Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session CF: Mini-Symposium on Electromagnetic Form Factors - from the Nucleon to Nuclei II |
Hide Abstracts |
Chair: Toshimi Suda, RIKEN, Nishina Center, Japan Room: Kohala 3 |
Thursday, October 15, 2009 9:00AM - 9:15AM |
CF.00001: Photon-pion transition form factor and pion distribution amplitude Anatoly Radyushkin The pion distribution amplitude (DA) $\varphi_\pi (x)$ [1,2] is an important function accumulating information about momentum sharing between the quarks of the pion when the latter is in its valence $\bar q q$ configuration. It is an inherent element of perturbative QCD calculations of hard exclusive reactions involving the pion. A scenario is investigated in which the leading-twist pion DA $\varphi_\pi (x)$ is approximated by the pion decay constant $f_\pi$ for all essential values of the light-cone fraction $x$. A model for the light-front wave function $\Psi (x, k_\perp)$ is proposed that produces such a DA and has a rapidly decreasing (exponential for definiteness) dependence on the light-front energy combination $ k_\perp^2/x(1-x)$. It is shown that this model easily reproduces the fit of recent large-$Q^2$ {\sc BaBar} data [3] on the photon-pion transition form factor. Some aspects of scenario with flat pion distribution amplitude are discussed. \\[4pt] [1]~A.~V.~Radyushkin, JINR-P2-10717 (1977); English translation: arXiv:hep-ph/0410276.\\[0pt] [2] G.~P.~Lepage and S.~J.~Brodsky, Phys.\ Lett.\ B {\bf 87}, 359 (1979).\\[0pt] [3] B.~Aubert {\it et al.} [{\sc BaBar} Collaboration], arXiv:0905.4778 [hep-ex]. [Preview Abstract] |
Thursday, October 15, 2009 9:15AM - 9:30AM |
CF.00002: ABSTRACT WITHDRAWN |
Thursday, October 15, 2009 9:30AM - 9:45AM |
CF.00003: Nucleon strangeness form factors from $N_f=2+1$ clover fermion lattice QCD Takumi Doi, Mridupawan Deka, Shao-Jing Dong, Terrence Draper, Keh-Fei Liu, Devdatta Mankame, Nilmani Mathur, Thomas Streuer Recent experiments of parity-violating electron scattering (PVES) make it possible to pin down the strangeness electromagnetic form factors in the nucleon. In my talk, I will present a theoretical calculation of strangeness electric and magnetic form factors from a full QCD lattice simulation using $N_f=2+1$ clover fermion configurations generated by CP-PACS/JLQCD collaborations. I will discuss the methodology which significantly improves the signal for the disconnected insertion calculation. Our lattice results are consistent with experimental values, and our errors are an order of magnitude smaller. I also present preliminary results for the strangeness parton moments in the nucleon. \\[4pt] [1] T. Doi et al. ($\chi$QCD collaboration), arXiv:0903.3232 [hep-ph]. [Preview Abstract] |
Thursday, October 15, 2009 9:45AM - 10:00AM |
CF.00004: Strange quark contribution to the electromagnetic properties of the nucleon, Results of the Gzero experiment Fatiha Benmokhtar The G0 experiment at Jefferson Laboratory measured the parity violating asymmetry in the cross section for polarized electrons scattered at backward angles off liquid hydrogen and deuterium. Measurements were made at two momentum transfers: 0.23 and 0.62 (GeV/$c$)$^{2}$. Combined with forward angle measurements on a hydrogen target the contribution of strange quarks to the proton's charge and magnetization distributions can be determined. These measurements also allow the extraction of the isovector axial form factor as seen in electron scattering. Final results of the complete separation of the strange electric, strange magnetic and the isovector axial form factors are presented. A variety of recent theoretical predictions of these form factors are discussed. [Preview Abstract] |
Thursday, October 15, 2009 10:00AM - 10:15AM |
CF.00005: Measurement of the gp--$>$etaP reaction with Crystal Ball detector at the Mainz Microtron (MAMI-C) Igor Strakovsky, Sergey Prakhov, Yakov Azimov, William Briscoe, Bernd Krusche, Michael Ostrick The gp--$>$etaP reaction has been measured with the Crystal Ball multiphoton spectrometer and TAPS calorimeter in the energy range from the production threshold of 707 to 1400 MeV. Bremsstrahlung photons produced by the 1.5 GeV electron beam of the Mainz Microtron MAMI-C and tagged by the Glasgow photon spectrometer were used for the eta-meson production. The available statistics of 3.8 x 10$^6$ gp--$>$etaP--$>$3pi0P--$>$6gP events allowed to study in detail the reaction dynamics at our energies. The gp--$>$etaP differential cross sections were determined for the full range of the production angles by dividing the data in 120 energy intervals. The systematic uncertainties in the differential cross sections are at the order of 4{\%}. The data have been used to evaluate the etaP multipoles in the vicinity of several low-lying I = 1/2 baryon resonances. These data and the extracted multipoles are compared to previous determinations. [Preview Abstract] |
Thursday, October 15, 2009 10:15AM - 10:30AM |
CF.00006: ABSTRACT WITHDRAWN |
Thursday, October 15, 2009 10:30AM - 10:45AM |
CF.00007: Electron scattering for exotic nuclei Toshimi Suda One of burning issues of nuclear physics today is to understand the structures of short-lived nuclei, some of which, especially at near the drip lines, were discovered to have peculiar structures, such as skin or halo. Electron scattering which is the best probe for the study of atomic nuclei, has never been applied due to difficulties for target preparation; their short lifetime and low production rate. In order to overcome the difficulties, we have proposed a novel internal-target scheme, SCRIT (Self-Confining RI Target). This technique is based on the ``ion-trapping'' phenomenon known at electron storage rings, which is seriously harmful for the ring performances. SCRIT uses the phenomena positively to form the targets of exotic nuclei on the electron beam. The feasibility study of this scheme has been done using a prototype. The results of the study using stable $^{133}$Cs ions, which completely mimicked the usage of short-lived nuclei, show that the SCRIT scheme works, and a luminosity of higher than 10$^{26}$ /cm$^{2}$/s is achievable using only 10$^{6}$ ions, which is high enough for elastic scattering. A door to completely untouched fields in nuclear physics is now ready to open. An electron scattering facility in RIKEN RI Beam Factory is under construction. [Preview Abstract] |
Thursday, October 15, 2009 10:45AM - 11:00AM |
CF.00008: Development of a Recoil Ion Detector for Self-Confining RI Target (SCRIT) Kazuyoshi Kurita, Takashi Emoto, Kenichi Ishii, Sachiko Ito, Atsuhiro Kuwajima, Akira Noda, Toshiyuki Shirai, Toshimi Suda, Tadaaki Tamae, Hiromu Tongu, Masanori Wakasugi, Shuo Wang, Yasushige Yano SCRIT is a radioactive isotope target formed by an electrostatic trap in an electron storage ring.~~ We have recently proved that the principle of SCRIT can be applied to realize electron scattering experiments for unstable nuclei. We started an R{\&}D for a recoil ion detector by measuring the background rate inside an electron storage ring at Kaken Storage Ring (KSR) using micro channel plates. After several trial measurements, we came up to a solution to reduce 10MHz background to about 10kHz level. The background radiation which could not be reduced by applying repelling potential on fine meshes was found to be photons. Two sets of electrostatic mirrors were combined to guide the recoil ions to a low background environment. The current status of the recoil arm development will be reported. [Preview Abstract] |
Thursday, October 15, 2009 11:00AM - 11:15AM |
CF.00009: Electric quadrupole moment of the $^{33}$Al ground state K. Asahi, H. Ueno, D.L. Balabanski, J.M. Daugas, M. Depuydt, M. De Rydt, L. Gaudefroy, S. Grevy, Y. Hasama, Y. Ichikawa, D. Kameda, P. Morel, T. Nagatomo, L. Perrot, K. Shimada, Ch. Stoedel, J.C. Thomas, Y. Utsuno, W. Vanderheijden, N. Vermeulen, P. Vingerhoets, E. Yagi, K. Yoshida, A. Yoshimi, G. Neyens The ground-state $Q $moment of $^{33}$Al has been measured by applying the $\beta $-ray-detected nuclear magnetic resonance technique to spin-polarized $^{33}$Al fragments produced in the projectile fragmentation reaction. The obtained $Q $moment, $\vert Q_{exp}(^{33}$Al)\textit{$\vert $ }= 132(16) $e$mb, shows a significant deviation from the theoretical value predicted in the shell model calculation with the USD interaction. The deviation will be discussed in context of possible erosion of the $N $= 20 shell gap, by comparing the experimental $Q$ and theoretical predictions from the large scale shell model calculation and the particle-vibration coupling calculation. [Preview Abstract] |
Thursday, October 15, 2009 11:15AM - 11:30AM |
CF.00010: Deeply Virtual Compton Scattering on $^{4}$He with CLAS Hovanes Egiyan The introduction of the Generalized Parton Distribution (GPD) formalism transformed the landscape for probing the deep inelastic structure of hadrons. Deeply Virtual Compton Scattering (DVCS) provides us with the cleanest way of accessing these GPDs. Recent DVCS experiments have mainly focused on proton targets, demonstrating the applicability of the GPD formalism above momentum transfers of $Q^2=2$ GeV$^2$, while relatively less effort has been devoted to the understanding of nuclei in terms of GPDs. Studies of the DVCS process on nuclei can provide us with information on the quark-gluon structure of nuclei, as well as significantly improve our understanding of the modifications of nucleons in the nuclear medium. In this talk we will review the existing data on nuclear DVCS, and will describe the new experiment at Jefferson Lab to measure the Compton form-factor of the helium nucleus. [Preview Abstract] |
Thursday, October 15, 2009 11:30AM - 11:45AM |
CF.00011: A Precision Measurement of the Neutron Radius in $^{208}$Pb Dustin McNulty The upcoming $^{208}$Pb Radius Experiment (PREx) at Jefferson Lab's Hall A will determine the neutron radius R$_{\mathrm{n}}$ of Lead with $\pm1\%$ projected precision. The experiment will measure the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from $^{208}$Pb at an energy of 1.05 GeV and scattering angle of 5$^{\circ}$. In this way, the neutrons are isolated by the weak charge probe and thus allow for a model independent measurement of R$_{\mathrm{n}}$ analogous to the classic measurements of the proton radius R$_{\mathrm{p}}$. The theoretical corrections to the measured asymmetry are either small or well understood providing a clean extraction of the neutron form factor and charge density. In addition to being a fundamental test of nuclear theory, a precise measurement of R$_{\mathrm{n}}$ pins down the density dependence of the symmetry energy of neutron rich nuclear matter which has impacts on neutron star structure, heavy ion collisions, and atomic parity violation experiments. [Preview Abstract] |
Thursday, October 15, 2009 11:45AM - 12:00PM |
CF.00012: Nuclear Charge Radius of $^{8}$He P. Mueller, I.A. Sulai, K. Bailey, R.J. Holt, R.V.F. Janssens, Z.-T. Lu, T.P. O'Connor, A.C.C. Villari, J.A. Alcantara-Nunez, M. Dubois, C. Eleon, G. Gaubert, N. Lecesne, M.G. Saint-Laurent, J.C. Thomas, R. Alves-Conde, G.W.F. Drake, L.-B. Wang $^{8}$He is the most neutron-rich matter to have been synthesized on Earth: it consists of two protons and six neutrons, and remains stable for an average of 0.2 seconds. It is often viewed as a $^{4}$He core with four additional neutrons forming a neutron halo. Because of its intriguing properties, $^{8}$He has the potential to reveal new aspects of the fundamental forces among the constituent nucleons. We have recently succeeded in laser trapping and cooling this exotic helium isotope, and have performed precision laser spectroscopy on individual trapped atoms. Based on the frequency shifts of atomic transitions measured along the isotope chain $^{4}$He - $^{6}$He - $^{8}$He, the nuclear charge radius of $^{8}$He has been determined for the first time. Comparing this result with the values predicted by a number of nuclear structure calculations, we test theoretical understanding of the nuclear forces in the extremely neutron-rich environment. [Preview Abstract] |
Thursday, October 15, 2009 12:00PM - 12:15PM |
CF.00013: Experimental Probes of Two-Photon Exchange Michael Kohl The observed discrepancy in measurements of the proton electric to magnetic form factor ratio between the Rosenbluth and recoil polarization method has been interpreted as due to previously neglected effects of two-photon exchange (TPE). Calculations involving TPE in turn lead to changes in the angular dependence of elastic cross sections and double polarization observables. Evidence for TPE can be directly and most stringently tested by comparison of positron-proton and electron-proton elastic cross sections. Further, the imaginary part of the TPE amplitude gives rise to transverse single-spin asymmetries for polarized beam or target. The experimental efforts to address TPE will be reviewed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700