The status of strangeonium spectroscopy is re-assessed following our recent high statistics study of K/sup /minus// induced hypercharge exchange reactions. The implications of our results for the status of glueball, or otherwise exotic, candidates observed in the same decay modes but produced by different mechanisms are also discussed. 11 refs., 8 figs

Aston, D.

Awaji, N.

Bienz, T.

Bird, F.

D'Amore, J.

Dunwoodie, W.

Endorf, R.

Fujii, K.

Hayashii, H.

Iwata, S.

UNT Digital Library

H<? SLAC-PDB—4768 DE89 006066 THE STRANGEONIUM SPECTRUM SEEN IN LASS; IMPLICATIONS FOR GLUEBALL SPECTROSCOPY* D. Aston,1 N. Awaji 2 T. Bienz,1 F. Bird,1 J. D'Amorc,3 W. Dunwoodit,1 R. Endorf.3 K. Fujii,2 H. Hayashii,2 S. lwaia,2 W.B. Johnson,1 R. Kajilcawa,2 P. Kunz.' D.W.G.S. Leilh,1 L. Levinson,1 T. Matsui,2 B.T. Meadows,3 A. Miyamoto.2 M. Nussbaura,' H. Ozaki,2 C O . PakT2 B.N. Ratcliff,1 D. Schultz.' S. Shapiro.1 T. Shinmnura,2 P. K. Sinervo,1 A. Sugiyama 2 S, Suzuki,2 a Tamopolsky,1 T. Tiuchi,2 N. Toge,1 K. Vksi* A. Waite,' S. Williams' ^Stanford Linear Accelerator Center, Stafford University, Stanford, California 94309 2Sagoya University, Furo-cho, Ckikusa-ku, Nagoya 464, Japan University ofCirxitvuui. Cincinnati, Ohio 4522 J institute for Nuclear Study, University of Tokyo, Midori-cho. Tokyo IS8, Japan ABSTRACT The status of strangeonium spectroscopy is re-assessed following our recent high statistics study of K~ induced hypcichargc exchange reactions. The implications of our results for the status of glueball, or otherwise exotic, candidates observed in the same decay modes but produced by different mechanisms arc also discussed. INTRODUCTION As recently as 1986.' only the l\tt\\ 0(1020) and ft 1525) were clearly estab­lished as ss members of comptae meson nonets predicted by the quark model. The •/1850) was a good candidate for the 3 - nonet, although us spin was undetermined. With the exception of the ground state t\tr\', calculation of the octet-singlet mixing an­gles gives values close to the magic value of 35°. so that these states have almost pure s quark content. The f,(1420). or E meson, had been assigned to die J p c = l + + nonet, although there was considerable doubt about its spin-parity EXPERIMENTAL DETAILS This talk reviews the analyses of three hyperchargc exchange reactions from a 4,1 event/no sample of 11 GcV/c K~p interactions detected in ihe LASS spectrometer at SLAC.2 The spectrometer is situated in a clean RF separaicd beam, has an efficient trigger for final stales with 22 charged panicles and a flat acceptance over the fall solid WntwuponedrnpanbyiheDepanrntMorEnagyund^fCOmraciNu D£ ACM-lbSFOOSlS.uv Nation! Science Famdatton under g-aw Not PHY82-09I44, PHY85-138CB. and Ihe Japan U.S. Cooperative Research Project on High Energy Physics Invited talk presented by D Aston at the BNL Workshop on Clueballs, Hybrids, and Exotic Hadrons. August 29Septe,*ber 1,1988 0*. angle. Efficient track-finding and topology reconstruction combined with good pani­cle identification and application of geometric and kinematic constraints at all decay vertices enabled us to find clean data samples of the reactions: K'p -» K" K+A (1) K- p -» K? K? A (2) K" p -» K + K J J ^ A (3) In each case, all V° decay products arc fully reconstructed. All these final states are dominated by hypercharge exchange production of a forward meson system at small momentum transfer t ' s l i - i m m l from the incident beam. Space constraints permit only a brief description of the analyses; further details can bt found in Refs 3—4, 5 and 6 for reactions (I), (2) and (3) respectively, and in the talk of Blair Ratcliff7 else­where in these proceedings. ss RESULTS The production mechanism is extremely important for selecting si states; the meson final state is not necessarily a good indicator. For example, the K~K+ spectrum produced in reaction <l> is totally different from that produced at a similar energy by charge exchange with a rr beam", Hypercharge exchange produces dominantly 1 = 0 ss" stales in reactions (1—3). Figure 1 shows the KK spectra from reactions (1) and (2): the fit 1525) is clearly seen in both reactions and dominates the K°K£ spectrum Sine: there is no Bose-Einsiein restriction to even spin, the K - K + spectrum also shows a large <t»(1020) and evidence of the $;{ 1850). The corresponding Dalilz plots (Fig 2) show that the continuum in K"1C above -1,7GeV/c2 is largely due to drffractive production of N*—>K+A. As expected, there is no evidence of such a mechanism in Fig. 2b. Figure 3 shows the results of a spherical harmonic moments analysis in the Got­tfried-Jackson frame of the low t'data from reaction (I) above the fad525). The peak at ~1.85GeV/c2 in the moments up to L = 6 , but not higher, clearly demonstrates that the4>j(]850) has spin 3. There is also some activity around 2.2GeV/c2 in all moments up to I- = 8; moments with L > 8 (not shown) are consistent with 2ero A complete amplitude analysis of the %(1850) region at both low and high t' show;, that these dam arc consistent wi:h a simple model where the leading F-wave interferes with an imaginary diffractive background as iiggested by the Dalitz plot. Figure 4 shows lin­ear combinations of the moments which in this model arc dominated by interferences between the leading F-wave and S. P and D amplitudes- The superimposed curves arc a fit to the model which gives (^(1850) parameters consistent with fits to I § and the F wave extracted from the amplitude analysis (see Fig. 13 of Kef. 7). , MASTER^ fjHi-rflt'T.iTinnjrr-w'f: - ^ * ! " , f , , T i r U W L P " T " Fig. 1. The KK mass spectra from Fig. 2. The DaliU plots from (a) reaction (a) reaction < I) and (b) reaction (2). (1J and (b) reaction <2). Wc have exjended this model to the high mass data and find thai the effect at 2 2 GeV/c 3, as suggested by the vanishing 1. > 8 moments, is consistent with a leading C-wave interfering with a similar background. Figure 5 shows the constructive interference terms with S. P, D and F ampli­tudes; their sum (Fig. 14 of Rcf. 7) shows a signal in the 2 16—2.280cV/c 2 range with significance -3o\ while the t'^and tg moments differ from zero by 3 3 and 2.3o respectively over the same range S u c h a J p c = 4 + + stale, ihe r.li22IO), has nmi and width consistent with those of the X(222(l) seen by the Mark III collaborationy and fits well as the si member of the 4* nonet predicted by the quark model It should alsu be noted that our data f'om reaction (2i in this mass region are consistent with the K?Ks spectrum seen by the Mark III and I>M2 collaborations in radiative INf decay A similar comparison of the low mass spectrum from reaction £2} shows the striking absence of the f;( 17201 from our data, strongly suggesting that this state is not a conventional ss meson Amplitude analysis of the fjt 1525} region reveals evi-t AOL ZOO 4 0 0 3 JJ 200 in 3 0 0 20O 100 -100 T 1 1 r A '••*S*V J 1 1 V-<0A»* J i — i » •? AV* _L _L " 1 1 1 1 -»5 J 1 I L w* J _ _l_ a. j _ 1 1 1 1 1 I i 1 _ •*.• (yV»i J 1 I L ^WW .6 >B 2 0 2.2 2 4 16 1 8 2 0 2 t 2 A I 6 l.S 2.0 2 2 2 4 m i n i Pig. 3. The unnonnalised M = 0 KK moments from reaction (1) above the fit 1525) with i'< O^tGeV/c)2 required, dence for an underlying S-wave, shown in Fi£. 12a of Rcf. 1 v*hich, though poorly measured, is significant at the 50 level and is produced wath a cross-section consisicnt wild expeciaiion for the underlying ss~ 0 + + tnplct state Finally, the threshold region shown in Fig, 6 has a surprising duster of six events below 1.03GeV/c ;. Although not inconsistent with the fo<975j, the pole on the real axis inferred by Au et al '" from the KK and nit S-wave scattering data provides a better description of these events at the 90% confidence level Figure 7 shows the total KKit mass spectrum from reactions (3), Its dominant features are a sharp rise at K*K threshold and an enhancement in the region of the f ;< 1530) 11 There is little evidence of the ^{1420} or the TH1440). and just a few •<r.s;>' R*(f,F;w u i.ii i 1—_J—Li * t . . . . j . . ftt(F,l£>- I t it. •ex • • * ' 17 U IB i IT I I i t 2 I t ID I I Z M E - r (GeV/e*) Fig 4. Moments sums from reaction (1) dominated by leading F-wavc interference terms according to the model described in the texi. events consistent with the ft(128S). A three body PWA reveals that production of J P=1 H K* waves dominates below 1.6GeV/c2. There is evidence of interference between the K* bands which begins destructively at K*K threshold, but becomes constructive by -1.46 GcV/c2. This effect is seen quite clearly in the Dalitz plots of Fig. 8 and was aho present in the data of Ref. 11. By combining the 1 + waves into G-parity eigenstates (see Fig. 15 b-c of Ref 7) and using the fact that C = G for I - 0 stai-s. we infer the existence of a J F C = J + - Ss s t a t e > t h c hi(1380). right at K*K threshold and confirm the ^ f}( 1530). These states complete the two 1 + nonets expected in the quark model and are consistent with having large ss content. It is intriguing that if we then assume, magic mixing for these nonets, the cal­culated Masses of the K] states arc very close to the physically observed masses. t I * ! H* • • • * c o i—- • -^ I M | "*f V L. I— 2* : * f ' 0 •V. *r d ' . ' o " "ft/^1t r n ' Y"i ° k i I: ! 2.c ;.; : ?/» 2,c .".: »•: .• "K «• ^ « v t ! . . „ , . . Fig. 5. Moments sums from reac­tion (1) dominated by leading G~ wave interference terms according to the model descr .bed in the text o O a C v & • J J i " - 1 1 1 _.—1 1 , l — . 1 1 M K ; K ; < G ' V / ^ ) Fig. 6 The KK threshold icgion o."reaction (2) CONCLUSIONS The leading natural J* nonets up to 4 + all now have good candidates for their mainly ss members; in each case the masses are consistent with magic mixing. There arc also now two strong candidates to be the strangeonium members of the I + nonets. 5 the fi<mf>) and hf(l380). The possibility of an ss scalar underneath the fid525) suggests a normal pattern of mass splittings for this nonet also. However, there arc too many 0 + mesons! The X(2220) may well be a conventional ss" state, but there is strong evidence that the fid420), n( 1440) and fi(1720) are not. O - i L If-k z i i ; 0 ^.^_k. >4 •£ 18 2 0 Fig. 7. The KKJI mass spectrum from reactions (3). 12 10 06 06 \ 04 > « o 1 2 08 0 6 04 1 3 4 c U I K . < l 46 •+- . ( -1 4 6 < y n . < 1 58 0 4 0 6 0.8 1 1 2 M | w (CeV/c*)8 Fig 8. KKir. Dalitz plots from reactions (3) near K*K threshold. REFERENCES 1. Particle Data Group, Phys. Lett. 170B, (1986). 2. D. Aston etal,. The LASS Spectrometer, SLAC-REP-298, (1986) 3. D. Asion c: al., Phys. Lett. 208B. 324, (1988). 4. D. Aston et al., DPNU-88-24 / SLAC-PUB-4661 (1988). 5. D. Aston et al., Nucl. Phys. B301. 525. (1988) 6. D. Aston et al.. Phys. Lett. 201B. 573. (1988). 7. Talk by B. Ratcliff elsewhere in these proceedings and SLAC-PUB-4709 (1988). 8. C Evangclista et al., Nucl. Phys. B154, 381. (1979). 9. R M. Baltmsaitis et al., Phys. Rev. Lett.. 56, 107, (1986). 10. K. L. Au. D. Morgan and M. R. Pennington. Phys. Rev. DJ5. 1633, (1987). 11 Ph. Gavillei et al.. 2. Phys. C16, 119. (1982). (> 

The strangeonium spectrum seen in LASS; implications for glueball spectroscopy

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The strangeonium spectrum seen in LASS; implications for glueball spectroscopy

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