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STARTING POINT Budapest july 2001

STARTING POINT Budapest july 2001. CHARM MIXING AND CP VIOLATION IN FOCUS AT FERMILAB. CHARM MIXING AND CP VIOLATION IN FOCUS AT FERMILAB. EPS-HEP2001 Budapest , july 12-18, 2001. SERGIO P. RATTI INFN and Dipartimento di Fisica Nucleare e Teorica - PAVIA

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STARTING POINT Budapest july 2001

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  1. STARTING POINT Budapest july 2001

  2. CHARM MIXING AND CP VIOLATION IN FOCUS AT FERMILAB CHARM MIXING AND CP VIOLATION IN FOCUS AT FERMILAB EPS-HEP2001 Budapest, july 12-18, 2001 SERGIO P. RATTI INFN and Dipartimento di Fisica Nucleare e Teorica - PAVIA for the FOCUS COLLABORATION

  3. Outline of the talk Basic phenomenolgy:Do-Do mixing: lifetime mixing: yCP=DG/2G DCS decay DoK+p- (from D*) Comparison with other experiments D-D asymmetries: search for CP Conclusions

  4. Do-Do MIXING THE MIXING AMPLITUDE SQUARE IS: INTEGRATING |Amix|2 OVER TIME, MIXING IS DESCRIBED BY:

  5. BOX or DCS For a HADRONIC DECAY Do K+p- Do K-p+ is C.F. Do K+p-is WRONG SIGN D.C.S. or from mixing box diagram STRONG PHASE d y’= y cos d - x sin d x’= x cos d + y sind R’=(x’2+y’2)/2 RWS=G(Do K+p- )/G(Do K-p+ ) e-Gt[RDCS+R’/2 t2 +y’ t RDCS]

  6. Do-Do lifetime mixing

  7. LIFETIMEMIXING assuming CP conserved : CP|k+k->=+1; CP |k-p+>=equal mixture. Therefore: Thus:

  8. Mkk Mkk Mkk Mkk SAMPLE HANDLING DoKK is CP=+1 need over 10,000 ev. to reach 1% error int

  9. t MEASUREMENTS 119,738 events 10,331 events Fit spanning over ~10 t !! Fitting t(Do[Kp]) and ycp

  10. Mass (GeV) Phys. Lett. B485, 62 (2000) Results yCP= 3.42  1.39  0.74 % tkp=409.40  1.34  ?? fs

  11. Just for the fun of it!!! From: 21 t(Kp) = and yCP get t(KK)= ; G1+G2G1 G1-G2 ycp= get t-=1/G2; get DG. G1+G2 From: SPECULATIONS Purely speculative:DG= 42  17 ns-1 t(KK)= t1=(395.8±5.5) fs t2= (415.5 ± 11.5) fs

  12. Comparison of yCP measurements semileptonic

  13. DoK+p- from D*

  14. The CLUE of the WRONG SIGN STUDIES when the nature of the Do meson is identified by the parent D* is the RESPONSE OF THE CERENKOV COUNTERS to solve the K p AMBIGUITY MORE SO since we have to directly compare K-p+ to K+p- single misidentification implies “regular background” DOUBLE MISIDENTIFICATION WOULD RETAIN THE EVENT BUT IN THE WRONG CATEGORY!!!! STARTING FROM OVER 200,000 D* EVENTS, this study required a sistematic Montecarlo investigation to sort out the wrong sign K+p- signal (either DCS decay or BOX diagram decay) from the overwelming background.

  15. Simulate 3 different types of background, i.e.: Dop+p-; DoK+K-; partially reconstructed D’s and DoKp double misidentified; double misid.Do‘s handled withadequate Cerenkov cuts. Subdivide the DM distribution into 1 MeV bins and fit the remaining backgrounds plus signal to M(Kp). When the wrong Kp have mass around the right Kp! DM=MD*-MD is at the peak!

  16. Make a total of 80 fits (wrong sign and right sign) on 40 1 MeV strips

  17. DM Y=36760 ± 195 Y=148.5 ± 31.3

  18. RDCSC(%) Events CLEO E791 ALEPH CLEO II.V 0.77 ± 0.25 ± 0.25 0.68 ± 0.07 1.77 ± 0.31 0.332 ± 0.040 19 34 21 45 +0.34 -0.33 +0.60 -0.56 +0.063 -0.065 Phys. Rev. Lett. 86,2955,2001 We obtain: RWS=(0.405 ± 0.085 ± 0.025)% Of course -as we have seen- RWS becomes afunction of t in presence of mixing Consistent with SM Cabibbo tg4q

  19. Rws=(0.404 ±.085±.025 with mixing assumption and t/t=1.578±.008 (t/t)2=3.61±.03 estimate t/t and (t/t)2 using MC

  20. CP asymmetries

  21. 1623±47 1706±53 6860±110 7355±112 68607±282 73710±292 19633±149 18501±144 CP asymmetry for D mesons

  22. Parameter A for D mesons Comparison to other experimentss No evidence for CP violation so far. Our limit on K+K- needs tagged Do ‘s from D*, which cuts our sample by~80%. Our limits: most precise published measurements reflecting our large statistics.

  23. can we speculate that Do-Do mixing is 0? yCP=(3.42±1.39±0.74)% has a 90% CL limit 0. Rws=(0.404 ±.085 ±.025)% would be RDCSDin absence of mixing if mixing Rws compatible with CLEO II No evidence for CP violation at 1% level semileptonic decays still to be tackled CP=-1 states still to be adressed Conclusions

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