GPU-optimized Code for Long-term Simulations of Beam-beam Effects in Colliders

We report on the development of the new code for long-term simulation of beam-beam effects in particle colliders. The underlying physical model relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for beam-beam interaction. The computations are accelerated through a parallel implementation on a hybrid GPU/CPU platform. With the new code, a previously computationally prohibitive long-term simulations become tractable. We use the new code to model the proposed medium-energy electron-ion collider (MEIC) at Jefferson Lab

GPU Accelerated Long-Term Simulations of Beam-Beam Effects in Colliders

We present an update on the development of the new code for long-term simulation of beam-beam effects in particle colliders. The underlying physical model relies on a matrix-based arbitrary-order particle tracking (including a symplectic option) for beam transport and the generalized Bassetti-Erskine approximation for beam-beam interaction. The computations are accelerated through a parallel implementation on a hybrid GPU/CPU platform. With the new code, previously computationally prohibitive long-term simulations become tractable. The new code will be used to model the proposed Medium-energy Electron-Ion Collider (MEIC) at Jefferson Lab

Incidence of angioedema after initiation of angiotensin-converting enzyme inhibitors in adults with heart failure

Background: Angioedema, a potentially life-threatening adverse event associated with angiotensin-converting enzyme inhibitor (ACEI) use, occurs more often among Black patients than non-Black patients. Specific angioedema incidence rates (IRs) among heart failure (HF) patients initiating an ACEI are limited. Objectives: To provide estimates of angioedema incidence among HF patients initiating an ACEI, particularly among Black patients. Methods: We conducted a retrospective cohort study among adult (≥18 years) patients with HF who initiated ACEI use at 5 health care delivery systems within the Cardiovascular Research Network between July 2015 and May 2019. We required patients to have ≥12 months of continuous medical and prescription drug coverage and no ACEI dispensings in the 1 year before treatment initiation. Our primary outcome was serious angioedema, defined as a primary or secondary diagnosis of ICD-9 code 995.1 (‘Angioneurotic edema not elsewhere classified’) or ICD-10 codes in the T78.3 series (‘Angioneurotic edema’) during hospitalization. Our secondary out-come was ‘any angioedema’, which included serious angioedema and non-serious angioedema that was diagnosed in the outpatient setting. We followed patients from ACEI initiation until first angioedema diagnosis or a censoring event (treatment discontinuation, initiation of another renin-angiotensin-aldosterone system blocking agent, disenrollment, death, or end of 365-day follow-up or study). We calculated crude IRs and exact 95% confidence intervals (CI) for angioedema among HF patients initiating an ACEI. Results: We identified 14 ,241 ACEI users, of which 6,156 (43 .2%)were women and 2,105 (15%) were self-reported Black. Mean age was 70 ± 14 years. We observed 6 serious angioedema events overall (IR: 0.8/1,000 person-years (PYs), 95% CI: 0.3-1.7), with 2 events occurring among Black patients (IR: 1.8/1,000 PYs, 95%CI: 0.2-6.5) and 4 events among non-Black patients (IR: 0.6/1,000PYs, 95% CI: 0.2-1.5). We observed 43 angioedema events overall (IR: 5.4/1,000 PYs, 95% CI: 3.9-7.3), with 21 events occurring among Black patients (IR: 19/1,000 PYs, 95% CI: 11.8-29.1) and 22 events among non-Black patients (IR: 3.2/1,000 PYs, 95%CI: 2.0-4.9). Conclusions: Our estimate of angioedema incidence among HF patients who initiated an ACEI (5.4 events/1,000 PYs) is slightly higher than a previously published estimate (3.3/1,000 PYs) among a similarly-defined population identified through administrative claims data. Similar to prior reports, we found a higher incidence of angioedema, both serious and non-serious, among Black ACEI users than among non-black ACEI users

High-Fidelity Simulations of Long-Term Beam-Beam Dynamics on GPUs

Future machines such as the Electron Ion Collider (MEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations typically requiring millions of turns. Until recently, most of the methods have involved using linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order. The code is called GHOST for GPU-accelerated High-Order Symplectic Tracking. As of now, there is no other code in existence that can accurately model the single-particle non-linear dynamics and the beam-beam effect at the same time for a large enough number of turns necessary to verify the long-term stability of a collider. Our approach relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for the beam-beam interaction

Long-Term Simulations of Beam-Beam Dynamics on GPUs

Future machines such as the electron-ion colliders (JLEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations which require millions of turns. Until recently, most of the methods used linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order and colliding them at each turn. The code is called GHOST for GPU-accelerated High-Order Symplectic Tracking. As of now, there is no other code in existence that can accurately model the single-particle non-linear dynamics and the beam-beam effect at the same time for a large enough number of turns required to verify the long-term stability of a collider. Our approach relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for the beam-beam interaction

On the growth of nonuniform lattices in pinched negatively curved manifolds

We study the relation between the exponential growth rate of volume in a pinched negatively curved manifold and the critical exponent of its lattices. These objects have a long and interesting story and are closely related to the geometry and the dynamical properties of the geodesic flow of the manifold

Control of Synchrotron Radiation Effects During Recirculation With Bunch Compression

Studies of beam quality preservation during recirculation * have been extended to generate a design of a compact arc providing bunch compression with positive momentum compaction ** and control of both incoherent and coherent synchrotron radiation (ISR and CSR) effects using the optics balance methods of diMitri et al.***. In addition, the arc/compressor generates very little micro-bunching gain. We detail the beam dynamical basis for the design, discuss the design process, give an example solution, and provide simulations of ISR and CSR effects. Reference will be made to a complete analysis of micro-bunching effects ****

The first determination of Generalized Polarizabilities of the proton by a Virtual Compton Scattering experiment

Absolute differential cross sections for the reaction (e+p -> e+p+gamma) have been measured at a four-momentum transfer with virtuality Q^2=0.33 GeV^2 and polarization \epsilon = 0.62 in the range 33.6 to 111.5 MeV/c for the momentum of the outgoing photon in the photon-proton center of mass frame. The experiment has been performed with the high resolution spectrometers at the Mainz Microtron MAMI. From the photon angular distributions, two structure functions which are a linear combination of the generalized polarizabilities have been determined for the first time.Comment: 4 pages, 3 figure

Search for a new gauge boson in the A′A' Experiment (APEX)

We present a search at Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling $\alpha'$ to electrons. Such a particle $A'$ can be produced in electron-nucleus fixed-target scattering and then decay to an $e^+e^-$ pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175--250 MeV, found no evidence for an $A'\to e^+e^-$ reaction, and set an upper limit of $\alpha'/\alpha \simeq 10^{-6}$. Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.Comment: 5 pages, 5 figures, references adde