Schmid, P

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JlmepaTypa H.AHreJïOB, K. II.BnnmeBCKaa, B.R.TPKHIKH H J^ P. n p e n p H H T OHM, 1-9536, Jlycma, 1976. H.ÀHrejiOB, K.IÏ.BHiiiHeBCKaiï, B.R.FPHIHHH H ^p. "Hca/ie^oBaHHe pox^eraa pesonancoB B 3Ï]P -B3aHM0#eMcTBHflx npH 40 FsB/c". $0KJia£, npe^CTaBjiôHHHîl Ha XYUi Mes^ynapo^Hyc K0H$e-peHUHD HO <pM3HK6 BHCOKHX 3 H e p r H Î t (TÔHJIHCH, 15-21 h m h , 1976). H. AHrejiOB, K.n.BHHHeBCKaa, B.T.TPHIUHH M # p . "HCCJie^OBaHHe 3 < | x | >eKT0B T0Xjr,eCTBeHHOCTH M B^HflHKfl p o a y ^ e H H f l J^^-mesoHOB Ha KoppejiamfH qaCTHIÎ B OïjP -B3aHM0^eMCTBKHX npa £ =40 ^ B / c " . JOKJia^, npe^CTaBJieHHH» Ha XTBL Mex^yHapo^Hyi) K0H$epeHi^Hi) no $H3HKS BMCOKHX sHepraM ( TOB-RUCH, 15-21 HDJia, 1976). H.AHrejiOB, K.ÏÏ.BHiUHeBCKaH, B . R . r p H i O K H H «rçp. "îfey^eHHe . n B y x y a c T M ^ H H x Koppe;iHijHii ra io ia-KBaHTOB H 3apflX6HHHX MaCTim B ^ J>-B3aHMQ-^ e a c T B H S x npH P = 40 rsB/c". Jlooaje;,. n p e i -CTaBJieHHui! H a XYUI Me^yHapo^nyx) KOH^epemjHD nO {J3H3KK6 BHCOKHX 3HeprHl (TÔHJÏHCK, 15-21 HD— a n , 1976). INCLUSIVE PARTICLE AND RESONANCE PRODUCTION Aachen-Berlin-Bonn-CERN-Cracov-London-Vienna-Warsav Collaborât ion P.Schmid CERN, Geneva, Switzerland T h i s t a l k summar ises w o r k on i n c l u s i v e r e s o n a n c e p r o d u c t i o n done by t h e A a c h e n - B e r l i n - B o n n - C E R N - C r a c o w - L o n d o n - V i e n n a - W a r s a w C o l l a b o r a t i o n d u r i n g t h e p a s t y e a r [ 1 ] . I t i s b a s e d on a b o u t 1.1 m i l l i o n e v e n t s coming f r o m t h e f o l l o w i n g b u b b l e chamber e x p e r i m e n t s : t r + p a t 8, 16 and 23 G e V / c , TT~p a t 16 GeV /c and K~p a t 10 and 16 GeV /c . The r e s o n a n c e s p°, f , n , « , K* K* , n n A + + and I ± , o o c a r e s t u d i e d . R e s u l t s a r e p r e s e n t e d on 8 9 0 1 4 2 0 , 1J»!> - s e p a r a t i o n o f f r a g m e n t a t i o n and c e n t r a l p r o d u c t i o n o f s e c o n d a r y p a r t i c l e s ; ~ u n i v e r s a l i t y o f t r a n s v e r s e momentum s p e c t r a ; - d i r e c t p a r t i c l e p r o d u c t i o n and c o n t r i b u t i o n s f r o m r e s o n a n c e d e c a y s . The e n e r g y d e p e n d e n c e o f t o t a l p r o d u c t i o n c r o s s s e c t i o n s o f r e s o n a n c e s i s d i s c u s s e d s e p a r a t e l y by P . C h l i a p n i k o v a t t h i s C o n f e r e n c e . SEPARATION OF FRAGMENTATION AND CENTRAL PRODUCTION OF SECONDARY PARTICLES L o n g i t u d i n a l momentum s p e c t r a o f p ° p r o d u c t i o n i n tt p and tt p i n t e r -a c t i o n s a t 16 G e V / c a r e v e r y s i m i l a r . They d i f f e r , h o w e v e r , f r o m t h e c o r r e s p o n d i n g s p e c t r a i n pp i n t e r a c t i o n s a t 24 G e V / c as s e e n i n f i g . 1 . Whereas t h e s p e c t r a c o i n c i d e f o r y < 0 , p p r o d u c t i o n i s much s t r o n g e r in t h e f o r w a r d d i r e c t i o n f o r ttp t h a n i t i s f o r pp i n t e r a c t i o n s . The d i f f e r e n c e can be i n t e r p r e t e d as b e i n g d u e t o d i f f e r e n t beam f r a g m e n t a t i o n . A quantit-a t i v e e s t i m a t e o f beam f r a g m e n t a t i o n and c e n t r a l components c a n be o b t a i n e d by o + * c o m p a r i n g i n v a r i a n t c r o s s s e c t i o n s f o r p p r o d u c t i o n i n 7t p w i t h K - . * p r o d u c t i o n i n K p i n t e r a c t i o n s a t 16 GeV/c ( f i g . 2 ) . As K is m a i n l y p r o d u c e d by k a o n f r a g m e n t a t i o n , t h e d i f f e r e n c e o f t h e two s p e c t r a may b e c o n s i d e r e d a s a n e s t i m a t e o f t h e c e n t r a l component o f p p r o d u c t i o n . U s i n g t h e c r o s s s e c t i o n s °pC ( T +p) = 4 . 7 ± 0 . 4 tub <x * D ( K ~ p ) - 3 . 3 ± 0 . 4 mb a t 16 GeV/c t h e f o l l o w i n g e s t i m a t e s h a v a b«en o b t a i a & i l ; t ' %-K p cfpo - 1.6 ± 0.5 ab ° K * ° " 0 , 2 m b w h e r e F and C stand f o r fragmentation and central production, respectively.-. These e s t i m a t e s a r e c o n s i s t e n t w i t h the interpretation of f i g . I a& g a b o v e . S i m i l a r l y s p e c t r a f o r the production of E * 1 3 8 t ; ^1385 0 1 1 1 7 compared i n K p i n t e r a c t i o n s a t 16 G e V / c ( f i g . 3). I f £ + and £~ are p r o d u c e d by a " c e n t r a l " p r o c e s s , t h e y s h o u l d h a v e t h e same c r o s s s e c t i o n , a s the t o t a l c h a r g e o f t h e i n i t i a l s t a t e i s z e r o . A2-9 I n the p r o t o n f r a g m e n t a t i o n r e p i o n r " p r o d u c t i o n s h o u l d b e s m a l l a s i t r e q u i r e s d o u b l e c h a r p e e x c h a n g e , w h e r e a s I p r o d u c t i o n i s a l ­lowed. Indeed the d i f f e r e n c e o f t w o s n e c t r a i s v e r y s u g g e s t i v e o f a f r a g m e n t a t i o n c o m n o n e n t . W i t h the c r o s s s e c t i o n s + ( K " n ) = 0 .41+0.OS mb and a E . ( K " p ) = 0 . 2 7 ± 0 .04 mb a t 10 C e V / c ( l e ) one a r r i v e s a t f r a p p e n t a t i o n and c e n t r a l components o f F 4 = 0 .14+ 0 .07 mb C . = 0 .27± 0 . 0 4 mb A di f f e r e n t t e c h n i q u e has been used by t h e Birmingham- B r u s s e l s -CEPN- Mons C o l l a b o r a t i o n t o s e p a r a t e f r a g m e n t a t i o n and c e n t r a l p r o d u c t i o n o f A ' s i n K + p i n t e r a c t i o n s a t 8 and 16 GeV/c ( 2 ) . C o n t r i b u t i o n s from beam and t a r g e t f r a g m e n t a t i o n h a v e been o b t a i n e d b y f i t t i n g t r i p l e - R e g g e e x ­p r e s s i o n s t o t h e d i s t r i b u t i o n s o f l a r g e | x | and b y e x t r a p o l a t i n g them t o s m a l l |X| ( F i g . 4 ( a ) ) . The c e n t r a l comnonent o f I p r o d u c t i o n i s o b t a i n ­e d by s u b t r a c t i n g t h e sum o f the two f r a g m e n t a t i o n components from t h e o v e r a l l spec t rum ( F i g . 4 ( b ) ) . F i g . 4 a ) I n v a r i a n t x d i s t r i b u t i o n f o r ô n r o d u c t i o n K p i n t e r a c t i o n s a t 8.2 GeV. The c u r v e s r e p r e s e n t f i t s o f t r i p l e P e g g e e x p r e s s i o n s t o t h e f r a g ­m e n t a t i o n r e g i o n s . b ) D i f f e r e n c e b e t w e e n d a t a and f r a g m e n t a t i o n components o f f i g . 4 ( a ) r e p r e s e n t i n g the c e n t r a l component o f A p r o d u c t i o n . 2 . UNIVEPSAI.ITY OF TP/NSVEPSE SPECTPA I n c l u s i v e d i s t r i b u t i o n s o f p r o d u c e d p a r t i c l e s h a v e been found t o d e -T pend on the mass o f the p a r t i c l e ( 3 ) . S n e c t r a f o r h e a v y p a r t i c l e s a r e a p p r o x i ­m a t e l y e x p o n e n t i a l be tween =0 and 2 ( G e V / c ) . Fo r l i g t h p a r t i c l e s l i k e 2 n i o n s and kaons t h e s n e c t r a h a v e a much s t e e p e r s l o p e a t s m a l l p^, wh ich g r a ­d u a l l y d e c r e a s e s t o about t h e same s l o p e as f o r h e a v y p a r t i c l e s above pi I 2 ( G e V / c ) . A p a r t from some s t r u c t u r e a t v e r y s m a l l n_ , r e sonances t u r n ou t t o 2 have s p e c t r a w i t h an e x p o n e n t i a l f a l l - o f f out t o about 2 ( G e V / c ) w i t h s l o p e s s i m i l a r t o the ones o f h e a v y n a r t i c l e s . Some resonance s n e c t r a a r e shown i n F i g . 5 ( a , b , c ) and compared t o s p e c t r a o f p i o n s and k a o n s , r e s p e c t i v e l y . A2-10 A s u r p r i s i n g l y s i m i l a r s l o p e i s f o u n d f o r a l l r e s o n a n c e s s t u d i e d i n c l u s i v e l y i n d e p e n d e n t o f t h e i n i t i a l s t a t e o v e r a l a r g e r a n g e o f l a b . momenta ( 6 - 200 G e V / c , see T a b l e I ) . M o r e o v e r t h e same s l o p e i s f o u n d f o r " q u a s i " ~ i n c l u s i v e p ± 2 d i s t r i b u t i o n s o f n and u p r o d u c t i o n [ I f ] ( f i g . 6 ) . T h i s combined e v i d e n c e l e a d s t o t h e c o n j e c t u r e of universality o f t h e s l o p e o f p ^ s p e c t r a o f d i r e c t l y p r o d u c e d p a r t i c l e s . "Second o r d e r " e f f e c t s l i k e - s y s t e m a t i c d i f f e r e n c e s o f s l o p e s f o r c e r t a i n b « a a s o r p r o d u c e d p a r t i c l e s d i s t r i b u t i o n s f o r t h e i n c l u s i v e r e a c t i o n s TT+p -> ( n , w» p ° ) + c h a r g e d p a r t i c l e s a t 16 G e V / c [ i f ] . - a s l o w d e c r e a s e o f s l o p e s w i t h i n c r e a s i n g e n e r g y c a n n o t b e e s t a b l i s h e d w i t h p r e s e n t l y a v a i l a b l e d a t a . S l o p e u n i v e r s a l i t y w i l l be u s e d i n t h e f o l l o w i n g as a method o f e s t i m a t i n g p r o d u c t i o n c r o s s s e c t i o n s . • The f i r s t example c o n c e r n s n and tu p r o d u c t i o n m Î p i n t e r a c t i o n s a t 16 G e V / c [ I f ] . W i t h b u b b l e chamber d a t a t h e s e r e s o n a n c e s c a n o n l y be o b s e r v e d when a l l o t h e r p a r t i c l e s i n t h e f i n a l s t a t e a r e c h a r g e d ( o r o b s e r v e d V ° s ) . To compare them t o P p r o d u c t i o n , P's s h o u l d be s t u d i e d i n s i m i l a r " q u a s i " - i n c l u s i v e r e a c t i o n s , i . e . p r o d u c e d w i t h c h a r g e d p a r t i c l e s 2 o n l y . T h e r a t i o o f t h e p r o d u c t i o n c r o s s s e c t i o n i n t h e p ^ r a n g e w h e r e a l l t h r e e r e s o n a n c e s h a v e e x p o n e n t i a l d i s t r i b u t i o n s w i t h a l m o s t i d e n t i c a l s l o p e s i s f o u n d t o be N : us : P - 0 . 3 : 0 . 8 : 1. Based o n s l o p e u n i v e r s a l i t y and o n t h e s i m i l a r i t y o f x and y d i s t ­r i b u t i o n s [ I f 3, t h e s e r a t i o s a r e assumed t o be t r u e a l s o f o r t h e f u l l y i n c l u s i v e c a s e and t h e f o l l o w i n g c r o s s s e c t i o n s f o r n and ui p r o d u c t i o n a r e o b t a i n e d : « 1 . 5 ± 0 . 3 mb 0 = 4 . 0 ± 0 . 6 mb Î . DIRECT PARTICLE PRODUCTION AND CONTRIBUTIONS FROM RESONANCE DECAYS S l o p e s o f d i s t r i b u t i o n s f o r i n c l u s i v e r e s o n a n c e p r o d u c t i o n As cross s e c t i o n s f o r r e s o n a n c e p r o d u c t i o n a r e l a r g e , many o f t h e f i n a l p a r t i c l e s o b s e r v e d a r e i n f a c t d e c a y p r o d u c t s . W i t h some p l a u s i b l e a s s u m p t i o n s [ i h ] i t is s t r a i g h t f a w a r d t o c a l c u l a t e t h e c o n t r i b u t i o n o f t h e i m p o r t a n t r e s o n a n c e s , t h e c r o s s s e c t i o n s o f w h i c h h a v e b e e n m e a s u r e a t 16 G e V / c , t o t h e f i n a l p a r t i c l e y i e l d ( T a b l e I I ) . A l m o s t h a l f o f t h e p r o d u c t i o n c r o s s s e c t i o n o f t h e p a r t i c l e s l i s t e d i n T a b l e I I c a n be a c c o u n t e d f o r by known r e s o n a n c e s . As p o s s i b l e c o n t r i b u t i o n s f r o m b r o a d o r h i g h mass r e s o n a n c e s a r e d i f f i c u l t , t o m e a s u r e , t h e numbers o b t a i n e d c a n b e used t o g e t u p p e r bounds f o r t h e f r a c t i o n o f d i r e c t l y p roduced p a r t i c l e s . TABLE I I T h i s p e r c e n t a g e h o l d s f o r t r u e A s , i . e . a f t e r s u b t r a c t i n g l°s f r o m t h e o b s e r v e d A y i e l d . An e x p e r i m e n t a l t e c h n i q u e has b e e n d e v e l o p e d t o e s t a b l i s h d i f f e r e n t i a l s p e c t r a o f d e c a y p r o d u c t s w h i c h can t h e n be s u b t r a c t e d f r o m t h e o v e r a l l p a r t i c l e s p e c t r a . Such an a n a l y s i s has b e e n done f o r n e g a t i v e p i o n s p r o d u c e d i n tt p i n t e r a c t i o n s and f o r n e u t r a l kaons i n K p i n t e r a c t i o n s b o t h a t 16 GeV/ [ l g ] . As e x p e c t e d f r o m p u r e k i n e m a t i c s , f i g . 7 ( a ) shows t h a t d e c a y p i o n s a r A2-11 the more peaked at small p^ 2 the smaller the Q-value of the resonance and the heavier the mass recoiling against the pion. Sunning up the contributions 2 of all meson resonances studied (fig. 7(b)), the particular form of the p ± spectrum of pions can well be reproduced. Because of the heavy recoiling mass, pions coming from baryon resonances are expected to contribute even more to the peak oX small p^ . Fig. 7 p ± 2 distributions of TT~ production in IT p interaction at 16 GeV/c CM. a) Inclusive if distribution and spectra of tt s coming from n, u, P and f resonances b) Inclusive TT~ distributions, sum of all TT S from (N, w , P, f) decay (broken line) and difference of the two distributions (full line). Having shown that pions *4 small p^ mainly come from resonance decays, one can try to get another upper bound on direct pion production using the conjecture of slope universality! As seen in fig. 4(a) the 2 p spectrum of pi< is compatible with the exponential P spectrum above p ^0.8 GeV where decay-pions are expected to play a less important role, . 2 2 Extrapolating the exponential spectrum at large p^ down to p^ = 0 , one obtains an upper bound for direct pion production of 20Z of the total pion 2 yield. Taking into account the large p^ tail of decay-pions one arrives at a best estimate of about 102. In Table III we compare the production cross cross sections for meson resonances and the estimate for directly produced pfbns with quark model predictions by Anisovitch and Shekhler [4]. Although the predictions are only valid for a large number of produced quarks, i.e. high energies, the quantitative agreement between data and predictions is surprisingly good for resonances not containing strange quarks. The pre­dictions for <Ji and n production, however, are off by one order of magnitude which may indicate some dynamical mechanism like the Zweig-Iizuka rule for suppressing these states. I would like to thank the Birmingham-Brussels-CERN-Mons Collaboration for allowing me to include unpublished results. I am especially grateful to Drs. V. T. Cocconi, M, J. Counihan, H. G. Kirk, P. K. Malhotra, F. Mandl, D. R. 0. Morrison and H. Saarikko for their assistance in preparing this talk. REFERENCES [la] M. Deutschmaira et al,, Nucl. Phys. B103 (1976) 426. tlb] J . B a r t k e e t al. , Hucl.Phys. , B 1 0 7 ( 1 9 7 6 ) 9 3 . [le] Inclusive Production of K*(89Q) and K*(l420) in K~p Interactions at 10 and 16 GeV/c, Aachen-Berlin-CERN-London~Vienna Collaboration, H. G. Kick et al., CERN/EP/PHYS 76-13. [ld] Inclusive A + +(1236) Production in ff+p., IT p and K p Interactions at 16 GeV/c, Aachen-Berlin-Bonn-CERN-Cracow-Heidelberg-London-Vienna-Warsaw Collaboration. [le] Inclusive Production of £"(1385) in K p Interactions at 10 and 16 GeV/c, Aachen-*Ber1in-CERN-London-Vienna Col1aboration. [If] Eta and Omega Meson Production in Medium Energy ir~p and K p Collisions, Aachen-Berlin-Bonn-CERN-Cricov-London-Vierma-Warsaw Collaboration, CERN/EP/PHYS 76-28. [1g] A Study of Indirect Pion Production in IR+p Interactions at 16 GeV/c, Aachen-Berlin-Bonn-CERN-Cracow-Heidelberg-Warsaw Collaboration, CERN/EP/PHYS 76-27. [lh] Inclusive Yields and Transverse Spectra of the Mesons Comparison with the Quark Model and the Problem of "Direct" Pion Production, Aachen-Berlin-Bonn-CERN-Cracov-London-Vienna-tfarsaw Collaboration, CERN/EP/PHYS 76-30. [2] The Reactions K +p -*• AX + + and K +p -*• at Incident Momenta of 8.2 and 16 GeV/c, Biraingha«~Brussels-CERN-Mons Collaboration, P.. V. Chliapnikov et al., CERN/EP/PHYS 76-11. [3] See e.g. Experimental Review of Strong Interactions at High Energy, D . R . 0 . Morrison, Lectures at the Fifth Hawaii Topical Conference in Particle Physics, 1973. U3 V. V. Anisovitch and V. M. Shekhter, Nucl. Phys. B (73) 455. [5] H. A. Gordon et «1., Phys. Letters 34B (75) 284. [6] V. -Blobel et al., Phys. Letters 489 (74) 73. [7] D. Fong et a i . , Phys. Letters 60B (75) 124. [8] R. Singer et al., Phys. Letters 60B (76) 385. [9] Aachen-Berlin-Bonn-CERN-Cracow-London-Vienna-Warsaw Collaboration F. Mandl, private communication. * [103 Study of IT(1385) Inclusive Production in K~p Interactions a t 4.2 GeV/c, Aa.terdas-CERN-Nijmegen-Oxford Collaboration, CERN/EP/PHYS 76-23. TABLE III C o m p a r i s o n o f p a r t i c l e r a t i o s i n 16 G e V / c TT + p i n t e r a c t i o n s w i t h q u a r k model p r e d i c t i o n s [4]. A2-12 

Inclusive particle and resonance production

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