Experimental Demonstration of a Large Transverse Emittance Ratio 11∶1 in the Relativistic Heavy Ion Collider for the Electron-Ion Collider.

The Electron-Ion Collider (EIC), to be constructed at Brookhaven National Laboratory, will collide polarized high-energy electron beams with hadron beams, achieving luminosities of up to 1.0×10^{34} cm^{-2} s^{-1} in the center-of-mass energy range of 20-140 GeV. To achieve such high luminosity, the EIC will employ small and flat beams at the interaction point. In the hadron storage ring of the EIC, the ratio of horizontal to vertical emittances is approximately 11∶1. In contrast, in previous or existing hadron colliders, the horizontal and vertical emittances are typically similar or closely matched. At the Relativistic Heavy Ion Collider (RHIC), we experimentally demonstrated a large transverse emittance ratio of 11∶1 with gold ion beams at a particle energy of 100 GeV per nucleon, thanks to stochastic cooling and fine decoupling. Furthermore, we demonstrated collisions with flat beams, featuring a transverse beam size ratio of 3∶1 for the first time at the RHIC.

Experimental Demonstration of Hadron Beam Cooling Using Radio-Frequency Accelerated Electron Bunches.

Cooling of beams of gold ions using electron bunches accelerated with radio-frequency systems was recently experimentally demonstrated in the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. Such an approach is new and opens the possibility of using this technique at higher energies than possible with electrostatic acceleration of electron beams. The challenges of this approach include generation of electron beams suitable for cooling, delivery of electron bunches of the required quality to the cooling sections without degradation of beam angular divergence and energy spread, achieving the required small angles between electron and ion trajectories in the cooling sections, precise velocity matching between the two beams, high-current operation of the electron accelerator, as well as several physics effects related to bunched-beam cooling. Here we report on the first demonstration of cooling hadron beams using this new approach.

A storage ring experiment to detect a proton electric dipole moment.

A new experiment is described to detect a permanent electric dipole moment of the proton with a sensitivity of 10-29 e ⋅ cm by using polarized "magic" momentum 0.7 GeV/c protons in an all-electric storage ring. Systematic errors relevant to the experiment are discussed and techniques to address them are presented. The measurement is sensitive to new physics beyond the standard model at the scale of 3000 TeV.

Three-dimensional stochastic cooling in the relativistic heavy ion collider.

Three-dimensional stochastic cooling of 100 GeV/nucleon gold beams has been achieved in the Relativistic Heavy Ion Collider (RHIC). We discuss the physics and technology of the cooling systems and present results with a beam. A factor of 2 increase in luminosity was achieved and another factor of 2 is expected.

Operational stochastic cooling in the relativistic heavy-ion collider.

Operational stochastic cooling of 100 GeV/nucleon gold beams has been achieved in the BNL Relativistic Heavy-Ion Collider. We discuss the physics and technology of the longitudinal cooling system and present results with the beams. A simulation algorithm is described and shown to accurately model the system.

Polarized proton collisions at 205 GeV at RHIC.

The Brookhaven Relativistic Heavy Ion Collider (RHIC) has been providing collisions of polarized protons at a beam energy of 100 GeV since 2001. Equipped with two full Siberian snakes in each ring, polarization is preserved during acceleration from injection to 100 GeV. However, the intrinsic spin resonances beyond 100 GeV are about a factor of 2 stronger than those below 100 GeV making it important to examine the impact of these strong intrinsic spin resonances on polarization survival and the tolerance for vertical orbit distortions. Polarized protons were first accelerated to the record energy of 205 GeV in RHIC with a significant polarization measured at top energy in 2005. This Letter presents the results and discusses the sensitivity of the polarization survival to orbit distortions.

Mechanism of electron multipacting with a long-bunch proton beam.

The energy gain and motion of electrons can quantitatively describe the mechanism of electron multipacting in a long-bunched proton machine. Strong multipacting usually happens around the bunches' tails due to the high energy of electrons when they hit the chamber surface. We investigated several important parameters of electron multipacting, proving that it is sensitive to the beam's intensity, the shape of its longitudinal profile, its transverse size, the secondary emission yield, and the energy at peak secondary emission yield. Our analyses, simulations, and experiments are all in agreement.

Inhibition of T-cell invasion across cultured fibroblast monolayers by phenothiazine-related calmodulin inhibitors: impairment of lymphocyte motility by trifluoperazine and chlorpromazine, and alteration of the monolayer by pimozide.

Phenothiazines inhibit the typical shape changes displayed by activated lymphocytes and thereby their migration through polycarbonate filters. The structure activity relationship of this effect is distinct from calmodulin inhibition. Our aim was to study this effect of phenothiazines on lymphocyte migration in an environment with living solid tissue cells. We assessed the effect of trifluoperazine and chlorpromazine (TFP and CP, two strong inhibitors of lymphocyte motility) and pimozide (PIM, a much weaker inhibitor of lymphocyte motility but a strong inhibitor of calmodulin) on invasion of human Molt-4 T-cells across precultured fibroblast monolayers. As expected invasion was inhibited by TFP and CP in the micromolar range that also inhibited motility. Surprisingly, PIM inhibited monolayer invasion at least as efficiently as TFP and CP (from 2.25 microM on). Preincubation of the monolayers or the lymphoid cells show that PIM exerted this novel invasion inhibiting effect on the monolayer. TFP and CP had a much weaker effect on the monolayer. Since these three compounds inhibit calmodulin in the same order, it is likely that this effect on the monolayer was caused by inhibition of a calmodulin-dependent pathway. KN-62, a specific inhibitor of calmodulin-dependent protein kinase II acted on the monolayer like PIM, whereas ML-7, a specific inhibitor of myosin regulatory light chain kinase, inhibited lymphoid cell motility like TFP and CP. In conclusion, invasion of T-cells across cellular monolayers is inhibited both by PIM and by phenothiazines like TFP and CP, but via distinct mechanisms: TFP and CP inhibit lymphocyte motility via a calmodulin independent pathway, whereas PIM impairs the monolayer's tolerance for invasion, most likely via a calmodulin and CamKII dependent pathway.