Data are presented on production by 200-GeV/c hadrons incident on beryllium of both single particles and jets (groups of particles) with high p_T (transverse momentum). The experiment was performed in a wide-aperture multiparticle spectrometer at Fermilab. The jet and single-particle cross sections have a similar shape from p_T=3 to 5 GeV/c but the jet cross section is over two orders of magnitude larger. The distributions of charged-particle momenta show striking similarities to those observed in lepton-induced processes

Abrams, R.

Ashford, V.

Bromberg, C.

Delzenero, R.

Dzierba, A.

Erhan, S.

Fox, G.

Goldberg, H.

Gomez, R.

Haggerty, H.

Juhala, R.

Kropac, W.

Lorenz, E.

Malamud, E.

Margulies, S.

McLeod, D.

Medinnis, M.

Mori, S.

Pine, J.

Rohlf, J.

Schlein, P.

Solomon, J.

Stampke, S.

Stanek, R.

Yung, K.

English

Caltech Authors - Main

VoLUME 38, NuMBER 25 PHYSICAL REVIEW LETTERS 20 JUNE 1977 
Observation of the Production of Jets of Particles at High Transverse Momentum 
and Comparison with Inclusive Single-Particle Reactions* 
C. Bromberg, G. Fox, R. Gomez, J. Pine, S. Stampke, and K. Yung 
California Institute of Technology, Pasadena, California 91125 
and 
S. Erhan, E. Lorenz, t M. Medinnis, J. Rohlf, and P. Schlein 
University of California, Los Angeles, California 90024 
and 
V. Ashford, H. Haggerty, R. Juhala,t E. Malamud, and S. Mori 
Fermi National Accelerator Laboratory, Batavia, Illinois 60510 
and 
R. Abrams, R. Delzenero, H. Goldberg, S. Margulies, D. McLeod, J. Solomon, and R. Stanek 
University of Illinois at Chicago Circle, Chicago, illinois 60680 
and 
A. Dzierba and W. Kropac§ 
Indiana University, Bloomington, Indiana 47401 
(Received 11 April 1977) 
Data are presented on production by 200-Ge VIc hadrons incident on beryllium of both 
single particles and jets (groups of particles) with highPT (transverse momentum). The 
experiment was performed in a wide-aperture multiparticle spectrometer at Fermilab, 
The jet and single-particle cross sections have a similar shape fromPT =3 to 5 GeV/c 
but the jet cross section is over two orders of magnitude larger. The distributions of 
charged-particle momenta show striking similarities to those observed in lepton-in-
duced processes. 
Interest in high-P T physics was originally stim-
ulated by the observation of unexpectedly large 
yields of single particles for p T~ 3 GeV /c. 1 The 
motivation of our experiment is to shed light on 
the dynamics of these rare processes by studying 
both the particles produced in conjunction with a 
single high-P T particle and the structure of events 
in which high p T is found as the sum of the trans-
verse momenta of several particles. The data 
presented in this Letter are the result of an ini-
tial run at Fermilab and details of the apparatus 
and additional data will be presented elsewhere. 2 
The spectrometer is shown schematically in 
Fig. 1. Beam particles with a momentum of 200 
GeV I c struck a beryllium target either 3 or 6 
em thick. Charged particles emerging from the 
target at lab angles -:s 150 mrad and momenta~ 2 
GeV I c were analyzed by track chambers and the 
spectrometer magnet which was set to give a 
transverse momentum kick of 0.38 GeV /c. Be-
hind the last track chamber were two calorime-
ters, each divided into four separate modules. 
The modules consisted of a front section com-
prised of six alternating layers of 0.25 in. of 
scintillator and 0.56 in. of lead, totaling about 15 
radiation lengths or about 0.5 nuclear absorption 
length, and a rear section comprised of fifteen 
layers of 0.25 in. of scintillator and 2 in. of iron, 
totaling about 4.5 absorption lengths. The lead 
(electron) sections and iron (hadron) sections 
were viewed by separate phototubes. In addition, 
each module was viewed at the top and bottom. 
Pulse-height analysis gave a measure of the ener-
gy and mean vertical position of the interactions. 
Event triggers for the experiment were derived 
from the calorimeter module signals, weighted 
by their mean lab angle so that they were an ap-
proximate measure of transverse momentum. 
Two types of trigger were used, which we have 
called single particle and jet. For the former, it 
was required that the sum of the transverse mo-
menta in the electron and hadron sections of any 
individual module be greater than a preset trigger 
bias of 3 Ge VIc. The jet trigger demanded that 
1447 
VOLUME 38, NUMBER 25 PHYSICAL REVIEW LETTERS 20 JUNE 1977 
0 
4 
z 8 
meters 
12 
16 
Beam t 
Torget-t 
A 
x meters 
-o.s 0 0.5 
FIG. 1. Plan view of the spectrometer, with tracks 
from a typical event. A-D andF' indicate proportional 
planes, while E andF are spark chambers 
the total transverse momentum of all four modules 
of either calorimeter be above a preset level: Da-
ta with thresholds of 3, 4, and 4.5 GeV/c were 
used in this analysis. In Fig. 1, the jet-trigger 
pT is 5,31 GeV/c in the right-hand-side calorime-
ter. 
The mean number of reconstructed tracks which 
come from the beryllium vertex and pass through 
the magnet is about ten for jets and one less for 
single-particle triggers. Furthermore the cham-
bers in front of the magnet measure, on the aver-
age, four to five additional charged particles per 
event which are outside the magnet acceptance. 
Individual spark-chamber-gap efficiencies are 
estimated at 90% up to multipliCities of fifteen 
and the overall efficiency of track finding, away 
from the beam direction, is estimated to be (95 
± 5~. The number of spurious high-transverse-
momentum tracks is shown to be small both by 
comparing calorimeter and track energies and 
also by the lack of a high-momentum tail in our 
charged-particle p T spectrum. The momentum 
resolution of the track chambers is ap/p2 =0.0007 
(GeV/cr 1• For the calorimeters we measure an 
energy resolution t:..E/E of 0.33/;-E for electron 
modules and 1.03/;-E for hadron modules (stan-
1448 
IOOr:-----------------, 
Ed3a-/d 3p 
fLb/(Gev/d 
per nucleon 
BtOS 
0 + 
o JET 3 
x JET 4 GeV Bios 
• JET 4.5 
-Best estimate of 
JET cross·-section 
---100 x single particle 
cross-section 
. Bias 
•. x~\- + 
• I 
.\··~t~r 
'\ I • 1 \~ 
Bios \~ 
cross-sectiOn \ 
• This experiment \ 
-Chicago-Princeton \ 
All chorge_d particle \ \ t 
o.oo 1 o!:--!----c2!:-----,3!:--4L..L___j5'-----__j6,..-----'--' 
PT GeV/c 
FIG. 2. The single-particle and jet cross sections 
averaged over the c.m. system rapidty (y) region of 0.1 
to 0,44. The jet definition is all particles into the cal-
orimeter, while the plotted data are an average of 
equal amounts of 11'- and proton beam. The jet cross 
sections for the separate beam types 11'- andp are 
equal to within 20% for 4<p.LJET < 5 GeV/c. The single-
particle data correspond to a proton beam only and the 
Chicago-Princeton results (Ref. 3) were taken at a lab 
angle of 77 mrad (y ~ 0,25) and have been summed over 
all charged particles for comparison with our data. 
dard deviations, E in GeV). 
The single-particle trigger is straightforward 
to analyze. Taking events with a single-particle 
track with P T> 2 GeV I c, we find the acceptance-
corrected invariant cross section plotted in Fig. 
2 using a sample of the events in which the track 
enters a fiducial region in the middle of the cal-
orimeter. Our data can be directly compared to 
the more precise measurements of the Chicago-
Princeton3 collaboration and there is good agree-
ment above the calorimeter trigger threshold of 
3 GeV/c. 
The novel feature of our experiment is the jet 
trigger defined above. The contributions to jet 
PT divide into three categories: (i) charged parti-
cles (typical multiplicity three) measured by the 
track chambers and comprising 57% of the jet mo-
mentum4; (ii) photons (presumably from 1r0, 'Y/, 
etc., decay) measured in the electron calorimeter 
and making up 30% of the jet momentum; and 
(iii) neutral hadrons or apparent neutrals. These 
latter are deduced by subtracting the charged-
VOLUME 38, NUMBER 25 PHYSICAL REVIEW LETTERS 20 JUNE 1977 
track energies from the hadron calorimeter sig-
nals module by module; the resultant resolution 
in energy is poor because of the subtraction and 
modest calorimeter resolution. This third cate-
gory includes neutrons, KL 0, and nonvertex tracks 
(Ks 0, A, and reconstruction losses) and we find 
that it carries between 6 and 24% of the jet p T 
with 13% as our best estimate. The jet cross sec-
tion presented in Fig. 2 has been corrected for 
geometric acceptance but not for the trigger bias 
of the calorimeter. However, comparison of the 
three trigger thresholds shown in Fig. 2 allows 
us to extract an unbiased jet cross section shown 
as the broad solid line. The uncertainty in the 
hadronic neutral component, discussed above, 
leads to a cross-section uncertainty of ± 30% (p T 
=3 GeV/c) to ±5~ (PT=5 GeV/c) not indicated in 
Fig. 2. 
Independent of the uncertainty in the hadronic 
neutral estimate, the striking feature of Fig. 2 
is the very large (over two orders of magnitude) 
ratio of jet to single-particle cross section. This 
result had been predicted in models 5- 7 which pos-
tulate that large-P T hadrons come from the frag-
mentation of quarks produced in an elementary 
hard collision between constituent quarks in the 
initial hadrons. Note that there are no clear res-
onance signals in our jet data and the large jet 
cross section is not simply due to a sum of low-
IOOc----------------------------. 
1-
0.1 t:--
• 2.6 < p~ET < 3 
x 3 < p~ET < 4 GeV/c 
o 4 < p~ET < 5 
• v p - JL- + hadrons 
z = Px/P~ET 
0.0 I OL_..L.._-::'-::-__L_---:'-.,---' __ .L._ I. .L._ l_ji--:-.L._ I...LI __ ___j 
0.2 0.4 0.6 0.8 I. 0 
FIG. 3, The distribution in transverse momentum 
fraction z for three jetpL ranges compared with neu-
trino scattering {Refs. 7 and 8). The comparison fails 
below z ~ 0.2 as the neutrino data have significant con-
tributions from the fragmentation of the target proton. 
mass resonances. 
Motivated by the constituent models, we define 
the jet plane as that plane formed by the jet mo-
mentum vector and the direction of the incident 
hadrons and plot in Fig. 3 the transverse momen-
tum fraction z =Px,jpTJET, where pTJET is the 
transverse momentum of the jet and Px' is the 
component of the transverse momentum of indi-
vidual charged particles in the jet plane. There 
is a striking similarity between our z distribu-
tions and those for lepton-induced processes.7 •8 
Furthermore our data show evidence for the co-
planar structure of events suggested by constitu-
ent models. For the charged particles (both jet 
and nonjet members) in these events we find a 
sharp exponential dependence with a mean of 0.20 
Ge VIc for the component of the transverse mo-
mentum out of the jet plane. Also the two-dimen-
sional momentum perpendicular to the jet axis is 
strongly cut off for the jet members. In Ref. 2, 
we explore fully these points and the relation of 
our experimental jet definition to theory. 
Finally Fig. 4 shows the momentum distribution 
of charged particles on the away side (cf. Fig. 1). 
The first striking feature is that these away-side 
particles balance the transverse momentum of 
101::-
I do-
O'CfZ 
1::--
0.1 =--
o All JET triggers } 
• Single particle triggers p~ET > 
" JET"= single particle~ 0 85 2.6 GeV/c PT PT . . 
x JET triggers 4 < p~ET < 5 GeV/c 
f o •' distribution I ~ • / Towards side f o • '-. (This experiment) 
~' ...... 
. ' +0 ~ ', 70 ', ~ ' ~ 
Z = -px•/P~ET f + 
o.o 1 0L__j_---:o:L. 2~l___jo.L4__l-:o:L.6,--L-_jo.-=-s___L __ I.L.o:=..l.,---~l__..l 
FIG. 4, Distributions in momentum fraction z for 
particles on the away side. The shifting of scale for 
single particles is motivated by the quark model {Refs. 
7 and 9) which suggests that single particles carry from 
80 to 90% of the momentum of the high-PL quark {jet), 
The data are integrated over the whole away side and 
include a correction for spectrometer acceptance which 
is valid for the higher-momentum particles, z?; 0,25. 
1449 
VOLUME 38, NUMBER 25 PHYSICAL REVIEW LETTERS 20 }UNE 1977 
single-particle and jet triggers in a similar way. 
This is expected in the quark picture7 •9 but seems 
difficult to understand in the constituent inter-
change model.10 Again, the away- and trigger-
(towards) side z distributions have similar shapes 
but differ by a factor of- 2.5 in magnitude at large 
z. In constituent models, this difference is a di-
rect reflection of the transverse momentum of 
quarks inside hadrons. 9 
Our data give strong support to the idea that the 
same constituents (quarks presumably) are probed 
by both high-P T hadron and lepton collisions. We 
are currently continuing our analysis on the com-
pleted experiment which has 10 times the data 
presented here, taken with a liquid-hydrogen tar-
get and incident proton and meson beams. 
We are grateful for the assistance given to us 
by the staffs of the Accelerator Division, the 
Meson Department, and the Research Services 
Department at Fermilab. 
*Work supported in part by the U. S. Energy Research 
and Development Administration under Contracts No. 
E(ll-1)-68 (Caltech) and No. E(11-1)-2009 (Indiana); 
and by the National Science Foundation under Grants 
No. PHY-76-80660 (U.C.L.A.) and No. MPS-73-04640 
(Illinois). 
tPermanent address: Max-Planck-Institut fiir Physik 
und Astrophysik, Munich, Germany. 
tPresently at Oak Ridge National Laboratory, Oak 
Ridge, Tenn. 37830. 
§Presently at California Institute of Technology, Pasa-
dena, Calif. 91125. 
1P. Darriulat, in Proceedings of the Eighteenth Inter-
national Conference on High Energy Physics, Tbilisi, 
U.S.S.R., 1976, edited by N. N. Bogolubov et aJ.. (The 
Joint Institute for Nuclear Research, Dubna, U.S.S.R., 
1977). 
2c. Bromberg et aJ. • , "Production of Jets and Single-
Particles at Highp T in 200-GeV Hadron Beryllium Col-
lisions'' (to be published1. 
3J. W. Cronin et aJ. ., Phys. Rev. D 11, 3105 (1975). 
Figure 2 shows more recent data [D.Antreasyan et aJ.., 
Phys. Rev. Lett. 38, 115 (1977), and private communi-
cation of new results with a Be targetl. 
4The percentage of jet Pr carried by the three compo-
nents varies slightly with the jet Pr and more signifi-
cantly with the hadronic neutral estimate used. The 
quoted percentages correspond to the cut 4<PrJET < 5 
Ge VIc and a 13% hadronic neutral contribution. 
5s. M. Berman, J.D. Bjorken, and J. B. Kogut, Phys. 
Rev. D 4, 3388 (1971). 
6s. D.-Ellis and M. B. Kislinger, Phys. Rev. D 9, 
2027 (197 4). -
7R. D. Field and R. P. Feynman, Phys. Rev. D 15, 
2590 (1977). 
8J. C. VanderVelde, "Neutrino-Proton Interactions 
in the 15-Foot Bubble Chamber and Properties of Ha-
dron Jets" (to be published). 
9G. C. Fox, in BNL Report No. BNL-50598, edited 
by H. Gordon and R. F. Peierls, Proceedings of the 
American Physical Society Meeting, Division of Parti-
cles and Fields, Upton, New York, 1976 (unpublished). 
10D. Sivers, S. Brodsky, and R. Blankenbecler, Phys. 
Rep. 23C, 1 (1976). 
Measurement of the Proton Structure Function from Muon Scattering* 
H. L. Anderson, V. K. Bharadwaj, N. E. Booth, R, M. Fine, t W. R. Francis, t B. A. Gordon, 
R. H. Heisterberg, § R. G. Hicks, T, B. W. Kirk, 11 G. I. Kirkbride,~ 
W, A. Loomis, H. S. Matis, L. W. Mo, § L. C. Myrianthopoulos, 
F, M. Pipkin, S. H. Pordes, ** T. W. Quirk, W. D. Shambroom, 
A. Skuja, tt M. A. Staton, W. S. C. Williams, L. J. Verhey, U 
Richard Wilson, and S. C. Wright 
Enrico Fermi Institute, The University of Chicago, Chicago, nlinois 60637, and High Energy Physics Laboratory 
and Department of Physics, Harvard University, Cambridge, Massachusetts 02138, and Department of Physics, 
The University of illinois at Urbana -Champaign, Urbana, Illinois 61801, and Department of Mtclear Physics, 
The University of Oxford, Oxford OX1 3RH, England 
(Received 25 April 1977) 
Results on the proton structure function, vW 2 are presented for 0,3 < q2 <50 GeV2 and 5 
< v < 130 GeV. They are compared to earlier data and displayed to demonstrate violations 
of scaling. Values are reported for the energy-momentum sum rule and for R"" CJL/CJr 
over a limited kinematic region. 
In this Letter we report values of the structure 
function vW2 of the proton obtained by measuring 
the inelastic scattering of muons from hydrogen 
at the Fermi National Accelerator Laboratory. 
The data were taken with the muon-scattering fa-
cility constructed by this group. 
1450 


Observation of the Production of Jets of Particles at High Transverse Momentum and Comparison with Inclusive Single-Particle Reactions

VoLUME 38, NuMBER 25 PHYSICAL REVIEW LETTERS 20 JUNE 1977 
Observation of the Production of Jets of Particles at High Transverse Momentum 
and Comparison with Inclusive Single-Particle Reactions* 
C. Bromberg, G. Fox, R. Gomez, J. Pine, S. Stampke, and K. Yung 
California Institute of Technology, Pasadena, California 91125 
and 
S. Erhan, E. Lorenz, t M. Medinnis, J. Rohlf, and P. Schlein 
University of California, Los Angeles, California 90024 
and 
V. Ashford, H. Haggerty, R. Juhala,t E. Malamud, and S. Mori 
Fermi National Accelerator Laboratory, Batavia, Illinois 60510 
and 
R. Abrams, R. Delzenero, H. Goldberg, S. Margulies, D. McLeod, J. Solomon, and R. Stanek 
University of Illinois at Chicago Circle, Chicago, illinois 60680 
and 
A. Dzierba and W. Kropac§ 
Indiana University, Bloomington, Indiana 47401 
(Received 11 April 1977) 
Data are presented on production by 200-Ge VIc hadrons incident on beryllium of both 
single particles and jets (groups of particles) with highPT (transverse momentum). The 
experiment was performed in a wide-aperture multiparticle spectrometer at Fermilab, 
The jet and single-particle cross sections have a similar shape fromPT =3 to 5 GeV/c 
but the jet cross section is over two orders of magnitude larger. The distributions of 
charged-particle momenta show striking similarities to those observed in lepton-in-
duced processes. 
Interest in high-P T physics was originally stim-
ulated by the observation of unexpectedly large 
yields of single particles for p T~ 3 GeV /c. 1 The 
motivation of our experiment is to shed light on 
the dynamics of these rare processes by studying 
both the particles produced in conjunction with a 
single high-P T particle and the structure of events 
in which high p T is found as the sum of the trans-
verse momenta of several particles. The data 
presented in this Letter are the result of an ini-
tial run at Fermilab and details of the apparatus 
and additional data will be presented elsewhere. 2 
The spectrometer is shown schematically in 
Fig. 1. Beam particles with a momentum of 200 
GeV I c struck a beryllium target either 3 or 6 
em thick. Charged particles emerging from the 
target at lab angles -:s 150 mrad and momenta~ 2 
GeV I c were analyzed by track chambers and the 
spectrometer magnet which was set to give a 
transverse momentum kick of 0.38 GeV /c. Be-
hind the last track chamber were two calorime-
ters, each divided into four separate modules. 
The modules consisted of a front section com-
prised of six alternating layers of 0.25 in. of 
scintillator and 0.56 in. of lead, totaling about 15 
radiation lengths or about 0.5 nuclear absorption 
length, and a rear section comprised of fifteen 
layers of 0.25 in. of scintillator and 2 in. of iron, 
totaling about 4.5 absorption lengths. The lead 
(electron) sections and iron (hadron) sections 
were viewed by separate phototubes. In addition, 
each module was viewed at the top and bottom. 
Pulse-height analysis gave a measure of the ener-
gy and mean vertical position of the interactions. 
Event triggers for the experiment were derived 
from the calorimeter module signals, weighted 
by their mean lab angle so that they were an ap-
proximate measure of transverse momentum. 
Two types of trigger were used, which we have 
called single particle and jet. For the former, it 
was required that the sum of the transverse mo-
menta in the electron and hadron sections of any 
individual module be greater than a preset trigger 
bias of 3 Ge VIc. The jet trigger demanded that 
1447 
VOLUME 38, NUMBER 25 PHYSICAL REVIEW LETTERS 20 JUNE 1977 
0 
4 
z 8 
meters 
12 
16 
Beam t 
Torget-t 
A 
x meters 
-o.s 0 0.5 
FIG. 1. Plan view of the spectrometer, with tracks 
from a typical event. A-D andF' indicate proportional 
planes, while E andF are spark chambers 
the total transverse momentum of all four modules 
of either calorimeter be above a preset level: Da-
ta with thresholds of 3, 4, and 4.5 GeV/c were 
used in this analysis. In Fig. 1, the jet-trigger 
pT is 5,31 GeV/c in the right-hand-side calorime-
ter. 
The mean number of reconstructed tracks which 
come from the beryllium vertex and pass through 
the magnet is about ten for jets and one less for 
single-particle triggers. Furthermore the cham-
bers in front of the magnet measure, on the aver-
age, four to five additional charged particles per 
event which are outside the magnet acceptance. 
Individual spark-chamber-gap efficiencies are 
estimated at 90% up to multipliCities of fifteen 
and the overall efficiency of track finding, away 
from the beam direction, is estimated to be (95 
± 5~. The number of spurious high-transverse-
momentum tracks is shown to be small both by 
comparing calorimeter and track energies and 
also by the lack of a high-momentum tail in our 
charged-particle p T spectrum. The momentum 
resolution of the track chambers is ap/p2 =0.0007 
(GeV/cr 1• For the calorimeters we measure an 
energy resolution t:..E/E of 0.33/;-E for electron 
modules and 1.03/;-E for hadron modules (stan-
1448 
IOOr:-----------------, 
Ed3a-/d 3p 
fLb/(Gev/d 
per nucleon 
BtOS 
0 + 
o JET 3 
x JET 4 GeV Bios 
• JET 4.5 
-Best estimate of 
JET cross·-section 
---100 x single particle 
cross-section 
. Bias 
•. x~\- + 
• I 
.\··~t~r 
'\ I • 1 \~ 
Bios \~ 
cross-sectiOn \ 
• This experiment \ 
-Chicago-Princeton \ 
All chorge_d particle \ \ t 
o.oo 1 o!:--!----c2!:-----,3!:--4L..L___j5'-----__j6,..-----'--' 
PT GeV/c 
FIG. 2. The single-particle and jet cross sections 
averaged over the c.m. system rapidty (y) region of 0.1 
to 0,44. The jet definition is all particles into the cal-
orimeter, while the plotted data are an average of 
equal amounts of 11'- and proton beam. The jet cross 
sections for the separate beam types 11'- andp are 
equal to within 20% for 4<p.LJET < 5 GeV/c. The single-
particle data correspond to a proton beam only and the 
Chicago-Princeton results (Ref. 3) were taken at a lab 
angle of 77 mrad (y ~ 0,25) and have been summed over 
all charged particles for comparison with our data. 
dard deviations, E in GeV). 
The single-particle trigger is straightforward 
to analyze. Taking events with a single-particle 
track with P T> 2 GeV I c, we find the acceptance-
corrected invariant cross section plotted in Fig. 
2 using a sample of the events in which the track 
enters a fiducial region in the middle of the cal-
orimeter. Our data can be directly compared to 
the more precise measurements of the Chicago-
Princeton3 collaboration and there is good agree-
ment above the calorimeter trigger threshold of 
3 GeV/c. 
The novel feature of our experiment is the jet 
trigger defined above. The contributions to jet 
PT divide into three categories: (i) charged parti-
cles (typical multiplicity three) measured by the 
track chambers and comprising 57% of the jet mo-
mentum4; (ii) photons (presumably from 1r0, 'Y/, 
etc., decay) measured in the electron calorimeter 
and making up 30% of the jet momentum; and 
(iii) neutral hadrons or apparent neutrals. These 
latter are deduced by subtracting the charged-
VOLUME 38, NUMBER 25 PHYSICAL REVIEW LETTERS 20 JUNE 1977 
track energies from the hadron calorimeter sig-
nals module by module; the resultant resolution 
in energy is poor because of the subtraction and 
modest calorimeter resolution. This third cate-
gory includes neutrons, KL 0, and nonvertex tracks 
(Ks 0, A, and reconstruction losses) and we find 
that it carries between 6 and 24% of the jet p T 
with 13% as our best estimate. The jet cross sec-
tion presented in Fig. 2 has been corrected for 
geometric acceptance but not for the trigger bias 
of the calorimeter. However, comparison of the 
three trigger thresholds shown in Fig. 2 allows 
us to extract an unbiased jet cross section shown 
as the broad solid line. The uncertainty in the 
hadronic neutral component, discussed above, 
leads to a cross-section uncertainty of ± 30% (p T 
=3 GeV/c) to ±5~ (PT=5 GeV/c) not indicated in 
Fig. 2. 
Independent of the uncertainty in the hadronic 
neutral estimate, the striking feature of Fig. 2 
is the very large (over two orders of magnitude) 
ratio of jet to single-particle cross section. This 
result had been predicted in models 5- 7 which pos-
tulate that large-P T hadrons come from the frag-
mentation of quarks produced in an elementary 
hard collision between constituent quarks in the 
initial hadrons. Note that there are no clear res-
onance signals in our jet data and the large jet 
cross section is not simply due to a sum of low-
IOOc----------------------------. 
1-
0.1 t:--
• 2.6 < p~ET < 3 
x 3 < p~ET < 4 GeV/c 
o 4 < p~ET < 5 
• v p - JL- + hadrons 
z = Px/P~ET 
0.0 I OL_..L.._-::'-::-__L_---:'-.,---' __ .L._ I. .L._ l_ji--:-.L._ I...LI __ ___j 
0.2 0.4 0.6 0.8 I. 0 
FIG. 3, The distribution in transverse momentum 
fraction z for three jetpL ranges compared with neu-
trino scattering {Refs. 7 and 8). The comparison fails 
below z ~ 0.2 as the neutrino data have significant con-
tributions from the fragmentation of the target proton. 
mass resonances. 
Motivated by the constituent models, we define 
the jet plane as that plane formed by the jet mo-
mentum vector and the direction of the incident 
hadrons and plot in Fig. 3 the transverse momen-
tum fraction z =Px,jpTJET, where pTJET is the 
transverse momentum of the jet and Px' is the 
component of the transverse momentum of indi-
vidual charged particles in the jet plane. There 
is a striking similarity between our z distribu-
tions and those for lepton-induced processes.7 •8 
Furthermore our data show evidence for the co-
planar structure of events suggested by constitu-
ent models. For the charged particles (both jet 
and nonjet members) in these events we find a 
sharp exponential dependence with a mean of 0.20 
Ge VIc for the component of the transverse mo-
mentum out of the jet plane. Also the two-dimen-
sional momentum perpendicular to the jet axis is 
strongly cut off for the jet members. In Ref. 2, 
we explore fully these points and the relation of 
our experimental jet definition to theory. 
Finally Fig. 4 shows the momentum distribution 
of charged particles on the away side (cf. Fig. 1). 
The first striking feature is that these away-side 
particles balance the transverse momentum of 
101::-
I do-
O'CfZ 
1::--
0.1 =--
o All JET triggers } 
• Single particle triggers p~ET > 
" JET"= single particle~ 0 85 2.6 GeV/c PT PT . . 
x JET triggers 4 < p~ET < 5 GeV/c 
f o •' distribution I ~ • / Towards side 
f o • '-. (This experiment) 
~' ...... 
. ' +0 ~ ', 70 ', 
~ ' 
~ 
Z = -px•/P~ET f + 
o.o 1 0L__j_---:o:L. 2~l___jo.L4__l-:o:L.6,--L-_jo.-=-s___L __ I.L.o:=..l.,---~l__..l 
FIG. 4, Distributions in momentum fraction z for 
particles on the away side. The shifting of scale for 
single particles is motivated by the quark model {Refs. 
7 and 9) which suggests that single particles carry from 
80 to 90% of the momentum of the high-PL quark {jet), 
The data are integrated over the whole away side and 
include a correction for spectrometer acceptance which 
is valid for the higher-momentum particles, z?; 0,25. 
1449 
VOLUME 38, NUMBER 25 PHYSICAL REVIEW LETTERS 20 }UNE 1977 
single-particle and jet triggers in a similar way. 
This is expected in the quark picture7 •9 but seems 
difficult to understand in the constituent inter-
change model.10 Again, the away- and trigger-
(towards) side z distributions have similar shapes 
but differ by a factor of- 2.5 in magnitude at large 
z. In constituent models, this difference is a di-
rect reflection of the transverse momentum of 
quarks inside hadrons. 9 
Our data give strong support to the idea that the 
same constituents (quarks presumably) are probed 
by both high-P T hadron and lepton collisions. We 
are currently continuing our analysis on the com-
pleted experiment which has 10 times the data 
presented here, taken with a liquid-hydrogen tar-
get and incident proton and meson beams. 
We are grateful for the assistance given to us 
by the staffs of the Accelerator Division, the 
Meson Department, and the Research Services 
Department at Fermilab. 
*Work supported in part by the U. S. Energy Research 
and Development Administration under Contracts No. 
E(ll-1)-68 (Caltech) and No. E(11-1)-2009 (Indiana); 
and by the National Science Foundation under Grants 
No. PHY-76-80660 (U.C.L.A.) and No. MPS-73-04640 
(Illinois). 
tPermanent address: Max-Planck-Institut fiir Physik 
und Astrophysik, Munich, Germany. 
tPresently at Oak Ridge National Laboratory, Oak 
Ridge, Tenn. 37830. 
§Presently at California Institute of Technology, Pasa-
dena, Calif. 91125. 
1P. Darriulat, in Proceedings of the Eighteenth Inter-
national Conference on High Energy Physics, Tbilisi, 
U.S.S.R., 1976, edited by N. N. Bogolubov et aJ.. (The 
Joint Institute for Nuclear Research, Dubna, U.S.S.R., 
1977). 
2c. Bromberg et aJ. • , "Production of Jets and Single-
Particles at Highp T in 200-GeV Hadron Beryllium Col-
lisions'' (to be published1. 
3J. W. Cronin et aJ. ., Phys. Rev. D 11, 3105 (1975). 
Figure 2 shows more recent data [D.Antreasyan et aJ.., 
Phys. Rev. Lett. 38, 115 (1977), and private communi-
cation of new results with a Be targetl. 
4The percentage of jet Pr carried by the three compo-
nents varies slightly with the jet Pr and more signifi-
cantly with the hadronic neutral estimate used. The 
quoted percentages correspond to the cut 4<PrJET < 5 
Ge VIc and a 13% hadronic neutral contribution. 
5s. M. Berman, J.D. Bjorken, and J. B. Kogut, Phys. 
Rev. D 4, 3388 (1971). 
6s. D.-Ellis and M. B. Kislinger, Phys. Rev. D 9, 
2027 (197 4). -
7R. D. Field and R. P. Feynman, Phys. Rev. D 15, 
2590 (1977). 
8J. C. VanderVelde, "Neutrino-Proton Interactions 
in the 15-Foot Bubble Chamber and Properties of Ha-
dron Jets" (to be published). 
9G. C. Fox, in BNL Report No. BNL-50598, edited 
by H. Gordon and R. F. Peierls, Proceedings of the 
American Physical Society Meeting, Division of Parti-
cles and Fields, Upton, New York, 1976 (unpublished). 
10D. Sivers, S. Brodsky, and R. Blankenbecler, Phys. 
Rep. 23C, 1 (1976). 
Measurement of the Proton Structure Function from Muon Scattering* 
H. L. Anderson, V. K. Bharadwaj, N. E. Booth, R, M. Fine, t W. R. Francis, t B. A. Gordon, 
R. H. Heisterberg, § R. G. Hicks, T, B. W. Kirk, 11 G. I. Kirkbride,~ 
W, A. Loomis, H. S. Matis, L. W. Mo, § L. C. Myrianthopoulos, 
F, M. Pipkin, S. H. Pordes, ** T. W. Quirk, W. D. Shambroom, 
A. Skuja, tt M. A. Staton, W. S. C. Williams, L. J. Verhey, U 
Richard Wilson, and S. C. Wright 
Enrico Fermi Institute, The University of Chicago, Chicago, nlinois 60637, and High Energy Physics Laboratory 
and Department of Physics, Harvard University, Cambridge, Massachusetts 02138, and Department of Physics, 
The University of illinois at Urbana -Champaign, Urbana, Illinois 61801, and Department of Mtclear Physics, 
The University of Oxford, Oxford OX1 3RH, England 
(Received 25 April 1977) 
Results on the proton structure function, vW 2 are presented for 0,3 < q2 <50 GeV2 and 5 
< v < 130 GeV. They are compared to earlier data and displayed to demonstrate violations 
of scaling. Values are reported for the energy-momentum sum rule and for R"" CJL/CJr 
over a limited kinematic region. 
In this Letter we report values of the structure 
function vW2 of the proton obtained by measuring 
the inelastic scattering of muons from hydrogen 
at the Fermi National Accelerator Laboratory. 
The data were taken with the muon-scattering fa-
cility constructed by this group. 
1450 


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Observation of the Production of Jets of Particles at High Transverse Momentum and Comparison with Inclusive Single-Particle Reactions

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