117036088
Comparison of multipole expansion and exact form of the eddy current field of the AGS Booster
Studies are made on magnetic field representation using a multipole expansion as well as the exact form to calculate the magnetic field produced by eddy currents in the vacuum chamber of the AGS Booster as well as the field produced by three turn correction coils attached to the top and bottom of the vacuum chamber. The multiple representation of the chamber field does not converge to the next field when X > 30mm and limits the particle motion. When the exact form of the chamber field is used, initial amplitudes in the horizontal plane (measured at QF) can be nearly as large as the chamber half aperture. Use of three turn correction coils to compensate the eddy current fields seems to reduce rather than increase the acceptance. 6 figs., 3 tabs.
121911294
The RHIC design overview
The salient performance objectives for the Relativistic Heavy Ion Collider (RHIC) are presented and the rationale for the design choices of the major collider systems is conveyed. RHIC provides collisions of heavy ions covering the entire mass range from protons to gold. For the prototypical case of Au-on-Au, one obtains energies up to 100 GeV/n per beam and luminosities of B2 � 10 26 cm � 2 s � 1 , averaged over a 10-h storage time. Operation with polarized protons is also possible. The overall accelerator complex used for gold ions consists of the Tandem Van de Graaff, the Booster, the AGS, and the Collider itself, and the scenario for the beam transfer between machines is described. The two separate collider rings cross at six interaction points, where the lattice design provides low-beta insertions for maximum luminosity. The interaction diamond length of o20 cm rms is achieved by bunched beam operation and holding the 56 bunches in a 197 MHz radio-frequency (RF) system after their acceleration in a 28 MHz RF system. The rings are constructed with superconducting magnets, which have a cold bore aperture of 6.9 cm in the arcs. The RHIC specific design challenges posed by intrabeam scattering of heavy ions, passage through transition energy with slow-ramping superconducting magnets, and control of magnetic errors in the low-beta triplet quadrupoles are addressed. r 2002 Elsevier Science B.V. All rights reserved.
120908048
Comment on “Quasiperiodic spin-orbit motion and spin tunes in storage rings”
120417645
Snakes and spin rotators for high energy accelerators
Abstract A modification to the continuous family of snake and spin rotators, discovered by Steffen, is discussed. A compact snake configuration is found to have the advantages of requiring a smaller total integrated dipole magnet strength and a smaller transverse displacement for circulating particles. A split snake configuration has the advantage of allowing an entire experimental insertion region to be located between the two halves of the snake. Such configurations could serve as both a snake and a 90° spin rotator for experiments requiring different helicity states. General properties of these snake configurations are discussed.
124338422
FIRST OBSERVATION OF A SNAKE DEPOLARIZING RESONANCE
Using a 104MeV stored polarized proton beam and a full Siberian snake, we recently found evidence for a so-called {open_quotes}snake{close_quotes} depolarizing resonance. A full Siberian snake forces the spin tune {nu}{sub s} to be a half integer. Thus, if the vertical betatron tune {nu}{sub y} is set near a quarter integer, then the {nu}{sub s}=n{plus_minus}2{nu}{sub y} second-order snake resonance can depolarize the beam. Indeed, with a full Siberian snake, we found a deep depolarization dip when {nu}{sub y} was equal to 4.756; moreover, when {nu}{sub y} was changed to 4.781, the deep dip disappeared and the polarization was preserved. {copyright} {ital 1997} {ital The American Physical Society}
96454816
Design and fabrication of a multi-purpose Panofsky magnet
A fast, flexible magnet system, consisting of a Panofsky style ferrite picture-frame magnet and pulsed power supply, has been developed. Magnet specifications are: 8 cm /spl times/8 cm aperture, 23 cm length, 500 A pulsed/l60 A DC, and 1 /spl mu/s risetime. Designed for general accelerator physics studies, the magnet may be quickly converted from dipole to quadrupole or sextupole and higher multipole configurations by easily changing winding end terminations. In the quadrupole configuration a field gradient of 0.5 T/m is achieved at 500 A. This magnet has become an important tool for nonlinear beam dynamics experiments at the IUCF Cooler Ring.<<ETX>>
53550475
Subthreshold cascade production in heavy ion collisions
Using a gauged flavor SU(3)-invariant hadronic Lagrangian, we have calculated the cross sections for the strangeness-exchange reactions in the Born approximation. These cross sections are then used in the Relativistic Vlasov-Uehling-Uhlenbeck (RVUU) transport model to study Ξ production in Ar+KCl collisions at incident energy of 1.76A GeV and impact parameter b = 3.5 fm. We find that including the contributions of hyperonhyperon scattering channels strongly enhances the yield of Ξ, leading to the abundance ratio which is essentially consistent with the recently measured value of by the HADES collaboration at GSI.
120447270
LEE-WICK FIELD AS A DARK ENERGY CANDIDATE
As a possible alternative solution for the hierarchy problem in the standard model, Lee-Wick theory where a field has higher derivative kinetic operators has been paid attentions recently. Also in modern cosmology, the observations suggest that the current universe is under accelerating expansion dominated by dark energy. Furthermore, they marginally prefer the dark energy equation of state parameter ωDE to cross the phantom divide -1 at present. Lee-Wick theory has the same structure as so-called quintom model except the form of potentials and the sign of the slope of the potentials. Thus, this model can produce the stable late time phantom-dominated solution and maybe able to explain the current cosmology. However, without fine tuning of its mass we may not be able to produce the viable values of observational quantities in this model.
41568305
Lagrangian perturbation theory: exact one-loop power spectrum in general dark energy models
Recently, we found that the correction for the Einstein–de Sitter (EdS) assumption on the one-loop matter power spectrum for general dark energy models using the standard perturbation theory is not negligible (Lee et al., arXiv:1407.7325, 2014). Thus, we investigate the same problem by obtaining the exact displacement vector and kernels up to the third order for the general dark energy models in the Lagrangian perturbation theory (LPT). Using these exact solutions, we investigate the present one-loop matter power spectrum in the $$\Lambda $$ΛCDM model with $$\Omega _{m0} = 0.25 (0.3)$$Ωm0=0.25(0.3) to obtain a $$0.2 (0.18)$$0.2(0.18) % error correction compared to that obtained from the EdS assumption for the $$k = 0.1\,\mathrm{h\, Mpc}^{-1}$$k=0.1hMpc-1 mode. If we consider the total matter power spectrum, the correction is only $$0.05 (0.03)$$0.05(0.03) % for the same mode. It means that the EdS assumption is a good approximation for the $$\Lambda $$ΛCDM model in LPT theory. However, one can use this method for general models where the EdS assumption is improper.
118495503
Factorization at subleading power and irreducible uncertainties in $ \bar{B} \to {X_s}\gamma $ decay
Using methods from soft-collinear and heavy-quark effective theory, a systematic factorization analysis is performed for the $ \bar{B} \to {X_s}\gamma $ photon spectrum in the endpoint region $ {m_b} - 2{E_\gamma } = \mathcal{O}\left( {{\Lambda_{\text{QCD}}}} \right) $. It is proposed that, to all orders in 1/mb, the spectrum obeys a novel factorization formula, which besides terms with the structure H J ⊗ S familiar from inclusive $ \bar{B} \to {X_u}l\bar{\nu } $ decay distributions contains “resolved photon” contributions of the form $ H\;J \otimes S \otimes \bar{J} $ and $ H\;J \otimes S \otimes \bar{J} \otimes \bar{J} $. Here S and $ \bar{J} $ are new soft and jet functions, whose form is derived. These contributions arise whenever the photon couples to light partons instead of coupling directly to the effective weak interaction. The new contributions appear first at order 1/mb and are related to operators other than Q7γ in the effective weak Hamiltonian. They give rise to non-vanishing 1/mb corrections to the total decay rate, which cannot be described using a local operator product expansion. A systematic analysis of these effects is performed at tree level in hard and hard-collinear interactions. The resulting uncertainty on the decay rate defined with a cut Eγ > 1.6 GeV is estimated to be approximately ±5%. It could be reduced by an improved measurement of the isospin asymmetry Δ0− to the level of ±4%. We see no possibility to reduce this uncertainty further using reliable theoretical methods.
118516615
Emergence of supersymmetry on the surface of three-dimensional topological insulators
We propose two possible experimental realizations of a (2 + 1)-dimensional spacetime supersymmetry at a quantum critical point on the surface of three-dimensional topological insulators. The quantum critical point between the semi-metallic state with one Dirac fermion and the s-wave superconducting state on the surface is described by a supersymmetric conformal field theory within the ϵ-expansion. We predict the exact voltage dependence of the differential conductance at the supersymmetric critical point.