16422980
Rare radiative b decays in the standard model
A status report on the theory and phenomenology of rare radiative $B$ decays in the standard model is presented with emphasis on the measured decays $B \to X_s \gamma$ and $B \to K^* \gamma$. Standard model is in agreement with experiments though this comparison is not completely quantitative due to imprecise data and lack of the complete next-to-leading order contributions to the decay rates. Despite this, it is possible to extract non-perturbative parameters from the shape of the photon energy spectrum in $B \to X_s \gamma$, such as the $b$-quark mass and the kinetic energy of the $b$ quark in $B$ hadron. The measured decay rate $\BBGAMAXS =(2.32\pm 0.67) \times 10^{-4}$ can also be used to extract the CKM ratio $\absvts/\absvcb$, yielding $\absvts/\absvcb =1.10 \pm 0.43$. Issues bearing on the determination of the parameters of the CKM matrix from the CKM-suppressed decays $B \to X_d + \gamma$ and $B \to (\rho,\omega) + \gamma$ are also discussed. It is argued that valuable and independent constraints on the CKM matrix can be obtained from the measurements of these decays, in particular those involving neutral $B$-mesons (to appear in the Proceedings of the XXXth Rencontres de Moriond ``Electroweak Interactions and Unified Theories'', Les Arcs, France, March 1995).
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.
119012010
$B$ Decays, Flavour Mixings and CP Violation in the Standard Model
These lectures review the progress made in our present understanding of $B$ decays. The emphasis here is on applications of QCD to $B$ decays and the attendant perturbative and non-perturbative uncertainties, which limit present theoretical precision in some cases but the overall picture that emerges is consistent with the standard model (SM). This is illustrated by quantitatively analyzing some of the key measurements in $B$ physics.
120435310
A calculation of the electromagnetic vacuum polarization in lattice QCD
Abstract We present a calculation of the electromagnetic current vacuum polarization in the framework of lattice QCD. A 16th order hopping-parameter expansion of 〈 J em μ J em μ 〉 0 is reported on an 8 4 lattice. It gives a reasonable description of the mass m J ψ and the electromagnetic current-vector meson coupling constant f J ψ , in the vector meson dominance approximation.
117634637
The LHC signatures of the extended gauge structures in supersymmetry
7193216
Tetraquark interpretation of the BELLE data on the anomalous Upsilon(1S)pi+ pi- and Upsilon(2S)pi+ pi- production near the Upsilon(5S) resonance.
We analyze the Belle data [K. F. Chen (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008); I. Adachi (Belle Collaboration), arXiv:0808.2445] on the processes e+ e- --> Upsilon(1S)pi+ pi-, Upsilon(2S)pi+ pi- near the peak of the Upsilon(5S) resonance, which are found to be anomalously large in rates compared to similar dipion transitions between the lower Upsilon resonances. Assuming these final states arise from the production and decays of the J(PC)=1(--) state Y(b)(10,890), which we interpret as a bound (diquark-antidiquark) tetraquark state [bq][bq], a dynamical model for the decays Y(b) --> Upsilon(1S)pi+ pi-, Upsilon(2S)pi+ pi- is presented. Depending on the phase space, these decays receive significant contributions from the scalar 0(++) states, f0(600) and f0(980), and from the 2(++) qq-meson f(2)(1270). Our model provides excellent fits for the decay distributions, supporting Y(b) as a tetraquark state.
119277394
No existence of black holes at LHC due to minimal length in quantum gravity
A bstractWe investigate the impact of the Generalized Uncertainty Principle (GUP), proposed by some approaches to quantum gravity such as String Theory and Doubly Special Relativity Theories (DSR) on the production of mini black holes, and show that the minimum black hole mass is formed at energies higher than the energy scales of LHC which possibly agrees with the recent experimental results of LHC [1, 2].
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.