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At least 19 records

How to Reach a Thousand-Second in-Plane Polarization Lifetime with 0.97 - GeV / c Deuterons in a Storage Ring

Here, we observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10 -29 $e$ cm.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Measurement of the absolute differential cross section of proton–proton elastic scattering at small angles

The differential cross section for proton-proton elastic scattering has been measured at a beam kinetic energy of 1.0 GeV and in 200 MeV steps from 1.6 to 2.8 GeV for centre-of-mass angles in the range from 12°-16° to 25°-30°, depending on the energy. A precision in the overall normalisation of typically 3% was achieved by studying the energy losses of the circulating beam of the COSY storage ring as it passed repeatedly through the windowless hydrogen target of the ANKE magnetic spectrometer. It is shown that the data have a significant impact upon the results of a partial wave analysis. Furthermore, after extrapolating the differential cross sections to the forward direction, the results are broadly compatible with the predictions of forward dispersion relations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

The Experimental Programs on Light Pseudoscalar Meson Decays

The decays of the low-lying pseudoscalar mesons (?0, ?, and ??) allow access to a plethora of physics probes, from measurements of fundamental properties of matter such as the up-down quark mass ratio, to studies of channels that access higher-order terms in Chiral Perturbation theory, to tests of fundamental symmetries and searches for signatures of physics beyond the Standard Model. Several experiments have studied pseudoscalar decays: these experiments include PrimEx in Hall B at Jefferson Lab, A2 at the MAMI electron accelerator facility, the KLOE-II experiment at the DA?NE ?-factory, WASA-at-COSY at the cooler synchrotron COSY storage ring, and BESIII at the Beijing charm factory. In Hall D at Jefferson Lab, PrimEx-eta uses the Primakoff process to measure the ? radiative width using the GlueX spectrometer. In the near future the Jefferson Lab Eta Factory (JEF) experiment will use the GlueX spectrometer with an upgraded forward calorimeter to study ?(?) decay channels with a focus on all-neutral final states. Finally, a proposal for a new experiment, ``Rare Eta Decays with a TPC for Optical Photons'' (REDTOP) utilizing a proton beam on fixed targets, is under development. Highlights from previous and ongoing experiments and plans for future experiments will be presented.

Taylor, Simon↗

Computation and consequences of high order amplitude- and parameter-dependent tune shifts in storage rings for high precision measurements

Nonlinear effects of the various electric field and magnetic field components of storage rings to confine the particles and bend their trajectory can cause substantial amplitude-dependent tune shifts within the beam. Furthermore, tune shifts are often sensitive to variations of system parameters, e.g. total particle momentum offsets $δp$. Such amplitude- and parameter-dependent tune shifts influence the dynamics and stability of a beam in particle storage rings. Thus, it is critical for high precision measurements to analyze and understand these influences. On this basis, we present in this paper normal form methods for the calculation of high order amplitude and system parameter dependencies of the horizontal and vertical tunes in storage rings using the differential algebra (DA) framework within COSY INFINITY. A storage ring is simulated using COSY INFINITY to generate a DA Poincaré return map describing the transverse phase space behavior after each revolution in the storage ring. The map is expanded around the parameter-dependent closed orbit of the system before transforming the resulting map into normal form coordinates to extract the high order tune dependencies on the phase space amplitude and variation in the system parameters. As a specific example, a storage ring similar to the Storage Ring of the Muon g-2 Experiment at Fermilab (E989) is investigated.

43 PARTICLE ACCELERATORS↗

Search for electric dipole moments of light ions in storage rings

The Standard Model (SM) of Particle Physics is not capable to account for the apparent matterantimatter asymmetry of our Universe. Physics beyond the SM is required and is searched for by (i) employing highest energies (e.g., at LHC), and (ii) striving for ultimate precision and sensitivity (e.g., in the search for electric dipole moments (EDMs)). Permanent EDMs of particles violate both time reversal (T) and parity (P) invariance, and are via the CPT-theorem also CP-violating. Finding an EDM would be a strong indication for physics beyond the SM, and pushing upper limits further provides crucial tests for any corresponding theoretical model, e.g., SUSY. Direct searches of proton and deuteron EDMs bear the potential to reach sensitivities beyond 10{sup −29} e cm. For an all-electric proton storage ring, this goal is pursued by the US-based srEDM collaboration [2], while the newly found Julich-based JEDI collaboration [1] is pursuing an approach using a combined electric-magnetic lattice which shall provide access to the EDMs of protons, deuterons, and {sup 3}He ions in the same machine. In addition, JEDI has recently proposed to perform a direct measurement of the proton and/or deuteron EDM at COSY using resonant techniques involving Wien filters.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Software package for modeling spin–orbit motion in storage rings

A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Jülich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 10{sup 6}–10{sup 9} particles in a beam during 10{sup 9} turns in an accelerator (about 10{sup 12}–10{sup 15} integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin–orbit dynamics.

43 PARTICLE ACCELERATORS↗

Asymmetric Ir-catalyzed hydrogenation of 4-R-1,3-dihydro-2H-1,5-benzodiazepin-2-ones using a novel phosphoramidite ligand

A novel chiral phosphoramidite ligand, (S{sub a})-2-[N-ethyl-N-(1-naphthylmethyl)amino]-dinaphtho[2,1-d:1´,2´-f][1,3,2]dioxaphosphepane, was obtained and tested in Ir-catalyzed asymmetric hydrogenation of a series of 4-R-1,3-dihydro-2H-1,5-benzodiazepin-2-ones, wherein up to 74% ee was achieved. The structure of the resulting compounds was determined based on one- and two-dimensional NMR ({sup 1}H, {sup 13}C, {sup 31}P, {sup 1}H—{sup 1}H COSY, {sup 1}H—{sup 1}H ROESY, {sup 1}H—{sup 13}C HSQC and {sup 1}H—{sup 13}C HMBC) spectroscopy data.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Design of in-flight fragment separator using high-power primary beams in the energy of a few hundred MeV/u

An in-flight fragment separator usually requires large acceptance and high momentum resolution to minimize the loss of a rare isotope beam of interest produced at a thin target, which is especially important when {sup 238}U fission reactions in the energy of 200 MeV/u are used. The production target and beam dump are located in the pre-separator, where a beam power of up to 400 kW is dissipated. The area is surrounded by thick radiation shielding walls, which result in long drift spaces between adjacent magnetic components at various locations and an asymmetrical layout. Efforts have been made to minimize non-linear effects in the pre-separator beam optics with trials of different separator configurations and correction schemes using COSY Infinity and GICOSY. The main separator is configured to be mirror symmetric such that correction with hexapole and octupole coils can be more readily applied. The separator configuration was finalized to allow the facility design to proceed and the key components including superconducting magnets have been designed and prototyped. In addition, the separator design has been evaluated using LISE++ including a set of wedge degraders at dispersive focal planes to improve the yield and purity of selected isotope beam.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS

Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t{sub 1} and t{sub 3} periods, respectively. In addition to through-space and through-bond {sup 13}C/{sup 1}H and {sup 13}C/{sup 13}C chemical shift correlations, the 3D {sup 1}H/{sup 13}C/{sup 1}H experiment also provides a COSY-type {sup 1}H/{sup 1}H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices ({sup 1}H/{sup 1}H chemical shift correlation spectrum) at different {sup 13}C chemical shift frequencies from the 3D {sup 1}H/{sup 13}C/{sup 1}H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D {sup 1}H/{sup 13}C/{sup 1}H experiment would be useful to study the structure and dynamics of a variety of chemical and biological solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Width of the {phi} meson in nuclear matter

The ratios of the cross sections for {phi}-meson production induced by 2.83-GeV protons on Cu, Ag, and Au nuclei to the respective cross section for C nuclei were measured at the ANKE-COSY facility in the momentum range of 0.6-1.6 GeV/c and the angular range of 0 Degree-Sign -8 Degree-Sign . The product {phi} mesons were identified by their decay {phi} {yields} K{sup +}K{sup -}. The procedure used to separate kaon pairs was described in detail, and all sources of the background and their contribution to the resulting error in the values found for the above cross-section ratios were analyzed. The A dependence of the cross section for {phi}-meson production was shown to obey the A{sup 0.56{+-}0.03} law. The total width of the {phi} meson at a normal nuclear density was extracted from a comparison of the measured cross-section ratios with the results of calculations based on two theoretical models. The resulting width value exceeds substantially both the vacuum width and the width expected in the absence of the nuclear-matter effect on the properties of the {phi} meson.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Spin observables in proton-deuteron scattering and T-invariance test

The total cross section for the interaction of transversely polarized protons p{sub p}{sup y} and deuterons that have a tensor polarization P{sub x}{sup z} provides a null-test signal of T-invariance violation under the condition of P invariance. The relevant experiment is planned by the PAX Collaboration at the COSY accelerator with protons accelerated to the energy of 135 MeV. A modified Glauber theory is used here to calculate the differential spin observables A{sub y}, C{sub y,y}, C{sub xz,y}, C{sub z,x}, and C{sub x,z} and the differential and total cross sections for proton-deuteron scattering in the case of T-even P-even proton-nucleon interactions. This makes it possible to estimate background conditions of the planned experiment.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Spin Physics at ANKE-COSY

The COSY accelerator (Jülich, Germany) provides beams of polarised protons and deuterons. The ANKE facility at COSY is equipped with polarised hydrogen and deuterium atomic gas targets. The reactions investigated with polarised probes at ANKE include the deuteron break-up at small and large momentum transfer, the pion production processes in pp and pn collisions and the near-threshold η meson production in dip d-vector p→{sup 3}Heη process. Use of the polarised deuteron beam properties allowed a precision measurement of the η meson mass. The future experimental program covers the study of the elementary pp and pn-interaction with polarised beams up to the maximal COSY energy, and a double polarised measurement of the A {sub x, z }spin correlation parameter in the pN → {pp}{sub s }π process.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Polarization of stored beam by spin-filtering at COSY

In the challenging aim to achieve polarized antiproton, the PAX collaboration performed dedicated measurements of the spin-dependent polarizing cross section for p - p scattering at COSY. The result, under a very nice control of the process, agrees with the theoretical previsions, and confirms the pursuability of the spin-filtering for polarizing antiprotons.

43 PARTICLE ACCELERATORS↗

ABC effect and resonance d*(2380)

A new state in the two-baryon system with mass 2380 MeV and width 80 MeV has been detected in the experiments at the Juelich Cooler Synchrotron (COSY). The new particle denoted now d*(2380) has quantum numbers I(J{sup p}) = 0(3{sup +}). The total cross sections for the d and {sup 4}He fusion reactions show similar to each other resonance-like energy dependence. The resonance-like structure is sensed in the double-pionic fusion channels and polarized np scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Realistic Modeling of the Muon g-2 Experiment Beamlines at Fermilab

The main goal of the Muon g-2 Experiment at Fermilab (E989) is to measure the muon anomalous magnetic moment (a, also dubbed as the "anomaly’’) to unprecedented precision. This new measurement will allow to test the completeness of the Standard Model (SM) and to validate other theoretical models beyond the SM. Simulations of the beamlines from the pion production target to the entrance of the g-2 Storage Ring using COSY INFINITY contribute to the understanding and characterization of the muon beam production in relation to the statistical and systematics uncertainties of the E989 measurement. The effect of nonlinearites from fringe fields and high-order contributions on the beam delivery system performance are considered, as well as interactions with the beamline elements apertures, particle decay channels, spin dynamics, and beamline misalignments.

43 PARTICLE ACCELERATORS↗

A complete low-energy polarized proton-deuteron breakup experiment

An experiment at low energy will be done at the COSY cooler synchrotron and storage ring in order to study the three-particle final states of proton-deuteron scattering reactions measuring a complete set of single and double spin observables over large areas of phase space. The physics objective is to test the predictive power of chiral effective field theory at an energy where convergence is guaranteed and few previous measurements exist. A direct comparison between theoretical predictions and experimental data will be enabled by the use of the so called sampling method.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Development of a Bunched Beam Electron Cooler based on ERL and Circulator Ring Technology for the Jefferson Lab Electron-Ion Collider

Jefferson Lab is in the process of designing an electron ion collider with unprecedented luminosity at a 45 GeV center-of-mass energy. This luminosity relies on ion cooling in both the booster and the storage ring of the accelerator complex. The cooling in the booster will use a conventional DC cooler similar to the one at COSY. The high-energy storage ring, operating at a momentum of up to 100 GeV/nucleon, requires novel use of bunched-beam cooling. There are two designs for such a cooler. The first uses a conventional Energy Recovery Linac (ERL) with a magnetized beam while the second uses a circulating ring to enhance both peak and average currents experienced by the ion beam. This presentation will describe the design of both the Circulator Cooling Ring (CCR) design and that of the backup option using the stand-alone ERL operated at lower charge but higher repetition rate than the ERL injector required by the CCR-based design.

Benson, Stephen V.↗

Development of a bunched beam electron cooler for the Jefferson Lab electron-ion collider

Jefferson Lab is in the process of designing an electron-ion collider with unprecedented luminosity at a 65 GeV center-of-mass energy. This luminosity relies on ion cooling in both the booster and the storage ring of the accelerator complex. The cooling in the booster will use a conventional DC cooler similar to the one at COSY. The high-energy storage ring, operating at a momentum of up to 100 GeV/nucleon, requires novel use of bunched-beam cooling. We will present a new design for a Circulator Cooler Ring for bunched-beam electron cooling. This requires the generation and transport of very high-charge magnetized bunches, acceleration of the bunches in an energy recovery linac, and transfer of these bunches to a circulating ring that passes the bunches 11 times through the proton or ion beam inside cooling solenoids. This design requires the suppression of the effects of space charge and coherent synchrotron radiation using shielding and RF compensation.

Benson, Stephen V.↗