arXiv subjects

N. H. Buttimore

Publications and source records attributed to N. H. Buttimore.

13 recordsLinked to original sources

arXiv2022

Precision small scattering angle measurements of proton-proton and proton-nucleus analyzing powers at the RHIC hydrogen jet polarimeter

At RHIC, the hydrogen jet target polarimeter (HJET) is used to measure proton beam polarization with accuracy $σ_P^\text{syst}/P\lesssim0.5\%$ by counting low energy (1--10 MeV) recoil protons in left-right symmetric detectors. The HJET performance also allowed us to precisely measure $pp$ and $p$A (where A is any ion stored at RHIC) analyzing powers in the CNI region. The results of the measurements are discussed.

hep-ex↗

arXiv2022

On the possibility of measuring the polarization of a ${}^3\rm{He}$ beam at EIC by the HJET polarimeter

The requirements for hadron polarimetry at the future Electron Ion Collider (EIC) include measurements of the absolute helion (${}^3\text{He}$, $h$) beam polarization with systematic uncertainties better than $σ^\text{syst}_P/P\lesssim1\%$. Here, we consider a possibility to utilize the Polarized Atomic Hydrogen Gas Jet Target (HJET) for precision measurement of polarization of the $\sim$100 GeV/n helion beam. HJET, which serves to determine absolute proton beam polarization at the Relativistic Heavy Ion Collider, provides the accuracy of about $δ^\text{syst}P/P\sim0.5\%$. Potential problems for adapting the HJET method for the EIC helion beam include (i) necessity to know the ratio of $p^\uparrow{h}$ and $h^\uparrow{p}$ analyzing powers $A_\text{N}^{ph}(t)/A_\text{N}^{hp}(t)$ with high precision, ({ii) possible beam ${}^3\text{He}$ breakup, and (iii) operation in a 10 ns bunch spacing beam. Preliminary results of an analysis discussed here indicate that the listed problems can be overcome and the helion beam absolute polarization can be measured by HJET with the required accuracy.

hep-ph↗

arXiv2021

Science Requirements and Detector Concepts for the Electron-Ion Collider: EIC Yellow Report

This report describes the physics case, the resulting detector requirements, and the evolving detector concepts for the experimental program at the Electron-Ion Collider (EIC). The EIC will be a powerful new high-luminosity facility in the United States with the capability to collide high-energy electron beams with high-energy proton and ion beams, providing access to those regions in the nucleon and nuclei where their structure is dominated by gluons. Moreover, polarized beams in the EIC will give unprecedented access to the spatial and spin structure of the proton, neutron, and light ions. The studies leading to this document were commissioned and organized by the EIC User Group with the objective of advancing the state and detail of the physics program and developing detector concepts that meet the emerging requirements in preparation for the realization of the EIC. The effort aims to provide the basis for further development of concepts for experimental equipment best suited for the science needs, including the importance of two complementary detectors and interaction regions. This report consists of three volumes. Volume I is an executive summary of our findings and developed concepts. In Volume II we describe studies of a wide range of physics measurements and the emerging requirements on detector acceptance and performance. Volume III discusses general-purpose detector concepts and the underlying technologies to meet the physics requirements. These considerations will form the basis for a world-class experimental program that aims to increase our understanding of the fundamental structure of all visible matter

physics.ins-det↗

arXiv2019

Precision Small Scattering Angle Measurements of Elastic Proton-Proton Single and Double Spin Analyzing Powers at the RHIC Hydrogen Jet Polarimeter

The Polarized Atomic Hydrogen Gas Jet Target polarimeter is employed by the Relativistic Heavy Ion Collider (RHIC) to measure the absolute polarization of each colliding proton beam. Polarimeter detectors and data acquisition were upgraded in 2015 to increase solid angle, energy range and energy resolution. These upgrades and advanced systematic error analysis along with improved beam intensity and polarization in RHIC runs 2015 ($E_\textrm{beam}=100\,\text{GeV}$) and 2017 ($255\,\text{GeV}$) allowed us to greatly reduce the statistical and systematic uncertainties for elastic spin asymmetries, $A_N(t)$ and $A_NN(t)$, in the Coulomb-nuclear interference momentum transfer range $0.0013<-t<0.018\,\text{GeV}^2$. For the first time hadronic single spin-flip $r_5$ and double spin-flip $r_2$ amplitude parameters were reliably isolated at these energies and momentum transfers. Measurements at two beam energies enable a separation of Pomeron and Regge pole contributions to $r_5(s)$ and $r_2(s)$, indicating that the spin component may persist at high energies.

hep-ex↗

arXiv2007

Dynamics of polarization buildup by spin filtering

There has been much recent research into polarizing an antiproton beam, instigated by the recent proposal from the PAX (Polarized Antiproton eXperiment) project at GSI Darmstadt. It plans to polarize an antiproton beam by repeated interaction with a polarized internal target in a storage ring. The method of polarization by spin filtering requires many of the beam particles to remain within the ring after scattering off the polarized internal target via electromagnetic and hadronic interactions. We present and solve sets of differential equations which describe the buildup of polarization by spin filtering in many different scenarios of interest to projects planning to produce high intensity polarized beams. These scenarios are: 1) spin filtering of a fully stored beam, 2) spin filtering while the beam is being accumulated, i.e. unpolarized particles are continuously being fed into the beam, 3) the particle input rate is equal to the rate at which particles are being lost due to scattering beyond ring acceptance angle, the beam intensity remaining constant, 4) increasing the initial polarization of a stored beam by spin filtering, 5) the input of particles into the beam is stopped after a certain amount of time, but spin filtering continues. The rate of depolarization of a stored polarized beam on passing through an electron cooler is also shown to be negligible.

hep-ph↗

arXiv2007

Helicity amplitudes and crossing relations for antiproton proton reactions

Antiproton proton annihilation reactions allow unique access to the moduli and phases of nucleon electromagnetic form factors in the time like region. We present the helicity amplitudes for the unequal mass single photon reaction $p \bar{p}\to l^+ l^-$ in the s channel including the lepton mass. The relative signs of these amplitudes are determined using simple invariance properties. Helicity amplitudes for the annihilation reaction $p \bar{p} \to N \bar{N}$ are also given, where $N$ is any spinor particle with structure. Crossing relations between the $e p \to e p$ scattering and the $p \bar{p}\to l^+ l^-$ annihilation channels are discussed and the crossing matrix for the helicity amplitudes is given. This matrix may be used to verify known expressions for the space like helicity amplitudes due to one photon exchange.

hep-ph↗

arXiv2007

Spin Observables for Polarizing Antiprotons

The PAX project at GSI Darmstadt plans to polarize an antiproton beam by repeated interaction with a hydrogen target in a storage ring. Many of the beam particles are required to remain within the ring after interaction with the target, so small scattering angles are important. Hence we concentrate on low momentum transfer (small t), a region where electromagnetic effects dominate the hadronic effects. A colliding beam of polarized electrons with energy sufficient to provide scattering of antiprotons beyond ring acceptance may polarize an antiproton beam by spin filtering. Expressions for spin observables are provided and are used to estimate the rate of buildup of polarization of an antiproton beam.

hep-ph↗

arXiv2006

Antiproton polarization induced by lepton interactions

We present expressions for electromagnetic helicity amplitudes and spin observables for any elastic spin 1/2 - spin 1/2 scattering to first order in QED. In particular all electromagnetic helicity amplitudes and spin observables for elastic antiproton-electron and antiproton-proton scattering via single t-channel photon exchange are presented. Spin observables are required to describe the rate of increase of polarization in spin filtering. The PAX collaboration at GSI Darmstadt is interested in the buildup of polarization of an antiproton beam by repeated interaction with a hydrogen gas target in a storage ring. In order for the beam particles to remain in the ring after scattering it is important to consider small angle scattering, hence small momentum transfer t. In the low momentum transfer region electromagnetic effects dominate the hadronic effects. Of immediate importance is whether the polarization of an antiproton beam can be built up by spin filtering off polarized electrons either in a target or in a beam. We present the theoretical background for this discussion.

hep-ph↗

arXiv2006

Polarisation observables in lepton antilepton to proton antiproton reactions including lepton mass

General expressions, including the lepton mass, for the spin averaged differential cross section for the annihilation reaction lepton antilepton to proton antiproton are given, as well as general formulae for the single and double spin asymmetries in the centre of mass frame. In particular we discuss the single spin asymmetry, normal to the scattering plane, which measures the relative phase difference between nucleon electromagnetic form factors $G_E$ and $G_M$. Recent experimental investigations of these form factors in the space and time like region are reviewed. It is thought that measurements of the phase of these form factors will provide fundamental information on the internal nucleon structure. The phases between $G_E$ and $G_M$ are accessible through polarisation observables measured in the antiproton proton to lepton antilepton reaction, or in its time reversed process.

hep-ph↗

arXiv2006

Spin dependent elastic antiproton interactions

Relativistic formulae for spin averaged and spin dependent one photon exchange differential cross sections are developed for spin half fermion fermion elastic scattering. Spin transfer cross sections are important for the Polarized Antiproton eXperiments (PAX) project at GSI Darmstadt. In particular, cross sections for polarization transfer in antiproton electron and antiproton proton elastic collisions are presented.

hep-ph↗

arXiv2001

An absolute polarimeter for high energy protons

A study of the spin asymmetries for polarized elastic proton proton collisions in the electromagnetic hadronic interference (CNI) region of momentum transfer provides a method of self calibration of proton polarization. The method can be extended to non-identical spin half scattering so that, in principle, the polarization of a proton may be obtained through an analysis of its elastic collision with a different polarized particle, helium 3 for instance. Sufficiently large CNI spin asymmetries provide enough information to facilitate the evaluation of nearly all the helicity amplitudes at small t as well as the polarization of both initial spin half fermions. Thus it can serve equally well as a polarimeter for helium 3.

hep-ph↗

arXiv2000

Bounds in proton-proton elastic scattering at low momentum transfer

We present a bound on the imaginary part of the single helicity-flip amplitude for spin 1/2-spin 1/2 scattering at small momentum transfer. The variational method of Lagrange multipliers is employed to optimize the single-flip amplitude using the values of the total cross section, the elastic cross section and diffraction slope as equality constraints in addition to the inequality constraints resulting from unitarity. Such bounds provide important information related to the determination of polarization of a proton beam. In the case of elastic proton collisions the analyzing power at small scattering angles inside the Coulomb Nuclear Interference region offers a method of measuring the polarization of a proton beam, the accuracy of the polarization measurement depending on the single helicity-flip amplitude. The bound obtained on the imaginary part of the single helicity-flip amplitude indicates that the analyzing power for proton-proton collisions in the Coulomb nuclear interference region should take positive nonzero values at high energies.

hep-ph↗

arXiv1999

The spin dependence of high energy proton scattering

Motivated by the need for an absolute polarimeter to determine the beam polarization for the forthcoming RHIC spin program, we study the spin dependence of the proton-proton elastic scattering amplitudes at high energy and small momentum transfer.We examine experimental evidence for the existence of an asymptotic part of the helicity-flip amplitude phi_5 which is not negligible relative to the largely imaginary average non-flip amplitude phi_+. We discuss theoretical estimates of r_5, essentially the ratio of phi_5 to phi_+, based upon extrapolation of low and medium energy Regge phenomenological results to high energies, models based on a hybrid of perturbative QCD and non-relativistic quark models, and models based on eikonalization techniques. We also apply the model-independent methods of analyticity and unitarity.The preponderence of evidence at available energy indicates that r_5 is small, probably less than 10%. The best available experimental limit comes from Fermilab E704:those data indicate that |r_5|<15%. These bounds are important because rigorous methods allow much larger values. In contradiction to a widely-held prejudice that r_5 decreases with energy, general principles allow it to grow as fast as ln(s) asymptotically, and some models show an even faster growth in the RHIC range. One needs a more precise measurement of r_5 or to bound it to be smaller than 5% in order to use the classical Coulomb-nuclear interference technique for RHIC polarimetry. As part of this study, we demonstrate the surprising result that proton-proton elastic scattering is self-analysing, in the sense that all the helicity amplitudes can, in principle, be determined experimentally at small momentum transfer without a knowledge of the magnitude of the beam and target polarization.

hep-ph↗