Strange multibaryon states with Λ hyperon systems in pA collision at 10 GeV/<Emphasis Type="Italic">c</Emphasis>

Experimental data from the 2m propane bubble chamber have been analyzed for exotic baryon states search. A number of peculiarities were found in the effective mass spectra of Λπ⁺ (Σ*⁺ (1382), PDG), Λp, and Λpp subsystems. A few events detected on the photographs of the propane bubble chamber exposed to a 10 GeV/c proton beam were interpreted as S = −2H ⁰ light(<M _(ΛΛ)) and heavy H ^{0, +}. A new event detected on the photographs of the propane bubble chamber was interpreted as heavy H ⁺ (2488) dibaryon by weak decay channels of K ⁻ pp or Σ⁺ pπ⁻. The text was submitted by the author in English.     

NA60 results on thermal dimuons

The NA60 experiment at the CERN SPS has measured muon pairs with unprecedented precision in 158 A GeV In–In collisions. A strong excess of pairs above the known sources is observed in the whole mass region 0.2<M<2.6 GeV. The mass spectrum for M<1 GeV is consistent with a dominant contribution from π ⁺ π ⁻→ρ→μ ⁺ μ ⁻ annihilation. The associated ρ spectral function shows a strong broadening, but essentially no shift in mass. For M>1 GeV, the excess is found to be prompt, not due to enhanced charm production, with pronounced differences to Drell–Yan pairs. The slope parameter T _eff associated with the transverse momentum spectra rises with mass up to the ρ, followed by a sudden decline above. The rise for M<1 GeV is consistent with radial flow of a hadronic emission source. The seeming absence of significant flow for M>1 GeV and its relation to parton–hadron duality is discussed in detail, suggesting a dominantly partonic emission source in this region. A comparison of the data to the present status of theoretical modeling is also contained. The accumulated empirical evidence, including also a Planck-like shape of the mass spectra at low p _T and the lack of polarization, is consistent with a global interpretation of the excess dimuons as thermal radiation. We conclude with first results on ω in-medium effects.     

Secondary ion emission from bismuth under bombardment with Bi m ? and Au m ? cluster ions

The mass spectra of secondary cluster ions Bi _n ⁺ (n = 1–9) from bismuth sputtered by (6–21) keV Au _m ⁻ (m = 1–9) and Bi _m ⁻ (m = 1–5) cluster ions have been investigated. New features of manifestation of dense nonlinear cascades and thermal spikes have been revealed. It is concluded that the thermal spike regime makes a significant contribution to the mechanism of formation of small cluster ions, containing up to seven atoms for a bismuth target.     

Secondary-ion emission of amino acids

Secondary-ion mass spectroscopy (SIMS) is a hydrogen, isotope and compound sensitive analytical technique of extremely high absolute sensitivity. Continuing earlier measurements for carboxylic acids, adsorbed alcohols etc., we have carried out a systematical investigation of secondary-ion emission from metal-supported amino acids, containing various functional groups (e.g., alanine, phenylalanine, cysteine, arginine). In order to avoid damage effects we applied extremely small primary-ion current densities in the 10⁻⁹ A·cm⁻² range. The main results of our investigations can be summarized as follows:

Search for low-mass exotic mesonic structures: II. Attempts to understand the results

Our previous paper, part I of the same study, shows the different experimental spectra used to draw a conclusion on the genuine existence of narrow, weakly excited mesonic structures having masses below and a little above the pion (M = 139.56 MeV) mass. This study [1] was instigated by the observation, in the Σ⁺ disintegration—Σ⁺ → pP ⁰, P ⁰ → μ⁻μ⁺ [2]—of a narrow range of dimuon masses. The authors make a conclusion on the existence of a neutral intermediate state P ₀ with a mass M = (214.3 ± 0.5) MeV. We present here some attempts to understand the possible nature of the structures observed in part I. The text was submitted by the authors in English.     

Tunable near-infrared optical properties of three-layered gold–silica–gold nanoparticles

The absorption spectra of gold–silica–gold nanoshells have been investigated by using Mie theory with variation of the geometry. With an increase in core radius the plasmon resonance for the lower energy mode ω ₋⁻ shows a distinct redshift while for the high-energy mode ω ₋⁺ shows a blueshift. It is surprising that with increasing middle layer thickness the resonance of ω ₋⁻ mode blueshifts first and then redshifts. In addition, an increase of the dielectric constant of the middle layer is found to reduce the resonance energies of the particle. The tunable near-infrared optical properties are discussed in terms of plasmon hybridization theory.     

Theψ-particles in an SU4 scheme with anomalous currents

The recently discovered narrow peaks (theψ-particles) in e⁺e⁻ system at 3.105 and 3.695 GeV are interpreted as hadrons in a broken SU₄ symmetry scheme. A new additional additive quantum number, parachargeZ, is combined with the usual SU₃ quantum numbers in the group SU₄. Theψ (3.1) is assigned to a near ideally mixed15⊕1 multiplet of vector mesons (containing theρ) as theI=Y=0, charge conjugationC=−combination ofZ=±1.members. Theψ (3.7) is assigned correspondingly to another mixed15⊕1 multiplet containing theρ′ (1600). The hadronic electromagnetic interactions are modified by the addition of (non-minimal) anomalous pieces that can changeZ. The decays of theψ-particles are discussed. New enlarged SU₄ multiplets of other hadrons are proposed. Tests of our scheme are put forward. The most crucial test will be the observation of two rather broad resonances in e⁺ e⁻ collisions with masses around 4.2 GeV and 5.1 GeV. Another prediction is the presence of energetic photons in the decays of theψ-particles. Important results concerning the recently observed phenomena in the process e⁺e⁻→hadrons follow in this scheme.     

Emission of quasi-thermal ions from a solid bombarded by cluster ions

Comparative studies of the emission of quasi-thermal atomic and cluster ions from V, Nb, Ta, Au, and In targets bombarded by cluster ions Au _m ⁻(m = 1–9), as well as from Si and Bi targets bombarded by cluster ions Au _m ⁻(m = 1–9) and Bi _m ⁻(m = 1–5), with energy E ₀ ranging from 6 to 21 keV are carried out. In the case of bombardment by heavy cluster ions, the fraction of the quasi-thermal component in the energy spectra of sputtered atomic ions reaches 50 (for V, In, and Au), 70 (Nb), or more than 90% (Ta). In addition, quasi-thermal ions play a considerable part in the emission of small cluster ions Au₂⁺, In₂⁺, In₃⁺, and Bi _n ⁺(n = 2–7). The results of the generalizing investigation favor the presence of thermal spike conditions at cluster bombardment and their appreciable contribution to the emission of atomic and small cluster ions.     

Fragmentation of sputtered Si<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>O<Stack><Subscript><Emphasis Type="Italic">m</Emphasis></Subscript><Superscript>+</Superscript></Stack> clusters: Release kinetic and dissociation energies

The spectra of kinetic energies of positive Si _n O _m ⁺ cluster ions (n = 2–5, m = 2–7) have been measured using a double focusing ion microanalyzer with reverse geometry at instants 10⁻⁵ to 10⁻⁴ s after emission. The dissociation energies have been determined within the evaporative ensemble model and the theory of unimolecular decay reactions. The results obtained are compared with the binding energies of neutral Si _n O _m clusters.     

Colour effects in Drell-Yan process

We examine the predictions of gauge theories with colour excitation for the processpp →μ ⁺ μ ⁻ X. Relative to the predictions of quark parton model (with three colours) we find enhancements as large as a factor 3 – 4 for the cross-sectionM ³ d ² σ/dMdy|_y=0 in the region 0·03 ≲M/√s ≲ 0·2 at √s=62 GeV,M being the invariant mass andy the rapidity of the muon pair. We study the sensitivity of this result to the colour gluon mass and the underlying parametrisation of the quark and gluon distribution functions.     

Search for and study of low-mass scalar mesons in reactions np → npπ+π? at neutron beam momentum Pn = (3.83 ± 0.12) GeV/c

The results of a search for and study of the scalar 0⁺ [0⁺⁺] σ₀ mesons in a π⁺π⁻ system produced in the reaction np → npπ⁺π⁻ at the quasi-monochromatic neutron beam momentum P _n = (3.83 ± 0.12) GeV/c are presented as derived from analyzing the data obtained during the exposure of a 1-meter hydrogen bubble chamber at the Laboratory of High Energy, Joint Institute for Nuclear Research (LHE JINR). It is found that there is a significant bump in the effective mass distribution at M_{p⁺ p^-} = (404 ±5)MeV/c²M_{\pi ^ + \pi ^ - } = (404 \pm 5)MeV/c^2 and Γ_res^exp = (14±5.4) MeV/c ², which is observed with more than four standard deviations from the background. The spin of this resonance is estimated to be most likely equal to zero. Its quantum numbers are found to be 0⁺ [0⁺⁺].     

Rare t-quark decays t → clj+lk? and t → c?jvk induced by doublets of scalar leptoquarks within the minimal four-color-symmetry model

The rare t-quark decays t → cl _j ⁺ l _k ⁻ and t → cṽ _j k _k induced by scalar-leptoquark doublets are considered within the minimal model involving four-color quark-lepton symmetry and the Higgs mechanism of quark and lepton mass splitting. The partial widths with respect to the decays being considered and the total widths Γ(t → cl ⁺′l ⁻) = Σ_j,k Γ(t → cl _j ⁺ l _k ⁻ ) and Γ(t → cl ⁺′l ⁻) = Σ_j,kΓ(t → cṽ _j v _k ) with respect to, respectively, the charged leptonic and neutrino modes are calculated. It is shown that, at scalar-leptoquark masses higher than the t-quark mass (m _S > m _t), the branching ratios for these modes are Br(t → cl ⁺′l ⁻) ≈ (3.5−0.4) × 10⁻⁵ and Br(t → cṽ′v) ≈ (7.1−0.8) × 10⁻⁵ at m _s = 180–250 GeV and an appropriate value of the leptoquark-mixing angle (sin β ≈ 0.2) and can increase for m _S < m _t to Br(t → cl ⁺′l ⁻) ≈ 0.03−0.002 and Br(t → cl ⁺′l ⁻) ≈ 0.46−0.05 for the charged mode at m _S = 150–170 GeV for sin β ≈ 1 and sin β ≈ 0.2, respectively. In the cases being considered, t-quark decays to pairs of charged leptons can be accessible to detection at LHC. In the last case, these decays could manifest themselves (for example, in dilepton events) at the Tevatron as well. Original Russian Text ? P.Yu. Popov, A.D. Smirnov, 2006, published in Yadernaya Fizika, 2006, Vol. 69, No. 6, pp. 1006–1016.     

Doppler spectroscopy of a beam in the channel of a H− ion source

It is shown that high-accuracy contact-free measurements of the divergence and emittance of an accelerated H⁻ ion beam at the exit from the source can in principle be performed by passive Doppler spectroscopy of a beam of excited hydrogen atoms produced by neutralization of the ions with excitation on the residual gas in the source channel. The intensity of the H_α-line radiation detected by the Doppler system is calculated, taking into account the principal processes leading to the excitation and deexcitation of the 3s, 3p, and 3d levels of the hydrogen atoms in the beam, for residual gas densities of the order of 10⁻⁴–10⁻⁵ Torr in the source channel. The computed H_α-line intensity was confirmed experimentally, making it possible to perform photoelectronic detection of the spectral contour of the line in the current mode rather than the photon-counting mode. Zh. Tekh. Fiz. 68, 15–18 (June 1998)     

Fluorescence studies of CS2 and SO2 at 121.6, 73.6–74.4 and 58.4 nm

The fluorescence spectra of CS₂ and SO₂ have been studied at three incident photon wavelengths of 121.6, 73.6–74.4 and 58.4 nm and relative production cross sections for different product states have been measured. The CS(A ¹Π→X ¹Σ⁺) system between 240 and 290nm has been obtained when CS₂ is photoexcited at 121.6nm whereas CS ₂ ⁺ (B ²Σ _u ⁺ →X ²Π _g ) and CS ₂ ⁺ (A ²Π _u →X ²Π _g ) systems have been produced between 276 and 295 and 437 and 555nm respectively when excited by both the incident photon wavelengths of 73.6–74.4 and 58.4nm. The fluorescence spectra of SO₂ obtained at 121.6 and 73.6–74.4nm include the vibrational bands of SO(A ³Π→X ³Σ⁻) and SO(B ²Π⁻→X ³Σ⁻) systems from 240 to 268 and 268 to 442nm respectively whereas the emission spectrum at 58.4nm, has contributions from the two SO systems and SO⁺(A ²Π→X ²Π) system. In all these emission spectra, the fluorescence bands of different systems have been analyzed and their relative production cross sections have been measured. The results obtained in the present investigations have been compared with a few recent reliable measurements reported in literature.     

Low mass Higgs signals at the LHC in the Next-to-Minimal Supersymmetric Standard Model

In the NMSSM, because of introducing a complex singlet superfield, the lightest CP-odd Higgs boson, a ₁, can be a singlet-like state with a tiny doublet component in large regions of parameter space. In this paper, we examine the discovery potential of a ₁ produced in association with a bottom–antibottom pair at the LHC through τ ⁺ τ ⁻ and γγ decay modes. It is shown that an a ₁ with mass ≤M _Z can be extracted from the SM backgrounds by using the τ ⁺ τ ⁻ decay channel, a possibility precluded to the MSSM. In contrast, the γγ decay mode is overwhelmed by backgrounds despite the fact that the branching ratio of this mode can reach unity when a ₁ is a pure singlet.     

Black holes with metric and fields of the same form

We present two rotating black hole solutions with axion ξ, dilaton f{\phi} and two U(1) vector fields. Starting from a non-rotating metric with three arbitrary parameters, which we have found previously, and applying the “Newman–Janis complex coordinate trick” we get a rotating metric g _μν with four arbitrary parameters namely the mass M, the rotation parameter a and the charges electric Q _E and magnetic Q _M . Then we find a solution of the equations of motion having this g _μν as metric. Our solution is asymptotically flat and has angular momentum J = M a, gyromagnetic ratio g = 2, two horizons, the singularities of the solution of Kerr, axion and dilaton singular only when r = a cos θ = 0 etc. By applying to our solution the S-duality transformation we get a new solution, whose axion, dilaton and vector fields have one more parameter. The metrics, the vector fields and the quantity l = x+ie^-2f{\lambda=\xi+ie^{-2\phi}} of our solutions and the solution of: Sen for Q _E , Sen for Q _E and Q _M , Kerr–Newman for Q _E and Q _M , Kerr, Reference Kyriakopoulos [Class. Quantum Grav. 23:7591, 2006, Eqs. (54–57)], Shapere, Trivedi and Wilczek, Gibbons–Maeda–Garfinkle–Horowitz–Strominger, Reissner–Nordstr?m, Schwarzschild are the same function of a, and two functions ρ ² = r(r + b) + a ² cos² θ and Δ = r(r + b) − 2Mr + a ² + c, of a, b and two functions for each vector field, and of a, b and d respectively, where a, b, c and d are constants. From our solutions several known solutions can be obtained for certain values of their parameters. It is shown that our two solutions satisfy the weak the dominant and the strong energy conditions outside and on the outer horizon and that all solutions with a metric of our form, whose parameters satisfy some relations satisfy also these energy conditions outside and on the outer horizon. This happens to all solutions given in the “Appendix”. Mass formulae for our solutions and for all solutions which are mentioned in the paper are given. One mass formula for each solution is of Smarr’s type and another a differential mass formula. Many solutions with metric, vector fields and λ of the same functional form, which include most physically interesting and well known solutions, are listed in an “Appendix”.     

Electronic and electronic-vibrational phenomena in the new organic conductor ϰ-(ET)2[Hg(SCN)2Cl] with a metal-insulator transition

The reflection spectra and optical conductivity spectra of the new organic conductor ϰ-(ET)₂[Hg(SCN)₂Cl] with a metal-insulator transition in the spectral regions 700–5500 and 9000–40 000 cm⁻¹ have been studied in polarized light at 300 K. A comparisonis made between the spectra obtained and the corresponding spectra of related isostructural conductors based on the ET molecule, and also the properties of the crystal structure of the investigated compounds. An electronic transition between the ET molecules of the dimer (ET) ₂ ⁺ in the spectral region 700–5500 cm⁻¹ has been identified, as have the features of the electronic-vibrational structure arising as a consequence of the interaction of this transition with the completely symmetric intramolecular vibrations of the ET molecule. It is found that the conductor with the stronger dimer interaction between the ET molecules has the higher the transition temperature. Fiz. Tverd. Tela (St. Petersburg) 39, 1313–1319 (August 1997)     

Study of Bs→φ?+?? decay in a single universal extra dimension model

Using form factors derived from the light-cone sum rules, we investigate B _s →φℓ ⁺ ℓ ⁻ (ℓ=e,μ,τ) in a single universal extra dimension model (UED). In UED, there is only one new parameter with respect to the Standard Model (SM), which is the inverse of the compactification radius R of the extra dimension. In this work, the branching ratios, the dilepton invariant mass spectra, the forward–backward asymmetries, and the lepton polarization asymmetries of B _s →φℓ ⁺ ℓ ⁻ are calculated. For a lower value of 1/R, there are some considerable discrepancies between the UED and SM. However, with the increase of 1/R, the effect of UED tends to diminish; in particular for 1/R≥1000 GeV, two models have approximately the same predictions. Compared with data from CDF for B _s →φμ ⁺ μ ⁻, we find that the 1/R tends to be larger than 350 GeV. We also find that the zero crossing point of the forward–backward asymmetry of B _s →φμ ⁺ μ ⁻ becomes smaller, which would be an important platform for probing the UED effect. These results could be tested in the Large Hadron Collider (LHC) at CERN and the future super-B factory.     

Kinetics of the photoconductivity and absorption in the D −(A +) bands in doped silicon

The photoconductivity (PC) spectra and the induced absorption of background radiation in the energy range 10–40 meV are investigated in weakly compensated B-, Ga-, and As-doped silicon at 4.2 K. It is shown that dips corresponding to the photoionization of long-lived excited states of B and As are observed in the PC spectra on the D ⁻(A ⁺) bands. It is found that the frequency dependence of the PC spectra corresponds to excitation relaxation times of the order of 10⁻⁴ s for the states in the D ⁻ (A ⁺) bands. It is established that in electric fields E>100 V/cm the PC decreases sharply, while the induced absorption of the background radiation changes very little. This confirms the conclusion that the excitation of the D ⁻ (A ⁺) itself makes the main contribution to the PC. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 4, 224–227 (25 August 1997)     

Weak e+e− lines from internal pair conversion observed in collisions of 238U with heavy nuclei

We present the results of a Doppler-shift correction to the measured e⁺e⁻–sum-energy spectra obtained from e⁺e⁻–coincidence measurements in ²³⁸U +²⁰⁶Pb and ²³⁸U +¹⁸¹Ta collisions at beam energies close to the Coulomb barrier, using an improved experimental setup at the double-Orange spectrometer of GSI. Internal-Pair-Conversion (IPC) e⁺e⁻ pairs from discrete nuclear transitions of a moving emitter have been observed following Coulomb excitation of the 1.844 MeV (E1) transition in ²⁰⁶Pb and neutron transfer to the 1.770 MeV (M1) transition in ²⁰⁷Pb. In the collision system ²³⁸U +¹⁸¹Ta, IPC transitions were observed from the Ta-like as well as from the U-like nuclei. In all systems the Doppler-shift corrected e⁺e⁻–sum-energy spectra show weak lines at the energies expected from the corresponding γ–ray spectra with cross sections being consistent with the measured excitation cross sections of the γ lines and the theoretically predicted IPC coefficients. No other than IPC e⁺e⁻–sum-energy lines were found in the measured spectra. The transfer cross sections show a strong dependence on the distance of closest approach (R_min), thus signaling also a strong dependence on the bombarding energy close to the Coulomb barrier. Received: 22 July 1997 / Revised version: 15 October 1997