Precision measurement of W boson mass portends stricter limits for Higgs particle

March 12, 2009

Batavia, Ill.-Scientists of the DZero collaboration at the Department of Energy's Fermi National Accelerator Laboratory have achieved the world's most precise measurement of the mass of the W boson by a single experiment. Combined with other measurements, the reduced uncertainty of the W boson mass will lead to stricter bounds on the mass of the elusive Higgs boson.

The W boson is a carrier of the weak nuclear force and a key element of the Standard Model of elementary particles and forces. The particle, which is about 85 times heavier than a proton, enables radioactive beta decay and makes the sun shine. The Standard Model also predicts the existence of the Higgs boson, the origin of mass for all elementary particles.

Precision measurements of the W mass provide a window on the Higgs boson and perhaps other not-yet-observed particles. The exact value of the W mass is crucial for calculations that allow scientists to estimate the likely mass of the Higgs boson by studying its subtle quantum effects on the W boson and the top quark, an elementary particle that was discovered at Fermilab in 1995.

Scientists working on the DZero experiment now have measured the mass of the W boson with a precision of 0.05 percent. The exact mass of the particle measured by DZero is 80.401 +/- 0.044 GeV/c2. The collaboration presented its result at the annual conference on Electroweak Interactions and Unified Theories known as Rencontres de Moriond last Sunday.

"This beautiful measurement illustrates the power of the Tevatron as a precision instrument and means that the stress test we have ordered for the Standard Model becomes more stressful and more revealing," said Fermilab theorist Chris Quigg.

The DZero team determined the W mass by measuring the decay of W bosons to electrons and electron neutrinos. Performing the measurement required calibrating the DZero particle detector with an accuracy around three hundredths of one percent, an arduous task that required several years of effort from a team of scientists including students.

Since its discovery at the European laboratory CERN in 1983, many experiments at Fermilab and CERN have measured the mass of the W boson with steadily increasing precision. Now DZero achieved the best precision by the painstaking analysis of a large data sample delivered by the Tevatron particle collider at Fermilab. The consistency of the DZero result with previous results speaks to the validity of the different calibration and analysis techniques used.

"This is one of the most challenging precision measurements at the Tevatron," said DZero co-spokesperson Dmitri Denisov, Fermilab "It took many years of efforts from our collaboration to build the 5,500-ton detector, collect and reconstruct the data and then perform the complex analysis to improve our knowledge of this fundamental parameter of the Standard Model."

The W mass measurement is another major result obtained by the DZero experiment this month. Less than a week ago, the DZero collaboration submitted a paper on the discovery of single top quark production at the Tevatron collider. In the last year, the collaboration has published 46 scientific papers based on measurements made with the DZero particle detector.

Fermi National Accelerator Laboratory

---

---

	True Nature of the Higgs Mechanism: A Hypothesis Associated with the Large Hadron Collider (LHC), Geneva by Chandrakanth Natekar (Author), Prashanth Vitla (Author), Prashanth Vitla (Cover Design), Sai Sambat (Cover Design), Sudesh Mahan (Cover Design) "Science is a simple phenomenon of Nature, but it is the known that is preventing us from mastering the unknown". True Nature of the Higgs Mechanism dwells upon some of the fundamental aspects of the universal binding force and hitherto unrecognized balancing force. Its prime focus is on the Higgs Mechanism and the puzzling mass of W & Z bosons. The hypotheses presented in this book will reveal the 'True Nature of the Higgs Mechanism' and the "True Nature of W & Z Bosons". These hypotheses can be experimentally verified at the Large Hadron Collider (LHC), Geneva. Alternately, the available data of the previous experiments of the Large Electron Positron Collider (LEP), Fermilab's Tevatron, Stanford SLAC and other colliders can also be used to check the scientific validity of these...
	The Infinity Puzzle: Quantum Field Theory and the Hunt for an Orderly Universe by Frank Close (Author) Speculation is rife that by 2012 the elusive Higgs boson will be found at the Large Hadron Collider. If found, the Higgs boson would help explain why everything has mass. But there’s more at stake—what we’re really testing is our capacity to make the universe reasonable. Our best understanding of physics is predicated on something known as quantum field theory. Unfortunately, in its raw form, it doesn’t make sense—its outputs are physically impossible infinite percentages when they should be something simpler, like the number 1. The kind of physics that the Higgs boson represents seeks to “renormalize” field theory, forcing equations to provide answers that match what we see in the real world. The Infinity Puzzle is the story of a wild idea on the road to acceptance. Only Close...
	The God Particle: If the Universe Is the Answer, What Is the Question? by Leon Lederman (Author), Dick Teresi (Author) A fascinating tour of particle physics from Nobel Prize winner Leon Lederman.   At the root of particle physics is an invincible sense of curiosity. Leon Lederman embraces this spirit of inquiry as he moves from the Greeks' earliest scientific observations to Einstein and beyond to chart this unique arm of scientific study. His survey concludes with the Higgs boson, nicknamed the God Particle, which scientists hypothesize will help unlock the last secrets of the subatomic universe, quarks and all—it's the dogged pursuit of this almost mystical entity that inspires Lederman's witty and accessible history.
	Higgs Force: The Symmetry-Breaking Force that Makes the World an Interesting Place by Nicholas Mee (Author) Higgs Force is a gripping account of the scientists who have revealed the hidden structure of the natural world. It is the story of the fundamental components of matter and the forces that bind them together; a tale that is woven around the symmetry at the heart of the universe and the mystery of how this symmetry is broken. The book is divided into three parts. The first three chapters provide the broad historical and philosophical context. The next three describe, in turn, each of the forces that are important in particle physics. The final three chapters are about the modern synthesis of the particles and forces and the search for the last missing piece in the particle physics jigsaw.
	Deep Down Things: The Breathtaking Beauty of Particle Physics by Bruce A. Schumm (Author) A useful scientific theory, claimed Einstein, must be explicable to any intelligent person. In Deep Down Things, experimental particle physicist Bruce Schumm has taken this dictum to heart, providing in clear, straightforward prose an elucidation of the Standard Model of particle physics—a theory that stands as one of the crowning achievements of twentieth-century science. In this one-of-a-kind book, the work of many of the past century's most notable physicists, including Einstein, Schrodinger, Heisenberg, Dirac, Feynman, Gell-Mann, and Weinberg, is knit together in a thorough and accessible exposition of the revolutionary notions that underlie our current view of the fundamental nature of the physical world. Schumm, who has spent much of his life emmersed in the subatomic world, goes...
	Massive: The Missing Particle That Sparked the Greatest Hunt in Science by Ian Sample (Author) In Massive, prize-winning science journalist Ian Sample tells the story of the race to locate the Higgs Boson, the elusive particle whose existence remains to be proven. Since 1964, when Peter Higgs described an over-arching theory of mass that depended on the Higgs boson, the scientific community has been possessed by the increasingly competitive race to prove its existence. The ensuing four-decade quest has cost billions of dollars and consumed the attention of scientific luminaries and of politicians eager to ensure that their home country would be the one to get credit for discovering the long-sought-after particle. Now, with the Large Hadron Collider up and running, the discovery of the Higgs boson seems finally to be within our grasp. Sample’s Massive provides the juicy...
	The Quantum Frontier: The Large Hadron Collider by Don Lincoln (Author) The highest-energy particle accelerator ever built, the Large Hadron Collider runs under the border between France and Switzerland. It leapt into action on September 10, 2008, amid unprecedented global press coverage and widespread fears that its energy would create tiny black holes that could destroy the earth. By smashing together particles smaller than atoms, the LHC recreates the conditions hypothesized to have existed just moments after the big bang. Physicists expect it to aid our understanding of how the universe came into being and to show us much about the standard model of particle physics—even possibly proving the existence of the mysterious Higgs boson. In exploring what the collider does and what it might find, Don Lincoln explains what the LHC is likely to teach us about...
	Search for the Higgs Boson by John V. Lee (Editor) The Higgs boson is an undiscovered elementary particle, thought to be a vital piece of the closely fitting jigsaw of particle physics. Like all particles, it has wave properties akin to those ripples on the surface of a pond which has been disturbed; indeed, only when the ripples travel as a well defined group is it sensible to speak of a particle at all. In quantum language the analogue of the water surface which carries the waves is called a field. Each type of particle has its own corresponding field. The Higgs field is a particularly simple one - it has the same properties viewed from every direction, and in important respects in indistinguishable from empty space. Thus physicists conceive of the Higgs field being "switched on", pervading all of space and endowing it with "grain" like...
	Exploring Fundamental Particles by Lincoln Wolfenstein (Author), Joao P. Silva (Author) The search for the elementary constituents of the physical universe and the interactions between them has transformed over time and continues to evolve today, as we seek answers to questions about the existence of stars, galaxies, and humankind. Integrating both theoretical and experimental work, Exploring Fundamental Particles traces the development of this fascinating field, from the discoveries of Newton, Fermi, and Feynman to the detection of CP violation and neutrinos to the quest to observe the Higgs boson and beyond. An Accessible yet In-Depth Account of How Fundamental Particles Shape Our World The book first examines the experiments and theoretical ideas that gave rise to the standard model. It discusses special relativity, angular momentum, spin, the Dirac electron, quantum...
	Book (The God Particle) by Acclaimed Books A SIMPLE TALE OF SUBATOMIC PARTICLE METAPHYSICS In the summer of 2008, a long awaited scientific experiment was started at the CERN particle accelerator near Geneva. The experiment involved the high-speed collision of subatomic particles and the objective was to prove the existence of the Higgs boson, more commonly known as 'The God Particle'. To the great disappointment of the worldwide scientific community and the relief of many people who were concerned that this experiment might trigger a reaction that would destroy our planet, a technical hitch caused the experiment to be abandoned at the crucial moment. Book is the first episode in a humorous journey that began in the chaos of that failed experiment. God Particles; both elusive and...