

 21 Mar 1994

CLNS 94/1266CLEO 94-1 January 7, 1994 Observation of a New Charmed Strange Meson

Y. Kubota,1 M. Lattery,1 J.K. Nelson,1 S. Patton,1 D. Perticone,1 R. Poling,1 V. Savinov,1S. Schrenk,1 R. Wang,1 M.S. Alam,2 I.J. Kim,2 B. Nemati,2 J.J. O'Neill,2 H. Severini,2

C.R. Sun,2 M.M. Zoeller,2 G. Crawford,3 C. M. Daubenmier,3 R. Fulton,3 D. Fujino,3K.K. Gan,3 K. Honscheid,3 H. Kagan,3 R. Kass,3 J. Lee,3 R. Malchow,3 F. Morrow,3

Y. Skovpen,3\Lambda M. Sung,3 C. White,3 F. Butler,4 X. Fu,4 G. Kalbfleisch,4 W.R. Ross,4P. Skubic,4 J. Snow,4 P.L. Wang,4 M. Wood,4 D.N. Brown,5 J.Fast ,5 R.L. McIlwain,5

T. Miao,5 D.H. Miller,5 M. Modesitt,5 D. Payne,5 E.I. Shibata,5 I.P.J. Shipsey,5P.N. Wang,5 M. Battle,6 J. Ernst,6 Y. Kwon,6 S. Roberts,6 E.H. Thorndike,6 C.H. Wang,6 J. Dominick,7 M. Lambrecht,7 S. Sanghera,7 V. Shelkov,7 T. Skwarnicki,7 R. Stroynowski,7I. Volobouev,7 G. Wei,7 P. Zadorozhny,7 M. Artuso,8 M. Goldberg,8 D. He,8 N. Horwitz,8

R. Kennett,8 R. Mountain,8 G.C. Moneti,8 F. Muheim,8 Y. Mukhin,8 S. Playfer,8Y. Rozen,

8 S. Stone,8 M. Thulasidas,8 G. Vasseur,8 G. Zhu,8 J. Bartelt,9 S.E. Csorna,9Z. Egyed,

9 V. Jain,9 K. Kinoshita,10 K.W. Edwards,11 M. Ogg,11 D.I. Britton,12E.R.F. Hyatt, 12 D.B. MacFarlane,12 P.M. Patel,12 D.S. Akerib,13 B. Barish,13 M. Chadha,13S. Chan,

13 D.F. Cowen,13 G. Eigen,13 J.S. Miller,13 C. O'Grady,13 J. Urheim,13A.J. Weinstein,

13 D. Acosta,14 M. Athanas,14 G. Masek,14 H.P. Paar,14 J. Gronberg,15R. Kutschke, 15 S. Menary,15 R.J. Morrison,15 S. Nakanishi,15 H.N. Nelson,15 T.K. Nelson,15C. Qiao,

15 J.D. Richman,15 A. Ryd,15 H. Tajima,15 D. Schmidt,15 D. Sperka,15M.S. Witherell,

15 M. Procario,16 R. Balest,17 K. Cho,17 M. Daoudi,17 W.T. Ford,17D.R. Johnson, 17 K. Lingel,17 M. Lohner,17 P. Rankin,17 J.G. Smith,17 J.P. Alexander,18C. Bebek, 18 K. Berkelman,18 K. Bloom,18 T.E. Browder,18 D.G. Cassel,18 H.A. Cho,18D.M. Coffman,

18 P.S. Drell,18 R. Ehrlich,18 M. Garcia-Sciveres,18 B. Geiser,18B. Gittelman, 18 S.W. Gray,18 D.L. Hartill,18 B.K. Heltsley,18 C.D. Jones,18 S.L. Jones,18J. Kandaswamy,

18 N. Katayama,18 P.C. Kim,18 D.L. Kreinick,18 G.S. Ludwig,18 J. Masui,18J. Mevissen, 18 N.B. Mistry,18 C.R. Ng,18 E. Nordberg,18 J.R. Patterson,18 D. Peterson,18D. Riley, 18 S. Salman,18 M. Sapper,18 F. W"urthwein,18 P. Avery,19 A. Freyberger,19J. Rodriguez,

19 R. Stephens,19 S. Yang,19 J. Yelton,19 D. Cinabro,20 S. Henderson,20T. Liu, 20 M. Saulnier,20 R. Wilson,20 H. Yamamoto,20 T. Bergfeld,21 B.I. Eisenstein,21G. Gollin,

21 B. Ong,21 M. Palmer,21 M. Selen,21 J. J. Thaler,21 A.J. Sadoff,22 R. Ammar,23S. Ball, 23 P. Baringer,23 A. Bean,23 D. Besson,23 D. Coppage,23 N. Copty,23 R. Davis,23N. Hancock,

23 M. Kelly,23 N. Kwak,23 and H. Lam23

(CLEO Collaboration)

1

1University of Minnesota, Minneapolis, Minnesota 55455 2State University of New York at Albany, Albany, New York 12222

3Ohio State University, Columbus, Ohio, 43210 4University of Oklahoma, Norman, Oklahoma 73019

5Purdue University, West Lafayette, Indiana 47907 6University of Rochester, Rochester, New York 14627

7Southern Methodist University, Dallas, Texas 75275

8Syracuse University, Syracuse, New York 13244 9Vanderbilt University, Nashville, Tennessee 37235 10Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 24061 11Carleton University, Ottawa, Ontario K1S 5B6 and the Institute of Particle Physics, Canada

12McGill University, Montr'eal, Qu'ebec H3A 2T8 and the Institute of Particle Physics, Canada

13California Institute of Technology, Pasadena, California 91125 14University of California, San Diego, La Jolla, California 92093

15University of California, Santa Barbara, California 93106 16Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213

17University of Colorado, Boulder, Colorado 80309-0390

18Cornell University, Ithaca, New York 14853 19University of Florida, Gainesville, Florida 32611 20Harvard University, Cambridge, Massachusetts 02138 21University of Illinois, Champaign-Urbana, Illinois, 61801

22Ithaca College, Ithaca, New York 14850 23University of Kansas, Lawrence, Kansas 66045

(January 7, 1994)

Abstract Using the CLEO-II detector, we have obtained evidence for a new mesondecaying to D

0K+. Its mass is 2573:2+1:7

\Gamma 1:6 \Sigma 0:8 \Sigma 0:5 MeV/c2 and its width is16+5

\Gamma 4 \Sigma 3 MeV/c2. Although we do not establish its spin and parity, the newmeson is consistent with predictions for an L = 1, S = 1, JP = 2+ charmed

strange state. PACS numbers: 13.25.+m, 14.40.Jz

Typeset using REVTEX \Lambda Permanent address: INP, Novosibirsk, Russia

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Mesons whose quarks have one unit of orbital angular momentum exist in four states.In mesons with one heavy quark, models inspired by Heavy Quark Symmetry indicate we should consider the four states as two doublets [1,2]. The members of one doublet, whose lightquark's total angular momentum is j

` = 3=2 are relatively narrow; they have J P = 1+; 2+.The mesons in the other doublet, with j

` = 1=2 and J P = 0+; 1+, are predicted to be verybroad [2]. When the heavy quark is a charm quark, the light quark can be either an up,

a down, or a strange quark. Thus there should be 12 L = 1 charmed mesons: 6 relativelynarrow states and 6 broad states.

All of these narrow resonances have been observed [3,4], except for the charmed strangeJ P = 2+ meson, designated D

\Lambda +s2 [5]. The allowed decay modes of the D\Lambda +s2 are DK andD

\Lambda K, both proceeding through a D-wave. Because of the limited phase space, the latteris highly suppressed. Godfrey and Kokoski predict the partial width for the decay to DK

to be 6 to 10 times larger than for D\Lambda K [2]. The decay to D+s ss0 is forbidden by isospinconservation; modes such as D+

s ssss are OZI-suppressed. Thus we have searched for thedecays D\Lambda + s2 ! D0K+ and D

\Lambda 0K+. Throughout this paper charge-conjugate reactions areimplied.

The data used in this analysis were collected with the CLEO-II detector at the CornellElectron Storage Ring (CESR). The detector consists of a charged particle tracking system surrounded by time-of-flight (TOF) scintillation counters. These are followed by an electro-magnetic calorimeter, which consists of 7800 thallium-doped CsI crystals. The inner detector is operated in a 1.5 T solenoidal magnetic field generated by a superconducting coil. Finally,the magnet coil is surrounded by iron slabs and muon counters. A detailed description of the detector can be found elsewhere [6].The data were taken at center-of-mass energies equal to the masses of the \Upsilon (3S) and \Upsilon (4S), and in the continuum above and below the \Upsilon (4S). The total integrated luminosityis 2.16 fb

\Gamma 1. Events were required to have a minimum of five charged tracks and energy inthe calorimeter of at least 15% of the center-of-mass energy.

Specific ionization measurements from the main drift chamber and TOF measurementswere used to identify charged particles. Particles were required to pass a consistency cut for the hypothesis in question: kaon or pion. We define O/2 j ( \Delta QoeQ )2 + ( \Delta ToeT )2, where \Delta Q is thedifference between the measured and expected specific ionization for the hypothesis. Simi- larly, \Delta T is the difference between the measured and expected time for the same hypothesis.Time-of-flight information was only used when the track's polar angle with respect to the beamline, `, met the requirement j cos `j ^ 0:71. For a track to be considered a pion or kaoncandidate, O/2 ^ 6:25 was required for the corresponding hypothesis.

Energy clusters in the calorimeter not matched to a charged track and which had E *50 MeV were accepted as photon candidates. To reconstruct ss0's, we used pairs of photons from the "good barrel" region, j cos `j ^ 0:71, which has the best energy resolution, or onephoton from the "good barrel" and one photon from the "good endcap" region (0:86 ^ j cos `j ^ 0:94), which has nearly as good resolution. The invariant mass of the two photonswas required to be within 2.5 standard deviations of the ss0 mass; the ss0 candidates were then kinematically fit to the ss0 mass to improve momentum resolution. The ss0's usedto reconstruct D0's were required to have a minimum energy of 300 MeV; those used to reconstruct the decay D\Lambda 0 ! D0ss0 were only required to have an energy greater than150 MeV.

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We reconstructed D0's in the decay modes D0 ! K\Gamma ss+ and D0 ! K\Gamma ss+ss0. In bothcases, the D0 candidates were required to have a measured invariant mass within 1.65 stan- dard deviations of the observed D0 mass peak. The r.m.s. mass resolutions are 10 MeV/c2for the K

\Gamma ss+ mode and 14 MeV/c2 for the K\Gamma ss+ss0 mode. The decay angle, ffK

\Gamma , is definedas the angle between the K

\Gamma direction in the D0 rest-frame and the D0 direction in the labframe. We required D

0 ! K\Gamma ss+ candidates satisfy cos ffK

\Gamma ^ 0:8. This requirement is ef-fective in reducing the background because the signal is flat in cos ff

K

\Gamma , while the backgroundpeaks at 1.

In order to reduce the combinatoric background in the D0 ! K\Gamma ss+ss0 mode, a parameteris calculated for each D0 candidate, based on its position in the Dalitz plot. The parameter varies from 0 to 1, and depends on the square of the amplitude for decay to the observedlocation in the Dalitz plot. The calculation takes into account the three most important two-body decays and the non-resonant three-body decay which feed into this final state [7].The two-body decays included are K

\Gamma ae+, K\Lambda \Gamma ss+ and K\Lambda 0ss0. We require that the parameterbe greater than or equal to 0.1. The efficiency of this cut was determined from the inclusive

D0 ! K\Gamma ss+ss0 sample.The D0 candidates were then combined with each positively charged track consistent with being a kaon. In the search for D\Lambda +s2 ! D0K+, there are several sources of backgroundto consider. There is combinatorial background from the various combinations of real and "fake" D0's with real and "fake" K+'s. The "fake" D0's are incorrectly reconstructed D0candidates; the "fake" K+'s are misidentified tracks, mostly pions. The background from real D0's and fake K+'s includes a component from the decay of the D\Lambda J (2470)+ to D0ss+. If thesepions are misidentified as kaons, the D0K+ mass reconstructed is "reflected" into the mass region near our expected signal. This contribution to the background has been measured byrecalculating the energy of the K+ tracks using the pion mass and the measured momenta. The new momentum-energy four-vectors were then combined with our D0 candidates. Weobserved a peak near 2470 MeV/c2 in the D0ss+ mass distribution. Fitting the peak, we found 27 \Sigma 21 events in the K\Gamma ss+ mode and 23 \Sigma 16 events in the K\Gamma ss+ss0 mode. Using a MonteCarlo simulation, we have parameterized a shape for this reflected D

\Lambda J (2470)+ backgroundwhich will be included in our fits to the data. No other resonance was observed in the D

0ss+mass distribution; in particular there was no peak from partially reconstructed D

J (2440)+'s.The widths of the j ` = 1=2 mesons are predicted to be very large [2], and thus should notsignificantly modify the shape of the background.

To reduce the background from misidentified pions, we imposed an additional ID require-ment on the K+ track. We required that the O/2 for the pion hypothesis for this track be at least 2 units larger than that for the kaon hypothesis. The effectiveness of this cut wasevaluated using the D

s1(2536)+ feed-down peak described below. The cut has an efficiencyof 79 \Sigma 10%, while reducing the background by about a factor of three.

The decay angle, ffK+, is defined as the angle between the direction of the K+ in theD0K+ rest-frame and the D0K+ direction in the lab frame. We required that the D0K+ combinations have cos ffK+ ^ 0:8. This reduces the combinatoric background which peaksnear cos ff

K+ = 1, and also eliminates some of the background from the D\Lambda J (2470)+. Thedistribution of the signal events in this angle is unknown, except that it must be symmetric

about cos ffK+ = 0. Our overall efficiency for reconstructing the D0K+, D0 ! K\Gamma ss+combinations is 29 \Sigma 4%. The efficiency for reconstructing the D0K+, D0 ! K

\Gamma ss+ss0

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combinations is 8:9 \Sigma 1:4%.Finally, to reduce the background, we take advantage of the hard fragmentation of contin- uum charm and impose a cut on the x of each D0K+ combination. We define x j p=pm andp

m j fE2beam \Gamma [M (D0K+)]2g1=2. For the K\Gamma ss+ mode, we require x * 0:7; for the K\Gamma ss+ss0mode we require x * 0:8 because of the larger combinatoric background. The D0K+ combi-

nations passing all of the above criteria are shown in Fig. 1. To improve the mass resolution,we calculated the "corrected" mass, M

\Lambda j M (D0K+) \Gamma M (D0) + 1864:5 MeV=c2, using themeasured invariant masses and the known D

0 mass.Two features are prominent in Fig. 1: a feed-down peak from the D

s1(2536)+ at about2392 MeV/c2, and a broader peak near 2575 MeV/c2, which is a new resonance. Each of

these is discussed below.The feed-down peak at 2392 MeV/c2 is from the D

s1(2536)+, the narrow cs 1+ state. Itdecays predominantly to D \Lambda K. The Q value for the D\Lambda 0 ! D0ss0 decay is very small, soeven though the ss

0 is not detected, the peak at 2392 MeV/c2 is still very narrow.Also shown in Fig. 1 is a histogram of M

\Lambda for (K\Gamma ss+)K+ and (K\Gamma ss+ss0)K+ combi-nations, where the K \Gamma ss+ and K\Gamma ss+ss0 combinations were chosen from the D0 mass side-bands. The K \Gamma ss+ combinations were chosen from 1800.0 to 1816.5 MeV/c2 and 1912.5 to1929.0 MeV/c 2. The K\Gamma ss+ss0 combinations were chosen from 1777.0 to 1800.0 MeV/c2 and1927.0 to 1950.0 MeV/c

2. This histogram suggests that about half of our background comesfrom fake D 0's; the other half must come from real D0's combined with real and fake K+'s.There appears to be some signal in the sideband histogram under both the feed-down peak

and the new resonance. This is due to D0 ! K\Gamma ss+ss0 events in which a poorly measuredphoton, or the wrong photon, was used to form the ss0. We have corrected for this effect in the cross-section calculation below. The mass and width measurements are not significantlyinfluenced by this effect. We have also examined the wrong-sign combinations, D0K

\Gamma , andsee no enhancements in the invariant mass distribution of such combinations.

To extract the mass and width of the new resonance, we fit the M \Lambda distribution for theD 0K+ combinations, as shown in Fig. 2. The fits were done separately for the two D0 decaymodes. To parameterize the signal we used a spin-2 relativisitic Breit-Wigner convoluted

with a Gaussian of fixed resolution. The r.m.s resolution, oe, was determined by a MonteCarlo simulation.

For the D0 ! K\Gamma ss+ events the Gaussian had oe = 3:2 MeV/c2. The background, inthe mass range from 2430 to 2750 MeV/c2, was fit with a first-order polynomial, plus the D\Lambda J (2470)+ background function with a fixed area of 27 events. The fit finds 116+30\Gamma 26 signalevents. The mass is 2573:3+2:2

\Gamma 2:1 MeV/c2 and the natural width is 15:6+6:5\Gamma 4:8 MeV/c2 (statisticalerrors only). We fit the D0 ! K

\Gamma ss+ss0 data using the same fitting functions, but withoe = 3:7 MeV/c

2. The number of D\Lambda J (2470)+ background events was fixed at 23. We find101 +29 \Gamma 23 signal events. Using this mode, the mass is measured to be 2573:1+2:7\Gamma 2:3 MeV/c2, andthe natural width to be 17:6+9:0

\Gamma 6:0 MeV/c2 (statistical errors only), in good agreement withthe first mode.

Although the fits were done separately for the two D0 decay modes, the data are combinedin Fig. 2 with the sum of the fitting functions. The complete signal and background fit is

shown by the solid line. The total background is shown by the dashed line. The dottedline shows the polynomial representing the combinatoric background. The shape of the D\Lambda J (2470)+ background, with the area scaled up by a factor of 5, is shown at the bottom by

5

the dash-dot line. The total signal has a significance of more than six standard deviations.Following the nomenclature of the Particle Data Group for a meson of unknown spin [5], we will use the temporary designation "D\Lambda sJ (2573)+" for this new resonance. We estimate thesystematic error on the D

\Lambda +sJ -D0 mass difference to be \Sigma 0:8 MeV/c2 and on the width to be\Sigma 3 MeV/c

2. This includes contributions from varying the assumed mass resolution and spin,the mass of the D

\Lambda J (2470)+ and the number of events it contributes to the background, theorder of the polynomial used for the combinatoric background, the binning, and other details

of the fitting. The largest contribution to the systematic error on the width, \Sigma 1:8 MeV/c2,comes from varying the order of the polynomial used to fit the background. The next largest, \Sigma 1:5 MeV/c2, comes from the uncertainty in the number of D\Lambda J (2470)+ events in thebackground. The latter also contributes the majority of the systematic error on the mass: \Sigma 0:6 MeV/c2. These systematic errors are common to both D0 decay modes. Averaging thetwo sets of values, we find that the D

\Lambda +sJ has a natural width of 16+5

\Gamma 4 \Sigma 3 MeV/c2 and a massof 2573:2+1:7

\Gamma 1:6 \Sigma 0:8 \Sigma 0:5 MeV/c2, where the third error on the mass is due to the uncertaintyin the D0 mass.

Our width measurement implies that this new state decays strongly. Assuming this is so,angular momentum and parity conservation require that its spin-parity be in the so-called

"normal" series: 0+, 1\Gamma , 2+, 3\Gamma , etc.To measure the production cross section for x * 0:7 times the branching ratio to D0K+, we have remeasured the yield in the second decay mode with the x cut reduced to 0.7. Wehave also removed our cuts on cos ff

K+ in both modes, since the distribution of the signalevents in this variable is unknown. For the D0 ! K

\Gamma ss+ss0 mode, the number of events wasreduced by 22% to account for the peaking of the background under the signal. An error

of 9% was included in the systematic error to account for the uncertainty in this correction.Using the recent CLEO measurement of B(D0 ! K

\Gamma ss+) = 3:91 \Sigma 0:19% [8], the ParticleData Group's value for the ratio B(D

0 ! K\Gamma ss+ss0)=B(D0 ! K\Gamma ss+) = 3:10 \Sigma 0:26 [5] andour measured luminosity of 2:16 \Sigma 0:02 fb

\Gamma 1, we find that for x * 0:7, the cross sectiontimes branching fraction is oe(x * 0:7) \Delta B(D

\Lambda +sJ ! D0K+) = 4:4 \Sigma 0:9 \Sigma 0:7 pb. The firsterror reflects the uncertainty in the number of events, both statistical and systematic. It was

calculated separately for the two modes and averaged. The second error is the systematicerror common to both modes and is dominated by the uncertainty in the efficiencies.

We have also searched for the decay of this new resonance to D\Lambda 0K+, D\Lambda 0 ! D0ss0. Thismode is allowed for the D

\Lambda +s2 , but expected to be highly suppressed by the limited phasespace. We used the same D

0 decay modes and similar cuts as in the previous analysis. Inaddition, we consider the helicity angle of the ss

0 from the D\Lambda 0 decay. The helicity angle, `ss,is defined as the angle between the D \Lambda +sJ and the ss0, both measured in the D\Lambda 0 rest-frame.For any meson with spin-parity in the "normal" series, the helicity angle of the ss

0 from theD \Lambda 0 decay must have a sin2 `ss distribution. We require j cos `ssj ^ 0:75.We find no signal above background and set the following limit on the ratio of branching

fractions:

B(D\Lambda sJ (2573)+ ! D\Lambda 0K+)B(D

\Lambda sJ (2573)+ ! D0K+) ! 0:33

at the 90% confidence level. For the D\Lambda +s2 , this ratio is predicted to be , 0:1-0.16 [2].

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In summary, we find a signal with a signifcance of more than six standard deviations fora meson decaying to D0K+. The mass and natural width of the new state are measured to be 2573:2+1:7\Gamma 1:6 \Sigma 0:8 \Sigma 0:5 MeV/c2 and 16+5\Gamma 4 \Sigma 3 MeV/c2 respectively. Though its spin-parity isnot established, it must be in the "normal" 0+, 1

\Gamma , 2+, 3\Gamma : : : series. We tentatively identifythis state as the

D\Lambda +s2 , the 2+ partner of the Ds1(2536)+. It is 38:1+1:7\Gamma 1:6 \Sigma 0:8 MeV/c2 heavierthan the D+ s1, which has J P = 1+ [4]. This splitting is comparable to that seen betweenthe D 1(2420)0 and the D\Lambda 2(2460)0, the neutral 1+ and 2+ states. Thus the D+s1 and this newresonance appear to form a similar doublet. Its width is inconsistent with that predicted

for a 0+ state, while both its width and decay modes are consistent with predictions for theD

\Lambda +s2 [2].We gratefully acknowledge the effort of the CESR staff in providing us with excellent

luminosity and running conditions. This work was supported by the National Science Foun-dation, the U.S. Dept. of Energy, the Heisenberg Foundation, the SSC Fellowship program of TNRLC, and the A.P. Sloan Foundation.

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REFERENCES [1] N. Isgur and M.B. Wise, Phys. Rev. Lett. 66, 1130 (1991).[2] S. Godfrey and R. Kokoski, Phys. Rev. D 43, 1679 (1991). We have recalculated the

relative widths for D\Lambda +s2 ! DK and D\Lambda +s2 ! D\Lambda K using the measured meson masses.[3] ARGUS Collaboration, H. Albrecht et. al., Phys. Rev. Lett. 56, 549 (1986); Phys. Lett. B 230, 162 (1989); Phys. Lett. B 231, 208 (1989); Phys. Lett. B 232, 398 (1989); E691Collaboration, J. C. Anjos et. al., Phys. Rev. Lett. 62, 1717 (1989); CLEO Collaboration, P. Avery et. al., Phys. Rev. D 41, 774 (1990).[4] CLEO Collaboration, J. P. Alexander et al., Phys. Lett. B 303, 377 (1993). [5] Particle Data Group, K. Hikasa et. al., Phys. Rev. D 45, S1 (1992).[6] CLEO Collaboration, Y. Kubota et. al., Nucl. Instrum. Methods Phys. Res., Sect A 320,

66 (1992).[7] E691 Collaboration, J. C. Anjos et. al., Phys. Rev. D 48, 56 (1993). [8] CLEO Collaboration, D. S. Akerib et. al., Phys. Rev. Lett. 71, 3070 (1993).

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FIGURES FIG. 1. M \Lambda , "corrected" invariant mass, of (K\Gamma ss+[ss0])K+ combinations. Data points arefor

K\Gamma ss+[ss0] combinations in the D0 signal region; the histogram shows M \Lambda for (K\Gamma ss+[ss0])K+combinations where the K

\Gamma ss+[ss0] combinations were chosen in D0 sidebands.

FIG. 2. Histogram of M \Lambda (D0K+), with fit. The solid line shows the complete signal andbackground fitting functions. The sum of the background functions is shown by the dashed line. The dotted line shows just the polynomial used to represent the combinatoric background. Theshape of the D

\Lambda J (2470)+ background function is shown at the bottom by the dash-dot line, withthe area scaled up by a factor of 5.

9

