Nonleptonic two body $B_c$ decays including radially excited $ψ(2S)$ or $η_c(2S)$ mesons in the final state are studied using the perturbative QCD approach based on $k_T$ factorization. The charmonium distribution amplitudes are extracted from the $n = 2, l = 0$ Schr$\ddot{o}$dinger states for the harmonic oscillator potential. Utilizing these distribution amplitudes, we calculate the numerical results of the $B_c\rightarrow ψ(2S),η_c(2S)$ transition form factors and branching fractions of $B_c\rightarrow ψ(2S)π, η_c(2S)π$ decays. The ratio between two decay modes $B_c\rightarrow ψ(2S)π$ and $B_c\rightarrow J/ψπ$ is compatible with the experimental data within uncertainties, which indicate that the harmonic oscillator wave functions for $ψ(2S)$ and $η_c(2S)$ work well. It is found that the branching fraction of $B_c\rightarrow η_c(2S)π$, which is dominated by the twist-3 charmonium distribution amplitude, can reach the order of $10^{-3}$. We hope it can be measured soon in the LHCb experiment.
In the QCD factorization (QCDF) approach we study the direct $CP$ violation in $\bar{B}^{0}\rightarrowρ^0(ω)ρ^0(ω)\rightarrowπ^+π^-π^+π^-$ via the $ρ-ω$ mixing mechanism. We find that the $CP$ violation can be enhanced by double $ρ-ω$ mixing when the masses of the $π^+π^-$ pairs are in the vicinity of the $ω$ resonance, and the maximum $CP$ violation can reach 28{\%}. We also compare the results from the naive factorization and the QCD factorization.
In the perturbative QCD (PQCD) approach we study the direct $CP$ violation in $B^+_{c}\rightarrow D_{(s)}^+ρ^0(ω) \rightarrow D_{(s)}^+π^+π^-$ via the $ρ-ω$ mixing mechanism. We find that the $CP$ violation can be enhanced by $ρ-ω$ mixing when the invariant masses of the $π^+π^-$ pairs are in the vicinity of the $ω$ resonance. For the decay process $B^+_{c}\rightarrow D^+ρ^0(ω) \rightarrow D^+π^+π^-$, the maximum $CP$ violation can reach 7.5 {\%}.
We calculate the magnetic dipole and electric quadrupole moments associated with the radiative $Ω_{Q}^{*}\rightarrowΩ_{Q}γ$ and $Ξ_{Q}^{*}\rightarrowΞ^{\prime}_{Q}γ$ transitions with $Q=b$ or $c$ in the framework of light cone QCD sum rules. It is found that the corresponding quadrupole moments are negligibly small while the magnetic dipole moments are considerably large. A comparison of the results on the considered multipole moments as well as corresponding decay widths with the predictions of the vector dominance model is performed.
We calculate the direct $CP$ violation for the decay process of ${B}^{0}\rightarrow π^{0}π^{0}$, ${B}^{+}\rightarrow π^{0}π^{+}$, ${B}^{0}\rightarrow K^{0}π^{0}$ and ${B}^{+}\rightarrow K^{+}π^{0}$ via isospin symmetry breaking effects from the $π^{0}-η-η'$ mixing mechanism in perturbative QCD approach. Isospin symmetry breaking originates from the electroweak interaction and the u-d quark mass difference through the strong interaction which are known to be tiny. However, we find that isospin symmetry breaking at the leading order changes the $CP$ violation from the new strong phases. Our calc…
The strong $D_{2}^{*}(2460)^{0}\rightarrow D^+ π^- $ and $D_{s2}^{*}(2573)^{+}\rightarrow D^{+} K^{0}$ transitions are analyzed via three point QCD sum rules. First, we calculate the corresponding strong coupling constants $g_{D_2^*Dπ}$ and $g_{D_{s2}^*DK}$. Then, we use them to calculate the corresponding decay widths and branching ratios. Making use of the existing experimental data on the ratio of the decay width in the pseudoscaler $D$ channel to that of the vector $D^*$ channel, finally, we estimate the decay width and branching ratio of the strong $D_2^*(2460)^0 \rightarrow D^*(2010)^+π^…
In the framework of Perturbative QCD (PQCD) approach we study the direct $CP$ asymmetry for the decay channel $\bar{B}_{s}\rightarrow Pπ^+π^-$ around the resonance range via the $ρ-ω$ mixing mechanism (where P refer to pseudoscalar meson). We find that the $CP$ asymmetry can be enhanced by $ρ-ω$ mixing when the masses of the $π^+π^-$ pairs are at the area of $ρ-ω$ resonance, and the maximum $CP$ asymmetry can reach 59{\%} for the relevant decay channels.
Exclusive $B_c^\ast \rightarrow D_{s}~ν\barν$ decay is studied in the framework of the three--point QCD sum rules approach. The two gluon condensate contributions to the correlation function are calculated and the form factors of this transition are found. The decay width and total branching ratio for this decay is also calculated.
We discuss in detail the calculation of the leading order QCD corrections to the Effective Hamiltonian which governs $b \rightarrow s\, γ$ and $b \rightarrow s \, g$ transitions in three different regularization schemes (HV, NDR and DRED). We show that intermediate stages of the calculation do depend on the regularization, but the same scheme independent coefficients can be obtained in all the considered schemes. A detailed discussion of the results already present in the literature is also given.
We employ the generalized parton picture to analyze the reaction $π^- p \rightarrow D^- Λ_c^+$. Thereby it is assumed that the process amplitude factorizes into one for the perturbatively calculable subprocess $\bar{u}\ u\rightarrow \bar{c}\ c$ and hadronic matrix elements that can be parameterized in terms of generalized parton distributions for the $π^-\rightarrow D^-$ and $p\rightarrow Λ_c^+$ transitions, respectively. Representing these parton distributions in terms of valence-quark light-cone wave functions for $π$, $D$, $p$ and $Λ_c$ allows us to make numerical predictions for unpolarize…
In this work, we analyse the CP-averaged branching ratios and direct CP-violating asymmetries of the four-body decays B_{S} \rightarrow ππππdecay from the S-wave resonances, f_{0}(980) and f_{0}(500) and P-wave resonances, ρ(770) by introducing the S-wave and P-wave ππdistribution amplitudes within the framework of the perturbative QCD approach. We also calculate branching ratios of the two-body decays B^{0}_{S}\rightarrowρ^{0}ρ^{0}, B^{0}_{S}\rightarrowρ^{+}ρ^{-} from the corresponding quasi-two-body decays models and compare our results with those obtained in previous perturbative QCD approa…
Rare exclusive $B_c^\ast \rightarrow D_{s}~l^+ l^-$ decays are analyzed in the framework of the three--point QCD sum rules approach. The two gluon condensate corrections to the correlation function are included and the form factors of this transition are evaluated. Using the form factors, the decay width and integrated decay rate for these decays are also calculated.
The form factors of the semileptonic $χ_{b2}(1P)\rightarrow B_{c}\bar{l}ν$ decay are calculated using the QCD sum rule approach. The results obtained are then used to estimate the decay widths of this transition in all lepton channels. The orders of decay rates indicate that this transition is accessible at LHC for all lepton channels.
We have analyzed the $D\rightarrow πK, KK$ decay with the naive factorization (NF), QCD factorization (QCDF)and QCD factorization including soft-gluon exchanges (QCDF+SGE). In these decay channels, the soft-gluon effects are firstly calculated with light cone QCD sum rules. Comparing the three kind approaches, we can find the calculation results have made much more improved QCD factorization (QCDF) than the naive factorization (NF), and the calculation results have also made improved QCD factorization including soft-gluon exchanges (QCDF+SGE) than the QCD factorization (QCDF) in the color-supp…
With only the tree level operator, the decay of $Λ_b\rightarrow pK$ is predicted to be one order smaller than the experimental data. The QCD penguin effects should be taken into account. In this paper, we explore the one-loop QCD corrections to the decay of $Λ_b\to pK$ within the framework of QCD factorization approach. For the baryon system, the diquark approximation is adopted. The transition hadronic matrix elements between $Λ_b$ and $p$ are calculated in the light front quark model. The branching ratio of $Λ_b\rightarrow pK$ is predicted to be about $4.85\times 10^{-6}$ which is consistent…
In this work, we investigate those $B_{c}\rightarrow D^{(*)}T$ decays in perturbative QCD approach, based on $k_T$ factorization, where T denotes a light tensor meson. For all decays considered in this work, there are no contributions from factorizable emission diagrams because the emitted meson is the tensor meson. We find that the annihilation amplitudes are dominant in these decays due to the large Cabibbo-Kobayashi-Maskawa elements, which are only calculable in the pQCD approach. The numerical results show that the predictions for the branching ratios of most decays are in the order of $10…
We calculate the form factors for the heavy-to-light transitions $B\rightarrow π,K $ by means of QCD sum rules using $π$ and $K$ light-cone wave functions. Higher twist contributions as well as gluonic corrections are taken into account. The sensitivity to the shape of the leading-twist wave functions and effects of SU(3)-breaking are discussed. The results are compared with quark model predictions and with the results from QCD sum rules for three-point correlators.
We analyze the semileptonic $ B_{s} \rightarrow D_{s2}^{*}(2573)\ell\bar{ν}_{\ell}$ transition, where $\ell=τ,~μ$ or $e$, within the standard model. We apply the QCD sum rule approach to calculate the transition form factors entering the low energy Hamiltonian defining this channel. The fit functions of the form factors are used to estimate the total decay widths and branching fractions in all lepton channels. The orders of branching ratios indicate that this transition is accessible at LHCb in near future.
We analyze, in the antenna subtraction framework, the real radiation antenna functions for processes involving the production of a pair of heavy quarks and two gluons by an uncolored initial state at NNLO QCD. We provide explicit expressions for these functions and discuss their infrared singular behaviour. Our main results are the corresponding integrated antenna functions which are computed analytically. They are expressed in terms of harmonic polylogarithms.
We present a systematic light-cone QCD sum rule study of the exclusive rare radiative decay $Λ_b\rightarrowΛγ$ and rare semileptonic decay $Λ_b\rightarrowΛl^+l^-$ within the framework of the standard model. Although some LCSR studies on these rare processes can be found in different literatures, it is necessary to reanalyze them systematically for the reason that either the baryonic distribution amplitudes are improved or different interpolating currents for the $Λ_b$ baryon may lead to quite different results. In addition, the rare process $Λ_b\rightarrowΛγ$ has not yet been analyzed by LCSR …
We calculate the transition form factors of the semileptonic $B_c\rightarrow χ_{c2} l \barν $ in the framework of QCD sum rules taking into account the two-gluon condensate corrections. Using the obtained results of form factors we estimate the decay widths and branching ratios related to this transition at all lepton channels. A comparison of the obtained results with the predictions of other non-perturbative approaches are also made. The orders of branching ratios for different lepton channels indicate that the $B_c\rightarrow χ_{c2} l \barν $ transition can be studied at LHC using the colle…
We estimate the decay rates of $η_c\rightarrow 2γ$, $η_c'\rightarrow 2γ$, and $J/ψ\rightarrow e^+ e^-$, $ψ^\prime\rightarrow e^+e^-$, by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism. The Bethe-Salpeter equation with a QCD-inspired interquark potential are used to calculate the wave functions and decay widths for these $c\bar{c}$ states. We find that the relativistic correction to the ratio $R\equiv Γ(η_c \rightarrow 2γ)/ Γ(J/ ψ\rightarrow e^+ e^-)$ is negative and tends to compensate the positive contribut…
We present a complete calculation of the effective lagrangian for $b \rightarrow s$ processes with $QCD$ corrections, in the leading logarithm approximation, for the cases $m_t=m_w$ and $m_t \gg m_w$. The effective lagrangian is then applied to estimate the $b \rightarrow s γ$ decay rate. We find that it is enhanced by a factor of 6 for the case $m_t=m_w$, and a factor of about 2 for $m_t \gg m_w$. Our results differ from those found in the literature, but are not very different numerically for $m_t=m_w$.
We study the $B_{c}$$\rightarrow$$ψ(2S)$K, $η_{c}(2S)$K, $ψ(3770)$K decays with perturbative QCD approach (pQCD) based on $k_T$ factorization. The new orbitally excited charmonium distribution amplitudes $ψ(1^{3}D_{1})$ based on the Schrödinger wave function of the $n=1$, $l=2$ state for the harmonic-oscillator potential are employed. By using the corresponding distribution amplitudes, we calculate the branching ratio of $B_{c}$$\rightarrow$$ψ(2S)$K, $η_{c}(2S)$K, $ψ(3770)$K decays and the form factors $A_{0,1,2}$ and $V$ for the transition $B_{c}$$\rightarrow$$ψ(1^{3}D_{1})$. We obtain the br…
We present the two-loop master integrals relevant to the ${\mathcal O}(αα_s)$-corrections to the decay $H \rightarrow b \bar{b}$ through a $H t \bar{t}$-coupling. We keep the full dependence on the heavy particle masses, but neglect the $b$-quark mass. The occurring square roots can be rationalised and the result is expressed in terms of multiple polylogarithms.
In the events of the type $e^+e^- \rightarrow W^+W^- \rightarrow$ 4 jets, $e^+e^- \rightarrow t\bar{t} \rightarrow bW^+\bar{b}W^-$, particle production could depend in a non-trivial way on the kinematics of the process. It is shown that QCD interference effects are negligible for energetic perturbative emission, but soft perturbative gluons and non-perturbative fragmentation could induce colour correlations. Possible consequences for LEP 2 and NLC events are briefly addressed.
Within the QCD factorization approach, we study the $CP$ violations in $B^-\rightarrow K^-π^+π^-$ and $B^-\rightarrow K^- f_0(500)$ decays. We find the experimental data of the localized $CP$ asymmetry in $B^-\rightarrow K^-π^+π^-$ decays in the region $m_{K^-π^+}^2<15$ $\mathrm{GeV}^2$ and $0.08<m_{π^+π^-}^2<0.66$ $\mathrm{GeV}^2$ can be explained by the interference of two intermediate resonances, $ρ^0(770)$ and $f_0(500)$ when the parameters in our interference model are in the allowed ranges, i.e. the relative strong phase $δ\in[0, 1.745]\cup[3.578, 6.266]$ and the end-point divergence par…
The isovector axial vector form factors of $N \rightarrow Δ$ transition are calculated by employing Light-cone QCD sum rules. The analytical results are analysed by both the conventional method, and also by a Monte Carlo based approach which allows one to scan all of the parameter space. The predictions are also compared with the results in the literature, where available. Although the Monte Carlo analysis predicts large uncertainties in the predicted results, the predictions obtained by the conventional analysis are in good agreement with other results in the literature.
We make a systematic investigation on the two-body nonleptonic decays $B_c\rightarrow J/Ψ(η_c),M$ by employing the perturbative QCD approach based on $k_T$ factorization, where $M$ is a light pseudoscalar or vector or a heavy charmed meson. We predict the branching ratios and direct CP asymmetries of these $B_c$ decays and also the transverse polarization fractions of $B_c\rightarrow J/ΨV,J/ψD^{*}_{(s)}$ decays. It is found that these decays have a large branching ratios of the order of $10^{-4} - 10^{-2}$ and could be measured by the future LHC-b experiment. Our predictions for the ratios of …
We investigate $J/ψ$ decays into octet baryon-antibaryons pairs. The decay amplitudes are computed within the collinear QCD factorisation framework. The subleading amplitude, which describes the decay of longitudinally polarised charmonium, is computed using twist-4 three-quark distribution amplitudes. The obtained results are used for a qualitative analysis of the experimental data. It is found that the polarisation parameter $α_B$ can be described with an accuracy $10-30\%$, which may indicate that the pQCD contribution dominates this observable.
In the framework of perturbative QCD, the radiative decays $J/ψ\rightarrowγη^{(\prime)}$ are revisited in detail, where the involved one-loop integrals are evaluated analytically with the light quark masses kept. We have found that the sum of loop integrals is insensitive to the light quark masses and the branching ratios $\mathcal{B}(J/ψ\rightarrowγη^{(\prime)})$ barely depend on the shapes of $η^{(\prime)}$ distribution amplitudes. With the parameters of $η-η^{\prime}$ mixing extracted from low energy processes and $J/ψ\rightarrowγη^{(\prime)}$ by means of nonperturbative matrix elements $\l…
Decays $J/ψ\to B\bar B$ into octet baryon-antibaryons pairs are studied within the QCD factorisation framework. The next-to-leading power correction to the leading-order decay amplitude is calculated for the first time. The phenomenological analysis also includes the interference with the electromagnetic decay $J/ψ\to γ^*\to B\bar B$. The branching fractions and the angular coefficients $α_B$ are described with an accuracy of about $20\%$. The obtained results allow us to conclude that the calculated amplitudes provide a dominant contribution and therefore QCD factorisation provides a suitable…
We review the recent theoretical progress in heavy quarkonium spectroscopy within the boundstate theory based on perturbative QCD. New microscopic pictures of the heavy quarkonium systems are obtained.
The nonleptonic two-body $Λ_b\rightarrow Λψ$ decays with $ψ=J/ψ$ or $ψ(2S)$ are investigated based on the perturbative QCD approach. These are color-suppressed processes in which the nonfactorizable contributions are confirmed to be dominant. Angular momentum conservation allows us to describe the concerned decays by four independent complex helicity amplitudes. It is observed that the negative-helicity states for the $Λ$ baryon are preferred as expected in the left-handed nature of the charged-current interaction. The obtained results for the helicity amplitudes are used to compute the branch…
Non perturbative results from lattice QCD will be discussed, namely: Vacuum Condensates and QCD Sum Rules; $U_A(1)$ and Topology; Confinement of Color.
We calculate the two-loop QCD corrections to paracharmonium decays $eta_{c} rightarrow gamma gamma$ and $eta_{c} rightarrow g g$ involving light-by-light scattering diagrams with light quark loops. Artificial large mass expansion and convergence improvement techniques are used to evaluate these corrections. The obtained corrections to the decays $eta_{c} rightarrow gamma gamma$ and $eta_{c} rightarrow g g$ account for $-1.25 %$ and $ -0.73 %$ of the leading order contribution, respectively.
Using the global properties of the QCD partition function we determine an all order perturbative beta function in the background gauge field method to find out that it has a simple expressions whose properties and consequences align with other recent results in the QCD literature. We further compute the non-perturbative beta functions for the coupling constant and the theta angle in the background of an instanton field with winding number $n$. We solve for the theta angle in the non-perturbative region to determine that it is approximately zero. By extrapolating to the full QCD beta functions …
Based on parametric reasoning, we provide a simple dynamical picture of how a perturbative parton cascade, in interaction with a QCD medium, fills phase space as a function of time.
Evidence is reviewed suggesting that QCD remains a perturbative theory with a (relatively) small coupling constant down to a distinct infrared boundary on perturbative physics, a boundary corresponding to the momentum scale associated with a beta-function pole.
In this note, we study the contributions from the S-wave resonances, f_{0}(980) and f_{0}(1500), to the B^{0}_{s}\rightarrow ψ(3770)π^ {+}π^{-} decay by introducing the S-wave ππdistribution amplitudes within the framework of the perturbative QCD approach. Both resonant and nonresonant contributions are contained in the scalar form factor in the S-wave distribution amplitude Φ^S_{ππ}. Since the vector charmonium meson ψ(3770) is a S-D wave mixed state, we calculated the branching ratios of S-wave and D-wave respectively, and the results indicate that f_{0}(980) is the main contribution of the …
In these lectures we give a concise introduction to the ideas of renormalon calculus in QED and QCD. We focus in particular on the example of the Adler D function of vacuum polarization, and on relations between perturbative renormalon ambiguities and corresponding non-perturbative Operator Product Expansion (OPE) ambiguities. Recent work on infrared freezing of Euclidean observables is also discussed.
We report on studies of next-to-leading order (NLO) QCD corrections to the process $pp\rightarrow e^+ν_eμ^+ν_μjj$ which is associated with vector-boson fusion (VBF) production of an intermediate $W^+W^+$ pair. The impact of s-channel diagrams and interference contributions in VBF kinematics is analyzed at leading order (LO) and found to be entirely negligible. The NLO corrections are around 5% of the LO cross section, and the scale dependence is reduced to about ~1%. We introduce a dynamic scale which improves the K factor in the high-energy tails of the distributions.
In this work, we study the branching ratios of B^{0}_{s}\rightarrow a_{0}(980)[ \rightarrow K\overline{K}, πη]a_{0}(980), B^{0}_{s} \rightarrow f_{0}(980)[ \rightarrow π^{+}π^{-}, K^{+}K^{-}]f_{0}(980) and B^{0}_{s} \rightarrow f_{0}(500)[ \rightarrow π^{+}π^{-}]f_{0}(500) decays in the pQCD approach, in which the scalar mesons a_{0}(980), f_{0}(980) and f_{0}(500) are regarded as the lowest-lying q\overline{q} state. In the SU(3) nonet, there exists a mixing between the scalars f_{0}(980) and f_{0}(500), so we have considered the mixing effect in our calculations to obtain more reliable data,…
Using recent measurements of the b-quark fragmentation distribution obtained in $e^+e^- \to b \bar{b}$ events registered at the Z pole, the non-perturbative QCD component of the distribution has been extracted independently of any hadronic physics modelling. This distribution depends only on the way the perturbative QCD component has been defined. When the perturbative QCD component is taken from a parton shower Monte-Carlo, the non-perturbative QCD component is rather similar with those obtained from the Lund or Bowler models. When the perturbative QCD component is the result of an analytic N…
Within the framework of the Fock-Feynman-Schwinger (equivalently, worldline) casting of QCD a four-point process, mediated by a closed quark loop, is studied in the Sudakov kinematical region, first perturbatively and subsequently with the inclusion of non-perturbative contributions through the use of the stochastic vacuum model. Deformations of the, first order, perturbative results are determined. Finally, the resummation of the leading logarithmic terms is performed and physical implications of the result are discussed.
We summarize the current status of our understanding of the structure of the perturbative QCD expressions for the QCD generalization of the Crewther relation.
Using the Kirschner-Lipatov equation as a basis, we study high energy elastic quark-quark amplitudes, which correspond to secondary Reggeons and pion exchange in the double-logarithmic approximation of perturbative QCD.
A brief review of jet physics is presented with an emphasis upon open theoretical problems (non-perturbative domain; hadronization and confinement) and new phenomena (hadroproduction in heavy ion collisions).
By using the 3-point QCD sum rules, we calculate the transition form factors of $D$ decays into the spin triplet axial vector mesons $a_1(1260)$, $f_1(1285) $, $f_1(1420)$. In the calculations, we consider the quark contents of each meson in detail. In view of the fact that the isospin of $a_1(1260)$ is one, we calculate the $D^+ \rightarrow a_1^0 (1260)$ and $D^0 \rightarrow a_1^- (1260)$ transition form factors separately. In the case of $ f_1(1285), f_1(1420)$, the mixing between light flavor $SU(3)$ singlet and octet is taken into account. Based on the form factors obtained here, we give p…
We work out the semileptonic $Λ_b\rightarrow Λ\ell^+ \ell^-$ transition in standard as well as different supersymmetric models. In particular, considering the parametrization of the matrix elements entered the low energy effective Hamiltonian in terms of form factors in full QCD, we calculate the amplitude and differential decay rate responsible for this decay channel in supersymmetric models. We then use the form factors calculated via light cone QCD sum rules in full theory to analyze the differential branching ratio and lepton forward-backward asymmetry of this decay channel in different su…
This talk brings attention to what is knowable from perturbative QCD theory on two-parton distribution functions in the light of CDF measuruments of the inclusive cross section for double parton scattering.
The anomalous dimensions of high-twist operators in deeply inelastic scattering ($γ_{2n}$) are calculated in the limit when the moment variable $N \rightarrow 1$ (or $x_B\rightarrow 0$) and at large $Q^2$ (the double logarithmic approximation) in perturbative QCD. We find that the value of $γ_{2n}(N-1)$ in this approximation behaves as ${N_c α_S \over π(N-1)} n^2(1 + {δ\over 3} (n^2-1))$ where $δ\approx 10^{-2}$. This implies that the contributions of the high-twist operators give rise to an earlier onset of shadowing than was estimated before. The derivation makes use of a Pomeron exchange ap…
This is a written version of two lectures given at the First School on Field Theory and Gravitation in Vitoria (Brasil) April 15-19, 1997. We discuss the foundation of QCD as the theory of strong interactions and the perturbative analysis of e^+e^- annihilation into hadrons. Typical concepts of perturbative QCD studies, such as collinear singularities, jets, Sudakov form factors, are explained working out this case.
This is a short write-up of lectures at UK Theory Institute, Swansea UK, Sept.99; and XVII School ``QCD: Perturbative or Non-perturbative?'' Lisbon,Portugal, Oct.99. The covered topic include (i) discussion of the scales at which perturbative description should be changed by the non-perturbative one. A number of various examples are considered, leading to different scales, related to instantons or confinement effects; (ii) Instanton vacuum as an Instanton Liquid; (iii) The phase diagram of QCD at finite temperature and density, and especially description of a recent progress in Color Supercond…
We present the ${\cal O}(α_s^3)$ virtual QCD corrections to the process $h \rightarrow g+g+g$ due to interference of born and two-loop amplitudes, where $h$ is a massive spin-2 particle and $g$ is the gluon. We assume that the SM fields couple to $h$ through the SM energy momentum tensor. Our result constitutes one of the ingredients to full NNLO QCD contribution to production of a massive spin-2 particle along with a jet in the scattering process at the LHC. In particular, this massive spin-2 could be a KK mode of a ADD graviton in large extra dimensional model or a RS KK mode in warped extra…
We present the perturbative (PT) and non-perturbative (NP) analysis of the cumulative out-of-event-plane momentum distribution in e+e- annihilation in the near-to-planar three-jet region. A physical interpretation based on simple QCD considerations and kinematical relations will be given, with the aim of extending the described techniques to other multi-jet processes and, possibly, to hadron-hadron collisions.
As one of the simplest hadronic processes, $γγ\rightarrow M^{+}M^{-}$ ($M=π,K$) could be a good testing ground for our understanding of the perturbative and nonperturbative structure of QCD, and will be studied with high precision at BELLE-\RNum{2} in the near future. In this paper, we revisit these processes with twist-3 corrections in the perturbative QCD approach based on the $k_{T}$ factorization theorem, in which transverse degrees of freedom as well as resummation effects are taken into account. The influence of the distribution amplitudes on the cross sections are discussed in detail. O…
Using the related form factors from full QCD which recently are available, we provide a comprehensive analysis of the $Λ_b \rightarrow Λ\ell^+ \ell^-$ transition in universal extra dimension model in the presence of a single universal extra dimension called the Applequist-Cheng-Dobrescu model. In particular, we analyze some related observables like branching ratio, forward-backward asymmetry, double lepton polarization asymmetries and polarization of the $Λ$ baryon in terms of compactification radius and corresponding form factors. We present the sensitivity of these observables to the compact…
