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Nuclear and Particle Physics Colloquia

Mondays ~ Refreshments 3:30pm Talk: 4:00pm ~ Kolker Room, 26-414

 

Committee:
William Detmold, Chair ~ Mike Williams ~ Lindley Winslow

 

Colloquia Archives

 

February 13, 2017

hosted by: Jesse Thaler

Yuval Grossman, Cornell University

Polarization

Abstract: Determining polarization of particles is an important tool to probe the Dirac structure of couplings. I will discuss several ideas of how to probe polarization in cases where the traditional methods do not work, in particular, how to measure b quark polarization in high energy processes and the photon polarization in
two body decays.

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)



February 20, 2017



Presidents' Day Holiday

 



February 27, 2017

hosted by:  Will Detmold


Joseph Carlson, Theoretical Division, Los Alamos National Lab

The long- and short- of cold atoms and nuclei

Abstract: I will discuss the interplay of short- and long-distance physics in cold Fermionic atoms and in nuclei. In cold atom physics in the unitary regime (where there is only one length scale) the connection is clear and leads to definite predictions for their basic properties. In nuclei the connections are more subtle, but yield interesting insights on the properties of nuclei and nucleonic matter including momentum distributions, inclusive electron and neutrino scattering from nuclei, important for accelerator neutrino experiments and cold dense nucleonic matter as occurs in neutron stars.

 

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)



March 6, 2017

hosted by: n/a


Anna Frebel, MIT

Observing the signature of a single prolific r-process event in an
ultra-faint dwarf galaxy

Abstract: The heaviest chemical elements in the periodic table are synthesized through the rapid neutron-capture (r-) process but the astrophysical site where r-process nucleosynthesis occurs is still unknown. The best candidate sites are ordinary core-collapse supernovae and mergers of binary neutron stars. Through their stars, 13 billion year old ultra-faint dwarf galaxies preserve a "fossil" record of early chemical enrichment that provides the means to isolate and study clean signatures of individual nucleosynthesis events. Until now, ultra-faint dwarf galaxy stars displayed extremely low abundances of heavy elements (e.g. Sr, Ba). This supported supernovae as the main r-process site. But based on new spectroscopic data from the Magellan
Telescope, we have found seven stars in the recently discovered ultra-faint dwarf Reticulum II that show extreme r-process overabundances, comparable only to the most extreme ancient r-process enhanced stars of the Milky Way's halo. This r-process enhancement implies that the r-process material in Reticulum II was synthesized in a single prolific event. Our results are clearly incompatible with r-process yields from an ordinary core-collapse supernova but instead consistent with that of a neutron star merger. This first signature of a neutron star merger in the early universe holds the key to finally, after 60 years, identifying the cosmic r-process production site, in addition to being a uniquely stringent constraint on the metal mixing and star formation history of this galaxy from the early universe.

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)



March 13, 2017

hosted by: Or Hen

John Behr, TRIUMF

Beta-decay correlations with laser-trapped 37K in the LHC era

Abstract: We have measured the beta asymmetry with respect to the nuclear spin in 37K decay to be -0.5706+-0.0018. Ours is the most accurate beta asymmetry measurement in any nucleus or the neutron, and is in agreement with the Standard Model of particle physics. I will show our constraints on beyond-Standard Model physics complementary to other beta decay measurements. I will also describe our planned improvements to our laser-cooled atom trap techniques, including measurement of the asymmetry of the low-energy nuclear recoils. We hope to reach accuracy sufficient to complement pion decay and high-energy experiments, probing coupling strengths of possible new bosons to first-generation particles.

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)

 



March 20, 2017

hosted by: n/a

Aron Bernstein, MIT

Nuclear Weapons from Beginning to End?

Abstract: In January the Bulletin of the Atomic Scientists moved the Doomsday Clock" closer to midnight stating that "Over the course of 2016, the global security landscape darkened as the international community failed to come effectively to grips with humanity's most pressing existential threats, nuclear weapons and climate change."


This talk will present an objective overview of the nuclear arms race with an emphasis on the current escalating dangers. A brief sketch of how nuclear weapons work and some ironic lessons from history will be presented. Our current overkill capacity will be illustrated by the explosive power of one nuclear submarine. An examination of some possible pathways to nuclear conflict will be presented. If time permits current non-proliferation efforts such as the Iran agreement, and problems with North Korea will be included, A personal outlook about preventing future nuclear weapons use along with the vital role of education and scientist's participation will be presented.

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)



March 27, 2017



SPRING BREAK

No talk this week



April 3, 2017

hosted by: Will Detmold


Martha Constantinou, Temple University

The Proton Spin Puzzle from Lattice QCD

Abstract: Quantum Chromodynamics (QCD) is the theory of the strong interactions that binds quarks and gluons to form the nucleons, the fundamental constituents of the visible matter.


Understanding nucleon structure is considered a milestone of hadronic physics and new facilities are planned devoted to its study. A future Electron-Ion-Collider proposed by the scientific community will greatly deepen our knowledge on the fundamental constituents of the visible world. To achieve this goal, a synergy between the experimental and theoretical sectors is imperative, and Lattice QCD is in a unique position to provide input from first principle calculations. Over the last years Lattice QCD has made significant progress yielding results that can be compared to experimental measurements with controlled systematics.


In this talk we will discuss recent progress in nucleon structure from Lattice QCD using state-of-the-art simulations with pion mass tuned at its physical value. Emphasis will be given on quantities that have implication on the proton spin in order to address the question: “Where does the spin of proton come from”? Along the line of understanding this long-standing puzzle we will also highlight developments on the evaluation of the gluon momentum fraction.

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)



April 10, 2017

hosted by: Jesse Thaler


Chris Rogan, Harvard University

TBA

Abstract: TBA

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)



April 17, 2017



PATRIOTS DAY

No talk this week



April 24, 2017

hosted by: Lindley Winslow


TBA

TBA

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)

 



May 1, 2017

hosted by: Jesse Thaler

Henriette Elvang, University of Michigan

TBA

Abstract: TBA

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)



May 8, 2017

hosted by: TBA

Cynthia Keppel, Jefferson Lab

TBA

Abstract: TBA

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)



May 15, 2017

hosted by: Mike Williams



Mike Williams, MIT

TBA

Abstract: TBA

time:    4:00 p.m.
place:   Kolker Room (26-414)

(refreshments at 3:30 p.m.)