$$\bar K$$ optical potential at finite temperatureoptical potential at finite temperature

The \(\bar K\) optical potential is microscopically calculated from the \(\bar K\)N effective interaction in nuclear matter at T=0 and finite temperature, with the aim to adapt our calculations to the experimental conditions in heavy-ion collisions. In the rank of densities (0-2_ρ0), the finite temperature \(\bar K\) optical potential shows a smoother behaviour compared to the T=0 case. The model has also been applied to the study of the ratio between K⁺ and K^? produced at GSI with T around 70 MeV. The results point at the necessity of introducing an attractive \(\bar K\) optical potential.     

VEPP-2000 project: Collider,detectors, and physics program

The new VEPP-2000 e⁺e^? collider of maximum energy 2000 MeV, which is under construction at the Budker Institute of Nuclear Physics (Siberian Division, Russian Academy of Sciences, Novosibirsk), is briefly described. Experiments at VEPP-2000 will be performed with two upgraded detectors, CMD-2M and SND. A precise measurement of the total cross section for the process e⁺e^? → hadrons and of the partial cross sections for its exclusive hadronic channels is the main point of the physics program for this machine. These measurements will be aimed at testing QCD and the VMD and CVC models, as well as at refining the hadron contribution to fundamental constants such as the muon anomalous magnetic moment \(a_\mu = \frac{{g - 2}}{2}\) and the fine-structure constant α_em(M _Z ² ). Measurements of the nucleon form factors in the reactions e⁺e^? → p\(\bar p\), n\(\bar n\) at their threshold will also be of great importance.     

On the structure of the von Neumann algebras generated by local functions of the free bose field

It is shown that the von Neumann algebra\(R_\mathfrak{B} \)(B) generated by any scalar local functionB(x) of the free fieldA ₀(x) is equal either to\(R_\mathfrak{B} \)(A ₀) or to\(R_\mathfrak{B} \)(:A ₀ ² :). The latter statement holds if the state space space\(\mathfrak{H}_B \) obtained from the vacuum state by repeated application ofB(x) is orthogonal to the one particle subspace. In the proof of these statements, space-time limiting techniques are used.     

Pentaquarks—status report

I discuss the recent experimental and theoretical developments following the discovery of the 8⁺ pentaquark, an exoticuudd \(\bar s\) baryon resonance observed in theKN channel by several experiments, and an exotic Ξ^*?? (ddss \(\bar u\)) reported by NA49 at CERN. I focus on the theoretical interpretation of the data, both in terms of quark and chiral degrees of freedom, on the predictions for related exotic states, and on several unresolved questions raised by the experimental data, such as why some experiments observe the pentaquarks and other don't, the apparently extremely narrow width of the Θ⁺ and the determination of its parity. I also describe the likely properties of the proposed heavy-quark pentaquarks, an anticharmed exotic baryon Θ _c uudd \(\bar c\) and Θ _b ⁺ (uudd \(\bar b\)) which are expected to be extremely narrow or even stable against strong decays. H1 recently reported observation of a possible Θ _c candidate inD ^*? p channel. Pentaquarks are also being searched for ine ⁺ e ^? annihilation and γγ collisions in the LEP data and atB-factories.     

Dominant decays of scalar leptoquarks and scalar gluons in the minimal four-color symmetry model

Fermionic and weak decays of the scalar leptoquarks S = S ₁ ⁽⁺⁾ , S ₁ ^(?) , and S _m and the scalar gluons F = F ₁ and F ₂ predicted by the minimal model involving four-color symmetry and the Higgs mechanism of quark-and lepton-mass splitting are considered. The widths and the branching ratios are calculated for these decays, and the results are analyzed versus the couplings and masses of decaying particles. It is shown that, at relatively small mass splittings Δm within scalar doublets (Δm < m _W), the fermionic decays S ₁ ⁽⁺⁾ → tl _j ⁺ , S ₁ ^(?) → v _i \(\tilde b\), S _m → t \(\tilde \nu \) _j, F ₁ → t \(\tilde b\), and F ₂ → t \(\tilde t\), which are characterized by few-GeV widths for m _S, m _F < 1 TeV and decay branching ratios close to unity, are dominant, but that, for Δm > m _W, the weak decays S → S′W and F → F’W compete with the above fermionic decays. In the case of m _S < m _t, the processes S ₁ ⁽⁺⁾ → cl _j ⁺ , S ₁ ^(?) → v _i \(\tilde b\), S _m → bl _j ⁺ , and S _m → c \(\tilde \nu \) _j, whose total branching ratios are Br(S ₁ ⁽⁺⁾ → cl ⁺) ≈ Br(S ₁ ^(?) → v \(\tilde b\)) ≈ 1, Br(S _m → bl ⁺) ≈ 0.9, and Br(S _m → c \(\tilde \nu \)) ≈ 0.1, appear to be dominant decays of scalar leptoquarks. Searches for these decays at LHC and the Tevatron are of interest.     

Neutron-antineutron oscillations in the trapping box

The problem of n-\(\bar n\) oscillations for ultracold neutrons confined within a trap is reexamined. It is shown that the growth of the \(\bar n\) component with time is to a decent accuracy given by \(P(\bar n) = \varepsilon _{n\bar n}^2 t_L t\), where \(\varepsilon _{n\bar n}\) is the mixing parameter and t _L ～ 1 s is the neutron propagation time between subsequent collisions with the trap walls. Possible corrections to this law and open questions are discussed.     

Calculation of the fine structure of the triplet state $$\tilde a^3 A_2 $$ of the ozone molecule by the method of multiconfiguration self-consistent field

The zero-field splitting of the \(\tilde a^3 A_2 \) state of the O₃ molecule is interpreted on the basis of ab initio quantum-chemical calculations. The spin—orbit coupling with the ground X¹A₁ state is shown to make the main contribution to the zero-field splitting of the \(\tilde a^3 A_2 \) term (the state of the ³σπ type). The calculated parameters D and E agree well with experiment.     

Schrödinger equation in multiply connected spaces and phase optics

The magnetic vector potential\(\vec A\) in a field free spaceR ₀ cannot be removed by gauge transformations in general, ifR ₀ is multiply connected.Aharonov andBohm ¹ have noticed recently that\(\vec A\) therefore should have more physical meaning than only to give the magnetic field by differentiation. They could show that\(\vec A\) inR ₀ may influence the phase ofSchrödinger'sψ-function in an observable manner. We want to point out here that this influence can be expressed in a simple, general form: “A closed magnetic field line operates uponψ like ae Φ/?-phase-shifter placed on any area bounded by the field line.” Surface like phase shifters are familiar in phase optics. There exists a narrow relationship between electron scattering at magnetic fields and some special problems of phase optics. An electron phase contrast microscope is discussed.     

Die absolute Intensität der durch Elektronenstoß in einer dicken Wolfram-Antikathode erzeugtenL α -Strahlung

The number\(N_{L_\alpha }^{dir} \) (produced) ofL _α -photons produced by electron-bombardment in a thick target of tungsten per incident electron has been measured absolutely with the Ross-filter method and relatively with the crystal-spectrometer method in the energyregion up to the 3.6 times theL _III-ionization energy\(E_{L_{III} } \). The result can be presented in the following empirical form:\(N_{L_\alpha }^{dir} \) (produced)=4π·?·(U ₀?1) ⁿ with ?=0.52·10^?4±5% andn=1.44±0.02\((U_0 = E_0 /E_{L_{III} }< 3.6)\). Out of this the number\(n_{L_{III} } \) ofL _III-ionizations per electron which is slowed down to the energy\(E_{L_{III} } \) within the target, has been evaluated. The computation of\(n_{L_{III} } \) out of the elementary process by usingBethe's non-relativistic formulae for totalL _III-ionization cross sectionQ _L and energy loss-dE/ds is in full agreement with experiment in the region 2<U ₀<3.6, if the constants in\(Q_{L_{III} } \) are chosen as follows:\(B = 4E_{L_{III} } , b_{L_{III} } = 0.25 \cdot 5.89\). By comparison of this result for\(b_{L_{III} } \) with the corresponding value ofb _K in the totalK-ionization cross-sectionQ _K for copper (b _K=0.35·2.26) it is concluded that\(Q_{L_{III} } \) is considerably higher than predicted by theory. The necessary correction factors as e.g. loss ofL _III-ionizations by rediffusion of electrons and portion of indirectly producedL _α -radiation-radiation are determined for tungsten quantitatively.     

Analysis of th e $$Hb\bar b$$ coupling constant and CP-violation eff ects at th e futur e e+ e− collid er

The \(e^ + e^ - \to b\bar bv\bar v\) process, where υ is an electron, muon, or τ-lepton neutrino, is analyzed in detail for the general form of the coupling constant of a Higgs boson with b quarks, with the (m _b /v)(a+Iγ₅b) parameterization of the \(Hb\bar b\) interaction. This process is shown to be highly sensitive to this coupling constant. Experiments at the future with \(\sqrt s = 500 - GeV\) linear collider will provide limits of 2 and 20% for deviations of the parameters a and b, respectively, from their Standard Model values. Results concerning the \(e^ + e^ - \to b\bar bv\bar v\) process in combination with the independent measurements of the partial width \(\Gamma _{H \to b\bar b}\) can testify to the CP origin of the Higgs sector of the theory.     

Surface superconductivity and<Emphasis Type="Italic">H</Emphasis><Subscript><Emphasis Type="Italic">c3</Emphasis></Subscript> in UPt<Subscript>3</Subscript>

Ginzburg-Landau (GL) theory is used to study surface superconductivity for UPt₃ for various order parameter symmetries (OPS), andH _c3 is found for all principal directions of the surface normal\(\hat n\) and the field [1]. Assuming specular reflection, and allowing for reorientation of the antiferromagnetic symmetry breaking field in the models withE _1g ,E _2g ,E _1u , orE _2u symmetry, the experiments of Keller et al. [2] with\(\hat n = \hat a\) can be qualitatively explained for all OPS except possiblyA _1u ⊕B _1u . The implied GL parameters then predict qualitatively different and OPS dependent behavior for\(\hat n = \hat a^* \) and\(\hat n = \hat c\). Study ofH _c3 for these surfaces would give strong clues about the OPS of UPt₃.     

Parametrization of supersingular perturbations in the method of rigged Hilbert spaces

A classification of bounded below supersingular perturbations à of a self-adjoint operator A ? 1 is suggested. In the A-scale of Hilbert spaces \(\mathcal{H}_{ - k} \sqsupset \mathcal{H} \sqsupset \mathcal{H}_k \) = Dom A ^k/2, k > 0, a parametrization of operators à in terms of bounded mappings S: \(\mathcal{H}_k \to \mathcal{H}_{ - k} \) such that ker S is dense in \(\mathcal{H}_{k/2} \) is obtained.     

Phenomenology of light- and strange-quark simultaneous production at high energies

This letter presents an extension of EPL116(2017)62001 to light- and strange-quark nonequilibrium chemical phase-space occupancy factors (γ_q,s). The resulting damped trigonometric functionalities relating γ_q,s to the nucleon-nucleon center-of-mass energies (\(\sqrt {{s_{NN}}} \)) looks very similar except different coefficients. The phenomenology of the resulting γ_q,s(\(\sqrt {{s_{NN}}} \)) describes a rapid decrease at \(\sqrt {{s_{NN}}} \) ? 7GeV followed by a faster increase up to ~20 GeV. Then, both γ_q,s become nonsensitive to \(\sqrt {{s_{NN}}} \). Although these differ from γ _s (\(\sqrt {{s_{NN}}} \))obtained at γ _q (\(\sqrt {{s_{NN}}} \))=1, various particle ratios including K⁺/π⁺, K^?/π^?, Λ/π^?, Λ?/π^?, Ξ⁺/π⁺, and Ω/π^?, can well be reproduced, as well. We conclude that γ_q,s(\(\sqrt {{s_{NN}}} \)) should be instead determined from fits of various particle yields and ratios but not merely from fits to the particle ratio K⁺/π⁺.     

Contributions of scalar leptoquarks to the cross sections for the production of quark-antiquark pairs in electron-positron annihilation

The contributions of scalar-leptoquark doublets to the cross sections \(\sigma _{Q\tilde Q} \), for the production of quark-antiquark pairs in electron-positron annihilation are calculated within the minimal model based on the four-color symmetry of quarks and leptons. These contributions are analyzed versus the scalar-leptoquark masses and the mixing parameters of the model at colliding-particle energies in the range 250–1000 GeV. It is shown that the contributions in question are of greatest importance for processes leading to t-quark production. In particular, it is found that, with allowance for the contribution of the scalar leptoquark of charge 5/3 and mass in the range 250–500 GeV, the cross section \(\sigma _{t\tilde t} \) calculated at a mixing-parameter value of k_t ～ 1 may be severalfold larger than the corresponding cross section \(\sigma _{t\tilde t}^{(SM)} \) within the Standard Model. The possibility of setting constraints on the scalar-leptoquark masses and on the mixing parameters by measuring such contributions at future electron-positron colliders is indicated.     

Quark-hadron duality and production of charmonia and doubly charmed baryons in <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> anninhilation

The cross sections for the production of charmonia and doubly charmed baryons in e ⁺ e ^? annihilation at an interaction energy of \(\sqrt s \) = 10.6 GeV are predicted under the assumption of quark—hadron duality. The method used is shown to remove some contradictions between experimental data and perturbative QCD.     

Effective conductivity of 2D isotropic two-phase systems in a magnetic field

Using the linear fractional transformation, which connects the effective conductivities \(\hat \sigma _e \) of isotropic two-phase systems with and without magnetic field, explicit approximate expressions for \(\hat \sigma _e \) in a magnetic field are obtained. They allow one to describe \(\hat \sigma _e \) of various inhomogeneous media at arbitrary phase concentrations x and magnetic fields. The x-dependence plots of \(\hat \sigma _e \) at some values of inhomogeneity and magnetic field are constructed. Their behavior is qualitatively compatible with the existing experimental data. The obtained results are applicable to different two-phase systems (regular and irregular as well as random), which satisfy the symmetry and self-duality conditions, and admit direct experimental checking.     

Hadron production at forward rapidity in nuclear collisions at RHIC

The main experimental results obtained by the BRAHMS experiment at Relativistic Heavy Ion Collider (RHIC) for Au+Au collisions at \(\sqrt {s_{NN} } \) =62.4, 200 GeV and d+Au collisions at \(\sqrt {s_{NN} } \) = 200GeV are presented. The m _T spectra and the Gaussian-like rapidity densities of produced pions and kaons in Au+Au central collisions at \(\sqrt {s_{NN} } \) = 200 are GeV shown, and their rapidity densities are compared with results from models. The net-proton yield in the same system is compared with that from AGS and SPS energies to study the high energy collision scenario-transparency and stopping. The rapidity, energy and centrality dependence of the nuclear modification factors in both systems are compared with models to differentiate between the initial and final state effect.     

New feature of low $$p_{T}$$ charm quark hadronization in pp collisions at $$\sqrt{s}=7$$s=7 TeV

Treating the light-flavor constituent quarks and antiquarks whose momentum information is extracted from the data of soft light-flavor hadrons in pp collisions at \(\sqrt{s}=7\) TeV as the underlying source of chromatically neutralizing the charm quarks of low transverse momenta (\(p_{T}\)), we show that the experimental data of \(p_{T}\) spectra of single-charm hadrons \(D^{0,+}\), \(D^{*+}\) \(D_{s}^{+}\), \(\varLambda _{c}^{+}\) and \(\varXi _{c}^{0}\) at mid-rapidity in the low \(p_{T}\) range (\(2\lesssim p_{T}\lesssim 7\) GeV/c) in pp collisions at \(\sqrt{s}=7\) TeV can be well understood by the equal-velocity combination of perturbatively created charm quarks and those light-flavor constituent quarks and antiquarks. This suggests a possible new scenario of low \(p_{T}\) charm quark hadronization, in contrast to the traditional fragmentation mechanism, in pp collisions at LHC energies. This is also another support for the exhibition of the soft constituent quark degrees of freedom for the small parton system created in pp collisions at LHC energies.     

Evidence for a narrow anti-charmed baryon state

We report an observation of a narrow resonance state inD ^*? andD ^*+ \(\bar p\) in inelastic electron-proton collisions at centre-of-mass energies of 300 and 320 GeV at HERA. The resonance has a mass of 3099±3 (stat.)±5 (syst). MeV and width of 12±3 (stat.) MeV, compatible with the experimental resolution. The resonance is interpreted as an anti-charmed baryon with a minimal constituent quark composition ofuudd \(\bar c\), together with the charge conjugate.     

Top-quark <Emphasis Type="Italic">p</Emphasis><Subscript><Emphasis Type="Italic">T</Emphasis></Subscript>-spectra at CMS and flavor independence of <Emphasis Type="Italic">z</Emphasis>-scaling

We present new results of analysis of top-quark differential cross sections obtained by the CMS Collaboration in pp collisions in the framework of the z-scaling approach. The spectra are measured over a wide range of collision energy \(\sqrt s = 7,8,13TeV\) and transverse momentum p _T = 30?500 GeV/c of top-quark using leptonic and jet decay modes. Flavor independence of the scaling function ψ(z) is verified in the new kinematic range. The results of analysis of the top-quark spectra obtained at the LHC are compared with similar spectra measured in \(\overline p p\) collisions at the Tevatron energy \(\sqrt s = 1.96TeV\). A tendency to saturation of ψ(z) for the process at low z and a power-law behavior of ψ(z) at high z is observed. The measurements of high-p _T is observed. The measurements of highspectra of the top-quark production at highest LHC energy is of interest for verification of self-similarity of particle production, understanding flavor origin and search for new physics symmetries with top-quark probe.