Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session C16: Light Nuclei Beyond the Standard ModelInvited
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Sponsoring Units: GFB DPF Chair: Kenneth Nollett, San Diego State Univesrity Room: Washington 3 |
Saturday, January 28, 2017 1:30PM - 2:06PM |
C16.00001: Electric dipole moments of light nuclei Invited Speaker: Emanuele Mereghetti "Electric dipole moments (EDMs) are extremely sensitive probes of physics beyond the Standard Model (SM). A vibrant experimental program is in place, with the goal to improve the existing neutron EDM bound by one/two orders of magnitude, and to test new ideas for the measurement of EDMs of light ions, such as deuteron and helium, at a comparable level. The success of this program, and its implications for physics beyond the SM, relies on the precise calculation of the EDMs in terms of the couplings of CP-violating operators. In light of the non-perturbative nature both of QCD at low energy and of the nuclear interactions, these calculations have proven difficult, and are affected by large theoretical uncertainties. In this talk I will review the progress that in recent years has been achieved on different aspects of the calculation of hadronic and nuclear EDMs. In particular, I will discuss how the interplay between lattice QCD and Chiral Effective Field Theory (EFT) has allowed to reduce a set of hadronic uncertainties. Finally, I will discuss how the measurements of th EDMs of one, two and three nucleon systems can be used to discriminate between various possible mechanisms of time-reversal violation at high energy." [Preview Abstract] |
Saturday, January 28, 2017 2:06PM - 2:42PM |
C16.00002: Is there a sign of new physics in beryllium transitions? Invited Speaker: Bartosz Fornal A 6.8$\sigma$ anomaly in the invariant mass distribution of $e^+ e^-$ pairs produced via internal pair creation in $^8{\rm Be}$ nuclear transitions has been reported recently by Krasznahorkay et al.$~$in Phys.$~$Rev.$~$Lett.$~$116 (2016) 042501. The data can be explained by a $\sim\,$17 MeV vector gauge boson $X$ produced in the transition of an excited beryllium state to the ground state, $^8{\rm Be}^* \rightarrow \, ^8{\rm Be} \, X$, followed by the decay $X \rightarrow e^+ e^-$. We find that the gauge boson $X$ can be associated with a new ``protophobic'' fifth force (i.e.$~$with a coupling to protons suppressed compared to its coupling to neutrons) with a characteristic range of $\sim\,$10 fm and milli-charged couplings to first generation quarks and electrons. We show that such a ``protophobic'' gauge boson is consistent with all available experimental constraints and we discuss several ways to embed this new particle into an anomaly-free extension of the Standard Model. One of the most appealing theories of this type is a model with gauged baryon number, in which the new gauge boson kinetically mixes with the photon, and provides a portal to the dark matter sector. Apart from the phenomenological richness of the model, it can also alleviate the current 3.6$\sigma$ discrepancy between the predicted and measured values of the muon's anomalous magnetic moment. [Preview Abstract] |
Saturday, January 28, 2017 2:42PM - 3:18PM |
C16.00003: Parity violation in few-nucleon systems Invited Speaker: Matthias Schindler Parity-violating interactions between nucleons are the manifestation of an interplay between strong and weak quark-quark interactions at the hadronic level. Because of the short range of the weak interactions, these parity-violating forces provide a unique probe of low-energy strong interactions. In addition, a better understanding of parity violation in nuclei could also shed light on problems in the hadronic weak interactions involving strange quarks. An ongoing experimental program is mapping out the weak component of the nuclear force in few-nucleon systems. Recent theoretical progress in analyzing and interpreting hadronic parity violation in such systems, based on effective field theory methods, will be described. [Preview Abstract] |
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