D.C.) 2.5 10 7... Kl  +  - ~ 2.7 10 4 Kl  0  0 ~ 1.0 10 4 Kl  ~ 0.5 10 4 K +/- 3 10 8 Tagged K + (K - ) 0.7 10 8 Reconstructed K + (K - ) 5 10 7

17.  ’   +  - 7  favourable S/B 223 events selected in ‘00 22 ± 7 background sidebands 196 ± 20 expected signal M  ’ = 958.0  0.6 MeV/c 2 BR(  ’  ) = (6.9 ± 0.6 ± 0.5)  10 -5 (PDG2000: BR = (6.7 ± 1.5)  10 -5 )  P = (-14 ± 1.6) o  ’  Branching Ratio and  ’  mixing angle

18.  f 0      decay Fit Procedure: First fit: (E,p) and TOF constraints applied Pairing: best  ’s pairing with 2  o +M  o  o > 700 MeV Second fit: constraints on  o masses also required Preliminary result: Excess of 1960  56 events BR(  f 0      ) = ( 0.79 ± 0.02 ± 0.08 ) · 10 -4

19. (E +  E  )/  3 GeV            (direct) e + e    3 contributions to Dalitz plot ~0.3M events in the fit the mass and width of the , the  M(     ) and the direct decay contribution are left free       A 1 (x10 -2 )  1 (deg) M(  +,- ) M(  0 )   M(+,-) 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 (  decay and e + e - ) average: M(  0 ) - M(  +,- ) = 0.4  0.8 Efficiency (X,Y) from Montecarlo: fine tuning in progress to reduce systematic effects on M(  0 ) (now at 2 MeV level) E 0 – m  0 GeV

20. Measurement of  (e + e -   +  - ) @  s 1 GeV Hadronic cross section below the  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  had  

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

22. KLOE contribution to the measurement The KLOE detector @DA  NE can study: the  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 e  e  data the fit can be analitically extrapolated in the timelike region and used to test  data

23. The fiducial volume Two fiducial volumes are currently studied: small angle:   169 o highest cross section; small bckd from  ; no photon tagging available   resonance large angle: 60 o <   <120 o large bckd from , especially at low Q 2 ; possibility of using the calorimeter to discriminate  m  at threshold the pions must be central (55 o - 125 o ) to cut down the background

24. The Event Generator : EVA EVA generates the process ee , with a hard photon (E  >10MeV) emitted by ISR or by FSR (and a soft photon) At present accurate simulation is limited to polar angles of the  system: 5 o <   <21 o  159 o <   <175 o 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 Backgrounds come from: - the acceptance  acc is evaluated from MC - the global selection efficiency  sel is evaluated from DATA+MC - the trigger efficiency  trig is evaluated from DATA the Luminosity is measured using the Bhabha scattering at large angles e + e - e + e -  (radiative Bhabha) e + e -      e + e -        0 (BR = 15.5 %) e + e -      (Final State Radiation)

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  and ee  events  and  (FSR) events are suppressed by the acceptance cuts and, anyhow, they populate the high M  region Efficiency of likelihood function = efficiency on pions = (1-eff) for electrons

27. Cutting on M trk After the likelihood cut the signal peak is clearly visible in the M trk 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 M trk side Before Likelihood ( Rad. Bhabhas ) After Likelihood   M trk is defined by the following relation

28. The pion form factor The error on the small angle points will decrease by ~3 once we can lower the angular cut  s = M   (MeV) |F  (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)

29. Ks tagging Clean Ks selection by time of flight of K L interacting in calorimeter    distribution KSKS E cl  100 MeV |cos(  cl )|  0.7  * = [0.195,0.245] E cl  100 MeV |cos(  cl )|  0.7  * = [0.195,0.245] “KL”  TAG ~ 30 %

30. Analysis of K S  e (1)  ee  L interacting in EMC (KLCRASH) Events selection summary Kcrash tag Kinematics preselection Track to cluster association to apply time of flight  e identification Close kinematically the event to get p Normalization to K S    

31. Analysis of K S  e  2 methods to estimate TCA, T 0 and calorimeter trigger efficiencies: 2.Efficiencies directly from data using K S      L   e control sample     1.Single particle efficiencies taken from data using K S     subsamples and K L  e         control samples. Efficiencies for          ,  , e used to weight the Monte Carlo:        E miss (  e)-P miss (MeV) E miss (e  )-P miss (MeV)

32. K S  e signal The fit is performed in the variable E miss -P miss A fit is performed on data using MC spectra for background and signal CMD2 : BR(K S  e ) = [7.2 ± 1.2]  10 -4 KLOE preliminary result: BR(K S  e ) = [7.47 ± 0.51(stat)]  10 -4 (systematics under evaluation) In a 5MeV window: signal248  17 background9.0  1.4 K S  e and K S    - MC FIT Data: 2000 11.5 pb -1      N(K S  e    19 events E miss -P miss

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  had near threshold / 1 GeV Machine Development continues Octupole installation Interaction Regions will be Upgraded in 2002 A Peak-Luminosity of 10 32 cm -2 s -1 is needed to address CP/ CPT studies (Double Ratio – Interferometry )