3. Investigating QCD at Fixed Target Energies
Quantum Chromodynamics (QCD) describes the strong force that binds quarks within hadrons, the class of strongly interacting particles that includes the proton and the neutron. QCD has some similarities to QED (Quantum Electrodynamics), the quantum theory of the electromagnetic force. However, there are substantial differences that affect our ability to make calculations using these theories. Calculations based on QED are the most accurate in all of physics, while those involving QCD can often only be approximated. These differences arise partly from the charge structure of the two theories. QED has a single charge, the familiar electric charge. QCD has three types of charge, referred to as "colors" (the "Chromo" in Chromodynamics), which combine to yield neutral (colorless) states in analogy to the way three primary colors combine to create white, or colorless, light.
As a consequence of the existence of three types of QCD charge, instead of being mediated by a single massless particle (the photon of QED), QCD involves eight massless intermediaries, known as gluons (that "glue" quarks together). Moreover, while a photon is electrically neutral and does not interact directly with other photons, gluons carry color charge and interact strongly with one another.
The QCD force is about 100 times stronger than QED, and includes more complicated interactions than QED (because of the gluon-gluon interaction). In addition, although the QED force between charged particles becomes weaker with distance, at typical intra-quark distances in hadrons the QCD force between quarks is approximately constant. Thus the energy in the color field increases linearly with the distance between the quarks (until there is enough energy in the field to create quark-antiquark pairs). This property leads to the confinement of quarks within ordinary (colorless) matter, enabling the weaker QED force to dominate on atomic scales (with the happy results that atoms have the structure they do and that we exist to comprehend such things as QED and QCD).
Quark confinement also makes QCD more difficult to study at fixed target energies. This follows from the uncertainty principle, distance and momentum measurements are inversely related (large distances result in small amounts of momentum being transferred between interacting particles, at small distances large amounts of momentum can be exchanged). Thus, a mathematical technique known as perturbation theory, which is most reliable under circumstances in which an interaction is weak, can be employed to carry out very precise QED calculations in the kinematic regime of large distances and low momentum transfers. These conditions are relatively easy to access at fixed target energies. In contrast, the QCD force is weak only at small distances and large momentum transfers, a regime most easily reached in the highly energetic collisions characteristic of collider interactions.
Studying QCD at fixed target energies must necessarily involve experiments that address simple interactions that can be calculated reasonably accurately at lower energies, or that focus on processes that benefit from the increased precision of very high event rates achieved in fixed target experiments.
3.2 E609 -
THE STRUCTURE OF HIGH PT HADRONIC INTERACTIONS
Argonne National Laboratory, Fermilab,
Lehigh University, University of Pennsylvania, Rice University, University of
Wisconsin – Madison
Following the discovery of quarks in deep inelastic scattering of electrons on protons, Bjorken and associates predicted that in hadron-hadron collisions one could expect to see hadron jets at high transverse momentum, with the properties of approximate coplanarity and approximate balance of transverse momentum, associated with a 2-body collision of constituents of the colliding hadrons. In order to search for such jet pairs, and if found, to study the interactions giving rise to parton-parton scattering within nucleons and mesons, experiment E395 and its successor E609 were designed.
In order to detect multiparticle high-pT "jets", collaborators designed and developed the first 2-dimensional segmented calorimeter detector, and introduced the wave-shifter readout technique. E395/609 detected jet pairs of approximately the predicted properties. They measured the magnitude of parton-parton scattering, the difference in momentum fractions carried by quarks in the pion and the proton (the pion has a pair of quarks, the proton has three quarks), the parton transverse momentum in the colliding hadrons, and other features of parton scattering.
E609 Degree Recipients
Jack Gerald Fleischman Ph.D. University of Pennsylvania
Kenneth Johns Ph.D. Rice University
Clara Kuehn Ph.D. University of Wisconsin
Martin Richard Marcin Ph.D. Rice University
Robert Christopher Moore Ph.D. Rice University
Charles Joseph Naudet Ph.D. Rice University
Kenneth Scott Nelson Ph.D. University of Wisconsin
Hsiuan-Jeng Shih Ph.D. Lehigh University
E609 Publications
Evidence
that High-pT Jet Pairs Give Direct
Information on Parton-Parton Scattering., M.D. Corcoran, et al., Phys. Rev. Lett. 44, 514 (1980).
Comparison of High-pT Events Produced by Pions and Protons., M.D. Corcoran, et al., Phys. Rev. Lett. 41, 9, (1978).
A Study of Parton Transverse Momentum Using Jets from Hadron Interactions., M.D. Corcoran, et al., Phys. Rev. D21, 641 (1980).
Measurement of the Single Jet Invariant Cross-Section at Fermilab., L.R. Cormell, et al., Phys. Lett. B150, 322 (1985).
Measurement of the DiJet Cross-Section in 400 GeV p p Interactions,. M.W. Arenton, et al., Phys. Rev. D31, 984 (1985).
Evidence for
Higher Twist Effects in Hard p p Collisions at 200 GeV/c., C. Naudet, et al., Phys. Rev. Lett. 56, 808 (1986)
Measurement of Massive L Kso p+ p+ p- p- Events above 5 GeV/c-squared., M.W. Arenton, et al., Nucl. Phys. B274, 707 (1986).
Invariant Cross Section atÖ s = 28 GeV for Coplanar High-pT Clusters Selected by a Hardware Trigger., K.S. Nelson, et al., Nucl. Phys. B294, 1022 (1987).
Jet Production from Nuclei at 400 GeV/c., H.E. Miettinen, et al., Phys. Lett. B207, 222 (1988).
Energy Flow in Hard Proton-Nucleus Collisions at 400 GeV/c., R.C. Moore, et al., Phys. Lett. B244, 347 (1990).
Evidence for Multiple Scattering of High-Energy Partons in Nuclei., M.D. Corcoran, et al., Phys. Lett. B259, 209 (1991).
Anomalous Nuclear Enhancements in Hard p A collisions at Fermilab Energies., T. Fields, et al., Nucl. Phys. A544, 565 ( 1991).
Experimental Information on
the Pion Gluon Distribution Function., A. Bordner, et al., Z. Phys. C72, 249 (1996).
3.3 E683 -
Photoproduction of High Pt Jets
Ball State, Fermilab, Iowa, Maryland,
Michigan, Rice, Vanderbilt
E683 was the last in a series of experiments designed to study jet production in proton-proton, pion-proton, and photon-proton collisions. Some of the earlier experiments (E395, E609) were done at beam energies of 400 GeV, before the Tevatron era. Experiments done by other groups (E557) also studied jet production at Tevatron energies. To understand the context of these experiments, one needs to understand that in the early 80's the existence of parton scattering and jet production was far from established. Earlier claims of the observation of jets in limited-solid-angle detectors had been quite controversial. It took the large-acceptance fixed-target experiments (E609 and E557) and especially the advent of the proton-antiproton colliders to firmly establish the existence of parton scattering and jet production.
E683 studied the photoproduction of high transverse momentum jets in the Wide Band Photon beam, with a tagged photon beam ranging in energy from 150 GeV to 350 GeV. For comparison and calibration, E683 also took some data with a pion beam of mean energy 250 GeV. Photoproduction is interesting because, due to its much harder parton distribution function (compared to protons or pions), the photon delivers a much larger fraction of the available CM energy to the hard scattering process, leaving less energy in the spectator system. Thus, photoproduction gives a cleaner jet signal compared to hadroproduction. The emergence of the jet signal was indeed clearly observed in E683 in photon-proton collisions, even with an unbiased trigger. The jet signal was much cleaner for photon-initiated events than for pion-initiated events.
An expectation from leading order QCD theoretical calculations, is that there should be a sharp distinction between the point-like interaction of the photon (the "direct" process) and its pion-like interaction (the "resolved" process). In higher order QCD, the distinction between these two processes is blurred, and in fact E683 did not observe a separation of the photoproduced jet events into these two distinct classes.
In addition to a proton target, E683 studied nuclear effects. Uncertainty principle arguments predict that hadronization occurs outside the nucleus. The parton can rescatter off nuclear matter as it exits the nucleus. Evidence for such rescattering effects had been seen in p-nucleus interactions in earlier experiments, and these effects were also quite evident in the photon-nucleus and pion-nucleus data from E683.
E683 Degree Recipients
Drew Alton M.S. Ball State University
Bill Davis M.S. Ball State University
Chafiq Halli Ph.D. University of Maryland
Don Lincoln Ph.D. Rice University
Gregory Peter Morrow Ph.D. Rice University
Donna Lynne Naples Ph.D. University of Maryland
Michael M. Traynor Ph.D. Rice University
E683 Publications
The Emergence of Jet Dominance in gamma-p Interactions at Fixed Target Energies., D. Alton, et al., Phys. Rev. D56, 5301 (1997).
Observation of Jet Production by Real Photons., D. Adams, et al., Phys. Rev. Lett. 72, 2337 (1994).
A-Dependence of Photoproduced Dijets., D. Naples, et al., Phys. Rev. Lett. 72, 2341 (1994).
3.4 E690 - Study of Charm and Bottom Production
Columbia, Fermilab, Guanajuato (Mexico),
Massachusetts , Michoacan SNH (Mexico),
Texas A&M
This experiment studies proton diffraction, pp®pX, using 800 GeV protons scattering from liquid hydrogen, measuring a diffracted forward proton in a forward beam spectrometer, and looking at the recoil system X in a magnetic spectrometer. The detector and its data acquisition system were designed to tolerate interaction rates on the order of 1 MHz, reading 100K events per second into a pipelined hardware processor, and ultimately recording on tape more than 10K events per second of beam. In three months of running, E690 recorded more than 5 billion events, with periods of sustained running yielding 200K events per spill. The trigger required the coincidence of an incoming beam particle, an outgoing beam particle within the acceptance of the forward spectrometer but scattered out of the small beam envelope, and at least one particle in the magnetic spectrometer.
The tracks were reconstructed with the hardware processor after the run, writing all raw data and track information for every event, and selecting candidates with momentum balance for a secondary output. All events were then processed through a vertex reconstruction program that reconstructed every event in as much detail as possible, writing out everything as well as a secondary output containing candidates for complete event reconstruction, and events with identified strange particles. The data set contains a few hundred million reconstructed V0's and approximately ten million fully reconstructed events, recorded with good resolution and a geometric acceptance that favors diffractive production of heavy particles.
Continuing analysis efforts are focusing on diffraction of heavy particles: antibaryons, strange particles, charm particles, ... and on particle spectroscopy. With high statistics for a large number of exclusive reactions, E690 can determine production cross-sections and parameters of many resonances. For example, in double Pomeron production, pp®p(M)p, there are large, clean signals for meson resonances that have been considered candidates for non-q-mesons. For the general study of heavy particle production in diffraction, E690 expects to perform doubly inclusive measurements for a variety of heavy particles, measuring the momentum of the scattered forward proton and the momentum of a particular heavy particle type. Along with the measurements of exclusive reaction cross sections and distributions, E690 data will allow detailed modeling of diffractive production in pp interactions. These models can be compared, for example, with diffraction in deep inelastic ep scattering.
E690 Degree Recipients
S. Lee Ph.D. University Massachusetts at
Amherst
Kyriacos Markianos Ph.D. University Massachusetts at
Amherst
M. Reyes Ph.D. Cinvestav
M. Sosa Ph.D. University of Guanajuato
E690 Publications
Partial Wave Analysis of the Centrally Produced KS KS System at 800 GeV/c., M.A. Reyes, et al., Phys. Rev. Lett. 81, 4079 (1998).
Spin Parity Analysis of the Centrally Produced KoK p System at 800 GeV/c., M. Sosa, et al., Phys. Rev. Lett. 83, 913 (1999).
3.5 E704 -
Experiments with the Polarized Beam Facility
ANL, Fermilab, Hiroshima (Japan),
IHEP/Protvino (Russia), Iowa,
Kyoto (Japan), Kyoto Education (Japan),
Kyoto Sangyo (Japan), LANL,
LAPP/Annecy (France), Northwestern,
Univ. of Occup. & Env. Health (Japan),
Rice, Saclay (France), Trieste (Italy), Udine (Italy)
E704 (and E581) had the highest energy polarized proton beam and the only polarized anti-proton beam to date. A number of survey experiments and also preliminary measurements relevant to gluon spin were made before the beam was decomissioned to make way for SSC test beams. Among the experiments were spin dependent total cross sections, inclusive charged and neutral pion and eta production, spin transfer to lambdas, and spin effects in the inverse Primakoff effect. Also, polarimetry methods were developed which can be used at other accelerators. There are several experimental indications that spin effects are significant at high energy. The presence of these large effects, particularly in inclusive reactions, is investigated by measuring at high pT and high xF for various reactions.
E581/704 Degree Recipients
N. Akchurin Ph.D. University of Iowa
A. Bravar Ph.D. University of Iowa
S. Makino Ph.D. Kyoto University
A.H. Mohammadzadeh M.S. Rice University
T. Nagamine Ph.D. Kyoto University
N. Saito Ph.D. Kyoto University
Joseph Lasalle White M.S. Rice University
Qiuan Zhu Ph.D. Rice University
E581/704 Publications
Analyzing-Power Measurement in Inclusive p o Production at High xF., B.E. Bonner, et al., Phys. Rev. Lett. 61, 1918 (1988).
Analyzing-Power Measurements of Coulomb-Nuclear Interference with the Polarized-Proton and -Antiproton Beams at 185 GeV/c., N. Akchurin, et al., Phys. Lett. B229, 299 (1989).
Measurements of the Analyzing Power in the Primakoff Process with a High-Energy Polarized Proton Beam., D.C. Carey, et al., Phys. Rev. Lett. 64, 357 (1990).
First Results for the Two-Spin Parameter ALL in po Production by 200 GeV Polarized Protons and Antiprotons., D.L. Adams, et al., Phys. Lett. B261, 197 (1991).
Comparison of Spin Asymmetries and Cross Sections in p o Production by 200 GeV Polarized Antiprotons and Protons., D.L. Adams, et al., Phys. Lett. B261, 201 (1991).
Analyzing Power in Inclusive p+and p- Production at High xF with a 200 GeV Polarized Proton Beam., D.L. Adams, et al., Phys. Lett. B264, 462 (1991).
High-xT Single-Spin Asymmetry in po and h production at xF = 0 by 200 GeV Polarized Antiprotons and Protons., D.L. Adams, et al., Phys. Lett. B276, 531 (1992).
Analyzing Power Measurement of pp Elastic scattering in the Coulomb-Nuclear Interference Region with the 200 GeV/c Polarized-Proton Beam at Fermilab., N. Akchurin, et al., Phys. Rev. D48, 3026 (1993).
Measurement of the Double-Spin Asymmetry ALL for inclusive Multi-Gamma Pair Production with 200 GeV/c Polarized Proton Beam and Polarized Proton Target., D.L. Adams, et al., Phys. Lett. B336, 269 (1994).
Measurement of Single Spin Asymmetry for Direct Photon Production in pp Collisions at 200 GeV., D.L. Adams, et al., Phys. Lett. B345, 569 (1995).
Analyzing Power Measurement in Inclusive Lambda Production with a 200 GeV Polarized Proton Beam., A. Bravar, et al., Phys. Rev. Lett.75, 3073 (1995).
Single Spin Asymmetries and Invariant Cross Sections of the High Transverse-Momentum Inclusive po Production in 200 GeV p p and anti-p p Interactions., D.L. Adams, et al., Phys.Rev. D53, 4747 (1996).
Single-Spin Asymmetries in Inclusive Charged Pion Production by Transversely Polarized Antiprotons., A. Bravar, et al, Phys. Rev. Lett. 77, 2626 (1996).
Measurement of the Differences in the Total Cross Section for Antiparallel and Parallel Longitudinal Spins and a Measurement of Parity Nonconservation with Incident Protons and Antiprotons at 200 GeV/c., D.P. Grosnick, et al., Phys. Rev. D55, 1159 (1997).
Spin Transfer in Inclusive Lambda Production by Transversely Polarized Protons at 200 GeV/c., A. Bravar, et al., Phys. Rev. Lett. 78, 4003 (1997).
3.6 E705 - Charmonium
and Direct g Production at 300 GeV/c
South Alabama, Arizona, Athens (Greece), Duke, Fermilab,
INFN/Florence (Italy), McGill (Canada), Nanjing (PRC), Northwestern,
Prairie View A&M, Shandong (PRC),
SSCL, Virginia
E705, performed in the High Intensity Lab of the Proton Area, continued the study of the production of charm-anticharm bound states, also referred to as "charmonium", that had been part of the previous E537 experiment achievements. In order to study various excited states of the charm-anticharm system, the detection of dimuons was not sufficient, but it had to be complemented with the detection of high energy photons (or gamma rays), since excited states will decay into the J/y ground state by the emission of a photon. To this purpose, the experiment apparatus was upgraded by the inclusion of a 30-ton scintillating glass electromagnetic calorimeter, capable of measuring the energy and position of high energy gamma rays. Using very high flux pion beams, it was possible to study the processes responsible for the formation of charm-anticharm pairs, both in the ground and excited states. This in turn allowed clarification of several aspects Quantum Chromodynamics (QCD). An unexpected result of E705 was the first and, to date, only observation of the high-energy production of an excited state of charmonium, the 1P1 state, that cannot be produced directly in e+e- interactions, where most of charmonium spectroscopy had been studied.
E705 Degree Recipients
Tom Lecompte Ph.D. Northwestern University
A. Manousakis-Katsikakis Ph.D. University of Athens
Panos Pramantiotis Ph.D. University of Athens
Marzia Rosati Ph.D. McGill University
Qifeng Shen Ph.D. Duke University
Andre Simard M.S. McGill University
Yao Tan Ph.D. Northwestern University
Richard Tesarek Ph.D. Duke University
Timothy Turkington Ph.D. Duke University
Spiros Tzamarias Ph.D. University of Athens
George Zioulas Ph.D. McGill University
E705 Publications
Production of J/y via y’ and cc Decay in 300 GeV/c p and p± Nucleon Interactions., L. Antoniazzi, et al., Phys. Rev. Lett. 70, 383 (1993).
Measurement of J/y and y’ Production in 300 GeV/c Proton, Antiproton, and p± Interactions with Nuclei., L. Antoniazzi, et al., Phys. Rev. D46, 4828 (1992).
Search for Hidden Charm Resonance States Decaying into J/y or y ' plus Pions., L. Antoniazzi et al., Phys. Rev. D50, 4258 (1994).
Production of c Charmonium via 300 GeV/c p and p± Interactions on a Lithium Target., L. Antoniazzi, et al., Phys. Rev. D49. 543 (1994).
3.7 E706 - Direct g Production in Hadron Induced
Collisions
UC/Davis, Delhi (India), Fermilab,
Michigan State, Northeastern,
Oklahoma, Pennsylvania State,
Pittsburgh, Rochester
Due to the nature of the strong interaction, reliable theoretical Quantum Chromodynamics (QCD) calculations have been difficult to achieve for most processes. However, those interactions that produce high transverse momentum particles are amenable to perturbative techniques in the context of the parton model. Perturbative QCD calculations for the production of photons emerging with high transverse momentum have been completed at next-to-leading order (NLO) in the strong coupling constant. Such direct photons provide insight into the structure of the interacting hadrons and the interactions between their constituents, and have long been viewed as an ideal probe of the gluon content of hadrons in a kinematic regime not directly accessible in most other processes.
In the Meson West beamline, experiment E706 studied high energy hadronic interactions that produce direct photons with large transverse momentum. A large, finely segmented lead and liquid argon sampling calorimeter was designed and built for this experiment. The calorimeter was used to select events based upon weighted energy deposits, and to reconstruct photon four vectors (and electron energies). The Meson West spectrometer also concurrently collected data for experiment E672, using a high-mass dimuon trigger to select events. The data from the two experiments were written to shared data tapes, and then independently analyzed.
E706 accumulated large samples of data involving hard scatters of protons at 800 GeV/c and secondary protons and pions at 500 GeV/c incident upon hydrogen, beryllium, and copper targets. The data showed that direct photons are produced at a rate that is approximately a factor of two larger than anticipated based on NLO perturbative QCD calculations. Other characteristics of the E706 data, including results on pion production at high transverse momentum as well as high-mass photon-pion pairs, provide evidence that the NLO QCD calculations do not adequately account for gluon emissions. The E706 measurement of the pT spectrum of high transverse momentum charged D mesons provides another such indication. The results have spurred significant interest, debate, and effort in the theoretical community. The results of recent sophisticated theoretical calculations indicate that large additional contributions to direct photon production, beyond those included at NLO, can in fact be expected within the framework of QCD from the effects of initial-state gluon radiation. This re-evaluation of QCD calculations, which was motivated by the striking differences between the E706 results and NLO QCD, will yield a deeper understanding of direct photon production. Combining the consequences of these new theoretical developments and the high precision direct photon measurements from E706 into global evaluations of the parton distribution functions, should also contribute new insights into the gluon distribution.
E706 Degree Recipients
Leonard Apanasevich Ph.D. Michigan State University
John P. Bacigalupi Ph.D. University of California at
Davis
Giuseppe Ballocchi Ph.D. University of Rochester
Lucyna de Barbaro Ph.D. University of Rochester
Michael Begel Ph.D. University of Rochester
Charles Robert Benson M.S. University of Rochester
Richard Scott Benson Ph.D. University of Minnesota
Steven R. Blusk Ph.D. University of Pittsburgh
David Shaw Brown Ph.D. Michigan State University
Paoti Chang Ph.D. Northeastern University
Brajesh Chandra Choudhary Ph.D. University of Delhi
Woo-Hyun Chung Ph.D. University of Pittsburgh
William Edward DeSoi Ph.D. University of Rochester
Wieslaw Dlugosz Ph.D. Northeastern University
Sajan Easo Ph.D. Pennsylvania State University
Keith W. Hartman Ph.D. Pennsylvania State University
Vijay Kapoor Ph.D. University of Delhi
Ioanis Kourbanis Ph.D. Northeastern University
John F. Kuehler Ph.D. University of Oklahoma
Armando Lanaro Ph.D. University of Rochester
Christopher B. Lirakis Ph.D. Northeastern University
Sudhindra Mani Ph.D. University of Pittsburgh
John Philip Mansour Ph.D. University of Rochester
George B. Osborne III Ph.D. University of Rochester
Eric Jon Prebys Ph.D. University of Rochester
Robert Martin Roser Ph.D. University of Rochester
Alexandros Pericles Sinanidis Ph.D. Northeastern University
Dana Duane Skow Ph.D. University of Rochester
Lee Ronald Sorrell Ph.D. Michigan State University
David Striley Ph.D. University of Missouri
Nikos Varelas Ph.D. University of Rochester
P. D. D. S. Weerasundara Ph.D. University of Pittsburgh
Carlos M. Yosef Ph.D. Northeastern University
Vishnu V. Zutshi Ph.D. University of Delhi
Inclusive production of omega mesons at large transverse momenta in p- Be interactions at 515 GeV/c., L. Apanasevich, et al., hep-ex/0004012, submitted to Phys. Rev. D.
Production of J/y mesons in p Be collisions at 530 and 800 GeV/c., A. Gribushin, hep-ex/9910005, to be published in Phys. Rev. D, 1120XX (2000).
Evidence for Parton Effects in High-pT Particle Production., L. Apanasevich, et al., Phys. Rev. Lett. 81, 2642 (1998).
Production of charm mesons at high transverse momentum in 515 GeV/c p- nucleon collisions., L. Apanasevich, et al., Phys. Rev. D56, 1391 (1997).
Production
of Charmonium States in p-
Be Collisions at 515 GeV/c., V. Koreshev, et al.,
Phys. Rev. Lett., 77, 4294 (1996).
Production
of J/y
and y(2S)
mesons in p-
Be collisions at 515 GeV/c., A. Gribushin,
et al., Phys. Rev. D53, 4723 (1996).
Bottom Production in p- Be Collisions at 515 GeV/c., R. Jesik, et al., Phys. Rev. Lett., 74, 495 (1995). Structure of the recoiling system in direct-photon and po production by p- and p beams at 500 GeV/c., G. Alverson, et al., Phys. Rev. D49, 3106 (1994).
Production of direct-photons and neutral mesons at large transverse momenta by p-and p beams at 500 GeV/c., G. Alverson, Phys. Rev. D48, 5 (1993).
Production of p mesons at high-pT in p- Be and p Be collisions at 500 GeV/c., G. Alverson, Phys. Rev. D45, R3899 (1992).
Direct Photon Production at High-pT in p- Be and p Be Collisions at 500 GeV/c., G. Alverson, Phys. Rev. Lett. 68, 2584 (1992).
3.8 E711 -
Dihadron Production
Argonne
National Laboratory, Fermilab, Florida State, Michigan
While it is generally agreed that hadronic matter is composed of quarks, some of the basic scattering amplitudes, (or properties) were not known. This experiment was designed to measure the energy, angular, and charge dependence of massive di-hadron production over a large solid angle in intense proton and pion beams. The focus of this experiment included the transverse momentum region that exploits various properties of high transverse momentum triggered events, namely identifying jet-like structures from recoiling trigger particles; the spatial correlation between the trigger particle and the hadron; and the fraction of the jet momentum carried by the leading hadron in the jet. Unlike single particle triggers, many of the characteristics of quark-quark scattering are more accurately observed using the symmetric configuration studied in this experiment. The results provided tests of QCD and other hadronic theories in hard scattering (high energy) collisions. The di-hadron production spectra provided the most direct method of measuring the energy, angular and charge dependence of the sub-constituent quark-quark scattering mechanism.
Using a number of different nuclear targets, scattering characteristics were shown to vary linearly with atomic weight, for various charge states. It was also shown that the angular distributions were also independent of the target type, and showed a small dependence on charge, thus indicating in general that the data agreed with previous measurements for other energy ranges, and with QCD calculations.
Another important result of the experiment was finding that the average fraction of the jet momentum carried by the leading hadron in that jet was independent of whether the event had a single jet or two jets, and independent of the target type. These results were consistent with QCD theoretical model predictions. In general, these studies suggest that many processes, at the level of quarks, are not affected by interactions taking place at the nuclear level. Also, at these energies, measured characteristics including the angular and charge dependencies are described well by the QCD-parton model.
E711 Degree Recipients
Gianluigi Boca Ph.D. Florida State University
Mary Anne Clare Cummings Ph.D. University of Michigan
Kathleen Ruth Turner Streets Ph.D. Florida State University
Herman Brenner White Jr. Ph.D. Florida State University
E711 Publication:
Atomic Weight Dependence of the Production of Hadron Pairs by 800 GeV/c Protons on Nuclear Targets., K. Streets, et al., Phys. Rev. Lett. 66, 864 (1991).
Average
Fraction of Jet Momentum Carried by High pT Hadrons.,
G. Boca, et al., Z. Phys. C49, 543 (1991).
Massive Hadron Pair Production by 800 GeV/c Protons on Nuclear Targets., H.B. White, et al., Phys. Rev. D48, 3996 (1993).
3.9 E772 -
the Quark-Antiquark Sea in Nuclei
Case Western Reserve, Fermilab,
Illinois/Chicago, LANL, Northern Illinois,
Rutgers, South Carolina, SUNY/Stony
Brook, Texas/Austin, Washington
E-772 made a precision measurement of the ratio of the yield of muon pairs from heavy nuclei to that from deuterium. This ratio of dimuon pairs (with masses from 6-9 GeV and 11-15 GeV, called Drell-Yan dimuons), is directly proportional to the distribution of anti-quarks in the proton and hence is sensitive to possible modifications of the sea of anti-quarks due to the nuclear environment. The experiment also studied the nuclear dependence of the yield of dimuons from the decay of J/y and y' resonances.
E772 Degree Recipients
Rurngsheng Guo-Sheng M.S. Northern Illinois University
Ming-jer Wang Ph.D. Case Western Reserve University
Nuclear Dependence of Dimuon Production at 800 GeV/c., D.M. Alde, et al., Phys. Rev. Lett. 64, 2479 (1990).
A-Dependence of J/y and y ' Production at 800 GeV/c., D.M. Alde, et al., Phys. Rev. Lett. 66, 133 (1991).
Nuclear Dependence of the Production of Upsilon Resonances at 800 GeV., D.M. Alde, et al., Phys. Rev. Lett. 66, 2285 (1991).
Limit on the /Asymmetry of the Nucleon Sea from Drell-Yan Production., P.L. McGaughey, et al., Phys. Rev. Lett. 69, 1726 (1992).
Cross Sections for the Production of High-Mass Muon Pairs from 800 GeV Proton Bombardment of Deuterium., P.L. McGaughey, et al., Phys. Rev. D50, 3038, (1994).
Test of Scaling of the Massive Dihadron Cross Section., D.M. Kaplan, et al., Phys. Rev. D41, 2334 (1990).
Improved Limit on Axion Production in 800 GeV Hadronic Showers., R. Guo, et al., Phys. Rev. D41, 2924 (1990).
