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Slide1 : E831/FOCUS RECENT RESULTS Angel M. López University of Puerto Rico Mayaguez, Puerto Rico


Slide2 : Cal-Davis, CBPF(Brazil), CINVESTAV (Mexico), Colorado, Fermilab, Frascati, Illinois, Korea University, Seoul (Korea), Milan, North Carolina, Pavia, Puebla(Mexico), Puerto Rico, South Carolina, Tennessee, Wisconsin, Vanderbilt http://www-focus.fnal.gov/


Focus Spectrometer : Focus Spectrometer


Main FOCUS Upgrades : Main FOCUS Upgrades Si Planes Inside Segmented Target Fast Hadron Calorimeter Lead-glass Inner EM Calorimeter Improved and Expanded Muon Detection Improved Cerenkov Identification


A LARGE VARIETY OF CHARM PHYSICS TOPICS : A LARGE VARIETY OF CHARM PHYSICS TOPICS SPECTROSCOPY LIFETIMES DOUBLY CABBIBO SUPPRESSED DECAYS RARE AND FORBIDDEN DECAYS MIXING CP VIOLATION RESONANCE STRUCTURE (DALITZ) SEMILEPTONIC DECAYS PRODUCTION DYNAMICS


OUTLINE : OUTLINE SPECTROSCOPY MESONS D*0 - D0 MASS DIFFERENCE D** SIGNALS BARYONS ΣC0 , ΣC++ , ΛC+ MASS DIFFERENCES ΣC , ΛC* SPECTROSCOPY ΞC+ DECAYS DS+ and ΛC+ LIFETIMES DOUBLY CABBIBO SUPRESSED DECAYS CP VIOLATION D0 , D0BAR MIXING RARE AND FORBIDDEN DECAYS


PRELIMINARY D*D Mass Splittings : We are seeing very strong D*o Do  signals in FOCUS with our new & improved E&M calorimeters. Project a final sample of 25000 D*o Do  decays . CLEO92 has provided the best past data on D0* mass, widths, and branching ratios from ~1200 D*o Do  decays ~50% FOCUS D*o - Do D*+ - D+ IE-IE 0’s only PRELIMINARY D*D Mass Splittings


PRELIMINARY Mass splittings : PRELIMINARY Mass splittings PDG98 PDG98 Both °samples consistent with PDG98 already w/ smaller errors ! S/N 24% of FOCUS


We are even getting our first glimpse at Ds*+ : We are even getting our first glimpse at Ds*+ Preliminary ~20% FOCUS IE  only Ds*+  Ds+ 


“Golden” signals with pi0’s : “Golden” signals with pi0’s Signals based on 20% of FOCUS No optimization of  cuts! # per 5 MeV Can study a rich new set of charm decay Many are required to complete isospin amplitude triangles


Beyond the D* : Beyond the D* HQET predicts 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.


PRELIMINARY D** signals ~27% FOCUS : PRELIMINARY D** signals ~27% FOCUS WS WS WS D2*0 (2460) D2*+ (2460) D1(2420) D2*0(2460) Do1 , D*o2  D*-+(D)+ reflection unresolved in E687 except by angular cuts Ds+*D0K DsJ(2573)+? Ds**  (D)K+ D1(2420) absent by parity We observe 2 peaks in D*+- 1 real peak in D+- 1 real peak in D0+ 1? peak in D0K+ Also see reflections at M-m from D*°D with missing ° Angular distributions can often be used to disentangle states and confirm HQET predictions.


Preliminary c - c mass differences : Preliminary c - c mass differences M= 167.450.170.36 MeV Theoretically one expects M(c0) > M(c++) But world’s data including our measurement has M(c0) < M(c++) by about 1.5 M= 0.280.310.15 MeV M=167.170.260.27 MeV c++ - c+ c0 - c+ c++ -  c0


A Gallery of +c decays : A Gallery of +c decays - + + K-++ +K-+ pK-+ SCSD 1st reported by Selex HQ98 ~70% Focus ~20% Focus ~30% Focus ~75% Focus Using the 3 favored decay modes, we project a sample of 860 +c decays ~30 times the E687 lifetime sample which provides the best c lifetimes


Studies of Cabibbo Suppressed decays : 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 five DCS Decays ( 2.50.5 decays are new!) 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


DCSD : D+  K+ +- : DCSD : D+  K+ +- ~40% of FOCUS Data Y(D+)=17228Y(Ds+)=22421 (K+ +-)/ (K- + +) = (0.650.11)%  3 tan4Cabbibo  (+/0)  tan4C CL1<0.1 CL1<110-8 Preliminary FOCUS K+ +-)/K- + + = (0.68  0.15)% PDG98 Our results already much better than PDG98 (  3  E791) M(K+ +-)


PRELIMINARY (~40%) D° DCSD : PRELIMINARY (~40%) D° DCSD K rs K ws WS mass &  fixed by RS 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 Y=60.337±21.40 - K+ + D0 - D*+ D*+ DCSD mixed CF


Relative WS/RS ratio versus CITADL Cuts : 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 Cut variations on 19/155 with K candidates. ws/rs Mis-id yield MC study Relative WS/RS ratio versus CITADL Cuts W -WK


PRELIMINARY D +sK+K+- : PRELIMINARY D +sK+K+- ~50% PRELIMINARY This is the first observation of D+s DCSD The rate relative to K-K++ is 1.5% (~6  tan4Cabbibo)


PRELIMINARY D+ K+K-K+~40% FOCUS : PRELIMINARY D+ K+K-K+~40% FOCUS Y(D+ ) = 27±7 Y(Ds+ ) = 28±7 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 +) = (1.450.39)10-4 Just below 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 No evidence for D+  K A KKK Dalitz analysis may shed light on the KKK decay mechanism.


Kinky decays of the c+ : Kinky decays of the c+ c+- K++ ~75% FOCUS Y=607 in ~22% FOCUS Y=253 in ~22% FOCUS CLEO saw 487 events E687 saw 56 events We have unique abilities to reconstruct the - n  - Will study (1385)  since only contributions are internal W and WX


Preliminary measurement of the Ds+ lifetime : Preliminary measurement of the Ds+ lifetime Using E791  (Ds+) = 0.518  0.014  0.007 ps We project:WA is  (Ds+) / (Do) = 1.214  0.017 We use 5668 Ds+ decays in ~50% of FOCUS to suppresses long-lived backgnd from D+K- + +K+ Also allows us to enhance S/N with cos  cut cos K Theory  (Ds+) / (Do) =1.07 1.20 Ds+ and Do have unique CF non-spectator decays WA WX


Search for CP violating SCSD decays : Search for CP violating SCSD decays E791 FOCUS (26%) DK We normalize to DK-+ to eliminate 4% production asymmetry. World’s best data using 26% of Focus! Look for (DK+K-)  (DK+K-) Tag D charm through D* D Much less DK Reflection


Semileptonic Mixing Searches : Semileptonic Mixing Searches D*+ D*+  from another event Limit follows from fitting time evolution of WS and RS signal. No DCSD interference.


Mixing sensitivity : Mixing sensitivity FOCUS projected sensitivity is rmix ~ 0.15% Including electrons we project rmix ~ 0.1% 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 from 5000-10000 D°K+ K- decays. This should give us a lifetime measurement for CP even states of better than ()/ < 1.5%