1,252 research outputs found
Nonperturbative calculation of the anomalous magnetic moment in the Yukawa model within truncated Fock space
Within the covariant formulation of light-front dynamics, we calculate the
state vector of a physical fermion in the Yukawa model. The state vector is
decomposed in Fock sectors and we consider the first three ones: the single
constituent fermion, the constituent fermion coupled to one scalar boson, and
the constituent fermion coupled to two scalar bosons. This last three-body
sector generates nontrivial and nonperturbative contributions to the state
vector, which are calculated numerically. Field-theoretical divergences are
regularized using Pauli-Villars fermion and boson fields. Physical observables
can be unambiguously deduced using a systematic renormalization scheme we have
developed previously. As a first application, we consider the anomalous
magnetic moment of the physical fermion.Comment: 24 pages, 16 figure
Two-fermion relativistic bound states in Light-Front Dynamics
In the Light-Front Dynamics, the wave function equations and their numerical
solutions, for two fermion bound systems, are presented. Analytical expressions
for the ladder one-boson exchange interaction kernels corresponding to scalar,
pseudoscalar, pseudovector and vector exchanges are given. Different couplings
are analyzed separately and each of them is found to exhibit special features.
The results are compared with the non relativistic solutions.Comment: 40 pages, to be published in Phys. Rev. C, .tar.gz fil
Trouble in Asymptopia---the Hulthen Model on the Light Front
We use light-front dynamics to calculate the electromagnetic form-factor for
the Hulthen model of the deuteron. For small momentum transfer Q^2 < 5 GeV^2
the relativistic effects are quite small. For Q^2 = 11 GeV^2 there is about a
13% discrepancy between the relativistic and non-relativistic approaches. For
asymptotically large momentum transfer, however, the light-front form factor,
log Q^2 /Q^4, markedly differs from the non-relativistic version, 1/Q^4. This
behavior is also present for any wave function, such as those obtained from
realistic potential models, which can be represented as a sum of Yukawa
functions. Furthermore, the asymptotic behavior is in disagreement with the
Drell-Yan-West relation. We investigate precisely how to determine the
asymptotic behavior and confront the problem underlying troublesome form
factors on the light front.Comment: 20 pages, 8 figures Accepted by Phys. Rev
Uakitite, VN, a new mononitride mineral from uakit iron meteorite (IIAB)
Uakitite was observed in small troilite–daubréelite (±schreibersite) inclusions (up to 100 µm) and in large troilite–daubréelite nodules (up to 1 cm) in Fe-Ni-metal (kamacite) of the Uakit iron meteorite (IIAB), Republic of Buryatia, Russia. Such associations in the Uakit meteorite seemed to form due to high-temperature (>1000 °C) separation of Fe-Cr-rich sulfide liquid from Fe-metal melt. Most inclusions represent alternation of layers of troilite and daubréelite, which may be a result of solid decay of an initial Fe-Cr-sulfide. These inclusions are partially resorbed and mainly located in fissures of the meteorite, which is now filled with magnetite, and rarely other secondary minerals. Phase relations indicate that uakitite is one of the early minerals in these associations. It forms isometric (cubic) crystals (in daubréelite) or rounded grains (in schreibersite). The size of uakitite grains is usually less than 5 µm. It is associated with sulfides (daubréelite, troilite, grokhovskyite), schreibersite and magnetite. Carlsbergite CrN, a more abundant nitride in the Uakit meteorite, was not found in any assemblages with uakitite. Physical and optical properties of uakitite are quite similar to synthetic VN: yellow and transparent phase with metallic luster; Mohs hardness: 9–10; light gray color with a pinky tint in reflected light; density (calc.) = 6.128 g/cm3. Uakitite is structurally related to the osbornite group minerals: carlsbergite CrN and osbornite TiN. Structural data were obtained for three uakitite crystals using the electron backscatter diffraction (EBSD) technique. Fitting of the EBSD patterns for a synthetic VN model (cubic, Fm-3m, a = 4.1328(3) Å; V = 70.588(9) Å3; Z = 4) resulted in the parameter MAD = 0.14–0.37° (best-good fit). Analytical data for uakitite (n = 54, in wt. %) are: V, 71.33; Cr, 5.58; Fe, 1.56; N, 21.41; Ti, below detection limit (<0.005). The empirical formula (V0.91Cr0.07Fe0.02)1.00N1.00 indicates that chromium incorporates in the structure according to the scheme V3+ → Cr3+ (up to 7 mol. % of the carlsbergite end-member). © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Foundation for Basic Research, RFBR: 17-05-00129, IGM SD 0330-2016-0005Government Council on Grants, Russian FederationMinistry of Science and Higher Education of the Russian FederationFunding: The investigations were partly supported by RFBR (grant 17-05-00129) and the State assignment project (IGM SD 0330-2016-0005). This work was also supported by the Initiative Project of Ministry of Science and Higher Education of the Russian Federation and by Act 211 of the Government of the Russian Federation, agreement no. 02.A03.21.0006
Similarity Renormalization, Hamiltonian Flow Equations, and Dyson's Intermediate Representation
A general framework is presented for the renormalization of Hamiltonians via
a similarity transformation. Divergences in the similarity flow equations may
be handled with dimensional regularization in this approach, and the resulting
effective Hamiltonian is finite since states well-separated in energy are
uncoupled. Specific schemes developed several years ago by Glazek and Wilson
and contemporaneously by Wegner correspond to particular choices within this
framework, and the relative merits of such choices are discussed from this
vantage point. It is shown that a scheme for the transformation of Hamiltonians
introduced by Dyson in the early 1950's also corresponds to a particular choice
within the similarity renormalization framework, and it is argued that Dyson's
scheme is preferable to the others for ease of computation. As an example, it
is shown how a logarithmically confining potential arises simply at second
order in light-front QCD within Dyson's scheme, a result found previously for
other similarity renormalization schemes. Steps toward higher order and
nonperturbative calculations are outlined. In particular, a set of equations
analogous to Dyson-Schwinger equations is developed.Comment: REVTex, 32 pages, 7 figures (corrected references
Nataliakulikite, Ca4Ti2(Fe3+,fe2+)(Si,fe3+,al)o11, a new perovskite-supergroup mineral from hatrurim basin, negev desert, Israel
Nataliakulikite, Ca4Ti2(Fe3+,Fe2+)(Si,Fe3+,Al)O11, is a mineral intermediate between perovskite CaTiO3 and brownmillerite Ca2(Fe,Al)2O5. It was discovered as a minor mineral in a high-temperature pyrometamorphic larnite-gehlenite rock at the Nahal Morag Canyon of the Hatrurim Basin, Israel. Nataliakulikite is associated with larnite, flamite, gehlenite, magnesioferrite, Fe3+-rich perovskite, fluorapatite, barite, Hashemite, and retrograde phases (afwillite, hillebrandite, portlandite, calcite, ettringite, hydrogarnet, and other hydrated Ca-silicates). The mineral forms brown subhedral or prismatic grains (up to 20 µm) and their intergrowths (up to 50 µm). Its empirical formula (n = 47) is (Ca3.992Sr0.014U0.004)(Ti1.933Zr0.030Nb0.002) (Fe3+0.610Fe2+0.405Cr0.005Mn0.005)(Si0.447Fe3+0.337Al0.216)O11 and shows Si predominance in tetrahedral site. The unit-cell parameters (HRTEM data) and space group are: a = 5.254, b = 30.302, c = 5.488 Å, V = 873.7 Å3, Pnma, Z = 4. These dimensions and Electron backscatter diffraction (EBSD) data strongly support the structural identity between nataliakulikite and synthetic Ca4Ti2Fe3+2O11 (2CaTiO3·Ca2Fe3+2O5), an intermediate compound in the system CaTiO3-Ca2Fe3+2O5. In general, this mineral is a Si-Fe2+-rich natural analog of synthetic Ca4Ti2Fe3+2O11. The X-ray powder diffraction data (CuKα-radiation), calculated from unit-cell dimensions, show the strongest lines {d [Å], (Icalc)} at: 2.681(100), 1.898(30), 2.627(26), 2.744(23), 1.894(22), 15.151(19), 1.572(14), 3.795(8). The calculated density is 4.006 g/cm3. The crystal structure of nataliakulikite has not been refined because of small sizes of grains. The Raman spectrum shows strong bands at 128, 223, 274, 562, and 790 cm−1. Nataliakulikite from the Hatrurim Basin crystallized under the conditions of combustion metamorphism at high temperatures (1160–1200◦C) and low pressures (HT-region of the spurrite-merwinite facies). © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 0330-2016-0004, 17-17-01056, IGM SD 0330-2016-0005Ben-Gurion University of the Negev, BGUThis research was funded by the Russian Science Foundation, grant number 17-17-01056. The field work and sample collection was partly supported the State assignment projects (IGM SD 0330-2016-0005, 0330-2016-0004). Acknowledgments: The authors would like to thank M.V. Khlestov (IGM SD RAS) for technical assistance at SEM studies. Yevgeny Vapnik (Ben-Gurion University, Beer-Sheva, Israel) is thanked for providing of fruitful field trips in the Hatrurim Basin in 2004 and 2019. The last version of the manuscript was improved through comments and suggestions by T. Perepelova (IGM, Novosibirsk). We are highly appreciative of the valuable comments and suggestions of two anonymous reviewers
Charm production nearby threshold in pA-interactions at 70 GeV
The results of the SERP-E-184 experiment at the U-70 accelerator (IHEP,
Protvino) are presented. Interactions of the 70 GeV proton beam with C, Si and
Pb targets were studied to detect decays of charmed , ,
, mesons and baryon near their production threshold.
Measurements of lifetimes and masses are shown a good agreement with PDG data.
The inclusive cross sections of charm production and their A-dependencies were
obtained. The yields of these particles are compared with the theoretical
predictions and the data of other experiments. The measured cross section of
the total open charm production ( = 7.1
2.3(stat) 1.4(syst) b/nucleon) at the collision c.m. energy
= 11.8 GeV is well above the QCD model predictions. The
contributions of different species of charmed particles to the total cross
section of the open charm production in proton-nucleus interactions vary with
energy.Comment: 4 pages, 6 pages, 38th International Conference on High Energy
Physics 3-10 August 2016, Chicago, US
Deuteron Magnetic and Quadrupole Moments with a Poincar\'e Covariant Current Operator in the Front-Form Dynamics
The deuteron magnetic and quadrupole moments are unambiguosly determined
within the front-form Hamiltonian dynamics, by using a new current operator
which fulfills Poincar\'e, parity and time reversal covariance, together with
hermiticity and the continuity equation. For both quantities the usual
disagreement between theoretical and experimental results is largely removed.Comment: To appear in Phys. Rev. Let
Hyperon-Nucleon Final State Interaction in Kaon Photoproduction of the Deuteron
Final state hyperon-nucleon interaction in strangeness photoproduction of the
deuteron is investigated making use of the covariant reaction formalism and the
P-matrix approach to the YN system. Remarkably simple analytical expression for
the amplitude is obtained. Pronounced effects due to final state interaction
are predicted including the manifestation of the 2.13 GeV resonance.Comment: LaTeX, 13 page
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