Thursday, September 9
2:30 Theoretical Physics Seminar
- Curia II
Speaker: J. Laiho, Fermilab
Title: Improving the Lattice Calculations of e'/e
3:30 DIRECTOR'S COFFEE BREAK - 2nd Flr X-Over
4:00 Accelerator Physics and Technology Seminar - 1 West
Speaker: L. Jin, University of Kansas
Title: Coherent Beam-Beam Effects in Storage-Ring Colliders
Friday, September 10
3:30 p.m. Wine & Cheese - 2nd Flr X-Over
4:00 p.m. Joint Experimental Theoretical Physics Seminar - 1 West
Speaker: A. Khanov, University of Rochester
Title: Top Cross Section Measurement in the Lepton + Jets
Channel with B-Tagging at DZero
Thursday, September 9|
Aztec Tortilla soup
Hot Italian Sub $4.75
Chicken Picata $3.75
Thai Beef $3.75
Roast Beef Cheddar on Kaiser Roll $4.75
Beef Strombolis $2.85
Marinated or Cajun Chicken Caesar Salads $4.75
Wilson Hall Cafe Menu
Why We Care About the Top Quark: CDF Explains |
The CDF Detector|
Fermilab's CDF and DZero experiments announced the discovery of the top quark March 2, 1995, confirming earlier evidence found in 1994 by CDF. So why, ten years later, are scientists at the world's highest energy particle accelerator laboratory still spending their days and nights studying the top?
"The top is unique--it has a big mass, which makes it very different from the other five quarks," explained Fermilab theorist Tim Tait. "If we can measure its properties precisely, we're likely to gain insight into completely new physics."
Like the electron, the top quark is one of the fundamental particles of nature. Unlike the electron and other quarks, it is extremely heavy, with a mass almost 200 times that of the proton. The top's large mass gives it a special role in electroweak symmetry breaking, the phenomenon that physicists believe gives mass to all the particles in the universe and whose nature has yet to be revealed. The Standard Model, the conventional theory of particle physics, puts the still-unobserved neutrally charged Higgs boson at the heart of electroweak symmetry breaking. Precise measurements of the top quark's properties will advance physicists' knowledge of electroweak symmetry breaking and the properties of the Higgs.
FYI: AIP Bulletin of Science Policy News, September 8, 2004:|
Status of FY 2005 Appropriations Bills
The new fiscal year starts in a little over three weeks, and twelve of the
thirteen appropriations bills are far from complete. As Congress returns
to work this week, it faces a daunting work load beset by real time constraints
in a highly partisan environment. This FYI reviews the status of the appropriations
bills of greatest interest to the physics community. A subsequent FYI will look
at some of the constraints to the completion of these bills.
ENERGY AND WATER DEVELOPMENT APPROPRIATIONS BILL:
The House passed its version of this FY 2005 funding bill on June 25. The Senate bill has not cleared the subcommittee.
H.R. 4614 would increase the high energy physics budget by 2.7%; the nuclear physics budget by +6.5%, the basic energy sciences budget by +8.8%, the fusion energy sciences budget by +5.1%, and the advanced scientific computing research budget by +15.7%. The only budget that would be cut is that for Biological and Environmental Research, by a proposed -10.9%. All figures are as compared to the current year's budget.
The House bill provides no funding for the Robust Nuclear Earth Penetrator, Advanced Concepts Research, Enhanced Test Readiness, and the Modern Pit Facility.
The Spin is In! CDF II Looks at Top Decay|
Run I measurement of W polarization in the single b-tagged sample using
matched b-quarks with the lepton from W decay. Points represent the
data, while the shaded area denotes the signal-plus-background
expectation. Inset shows the negative log likelihood as a function
of the forbidden spin +1 fraction. The best fit to these data is
where this curve is a minimum. (Click on image for larger version.)|
The discovery of the top quark by CDF and DZero in 1995 was
accompanied by the observation that the top quark mass is very
large, nearly that of a gold nucleus. Run II offers the first
chance to precisely measure properties of the top quark which
might reveal hints to explain this puzzling mass.
CDF has tested the polarization of the W boson produced in the
decay of a top quark. The polarization refers to the direction
of the W-boson's intrinsic angular momentum ("spin") with respect
to its direction of motion. Quantum mechanics says that this
spin must point in one of three directions with respect to the
W-boson's motion, referred to as right-handed, left-handed and
longitudinal. Each time a top decays, experimentalists can
measure how often each polarization state occurs. The fraction
of a particular polarization is determined by the interactions
in top decay. The left-handed part is a familiar piece of the weak
interaction, which has no right handed term. The longitudinal part
comes from the symmetry breaking mechanism that gives the particles
their masses, and is huge for the top quark. All told, we should see
30% left-handed W bosons, 70% longitudinal W bosons, and no
right-handed W bosons. If top has different interactions, however,
or the masses are due to another effect, all bets are off!
Run II measurements of W polarization. At left, a measurement of the
longitudinal fraction in the dilepton sample using lepton momentum. Points
represent the data, the best fit to these data is denoted by the black
line. At right, a measurement of the longitudinal fraction in the
lepton-plus-jets sample using the decay angle of the W boson. Points
represent the data, the best fit to these data is denoted by the red
line. (Click on image for larger version.)|
A recent analysis on Run I CDF data by a team from Rochester and
Ohio State using matched b-quarks with the lepton from W decay as
a "polarimeter" measured the fraction of the forbidden right-handed
state to be < 0.18 at 95% CL. CDF also has two new measurements
using Run II data: One team at the University of Michigan used
lepton momentum and measured the longitudinal fraction to be < 0.59
at 95% CL in the dilepton sample, and
0.88 +0.12 -0.47 (stat.+ syst.)
in the lepton-plus-jets sample. A second team at the University of
Illinois at Urbana-Champaign used the decay angle of the W boson and
found the longitudinal fraction to be
0.89 +0.11 -0.38 (stat. + syst.) in the lepton-plus-jets sample.
So far, these results are consistent with top being just another quark,
but expected deviations which might lead to an explaination of the top's
weight problem might be subtle and therefore require a more precise
measurement. As Run II continues to accumulate data, this polarization
test will lead to closer scrutiny of the nature of top.
W polarization analysis group, from left to right: Nathan
Goldschmidt (U. of Michigan), Ben Kilminster (Ohio State U.), and
Trevor Vickey (U. of Illinois at Urbana-Champaign). Not pictured:
Ken Bloom, Stephen Miller, David Gerdes and Dan Amidei (U. of
Michigan), Kevin McFarland (U. of Rochester), Tony Liss (U. of
Illinois at Urbana-Champaign). (Click on image for larger version.)|
Result of the Week Archive
Fermilab Health Fair Today|
Fermilab's Semi-Annual Health Fair is today from 11:00 a.m. to 2:00 p.m.
in the Atrium of Wilson Hall.
Yoga Presentation Today
As part of the Fermilab Health Fair, Christopher Baxter of Universal Sprit Yoga
will demonstrate yoga techniques in the Atrium of Wilson Hall today at
Budker Seminar Tonight
There will be a Budker Seminar Held on Thursday, September 9 in the
Users' Center Music Room.
Talk Title: "Strand and Cable Studies for High Field Magnets"
Speaker: Bernardo Bordini
Location: Users' Center Music Room
Pizza, beer and soft drinks will be served at 6:00 p.m.
UEC Career Night Tonight
The Fermilab UEC will be hosting a
Career Night on Thursday, September 9
from 7:00 p.m. to 9:00 p.m. in One West.
The talks are aimed at graduate students
and young physicists, but everybody is
welcome. Wine and cheese will be served
from 6:00 p.m. to 7:00 p.m. For more
information, contact a member of the
Organizing Committee: Ken Bloom,
Sharon Hagopian, Lydia Lobo, or Paul