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Re: Muon Anomalous Mag. moment

That's what he wrote in <Nature>. A number of people were quoted
as disagreeing in a subsequent issue. The following letter was not
accepted by Nature on the grounds that it was too late. Marciano and
I traded comments on my submitted letter. I have resubmitted the letter
to the British equivalent of Physics Today.
I am in the process of working with one of our post-docs on a
somehwat expanded discussion of the real significance of the g-2 result.
Here is the submitted letter (in Latex format):


Dear Editor:
I am submitting the following LaTeX document as a letter to the
Editor.
Sincerely,
Jack Uretsky
High Energy Physics Division, Argonne National Lab, Argonne, IL 60439
phone 630-252-6212 FAX 630-252-5047
\documentclass[11pt]{report}
\usepackage{graphics}
\hoffset -.68in
\voffset - 1.0in
\textwidth 6.5in
\textheight 8.in
\title{CONCEPTUAL CALCULUS}
\author{JACK L. URETSKY \\ High Energy Physics Division,
Argonne National Laboratories, email: jlu@hep.anl.gov}
\date{\today}
\begin{document}
\indent Katie Pennicott's lucid account in the March issue of {\em Physics
World of the beautiful preliminary results from the muon g-2 experiment
now in progress at Brookhaven\footnote{Brown, H. {\em et al.}
Phys.Rev.Lett.86:2227-2231,2001} unfortunately obscures the
significance of that experiment. While there is a possibility, as Vernon
Hughes and John Ellis suggest, that the experiment may eventually provide
evidence for ``new physics'' such as supersymmetry,
that evidence must, in my opinion, await better theoretical understanding
of the muon magnetic moment, as Yndur\'{a}in has already pointed
out\footnote{Yndur\'{a}in http//xxx.lanl.gov/abs/ hep-ph/0102312}.
The precision of the experimentalmeasurement, in other words, challenges
our ability to calculate the expected result of that measurement.

\indent The uncertainty of the Brookhaven g-2 measurement is now about 1.5
in units of $10^{10}\frac{g-2}{2}$ (1.3 parts per million), with 1 year of
data yet to be analyzed according to reference 2.. Weak and electromagnetic
contributions to g-2 can be calculated according to a well-understood theory
with about 1/30'th of the uncertainty of
the measurement, as is noted in the reference. The difference
between that calculation and the measurement is 71.8 with the uncertainty
of the experimental result. That difference
is ascribed to hadronic effects. Accordingly, the true significance
of the new result is that it measures the hadronic contribution to the
muon g-2 with a precision of the order of 1\%. That precision may
increase appreciably when the Brookhaven group completes its analysis.

\indent Yndur\'{a}n, in reference 2, invites our attention to 4 different
published estimates of the hadronic contribution ranging from 69.2 to 72.5,
each with a quoted uncertainty of the order of a percent.
The "theoretical prediction" used by the authors of
reference 1 uses only the lowest estimate, leading to an
apparent discrepancy between theory and experiment of about $2.6 \sigma$.
A different choice of estimate would have indicated that theory and
experiment were in agreement, within the quoted uncertainties.

\indent The Brookhaven experiment, when it is completed, threatens
to challenge our understanding of the hadronic contribution to g-2
at a level approaching 1 part in 1000. There is no theory of hadrons
that predicts cross sections with such precision. Such theory should
presumably grounded in quantum chromodynamics (QCD), which does
not yet lend itself to such predictions of that accuracy.

\indent There is a phenomenology that relates the hadronic contribution
to g-2 to other experiments and provides the basis for current estimates.
Whether this phenomenology is completely consistent with QCD is still an
open question. Deviation between QCD predictions and phenomenology would
provide one kind of evidence for new physics.
Deviation between an unambiguous prediction from phenomenology and the new
measurement of the hadronic contribution to g-2 would provide another
kind of evidence for new physics. It is clear that we have no such
unambiguous prediction at present.

\indent Given the present state of our understanding of hadronic physics,
a disagreement of the order of a few percent between experiment and
the present estimates of the hadronic contribution to g-2 is not
in my opinion a basis for claiming a disagreement
between standard physics and experiment. In the words of the author of
reference 2,
``To advertise evidence for SUSY or any other kind of
{\em nonstandard physics} on such a basis is, to put things in as
mild a way as possible, misleading''.

{\bf Acknowledgement} I am grateful to Cosmas Zachos for some stimulating
and helpful discussions.

Jack Uretsky
\end{document}
--
Franz Kafka's novels and novella's are so Kafkaesque that one has to
wonder at the enormity of coincidence required to have produced a writer
named Kafka to write them.
Greg Nagan from "The Metamorphosis" in
<The 5-MINUTE ILIAD and Other Classics>



On Wed, 3 Jan 2001, Bernard Cleyet wrote:

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This is old hat to you people?

bc



-------- Original Message --------
Subject: This Week's Colloquium
Date: Mon, 23 Apr 2001 08:52:07 -0700
From: Julie Reiner <reiner@cats.ucsc.edu>
To: colloq@physics.ucsc.edu

Speaker:William J. MarcianoBrookhaven National Laboratory Title:The Muon
Anomalous Magnetic Moment: A Harbinger For "New Physics" Abstract: The
anomalous magnetic moment, g-2, of the muon is being measured at
Brookhaven National Laboratory to better than 1 part per million. Recent
results indicate a deviation by 2.6 sigma from theoretical expectations.
If confirmed, the effect could be a harbinger of exciting new physics
such as supersymmetry which might dramatically alter our perception of
space-time. In this talk, the history, current status and future
expectations of anomalous magnetic moment experiments and theory are
described. Implications of a deviation for future high energy physics
experiments are also discussed. DATE:Thursday, April 26, 2001TIME:4:00
P.M.
PLACE:Thimann 1

Coffee and cookies will be served at 3:30 pm in the Kerr Lobby.

NOTE:Colloquia schedule / information is now available on the World
WideWeb: http://physics.ucsc.edu/events/colloquia.html

--Boundary_(ID_Fdwe/r5AysCk6Yx2cg7U6Q)
Content-type: text/html; charset=us-ascii

<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
This is old hat to you people?
<p>bc
<br>&nbsp;
<br>&nbsp;
<p>-------- Original Message --------
<table BORDER=0 CELLSPACING=0 CELLPADDING=0 >
<tr>
<th ALIGN=RIGHT VALIGN=BASELINE NOWRAP>Subject:&nbsp;</th>

<td>This Week's Colloquium</td>
</tr>

<tr>
<th ALIGN=RIGHT VALIGN=BASELINE NOWRAP>Date:&nbsp;</th>

<td>Mon, 23 Apr 2001 08:52:07 -0700</td>
</tr>

<tr>
<th ALIGN=RIGHT VALIGN=BASELINE NOWRAP>From:&nbsp;</th>

<td>Julie Reiner &lt;reiner@cats.ucsc.edu></td>
</tr>

<tr>
<th ALIGN=RIGHT VALIGN=BASELINE NOWRAP>To:&nbsp;</th>

<td>colloq@physics.ucsc.edu</td>
</tr>
</table>

<p><style type="text/css"><!--
blockquote, dl, ul, ol, li { margin-top: 0 ; margin-bottom: 0 }
--></style>
Speaker:<x-tab></x-tab>William
J. Marciano<x-tab></x-tab>Brookhaven National Laboratory&nbsp;Title:<x-tab></x-tab><b><font color="#000000">The
Muon Anomalous Magnetic Moment: A Harbinger For "New Physics"</font></b>&nbsp;Abstract:&nbsp;<font color="#000000">The
anomalous magnetic moment, g-2, of the muon is being measured at Brookhaven
National Laboratory to better than 1 part per million. Recent results indicate
a deviation by 2.6 sigma from theoretical expectations. If confirmed, the
effect could be a harbinger of exciting new physics such as supersymmetry
which might dramatically alter our perception of space-time. In this talk,
the history, current status and future expectations of anomalous magnetic
moment experiments and theory are described. Implications of a deviation
for future high energy physics experiments are also discussed.</font>&nbsp;<x-tab></x-tab>DATE:<x-tab></x-tab><x-tab></x-tab>Thursday,
April 26, 2001<x-tab></x-tab>TIME:<x-tab></x-tab><x-tab></x-tab>4:00 P.M.
<br><x-tab></x-tab>PLACE:<x-tab></x-tab><x-tab></x-tab>Thimann 1
<p><x-tab></x-tab>Coffee and cookies will be served at 3:30 pm in the Kerr
Lobby.
<p><x-tab></x-tab>NOTE:<x-tab></x-tab>Colloquia schedule / information
is now available on the World Wide<x-tab></x-tab><x-tab></x-tab>Web: <A HREF="http://physics.ucsc.edu/events/colloquia";>http://physics.ucsc.edu/events/colloquia</A><span
</span>.html&nbsp;</html>

--Boundary_(ID_Fdwe/r5AysCk6Yx2cg7U6Q)--


--
Franz Kafka's novels and novella's are so Kafkaesque that one has to
wonder at the enormity of coincidence required to have produced a writer
named Kafka to write them.
Greg Nagan from "The Metamorphosis" in
<The 5-MINUTE ILIAD and Other Classics>