HUNGARIAN ACADEMY OF SCIENCESCENTRAL RESEARCH INSTITUTE FOR PHYSICS 13/1969 /Ас Эо. 33 ^

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/А с Эо. 3 3 ^

KFKI

13/1969

A REMARK O N THE OBSERVATION O F S ° MESON

T. Gémesy and G. Surányi

HUNGARIAN ACADEMY OF SCIENCES CENTRAL RESEARCH INSTITUTE FOR PHYSICS

/

B U D A P E S T

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A REMARK ON THE OBSERVATION OF S° MESON T. Gémesy and G. Surányi

Central Research Institute for Phyeics, Budapest Hungary

In the search of the dubious 9° meson first found by Feldman [1] in 1965 one can utilize in a Xenon chamber experiment the у -s emerging from the charge exchange interaction

TT+ + n - * - p +

x°

/ 1 /

- where the unknown particle

X°

decays into four photons which may form an S° resonance. An experiment using this method was made by Strugalski et al [2,33 at 2.34- GeV/с. However there are a lot of channels at this energy which give a proton and two tt°'í in the final state having dif

ferent effective masses. In order to use this experimental method of finding S° resonance one must rule out the possibility of the existence of a back-- ground channel, which could give a bump as a kinematical effect in the

fr° тг° effective mass distribution at about the energy of 720 MeV.

The channel in question having probably higher cross section than the S°

at this energy is

тг+ + n N * + + tt° ■* p + тг° + it0 /2/

In this letter we calculate the тт0тг0 effective mass distribution in the channel mentioned above.

As

it is experimentally and theoretically verified this process goes via P exchange so the Stodolsky-Sakurai model [4-] can be used. Let'us define a coordinate system in the rest frame of N*+ in a way that the x and у axis should lie in the production plane, x is along the direction of the pion directly produced in Eq. (2 ), the z axis is perpendicular to the production plane. In this frame of reference the effective mass squared of ^ where denotes the pion given by the decay of N*+ can be easily evaluated:

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2

м = 2 m + Е - Р ^sin0 cos

1Т I* ")

TT 1 /

/3/

where E7T°' P^ttJ' ^{p ti}° аге ^■*1е energies and momenta of ^it° and ^tt° , and Ф-п ^are Ihe polar and azimuthal angles. According to the Stodolsky- Sakurai model the angular distribution of tt° with respect to the normal of the production plane is f (0-^, Фтг-j,) = + 3cos20ni) [5] and there

fore the effective mass distribution is given by 2tt ]

r 1“ /

1

¹ ^{б (}^m2 - 2 (m2 + E E - P „

J

^V

О \

4 °

n?

• ^1 + ЗСОБ2©^ ^ d c o s © ^ d ф

IT . т 7T ■

M 16Pir° Pv°2

5 - 3

2m2 ° + 2E о E о - M 2

* *! л2

2Ртт° Ртт°

/4/

Comparing this and the corresponding phase-space distributions /Fig.l/ one can conclude that the ir+n -> N* fiT° channel does not affect the observa

tion of the hypothetical S° x’esonance.

The M 7ro 7To effective mass distribution for reaction (2) and the corresponding phase space distribution

Completing this calculation we have made a series of Monte-Carlo calculations with other kind of angular distributions which have resulted the same conclusion.

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- 3 -

References

Ш M. Feldman, Phys. Rev. Lett., ЗА, 869 Л 9 6 5 /

[2] Z.S. Strugalskl et al. Study of Neutral Bosons Decaying into тг°

Mesons and у Quanta, to be published

[33 Z.S. Strugalski et al. The e° Meson, to be published [4] L. Stodolsky, J.J. Sakurai, Phys.Rev.Lett., 13-, 90 /1963/

I5 ] Lecture given by N. Schmitz at the 1965 Easter School for Physiciöts.

CERN 65-24.

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Q ' I

Printed in the Central Research Institute for Physics, Budapest Kiadja a Könyvtár- és Kiadói Osztály. O.v.: Dr.Farkas Istvánná Szakmai lektor: Frenkel Andor Nyelvi lektor: Sebestyén Ákos Példányszám: Munkaszám: 4Л96 Budapest, 1969* május 5*

Készült a KFKI házi sokszorosítójáhan. F.v.: Gyenes Imre

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