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The FOCUS Collaboration

The FOCUS Collaboration. Tampere, july 15-21th, 1999. Univ. of California- Davis , CBPF -Rio de Janeiro, CINVESTAV -Mexico City, Univ. Colorado - Boulder , FERMILAB , Univ. of Illinois -Urbana-Champaign, Indiana Univ.-Bloomington, Korea Univ.-Seoul, INFN and Univ.- Milano ,

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The FOCUS Collaboration

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  1. The FOCUS Collaboration Tampere, july 15-21th, 1999 Univ. of California-Davis, CBPF-Rio de Janeiro, CINVESTAV-Mexico City, Univ. Colorado-Boulder, FERMILAB, Univ. of Illinois-Urbana-Champaign, Indiana Univ.-Bloomington, Korea Univ.-Seoul, INFN and Univ.-Milano, Univ. of North Carolina-Ashville, INFN and Univ.-Pavia, Univ. of Puerto Rico-Mayaguez, Univ. of South Carolina-Columbia, Univ. of Tennessee-Knoxville, Vanderbilt Univ.-Nashville, Univ. of Wisconsin-Madison, Yonsei Univ.-Seoul

  2. Spectrometer Layout • Excellent vertex resolution - 28fs • Great particle ID: three Cerenkov counters, two EM calorimeters (e,g ), two muons detectors • Unique ability to identify hadrons (neutrons and K0L)

  3. 1.1 million reconstructed!! GOLDEN MODES ONLY MESON GOLDEN MODES

  4. I have to write the “outlines” • OUTLINES • meson spectroscopy • baryon spectroscopy • lifetime measurements

  5. Preliminary D*Dp0 mass splitting ~50% of the full FOCUS sample Although the D*+ - Do mass difference is very well measured, the D*o - Do mass difference requires  detection. We are seeing very strong signals in FOCUSwith our new & improved EM calorimeters. CLEO92 has provided the best past data on D0* mass, widths, and branching ratios from ~1200 D*o-Do decays D*o - Do D*+ - D+ IE-IE 0’sonly

  6. Independent analysis (24% of FOCUS statistics) K p K 2p K p K 2p sidebands K p K 2p

  7. PDG98 PDG98 S/N Preliminary results 24% of FOCUS Both °samples consistent with PDG98 already w/ smaller errors!

  8. Preliminary Ds*+ Ds+ ~20% FOCUS IE g only

  9. Beyond the D* • HQETpredicts a rich L=1 spectrum • 2 broad states with s-wave  decays (CLEO has evidence for 1) • 2 narrow states with d-wave  decays (seen in e+ e- &  N) • Predictions are made for masses, widths, and angular distributions and the relationship to B** splitting. • FOCUS has PRELIMINARY signals for • D01D* D0*2D* • D0*2D D+*2D • D*s?K D The low multiplicity of primary vertex gives photoproduction an advantage for D** study.

  10. Preliminary D** signals 55% of full sample reflection D2*0 (2460) • We observe • 2 peaks in D*+- • 1 real peak in D+- • 1 real peak in D0+ • 1 real peak in D0K+ • Also seereflections from D*°D with missing ° • Angular distributions can often be used to disentangle states and confirm HQET predictions. D1(2420) D2*0(2460) D1(2420) absent by parity WS WS Ds+*D0K Ds** (D)K+ Do1 , D*o2  D*-+(D)+ DsJ(2573)+? D2*+ (2460) 27 % of FOCUS WS WS

  11. Preliminary D** analysis with tighter cuts ~55% of FOCUS D2*+ (2460) D1(2420) D2*0(2460) ~10% of FOCUS m(D°+) - m(D°) angular cuts applied to separate D1 from D2* tighter detachment cut 55% total sample

  12. Charmed Baryon Spectroscopy • 17 states have been observed • Unobserved states:Sc*+(2518), Xc1(X’cp), excited Wc states, higher excited states.. • There is a theoretical interest on charmed baryons mass splitting, but the experimental • errors are still quite large. Precise measurements can help to better understand it.

  13. Lc+ signals pK-p+channel from 80% of the data sample large and clean samples make precision studies of excited states possible channels with L0 and Ks0 30% of full sample May use to increase statistics for excited states BR measurement (PDG98: error 25%-35% ) Lc+p Kosp-p+ Lc+Lop-p+p+

  14. …and other Lc+ decays channels CLEO 487 ev Only by E687 56 ev Lc+X-K+p+ (75% of the full sample) More channels are under study: pK+K-, pKs0,L0p+, pp+p- (22% of the full sample) Interesting resonant structures to study the non-spectator diagrams

  15. Sc mass splitting  Decay chain:Sc++,0Loc p±  Used only a clean LcpKp+ signal from 80% of the full sample Background from Lc sidebands

  16. Preliminary results Fit studies • Sc, Sc* • Lc*+ feed-down • fake Lc+ , spurious p Systematic error

  17. Sc excited states Used looser cuts than the Sc DM analysis DM and width measurements only from CLEO Sc*0: 232.6± 1.0± 0.8 MeV Sc*++: 234.5± 1.1± 0.8 MeV

  18. Lc excited states Lc*+(2625) , Lc*+(2593)  Exp. results from ARGUS, CLEO, E687 Sc resonant components for Lc*+(3/2-) state via D wave for Lc*+(1/2-) state via S wave FOCUS DM (Lc*- Lc )

  19. Xc+X-p+p+ Xc0X-p+ Xc+ and Xc0 PDG Mass errors: Xc+: 1.4 MeV Xc0 :1.8 MeV 75% of the full sample Xc+S-K-p+ Xc+L0K-p+p+ 20% of the the full sample 30% of the full sample

  20. Cabibbo suppressed Xc+ p K-p+ M = 2473.4  1.8 MeV W = 8.5  1.5 MeV Y = 109  21 EV S/N = 0.9  0.2 Lc+ Y = 1867  51 S/N = 5.9 0.6 M = 2474  2 W = 7.6  1.6 Y = 73  18 S/N = 0.7  0.2 Lc+ Y = 1711  49 S/N = 6.1 0.6 First reported by Selex at HQ-98 Tight selection on p and K- Future BR measurement Xc+ Xc+ 50% of the full sample

  21. FOCUS preliminary t(Ds)=(0.506±.008) ps PDG-98t(Ds)=(0.467±.017) ps

  22. t(Lc+)= (0.2045±.0034) ps PDG-98t(Lc+)=(0.206±.012) ps

  23. Conclusions • FOCUS hasreconstructedover 1.1million “golden mode” charmed mesons. • Preliminary results on partial data sets look very promising. Systematics (delicate) are under study. • FOCUS can do very precise and new measurements in the charm hadron spectroscopy sector. • It is important to determine the masses and widths of the baryon states. FOCUS in a good position to measure them. • It is important to measure the lifetimes of the Ds meson and all charmed baryons. FOCUS in a good position to provide all of them.

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