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