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Old Dominion University

Physics Faculty Publications

2012

Articles 1 - 27 of 27

Full-Text Articles in Physical Sciences and Mathematics

Measurement Of The Neutron F2 Structure Function Via Spectator Tagging With Clas, N. Baillie, S. Tkachenko, J. Zhang, P. Bosted, S. Bültmann, M. E. Christy, H. Fenker, K. A. Griffioen, C. E. Keppel, S. E. Kuhn, K. P. Adhikari, D. Adikaram, M. J. Amaryan, H. Baghdasaryan, G. Dodge, N. Guler, C. E. Hyde, A. Klein, A. Klimenko, L. B. Weinstein Apr 2012

Measurement Of The Neutron F2 Structure Function Via Spectator Tagging With Clas, N. Baillie, S. Tkachenko, J. Zhang, P. Bosted, S. Bültmann, M. E. Christy, H. Fenker, K. A. Griffioen, C. E. Keppel, S. E. Kuhn, K. P. Adhikari, D. Adikaram, M. J. Amaryan, H. Baghdasaryan, G. Dodge, N. Guler, C. E. Hyde, A. Klein, A. Klimenko, L. B. Weinstein

Physics Faculty Publications

We report on the first measurement of the F2 structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲ 100MeV/c and their angles to ≳ 100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The Fn2 data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 < Q2 < 4.52 GeV2, with uncertainties from nuclear corrections estimated to be less …

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Photon Impact Factor And 𝑘T Factorization In The Next-To-Leading Order, Ian Balitsky Jan 2012

Photon Impact Factor And 𝑘T Factorization In The Next-To-Leading Order, Ian Balitsky

Physics Faculty Publications

The photon impact factor for the BFKL pomeron is calculated in the next-to-leading order (NLO) approximation using the operator expansion in Wilson lines. The result is represented as a NLO kT-factorization formula for the structure functions of small-x deep inelastic scattering.

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Design And Development Of Superconducting Parallel-Bar Deflecting/Crabbing Cavities, Subashini De Silva, Jean R. Delayen Jan 2012

Design And Development Of Superconducting Parallel-Bar Deflecting/Crabbing Cavities, Subashini De Silva, Jean R. Delayen

Physics Faculty Publications

The superconducting parallel-bar cavity is a deflecting/crabbing cavity with attractive properties that is being considered for a number of applications. We present the designs of a 499 MHz deflecting cavity developed for the Jefferson Lab 12 GeV Upgrade and a 400 MHz crabbing cavity for the LHC High Luminosity Upgrade. Prototypes of these two cavities are now under development and fabrication.

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Development Of Superconducting 500 Mhz Multi-Spoke Cavity For Electron Linacs, Dmitry Gorelov, Charles H. Boulware, Terry Grimm, Jean R. Delayen, C. S. Hopper, R. G. Olgave, Subashini U. De Silva Jan 2012

Development Of Superconducting 500 Mhz Multi-Spoke Cavity For Electron Linacs, Dmitry Gorelov, Charles H. Boulware, Terry Grimm, Jean R. Delayen, C. S. Hopper, R. G. Olgave, Subashini U. De Silva

Physics Faculty Publications

Multi-spoke cavities are well-known options for acceleration of heavy and light ions. A recently developed multi-spoke cavity for β=1 presents an attractive opportunity to use this cavity type for electron accelerators. One of the main attractive features of this cavity type is its compactness for relatively low frequency. A simplified design at 500 MHz allowed building of a multi-spoke cavity and cryomodule in a 2-year time frame with confidence and development of effective manufacturing techniques. It also constitutes an important step in proving the usefulness of this kind of cavity design for new applications in the electron machines. Niowave is …

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Rf Modeling Using Parallel Codes Ace3p For The 400-Mhz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity For The Lhc Hilumi Upgrade, Zenghai Li, Lixin Ge, Jean R. Delayen, Subashini U. De Silva Jan 2012

Rf Modeling Using Parallel Codes Ace3p For The 400-Mhz Parallel-Bar/Ridged-Waveguide Compact Crab Cavity For The Lhc Hilumi Upgrade, Zenghai Li, Lixin Ge, Jean R. Delayen, Subashini U. De Silva

Physics Faculty Publications

Schemes utilizing crab cavities to achieve head-on beam-beam collisions were proposed for the LHC HiLumi upgrade. These crabbing schemes require that the crab cavities be compact in order to fit into the tight spacing available in the existing LHC beamlines at the location where the crab cavities will be installed. Under the support of US LARP program, Old Dominion University and SLAC have joint efforts to develop a 400-MHz compact superconducting crab cavity to meet the HiLumi upgrade requirements. In this paper, we will present the RF modeling and analysis of a parallel-bar/ridged-waveguide shaped 400-MHz compact cavity design that can …

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High Power Test Of Rf Separator For 12 Gev Upgrade Of Cebaf At Jefferson Lab, S. Ahmed, M. Wissmann, J. Mammosser, M. Spata, C. Hovater, Geoffrey A. Krafft, Jean R. Delayen Jan 2012

High Power Test Of Rf Separator For 12 Gev Upgrade Of Cebaf At Jefferson Lab, S. Ahmed, M. Wissmann, J. Mammosser, M. Spata, C. Hovater, Geoffrey A. Krafft, Jean R. Delayen

Physics Faculty Publications

CEBAF at JLab is in the process of an energy upgrade from 6 GeV to 12 GeV. The existing setup of the RF separator cavities in the 5th pass will not be adequate enough to extract the highest energy (11 GeV) beam to any two existing halls (A, B or C) while simultaneously delivering to the new hall D in the case of the proposed 12 GeV upgrade of the machine. To restore this capability, several options including the extension of existing normal conducting (NC) and a potential 499 MHz TEM-type superconducting (SC) cavity design have been investigated using computer …

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Development Of Spoke Cavities For High Velocity Applications, C. S. Hopper, R. G. Olave, Jean R. Delayen Jan 2012

Development Of Spoke Cavities For High Velocity Applications, C. S. Hopper, R. G. Olave, Jean R. Delayen

Physics Faculty Publications

In response to recent interest in alternatives to TM-type cavities for low-frequency, high-velocity applications we have initiated a program for the development of multispoke superconducting cavities. We have completed the electromagnetic design for two-spoke cavities operating at 325, 352, 500, and 700 MHz with a design velocity of β0 = 0.82 or β0 = 1. We present the results of the optimization, higher order mode (HOM) analysis, multipacting analysis, and an initial analysis of multipole effects of the fundamental accelerating mode.

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Meic Design Progress, S. Ahmed, Y. Zhang, Y.S. Derbenev, D. Douglas, R. Ent, A. Hutton, A. Kimber, G.A. Krafft, R. Li, F. Lin, V. S. Morozov, P. Nadel-Turonski, E. W. Nissen, R. Rimmer, F.C. Pilat, T. Satogata, C. Tennant, Balsa Terzić, H. Wang, S. Wang, B. C. Yunn, D. P. Barber, Y. Filatov, C. Hyde, A. M. Kondratenko, S. L. Manikonda, P. N. Ostroumov, M. K. Sullivan Jan 2012

Meic Design Progress, S. Ahmed, Y. Zhang, Y.S. Derbenev, D. Douglas, R. Ent, A. Hutton, A. Kimber, G.A. Krafft, R. Li, F. Lin, V. S. Morozov, P. Nadel-Turonski, E. W. Nissen, R. Rimmer, F.C. Pilat, T. Satogata, C. Tennant, Balsa Terzić, H. Wang, S. Wang, B. C. Yunn, D. P. Barber, Y. Filatov, C. Hyde, A. M. Kondratenko, S. L. Manikonda, P. N. Ostroumov, M. K. Sullivan

Physics Faculty Publications

This paper will report the recent progress in the conceptual design of MEIC, a high luminosity medium energy polarized ring-ring electron-ion collider at Jefferson lab. The topics and achievements that will be covered are design of the ion large booster and the ERL-circulator-ring-based electron cooling facility, optimization of chromatic corrections and dynamic aperture studies, schemes and tracking simulations of lepton and ion polarization in the figure-8 collider ring, and the beam-beam and electron cooling simulations. A proposal of a test facility for the MEIC electron cooler will also be discussed.

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Beam Dynamics Studies For Transverse Electromagnetic Mode Type Rf Deflectors, Shahid Ahmed, Geoffrey A. Krafft, Kirsten Deitrick, Subashini U. De Silva, Jean R. Delayen, Mike Spata, Michael Tiefenback, Alicia Hofler, Kevin Beard Jan 2012

Beam Dynamics Studies For Transverse Electromagnetic Mode Type Rf Deflectors, Shahid Ahmed, Geoffrey A. Krafft, Kirsten Deitrick, Subashini U. De Silva, Jean R. Delayen, Mike Spata, Michael Tiefenback, Alicia Hofler, Kevin Beard

Physics Faculty Publications

We have performed three-dimensional simulations of beam dynamics for transverse electromagnetic mode (TEM) type rf deflectors: normal and superconducting. The compact size of these cavities as compared to the conventional TM110 type structures is more attractive particularly at low frequency. Highly concentrated electromagnetic fields between the parallel bars provide strong electrical stability to the beam for any mechanical disturbance. An array of six 2-cell normal conducting cavities or a single cell superconducting structure is enough to produce the required vertical displacement at the target point. Both the normal and superconducting structures show very small emittance dilution due to the …

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Observation Of A Narrow Structure In 1H(Ykso)X Via Interference With Φ-Meson Production, M. J. Amaryan, G. Gavalian, C. Nepali, M. V. Polyakov, W. J. Briscoe, G. E. Dodge, C. E. Hyde, F. Klein, V. Kuznetsov, I. Strakovsky, J. Zhang Jan 2012

Observation Of A Narrow Structure In 1H(Ykso)X Via Interference With Φ-Meson Production, M. J. Amaryan, G. Gavalian, C. Nepali, M. V. Polyakov, W. J. Briscoe, G. E. Dodge, C. E. Hyde, F. Klein, V. Kuznetsov, I. Strakovsky, J. Zhang

Physics Faculty Publications

We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian width σ = 6 MeV in the missing mass of KS in the reaction γ+p → pKSKL. The observed structure may be due to the interference between a strange (or antistrange) baryon resonance in the pKL system and the φ(KSKL) photoproduction leading to the same final state. The statistical significance of the observed excess of events estimated as the log-likelihood ratio of the resonant signal + background hypothesis and the φ-production-based background-only hypothesis …

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Comparison Of Forward And Backward Pp Pair Knockout In 3He(E,E'Pp)N, H. Baghdasaryan, L. B. Weinstein, J. M. Laget, K. P. Adhikari, M. Aghasyan, M. J. Amaryan, M. Anghinolfi, J. Ball, M. Battaglieri, A. S. Biselli, G. Dodge, C. E. Hyde, S. E. Kuhn, H. Seraydaryan Jan 2012

Comparison Of Forward And Backward Pp Pair Knockout In 3He(E,E'Pp)N, H. Baghdasaryan, L. B. Weinstein, J. M. Laget, K. P. Adhikari, M. Aghasyan, M. J. Amaryan, M. Anghinolfi, J. Ball, M. Battaglieri, A. S. Biselli, G. Dodge, C. E. Hyde, S. E. Kuhn, H. Seraydaryan

Physics Faculty Publications

Measuring nucleon-nucleon short range correlations (SRCs) has been a goal of the nuclear physics community for many years. They are an important part of the nuclear wave function, accounting for almost all of the high-momentum strength. They are closely related to the EMC effect. While their overall probability has been measured, measuring their momentum distributions is more difficult. In order to determine the best configuration for studying SRC momentum distributions, we measured the 3He(e,e'pp)n reaction, looking at events with high-momentum protons (pp > 0.35 GeV/c) and a low-momentum neutron (p …

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Evidence For The Onset Of Color Transparency In Ρ0 Electroproduction Off Nuclei, L. El Fassi, L. Zana, H. Hafidi, M. Holtrop, B. Mustapha, W. K. Brooks, H. Hakobyan, Z. Zheng, K. P. Adhikari, D. Adikaram, M. J. Amaryan, H. Baghdasaryan, S. Bültmann, G. E. Dodge, C. E. Hyde, A. Klein, S. E. Kuhn, M. Mayer, H. Seraydaryan, L. B. Weinstein Jan 2012

Evidence For The Onset Of Color Transparency In Ρ0 Electroproduction Off Nuclei, L. El Fassi, L. Zana, H. Hafidi, M. Holtrop, B. Mustapha, W. K. Brooks, H. Hakobyan, Z. Zheng, K. P. Adhikari, D. Adikaram, M. J. Amaryan, H. Baghdasaryan, S. Bültmann, G. E. Dodge, C. E. Hyde, A. Klein, S. E. Kuhn, M. Mayer, H. Seraydaryan, L. B. Weinstein

Physics Faculty Publications

We have measured the nuclear transparency of the incoherent diffractive A( e , e ′ ρ0 ) process in 12C and 56Fe targets relative to 2H using a 5 GeV electron beam. The nuclear transparency, the ratio of the produced ρ0 ʼs on a nucleus relative to deuterium, which is sensitive to ρA interaction, was studied as function of the coherence length (lc), a lifetime of the hadronic fluctuation of the virtual photon, and the four-momentum transfer squared (Q2). While the transparency for both 12C and 56Fe …

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Anomalous Centrality Evolution Of Two-Particle Angular Correlations From Au-Au Collisions At √ˢᴺᴺ = 62 And 200 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, D. Plyku, Star Collaboration Jan 2012

Anomalous Centrality Evolution Of Two-Particle Angular Correlations From Au-Au Collisions At √ˢᴺᴺ = 62 And 200 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, D. Plyku, Star Collaboration

Physics Faculty Publications

We present two-dimensional (2D) two-particle angular correlations measured with the STAR detector on relative pseudorapidity η and ϕ for charged particles from Au-Au collisions at √ˢᴺᴺ = 62 and 200 GeV with transverse momentum pt ≥ 0.15 GeV/c, │η│ ≤ 1, and 2 π in azimuth. Observed correlations include a same-side (relative azimuth <π/2) 2D peak, a closely related away-side azimuth dipole, and an azimuth quadrupole conventionally associated with elliptic flow. The same-side 2D peak and away-side dipole are explained by semihard parton scattering and fragmentation (minijets) in proton-proton and peripheral nucleus-nucleus collisions. Those structures follow N-N binary-collision scaling in Au-Au collisions until midcentrality, where a transition to a qualitatively different centrality trend occurs within one 10% centrality bin. Above the transition point the number of same-side and away-side correlated pairs increases rapidly relative to binary-collision scaling, the η width of the same-side 2D peak also increases rapidly (η elongation), and the ϕ width actually decreases significantly. Those centrality trends are in marked contrast with conventional expectations for jet quenching in a dense medium. The observed centrality trends are compared to perturbative QCD predictions computed in HIJING, which serve as a theoretical baseline, and to the expected trends for semihard parton scattering and fragmentation in a thermalized opaque medium predicted by theoretical calculations and phenomenological models. We are unable to reconcile a semihard parton scattering and fragmentation origin for the observed correlation structure and centrality trends with heavy-ion collision scenarios that invoke rapid parton thermalization. If the collision system turns out to be effectively opaque to few-GeV partons the present observations would be inconsistent with the minijet picture discussed here.

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Inclusive Charged Hadron Elliptic Flow In Au + Au Collisions At √ˢᴺᴺ = 7.7-39 Gev, L. Adamczyk, G. Agakishiev, S. Bültmann, I Koralt, D. Plyku, Star Collaboration Jan 2012

Inclusive Charged Hadron Elliptic Flow In Au + Au Collisions At √ˢᴺᴺ = 7.7-39 Gev, L. Adamczyk, G. Agakishiev, S. Bültmann, I Koralt, D. Plyku, Star Collaboration

Physics Faculty Publications

A systematic study is presented for centrality, transverse momentum pT, and pseudorapidity (η) dependence of the inclusive charged hadron elliptic flow v2 at midrapidity (|η| < 1.0) in Au + Au collisions at √ˢᴺᴺ = 7.7, 11.5, 19.6, 27, and 39 GeV. The results obtained with different methods, including correlations with the event plane reconstructed in a region separated by a large pseudorapidity gap and four-particle cumulants (v2{4}), are presented to investigate nonflow correlations and v2 fluctuations. We observe that the difference between v2{2} and v2{4} is smaller at the lower collision energies. Values of v2, scaled by the initial coordinate space eccentricity, v2/ϵ, as a function of pT are larger in more central collisions, suggesting stronger collective flow develops in more central collisions, similar to the results …

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Energy And System Size Dependence Of Two- And Four-Particle Ν2 Measurements In Heavy-Ion Collisions At √ˢᴺᴺ = 62.4 And 200 Gev And Their Implications On Flow Fluctuations And Nonflow, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, M. Bueltmann, Star Collaboration Jan 2012

Energy And System Size Dependence Of Two- And Four-Particle Ν2 Measurements In Heavy-Ion Collisions At √ˢᴺᴺ = 62.4 And 200 Gev And Their Implications On Flow Fluctuations And Nonflow, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, M. Bueltmann, Star Collaboration

Physics Faculty Publications

We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants ν2 ν2{2} and ν2{4}) for Au + Au and Cu + Cu collisions at center-of-mass energies √ˢᴺᴺ = 62.4 and 200 GeV. The difference between ν2{2}2 and ν2{4}2 is related to ν2fluctuations (σν2) and nonflow (δ2). We present an upper limit to σν2/ν2. Following the assumption that eccentricity fluctuations σε dominate ν2 fluctuations σν2/ν2 ≈ σε/ε we …

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Directed And Elliptic Flow Of Charged Particles In Cu + Cu Collisions At √ˢᶰᶰ =22.4 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, X. Zhu, Star Collaboration Jan 2012

Directed And Elliptic Flow Of Charged Particles In Cu + Cu Collisions At √ˢᶰᶰ =22.4 Gev, G. Agakishiev, M. M. Aggarwal, S. Bueltmann, I. Koralt, X. Zhu, Star Collaboration

Physics Faculty Publications

This paper reports results for directed flow v1 and elliptic flow v2 of charged particles in Cu + Cu collisions at √ˢᶰᶰ = 22.4 GeV at the Relativistic Heavy Ion Collider. The measurements are for the 0-60% most central collisions, using charged particles observed in the STAR detector. Our measurements extend to 22.4-GeV Cu + Cu collisions the prior observation that v1 is independent of the system size at 62.4 and 200 GeV and also extend the scaling of v1 with η/ybeam to this system. The measured v2pT in Cu + Cu …

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Di-Electron Spectrum At Mid-Rapidity In P+P Collisions At √S=200 Gev, L. Adamczyk, S. Bueltmann, I. Koralt, D. Plyku, Y. Zoulkarneeva, Star Collaboration Jan 2012

Di-Electron Spectrum At Mid-Rapidity In P+P Collisions At √S=200 Gev, L. Adamczyk, S. Bueltmann, I. Koralt, D. Plyku, Y. Zoulkarneeva, Star Collaboration

Physics Faculty Publications

We report on the mid-rapidity mass spectrum of di-electrons and cross sections of pseudoscalar and vector mesons via e+e- decays, from √s = 200 GeV p + p collisions, measured by the large-acceptance experiment STAR at the Relativistic Heavy Ion Collider. The ratio of the di-electron continuum to the combinatorial background is larger than 10% over the entire mass range. Simulations of di-electrons from light-meson decays and heavy-flavor decays (charmonium and open charm correlation) are found to describe the data. The extracted ω → e+e- invariant yields are consistent with previous measurements. The mid-rapidity …

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Virtual Compton Scattering And The Generalized Polarizabilities Of The Proton At Q2 = 0.92 And 1.76 Gev2, H. Fonvielle, G. Laveissiere, N. Degrande, C. Jutier, L. Todor, G. E. Dodge, C. E. Hyde, K. Mccormick, P. E. Ulmer, L. B. Weinstein Jan 2012

Virtual Compton Scattering And The Generalized Polarizabilities Of The Proton At Q2 = 0.92 And 1.76 Gev2, H. Fonvielle, G. Laveissiere, N. Degrande, C. Jutier, L. Todor, G. E. Dodge, C. E. Hyde, K. Mccormick, P. E. Ulmer, L. B. Weinstein

Physics Faculty Publications

Virtual Compton scattering (VCS) on the proton has been studied at the Jefferson Laboratory using the exclusive photon electroproduction reaction ep → epγ. This paper gives a detailed account of the analysis which has led to the determination of the structure functions PLL − PTT/ε and PLT and the electric and magnetic generalized polarizabilities (GPs) αE(Q2)and βM(Q2) at values of the four-momentum transfer squared Q2 = 0.92 and 1.76 GeV2. These data, together with the results of VCS experiments at lower momenta, help building a …

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System Size And Energy Dependence Of Near-Side Dihadron Correlations, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, S. Bueltmann, I. Koralt, D. Plyku Jan 2012

System Size And Energy Dependence Of Near-Side Dihadron Correlations, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, S. Bueltmann, I. Koralt, D. Plyku

Physics Faculty Publications

Two-particle azimuthal (Δφ) and pseudorapidity (Δη) correlations using a trigger particle with large transverse momentum (PT)in d+Au, Cu+Cu, and Au+Au collisions at √ sNN = 62.4 GeV and 200 GeV from the STAR experiment at the Relativistic Heavy Ion Collider are presented. The near-side correlation is separated into a jet-like component, narrow in both Δφ and Δη, and the ridge, narrow in Δφ but broad in Δη. Both components are studied as a function of collision centrality, and the jet-like correlation is studied as a function of the trigger and associated PT. The behavior of the …

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Superconducting Spoke Cavities For Electron And High-Velocity Proton Linacs, J. R. Delayen Jan 2012

Superconducting Spoke Cavities For Electron And High-Velocity Proton Linacs, J. R. Delayen

Physics Faculty Publications

Spoke resonantors are currently under development for many proton machines but these structures are also considered for high beta electron linacs as well. These structures compare well to traditional elliptical cavities.

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Measurement Of Exclusive Πº Electroproduction Structure Functions And Their Relationship To Transverse Generalized Parton Distributions, Clas Collaboration, K. P. Adhikari, M. J. Amaryan, R. P. Bennett, S. Koirala, S. E. Kuhn, M. Mayer, L. B. Weinstein, I. Bedlinsky, V. Kubarovsky Jan 2012

Measurement Of Exclusive Πº Electroproduction Structure Functions And Their Relationship To Transverse Generalized Parton Distributions, Clas Collaboration, K. P. Adhikari, M. J. Amaryan, R. P. Bennett, S. Koirala, S. E. Kuhn, M. Mayer, L. B. Weinstein, I. Bedlinsky, V. Kubarovsky

Physics Faculty Publications

Exclusive π0 electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in Q2, xB , t , and ϕπ , in the Q2 range from 1.0 to 4.6  GeV2 , −t up to 2  GeV2 , and xB from 0.1 to 0.58. Structure functions σT+ϵσL , σTT , and σLT were extracted as functions of t for each of 17 combinations of Q2 and xB . …

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Measurement Of The Generalized Form Factors Near Threshold Via ˠ*P→Nπ+ At High Q², Clas Collaboration, K. Park, R. W. Gothe, K. P. Adhikari, D. Adikaram, R. P. Bennett, C. E. Hyde, A. Klein, S. E. Kuhn, H. Seraydaryan Jan 2012

Measurement Of The Generalized Form Factors Near Threshold Via ˠ*P→Nπ+ At High Q², Clas Collaboration, K. Park, R. W. Gothe, K. P. Adhikari, D. Adikaram, R. P. Bennett, C. E. Hyde, A. Klein, S. E. Kuhn, H. Seraydaryan

Physics Faculty Publications

We report on the first measurement of the F2 structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲ 100  MeV/c and their angles to ≳ 100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The Fn2 data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 < Q2 2, with uncertainties from nuclear corrections estimated to be less …

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Characteristics And Fabrication Of A 499 Mhz Superconducting Deflecting Cavity For The Jefferson Lab 12 Gev Upgrade, Hyekyoung Park, Subashini U. De Silva, Jean R. Delayen Jan 2012

Characteristics And Fabrication Of A 499 Mhz Superconducting Deflecting Cavity For The Jefferson Lab 12 Gev Upgrade, Hyekyoung Park, Subashini U. De Silva, Jean R. Delayen

Physics Faculty Publications

A 499 MHz parallel bar superconducting deflecting cavity has been designed and optimized [1,2] for a possible implementation at the Jefferson Lab. Previously the mechanical analysis [3], mainly stress, was performed. Since then pressure sensitivity was studied further and the cavity parts were fabricated. The prototype cavity is not completed due to the renovation at Jefferson Lab which resulted in the temporary shutdown of the electron beam welding facility. This paper will present the analysis results and facts encountered during fabrication. The unique geometry of the cavity and its required mechanical strength present interesting manufacturing challenges.

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Engineering Of A Superconducting 400 Mhz Crabbing Cavity For The Lhc Hilumi Upgrade, Dmitry Gorelov, Terry Grimm, Subashini Uddika De Silva, Jean Roger Delayen Jan 2012

Engineering Of A Superconducting 400 Mhz Crabbing Cavity For The Lhc Hilumi Upgrade, Dmitry Gorelov, Terry Grimm, Subashini Uddika De Silva, Jean Roger Delayen

Physics Faculty Publications

The recently developed new simplified design for the 400 MHz LHC crabbing cavity presents attractive properties compared to conventional designs. The proposed approach can be equally compact in both transverse dimensions and allows horizontal as well as vertical deflection of the beam in the collider. The significant modification of the parallel-bar design with the bars merged to the side walls of the cavity gives improved properties, such as better mode separation and reduced surface fields [1]. A transverse deflecting voltage of 4.2 MV in a single cavity can be expected with the peak surface electric field lower then 45 MV/m …

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Multipacting Analysis Of High-Velocity Superconducting Spoke Resonators, C. S. Hopper, J. R. Delayen Jan 2012

Multipacting Analysis Of High-Velocity Superconducting Spoke Resonators, C. S. Hopper, J. R. Delayen

Physics Faculty Publications

Some of the advantages of superconducting spoke cavities are currently being investigated for the high-velocity regime. When determining a final, optimized geometry, one must consider the possible limiting effects multipacting could have on the cavity. We report on the results of analytical calculations and numerical simulations of multipacting electrons in superconducting spoke cavities and methods for reducing their impact.

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Ρ0 Photoproduction In Auau Collisions At √ Snn = 62.4 Gev Measured With The Star Detector, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, S. Bueltmann, I. Koralt, D. Plyku Jan 2012

Ρ0 Photoproduction In Auau Collisions At √ Snn = 62.4 Gev Measured With The Star Detector, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, S. Bueltmann, I. Koralt, D. Plyku

Physics Faculty Publications

Vector mesons may be photoproduced in relativistic heavy-ion collisions when a virtual photon emitted by one nucleus scatters from the other nucleus, emerging as a vector meson. The STAR Collaboration has previously presented measurements of coherent ρ0 photoproduction at center of mass energies of 130 GeV and 200 GeV in AuAu collisions. Here, we present a measurement of the cross section at 62.4 GeV; we find that the cross section for coherent ρ0 photoproduction with nuclear breakup is 10.5 ± 1.5 ± 1.6mb at 62.4 GeV. The cross-section ratio between 200 GeV and 62.4 GeV is 4.4 ± 0.6, …

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Design Of Electron And Ion Crabbing Cavities For An Electron-Ion Collider, A. Castilla, Jean R. Delayen, Geoffrey A. Krafft Jan 2012

Design Of Electron And Ion Crabbing Cavities For An Electron-Ion Collider, A. Castilla, Jean R. Delayen, Geoffrey A. Krafft

Physics Faculty Publications

Beyond the 12 GeV upgrade at the Jefferson Lab a Medium Energy Electron-Ion Collider (MEIC) is being considered. In order to achieve the desired high luminosities at the Interaction Points (IP), the use of crabbing cavities is under study. In this work, we will present up to date designs of superconducting cavities, considered for crabbing both ion and electron bunches. A discussion of properties such as peak surface fields and Higher Order Modes (HOMs) separation will be presented.

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