observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

6
V01ume 468, num6er 3 PHY51C5 LE77ER5 1 0ct06er 1973 085ERVA710N 0F ~r ° ME50N5 W17H LAR6E 7RAN5VER5E M0MEN7UM 1N H16H-ENER6Y PR070N-PR070N C0LL1510N5 F.W. 81J55ER *1 , L. CAM1LLER1, L. D1 LELLA, 6.6LADD1N6 *2 , A. PLACC1, 8.6. P0PE, A.M. 5M17H, J.K. Y0H *3 and E. 2AVA771N1 CERN, 6eneva, 5w1t2er1and 8.J. 8LUMENFELD *4 and L.M. LEDERMAN *5 C01um61a Un1ver51ty *6, N. Y., U5A and R.L. C00L *5 , L. L177 and 5.L. 5E6LER R0ckefe11er Un1ver51ty *7, N. Y., U5A Rece1ved 10 Au9u5t 1973 1nvar1ant cr055-5ect10n5are pre5ented f0r the 1nc1u51vereact10n p + p ~ n0 + anyth1n9, Mea5urement5 0f 1ar9e tran5ver5e m0mentum n°•5 (2.5 6ev/c < p• < 9 6ev/c) were made near 90 ° at the cERN 15R at f1ve centre-0f- ma55 ener91e5 (x/~"= 23.5, 30.6, 44.8, 52.7 and 62.4 6eV). At 1ar9eP L, the 1nvar1ant cr055-5ect10n5are 5een t0 vary•• w1th 5 and p•, 1n 900d a9reement w1th a f1t 0f the f0rm Ap~fnF(p~/xR), w1th n ~ 8 and F(p~/x/~5) ~ exp(-26p~/x/5). A we11-kn0wn a5pect 0f h19h-ener9y c0111510n5 ha5 6een the fa11ure t0 065erve the pr0duct10n 0f part1c1e5 w1th 1ar9e tran5ver5e m0mentum. Exten51ve mea5ure- ment5 at acce1erat0r5 and w1th c05m1c ray5 had 5h0wn a 5teep exp0nent1a1 dec11ne 1n the pr06a6111ty f0r ha- dr0n1ca11y 1nduced tran5ver5e m0menta [e.9. 1 ]. 7he 065ervat10n5 pre5ented here dem0n5trate an ener9y- dependent f1atten1n9 0f th15 6ehav10ur, 5uch that the cr055-5ect10n at P1 --- 6 6eV/c and x/5- = 52.7 6eV 15 5even 0rder5 0f ma9n1tude h19her than an extrap01a- t10n 0f the we11-kn0wn exp0nent1a1 [2]. 1nc1u51ve 7r ° pr0duct10n at 1ar9e tran5ver5e m0- menta wa5 5tud1ed at the CERN 1nter5ect1n9 5t0ra9e R1n95. Neutra1 p10n5 that emer9ed near 90 ° 1n the centre-0f-ma55 were 1dent1f1ed 6y e1ectr0ma9net1c 5h0wer5 1n e1ther 0f tw0 5pectr0meter5, each w1th a u5efu1 1a60rat0ry 5011d an91e 0f 0.59 5r. 7he 5pectr0m- eter5 are the 5ame 0ne5 that were u5ed t0 5earch f0r h19h-ener9y e1ectr0n5 and 1ar9e ma55 e+e - pa1r5 [3]. F19. 1 5h0W5 a 5Chemat1C repre5entat10n 0f the ap- paratu5, wh1ch c0n515ted 0f tw0 1dent1ca1 5pectr0meter5 0n the 1nner and 0uter 51de5 0f the c0111d1n9 pr0t0n 6eam5. Each 5pectr0meter c0n515ted 0f: 1) ten p1ane5 0f w1re 5park cham6er m0du1e5; 11) f0ur 5et5 0f 5c1nt11- 1at10n c0unter h0d05c0pe5: A, 8, 2 and 57; 111) an ar- ray 0f 51xteen 1ead-91a55 c0unter5, 3.1 rad1at10n 1en9th5 th1ck; and 1v) an array 0f 51xty 1ead-91a55 5h0wer c0unt- er5, 14.8 rad1at10n 1en9th5 th1ck. 7he A and 8 h0d0- 5c0pe5 were u5ed f0r tr199er1n9 and f0r track ver1f1ca- t10n. 7he 2 c0unter5 were u5ed t0 mea5ure 10n12at10n 1055; and the 57 c0unter5, wh1ch were p1aced after the 1ead-91a55 c0unter5, were u5ed dur1n9 ca116rat10n run5 t0 detect part1c1e5 pa551n9 5tra19ht thr0u9h a11 0f the 5h0wer detect0r5.7he f1r5t array 0f 1ead-91a55, wh05e th1ckne55 t0 hadr0n5 wa5 0n1y 0.15 1nteract10n 1en9th5, wa5 emp10yed t0 5e1ect event5 c0nta1n1n9 e1ectr0n5 0r * 1 0n 1eave fr0m 11 1n5t1tut far Exper1menta1phy51k,Ham6ur9 6ermany. *2 Pre5ent addre55:Phy51c5 Department, Un1ver51ty0f 1U1n015, Ur6ana, 1111n015, U5A. *3 Pre5ent addre55:Nev15 La60rat0r1e5, C01um61a Un1ver51ty, 1rv1n9t0n, NY, U5A. *4 Nat10na1 5c1ence F0undat10n Pred0ct0ra1 Fe110w. *5 V151t1n95c1ent15t at CERN, 6eneva, 5w1t2er1and. *6 Re5earch 5upp0rted 1n part 6y the Nat10na1 5c1ence F0un- dat10n. *7 Re5earch 5upp0rted 1n part 6y the U5 At0m1c Ener9y C0m- m15510n under c0ntract A7 (11-1) 2232A. 471

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Page 1: Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

V01ume 468, num6er 3 PHY51C5 LE77ER5 1 0ct06er 1973

0 8 5 E R V A 7 1 0 N 0 F ~r ° M E 5 0 N 5 W 1 7 H L A R 6 E 7 R A N 5 V E R 5 E M 0 M E N 7 U M

1N H 1 6 H - E N E R 6 Y P R 0 7 0 N - P R 0 7 0 N C 0 L L 1 5 1 0 N 5

F.W. 81J55ER *1 , L. CAM1LLER1, L. D1 LELLA, 6 . 6 L A D D 1 N 6 *2 , A. PLACC1,

8 .6 . P0PE, A.M. 5M17H, J.K. Y0H *3 and E. 2AVA771N1

CERN, 6eneva, 5w1t2er1and

8.J. 8LUMENFELD *4 and L.M. LEDERMAN *5

C01um61a Un1ver51ty *6, N. Y., U5A

and

R.L. C 0 0 L *5 , L. L177 and 5.L. 5 E 6 L E R R0ckefe11er Un1ver51ty *7, N. Y., U5A

Rece1ved 10 Au9u5t 1973

1nvar1ant cr055-5ect10n5 are pre5ented f0r the 1nc1u51ve react10n p + p ~ n0 + anyth1n9, Mea5urement5 0f 1ar9e tran5ver5e m0mentum n°•5 (2.5 6ev/c < p• < 9 6ev/c) were made near 90 ° at the cERN 15R at f1ve centre-0f- ma55 ener91e5 (x/~" = 23.5, 30.6, 44.8, 52.7 and 62.4 6eV). At 1ar9e P L, the 1nvar1ant cr055-5ect10n5 are 5een t0 vary•• w1th 5 and p•, 1n 900d a9reement w1th a f1t 0f the f0rm Ap~fnF(p~/xR), w1th n ~ 8 and F(p~/x/~5) ~ exp(-26p~/x/5).

A we11-kn0wn a5pect 0f h19h-ener9y c0111510n5 ha5 6een the fa11ure t0 065erve the pr0duct10n 0f part1c1e5 w1th 1ar9e tran5ver5e m0mentum. Exten51ve mea5ure- ment5 at acce1erat0r5 and w1th c05m1c ray5 had 5h0wn a 5teep exp0nent1a1 dec11ne 1n the pr06a6111ty f0r ha- dr0n1ca11y 1nduced tran5ver5e m0menta [e.9. 1 ]. 7he 065ervat10n5 pre5ented here dem0n5trate an ener9y- dependent f1atten1n9 0f th15 6ehav10ur, 5uch that the cr055-5ect10n at P1 --- 6 6eV/c and x/5- = 52.7 6 e V 15 5even 0rder5 0f ma9n1tude h19her than an extrap01a- t10n 0f the we11-kn0wn exp0nent1a1 [2].

1nc1u51ve 7r ° pr0duct10n at 1ar9e tran5ver5e m0- menta wa5 5tud1ed at the CERN 1nter5ect1n9 5t0ra9e R1n95. Neutra1 p10n5 that emer9ed near 90 ° 1n the centre-0f-ma55 were 1dent1f1ed 6y e1ectr0ma9net1c 5h0wer5 1n e1ther 0f tw0 5pectr0meter5, each w1th a u5efu1 1a60rat0ry 5011d an91e 0f 0.59 5r. 7he 5pectr0m- eter5 are the 5ame 0ne5 that were u5ed t0 5earch f0r

h19h-ener9y e1ectr0n5 and 1ar9e ma55 e+e - pa1r5 [3]. F19. 1 5h0W5 a 5Chemat1C repre5entat10n 0f the ap-

paratu5, wh1ch c0n515ted 0f tw0 1dent1ca1 5pectr0meter5 0n the 1nner and 0uter 51de5 0f the c0111d1n9 pr0t0n 6eam5. Each 5pectr0meter c0n515ted 0f: 1) ten p1ane5 0f w1re 5park cham6er m0du1e5; 11) f0ur 5et5 0f 5c1nt11- 1at10n c0unter h0d05c0pe5: A, 8, 2 and 57 ; 111) an ar- ray 0f 51xteen 1ead-91a55 c0unter5, 3.1 rad1at10n 1en9th5 th1ck; and 1v) an array 0f 51xty 1ead-91a55 5h0wer c0unt- er5, 14.8 rad1at10n 1en9th5 th1ck. 7he A and 8 h0d0- 5c0pe5 were u5ed f0r tr199er1n9 and f0r t rack ver1f1ca- t10n. 7he 2 c0unter5 were u5ed t0 mea5ure 10n12at10n 1055; and the 57 c0unter5, wh1ch were p1aced after the 1ead-91a55 c0unter5, were u5ed dur1n9 ca116rat10n run5 t0 detect part1c1e5 pa551n9 5tra19ht thr0u9h a11 0f the 5h0wer detect0r5.7he f1r5t array 0f 1ead-91a55, wh05e th1ckne55 t0 hadr0n5 wa5 0n1y 0.15 1nteract10n 1en9th5, wa5 emp10yed t0 5e1ect event5 c0nta1n1n9 e1ectr0n5 0r

* 1 0n 1eave fr0m 11 1n5t1tut far Exper1menta1phy51k, Ham6ur9 6ermany.

*2 Pre5ent addre55:Phy51c5 Department, Un1ver51ty 0f 1U1n015, Ur6ana, 1111n015, U5A.

*3 Pre5ent addre55:Nev15 La60rat0r1e5, C01um61a Un1ver51ty, 1rv1n9t0n, NY, U5A.

*4 Nat10na1 5c1ence F0undat10n Pred0ct0ra1 Fe110w. *5 V151t1n9 5c1ent15t at CERN, 6eneva, 5w1t2er1and. *6 Re5earch 5upp0rted 1n part 6y the Nat10na1 5c1ence F0un-

dat10n. *7 Re5earch 5upp0rted 1n part 6y the U5 At0m1c Ener9y C0m-

m15510n under c0ntract A7 (11-1) 2232A.

471

Page 2: Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

V01ume 468, num6er 3 PHY51C5 LE77ER5 1 0ct06er 1973

1 82 2 1

W1RE 5PARK PLA571C CHAM8ER5 1 V 5C~N71LLA70R5

1

/ LEAD 6LA55 (~ERENK0V 1N7ER5EC710N

C0UN7ER5 RE610N

F19. 1.5chemat1c d1a9xam 0f the apparatu5.

0r ph0t0n5 [4]. A 119ht 50urce that c0n515ted 0f a 5ma11 Na1(71) cry5ta1 d1ffu5ed w1th 241Am wa5 91ued t0 each 0f the 152 1ead-91a55 c0unter5 t0 pr0v1de c0nt1nua1 m0n1t0r1n9 0f the re5p0n5e 0f the detect0r5 [5]. F0r the data at x F = 44.8 and 52.7 6eV, there wa5 a 0.17 cm th1ck 5heet 0f P6 1mmed1ate1y preced1n9 the 2 c0unter5 0f the 1n51de 5pectr0meter. Further deta115 0n the a55em61y and 0perat10n 0f the 5pectr0meter5, and 0n the ca116rat10n and m0n1t0r1n9 0f the 5h0wer c0unt- er5, are 91ven e15ewhere [6].

1n add1t10n, tw0 1 m 2 5c1nt111at10n c0unter5, ~1 and 22, were each centred ar0und a d0wn5tream 15R vacuum p1pe 5.65 m fr0m the cr0551n9 p01nt. 7he c01n- c1dence ~1 ~2 wa5 t1med t0 5e1ect an a1m05t pure 5am- p1e 0f 6eam-6eam c0111510n5.

7w0 5et5 0f 1091ca1 c01nc1dence5 were u5ed t0 5en5e arr ° and tr199er the detect0r5. F0r the data taken w1th- 0ut the P6 5heet, each 5et 0f 1091c re4u1red the pre5- ence 0f e1ther a ~1 Y•2 c01nc1dence 0r a c01nc1dence 6etween an A c0unter and a 8 c0unter 0n the 5ame

51de. When the P6 5heet wa5 1n p1ace 0n the 1n51de 5pectr0meter, w1th (]~1 ]~2 0r A8) re4u1rement wa5 chan9ed t0 21 ~2 0n1y. An add1t10na1 re4u1rement 1n each tr199er wa5 that 0ne 0f the tw0 5pectr0meter5 5h0u1d c0nta1n a 5h0wer wh1ch dep051ted at 1ea5t 0.5 6eV 1n the f1r5t array 0f 1ead-91a55 c0unter5, and wh1ch exceeded a 91ven ener9y thre5h01d 1n the 5ec0nd array. 7h15 thre5h01d ener9y wa5 0.8 6eV f0r the f1r5t tr19- 9er, and 1.5 6eV f0r the 5ec0nd tr199er. 7he rate 0f the f1r5t tr199er wa5 e1ectr0n1ca11y 5uppre55ed 6y a carefu11y m0n1t0red fact0r 0f a60ut 100, 50 that 1e55 fre4uent, h19h p• event5 1n the 5ec0nd tr199er w0u1d n0t 6e 610cked 6y dead-t1me. A 10wer ener9y 60und 0f 2.5 6eV wa5 5et f0r the pre5entat10n 0f the5e data 6ecau5e 0f the c0m61ned effect5 0f ener9y re501ut10n, ener9y 5har1n9 1n the d1fferent 5et5 0f 610ck5, and thre5h01d5.

7he data pre5ented 1n th15 paper were taken dur1n9 the f0ur-m0nth per10d fr0m 5eptem6er t0 decem6er 1972. Run5 were made at f1ve va1ue5 0f the t0ta1 centre 0f-ma55 ener9y: X,/5 -= 23.5, 30.6, 44.8, 52.7 and 62.4 6eV. 7he 15R 1um1n051ty wa5 mea5ured at each en- er9y 6y mean5 0f the Van der Meer meth0d [7]. 7he runn1n9 t1me 5pent at the f1ve ener91e5 c0rre5p0nded t0 the f0110w1n9 num6er5 0f pr0t0n-pr0t0n c0111510n5: 8.1× 107 , 9.7X 108 , 3.4X 109 , 1.8X 1010and 1.2 X 107, re5pect1ve1y.

7w0 meth0d5 were u5ed t0 ana1y5e the. 1n51de 5pec- tr0meter data that were taken w1th the P6 5heet 1n p1ace. 1n the f1r5t appr0ach 0n1y th05e event5 were 5e1ected where at 1ea5t 0ne ph0t0n c0nverted 1n the P6 5heet. 7he 5e1ect10n cr1ter1a demanded: 1) that the w1re 5park cham6er5 after the P6 5heet c0nta1n a 5uf- f1c1ent num6er 0f 5park5; 11) that the 2 c0unter5 1nd1- cate an 10n12at10n 1055 9reater than 1.6 t1me5 m1n1- mum; and, 111) that the ener9y d15tr16ut10n 1n each 0f the 1ead-91a55 array5 6e c0n515tent w1th e1ectr0ma9- net1c 5h0wer1n9.7he 5ec0nd meth0d 0f ana1y515, wh1ch wa5 app11ed t0 a11 0f the data, u5ed 0n1y the ener9y d15- tr16ut10n 1n the 6ad-91a55.

7he 6ack9r0und 0f acc1denta1 c01nc1dence5 wa5 5tud1ed fr0m data taken w1th a 5pec1a1 tr199er 1n wh1ch 50me 0f the c01nc1dence 1nput5 had 6een de1ayed. 51n- 91e 6eam data were taken t0 check f0r 6eam-9a5 and 6eam-wa11 6ack9r0und5.7he t0ta1 6ack9r0und wa5 ne9- 119161e f0r th05e event5 that c0nverted 1n the P6 5heet. F0r the ana1y515 that d1d n0t re4u1re c0nver510n, the 6ack9r0und wa5 6e10w 5% f0r p• < 6 6eV/c, a1th0u9h

472

Page 3: Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

V01ume 468, num6er 3 PHY51C5 LE77ER5 1 0ct06er 1973

10 "3 P,,

%

>~

10-~

uJ 10-

10-33

10-3~

1 1

0

10-30

10-3~

10-32

10-33

10•34

1 ~ 1 1 1 1 1 1 1 1

0-

c~ %

1 ~ V ~ = 4 4 . 8 6eV

1

f1

1NCLU51VE CR055 5EC710N5 FR0M 7W0 D1FFEREN7 ME7H0D5 0F ANALY515

0 C0NVER510N REQU1RED • C0NVER510N N07 REQU1RED

= 5 2 . 7 6 e V

• 1

1 , ~ 1 ~ , , , 1 ~ , , t . . . . 1 , , , 1 . . . . 1 , , , , 1 , 1 ~ 3 4 5 6 7 8 9

P2 16eV/c )

"7

>,

t ,1

F19~ 2,. A c0mpar150n 0f 1nva~1ant cr055-5ect10n5 f0r 1nc1u51ve n 0 pr0duct10n 06ta1ned fr0m the tw0 meth0d5 de5cr16ed 1n the text. 7he5e data c0me fr0m th05e run5 where the 1n51de detect0r had a 1ead 5heet t0 c0nvert 3• ray5.

1t d1d r15e t0 appr0x1mate1y 20% at P1 = 7 6eV/c. 7he 5011d an91e and 1r ° detect10n eff1c1ency f0r the

tw0 meth0d5 were 06ta1ned fr0m a M0nte Car10 pr0- 9ram that ca1cu1ated the 5h0wer deve10pment 1n the P6 5heet and 1n the 1ead-91a55.7he M0nte Car10 pr0- 9ram wa5 checked 6y c0mpar1n9 1t5 pred1ct10n5 w1th the ca116rat10n data taken at the CERN Pr0t0n 5yn- chr0tr0n and at the Dare56ury E1ectr0n 5ynchr0tr0n, u51n9 1nc1dent e1ectr0n5 and ph0t0n5 0f kn0wn ener9y.

Kn0w1ed9e 0f the 1um1n051ty, 6ack9r0und-5u6- tracted rate5, and acceptance wa5 1n5uff1c1ent t0 deter- m1ne the 1nc1u51ve cr055-5ect10n fr0m 0ur data. 1t wa5 a150 nece55ary t0 kn0w the tr199er1n9 61a5 that re5u1ted fr0m the re4u1rement 0f e1ther the 2;1 ~2 c01nc1dence, 0r the detect10n 0f at 1ea5t 0ne track c0m1n9 fr0m the

1nter5ect10n re910n. 7h15 61a5 wa5 deduced 6y d1v1d1n9 the data 1nt0 three cate90r1e5: 1) event5 w1th E 1 ~2 and a track: 11) event5 w1th 2;1 2;2 and n0 track; 111) event5 w1th n0 2;12;2 and a track. 1t wa5 a55umed that the 06- 5ervat10n 0f a track at 1ar9e an91e5 wa5 1ndependent 0f the pre5ence 0f the ~1 2;2 c01nc1dence. 7h15 a5- 5umpt10n a110wed an e5t1mate t0 6e made 0f the 512e 0f the undetected c1a55 0f h19h P.t event5, th05e hav1n9 n0 2; 1 2;2 and n0 track. 1nc1u51ve cr055-5ect10n5 were then 06ta1ned f0r each centre-0f.ma55 ener9y 6y add1n9 1n the e5t1mate 0f th15 f0urth cate90rY. 7he c0rrect10n t0 the (2;1 2;2 0r A8) data wa5 f0und t0 6e 1ndependent 0fp~. 1t am0unted t0 a mu1t1- p11cat1ve fact0r 0f 1.49 at 23.5 6eV, 1.37 at

30.6 6eV, 1.21 at 44.8 6eV, 1.14 at 52.7 6eV and

473

Page 4: Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

V01ume 468, num6er 3 PHY51C5 L E 7 7 E R 5 1 0c t06er 1973

10 -~ , , , , 1 • • • •

~x 0 , t 1

~ x ~ 0 vV

10-32 •7,

10-33 ~rr~ • 101- 0

0•V

~ 0 v v •

10-34

1 1 1 1 r 1 1 , , , 1 • 1 , 1 1 1 1 1 1

1NVAR1AN7 CR055 5EC710N5 F0R p,,p ~ ~°*ANY7H1N0

V5 7RAN5VER5E M0MEN7UM

5YM80L ~ (6eV)

• 23 .5

a 30.6 0 ~ .8

• 52 .7

0 62./,

3-

031 0.1 10-35 •

2 3 ~ 5 6 7 8 9 p~ (6eV/c)

F19. 3 . 7 h e tran5ver5e m 0 m e n t u m dependence 0 f 1nvar1ant cr055-5ect10n5 0f f1ve centre-0f-ma55 ener91e5. 7he err0r5 are 5tat15t1ca1

0n1y.

1.10 at 62.4 6eV. 7he 5y5temat1c uncerta1nty 1n th15 c0rrect10n 15 e5t1mated a5 ran91n9 fr0m 5% t0 10%. F0r the E 1 22 0n1y data, wh1ch are pre5ented at ~ = 44.8 and 52.8 6eV, the c0rrect10n5 were f0und t0 6e 5119ht1y 1ar9er and p•-dependent. U5e 0f the 5ame a5- 5umpt10n 91ven a60ve re5u1ted 1n a typ1ca1 c0rrect10n 0f 1.27 + 0.05 a t p L = 5 6eV/c and x/7 = 52.7 6eV.

F19. 2 c0mpare5 the re5u1t5 fr0m the tw0 meth0d5 0f ana1y515.7he c0mpar150n wa5 1ntended t0 ver1fy the tw0-ph0t0n nature 0f the event5.51nce the c0n- ver510n eff1c1ency 15 a kn0wn funct10n 0f the num6er 0f ph0t0n5, the a9reement 0f the5e 5pectra 15 c0n515- tent w1th the hyp0the515 that a11 0f 0ur e1ectr0ma9- net1c 5h0wer5 0r191nated fr0m tw0 ph0t0n5. F0r ex-

amp1e, 1f the detect10n eff1c1ency were ca1cu1ated 6y a55um1n9 the detected event5 t0 6e e1ther 51n91e 7•5, 0r 2n °•5 fr0m K~ decay, then the re5U1t5 0f the tw0 meth0d5 0f ana1y515 w0u1d d1ffer 6y 35%.

F19.3 5h0w5 the 5pectra f0r a11 f1ve centre-0f-ma55 ener91e5. A 115t 0f cr055-5ect10n5 15 91ven 1n ta61e 1.7he 50urce5 0f uncerta1nty 1n the5e data can 6e enumer- ated a5 f0110w5: 1) the 5tat15t1ca1 err0r5, wh1ch are p10t- ted 1n the f19ure; 11) a ca116rat10n uncerta1nty 0f +6% 1n the ener9y 5ca1e. Dur1n9 the c0ur5e 0f the exper1- ment, a chan9e wa5 065erved 1n the re1at1ve ca116rat10n 0f the 1ead-91a55 detect0r5.7h15 wa5 traced t0 a dark- en1n9 0f the 1ead-91a55 that wa5 pr0duced 6y rad1at10n dama9e. C0rrect10n fact0r5 t0 the data were der1ved

474

Page 5: Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

V01ume 468, num6er 3 PHY51C5 LE77ER5 1 0ct06er 1973

7a61e 1

1nc1u51ve W e cr055-5ect10n5 f0r f£ve centre-0f-ma55 ener91e5 (Err0r5 are 5tat15t10a1 0n17)

¢~5 - 2 3 . 5 6eV

P

( 6eV /c )

2.80

2.94

3.13

3.34

3.48

3.68

3.91

4.28

4.64

E(d30/d~ 3 )

(cm 2 c 3 6eV .-2 5 r - 1 )

(1.72 • 0.14) x 10 -31

(9.99 • 0.78) x 10 -~2

(4.43 -* 0.48) x 10 -3~

(1.56 • 0.27) x 10 -~

(1.14 • 0.22) x 10 -~

(7.84 • 1.72) × 10 -~3

(2.24 • 0.67) × 10 -3~

(6,60 • 3.81) x 10 -3~

(5.82 • 3.36) x 10 -~

~5 - 30.6 6eV

P•

(0eV;

2 . 9 6

3 . 0 5

3 . 1 4

3 . 2 3

3 . 3 2

3 . 4 1

3 . 5 3

3 .60

3 .71

3 .82

3 . 9 9

4 . 2 0

4 . 4 8

4 . 9 0

5.28

5 . 9 0

6 . 3 6

E(d30/d~ ~ )

(cm 2 c 3 6eV -2 5r-1)

(1.66 • 0.08) × 10 -~

(1.23 • 0.07) x 10 7M

(8.67 • 0.05) × 10 -~

(5.97 • 0.43) × 10 -~

(4.50 • 0 . 3 6 ) x 10 -~2

( 3 . 7 3 • 0 . 3 2 ) x 10 -~2

(2.17 • 0.20) x 10 -~2

(1.90 • 0 . 2 7 ) x 10 -32

( 1 . 2 7 • 0 . 1 5 ) x 10 -:~2

( 9 . 4 0 • 1 . 2 6 ) x 10 - ~

(4.24 • 0.66) x 10 -~3

(3.17 • 0.49) x 10 -~

(9.46 • 1.99) x 10 -3~

(5.04 • 1.30) x 10 -5~

( 1 . 7 7 • 0 . 7 3 ) x 10 - ~

(6.21 • 6.21) x 10 -35

(1.13 • 0 . 8 0 ) x 10 -3~

- 4 4 . 8 6eV

P1

2 . 6 4

2 . 7 9

3 . 0 0

3 . 1 7

3 . 3 2

3 . 4 2

3 . 5 1

3 . 6 0

3 . 6 9

3 . 7 8

3 . 8 7

3 . 9 6

4.05

4.14

4.27

4.42

4.61

4 . 9 3

5 . 3 8

5.86

E(d~01d~)

(cm 2 c ~ 6eV -~ 5r-*)

1.15 • 0.25) x 10 -~°

~.47 • 1.44) × 10 -~

).17 • 1.12) x 10 -5*

2.20 • 0.58) x 10 7M

L . 1 0 • 0.06) x 10 -~1

/ . 71 • 0 . 49 ) x 10 - : ~

5.87 • 0.42) x 10 -~

~ . 7 9 • 0.23) x 10 -~

3.48 • 0.19) x 10 "5=

2.97 • 0.17) x 10 -32

2.24 • 0.15) x 10 -~2

1.49 • 0.12) x 10 -~

1.45 • 0.12) x 10 -32

1.21 • 0.10) × 10 -~2

8.18 • 0.71) x 10 -~

5 . 7 8 • 0.49) x 10 -53

3.09 • 0.35) × 10 -~3

1.38 • 0.14) x 10 -33

7 . 3 6 • 0.99) x 10 - ~

1.98 • 0.50) x 10 -3~

~5 = 52.7 0eV

P•

(6ev1c)

2 . 5 9

2.68

2 .78

2 .87

2 .96

3 . 0 5

3.14

3.23

3.32

3.45

3.61

3 . 6 9

3 . 7 8

3.88

3 . 9 7

4.05

4.14

4.23

4 . 3 3

4 . 4 2

4.51

4.60

4.69

4.82

4.92

5 . 0 7

5 . 2 5

5 . 3 9

5 . 5 3

5.83

6 . 3 0

6 . 7 6

7 . 2 2

7 . 6 7

8 . 1 3

8.58

9 . 0 1

E(d 30/dp 3 )

(cm 2 c ~ 6eV -2 5r-1)

(1.64 • 0.11) × 10 -3°

1 .08 +- 0 . 0 5 ) x 10 -30

8 . 3 7 • 0 . 4 5 ) x 10 -31

6 . 5 4 • 0 . 3 9 ) x ~0 -31

4 . 3 6 • 0 . 3 2 ) x 10 -3 ]

3 . 5 9 • 0 . 2 9 ) x 10 -31

2 .26 • 0 . 2 3 ) x 10 -31

2 . 1 8 • 0 . 2 2 ) x 10 -~1

1 . 8 2 • 0 . 2 0 ) × 10 -31

1.41 • 0.14) x 10 -31

7.88 • 0.96) x 10 -32

~.96 -+ 0.16) × 10 -32

1.07 • 0.14) x 10 -a2

3.~8 • 0.12) x 10 -~2

2 .47 • 0.11) x 10 -52

2 . 1 9 • 0 . 0 6 ) × 10 -~2

1.66 • 0.05) x 10 -32

1.30 • 0.05) × 10 -~2

1.00 • 0.04) x 10 -32

8.23 • 0.35) x 10-33

6.89 • 0.31) x 10 -33

5.32 • 0.27) x 10 -33

4.32 t 0.24) x 10 -3~

3.67 • 0.19) x 10 -33

3.03 • 0.18) × 10 -33

2.23 t 0.12) x 10 -33

1.36 t 0.09) x 10 -33

8.84 • 1.15) x 10 -3~

7.57 • 0.66) x 10 -3~

3.90 • 0.29) x 10:3~

1.49 • 0.17) x 10 -~

6.91 -+ 1.15) × 10 -35

5.11 • 0.96) × 10 -3~

1.02 • 0.42) x 10 "35

1.11 • 0.43) x 10 "35

4.71 • 2.75) x 10 "3~

~.99 • 2.16) x 10 -~

¢~5 - 62.4 6eV

P•

(6eV1c)

2.89

3.08

3.25

3 . 4 4

3 . 6 4

3 . 9 2

4 . 1 8

4.56

E ( d 5 0 / d ~ 5 )

(era 2 c 5 0eV - 2 5 r - 1 )

(1.14 • 0.13) x 10 "3°

(4.72 • 0.81) x 10 -31

(3.92 -+ 0.69) x 10 -31

(2.21 -+ 0.49) x 10 -51

(7.92 • 2.40) x 10 -32

(6.94 • 2.10) x 10 -32

(4.00 • 1.22) x 10 "32

(1.62 • 0.73) x 10 -32

fr0m three 5et5 0f 1nf0rmat10n: the mea5urement5 0f a f1na1 ca116rat10n run at the CERN P5 d0ne 1mmed1- ate1y after the end 0f the exper1ment, the day-t0-day mea5urement5 0f the re1at1ve ca116rat10n, and the mea5- urement5 d0ne w1th 5tra19ht-thr0u9h part1c1e5 at the 15R. 7he +6% ener9y uncerta1nty re5u1t5 1n a n0rma11- 2at10n uncerta1nty 0f appr0x1mate1y -+45% at p• = 3 6eV/c, and appr0x1mate1y +-55% at p• = 5 6eV/c. 7h15 err0r 15 1ndependent 0f 5 and w111 n0t 5u65tant1a1- 1y chan9e the 5m00th fa11-0ff 1n p•. 111) An 5-dependent 6ut p.-1ndependent err0r 0f +-5% 1n n0rma112at10n at each 15R ener9y, wh1ch c0me5 fr0m the 1um1n051ty determ1nat10n u51n9 the Van der Meer meth0d. 1v) A p•-dependent and 5-dependent 5y5temat1c uncerta1nty that c0me5 f0rm the determ1nat10n 0f the tr199er 61a5 and detect10n eff1c1ency. 7h15 15 15% near p• --- 2.5 6eV/c, and 5% a60ve p• = 3 6eV/c.

7h15 1nvar1ant cr055-5ect10n5 wh1ch are 91ven f0r x/5 = 44.8 and 52.7 6eV are 5119ht1y h19her than th05e wh1ch have 6een pre5ented at the 5ame ener91e5 f0r 1n- c1u51ve char9ed p10n pr0duct10n near 90 ° [8, 9]. 7he uncerta1nty 1n 0ur ca116rat10n, h0wever, prevent5 u5 fr0m attach1n9 much 519n1f1cance t0 th15 d1fference.

An accepta61e f1t t0 the data f0r a11 ener91e5 can 6e made w1th the f0rm E(d3a/dp 3) = Ap-~nF(p~/x/~). Ch0051n9 F(p.L/x/~5 ) = exp(-6p.L/x/~ ) 9ave n =

( 8 . 2 4 +- 0.05), A -- ( 1 . 5 4 +- 0.10) X 10 -26, and 6 = (26.10 +- 0.50). 7he err0r5 f0r th15 f1t are 5tat15t1ca1 0n1y. 7he ×2 wa5 140.7 f0r 88 de9ree5 0f freed0m. 8ecau5e 0f the 5y5temat1c uncerta1nt1e5 ment10ned a60ve, a t0ta1 err0r 0f +0.70 mu5t 6e a5cr16ed t0 the va1ue 0f n. A p10t 0f the funct10n F 15 5h0wn 1n f19.4.

A 1ar9e num6er 0f the0ret1ca1 m0de15 have recent- 1y 6een pr0p05ed t0 attempt t0 acc0unt f0r the f1at- ten1n9 0f the p•-d15tr16ut10n at 90 °. M05t 0f the5e make u5e 0f 50me f0rm 0f 10ca1 5tructure 1n51de the pr0t0n t0 pr0v1de the h19h p2 1n the f1na1 5tate. 1n- deed, the p05516111ty.0f a 6reak 1n the 5teep exp0nen: t1a1 510pe 065erved at 10w p . wa5 ant1c1pated 6y 8er- man, 8j0rken and K09ut [10]. H0wever, the e1ectr0- ma9net1c f0rm they pred1ct, p.-4F(p~/Vr5), 15 n0t 06- 5erved 1n 0ur exper1ment. 0n the 0ther hand, a c0n- 5t1tuent exchan9e m0de1 pr0p05ed 6y 81anken6ec1er, 8r0d5ky and 6un10n [ 11], and extended 6y 0ther5 [12], d0e5 91ve an exce11ent acc0unt 0f the data.

We w15h t0 thank R. 80uh0t, 6 . 510her, 8.5m1th, J. L1nd5ay and F. D0u9hty f0r techn1ca1 a5515tance; J.5.8ea1e f0r he1p w1th 0n-11ne pr09ramm1n9; and

4 7 5

Page 6: Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

V01ume 468, num6er 3 PHY51C5 LE77ER5 1 0ct06er 1973

10-~

x 1027

1 J J

~6

10-25

A 5CAL1N6 0F 7HE 1NCLU51VE n ° CR055 5EC710N

A7 LAR6E 7RAN5VER5E M0MEN7A

5YM80L ~ (0eV) J

• 23.5 A 30.6 [] 44.8

• 52.7

0 62.4 1 1 • 1 1 = 1 J 1 J 1 t 1 = 1

0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.20

] 1 1

0.18

F19. 4 .7he funct10nF(p~/~/5 -) = p~E(d30/dp3), a5 deduced fr0m0urmea5urement5, u51n9 the 6e5t f1t va1ue n = 8.24.7he err0r5 are 5tat15t1ca1 0n1y.

M.A. Hu6er, W. 5w1atek and W. Du1nker f0r a1d 1n the 1a60rat0ry. 7 h e C01um61a and R0ckefe11er Un1ver51ty

c011a60rat0r5 w15h e5pec1aUy t0,expre55 the1r apprec1a-

t10n f0r the 9ener0u5 h05p1ta11ty 0 f CERN. We are a11

1nde6ted t0 the 15R 5taff f0r the 0ut5tand1n9 5ucce55

the 0perat10n 0 f th15 mach1ne repre5ent5•

R e f e r e n c e 5

[1] 6. C0cc0n1, Nu0v0 C1m. 57A (1968) 837; K. 1maeda, Nu0v0 C1m. 48A (1967) 482; and reference5 there1n.

[2] Pref1m1nary data 0n the pr0duct10n 0f 1ar9e tran5ver5e- m0mentum ~r°~5 were pre5ented 6y th15 c011a60rat10n a60ut 0ne year a90.5ee Pr0c. 16th 1nt. C0f. 0n H19h- ener9y phy51c5, 8atav1a, ed5. J.D. Jack50n and A. R06ert5 (NAL, 8atav1a, 1972), V01. 3, p. 317.

[3] F.W. 81155er et a1., Pr0c.Vander611t C0~f. 0n New re5u1t5 fr0m exper1ment5 0n h19h-ener9y part1c1e5 c0111510n5, /~1a5hv111e, 7enne55ee, March 1973.

[4] 8.J. 81umenfe1d, L.M. Lederman, R.L. C001 and 5.L. 5e91er, Nuc1ear 1n5tr• 97 (1971) 427.

[5] J. Menefee and Y. Ch0, 1EEE 7ran5• Nuc1. 5c1. N5-13, 159 (1966)•

[6] J.5.8ea1e et a1., A 1ead-91a55 Cerenk0v detect0r f0r e1ec- tr0n5 and ph0t0n5, Pr0c. 1nt. C0nf. 0n 1n5trumentat10n f0r h19h-ener9y phy51c5, Fra5cat1, May 1973.

[7] 5. Van der Meer, CERN 1nterna1 Rep0rt 15R-P0/68-31 (1968) unpu6115hed•

[8] M.6anner et a1., Phy5. Lett. 448 (1973) 537. [9] 8. A1per et a1., Phy5. Lett. 448 (1973) 521.

[10] 5.M. 8erman, J.D. 8j0rken and J.8. K09ut, Phy5. Rev. D4 (1971) 3388.

[ 11 ] R. 81anken6ec1er, 5.J. 8r0d5ky and J.F. 6un10n. Phy5. Lett. 428 (1972) 461.

[12] P.V. Land5h0ff and J.C. P01k1n9h0rne, prepr1nt5 DAM7P 72/43 and DAM7P 72/48.

476