35 research outputs found
The BNL Muon Anomalous Magnetic Moment Measurement
The E821 experiment at Brookhaven National Laboratory is designed to measure
the muon magnetic anomaly, a_mu, to an ultimate precision of 0.4 parts per
million (ppm). Because theory can predict a_mu to 0.6 ppm, and ongoing efforts
aim to reduce this uncertainty, the comparison represents an important and
sensitive test of new physics. At the time of this Workshop, the reported
experimental result from the 1999 running period achieved a_mu = 11 659
202(14)(6)x 10^-10 (1.3 ppm) and differed from the most precise theory
evaluation by 2.6 standard deviations. Considerable additional data has already
been obtained in 2000 and 2001 and the analysis of this data is proceeding
well. Intense theoretical activity has also taken place ranging from
suggestions of the new physics which could account for the deviation to careful
re-examination of the standard model contributions themselves. Recently, a
re-evaluation of the pion pole contribution to the hadronic light-by-light
process exposed a sign error in earlier studies used in the standard theory.
With this correction incorporated, experiment and theory disagree by a modest
1.6 standard deviations.Comment: To be published in the Proceedings of the Workshop on Electromagnetic
Probes of Fundamental Physics, Erice, 16 - 21 October 2001 (On behalf of the
Brookhaven E821 Collaboration) Uses 13 ps/eps figures. 14 pages tota
Next Generation Muon g-2 Experiments
I report on the progress of two new muon anomalous magnetic moment
experiments, which are in advanced design and construction phases. The goal of
Fermilab E989 is to reduce the experimental uncertainty of from
Brookhaven E821 by a factor of 4; that is, , a relative uncertainty of 140~ppb. The method follows the same
magic-momentum storage ring concept used at BNL, and pioneered previously at
CERN, but muon beam preparation, storage ring internal hardware, field
measuring equipment, and detector and electronics systems are all new or
upgraded significantly. In contrast, J-PARC E34 will employ a novel approach
based on injection of an ultra-cold, low-energy, muon beam injected into a
small, but highly uniform magnet. Only a small magnetic focusing field is
needed to maintain storage, which distinguishes it from CERN, BNL and Fermilab.
E34 aims to roughly match the previous BNL precision in their Phase~1
installation.Comment: 8 pages, 5 figures, 2 tables, Invited talk given at the FCCP 2015
Worksho
The Physics Case for the New Muon (g-2) Experiment
This White Paper briefly reviews the present status of the muon (g-2)
experiment and the physics motivation for a new effort. The present comparison
between experiment and theory indicates a tantalizing deviation.
An improvement in precision on this comparison by a factor of 2--with the
central value remaining unchanged--will exceed the ``discovery'' threshold,
with a sensitivity above . The 2.5-fold reduction improvement goal of
the new Brookhaven E969 experiment, along with continued steady reduction of
the standard model theory uncertainty, will achieve this more definitive test.
Already, the (g-2) result is arguably the most compelling indicator of
physics beyond the standard model and, at the very least, it represents a major
constraint for speculative new theories such as supersymmetry or extra
dimensions. In this report, we summarize the present experimental status and
provide an up-to-date accounting of the standard model theory, including the
expectations for improvement in the hadronic contributions, which dominate the
overall uncertainty. Our primary focus is on the physics case that motivates
improved experimental and theoretical efforts. Accordingly, we give examples of
specific new-physics implications in the context of direct searches at the LHC
as well as general arguments about the role of an improved (g-2) measurement. A
brief summary of the plans for an upgraded effort complete the report.Comment: 18 pages, 7 figure
Why do we need the new BNL muon g-2 experiment now?
New final results from the CMD-2 and SND e+e- annihilation experiments,
together with radiative return measurements from BaBar, lead to recent
improvements in the standard model prediction for the muon anomaly. The
uncertainty at 0.48 ppm--a largely data-driven result--is now slightly below
the experimental uncertainty of 0.54 ppm. The difference, a_mu(expt)- a_mu(SM)
= (27.6 +/- 8.4) x 10^-10, represents a 3.3 standard deviation effect. At this
level, it is one of the most compelling indicators of physics beyond the
standard model and, at the very least, a major constraint for speculative new
theories such as SUSY or extra dimensions. Others at this Workshop detailed
further planned standard model theory improvements to a_mu. Here I outline how
BNL E969 will achieve a factor of 2 or more reduction in the experimental
uncertainty. The new experiment is based on a proven technique and track
record. I argue that this work must be started now to have maximal impact on
the interpretation of the new physics anticipated to be unearthed at the LHC.Comment: Invited Talk, Tau-06 Workshop, 10 pages, 5 figure
Measurement of the muon anomaly to high and even higher precision
Our recent series of measurements at Brookhaven National Laboratory
determined the muon anomalous magnetic moment \amu to a precision of 0.5 ppm.
The final result--representing the average of five running periods using both
positive and negative muons--is \amu ^\pm = 11 659 208(6) \times 10^{-10}. It
lies 2.7 standard deviations above the standard model expectation, which is
based on updates given at this Workshop. Importantly, only the
annihilation and new KLOE radiative return data are used for the hadronic
vacuum polarization input. Because the systematic limit has not been reached in
the experiment, a new effort has been proposed and approved with the highest
scientific priority at Brookhaven. The goal is an experimental uncertainty of
0.2 ppm, a 2.5-fold reduction in the overall experimental uncertainty. To do so
will require a suite of upgrades and several qualitative changes in the
philosophy of how the measurement is carried out. I discuss the old and new
experiments with a particular emphasis on the technical matters that require
change for the future.Comment: 10 pages, Proceedings of the 8th International Workshop on Tau-Lepton
Physic
The Muon Anomalous Magnetic Moment and the Standard Model
The muon anomalous magnetic moment measurement, when compared with theory,
can be used to test many extensions to the standard model. The most recent
measurement made by the Brookhaven E821 Collaboration reduces the uncertainty
on the world average of a_mu to 0.7 ppm, comparable in precision to theory.
This paper describes the experiment and the current theoretical efforts to
establish a correct standard model reference value for the muon anomaly.Comment: Plenary Talk; PANIC'02 XVI Particles and Nuclear International
Conference, Osaka, Japan; Sept. 30 - Oct. 4, 2002; Report describes the
published 0.7 ppm result and updates the theory statu
Coherent anti-Stokes Raman scattering microscopy for quantitative characterization of mixing and flow in microfluidics
Functional Crosstalk between Type I and II Interferon through the Regulated Expression of STAT1
Small "priming" quantities of type I interferon enhance cellular responses to type II interferon by maintaining basal levels of STAT1, explaining the observed crosstalk between these two cytokines