17946700
CP-violation in charm
I review recent results in theoretical and experimental analyses of CP-violation in charmed transitions, paying particular attention to constraints on parameters of beyond the Standard Model interactions.
17946700
CP-violation in charm
I review recent results in theoretical and experimental analyses of CP-violation in charmed transitions, paying particular attention to constraints on parameters of beyond the Standard Model interactions.
35942201
Is B-->Xs gamma equal to b-->s gamma ? Spectator contributions to rare inclusive B decays.
In $B \to X_s \gamma $ there are perturbative $QCD$ corrections at order $\alpha_s$ not only to the single quark line process $ b \to s \gamma$ but also coming from a set of diagrams where the weak interaction vertex involves a gluon which interacts with the spectator quark in the B hadron. We discuss the impact of the full set of these diagrams. These can influence the decay rate and also the line shape of the photon spectrum as they favor a softer photon energy than does the pure spectator decay $b \to s \gamma$. A subset of these diagrams generate differences in the decay rates for charged and neutral B's , $B^+ \to X_s \gamma$ vs. $B^0 \to X_s \gamma$ which can be searched for experimentally, although our calculation indicates that the effect will be hard to observe. Bound state effects turn out to be required to give rise to spectator corrections to the decay rate at order $\alpha_s$. The resulting contribution to the total rate is rather small (of about $5 \% $ ), although the effect is somewhat larger on portions of the photon spectrum.
204926535
Angles from $B$ Decays with Charm
Proceedings of the CKM 2005 Workshop (WG5), UC San Diego, 15-18 March 2005.
117694102
B0 anti-B0 mixing beyond factorization
We present a calculation of the B°-B° mixing matrix element in the framework of QCD sum rules for three-point functions. We compute α s corrections to a three-point function at the three-loop level in QCD perturbation theory, which allows one to extract the matrix element with next-to-leading order (NLO) accuracy. This calculation is imperative for a consistent evaluation of experimentally measured mixing parameters since the coefficient functions of the effective Hamiltonian for B 0 -B 0 mixing are known at NLO. We find that radiative corrections violate factorization at NLO; this violation is under full control and amounts to 10%. The resulting value of the B parameter is found to be B B (m b ) = 1 + 0.1 P T - 0.05 n o n - P T .
118410106
Lifetime difference in Bs mixing: Standard Model and beyond
Abstract We present a calculation of 1 / m b 2 corrections to the lifetime differences of B s mesons Δ Γ B s in the heavy-quark expansion. We find that they are small to significantly affect Δ Γ B s and present the result for lifetime difference including non-perturbative 1 / m b and 1 / m b 2 corrections. We also analyze the generic Δ B = 1 New Physics contributions to Δ Γ B s and provide several examples.
118691409
Gödel-type universes and chronology protection in Hořava–Lifshitz gravity
Abstract In the attempts toward a quantum gravity theory, general relativity faces a serious difficulty since it is non-renormalizable theory. Hořava–Lifshitz gravity offers a framework to circumvent this difficulty, by sacrificing the local Lorentz invariance at ultra-high energy scales in exchange of power-counting renormalizability. The Lorentz symmetry is expected to be recovered at low and medium energy scales. If gravitation is to be described by a Hořava–Lifshitz gravity theory there are a number of issues that ought to be reexamined in its context, including the question as to whether this gravity incorporates a chronology protection, or particularly if it allows Godel-type solutions with violation of causality. We show that Hořava–Lifshitz gravity only allows hyperbolic Godel-type space-times whose essential parameters m and ω are in the chronology respecting intervals, excluding therefore any noncausal Godel-type space-times in the hyperbolic class. There emerges from our results that the famous noncausal Godel model is not allowed in Hořava–Lifshitz gravity. The question as to whether this quantum gravity theory permits hyperbolic Godel-type solutions in the chronology preserving interval of the essential parameters is also examined. We show that Hořava–Lifshitz gravity not only excludes the noncausal Godel universe, but also rules out any hyperbolic Godel-type solutions for physically well-motivated perfect-fluid matter content.
123177090
Two-dimensional Lorentz-violating Chern-Simons-like action
Abstract We demonstrate generation of the two-dimensional Chern–Simons-like Lorentz-breaking action via an appropriate Lorentz-breaking coupling of scalar and spinor fields at zero as well as at the finite temperature and via the noncommutative fields method and study the dispersion relations corresponding to this action.
209835249
f(R)-Brane
Abstract We investigate the existence of brane solutions in braneworld scenarios described by real scalar field in the presence of modified f ( R ) gravity with a single extra dimension. In the case of constant curvature, we obtain first-order differential equations which solve the equations of motion and ease the search for explicit analytical solutions. Several examples of current interest are investigated to illustrate the results of the present work.
119195088
Effective superpotential in the generic higher-derivative superfield supersymmetric three-dimensional gauge theory
We formulate a generic three-dimensional superfield higher-derivative gauge theory coupled to the matter, which, in certain cases reduces to the three-dimensional scalar super-QED, or supersymmetric Maxwell-Chern-Simons or Chern-Simons theories with matter. For this theory, we explicitly calculate the one-loop effective potential.
119127214
On the aether-like Lorentz-breaking action for the electromagnetic field
We study the generation of aether-like Lorentz-breaking actions in three, four and five dimensions via an appropriate Lorentz-breaking coupling of electromagnetic and spinor fields. Special attention is given to the four-dimensional case where we discuss the issue of ambiguities.