C.E. Allgower

Polarized proton collider at RHIC

Abstract In addition to heavy ion collisions (RHIC Design Manual, Brookhaven National Laboratory), RHIC will also collide intense beams of polarized protons (I. Alekseev, et al., Design Manual Polarized Proton Collider at RHIC, Brookhaven National Laboratory, 1998 [2]), reaching transverse energies where the protons scatter as beams of polarized quarks and gluons. The study of high energy polarized protons beams has been a long term part of the program at BNL with the development of polarized beams in the Booster and AGS rings for fixed target experiments. We have extended this capability to the RHIC machine. In this paper we describe the design and methods for achieving collisions of both longitudinal and transverse polarized protons in RHIC at energies up to s =500 GeV .

Measurement of neutron detection efficiencies in NaI using the Crystal Ball detector

A light-emitting apparatus according to the present invention includes: a board on which a plurality of light source units are provided; a partition member provided on the board and enclosing each of the light source units; and a fixing member arranged in a boundary portion between two or more light source units that are adjacent to each other and fixing the board and the partition member.

The pp elastic scattering analyzing power measured with the polarized beam and the unpolarized target between 1.98 and 2.80 GeV

Abstract A polarized proton beam extracted from SATURNE II was scattered on an unpolarized CH2 target. The angular distribution of the beam analyzing power Aoono was measured at large angles from 1.98 to 2.8 GeV and at 0.80 GeV nominal beam kinetic energy. The same observable was determined at the fixed mean laboratory angle of 13.9° in the same energy range. Both measurements are by-products of an experiment measuring the spin correlation parameter Aoon.

Dependence of proton beam polarization on ion source transition configurations

The polarization of extracted SATURNE II proton beam as a function of different ion source configurations was studied. Two distinct experiments were necessary for this purpose. In the first one, the LEFT-RIGHT instrumental asymmetry of the beam polarimeter was determined using an unpolarized beam. In the second one this correction factor was applied to asymmetries measured with the beam from the polarized ion source in all polarization states. The measurements were carried out at the proton beam kinetic energy 0.80 GeV, where the pp-elastic scattering analyzing power is near its maximum. The results confirmed that the two so-called “unpolarized states” of the source were polarized to several percent, whereas the absolute values of the beam polarizations in the so-called “polarized states” were equal and opposite. It was observed that the hexapole lens of the ion source produced beam polarization in the absence of any transition. The beam polarization as a function of hexapole current, transition field attenuation, and spin rotation solenoid current was measured. It was also shown how to obtain a strictly unpolarized beam using the polarized source only. The results obtained with the SATURNE II ion source HYPERION may also be relevant to similar sources at other accelerators.

Angular dependence of pp spin correlation and rescattering observables between 1.80 and 2.10 GeV

A polarized proton beam extracted from SATURNE II and the Saclay polarized proton target were used to determine the spin correlation parameter Aoosk and the rescattering observablesKos″ so; Dos″ok, Nos″sn, andNonsk at 1.80 and 2.10 GeV. The beam polarization was oriented perpendicular to the beam direction in the horizontal scattering plane and the target polarization was directed either along the vertical axis or longitudinally. Left-right and up-down asymmetries in the second scattering were measured. A check for the beam optimization with the beam and target polarizations oriented vertically provided other observables, of which results forDonon andKonno at 1.80, 1.85, 2.04, and 2.10 GeV are listed here. The new data at 2.10 GeV suggest a smooth energy dependence of spin triplet scattering amplitudes at fixed angles in the vicinity of this energy.

Measurement of the branching ratio for eta--->pi**0gammagamma decay

The branching ratio (BR) for the rare decay {eta}{yields}{pi}{sup 0}{gamma}{gamma} was measured with the Crystal Ball multiphoton spectrometer. The result, BR({eta}{yields}{pi}{sup 0}{gamma}{gamma})=(3.5{+-}0.7{sub stat}{+-}0.6{sub syst})x10{sup -4}, is in agreement with calculations of chiral perturbation theory to third order. We have used a sample of 28 million {eta} mesons produced at the BNL Alternating Gradient Synchrotron using the {pi}{sup -}p{yields}{eta}n reaction close to threshold. We detail the intricate extraction of the signal, which has about 1.6 thousand {eta}{yields}{pi}{sup 0}{gamma}{gamma} events, from the overwhelming background of {eta}{yields}3{pi}{sup 0} decays and from the {pi}{sup -}p{yields}{pi}{sup 0}{pi}{sup 0}n reaction.

Measurement of K{sup -}p {r_arrow}{eta}{Lambda} near threshold.

We present measurements of the differential and total cross sections and the {Lambda} polarization for the reaction K{sup -}p{yields}{eta}{Lambda} from threshold to p{sub K}-=770 MeV/c, with much better precision than previous measurements. Our cross-section data show a remarkable similarity to the SU(3) flavor-related {pi}{sup -}p{yields}{eta}n cross-section results. The reaction K{sup -}p{yields}{eta}{Lambda} at threshold is dominated by formation of the intermediate {Lambda}(1670)1/2- state.

Measurement of K- p --> eta Lambda near threshold

We present measurements of the differential and total cross sections and the {Lambda} polarization for the reaction K{sup -}p{yields}{eta}{Lambda} from threshold to p{sub K}-=770 MeV/c, with much better precision than previous measurements. Our cross-section data show a remarkable similarity to the SU(3) flavor-related {pi}{sup -}p{yields}{eta}n cross-section results. The reaction K{sup -}p{yields}{eta}{Lambda} at threshold is dominated by formation of the intermediate {Lambda}(1670)1/2- state.