NPAC (Nuclear/Particle/Astro/Cosmo) Forum

The talk will focus on the provision of mass for the charged fermions, i.e., the Yukawa couplings in the Standard Model. In particular, the recent 5-sigma CMS measurement of Higgs to ττ decays will be presented. Additionally, the talk will cover potential physics beyond the Standard Model using the Higgs boson to search for weakly interacting massive particle dark matter.
Host: 
Sridhara Dasu
Speaker: Laura Dodd UW-Madison

 

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Room and Building: 
4274 Chamberlin hall
Host: 
Sridhara Dasu
Speaker: Isobel Ojalvo Princeton

 

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Room and Building: 
4274 Chamberlin hall
We assess the utility of an optimization-based data assimilation (D.A.)
technique for treating the problem of nonlinear neutrino flavor
transformation in core-collapse supernovae. D.A. was invented for
numerical weather prediction, and it shares some features of machine
learning for the purposes of predictive power. Within the D.A. framework,
one uses measurements obtained from a physical system to estimate the
state variable evolution and parameter values of the associated model.
Formulated as an optimization procedure, D.A. can offer an
integration-blind approach to predicting model evolution, which offers an
advantage for models that thwart solution via traditional numerical
integration techniques. Further, D.A. performs most optimally for models
whose equations of motion are nonlinearly coupled. In this exploratory
work, we consider a simple steady-state model with two mono-energetic
neutrino beams coherently interacting with each other and a background
medium. As this model can be solved via numerical integration, we have an
independent consistency check for D.A. solutions.

We find that the procedure can capture key features of flavor evolution
over the entire trajectory, even given measurements of neutrino flavor
only at the endpoint, and with an assumed known initial flavor
distribution. Further, the procedure permits an examination of the
sensitivity of flavor evolution to estimates of unknown model parameters,
locates degeneracies in parameter space, and can identify the specific
measurements required to break those degeneracies.
Host: 
Baha Balantekin
Speaker: Eve Armstrong University of Pennsylvania

 

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Room and Building: 
5280 Chamberlin Hall
The recent observations of the GW170817 electromagnetic counterpart
suggest lanthanides were produced in this neutron star merger event.
However many questions regarding heavy element production in mergers
remain: can such events account for all the r-process lanthanide material
observed in the galaxy? are precious metals such as gold produced in
sufficient amounts? are actinides produced? where within the merger
environment does nucleosynthesis occur and under what specific conditions?
Such questions can only be answered with careful studies of the nuclear
physics uncertainties affecting r-process calculations. Here I will
discuss recent extended calculations of beta-delayed fission and their
implications for r-process nucleosynthesis. The influence of fission
fragment distributions will also be addressed with a particular emphasis
on the unknown origin of the r-process rare-earth peak at A~164. Since the
rare-earth peak is formed as the r-process path begins to draw closer to
stability, the rare-earth nuclei contributing to peak formation will soon
be within reach of nuclear physics experiments performed at, for example,
the CPT at CARIBU and the upcoming FRIB. Here I will present the latest
results for the masses found to produce the rare-earth peak in a low
entropy accretion disk wind scenario and compare directly with recent mass
measurements from the CPT at CARIBU. Such collaborative efforts between
theory and experiment could soon be in a position to make definitive
statements regarding the mechanism of rare-earth peak formation and thus
the astrophysical site of the r process.
Host: 
Baha Balantekin
Speaker: Nicole Vassh University of Notre Dame

 

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Room and Building: 
5280 Chamberlin Hall
Galactic sources that accelerate particles to PeV energies (“PeVatrons”) are expected to exist, but to date only the Galactic Center has been identified as such. One of the signatures of a PeVatron is a hard gamma-ray spectrum that extends without any apparent spectral cutoff to at least tens of TeV. High-energy (> 50 TeV) gamma-ray observations are therefore essential in identifying PeVatron candidates. The High Altitude Water Cherenkov Observatory (HAWC) has sensitivity to gamma rays in this previously largely unexplored energy regime. HAWC is well suited to performing all-sky surveys due to its large instantaneous field of view (~2 sr) and high duty cycle (> 95%). I will discuss candidate sources seen above 50 TeV in the first 1000 days of HAWC data and discuss potential connections to the IceCube neutrinos. I will also briefly discuss the energy estimation method used by HAWC.
Host: 
Stefan Westerhoff
Speaker: Kelly Malone Penn State

 

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Room and Building: 
5310 Chamberlin Hall
Of the four known fundamental forces the weak force has many unique properties. It is the only standard model force that couples to all known fermions, that has massive exchange bosons, and that induces particle flavor changes. Even more surprising is that the weak force maximally violates parity symmetry, and has even been demonstrated to break charge-parity (CP) symmetry, meaning the weak force interacts differently with matter and anti-matter. This last property may hold the key to understanding several fundamental mysteries of the universe from the three-generation structure of matter, to the missing link between the big bang and the observed universe.

Neutrinos only interact via the weak force which means they are hard to detect, but provide a unique test bed for studying the weak interaction. Over the past few decades it was discovered that neutrinos have mass and change flavors. Studying the way neutrinos change flavors, termed neutrino oscillations, allows us to search for a new source of CP-violation. Measuring and understanding the ways neutrinos interact with nuclear matter is key to studiying neutrino oscillations and has proved to be more difficult than previously thought. The next-generation Deep Underground Neutrino Experiment (DUNE) will usher in an era of high precision neutrino physics with the worlds most intense neutrino beam and massive high resolution detectors, increasing the impact of neutrino interaction measurements. I will discuss the theoretical framework we use to describe neutrino oscillations, as well as the difficulties in making neutrino interaction measurements and how they can be mitigated moving forward.
Host: 
Sridhara Dasu
Speaker: Daniel Cherdack Colorado State University

 

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Room and Building: 
4274 Chamberlin Hall
We present an update of selected results and recent activities and plans for the Pierre Auger Observatory. Located near Malargue, Argentina, Auger is the world's largest cosmic ray air shower array. Auger has recently reported a significant detection of large scale anisotropy in the arrival direction of the highest energy cosmic rays. We also describe recent efforts to integrate spectral and composition measurements and what these results tell us about the nature and origin of cosmic ray sources. We address some points of tension between results reported by Auger and those of the Telescope Array (TA), and describe a project involving our group at CWRU to obtain an in-situ cross-calibration between Auger and TA surface detector stations. Finally we describe progress toward the development of the array detector upgrade, called AugerPrime, which aims for improved composition measurements.
Host: 
Justin Vandenbroucke
Speaker: Corbin Covault Case Western Reserve University

 

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Room and Building: 
5280 Chamberlin Hall

With the completion of Deep Underground Neutrino Experiment (DUNE) in the next decade, the continuation of this exciting era in neutrino physics is assured. Deep underground, based on Liquid Argon Time Projection Chamber (LArTPC) technology, with a total fiducial mass of 40-kton and utilizing the high-intensity neutrino beam produced at the Long Baseline Neutrino Facility (LBNF) at Fermilab, the DUNE program is rich and diverse. The center of this program is the measurement of the charge-parity violating phase (δCP), a free parameter in the PMNS matrix, which describes the relationship between neutrino propagating eigenstates and interaction eigenstates. This parameter can be measured by a sensitive measurement of neutrino interference and may be the primary source of the matter-antimatter asymmetry in the universe. DUNE is also sensitive to the neutrino ensemble from core-collapse supernovae, providing a unique tool to study astrophysical phenomena. In both situations, the neutrino source (supernova or LBNF), propagation and detection (LArTPC in DUNE) define a quantum system. Understanding and simulating this phenomenologically rich quantum system is important to the success of the DUNE program and opens up additional avenues of investigation.

Host: 
Sridhara Dasu
Speaker: Jonathan Miller Fermilab

 

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Room and Building: 
4274 Chamberlin Hall
Everything we know about the microscopic world tells us that the universe should be composed of equal parts matter and antimatter. All known particle interactions and decays always produce equal amount of each.
Yet all the known, observable, universe is composed solely of matter, suggesting that a small surplus of matter might have taken form shortly after the Big Bang.
A possible explanation for this asymmetry may be that neutrinos, unlike all other fundamental particles of Nature, may have behavior that distinguishes matter and antimatter. Ironically, the property that allows this is that neutrinos
and antineutrinos may be the same thing. Many experiments worldwide that are running or under construction, are investigating this possibility.
This talk will discuss this problem and the different approaches to address it in both present and upcoming neutrino
experiments, with particular emphasis on long baseline neutrino oscillations with DUNE and neutrinoless double beta decay with SNO+. The physics goals and expectations of these experiments will also be discussed.
Host: 
Sridhara Dasu
Speaker: Nuno Barros University of Pennsylvania

 

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Room and Building: 
4274 Chamberlin Hall

The experiments at the Large Hadron Collider (LHC) at CERN are at the energy frontier of particle physics, searching for answers to fundamental questions of nature. In particular, dark matter (DM) presents strong evidence for physics beyond the standard model (SM). However, there is no experimental evidence of its non-gravitational interaction with SM particles. If DM has non-gravitational interactions with the SM particles, we could be producing the DM particles in the proton-proton collisions at the LHC. While the DM particles would not produce an observable signal in the detector, they may recoil with large transverse momentum against visible particles resulting in an overall transverse momentum imbalance in the collision event. In this talk, I will review the searches for DM particles in these missing momentum final states at the Compact Muon Solenoid (CMS) experiment. I will also discuss the prospects for discovering dark matter at the High Luminosity-LHC and other future experiments.

Host: 
Sridhara Dasu
Speaker: Zeynep Demeragli MIT

 

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Room and Building: 
4274 Chamberlin Hall

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