Stephen J Wimpenny
Professor of Physics
Ph.D. 1980, Sheffield University, England.
Experimental High Energy Physics


Phone:             (951) 827-3868
Fax:                 (951) 827-3345
E-mail:      stephen.wimpenny@ucr.edu
Department of Physics
University of California, Riverside CA 92521
  

Research

The D0 detector is one of the two large multi-purpose detectors at the Fermilab Tevatron in Illinois. With a center-of-mass energy of 1.96 TeV, the Tevatron has the highest collision energy of any machine in the world. This provides a unique window to research at the shortest distance scales and allows fundamental tests of the particle theory. The UCR group have been active members of the D0 Collaboration since 1986 and have contributed to the detector hardware, the control system and various of the data analyses.  The present group is led by Professor Wimpenny and consists of three faculty, two postdoctoral researchers and two graduate students, The UCR group have focussed their research into two areas: top quark studies (Professor Wimpenny, Dr. Heinson) and electroweak physics (Professor Ellison).

Today we know that the top (t) quark is the +2/3 charge partner of the bottom (b) quark and is the most massive fundamental particle known to science. At the start of the D0 experiment in 1992 it had not been observed, despite some 15 years of searching. By the end of the second data-taking run in 1995 it had been discovered jointly by D0 and its sister experiment CDF. The observations, based on the simultaneous production of a t- and and and anti t- quark were published  in March 1995. The UCR group played a central role in four of the seven analyses which contributed to the discovery. Subsequent research has focused on the refinement of the measurements of the quark mass and production cross section. Some 10 years later  we are operating a greatly improved detector and we are analyzing a data sample more that ten times larger than that of the 1995 analyses.

An important piece ot top quark physics which has yet to be confirmed is the production of single top quarks via the electroweak interaction. At UCR, the search for this second type of t-quark phyiscs is led by Dr. Ann Heinson, who has also been co-leader of the D0 single top research team since its inception in 1997. This is a very challanging piece of research and requires the use sophisticated analyses techniques. Sometime during the next two years this analysis is expected to lead to the first experimental observation of this new process.

In 2008 a new accelerator, the Large Hadron Collider (LHC), will come on-line at the CERN laboratory which lies on the boarder of France and Switzerland. This will take over from the Tevatron and the world's highest energy collider. With a center-of-mass energy of 14 TeV, it is almost an order or magnitude higher in energy than the Fermilab machine and it will provide a unique research tool into the late 2000's and  early 2010's. UCR is working on one of the two big detectors for the LHC known as the Compact Muon Solenoid (CMS) experiment. This effort is led by Professors Clare, Wimpenny and Hanson and will be supplemented by the present D0 research team who will start to transition into CMS over the next year or so.


 Fermilab LPC Topological Working Group

Dilepton+Jets+MET Topological Group


Graduate Lectures on Hadron Collider Physics
 

W and Z Mass and Width , Survey of W and Z Mass and Width results from Fermilab and Lep/Lep II, UC Riverside, January 11th, 2006

Missing Energy Physics , Introduction to Missing energy and its use in conventional Physics studies, UC Riverside, January 25th, 2006

Missing Energy Physics - Part 2, Lepton Coupling Universality in W-decays, UC Riverside, February 1st, 2006

Missing Energy Physics - Part 3, Missing Energy and the search for New Physics, UC Riverside, February 8th, 2006

Measurement of the Z Boson Mass at Lep I, A guide to Z Mass reconstruction at Lep I, UC Riverside, February 15th, 2006

Measurement of the W Boson Mass at Lep II, A guide to W Mass reconstruction at Lep II, UC Riverside, February 22nd, 2006

Measurement of the W and Z Boson Masses at the Fermilab Tevatron, A guide to W and Z Mass reconstruction at Fermilab, UC Riverside, March 15th, 2006

Top Quark Physics - Part 1: The Road to Discovery, Introduction to top quark physics and the discovery analyses of 1995, UC Riverside, April 4th, 2006.

Top Quark Physics - Part 2: Results at 1.8 TeV , Review of the cross section and mass measurements at 1.8 TeV, UC Riverside, April 13th, 2006.

Top Quark Physics - Part 3: Results at 1.8 TeV , Top quark kinematics and the search for electroweak sigle top quark production, UC Riverside, April 20th, 2006.

Physics before discoveries at the LHC, Discussion of CMS startup: the pilot run and run1, Kati Lassila-Perini - Helsinki Inst. of Physics/ Moriond 2006 Talk,
UC Riverside, April 27th-May11th, 2006.

Top Quark Physics - Part 4: Results at 1.96 TeV , Survey of the latest D0 and CDF results from Run 2, UC Riverside, May 18th, 2006.

Higgs Hunting at Lep , Review of the Lep I and II Higgs Search Results, UC Riverside, May 25th, 2006.

Higgs Hunting at the Tevatron - Spring 2006 , Review of the Tevatron Higgs Search Results, Per Jonsson - Imperial College London/Moriond 2006 Talk,
(with updates from Bob, John and Steve), UC Riverside, June 1st, 2006.

Higgs Searches at Tevatron - Summer 2006, Review of the Tevatron Higgs Search Results, Lars Sonnenschein - LPNHE Paris/Hadron Collider Physics (HCP) 2006 Talk,
(with updates from Bob), UC Riverside, October 12th, 2006.

Higgs Hunting at the LHC - Summer 2006 , Higgs Hunting at the LHC, A. Nikitanko - Imperial College London/ITEP Moscow, Hadron Collider Physics (HCP) 2006 Talk,
UC Riverside, October 19th, 2006.


Selected Publications

Search for Single Top Quark Production

"Multivariate searches for single top quark production with the D0 detector",
V. Abavzov et. al., D0 Collaboration - hep-ex/0604020, (submitted to Phys. Rev. D.), (2006).

"Search for Single Top Production using Neural Networks",
V. Abazov et al., D0 Collaboration - Phys. Lett. B517, 282-294, (2001).

"Search for Electroweak Production of Single Top Quarks in ppbar Collisions",
B. Abbott et al., D0 Collaboration - Phys Rev. D63, 031101, (2001).


Studies of Top Quark Pair Physics

"A Precision Measurement of the Mass of the Top Quark",
V. Abazov et al., D0 Collaboration - Nature 429, 638-642, (2004).

"The ttbar Production Cross Section in ppbar Collisions at 1.8 TeV",
V. Abazov et al., D0 Collaboration - Phys. Rev. D67, 012004, (2003).

"Measurement of the Top Quark Mass Using Dilepton Events",
B. Abbott et al., D0 Collaboration - Phys. Rev. Lett. 60, 2063-2068, (1998).

"The Top Quark",
S.J. Wimpenny and B.L. Winer, Ann. Rev. Nucl. Part. Sci. 46, 149-195, (1996)

"Observation of the Top Quark",
S. Abachi et al., D0 Collaboration - Phys. Rev. Lett. 74, 2632-2637, (1995).

"Search for the Top Quark in ppbar Collisions at 1.8 TeV",
S. Abachi et al., D0 Collaboration - Phys. Rev. Lett. 72, 2138-2142, (1994).


Other Topics

"Studies of Intermediate Vector Boson Production and Decay in UA1 at the CERN Proton-Antiproton Collider",
C. Albajar et al., UA1 Collaboration - Zeit. Phys. C44, 15-61, (1989).

"A Measurement of the Spin Asymmetry and Determination of the Structure Function g1 in Deep Inelastic Muon-Proton Scattering",
J. Ashman et al., European Muon Collaboration - Phys. Lett. B206, 364-370, (1988).

"Search for B0-B0bar Oscillations at the CERN Proton-Antiproton Collider",
C. Albajar et al., UA1 Collaboration - Phys. Lett. 186B, 247-254, (1987).

"A Detailed Study of the Proton Structure Functions in Deep Inelastic Muon-Proton Scattering",
Nucl. Phys. B258, 189-266, (1985).

"The Ratio of the Nucleon Structure Functions F2(n) for Iron and Deuterium",
J.J. Aubert et al., European Muon Collaboration - Phys. Lett. 123B, 275-278, (1983).



See also: Link to DØ Publications


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