The framework of point form relativistic quantum mechanics is used to construct interacting four-momentum operators in terms of creation and annihilation operators of underlying constituents. It is shown how to write the creation and annihilation operators in terms of discrete momenta, arising from discrete subgroups of the Lorentz group, in such a way that the Poincaré commutation relations ar...

We analyze the indirect astrophysical signatures of secluded models of WIMP dark matter, characterized by a weak-scale rate for annihilation into light MeV-scale mediators which are metastable to decay into Standard Model states. Such scenarios allow a significant enhancement of the annihilation cross section in the galactic halo relative to its value at freeze-out, particularly when the mediat...

Monolayer MoS2 is a direct-gap two-dimensional semiconductor that exhibits strong electron-hole interactions, leading to the formation of stable excitons and trions. Here we report the existence of efficient exciton-exciton annihilation, a four-body interaction, in this material. Exciton-exciton annihilation was identified experimentally in ultrafast transient absorption measurements through th...

We present a geometric interpretation of the so-called annihilation range in reactions of the type p̄p → two light mesons based upon Lorentz effects in the highly relativistic final states (γ = Ecm/2mc ≃ 6.8 − 8.0). Lorentz-boosted meson wave functions, within the framework of the constituent quark model, result in a richer angular dependence of the annihilation amplitudes and thus in higher par...

We review the prospects for probing new physics with neutrino astrophysics. High energy neutrinos provide an important means of accessing physics beyond the electroweak scale. Neutrinos have a number of advantages over conventional astronomy and, in particular, carry information encoded in their flavor degree of freedom which could reveal a variety of exotic neutrino properties. We also outline...

In this note, we introduce a graph invariant called the annihilation number and show that it is a sharp upper bound on the independence number. While the invariant does not distinguish between different graphs with the same degree sequence – since it is determined solely by the degrees – it still outperforms many well known upper bounds on independence number. The process which leads to the ann...

Recent studies have considered modifications to the standard weakly interacting massive particle scenario in which the pair annihilation cross section (times relative velocity v) is enhanced by a factor 1/upsilon to approximately 10(-3) in the Galaxy, enough to explain several puzzling Galactic radiation signals. We show that in these scenarios a burst of weakly interacting massive particle ann...

Dilepton production from both pion-pion and kaon-antikaon annihilation in heavy-ion collisions is studied using the relativistic transport model. The formation of a rho meson from pion-pion annihilation and a phi meson from kaon-antikaon annihilation, their propagation in the medium, and their decay into dileptons are explicitly treated. Including the medium modifications of the masses and widt...

From the relic density measurement by WMAP the WIMP annihilation cross section can be determined in a model independent way. If the WIMPS are postulated to be the neutralinos of Supersymmetry, then only a limited region of the supersymmetric parameter space matches this annihilation cross section. It is shown that the resulting positrons, antiprotons and gamma rays from the neutralino annihilat...

Hadronic annihilation rate of 1 heavy quarkonium is given to next-to-leading order in αs and leading order in v using a recently developed factorization formalism which is based on NRQCD. The result includes both the annihilation of P-wave color-singlet QQ̄ component, and the annihilation of S-wave color-octet QQ̄ component of the quarkonium. The notorious infrared divergences due to soft gluons,...