OBSERVATION OF A 0++(750) GLUONIUM CANDIDATE IN MEASUREMENTS OF πN ↑ →π+π-N ON POLARIZED TARGET AT 6, 12 AND 17.2 GeV/c

HAL Id: jpa-00224546

https://hal.archives-ouvertes.fr/jpa-00224546

Submitted on 1 Jan 1985

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

OBSERVATION OF A 0++(750) GLUONIUM

CANDIDATE IN MEASUREMENTS OF π N ↑ → π +π-N ON POLARIZED TARGET AT 6, 12 AND 17.2 GeV/c

M. Svec

To cite this version:

M. Svec. OBSERVATION OF A 0++(750) GLUONIUM CANDIDATE IN MEASUREMENTS OF

πN ↑ → π+π-N ON POLARIZED TARGET AT 6, 12 AND 17.2 GeV/c. Journal de Physique Collo-

ques, 1985, 46 (C2), pp.C2-281-C2-284. �10.1051/jphyscol:1985232�. �jpa-00224546�

JOURNAL DE PHYSIQUE

Colloque C2, supplement au n°2, Tome *6, fevrier 1985 page C2-281

OBSERVATION OF A 0

( 7 5 0 ) GLUONIUM CANDIDATE IN MEASUREMENTS OF ITNI^TT

TT

N ON POLARIZED TARGET AT 6 , 12 AND 1 7 . 2 G e V / c

M. Svec

Département de Physique des Particules Elémentaires, Centre d'Etudes Nucléaires, Saclay, France

Résumé - Des mesures de la réaction ilN^.—JTT H N, sur cible polarisée, à 6, 12 et 17,2 GeV/c fournissent une évidence pour l'existence d'un nouvel état résonnant 0 (750) avec une largeur de désintégration TT TT de 100 MeV ou moins. Le méson 0 (750) est mieux ^compris comme étant l'état gluonium 0 (gg) de plus basse masse.

Abstract - Measurements of "trN,,.—>T IT N reaction on polarized target at 6, 12 and 17.2 GeV/c provide evidence for a new resonant state 0'*"

'(750) with a TT*it" decay width of 100 MeV or less. The 0*

(750) meson is best understood as the lowest mass 0

(gg) gluonium state.

We performed a model independent amplitude analysis of the Saclay data on tr^Ti^—»ir*ir" p at 6 and 12 GeV/c and the Cern-Munich-Cracow data on n'p^.— 9 ir*ir" n at 17.2 GeV/c. These experiments with transversely polarized targets enable to separ- ate the S-wave contribution from other angular momentum states in IT IT production without model dependent assumptions. For dipion mass m ;S 1 GeV only S - and P-waves contribute to the TT Tl~ angular distribution. We obtain two sets of solutions (Solutions 1 and 2) for the moduli squared of the S - and P-wave transversity ampli- tudes with similar t-structure and m-dependence in both solutions. A complete account of this work will be published elsewhere. Here we report only our results concerning the S-wave amplitudes \SI and |sl corresponding to recoil nucleon transversity "up" and "down" with respect to the scattering plane.

The amplitudes | S| and \ S1 show resonant structures around 730 or 750 MeV in both solutions at all energies (Figure 1 ) . We calculate the S-wave partial wave cross-section Ig=|S| + |s|

for all four combinations of solutions to obtain Is (1,1) Ig(l,2), Ig(2,l) and Ig(2,2). To compare their shapes we present in Figure 2 the values of Ig normalized to 1 at their maximum values. All combxantions for Ig at a given energy show similar resonant shapes around 750 MeV. The width of this 0

(750) resonance is 100 MeV or less at larger momentum transfers. The contribution of the S-wave to the total irir" production at 750 MeV is in the range from 8-16% for I

(l,l), and from 20-40% for Is(2,2). This ambiguity in the decay rates of 0

(750) and J>°(770) into IT it" cannot be resolved by data on polarized target only. The solutions

for Ig in it N—> IT " N based on model dependent analyses of unpolarized data show no resonant structure

' . Several previous model dependent analyses of rf*tt~ production data on unpolarized and polarized target did suggest a possibility of a 0* reso- nance around 750 MeV.

The observed 0 (750) state is too light to be a qq state. The mass M of a qq state increases with its angular momentum L: M=M (2n+L) where n is the degree of radial excitation. The lowest mass L-=0 states are the J

=0~"

" and 1 nonets. Sca- lar mesons O^which are P

qq states have masses expected to be around 1000 MeV or higher. The established scalar mesons are 1-1 state S(975) and 6(1300), 1=1 state

£(980) and 1=4 state *C(1350). They are understood to be

P

qq states (with qqqq

Permanent address : Dawson College and McGill University, Montreal, PQ, Canada

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985232

C2-282 JOURNAL DE PHYSIQUE

i + n - *+*-p

I I I

I I

Plab=5.88 GeVIc. . 2 L l l l L . 4

SACLAY Fig. 1 ~ o d u l i square9 of thz wo

--- S-"ave amplitudes IS, and IS, 5

I S l2 Solution 2

for recoil nucleon transversities

"up" and "down" relative to the

.5- ^- scattering plane. The amplitudes

are normalized to 1 at their maxi- mum values in order to compare

I their shape and mass dependence.

I I

I S l2 solution t

.5 -

0 .

*+n- *+*-p

PI, =11.85 GeVlc. . 2 L I t l L .4

1s12 Solution 2

. 5 -

0 'I

lS12so~ution t I

.5 -

Plab=17.2 GeVIc. , 0 0 5 ~ l i l L .2

.5 ^-

0 , I ^{I I}

.5-

0 I I

I

.5 .7 .9 .5 .7 .9

rn (?T+?T-),G~v

Fig. 2 S-wave artia3 cross- sections I = ( S I B + (?I normali- zed to 1 a? their maximum value.

The amplitude analysis gives a 4-fold ambiguity. All four so- lutions have a similar shape at each energy. The comparison is made with data on IS(rrti7-+ nod)

from ref.4. Note that the cross sections I (Tf~+rr% N) are in the physical region of t an S 9

not extrapolations to t=+m,. .

1.0 -Plab=17.2GeVc. .OOSLltIL.2 CERN- MUNICH- CRACOW

.8 ^- - .6 ^-

.4 ^- -

. * - + t t

^Is (1.21~2.068

--a- fs (2.1)x1.181

c2-284 JOURNAL DE PHYSIQUE

components) and populate the 0"quarkon.um should be a qqqq state in the MIT model ? . nonet3. It was suggested that oC+(700) However a detailed stud of qqqq systems conclude that pure multiquark hadrons do not existB. with n+f decay Zi . We also ex- clude the possibility that 0*(750) is a hybrid state qqg. The 'lowest mass hybrid state must be 0 or 1 . Calculations based on bag models, QCD sum rules, latqge QCD and a string model all estimate the masses of 0++(qGg) states above 1500 Me\ .

Lattice QCD calculations by several all conclude that the gluonium ground state 0++ has a mass nearpO meson: 740 * 40 eV. In bag models an adjust- ment of parameters yields a close results of 780 M e V 1 ' . The 100 MeV width f the w(750) state is also consistent with the standard glueball phenomenology1'. The credibility of lattice QCD calculations i~~strengthened by the restoration of Lorentz invariance in the continuum limit , small finite-size effects in calcula- tions of 0+* and 2*+ masses on large lattice$%nd satisfactory predictions ofpO,

KO* and K masses19. We thus propose to identify the observed 0++(750) meson with

the o'+(~~) gluonium ground state. Since the calculated and observed masses are so

close we also conclude that 0++(750) has no qq content or only a weak q { mixing.

Reaction pp -, plr+n-p was measured2' at ISR in a search for scalar gluonium states, The pronounced structures at'm(r?1~-)s750 MeV reported in the S - and P-wave interference moments H(11) and H(31) are consistent with 0+'(750) and p0 (770) interference. The experiment does not separate the S - and P-wave amplitudes and averages over the five S-wave amplitudes involved. Consequently it is not a con- clusive study. The anomalous energy dependence of pp and np elastic polarizations and the departure from mirror symmetry inTTN elastic olarizations at intermediate energies require a lorlying vacuum Regge trajectory2' corresponding to the 0++(750) meson. These anomalous structures in the polarization data may be the first evi- dence for gluonium exchange in two-body reactions.

I am very grateful to L.van Rossum for many valuable discussions and encourage- ment in this work. I like to thank A.de Lesquen, A.Penzo, H.Navelet and J.Soffer for interesting comments and the CERN-Munich-Cracow collaboration for their data.

This work was supported by Fonds F.C.A.C., Minist'ere de 1'Education du Qu6bec, Canada and, in part, by Commissariat 2 llEnergie Atomique, CEN-Saclay, France.

References

DE LESQUEN A. et al., Measurement of the reaction rr*n+-?~+rr-~ at 5.98 GeV/c and 11.85 GeV/c using a transversely polarized target. Phys. Rev. D, to appear BECKER H. et al., Nucl. Phys. =(1979)310, =(1979)46

PARTICLE DATA GROUP, Rev. Mod. Phys. 56(1984)p.S159 CASON N.M. et al., Phys. Rev. ~ ( 1 9 8 3 1 5 8 6 ESTABROOKS P. et al., AIP Conf. Proc. 2(1973)37 DONOHUE J.T., LEROYER Y., Nucl. Phys. =(1979)123 JAFFE R.J., Phys. Rev. =(1977)267

BICKERSTAFF R.P., MCKELLAR B.H., Z. Phys. =(1982)171 WEINSTEIN J., INSGUR N., Phys. Rev. =(1983)588 LIU B.A., LIU K.F., Phys. Rev. =(1984)613 CLOSE F.E., Nucl. Phys. m(1984)55c ISHIKAWA K. et al., Phys. Lett. =(1982)429

ISHIKAWA K. et al., Z. Phys. %(1983)327, -(1983)167 BERG B., BILLOIRE A., Nucl. Phys. 3(1983)109 HAMBER H.W., HELLER URS M., Phys. Rev. m(1984)928 HANSSON T.M. et al., .Phys. Rev. =(1982)2069

FRITZCH H. , MINKOWSKI O., Nuov. Cim. 3OJ(1975)409 KIMLTRA N., UKAWA A., Nucl. Phys. =(1982)637 SCHIERHOLZ G., TEPER M., Phys. Lett. =(1984)69 SCHIERHOLZ G., TEPER M., Phys. Lett. =(1984)64

FUKUGITA M., KANEKO T., UKAWA A., Nucl. Phys. =(I9841637 AKESSON et al., Phys. Lett. =(1983)268

DASH J.W., NAVELET H., Phys. Rev. =(1976)1940

GIRARDI G., NAVELET H., Phys. Rev. m(1976)280