On CPT Symmetry: Cosmological, Quantum-Gravitational and other possible violations and their phenomenology

I discuss various ways in which CPT symmetry may be violated, and their phenomenology in current or immediate future experimental facilities, both terrestrial and astrophysical. Specifically, I discuss first violations of CPT symmetry due to the impossibility of defining a scattering matrix as a consequence of the existence of microscopic or macroscopic space-time boundaries, such as Planck-scale Black-Hole (event) horizons, or cosmological horizons due to the presence of a (positive) cosmological constant in the Universe. Second, I discuss CPT violation due to breaking of Lorentz symmetry, which may characterize certain approaches to quantum gravity, and third, I describe models of CPT non invariance due to violations of locality of interactions. In each of the above categories I discuss experimental sensitivities. I argue that the majority of Lorentz-violating cases of CPT breaking, with minimal (linear) suppression by the Planck-mass scale, are already excluded by current experimental tests. There are however some (stringy) models which can evade these constraints.Comment: 27 pages latex, Conference talk Beyond the Desert 200

Simultaneous Extraction of the Fermi constant and PMNS matrix elements in the presence of a fourth generation

Several recent studies performed on constraints of a fourth generation of quarks and leptons suffer from the ad-hoc assumption that 3 x 3 unitarity holds for the first three generations in the neutrino sector. Only under this assumption one is able to determine the Fermi constant G_F from the muon lifetime measurement with the claimed precision of G_F = 1.16637 (1) x 10^-5 GeV^-2. We study how well G_F can be extracted within the framework of four generations from leptonic and radiative mu and tau decays, as well as from K_l3 decays and leptonic decays of charged pions, and we discuss the role of lepton universality tests in this context. We emphasize that constraints on a fourth generation from quark and lepton flavour observables and from electroweak precision observables can only be obtained in a consistent way if these three sectors are considered simultaneously. In the combined fit to leptonic and radiative mu and tau decays, K_l3 decays and leptonic decays of charged pions we find a p-value of 2.6% for the fourth generation matrix element |U_{e 4}|=0 of the neutrino mixing matrix.Comment: 19 pages, 3 figures with 16 subfigures, references and text added refering to earlier related work, figures and text in discussion section added, results and conclusions unchange

Determination of sin2 θeff w using jet charge measurements in hadronic Z decays

The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing the original quark and antiquark is measured for bb̄ and cc̄ events in subsamples selected by their long lifetimes or using fast D*'s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation between charges of opposite hemispheres and agrees with predictions of hadronisation models with a precision of 2%. It is shown that differences between light quark charge separations and the measured average can be determined using hadronisation models, with systematic uncertainties constrained by measurements of inclusive production of kaons, protons and A's. The separations are used to measure the electroweak mixing angle precisely as sin2 θeff w = 0.2322 ± 0.0008(exp. stat.) ±0.0007(exp. syst.) ± 0.0008(sep.). The first two errors are due to purely experimental sources whereas the third stems from uncertainties in the quark charge separations

A precision measurement of electroweak parameters in neutrino-nucleon scattering

The CCFR collaboration reports a precise measurement of electroweak parameters derived from the ratio of neutral-current to charged-current cross-sections in neutrino-nucleon scattering at the Fermilab Tevatron. We determine sin2 θ(on-shell)W = 0.2236 ± 0.0028 (expt.) ± 0.0030 (model) for Mtop = 175 GeV, MHiggs = 150 GeV. This is equivalent to MW = 80.35 ± 0.21 GeV. The good agreement of this measurement with Standard Model expectations implies the exclusion of additional vvqq contact interactions at 95% confidence at a mass scale of 1-8 TeV, depending on the form of the contact interaction

A precision measurement of electroweak parameters in neutrino-nucleon scattering

The CCFR collaboration reports a precise measurement of electroweak parameters derived from the ratio of neutral-current to charged-current cross-sections in neutrino-nucleon scattering at the Fermilab Tevatron. We determine sin θ = 0.2236 ± 0.0028 (expt.) ± 0.0030 (model) for M = 175 GeV, M = 150 GeV. This is equivalent to M = 80.35 ± 0.21 GeV. The good agreement of this measurement with Standard Model expectations implies the exclusion of additional vvqq contact interactions at 95% confidence at a mass scale of 1-8 TeV, depending on the form of the contact interaction. 2 (on-shell) W top Higgs

Further evidence for the decay k+ → π+νν̄

The rare kaon decay K+→π+νν̄ was observed in a data set with comparable sensitivity. The observable signature for K+→π+νν̄ decay from kaons involved the π+ track and π+ decay products. The maximum pion momentum from K+→π+νν̄ decay at rest was found to be 227 MeV/c

Physics at a Fermilab Proton Driver

This report documents the physics case for building a 2 MW, 8 GeV superconducting linac proton driver at Fermilab

Nonperturbative Strange Sea in Proton Using Wave Functions Inspired by Light Front Holography

We use different light-front wave functions (two inspired by the AdS/QCD formalism), together with a model of the nucleon in terms of meson–baryon fluctuations to calculate the nonperturbative (intrinsic) contribution to the s(x)−s¯(x) asymmetry of the proton sea. The holographic wave functions for an arbitrary number of constituents, recently derived by us, give results quite close to known parametrizations that appear in the literature