The U.S. ATLAS Operations Program aims to provide U.S. university scientists with access to the unique LHC science opportunities through a balanced program that encompasses: (1) the technical effort associated with maintenance and operation of the U.S.-built detector subsystems, essential in achieving a detailed understanding of the detector for physics results; (2) the maintenance and refinement of software, computing and physics analysis support, critical in allowing scientists at U.S. universities to fully exploit the physics potential of the LHC, in part through the establishment of university-based Tier 2 computing centers in the U.S. and the expansion of the existing worldwide grid of resources; (3) an R&D program for detector upgrades, to maximize the physics output during the long period of running expected for the LHC and maintain U.S. intellectual leadership in accelerator-based particle physics; and (4) a strong education and outreach program. The ATLAS collaboration, consisting of 151 institutes from 34 countries, is completing construction of the ATLAS detector at the Large Hadron Collider (LHC) at CERN, and preparing for initial data taking in 2007. The 34 institutions of U.S. ATLAS, with the support of NSF, have made major and unique contributions to the construction of the ATLAS detector, and continue to provide critical support for the ATLAS computing and software program, and pre-operations tasks as the detector is commissioned at CERN.
Intellectual Merit: The goal of the U.S. ATLAS Operations Program is to empower U.S. physicists to address some of the most profound questions in particle physics today: what is the physical origin of mass? Do supersymmetric particles exist and will they shed light on the nature of dark matter? Does space-time have extra spatial dimensions? Answers to these questions would provide a major advance toward completing a unified view of the particles in nature, the forces with which particles interact, and their role in the past and future of our universe. This is a time when particle physics researchers have unusually compelling indications that the step to be taken by the LHC, leading to collision energies far beyond those available at existing facilities, will lead to especially important discoveries with implications over a broad field of fundamental science. This program rests on the especially strong scientific case for investigating the energy regime that will be accessed by the LHC, and benefits from a program in which the international community is providing a major part of the investment. The bold initiative of the NSF, in partnership with the DOE, to carry out a very significant portion of the construction and operations of the ATLAS detector has opened up this opportunity for U.S. scientists.
Broader Impacts: This proposal will enhance the computing infrastructure for research, education and beyond. The LHC computing requirements are driving a paradigm shift towards global computing with potentially significant economic impacts, and our students will be at the forefront in using these new technologies. NSF-ATLAS groups continue to expand their education and outreach programs, with a particular focus on high school teachers and students (closely coordinated with QuarkNet), and on outreach to under-represented populations. We plan on strengthening and expanding our outreach efforts in the run-up to ATLAS data taking, including plans to help establish a computing center in Africa as part of our expanding network of worldwide grid facilities. This site will provide a platform on which to launch a program of Grid-based outreach in Africa. Starting in a few years the LHC will be the major accelerator-based program in which to train the next generation of physicists. Support for R&D activities will lay the groundwork for new technologies that might be adopted by other fields.
The intellectual merit and broader impacts of the US ATLAS program supported by this grant are great. This grant provided partial support for the technical manpower for maintenance and operations, computing and research and development for future upgrades of the ATLAS detector at the Large Hadron Collider (LHC) at the CERN particle physics laboratory in Geneva, Switzerland. The LHC is the world's highest energy particle accelerator, colliding protons against protons at center of mass energies of 7 trillion electron volts (or 7,000 times the mass of a single proton). The ATLAS detector is one of the world's largest and most complex detectors - it serves as a precision "microscope" to study the collisions of protons which have such a high energy that they recreate (in miniature) the conditions that existed shortly after the big bang. It takes a vast army of physicists to design, build and operate the ATLAS detector (over 500 in the US alone, and about 2,500 worldwide). This grant alone supported physicists from about 19 different universities across the United States in this research. By precisely studying the debris from these collisions using a variety of specialized subdetectors in ATLAS, we hope to make fundamental and paradigm changing observations about our universe. The questions we will ask (and hopefully answer) range from the origin of mass (or does the HIggs particle exist?), to discovering new fundamental particles that might be the stuff that dark matter is made of, to perhaps observing additional space dimensions beyond the three we are familiar with. These are just some of the highlights of the great many questions we are answering with ATLAS. Any of these would be astonishing discoveries. This grant support the activities during the operating phase of the ATLAS detector (which took almost two decades to design and build). Since the phenomena we are studying are exceedingly rare, we require very large numbers of collisions gathered over long running periods in order to discover these new phenomena. During the period of this grant we saw the number of collisions multiply a millionfold, nearly achieving the ultimate design number, and allowing us to begin the exploration of a new energy regime. We have to date published over 100 scientific papers on the measurements, searches and discoveries we have carried out. The Higgs particle remains elusive, but the range of mass that it can have, if it exists, has been narrowed dramatically through our studies, and we will have definitive answers on its existance in the next year or so. The search for other more exotic particles has shown that they must have exceedingly high masses, if they exist at all. Recently we discovered the first new particle at the LHC, called a chi particle (an analog of an excited state of the hydrogen atom that played an important role in the development of quantum mechanics about a century ago). The broader impacts of this research, beyond the exciting physics questions being addressed, include the development of vast computing grids with tems of thousands of linked cpu's and huge data volumes on disk that are used to store and analyze the complex collisions observed in our detector, and the training of scientists that eventually go on to use their skills in many other fields of human endeavour. The search for the Higgs and the sheer size and complexity of our detector has fired the imagination of the public and inspired a new generation of students to consider science as a career path. The adventure has only just begun, and we look forward to many new discoveries the decade to come.
