36954367
A transitionless lattice for the Fermilab Main Injector
Medium energy (1 to 30 GeV) accelerators are often confronted with transition crossing during acceleration. A lattice without transition, which is a design for the Fermilab Main Injector, is presented. The main properties of this lattice are that the gamma /sub t/ is an imaginary number, the maxima of the dispersion function are small, and it has two long-straight sections with zero dispersion.<<ETX>>
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}
120908048
Comment on “Quasiperiodic spin-orbit motion and spin tunes in storage rings”
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>>
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.
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.
14480613
Constraints on the dark energy equation of state from the separation of CMB peaks and the evolution of {alpha}
We introduce a simple parametrization of the dark energy equation of state, {omega}, which is motivated from theory and recent experimental data. The theory is related to the tracker solution to alleviate the fine-tuning problem. Recent experimental data indicates that the present value of {omega} is close to -1. We analyze the evolution of {omega} from the separation of CMB peaks and the time variation of the fine structure constant, {alpha}. We find that -1.00{<=}{omega}{sup (0)}{<=}-0.971{sub -0.027}{sup +0.017} and 1.76{sub -0.42}{sup +0.29}x10{sup -4}{<=}(d{omega}/dz){sub z=0}{<=}0.041{sub -0.037}{sup +=} 0{sup .016} at 95% confidence level.
123098353
Vector Meson Dispersion in Medium
118377735
Free energy versus internal energy potential for heavy quark systems at finite temperature
Using the QCD sum rule with its operator product expansion reliably determined from lattice calculations for the pressure and energy density of hot QCD matter, we calculate the strength of the $J/\ensuremath{\psi}$ wave function at the origin and find that it decreases with temperature when the temperature is in the vicinity of the transition temperature. This result is shown to follow exactly that obtained from the solution of the Schr\"odinger equation for a charm and anticharm quark pair with a temperature independent quark mass using the free energy from lattice calculations as the potential and is in sharp contrast to that using the deeper potential associated with the internal energy, which shows an enhanced strength of the $J/\ensuremath{\psi}$ wave function at the origin. Our result thus suggests that the free energy potential from lattice calculations is the appropriate heavy-quark potential for analyzing the charmonium spectrum at a finite temperature.
17171580
Emergence of classicality in quantum phase transitions
We show that classicality emerges during quantum phase transitions due to parametric interactions without coupling to environments. The Wigner functions are explicitly calculated for the Gaussian vacuum, number, and thermal states of a free scalar field that describes the spinodal instability regime. The Wigner functions are sharply peaked around their classical trajectories during the phase transition and exhibit classical correlation only for unstable long wavelength modes but retain quantum coherence for short wavelength modes. Thus classicality emerges from the quantum evolution of phase transitions without a classical order parameter. We define a quantal ordering parameter that is linear in the field variable and satisfies the classical field equation.
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.