K -> pi gamma decays and space-time noncommutativity

We propose the K -> pi gamma decay mode as a signature of the violation of the Lorentz invariance and the appearance of new physics via space-time noncommutativity.Comment: 3 pages, 1 figure included, version to appear in Phys. Rev.

Neleptonski B raspadi bez promjene sarma i stranosti

Decay rates of the B-meson are studied through charmless and strangless transitions into π, ρ , ω and γ systems. The important features of these modes are their clean signatures. The CLEO II collaboration has recently reported the value BR(B0 → π +π −) = (1.3 +0.8 −0.6 ± 0.2) × 10−5 . This value is tests our approach to nonleptonic B-decays within the standard model (SM). Since B → γγ is far beyond our experimental reach, we believe that the correct determination of the order of magnitude ∼ 10−10 for BR(B → γγ) provides the most reliable value needed at this moment. The most recent experimental report by the CLEO collaboration on BR(B → K∗γ) = (4.5 ± 1.5 ± 0.9) × 10−5 represents a confirmation of our SM prediction for the B → K∗γ decay. This experimental result, despite of its great importance for the SM and the physics beyond the SM, enables us to predict the value BR (B → ργ) ∼= (3.5 ± 3.3) × 10−6 .Proučavani su raspadi B-mezona bez promjene šarma i stranosti u π, ρ, ω i γ konačna stanja. Važna osobina ovih modova su njihovi čisti eksperimentalni signali. CLEO II kolaboracija nedavno je objavila vrijednost BR(B0 → π +π −) = (1.3 +0.8 −0.6 ± 0.2) × 10−5 . Ta se vrijednost može upotrijebiti za test našeg pristupa objašnjenju neleptonskih B-raspada unutar standardnog modela (SM). Budući je B → γγ daleko izvan našeg eksperimentalnog dosega, vjerujemo da korektno određeni red veličine ∼ 10−10 za BR(B → γγ) predstavlja najrealniju vrijednost potrebnu u ovom trenutku. Najnoviji eksperimentalni izvještaj CLEO kolaboracije o mjerenju BR(B → K∗γ) = (4.5 ± 1.5 ± 0.9) × 10−5 predstavlja potvrdu naše teoretske (SM) predikcije B → K∗γ raspada. Taj eksperimentalni rezultat i pored važnosti za standardni model i fiziku izvan tog modela omogućuje nam predikciju jakosti raspada BR(B → ργ) ≃ (3.5 ± 3.3) × 10−6

Non-commutative SU(N) gauge theories and asymptotic freedom

In this paper we analyze the one-loop renormalization of the $\theta$-expanded $\rm SU(N)$ Yang-Mills theory. We show that the {\it freedom parameter} $a$, key to renormalization, originates from higher order non-commutative gauge interaction, represented by a higher derivative term $b h \theta^{\mu\nu}\hat F_{\mu\nu}\star\hat F_{\rho\sigma}\star\hat F^{\rho\sigma}$. The renormalization condition fixes the allowed values of the parameter $a$ to one of the two solutions: $a=1$ or $a=3$, i.e. to $b=0$ or to $b=1/2$, respectively. When the higher order interaction is switched on, ($a=3$), pure non-commutative SU(N) gauge theory at first order in $\theta$-expansion becomes one-loop renormalizable for various representations of the gauge group. We also show that, in the case $a=3$ and the adjoint representation of the gauge fields, the non-commutative deformation parameter $h$ has to be renormalized and it is asymptotically free.Comment: 16 pages, no figure

Neleptonski B raspadi bez promjene sarma i stranosti

Decay rates of the B-meson are studied through charmless and strangless transitions into π, ρ , ω and γ systems. The important features of these modes are their clean signatures. The CLEO II collaboration has recently reported the value BR(B0 → π +π −) = (1.3 +0.8 −0.6 ± 0.2) × 10−5 . This value is tests our approach to nonleptonic B-decays within the standard model (SM). Since B → γγ is far beyond our experimental reach, we believe that the correct determination of the order of magnitude ∼ 10−10 for BR(B → γγ) provides the most reliable value needed at this moment. The most recent experimental report by the CLEO collaboration on BR(B → K∗γ) = (4.5 ± 1.5 ± 0.9) × 10−5 represents a confirmation of our SM prediction for the B → K∗γ decay. This experimental result, despite of its great importance for the SM and the physics beyond the SM, enables us to predict the value BR (B → ργ) ∼= (3.5 ± 3.3) × 10−6 .Proučavani su raspadi B-mezona bez promjene šarma i stranosti u π, ρ, ω i γ konačna stanja. Važna osobina ovih modova su njihovi čisti eksperimentalni signali. CLEO II kolaboracija nedavno je objavila vrijednost BR(B0 → π +π −) = (1.3 +0.8 −0.6 ± 0.2) × 10−5 . Ta se vrijednost može upotrijebiti za test našeg pristupa objašnjenju neleptonskih B-raspada unutar standardnog modela (SM). Budući je B → γγ daleko izvan našeg eksperimentalnog dosega, vjerujemo da korektno određeni red veličine ∼ 10−10 za BR(B → γγ) predstavlja najrealniju vrijednost potrebnu u ovom trenutku. Najnoviji eksperimentalni izvještaj CLEO kolaboracije o mjerenju BR(B → K∗γ) = (4.5 ± 1.5 ± 0.9) × 10−5 predstavlja potvrdu naše teoretske (SM) predikcije B → K∗γ raspada. Taj eksperimentalni rezultat i pored važnosti za standardni model i fiziku izvan tog modela omogućuje nam predikciju jakosti raspada BR(B → ργ) ≃ (3.5 ± 3.3) × 10−6

High energy Compton scattering in the NCQED

We discuss the behavior of head-to-head $e\gamma\to e\gamma$ scattering process in the noncommutative quantum electrodynamics on the Moyal space amid its unresolved forward scattering singularity. We model the effect of the currently unknown resolution to this collinear singularity by cut-offs which are functions of the control variable $s/\Lambda_{\rm NC}^2$ and find that such cut-off functions can suppress NC corrections to the inverse Compton scattering to negligible. We also notice that such cut-offs leave the integral cross section of the forward region larger than the backward region all the time, making the former potentially easier to observe. Our estimations indicate that such an effect may be visible in the future collider experiments when the scale of noncommutativity $\Lambda_{\rm NC}\gtrsim1$ TeV.Comment: 4 pages, 1 figur

Seiberg-Witten maps and scattering amplitudes of NCQED

The connection between tree-level scattering amplitudes and the Seiberg-Witten (SW) map in the Moyal deformed U(1) noncommutataive quantum electrodynamics (NCQED) is studied. We show that in the minimal U(1) NCQED based on a reversible Seiberg-Witten (SW) map, SW map induced interactions cancel each other in all tree-level scattering amplitudes and leave them identical to the Moyal NCQED without SW map. On the other hand, the two-by-two Compton and light-by-light scattering amplitudes deviate from minimal model when irreversible SW map is used. Therefore the risibility of SW map and equivalence between NCQED before and after SW map manifest themselves as an identity between the tree-level scattering amplitudes.Comment: 11 pages, 10 figures. Version to be published in Phys. Rev.

Seiberg-Witten map Invariant Scatterings

We investigate Scattering amplitudes of the reversible $\theta$-exact Seiberg-Witten (SW) map based noncommutative (NC) quantum electrodynamics, and show explicitly the SW map invariance for all tree-level NCQED $2\to2$ proceses, including M\"oller, Bhabha, Compton, pair annihilation, pair production and light-by-light $(\gamma\gamma\to\gamma\gamma)$ scatterings. We apply our NCQED results to the $\gamma\gamma\to\gamma\gamma$ and $\gamma\gamma\to\ell^+\ell^-$ exclusive processes, convoluted to the ultraperipheral lead $^{208}$Pb ion-ion collisions, recently measured by the ATLAS collaboration at LHC. We demonstrate that $\gamma\gamma\to\gamma\gamma$ is the more appropriate channel to probe NC scale $\Lambda_{\rm NC}$ while both are less efficient than some other probes.Comment: 54 pages, 15 figures. Version, to be published in Phys. Rev. D, containing important angular distributions of light-by-light scatterings in the PbPb collision at the ATLAS and the next-generation collider experiments like FC