Dynamical Properties of Baryons

The internal structure of composite particles is conveniently described in terms of form factors (FFs)—these are experimentally accessible in annihilation and scattering of elementary reactions, and are theoretically calculable by all models that describe the properties of particles. FFs depend only on one kinematical variable, q2. This is the four-momentum transferred by the virtual photon that carries the interaction. Important developments in accelerator and detector techniques have brought impressive advances, both by extending the kinematical region and by reaching a higher precision. A critical review on the underlying methods and findings in polarized and unpolarized experiments is presented. The unique role played by polarization in determining the ratio of electric to magnetic form factors in the space-like region, and the extraction of individual form factors in the whole kinematical region, are described. Recent results at electron accelerators and electron–positron colliders confirm the existence of periodical structure in the annihilation cross section. We suggest a global framework which describes the dynamical structure of charge distribution in baryons, in order to build a coherent view of the creation and annihilation of baryonic matter.

On the Possibility of Separating Coherent and Incoherent (Anti)neutrino Scattering on Nuclei

The discovery of coherent neutrino–nucleus scattering in the COHERENT experiment opened a source of new information for fundamental investigations in the realms of neutrino and nuclear physics, as well as in the realms of searches for new physics beyond the Standard Model. Owing to substantial momentum transfers, a feature peculiar to the kinematical region of this experiment is that the effect of coherence is mixed with a sizable incoherent contribution rather than being seen in a pure form. On one hand, this leads to additional systematic uncertainties in studying the neutrino component of the coherence effect as such. On the other hand, this makes it possible to study a dynamical transition between the coherent and incoherent scattering modes and, in principle, to separate them experimentally. In our opinion, a consistent measurement of the coherent and incoherent cross sections for (anti)neutrino scattering on a nucleus in the same experiment seems a unique possibility, and its implementation would of course provide new data for neutrino physics, as well as for nuclear and new physics. In the present study, it is shown that this possibility is implementable not only in experiments that explore coherent neutrino and antineutrino scattering on various nuclei at accelerators, where the neutrino energy reaches several hundred MeV units but also in reactor experiments, where antineutrino energies do not exceed 10 MeV. The respective estimation is based on the approach that controls qualitatively a ‘‘smooth transition’’ of the cross section for (anti)neutrino–nucleus scattering from a coherent (or elastic) to an incoherent (inelastic) mode. In the former case, the target nucleus remains in the initial quantum state, while, in the latter case, its quantum state changes. Observation of a specific number of photons that have rather high energies and which remove the excitation of the nucleus after its inelastic interaction with (anti)neutrinos is proposed to be used as a signal from such an inelastic process. An upper limit on the number of such photons is obtained in this study.

The transverse polarization of $$\Lambda $$ hyperons in $$e^+e^-\rightarrow \Lambda ^\uparrow h X$$ processes within TMD factorization

We investigate the transverse polarization of the $$\Lambda $$ Λ hyperon in the processes $$e^+e^-\rightarrow \Lambda ^\uparrow \pi ^\pm X$$ e + e - → Λ ↑ π ± X and $$e^+e^-\rightarrow \Lambda ^\uparrow K^\pm X$$ e + e - → Λ ↑ K ± X within the framework of the transverse momentum dependent (TMD) factorization. The transverse polarization is contributed by the convolution of the transversely polarizing fragmentation function (PFF) $$D_{1T}^\perp $$ D 1 T ⊥ of the lambda hyperon and the unpolarized fragmentation function $$D_1$$ D 1 of pion/kaon. We adopt the spectator diquark model result for $$D_{1T}^{\perp }$$ D 1 T ⊥ to numerically estimate the transverse polarization in $$e^+e^-\rightarrow \Lambda ^\uparrow h X$$ e + e - → Λ ↑ h X process at the kinematical region of Belle Collaboration. To implement the TMD evolution formalism of the fragmentation functions, we apply two different parametrizations on the nonperturbative Sudakov form factors associated with the fragmentation functions of the $$\Lambda $$ Λ , pion and kaon. It is found that our prediction on the polarization in the $$\Lambda \pi ^+$$ Λ π + production and $${\bar{\Lambda }} \pi ^-$$ Λ ¯ π - is consistent with the recent Belle measurement in size and sign, while the model predictions on the polarizations in $$\Lambda \pi ^-$$ Λ π - and $$\Lambda K^\pm $$ Λ K ± productions show strong disagreement with the Belle data. The reason for the discrepancies is discussed and possible approaches to improve the calculation in the future are also discussed.

Revisiting the production of $$J/\psi $$ pairs at the LHC

We consider the prompt double $$J/\psi $$ J / ψ production in pp collisions at the LHC in the framework of $$k_T$$ k T -factorization QCD approach. Using the fragmentation mechanism, we evaluate the color octet contributions to the production cross sections taking into account the combinatorial effects of multiple gluon radiation in the initial state driven by the Ciafaloni–Catani–Fiorani–Marchesini evolution equation. We demonstrate the importance of these contributions in a certain kinematical region covered by the CMS and ATLAS measurements. On the other hand, the experimental data taken by the LHCb Collaboration at forward rapidities and moderate transverse momenta can be described well by $${{{\mathcal {O}}}}(\alpha _s^4)$$ O ( α s 4 ) color singlet terms and contributions from the double parton scattering mechanism. The extracted value of the effective cross section is compatible with many other estimations based on different final states.

Bs → K*0 decay form factors from covariant confined quark model

We evaluate Bs → K*0 transition form factors in the full kinematical region within the covariant confined quark model. The calculated form factors can be used to calculate the Bs → K*0 μ+μ– rare decay branching ratio, which was recently measured by LHCb collaboration.

D → π and D → K semileptonic form factors with Nf = 2 + 1 + 1 twisted mass fermions

We present a lattice determination of the vector and scalar form factors of the D → π(K)lv semileptonic decays, which are relevant for the extraction of the CKM matrix elements |Vcd| and |Vcs| from experimental data. Our analysis is based on the gauge configurations produced by the European Twisted Mass Collaboration with Nf = 2 + 1 +1 flavors of dynamical quarks. We simulated at three different values of the lattice spacing and with pion masses as small as 210 MeV. The matrix elements of both vector and scalar currents are determined for a plenty of kinematical conditions in which parent and child mesons are either moving or at rest. Lorentz symmetry breaking due to hypercubic effects is clearly observed in the data and included in the decomposition of the current matrix elements in terms of additional form factors. After the extrapolations to the physical pion mass and to the continuum limit the vector and scalar form factors are determined in the whole kinematical region from q2 = 0 up to [see formula in PDF] accessible in the experiments, obtaining a good overall agreement with experiments, except in the region at high values of q2 where some deviations are visible.

Towards a unified description of the electroweak nuclear response

We briefly review the growing efforts to set up a unified framework for the description of neutrino interactions with atomic nuclei and nuclear matter, applicable in the broad kinematical region corresponding to neutrino energies ranging between few MeV and few GeV. The emerging picture suggests that the formalism of nuclear many-body theory (NMBT) can be exploited to obtain the neutrino-nucleus cross-sections needed for both the interpretation of oscillation signals and simulations of neutrino transport in compact stars.

Impact of scalar mesons on the rare B-decays

In the wake of exploring uncertainty in the full angular distribution of the [Formula: see text] caused by the presence of the intermediate scalar [Formula: see text] meson, we perform the straightforward calculation of the [Formula: see text] (S is a scalar meson) transition form factors in the full kinematical region within the covariant quark model. We restrict ourselves by the scalar mesons below 1 GeV: [Formula: see text]. As an application of the obtained results we calculate the widths of the semileptonic and rare decays [Formula: see text], [Formula: see text] and [Formula: see text]. We compare our results with those obtained in other approaches.

ULTRA-HIGH ENERGY NEUTRINO DISPERSION IN PLASMA AND RADIATIVE TRANSITION νL → νR+γ

Qualitative analysis of additional energy of neutrino and antineutrino in plasma is performed. A general expression for the neutrino self-energy operator is obtained in the case of ultra-high energies when the local limit of the weak interaction is not valid. The neutrino and antineutrino additional energy in plasma is calculated using the dependence of the W- and Z-boson propagators on the momentum transferred. The kinematical region for the neutrino radiative transition (the so-called "neutrino spin light") is established for some important astrophysical cases. For high energy neutrino and antineutrino, dominating transition channels in plasma, νe + e+ → W+, [Formula: see text] and [Formula: see text], are indicated.