PRELIMINARY RESULTS ON CHARGED PARTICLE PRODUCTION AT HIGH TRANSVERSE MOMENTA IN p-p COLLISIONS AT 90° AT THE CERN-ISR (P. 423)

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PRELIMINARY RESULTS ON CHARGED PARTICLE PRODUCTION AT HIGH TRANSVERSE MOMENTA

IN p-p COLLISIONS AT 90° AT THE CERN-ISR (P.

423)

L. Caroll

To cite this version:

L. Caroll. PRELIMINARY RESULTS ON CHARGED PARTICLE PRODUCTION AT HIGH

TRANSVERSE MOMENTA IN p-p COLLISIONS AT 90° AT THE CERN-ISR (P. 423). Journal de

Physique Colloques, 1973, 34 (C1), pp.C1-407-C1-408. �10.1051/jphyscol:1973156�. �jpa-00215236�

HIGH TRANSVERSE MOMENTUM AT

ISR

PRELIMINARY RESULTS ON CHARGED PARTICLE PRODUCTION AT HIGH TRANSVERSE MOMENTA IN p-p COLLISIONS AT 90' AT THE CERN-ISR (P. 423)

L.J. CAROLL Liverpool University

The preliminary data presented here were obtained Cerenkov counters were used to separate pions, kaons with a spectrometer at 90' to the proton beams at and protons or anti-protons. A range of laboratory

the CERN-ISR. momenta from 1.6 to 5.2 G e ~ / c was covered with five.

The experimental arrangement is shown in Fig. 1. different combinations of gaz pressures and magnetic Particle momenta were measured using a bending magnet fields.

and magnetostrictive spark chambers. Two threshold gas

Fig. 1.- Layout of the spectrometer.

The trigger was a coincidence between six planes of scintillation counters with the additional restric- tion that only certain combinations of vertical ele- ments of hodoscopes 3 and 4 were allowed, to reduce the number of lower momenta triggers. Any systematic bias introduced by the geometry was reduced by fre- quent reversal of the magnet polarity during data taking.

The cross-sections were determined with the help of a Monte Carlo program simulating events in the appa- .rat&$. At this stage of the analysis, we do not wish

to quote absolute cross-sections.

The charged particle composition for this range of PT is shown in Fig.

2

for 6

=

44.6 GeV. For compa- rison, results of our measurements at low pT for

&

=

30.6 GeV are includd (Rd.

12

I). It can be seen that there is a rapid change in particle composition

(fraction of all charged particles)

up to about 1 G ~ v / ~ . ~b~~~ this momentum, the &str-- ^Fig.

^2.-

Charged Particle composition for high trans- verse momentum particles for Olab

=

89O at butions are flat, except perhaps for the highest

pT fi

=

44.6 GeV. The values of p

<

0.5 GeVIc bin where the statistics are poor. are at a

⁼

30.6 GeV. (Ref.

[2]f

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1973156

C1-408 L.J. CAROLL At p r e s e n t t h e r a t i o of p o s i t i v e t o n e g a t i v e p i o n s

i s p o o r l y determined b u t i t remains a b o u t 1.1 t o 1.2 e x c e p t perhaps a t t h e h i g h e s t v a l u e s of

pT

.

^{It i s}

i n t e r e s t i n g t o compare t h i s behaviour w i t h t h a t ob- s e r v e d a t lower pT

.

There, t h e r a t i o i s observed t o rise s t e a d i l y from 1.02

*

0.02 a t 0.25 GeV/c t o 1.17 0.03 a t 1 GeV/c (Ref. [ 2 ] ) .

I n F i g . 3 , t h e i n v a r i a n t c r o s s - s e c t i o n f o r p i o n p r o d u c t i o n a t

fi

^{= 44.6 GeV} i s compared w i t h o u r r e s u l t s o b t a i n e d a t

6

= 23.4 and 63.0 GeV. Although we a r e n o t q u o t i n g a b s o l u t e c r o s s - s e c t i o n s , we be-

l i e v e we u n d e r s t a n d t h e S-dependence o f o u r measure- ments t o f 10 %. Within t h e s m a l l r e g i o n o f o v e r l a p , t h e r e i s evidence f o r a n S-dependence i n t h e c r o s s - s e c t i o n which v a r i e s from 1.6 -f. 0.3 a t

pT = 1.48 GeV/c t o 2.5 i- 0.6

a t

pT = 2.28 GeV/c between t h e extreme e n e r g i e s . T h i s S-dependence, a l t h o u g h s i g n i f i c a n t , i s much l e s s pronounced t h a n t h e f a c t o r of t e n r e p o r t e d by t h e CERN-Columbia- R o c k e f e l l e r c o l l a b o r a t i o n (Ref. [3 1) f o r n e u t r a l p i o n s .

F i g . 3.- S-dependence of p i o n s w i t h h i g h t r a n s v e r s e momentum.

REFERENCES

111

ALPER (B.) e t a l . , P h y s i c s L e t t e r s (1973) 527 [3

1

B ~ ~ S S E R (F.W.) e t a l . , O b s e r v a t i o n o f rro Mesons [ 2 ] ALPER (B.) e t a l . , Large-angle i n c l u s i v e produc- w i t h Large T r a n s v e r s e Momentum i n High Energy t i o n of p r o t o n s , a n t i p r o t o n s , and kaons and P r o t o n - p r o t o n c o l l i s i o n s (Submitted t o P h y s i c s p a r t i c l e composition a t t h e CERN-ISR (Submit- L e t t e r s ) .

t e d t o P h y s i c s L e t t e r s ) .