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| BNL E749 | |
|---|---|
| Name | E749 |
| Lab | Brookhaven National Laboratory |
| Location | Upton, New York |
| Facility | Alternating Gradient Synchrotron |
| Timeframe | 1980s |
| Spokesperson | Thomas Kirk |
| Collaborators | Columbia University, University of Rochester, Fermilab |
| Field | High Energy Physics, Particle Physics |
BNL E749
BNL E749 was a fixed-target particle physics experiment conducted at Brookhaven National Laboratory on the Alternating Gradient Synchrotron aimed at precision studies of strange and charmed hadron production and decay. The program combined detector technologies and beam instrumentation to measure branching fractions, lifetimes, and production cross sections with implications for models associated with quark hadronization, weak decay dynamics, and perturbative Quantum Chromodynamics. E749 operated within a landscape that included contemporaneous projects at Fermilab, CERN, and national laboratories engaged in flavor physics and heavy-quark phenomenology.
E749 focused on producing and detecting secondary hadrons from a high-intensity proton beam striking fixed targets at the Alternating Gradient Synchrotron. The physics goals tied to precision determinations of branching ratios and lifetimes for hyperons and charmed mesons, tests of conservation laws in weak decays, and validation of fragmentation functions predicted by Quantum Chromodynamics. The collaboration placed emphasis on systematic control, using redundant subsystems developed in consultation with teams from Columbia University, University of Rochester, and Fermilab. Results from E749 were compared with measurements from CLEO, ARGUS (particle detector), and experiments at the European Organization for Nuclear Research to refine hadronic-production models.
The experiment used a primary proton beam provided by the Alternating Gradient Synchrotron incident on segmented metal targets similar to those used in contemporary fixed-target programs at Brookhaven National Laboratory and Fermilab. Downstream of the target, a magnetic spectrometer configured with dipole magnets, multiwire proportional chambers, and drift chambers provided momentum analysis akin to instrumentation at CERN SPS experiments. Time-of-flight counters, scintillation hodoscopes, and Čerenkov detectors supplied particle identification reminiscent of systems employed by WA89 and E791 (Fermilab). Electromagnetic calorimetry and muon identification layers borrowed design concepts from CLEO and E537 (Brookhaven) to discriminate electrons, photons, and muons in decay chains. Trigger logic coordinated with data acquisition computers modeled after systems at SLAC and Lawrence Berkeley National Laboratory enabled high-rate readout and online event selection.
Data acquisition combined hardware triggers sensitive to signatures of strange and charm decays with software filters executing on minicomputers derived from architectures used at Brookhaven National Laboratory and partner universities. Event reconstruction leveraged pattern-recognition algorithms parallel to those developed for CERN fixed-target analyses, performing track fitting with Kalman-filter techniques comparable to methods in Fermilab charm experiments. Particle identification integrated Čerenkov responses and time-of-flight measurements to separate kaons, pions, protons, and leptons for branching-fraction extraction similar to procedures in CLEO and ARGUS (particle detector). Systematic uncertainties were evaluated through control samples drawn from calibration runs, studies inspired by procedures from E791 (Fermilab), and cross-checks with Monte Carlo simulations using generators analogous to those distributed by groups at SLAC and CERN. Results were processed with statistical methods consistent with analyses from Particle Data Group compilations and frequentist confidence-interval constructions employed across high-energy physics.
E749 reported measurements of production cross sections for strange baryons and charmed mesons that contributed to global averages used in reviews by the Particle Data Group. Lifetimes and branching ratios for selected hyperons and D-meson decay modes were published, providing inputs that constrained heavy-quark effective-theory parameters and fragmentation models used in Quantum Chromodynamics phenomenology. Observed decay asymmetries and relative production rates were compared with results from CLEO, ARGUS (particle detector), and Fermilab fixed-target experiments, prompting refinements in theoretical descriptions of hadronization. Several intermediate conference proceedings presented by collaboration members at meetings hosted by American Physical Society divisions and international symposia influenced subsequent experimental proposals at Brookhaven National Laboratory and Fermilab.
Measurements from E749 affected phenomenological parameterizations of fragmentation functions and feed-down contributions in heavy-flavor production models used at CERN collider experiments and Fermilab fixed-target programs. The experiment's systematic techniques informed detector designs and data-acquisition strategies in later charm and strangeness experiments, including instrumentation upgrades at Brookhaven National Laboratory and proposals submitted to Fermilab and CERN. E749's results were incorporated into global fits and review articles by the Particle Data Group, and collaboration members subsequently contributed expertise to experiments such as E791 (Fermilab), CLEO, and projects at SLAC and Lawrence Berkeley National Laboratory. The legacy of E749 persists in methodological practices and in data points used to benchmark theoretical models in heavy-flavor physics.
The collaboration assembled personnel and institutions including Columbia University, University of Rochester, and groups with experience from Fermilab and Brookhaven National Laboratory. Financial and technical support came from funding agencies and program offices associated with United States Department of Energy research programs and national laboratory facilities common to U.S. high-energy physics projects. Institutional partnerships fostered transfer of detector technology and analysis software between university groups and national laboratory divisions, contributing to sustained capabilities in hadron spectroscopy and heavy-flavor experimentation.
Category:Brookhaven National Laboratory experiments