Marjorie Shapiro

Research Expertise and Interest

physics, particle physics, particle experiments, probing the most basic interactions in nature, quarks, leptons, collider detector, the atlas experiment, electroweak symmetry breaking, mass, design of the silicon strip detectors, pixel detectors

Research Description

I am an experimental particle physicist whose interests lie in probing the most basic interactions in nature. There now exists a theory of the Strong and Electroweak interactions ("the Standard Model") that has been tested to high accuracy and that explains almost all existing experimental data. The great success of this theory provides a framework for asking even more basic questions: What is the physics that generates quark and lepton masses? What determines the size of the Fermi constant? What is the mechanism responsible for the CP noninvariance observed in nature? It is such questions that my collaborators and I hope to address.

Many extensions to the Standard Model offer possible answers to these questions. In a large class of theories we expect new phenomena to appear when quarks or leptons collide at center-of-mass energies in the range of 100 GeV to 1 TeV. At the present time, hadron colliders are the only means of reaching these energies.

Current Projects

I am currently a collaborator on two collider experiments: the Collider Detector at Fermilab (CDF) and the Atlas experiment at CERN. Both of these experiments have substantial Lawrence Berkeley National Laboratory involvement.

CDF was built by a collaboration of physicists from the U.S., Japan and Italy. It has been operating at the Tevatron pbarp collider since 1987. The Tevatron produces collisions with a center-of-mass energy of 1.8 TeV, the highest energy currently available anywhere. Among the most important work done with CDF to date are the discovery of the top quark and the world's most precise measure ment of the W boson mass.

Both the CDF detector and the Fermilab Tevatron are scheduled to undergo major upgrades beginning in 1996. The goal of the accelerator upgrade is to increase the collision rate (luminosity) by a factor of 5-10. The experimental upgrades are designed to allow us to exploit these accelerator improvements. At Berkeley we are involved in the design and construction of a new silicon strip vertex detector for CDF. This detector will play a major role in the study of the top quark and in the search for CP non-invariance in the decay of B mesons. The upgraded CDF is expected to take data starting in Spring 1999. During the period from 1996 to 1999, we will be building the upgrades, but we will also be analyzing data taken with the existing CDF detector. The Berkeley /LBNL group's physics goals for the upgraded CDF are: 1) Study the properties of the top quark, including measurement of the top quark mass with a precision of ~ 4-5 GeV/c2. 2) Improve the current measurement of the W boson mass to a precision of ~ 0.05%. 3) Observe and characterize CP non-invariance in the decay of B mesons.

The Large Hadron Collider (LHC) is a pp collider with center -of-mass energy 14 TeV that is scheduled for completion in 2004. Although we are still years away from accelerator turn-on, design of the LHC experiments is underway.

The primary physics motivation for the LHC is to search for phenomena that give insight into electroweak symmetry breaking. It is this process that is believed to give mass to all elementary particles. Some possible physics signals at the LHC are: the existence of one or more fundamental scalar particles (Higgs bosons) or the presence of "supersymmetric" partners for the known elementary particles.

Berkeley/LBNL is working on the inner tracking detector for the Atlas experiment. We are currently involved in the design of the silicon strip detectors and of pixel detectors. Our work has been in the areas of high speed, radiation hard electronics and of mechanical design of modules. This project involves many serious technical channels.

In the News

Higgs fever: Overflow crowd hears about new particle

A July 13 lecture and panel discussion drew overflow crowds to hear about the newly discovered Higgs boson. Physicists Beate Heinemann and Lawrence Hall explained the theory and experiment behind this “third” kind of stuff, while three others explored the implications of the discovery.

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