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High Energy and Nuclear Seminar (Spring 06)The group has a weekly Friday seminar as well as Tuesday brown bag lunch meeting. The later generally involves a talk by students or other members of the group, and offers an informal settings for discussion of current issues. |
| Past Seminars: Fall 05 |
HET Group Graduate Students Discussion
Solitons and Quantization
Mohamed Anber
UMASS, Amherst
May 15th, 2006, 23:00pm
419B LGRC
Solitons are special solutions of non-linear equations. They play an important
role in many branches of physics.In this talk I will give a breif intoduction
to the subject as well as some examples. Then I will move to the problem of
quantization around classical orbits (solitons in our case) and I will describe
one method of doing that.
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Friday Seminar
Geometric Langlands Conjectures
Ivan Mirkovic
UMASS, Amherst, Mathematics Department
May 12th, 2006, 2:00pm
1033 LGRC
In 68 Langlands formulated conjectural extension and unification of several areas of mathematics such as number theory and representation theory. The work on these conjectures has been one of the principal efforts in mathematics. The geometric part of this program deals with bundles over Riemann surfaces, i.e., complex curves. It has recently been resolved by Witten and Kapustin (on the level of physics) as a reduction to dimension two of the four dimensional super Yang-Mills theory. Witten has since extended the main idea to complex surfaces using dimensional reduction of a 6d theory but this will not be in the talk.
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Friday Seminar
Supersolidity of Helium-4
Boris Svistunov
UMASS, Amherst
May 5th, 2006, 2:00pm
1033 LGRC
As it was discovered two years ago by Kim and Chan, and recently
confirmed by other experimental groups, solid Helium can support--
under certain conditions--a superflow of its own atoms. This
phenomenon, known as supersolidity, can be qualitatively described by
a two-component model in which ``normal" component is responsible for
the solid behavior, while another component is responsible for the
superflow. On the basis of
first principle simulations of up to 1000 He atoms, I will show that
a perfect He-4 crystal is not a supersolid. I will
discuss inhomogeneous (defect induced) scenarios of supersolidity
and, in particular, will present a numeric observation of a new
metastable state of matter: superfluid glass.
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Tuseday Baglunch
Parity-violating Electron Scattering and Strangeness in the Nucleon
Lisa Kaufman
UMASS, Amherst
May 2nd, 2006, 12:00pm
LGRC 419B
Parity violation in elastic electron scattering is sensitive to
possible strange quark contributions to the vector structure of the
nucleon, and this provides an opportunity to isolate effects of the
qq-bar sea. The HAPPEX collaboration in Hall A at Jefferson Lab has
measured the parity-violating asymmetry in the scattering of
longitudinally-polarized 3 GeV electrons from Hydrogen and Helium
cryogenic targets at a scattering angle of 6 degrees and low Q^2.
The asymmetry for Hydrogen is sensitive to a linear combination of
the strange quark contributions to the electric (G_E^s) and magnetic
(G_M^s) form factors of the proton while the Helium asymmetry is
senstive only to G_E^s. The combination of the two measurements
allows G_E^s and G_M^s to be separately determined. Preliminary
results from the complete data set will be presented.
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Friday Seminar
Ricci flow and black holes
Toby Wiseman
Harvard University
April 28th, 2006, 2:00pm
1033 LGRC
I will give an elementary introduction to Ricci flow, a first-order
flow equation on the space of Euclidean signature metrics. It arises
as the gradient flow of the Euclidean Einstein-Hilbert action, and
also results from the worldsheet renormalization group in string
theory. I will describe how black holes evolve under Ricci flow,
using the example of
gravity in a thermal box. I will then discuss the physical relevance
of the geometries resulting from the flow for understanding the off-
shell behaviour of quantum gravity.
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Tuseday Baglunch
A New Model for Inflationary Magnetic
Fields
Mohamed Anber
UMASS, Amherst
April 25th, 2006, 12:00pm
LGRC 419B
Magnetic fields are present throughout the whole universe and they play an
important role from cosmic rays to structure formation. However, the origin of
these fields remains a mystery until today. Inflation is an important
mechanism by which those fields might be generated.
We present a new mechanism for the
generation of the primeval magnetic fields in a model of inflation
called N-flation. Calculations show the possibility of producing strong fields
coherent over lengths ~ kpc. However, this model puts constraints on the
scale of the Hubble parameter during inflation.
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Friday Seminar
Black rings
Henriette Elvang
MIT
April 14th, 2006, 2:00pm
1634 LGRC
Black rings are donut shaped black holes in 4+1 dimensions. In this
talk I
will give an introduction to black holes in higher dimensions, in
particular with focus on black rings. New work regarding the
dynamics and
stability of black rings will be discussed.
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Tuseday Baglunch
Compton Scattering in the Intermediate Lab and at BIG Labs
Rory Miskimen
UMASS, Amherst
April 11th, 2006, 12:00pm
LGRC 419B
At the present time our Intermediate lab for physics majors
doesn't have a lab involving nuclear/particle physics or
radioactivity.
I'll briefly discuss an experiment under construction for the ILab to
study the quantum entanglement of gamma-ray pairs.
Moving up the size scale from table-top to an experiment that would
fill a
gymnasium, I'll present results for the first measurement of the mean
square polarizability radii of the proton. If time allows, plans
for the
development of a polarized scintillating proton target for Compton
scattering
experiments, and what we learn in these experiments, will be
discussed.
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Departmental Colloquium
Neutrino Astronomy with IceCube
Jordan Goodman
University of Maryland
April 7th, 2006 Friday 4:00 p.m
Hasbrouck 124
IceCube is a one-cubic-kilometer international high-energy neutrino observatory being built and installed in the clear deep ice below the South Pole Station. IceCube will, when completed in 2011, consist of 80 “strings” each with 60 optical modules which will detect light from neutrino interactions. As of spring 2006 nine strings are deployed and operating. IceCube will open unexplored bands for astronomy, including the PeV (1015 eV) energy region, where the Universe is opaque to high energy gamma rays originating from beyond the edge of our own galaxy, and where cosmic rays do not carry directional information because of their deflection by magnetic fields. This talk will explore the various questions which a km3 neutrino detector can address, such as: the origin of ultra high energy cosmic rays, gamma ray bursts and dark matter. In addition to details about IceCube, the status and plans for other neutrino telescopes will be discussed.
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Seminar
Presentation about TheThree-Year WMAP Data Release
Lorenzo Sorbo
UMASS, Amherst
April 5th, 2006, 2:00pm
LGRC 1033
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Tuseday Baglunch
Energy-Momentum Divergences and the Renormalization of Gravity
Hael Collins
UMASS, Amherst
April 4th, 2006, 12:00pm
LGRC 419B
A quantum field propagating in a general classical space-time
produces divergences that require the renormalization of the
parameters of the gravitational action. This talk describes this
renormalization, first using the cosmological constant as a familiar
example before treating an isotropically expanding universe. To keep
the presentation more accessible, I shall concentrate on the case of
the scalar field in its nominal vacuum state, but I shall also
outline the approach, and its challenges, for a more general
effective state.
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Friday Seminar
Top Quark Production at Hadron Colliders
Joao Guimaraes da Costa
Harvard
March 31st, 2006 Friday 2:00 p.m
LGRC 1033
The top quark has been discovered ten years ago at the Tevatron Collider at Fermilab. The small data samples collected until recently did not permit precise measurements ofthe top quark properties. However, a new era of high-statistics top quark physics is just starting and full reconstruction of top decays will be pivotal. In this talk, I will describe how top quarks are produced and identified at hadron colliders. I will focus on the latest measurements of the top quark pair-production cross section and the top mass at the CDF experiment, which benefited from recent improvements in b-quark identification. These measurements have reached a new level of precision and provide a window into the physics at the Large Hadron Collider
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Tuseday Baglunch
Effective Field Theory for Hadronic Molecules
Frabrizio Gabbiani
Wayne State University
March 28th, 2006, 12:00pm
LGRC 419B
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Friday Seminar
Single Top Quark Physics
Reinhard Schwienhorst
Michigan State
March 17th, 2006 Friday 2:00 p.m
LGRC 1033
Even though it has been over ten years since the top
quark discovery, still only very little is known experimentally
about this elusive particle. We are currently investigating the top
quark and its interactions at the Fermilab Tevatron proton-
antiproton collider. Of particular interest is the electroweak
interaction of the top quark because of its link to electroweak
symmetry breaking. At the Tevatron, this interaction produces a
unique final state signature of only a single top quark. I will
present the status of searches for electroweak production of single
top quarks.
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Seminar
Electric Dipole Moments and the Origin of Baryonic Matter
Michael Ramsey-Musolf
CalTech
Wednesday, March 15th, 2006 ,2:00pm
LGRC 1033
The origin of the baryon asymmetry of the universe (BAU) remains an
important, open problem at the interface of nuclear physics,
cosmology, and
particle physics. A successful explanation of the BAU requires the
presence
of new CP-violating interactions beyond those contained in the
Standard
Model, and a new generation of searches for the permanent electric dipole
moments of the neutron, electron, and neutral atoms will probe for
the
evidence for new CP-violation. In this talk, I discuss the
prospective
implications of these measurements for the BAU and present new
developments
in a systematic, theoretical formulation of the BAU using non-
equilibrium
quantum field theory methods.
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Seminar
Studying Earthly Neutrinos
Neutrinos
Michal Decowski
UC Berkeley
Monday, March 13th, 2006, 1:20 pm
LGRC 1033
Since the 1950's, physicists have used nuclear reactors to study the
properties of antineutrinos. In 1956, one of the first such
experiments, Project Poltergeist, proved the existence of
antineutrinos. The initial experiments were only a few meters away
from the reactor core, the source of electron antineutrinos. Over the
years the experiments steadily increased their baselines, with the
goal to test and ultimately establish neutrino disappearance. That
goal was reached in 2002, when the KamLAND Collaboration, using a one
kton liquid scintillator detector, reported the first observation of
electron antineutrino disappearance from 53 Japanese reactors at an
effective baseline of ~180 km. KamLAND has since observed distortions
in the antineutrino energy spectrum, a telltale sign of neutrino
oscillation. The experiment has also measured a key neutrino
oscillation parameter, the solar mass-splitting, to unprecedented
levels. Reactors, however, are not the only source of antineutrinos
on Earth. Radioactive decays in the Earth also produce antineutrinos
and the heat released in that process may be the driving force for
mantle convection, which is responsible for terrestrial phenomena
such as earthquakes and plate tectonics. KamLAND can detect
geologically produced electron antineutrinos from the U238 and Th237
decay chains. Earth composition models predict that these are
responsible for the majority of the radiogenic heat; detection of
geoneutrinos from these two decays will allow the models to be
directly tested for the first time. I will discuss how KamLAND's
measurements have further solidified the case for neutrino
oscillation and the exciting recent detection of geoneutrinos.
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Friday Seminar
LIGO Perks Up Its Ears
Peter Shawhan
CalTech
March 10th, 2006, 2:00pm
LGRC 1033
The Laser Interferometer Gravitational-wave Observatory is the
largest component in a worldwide effort to detect gravitational waves
reaching the Earth. Potential sources of detectable gravitational
waves include binary systems of neutron stars or black holes; core
collapse supernovae; cosmic strings; rapidly spinning neutron stars;
and a cosmic gravitational wave background. After several years of
commissioning, the LIGO detectors have essentially reached their
sensitivity goals and are beginning long-term observing. Many
searches for gravitational waves have already been carried out using
data from a series of short "science runs", and several more searches
are underway.
To view the transparencies of this talk, click at these link: pdf
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Departmental Colloquium
The Landscape of Particle Astrophysics
Rene Ong
UCLA
March 8th, 2006 Wednesday 4:00 p.m
Hasbrouck 124
During the last decade, there has been rapidly growing interest in the field of particle astrophysics. This interest has followed from numerous exciting discoveries in this broad area between physics and astronomy. But what exactly is particle astrophysics and what are some of its primary scientific goals? This talk will attempt to answer these questions – first by considering the key scientific questions of interest and then by outlining the experimental programs being developed to address them. Special consideration will be given to very high energy (VHE) particle astrophysics – the study of the universe using gamma rays, cosmic rays, and neutrinos at TeV energies and beyond.
To view the transparencies of this talk, click at these link: pdf
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Friday Seminar
Probing the Origin of Neutrino Mass with Double Beta Decay
Carter Hall
SLAC
March 3rd, 2006 Friday 2:00 p.m
LGRC 1033
Neutrino oscillation experiments have provided overwhelming evidence in the last ten years that neutrinos have a small but non-zero mass. On the other hand, experiments which can measure the absolute mass of the neutrino have so far only been able to set upper limits. These limits already tell us that the mass of the neutrino is many orders of magnitude smaller than the charged leptons and quarks, which could be an indication that the origin of neutrino mass is fundamentally different from the other standard model fermions. Neutrinos are also unique in that they are the only known fermions which are electrically neutral, and in fact may be their own anti-particles. The particle/anti-particle nature of the neutrino is closely related to the question of neutrino mass, and may shed some light on physics at very high energy which is otherwise inaccessible to experimentalists. Neutrinoless double beta decay is the only practical tool we have for addressing the particle/anti-particle nature of the neutrino, and it may also tell us about the absolute scale of the neutrino mass spectrum. In this talk I will review the current status of experimental searches for neutrinoless double beta decay, with emphasis on the Enriched Xenon Observatory (EXO), a proposal to search for double beta decay in Xenon-136.
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Tuseday Baglunch
About pseudo-Goldstone boson quintessence
Lorenzo Sorbo
Umass, Amherst
February 28th, 2006, 12:00pm
LGRC 419B
In models of quintessence, cosmic acceleration is due to
some slowly evolving scalar condensate. A large variety of
quintessence potentials has been proposed, with different
motivations. A potential associated to a pseudo-Goldstone boson is
among the most natural ones from the point of view of quantum field
theory. I will discuss the motivations and the implications of such
a potential. In particular, I will focus on the fact that a decay
constant of the order of the Planck scale or larger is needed for
the phenomenology of this model. However, such a large decay
constant seems to be unnatural (if not totally forbidden) in string
theory. I will show how, if there are actually many pseudo-
Goldstone bosons, the bound originating from string theory can be
evaded, potentially leading to a richer phenomenology
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Friday Seminar
LIGO's Eyes-Wide-Open Search for Gravitational Waves
Laura Cadonati
Massachusetts Institute of Technology
February 24th, 2006, 2:00pm
LGRC 1033
The Laser Interferometer Gravitational-wave Observatory (LIGO) aims to make the first direct observation of gravitational waves, the tiny distorsions of space-time that originate from the universe's most violent events, according to the predictions of General Relativity. Such detection will provide a fundamental new tool for the understanding of our universe. To achieve its goal, LIGO uses three interferometers of km-scale length, two in Hanford, WA, and one in Livingston, LA, measuring differences in length of one part in 1021 , or 10^-18 m, one thousand times smaller than the nuclear diameter. The detectors have now reached their design sensitivity and the LIGO Scientific Collaboration is actively searching for gravitational wave signatures in the interferometers’ data. In this talk I will present one of these ongoing efforts, the "eyes-wide- open" search for unmodeled bursts of gravitational waves. I will describe its challenges and the methods used to optimize the detection efficiency and to suppress the false alarm rate with minimal assumptions on the signal's morphology. I will present the most recent upper limit results and discuss possible future directions for the LIGO burst analysis.
To view the transparencies of this talk, click at these link: pdf
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Friday Seminar
Using Reactor Neutrinos to Study Neutrino Oscillations
Jon Link
Columbia University
Feb 17th, 2006 Friday 2:00 p.m
LGRC 1033
The physics of neutrino oscillations will be discussed in the context of
the last unmeasured mixing angle, theta_13. There are two main
approaches to measuring theta_13: nu_e appearance in an accelerator
induced nu_mu beam, and nu_e disappearance in a reactor induced electron
antineutrino beam. The primary focus of the talk will be on the reactor
approach. The need for precision $(down to $sin2 2\theta_{13} < 0.01)$, the
challenges to achieving that precision, and the solutions proposed to
meet those challenges will be discussed. Finally, the synergies in
combining the results from the appearance and disappearance measurements
will be shown.
To view the transparencies of this talk, click at these link: pdf
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Tuesday Baglunch
Status of ATLAS: Toward Physics at the TeV Scale
Stephane Willocq
Umass, Amherst
Feb 14th, 2006 Tuesday 2:00 p.m
LGRC 419B
To view the transparencies of this talk, click at these link: pdf
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Tuesday Baglunch
How Large is the "Natural" g-facor
B. Holstein
Umass, Amherst
February 7th, 2006 Tuesday 12:00 Noon
LGRT 419B
Every student learns in his/her first quantum mechanics course that the
gyromagnetic ratio (g-factor) of an ideal Dirac particle is 2 and this is
strongly confirmed experimentally by measurements on charged e,mu,tau systems.
We wish to ask the question whether there is a "natural" g-factor for a particle
of higher spin. One answer was given by Belinfante over fifty years
ago---$g(S)=1/S$---and is called the Belinfante conjecture. We shall show that
in light of modern arguments this conjecture is incorrect and should be replaced
by the simple result $g(S)=2$.
To view the transparencies of this talk, click at these link: pdf
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