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NA48/1 Status Report

NA48/1 Status Report. Augusto Ceccucci/CERN. CERN-NA48/1: Cambridge, CERN, Chicago, Dubna, Edinburgh, Northwestern, Ferrara, Florence, Mainz, Orsay, Perugia, Pisa, Saclay, Siegen, Turin, Warsaw, Wien. Outline. Introduction Status of the Collaboration (PhD students, authors,…)

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NA48/1 Status Report

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  1. NA48/1 Status Report Augusto Ceccucci/CERN CERN-NA48/1: Cambridge, CERN, Chicago, Dubna, Edinburgh, Northwestern, Ferrara, Florence, Mainz, Orsay, Perugia, Pisa, Saclay, Siegen, Turin, Warsaw, Wien NA48/1 Status Report to SPSC

  2. Outline • Introduction • Status of the Collaboration (PhD students, authors,…) • KS results • NA48/1 Phase I (SPS 2000 run) • KS→3p0 (Preliminary) • KS→gg (shown already @SPSC in Nov. 2002, PLB 551) • KS→p0gg (CERN-EP/2003-052; hep-ex/0309022, accepted by PLB) • NA48/1 Phase II (SPS 2002 run) • KS→p0 ee (CERN-EP/2003-062; hep-ex/0903075, accepted by PLB) • KS→p0 mm (New preliminary result) • Neutral hyperons: • X0 Semi-leptonic decays • X0 Radiative decays • Outlook NA48/1 Status Report to SPSC

  3. Collaboration Issues • 114 Scientific authors • Monthly analysis meetings • Insist on independent analyses • 12 PhD Students (either finished or quite advanced analyses) • Matthias Behler (Mainz) • Marco Clemencic (Torino) • Teresa Fonseca (Northwestern) • Guillaume Gouge (Saclay) • Andreas Hirstius (Mainz) • Ermanno Imbergamo (Perugia) • Venelin Kozhuharov (Dubna) • Peter Marouelli (Mainz) • Ulrich Moosbrugger (Mainz) • Mitesh Patel (Cambridge) • Mauro Piccini (Perugia) • Mark Slater (Cambridge) + Several Master/Diploma theses NA48/1 Status Report to SPSC

  4. NA48 Detector & Data Taking NA48: ’/ 1997 ’/ 1998 ’/ 1999 no spectrometer 2000 KL NA48/1 KS ’/lower inst. intensity 2001 2002 NA48/1: KS 2003 NA48/2: K Total: 5.3M KL00 1996 Kaons produced by 400 GeV protons from the CERN SPS on a Be target: EK~110 GeV NEAR (KS) beam ~ 6.2 m long NA48/1 Status Report to SPSC

  5. Results from the 2000 dataNA48/1 Phase I NA48/1 Status Report to SPSC

  6. Search for CP-violation in KS → 3p0 CP-Violating In SMh000~e • Near Beam • NA48/1 (2000) ~6.5 106 3p0 • Far Beam: • NA48 2000 > 107KL→3p0 • To normalise the acceptance • Analysis in bins of energy D(E) is the K0 K0dilution (from NA31) NA48/1 Status Report to SPSC

  7. KS→ 3p0 CPT TEST: KL ~ (e+dCPT)K1 + K2 KS ~ K1 + (e-dCPT)K2 From the 2 parameter fit, using BS unitarity relation: Im dCPT = (-1.2 ± 3.0) × 10-5 Assuming CPT conservation in decay: M(K0) –M(K0) = (- 1.7 ± 4.2) × 10-19 GeV/c2 Im h000 From one parameter fit: BR(KS→3p0) < 3.0 × 10-7 90%CL BRSM ~ 1.8× 10-9 Re h000 NA48/1 Status Report to SPSC

  8. First Observation of KS  Dalitz • The rejection of the Dalitz decays is complicated since no drift chambers were available in 2000 • Impose MKto reconstruct decay vertex zvertex • Decays with missing particles are reconstructed downstream • Keep a short fiducial region: -1 < zvertex < 8 m • zp0= decay vertex reconstructed pairing 2 g assuming a p0 decay • The zp0 closest to the exit of the collimator is z*p0 • The events with small z*p0 are rejected Pile-up Collimator NA48/1 Status Report to SPSC

  9. KS  first observation CERN-EP/2003-052 (hep-ex/0309022) Zq=q2/MK2 BR(KS γγ, zq0.2 ) = (4.9 ± 1.8 )×10-8 CHPT predicts (Ecker, Pich and PLB 189 1987): BR(KS ) zq > 0.2 =3.8  10 –8 NA48/1 Status Report to SPSC

  10. Results from 2002 dataNA48/1 phase II NA48/1 Status Report to SPSC

  11. Kaon Rare Decays and the SM JCP=2(Triangle Area) is the unique measure of CP-Violation in SM JCP = Im(Vud*VusVts*Vtd) ~ cosqc sinqcIm lt In the Wolfenstein parameterisation (l, A, h, r): Im lt = A2l5h, Re lt = A2l5r (holy grail) CP-Violation NA48/1 Status Report to SPSC

  12. KL,S→p0ee (mm) • Short Distance (Direct CP-Violation) • From Standard Model fit: Im lt = (1.36 ± 0.12) 10-4 • B(KL→p0ee)CPV-dir = (3.2 ± 0.4) × 10-12( hep-ph/0308008) • Indirect CP-Violation • BR(KL→p0 ee) CPV-ind ~1/330 BR(KS → p0 ee) Essential to measure BR(KS → p0 ee) • CP-Conserving contribution • BRCPC < 3 ×10-12( hep-ph/0308008) • They fix the 3 counter-terms from KL→p0gg and KS→gg measured by NA48 and NA48/1 NA48/1 Status Report to SPSC

  13. KS→ p0 ee KS→ p0p0D→ggee(g) KS→p0 ee MC MC • To reject the KS→ p0p0Ddecays that may mimic KS→p0 ee if a g is lost, a cut mee>0.165GeV/c2 is applied NA48/1 Status Report to SPSC

  14. KS→p0 ee e+-e-+ (Odd Sign) DATA e+-e-+ DATA vs. MC Blind Control & Signal regions meegg (GeV/c2) mee (GeV/c2) NA48/1 Status Report to SPSC

  15. KS→p0 ee e+-e+- (Same Sign) DATA e+-e+- DATA vs. MC Search region meegg (GeV/c2) mee (GeV/c2) NA48/1 Status Report to SPSC

  16. KS→p0 ee Background from KL,S→eegg : measured using NA48 KL data from 2001 N(KL→eegg, 2001)  10 × N(KL,S→eegg, 2002) meegg(GeV/c2) mgg(GeV/c2) NA48/1 Status Report to SPSC

  17. KS→p0 ee Accidental backgrounds • DC proton beam • Read out window: ~ 200ns • Use time side band to measure background from time-overlapping fragments from differ decays • Major component: • epn+ p0(p0) • Confirmed relaxing E/P cuts meegg (GeV/c2) mgg (GeV/c2) NA48/1 Status Report to SPSC

  18. KS→p0 ee SUMMARY OF BACKGROUNDS: • Many other sources investigated and found to be negligible (e.g. neutral cascade decays) • Blind analysis: Control and signal region remained masked until the study of the background was finished NA48/1 Status Report to SPSC

  19. KS→p0 ee • 7 candidates in the • signal region • 0 in control region • Background 0.15 • The probability that all 7 • events are background • is ~10-10 meegg (GeV/c2) mgg (GeV/c2) First observation of KS→p0 ee NA48/1 Status Report to SPSC

  20. The 7 KS→p0ee candidates Meegg (GeV/c2) t/tS Mgg (GeV/c2) Mee (GeV/c2) NA48/1 Status Report to SPSC

  21. KS→p0 ee Accepted for publication by PLB BR(KS→p0ee, mee>165 MeV/c2) = (3.0+1.5-1.2(stat)± 0.2(syst))×10-9 • Assuming vector interaction and unity form factor: • In remarkable agreement with L. Sehgal prediction: ~5.5 ×10-9 NP B19 (1970) • In the notation of D’Ambrosio et al. JHEP 08 (1998 004): • BR(KS→p0ee) ~ 5 |as|2 |as|=1.06+0.26-0.21 (stat)± 0.05 (syst) BR(KS→p0ee) = (5.8 +2.8-2.3(stat) ± 0.8(syst))×10-9 NA48/1 Status Report to SPSC

  22. Sensitivity to Im lt IF the interference is constructive some sensitivity to Im lt is retained NA48/1 Status Report to SPSC

  23. The overall picture G. Isidori STILL A LARGE WINDOW OF OPPORTUNITY EXISTS NA48/1 Status Report to SPSC

  24. NEW RESULT!!KS→p0mm NA48/1 Status Report to SPSC

  25. Search for KS→p0mm • The considerations made before for KL→p0 ee apply also to KL→p0mmbut the CP-conserving contributions need more attention • A measurement of KS→p0mmis quite complementary to the KS→p0 ee one • Different backgrounds • Larger acceptance (no Dalitz background) • In principle one can relate KS→p0mmand KS→p0 ee to extract the form factor (for example the aS and bS parameters) NA48/1 Status Report to SPSC

  26. Backgrounds to KS→p0mm NA48/1 Status Report to SPSC

  27. Ready to open box? The red dots are the events passing 0 < t K < 3 tS KL→p0p+p- m m NA48/1 Status Report to SPSC

  28. Six candidates!! NA48/1 Status Report to SPSC

  29. The six KS→p0mmcandidates • Consistent with signal • Measurement of BR • in progress NA48/1 Status Report to SPSC

  30. Neutral hyperons Admittedly, the run 2002 has not been optimised for hyperon physics: • The production angle was not chosen to maximise the hyperon flux • There was no provision to rotate and flip the hyperon polarisation • The acceptance was limited by the lack of tracking in the beam pipe volume • A very selective trigger was employed to keep rate within assigned bandwidth • Large downscaling factor for the minimum bias was used for the same reason Nevertheless: • We accumulated a sample of semi-leptonic X0decays which is at least four times the whole world statistics • We have the first convincing observation of the decay    +m-n • We have accumulated a high-statistic sample of X0 radiative decays NA48/1 Status Report to SPSC

  31. First Observation • The b decay of X0 is the only source of S + in the neutral beam • The plot shows the pp0 invariant mass for decays with one identified m NA48/1 Status Report to SPSC

  32. Radiative decays: X 0→L g • Precise measurement of decay asymmetry of • X0 →L gunderway • Nature of backgrounds under study NA48/1 Status Report to SPSC

  33. Outlook • The analysis of the 2000 data is almost completed • We are publishing the first observation of KS→p0 eewhich was the main motivation of the 2002 run: • Indirect CP-violation in KL→p0 ee (mm) is large and cannot be neglected! • To study the form-factor is interesting but significantly larger statistics should be accumulated • The analyses of the neutral hyperon decays are advancing NA48/1 Status Report to SPSC

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