Nuclear Physics Seminar

semester, 2016


Friday, January 22nd 2016
11:15 am:
Organizational Meeting

Friday, January 29th 2016
11:15 am:
To be announced.

Friday, February 5th 2016
11:15 am:
There will be no seminar this week.

Friday, February 12th 2016
11:15 am:
There will be no seminar this week.

Friday, February 19th 2016
11:15 am:
There will be no seminar this week.

Friday, February 26th 2016
11:15 am:
Speaker: Yao Leon Meng, University of Minnesota
Subject: Feasibility of Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT)

Boron Neutron Capture Therapy is a promising option for the treatment of glioblastoma and other recurrent brain/neck/breast cancers. Although successful clinical trials have been made using nuclear reactors, BNCT application need neutron sources which are suitable to be installed in hospitals. Particle accelerators are appropriate for this purpose. I will overview the possible nuclear reactions as a neutron source 7Li(p,n)7Be, Be9(p,n)B9, D+T, etc and the corresponding target design,neutron moderation challenge. I will introduce the application of nuclear data library and Geant4 Monte Carlo code in BNCT study. The progress of new pre-clinical neutron absorbing agents based on nano medicine and other techniques will also be reviewed briefly.


Friday, March 4th 2016
11:15 am:
Speaker:  Dr. Rajan Gupta, Los Alamos National Lab
Subject: Nucleon Matrix Elements: From Charges to nEDM

In this talk I will present the progress we have made in the calculation of the matrix elements of quark bilinear operators within nucleons using lattice QCD. These are needed to probe many phenomenologically interesting quantities including (i) the isovector and flavor diagonal charges g_A, g_S and g_T; (ii) the electric, magnetic and axial vector form factors; (iii) generalized parton distribution functions (GPDs); (iv) the nucleon sigma term; (v) strangeness of the nucleon and (vi) the matrix elements of novel CP violating operators and their contributions to the neutron electric dipole moment. Strategies for obtaining high statistics results using the all-mode-averaging method and for for mitigating excited-state contamination will be discussed. I will present high statistics results for the charges and quark electric dipole moments and their implications for Split SUSY. I will also describe a new method for calculating the quark chromo electric dipole moments.


Friday, March 11th 2016
11:15 am:
Speaker: Mikhail Voloshin, University of Minnesota
Subject: Heavy Exotic Mesons and Baryons

According to the original quark model template there are mesons consisting of a quark and anantiquark, and baryons made from three quarks. Strongly interacting particles that do not fit this template are called exotic. Experimental findings of recent years have uncovered existence of exotic mesons: tetraquarks, and baryons: pentaquarks, containing an additional heavy quark-antiquark pair. All such well established exotic states contain heavy quarks (c or b). I discuss some properties of such particles and the current theoretical approaches to understanding their internal dynamics.


Friday, March 18th 2016
11:15 am:
There will be no seminar this week, spring break.

Friday, March 25th 2016
11:15 am:
Speaker: Projjwal Banerjee, University of Minnesota
Subject: Neutron_capture in Metal-Free and Metal-Poor Stars

We propose a new site for neutron-capture process in massive metal-free and metal-poor stars during the late stages of their evolution. We find that a wide range of neutron-capture abundance patterns can be produced. This can explain the fact that neutron-capture elements have been observed in most of the metal-poor stars even at the lowest metallicities and that the observed patterns of these elements show deviations from the solar-r process pattern.


Friday, April 1st 2016
11:15 am:
There will be no seminar this week.

Friday, April 8th 2016
11:15 am:
Speaker: Evan O'Connor, North Carolina State University
Subject: The Death of Massive Stars

Core collapse marks the end stage of stellar evolution and the beginning of one of the most energetic events in the modern universe. The transformation of the iron core in an evolved massive star to a neutron star releases a huge amount of gravitational binding energy, the equivalent of a few tenths of a solar mass. This energy source is tapped to produce the explosion we see as a core-collapse supernova. Core-collapse supernovae are a cornerstone of astrophysics. They unbind the nucleosynthetic products of massive stars, trigger local star formation, are the birth place for both neutron stars and black holes, the site of long gamma-ray bursts, and the list goes on.

At the heart of core-collapse supernovae is the central engine that turns the initial implosion of the iron core into an explosion that eventually propagates out through the star (or fails and produces stellar mass black holes). In order to understand this engine we must perform multidimensional hydrodynamic simulations that includes state of the art hydrodynamics, neutrino transport, nuclear microphysics, and treatments of gravity, among others, that make this problem truly rich in physics. In this talk, I will give an update on the present status of understanding the core-collapse supernova central engine including showing recent multidimensional results using a new neutrino transport scheme developed in the hydrodynamics package FLASH. I will also discuss the progenitor dependence of core-collapse supernovae and how we can use observables of the central engine, namely neutrinos, to constrain the late stages of stellar evolution.

Faculty Host: Yong-Zhong Qian

Friday, April 15th 2016
11:15 am:
Speaker: Dr. Marlene Nahrgang, Duke University
Subject: The QCD phase transition and its signatures in heavy-ion collisions

For a complete understanding of the QCD phase diagram it is important to connect first-principle thermodynamic calculations to experimental data from heavy-ion collision experiments of the RHIC Beam Energy Scan. In particular, the potential to discover the QCD critical point experimentally is of great interest. In this talk I will review the theoretical concepts of critical fluctuations at the QCD phase transition and discuss the current status of modeling these fluctuations in the dynamical evolution of heavy-ion collisions. Within the model of nonequilibrium chiral fluid dynamics I will show how different equations of state at finite baryochemical affect the dynamical domain formation at a first-order phase transition. Special emphasis is put on observables which are sensitive to the critical point and how they are affected by the out-of-equilibrium dynamics in heavy-ion collisions.


Friday, April 22nd 2016
11:15 am:
Speaker: Ming Li, University of Minnesota
Subject: Achieving High Baryon Densities in the Fragmentation Region in Heavy Ion Collisions at Top RHIC Energy

Based on our previous calculations of the energy-momentum tensor of the Glasma state, we calculated the back-reaction of the Glasma on the receding nuclei. We were able to obtain the rapidity loss and the excitation energy of the nuclear fragments. Consequently, Baryon and energy densities in the fragmentation region can be estimated using a simple space-time picture of the collision. For Au-Au central collisions at top RHIC energy, we found baryon density more than ten times larger than the normal nuclear matter. Energy density also much exceeds the critical energy density for the formation of quark-gluon plasma, indicating the transition to high baryon density quark-gluon plasma in the fragmentation region.


Friday, April 29th 2016
11:15 am:
Speaker: Ming Li, University of Minnesota
Subject: Achieving High Baryon Densities in the Fragmentation Region in Heavy Ion Collisions at Top RHIC Energy

Based on our previous calculations of the energy-momentum tensor of the Glasma state, we calculated the back-reaction of the Glasma on the receding nuclei. We were able to obtain the rapidity loss and the excitation energy of the nuclear fragments. Consequently, Baryon and energy densities in the fragmentation region can be estimated using a simple space-time picture of the collision. For Au-Au central collisions at top RHIC energy, we found baryon density more than ten times larger than the normal nuclear matter. Energy density also much exceeds the critical energy density for the formation of quark-gluon plasma, indicating the transition to high baryon density quark-gluon plasma in the fragmentation region.


Friday, May 6th 2016
11:15 am:
There will be no seminar this week.

Friday, September 9th 2016
10:10 am:
Subject: Organizational Meeting

Friday, September 23rd 2016
10:10 am:
The Nuclear seminar has been cancelled for this week.

Friday, September 30th 2016
10:10 am:
The Nuclear seminar has been cancelled again this week.

Friday, October 7th 2016
10:10 am:
Speaker: Christopher Plumberg, University of Minnesota
Subject: Event-by-event fluctuations and their consequence for Hanbury Brown-Twiss interferometry

The relativistic heavy-ion program is dedicated to systematically probing the properties of the atomic nucleus and the theory of quantum chromodynamics at extremely high temperatures and energy densities. Numerous observables have been developed and studied over the past several decades, allowing one to extract valuable information about heavy-ion collisions and their evolution, including total multiplicity, anisotropic flows, mean pT, interferometric radii, and so on. Many of these observables have been studied on an event-by-event basis, allowing them, along with their event-by-event probability distributions, to be used for constraining the role of event-by-event fluctuations in the evolution of heavy-ion collisions.
In this talk, I will discuss the possibility of treating the Hanbury Brown-Twiss radii as event-by-event observables, and consider the ways in which their event-by-event probability distributions might be related to interesting theoretical quantities, such as transport coefficients in the quark-gluon plasma, or used to constrain viable models of the initial state in heavy-ion collisions. I will also briefly discuss some recent efforts to extend these results to explore the effects of hydrodynamic fluctuations in heavy-ion collisions.


Friday, October 14th 2016
10:10 am:
There will be no seminar this week.

Friday, October 21st 2016
10:10 am:
Speaker: Sean Bartz, Macalester University
Subject: Chiral phase transition and meson melting in a soft-wall model of AdS/QCD

The AdS/CFT correspondence describes many features of non-perturbative QCD. A phenomenological approach called AdS/QCD uses a dilaton field to break conformal symmetry. This describes the linear confinement of hadronic spectra at zero temperature. Using an AdS-black hole metric allows for the study of the behavior of hadrons interacting with a hot, dense medium like the quark-gluon plasma.

We present an improved AdS/QCD model for meson spectra and chiral dynamics at finite temperature and baryon chemical potential. We find a second-order chiral phase transition in the chiral limit, with a critical temperature of 155 MeV, consistent with lattice calculations, and critical baryon chemical potential of 566 MeV. For physical quark mass the transition is a rapid crossover, with a pseudo-transition temperature and density of 151 MeV and 559 MeV, respectively. Using a pure AdS-Schwarzschild metric, the light meson bound states are found to melt before the chiral phase transition occurs. This behavior may be modified with appropriate parameterization of the metric.


Friday, October 28th 2016
10:10 am:
Speaker: Yong-Zhong Qian, University of Minnesota
Subject: Effects of eV-Scale Sterile Neutrinos on Supernova Explosion and Nucleosynthesis

We show that for the active-sterile flavor mixing parameters suggested by the reactor neutrino anomaly, substantial conversion between neutrinos (antineutrinos) of the electron and sterile flavors occurs in regions with electron fraction close to 1/3 near the core of an 8.8 solar mass supernova. Compared to the case without such conversion, the neutron-richness of the ejected material is enhanced to allow production of elements from Sr, Y, and Zr up to Cd in broad agreement with observations of the metal-poor star HD 122563. Active-sterile flavor conversion also strongly suppresses neutrino heating at times when it is important for the revival of the supernova shock. Our results suggest that simulations of supernova explosion and nucleosynthesis may be used to constrain active-sterile mixing parameters in combination with neutrino experiments and cosmological considerations.


Friday, November 4th 2016
10:10 am:
Speaker: Joe Kapusta, University of Minnesota
Subject: Including Noise in Relativistic Hydrodynamics

Friday, November 11th 2016
10:10 am:
Speaker: Zewei Xiong, University of Minnesota
Subject: Oscillations of Solar High-Energy Neutrinos

Friday, November 18th 2016
10:10 am:
Speaker: Cheng-Hsien Li, University of Minnesota
Subject: Neutrinos from SN1987A in light of recent simulation.

It has been nearly three decades since the first and the only detection of neutrinos from stellar collapse. I will begin with a discussion of supernova neutrino emission and then examine the historical SN1987A event with the state-of-the-art 1D hydrodynamic simulation results from Mirizzi et al.(2016). A simple goodness-of-fit test is presented to demonstrate the incompatibility between the last three Kamiokande-II events, if they are associated with the core collapse of SN1987A, and the rapid cooling of the proto-neutron star prescribed by the convection treatment in the simulation. The implications will be briefly discussed.


Friday, December 2nd 2016
10:10 am:
Speaker: Ming Li, University of Minnesota
Subject: Revisiting the (quasi)particle spectrum in the Glasma

Friday, December 9th 2016
10:10 am:
Speaker: Yao Leon Meng, University of Minnesota
Subject: Applications of proton-nucleus reactions at the MeV scale for brain cancer therapy and space exploration

Friday, December 16th 2016
10:10 am:
There will be no seminar this week.

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