Narrow Results

The Feynman diagram generator FeynArts and the computer algebra program FormCalc allow for an automatic computation of 2→2 and 2→3 scattering processes in High Energy Physics. We have extended this package by four new kinematical routines and adapted one existing routine in order to accomodate also two- and three-body decays of massive particles. This makes it possible to compute automatically two- and three-body particle decay widths and decay energy distributions as well as resonant particle production within the Standard Model and the Minimal Supersymmetric Standard Model at the tree- and loop-level. The use of the program is illustrated with three standard examples: , , and .

We describe an algorithm for the generation of relativistic kinematics for collision and decay processes with multiparticle final states. In the framework of this algorithm it is possible to generate different kinematics covering most of practically interesting cases. One gets a possibility to introduce different sets of integration variables. As a result different sets of kinematical singularities can be regularized. To smooth sharp peaks some regularization formulas and procedures are used covering most typical cases. The algorithm is realized in the package CompHEP created for automatic calculations of collision and decay processes.

Based on the mass relation derived under the assumption that for the almost ideally mixing meson nonets, the corrections deduced by the flavor-dependent quarkonia transition can be ignored, the mass of the isodoublet of the 2 ¹S₀ nonet is predicted to be 1391.8±67.7 MeV. The quarkonia content of isoscalar states of the 2 ¹S₀ nonet, i.e. η(1295) and η(1475), is given, and some predictions on the decays of the two isoscalar state are presented. These predictions can be tested in Beijing Electron Positron Collider Bejing Spectrometers (BEPC/BES) with 58 million J/ψ events in the near future.

In this brief review, we summarize the current theoretical knowledge of heavy quarkonium inclusive decays, with emphasis on recent progress made in the framework of QCD effective field theories. In the appendix, we list the imaginary parts of the matching coefficients of dimensions six and eight NRQCD four-fermion operators as presently known.

In the framework of meson–meson mixing, in the presence of the a₄(2040), and f₄(2050) being the 1 ³F₄ states, we suggest that the f′₄, the ninth member of the 1 ³F₄ meson nonet, has a mass of about 2084 MeV, and some predictions on the f₄ and f′₄ decaying into two photons and pseudoscalar mesons are presented. Also, the mass of the lowest lying 4⁺⁺ glueball is predicted to be about 3.15 GeV by using the meson-glueball mass relation derived from the glueball dominance picture, which is in agreement with 3.42 GeV, the average value of the recent predicted results was given by lattice QCD, potential model, semi-relativistic potential model and quasi-particle model.

We review recent measurements of heavy B hadron states including masses and lifetimes of the meson as well as excited B states . We discuss properties of the meson such as lifetime, lifetime difference ΔΓ_s/Γ_s and CP violation in decays. We also summarize new measurements of the masses and lifetimes of bottom baryons including the baryon, the Σ_b baryon states as well as the and baryons.

We consider the decay modes of the heavy bound states originating from Higgs boson exchange between quark–antiquark pair. In case of a small coupling between the fourth and lower generation the main decay mode is annihilation. We show that for a vector state the dominant decay modes are Higgs-gamma and Higgs-Z decays, while for a pseudoscalar state the strong two-gluon decay mode dominates. The bound states are very narrow. The ratio of the total width to the binding energy is less than 1% if we are not extremely close to the critical quark mass where the binding energy is very small. The discussed decay modes exist for any fermion–antifermion bound states including heavy leptons and heavy neutrinos if their masses are high enough to form a bound state due to attractive Higgs boson exchange potential.

We present a review of heavy flavor physics results from the CDF and DØ Collaborations operating at the Fermilab Tevatron Collider. A summary of results from Run 1 is included, but we concentrate on legacy results of charm and b physics from Run 2, including results up to Summer 2014.

A beam channel of polarized protons and antiprotons produced from decays of $\mathrm{\Lambda }$- and anti-$\mathrm{\Lambda }$-hyperons for the SPASCHARM experiment is to be built at IHEP U-70 accelerator in Protvino, Russia. The methods for tagging and measuring polarization of the beam (anti)protons are discussed in this report. The fast on-line beam tagging exploits the correlations between polarization and kinematics of (anti)protons originated from (anti)$\mathrm{\Lambda }$-decays. In the intermediate focus of primary target, decay (anti)protons of different transverse polarizations are spatially dispersed transversely with respect to the beam axis. The tagging system, consisting of fast beam detectors with good spatial resolution, measures the momentum and trajectory of each beam particle, including its position at the intermediate focus, thus allowing instant (on-line) assignment of the transverse polarization value to each (anti)proton. This system is also extremely useful for the beam channel tuning. While being fast and convenient, the polarization tagging fully relies on computing of particle transportation in the beam channel. In order to verify the real beam polarization and operating of the tagging system and beam channel, the independent absolute beam polarimetry is to be used. It is based on measuring the spin asymmetries in elastic scattering of beam (anti)protons in Coulomb-Nuclear Interference (CNI) and diffractive kinematic regions. It is estimated that less than one week of data taking would allow measuring an absolute beam polarization at the statistical accuracy of $\sim$4–5%.

A new experiment SPASCHARM for systematic study of polarization phenomena in the inclusive and exclusive hadronic reactions in the energy range of IHEP accelerator U-70 (12–50GeV) is currently under development. The universal experimental setup will detect dozens of various resonances and stable particles produced in collisions of unpolarized beams with the polarized target, and at the next stage, using polarized proton and antiproton beams. At the beginning, the final states consisting of light quarks ($u$, $d$, $s$) will be reconstructed, and later on the charmonium states will be studied. Measurements are planned for a variety of beams: ${\pi }^{\pm },K^{\pm },p$, antiprotons. Hyperon polarization and spin density matrix elements of the vector mesons will be measured along with the single-spin asymmetry (SSA). The 2$\pi$-acceptance in azimuth, which is extremely useful for reduction of systematic errors in measurements of spin observables, will be implemented in the experiment. The solid angle acceptance of the setup, $\mathrm{\Delta }\theta \approx 250$ mrad vertically and 350 mrad horizontally in the beam fragmentation region, covers a wide range of kinematic variables $p_T$ and $x_F$. This provides the opportunity for separating dependences on these two variables which is usually not possible in the setups with a small solid angle acceptance. Unlike some previous polarization experiments, the SPASCHARM will be able to simultaneously accumulate and record data on the both, charged and neutral particle production.

In 2014 BESIII collected a data sample of 567 $p{b}^{-1}$ at $E_{cm}$ = 4.6 GeV, which is just above the ${\mathrm{\Lambda }}_c^{+}$ pair production threshold. By analyzing this data sample, we have measured the absolute branching fractions for many decays of ${\mathrm{\Lambda }}_c^{+}$ for the first time. These decays include the semileptonic decays of $\mathrm{\Lambda }{e}^{+}\nu$, $\mathrm{\Lambda }{\mu }^{+}\nu$, the hadronic decays of $p{K}_s$, $p{K}^{-}{\pi }^{+}$, $p{K}^{-}{\pi }^{+}{\pi }^0$, $\mathrm{\Lambda }{\pi }^{+}$, $\mathrm{\Lambda }{\pi }^{+}{\pi }^0$, ${\mathrm{\Sigma }}^{+}{\pi }^{+}{\pi }^0$, $p{K}_s{\pi }^0$, $\mathrm{\Lambda }{\pi }^{+}{\pi }^{+}{\pi }^{-}$, $p{K}_s{\pi }^{+}{\pi }^{-}$, ${\mathrm{\Sigma }}^0{\pi }^{+}$, ${\mathrm{\Sigma }}^{+}{\pi }^0$, ${\mathrm{\Sigma }}^{+}\omega$, $p\varphi$, $p{K}^{+}{K}^{-}(\mathrm{\text{non}}-\varphi )$, $p{\pi }^{+}{\pi }^{-}$, $n{K}_s\pi +$, ${\mathrm{\Sigma }}^{-}{\pi }^{+}{\pi }^{+}({\pi }^0)$ and inclusive decay $\mathrm{\Lambda }$ + anything. The decays of $p{\pi }^{+}{\pi }^{-}$, $n{K}_s{\pi }^{+}$ and ${\mathrm{\Sigma }}^{-}{\pi }^{+}{\pi }^{+}{\pi }^0$ are observed for the first time and the others are measured with significantly improved precision. These results are important to benefit the development of the related theories, and provide important inputs for both charmed baryons and $B$ physics.

The charged lepton flavor violating decays are expected to be a direct indication of new physics. Recent results of searches for lepton flavor violating decays of τ-lepton with the B-factories' huge data samples are reported.