Nuclear Theory·nucl-th

Thursday·May 30, 2019

8 papers—5 primary·3 cross-listed

06
On the Equivalence of Three-Particle Scattering Formalisms
A. W. Jackura🇺🇸 · S. M. Dawid🇺🇸 · C. Fernández-Ramírez🇲🇽 · V. Mathieu🇪🇸 · M. Mikhasenko🇨🇭 · A. Pilloni🇮🇹 · S. R. Sharpe🇺🇸 · A. P. Szczepaniak🇺🇸
In recent years, different on-shell $3 \to 3$ scattering formalisms have been proposed to be applied to both lattice QCD and infinite volume scattering processes. We prove that the formulation in the infinite volume presented by Hansen and Sharpe in Phys.~Rev.~D92, 114509 (2015) and subsequently Briceño, Hansen, and Sharpe in Phys.~Rev.~D95, 074510 (2017) can be recovered from the $B$ -matrix representation, derived on the basis of $S$ -matrix unitarity, presented by Mai {\em et al.} in Eur.~Phys.~J.~A53, 177 (2017) and Jackura {\em et al.} in Eur.~Phys.~J.~C79, 56 (2019). Therefore, both formalisms in the infinite volume are equivalent and the physical content is identical. Additionally, the Faddeev equations are recovered in the non-relativistic limit of both representations.
↳ hep-phhep-latnucl-thPRD(2019)·93 citations
07
New physics via pion capture and simple nuclear reactions
Chien-Yi Chen🇨🇦 · David McKeen🇨🇦 · Maxim Pospelov🇨🇦
Light, beyond-the-standard-model particles $X$ in the 1-100 MeV mass range can be produced in nuclear and hadronic reactions but would have to decay electromagnetically. We show that simple and well-understood low-energy hadronic processes can be used as a tool to study $X$ production and decay. In particular, the pion capture process $π^{-} p \to X n \to e^{+} e^{-} n$ can be used in a new experimental setup to search for anomalies in the angular distribution of the electron-positron pair, which could signal the appearance of dark photons, axion-like particles and other exotic states. This process can be used to decisively test the hypothesis of a new particle produced in the $^{7} Li + p$ reaction. We also discuss a variety of other theoretically clean hadronic processes, such as $p + D (T)$ fusion, as a promising source of $X$ particles.
↳ hep-phhep-exnucl-exnucl-thPRD(2019)·8 citations
08
Dynamics of Phase Separation from Holography
Maximilian Attems🇪🇸 · Yago Bea🇪🇸 · Jorge Casalderrey-Solana🇪🇸 · David Mateos🇪🇸 · Miguel Zilhao🇪🇸
We use holography to develop a physical picture of the real-time evolution of the spinodal instability of a four-dimensional, strongly-coupled gauge theory with a first-order, thermal phase transition. We numerically solve Einstein's equations to follow the evolution, in which we identify four generic stages: A first, linear stage in which the instability grows exponentially; a second, non-linear stage in which peaks and/or phase domains are formed; a third stage in which these structures merge; and a fourth stage in which the system finally relaxes to a static, phase-separated configuration. On the gravity side the latter is described by a static, stable, inhomogeneous horizon. We conjecture and provide evidence that all static, non-phase separated configurations in large enough boxes are dynamically unstable. We show that all four stages are well described by the constitutive relations of second-order hydrodynamics that include all second-order gradients that are purely spatial in the local rest frame. In contrast, a Müller-Israel-Stewart-type formulation of hydrodynamics fails to provide a good description for two reasons. First, it misses some large, purely-spatial gradient corrections. Second, several second-order transport coefficients in this formulation, including the relaxation times $τ_{π}$ and $τ_{Π}$ , diverge at the points where the speed of sound vanishes.
↳ hep-thgr-qchep-phnucl-thJHEP(2020)·48 citations

Affiliations

first authorsco-authorsvia INSPIRE

On the Equivalence of Three-Particle Scattering Formalisms

New physics via pion capture and simple nuclear reactions

Dynamics of Phase Separation from Holography

Affiliations