A STUDY OF THE "LEADING" PA_R1,ICLE EFFECT IN HADRON PHYSICS OVER A
1WIDE ENERGY
RANGE
1
Michiyuki Chikawa
Resea1·ch Institute for Science and Technology, J(inki University
Takeharu Konishi
Department of Mathmatics and Physics, [{inki Unive1·sity
(Received December 1, 1989)
Abstract
A study of the "leading" particle effect is reported for the productions of Kaon, Lambda, anti-Lambda. and Sigma in the interactions of proton-proton at 405 GeV /c[.5,6,H), proton- antiproton at 3 and 4 GeV /c[lS-20)- And we compare the other experimental data which includes strangeness or non-strangeness mesons and ba.ryons over a. wide energy range, center of energy of 25 to 62 Ge V _ Even the in- tera.ctions at low energy, it is shown that the "leading" particle effect is presented clea.rly for baryoit productions and also observed for meson productions in case of the pa.rtides contain initial quarks.
Key Words: Proton-proton; proton-a.ntiproton; leaading effect.
Introduction
t.ion;a+ b-+ c +anything. ( 1) . A study of cha.raderistics in hadronic interactions
induced by proton-proton and proton-antiproton is reported in this paper. In these strong in- teractions, the ''leading' particle effect is appear clearly. And it seems that center of energy avail- able do not affect to the "leading' effect.
In sect. 2 definition of a quantity of the "lead- ing' effect is given, in sect. 3 the "leading' effect of the hadronic interactions are analyzed and in sect. 4 summary is presented.
In this interaction particles a and b are incident and target hadron, and particle c is the "leading' particle. Current study we use a variable in term of longitudinal fractional momentum because the variable can be suitable to express the "leading' effect. The varia.ble, Feynman x, is defined by
2 Definition quantity
of "leading"
In a given hadronic interaction, the "leading" par- ticle effect is indicated that the particle carries away sizahle fraction of the total available en- ergy[l ]. vVe consider following inclusive. interac-
x = - -p*
P~ax (2)
where p* and P:nax are the longitudinal momentum and its maximum in the center-of-mass(CM) sys- tem. The invariant cross section F(x) as a func- tion of FeynmaJrl variable is by following expres- sion;
E•
loo
daF(x) = - - d d dpr,
Pmax 0 X PT
(3)
where E* and PT are energy in the CM system and transverse momentum of the produced par- ticle. To quantilfy the "leading' effect, following
Table-1( a) The quark con positions and the number of spectator quarks of the hadrons in the final state for the proton-proton interactions, and
pp processes
initial state ( uud)+( uud)
final quark spectator L hadrons composition quark
baryon
p (uud) (uud) 3.2 ±0.2 [1 ,2]
n (udd) (ud) 1.92±0.05 [1,4]
Ao (uds) (ud) 1.02±0.10 [1] 1.75[11]
E+
( uus) (uu) 1.15±0.17 [ 1 ,8]E-
(dds) (d) 0.53±0.15 [1 ,9)j5 ( uu.d) nothing 0.30±0.05 [1 ,3)
f..._O ( uds) nothing 0.10±0.02 [ 1] 0.045[14)
meson
g+ (us) (u) [12)
Ko (ds
+
ds) (d) 0.28 [11]g- (u.s) nothing [13]
Table-1(b) for the antiproton-proton interactions.
pp processes
initial sta.te ( u.u.d)+( uud)
final quark spectator
hadrons composition quark L
X> 0 x<O baryon
p (uud) nothing ( Utf:d) 4 ±0.5(x
<
0)[]]
n (udd) nothing (ud)
Ao (uds) nothing ( u.d) 3.2±0.2 [18, l!l]
E+
(uus) nothing ( uu)E-
(dds) nothing (d)j5 ( uud) ( uud) nothing 4.5±0.5( X
>
0) [ 1)f..._O ( uds) ( ud) nothing 2.1±0.2 [18,19]
tneson
g+ (us) nothing ( u)
l\_·o (ds
+
ds) (J) (d) 0.76±0.04 [19,20)/\'- (us) (u) nothing
'lf+
(ud) (d) (u) [21]7r (ud) (u) (d)
-142-
variable is introduced.
J:,
F(x)dxL(xo, Xt, x2) =
Jio•
F(x)dx (4)The integration ranges x0 = 0.2, x1 = 0.4 and x2 = 0.8 are used in eq. (4), in order to reduce effect of the diffractive production (x >0.8) and of central production (x < 0.2).
3 The "leading" -hadron ef-
fect in the proton-proton and antiproton-proton in- teractions
We have studied the "leading" particle effect us- ing the quantity L in the reaction of proton- proton and proton-antiproton collisions for differ- ent hadron inclusive productions.
pp~ p
+
anything [2]pp~ p
+
anything [3]pp~ n + an~thing
[4]
pp -:-+ A 0
+
anything [5, 6]pp~
A
0 + anything [6, 7]pp~ E+ + anything [6, 8]
pp~ E- + anything
[9]
pp~ 1r+ + anything [10]
pp~ 1r- + anything
[11]
pp~ ](+ +·anything [12]
PP~ ]{- + anything [13]
pp~ / (0 + anything [5, 14)
pp~ p
+
anything [15, 16]pp ~ p +anything [17)
pp~ A 0 + anything [18, 19]
pp~
A
0 + anything [18, 19]pp~ ]{0 + anything [20) pp ~ 1r+ + anything [21]
Since the center of mass energy of the interactions are 13.8 to 62 GeV for proton-proton a.nd 2.7 to 13.8 GeV for antiproton-proton, it can be investi- gated the energy dependence of the quantity "L", and whether the "L" varies for interactions in- duced by different baryon. Table-1 shows prop- agating quarks of produced hadrons for pp and pp processes.
Fig.-1( a) The :L value vs. the number of propa- gating quarks for proton-proton interactions,
I .!
11 p Reactiolll p-p
p p
3 '"'\"
~···
l ' •
.r· ~·~· ... ·· .. ··j•
l>a'Y'"~;::
...\·~·
.··••····~k
:.~:::~
. .~:,. .·· "'~~,, Gev
X
~_./
o 405GeV/c0 ~ ;• K-
0 2 3 4 5
L(O. 2. 0. 4. 0. 8)
The values of L derived from the experimental x distributions of the different hadrons in the in- teractions above are shown in Fig.-1. Fig.-1(a) is for proton-proton, and Fig.-1(b) is for antiproton- proton interactions. We compare the quantity L with the following parametrization, function of the number of spectator quarks which are· concerning in the interactions[22).
F(x) = (1- x)a,
where a = 2n - 1, n is the number of quarks which need to be changed in the initial state to the wanted hadron in the final state. They are indicated by dot ted curve in the figures.
4 · Sumn1ary
Figures show that the quantity of L takes the val- ues around 4, 1 to 2, 0.5 and <0.5 when the num- ber of propagating quarks is 3(2), 2( 1), 1(0) and 0 for baryon(meson), respectively. Therefore, it seems that the quantity of L is the same value for different hadrons induced by proton-proton or antiproton-proton interactions when the number of spectating quarks is the same even almost of all interactions are annihilation process in proton antiproton interactions at very low energy(
Js
=3GeV).
It is very clea.r that the "leading' particle effect exists in the Feynmann x through 0.2 to 0.8 in
Fig.-1(b) and, for antiproton-proton in-teractions.
The curves superimposed indicate F(x) = (1-x)a for ba.ryon , and for meson in both figures.
Reaction j}-p
I i
.8
!!!!z:.
0 2 3 4 5
L(O. 2. 0_ 4. 0. 8)
ba.ryon-ba.ryon interactions. The "leading" parti- cle effect has a maximum in a situation when the final sta.te agree with the final state precisely, be- cause the baryon in final state includes much good quality by quantum number flow from initial state.
It agrees with the feature that the valence quark or the pair of valence quarks(diqua.rk) contributes significantly for the production of ''leading" par- ticles in proton-proton a.nd in proton-antiproton interactions.
References
(1] M. Basile et al., CERN-EP /81-86.
(2] A. Zichichi, Evidence for a close link between (pp) and (ee)physics, in Proc. 11Ettore Ma- jorama." Int. School of Subnuclear Physics, 18th Course, The high energy limit.
(3] M. Basile, G. Ca.ra Romano, L. Cifarelli, A. Continetal., Phys. Lett., 99B, 247(1981).
(4] M. Basile, G. Ca.ra Romano, L. Cifarelli, A. Contin et a.l., Phys. Lett., 92B, 367(1980).
(5] H. IGchimi, M. Fukawa, S. Kabe, F. Ochiai, A. Suzuki, Y. Yoshimura, K. Takahashi, T. Okusawa, K. Tanahashi, M. Teranaka,
0. Kusumoto, T. Konishi, H. Okabe, J. Yokota, Phys. Rev. D, 20, 37-52( 1979).
(6] T. Okusawa, M. Chikawa, T. Omori, Y. Takeo, M. Terana.ka, 0. Kusumoto, T. Konishi, H. Okabe, J. Yokota, T. Sato, M. Fukawa, H. Kichimi, F. Ochiai, R. Sugahara, A. Suzuki, Y. Yoshimura, K. Takahashi, Europhys. Lett., 5(6), pp.509- 515(1988).
(7] M. Basile, G. Cara Romano, L. Cifarelli, A. Contin et al., Nuovo Cimento Lett., 30, 389(1981) .
(8] M. Basile, G. Cara Romano, L. Cifarelli, A. Contin et al., Nuovo Cimento, 58A, 193(1980).
[9] M. Basile, G. Cara Romano, L. Cifarelli, A. Contin et al., Nuovo Cimento Lett., 29, 491(1980).
(10] M. Basile, G. Cara Romano, L. Cifa.relli, A. Contin et al., Nuovo Cimento Lett.,30, 487( 1981)
(11] M. Basile, G. Car a Romano, L. Cifarelli, A. Con tin et al., Nuovo Cimento,63A, 230(1981).
[12] M. Basile, G. Ca.ra Romano, L. Cifarelli, A. Con tin et a.l., Nuovo Cimento, 31, 97(1981).
(13] M. Basile, G. Cara R~rnano, L. Cifa.relli, - A. Contin et al., A comparison between
11beauty" and 11charm" production in (pp) in- teraction, CERN-EP/81-75.
[14] H. Kichimi, M. Fukawa, S. Kabe, F. Ochia.i, A. Suzuki, Y. Yoshimura,!{. Takahashi, T. Okusawa, K. Ana.hashi, M. Teranaka,
· 0. Kusumoto, T. Konishi, H. Okabe, J. Yokota, Phys. Lett., 72B, 411-414(1978).
(15] M. Basile, G. Cara Romano, L. Cifarelli, A. Contin et al., Nuovo Cimento Lett., 30, 273(1981).
(16] M. Basile, G. Cara Romano, L. Cifarelli, A. Contin et al., Charged particle multiplici- ties in (pp) interactions and comparison with {ee) data, preprint CERN EP /81-76.
-144-
(17) M. Ba.sile, G. Ca.ra Romano, L. Cifa.relli, A. Contin et a.l., The leading baryon effect in beanty-lambda production in {pp} interactions at
,fS
=62 Ge V, CERN-EP /81-72.[18] S. Noguchi, N. ·Fujiwara., M. Chikawa, M. Fukawa, H. Kichimi, E. Kohriki, 0. Kusumoto, J. MacNaughton, K. Miyano, S. Noguchi, F. Ochiai, T. Okusawa., A. Ono, T. Sa.t.o, R. Sugahara., A. Suzuki, K. Takahashi, S. Ya.ma.shita., Zeit Schrift fur Physik C, 24, 297-304( 1984).
[19] M. Chikawa., T. Okusa.wa, T. Konishi, Zeit Sch1·ift fur Physik C, 32, 21-25(1984).
[20]
F. Ochia.i, Y. Yoshimura., M. Chika.wa, N. Fujiwara., !vi. Fuka.wa., H. Kichimi, E. Kohriki, 0. Kusumoto, J. Ma.cN aughton, I<. Miya.no, S. Noguchi, T. Okusawa., A. Ono, T. Sa.to, R. Suga.hara., A. Suzuki, K. Takahashi, S. Yamashita., Zeit Schrift fur Physik C, 23, 369-375( 1984).[2.1] R.
Bra.ndelik et a.l., Phys. Lett., 67B, 358(1977).[22] J. S. Gunion, Phys. Lett. B,88, ].50(1979).
