Search

The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized $8.5\,\text{GeV}$ photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson $ρ$(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. We confirm a high degree of $s$-channel helicity conservation at small squared four-momentum transfer $t$ and are able to extract the $t$-dependence of natural and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full $t$ range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced $ρ(770)$ differ by two units are negligible for $-t, 15 pages, 11 figures

We report the total and differential cross sections for $J/ψ$ photoproduction with the large acceptance GlueX spectrometer for photon beam energies from the threshold at 8.2~GeV up to 11.44~GeV and over the full kinematic range of momentum transfer squared, $t$. Such coverage facilitates the extrapolation of the differential cross sections to the forward ($t = 0$) point beyond the physical region. The forward cross section is used by many theoretical models and plays an important role in understanding $J/ψ$ photoproduction and its relation to the $J/ψ-$proton interaction. These measurements of $J/ψ$ photoproduction near threshold are also crucial inputs to theoretical models that are used to study important aspects of the gluon structure of the proton, such as the gluon Generalized Parton Distribution (GPD) of the proton, the mass radius of the proton, and the trace anomaly contribution to the proton mass. We observe possible structures in the total cross section energy dependence and find evidence for contributions beyond gluon exchange in the differential cross section close to threshold, both of which are consistent with contributions from open-charm intermediate states., 15 pages 18 figures

We present a search for axion-like particles, $a$, produced in photon-proton collisions at a center-of-mass energy of approximately 4 GeV, focusing on the scenario where the $a$-gluon coupling is dominant. The search uses $a\to\gamma\gamma$ and $a\to\pi^+\pi^-\pi^0$ decays, and a data sample corresponding to an integrated luminosity of 168 pb$^{-1}$ collected with the GlueX detector. The search for $a\to\gamma\gamma$ decays is performed in the mass range of $180 < m_a < 480$ MeV, while the search for $a\to\pi^+\pi^-\pi^0$ decays explores the $600 < m_a < 720$ MeV region. No evidence for a signal is found, and 90% confidence-level exclusion limits are placed on the $a$-gluon coupling strength. These constraints are the most stringent to date over much of the mass ranges considered., Comment: 8 pages, 4 figures, 2 tables; updated to published version

From superconductors to atomic nuclei, strongly-interacting many-body systems are ubiquitous in nature. Measuring the microscopic structure of such systems is a formidable challenge, often met by particle knockout scattering experiments. While such measurements are fundamental for mapping the structure of atomic nuclei, their interpretation is often challenged by quantum mechanical initial- and final-state interactions (ISI/FSI) of the incoming and scattered particles. Here we overcome this fundamental limitation by measuring the quasi-free scattering of 48 GeV/c 12C ions from hydrogen. The distribution of single protons is studied by detecting two protons at large angles in coincidence with an intact 11B nucleus. The 11B detection is shown to select the transparent part of the reaction and exclude the otherwise large ISI/FSI that would break the 11B apart. By further detecting residual 10B and 10Be nuclei, we also identified short-range correlated (SRC) nucleon-nucleon pairs, and provide direct experimental evidence for the separation of the pair wave-function from that of the residual many-body nuclear system. All measured reactions are well described by theoretical calculations that do not contain ISI/FSI distortions. Our results thus showcase a new ability to study the short-distance structure of short-lived radioactive atomic nuclei at the forthcoming FAIR and FRIB facilities. These studies will be pivotal for developing a ground-breaking microscopic understanding of the structure and properties of nuclei far from stability and the formation of visible matter in the universe., Comment: Accepted for publication in Nature Physics. 28 pages, 19 figures, and 1 table including main text, Methods, and Supplementary materials

At the initial stage, the development of wave reactors, which will operate in the mode of wave nuclear burning (WNC), requires the study of the kinetics of the WNC fuel mode when changing both external parameters (flux density of an external neutron source, thermal parameters of heat transfer) and internal parameters (fuel composition, reactor material parameter, delayed neutrons). In order to confirm the possibility of WNC with enrichment, we study its impact on the criterion of WNC for thorium fuel Th232 at different enrichments in Pu239) and its behavior during the "ignition" stage. To confirm the fulfillment of the criterion of slow WNC depending on the neutron energy, we perform a numerical simulation of the thorium fuel WNC mode dynamics, taking into account the delayed neutrons in the thermal and epithermal regions of the neutron energies (0.015-10 eV)., 13 pages, 5 figures, in Ukrainian

Recent data from the PIONS$@$MAX-lab Collaboration, measuring the total cross section of the pion incoherent photoproduction $��d\to��^-pp$ near threshold, have been used to extract the E$_{0+}$ multipole and total cross section of the reaction $��n\!\to\!��^-p$, also near threshold. These are the first measurements of the reaction $��d\to��^-pp$ in the threshold region. The value of E$_{0+}$ is extracted through a fit to the deuteron data in a photoproduction model accounting for final-state interactions. The model takes an $S$-wave approximation for the elementary reaction $��n\!\to\!��^-p$ with E$_{0+}\! = $ const in the threshold region. The obtained value E$_{0+} = -31.86\pm 0.8$ (in $10^{-3}/m_{��^+}$ units) is in agreement with other existing results. Model predictions for the total cross section $��(��n\!\to\!��^-p)$ are also given., 7 pages, 4 figures, 2 tables

In this paper we deal with the problem of predicting a steady-state neutron spectrum in media of arbitrary composition and geometry. The analytical calculations of such spectrum are often too complex, if at all possible. We describe a method of Geant4-based Monte Carlo calculation of the steady-state neutron spectrum in a medium containing a fixed neutron source. In addition to the steady-state spectrum, we obtain the snapshots of the neutron spectrum evolution in time, which may be thought of as the non-equilibrium neutron spectra, and their form is of considerable interest for further studies., Comment: 18 pages, 10 figures; v2: Revised and extended, 23 pages, 13 figures; v3: more concise and focused revision, 22 pages, 13 figures; v4: revised text, new comparison added to Fig.13, 24 pages, 13 figures

We present the newly obtained results of two computer simulations of the epithermal neutron-nuclear burning in natural uranium. Each of them modeled the period of six months of the traveling wave reactor (TWR) operation -- for two different flux densities of an external neutron source. The simulation results confirm the existence of a nuclear burning wave at longer time scales, and reveal the dependence of the wave burning modes on the parameters of an external neutron source., Comment: 13 pages, 11 figures

We report a measurement of the $��^-$ photoproduction beam asymmetry for the reaction $\vec�� p \rightarrow ��^- ��^{++}$ using data from the GlueX experiment in the photon beam energy range 8.2--8.8 GeV. The asymmetry $��$ is measured as a function of four-momentum transfer $t$ to the $��^{++}$ and compared to phenomenological models. We find that $��$ varies as a function of $t$: negative at smaller values and positive at higher values of $|t|$. The reaction can be described theoretically by $t$-channel particle exchange requiring pseudoscalar, vector, and tensor intermediaries. In particular, this reaction requires charge exchange, allowing us to probe pion exchange and the significance of higher-order corrections to one-pion exchange at low momentum transfer. Constraining production mechanisms of conventional mesons may aid in the search for and study of unconventional mesons. This is the first measurement of the process at this energy., 7 pages, 5 figures

We report measurements of the photon beam asymmetry $��$ for the reaction $\vec�� p\to K^+��^0$(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected using a linearly polarized photon beam in the energy range of 8.2-8.8 GeV incident on a liquid hydrogen target. The beam asymmetry $��$ was measured as a function of the Mandelstam variable $t$, and a single value of $��$ was extracted for events produced in the $u$-channel. These are the first exclusive measurements of the photon beam asymmetry $��$ for the reaction in this energy range. For the $t$-channel, the measured beam asymmetry is close to unity over the $t$-range studied, $-t=(0.1-1.4)~$(GeV/$c$)$^{2}$, with an average value of $��= 1.00\pm 0.05$. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the $K^{*}$(892) Regge trajectory. A value of $��= 0.41 \pm 0.09$ is obtained for the $u$-channel integrated up to $-u=2.0$~(GeV/$c$)$^{2}$.

We report on the measurement of the $��p \rightarrow J/��p$ cross section from $E_��= 11.8$ GeV down to the threshold at $8.2$ GeV using a tagged photon beam with the GlueX experiment. We find the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section $d��/dt$ has an exponential slope of $1.67 \pm 0.39$ GeV$^{-2}$ at $10.7$ GeV average energy. The LHCb pentaquark candidates $P_c^+$ can be produced in the $s$-channel of this reaction. We see no evidence for them and set model-dependent upper limits on their branching fractions $\mathcal{B}(P_c^+ \rightarrow J/��p)$ and cross sections $��(��p \to P_c^+)\times\mathcal{B}(P_c^+ \to J/��p) $., 12 pages, 7 figures

We report on the measurement of the beam asymmetry $��$ for the reactions $\vec��p\rightarrow p��$ and $\vec��p \rightarrow p��^{\prime}$ from the GlueX experiment, using an 8.2--8.8 GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Lab. These measurements are made as a function of momentum transfer $-t$, with significantly higher statistical precision than our earlier $��$ measurements, and are the first measurements of $��^{\prime}$ in this energy range. We compare the results to theoretical predictions based on $t$--channel quasi-particle exchange. We also compare the ratio of $��_��$ to $��_{��^{\prime}}$ to these models, as this ratio is predicted to be sensitive to the amount of $s\bar{s}$ exchange in the production. We find that photoproduction of both $��$ and $��^{\prime}$ is dominated by natural parity exchange with little dependence on $-t$., 18 pages, 7 figures

The $��n \to ��^0 n$ differential cross section evaluated for 27 energy bins span the photon-energy range 290-813 MeV (W = 1.195-1.553 GeV) and the pion c.m. polar production angles, ranging from 18 deg to 162 deg, making use of model-dependent nuclear corrections to extract pi0 production data on the neutron from measurements on the deuteron target. Additionally, the total photoabsorption cross section was measured. The tagged photon beam produced by the 883-MeV electron beam of the Mainz Microtron MAMI was used for the 0-meson production. Our accumulation of 3.6 x 10^6 $��n \to ��^0 n$ events allowed a detailed study of the reaction dynamics. Our data are in reasonable agreement with previous A2 measurements and extend them to lower energies. The data are compared to predictions of previous SAID, MAID, and BnGa partial-wave analyses and to the latest SAID fit MA19 that included our data. Selected photon decay amplitudes $N^* \to ��n$ at the resonance poles are determined for the first time., 16 pages, 12 figures, 3 tables

For the first time an analytic expression was obtained for the inelastic neutron scattering law with an isotropic neutron source within the gas model, considering moderating medium temperature as a parameter. The inelastic scattering law is obtained, based on the solution of the kinematic problem of neutron inelastic scattering on a nucleus in laboratory coordinate system (L-system) in general case. I.e. in case not only a neutron but also a nucleus have arbitrary velocity vector in L-system. Analytic expressions are found for the neutron flux density and moderation spectrum in reactor fissile medium, both in case of the elastic scattering law, obtained earlier by the authors, and in case of the inelastic scattering law obtained in this paper. Both elastic and inelastic scattering laws are considered to be dependent on the medium temperature. The obtained expressions for neutron moderation spectra enable reinterpretation of physical nature of the processes that determine the shape of neutron spectrum in a wide energy range., 21 pages, 6 figures; v2: numerous corrections and revisions

The first experimental investigation of the near-threshold cross section for incoherent $��^-$ photoproduction on the deuteron $��$ d -> $��^-$ pp is presented. The experimental technique involved detection of the ~131 MeV gamma ray resulting from the radiative capture of photoproduced $��^-$ in the target. The total cross section has been measured using an unpolarized tagged-photon beam, a liquid-deuterium target, and three very large NaI(Tl) spectrometers. The data are compared to theoretical models that give insight into the elementary reaction $��$ n -> $��^-$ p and pion-nucleon and nucleon-nucleon final-state interactions., 8 pages, 6 figures, to be submitted to Physical Review C

The quasi-free $��d\to��^{-}p(p)$ differential cross section has been measured with CLAS at photon beam energies $E_��$ from 0.445 GeV to 2.510 GeV (corresponding to $W$ from 1.311 GeV to 2.366 GeV) for pion center-of-mass angles $\cos��_��^{c.m.}$ from -0.72 to 0.92. A correction for final state interactions has been applied to this data to extract the $��n\to��^-p$ differential cross sections. These cross sections are quoted in 8428 $(E_��,\cos��_��^{c.m.})$ bins, a factor of nearly three increase in the world statistics for this channel in this kinematic range. These new data help to constrain coupled-channel analysis fits used to disentangle the spectrum of $N^*$ resonances and extract their properties. Selected photon decay amplitudes $N^* \to ��n$ at the resonance poles are determined for the first time and are reported here.

We report measurements of the photon beam asymmetry Σ for the reactions ⃗γp→pπ0 and ⃗γp→pη from the GlueX experiment using a 9 GeV linearly polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous π0 measurements and are the first η measurements in this energy regime. The results are compared with theoretical predictions based on t-channel, quasiparticle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models.

We consider a model of neutron-nuclear wave burning. The wave of nuclear burning of the medium is initiated by an external neutron source and is the basis for the new generation reactors -- the so-called "traveling-wave reactors". We develop a model of nuclear wave burning, for which it is possible to draw an analogy with a mechanical dissipative system. Within the framework of the new model, we show that two burning modes are possible depending on the control parameters: a traveling autowave and a wave driven by an external neutron source. We find the autowave to be possible for certain neutron energies only, and the wave velocity has a continuous spectrum bounded below., Comment: 23 pages, 8 figures

We report measurements of the photon beam asymmetry $��$ for the reactions $\vec��p\to p��^0$ and $\vec��p\to p��$ from the GlueX experiment using a 9 GeV linearly-polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous $��^0$ measurements and are the first $��$ measurements in this energy regime. The results are compared with theoretical predictions based on $t$-channel, quasi-particle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models., 6 pages, 6 figures, Published in Physical Review C: Rapid Communication

In this paper we present the analytical expression for the neutron scattering law for an isotropic source of neutrons, obtained within the framework of the gas model with the temperature of the moderating medium as a parameter. The obtained scattering law is based on the solution of the kinematic problem of elastic scattering of neutrons on nuclei in the L-system in the general case. I.e. both the neutron and the nucleus possess the arbitrary velocity vectors in the L-system. For the new scattering law the flux densities and neutron moderation spectra depending on the temperature are obtained for the reactor fissile medium. The expressions for the moderating neutrons spectra allow reinterpreting the physical nature of the underlying processes in the thermal region., 26 pages, 6 figures

Using HF+BCS method we study light nuclei with nuclear charge in the range $2 \leq Z \leq 8$ and lying near the neutron drip line. The HF method uses effective Skyrme forces and allows for axial deformations. We find that the neutron drip line forms stability peninsulas at $^{18}$He and $^{40}$C. These isotopes are found to be stable against one neutron emission and possess the highest known neutron to proton ratio in stable nuclei.

Using the DIANA data on the charge-exchange reaction $K^+n \rightarrow pK^0$ on a bound neutron, in which the s-channel formation of the pentaquark baryon $��^+(1538)$ has been observed, we analyze the dependence of the background-subtracted $��^+ \rightarrow pK^0$ signal on the $K^0$ emission angle in the $pK^0$ rest frame. In order to describe the observed $\cos��_K^\mathrm{cms}$ distribution, invoking the interference between the nonresonant s-wave and the $��^+$-mediated higher-wave contributions to the amplitude of the charge-exchange reaction is required at a 2.8$��$ level. The spin--parity assignment of 1/2$^-$ for the $��^+$ baryon is ruled out at a statistical level of 2.9 standard deviations. A physically-meaningful selection in $\cos��_K^\mathrm{cms}$ based on the observed angular dependence of the $��^+ \rightarrow pK^0$ signal allows to boost the statistical significance of the signal up to 7.1 standard deviations. This is far in excess of previously reported signals and renders the $��^+$ existence more credible., 13 pages, 7 figures

We propose to enhance the kaon identification capabilities of the GlueX detector by constructing an FDIRC (Focusing Detection of Internally Reflected Cherenkov) detector utilizing the decommissioned BaBar DIRC components. The GlueX FDIRC would significantly enhance the GlueX physics program by allowing one to search for and study hybrid mesons decaying into kaon final states. Such systematic studies of kaon final states are essential for inferring the quark flavor content of hybrid and conventional mesons. The GlueX FDIRC would reuse one-third of the synthetic fused silica bars that were utilized in the BaBar DIRC. A new focussing photon camera, read out with large area photodetectors, would be developed. We propose operating the enhanced GlueX detector in Hall D for a total of 220 days at an average intensity of 5x10^7 {\gamma}/s, a program that was conditionally approved by PAC39, Comment: 25 pages, 29 figures

The charge-exchange reaction K^+ Xe --> K^0 p Xe' is investigated using the data of the DIANA experiment. The distribution of the pK^0 effective mass shows a prominent enhancement near 1538 MeV formed by \sim 80 events above the background, whose width is consistent with being entirely due to the experimental resolution. Under the selections based on a simulation of K^+Xe collisions, the statistical significance of the signal reaches 5.5\sigma. We interpret this observation as strong evidence for formation of a pentaquark baryon with positive strangeness, \Theta^+(uudd\bar{s}), in the charge-exchange reaction K^+ n --> K^0 p on a bound neutron. The mass of the \Theta^+ baryon is measured as m(\Theta^+) = 1538+-2 MeV. Using the ratio between the numbers of resonant and non-resonant charge-exchange events in the peak region, the intrinsic width of this baryon resonance is determined as \Gamma(\Theta^+) = 0.34+-0.10 MeV., Comment: 19 pages, 8 figures

The photoproduction processes gp-->a0(980)p and gp-->f0(980)p at energies close to threshold are considered. These reactions are studied in the \pi\pi p, \pi\eta p, and K-barK p channels. Production cross sections are estimated in different models. The role of the a0^0-f0 mixing is examined in the invariant \pi\pi-,\pi\eta-, and K-barK-mass spectra., Comment: 18 pages, 9 figures, 1 table; v2: added some refs

We show the existence of the strong inverse correlation between the temporal variations of the toroidal component of the magnetic field in the solar tachocline (the bottom of the convective zone) and the Earth magnetic field (the Y-component). The possibility that the hypothetical solar axions, which can transform into photons in external electric or magnetic fields (the inverse Primakoff effect), can be the instrument by which the magnetic field of the Sun convective zone modulates the magnetic field of the Earth is considered. We propose the axion mechanism of Sun luminosity and "solar dynamo -- geodynamo" connection, where the energy of one of the solar axion flux components emitted in M1 transition in 57Fe nuclei is modulated at first by the magnetic field of the solar tachocline zone (due to the inverse coherent Primakoff effect) and after that is resonantly absorbed in the core of the Earth, thereby playing the role of the energy modulator of the Earth magnetic field. Within the framework of this mechanism estimations of the strength of the axion coupling to a photon (g_{a \gamma} = 7.07e-11 1/GeV), the axion-nucleon coupling (g_{an} = 3.20e-7), the axion-electron coupling (g_{ae} = 5.28e-11) and the axion mass (m_a = 17eV) have been obtained. It is also shown that the claimed axion parameters do not contradict to any known experimental and theoretical model-independent limitations. We consider the effect of dark matter in the form of 17eV axions on the extragalactic back-ground light (EBL) and find that the theoretical spectral intensity of the EBL from decaying axions as a function of the observed wavelength is in good agreement with the known experimental data for the near ultraviolet, optical and near infrared bands (1500-20000 angstrom)., Comment: 85 pages, 31 figures. (v2: 84p., an important part about gamma-quanta channeling in magnetic tubes added along with the new Fig.11). arXiv admin note: text overlap with arXiv:hep-ph/9804291, arXiv:0711.4590, arXiv:astro-ph/0407207, arXiv:0903.1807, arXiv:astro-ph/9806129, arXiv:0903.2040, arXiv:astro-ph/0306588, arXiv:1107.4053, arXiv:astro-ph/0512509 by other authors

We consider the cotangent bundle T^*F_\lambda of a GL_n partial flag variety, \lambda = (\lambda_1,...,\lambda_N), |\lambda|=\sum_i\lambda_i=n, and the torus T=(C^*)^{n+1} equivariant cohomology H^*_T(T^*F_\lambda). In [MO], a Yangian module structure was introduced on \oplus_{|\lambda|=n} H^*_T(T^*F_\lambda). We identify this Yangian module structure with the Yangian module structure introduced in [GRTV]. This identifies the operators of quantum multiplication by divisors on H^*_T(T^*F_\lambda), described in [MO], with the action of the dynamical Hamiltonians from [TV2, MTV1, GRTV]. To construct these identifications we provide a formula for the stable envelope maps, associated with the partial flag varieties and introduced in [MO]. The formula is in terms of the Yangian weight functions introduced in [TV1], c.f. [TV3, TV4], in order to construct q-hypergeometric solutions of qKZ equations., Comment: Latex, 22 pages, misprints corrected, Section 7.4 edited

The analytical approximations for the moderating neutrons flux density like Fermi spectra, widely used in reactor physics, involve the probability function for moderating neutron to avoid the resonant absorption obtained using some restrictive assumptions regarding the acceptable resonances width. By means of multiplicative integral (Volterra integral) theory for a commutative algebra an analytical expression for the probability function is obtained rigorously without any restrictive assumptions., 7 pages, 2 figures

In recent Letter by An et al. [arXiv:1203.1669] Daya Bay measurements of non-zero value for the neutrino mixing angle {\theta}_{13} with a significance of 5.2 standard deviations were reported. The value of sin^2 {\theta}_{13} was determined with a {\chi}^2 constructed with pull terms accounting for the correlation of the systematic errors. We show that a direct applying of the KamLAND parameters of mixing to Daya Bay-experiment under nonequilibrium geoneutrino spectrum of the nuclear burning process within the framework of nonzero nuclear georeactor {\chi}^2 -hypothesis will produce a high uncertainty level and, as a result, a substantial distortion of the actual value of the neutrino mixing angle {\theta}_{13}., Comment: 2 pages, 1 figure (v2: a misprint in equation (1) corrected)

Based on the developed cross-correlation theory for remote location of neutrino source with two-detector setup for neutrino detection the modification of arrangement of the OPERA experiment is suggested. Within the framework of computing experiment based on the OPERA experimental data we show that the use of this theory makes it possible not only to determine with high accuracy the delay time between neutrino signals but to eliminate the errors of blind analysis by which all necessary time corrections for determination of signal "technologically unremovable" delay time between CERN and GSL are performed., 6 pages, 3 figures

We study polynomials p(x) satisfying a differential equation of the form p"(x)-h'(x)p'(x)+H(x)p(x)=0, where h(x)=x^3/3+ax. We prove a conjecture of A. Eremenko and A. Gabrielov., Latex, 9 pages

Differential cross sections for the process gn-->pi-p have been extracted from MAMI-B measurements of gd-->pi-pp, accounting for final-state interaction effects, using a diagrammatic technique taking into account the NN and piN final-state interaction amplitudes. Results are compared to previous measurements of the inverse process, pi-p--> ng, and recent multipole analyses., 6 pages, 4 figures. v2: Further clarifications and minor changes. A new figure inserted

We report a new extraction of nucleon resonance couplings using pi- photoproduction cross sections on the neutron. The world database for the process gamma n --> pi- p above 1 GeV has quadrupled with the addition of new differential cross sections from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab in Hall B. Differential cross sections from CLAS have been improved with a new final-state interaction determination using a diagramatic technique taking into account the NN and piN final-state interaction amplitudes. Resonance couplings have been extracted and compared to previous determinations. With the addition of these new cross sections, significant changes are seen in the high-energy behavior of the SAID cross sections and amplitudes., 11 pages, 7 figures, 2 tables

We interpret the GL_n equivariant cohomology of a partial flag variety of flags of length N in \C^n as the Bethe algebra of a suitable gl_N[t] module associated with the tensor power (\C^N)^{\otimes n}., Latex, 16 pages, misprints corrected

The incoherent pion photoproduction reaction gd-->pi-pp is considered theoretically in a wide energy region Eth =< Eg =< 2700 MeV. The model applied contains the impulse approximation as well as the NN- and piN-FSI amplitudes. The aim of the paper is to study a reliable way for getting the information on elementary gn-->pi-p reaction cross section beyond the impulse approximation for gd-->pi-pp. For the elementary gN-->piN, NN-->NN, and piN-->piN amplitudes, the results of the GW DAC are used. There are no additional theoretical constraints. The calculated cross section dSigma/dOmega(gd->pi-pp) are compared with existing data. The procedure used to extract information on the differential cross section dSigma/dOmega(gn-->pi-p) on the neutron from the deuteron data using the FSI correction factor R is discussed. The calculations for R versus pi-p CM angle ��_1 of the outgoing pion are performed at different photon-beam energies with kinematical cuts for "quasi-free" process gn-->pi-p. The results show a sizeable FSI effect R \neq 1 from S-wave part of pp-FSI at small angles close to ��_1 ~ 0: this region narrows as the photon energy increases. At larger angles, the effect is small (|R-1|<, 28 pages, 5 figures, 1 table

We introduce families of maximal commutative subalgebras, called Bethe subalgebras, of the group algebra of the symmetric group. Bethe subalgebras are deformations of the Gelfand-Zetlin subalgebra. We describe various properties of Bethe subalgebras., AmsLaTeX, 32 pages; references updated

We give an alternative description of the new data produced in the KamLAND experiment, assuming the existence of a natural nuclear reactor on the boundary of the liquid and solid phases of the Earth's core. Analyzing the uncertainty of antineutrino spectrum of georeactor origin, we show that the theoretical (which takes into account the soliton-like nuclear georeactor with power about 20 TW) reactor antineutrino spectrum describes with good accuracy the new experimental KamLAND-data. At the same time the parameters of mixing calculated within the framework of georeactor hypothesis are substantially closer to the data of solar flux SNO-experiment then the parameters of mixing obtained in KamLAND-experiment., Comment: 11 pages, 4 figures

We identify the Bethe algebra of the Gaudin model associated to gl(N) acting on a suitable representation with the center of the rational Cherednik algebra and with the algebra of regular functions on the Calogero-Moser space., Comment: Latex, 24 pages

Consider a tensor product of finite-dimensional irreducible gl_{N+1}-modules and its decomposition into irreducible modules. The gl_{N+1} Gaudin model assigns to each multiplicity space of that decomposition a commutative (Bethe) algebra of linear operators acting on the multiplicity space. The Bethe ansatz method is a method to find eigenvectors and eigenvalues of the Bethe algebra. One starts with a critical point of a suitable (master) function and constructs an eigenvector of the Bethe algebra. In this paper we consider the algebra of functions on the critical set of the associated master function and show that the action of this algebra on itself is isomorphic to the action of the Bethe algebra on a suitable subspace of the multiplicity space. As a byproduct we prove that the Bethe vectors corresponding to different critical points of the master function are linearly independent and, in particular, nonzero., Comment: Latex, 14 pages

We show that the stability condition for the soliton-like wave of nuclear burning in neutron-multiplicating medium is determined in general by two conditions. The first condition (necessary) is determined by relationship between the equilibrium concentration and critical concentration of active (fissile) isotope, that is a consequence of the Bohr-Sommerfeld quantization condition. The second condition (sufficient) is set by the so-called Wigner quantum statistics, or more accurately, by a ststistics of the Gaussian simplectic ensembles with respect to the parameter that describes the squared width of burning wave front of nuclear fuel active component., Comment: 26 pages, 6 figures

We construct a canonical isomorphism between the Bethe algebra acting on a multiplicity space of a tensor product of evaluation gl_N[t]-modules and the scheme-theoretic intersection of suitable Schubert varieties. Moreover, we prove that the multiplicity space as a module over the Bethe algebra is isomorphic to the coregular representation of the scheme-theoretic intersection. In particular, this result implies the simplicity of the spectrum of the Bethe algebra for real values of evaluation parameters and the transversality of the intersection of the corresponding Schubert varieties., Latex, 32 pages

High-quality cross sections for the reaction gamma+d->pi^0+d have been measured using the CLAS at Jefferson Lab over a wide energy range near and above the eta-meson photoproduction threshold. At backward c.m. angles for the outgoing pions, we observe a resonance-like structure near E_gamma=700 MeV. Our model analysis shows that it can be explained by eta excitation in the intermediate state. The effect is the result of the contribution of the N(1535)S_11 resonance to the amplitudes of the subprocesses occurring between the two nucleons and of a two-step process in which the excitation of an intermediate eta meson dominates., slightly modified title, additional paragraph and a table (Table 2) added on p. 5; to be submitted to EPJA, 6 pages, 3 figures

An energy-balance model of global climate, which takes into account a nontrivial role of galactic cosmic rays, is developed. The model is described by the fold catastrophe equation relative to increment of temperature, where galactic cosmic rays and insolation are control parameters. The comparison of the results of a computer simulation of time-dependent solution of the presented model and oxygen isotope records of deep-sea core V28-238 over the past 730 kyr are presented. The climate evolution in future 100 kyr is also predicted., 11 pages, 3 figures

The reaction pp -> dpi+eta has been measured at a beam energy of T=2.65 GeV (p=3.46 GeV/c) using the ANKE spectrometer at COSY-Juelich. The missing mass distribution of the detected dpi+ pairs exhibits a peak around the eta mass on top of a strong background of multi-pion pp -> dpi+(n(pi)) events. The differential cross section d^4(sigma)/d(Omega_d)d(Omega_pi+)d(p_d)d(p_pi+) for the reaction pp -> dpi+eta has been determined model independently for two regions of phase space. Employing a dynamical model for the a0+ production allows one then to deduce a total cross section of sigma(pp -> da0+ -> dpi+eta)=(1.1 +/- 0.3_(stat) +/- 0.7_(syst)) microbarn for the production of pi+eta via the scalar a0+(980) resonance and sigma(pp -> dpi+eta) = (3.5 +/- 0.3_(stat) +/- 1.0_(syst)) microbarn for the non-resonant production. Using the same model as for the interpretation of recent results from ANKE for the reaction pp -> dK+(bar(K0)), the ratio of the total cross sections is sigma(pp -> d(K+(bar(K0)))_(L=0))/sigma(pp -> da0+ -> dpi+eta) = 0.029 +/- 0.008_(stat) +/- 0.009_(syst), which is in agreement with branching ratios in the literature., 5 pages, 8 figures, 1 table

We review results on the Knizhnik-Zamolodchikov (KZ) and dynamical equations, both differential and difference, in the context of the $(gl_k,gl_n)$ duality, and their implications for hypergeometric integrals. The KZ and dynamical equations naturally exchange under the duality, which provides two kinds of integral formulae for hypergeometric solutions of the equations. This fact yields identities for hypergeometric integrals of different dimensions, the dimension of the first integral being the parameter of the second one, and vice versa. Similar identites exist between hypergeometric and q-hypergeometric integrals of Mellin-Barnes type of different dimensions. Those identites are multidimensional analogues of the equality of two integral representations for the Gauss hypergeometric function., Preprint, 29 pages, AmsLaTeX, to appear in Proceedings of IDAQUIS, (Infinite Dimensional Algebras and Quantum Integrable Systems), Faro, Portugal, July 21-25, 2003

An analytic formula for the two-loop QCD correction of the decay H --> 2 gamma is presented. To evaluate all master integrals a `Risch-like' algorithm was exploited., 5 pages, Latex, axodraw.sty

The energy-balance model of global climate, which is taking into account a nontrivial role of solar and galactic protons, is presented. The model is described by the equation of fold catastrophe relative to increment of temperature, where the variation of a solar insolation and cosmic rays are control parameters. It is shown that the bifurcation equation of the model describes one of two stable states of the climate system. The solution of this equation exhibits the property of the determined bistable behavior of climate at the global level and the possibility of appearance of the determined chaos of "the weathers" at the local levels. The results of the comparative analysis of the computer simulation of the time-dependent solution of energy-balance model of global climate and the oxygen isotope records for deep-sea core V28-238 over the past 730 kyr are presented, and the evolution of climate on 100 kyr forward is also predicted. It is shown that the proposed model successfully explains the nicety of the paleoclimatic records. The model is clear of all known difficulties of the Milankovich theory for the analysis and the interpretation of physical mechanism, by which the climate system responds to orbital forcing., Comment: 21 pages, 6 figures

We consider the reaction g+d -> pi+d in a wide energy range around and above the eta-meson photoproduction threshold at backward CM angles of the outgoing pion. Our theoretical analysis is essentially motivated by the recent measurements of the CLAS Collaboration at Jefferson Lab, where this kinematical region of the reaction has been thoroughly studied for the first time and a cusps in the energy dependence of the differential cross section in the region of Eg = 600-800 MeV has been observed. Our preliminary and qualitative analysis, based on single- and double-scattering diagrams, shows that the observed structure can be explained by the contribution of the double-scattering diagram with intermediate production of the eta meson. The effect, to a considerable extent, is formed due to the contribution of N(1535) resonance to the amplitudes of subprocesses on the nucleons., 16 pages, 7 figures, submitted to PRC

It is shown that solutions of the Bethe ansatz equations for the inhomogeneous arbitrary spin XXX or XXZ model satisfy certain identites which generalize those, recently obtained by K.Fabricius and B.M.McCoy, for solutions of the Bethe ansatz equations for the six-vertex model. Even in the last case, the given proof is simpler than the original one., 4 pages, amstex 2.2 and amssym.tex required

We give a construction of creation operators responsible for appearance of Bethe vectors with the same eigenvalues of the transfer-matrix for the inhomogeneous arbitrary spin XXZ model at roots of unity with particular quasiperiodic boundary conditions. This construction generalizes the similar one, recently obtained by K.Fabricius and B.M.McCoy, for the homogeneous six-vertex model with periodic boundary conditions. Even in the last case, the given proof for the main formulae are simpler than the original one., Comment: 9 pages, amstex 2.2 and amssym.tex required