共查询到20条相似文献,搜索用时 46 毫秒
1.
The nucleon excitation spectrum remains poorly known, with the masses, widths, EM couplings and even existence of many states not well established. A program of experiments using meson photoproduction off the nucleon is being carried out to improve this situation. A new large acceptance recoil polarimeter has been developed by the Edinburgh group for use in such reactions with the Crystal Ball at MAMI. This work summarizes the procedure used to measure recoil polarization with the new device and presents some preliminary results for the double polarization observable C_x in the reaction γp→pπ~0, compared to the current partial wave analysis. 相似文献
2.
U.Thoma 《中国物理C(英文版)》2009,33(12)
Multi-meson final states such as γp→pπ~0π~0 and γp → pπ~0η have been investigated with the Crystal-Barrel/TAPS experiment at ELSA. Baryon cascades via △π and △η and also via higher mass baryon resonances are clearly observed. Based on this data and on data from other reactions a partial wave analysis has been performed from which partial decay widths of various N~* and △~* states into the different pπ~0π~0 and pπ~0η decay channels have been determined, leading partly to unexpected results. In addition, polarisation observables have been investigated. The beam asymmetry Σ has been determined for both reactions and double polarisation data using a longitudinally polarised target and a circularly or linearly polarised photon beam has been taken. Given the angular coverage of the Crystal-Barrel/TAPS experiment this data covers almost the full angular range and phase space. This data will provide new and important information for the partial wave analyses and bring us one step closer towards a complete experiment. 相似文献
3.
F.Miyahara H.Fukasawa R.Hashimoto T.Ishikawa M.Itoh T.Iwata H.Kanda J.Kasagi H.Kato T.Kinoshita K.Maeda M.Matsuzawa T.Michigami K.Motiduki K.Murakami T.Nakabayashi K.Nawa T.Nomura K.Okamura H.Okamura H.Okuyama Y.Onodera Y.Saito T.Sasaki H.Shirnizu T.Shishido S.Suzuki K.Suzuki Y.Tajima S.Takita T.Takahashi H.Ueno S.Yamaguchi H.Yamazaki H.Y.Yoshida 《原子核物理评论》2009,26(Z1)
Differential and total cross sections of the γp→π~0 p and the γp→π~0 pn reaction were measured for photon energies between 640 and 1 150 MeV.The data have been compared with SAID and MAID model calculations.π~0 photoproduction on the deuteron shows a strong suppression of the 2nd resonance which is clearly seen in the γp→π~0 p reaction. 相似文献
4.
P. Bonamy P. Borgeaud M. Crozon J.P. Guillaud O. Guisan P. Le Du P. Sonderegger J.K. Bienlein S. Mango L. Paul H. Dinter 《Nuclear Physics B》1973,52(2):392-402
Measurements of the polarization parameter of the reactions π?p → π0n and π?p → ηn at 4.90 and 7.85 GeV/c and for a squared four-momentum transfer ?t ranging from 0.1 to 2.0 (GeV/c)2 have been achieved by using a butanol polarized proton target and detecting only the two γ's from the neutral meson decay. The background due to events involving bound protons has been separately measured and subtracted out. A large positive polarization has been found for the reaction π?p → π0n. It is consistent with other pion-nucleon scattering data connected by isospin conservation. The polarization for the reaction π?p → ηn is not significantly different from zero within the large experimental errors. 相似文献
5.
LI Yong-Jiang XU Wang W.M.Snow CAI Xiao-Lu FAN Gong-Tao FAN Guang-Wei LUO Wen PAN Qiang-Yan XU Ben-Ji YANG Li-Feng YAN Zhe 《中国物理C(英文版)》2010,34(9)
The measurement of parity-violating(PV)observables in few-nucleon system can shed light on our current understanding of the week interaction between nucleons.Theoretical models describe the nucleonnucleon weak interaction at low energies use a series of undetermined parameters.Two parity violating measurements have been considered: the capture of polarized slow neutrons on hydrogen((n)+p→d+γ)at Los Alamos National Laboratory for first phase and Oka Ridge National Laboratory for second phase and the helicity dependence of the deuteron photodisintegration cross section using circularly polarized photons((γ)+d→n+p*)at Shanghai Institute of Applied Physics.The goal of both experiments is to constraint the weak meson-nucleon couplings to a precision of 1 × 10-8.The introduction of both experiments is presented. 相似文献
6.
HAN Yun-cheng N.Chiga Y.Fujii K.Futatsukawa O.Hashimoto K.Hirose T.Ishikawa H.Kanda M.Kaneta D.Kawama Konno MA Yue K.Maeda T.Maruta N.Maruyama A.Matsumura Y.Miyagi K.Miwa S.N.Nakamura A.Sasaki H.Shimizu K.Shirotori K.Suzuki T.Tamae H.Tamura K.Tsukada WANG Tie-shan H.Yarnazaki 《原子核物理评论》2009,26(Z1)
The reactions γd→π~- pp and γd→npπ~+π~- have been studied in an energy range from 0.8 to 1.1 GeV at the tagged photon facility of Laboratory of Nuclear Science,T ohoku University.Charged pions and protons in the final state were measured by using the Neutral Kaon Spectrometer (NKS2).The analysis of the γd→π~- pp was mainly used to check the acceptance of the NKS2 and to calibrate the tagged photon energy.The photoproduction of the Δ~(++)Δ~- was identified in the γd→npπ~+π~- reaction.Since the data analyses are still in progress,we issue an interim report and preliminary results. 相似文献
7.
利用SLEGS开展夸克和胶子层次上的核物理研究 总被引:1,自引:1,他引:0
通过对国际上中能核物理的发展,特别是前沿领域中的现状的回顾,阐述了利用在上海原子核所计划建造的第三代同步辐射加速器(SSRF)上建立新一代的激光 电子康普顿背散射γ射线源(SLEGS)从事夸克和胶子层次上的中能核物理研究的科学目标及研究内容. The proposed SLEGS (Shanghai Laser Electron backscattering Gamma Source) will be a circular and linear polarization, new generation, high quality γ ray source with Eγ=0.2-0.87 GeV. The major scientific focus of nuclear physics research at SLEGS will be investigations of the microscopic quark gluon aspects of nucleons , nucleon resonance states and nuclei to test and develop non perturbative QCD. Using polarized photon induced reactions on unpolarized and polarized nucleon target such as γN→γ N, ... 相似文献
8.
Hwang SH Hicks K Ahn JK Nakano T Ahn DS Chang WC Chen JY Daté S Ejiri H Fujimura H Fujiwara M Fukui S Gohn W Hotta T Imai K Ishikawa T Joo K Kato Y Kohri H Kon Y Lee HS Maeda Y Miyabe M Mibe T Morino Y Muramatsu N Nakatsugawa Y Niiyama M Noumi H Oh Y Ohashi Y Ohta T Oka M Parker J Rangacharyulu C Ryu SY Sawada T Sugaya Y Sumihama M Tsunemi T Uchida M Ungaro M Yosoi M;LEPS Collaboration 《Physical review letters》2012,108(9):092001
The exclusive reaction γp→K(+)π(-)Σ(+) was measured for the first time using linearly polarized photons at beam energies from 1.85 to 2.96 GeV. Angular distributions in the rest frame of the K(+)π(-) system were fitted to extract spin-density matrix elements of the K(*0) decay. The measured parity spin asymmetry shows that natural-parity exchange is dominant in this reaction. This result clearly indicates the need for t-channel exchange of the κ(800) scalar meson. 相似文献
9.
10.
K. -H. Mütter 《Zeitschrift für Physik A Hadrons and Nuclei》1969,228(2):188-192
TheNN→NN andγN→πN differential cross sections for polarized targets are discussed in terms of invariant functions. In former fits of high energy experimental data certain of these invariant functions came out to be small. Based on these fits thepn→np,p¯p→ n¯n, γp→ nπ + andγn→ pπ ? differential cross sections are predicted to be independent of the target polarization. 相似文献
11.
P. Feller M. Fukushima N. Horikawa R. Kajikawa K. Mori T. Nakanishi T. Ohshima C.O. Pak M. Saito S. Suzuki Y. Tarui T. Yamaki T. Matsuda K. Mizushima N. Tokuda 《Physics letters. [Part B]》1975,55(2):241-244
The polarized target asymmetry in the reaction γp→π°p has been measured at c.m. angles around 100° for photon energies between 0.4 and 1.0 GeV by detecting both the recoil proton and the π°. The result is compared with recent analyses. 相似文献
12.
Capture γ-ray circular polarization measurements on the Mn(n, γ), Ni(n, γ), Ga(n, γ) and W(n, γ) reactions with polarized neutrons resulted in unambiguous spin assignments for 20 levels, 10 of which confirmed previous assignments. For another 20 levels the number of possible spin values has been reduced. 相似文献
13.
V.A. Getman V.G. Gorbenko A.Ya. Derkach Yu.V. Zhebrovskij I.M. Karnaukhov L.Ya. Kolesnikov A.A. Lukhanin A.L. Rubashkin P.V. Sorokin E.A. Sporov V.M. Sanin Yu.N. Telegin S.V. Shalatskij V.F. Grushin 《Nuclear Physics B》1981,188(3):397-413
The method is described of measuring the polarization observables Σ, P and T for the reaction γp → nπ+ in a double polarization experiment (polarized target + polarized beam). The measured angular distribution of these observables are presented for the photon energy range 280–420 MeV at c.m. pion emission angles between 30° and 150°. The obtained experimental data are included in the energy-independent multipole analysis of the reactions γp → Nπ. 相似文献
14.
The state of polarization of the recoil deuteron in γ+d → π0+d on unpolarized and target polarized deuterons is analyzed in detail. A new set of statistical tensors is introduced to describe non-oriented systems, such as the recoil deuteron in γ+d → π0+d, and their relationships to the vector and tensor polarization parameters are established. The new statistical tensors reduce, in the case of oriented systems, to Fano's statistical tensors. Numerical results are computed using two different deuteron models for polarized photon asymmetry, polarized target asymmetry and the vector and tensor polarizations of the recoil deuteron, and these are presented at various c.m. pion production angles at different energies in the region of the first π-N resonance. The study of these parameters is suggested as a promising source of information on isoscalar pion photoproduction amplitudes. 相似文献
15.
Prospects of measuring polarized photons emitted from a quark–gluon plasma (QGP) are discussed. In particular, the detection of a possible quark spin polarization in a QGP using circularly polarized photons emitted from the plasma is studied. Photons leave the QGP without further interaction and thus provide a primary probe for quark polarization within the QGP. We find that photon polarization cannot solely arise due to a possible QGP momentum space anisotropy, but may be enhanced due to it. In particular, for oblate momentum distributions and high photon energies, quark polarization is efficiently transfered to photon polarization. The role of competing sources of polarized photons in heavy-ion collisions is discussed. 相似文献
16.
We show that, according to QCD, the direct Compton process γq→qg in polarized photoproduction leads to strongly polarized gluon jets. We also show that this process is expected to dominate in the reaction γp→π+ + opposite side jet + X. The study of the opposite side jet will give direct evidence for the spin of the gluon. 相似文献
17.
The (e, e'γ) coincidence cross section is expressed in terms of the nuclear polarizabilities as a generalization of the standard (γ, γ') formalism for polarized photons. This formalism is well suited to determine nuclear spins in a model-independent way. Due to the presence of virtual photons of longitudinal and transverse polarization and variable momentum transfer, electroexcitation gives more complete information than scattering of real photons and allows one to study the polarizabilities as function of excitation energy and momentum transfer. 相似文献
18.
Zegers RG Sumihama M Ahn DS Ahn JK Akimune H Asano Y Chang WC Daté S Ejiri H Fujimura H Fujiwara M Hicks K Hotta T Imai K Ishikawa T Iwata T Kawai H Kim ZY Kino K Kohri H Kumagai N Makino S Matsumura T Matsuoka N Mibe T Miwa K Miyabe M Miyachi Y Morita M Muramatsu N Nakano T Niiyama M Nomachi M Ohashi Y Ooba T Ohkuma H Oshuev DS Rangacharyulu C Sakaguchi A Sasaki T Shagin PM Shiino Y Shimizu H Sugaya Y Toyokawa H Wakai A Wang CW Wang SC Yonehara K Yorita T Yoshimura M Yosoi M 《Physical review letters》2003,91(9):092001
Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6相似文献
19.
20.
ZOU Bing-Song 《中国物理C(英文版)》2009,33(12)
Complementary to the conventional experimental studies on N~* from πN and γ(~*)N reactions, the e~+e~-, pp and pp collisions can give novel insights into these N~* resonances. While the e~+e~- collisions through production and decay of vector charmonium ψ provide a nice isospin filter for a simultaneously study of N~*, △~*, Λ~*, ∑* and Ξ~*, the pp collisions should be the best place for producing those △~(*++) with large coupling to p+p though pp→n△~(*++) reaction, and the pp(-) collisions should be the best place for looking for those N~* with large coupling to σN. 相似文献