arXiv subjects

Bernd Surrow

Publications and source records attributed to Bernd Surrow.

At least 19 recordsLinked to original sources

arXiv2025

Realizing the Scientific Program with Polarized Ion Beams at EIC

Polarized ion beams at the Electron Ion Collider are essential to address some of the most important open questions at the twenty-first century frontiers of understanding of the fundamental structure of matter. Here, we summarize the science case and identify polarized $^2$H, $^3$He, $^6$Li and $^7$Li ion beams as critical technology that will enable experiments which address the most important science. Further, we discuss the required ion polarimetry and spin manipulation in EIC. The current EIC accelerator design is presented. We identify a significant R\&D effort involving both national laboratories and universities that is required over about a decade to realize the polarized ion beams and estimate (based on previous experience) that it will require about 20 FTE over 10 years (or a total of about 200 FTE-years) of personnel, including graduate students, postdoctoral researchers, technicians and engineers. Attracting, educating and training a new generation of physicists in experimental spin techniques will be essential for successful realization. AI/ML is seen as having significant potential for both acceleration of R\&D and amplification of discovery in optimal realization of this unique quantum technology on a cutting-edge collider. The R\&D effort is synergistic with research in atomic physics and fusion energy science.

nucl-ex↗

arXiv2022

Report of the Instrumentation Frontier Working Group for Snowmass 2021

Detector instrumentation is at the heart of scientific discoveries. Cutting edge technologies enable US particle physics to play a leading role worldwide. This report summarizes the current status of instrumentation for High Energy Physics (HEP), the challenges and needs of future experiments and indicates high priority research areas. The Snowmass Instrumentation Frontier studies detector technologies and Research and Development (R&D) needed for future experiments in collider physics, neutrino physics, rare and precision physics and at the cosmic frontier. It is divided into more or less diagonal areas with some overlap among a few of them. We lay out five high-level key messages that are geared towards ensuring the health and competitiveness of the US detector instrumentation community, and thus the entire particle physics landscape.

hep-ex↗

arXiv2016

Transverse double-spin asymmetries for electroweak gauge-boson production in high-energy polarized $p^{\uparrow} + p^{\uparrow}$ collisions

We consider the production of $W$ and $Z / γ^{*}$ gauge bosons in proton-proton collisions at a center-of-mass energy of $\sqrt{s} = 510 \mbox{GeV}$ available at RHIC at BNL, operating at high luminosity. We stress the importance of measuring the transverse double-spin asymmetries $A_{TT}$, in connection with available transversely polarized beams with a high degree of polarisation. We will discuss some theoretical issues related to the predicted asymmetries. These studies are contrasted to the 2017 RHIC running operation of transversely polarized beams of mid-rapidity $W$ and $Z$ boson production at a center-of-mass energy of $\sqrt{s}=510\,$GeV along with long-term prospects beyond 2020 at RHIC.

hep-ph↗

arXiv2015

R&D on GEM Detectors for Forward Tracking at a Future Electron-Ion Collider

We report the status of R&D on large triple-GEM detectors for a forward tracker (FT) in an experiment at a future Electron Ion Collider (EIC) that will improve our understanding of QCD. We have designed a detector prototype specifically targeted for the EIC-FT, which has a trapezoidal shape with 30.1 degrees opening angle. We are investigating different detector assembly techniques and signal readout technologies, but have designed a common GEM foil to minimize NRE cost for foil production. The assembly techniques comprise either a purely mechanical method including foil stretching as pioneered by CMS but with certain modifications, or gluing foils to frames that are then assembled mechanically, or gluing foils to frames that are then glued together. The first two assembly techniques allow for re-opening chambers so that a GEM foil can be replaced if it is damaged. For readout technologies, we are pursuing a cost-effective one-dimensional readout with wide zigzag strips that maintains reasonable spatial resolution, as well two-dimensional readouts - one with stereo-angle (u-v) strips and another with r-phi strips. In addition, we aim at an overall low-mass detector design to facilitate good energy resolution for electrons scattered at low momenta. We present design for GEM foils and other detector parts, which we plan to entirely acquire from U.S. companies.

physics.ins-det↗

arXiv2015

The RHIC SPIN Program: Achievements and Future Opportunities

Time and again, spin has been a key element in the exploration of fundamental physics. Spin-dependent observables have often revealed deficits in the assumed theoretical framework and have led to novel developments and concepts. Spin is exploited in many parity-violating experiments searching for physics beyond the Standard Model or studying the nature of nucleon-nucleon forces. The RHIC spin program plays a special role in this grand scheme: it uses spin to study how a complex many-body system such as the proton arises from the dynamics of QCD. Many exciting results from RHIC spin have emerged to date, most of them from RHIC running after the 2007 Long Range Plan. In this document we present highlights from the RHIC program to date and lay out the roadmap for the significant advances that are possible with future RHIC running.

nucl-ex↗

arXiv2014

Future prospects of di-jet production constraining $Δg(x)$ at low $\mathbf{x}$ at STAR at RHIC

One of the main objectives of the high-energy spin physics program at RHIC at BNL is the precise determination of the polarized gluon distribution function, $Δg(x)$. Polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=200\,$GeV and at $\sqrt{s}=500\,$GeV at RHIC provide an unique way to probe the proton spin structure. Inclusive measurements, such as inclusive jet and hadron production, have so far been the prime focus of various results at $\sqrt{s}=200\,$GeV constraining $Δg(x)$ for $0.05<x<0.2$. A recent global analysis provides for the first time evidence of a non-zero value of the gluon polarization $\int_{\tiny 0.05}^{\tiny 1}Δg (x)\, dx \,(Q^{2}=10\,{\rm GeV}^{2}) = 0.20^{+0.06}_{-0.07}$. First results of di-jet production at $\sqrt{s}=200\,$GeV by the STAR collaboration will allow a better constraint of the underlying event kinematics. Extending the current program to smaller values of $x$ is a key goal for the future high-energy spin physics program at RHIC. Forward di-jet production measurements at STAR beyond the current acceptance from $-1<η<+2$ to $+2.5<η<+4$, in particular those carried out at $\sqrt{s}=500\,$GeV, provides access to low $x$ values at the level of $10^{-3}$ where current uncertainties of $Δg(x)$ remain very large. Those measurements will eventually be complemented by a future Electron-Ion Collider facility probing $Δg(x)$ in polarized $\vec{e}+\vec{p}$ collisions.

hep-ex↗

arXiv2013

Recent results of high-energy spin phenomena of gluons and sea-quarks in polarized proton-proton collisions at RHIC at BNL

The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is carrying out a spin physics program in high-energy polarized proton collisions at $\sqrt{s}=200\,$GeV and $\sqrt{s}=500\,$GeV to gain a deeper insight into the spin structure and dynamics of the proton. One of the main objectives of the spin physics program at RHIC is the precise determination of the polarized gluon distribution function. The STAR detector is well suited for the reconstruction of various final states involving jets, $π^{0}$, $π^{\pm}$, e$^{\pm}$ and $γ$, which allows to measure several different processes. Recent results suggest a gluon spin contribution to the proton spin at the same level as the quark spin contribution itself. The production of $W$ bosons in polarized p+p collisions at $\sqrt{s}=500\,$GeV opens a new era in the study of the spin-flavor structure of the proton. $W^{-(+)}$ bosons are produced in $\bar{u}+d\;(\bar{d}+u)$ collisions and can be detected through their leptonic decays, $e^{-}+\barν_{e}\;(e^{+}+ν_{e})$, where only the respective charged lepton is measured. Results of $W^{-(+)}$ production suggest a large asymmetry between the polarization of anti-$u$ and anti-$d$ quarks.

hep-ex↗

arXiv2010

Recent STAR results and future prospects of $W^{\pm}$ boson production in polarized proton-proton collisions at RHIC

The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is providing fundamental measurements in high-energy polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=200-500\,$GeV to deepen our understanding on the spin structure and dynamics of the proton. This program has completed the first data taking period in 2009 of polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=500\,$GeV. This opens a new era in the study of the spin-flavor structure of the proton based on the production of $W^{-(+)}$ bosons. The measurement of the cross section and single-spin asymmetries for midrapidity decay positrons and electrons from $W^{+}$ and $W^{-}$ boson production in longitudinally polarized $\vec{p}+p$ collisions at $\sqrt{s}=500\,$GeV is presented.

hep-ex↗

arXiv2010

Recent STAR results in high-energy polarized proton-proton collisions at RHIC

The STAR experiment at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory is carrying out a spin physics program in high-energy polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=200-500\,$GeV to gain a deeper insight into the spin structure and dynamics of the proton. One of the main objectives of the spin physics program at RHIC is the extraction of the polarized gluon distribution function based on measurements of gluon initiated processes, such as hadron and jet production. The STAR detector is well suited for the reconstruction of various final states involving jets, $π^{0}$, $π^{\pm}$, e$^{\pm}$ and $γ$, which allows to measure several different processes. Recent results will be shown on the measurement of jet production and hadron production at $\sqrt{s}=200\,$GeV. The RHIC spin physics program has recently completed the first data taking period in 2009 of polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=500\,$GeV. This opens a new era in the study of the spin-flavor structure of the proton based on the production of $W^{-(+)}$ bosons. Recent STAR results on the first measurement of $W$ boson production in polarized $\vec{p}+\vec{p}$ collisions will be shown.

hep-ex↗

arXiv2008

Beam Performance of Tracking Detectors with Industrially Produced GEM Foils

Three Gas-Electron-Multiplier tracking detectors with an active area of 10 cm x 10 cm and a two-dimensional, laser-etched orthogonal strip readout have been tested extensively in particle beams at the Meson Test Beam Facility at Fermilab. These detectors used GEM foils produced by Tech-Etch, Inc. They showed an efficiency in excess of 95% and spatial resolution better than 70 um. The influence of the angle of incidence of particles on efficiency and spatial resolution was studied in detail.

physics.ins-det↗

arXiv2007

Triple GEM Detectors for the Forward Tracker in STAR

Future measurements of the flavor-separated spin structure of the proton via parity-violating W boson production at RHIC require an upgrade of the forward tracking system of the STAR detector. This upgrade will allow the reconstruction of the charge sign of electrons and positrons produced from decaying W bosons. A design based on six large area triple GEM disks using GEM foils produced by Tech-Etch Inc. has emerged as a cost-effective solution to provide the necessary tracking precision. We report first results from a beam test of three test detectors using Tech-Etch produced GEM foils and a laser etched two dimensional strip readout. The detectors show good operational stability, high efficiency and a spacial resolution of around 70 um or better, exceeding the requirements for the forward tracking upgrade. The influence of the angle of incidence of the particles on the spatial resolution of the detectors has also been studied in detail.

physics.ins-det↗

arXiv2007

Recent results of the STAR high-energy polarized proton-proton program at RHIC at BNL

The STAR experiment at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is carrying out a spin physics program colliding transverse or longitudinal polarized proton beams at $\sqrt{s}=200-500 $GeV to gain a deeper insight into the spin structure and dynamics of the proton. These studies provide fundamental tests of Quantum Chromodynamics (QCD). One of the main objectives of the STAR spin physics program is the determination of the polarized gluon distribution function through a measurement of the longitudinal double-spin asymmetry, $A_{LL}$, for various processes. Recent results will be shown on the measurement of $A_{LL}$ for inclusive jet production, neutral pion production and charged pion production at $\sqrt{s}=200 $GeV. In addition to these measurements involving longitudinal polarized proton beams, the STAR collaboration has performed several important measurements employing transverse polarized proton beams. New results on the measurement of the transverse single-spin asymmetry, $A_{N}$, for forward neutral pion production and the first measurement of $A_{N}$ for mid-rapidity di-jet production will be discussed.

hep-ex↗

arXiv2006

eRHIC - Accelerator and detector design studies

An electron-proton/ion collider facility (eRHIC) is under consideration at Brookhaven National Laboratory (BNL). An overview of the accelerator and detector design concepts will be provided.

physics.acc-ph↗

arXiv2006

eRHIC - A precision electron-proton/ion collider facility at Brookhaven National Laboratory

An electron-proton/ion collider facility (eRHIC) is under consideration at Brookhaven National Laboratory (BNL). Such a new facility will require the design and construction of a new optimized detector profiting from the experience gained from the H1 and ZEUS detectors operated at the HERA collider at DESY. The details of the design will be closely coupled to the design of the interaction region, and thus to the machine development work in general. An overview of the accelerator and detector design concepts will be provided.

hep-ex↗

arXiv2002

The first polarized Proton Collisions at the STAR experiment at RHIC

The first run of transverse polarized protons at RHIC was recently completed which opened a new era exploring the spin structure of the proton. A first measurement of the single transverse spin asymmetry, $A_{N}$, for leading $π_{0}$ production from transverse colliding polarized protons at $\sqrt(s)=200 $GeV, $X_{F}>0.25$ and $p_{T}\simeq 1-4 $GeV was a focus of the STAR collaboration during the first polarized proton run at RHIC. Two new subcomponents have been added to the STAR experiment to carry out such a measurement in polarized proton collisions: a forward $π_{0}$ detector system at approximately $7.8 $m of the STAR interaction region to reconstruct $π_{0}$ mesons from their decay products $(π_{0}\to γγ)$ and a beam-beam counter with large forward acceptance to provide a means of beam-related background suppression and relative luminosity measurement.

hep-ex↗

arXiv2002

Phenomenological studies of inclusive ep scattering at low momentum transfer Q^2

Phenomenological studies on the proton structure function F^2 have been carried out to investigate the behavior of F^2, i.e. its x and Q^2 dependence, in the transition from the deep-inelastic scattering region (Q^2 >> 1 GeV^2) to the photoproduction region (Q^2 approx. 0 GeV^2). An overview of various results of F^2 at low Q^2 is given. To quantify the behavior of F2 at low Q^2, the derivatives dln(F^2)/dln(x) for fixed Q^2 and dF^2/dlog(Q^2) for fixed x haven been determined and compared to expectations within the framework of perturbative and non-perturbative QCD. Furthermore, the derivatives were compared to results of the total inclusive diffractive cross-section and vector-meson production. An interpretation of inclusive ep results is given in the framework of the GVD/CDP picture with special emphasis on the limit of Q^2 --> 0 for fixed W^2 and x --> for fixed Q^2.

hep-ph↗

arXiv2001

Low-x scaling in $γ^*p$ total cross sections

We show that the experimental data for the total virtual-photon proton cross section, σ_{γ^*p} (W^2, Q^2), for x_{bj} \lsim 0.1 lie on a universal curve, when plotted against η= (Q^2 + m^2_0)/ Λ^2(W^2), where Λ^2 (W^2) = C_1 (W^2+W^2_0)^{C_2} is determined by the parameters m^2_0, C_1, C_2 and W^2_0. The observed scaling law follows from the generalized-vector-dominance/color-dipole picture of low-x deep inelastic scattering.

hep-ph↗

arXiv1998

The structure of the photon and its interactions

The OPAL experiment at LEP has performed a variety of measurements of photon-photon and electron-photon scattering at the electron-positron collider LEP to gain a deeper insight into the structure of the photon and its interactions. This review presents a summary of these results.

hep-ex↗