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Over 1 million reconstructed!!

Over 1 million reconstructed!!. Successor to E687. Designed to study charm particles produced by ~200 GeV photons using a fixed target spectrometer with upgraded Vertexing , Cerenkov , E+M Calorimetry , and Muon id capabilities. Includes groups from USA, Italy, Brazil, Mexico, Korea

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Over 1 million reconstructed!!

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  1. Over 1 million reconstructed!! Successor to E687. Designed to study charm particles produced by ~200 GeV photons using a fixed target spectrometer with upgraded Vertexing, Cerenkov, E+M Calorimetry, and Muon id capabilities. Includes groups from USA, Italy, Brazil, Mexico, Korea 1 million charm particles reconstructed into DK , K2 , K3 FOCUS first results <Luigi Moroni @ HEP99>

  2. Outline • I would like to illustrate the potential of FOCUS on the basis of some preliminary physics measurements obtained by analyzing partial subsets of our data sample. • Will limit my presentation to some crucial aspects of the charm meson physics • FOCUS charm baryon results are shown by S.Ratti in the “hadron spectroscopy” session of this conference • We are just beginning to learn how to exploit the full potential of our detector systems and hence • all of these analyses are non-optimal and • in all cases should be viewed as preliminary. FOCUS first results <Luigi Moroni @ HEP99>

  3. Studies of Cabibbo Suppressed decays • FOCUS’s powerful Cerenkov ID and very large data sample gives it unique opportunities to study Cabibbo Suppressed Decays • Will present evidence for three DCS Decays • Historically the pattern of Cabibbo suppression has been full of surprises and has yielded unique insight into hadronic decay mechanisms to challenge models • The rate for DCSD is often very different than tan4C • D° DCSD interferes with hadronic decay mixing. This is good news / bad news since small amplitudes are best measured through interference • Differences in DCSD/CF Dalitz plots can probe Do mixing (T. Liu) FOCUS first results <Luigi Moroni @ HEP99>

  4. 5913 E791 DCSD : D+ K++- ~100% of FOCUS Data Y(D+)=30237Y(Ds+)=53836 K++-)/K-+ +=(0.68  0.15)% PDG98 Our results much better than PDG98 (  5  E791) Preliminary FOCUS (K++-)/ (K-+ +)=(0.720.09)%  3tan4Cabbibo  (+/0)tan4C M(K++-) FOCUS first results <Luigi Moroni @ HEP99>

  5. PRELIMINARY D+K+KK+ ~100% FOCUS • Ds+K+K-K+is a SCSD • D+K+K-K+ is aC = -S DCSD which cannot occur via a spectator diagram. • (D +K+K-K+)/( D +) = (1.410.27)10-4 • Just on PDG 98 limit from E687 of Br < 1.410-4 CL=90% • Our rarest DCSD BR yet : (D +K+K-K+) / (K-++)  tan4C/2 • A KKK Dalitz analysis may shed light on the KKK decay mechanism. Y(D+ ) = 73.1±13 Y(Ds+ ) = 64.5±13 FOCUS first results <Luigi Moroni @ HEP99>

  6. Y=7221.6±87.80 + K+ M=0.1455 W=0.91 D0 D0 rmix PRELIMINARY (~40%) D° DCSD Here we look for WS D° decays where the kaon has the same sign as the D+* decay pion. This is also a classic way to search for mixing and could interfere with mixing. BR(DCSD) WS/RS K rs mixed CF Y=60.337±21.40 D*+ - WS mass &  fixed by RS + K+ DCSD D0 K ws D*+ - FOCUS first results <Luigi Moroni @ HEP99>

  7. PDG error Kp PDG Relative WS/RS ratio versus CITADL Cuts Study of double mis-id background ws/rs Miss-id yield MC study W -WK W -WK Slight variation in BR as pid cuts are tightened. Would expect exponential decrease if double mis-id. The signal level is consistent with existing world’s average but higher than CLEO’s recent measurement at APS FOCUS first results <Luigi Moroni @ HEP99>

  8. Dalitz Amplitude Analyses • Dalitz analyses are a traditional strength of E687 which has published on: • K- + +K- +o Ks- +K-K+- ++- • Dalitz analysis provides powerful probes on charm hadronic decay • Underscores the importance of quasi-two body decay and extends tests of factorization models to vector-pseudoscalar decay • Often highly unusual resonances dominate charm Dalitz plots. • Allows one to directly investigate non-spectator effects such as W-annihilation • Provides new handles on charm CP violation by comparing the phases and amplitudes that one gets for particles versus antiparticle decay. Best in Cabibbo suppressed decays. • Provides a preview of the FSI complication for beauty • Studies on many Dalitz plots studied by E687 are already underway. I will discuss two interesting Dalitz plots featuring decays with an unusual number of final state kaons. FOCUS first results <Luigi Moroni @ HEP99>

  9. Favored D decays with “unusual “ numbers of kaons Conventional spectatorbut withweird resonances? Too few kaons! An example is Ds BR is large ~1.4% suggesting a Cabibbo favored decay Cabibbo favored would produce a s s u d as final quarks and no kaons appear in the final state. How are they lost? NR Weak Annihilation ? Resonant Weak Annihilation? FOCUS first results <Luigi Moroni @ HEP99>

  10. Preliminary FOCUS Ds Dalitz plots (~100%) • Observe: • f0(980) • f2(1270) • f0 (1500) • Clearer in FOCUS • No evidence for WA • (770) • NR f2 f2 • Dominated byweirdresonances with simultaneous KK and  couplings • No evidence for non-spectator decays such as NR or  FOCUS first results <Luigi Moroni @ HEP99>

  11. PRELIMINARY D0Ks K+ K- Dalitz plot a0(980) f0(980) f(1020)? ~50% FOCUS Y=395S/N=17 Too many kaons Here we have only an s u u d quarks in the final state yet three kaons appear! 2 spectator diagrams with resonances which couple to ’s and K’s m²K+K- a0(980)? f0(980)? f(1020) We use D* tagging to determine strangeness of K°s m²K+Ko FOCUS first results <Luigi Moroni @ HEP99>

  12. E791 Search for CP violating SCSD decays Look for (DK+K-)  (DK+K-) Tag D charm through D* D DK We normalize to DK-+ to eliminate 4% production asymmetry. Much less DK Reflection FOCUS (59%) World’s best data using only 59% of Focus! FOCUS first results <Luigi Moroni @ HEP99>

  13. CP on D+KK++Dalitz plot (~59%) • FOCUS has already (59%) 4590  77 D  KK++with a S/B = 6.4 • Hopefully, we can do much more by comparing phases and amplitudes measured on the two CP conjugate Dalitz plots. • The level at which we can reproduce the Dalitz structures with just a simple model, is amazing! Mixture of (1020) K(892) K(1430) FOCUS first results <Luigi Moroni @ HEP99>

  14. WS + K+  D0 D0 rmix - Semileptonic Mixing Searches + RS K-  D0 D*+ +  from another event D*+ Limit follows from fitting time evolution of WS and RS signal. No DCSD interference. FOCUS first results <Luigi Moroni @ HEP99>

  15. Mixing sensitivity • FOCUS projected sensitivity is rmix ~ 0.18% • Including electrons we project rmix ~ 0.13% • Present E791 limit rmix < 0.50% (90% CL) We have unique advantages in searching for direct  differences between CP-even eigenstates such as D°K+ K-and states of mixed CP such as D° K- +or CP odd states such as Ks or Ks We expect a yield of about 10000 D°K+ K- decays. This should give us a lifetime measurement for CP even states of ()/  1.0% FOCUS first results <Luigi Moroni @ HEP99>

  16. K*l from 80% Focus RS-WS = 64244 M(K) FOCUS Semileptonic Physics • We improved all aspects of our lepton id system including an entirely rebuilt inner muon system, a new outer muon system, a rebuilt inner E&M calorimeter and an enhanced outer E&M calorimeter. • We project a ~50 fold increase over E687 which published form factors for each of these states Our projected Kl yield should make us very competitive with other charm experiments! Our vertex tagging gives us the ability to study Kl without D* tagging  Enormous yield FOCUS first results <Luigi Moroni @ HEP99>

  17. p - ~ K + p + p - D 0 _ _ D (recoil) D* + p - p + Soft pion tagging as means to absolute BF Can tag the presence of a D° by observing a right sign  which balances Pt with a reconstructed D . You then count the number of D° decays into a particular final state, correct by efficiency and ratio to find an absolute branching fraction. Low primary vertex multiplicity is a big advantage. Proof of Principle 1: Is there an excess of RS over WS events at low Pt ? Proof 2: Can we reconstruct both D’s in an event? FOCUS has a sample of 7500very clean events with both reconstructed D’s  10  E791 30% FOCUS

  18. ~  : p kinematic tag  : Double D reconstruction Df (Acoplanarity) Double D Vs D* tag sample . • They track each other! • These are the best data samples to study production dynamics The acoplanary is principally due to hard final state gluon emission. FOCUS first results <Luigi Moroni @ HEP99>

  19. Conclusions • What I left out: • a variety of high quality signals with Ks and  • new lifetime measurements for Ds+ and c • D* and Ds* spectroscopy • the whole chapter on c-baryons • for some of these, you could refer to S.Ratti presentation in “hadron spectroscopy” parallel session • Actually, a lot of very exciting physics can be done with one million of charm! • Stay tuned • FOCUS will present other new results pretty soon! FOCUS first results <Luigi Moroni @ HEP99>

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