NPAC (Nuclear/Particle/Astro/Cosmo) Forum

At low energies, parity violation in NN scattering
(including photons) is described by an effective field theory (EFT)
that includes only contact interactions. I will describe this EFT,
how it improves upon the standard (non-physical) description, how it
echoes the Danilov treatment, and how its predictions compare to
existing (presently under-constraining) measurements.
Host: 
Michael Ramsey-Musolf
Speaker: Roxanne Springer Duke University

 

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Room and Building: 
4274 Chamberlin
Milagro was a water Cherenkov detector that continuously viewed<br>
the entire overhead sky. The large field-of-view combined with<br>
the long observation time makes Milagro the most sensitive<br>
instrument available for surveys and especially for the study<br>
of large, low surface brightness sources. In this talk I will<br>
present recent results from Milagro including the identification<br>
of several new TeV sources associated with Fermi BSL (bright<br>
source list) objects within the Galactic plane. The success of<br>
Milagro has lead to the proposed High Altitude Water Cherenkov<br>
(HAWC) Observatory. HAWC will be built at a high altitude site<br>
(4100m a.s.l.) in central Mexico. The increased elevation, along<br>
with the re-optimization of the design will lead to a 15x<br>
sensitivity improvement compared to Milagro.
Host: 
Stefan Westerhoff
Speaker: Andrew Smith University of Maryland, College Park

 

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Room and Building: 
4274 Chamberlin
Host: 
Karsten Heeger
Speaker: Angelo Nuciotti University of Milan Bicocca

 

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Room and Building: 
4274 Chamberlin

Coupling dark matter (DM) to dark energy (DE) is one of the most promising way to build a unified description of the invisible sector of cosmology. It also glimpses beyond the concordance model LCDM in which DM and DE are assumed physically unrelated. However, such DM-DE couplings make the mass of the DM particles varying, therefore breaking the universality of free fall (Galileo's equivalence principle). Doing so, the strong equivalence principle, stating the universality of gravitational binding energy, does not hold anymore, particularly where DM is profuse like in the large-scale universe. Mass-varying DM therefore induces modifications of gravity. This gravitational feedback on ordinary matter can explain cosmic acceleration, which is then interpreted as the observable signature of the violation of the equivalence principle on cosmological scales. To embrace the various physics of DM-induced violation of the equivalence principle, we have developped a generalisation of Brans-Dicke tensor-scalar theories of gravitation, dubbed the Abnormally Weighting Energy (AWE) Hypothesis. In this approach, the variation of the inertial mass of DM particles induces a running of the gravitational coupling strength on cosmological scales that is observable in the late-time cosmic acceleration. Besides of describing both DM and DE, the AWE hypothesis allows measuring the density paramters of baryons and dark matter from the Hubble diagram *alone*, and its predictions are consistent with the independent cosmological tests of Cosmic Microwave Background (CMB) and Big Bang Nucleosynthesis (BBN). This interpretation also shed new light on the coincidence problem. We will end this seminar by showing how this mechanism could interestingly be applied to the physics of neutrino mass generation and mass-varying neutrinos by turning the spontaneous symmetry breaking of lepton number symmetry into a gravitational symmetry breaking.

Host: 
S Mantry
Speaker: Andre Fuzfa GAMASCO, University of Namur (FUNDP); Louvain U; Paris Observatory;

 

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Room and Building: 
4274 Chamberlin
The origins, acceleration mechanism(s), and propagation of high energy cosmic rays within the galaxy have been a mystery for nearly 100 years. Today's experiments are beginning to provide a more complete and definitive answer to these classic questions. I will discuss one such: the Cosmic Ray Energetics And Mass (CREAM) balloon-borne experiment. CREAM uses a complementary set of charge, energy, and tracking detectors on successive balloon flights around the Antarctic continent to directly measure individual CR nuclei's spectra over 5 orders of magnitude in energy. These spectra provide clues to CR origins and acceleration mechanisms. To better understand CR propagation, we have extended the Boron to Carbon ratio over an order of magnitude higher in energy than previous measurements. I will then explore a few ways ongoing and upcoming detections of CR signatures with gamma-ray and neutrino detectors may shed further light on the classic CR questions, both through direct and indirect detection.
Host: 
Albrecht Karle
Speaker: Terri J. Brandt Ohio State University

 

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Room and Building: 
5280 Chamberlin
We discuss electroweak phase transition (EWPT) in the secluded<br>
U(1)'-extended MSSM with/without CP violation.<br>
Unlike the MSSM, the EWPT can be strong first order without a light stop.<br>
In such a case, the singlet-like Higgs bosons and the charged Higgs bosons<br>
play an important role. It is found that at least two Higgs bosons should be<br>
less than 300 GeV for the strong first order phase transition.<br>
Depending on the charged Higgs boson mass, the lightest Higgs boson can be<br>
as large as 220 GeV. It is also found that the CP violating phase in the Higgs sector<br>
do not weaken the strength of the first order EWPT.<br>
Speaker: Eibun Senaha National Central University, Taiwan

 

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Room and Building: 
4274 Chamberlin
MINOS (Main Injector Neutrino Oscillation Search) is a
mature neutrino experiment that has been accumulating data using the NuMI neutrino beam since 2005. Data from 7 x 1020 protons-on-target have been recorded, primarily in low-energy neutrino mode. An update on the charge-current analysis will be presented as well as the recent electron appearance result. Additional results will be briefly reviewed along with prospects for future running in anti-neutrino mode.
Host: 
Karsten Heeger
Speaker: Christopher White Illinois Institute of Technology

 

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Room and Building: 
5280 Chamberlin
An enormous effort has been made to understand and model the nuclear force. The next step is to apply those models in an environment where three (or four) nucleons interact with each other and thoroughly test underlying assumptions of nuclear physics.

Traditionally three-nucleon calculations are carried out by solving Faddeev equations in a partial wave truncated basis, working either in momentum or coordinate space. We solve them directly as function of vector variables. The key advantage of our approach lies in its applicability at higher energies, where special relativity is expected to become relevant. We investigate relativistic three-boson scattering in the framework of Poincare invariant quantum mechanics. The main point here is the construction of unitary irreducible representations of the Poincare group, both for noninteracting and interacting particles. For three-body scattering the Faddeev scheme is reformulated relativistically.

Comparison of scattering observables obtained from relativistic and non-relativistic calculations based on simple Yukawa-type interactions lead to observations that should be relevant for more sophisticated interactions. These comparisons do not involve taking non-relativistic limits. Instead relativistic and non-relativistic three-body calculations are compared that contain interactions fitted to the same two-body data. All of the observed differences result form the different ways in which the two-body dynamics appears in the three-body problem.
Host: 
Baha Balantekin
Speaker: Charlotte Elster Ohio University, Athens

 

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Room and Building: 
4274 Chamberlin

Joint HEP Seminar/NPAC Forum

Host: 
Karsten Heeger
Speaker: Kevin Lesko Lawrence Berkeley National Laboratory

 

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Room and Building: 
4274 Chamberlin
We propose an inflationary scenario, M-flation, in which inflation is driven by three NXN Hermitian matrices Phi_i, i=1,2,3. The inflationary potential of our model in the most general form involves a commutator squared term, a cubic term involving product of a commutator with the field and a quadratic ``mass'' term. This class of potentials are strongly motivated by string theory. We show that one can consistently restrict the classical dynamics to a sector in which the Phi_i are proportional to the NXN irreducible representation of SU(2). In this sector our model effectively behaves as an N-flation with order N^2 number of fields, and therefore remove the fine-tunings associated with super-Planckian field and/or unnaturally small couplings in the chaotic type inflationry scenarios. Due to the matrix nature of the scalars 3N^2-1$ other scalar fields also affect the inflationary dynamics. These have the observational effects such as production of entropy (non-adiabatic) perturbations on cosmic microwave background. Moreover, the existence of these other scalars provides us with a natural preheating model for our setup.<br>
Host: 
Dan Chung
Speaker: Amjad Ashoorioon University of Michigan

 

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Room and Building: 
4274 Chamberlin

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