A5016219014- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Black Holes and Theoretical Physics
- Neutrino Physics Research
- Cosmology and Gravitation Theories
- Medical Imaging Techniques and Applications
- Algebraic and Geometric Analysis
- Dark Matter and Cosmic Phenomena
- Astrophysics and Cosmic Phenomena
- Particle Accelerators and Free-Electron Lasers
- International Science and Diplomacy
- Quantum chaos and dynamical systems
- IgG4-Related and Inflammatory Diseases
- Advanced NMR Techniques and Applications
- Methane Hydrates and Related Phenomena
- Mathematical Analysis and Transform Methods
- Inorganic Fluorides and Related Compounds
A. Alikhanyan National Laboratory
2012-2024
Yerevan State University
2021
Stanford University
2007
University of Bern
2007
European Organization for Nuclear Research
2007
The Abdus Salam International Centre for Theoretical Physics (ICTP)
1997
Combining our results for various O(alpha[s]) corrections to the weak radiative B-meson decay, we are able present first estimate of branching ratio at next-to-next-to-leading order in QCD. We find B(B[over ]-->X[s]gamma)=(3.15+/-0.23) x 10(-4) Egamma>1.6 GeV B[over ]-meson rest frame. The four types uncertainties:nonperturbative (5%), parametric (3%), higher-order and m(c)-interpolation ambiguity (3%) have been added quadrature obtain total error.
Weak radiative decays of the B mesons belong to most important flavor changing processes that provide constraints on physics at TeV scale. In derivation such constraints, accurate standard model predictions for inclusive branching ratios play a crucial role. current Letter we present an update these predictions, incorporating all our results O(α_{s}^{2}) and lower-order perturbative corrections have been calculated after 2006. New estimates nonperturbative effects are taken into account,...
We present in detail the calculation of virtual O(alpha_s) corrections to inclusive semi-leptonic rare decay b --> s l+ l-. also include those bremsstrahlung contributions which cancel infrared and mass singularities showing up corrections. In order avoid large resonant contributions, we restrict invariant squared lepton pair range 0.05 < s/mb^2 0.25. The analytic results are represented as expansions small parameters s/mb^2, z = mc^2/mb^2 s/(4 mc^2). new drastically reduce renormalization...
We present next-to-next-to leading logarithmic (NNLL) results for the double differential decay width $d\ensuremath{\Gamma}(\stackrel{\ensuremath{\rightarrow}}{b}{X}_{s}{\mathcal{l}}^{+}{\mathcal{l}}^{\ensuremath{-}})/[d\ifmmode \hat{s}\else \^{s}\fi{}d\mathrm{cos}(\ensuremath{\theta})],$ where $s=\ifmmode \^{s}\fi{}{m}_{b}^{2}$ is invariant mass squared of lepton pair and \ensuremath{\theta} angle between momentum b quark ${\mathcal{l}}^{+},$ measured in rest frame pair. From these we also...
In a recent paper, we presented calculation of the $\mathcal{O}({\ensuremath{\alpha}}_{s})$ virtual corrections to $\stackrel{\ensuremath{\rightarrow}}{b}{\mathrm{sl}}^{+}{l}^{\ensuremath{-}}$ and those bremsstrahlung terms that are needed cancel infrared divergences. present paper work out remaining $\stackrel{\ensuremath{\rightarrow}}{b}{\mathrm{sl}}^{+}{l}^{\ensuremath{-}},$ which do not suffer from collinear singularities. These new contributions turn be small numerically. addition, also...
The inclusive decay $\overline{B}\ensuremath{\rightarrow}{X}_{u}\ensuremath{\ell}\overline{\ensuremath{\nu}}$ is of much interest because its potential to constrain the CKM element $|{V}_{ub}|$. Experimental cuts required suppress charm background restrict measurements this shape-function region, where hadronic final state carries a large energy but only moderate invariant mass. In kinematic differential distributions satisfy factorization formula form...
We present new contributions to the decay matrix element ${\mathrm{\ensuremath{\Gamma}}}_{12}^{q}$ of ${B}_{q}\ensuremath{-}{\overline{B}}_{q}$ mixing complex, where $q=d$ or $s$. Our results constitute order ${\ensuremath{\alpha}}_{s}^{2}{N}_{f}$ corrections penguin Wilson coefficients entering with full dependence on charm quark mass. This is first step toward prediction $CP$ asymmetry ${a}_{\mathrm{fs}}^{q}$ quantifying violation in at next-to-next-to-leading logarithmic (NNLO) quantum...
A bstract Exclusive rare decays mediated by b → s ℓℓ transitions receive contributions from four-quark operators that cannot be naively expressed in terms of local form factors. Instead, one needs to calculate a matrix element bilocal operator. In certain kinematic regions, this operator obeys some type Operator Product Expansion, with coefficients can calculated perturbation theory. We review the formalism and, focusing on dominant SM O 1 , 2 we perform an improved calculation NLO matching...
The direct $\mathrm{CP}$ violation in the $\mathrm{SU}{(2)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(2)}_{R}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ model for $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ decay is investigated. calculated asymmetry wide range of parameters can be larger than standard and have an opposite sign to that latter.
We present the calculation of virtual- and bremsstrahlung corrections O(alpha_s) to matrix elements <d l+ l-|O_i|b>. This is missing piece in NNLL results for various observables associated with process B-> X_d l-, like branching ratio, CP-rate asymmetry forward-backward asymmetry. paper an extension analogous calculations done by some us X_s l-. As contributions diagrams induced operators O_1^u O_2^u a u-quark running quark loop are strongly CKM suppressed, they were omitted analysis B->X_s...
We propose formulas for computing the phase space integrals of $1\ensuremath{\rightarrow}3$ and $1\ensuremath{\rightarrow}4$ processes with massive particles in final states. As an application these formulas, we study state mass effects some interesting phenomenological cases, giving fully integrated analytic results corresponding spaces. consider also ${B}_{s}\ensuremath{-}{\overline{B}}_{s}$ process at next-to-next-to-leading order calculate one most complicated master integrals, which...
We calculate the set of $O({\ensuremath{\alpha}}_{s}^{2})$ corrections to branching ratio and photon energy spectrum decay process $\overline{B}\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ originating from interference diagrams involving electromagnetic dipole operator ${O}_{7}$ with chromomagnetic ${O}_{8}$. The evaluated here are one elements needed complete calculations at next-to-next-to-leading order in QCD. conclude that this does not change central value standard model...
A bstract We calculate a class of three-loop Feynman diagrams which contribute to the next-to-next-to-leading logarithmic approximation for width difference ΔΓ s in $$ {B}_s-{\overline{B}}_s <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>B</mml:mi> <mml:mi>s</mml:mi> </mml:msub> <mml:mo>−</mml:mo> <mml:mover> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> system. The considered contain closed fermion loop gluon propagator and constitute order α 2 N f , where is...
In a recent paper we presented calculation of NNLL virtual corrections to the forward-backward asymmetries in $b\to X_s\ell^+\ell^-$ decay. That result does not include bremsstrahlung which are free from infrared and collinear singularities. present remaining ${\cal O}(\alpha_s)$ The numerical effect calculated contributions is found be below 1%.
The uncertainty of the theoretical prediction $\bar B \to X_s γ$ branching ratio at NLL level is dominated by charm mass renormalization scheme ambiguity. In this paper we calculate those NNLL terms which are related to $m_c$, in order get an estimate corresponding level. We find that these significantly reduce (by typically a factor two) error on ${BR}(\bar γ)$ induced definition $m_c$. Taking into account experimental accuracy around 10% and future prospects $B$ factories, conclude...
We evaluate the most important tree-level contributions connected with b-> u \bar{u} d gamma transition to inclusive radiative decay \bar{B}-> X_d using fragmentation functions. In this framework singularities arising from collinear photon emission light quarks (u, and d) can be absorbed into (bare) quark-to-photon function. use as input function extracted by ALEPH group two-jet cross section measured at LEP, where one of jets is required contain a photon. To get scale \mu_F \sim m_b, we...
We calculate the set of O(alpha_s) corrections to double differential decay width dGamma_77/(ds_1*ds_2) for process B -> X_s gamma originating from diagrams involving electromagnetic dipole operator O_7. The kinematical variables s_1 and s_2 are defined as s_i=(p_b - q_i)^2/m_b^2, where p_b, q_1, q_2 momenta b-quark two photons. While (renormalized) virtual worked exactly a certain range s_2, we retain in gluon bremsstrahlung only leading power w.r.t. (normalized) hadronic mass...
We calculate the $O({\ensuremath{\alpha}}_{s})$ corrections to double differential decay width $d{\mathrm{\ensuremath{\Gamma}}}_{77}/(d{s}_{1}d{s}_{2})$ for process $\overline{B}\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}\ensuremath{\gamma}$, originating from diagrams involving electromagnetic dipole operator ${\mathcal{O}}_{7}$. The kinematical variables ${s}_{1}$ and ${s}_{2}$ are defined as ${s}_{i}=({p}_{b}\ensuremath{-}{q}_{i}{)}^{2}/{m}_{b}^{2}$, where ${p}_{b}$, ${q}_{1}$,...