11192776
Preservation of proton polarization by a partial Siberian snake.
A 9[degree] solenoidal spin rotator or 5% partial Siberian Snake was used to successfully accelerate polarized protons for the first time to 10.8 GeV kinetic energy in the Brookhaven Alternating Gradient Synchrotron with partial depolarization due to the intrinsic resonance crossing. It was found that a 5% partial snake can effectively overcome 18 imperfection resonances in this energy range. We also observed an interference between the spin flip induced by an intrinsic resonance and linear coupling due to the solenoid field of the partial snake.
17951392
Measurements of Single and Double Spin Asymmetry in pp Elastic Scattering in the CNI Region with Polarized Hydrogen Gas Jet Target
Precise measurements of the single spin asymmetry, AN and the double spin asymmetry, ANN, in proton‐proton (pp) elastic scattering in the region of four‐momentum transfer squared 0.001 < −t < 0.032 (GeV/c)2 have been performed using a polarized atomic hydrogen gas jet target and the RHIC polarized proton beam at 24 GeV/c and 100 GeV/c. The polarized gaseous proton target allowed us to achieve the measurement of ANN in the CNI region for the first time. Our results of AN and ANN provide significant constraints to determine the magnitude of poorly known hadronic single and double spin‐flip amplitudes at this energy.
118056950
The RHIC p‐Carbon CNI Polarimeter Upgrade For The Beam Polarization And Intensity Measurements
Proton polarization measurements in the AGS and RHIC (Relativistic Heavy Ion Collider at the beam energies 24–250 GeV) are based on proton‐carbon and proton‐proton elastic scattering in the Coulomb Nuclear Interference (CNI) region. Polarimeter operation in the scanning mode also gives polarization profile and beam intensity profile (beam emittance) measurements. Bunch by bunch emittance measurement is a very powerful tool for machine setup. Presently, the polarization and beam intensity profile measurements (in both vertical and horizontal planes) are restricted by the long target switching time and possible target destruction during this complicated motion. The RHIC polarimeters were operated near the limit of the counting rate for present silicon strip detectors. The ongoing polarimeter upgrade for the 2009 run will address all these problems. The upgrade should allow significant reduction of the polarization measurement errors by making feasible the complete polarization measurements, which includes p...
117489591
EXPERIMENTAL EFFECTS OF ORBIT ON POLARIZATION LOSS IN RHIC
We are performing several experiments during the RHIC ramp to better understand the impact of orbit errors on the polarization at our current working point. These will be conducted by exciting specified orbit harmonics during the final two large intrinsic resonance crossing in RHIC during the 250 GeV polarized proton ramp. The resultant polarization response will then be measured.
120986648
Rhic Polarized Proton New Working Point Commissioning
The RHIC 2003 polarized proton run showed a limitation on the luminosity due to the beam-beam effect at a betatron tune working point of (0.225,0.235). The integer parts of the horizontal and vertical betatron tunes are 28 and 29, respectively. The polarization transmission efficiency was also compromised because of the tight tune space due to the snake resonances. It was decided to explore the RHIC pp luminosity capability as well as the polarization capability with new working points during the RHIC pp 2004 Run. The working point (0.690.0.685) at a RHIC stored energy of 100GeVk was found to ameliorate the beam-beam effect, and also improve the polarization transmission efficiency as well as polarization lifetime during store. This paper reports the commissioning efforts and results of the new working point commissioning during the latest RHIC polarized proton run.
56408435
Optimization of the AGS superconducting helical partial snake strength.
Two helical partial snakes, one super-conducting (a.k.a cold snake) and one normal conducting (a.k.a warm snake), have preserved the polarization of proton beam up to 65% in the Brookhaven Alternating Gradient Synchrotron (AGS) at the extraction energy from 85% at injection. In order to overcome spin resonances, stronger partial snakes would be required. However, the stronger the partial snake, the more the stable spin direction tilted producing a stronger horizontal intrinsic resonance. The balance between increasing the spin tune gap generated by the snakes and reducing the tilted stable spin direction has to be considered to maintain the polarization. Because the magnetic field of the warm snake has to be a constant, only the cold snake with a maximum 3T magnetic field can be varied to find out the optimum snake strength. This paper presents simulation results by spin tracking with different cold snake magnetic fields. Some experimental data are also analyzed.
10679146
Conformal transformation of renormalized effective action in curved spacetimes.
The functional-differential equation which governs the conformal transformation of the renormalized effective action for a massless, conformally invariant quantized field is solved exactly. The formula so obtained can be used to obtain the effective action in any background spacetime once there exists a conformally related spacetime in which the effective action is known. A simple example is presented to see how our formula is useful to obtain the renormalized stress tensor in the \ensuremath{\zeta}-functional regularization scheme.
29696360
Nonperturbative effects on the Wilson coefficients and the Delta I=(1/2 rule in kaon decays.
We apply the vacuum-background-field method and the modified renormalization-group equation in the energy region {mu}{lt}1 GeV to correct the Wilson coefficients in the {Delta}{ital S}=1 effective weak Hamiltonian responsible for {ital K}{r arrow}2{pi} decays. We find that the change of {ital C}{sub {plus minus}} results in an enhancement to the {Delta}{ital I}={1/2} amplitude by a factor of 2 at the scale {mu}=0.6 GeV for {ital K}{r arrow}2{pi} decays.
35673041
Decays of excited charmed Lambda -type and Sigma -type baryons in heavy hadron chiral perturbation theory.
Ground states and some excited p-wave states of heavy baryons are studied within the framework of heavy hadron chiral perturbation theory. The effective Lagrangian is written out to terms of the next-to-leading order in 1/${\mathit{m}}_{\mathit{Q}}$ or 1/${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{\ensuremath{\chi}}}$. The coupling constants are estimated using the experimental data of \ensuremath{\Lambda} and \ensuremath{\Sigma} baryons in the static limit of the s quark. The single pion and double pion decay rates of these charmed baryons have been estimated. The numerical results show that both ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$(1/${2}^{\mathrm{\ensuremath{-}}}$) and ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$(3/${2}^{\mathrm{\ensuremath{-}}}$) are very narrow. We conclude that the two pion channel may offer the best hope for detecting the ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}$(3/${2}^{\mathrm{\ensuremath{-}}}$) and ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}$(1/${2}^{\mathrm{\ensuremath{-}}}$) p-wave doublet.
7473966
Renormalization of the quantum stress-energy tensor in inhomogeneous spacetimes: Adiabatic regularization method.
The adiabatic regularization method, known to be a particularly efficient method for numerical study of quantum field dynamics in curved spacetimes, is applicable to evaluate the renormalized stress-energy tensor for matter in any background metric which has sufficient symmetry to allow a decomposition of the quantized field into modes. In this paper we extend this method to more general spacetimes with a small inhomogeneity which is invariant under spatial reflection. We overcome the difficulty of the mode-mixing behavior arising from the inhomogeneity of spacetime and show a possible way of obtaining the WKB solution of the time-dependent mode function under the early-time approximation. As an illustration, we investigate the renormalization of the quantum stress-energy tensor for a massive scalar field with an arbitrary curvature coupling to the inhomogeneous conformally flat spacetime. Our expressions are useful in formulating the semiclassical theory of gravity and in the numerical study of the back reaction of quantized fields in the early Universe with a small inhomogeneity.
22146343
Effective action of a scalar field in a curved spacetime with a small inhomogeneity.
The effective action of a quantum field in an inhomogeneous spacetime is studied. We extend the Hartle-Hu method, which was developed to investigate the model in a homogeneous spacetime with a small anisotropy, to evaluate the one-loop effective action for a scalar field in a curved spacetime with a small inhomogeneity. Through a rather lengthy calculation we obtain the final expression which is then applied to numerically investigate the quantum-field effect on the dissipation of the space inhomogeneity in the early Universe