93 research outputs found
ULYSSES, Universal LeptogeneSiS Equation Solver: version 2
No full textULYSSES is a Python package that calculates the baryon asymmetry produced
from leptogenesis in the context of a type-I seesaw mechanism. In this release,
the new features include code which solves the Boltzmann equations for
low-scale leptogenesis; the complete Boltzmann equations for thermal
leptogenesis applying proper quantum statistics without assuming kinetic
equilibrium of the right-handed neutrinos; and, primordial black hole-induced
leptogenesis. ULYSSES version 2 has the added functionality of a pre-provided
script for a two-dimensional grid scan of the parameter space. As before, the
emphasis of the code is on user flexibility, rapid evaluation and is publicly
available at https://github.com/earlyuniverse/ulysses.Comment: 24 pages, 2 figure
Multi-track displaced vertices at B-factories
No full textAbstract We propose a program at B-factories of inclusive, multi-track displaced vertex searches, which are expected to be low background and give excellent sensitivity to non-minimal hidden sectors. Multi-particle hidden sectors often include long-lived particles (LLPs) which result from approximate symmetries, and we classify the possible decays of GeV-scale LLPs in an effective field theory framework. Considering several LLP production modes, including dark photons and dark Higgs bosons, we study the sensitivity of LLP searches with different number of displaced vertices per event and track requirements per displaced vertex, showing that inclusive searches can have sensitivity to a large range of hidden sector models that are otherwise unconstrained by current or planned searches
Enhanced Pauli blocking of light scattering in a trapped Fermi gas
No full textPauli blocking of spontaneous emission by a single excited-state atom has been predicted to be dramatic at low temperature when the Fermi energy EF exceeds the recoil energy ER. The photon scattering rate of a ground-state Fermi gas can also be suppressed by occupation of the final states accessible to a recoiling atom; however, suppression is diminished by scattering events near the Fermi edge. We analyse two new approaches to improve the visibility of Pauli blocking in a trapped Fermi gas. Focusing the incident light to excite preferentially the high-density region of the cloud can increase the blocking signature by 14%, and is most effective at intermediate temperature. Spontaneous Raman scattering between imbalanced internal states can be strongly suppressed at low temperature, and is completely blocked for a final state EF> 4ER in the high imbalance limit. 1
Search for B mesogenesis at BaBar
No full textA new mechanism has been proposed to simultaneously explain the presence of dark matter and the matter-antimatter asymmetry in the Universe. This scenario predicts exotic B -meson decays into a baryon and a dark-sector antibaryon (psi D) with branching fractions accessible at B factories. We present a search for B -> ?psi D decays using data collected by the BABAR experiment at SLAC. This reaction is identified by fully reconstructing the accompanying B meson and requiring the presence of a single ? baryon in the remaining particles. No significant signal is observed, and bounds on the B -> ?psi D branching fraction are derived in the range 0.13-5.2 x 10-5 for 1.0 < m psi D < 4.2 GeV/c2. These results set strong constraints on the parameter space allowed by the theory
Search for B mesogenesis at BaBar
No full textA new mechanism has been proposed to simultaneously explain the presence of dark matter and the matter-antimatter asymmetry in the Universe. This scenario predicts exotic B-meson decays into a baryon and a dark-sector antibaryon (ψD) with branching fractions accessible at B factories. We present a search for B→ΛψD decays using data collected by the BABAR experiment at SLAC. This reaction is identified by fully reconstructing the accompanying B meson and requiring the presence of a single Λ baryon in the remaining particles. No significant signal is observed, and bounds on the B→ΛψD branching fraction are derived in the range 0.13-5.2×10-5 for 1.0<4.2 GeV/c2. These results set strong constraints on the parameter space allowed by the theory
Search for B mesogenesis at B a B ar
No full textA new mechanism has been proposed to simultaneously explain the presence of dark matter and the matter-antimatter asymmetry in the Universe. This scenario predicts exotic B-meson decays into a baryon and a dark-sector antibaryon (ψD) with branching fractions accessible at B factories. We present a search for B→ΛψD decays using data collected by the BABAR experiment at SLAC. This reaction is identified by fully reconstructing the accompanying B meson and requiring the presence of a single Λ baryon in the remaining particles. No significant signal is observed, and bounds on the B→ΛψD branching fraction are derived in the range 0.13-5.2×10-5 for 1.0<mψD<4.2 GeV/c2. These results set strong constraints on the parameter space allowed by the theory
Search for B mesogenesis at BaBar
No full textA new mechanism has been proposed to simultaneously explain the presence of dark matter and the matter-antimatter asymmetry in the Universe. This scenario predicts exotic B -meson decays into a baryon and a dark-sector antibaryon (ψ D ) with branching fractions accessible at B factories. We present a search for B→ΛψD decays using data collected by the BABAR experiment at SLAC. This reaction is identified by fully reconstructing the accompanying B meson and requiring the presence of a single Λ baryon in the remaining particles. No significant signal is observed, and bounds on the B → Λ ψ D branching fraction are derived in the range 0.13 – 5.2 × 10 − 5 for 1.0 < m ψ D < 4.2 GeV / c 2. These results set strong constraints on the parameter space allowed by the theory
Search for an Axionlike Particle in B Meson Decays
No full textAxionlike particles (ALPs) are predicted in many extensions of the standard model, and their masses can naturally be well below the electroweak scale. In the presence of couplings to electroweak bosons, these particles could be emitted in flavor-changing B meson decays. We report herein a search for an ALP, a, in the reaction B±→K±a, a→γγ using data collected by the BABAR experiment at SLAC. No significant signal is observed, and 90% confidence level upper limits on the ALP coupling to electroweak bosons are derived as a function of ALP mass, improving current constraints by several orders of magnitude in the range 0.175 GeV<4.78 GeV
Search for baryogenesis and dark matter in B+ → Λc+ +invisible decays
No full textA mechanism of baryogenesis and dark matter production via B meson oscillations and decays has recently been proposed to explain the observed dark matter abundance and matter-antimatter asymmetry in the universe. This mechanism introduces a low-mass dark sector particle (ψD) with a nonzero baryonic charge. We present a search for this new state in B+→Λc+ψD decays using data collected at the Υ(4S) resonance by the BABAR detector at SLAC, corresponding to an integrated luminosity of 431.0 fb-1. The search leverages the full reconstruction of the B- meson in Υ(4S)→B+B- decays, accompanied by the reconstruction of a Λc+, to infer the presence of ψD. No significant signal is observed, and limits on the B+→Λc+ψD branching fraction are set at the level of 1.6×10-4 at 90% confidence level for 0.94<2.99 GeV. These results set strong constraints on the parameter space allowed by B-meson baryogenesis
Search for baryogenesis and dark matter in B+ → Λc+ +invisible decays
No full textA mechanism of baryogenesis and dark matter production via B meson oscillations and decays has recently been proposed to explain the observed dark matter abundance and matter-antimatter asymmetry in the universe. This mechanism introduces a low-mass dark sector particle (ψD) with a nonzero baryonic charge. We present a search for this new state in B+→Λc+ψD decays using data collected at the Υ(4S) resonance by the BABAR detector at SLAC, corresponding to an integrated luminosity of 431.0 fb-1. The search leverages the full reconstruction of the B- meson in Υ(4S)→B+B- decays, accompanied by the reconstruction of a Λc+, to infer the presence of ψD. No significant signal is observed, and limits on the B+→Λc+ψD branching fraction are set at the level of 1.6×10-4 at 90% confidence level for 0.94<2.99 GeV. These results set strong constraints on the parameter space allowed by B-meson baryogenesis
- …
