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Nuclear and Particle Physics Colloquia

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

 

Committee:
Markus Klute, Chair ~ William Detmold ~ Mike Williams

 

Colloquia Archives

 

February 9, 2015

hosted by: Christoph Paus

Rescheduled for Friday, February 27, 2015

 

Dr. Jan Bernauer, (MIT)

The Precision Frontier: Lepton-Proton Scattering

Abstract: The nucleon and its structure are the focus of intense study on all energy scales, in both current and upcoming experiments. It is one of the simplest systems in non-perturbative QCD and the accurate description of its properties is a touchstone for theoretical calculations.

 

Recent precision experiments have provided a wealth of information, but have also illuminated two glaring discrepancies: the proton radius puzzle and the form factor ratio divergence. The former, still unsolved, may have opened the door to discovery of physics beyond the Standard Model, while a solution to the latter seems in reach.

 

In this talk, I will discuss the Mainz high precision form factor measurement and global form factor analysis, which are corner stones of the radius puzzle; the OLYMPUS experiment, which is poised to give the final confirmation of the solution to the ratio problem; the MUSE experiment, which will provide a missing piece for the proton radius puzzle; and the proposed DarkLight experiment, which will search for physics beyond the Standard Model at the intensity frontier

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

(refreshments at 3:30 p.m.)



February 17, 2015 (Rescheduled date due to Monday Holiday)

hosted by:  Richard Milner



Dr. Or Hen, (Tel-Aviv University)

Short-Range Correlations in Imbalanced Fermi Systems

Abstract: The atomic nucleus is composed of two different kinds of fermions, protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority fermions, usually neutrons, to higher average momentum. In this talk I will present results from high-energy electron scattering experiments, which show that short-range interactions between the fermions form correlated, high-momentum, neutron-proton pairs. Thus, in neutron-rich nuclei the probability of finding a high-momentum (k>kFermi) proton (a minority Fermion) is greater than that of a neutron (a majority Fermion). This has wide ranging implications for atomic, nuclear, and astro physics, including neutrino-nucleus scattering, the EMC effect, the NuTeV anomaly, the nuclear symmetry energy, and more. This feature is universal for imbalanced interacting Fermi systems and can also be observed experimentally in two-spin states ultra-cold atomic gas systems.

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

(refreshments at 3:30 p.m.)




February 23, 2015

hosted by:  Christoph Paus



Dr. Michael Hance, (Lawrence Berkeley National Laboratory)

Searching for Exotic New Physics at the LHC

Abstract: The Standard Model of particle physics provides an excellent description of particle interactions at high energies and small distance scales. With the recent discovery of the Higgs boson, the predicted particle content of the Standard Model is now complete. However, the Standard Model cannot explain certain phenomena, such as the origin of non-zero neutrino masses, the nature of dark matter, and why the Higgs mass appears to be very finely tuned. This suggests that there exist particles and forces beyond the Standard Model, possibly at an energy scale that we can reach with modern technology. The Large Hadron Collider (LHC) and the ATLAS experiment were built to test the Standard Model in an unexplored region of the high-energy particle interactions, and to search for qualitatively new particles and forces not predicted by the Standard Model.

 

After a description of the LHC and the ATLAS experiment, and a review of our important achievements from the first run of the LHC, I will describe our efforts to look for exotic new physics in high-energy collisions. I will focus on searches for large extra dimensions, new heavy bosons, and on model-independent searches that can be used to constrain broad classes of new physics models. I will conclude with prospects for discovery in the upcoming high-energy run at the LHC, which will begin this spring.

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

(refreshments at 3:30 p.m.)



March 2, 2015

hosted by: Gunther Roland



Dr. Kerstin Perez, (Columbia University)

Antideuteron Signatures of Dark Matter
with
the GAPS Experiment

Abstract: The question of the origin of dark matter, the mysterious matter known to permeate the universe, is one of the towering problems of 21st- century physics. Dozens of dark matter search experiments are currently planned or ongoing, but these efforts have been hampered by the large background rates from conventional astrophysical processes and the vast array of signatures that could indicate a dark matter interaction. The General Antiparticle Spectrometer (GAPS) experiment aims to advance these searches by detecting low-energy antideuterons that result from the self-annihilation of dark matter particles in the Galactic halo, providing an essentially background-free signature of dark matter. This signal probes supersymmetry, extra-dimensional theories, and other modes of dark matter production, complementing and extending the reach of current experiments. In this seminar, I will present the design and discovery potential of the balloon-borne GAPS experiment, which exploits a novel detection technique utilizing exotic atom capture and decay. In particular, I will detail the fabrication of lithium-drifted Silicon detectors that are essential to its success.

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

(refreshments at 3:30 p.m.)



March 9, 2015

hosted by: Mike Williams



Prof. Joseph Formaggio,  (MIT)

Morning Chirps: Using Frequency-Based Techniques to Measure Neutrino Mass

Abstract: Physicists have been attempting to measure the mass of the neutrino since the first theoretical proposals by Enrico Fermi, with particularly interest emerging since neutrino oscillations confirm that the masses are not zero. Current attempts to measure the neutrino mass require high-precision, high-throughput electron spectrometers to measure tritium beta decay, but known electrostatic techniques are reaching the end of their scalability. Here we show the first single-electron detection in a novel spectrometer. We detect single-electron cyclotron radiation emitted from mildly-relativistic electrons in a gaseous radioactive source. A relativistic shift in the cyclotron frequency provides a precise electron energy measurement, providing proof-of-concept for this technique's utility in future tritium neutrino mass searches.

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

(refreshments at 3:30 p.m.)


March 16, 2015

hosted by:  Mike Williams



Prof. Darren Grant, (University of Alberta)

Recent Results from IceCube’s DeepCore and Beyond

Abstract: Scientists have created the world's largest neutrino telescope, the IceCube Neutrino Observatory, in one of the planet’s most extreme environments at South Pole Station Antarctica. Instrumenting more than a cubic-kilometer of ice, the observatory is designed to detect interactions of the highest energy neutrinos expected to be produced in the Universe's most violent astrophysical processes In 2008, the original IceCube design was augmented to include a low-energy extension, called DeepCore, that reduced the neutrino energy detection threshold to approximately 10 GeV and launched a vibrant Antarctic-based particle physics program that provides world-leading indirect dark matter searches and very high statistic studies of atmospheric neutrinos. Building on the success of DeepCore, a new infill array called PINGU (the Precision IceCube Next Generation Upgrade) is now being proposed that would further reduce the in-ice energy threshold to a few GeV. Such a detector would be capable of significantly expanding the current low-energy program, including the potential to make a first determination of the neutrino mass ordering. In this talk I will discuss the latest DeepCore results and the status of the developments of the PINGU detector.

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

(refreshments at 3:30 p.m.)



March 23, 2015


                Spring Break



March 30, 2015

hosted by: Markus Klute and Aron Bernstein



Dr. Jan Friedrich, (Technical University of Munich)

The Pion Polarizability and More Low-Energy QCD from Primakoff Measurements at COMPASS

Abstract: For more than a decade, the COMPASS experiment at the CERN Super Proton Synchrotron has been tackling the measurement of the electromagnetic polarizability of the charged pion. This quantity is of fundamental interest in the low-energy sector of quantum chromodynamics. Previous experiments date back to the 1980's in Serpukhov (Russia), where the Primakoff method to study charged-pion interactions with quasi-real photons was first employed. Later also other techniques in photon-nucleon and photon-photon collisions were carried out at different machines. The COMPASS measurement demonstrates that the charged-pion polarizability is significantly smaller than the previous dedicated measurements, roughly by a factor two, with the smallest uncertainties realized so far.

 

Within the same experiment, largely in terms of getting control over the uncertainties for the measurement of the cross-section shape with a precision of about one percent, a variety of neighboring physics channels initiated by pion-photon collisions, was also studied and is sketched in this talk.

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

(refreshments at 3:30 p.m.)



April 6, 2015

hosted by:  Markus Klute



Dr. Stefania Gori, (Perimeter Institute for Theoretical Physics)

The Higgs as a Portal to New Physics

Abstract: The discovery of the Higgs boson at the Large Hadron Collider marks the culmination of a decades-long hunt for the last ingredient of the Standard Model. At the same time, this discovery has started a new era in the search for more fundamental physics. In this talk, I will discuss what we have learned from the Higgs discovery about the mechanism of electroweak symmetry breaking and the implications for the existence of additional Higgs bosons. I will then highlight the future prospects of the Higgs boson in shedding light on New Physics and in particular on the nature of Dark Matter.

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

(refreshments at 3:30 p.m.)



April 13, 2015

hosted by:  Will Detmold



Dr. Zoltan Fodor, (University of Wuppertal)

Ab Initio Calculation of the Neutron-Proton
Mass Difference

Abstract: The existence and stability of atoms relies on the fact that neutrons are more massive than protons. The mass difference is only 0.14% of the average. This tiny mass splitting has significant astrophysical and cosmological implications. A slightly smaller or larger value would have led to a dramatically different universe. Here we show, how this difference results from the competition between electromagnetic and mass isospin breaking effects. We compute the neutron-proton mass splitting and show that it is greater than zero by five standard deviations. Furthermore, splittings in the Sigma, Xi, D and Xi_cc isospin multiplets are determined providing also predictions. We perform lattice Quantum-Chromodynamics plus Quantum-Electrodynamics computations with four, non-degenerate Wilson fermion flavors. Four lattice spacings and pion masses down to 195 MeV are used.

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

(refreshments at 3:30 p.m.)


April 20, 2015


                Patriot's Day



April 27, 2015

hosted by:  Will Detmold



Prof. Manoj Kaplinghat, (University of California, Irvine)

The Revival of Self-Interacting Dark Matter

Abstract: Self-interacting dark matter (SIDM) was proposed to solve some puzzles in structure formation 15 years ago but was shelved by the astronomy community rather quickly. This talk will summarize the current status of structure formation puzzles, the revival of SIDM and recent work in model building related to SIDM. The talk will end with some predictions for SIDM models in the standard direct and indirect searches.

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

(refreshments at 3:30 p.m.)


May 4, 2015

hosted by:  Will Detmold



Prof. Michael Williams, (MIT)

Executing a Pincer Movement on the Standard Model at LHCb

Abstract: The LHCb experiment became the world's premier flavor physics laboratory during the LHC's first run. I will summarize the cur-rent status of the field with emphasis on model-independent con-straints on theories beyond the Standard Model that involve particles at the O(1-10 TeV) scale. I will also highlight a few interesting anoma-lies that have emerged. LHCb is not just a flavor physics experiment, however, and I will demonstrate this by showing unique studies at LHCb that probe unexplored regions of proton structure or search for new low-mass particles. I will then look ahead to the second and third LHC runs, and demonstrate the power of a 40 MHz triggerless readout with real-time analysis, e.g., in searching for dark photons.

 

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

(refreshments at 3:30 p.m.)


May 11, 2015

hosted by:  Will Detmold



Prof. Ulf-G Meissner, (University of Bonn)

Life on Earth - an Accident?

Abstract: In this talk, I discuss the sensitivity of the generation of the light and the life-relevant elements like carbon and oxygen under changes of the parameters of the Standard Model pertinent to nuclear physics. Chiral effec-tive field theory allows for a systematic and precise description of the forces between two, three, and four nucleons. In this framework, variations under the light quark masses and the electromagnetic fine structure constant can also be consistently calculated. Combining chiral nuclear effective field theo-ry with Monte Carlo simulations allows to further calculate the properties of nuclei, in particular of the Hoyle state in carbon, that plays a crucial role in the generation of the life-relevant elements in hot, old stars. The dependence of the triple-alpha process on the fundamental constants of Nature is calcu-lated and some implications for our anthropic view of the Universe are dis-cussed.  

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

(refreshments at 3:30 p.m.)