The FOCUS CollaborationThe 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, 1999Tampere, july 15-21th, 1999
Spectrometer LayoutSpectrometer 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 K0L)
1.1 million reconstructed!!
GOLDEN MODESGOLDEN MODES
ONLY MESONGOLDEN MODES
I have to write the “outlines”
OUTLINES
•meson spectroscopy•baryon spectroscopy
•lifetime measurements
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 FOCUS with 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
~50% of the full FOCUS sample
D*o - DoD*+ - D+
IE-IE 0’s only
Preliminary D*Preliminary D*DD00 mass splitting mass splitting
sidebands
Independent analysis Independent analysis (24% of FOCUS statistics)(24% of FOCUS statistics)
K 2K
K K 2
K K 2
PDG98
PDG98
Both °samples consistent with PDG98 already w/ smaller errors !
S/N
24% of FOCUS
Preliminary resultsPreliminary results
~20% FOCUS
IE only
Preliminary DPreliminary Dss**++ D Dss++
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
D01D* D0*
2D*
D0*2D D+*2D
D*s?K DThe low multiplicity of primary vertex gives photoproduction an advantage for D** study.
Beyond the D*Beyond the D*
Preliminary D** signalsPreliminary D** signals 55% offull sample
D2*0 (2460)
reflection
D1(2420) D2*0(2460)
D2*+ (2460)
Do1 , D*o
2 D*-+(D)+ 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 real peak in D0K+
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
WS WS
m(D°+) - m(D°)
~10% of FOCUS
Preliminary D** analysis Preliminary D** analysis with tighter cutswith tighter cuts
~55% of FOCUS
tighter detachment cut angular cuts applied to separateD1 from D2
*
D1(2420)D2
*0(2460)D2
*+ (2460)
55% total sample55% total sample
•17 states have been observed•Unobserved states: cc
*+*+(2518), (2518), c1c1((’’cc), excited ), excited cc states, higher excited states.. states, higher excited states..•There is a theoretical interest on charmed baryons mass splitting, but the experimentalerrors are still quite large. Precise measurements can help to better understand it.
Charmed Baryon SpectroscopyCharmed Baryon Spectroscopy
cc++ signals signals
channels with channels with 00 and K and Kss00
30% of full sample
May use to increase statistics for excited statesBR measurement (PDG98: error 25%-35% )
pKpK--++ channel from 80% ofthe data sample
large and clean samples makeprecision studies of excited states
possible
c+ o -++c
+ p s -+
cc++--KK++++
(75% of the full sample)
(22% of the full sample)Interesting resonant structures to study
the non-spectator diagrams
CLEO 487 ev
Only by
E68756 ev
More channels are under study:
pKpK++KK--, pK, pKss00,,00++,,
pp++--
……and otherand othercc++
decays channelsdecays channels
cc mass splitting mass splitting
Background from c sidebands
Decay chain: cc++,0++,0
c c ±±
Used only a clean ccpKpK++ signal from 80% of the full sample
Systematic error
Preliminary resultsPreliminary results
Fit studies
• c, c*
• c*+ feed-down
• fake c+ , spurious
Used looser cuts than the cM analysis
M and width measurements only from CLEOc
*0: 232.6± 1.0± 0.8 MeVc
*++: 234.5± 1.1± 0.8 MeV
cc excited states excited states
cc excited states excited states
Exp. results from ARGUS, CLEO, E687
c resonant componentsfor c
*+(3/2-) state via D wavefor c
*+(1/2-) state via S wave
cc*+*+(2625) , (2625) , cc
*+*+(2593)(2593)
MM (cc**- - c c )
FOCUSFOCUS
cc++ and and cc
00
c+ 0K-++ c
+ -K-+
75% ofthe full sample
20% of thethe full sample
30% of the full sample
PDG Mass errors:cc
++: 1.4 MeV: 1.4 MeVcc
0 0 :: 1.8 MeV1.8 MeV
c+ -++ c
0 -+
Cabibbo suppressed Cabibbo suppressed cc++ p K p K--++
50% of the full sample
First reported by Selex at HQ-98
Tight selection on pp and KK--
Future BR measurement
cc++
Y = 1711 49S/N = 6.1 0.6
cc++
M = 2474 2W = 7.6 1.6Y = 73 18
S/N = 0.7 0.2
cc++
Y = 1867 51S/N = 5.9 0.6
cc++
M = 2473.4 1.8 MeVW = 8.5 1.5 MeV
Y = 109 21 EVS/N = 0.9 0.2
FOCUS preliminary
(Ds)=(0.506±.008) ps
PDG-98PDG-98 (Ds)=(0.467±.017) ps
(c+)=
(0.2045±.0034) ps
PDG-98PDG-98 (c+)=(0.206±.012) ps
• FOCUS has reconstructed over 1.1over 1.1 million “golden mode” million “golden mode” charmed mesonscharmed mesons..•Preliminary results on partial data sets look very promising. Systematics (delicate)(delicate) are under study.•FOCUS can do very precise and new measurementsvery precise and new measurements in the charm hadron spectroscopy sector.•It is important to determine the massesmasses and widthswidths of the baryon states. FOCUS in a good positionFOCUS 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 positionFOCUS in a good position to provide all of them.
ConclusionsConclusions