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G. Duplancic

Publications and source records attributed to G. Duplancic.

16 recordsLinked to original sources
arXiv2010

Probability distribution of the vacuum energy density

As the vacuum state of a quantum field is not an eigenstate of the Hamiltonian density, the vacuum energy density can be represented as a random variable. We present an analytical calculation of the probability distribution of the vacuum energy density for real and complex massless scalar fields in Minkowski space. The obtained probability distributions are broad and the vacuum expectation value of the Hamiltonian density is not fully representative of the vacuum energy density.

hep-th↗
arXiv2008

B, Bs -> K form factors: an update of light-cone sum rule results

We present an improved QCD light-cone sum rule (LCSR) calculation of the B -> K and Bs -> K form factors, by including SU(3)-symmetry breaking corrections. We use recently updated K-meson distribution amplitudes which incorporate the complete SU(3)-breaking structure. By applying the method of the direct integration in the complex plane, which is presented in a detail, the analytical extraction of the imaginary parts of LCSR hard-scattering amplitudes becomes unnecessary and therefore the complexity of the calculation is greatly reduced. The values obtained for the relevant B_{(s)} -> K form factors are as follows: f^+_{BK}(0)= 0.36^{+0.05}_{-0.04}, f^+_{B_sK}(0)= 0.30^{+0.04}_{-0.03} and f^T_{BK}(0)= 0.38\pm 0.05, f^T_{B_sK}(0)= 0.30\pm 0.05. By comparing with the B -> pi form factors extracted recently by the same method, we find the following SU(3) violation among the B -> light form factors: f^+_{BK}(0)/f^+_{Bπ}(0) = 1.38^{+0.11}_{-0.10}, f^+_{B_sK}(0)/f^+_{Bπ}(0) = 1.15^{+0.17}_{-0.09}, f^T_{BK}(0)/f^T_{Bπ}(0) = 1.49^{+0.18}_{-0.06} and f^T_{B_sK}(0)/f^T_{Bπ}(0) = 1.17^{+0.15}_{-0.11}.

hep-ph↗
arXiv2008

Light-cone sum rules for $B \to π$ form factors revisited

We reconsider and update the QCD light-cone sum rules for $B\to π$ form factors. The gluon radiative corrections to the twist-2 and twist-3 terms in the correlation functions are calculated. The $\bar{MS}$ $b$-quark mass is employed, instead of the one-loop pole mass used in the previous analyses. The light-cone sum rule for $f^+_{Bπ}(q^2)$ is fitted to the measured $q^2$-distribution in $B\to πl ν_l$, fixing the input parameters with the largest uncertainty: the Gegenbauer moments of the pion distribution amplitude. For the $B\to π$ vector form factor at zero momentum transfer we predict $f^+_{Bπ}(0)= 0.26^{+0.04}_{-0.03}$. Combining it with the value of the product $|V_{ub}f^+_{Bπ}(0)|$ extracted from experiment, we obtain $|V_{ub}|=(3.5\pm 0.4\pm 0.2\pm 0.1) \times 10^{-3}$. In addition, the scalar and penguin $B\to π$ form factors $f^0_{Bπ}(q^2)$ and $f^T_{Bπ}(q^2)$ are calculated.

hep-ph↗
arXiv2004

The Skyrme model predictions for the ${\bf 27}_{J=3/2}$ mass spectrum and the ${\bf 27}_{3/2}$-$\bar{\bf 10}$ mass splittings

The ${\bf 27}_{J=3/2}$-plet mass spectrum and the ${\bf 27}_{3/2}$-$\bar{\bf 10}$ mass splittings are computed in the framework of the minimal SU(3)$_f$ extended Skyrme model. As functions of the Skyrme charge $e$ and the SU(3)$_f$ symmetry breaking parameters the predictions are presented in tabular form. The predicted mass splitting ${\bf 27}_{3/2}$-$\bar{\bf 10}$ is the smallest among all SU(3)$_f$ baryonic multiplets.

hep-ph↗
arXiv2004

Rare $Ω^{-} \to Ξ(1530)^{0} π^-$ decay in the Skyrme model

Rare nonleptonic $Ω^{-} \to Ξ(1530)^{0} π^-$ decay branching ratio is estimated by means of the QCD enhanced effective weak Hamiltonian supplemented by the SU(3) Skyrme model used to estimate the nonperturbative matrix elements. The whole scheme is equivalent to that which works well for the nonleptonic hyperon and $Ω^{-}$ decays. The computed rate is in a good agreement with data.

hep-ph↗
arXiv2004

Moments of inertia, nucleon axial-vector coupling, the {\bf 8}, {\bf 10}, $\bar{\bf 10}$ and ${\bf 27}_{3/2}$ mass spectrums and the higher SU(3)_f representation mass splittings in the Skyrme model

The broad importance of a recent experimental discovery of pentaquarks requires more theoretical insight into the structure of higher representation multiplets. The nucleon axial-vector coupling, moments of inertia, the {\bf 8}, {\bf 10}, $\bar{\bf 10}$, and ${\bf 27}_{3/2}$ absolute mass spectra and the higher SU(3)$_f$ representation mass splittings for the multiplets ${\bf 8}$, ${\bf 10}$, $\bar{\bf 10}$, ${\bf 27}$, ${\bf 35}$, $\bar{\bf 35}$, and $\bf 64$ are computed in the framework of the minimal ${\rm SU(3)_f}$ extended Skyrme model by using only one free parameter, i.e., the Skyrme charge $e$. The analysis presented in this paper represents simple and clear theoretical estimates, obtained without using any experimental results for higher ($\bar{\bf 10}$,...) multiplets. The obtained results are in good agreement with other chiral soliton model approaches that more extensively use experimental results as inputs.

hep-ph↗
arXiv2004

Absorption of solar radiation by solar neutrinos

We calculate the absorption probability of photons radiated from the surface of the Sun by a left-handed neutrino with definite mass and a typical momentum for which we choose |p_1|=0.2 MeV, producing a heavier right-handed antineutrino. Considering two transitions the ν_1 -> ν_2 and ν_2 -> ν_3 we obtain two oscillation lengths L_{12}=4960.8 m, L_{23}=198.4 m, two absorption probabilities P_{12}^{abs.}=2.5 10^{-67}, P_{23}^{abs.}=1.2 10^{-58} and the two absorption ranges R_{12}^{abs.}=4.47 10^4 R_{\odot}=208.0 au, R_{23}^{abs.}=0.89 10^4 R_{\odot}=41.4 au, using a neutrino mass differences of \sqrt{|Δm^2_{12}|}=10 meV, \sqrt{|Δm^2_{23}|}=50 meV and associated transition dipole moments. We collect all necessary theoretical ingredients, i.e. neutrino mass and mixing scheme, induced electromagnetic transition dipole moments, quadratic charged lepton mass asymmetries and their interdependence.

hep-ph↗
arXiv2004

Reduction method for dimensionally regulated one-loop N-point Feynman integrals

We present a systematic method for reducing an arbitrary one-loop N-point massless Feynman integral with generic 4-dimensional momenta to a set comprised of eight fundamental scalar integrals: six box integrals in D=6, a triangle integral in D=4, and a general two-point integral in D space time dimensions. All the divergences present in the original integral are contained in the general two-point integral and associated coefficients. The problem of vanishing of the kinematic determinants has been solved in an elegant and transparent manner. Being derived with no restrictions regarding the external momenta, the method is completely general and applicable for arbitrary kinematics. In particular, it applies to the integrals in which the set of external momenta contains subsets comprised of two or more collinear momenta, which are unavoidable when calculating one-loop contributions to the hard-scattering amplitude for exclusive hadronic processes at large momentum transfer in PQCD. The iterative structure makes it easy to implement the formalism in an algebraic computer program.

hep-ph↗
arXiv2003

The Z -> gamma gamma, gg Decays in the Noncommutative Standard Model

On noncommutative spacetime, the Standard Model allows new, usually Standard Model forbidden, triple gauge boson interactions. In this letter we propose the Standard Model strictly forbidden Z -> gamma gamma and Z -> gg decay modes coming from the gauge sector of the Noncommutative Standard Model as a place where noncommutativity could be experimentally discovered.

hep-ph↗
arXiv2003

NLO calculations of the exclusive processes in pQCD

We present a generally applicable reduction formalism which makes it possible to express an arbitrary tensor and scalar one-loop Feynman integral, with N external lines and massless propagators, in terms of a basic set of eight fundamental scalar Feynman integrals with 2, 3, and 4 external lines, for arbitrary external kinematics. The formalism is particularly suitable for the NLO calculations of exclusive processes at large momentum transfer in pQCD, where all previously developed reduction methods fail due to the presence of collinear external on-shell lines.

hep-ph↗
arXiv2002

IR finite one-loop box scalar integral with massless internal lines

The IR finite one-loop box scalar integral with massless internal lines has been recalculated. The result is very compact, simple and valid for arbitrary values of the relevant kinematic variables. It is given in terms of only two dilogarithms and a few logarithms, all of very simple arguments.

hep-ph↗
arXiv2001

Nonleptonic $Ω^{-}$ decays and the Skyrme model

Nonleptonic $Ω^{-}$ decay branching ratios are estimated by means of the QCD enhanced effective weak Hamiltonian supplemented by the SU(3) Skyrme model used to estimate the nonperturbative matrix elements. The model has only one free parameter, namely the Skyrme charge $e$, which is fixed through the experimental values of the octet-decuplet mass splitting $Δ$ and the axial coupling constant $g_{A}$. The whole scheme is equivalent to that which works well for the nonleptonic hyperon decays. The ratios of calculated amplitudes are in agreement with experiment. However, the absolute values are about twice too large if short-distance corrections and only ground intermediate states are included.

hep-ph↗
arXiv2001

Dimensionally regulated one-loop box scalar integrals with massless internal lines

Using the Feynman parameter method, we have calculated in an elegant manner a set of one$-$loop box scalar integrals with massless internal lines, but containing 0, 1, 2, or 3 external massive lines. To treat IR divergences (both soft and collinear), the dimensional regularization method has been employed. The results for these integrals, which appear in the process of evaluating one$-$loop $(N\ge 5)-$point integrals and in subdiagrams in QCD loop calculations, have been obtained for arbitrary values of the relevant kinematic variables and presented in a simple and compact form.

hep-ph↗
arXiv2001

Skyrme model and nonleptonic hyperon decays

This report is an attempt to explain both s- and p-wave nonleptonic hyperon decays by means of the QCD enhanced effective weak Hamiltonian supplemented by the SU(3) Skyrme model used to estimate nonperturbative matrix elements. The model has only one free parameter, namely, the Skyrme charge $e$, which is fixed through the experimental values of the octet-decuplet mass splitting $Δ$ and the axial coupling constant $g_{A}$. Such a dynamical approach produces nonleptonic hyperon decay amplitudes that agree with experimental data reasonably well.

hep-ph↗