Nuclear Commons^™

Measurement Of Target And Double-Spin Asymmetries For The Ep → Eπ+(N) Reaction In The Nucleon Resonance Region At Low Q², Clas Collaboration, K. P. Adhikari, S E. Kuhn, D. Adikaram, M. J. Amaryan, S. Bültmann, Gail Dodge, N. Guler, L. B. Weinstein

Physics Faculty Publications

We report measurements of target- and double-spin asymmetries for the exclusive channel ^→e^→p → eπ⁺(n) in the nucleon resonance region at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). These asymmetries were extracted from data obtained using a longitudinally polarized NH₃ target and a longitudinally polarized electron beam with energies 1.1, 1.3, 2.0, 2.3, and 3.0 GeV. The new results are consistent with previous CLAS publications but are extended to a low Q² range from 0.0065 to 0.35(GeV/c)². The Q² access was made possible by a custom-built Cherenkov detector …

Studies Of Two-Nucleon Interactions And Few-Body Electromagnetic Structure In Chiral Effective Field Theory, Maria Piarulli

Physics Theses & Dissertations

A coordinate-space nucleon-nucleon potential is constructed in chiral effective field theory (χEFT) retaining pions, nucleons and Δ-isobars as explicit degrees of freedom. The calculation of the potential is carried out by including one-and two-pion-exchange contributions up to next-to-next-to-leading order (N2LO) and contact interactions tip to next-to-next-to-next-to-leading order (N3LO). The low-energy constants multiplying these contact interactions are fitted to the 2013 Granada database in the laboratory-energy range 0–300 MeV. Three versions of this chiral potential, corresponding to three different cutoffs, have been developed. The cutoff regularizes the one- and two-pion exchange as well as the contact part of the potential. A …

Control Of Synchrotron Radiation Effects During Recirculation With Bunch Compression, D. R. Douglas, S. V. Benson, R. Li, Y. Roblin, C. D. Tennant, Geoffrey A. Krafft, Balŝa Terzić, C. -Y. Tsai

Physics Faculty Publications

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 ****.

Virtuality Distributions And Pion Transition Form Factor, A. V. Radyushkin

Physics Faculty Publications

Using the example of hard exclusive transition process ᵞ*ᵞ → π⁰ at the handbag level, we outline basics of a new approach to transverse momentum dependence in hard processes. In coordinate representation, matrix elements of operators (in the simplest case, bilocal 𝒪(0, z)) describing a hadron with momentum p, are functions of (pz) and z² parametrized through virtuality distribution amplitudes (VDA) Φ(x, σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z⁺ = 0, we introduce the transverse momentum distribution amplitude (TMDA) Ψ(x, k_⊥), and write it in terms of VDA …

Isolation Of Flow And Nonflow Correlations By Two And Four Particle Cumulant Measurements Of Azimuthal Harmonics In √Sɴɴ = Gev Au+Au Collisions, N. M. Abdelwahab, L. Adamczyk, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, S. Bültmann

Physics Faculty Publications

A data-driven method was applied to Au+Au collisions at √Sɴɴ = 200 GeV made with the STAR detector at RHIC to isolate pseudorapidity distance Δ η-dependent and Δ η-independent correlations by using two- and four-particle azimuthal cumulant measurements. We identified a Δ η-independent component of the correlation, which is dominated by anisotropic flow and flow fluctuations. It was also found to be independent of η within the measured range of pseudorapidity | η | < 1. In 20-30% central Au+Au collisions, the relative flow fluctuation was found to be 34% ± 2%(stat.) ± 3%(sys.) for particles with transverse momentum p_T less than 2 GeV/c. The Δ η-dependent part, attributed to nonflow correlations, is found to be 5% ± 2%(sys.) relative to the flow of the …

The Heavy Photon Search Test Detector, M. Battaglieri, S. Boyarinov, S. Bueltmann, V. Burkert, A. Celentano, G. Charles, W. Cooper, C. Cuevas, N. Dashyan, R. Devita, L. B. Weinstein

Physics Faculty Publications

The Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experiment׳s technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in the …

Charged-To-Neutral Correlation At Forward Rapidity In Au + Au Collisions At √S(Nn)=200 Gev, L. Adamczyk, J. K. Adkins, G. Agakishiev, A. A. Aggarwal, Z. Ahammed, I. Alekseev, S. Bültmann

Physics Faculty Publications

Event-by-event fluctuations of the multiplicities of inclusive charged particles and photons at forward rapidity in Au + Au collisions at √s(NN) = 200 GeV have been studied. The dominant contribution to such fluctuations is expected to come from correlated production of charged and neutral pions. We search for evidence of dynamical fluctuations of different physical origins. Observables constructed out of moments of multiplicities are used as measures of fluctuations. Mixed events and model calculations are used as base lines. Results are compared to the dynamical net-charge fluctuations measured in the same acceptance. A nonzero statistically significant signal of dynamical fluctuations …

E00-110 Experiment At Jefferson Lab Hall A: Deeply Virtual Compton Scattering Off The Proton At 6 Gev, M. Defurne, M. Amaryan, K. A. Aniol, M. Beaumel, H. Benaoum, P. Bertin, C. E. Hyde, P.E. Ulmer, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

We present final results on the photon electroproduction (^→e p → epγ) cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region from Jefferson Lab experiment E00-110. Results from an analysis of a subset of these data were published before, but the analysis has been improved, which is described here at length, together with details on the experimental setup. Furthermore, additional data have been analyzed, resulting in photon electroproduction cross sections at new kinematic settings for a total of 588 experimental bins. Results of the Q² and x_B dependencies of both …

Measurement Of Parity-Violating Asymmetry In Electron-Deuteron Inelastic Scattering, D. Wang, K. Pan, R. Subedi, Z. Ahmed, K. Allada, S. Golge, C. E. Hyde

Physics Faculty Publications

The parity-violating asymmetries between a longitudinally polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep-inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were published …

Precision Measurements Of Aⁿ1 In The Deep Inelastic Regime, D. S. Parno, D. Flay, M. Posik, M. Canan, C. Hyde, The Jefferson Lab Hall A Collaboration

Physics Faculty Publications

We have performed precision measurements of the double-spin virtual-photon asymmetry A₁ on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized ³He target. Our data cover a wide kinematic range 0.277 <= x <= 0.548 at an average Q² value of 3.078(GeV/c)², doubling the available high-precision neutron data in this xrange. We have combined our results with world data on proton targets to make a leading-order extraction of the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. Our data are consistent with …

Separated Response Functions In Exclusive, Forward Π± Electroproduction On Deuterium, G. M. Huber, H. P. Blok, A. Klein, L. M. Qin, K. Vansyoc, Jefferson Lab, Fπ Collaboration

Physics Faculty Publications

Background: Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, Q², and at different four-momentum transfer, t, can be used to probe QCD's transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in π^- and π⁺ electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form …

Spectroscopy Of Li-9 (Lambda) By Electroproduction, G. M. Urciuoli, D. Hayes, C. E. Hyde, H. F. Ibrahim, P.E. Ulmer, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

Background: In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei provides information on the details of the effective hyperon-nucleon interaction.

Purpose: To obtain a high-resolution binding-energy spectrum for the ⁹Be(e, e' K⁺)⁹_ΛLi reaction.

Method: Electroproduction of the hypernucleus ⁹_ΛLi has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a ⁹Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a ring imaging Cherenkov detector were …

Precise Determination Of The Deuteron Spin Structure At Low To Moderate Q² With Clas And Extraction Of The Neutron Contribution, The Clas Collaboration, N. Guler, S E. Kuhn, Y. Prok, K. P. Adhikari, D. Adikaram, M. J. Amaryan, L. El Fassi, C. E. Hyde, A. Klein, L. B. Weinstein, Z. W. Zhao

Physics Faculty Publications

We present the final results for the deuteron spin structure functions obtained from the full data set collected in 2000–2001 with Jefferson Lab's continuous electron beam accelerator facility (CEBAF) using the CEBAF large acceptance spectrometer (CLAS). Polarized electrons with energies of 1.6, 2.5, 4.2, and 5.8 GeV were scattered from deuteron (¹⁵ND₃ ) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double-spin asymmetry, the virtual photon absorption asymmetry A^d₁ and the polarized structure function g^d₁ were extracted over a wide kinematic range (0.05GeV² < Q2 < 5GeV² and 0.9 …

Measurement Of The Emc Effect In The Deuteron, K. A. Griffioen, J. Arrington, M. E. Christy, R. Ent, N. Kalantarians, C. E. Keppel, S E. Kuhn

Physics Faculty Publications

We determined the structure function ratio R^d_EMC=F^d₂/(Fⁿ₂+F^p₂) from recently published Fⁿ₂/F^d₂ data taken by the BONuS experiment using CLAS at Jefferson Lab. This ratio deviates from unity, with a slope dR^d_EMC/dx=−0.10 ± 0.05 in the range of Bjorken x from 0.35 to 0.7, for invariant mass W>1.4 GeV and Q²>1 GeV² . The observed EMC effect for these kinematics is consistent with conventional nuclear physics models that include off-shell corrections, as well as with empirical analyses …

Precision Measurement Of The Longitudinal Double-Spin Asymmetry For Inclusive Jet Production In Polarized Proton Collisions At √S= 200gev, L. Adamczyk, J.K. Adkins, G. Agakishiev, S. Bültmann, I. Koralt, Star Collaboration

Physics Faculty Publications

We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, A_LL, in polarized pp collisions at center-of-mass energy √s = 200 GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. The measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x > 0.05.

Cross Sections For The Exclusive Photon Electroproduction On The Proton And Generalized Parton Distributions, H. S. Jo, D. Adikaram, M. J. Amaryan, L. El Fassi, N. Guler, A. Klein, S E. Kuhn, Y. Prok, L. B. Weinstein, J. Zhang, Z. W. Zhao

Physics Faculty Publications

Unpolarized and beam-polarized fourfold cross sections (d⁴σ/dQ²dx_Bdtdϕ) for the ep → e'p'γ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 (Q²;x_B;t) bins over the widest phase space ever explored in the valence-quark region. Several models of generalized parton distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD H, expected to be the dominant contributor to these observables. Through a leading-twist …

Measurement Of Single And Double Spin Asymmetries In Semi-Inclusive Deep-Inelastic Scattering On Proton And Deuteron, Suman Bandhu Koirala

Physics Theses & Dissertations

The EG1-DVCS experiment with CLAS at Jefferson Lab collected semi-inclusive pion electro-production data on longitudinally polarized solid state NH₃ and ND₃ targets with longitudinally polarized electrons of approximately 6 GeV energy. Data on all three pion channels, π +, π– and π⁰, were collected simultaneously. The charged pions were identified by their time-of-flight information whereas the neutral pions were reconstructed from the invariant mass of two photons. The experiment covered a wide kinematic range: 1 GeV ² ≤ Q² ≤ 3.2 GeV², 0.12 ≤ xB ≤ 0.48, 0.0 GeV ≤ P_{h⊥ …}

Direct Measurements Of Two Photon Exchange On Lepton-Proton Elastic Scattering Using Simultaneous Electron-Positron Beams In Clas, Dasuni Kalhari Adikaram

Physics Theses & Dissertations

The electric (GE) and magnetic ( GM) form factors of the proton are fundamental observables which characterize its charge and magnetization distributions. There are two methods to measure the proton form factors: the Rosenbluth separation method and the polarization transfer technique. However, the ratio of the electric and magnetic form factors measured by those methods significantly disagree at momentum transfer Q² > 1 GeV². The most likely explanation of this discrepancy is the inclusion of two-photon exchange (TPE) amplitude contributions to the elastic electron-proton cross section which significantly changes the extraction of GE from the …

Narrow-Band Emission In Thomson Sources Operating In The High-Field Regime, Balša Terzić, Kirsten Deitrick, Alicia S. Hofler, Geoffrey A. Krafft

Physics Faculty Publications

We present a novel and quite general analysis of the interaction of a high-field chirped laser pulse and a relativistic electron, in which exquisite control of the spectral brilliance of the up-shifted Thomson-scattered photon is shown to be possible. Normally, when Thomson scattering occurs at high field strengths, there is ponderomotive line broadening in the scattered radiation. This effect makes the bandwidth too large for some applications and reduces the spectral brilliance. We show that such broadening can be corrected and eliminated by suitable frequency modulation of the incident laser pulse. Furthermore, we suggest a practical realization of this compensation …

Beam-Energy Dependence Of Charge Separation Along The Magnetic Field In Au + Au Collisions At Rhic, L. Adamczyk, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer, G. S. Averichev, A. Banerjee, D. R. Beavis, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, H. Bichsel, M. Zyzak, Et Al., Star Collaboration

Physics Faculty Publications

Local parity-odd domains are theorized to form inside a quark-gluon plasma which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge separation along the magnetic field axis via the chiral magnetic effect. The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this Letter, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with …

Polarized Light Ions And Spectator Nucleon Tagging At Eic, V. Guzey, D. Higinbotham, C. Hyde, P. Nadel-Turonski, K. Park, M. Sargsian, M. Strikman, C. Weiss

Physics Faculty Publications

An Electron-Ion Collider (EIC) with suitable forward detection capabilities would enable a unique experimental program of deep-inelastic scattering (DIS) from polarized light nuclei (deuterium ²H, helium ³He) with spectator nucleon tagging. Such measurements promise significant advances in several key areas of nuclear physics and QCD: (a) neutron spin structure, by using polarized deuterium and eliminating nuclear effects through on-shell extrapolation in the spectator proton momentum; (b) quark/gluon structure of the bound nucleon at x > 0.1 and the dynamical mechanisms acting on it, by measuring the spectator momentum dependence of nuclear structure functions; (c) coherent effects in QCD, by exploring shadowing …

J/Ѱ Polarization In P+P Collisions At √S = 200 Gev In Star, L. Adamczyk, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, S. Bültmann

Physics Faculty Publications

We report on a polarization measurement of inclusive J/Ѱ mesons in the di-electron decay channel at mid-rapidity at 2 < p_T < 6 GeV/c in p + p collisions at √s = 200 GeV. Data were taken with the STAR detector at RHIC. The J/Ѱ polarization measurement should help to distinguish between different models of the J/Ѱ production mechanism since they predict different p_T dependences of the J/Ѱ polarization. In this analysis, J/Ѱ is studied in the helicity frame. The polarization parameter λ_θ measured at RHIC becomes smaller towards high p_T, indicating more longitudinal J/Ѱ polarization as p_T increases. The result is compared with predictions of presently available models.

Dielectron Azimuthal Anisotrophy At Mid-Rapidity In Au+Au Collisions At √ˢᶰᶰ = 200 Gev, L. Adamczyk, J. K. Adkins, G. Agakishiev, S. Bültmann, I Koralt, Star Collaboration

Physics Faculty Publications

We report on the first measurement of the azimuthal anisotropy v₂ of dielectrons (e⁺e^- pairs) at mid-rapidity from √ˢᶰᶰ = 200 GeV Au + Au collisions with the STAR detector at the Relativistic Heavy Ion Collider (RHIC), presented as a function of transverse momentum p_T for different invariant-mass regions. In the mass region M_ee < 1.1 GeV/c² the dielectron v₂measurements are found to be consistent with expectations from π⁰, η, ω, and Φ decay contributions. In the mass region 1.1 < M_ee < 2.9 GeV/c², the measured dielectron v₂is consistent, within experimental …

Data Analysis Techniques, Differential Cross Sections, And Spin Density Matrix Elements For The Reaction ᵞp → Φp, K.P. Adhikari, D. Adikaram, M.J. Amaryan, A. Klein, S. Koirala, Clas Collaboration

Physics Faculty Publications

High-statistics measurements of differential cross sections and spin density matrix elements for the reaction ᵞp → ϕp have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies (√s) from 1.97 to 2.84 GeV, with an extensive coverage in the ϕ production angle. The high statistics of the data sample made it necessary to carefully account for the interplay between the ϕ natural lineshape and effects of the detector resolution, that are found to be comparable in magnitude. We study both the charged-(ϕ → K⁺ K^-) and neutral( ϕ → (K^O_SK …

Exclusive Πᵒ Electroproduction At W > 2 Gev With Clas, I. Bedlinskiy, K. P. Adhikari, L. El Fassi, A. Klein, S. E. Kuhn, Clas Collaboration

Physics Faculty Publications

Exclusive neutral-pion electroproduction (ep → e'p'π⁰ was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections d⁴σ/dtdQ²dx_BdΦ_π and structure functions σ_T+ ϵσ_L, σ_TT, and σ_LT as functions of t were obtained over a wide range of Q² and x_B. The data are compared with Regge and handbag theoretical calculations. Analyses in both frameworks find that a large dominance of transverse processes is necessary to explain the experimental results. For the Regge analysis it is found …

Event Plane Dependent Dihadron Correlations With Harmonic Vⁿ Subtraction In Au + Au Collisions At √ˢᴺᴺ = 200 Gev, H. Agakishiev, M. M. Aggarwal, Z. Ahammed, S. Bueltmann, D. Plyku, Star Collaboration

Physics Faculty Publications

STAR measurements of dihadron azimuthal correlations (ΔΦ) are reported in midcentral (20-60%) Au + Au collisions at √ˢᴺᴺ = 200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane, Φ_s = | Φ_t- Ψ_EP|. The elliptic (v₂), triangular (v₃), and quadratic (v₄) flow harmonic backgrounds are subtracted using the zero yield at minimum (ZYAM) method. It is found that a finite near-side (|ΔΦ| < π/2) long-range pseudorapidity correlation (ridge) is present in the in-plane direction (Φ_s ~ 0). The away-side (|ΔΦ| > π/2) correlation shows a modification from d+ Au data, varying with Φ_s. …

Measurement Of "Pretzelosity" Asymmetry Of Charged Pion Production In Semi-Inclusive Deep Inelastic Scattering On A Polarized ³He Target, Y. Zhang, X. Qian, K. Allada, C. Dutta, M. Canan, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

An experiment to measure single-spin asymmetries of semi-inclusive production of charged pions in deep-inelastic scattering on a transversely polarized ³He target was performed at Jefferson Laboratory in the kinematic region of 0.16 < x < 0.35 and 1.4 < Q² < 2.7 GeV². Pretzelosity asymmetries on ³He, which are expressed as the convolution of the h^┴_1T transverse-momentum-dependent distribution functions and the Collins fragmentation functions in the leading order, were measured for the first time. Under the effective polarization approximation, we extracted the corresponding neutron asymmetries from the measured ³He asymmetries and cross-section ratios between the proton and ³He. Our results show that …

J/Ψ Production At Low Pᵀ In Au + Au And Cu + Cu Collisions At √ˢᴺᴺ = 200 Gev With The Star Detector, L. Adamczyk, J. K. Adkins, G. Agakishiev, S. Bültmann, I. Koralt, Star Collaboration

Physics Faculty Publications

The J/ψ p_T spectrum and nuclear modification factor (R_AA) are reported for p_T < 5 GeV/c and |y| < 1 from 0% to 60% central Au + Au and Cu + Cu collisions at √ˢᴺᴺ = 200 GeV at STAR. A significant suppression of p_T - integrated J/ψ production is observed in central Au + Au events. The Cu + Cu data are consistent with no suppression, although the precision is limited by the available statistics. R_AA in Au + Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with p_T. The data are compared to high-p_T STAR results and previously published BNL Relativistic Heavy Ion Collider results. Comparing with model calculations, it is found that the invariant yields …

Single Spin Asymmetries In Charged Kaon Production From Semi-Inclusive Deep Inelastic Scattering On A Transversely Polarized He-3 Target, Y. X. Zhao, Y. Wang, K. Allada, K. Aniol, J. R. M. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, P. C. Bradshaw, M. Canan

Physics Faculty Publications

We report the first measurement of target single spin asymmetries of charged kaons produced in semi-inclusive deep inelastic scattering of electrons off a transversely polarized 3He target. Both the Collins and Sivers moments, which are related to the nucleon transversity and Sivers distributions, respectively, are extracted over the kinematic range of0.1 < x_bj < 0.4for K⁺ and K⁻ production. While the Collins and Sivers moments for K⁺ are consistent with zero within the experimental uncertainties, both moments for K⁻ favor negative values. The Sivers moments are compared to the theoretical prediction from a phenomenological fit to the world data. While …

Precision Measurement Of The Neutron Twist-3 Matrix Element D(2)(N): Probing Color Forces, M. Posik, D. Flay, D. S. Parrno, K. Allada, W. Armstrong, F. Benmokhtar, M. Canan, L. El Fassi, S. Golge, C. Hyde

Physics Faculty Publications

Double-spin asymmetries and absolute cross sections were measured at large Bjorken x (0.25 ≤ x ≤ 0.90), in both the deep-inelastic and resonance regions, by scattering longitudinally polarized electrons at beam energies of 4.7 and 5.9 GeV from a transversely and longitudinally polarized ³He target. In this dedicated experiment, the spin structure function g(2)(3He) was determined with precision at large x, and the neutron twist-3 matrix element d(2)(n) was measured at < Q²> of 3.21 and 4.32 GeV²/c², with an absolute precision of about 10^-5. Our results are found to be in agreement …