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The FOCUS Collaboration Univ. of California-Davis, CBPF-Rio de Janeiro, CINVESTAV-Mexico City, Univ. Colorado-Boulder, FERMILAB, Univ. of Illinois-Urbana-Champaign,

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Presentation on theme: "The FOCUS Collaboration Univ. of California-Davis, CBPF-Rio de Janeiro, CINVESTAV-Mexico City, Univ. Colorado-Boulder, FERMILAB, Univ. of Illinois-Urbana-Champaign,"— Presentation transcript:

1 The FOCUS Collaboration 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 Tampere, july 15-21th, 1999

2 Spectrometer Layout Excellent vertex resolution - 28fs Great particle ID: three Cerenkov counters, two EM calorimeters (e,  ), two muons detectors Unique ability to identify hadrons (neutrons and K 0 L )

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

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

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

8 ~20% FOCUS IE  only Preliminary D s * +  D s + 

9 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 D 0 1  D* D 0* 2  D* D 0 * 2  D D + * 2  D D* s?  K D The low multiplicity of primary vertex gives photoproduction an advantage for D** study. Beyond the D*

10 Preliminary D** signals 55% of full sample D 2 *0 (2460) reflection D 1 (2420)D 2 *0 (2460) D 2 *+ (2460) D o 1, D* o 2  D* -  +  (D  )  + D s +*  D 0 K D sJ (2573) + ? D s **  (D  )K + D 1 (2420) absent by parity We observe 2 peaks in D* +  - 1 real peak in D +  - 1 real peak in D 0  + 1 real peak in D 0 K + Also see reflections from D*  °D with missing  ° Angular distributions can often be used to disentangle states and confirm HQET predictions. WS 27 % of FOCUS WS

11 m(D°  + ) - m(D°) ~10% of FOCUS Preliminary D** analysis with tighter cuts ~55% of FOCUS tighter detachment cut angular cuts applied to separate D 1 from D 2 * D 1 (2420) D 2 *0 (2460) D 2 *+ (2460) 55% total sample

12 17 states have been observed  c *+ (2518),  c1 (  ’ c  ), excited  c states, higher excited states..Unobserved states:  c *+ (2518),  c1 (  ’ c  ), excited  c 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. Charmed Baryon Spectroscopy

13  c + signals channels with  0 and K s 0 30% of full sample May use to increase statistics for excited states BR measurement (PDG98: error 25%-35% ) pK -  + pK -  + channel from 80% of the data sample large and clean samples make precision studies of excited states possible c+ o  -++c+ o  -++  c +  p   s  -  +

14  c +  - K +  + (75% of the full sample) (22% of the full sample) Interesting resonant structures to study the non-spectator diagrams CLEO 487 ev Only by E ev More channels are under study: pK + K -, pK s 0,  0  +, p  +  - …and other  c + decays channels

15  c mass splitting Background from  c sidebands  c ++,0   c  ±  Decay chain:  c ++,0   c  ±  c  pK  +  Used only a clean  c  pK  + signal from 80% of the full sample

16 Systematic error Preliminary results Fit studies  c,  c *  c *+ feed-down fake  c +, spurious  

17 Used looser cuts than the  c  M analysis  M and width measurements only from CLEO  c *0 : 232.6± 1.0± 0.8 MeV  c *++ : 234.5± 1.1± 0.8 MeV  c excited states

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

19  c + and  c 0 c+ 0K-++c+ 0K-++ c+ -K-+c+ -K-+ 75% of the full sample 20% of the the full sample 30% of the full sample PDG Mass errors:  c + : 1.4 MeV  c 0 : 1.8 MeV c+ -++c+ -++ c0 -+c0 -+

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

21

22 FOCUS preliminary  ( D s )=(0.506±.008) ps PDG-98 PDG-98  (D s )=(0.467±.017) ps

23  (  c + )= (0.2045±.0034) ps PDG-98 PDG-98  (  c + )=(0.206±.012) ps

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


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