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Feb
1
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Navid Vafaei-Najafabadi
Stony Brook University
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Recruiting the 4th state of matter to miniaturize particle accelerators
Particle accelerators have been an invaluable tool for scientific discovery and research.
Future discoveries in high energy physics will require significantly more energetic
particles than those currently produced. However, simply scaling the current machines
to higher energies is a significant challenge because of their cost as well as the
required space. A fundamental limitation that dictates the size of these machines
is that the peak electric field used for accelerating particles must be below the
damage threshold of the accelerating structures. Using a plasma, an ensemble of ionized
atoms also known as the fourth state of matter, this limitation can be circumvented.
In particular, high amplitude waves can be generated in a plasma using a high-power
laser or a particle beam. The resulting structures have been shown to sustain accelerating
fields that are hundreds of times higher than those currently generated in particle
accelerators. In this talk, I will discuss how plasma waves are particularly well
suited for accelerating electrons, the status of the state-of-art research, as well
as the challenges that need to be overcome for plasma-based accelerators to form the
foundation of next generation of high-energy particle beams.
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Feb
8
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Wendy Freedman
University of Chicago
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This colloquium will be fully virtual.
Increasing Accuracy in Measurements of the Hubble Constant: Is There Evidence for
New Physics?
An important and unresolved question in cosmology today is whether there is new physics
that is missing from our current standard Lambda Cold Dark Matter (LCDM) model. Recent
measurements of the Hubble constant, Ho -- based on Cepheids and Type Ia supernovae
(SNe) -- are discrepant at the 4-5-sigma level with values of Ho inferred from measurements
of fluctuations in the cosmic microwave background (CMB). The latter assumes LCDM,
and the former assumes that systematics have been fully accounted for. If real, the
current discrepancy could be signaling a new physical property of the universe. I
will present new results based on an independent calibration of SNe Ho based on measurements
of the Tip of the Red Giant Branch (TRGB). The TRGB marks the luminosity at which
the core helium flash in low-mass stars occurs, and provides an excellent standard
candle. Moreover, the TRGB method is less susceptible to extinction by dust, to metallicity
effects, and to crowding/blending effects than Cepheid variable stars. I will address
the current uncertainties in both the TRGB and Cepheid distance scales, the promise
of upcoming James Webb Space Telescope data, as well as discuss the current tension
in Ho and whether there is need for additional physics beyond the standard LCDM model.
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Feb 15
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Jin Koda
Stony Brook University
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Increasing Accuracy in Measurements of the Hubble Constant: Is There Evidence for
New Physics?
Molecular gas and molecular clouds host virtually all star formation in the local
Universe, and therefore their formation and evolution are the first step leading to
star formation and galaxy evolution. In this talk, I will argue for long life and
evolutional timescales of molecular gas and clouds (~>100Myr), as opposed to the recently-(again)-suggested
short timescales (10-30Myr), by looking at their evolution through galactic rotation,
i.e., how they form and evolve through spiral arms and inter-arm regions, in the Milky
Way and in nearby galaxies. Although the popular spiral density-wave theory predicts
a rapid phase transition from atomic to molecular and then to atomic phases through
spiral arm passages, the observed fraction of molecular gas over atomic gas remains
high even in the inter-arm regions in MW-like spiral galaxies. Hence, the molecular
gas and clouds are not destroyed much toward the inter-arm regions. Recent ALMA data
show diverse molecular structures in the inter-arm regions of nearby galaxies, many
of which contain large masses. Their formation requires very long timescales (~100Myr)
just to assemble the masses. If they are destroyed quickly in the short timescales,
their formation would not catch up with the destruction; the galaxies should have
much more atomic gas than the observed. The long life and evolutional timescale of
molecular gas impacts the picture of star formation - the star formation has to be
triggered in the long-existing molecular structures, rather than starting at an onset
of gravitational collapse from diffuse atomic gas to dense molecular clouds.
Until August 14, 2022, a recording of this colloquium may be accessed here, using the following passcode:
91.?S1YD
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Feb 22
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Murray Holland
University of Colorado Boulder
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Extreme sensing, clocks, and squeezing atoms and molecules with light
I will describe recent ideas for lowering the temperature of ensembles of ultracold
atoms and molecules into the extreme quantum regime, for using interactions to entangle
atoms and molecules into non-classical quantum states, and for using these non-classical
states to realize quantum advantages for metrology, clocks, and matter-wave interferometry.
One such topic is a new experimentally demonstrated idea for laser cooling by Sawtooth
Wave Adiabatic Passage (SWAP). This is mostly relevant to atoms and molecules that
possess narrow linewidth transitions, such as the ultranarrow clock transitions, and
promises to be an important extension to the toolbox of AMO physics for laser cooling
and trapping. We are exploring ways to use optical cavities and cavity-mediated interactions
to entangle atoms so that we may improve optical clock performance, make repeated
quantum measurements beyond the standard quantum limit, and continuously track squeezed
quantum phases. These approaches take full advantage of the powerful combination of
the extreme optical coherence that is possible using atomic clocks, with the rich
possibilities offered by many-body physics that arises when the atoms interact strongly.
Atomic clocks have already progressed to the point that understanding how to take
advantage of quantum effects will be crucial in order to progress to the next generation
of devices.
Until August 21, 2022, a recording of this colloquium may be accessed here, using the following passcode:
=3V&hEVn
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Mar 1
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No colloquium.
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Mar 8
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Laura Cadonati
Georgia Institute of Technology
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Exploring the cosmic graveyard with gravitational waves
A new era in astrophysics has begun with the 2015 discovery of gravitational waves
from the collision of two black holes in data from the Laser Interferometer Gravitational-wave
Observatory (LIGO). The additional 2017 LIGO-Virgo detection of gravitational waves
from the collision of two neutron stars in coincidence with a gamma ray burst and
a kilonova, elevated multi-messenger astrophysics from concept to tool for discovery
and exploration. Many more gravitational wave signals have been observed since then
from collisions of compact binary coalescence, and gravitational waves are a new,
important probe for understanding the universe, with a rich science potential ranging
from astronomy to cosmology to nuclear physics. This talk will present a selection
of the latest results from LIGO and Virgo, with their GWTC-3 gravitational wave transient
catalog, and an outlook for the next decade.
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Mar 22
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Alexandra Gade
Michigan State University
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This colloquium will be fully virtual.
The science of FRIB: From the nuclear many-body challenge to the origin of the elements
in the Universe
There are approximately 300 stable and 3,000 known unstable (rare) isotopes. Estimates
are that over 7,000 different isotopes are bound by the nuclear force. It is now recognized
that the properties of many yet undiscovered rare isotopes hold the key to understanding
how to develop a comprehensive and predictive model of atomic nuclei, to accurately
model a variety of astrophysical environments, and to understand the origin and history
of elements in the Universe. Some of these isotopes also offer the possibility to
study nature's underlying fundamental symmetries and to explore new societal applications
of rare isotopes. This presentation will give a glimpse of the opportunities that
arise once the Facility for Rare Isotope Beams (FRIB) comes online at Michigan State
University in a few weeks.
Until September 18, 2022, a recording of this colloquium may be accessed here, using the following passcode:
&n5*qKQK
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Mar 29
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Dmitry Tsybychev
Stony Brook University
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Experimental studies of the electroweak symmetry breaking at CERN Large Hadron Collider
Understanding of electroweak symmetry breaking mechanism is one of the highest priority
problems facing the field of high-energy physics and most importantly whether such
breaking occurs solely through the weak interactions. The divergence of electroweak
interactions in the Standard Model of particle physics, in particular, scattering
of longitudinally polarized of heavy gauge bosons, at the TeV scale is solved by introduction
of a Higgs boson. We will present studies of the electroweak symmetry breaking at
ATLAS experiment at the Large Hadron Collider (LHC), operating at center-of-mass energies
of 7-14 TeV, the highest collision energy in the world.
Until September 25, 2022, a recording of this colloquium may be accessed here, using the following passcode:
d?n9qHse
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Apr 5
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Heather Gray
Berkeley
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Computing Challenges for Future Colliders — could quantum computing play a role?
High-energy physics is facing a daunting computing challenge with the large and complex
datasets expected from the HL-LHC in the next decade and future colliders to follow
the LHC. The landscape of computing has been evolving rapidly and field of quantum
computing in particular has been making dramatic progress in recent years. I will
outline the challenges facing high-energy physics, provide a brief introduction to
quantum computing focusing on recent progress and discuss recent work that may lead
to solutions for high-energy physics.
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Apr 12
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Dave Kawalll
University of Massachusetts
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An Anomaly in an Anomaly? First Results from the Fermilab Muon g-2 Experiment
The Fermilab muon g-2 experiment recently released its first measurement of the magnetic
behavior of the muon. Muons are like electrons, but heavier and short-lived. Their
magnetic properties can be predicted with impressive, sub-ppm precision through the
techniques of quantum field theory. An interesting feature is that an accurate prediction
requires the addition of quantum corrections that arise due the interactions of the
muon with all the other fundamental particles of nature such as electrons, photons,
quarks, etc. Comparison of experimental results with theoretical predictions then
serves as a powerful test of the completeness of the Standard Model of nature, and
the long-standing discrepancy we observe might indicate the need for new physics.
The concepts behind the Fermilab experiment and the many challenges it faces will
be presented, along with the comparison with theory and future prospects.
Until October 9, 2022, a recording of this colloquium may be accessed here, using the following passcode:
CyYyXU$0
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Apr 19
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Mark Palmer
Brookhaven National Laboratory
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An Energy Frontier Muon Collider: Progress Towards a Machine to Drive Particle Physics
Discovery
Muon colliders offer a unique path to multi-TeV, high-luminosity lepton collisions.
Muon collisions with a center-of-mass energy of 10 TeV or above would offer significant
discovery potential where the constituent collision energies exceed those of the LHC
program by an order of magnitude. Significant progress on the fundamental R&D and
design concepts for such a machine has led to a new international effort to assemble
a conceptual design within the next few years. This effort will assess the viability
of such a machine as a successor to the LHC program. The remaining challenges and
the R&D required to deliver a complete machine description will be described.
Until October 16, 2022, a recording of this colloquium may be accessed here, using the following passcode:
b*&J29Z8
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Apr 26
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John Wilkerson
University of North Carolina
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This colloquium will be fully virtual.
Probing the elusive nature of neutrinos
Neutrinos, enigmatic fundamental particles, were long assumed to be massless until
a series of revolutionary experiments over the past two decades revealed that they
actually exhibit complex behavior and must possess non-zero mass. From these and other
recent measurements we know that neutrinos have minuscule masses, at least 500,000
times lighter than the electron. Yet we still do not know the neutrino’s actual mass
nor why it is so light? Nor do we understand their fundamental nature, are they Dirac
or Majorana particles? If neutrinos are their own antiparticles, Majorana neutrinos,
then this would provide an explanation for their elusive lightness while at the same
time offering a potential explanation of the universe’s observed matter - antimatter
asymmetry. This talk will briefly review our current understanding of neutrinos, their
role in cosmology, astrophysics, and fundamental interactions, and then address the
questions of both how one “weighs” a neutrino and how to determine its Dirac or Majorana
nature. The techniques and latest results from cosmology, direct kinematical methods,
and double beta decay will be presented.
Until October 23, 2022, a recording of this colloquium may be accessed here, using the following passcode:
H4Uq.v$1
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May 3
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Matthew Dawber
Stony Brook University
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Graduate Colloquium
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