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In this article, experimental results about color transparency of hadrons in nuclei will be briefly reviewed. The current progress of a new experiment, EVA, will also be reported.

The very successful program of QCD and electroweak tests at the high energy hadron colliders have shown that the perturbative QCD has progressed towards becoming a ‘‘precision’’ theory. At the same time, it has been shown that with the help of Siberian Snakes it is feasible to accelerate polarized protons to high enough energies where the proven methods of collider physics can be used to probe the spin content of the proton but also where fundamental tests of the spin effects in the standard model are possible. With Siberian Snakes the Relativistic Heavy Ion Collider (RHIC) will be the first collider to allow for 250 GeV on 250 GeV polarized proton collisions.

A wide band damper system has been developed for the Brookhaven Alternating Gradient Synchrotron (AGS). The system consists of two sets of PUE pickups, analog and digital processing electronics, four 500 Watt wide band power amplifiers, and two pairs of strip line deflectors. The system is currently used to damp transverse coherent instabilities and injection errors, in both planes, for protons and all species of Heavy Ions. This paper discusses the system design and operation, focusing on the engineering considerations and problems encountered in the actual implementation. Operational data from both protons and Heavy Ion beams is presented.

The Siberian snakes are powerful tools in preserving polarization in high energy accelerators has been demonstrated at the Brookhaven Relativistic Heavy Ion Collider (RHIC). Equipped with two full Siberian snakes in each ring, polarization is preserved during acceleration from injection to 100 GeV. However, the Siberian snakes also introduce a new set of depolarization resonances, i.e. snake resonances as first discoverd by Lee and Tepikian [1]. The intrinsic spin resonances above 100 GeV are about a factor of two stronger than those below 100 GeV which raises the challenge to preserve the polarization up to 250 GeV. In 2009, polarized protons collided for the first time at the RHIC design store energy of 250 GeV. This paper presents the experimental measurements of snake resonances at RHIC. The plan for avoiding these resonanances is also presented.

Horizontal magnetic fields in accelerators induce depolarizing resonances, 180° spin rotators, commonly called Siberian snakes, eliminate the resonances by reversing the effect of the horizontal field every revolution.(AIP)

Overcoming depolarization resonances in medium class synchrotrons (3 to 50 GeV) is one of the key issues in accelerating a highly polarized proton beam up to very high energies. Since such synchrotrons, including the Alternating Gradient Synchrotron (AGS) and the J-PARC Main Ring, generally do not have sufficiently long straight sections to accommodate full Siberian snakes with reasonable beam excursions, the practical solution is to use partial Siberian snakes that rotate the particle spin about a horizontal axis by a fraction of 180 degrees. For the AGS, we designed and installed a new partial Siberian snake consisting of a helical dipole magnet with a double pitch structure. The helical structure reduced the amount of transverse coupling as compared to that achieved by the previous solenoidal partial snake. This coupling led to partial depolarization at certain energies from horizontal betatron oscillations. The helical magnetic field in the snake magnet was calculated using a 3D magnetic field code TOSCA, and was optimized by segmenting the helical pitch and varying the lengths of the segments. Fabrication errors were checked and verified to be within required tolerances. Finally, the transverse field was measured by rotating harmonic coils. After installation, we achieved a 37.5% improvement in polarization - from 40% with the old solenoid to 55% with the new helical snake, thereby demonstrating that the helical partial snake is an effective device to suppress depolarization resonances in medium-sized synchrotrons.

We measured the analyzing power A and the spin-spin correlation parameter A/sub n//sub n/, in large-P/sub perpendicular//sup 2/ proton-proton elastic scattering, using a polarized-proton target and the polarized-proton beam at the Brookhaven Alternating-Gradient Synchrotron. We also used our polarimeter to measure A at small P/sub perpendicular//sup 2/ at 13 GeV with good precision and found some deviation from the expected 1/P/sub lab/ behavior. At 18.5 GeV/c we found A/sub n//sub n/ = (-2 +- 16)% at P/sub perpendicular//sup 2/ = 4.7 (GeV/c)/sup 2/. Comparison with lower-energy data from the Argonne Zero-Gradient Synchrotron shows a sharp and surprising energy dependence for A/sub n//sub n/ at large P/sub perpendicular//sup 2/.

Using the new Brookhaven Alternating Gradient Synchrotron polarized proton beam and our polarized proton target, we measured the spin-spin correlation parameter A/sub n/n in 16.5-GeV/c proton-proton elastic scattering. We found an A/sub n/n of (6.1 +- 3.0)% at P/sub perpendicular/ /sup 2/ = 2.2 (GeV/c)/sup 2/. We also measured the analyzing power A in two independent ways, providing a good test of possible experimental errors. Comparing our new data with 12-GeV Argonne Zero Gradient Synchrotron data shows no evidence for strong energy dependence in A/sub n/n in this medium-P/sub perpendicular/ /sup 2/ region.

Accelerating polarized protons to 22 GeV/c at the Brookhaven Alternating Gradient Synchro- tron required both extensive hardware modifications and a difficult commissioning process. We had to overcome 45 strong depolarizing resonances to maintain polarization up to 22 GeV/c in this strong-focusing synchrotron. At 18.5 GeV/c we measured the analyzing power A and the spin-spin correlation parameter A/sub n//sub n/ in large- P/sub perpendicular//sup 2/ proton-proton elastic scattering, using the polarized proton beam and a polarized proton target. We also obtained a high-precision measurement of A at P/sub perpendicular//sup 2/ = 0.3 (GeV/c)/sup 2/ at 13.3 GeV/c. At 18.5 GeV/c we found that A/sub n//sub n/ = (-2 +- 16)% at P/sub perpendicular//sup 2/ = 4.7 (GeV/c)/sup 2/, where it was about 60% near 12 GeV at the Argonne Zero Gradient Synchrotron. This sharp change suggests that spin-spin forces may have a strong and unexpected energy dependence at high P/sub perpendicular//sup 2/.

We measured the analyzing power A and the spin-spin correlation parameter A/sub n//sub n/ in medium-P/sub perpendicular//sup 2/ proton-proton elastic scattering, using a polarized-proton target and the 18.5-GeVc Brookhaven Alternating-Gradient Synchrotron polarized-proton beam. We found sharp dips in both A and A/sub n//sub n/, which occur at different P/sub perpendicular//sup 2/ values. The unexpected sharp structure in the spin-spin force occurs near P/sub perpendicular//sup 2/ = 2.3 (GeVc)/sup 2/ where the elastic cross section has no apparent structure.

Calculations are presented of the parity-non-conserving (PNC) analyzing power A z for longitudinally polarized incoming protons in elastic p → α scattering below ∼50 MeV. The results are given in terms of the PNC as well as the regular, parity-conserving (PC) meson-nucleon coupling constants for single π- , ρ- and ω -exchange. The reliability and parameter dependence of the calculations are discussed in detail. The PC on-shell scattering parameters play an important role in particular for the angular dependence of A z , which must be known for the actual analysis of measurements and are taken from experiments directly (phase analysis) rather than model calculations. The PNC scattering amplitudes are calculated in DWBA with optical-model wave functions properly antisymmetrized.Short-range correlations between nucleon pairs are taken into account by a Jastrow factor whose appropriate choice is discussed in detail. While absorption from the elastic channel is taken into account by the optical-model wave function, intermediate breakup channels are not included explicitly in the matrix elements.

At the AGS an intense polarized proton beam was for the first time successfully accelerated to 22 GeV/c, preserving a polarization of ∼45%. Using this polarized beam a surprisingly strong energy dependence of the spin‐spin correlation parameter Ann in high p2⊥ elastic proton‐proton scattering was discovered.At the AGS an intense polarized proton beam was for the first time successfully accelerated to 22 GeV/c, preserving a polarization of ∼45%. Using this polarized beam a surprisingly strong energy dependence of the spin‐spin correlation parameter Ann in high p2⊥ elastic proton‐proton scattering was discovered.

Discussions during the Workshop on Siberian Snakes and Depolarizing Resonances Correcting Techniques are summarized. It has been firmly established theoretically depolarization can be avoided by means of Siberian Snakes. The results from the first experimental test are eagerly awaited.(AIP)

The properties of the insertion of a general spin rotator into a circular accelerator are examined. It is shown that even for a small rotation angle depolarization from weak imperfection resonances is avoided.

The list of topics in the many talks given during the Spin Physics sessions of this Intersections conference is nearly as long as the one of this conference: P and T Violation NN Interaction πp and πd Elastic Scattering Nuclear Matter Spin Effects Muon (g−2) Polarized Proton Beams Polarized Gas Targets This points to the almost trivial fact that spin is fundamental to our understanding of nuclear and particle physics. I will discuss in some detail only four of these topics. Needless to say this choice is very much personally biased and I apologize to all the speakers whose excellent contributions I did not include. (AIP)

Mini-workshop on Electron Cloud Clearing (ECL2): Dedicated to the Memory of Francesco Ruggiero, Geneva, Switzerland, 1 Mar 2007 - 2 Mar 2007; 3 pp. (2007)., Since 2001 RHIC has experienced electron cloud effects, which have limited the beam intensity. These include dy- namic pressure rises – including pressure instabilities, tune shifts, electrons, a reduction of the stability threshold for bunches crossing the transition energy, and possibly slow emittance growth. We summarize the main observations in operation and dedicated experiments, as well as counter- measures including baking, NEG coated warm beam pipes, solenoids, bunch patterns, anti-grazing rings, pre-pumped cold beam pipes, and scrubbing. This article is a condensed version of Ref. [1].

By modulating the RF voltage at near twice the synchrotron frequency we are able to modulate the longitudinal bunch shape. We show experimentally that this can be done while preserving the longitudinal emittance when the RF voltage modulation is turned on adiabatically. Experimental measurements are presented along with theoretical predictions.

Accelerator and beam physics (ABP) is the science of the motion, generation, acceleration, manipulation, prediction, observation and use of charged particle beams. It focuses on fundamental long-term accelerator and beam physics research and development. Accelerator and beam physics research has resulted in important advances in accelerator science, yet support for this research is declining. NSF has terminated its program in accelerator Science and funding by DOE through GARD and Accelerator Stewardship has been steady or declining. The declining support for accelerator research will slow advances and threaten student training and work-force development in accelerator science. We propose a robust and scientifically challenging program in accelerator and beam physics, which will position the field of US High Energy Physics to be productive and competitive for decades to come., Contribution to Snowmass 2021. arXiv admin note: substantial text overlap with arXiv:2101.04107

The recent successful commissioning and operation of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) requires the injection of gold ions of specified energy and intensity with longitudinal and transverse emittances small enough to meet the luminosity requirements of the collider. Ion beams with the desired characteristics are provided by a series of three accelerators, the Tandem, Booster and AGS. The current status and recent performance of these accelerators are reviewed in this paper.

We present a Circular Energy Recovery Collider (CERC) as an alternative approach for a high-energy high-luminosity electron-positron collider to current designs for high-energy electron-positron colliders either based on two storage rings with 100 km circumference or two large linear accelerators. Using Energy Recovery Linacs (ERL) located in the same-size 100 km tunnel would allow a large reduction of the beam energy losses, and therefore a reduction of the power consumption, while providing higher luminosity. It also opens a path for extending the center-of-mass (CM) energy to 500 GeV, which would enable double-Higgs production, and even to 600 GeV for production and measurements of the top Yukawa coupling. Furthermore, this approach would allow recycling of not only the energy but also of the particles. This feature opens the possibility for colliding fully polarized electron and positron beams., contribution to Snowmass 2021

The normal conducting helical dipole partial Siberian snake (warm snake) has been installed in the AGS at BNL. The polarized proton threw the warm snake but it is not perfectly because the warm snake has some hardware error which cause beam offset and deflection angle. This paper reports the measured proton beam orbit in the AGS with the warm snake.

Linear coupling, introduced by skew quadrupoles, has been used for several years to enhance the multi-turn injection efficiency of Au and other heavy ions in the AGS Booster. In this paper we describe our latest measurements of the injection process and compare with models.

During the summer of 2002, eight superconducting helical spin rotators were installed into RHIC in order to control the polarization directions independently at the STAR and PHENIX experiments. Without the rotators, the orientation of polarization at the interaction points would only be vertical. With four rotators around each of the two experiments, we can rotate either or both beams from vertical into the horizontal plane through the interaction region and then back to vertical on the other side. This allows independent control for each beam with vertical, longitudinal, or radial polarization at the experiment. In this paper, we present results from the first run using the new spin rotators at PHENIX.

Quantum information science is a growing field that promises to take computing into a new age of higher performance and larger scale computing as well as being capable of solving problems classical computers are incapable of solving. The outstanding issue in practical quantum computing today is scaling up the system while maintaining interconnectivity of the qubits and low error rates in qubit operations to be able to implement error correction and fault-tolerant operations. Trapped ion qubits offer long coherence times that allow error correction. However, error correction algorithms require large numbers of qubits to work properly. We can potentially create many thousands (or more) of qubits with long coherence states in a storage ring. For example, a circular radio-frequency quadrupole, which acts as a large circular ion trap and could enable larger scale quantum computing. Such a Storage Ring Quantum Computer (SRQC) would be a scalable and fault tolerant quantum information system, composed of qubits with very long coherence lifetimes. With computing demands potentially outpacing the supply of high-performance systems, quantum computing could bring innovation and scientific advances to particle physics and other DOE supported programs. Increased support of R$\&$D in large scale ion trap quantum computers would allow the timely exploration of this exciting new scalable quantum computer. The R$\&$D program could start immediately at existing facilities and would include the design and construction of a prototype SRQC. We invite feedback from and collaboration with the particle physics and quantum information science communities., Contribution to Snowmass 2021

In this white paper we describe concept of $e^+e^-$ linear collider recycling both the used particles and the used beam energy., 7 pages, 3 figures, Snowmass White paper

A superconducting helical magnet has been built for polarized proton acceleration in the Brookhaven AGS. This “partial Snake” magnet will help to reduce the loss of polarization of the beam due to machine resonances. It is a 3 T magnet some 1940 mm in magnetic length in which the dipole field rotates with a pitch of 0.2053 degrees/mm for 1154 mm in the center and a pitch of 0.3920 degrees/mm for 393 mm in each end. The coil cross-section is made of two slotted cylinders containing superconductor. In order to minimize residual offsets and deflections of the beam on its orbit through the Snake, a careful balancing of the coil parameters was necessary. In addition to the main helical coils, a solenoid winding was built on the cold bore tube inside the main coils to compensate for the axial component of the field that is experienced by the beam when it is off-axis in this helical magnet. Also, two dipole corrector magnets were placed on the same tube with the solenoid. A low heat leak cryostat was built so that the magnet can operate in the AGS cooled by several cryocoolers. The design, construction and performance of this unique magnet will be summarized.

As the next generation of large accelerator-based facilities are being considered at the Snowmass 2021 study high priority has to be given to environmental sustainability including energy consumption, natural resource use and the environmental impact of effluents. Typically, increased performance - higher beam energies and intensities - of proposed new facilities have come with increased electric power consumption. In the following we discuss the most important areas of development for the sustainability of accelerator-based research infrastructures in three categories - technologies, concepts and general aspects. To achieve the goal of increased performance with reduced energy consumption a focused R&D effort is required with the same or even higher priority as the traditional performance-related R&D. Such a recommendation was included in the recent European Strategy for Particle Physics Accelerator R&D Roadmap., Contribution to Snowmass 2021. arXiv admin note: substantial text overlap with arXiv:2201.07895

In 1995 the AGS upgrade met its design goal of 60 TP (1 TP=10/sup 12/ protons) per pulse, made possible by significant improvements in the AGS Booster and AGS. We summarize these improvements and outline strategies for future upgrades.

The 5thyear of RHIC operations, started in November 2004 and expected to last till June 2005, consists of a physics run with Cu-Cu collisions at 100 GeV/u followed by one with polarized protons (pp) at 100 GeV [1]. We will address here the overall performance of the RHIC complex used for the first time as a Cu-Cu collider, and compare it with previous operational experience with Au, PP and asymmetric d-Au collisions. We will also discuss operational improvements, such as a squeeze to 85cm in the high luminosity interaction regions from the design value of 1m, system improvements, machine performance and limitations, and address reliability and uptime issues.

High energy hadron collider operation requires accurate measurements of the beta functions and phase advances, to check the linear optics and to locate gradient errors. During the RHIC 2003 run, two AC dipoles with vertical and horizontal magnetic field were used to measure the linear optics at storage and at injection energies. The two AC dipoles are set up to adiabatically induce sizable coherent oscillations at a frequency close to the betatron frequencies. The beta functions and phase advances are then calculated from the 1024 turn-by-turn measurements available from all the RHIC BPMs (beam position monitors). Because the coherent excitation is adiabatic, the beam emittance is preserved after the measurement. The algorithm is discussed in this paper, and experimental results are presented.

Observations of high intensity effects on the proton performance of the AGS Booster are presented, including present operational limits and correction methods. The transverse emittances, optimum tune working points, damping of coherent transverse oscillations and correction of stopband resonances through third-order are discussed in addition to the observed tune spread due to space charge forces. The initial longitudinal phase space distribution, capture and acceleration parameters and measurements are also given. Operational tools and strategies relevant to the high intensity setup are mentioned. >