117844307
Results from the LEP and SLAC Colliders — An Update
Recent experimental results from the Large Electron Positron Collider LEP and the SLAC Linear Collider SLC are briefly summarized in this note. The data and analyses shown are selective and only those aspects having a direct (or indirect) bearing on the searches for the top quark and/or scalar particles (Higgs bosons and scalar leptons) are included here.
13281897
Majorana neutrinos and same-sign dilepton production at LHC and in rare meson decays
Abstract. We discuss same-sign dilepton production mediated by Majorana neutrinos in high-energy proton–proton collisions $pp\rightarrow \ell^+ \ell^{\prime +}X$ for $\ell, \ell^\prime = e, \mu, \tau$ at the LHC energy $ s^{1/2} =14$ TeV, and in the rare decays of the $K, D, D_s$, and B mesons of the type $M^+\rightarrow M^{\prime -}\ell ^+\ell ^{\prime+}$. For the pp reaction, assuming one heavy Majorana neutrino of mass $m_N$, we present discovery limits in the $\left(m_N,\left|U_{\ell N}U_{\ell^\prime N}\right|\right)$ plane where $U_{\ell N}$ are the mixing parameters. Taking into account the present limits from low-energy experiments, we show that at LHC one has sensitivity to heavy Majorana neutrinos up to a mass $m_N\leq 2--5$ TeV in the dilepton channels $\mu\mu, \tau\tau$, and $\mu\tau$, but the dilepton states $e\ell$ will not be detectable due to the already existing constraints from neutrinoless double beta decay. We work out a large number of rare meson decays, both for the light and heavy Majorana neutrino scenarios, and argue that the present experimental bounds on the branching ratios are too weak to set reasonable limits on the effective Majorana masses.
121188586
Heavy quark physics at HERA
Abstract A brief overview of the anticipated heavy quark physics at HERA is given. The topics discussed include heavy quark photo- and leptoproduction cross sections at HERA calculated in the context of perturbative QCD, various mechanisms of J / ϕ -leptoproduction and their rates, determination of the gluon density of the proton using open and bound charmed hadrons, and rare D 0 -meson decays. Some selected aspects of B -Physics at HERA are also discussed.
117634637
The LHC signatures of the extended gauge structures in supersymmetry
117235251
B Decays in the Standard Model - Status and Perspectives
These lectures review some of the progress made in the quantitative understanding of B decays. The emphasis here is on applications of QCD using perturbative and non-perturbative techniques. In some cases, however, phenomenological models must at present be invoked to make meaningful comparison with data. The resulting picture is consistent with the standard model (SM) and this agreement is quantified in terms of the branching ratios, mixing probabilities, and lifetimes which measure the charge current and effective flavour changing neutral current transitions involving B hadrons. This, in turn, enables a determination of five of the nine elements of the quark mixing matrix. We discuss several proposals on improving the precision on the parameters of this matrix in forthcoming experiments. Issues intimately related to the quark mixing matrix such as the profile of the unitarity triangle and CP-violating asymmetries in B decays are discussed. In particular, we emphasize the role of rare B decays and B^0 - $\overline{B^0}$ mixings in testing the SM quantitatively and in searching for physics beyond the SM.
10853970
Rare B decays in the standard model
Abstract We discuss the electromagnetic-penguin-dominated radiative B decays B → X s + γ , B ±(0) → K ∗±(0) + γ , and B s → φ + γ in the context of the Standard Model (SM) and their Cabibbo-Kobayashi-Maskawa (CKM)-suppressed counterparts, B → X d + γ , B ± → ϱ ± + γ , B 0 → ( ϱ 0 , ω ) + γ , and B s → K ∗0 + γ , using QCD sum rules for the exclusive decays. The importance of these decays in determining the parameters of the CKM matrix [1] is emphasized. The semileptonic decays B → X s l + l − are also discussed in the context of the SM and their role in determining the Wilson coefficients of the effective theory is stressed. Comparison with the existing measurements are made and SM-based predictions for a large number of rare B decays are presented.
118350400
The Generalized Uncertainty Principle and Quantum Gravity Phenomenology
In this article we examine a Generalized Uncertainty Principle which differs from the Heisenberg Uncertainty Principle by terms linear and quadratic in particle momenta, as proposed by the authors in an earlier paper. We show that this affects all Hamiltonians, and in particular those which describe low energy experiments. We discuss possible observational consequences. Further, we also show that this indicates that space may be discrete at the fundamental level.
120051381
Discreteness of space from GUP II: Relativistic wave equations
Abstract Various theories of Quantum Gravity predict modifications of the Heisenberg Uncertainty Principle near the Planck scale to a so-called Generalized Uncertainty Principle (GUP). In some recent papers, we showed that the GUP gives rise to corrections to the Schrodinger equation, which in turn affect all quantum mechanical Hamiltonians. In particular, by applying it to a particle in a one-dimensional box, we showed that the box length must be quantized in terms of a fundamental length (which could be the Planck length), which we interpreted as a signal of fundamental discreteness of space itself. In this Letter, we extend the above results to a relativistic particle in a rectangular as well as a spherical box, by solving the GUP-corrected Klein–Gordon and Dirac equations, and for the latter, to two and three dimensions. We again arrive at quantization of box length, area and volume and an indication of the fundamentally grainy nature of space. We discuss possible implications.
46115571
A proposal for testing quantum gravity in the lab
Attempts to formulate a quantum theory of gravitation are collectively known as {\it quantum gravity}. Various approaches to quantum gravity such as string theory and loop quantum gravity, as well as black hole physics and doubly special relativity theories predict a minimum measurable length, or a maximum observable momentum, and related modifications of the Heisenberg Uncertainty Principle to a so-called generalized uncertainty principle (GUP). We have proposed a GUP consistent with string theory, black hole physics and doubly special relativity theories and have showed that this modifies all quantum mechanical Hamiltonians. When applied to an elementary particle, it suggests that the space that confines it must be quantized, and in fact that all measurable lengths are quantized in units of a fundamental length (which can be the Planck length). On the one hand, this may signal the breakdown of the spacetime continuum picture near that scale, and on the other hand, it can predict an upper bound on the quantum gravity parameter in the GUP, from current observations. Furthermore, such fundamental discreteness of space may have observable consequences at length scales much larger than the Planck scale. Because this influences all the quantum Hamiltonians in an universal way, it predicts quantum gravity corrections to various quantum phenomena. Therefore, in the present work we compute these corrections to the Lamb shift, simple harmonic oscillator, Landau levels, and the tunneling current in a scanning tunneling microscope.