Electron-ion Collider Research Articles

In situ effective pumping speed measurements as a tool for non-evaporable getter activation and saturation monitoring

We have developed method of in situ effective pumping speed measurements based on injecting finite gas pulse into a vacuum volume and subsequent recording of pressure response using a Residual Gas Analyzer (RGA). The pressure burst caused by injected gas pulse falls exponentially in time and the exponential coefficient of such pressure decay is proportional to total effective pumping speed of all vacuum pumps acting on vacuum chamber volume. The effective pumping speed can be extracted from the dependence of injected gas species pressure vs time recorded by an RGA. Non-Evaporable Getters (NEGs) are widely used in multiple ultra and extremely high vacuum devices and applications during the last several decades. Areas of NEG applications were recently expanded into vacuum devices with relatively high-pressure levels (up to 10−7 Torr) by the invention of high capacity ZAO NEG which can be operated at elevated temperatures. The intrinsic property of all NEG-based vacuum pumps is the reduction of their pumping speed, called “NEG saturation”, after an extended period of operation. Typical time interval for such process can span from about a month and up to a few years depending on NEG type, vacuum level of NEG pump operation, and residual gas content. After that, the NEG pump will require a re-activation cycle to restore its pumping speed close to the initial value. For many applications it is difficult to realize what is the current pumping speed of NEG pump is and when the pump should be re-activated. A method for in situ effective pumping speed measurements developed in this study can be used as a tool for NEG-based pump activation and saturation monitoring. Application of such an approach to monitor pumping status of NEG pumps was utilized and will be continually used at Extended EBIS which was recently developed and commissioned for Relativistic Heavy Ion Collider (RHIC) and future Electron Ion Collider (EIC). The results obtained during commissioning are presented and discussed.

Intrinsic charm quark valence distribution of the proton

We provide a first quantitative indication that the wave function of the proton contains unequal distributions of charm quarks and antiquarks, i.e., a nonvanishing intrinsic valence charm distribution. A significant nonvanishing valence component cannot be perturbatively generated; hence, our results reinforce previous evidence that the proton contains an intrinsic (i.e., not radiatively generated) charm quark component. We establish our result through a determination of the parton distribution functions of charm quarks and antiquarks in the proton. We propose two novel experimental probes of this intrinsic charm valence component: D-meson asymmetries in Z+c-jet production at the LHCb experiment and flavor-tagged structure functions at the Electron-Ion Collider. Published by the American Physical Society 2024

Inclusive photoproduction of charmonia-bottomonia pairs

In this article we analyze the inclusive photoproduction of heavy charmonia-bottomonia pairs in the color glass condensate framework and demonstrate that the cross section of the process is sensitive to dipole and quadrupole forward scattering amplitudes (2- and 4-point correlators of Wilson lines). Using the phenomenological parametrizations of these amplitudes, we estimate numerically the production cross sections in the kinematics of the forthcoming Electron Ion Collider and the ultraperipheral collisions at the LHC. We found that the contribution controlled by the quadrupole amplitude is dominant, and for this reason, the suggested channel can be used as a gateway for studies of this nonperturbative object. Published by the American Physical Society 2024

Signatures of baryon junctions in semi-inclusive deep inelastic scattering

Local gauge invariance of the baryon wave function leads to the emergence of a baryon junction, where three (or N, in SU(N) gauge theory) string operators merge. The existence of baryon junction dramatically affects the dynamics of baryon stopping at high energies, and the corresponding predictions are supported by the recent data from STAR Collaboration at the Relativistic Heavy Ion Collider. Here we outline the ways in which the baryon junctions can be tested in semi-inclusive deep inelasttic scattering at Jefferson Laboratory and the future Electron Ion Collider.

Nuclear Parton Distribution Functions After the First Decade of LHC Data

We present a review of the conceptual basis, current knowledge, and recent progress regarding global analysis of nuclear parton distribution functions (PDFs). After introducing the theoretical foundations and methodological approaches for the extraction of nuclear PDFs from experimental data, we discuss how different measurements in fixed-target and collider experiments provide increasingly precise constraints on various aspects of nuclear PDFs, including shadowing, antishadowing, the EMC effect, Fermi motion, flavor separation, deuteron binding, and target-mass and other higher-twist effects. Particular emphasis is given to measurements carried out in proton–lead collisions at the Large Hadron Collider, which have revolutionized the global analysis during the past decade. These measurements include electroweak boson, jet, light hadron, and heavy flavor observables. Finally, we outline the expected impact of the future Electron Ion Collider and discuss the role and interplay of nuclear PDFs with other branches of nuclear, particle, and astroparticle physics.

Next-to-leading-order relativistic and QCD corrections to prompt pair photoproduction at future colliders* *Supported in part by the German Research Foundation DFG through Research Unit FOR 2926 "Next Generation Perturbative QCD for Hadron Structure: Preparing for the Electron-Ion Collider" (409651613). The work of X.B.J. was supported in part by National Natural Science Foundation of China (12061131006). The work of R.L. was

Within the framework of nonrelativistic-QCD factorization, we calculate both the next-to-leading-order relativistic and QCD corrections to prompt pair production, with feed-down from mesons, via photon-photon collisions at future colliders, including the Future Circular Lepton Collider (FCC-ee), the Circular Electron Positron Collider (CEPC), and the Compact Linear Collider (CLIC). We present total cross sections and distributions in single transverse momentum and rapidity, as well as in pair invariant mass. The relativistic and QCD corrections both turn out to be large and negative. However, the production rates are large enough for useful experimental studies.

The LHC as a Neutrino-Ion Collider

Proton-proton collisions at the LHC generate a high-intensity collimated beam of neutrinos in the forward (beam) direction, characterised by energies of up to several TeV. The recent observation of LHC neutrinos by FASERν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document} and SND@LHC signifies that this previously overlooked particle beam is now available for scientific investigation. Here we quantify the impact that neutrino deep-inelastic scattering (DIS) measurements at the LHC would have on the parton distributions (PDFs) of protons and heavy nuclei. We generate projections for DIS structure functions for FASERν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document} and SND@LHC at Run III, as well as for the FASERν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document}2, AdvSND, and FLArE experiments to be hosted at the proposed Forward Physics Facility (FPF) operating concurrently with the High-Luminosity LHC (HL-LHC). We determine that up to one million electron-neutrino and muon-neutrino DIS interactions within detector acceptance can be expected by the end of the HL-LHC, covering a kinematic region in x and Q2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q^2$$\\end{document} overlapping with that of the Electron-Ion Collider. Including these DIS projections in global (n)PDF analyses, specifically PDF4LHC21, NNPDF4.0, and EPPS21, reveals a significant reduction in PDF uncertainties, in particular for strangeness and the up and down valence PDFs. We show that LHC neutrino data enable improved theoretical predictions for core processes at the HL-LHC, such as Higgs and weak gauge boson production. Our analysis demonstrates that exploiting the LHC neutrino beam effectively provides CERN with a “Neutrino-Ion Collider” without requiring modifications in its accelerator infrastructure.

A few-degree calorimeter for the future electron-ion collider

Measuring the region 0.1<Q2<1.0 GeV2 is essential to support searches for gluon saturation at the future Electron-Ion Collider. Recent studies have revealed that covering this region at the highest beam energies is not feasible with current detector designs, resulting in the so-called Q2 gap. In this work, we present a design for the Few-Degree Calorimeter (FDC), which addresses this issue. The FDC uses SiPM-on-tile technology with tungsten absorber and covers the range of −4.6<η<−3.6. It offers fine transverse and longitudinal granularity, along with excellent time resolution, enabling standalone electron tagging. Our design represents the first concrete solution to bridge the Q2 gap at the EIC.

Novel 4x4 SiPM array readout with integrated preamplification stage, optimized for the PWO detectors of the EIC EEEMCal

We are reporting on a new readout circuit developed for the lead tungstate (PbWO4) scintillation detectors for the Electron Ion Collider (EIC) Electron Endcap Electromagnetic Calorimeter EEEMCal. The high magnetic field region precludes the use of photomultiplier tubes while the detector requirements specify good spectral resolution performance and fast pulse integration over a large dynamic range. We selected a silicon photomultiplier (SiPM) from Hamamatsu and produced a matrix of 4 x 4 sensors to cover the 20 mm × 20 mm scintillator coupling surface. Signal acquisition and amplification electronics boards were designed and integrated with the sensor board to produce a compact high performance readout package. A prototype detector was built and tested at Jefferson Lab with encouraging resolution and timing performance results.

Updated numerical study of transverse single-spin asymmetries in single-inclusive pion production from lepton-nucleon collisions

We revisit the analysis of transverse single-spin asymmetries AN in lepton-nucleon scattering where only a single pion is detected in the final state, ℓN↑→hX. This observable is the Electron-Ion Collider (EIC) analogue to AN in proton-proton collisions, p↑p→hX, that has been studied intensely for decades, especially at the Relativistic Heavy Ion Collider (RHIC). We incorporate new theoretical developments in the collinear twist-3 framework and utilize recent extractions of (Sivers-like and Collins-like) quark-gluon-quark correlators in the numerical computations. We compare our calculations to HERMES measurements as well as make predictions for Jefferson Lab, COMPASS, and EIC kinematics. We further explore the role of next-to-leading order (NLO) corrections to the (twist-2) unpolarized cross section (denominator of AN) and consider what can be deduced empirically about the potential numerical significance of the full NLO calculation of AN in this process. We consider sources of theoretical uncertainty in our predictions, which present potential opportunities then for future measurements to improve our understanding of AN and multi-parton correlations in hadrons.

Beam dynamics driven design of powerful energy recovery linac for experiments

Powerful ERL for experiments (PERLE) is a novel energy recovery linac (ERL) test facility [1], designed to validate choices for a 50 GeV ERL foreseen in the design of the Large Hadron Electron Collider and the Future Circular Collider and to host dedicated nuclear and particle physics experiments. Its main goal is to demonstrate the high current, continuous wave, multipass operation with superconducting cavities at 802 MHz. With very high beam power (10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERLs and becomes a “stepping stone” between the present state-of-the-art 1 MW ERLs and the future 100 MW scale applications. Published by the American Physical Society 2024

High-power test results for a cylindrical-shell silicon carbide higher-order-mode damper

The next high-current Electron-Ion Collider (EIC) is a new accelerator to be built at Brookhaven National Laboratory in collaboration with Thomas Jefferson National Accelerator Facility. In the EIC Electron Storage Ring (ESR), there will be beam currents of up to 2.5 A, which will excite massive higher-order-mode (HOM) power in the 17 single-cell 591 MHz superconducting radio-frequency (SRF) cavities. Damping the HOM power in the ESR SRF cavities is a challenge. A room temperature cylindrical shell shape silicon carbide (SiC) beamline HOM absorber (BLA) was chosen as the baseline design, due to its broadband and high-power capability, and previous demonstrations at other accelerator facilities, albeit at much lower power. Because the EIC BLA HOM power dissipation is significantly greater than the previous applications, it is imperative to carry out high-power testing to determine the maximum device performance levels achievable for thermal transport, rf breakdown, and mechanical stress, prior to finalizing the design. A SiC HOM absorber with a state-of-the-art geometry size was prototyped to verify the shrink-fit technique, test outgassing rate, and high-power handling capability. This paper presents the HOM damper’s prototyping and test results. Published by the American Physical Society 2024

Impact of inclusive electron ion collider data on collinear parton distributions

A study is presented of the impact of updated simulated inclusive electron ion collider deep inelastic scattering data on the determination of the proton and nuclear parton distribution functions (PDFs) at next-to-next-to-leading and next-to-leading order in QCD, respectively. The influence on the proton PDFs is evaluated relative to the HERAPDF2.0 set, which uses inclusive HERA data only, and also relative to the global fitting approach of the MSHT20 PDFs. The impact on nuclear PDFs is assessed relative to the EPPS21 global fit and is presented in terms of nuclear modification ratios. For all cases studied, significant improvements in the PDF uncertainties are observed for several parton species. The most striking impact occurs for the nuclear PDFs in general and for the region of high Bjorken x in the proton PDFs, particularly for the valence quark distributions. Published by the American Physical Society 2024

Polarized TMD fragmentation functions for J/ψ production

We calculate the matching, at leading order, of the transverse momentum-dependent fragmentation functions (TMDFFs) for light quarks and gluons fragmenting to a J/ψ onto polarized nonrelativistic QCD (NRQCD) TMDFFs. The NRQCD TMDFFs have an operator product expansion in terms of nonperturbative NRQCD production matrix elements. Using the results we obtain, we make predictions for the light quark fragmentation contribution to the production of polarized J/ψ in semi-inclusive deep inelastic scattering (SIDIS) both for unpolarized and longitudinally polarized beams. These results are an important contribution to polarized J/ψ production in SIDIS and thus are needed for comparison with experiments at the future Electron-Ion Collider. Published by the American Physical Society 2024

Role of sea quarks in the nucleon transverse spin

We present a phenomenological extraction of transversity distribution functions and Collins fragmentation functions by simultaneously fitting to semi-inclusive deep inelastic scattering and electron-positron annihilation data. The analysis is performed within the transverse-momentum-dependent factorization formalism, and sea quark transversity distributions are taken into account for the first time. We find the u¯ quark favors a negative transversity distribution, while that of the d¯ quark is consistent with zero according to the current accuracy. In addition, based on a combined analysis of world data and simulated data, we quantitatively demonstrate the impact of the proposed Electron-Ion Collider in China on precise determinations of the transversity distributions, especially for sea quarks, and the Collins fragmentation functions. Published by the American Physical Society 2024

Harmonics of lepton-jet correlations in inclusive and diffractive scatterings

Based on our previous work, we study the harmonic coefficient of both inclusive and diffractive azimuthal angle dependent lepton-jet correlations in the Hadron-Electron Ring Accelerator and the future electron-ion collider. Numerical calculations for inclusive and diffractive harmonics, and the ratio of harmonics in e+Au and e+p, indicate their strong discriminating power for nonsaturation models and saturation models. Additionally, we demonstrate that the t-dependent diffractive harmonics can serve as novel observables for the nuclear density profile. Published by the American Physical Society 2024

Hadron-level NLO predictions for QCD observables in photo-production at the Electron-Ion Collider

We present the first next-to-leading order accurate hadron-level predictions for inclusive QCD and jet observables in photo-production for electron-proton beams at the upcoming electron-ion collider. Our predictions show large K factors of about 60% and a dominating real correction. Published by the American Physical Society 2024

The high-performance DIRC for the ePIC detector at the EIC

The next-generation nuclear physics facility in the United States will be the Electron-Ion Collider (EIC), scheduled to be built at Brookhaven National Laboratory (BNL). Excellent particle identification (PID) is one of the key requirements for the EIC central detector called ePIC. Identification of the hadrons in the final state is critical to study how different quark flavors contribute to nucleon properties. A detector using the Detection of Internally Reflected Cherenkov light (DIRC) principle, with a radial size of only 7-8 cm, was chosen as the PID system for the ePIC barrel region. Within the framework of the EIC R&D programs, the development of a high-performance DIRC (hpDIRC) detector was undertaken with the aim of significantly advancing state-of-the-art performance. Key components of the hpDIRC detector are a 3-layer compound lens and small pixel-size photo sensors. Currently, the hpDIRC R&D program is focused on developing and validating the radiation hard 3-layer lens, quality assurance of the BaBar DIRC radiation bars, and the early stage of the hpDIRC prototype program with Cosmic Ray Telescope at Stony Brook University, in preparation for beam tests at Fermilab in 2024.

Heavy quarks in polarised deep-inelastic scattering at the electron-ion collider

We extend the FONLL general-mass variable-flavour-number scheme to the case of longitudinally polarised DIS structure functions, accounting for perturbative corrections up to Oαs2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathcal {O}\\left( \\alpha _s^2\\right) $$\\end{document}. We quantify the impact of charm quark mass and higher-order perturbative corrections on projected measurements of inclusive and charm-tagged longitudinal asymmetries at the Electron-Ion Collider (EIC) and at the Electron-ion collider in China (EicC). We demonstrate how the inclusion of these corrections is essential to compute predictions with an accuracy that matches the projected precision of the measurements. The computation is made publicly available through the open-source EKO and YADISM programs.

Improving Cathode Testing with a High-Gradient Cryogenic Normal Conducting RF Photogun

Future electron accelerator applications such as X-ray free electron lasers and colliders are dependent on significantly increasing beam brightness. With the observation that linac beam manipulation’s best preservation of max brightness is at the cathode, we are incentivized to create an environment where we can study how to achieve the highest possible photogun brightness. In order to do so, we intend to extract beams from high-brightness photocathodes with the highest achievable accelerating gradients we can manage in a klystron-powered radiofrequency (RF) photogun. We utilize here cryogenic normal conducting cavities to achieve ultra-high gradients via limitation of breakdown rates (BDR). The low temperatures should also reduce cathode emittance by reducing the mean transverse energy (MTE) of electrons near the photoemission threshold. To this end, we have designed and produced a new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBORG) for use in a new beamline at UCLA. We will introduce the enabling RF and photoemission physics as a primer for the new regime of high field low temperature cathodes we intend to enter. We further report the current status of the beamline commissioning, including the cooling of the photogun to 100 K, and producing 0.5 MW of RF feed power, which corresponds to cathode accelerating fields in the range of 80–90 MV/m. We further plan iterative improvements to both to 77 K and 1 MW corresponding to our ultimate goal &gt;120 MV/m. Our discussion will include future beamline tests and the consideration of the initial realization of an ultra-high-gradient photoinjector concept.