The rms-radius $R$ of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor $G_e(q^2)$ extrapolated to momentum transfer $q^2$=0, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies, and explore alternative parameterizations. The problem lies in the model dependence of the parameterized $G(q)$ needed for the extrapolation. This shape of $G(q
{"title":"Proton charge radius from electron scattering","authors":"I. Sick","doi":"10.3390/atoms6010002","DOIUrl":"https://doi.org/10.3390/atoms6010002","url":null,"abstract":"The rms-radius $R$ of the proton charge distribution is a fundamental quantity needed for precision physics. This radius, traditionally determined from elastic electron-proton scattering via the slope of the Sachs form factor $G_e(q^2)$ extrapolated to momentum transfer $q^2$=0, shows a large scatter. We discuss the approaches used to analyze the e-p data, partly redo these analyses in order to identify the sources of the discrepancies, and explore alternative parameterizations. The problem lies in the model dependence of the parameterized $G(q)$ needed for the extrapolation. This shape of $G(q<q_{min})$ is closely related to the shape of the charge density $rho (r)$ at large radii $r$, a quantity which is ignored in most analyses. When using our {em physics} knowledge about this large-$r$ density together with the information contained in the high-$q$ data, the model dependence of the extrapolation is reduced and different parameterizations of the pre-2010 data yield a consistent value for $R = 0.887 pm 0.012fm$. This value disagrees with the more precise value $0.8409 pm 0.0004 fm$ determined from the Lamb shift in muonic hydrogen.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85584104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report results of $v_1(y)$ and $dv_1/dy$ near mid-rapidity for $pi^{pm}$, $K^{pm}$, $K_s^0$, $p$, $overline{p}$, $Lambda$, $overline{Lambda}$ and $phi$ from Beam Energy Scan Au+Au collisions at $sqrt{s_{NN}} = $ 7.7 - 200 GeV using the STAR detector at RHIC. The $dv_{1}/dy$ of $pi^{pm}$, $K^{pm}$ and $K_s^0$ mesons remains negative over all beam energies. The $dv_1/dy$ of $p$ and $Lambda$ baryons shows a sign change around 10 - 15 GeV, while net baryons (net p and net $Lambda$) indicate a double sign change. The $dv_1/dy$ of $overline{p}$, $overline{Lambda}$ and $phi$ show a similar trend for $sqrt{s_{NN}}>$ 14.5 GeV. For the first time, $v_{1}$ measurements are used to test a quark coalescence hypothesis. Many measurements are found to be consistent with the particles being formed via coalescence of constituent quarks. The observed deviations from that consistency offer a new approach for probing the collision process at the quark level.
{"title":"Directed flow in Au+Au collisions from the RHIC Beam Energy Scan at the STAR experiment","authors":"S. Singha","doi":"10.22323/1.311.0004","DOIUrl":"https://doi.org/10.22323/1.311.0004","url":null,"abstract":"We report results of $v_1(y)$ and $dv_1/dy$ near mid-rapidity for $pi^{pm}$, $K^{pm}$, $K_s^0$, $p$, $overline{p}$, $Lambda$, $overline{Lambda}$ and $phi$ from Beam Energy Scan Au+Au collisions at $sqrt{s_{NN}} = $ 7.7 - 200 GeV using the STAR detector at RHIC. The $dv_{1}/dy$ of $pi^{pm}$, $K^{pm}$ and $K_s^0$ mesons remains negative over all beam energies. The $dv_1/dy$ of $p$ and $Lambda$ baryons shows a sign change around 10 - 15 GeV, while net baryons (net p and net $Lambda$) indicate a double sign change. The $dv_1/dy$ of $overline{p}$, $overline{Lambda}$ and $phi$ show a similar trend for $sqrt{s_{NN}}>$ 14.5 GeV. For the first time, $v_{1}$ measurements are used to test a quark coalescence hypothesis. Many measurements are found to be consistent with the particles being formed via coalescence of constituent quarks. The observed deviations from that consistency offer a new approach for probing the collision process at the quark level.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83382918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Measurement of femtoscopic correlations in heavy-ion collisions can provide information about spatial and temporal parameters of the particle emission region at kinetic freeze-out. In this work we present the measurement of two-pion and two-kaon femtoscopic correlations in 200 GeV Au+Au collisions at RHIC. The collision centrality and transverse momentum dependence of the three-dimensional radii, $R_{out}$, $R_{side}$ and $R_{long}$ is discussed.
{"title":"Two-pion and two-kaon femtoscopic correlations in Au+Au collisions at $sqrt{s_{NN}}$=200 GeV from STAR","authors":"G. Nigmatkulov","doi":"10.18502/ken.v3i1.1756","DOIUrl":"https://doi.org/10.18502/ken.v3i1.1756","url":null,"abstract":"Measurement of femtoscopic correlations in heavy-ion collisions can provide information about spatial and temporal parameters of the particle emission region at kinetic freeze-out. In this work we present the measurement of two-pion and two-kaon femtoscopic correlations in 200 GeV Au+Au collisions at RHIC. The collision centrality and transverse momentum dependence of the three-dimensional radii, $R_{out}$, $R_{side}$ and $R_{long}$ is discussed.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88654855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hybrid mesons consist of a quark-antiquark pair bound together by a gluonic field that is in an excited state. Measuring the spectrum of these states will provide valuable information on the gluonic degrees of freedom of QCD in the quark-confinement regime. A rich spectrum of hybrid meson states has been predicted, but only a few experiments have reported evidence of their existence. The GlueX experiment at Jefferson Lab is designed to search for and measure the spectrum of light-mass hybrid mesons, and it has began its physics run in Spring 2017. For the experiment, a 12 GeV electron beam incident on a diamond radiator is used to produce a linearly-polarized, coherent bremsstrahlung tagged-photon beam with a coherent peak at 9 GeV. The linearly-polarized photon beam is incident on a proton target located within the hermetic GlueX detector, which can detect many different final states to which the hybrid mesons are predicted to decay. Measurements with these initial data are discussed, including beam asymmetry measurements, the search for photoproduced $Xi$ baryons, and near-threshold charm production.
{"title":"Searching for Hybrid Mesons with GlueX","authors":"S. Dobbs","doi":"10.22323/1.310.0047","DOIUrl":"https://doi.org/10.22323/1.310.0047","url":null,"abstract":"Hybrid mesons consist of a quark-antiquark pair bound together by a gluonic field that is in an excited state. Measuring the spectrum of these states will provide valuable information on the gluonic degrees of freedom of QCD in the quark-confinement regime. \u0000A rich spectrum of hybrid meson states has been predicted, but only a few experiments have reported evidence of their existence. The GlueX experiment at Jefferson Lab is designed to search for and measure the spectrum of light-mass hybrid mesons, and it has began its physics run in Spring 2017. For the experiment, a 12 GeV electron beam incident on a diamond radiator is used to produce a linearly-polarized, coherent bremsstrahlung tagged-photon beam with a coherent peak at 9 GeV. The linearly-polarized photon beam is incident on a proton target located within the hermetic GlueX detector, which can detect many different final states to which the hybrid mesons are predicted to decay. Measurements with these initial data are discussed, including beam asymmetry measurements, the search for photoproduced $Xi$ baryons, and near-threshold charm production.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74849950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Precise measurements of the proton form factor ratio μpGEp/GMp from Rosenbluth separation measurements can be EM combined with Polarization based extractions to provide significant constraints on two-photon exchange contributions to the elastic e-p cross section. We present an overview of JLab experiment E05-017, the high-precision ’Super-Rosenbluth’ measurements of the proton form factor taken in Hall C of Jefferson Lab. We then examine what precision could be obtained for Super-Rosenbluth measurements using a low-intensity positron beam at Jefferson Lab.
{"title":"Super-Rosenbluth measurements with electrons and protons","authors":"M. Yurov, J. Arrington","doi":"10.1063/1.5040198","DOIUrl":"https://doi.org/10.1063/1.5040198","url":null,"abstract":"Precise measurements of the proton form factor ratio μpGEp/GMp from Rosenbluth separation measurements can be EM combined with Polarization based extractions to provide significant constraints on two-photon exchange contributions to the elastic e-p cross section. We present an overview of JLab experiment E05-017, the high-precision ’Super-Rosenbluth’ measurements of the proton form factor taken in Hall C of Jefferson Lab. We then examine what precision could be obtained for Super-Rosenbluth measurements using a low-intensity positron beam at Jefferson Lab.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82914508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-19DOI: 10.5506/APhysPolB.49.365
K. Jones, C. Thornsberry, J. Allen, A. Atencio, D. Bardayan, D. Blankstein, S. Burcher, A. B. Carter, K. Chipps, J. Cizewski, I. Cox, Z. Elledge, M. Febbraro, A. Fijałkowska, R. Grzywacz, M. Hall, T. King, A. Lepailleur, M. Madurga, S. Marley, P. O’Malley, S. Paulauskas, S. Pain, W. Peters, C. Reingold, K. Smith, S. Taylor, W. Tan, M. Vostinar, D. Walter
Transfer reactions have provided exciting opportunities to study the structure of exotic nuclei and are often used to inform studies relating to nucleosynthesis and applications. In order to benefit from these reactions and their application to rare ion beams (RIBs) it is necessary to develop the tools and techniques to perform and analyze the data from reactions performed in inverse kinematics, that is with targets of light nuclei and heavier beams. We are continuing to expand the transfer reaction toolbox in preparation for the next generation of facilities, such as the Facility for Rare Ion Beams (FRIB), which is scheduled for completion in 2022. An important step in this process is to perform the (d,n) reaction in inverse kinematics, with analyses that include Q-value spectra and differential cross sections. In this way, proton-transfer reactions can be placed on the same level as the more commonly used neutron-transfer reactions, such as (d,p), (9Be,8Be), and (13C,12C). Here we present an overview of the techniques used in (d,p) and (d,n), and some recent data from (d,n) reactions in inverse kinematics using stable beams of 12C and 16O.
{"title":"Development of the (d,n) proton-transfer reaction in inverse kinematics for structure studies","authors":"K. Jones, C. Thornsberry, J. Allen, A. Atencio, D. Bardayan, D. Blankstein, S. Burcher, A. B. Carter, K. Chipps, J. Cizewski, I. Cox, Z. Elledge, M. Febbraro, A. Fijałkowska, R. Grzywacz, M. Hall, T. King, A. Lepailleur, M. Madurga, S. Marley, P. O’Malley, S. Paulauskas, S. Pain, W. Peters, C. Reingold, K. Smith, S. Taylor, W. Tan, M. Vostinar, D. Walter","doi":"10.5506/APhysPolB.49.365","DOIUrl":"https://doi.org/10.5506/APhysPolB.49.365","url":null,"abstract":"Transfer reactions have provided exciting opportunities to study the structure of exotic nuclei and are often used to inform studies relating to nucleosynthesis and applications. In order to benefit from these reactions and their application to rare ion beams (RIBs) it is necessary to develop the tools and techniques to perform and analyze the data from reactions performed in inverse kinematics, that is with targets of light nuclei and heavier beams. We are continuing to expand the transfer reaction toolbox in preparation for the next generation of facilities, such as the Facility for Rare Ion Beams (FRIB), which is scheduled for completion in 2022. An important step in this process is to perform the (d,n) reaction in inverse kinematics, with analyses that include Q-value spectra and differential cross sections. In this way, proton-transfer reactions can be placed on the same level as the more commonly used neutron-transfer reactions, such as (d,p), (9Be,8Be), and (13C,12C). Here we present an overview of the techniques used in (d,p) and (d,n), and some recent data from (d,n) reactions in inverse kinematics using stable beams of 12C and 16O.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73926423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-13DOI: 10.5506/aphyspolbsupp.11.37
E. Grosse, A. Junghans
An increasing number of experimental data indicates the breaking of axial symmetry in many heavy nuclei already in the valley of stability: Multiple Coulomb excitation analysed in a rotation invariant way, gamma transition rates and energies in odd nuclei, mass predictions, the splitting of Giant Resonances (GR), the collective enhancement of nuclear level densities and Maxwellian averaged neutron capture cross sections. For the interpretation of these experimental observations the axial symmetry breaking shows up in nearly all heavy nuclei as predicted by Hartree-Fock-Bogoliubov (HFB) calculations [1] ; this indicates a nuclear Jahn-Teller effect. We show that nearly no parameters remain free to be adjusted by separate fitting to level density or giant resonance data, if advance information on nuclear deformations, radii etc. are taken from such calculations with the force parameters already fixed. The data analysis and interpretation have to include the quantum mechanical requirement of zero point oscillations and the distinction between static vs. dynamic symmetry breaking has to be regarded.
{"title":"Experimental signals for broken axial symmetry in excited heavy nuclei from the valley of stability","authors":"E. Grosse, A. Junghans","doi":"10.5506/aphyspolbsupp.11.37","DOIUrl":"https://doi.org/10.5506/aphyspolbsupp.11.37","url":null,"abstract":"An increasing number of experimental data indicates the breaking of axial symmetry in many heavy nuclei already in the valley of stability: Multiple Coulomb excitation analysed in a rotation invariant way, gamma transition rates and energies in odd nuclei, mass predictions, the splitting of Giant Resonances (GR), the collective enhancement of nuclear level densities and Maxwellian averaged neutron capture cross sections. For the interpretation of these experimental observations the axial symmetry breaking shows up in nearly all heavy nuclei as predicted by Hartree-Fock-Bogoliubov (HFB) calculations [1] ; this indicates a nuclear Jahn-Teller effect. We show that nearly no parameters remain free to be adjusted by separate fitting to level density or giant resonance data, if advance information on nuclear deformations, radii etc. are taken from such calculations with the force parameters already fixed. The data analysis and interpretation have to include the quantum mechanical requirement of zero point oscillations and the distinction between static vs. dynamic symmetry breaking has to be regarded.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75610411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-12-12DOI: 10.5506/APhysPolB.49.741
I. Anikin, N. Batzell, M. Boer, R. Boussarie, Vladimir M. Braun, Stanley J. Brodsky, A. Camsonne, W. Chang, L. Colaneri, S. Dobbs, A. Efremov, K. Gnanvo, O. Gryniuk, M. Guidal, V. Guzey, C. Hyde, Y. Ilieva, S. Joosten, Peter Kroll, K. Kumerički, Z. Meziani, D. Müller, K. Semenov-Tian-Shansky, S. Stepanyan, L. Szymanowski, V. Tadevosyan, O. Teryaev, M. Vanderhaeghen, E. Voutier, Jakub Wagner, Christian Weiss, Z. Zhao
Transverse momentum distributions and generalized parton distributions provide a comprehensive framework for the three-dimensional imaging of the nucleon and the nucleus experimentally using deeply virtual semi-exclusive and exclusive processes. The advent of combined high luminosity facilities and large acceptance detector capabilities enables experimental investigation of the partonic structure of hadrons with time-like virtual probes, in complement to the rich on-going space-like virtual probe program. The merits and benefits of the dilepton production channel for nuclear structure studies are discussed within the context of the International Workshop on Nucleon and Nuclear Structure through Dilepton Production taking place at the European Center for Theoretical Studies in Nuclear Physics and Related Areas (ECT$^{star}$) of Trento. Particularly, the double deeply virtual Compton scattering, the time-like Compton scattering, the deeply virtual meson production, and the Drell-Yan processes are reviewed and a strategy for high impact experimental measurements is proposed.
{"title":"Nucleon and nuclear structure through dilepton production","authors":"I. Anikin, N. Batzell, M. Boer, R. Boussarie, Vladimir M. Braun, Stanley J. Brodsky, A. Camsonne, W. Chang, L. Colaneri, S. Dobbs, A. Efremov, K. Gnanvo, O. Gryniuk, M. Guidal, V. Guzey, C. Hyde, Y. Ilieva, S. Joosten, Peter Kroll, K. Kumerički, Z. Meziani, D. Müller, K. Semenov-Tian-Shansky, S. Stepanyan, L. Szymanowski, V. Tadevosyan, O. Teryaev, M. Vanderhaeghen, E. Voutier, Jakub Wagner, Christian Weiss, Z. Zhao","doi":"10.5506/APhysPolB.49.741","DOIUrl":"https://doi.org/10.5506/APhysPolB.49.741","url":null,"abstract":"Transverse momentum distributions and generalized parton distributions provide a comprehensive framework for the three-dimensional imaging of the nucleon and the nucleus experimentally using deeply virtual semi-exclusive and exclusive processes. The advent of combined high luminosity facilities and large acceptance detector capabilities enables experimental investigation of the partonic structure of hadrons with time-like virtual probes, in complement to the rich on-going space-like virtual probe program. The merits and benefits of the dilepton production channel for nuclear structure studies are discussed within the context of the International Workshop on Nucleon and Nuclear Structure through Dilepton Production taking place at the European Center for Theoretical Studies in Nuclear Physics and Related Areas (ECT$^{star}$) of Trento. Particularly, the double deeply virtual Compton scattering, the time-like Compton scattering, the deeply virtual meson production, and the Drell-Yan processes are reviewed and a strategy for high impact experimental measurements is proposed.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80310159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The event-by-event fluctuations of identified particles in ultrarelativistic nucleus-nucleus collisions give information about the state of matter created in these collisions as well as the phase diagram of nuclear matter. In this proceedings, we present the latest results from ALICE on the centrality and pseudorapidity dependence of net-proton fluctuations, which are closely related to net-baryon fluctuations, as well as net-kaon and net-pion fluctuations. The effects of volume fluctuations and global baryon conservation on these observables are discussed. Furthermore, the correlated fluctuations between different particle species, quantified by the observable $nu_{dyn}$, are also shown as functions of multiplicity and collision energy and are compared with Monte Carlo models. These measurements are performed in Pb-Pb collisions at $sqrt{s_{mathrm{NN}}} = 2.76$ TeV using the novel Identity Method and take advantage of the excellent particle identification capabilities of ALICE.
{"title":"Measurements of the fluctuations of identified particles in ALICE at the LHC","authors":"A. Ohlson","doi":"10.22323/1.311.0031","DOIUrl":"https://doi.org/10.22323/1.311.0031","url":null,"abstract":"The event-by-event fluctuations of identified particles in ultrarelativistic nucleus-nucleus collisions give information about the state of matter created in these collisions as well as the phase diagram of nuclear matter. In this proceedings, we present the latest results from ALICE on the centrality and pseudorapidity dependence of net-proton fluctuations, which are closely related to net-baryon fluctuations, as well as net-kaon and net-pion fluctuations. The effects of volume fluctuations and global baryon conservation on these observables are discussed. Furthermore, the correlated fluctuations between different particle species, quantified by the observable $nu_{dyn}$, are also shown as functions of multiplicity and collision energy and are compared with Monte Carlo models. These measurements are performed in Pb-Pb collisions at $sqrt{s_{mathrm{NN}}} = 2.76$ TeV using the novel Identity Method and take advantage of the excellent particle identification capabilities of ALICE.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87315898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work is a pioneering study of backward-angle omega cross sections through the exclusive 1H(e,e'p)omega reaction using the missing mass reconstruction technique. The extracted cross sections are separated into the transverse (T), longitudinal (L), and LT, TT interference terms. The analyzed data were part of experiment E01-004 (Fpi-2), which used 2.6-5.2GeV electron beams and HMS+SOS spectrometers in Jefferson Lab Hall C. The primary objective was to detect coincidence pion in the forward-angle, where the backward-angle omega events were fortuitously detected. The experiment has central Q2 values of 1.60 and 2.45GeV2, at W=2.21GeV. There was significant coverage in phi and epsilon, which allowed separation of sigma_T,L,LT,TT. The data set has a unique u coverage of -u~0, which corresponds to -t>4GeV2. The separated sigma_T result suggest a flat ~1/Q^(1.33+/-1.21) dependence, whereas sigma_L seems to hold a stronger 1/Q^(9.43+/-6.28) dependence. The sigma_L/sigma_T ratio indicate sigma_T dominance at Q2=2.45 GeV2 at the ~90% confidence level. After translating the results into the -t space of the published CLAS data, our data show evidence of a backward-angle omega electroproduction peak at both Q2 settings. Previously, this phenomenon showing both forward and backward-angle peaks was only observed in the meson photoproduction data. Through comparison of our sigma_T data with the prediction of the Transition Distribution Amplitude (TDA) model, and signs of sigma_T dominance, promising indications of the applicability of the TDA factorization are demonstrated at a much lower Q2 value than its preferred range of Q2>10GeV2. These studies have opened a new means to study the transition of the nucleon wavefunction through backward-angle experimental observables.
{"title":"Exclusive Backward-Angle Omega Meson Electroproduction","authors":"Wenliang Li","doi":"10.2172/1408890","DOIUrl":"https://doi.org/10.2172/1408890","url":null,"abstract":"This work is a pioneering study of backward-angle omega cross sections through the exclusive 1H(e,e'p)omega reaction using the missing mass reconstruction technique. The extracted cross sections are separated into the transverse (T), longitudinal (L), and LT, TT interference terms. The analyzed data were part of experiment E01-004 (Fpi-2), which used 2.6-5.2GeV electron beams and HMS+SOS spectrometers in Jefferson Lab Hall C. The primary objective was to detect coincidence pion in the forward-angle, where the backward-angle omega events were fortuitously detected. The experiment has central Q2 values of 1.60 and 2.45GeV2, at W=2.21GeV. There was significant coverage in phi and epsilon, which allowed separation of sigma_T,L,LT,TT. The data set has a unique u coverage of -u~0, which corresponds to -t>4GeV2. \u0000The separated sigma_T result suggest a flat ~1/Q^(1.33+/-1.21) dependence, whereas sigma_L seems to hold a stronger 1/Q^(9.43+/-6.28) dependence. The sigma_L/sigma_T ratio indicate sigma_T dominance at Q2=2.45 GeV2 at the ~90% confidence level. After translating the results into the -t space of the published CLAS data, our data show evidence of a backward-angle omega electroproduction peak at both Q2 settings. Previously, this phenomenon showing both forward and backward-angle peaks was only observed in the meson photoproduction data. Through comparison of our sigma_T data with the prediction of the Transition Distribution Amplitude (TDA) model, and signs of sigma_T dominance, promising indications of the applicability of the TDA factorization are demonstrated at a much lower Q2 value than its preferred range of Q2>10GeV2. These studies have opened a new means to study the transition of the nucleon wavefunction through backward-angle experimental observables.","PeriodicalId":8464,"journal":{"name":"arXiv: Nuclear Experiment","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2017-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73239859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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