CERN NA3

CERN NA3
Name	CERN NA3
Institution	CERN
Experiment	NA3
Period	1970s
Location	Super Proton Synchrotron beamline at CERN
Spokesperson	Frank Close
Subjects	high-energy physics, charm quark, Drell–Yan process, deep inelastic scattering

CERN NA3

Introduction

NA3 was a fixed-target high-energy physics experiment at CERN that operated during the 1970s on the Super Proton Synchrotron. It pursued measurements of the Drell–Yan process, hadroproduction of charm quark states, and muon pair production using secondary hadron and proton beams. Collaborating institutions included groups from United Kingdom, France, Switzerland, Italy, and United States laboratories and universities associated with contemporary programs at DESY, SLAC, and Fermilab.

Experimental Setup and Beamline

The NA3 apparatus was installed on a high-intensity secondary beamline derived from the Super Proton Synchrotron primary proton extraction system and shared beam optics concepts with other SPS-era experiments such as NA10 and NA11. The beamline transported mixed hadron beams—pions, kaons, and protons—selected using magnetic spectrometers and momentum-defining collimators influenced by designs from British-Russian collaborations and techniques applied in CERN PS experiments. Beam instrumentation included beam counters and Cherenkov devices similar to systems used at Brookhaven National Laboratory and IHEP (Protvino). Targets were thin foils of atomic elements from light nuclei like beryllium to heavy nuclei such as tungsten, following target choices paralleling studies at FNAL.

Physics Goals and Measurements

Primary goals were precision studies of the Drell–Yan process, the production of muon pairs through quark-antiquark annihilation first formalized by work building on S. D. Drell and T.-M. Yan theory, and measurements of open and hidden charm quark production cross sections. NA3 sought to map parton-level phenomena relevant to the emerging Quantum Chromodynamics picture advanced by theorists including Murray Gell-Mann and Frank Wilczek, and to test parton distribution function behavior previously constrained by deep inelastic scattering results from SLAC and CERN WA1. The collaboration measured transverse momentum spectra, Feynman-x distributions, and nuclear dependence (A-dependence) of muon pair and charm yields, complementing concurrent measurements at Fermilab E605 and informing global fits used by groups such as those at CTEQ and MSTW.

Detector Components and Instrumentation

The detector incorporated large-acceptance magnetic spectrometers inspired by designs from CERN NA5 and CERN NA10, muon identification systems derived from absorber-based techniques used at Brookhaven, and tracking chambers following chamber technology from CERN PS programs. Tracking used multiwire proportional chambers and drift chambers similar to those in UA1 and UA2 experiments, while muon triggering relied on scintillator hodoscopes and iron absorbers akin to systems at ISR experiments. Momentum analysis employed dipole magnets comparable to magnets used in CERN ISR beamlines, and particle identification incorporated threshold Cherenkov counters and time-of-flight modules paralleling devices at DESY. Data acquisition systems adapted event-recording strategies influenced by developments at SLAC and Fermilab, with trigger logic optimized for high-mass muon-pair topologies like studies later pursued by CDF and D0.

Data Analysis and Results

NA3 reported differential cross sections for high-mass dimuon production that constrained models of quark-antiquark annihilation and sea antiquark distributions, producing results that were compared with perturbative QCD calculations by theorists such as John Ellis and Richard Feynman-inspired parton model expectations. Measurements of charmonium states (notably J/psi production) provided inputs to studies of color-singlet and color-octet production mechanisms developed by groups including Gavin Salam and others refining nonrelativistic QCD formalisms. Nuclear dependence measurements showed modifications of yields with atomic mass number, informing later investigations at Relativistic Heavy Ion Collider and experiments such as NA38 and NA50. NA3 results were incorporated into global analyses alongside data from E288, E605, and NA10, affecting extraction of parton distribution functions used by the Particle Data Group and Monte Carlo tuning efforts at CERN.

Impact and Legacy

The NA3 program influenced subsequent fixed-target and collider experiments by demonstrating techniques for high-rate muon spectroscopy, target-nucleus systematics, and open-charm detection that were adopted by NA38, NA50, NA49, and collider detectors at LHC experiments such as ALICE for heavy-flavor and quarkonium studies. Its measurements helped shape theoretical developments in Quantum Chromodynamics phenomenology, feeding into parton distribution extractions used by CMS and ATLAS and inspiring methodological cross-pollination with Fermilab fixed-target programs. NA3 alumni contributed to instrumentation and analysis efforts across high-energy physics institutions worldwide, reinforcing collaborative practices later embodied in long-term projects like CERN Neutrinos to Gran Sasso and multinational detector construction initiatives.

Category:Experiments at CERN