On the multistage nature of deformation of the microcrystalline aluminum-lithium alloy 1420 under superplasticity conditions

The constant-rate tensile deformation and creep of aluminum-lithium alloy 1420 with a grain size of 3 µm (obtained by equal-channel angular extrusion) exhibiting superplasticity at temperatures of 600–670 K and relative-deformation rates of 10^?2–10^?3 s^?1 are considered. It is shown that, upon tension at a constant rate V _m, a steady-state segment appears in the true stress σ_t-true strain ?_t dependence, which is described by the expression $\dot \varepsilon _t \sim \sigma _t^n \exp ( - U/kT)$ with constant coefficients, and that the rate of deformation $\dot \varepsilon _t$ is close to the creep rate at comparable stresses and strains. The conclusion is made that, upon deformation under superplasticity conditions, an equilibrium structure is formed, which remains unaltered in the process of further deformation until the sample goes over (because of geometrical conditions) to a prefracture state.     

Single decay-lepton angular distributions in polarizede + e − →\overline {tt} and simple angular asymmetries as a measure of CP-violating top dipole couplingsand simple angular asymmetries as a measure of CP-violating top dipole couplings

In the presence of an electric dipole coupling of $\overline {tt} $ to a photon, and an analogous ‘weak’ dipole coupling to the Z, CP violation in the process e⁺e^? → $\overline {tt} $ results in modified polarization of the top and the anti-top. This polarization can be analyzed by studying the angular distributions of decay charged leptons when the top or anti-top decays leptonically. Analytic expressions are presented for these distributions when eithert or $\overline t $ decays leptonically, including $\mathcal{O}$ (α_s) QCD corrections in the soft-gluon approximation. The angular distributions are insensitive to anomalous interactions in top decay. Two types of simple CP-violating polar-angle asymmetries and two azimuthal asymmetries, which do not need the full reconstruction of thet or $\overline t $ , are studied. Independent 90% CL limits that may be obtained on the real and imaginary parts of the electric and weak dipole couplings at a linear collider operating at √ s = 500 GeV with integrated luminosity 500 fb^? and also at √s = 1000 GeV with integrated luminosity 1000 fb^? have been evaluated. The effect of longitudinal electron and/or positron beam polarizations has been included.     

Absolute cross sections of electron attachment to molecular clusters: Part I. Formation of (CO2) N −

A procedure of determining absolute cross section σ^? of electron attachment to (CO₂)_N clusters at pair collisions in crossed beams is suggested. The cross section is measured as a function of energy (E = 0.1–50 eV) and of cluster mean size N in a beam $(\bar N = 2 - 4000 molecules)$ . It is found that, even at $\bar N > 200$ and E ≤ 3 eV, σ^? is equal to, or larger than, 7 × 10^?13 cm², i.e., by more than one order of magnitude exceeds the maximal cross section of CO₂ ionization by electron impact. The dependences σ^? $(\bar N,E)$ have two wide continua at E ≤ 5.2 eV and E ≥ 6.9 eV, which correlate well with known functions of CO₂ electron-impact-induced excitation. These continua are attributed largely to formation of (CO₂) _N ^? ions during electron thermalization and solvation in the clusters. At E → 0, the polarization capture of an incident electron by the cluster leads to a sharp increase in cross section σ^?(E). From the dependences σ^? $(\bar N,E)$ measured, the thermalization and sovation probabilities for electrons with E ≤ 0.8 eV and the rate of electron energy loss in the cluster are found.     

Diffusion Effects on the Breakdown of a Linear Amplifier Model Driven by the Square of a Gaussian Field

We investigate solutions to the equation ? _t ?? $\mathcal{D}$ Δ?=λS ²?, where S(x, t) is a Gaussian stochastic field with covariance C(x?x′, t, t′), and x∈ $\mathbb{R}$ ^d . It is shown that the coupling λ _cN (t) at which the N-th moment <? ^N (x, t)> diverges at time t, is always less or equal for $\mathcal{D}$ >0 than for $\mathcal{D}$ =0. Equality holds under some reasonable assumptions on C and, in this case, λ _cN (t)=Nλ _c (t) where λ _c (t) is the value of λ at which <exp[λ ∫ ^t ₀ S ²(0, s) ds]> diverges. The $\mathcal{D}$ =0 case is solved for a class of S. The dependence of λ _cN (t) on d is analyzed. Similar behavior is conjectured when diffusion is replaced by diffraction, $\mathcal{D}$ →i $\mathcal{D}$ , the case of interest for backscattering instabilities in laser-plasma interaction.     

Dephasing in the semiclassical limit is system-dependent

Dephasing in open quantum chaotic systems has been investigated in the limit of large system sizes to the Fermi wavelength ratio, L/λ_F 〉 1. The weak localization correction g ^wl to the conductance for a quantum dot coupled to (i) an external closed dot and (ii) a dephasing voltage probe is calculated in the semiclassical approximation. In addition to the universal algebraic suppression g ^wl ∝ (1 + τ_D/τ_?)^?1 with the dwell time τ_D through the cavity and the dephasing rate τ _? ^?1 , we find an exponential suppression of weak localization by a factor of ∝ exp[? $\tilde \tau $ /τ_?], where $\tilde \tau $ is the system-dependent parameter. In the dephasing probe model, $\tilde \tau $ coincides with the Ehrenfest time, $\tilde \tau $ ∝ ln[L/λ_F], for both perfectly and partially transparent dot-lead couplings. In contrast, when dephasing occurs due to the coupling to an external dot, $\tilde \tau $ ∝ ln[L/ξ] depends on the correlation length ξ of the coupling potential instead of λ_F.     

Alternative technique for Standard Model estimation of the rare kaon decay branchings \left. {BR(K \to \pi \nu \bar \nu )} \right|_{SM}

We estimate $BR(K \to \pi \nu \bar \nu )$ in the context of the Standard Model by fitting for λ _t≡V _tdV _ts ^* of the “kaon unitarity triangle” relation. To find the vertex of this triangle, we fit data from |? _K|, the CP-violating parameter describing K mixing, and a _ψ,K , the CP-violating asymmetry in B _d ⁰ → J/ψK ⁰ decays, and obtain the values $\left. {BR(K \to \pi \nu \bar \nu )} \right|_{SM} = (7.07 \pm 1.03) \times 10^{ - 11} $ and $\left. {BR(K_L^0 \to \pi ^0 \nu \bar \nu )} \right|_{SM} = (2.60 \pm 0.52) \times 10^{ - 11} $ . Our estimate is independent of the CKM matrix element V _cb and of the ratio of B-mixing frequencies ${{\Delta m_{B_s } } \mathord{\left/ {\vphantom {{\Delta m_{B_s } } {\Delta m_{B_d } }}} \right. \kern-0em} {\Delta m_{B_d } }}$ . We also use the constraint estimation of λ _t with additional data from $\Delta m_{B_d } $ and |V _ub|. This combined analysis slightly increases the precision of the rate estimation of $K^ + \to \pi ^ + \nu \bar \nu $ and $K_L^0 \to \pi ^0 \nu \bar \nu $ (by ?10 and ?20%, respectively). The measured value of $BR(K^ + \to \pi ^ + \nu \bar \nu )$ can be compared both to this estimate and to predictions made from ${{\Delta m_{B_s } } \mathord{\left/ {\vphantom {{\Delta m_{B_s } } {\Delta m_{B_d } }}} \right. \kern-0em} {\Delta m_{B_d } }}$ .     

Matter radii and wave function admixtures in 2n halo nuclei

We analyze longitudinal pion spectra from $\ensuremath \sqrt{s_{NN}}=2$ GeV to $\ensuremath \sqrt{s_{NN}}=20$ GeV within Landau??s hydrodynamical model and the UrQMD hybrid approach. From the measured data on the widths of the pion rapidity spectra, we extract the sound velocity c _s ² in the dense stage of the reactions. It is found that the sound velocity has a local minimum (indicating the softest point in the equation of state, EoS) at $\ensuremath \sqrt{s_{NN}}=4\mbox{--}9$ GeV, an energy range accessible at the Facility for Antiproton and Ion Research (FAIR) as well as the RHIC-Beam Energy Scan (RHIC-BES). This softening of the EoS is compatible with the formation of a QGP at the onset of deconfinement. The extracted sound velocities are then used to calculate an excitation function for the mean transverse mass of pions from the hybrid model. We find that, above $\ensuremath \sqrt{s_{NN}} \approx 10$ GeV, even the lowest c _s ² gives a considerably larger $\ensuremath \langle m_T\rangle$ of pions compared to data.     

Inelastic Character of Solitons of Slowly Varying gKdV Equations

In this paper we study soliton-like solutions of the variable coefficients, the subcritical gKdV equation $$u_t + (u_{xx} -\lambda u + a(\varepsilon x) u^m )_x =0,\quad {\rm in} \quad \mathbb{R}_t\times\mathbb{R}_x, \quad m=2,3\,\, { \rm and }\,\, 4,$$ with ${\lambda\geq 0, a(\cdot ) \in (1,2)}$ a strictly increasing, positive and asymptotically flat potential, and ${\varepsilon}$ small enough. In previous works (Mu?oz in Anal PDE 4:573?C638, 2011; On the soliton dynamics under slowly varying medium for generalized KdV equations: refraction vs. reflection, SIAM J. Math. Anal. 44(1):1?C60, 2012) the existence of a pure, global in time, soliton u(t) of the above equation was proved, satisfying $$\lim_{t\to -\infty}\|u(t) - Q_1(\cdot -(1-\lambda)t) \|_{H^1(\mathbb{R})} =0,\quad 0\leq \lambda<1,$$ provided ${\varepsilon}$ is small enough. Here R(t, x) := Q _c (x ? (c ? ??)t) is the soliton of R _t +? (R _xx ??? R + R ^m ) _x =?0. In addition, there exists ${\tilde \lambda \in (0,1)}$ such that, for all 0?<??? <?1 with ${\lambda\neq \tilde \lambda}$ , the solution u(t) satisfies $$\sup_{t\gg \frac{1}{\varepsilon}}\|u(t) - \kappa(\lambda)Q_{c_\infty}(\cdot-\rho(t)) \|_{H^1(\mathbb{R})}\lesssim \varepsilon^{1/2}.$$ Here ${{\rho'(t) \sim (c_\infty(\lambda) -\lambda)}}$ , with ${{\kappa(\lambda)=2^{-1/(m-1)}}}$ and ${{c_\infty(\lambda)>\lambda}}$ in the case ${0<\lambda<\tilde\lambda}$ (refraction), and ${\kappa(\lambda) =1}$ and c _??(??)?<??? in the case ${\tilde \lambda<\lambda<1}$ (reflection). In this paper we improve our preceding results by proving that the soliton is far from being pure as t ?? +???. Indeed, we give a lower bound on the defect induced by the potential a(·), for all ${{0<\lambda<1, \lambda\neq \tilde \lambda}}$ . More precisely, one has $$\liminf_{t\to +\infty}\| u(t) - \kappa_m(\lambda)Q_{c_\infty}(\cdot-\rho(t)) \|_{H^1(\mathbb{R})}>rsim \varepsilon^{1 +\delta},$$ for any ${{\delta>0}}$ fixed. This bound clarifies the existence of a dispersive tail and the difference with the standard solitons of the constant coefficients, gKdV equation.     

The Percolation Transition in the Zero-Temperature Domany Model

We analyze a deterministic cellular automaton σ ^?=(σ ⁿ :n≥0) corresponding to the zero-temperature case of Domany's stochastic Ising ferromagnet on the hexagonal lattice $\mathbb{N}$ . The state space $\mathcal{S}_\mathbb{H} = \left\{ { - 1, + 1} \right\}^\mathbb{H}$ consists of assignments of ?1 or +1 to each site of $\mathbb{H}$ and the initial state $\sigma ^0 = \left\{ {\sigma _{^x }^0 } \right\}_{x \in \mathbb{H}}$ is chosen randomly with P(σ ⁰ _x=+1)=p∈[0,1]. The sites of $\mathbb{H}$ are partitioned in two sets $\mathcal{A}$ and $\mathcal{B}$ so that all the neighbors of a site x in $\mathcal{A}$ belong to $\mathcal{B}$ and vice versa, and the discrete time dynamics is such that the σ ^? _x 's with ${x \in \mathcal{A}}$ (respectively, $\mathcal{B}$ ) are updated simultaneously at odd (resp., even) times, making σ ^? _x agree with the majority of its three neighbors. In ref. 1 it was proved that there is a percolation transition at p=1/2 in the percolation models defined by σ ⁿ , for all times n∈[1,∞]. In this paper, we study the nature of that transition and prove that the critical exponents β, ν, and η of the dependent percolation models defined by σ ⁿ , n∈[1,∞], have the same values as for standard two-dimensional independent site percolation (on the triangular lattice).     

Quasi-elastic electroproduction of charged \rho -mesons on nucleons

The electroproduction of charged $ \rho$ -mesons on the nucleon at intermediate energy is discussed for quasi-elastic kinematics. It is shown that at these kinematics both the longitudinal $ \sigma_{{L}}^{}$ and transverse $ \sigma_{{T}}^{}$ cross-sections are dominated by the $ \rho$ -meson t -pole contribution, and thus the corresponding dσ _L(T)/dt data can give a valuable information on the $ \rho$ -meson component of the nucleon cloud. The differential cross-sections for the reaction p(e, e ^′ $ \rho^{+}_{}$ )n at Q ² = 2 , 3.5GeV^2 and at the invariant mass W = 3 and 4GeV are calculated on the basis of quasi-elastic knockout mechanism with form factors. Questions about the gauge invariance of the electroproduction amplitude are considered and it is noted an important difference between photo- and electroproduction amplitudes.     

Strange hadron production in d+Au collisions at RHIC

We report the centrality dependence of transverse mass (m _t ) spectra at mid-rapidity for the identified strange hadrons K _S ⁰ , ? $\Lambda + \bar \Lambda $ and $\Xi ^ - + \bar \Xi ^ + $ in d+Au collisions at RHIC. The measured transverse momentum (p _T ) covers 0.4<p _T <6.0 GeV/c for K _S ⁰ , ø, $\Lambda + \bar \Lambda $ and 0.6<p _T <5.0 GeV/c for $\Xi ^ - + \bar \Xi ^ + $ . The binary collision normalized nuclear modification factors R _CP of these hadrons indicate that the Cronin effect in d+Au collisions has a distinct particle-type dependence. the R _CP ratios show a distinct baryons versus mesons dependence: the R _CP for $\Xi ^ - + \bar \Xi ^ + $ follows that for $\Lambda + \bar \Lambda $ while the R _CP for the ? is close to that for the K _S ⁰ . Similar features have also been observed in Au+Au collisions. Initial parton scattering alone is not sufficient to explain this particle-type dependence. Hadronization processes are likely to be important for determining hadron properties in high-energy collisions as suggested by coalescence and recombination models.     

Radiative decays and quark content of f 0(980) and φ(1020)

The quark structure of φ(1020) and f ₀(980) is studied on the basis of data on the radiative decays φ(1020) → γπ ⁰, γη, γη′, γ a ₀(980), γ f ₀(980) and f ₀(980) → γγ. The partial widths are calculated under the assumption that all the mesons under consideration are $\bar qq$ states: φ(1020) is a dominantly $s\bar s$ state ( $\eta ' = n\bar nsin\theta + s\bar scos\theta $ component contributes not more than 1%); η, η′, and π ⁰ are standard $q\bar q$ states, $\eta = n\bar ncos\theta - s\bar ssin\theta $ and $\eta ' = n\bar nsin\theta + s\bar scos\theta $ with θ?37°; and f ₀(980) is a e5 meson with the flavor wave function $n\bar ncos\varphi + s\bar ssin\varphi $ . The transition φ → γπ ⁰ specifies the admixture of the $n\bar n$ component in the φ meson: it is on the order of 0.5%. We argue that this order of $n\bar n$ value does not contradict data on the decay φ(1020) → γ a ₀(980). The partial widths calculated for the decays φ → γη, γη? are in reasonable agreement with experimental data. The measured branching-ratio value Br(φ→γf ₀(980))=(3.4±0.4 _?0.5 ^+1.5 ×10^?4) requires 25°≤|?|≤90°. For the decay f ₀(980) → γγ, the agreement with data, Γ(f ₀(980) → γγ)=0.28 _?0.13 ^+0.09 keV, is attained at either ?=85°±8° or ?=?46°±8°. A simultaneous analysis of the decays φ(1020) → γ f ₀(980) and f ₀(980) → γγ favors the solution with the negative mixing angle of ?=?48°±6°, setting f ₀(980) very close to the flavor octet (? _octet=±54.7°).     

Higgs bosons and neutrinos in the left-right model

The left-right asymmetric model featuring the bidoublet and two triplets of Higgs fields is investigated. It was established that, from an analysis of the reaction l ^?γ → W ^?ν_l, it is possible to deduce not only information about the properties of the singly charged Higgs bosons $\tilde \delta ^{( - )} $ and h ^(?) but also an answer to the question of whether the neutrino is a Majorana or a Dirac particle. The processes $f_i \bar f_j \to \Delta _1^{( - - )} \tilde \delta ^{( + )} $ and e^?μ^? → Δ _1,2 ^(—) γ leading to the production of doubly charged Higgs bosons are investigated. It is shown that information about the properties of singly charged Higgs bosons can also be obtained by studying the ultrahighenergy cosmic neutrinos from the reaction e ^?ν _e →μ^?ν_μ.     

Search for Θ+(1540) in exclusive proton-induced reaction p + C(N) \to \Theta ^ + \bar \kappa ^0 + C(N) at the energy of 70 GeV

A search for narrow Θ⁺(1540), a candidate for a pentaquark baryon with positive strangeness, has been performed in an exclusive proton-induced reaction $p + C(N) \to \Theta ^ + \bar \kappa ^0 + C(N)$ on carbon nuclei or quasifree nucleons at $E_{beam} = 70GeV(\sqrt s = 11.5GeV)$ studying nK ⁺, pK _S ⁰ , and pK _L ⁰ decay channels of Θ⁺(1540) in four different final states of the $\Theta ^ + \bar K^0 $ system. In order to assess the quality of the identification of the final states with neutron or K _L ⁰ , we reconstructed Λ(1520) → nK _S ⁰ and ? → K _L ⁰ K _S ⁰ decays in the calibration reactions p + C(N) → Λ (1520)K ⁺+C(N) and p+C(N) → p?+C(N). We found no evidence for a narrow pentaquark peak in any of the studied final states and decay channels. Assuming that the production characteristics of the $\Theta ^ + \bar K^0 $ system are not drastically different from those of the Λ(1520)K ⁺ and p? systems, we established upper limits on the cross-section ratios $\sigma (\Theta ^ + \bar K^0 )/\sigma (\Lambda (1520)K^ + ) < 0.02$ and $\sigma (\Theta ^ + \bar K^0 )/\sigma (p\phi ) < 0.15$ at 90% C.L. and a preliminary upper limit for the forward-hemisphere cross section $\sigma (\Theta ^ + \bar K^0 )$ nb/nucleon.     

Shifted identical bands: A new phenomenon

The levels in ¹⁶²Gd were identified in spontaneous fission studies. Its transition energies are remarkably similar to those in ¹⁶⁰Gd. From that work, an analysis of yrast bands in even-even proton to neutron-rich Ba to Pb nuclei led to the discovery of a new phenomenon, shifted identical bands (SIB). SIBs are yrast bands in neighboring nuclei (a, b) with moments of inertia which are identical when shifted by a constant amount κ, so J _1a (1+κ)=J _1b , from 2⁺ to 8⁺ and higher to 16⁺. Out of over 700 comparisons, 55 SIBs were found from stable to the most neutron-rich Ce-W nuclei with $\left| {\bar k} \right|$ between 1.5% and 13%, where the spread in κ is less than ±1%, and only four identical bands ( $\bar k \cong 0$ ). As examples, we found for ¹⁵⁸Sm-¹⁶⁰Gd, $\bar k = \left( { - 3.2_{ - 0.2}^{ + 0.1} } \right)\%$ (where the ± is the total spread in κ from ?3.1 to ?3.4); ¹⁵⁶Nd-¹⁶⁰Gd, (?10.6 _?0.2 ^+0.4 )%; ¹⁵⁸Sm-¹⁶⁰Sm, (3.4 _?0.3 ^+0.5 )%. The J ₁ values were fitted to a variable moment of inertia model with parameters J ₀ and C whose values correlate with the SIB J ₁ values. The SIBs are not correlated either with deformation or with the N _p N _n product of the IBA model.     

Search for the K L 0 → π0ν \tilde v decay at the INEP U-70 accelerator: The KLOD project

The rare decay K _L ⁰ → π⁰ν $ \tilde v $ branching ratio measurement is one of the clearest Standard Model test. Calculations based on the SM predict Br(K _L ⁰ → π⁰ν $ \tilde v $ ) ≈ 2.8 × 10^?11, but the most accurate experimental value Br(K _L ⁰ → π⁰ν $ \tilde v $ ) < 6.7 × 10^?8 (90% C.L.). We present design of a new experimental setup KLOD (U-70 accelerator, IHEP, Protvino) for K _L ⁰ → π⁰ν $ \tilde v $ branching ratio measurement. Sensitivity of the KLOD experiment will be enough for registration of 2.4 events K _L ⁰ → π⁰ν $ \tilde v $ for every 10 days of the data taking (according to SM predictions).     

Calibration of absolute jet energy scale in CMS detector using W → q \bar q process in pp-Collisions at \sqrt s = 7 TeV

Calibration of absolute jet energy scale in CMS experiment at $\sqrt s = 7$ TeV using the W-mass constraint in t $\bar t$ -events with W ?? q $\bar t$ decay is made. Data sample with an integrated luminosity of 3 fb^?1 is used. Calibration procedure is made for calorimetric jets, ??Jet-Plus-Track?? jets, and ??Particle-Flow?? jets. Statistical errors of calibration as well as systematical uncertainties of the method are up to 3%. The results are abstracted from degree thesis.     

Resonance structures in the \Lambda \bar \Lambda system

The results of studying the $\Lambda \bar \Lambda $ system produced in the reaction π^? p→ $\Lambda \bar \Lambda $ n at a π^?-meson energy of 40 GeV are reported. Experimental data (～2300 events) were obtained on the ITEP 6-meter spectrometer with a beam of the IHEP U-70 accelerator. The invariant-mass spectra for the events dominated by the singlet or triplet $\Lambda \bar \Lambda $ states were found to differ considerably from each other. The data give evidence for the existence of resonance $\Lambda \bar \Lambda $ states of the system in the mass regions near 2.3, 2.5, and 2.8 GeV.