共查询到20条相似文献,搜索用时 15 毫秒
1.
The reactions π~-p→ηn and γp→ηp are investigated within a dynamical coupled-channels model of meson production reactions in the nucleon resonance region. The meson-baryon channels included are πN, ηN, π△, σN, and ρN. The direct η-photoproduction process is studied within a formalism based on a chiral constituent quark model approach, complemented with a one-gluon-exchange mechanism, to take into account the breakdown of the SU(6) O(3) symmetry. In the models search, the following known nucleon resonances are embodied: S_(11)(1535), S_(11)(1650), P_(11)(1440), P_(11)(1710), P_(13)(1720), D_(13)(1520), D_(13)(1700), D_(15)(1675), and F_(15)(1680). Data for the π~-p→ηn reaction from threshold up to a total center-of-mass energy of W ≈ 2 GeV are satisfactorily reproduced. For the photoproduction channel, two additional higher mass known resonances, P_(13)(1900) and F_(15)(2000), are also considered. However, reproducing the data for γp→ηp requires, within our approach, two new nucleon resonances, for which we extract mass and width. 相似文献
2.
We have developed an analytic continuation method for extracting parameters of nucleon resonances within a Hamiltonian formulation of meson-nucleon reactions. The method was tested for simple solvable models and then applied for our recent coupled channels model (πN, ηN, π△, ρN, and σN ) of the πN and γ~*N reactions. The resonance pole positions and their properties are studied for P_(33) and P_(11) channels. 相似文献
3.
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
4.
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
5.
AN Chun-Sheng 《中国物理C(英文版)》2009,33(12)
Here we employ the extended chiral constituent quark model to investigate the five-quark com-ponents in the N~*(1535) resonance. The axial charge of N~*(1535) and the electromagnetic transition γ~*N→N~*(1535) are also analyzed. The results show that there may be sizable strangeness component in N~*(1535). 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.
YUAN Chang-Zheng 《中国物理C(英文版)》2008,32(6):452-454
The cross sections for e+e-→π+π-J/ψ, π+π-ψ(2S), K+K-J/ψ, DD, D0D-π++c.c., D*D+c.c., and D*D-* are measured using data sample collected on or near the T(4S) resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c2, corresponding to the so called Y(4260), is observed in π+π-J/ψ final state. In addition, there is another cluster of events at around 4.05 GeV/c2. Two resonant structures are observed in the π+π-J/ψ(2S) invariant mass distribution, one at 4361±9±9 MeV/c2 with a width of 74±15±10 MeV/c2, and another at 4664±11±5 MeV/c2 with a width of 48±15±3 MeV/c2. The rich structures observed in all these final states indicate that our understanding of the vector charmonium states above the open charm threshold is still poor, let alone the other possible dynamics such as charmonium hybrids or final state re-scattering and so on. 相似文献
8.
YANG Hong-Xun 《中国物理C(英文版)》2009,33(12)
Based on 58 million J/ψ data collected with the BES Ⅱ detector at the BEPC, Partial Wave Analysis(PWA) is performed on J/ψ→pp(-)π~0. The new excited baryon N(2065) is confirmed. Clear signals for other N~* states are observed and the corresponding masses, widths and spin-parity are also measured. Processes such as J/ψ→pp(-)η,pp(-)η' are also studied and the branching ratios are measured. 相似文献
9.
10.
TAO Jun-Quan CHEN Guo-Ming YANG Min BIAN Jian-Guo LI Zu-Hao LIANG Song MENG Xiang-Wei TANG Zhi-Cheng WANG Jian WANG Jian WANG Xian-You WANG Zheng XIAO Hong XU Ming ZANG Jing-Jing ZHANG Zhen-Xia 《中国物理C(英文版)》2011,35(3)
In the LHC experiment,the neutral pions produced during jet fragmentation are the background sources for all physics channels with high-energy photons in their final state.In this paper,the application of the three-dimensional parametric formula for electromagnetic(EM)showers,which we developed in the Alpha Magnetic Spectrometer Ⅱ experiment,is presented to distinguish the unconverted photons from the neutral pions.With the constructed electromagnetic calorimeter(ECAL)in a GEANT4 simulation,the parametric formulae were validated and the unconverted γ/π0 discrimination was performed with the Toolkit for Multivariate Data Analysis(TMVA)package in ROOT for different transverse energies ranging from 15 GeV to75 GeV,which is the most sensitive region for light Higgs(with mass~120 GeV)searches with the channel H→γγ.With this discrimination method and the selected transverse energy region,we can reject π0 with the efficiency from~40%(65-75 GeV)to~90%(15-25 GeV)when keeping 90% γefficiency. 相似文献
11.
Recent results on nucleon resonance studies in π~+π~-p electro- production off protons with the CLAS detector are presented. The analysis of CLAS data allowed us to determine all essential contributing mechanisms, providing a credible separation between resonant and non-resonant parts of the cross sections in a wide kinematical area of invariant masses of the final hadronic system 1.3 < W < 1.8 GeV and photon virtualities 0.2 < Q~2 < 1.5 GeV~2. Electrocouplings of several excited proton states with masses less than 1.8 GeV were obtained for the first time from the analysis of π~+π~-p exclusive electroproduction channel. 相似文献
12.
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
13.
Motivated by the recent lattice QCD results indicating that the topological charge contribution to the flavor singlet axial vector current can be traded off by the constituent quark masses, we investigate the radiative decays of pseudoscalar (π,K, η, η′), vector (ρ,K*, ω, ?) and axial vector (A 1) mesons using a simple relativistic constituent quark model. For both simplicity and relativity, we take advantage of the distinguished features in the light-cone quantization method: (1) the Fock-state expansion of meson wavefunctions are not contaminated by the vacuum fluctuation, (2) the assignment of meson quantum numbers are given by the Melosh transformation. Except the well-known constituent quark masses of (u,d,s) quarks and the spin-averaged meson masses, the only parameter in the model is the gaussian parameter β which determines the broadness (or sharpness) of radial wavefunction. The computed decay widths and the transition form factors of ρ, ω → π(η)γ*,K* →Kγ* andA 1 → πγ* at 0≤Q 2≤5 GeV2 and π0(η) → γ*γ at 0≤Q 2≤3 GeV2 are in a remarkably good agreement with the experimental data and the result forA 1 + → π+ γ* transition is quite consistent with the experiments of pion scattering on a nucleus using Primakoff effect. This model is potentially useful in the cocktail analyses of the dilepton productions in proton-proton, proton-nucleus and nucleus-nucleus collisions at SPS energies and a little above. 相似文献
14.
We present a preliminary analysis of the photon beam asymmetry observable (Σ) from the pho-toproduction reaction channel γn→pπ~- in the invariant mass range 1.6-2.3 GeV. The measurement was obtained using the near-4π CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, USA, employing a linearly polarised photon beam with an energy range 1.1-2.3 GeV, incident on a liquid deuterium target. The measurement will provide new data to address the poorly established neutron excitation spectrum and will greatly expand the sparse world data-set both in energy and angle. 相似文献
15.
del Amo Sanchez P Lees JP Poireau V Prencipe E Tisserand V Garra Tico J Grauges E Martinelli M Milanes DA Palano A Pappagallo M Eigen G Stugu B Sun L Brown DN Chistiakova MV Jensen F Kerth LT Kolomensky YG Lynch G Osipenkov IL Koch H Schroeder T Asgeirsson DJ Hearty C Mattison TS McKenna JA Khan A Randle-Conde A Blinov VE Buzykaev AR Druzhinin VP Golubev VB Kravchenko EA Onuchin AP Serednyakov SI Skovpen YI Solodov EP Todyshev KY Yushkov AN Bondioli M Curry S Kirkby D Lankford AJ Mandelkern M 《Physical review letters》2011,107(2):021804
We search for single-photon decays of the Υ(1S) resonance, Υ → γ + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A?, or a pair of dark matter particles, χχ. Both A? and χ are assumed to have zero spin. We tag Υ(1S) decays with a dipion transition Υ(2S) → π?π?Υ(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m(A?) ≤ 9.2 GeV and m(χ) ≤ 4.5 GeV in the sample of 98 × 10? Υ(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states. 相似文献
16.
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
17.
A chiral quark-model approach is extended to the study of the KN scattering at low energies. The process of K~-p→Σ~0π~0 at P_K≤ 800 MeV/c (i.e. the center mass energy W ≤ 1.7 GeV) is investigated. The A(1405)S_(01) dominates the reactions over the energy region considered here. Around P_K≌400 MeV/c, the A(1520)D_(03) is responsible for a strong resonant peak in the cross section. Our analysis suggests that there exist configuration mixings within the Λ(1405)S_(01) and A(1670)S_(01) as admixtures of the [70,~21,1/2] and [70,~28, 1/2] configurations. The Λ(1405)S_(01) is dominated by [70,~21,1/2], and A(1670)S01 by [70,~28, 1/2]. The non-resonant background contributions, i.e. u-channel and b-channel, also play important roles in the explanation of the angular distributions due to amplitude interferences. 相似文献
18.
We investigate the properties of the η-nucleus interaction by postulating the N~* (1535) dominance for ηN system.Since the mass gap of N~* and N is very close to the η meson mass,there is the possibility of the level crossing between the N~*-h and η modes in finite density.We postulate the N~* (1535) resonance for the ηN system and consider quite distinct N~* properties in finite density which are predicted by two independent chiral models.We find that we can obtain clearer information on the in-medium N~* properties and also on the η-nucleus interaction through the formation of the η-mesic nuclei by (π,N) reactions under the appropriate experimental conditions,which can be performed at existing and/or forthcoming facilities like J-PARC. 相似文献
19.
20.
S. Uehara 《中国物理C(英文版)》2008,32(6):499-503
We have measured the cross section for π+π- production in two-photon collisions using a data sample with an integrated luminosity of 85.9 fb-1 collected with the Belle detector. The f0(980) resonance is observed as a peak in the energy spectrum of the cross section. We also report preliminary results for γγ→π0π0 with two-photon center-of-mass energies ranging from 0.6 to 4.0 GeV, based on a 95 fb-1 data sample. We find at least four resonant structures including a peak from f0(980). In addition, there is evidence for Xc0 production. We also make a preliminary discussion of the angular dependence and cross section ratio of γγ→π+π- and γγ→π0π0. 相似文献