Heavy Higgs production in e+e− and e−e− collisions

V01ume 1648, num6er 4,5,6

HEAVY H1665

PHY51C5 LE77ER5

PR0DUC710N

1N e + e - A N D e - e -

12 Decem6er 1985

C0LL1510N5

Ken-1ch1 H 1 K A 5 A Phy51c5 Department, un1ver51ty 0f w15c0n51n, Mad150n, w1 53706, u5A

Rece1ved 13 5eptem6er 1985

Pr0duct10n 0f a heavy H19956050n 1n very h19h ener9y e+e and e-e 1nteract10n515 5tud1ed. 7he tw0-ph0t0n 6ack9r0und f0r the H --. w • w decay m0de 15 5h0wn t0 6e 519n1f1cantand 1t5 reduct10n 15 d15cu55ed, c0mpar150n 0f e+e - and e e c0111510n515 made.

1. 1ntr0duct10n. After the d15c0very [ 1 ] 0f the weak 1ntermed1ate 6050n5 W • and 2 0, the H1995 6050n rema1n5 the m05t 1ntr19u1n9 6ut t0ta11y unc0nf1rmed pred1ct10n 0f the 5tandard m0de1 [2]. 7he 0n1y exper1menta1 1nf0rmat10n c0ncern1n9 the H1995 5ect0r 15 the p parameter, the rat10 0f the neutra1- and the char9edcurrent effect1ve c0up11n9, 0r 2 2 p = M ~ V / M 2 c0520W,

wh1ch 15 very c105e t0 un1ty [1,3] and 5u99e5t5 that the H1995 f1e1d tran5f0rm5 a5 a d0u61et 0f the weak 5U(2) 9r0up. 7he 5tandard 5U(2) X U(1) the0ry w1th 0ne H1995 d0u61et 91ve5 a re1at10n 6etween the ma55 0f any part1c1e and the c0up11n9 0f that part1c1e w1th H1995 1n term5 0f the vacuum expectat10n va1ue. Unf0rtunate1y, ne1ther 15 kn0wn f0r the H1995 1t5e1f, 1eav1n9 1t5 ma55 unpred1cted. 5evera1 attempt5 t0 11m1t the a110wed ran9e 0f the H1995 ma55 have 6een made, wh1ch 5h0w5 that the ma55 cann0t 6e t00 d1fferent fr0m the weak 1nteract10n 5ca1e. Ar9ument5 6a5ed 0n the 5ta6111ty 0f the 5ymmetry-6r0ken vacuum 91ve a 10wer 60und [4] .1 MH 2 10 6eV. 0 n the 0ther hand, the re4u1rement 0f the va11d1ty 0f pertur6at10n expan510n 1ead5 t0 an upper 60und [6] MH ~ 1 7eV. A60ve th15 va1ue, the H1995 5ect0r 6ec0me5 5tr0n91y 1nteract1n9 [7] and we 105e much 0f the pred1ct1ve p0wer 0f the the0ry. Detect10n 0f a re1at1ve1y 119ht (MH ~ 100 6eV)

,1 F0r c05m0109Y-6a5ed11m1t5,5ee ref. [5]. 0370-2693/85/$ 03.30 • E15ev1er 5c1ence Pu6115her5 8.V. (N0rth-H011and Phy51c5 Pu6115h1n9 D1v1510n)

H1995 6050n ha5 6een eXten51ve1y d15Cu55ed 1n the 11terature ,2. E1eCtr0n--p051tr0n C0111510n5are m05t effect1ve 1n pr0duc1n9 and detect1n9 H1995 v1a react10n5 e+e - ~ 0(tt-) -~ H7 [9], e+e - ~ 2 -~ H£~ [10], and/0r e+e - ~ 2 H [ 1 1 - 1 3 ] . Recent1y pr0duct10n 0f a heav1er H1995 6050n ha5 attracted much attent10n. F0r MH 200 6 e V the H1995 part1c1e decay5 pred0m1nant1y 1nt0 weak 6050n pa1r5 W+W- and 2 2 (the rat10 6e1n9 2 : 1 a5ympt0t1ca11y) un1e55 there are n0 5uperheavy 9enerat10n5. Furtherm0re, the pr0duct10n pr0ce55 tend5 t0 6e d0m1nated 6y weak 6050n fu510n .3 a5 the H1995 ma55 1ncrea5e5.7he cr055 5ect10n f0r e+e - [14] pp [15,13] and ep [13] c0111510n5ha5 6een 06ta1ned. 1n th15 paper 1 exam1ne the pr0duct10n 0f the heavy H1995 6050n 1n e+e - and e - e - 1nteract10n5 v1a 9au9e 6050n fu510n. Part1cu1ar empha515 15 put 0n tw0 p01nt5. F1r5t, a prev10u51y unc0n51dered 6ack9r0und t0 the W+W- decay m0de - tw0-ph0t0n pr0duct10n 0f the W pa1r - 15 p01nted 0ut and ca1cu1ated. A1th0u9h th15 pr0ce55 15 5uppre55ed 6y a fact0r 0f a re1at1ve t0 re50nant H1995 pr0duct10n, 1t 9a1n5 an enhancement fact0r 0f 1ar9e 109ar1thm5, wh1ch make5 th15 6ack9r0und a 519n1f1cant 0ne. 7hen 1 d15cu55 h0w t0 reduce th15 6ack9r0und. 5ec0nd, 1 d15cu55 e1ectr0n-e1ectr0n c0111510n5 a5 a 50urce 0f heavy H1995.1n v1ew 0f the fact that future very-h19h-ener9y e+e - c0111d1n9mach1ne5 w111n0 10n9er 6e 5t0ra9e r1n95 6ut 11near c0111der5, ,2 F0r rev1ew5, 5ee ref. [8]. ~:3 7he 1mp0rtance 0f th15 mechan15m wa5 ftr5t p01nted 0ut 6y Cahn and Daw50n [ 15]. 385

V01ume 1648, num6er 4,5,6

PHY51C5 L E 7 7 E R 5

e e c0111510nmay 6e an 0pt10n f0r th05e acce1erat0r5. An advanta9e 0f e - e - 0ver e+e - 15 that there are n0 ann1h11at10n 6ack9r0und5. C0mpar150n 0f e e and e+e - 1n 60th the 519na1 and the 6ack9r0und 15 made.

2. 7w0-ph0t0n 6ack9r0Und. Pr0duct10n 0f the heavy H1995 6050n 1n e+e - c0111510n5wa5 f1r5t c0n51dered 6y J0ne5 and Petc0v [ 12]. 7he1r Ca1Cu1at10n 1nd1cate5 that the WW/22 fu510n mechan15m (5ee f19. 1) e+e - ~ (vv-W+*W-*) -+ v~H,

(1a)

e+e - ~ ( e + e - 2 * 2 *) ~ e+e-H

(16)

tend5 t0 d0m1nate the cr055 5eCt10n f0r 1ar9e H1995 ma55e5. 7hey re5tr1cted them5e1ve5 t0 LEP ener91e5, h0wever, hence t0 H1995 ma55 6e10w 180 6eV. 7he Ca5e 0f heav1er H1995 wa5 exam1ned 6y Daw50n and R05ner [14] wh0 c0nC1uded that the fu510n mechan15m (1) c0mp1ete1y d0m1nate5 the cr055 5ect10n a60ve LEP ener91e5. 7hey ca1cu1ated the 6ack9r0und pr0ce55e5 e+e - ~ W+W- ,

22,

ff,

(2)

and m05t 1mp0rtanf1y, ann1h11at10n 1nt0 a weak 6050n pa1r w1th 1n1t1a1-5tate 6rem55trah1un9 e+e - -~ W+W- 7, 2 2 7

(3)

and c1a1med that th15 6ack9r0und exceed5 the 519na1 f0r MH 2 400 (900) 6 e V at ~ = 1 (2) 7eV. 1n th15 5ect10n 1 exam1ne an0ther 6ack9r0und pr0ce55 (5ee f19. 2) e+e - ~ (e+e - 7*7*) ~ e + e - w + w - ,

(4)

wh1ch ha5 n0t 6een c0n51dered 50 far. A1th0u9h th15 pr0ce55 15 0f h19her 0rder 1n a than the fu510n pr0ce55 (1), 1t 15 fav0red 6y a 1ar9e 109ar1thm1c fact0r (109(5/m2))2 c0m1n9 fr0m ma55 51n9u1ar1ty. M0re0ver, the cr055 5ect10n 15 pr0p0rt10na1 t0 1/M2, n0t t0 1/5. 7he5e enhanc1n9 fact0r5 make th15 6ack9r0und an 1mp0rtant 0ne. N0te that th15 pr0ce55 c0ntr16ute5 0n1y

e-

e+

-

W

-

u

C

•

~"

e•

-

•

e--

-

e-

W* e•

f

,

e•

F19. 2. D1a9ram f0r tw0-ph0t0n pr0duct10n 0fW+W- pa1r. 7he 6106 repre5ent5 the 5um 0f the d1a9ram51n f19. 3. t0 the W+W- decay m0de 0f the H1995 6050n. 7here 15 n0 5uch 6ack9r0und f0r the 2 2 m0de. 7he cr055 5ect10n f0r (4) can 6e we11 e5t1mated u51n9 the effect1ve ph0t0n appr0x1mat10n [16,17]

da/dw 2 = w -2 a(77-~ w+w-; w 2) r d2(77)/dr,

(5)

where W 15 the W+W- center-0f-ma55 ener9y, r = W2/5 and d£(77)/dr 15 the effect1ve tw0-ph0t0n 1um1n051ty r d£(77)/dr = (0t/2n) 2 [109(5/m2)]2 X [(2 + r) 2109(1/7) -- 2(1 - r)(3 + 7)1 •

(6)

7he cr055 5ect10n f0r 77 -~ W+W- ha5 6een ca1cu1ated [ 18,19] fr0m d1a9ram5 0f f19. 3 : 0 ( 3 , 7 - W+W-; W2) = (81r0t213/M2 ) × {1 + (3/1672){1 + 1/72 + (1/72)(1 - 1/272)(1/3) 109[(1 + 3)/(1 - 3)]}}, (7) Where 7 = W/2MW, 3 = (1 -- 4M2W/W2)1/2. 7he 6aCk9r0Und Cr055 5ect10n 06ta1ned fr0m (5)-(7) 15 p10tted 1n f19. 4. 7he 519na1,4 fr0m W+W- fu• 4 7he re50nance 5hape 15 06ta1ned u51n9 the effect1ve W appr0x1mat10n [20] and an an5at2 f0r the W+W-- --*H

W+W- cr055 5ect10n wh1ch, when app11ed t0 22 ~ H ~ 22, rea50na61y repr0duce5 the ca1cu1at10nu51n9 the exact rem1t [21] f0r22 ~22.

e-

e+

F19. 1. WW and 2 2 fu510n d1a9ram f0r e+e - ~ H1995 + X.

386

12 Decem6er 1985

F19. 3. D1a9ram5f0r 73, -* W+W-•.

V01ume 1648, num6er 4,5,6 10

,

PHY51C5 LE77ER5 1

1

12 Decem6er 1985

at h19h ener91e5: the fma1 W•5 are preferent1a11y tran5ver5e. 1 ca1cu1ated the cr055 5ect10n f0r y y ~ V~LW~ where L den0te5 he11c1ty 0:

1

1

d0(y~/-~ ~ L W ~ ) / d c05/9* = (rra2f11W2) X [(1 + 3,-2)251n40*+3,-4]/(1 --/32c0520*) 2.

e-5

(9)

10-• 7he re5u1t1n9 cr055 5eCt10n f0r e+e - ~ e + e - ~ L W ~ v1a the tW0-ph0t0n mechan15m 15 5h0wn 1n f19. 4. 5e1ect10n 0f a he11c1ty-0 c0mp0nent make5 the 6ack9r0und a1m05t ne9119161e, 1eav1n9 the 519na1 a1m05t 1ntact. 7he 5eparat10n 0f the 10n91tud1na1 and tran5ver5e c0mp0nent5 0 f W can 6e ach1eved u51n9 the an9u1ar d15tr16ut10n 0f1ept0n/jet5 fr0m the W decay. 7he decay an9u1ar d15tr16ut10n 0f W w1th def1n1te he11c1ty 15

70

70

10-2:

~d

, 20(

1 ,

1 ,

• ~,

600 W (6eV)

1000

F19. 4. 519na1 and 6ack9r0und f0r H ~ W+W- 1n e+e - c0111510n5. 7he re50nance curve5 repre5ent the H1995cr055 5ect10n w1th f•m11e w1dth c0rrect10n f0rM H = 300, 500, 700 and 900 6eV. 7he upperm05t curve 15 the t0ta1 cr055 5ect10n f0r the tw0-ph0t0n 6ack9r0und. 7he 10wer tw0 5011dcurve5 5h0w the effect 0f the an9u1ar cut 1c05 0*1 < 0.75 and 0.50. 7he da5hed curve 15 the tw0-ph0t0n cr055 5ect10n 0f 10n91tud1na1 W pa1r5. 510n (1 a) f0r var10u5 H1995 ma55e5 15 a150 5h0wn. 7he re50nance 519na1 15 v1rtua11y 6ur1ed 1n the 6ack9r0und, e5pec1a11y f0r heav1er 1-11995. 1t 15 0f 9reat 1mp0rtance t0 reduce th15 6ack9r0und. At h19her ener91e5 W2 >>M2 , a 1ar9e p0rt10n 0f the cr055 5ect10n (7) c0me5 fr0m the f0rward/6ackward re910n re5u1t1n9 fr0m the t-/u-Channe1 W exchan9e. 7hu5 a cut 0n the 5catter1n9 an91e 5h0u1d 5uppre55 the cr055 5eCt10n. 7he d1fferent1a1 Cr055 5eCt10n f0r Y•t ~ W+W- ha5 6een eva1uated [19] : dtr/d c05 0* = (rrt~2/3/W2) [3 -- (16 + 6/72)/(1 --/32 c0520 *) + (32 + 6/3,4)/(1 -- f12 c0520*)2] ,

(8)

where 0* 15 the W - p01ar an91e fr0m the 3' d1rect10n 1n the 77CM frame. 7he effect 0 f t h e cut 1c05 0*1 < 0.75 0r 0.50 can 6e 5een 1n f19. 4; the 6ack9r0und cr055 5ect10n 15 dra5t1ca11y reduced at h19h W. N0t1ce that the 519na1 5h0u1d a150 6e reduced 6y a fact0r 0.75 0r 0.50 6y the cut. An0ther p055161e appr0ach t0 5uppre55 the 6ack9r0und 15 t0 extract the he11c1ty-0 W 6050n5. 7he heavy H1995 6050n 15 kn0wn t0 c0up1e d0m1nant1y w1th the 10n91tud1na1 c0mp0nent 0f the weak 6050m Meanwh11e, the pr0ce55 y~/~ W+W - 15 ••he11c1ty-c0n5erv1n9••

d F / d c05 0 0:~(1 ~7c05 0) 2 0c 51n20

he11c1ty +1 , he11c1ty 0 ,

(10)

where 0 15 the 1ept0n (4uark) p01ar an91e 1n the W re5t frame mea5ured fr0m the d1rect10n 0f W m0mentum 1n the W+W- CM frame. (1nterference 0f d1fferent he11c1ty c0mp0nent5 91ve5 an a21mutha1 an91e dependence ,5, wh1ch d0e5 n0t affect the p01ar an91e d15tr16ut10n after 1nte9rat1n9 0ver the a21mutha1 an91e.) We 5h0u1d n0te, h0wever, that the extract10n 0f the 10n91tud1na1 c0mp0nent 15 5tat15t1ca1 1n nature, un11ke the an9u1ar cut prev10u51y d15cu55ed. 7hu5 a 1ar9e 5tat15t1c5 15 needed t0 5eparate the 10n91tud1na1 519na1 fr0m the tran5ver5e 6ack9r0und. A5 n0ted 6ef0re, the 2 2 decay m0de 0f H1995 d0e5 n0t 5uffer fr0m the tw0-ph0t0n 6ack9r0und. 7he char9ed 1ept0n decay m0de 0 f 2 91ve5 a very c1ean 519na1. Unf0rtunate1y, the 6ranch1n9 rat10 0 f 2 ~ 9~ 15 0n1y 10% even after add1n9 a11 three 1ept0n 5pec1e5. M05t (~70%) 0f 2•5 decay 1nt0 jet5, where the 5eparat10n 0fW•5 and 2•5 15 n0t ea5y. Prec15e determ1nat10n 0f the 1nvar1ant ma55, mea5urement 0f the t0ta1 char9e 0r the 1ead1n9 char9e may he1p 1n d15t1n9u15h1n9 2•5 fr0m W•5 1n the1r hadr0n1c decay m0de5. 7here ex15t5 the 5ame 6ack9r0und 1n pp (p~) c0111der5. 7he 6ack9r0und 151e55 1mp0rtant here 6ecau5e 4uark5 have 5ma11er e1ectr1c char9e5 than e1ectr0n5. 1f we a55ume the 5ea d0m1nance 0f 5tructure funct10n5, the re1at1ve 1mp0rtance 0f th15 6ack9r0und 1n pp 15 ,5 7h15 a21mutha1 an91e dependence may a150 6e u5efu1 f0r the 5eparat10n. 387

V01ume 1648, num6er 4,5,6

PHY51C5 LE77ER5

25/162 ~ 0.15 t1me5 that 1n e+e - . 1t 151mp0rtant, h0wever, t0 make a further 5tudy 0f the tw0-ph0t0n 6ack9r0und 1n hadr0n c0U1der5.

3. e - e - c0111510n5. E1ectr0n-e1ectr0n c0111510n5 have n0t attracted much 1ntere5t 6ecau5e there 15 n0 ann1h11at10n pr0ce55. 7echn1ca11y m05t e+e - c0111d1n9 mach1ne5 have 6een 51n91e-r1n9 5t0ra9e r1n95 wh1ch d0 n0t a110w e e c0U1510n5exper1ment5 t0 6e perf0rmed. Future e+e - c0111der5 after LEP are expected t0 6e 11near c0111der5 [22], where the e e 0pt10n may 6e p055161e a5 we11. M05t 0f the 6ack9r0und5 0f heavy H1995 pr0duct10n d15cu55ed at the 6e91nn1n9 0f the prev10u5 5ect10n are ann1hf1at10n pr0ce55e5. 7hey are a65ent 1n e - e - c0111510n5. 7h15 fact make5 1t w0rthwh11e t0 5tudy e - e - c0111510n5 a5 a 50urce 0f heavy H1995. 7here are d1fference5 6etween e+e - and e e pr0duct10n mechan15m5. F1r5t, an e1ectr0n can em1t W-, 2 0, 0r 7, 6ut n0t W+. 50 there 15 n0 WW fu510n 1n e e c0111510n5, 1eav1n9 2 2 fu510n a10ne. 5ec0nd, 6ecau5e the f1na1 5tate ha5 tw0 e1ectr0n5, there 15 a cr055ed d1a9ram (5ee f19. 5). 7he cr055 5ect10n f0r the pr0ce55 e e ~ e - e - H 15 ca1cu1ated exact1y 6y a numer1ca1 meth0d 51m11art0 ref. [14] (5ee a150 ref5. [15,23]): 0 ( e - e - -+ e - e - H )

2e 3M 2

.

=2r 51n60Wc0560W 52 J

1

d21d2 2 f

-1

2,r

dc05/3

f

0

de

X {(0e4+ 60~a 2 + a4)(21+22~1+rH)(1~1+P1P2) + (02 - a2) 2 •212 2 [1 + c05(e + 0) 51n/~1 X [1 - c05 e 51n/3]/~1),

(11)

where P1 = {[21(1 + c05 e 51n/3) + 2r2] X [22(1 - c05(a+ 0) 51n 13) + 2r2]} - 1 ,

e-(P1) " 21 ~ e-(P~1) 21..... H , e-(p2) ( • e-(p2)

~

F19. 5. D1a9ram5f0r e" e ~ e-e-H. 388

12 Decem6er 1985

P2 = {[21(1 - c 0 5 e 51n/]) + 2r2] X [22(1 + C05(e + 0) 51n ~) + 2r21} - 1 , c05 0 = 1 - (2[2122)(21 + 22 - 1 + rH), and

0e=-•+ 51n20w, ae=-•, r . = M 2 /5 ,

= M22/5 .

7he 1nte9ra1 var1a61e5 21,22 are def1ned 6y

21 = 24. p;15

(1 = 1,2),

where 4 = P1 + P2 (m0menta are def1ned 1n f19. 5) and e, 9 are tw0 0f the Eu1er an91e5 wh1ch determ1ne the 0r1entat10n 0f the f1na1-5tate p1ane. 7he 1nte9rat10n 0ver 21 and 22 15 f0r the re910n 5at15fy1n9 the 1ne4ua11t1e5 0 ~<21,22 ~< 1 - - r H , (1

-

21)(1

-

21 +22~> 1 - r H ,

22) 1> r n .

1t turn5 0ut that the c0ntr16ut10n 0f the cr055 term (pr0p0rt10na1 t0 P1P2) 15 ne9119161e 1n the ent1re re910n 0f 1ntere5t, wh1ch 1nd1cate5 that the effect1ve 2 appr0x1mat10n 5h0u1d 6e very accurate 1f f1n1te-ma55 effect5 are pr0per1y 1nc0rp0rated. 7he 5ec0nd term 0f (11), wh1ch 15 a65ent f0r WW fu510n, c0ntr16ute5 ~ 4 7 % 0f the t0ta1 cr055 5ect10n. 7he H1995 pr0duct10n cr055 5ect10n ca1cu1ated fr0m e4. (11) 15 5h0wn 1n f19. 6.1t 15 ten t1me5 5ma11er than that 1n the e+e - 1nteract10n v1a WW fu510n (1a). 7h15 rat10 15 very c105e t0 the rat10 0f 2 2 and WW 1um1n051ty funct10n5 16(02

+

a2)/c0540W

=

0.106.

(12)

7he a60ve cr055 5ect10n 5eem5 t0 6e very 5ma1L We n0te that, h0wever, the cr055 5ect10n f0r e+e - ~/~+/~at the5e ener91e5 15 a150 5ma11:114 (29,7) f6 at X/r5-= 1 (2,4) 7eV. A55um1n9 an 1nte9rated 1um1n051ty 0f 1040 cm - 2 (= 10 f6 -1, wh1ch c0rre5p0nd5 t0 a 0neyear run at 1033 cm - 2 5-f), we 9et 100 event5 f0r M H < 300 (700, 1000) 6 e V at V~ = 1 (2,4) 6eV. A5 prev10u51y d15cu55ed, there are n0 ann1h11at10n 6ack9r0und5 t0 th15 pr0ce55. H0wever, there are n0nann1h11at10n 6ack9r0und5. 7he m05t 1mp0rtant 6ack9r0und 15 the tw0-ph0t0n pr0duct10n 0f W pa1r5 d15-

PHY51C5 LE77ER5

V01ume 1648, num6er 4,5,6 1

1

1

~

[

1

1

12 Decem6er 1985

needed. 7here 15 n0 6ack9r0und 0f th15 k1nd f0r the

t

H ..+2 2 m0de. E1ectr0n-e1ectr0n c0111510n5pr0v1de a c1ean 50urce 0f heavy H1995 6050n5 a5 there 15 n0 ann1h11at10n 6ack9r0und. 7he cr055 5ect10n 15 0ne-tenth 0f that 1n e+e 1nteract10n5, h0wever.

~

10-2

10-3

10-4

1

200

600

100C

1 w0u1d 11ke t0 thank M.6. 01550n f0r read1n9 the manu5cr1pt, K. Ha91wara, R.D. Pecce1, and D. 2eppenfe1d f0r u5efu1 d15cu5510n5. 7h15 re5earch wa5 5upp0rted 1n part 6y the Un1ver51ty 0f W15c0n51nRe5earch C0mm1ttee w1th fund5 9ranted 6y the W15c0n51nA1umn1 Re5earch F0undat10n, and 1n part 6y the U5 Department 0f Ener9y under c0ntract DE-AC02-76ER00881.

m H (6eV)

F19. 6. Cr055 5ect10n5f0r H1995pr0duct10n. 5011dcurve: a ( e - e - ~ e - e - H ) at ~ = 1, 2, and 4 7eV fr0m 6e10w t0 a60ve. Da5hed curve: a(e+e - ~ vv--H)at x/~ = 2 7eV. D0tted curve: a (e+e- ~ 2H) [ 11 ] at the 0p f1rna1x/~ f0r each MH.

cu55ed 1n 5ect10n 2 . 7 h e cr055 5ect10n f0r th15 6ack9r0und 15 the 5ame a5 that f0r e•e - c0111510n5w1th1n e4u1va1ent-ph0t0n appr0x1mat10n. 1t 15 m0re 5evere 1n e - e - 1nteract10n5 a5 the 519na115 ten t1me5 5ma11er. 7hu5 1t 15 very 1mp0rtant t0 5eparate the 2 2 f1na1 5tate, wh1ch d0e5 n0t 5uffer fr0m th15 6ack9r0und, fr0m the W+W- fma1 5tate. 0 t h e r 6ack9r0und5 1nc1ude d0u61e 6rem55trah1un9 0 f 2 2 , W - 2 , 0r W - W - pa1r5 (5ee f19. 7). 7h15 6ack9r0und 15 h19her 0rder 1n a and f1na1 9au9e 6050n pa1r5 are m05t1y 1n the f0rward d1rect10n. 50 1t 5h0u1d n0t 6e very d1ff1cu1t t0 treat th15 k1nd 0f 6ack9r0und.

4. 5Ummary. 7he cr055 5eCt10n f0r the tw0-ph0t0n 6aCk9r0und t0 the pr0ce55 e+e - -~ v~H, H -~ W+W- 15 much 1ar9er than the re50nance 519na1. An an9U1ar cut 0n the W d1rect10n rea50na61y reduce5 th15 6ack9r0und. 5e1ect10n 0f he11c1ty-0 W pa1r5 15 very effect1ve 1n 5uppre551n9 the 6aCk9r0und, a1th0u9h a 1ar9e 5tat15t1c5 15

/

1

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•1

F19. 7, Examp1e5 0f d1a9ram5f0r d0u61e 6rem55ttah1un9pr0duct10n 0f 9au9e 6050n pa1r5 1n e - e - c0111510n5

Reference5 [1] UA1 C011a6., 6. Arn150net a1., Phy5. Lett. 1228 (1983) 103; 1268 (1983) 298; UA2 C0Ua6., M. 8anner et a1., Phy5. Lett. 1228 (1983) 476; UA2 C011a6., P. 8a9na1a et a1., Phy5. Lett. 1298 (1983) 130. [2] 5. We1n6er9,Phy5. Rev. Lett. 19 (1967) 1264; A. 5a1am, 1n: E1ementary part1c1e the0ry, ec1.N. 5varth01m (A1m4u15tand W1k5eU,5t0ckh01m, 1968) p. 367. [3] J.E. K1m,P. Lan9acker, M. Lev1neand H.H. W1111am5, Rev. M0d. Phy5. 53 (1981) 211. [4] A.D. L1nde, JE7P Lett. 23 (1976) 64; 5. We1n6er9,Phy5. Rev. Lett. 36 (1976) 294. [5] A.H. 6uth and E.J. We1n6er9,Phy5. Rev. LetL 45 (1980) 1131; F•, W1tten, NucL Phy5. 8177 (1981) 477; P.J. 5te1rthardt, NucL Phy5. 8179 (1981) 492. [6] 8.W. Lee, C. Qu199and H.8. 7acker, Phy5. Rev. Lett. 38 (1977) 883; Phy5. Rev. D16 (1977) 1519. [7] M. Ve1tman, Acta Phy5. P010n. 88 (1977) 475. [8] J. E1115,M.K. 6a111ard and D.V. Nan0p0u105,Nuc1. Phy5. 8106 (1976) 292; M.K. 6a111ard, C0mm. Nuc1. Part. Phy5. 8 (1978) 31; 6. 8ar61eU1n1et a1., 7he pr0duct10n and detect10n 0f H1995part1c1e5 at LEP, ECFA/LEP W0rk1n96r0up Rep0rt 556/9/4, DE5Y 79/27; A.1. Va1n5hte1n,V.1. 2akhar0v and M.A. 5h1fman, 50v. Phy5. U5p. 23 (1980) 429; A. A11,Phen0men0109y 0f the H19956050n, DE5Y prepr1nt DE5Y 81-060. [9] F. W11c2ek,Phy5. Rev. Lett. 39 (1977) 1304. [10] J.D. 8j0rken, 1n: Pr0c. 1976 5LAC 5ummer 1n5t1tute, 5LAC-198 (1976) p. 1; E. Ma and J. 0kada, Phy5. Rev. D20 (1979) 1052; J. F1nj0rd, Phy~ 5cr. 21 (1980) 143. [11] 8.W. Lee, C. Qu199and H.8. 7hacker, Phy5. Rev. D16 (1977) 1519; 389

V01ume 1648, num6er 4,5,6

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[14] [15] [ 16]

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PHY51C5 LE77ER5

8.L. 10ffe and V.A. Kh02e, 50v. J. Part. Nuc1. 9 (1978) 50; 5.L. 61a5h0w, D.V. Nan0p0u105 and A. Y11d12,Phy5. Rev. D18 (1978) 1724. D.R.7. J0ne5 and 5.7. Petc0v, Phy5. Lett. 848 (1979) 440. D.A. D1cu5 and 5.5.D. W1Uen6r0ck, H1995 6050n5 fr0m vect0r 6050n fu510n 1n e+e- , ep and pp c0111510n5, Un1ver51ty 0f 7exa5 prepr1nt U776-12-85. 5. Daw50n and J.L. R05ner, Phy5. Lett. 1488 (1984) 497. R.N. Cahn and 5. Daw50n, Phy5. Lett 1368 (1984) 196; 1388 (1984) 464 (E). C.F. v0n We125f1cker, 2. Phya 88 (1934) 612; Ed. W1111am5,Phy5. Rev. 45 (1934) 729; K91. Dan5ke V1den5ka6. 5e15ka6. Mat.-Fy5. Medd. 13, N0. 4 (1934) 1.

12 Decem6er 1985

[17] 5. 8r0d5ky, 7. K1n05h1ta and H. 7era2awa, Phy5. Rev. D4 (1971) 1532. [18] 0.P. 5u5hk0v, V.V. F1am6aum and 1.8. Khr1p10v1ch, 50v. J. Nuc1. Phy5. 20 (1975) 537. [19] K.J. K1m and Y.-5. 75a1, Phy5. Rev. D8 (1973) 3109; 6. 7upper and M.A. 5amue1, Phy5. Rev. D23 (1981) 1933; M. Katuya, Phy5. Lett. 1248 (1983) 421. [20] 6. Kane, W1nd0w5 f0r new phy51c5 at 5uper c0111der5, Un1ver51ty 0f M1ch19an prepr1nt UM 7H 83-25; 6 . L Kane, W.W. Repk0 and W.8. R01n1ck, Phy5. Lett. 1488 (1984) 367; 5. Daw50n, Nuc1. Phy5. 8249 (1985) 42. [21] K. H1ka5a, paper 1n preparat10n. [22] 8. R1chter, Lar9e 11near c0111der5, 5LAC prepr1nt 5LAC-PU8-3371 (1984). [23] R.N. Cahn, Nuc1. Phy5. 8255 (1985) 341.