327 research outputs found

    Causal Fermion Systems: An Elementary Introduction to Physical Ideas and Mathematical Concepts

    Full text link
    We give an elementary introduction to the theory of causal fermion systems, with a focus on the underlying physical ideas and the conceptual and mathematical foundations.Comment: 24 pages, LaTeX, 3 figures, minor changes (published version

    Semileptonic Hyperon Decays

    Full text link
    We review the status of hyperon semileptonic decays. The central issue is the VusV_{us} element of the CKM matrix, where we obtain Vus=0.2250(27)V_{us}=0.2250 (27). This value is of similar precision, but higher, than the one derived from Kl3K_{l3}, and in better agreement with the unitarity requirement, Vud2+Vus2+Vub2=1|V_{ud}|^2+|V_{us}|^2+|V_{ub}|^2=1. We find that the Cabibbo model gives an excellent fit of the existing form factor data on baryon beta decays (χ2=2.96\chi^{2} = 2.96 for 3 degrees of freedom) with F+D=1.2670±0.0030F + D = 1.2670 \pm 0.0030, FD=0.341±0.016F - D = -0.341 \pm 0.016, and no indication of flavour-SU(3)-breaking effects. We indicate the need of more experimental and theoretical work, both on hyperon beta decays and on Kl3K_{l3} decays.Comment: 37 pages, 8 figures, 4 tables, Final version of this material is scheduled to appear in the Annual Review of Nuclear and Particle Science Vol. 5

    JEWEL 2.0.0: directions for use

    Get PDF

    Aspects Of Heavy Quark Theory

    Full text link
    Recent achievements in the heavy quark theory are critically reviewed. The emphasis is put on those aspects which either did not attract enough attention or cause heated debates in the current literature. Among other topics we discuss (i) basic parameters of the heavy quark theory; (ii) a class of exact QCD inequalities; (iii) new heavy quark sum rules; (iv) virial theorem; (v) applications (|V_cb| from the total semileptonic width and from the B->D* transition at zero recoil). In some instances new derivations of the previously known results are given, or new aspects addressed. In particular, we dwell on the exact QCD inequalities. Furthermore, a toy model is considered that may shed light on the controversy regarding the value of the kinetic energy of heavy quarks obtained by different methods.Comment: 67 pages, 6 Figures; plain LaTeX. Changes: Some equations in Sect.4 related to spin-nonsinglet sum rules are corrected. The references are updated

    Energy Level Diagrams for Black Hole Orbits

    Full text link
    A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy to atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational numbers, we are able to construct periodic tables of orbits and energy level diagrams of the accessible states around black holes. We also present a closed form expression for the rational q, thereby quantifying zoom-whirl behavior in terms of spin, energy, and angular momentum. The black hole atom is not just a theoretical construct, but corresponds to extant astrophysical systems detectable by future gravitational wave observatories.Comment: 8 page

    Do Proton-Proton collisions at the LHC energies produce Droplets of Quark-Gluon Plasma?

    Full text link
    The proton-proton (pppp) collisions at the Large Hadron Collider (LHC), CERN, Switzerland has brought up new challenges and opportunities in understanding the experimental findings in contrast to the conventional lower energy pppp collisions. Usually pppp collisions are used as the baseline measurement at the GeV and TeV energies in order to understand a possible high density QCD medium formation in heavy-ion collisions. However, the TeV pppp collisions have created a new domain of research, where scientists have started observing heavy-ion-like features (signatures) in high-multiplicity pppp collisions. This warrants a relook into TeV pppp collisions, if at all QGP-droplets are produced in such collisions. In this presentation, I discuss some of the new findings and concepts emerging out in pppp collisions at the LHC energies along with some of the new emergent phenomena in particle production.Comment: 5 pages, 4-captioned figures, Presented in the plenary session of Workshop on Frontiers in High Energy Physics (FHEP-2019), Hyderabad, India (To appear in Springer Proc.

    The temperature and entropy of CFT on time-dependent backgrounds

    Get PDF
    We express the AdS-Schwarzschild black-hole configuration in coordinates such that the boundary metric is of the FLRW type. We review how this construction can be used in order to calculate the stress-energy tensor of the dual CFT on the FLRW background. We deduce the temperature and entropy of the CFT, which are related to the temperature and entropy of the black hole. We find that the entropy is proportional to the area of an apparent horizon, different from the black-hole event horizon. For a dS boundary we reproduce correctly the intrinsic temperature of dS space.Comment: 19 pages, major revision, several comments added, version to appear in JHE

    Dark Force Detection in Low Energy e-p Collisions

    Get PDF
    We study the prospects for detecting a light boson X with mass m_X < 100 MeV at a low energy electron-proton collider. We focus on the case where X dominantly decays to e+ e- as motivated by recent "dark force" models. In order to evade direct and indirect constraints, X must have small couplings to the standard model (alpha_X 10 MeV). By comparing the signal and background cross sections for the e- p e+ e- final state, we conclude that dark force detection requires an integrated luminosity of around 1 inverse attobarn, achievable with a forthcoming JLab proposal.Comment: 38 pages, 19 figures; v2, references adde

    Vectorlike Confinement at the LHC

    Full text link
    We argue for the plausibility of a broad class of vectorlike confining gauge theories at the TeV scale which interact with the Standard Model predominantly via gauge interactions. These theories have a rich phenomenology at the LHC if confinement occurs at the TeV scale, while ensuring negligible impact on precision electroweak and flavor observables. Spin-1 bound states can be resonantly produced via their mixing with Standard Model gauge bosons. The resonances promptly decay to pseudo-Goldstone bosons, some of which promptly decay to a pair of Standard Model gauge bosons, while others are charged and stable on collider time scales. The diverse set of final states with little background include multiple photons and leptons, missing energy, massive stable charged particles and the possibility of highly displaced vertices in dilepton, leptoquark or diquark decays. Among others, a novel experimental signature of resonance reconstruction out of massive stable charged particles is highlighted. Some of the long-lived states also constitute Dark Matter candidates.Comment: 33 pages, 6 figures. v4: expanded discussion of Z_2 symmetry for stability, one reference adde
    corecore