The default assumption of early universe cosmology is that the postinflationary universe was radiation dominated until it was about 47000 years old. Direct evidence for the radiation dominated epoch extends back until nucleosynthesis, which began during the first second. However there are theoretical reasons to prefer a period of earlier matter domination, prior to nucleosynthesis, e.g. due to late decaying massive particles needed to explain baryogenesis. Axion cosmology is quantitatively affected by an early period of matter domination, with a different axion mass range preferred and greater inhomogeneity produced on small scales. In this work we show that such increased inhomogeneity can lead to the formation of axion miniclusters in axion parameter ranges that are different from those usually assumed. If the reheating temperature is below 58 MeV, axion miniclusters can form even if the axion field is present during inflation and has been previously homogenized. The upper bound on the typical initial axion minicluster mass is raised from 10 −10 M⊙ to 10 −7 M⊙, where M⊙ is a solar mass. These results may have consequences for indirect detection of axion miniclusters, and could conceivably probe the thermal history of the universe before nucleosynthesis.PACS numbers:

We show how CP violating B meson oscillations in conjunction with baryon number violating decays can generate the cosmological asymmetry between matter and anti-matter, and explore the parameter space of a simple, self-contained model, which can be tested via exotic B meson decays, and via the charge asymmetry in semi-leptonic decays of neutral B mesons.PACS numbers: I. INTRODUCTIONBaryogenesis-generating the cosmological asymmetry between matter and anti-matter-requires physics beyond the Standard Model (SM). The pioneering work of Sakharov[1] found three necessary conditions: baryon number violation, C and CP violation, and departure from thermal equilibrium. Baryon number violation occurs non-perturbatively in the Standard Model [2]. CP violation also occurs, however the standard model CP violation appears to be too small to explain the observed baryon asymmetry. Finally, the minimal Standard Model contains no mechanism for departure from thermal equilibrium.Recent work [3,4] has shown the possibility for low energy baryogenesis via the oscillations of neutral hadrons, in conjunction with new sources of CP and baryon number violation. In ref.[4], the oscillating hadrons were mesinos-bound states of a quark and an anti-squark. In that work a relatively long-lived squark decayed into anti-quarks via baryon number violating R-parity violating decays. A minimal model to capture this physics was studied in detail-that model contained three neutral Majorana fermions ('neutralinos') and a color triplet scalar ('squark'). The same model, in a different parameter region with lighter neutralinos, was shown to lead to baryogenesis via potentially observable baryon and CP violating neutral heavy flavor baryon oscillations [3,5]. A similar model, in which baryon number is conserved but also carried by dark matter, was shown to be capable of producing both the visible matter-anti-matter asymmetry and asymmetric dark matter [6] via B-meson decays. In the present work, we reexamine the simpler model of ref. [4], and show that for a different parameter range that was not considered in the previous work, baryon number violating decays of B 0 mesons are allowed by experiment, potentially observable, and could be the explanation for baryogenesis.The baryogenesis scenario described here begins in the pre-nucleosynthesis early universe with the decays of a long lived scalar into b−quarks and anti-quarks. These * Electronic address: anelson@phys.washington.edu † Electronic address: huangyu@uw.edu

No abstract

No abstract

Low-scale baryogenesis and dark matter generation can occur via the production of neutral B mesons at MeV temperatures in the early Universe, which undergo CP-violating oscillations and subsequently decay into a dark sector. In this work, we discuss the consequences of realizing this mechanism in a supersymmetric model with an unbroken U (1) R symmetry which is identified with baryon number. B mesons decay into a dark sector through a baryon number conserving operator mediated by TeV scale squarks and a GeV scale Dirac bino. The dark sector particles can be identified with sterile neutrinos and their superpartners in a type-I seesaw framework for neutrino masses. The sterile sneutrinos are sufficiently long lived and constitute the dark matter. The produced matter-antimatter asymmetry is directly related to observables measurable at B factories and hadron colliders, the most relevant of which are the semileptonic-leptonic asymmetries in neutral B meson systems and the inclusive branching fraction of B mesons into hadrons and missing energy. We discuss model independent constraints on these experimental observables before quoting predictions made in the supersymmetric context. Constraints from astrophysics, neutrino physics and flavor observables are studied, as are potential LHC signals with a focus on novel long lived particle searches which are directly linked to properties of the dark sector.