Drell–Yan process

Drell–Yan process
Name	Drell–Yan process
Discovered	1970
Discoverers	Sidney Drell; Tung-Mow Yan
Field	Particle physics
Relevant	Proton–proton collisions; proton–antiproton collisions; lepton pair production

Drell–Yan process is a mechanism for producing lepton pairs in hadron collisions via quark–antiquark annihilation mediated by electroweak bosons. It links perturbative quantum chromodynamics calculations with electroweak theory and provides precision probes of parton distribution functions, electroweak parameters, and physics beyond the Standard Model. The process plays a central role in analyses at major collider experiments and informs global PDF fits and searches for new resonances.

History and discovery

The process was proposed in 1970 by Sidney Drell and Tung-Mow Yan, contemporaneous with developments at Fermilab, CERN, SLAC National Accelerator Laboratory, Brookhaven National Laboratory, and DESY. Early experimental confirmation occurred at fixed-target experiments and collider programs including the CERN Intersecting Storage Rings, Fermilab Tevatron, and later the Large Hadron Collider. Key figures and institutions associated with its development include Sidney Drell, Tung-Mow Yan, James Cronin, Val Fitch, Murray Gell-Mann, Francis Low, Richard Feynman, and collaborations such as UA1, UA2, CDF, DZero, ATLAS, CMS, and LHCb.

Historical milestones tied to the process intersect with discoveries at Electron–proton collider HERA, precision tests at LEP, and neutrino studies at Super-Kamiokande. The Drell–Yan mechanism influenced parton model validation by researchers including James Bjorken, Richard D. Field, Georgi Varma, Guido Altarelli, Parisi, and the development of global PDF fitting efforts like CTEQ, MSTW, NNPDF, and HERAPDF. The discovery timeline paralleled major theoretical advances from Quantum electrodynamics pioneers and led to collaborations across Brookhaven, CERN, Fermilab, and DESY laboratories.

Theoretical framework

The perturbative description uses Quantum chromodynamics and Electroweak interaction gauge theory, with the hard subprocess q + q̄ → γ*, Z → ℓ+ℓ− embedded in factorization theorems developed by researchers at Cornell University, Princeton University, Harvard University, and Institute for Advanced Study. Calculations rely on parton distribution functions provided by groups like CTEQ, MSTW, NNPDF, ABM, and HERAPDF; matching and evolution employ Dokshitzer–Gribov–Lipatov–Altarelli–Parisi equations formulated by Gribov, Lipatov, Altarelli, and Parisi. The formalism incorporates electroweak mixing parameters from Glashow–Weinberg–Salam theory, with inputs constrained by measurements at LEP, SLAC, and Tevatron. Effective field theory techniques from Soft-Collinear Effective Theory groups at MIT, Caltech, and University of Chicago are used to organize logarithms and power corrections.

Experimental signatures and measurements

Collider experiments detect oppositely charged lepton pairs (electrons or muons) with invariant-mass spectra measured by collaborations such as ATLAS, CMS, LHCb, CDF, and DZero in environments provided by Large Hadron Collider, Tevatron, and fixed-target setups at Fermilab and CERN PS. Precision observables include differential cross sections, rapidity distributions, transverse momentum spectra, forward–backward asymmetry measured by ALEPH and OPAL at LEP, and angular coefficients studied by CDF and CMS. Detector systems from ATLAS and CMS employ calorimeters, muon spectrometers, and tracking provided by teams from University of Oxford, CERN, MIT, University of California, Berkeley, and INFN. Experimental inputs feed global analyses by CTEQ, NNPDF, and MSTW groups and inform tests of electroweak parameters from Particle Data Group compilations.

Higher-order corrections and resummation

Next-to-leading order and next-to-next-to-leading order QCD corrections were developed by theorists at Brookhaven National Laboratory, CERN Theory Division, SLAC, and University of Cambridge; authors include John Collins, Davison Soper, George Sterman, and Kirill Melnikov. Electroweak radiative corrections computed by groups at DESY, Fermilab, and Argonne National Laboratory are essential for precision. Soft-gluon resummation techniques from Sterman, Catani, de Florian, and Vogt address large logarithms; transverse-momentum resummation uses formalisms by Collins–Soper–Sterman and methods in Soft-Collinear Effective Theory developed at Caltech and Princeton. Matching fixed-order results with parton showers is implemented in Monte Carlo generators from PYTHIA, HERWIG, SHERPA, and matrix-element tools like MCFM and FEWZ by collaborations at CERN, Rutgers University, and University of Durham.

Applications in particle physics

The process provides measurements of weak mixing angle and Z-boson properties constrained with data from LEP, SLD, ATLAS, and CMS; it underpins determinations of parton densities by CTEQ, NNPDF, and MSTW and contributes to proton structure knowledge related to studies at HERA and future Electron–Ion Collider. Drell–Yan observables are used in searches for new gauge bosons, including hypothetical Z′ bosons explored by ATLAS and CMS, and for constraints on contact interactions and compositeness investigated by Tevatron and LHC collaborations. Precision inputs feed global electroweak fits coordinated by Particle Data Group and inform beyond-Standard-Model scenarios studied at CERN Theory Division, SLAC, Fermilab, and university groups worldwide.

Extensions and related processes

Extensions include associated production like Z+jet and W+jet measured by ATLAS and CMS, heavy-flavor analogs studied at LHCb and ALICE, and semi-inclusive processes relevant to transverse-momentum-dependent PDFs developed by teams at Jefferson Lab, MIT, and DESY. Related mechanisms include Drell–Yan-like production in proton–nucleus collisions probed at CERN SPS and RHIC, and future investigations at proposed facilities such as Future Circular Collider, International Linear Collider, and Electron–Ion Collider. Theoretical connections span to Higgs boson production, Top quark studies, and precision programs at LEP and proposed precision facilities coordinated by international collaborations.

Category:Particle physics processes