共查询到20条相似文献,搜索用时 15 毫秒
1.
We study J/ψ inclusive production in the decays of P-wave bottomonium χbJ(1P,2P) for J=0,1,2. Within the framework of the non-relativistic QCD(NRQCD) factorization method we calculate the contri-butions coming from four relevant processes including one color-singlet process and three color-octet ones,which are b(3PJ,1) → c(3S1,8) + c +,b(3S1,8) → c(3S1,1) + g + g,b(3S1,8) → c(3S1,1) + c + and b(3S1,8) → c(3S1,8) +g. Our calculation shows that the color-octet processes,especially the gluon fragmen-tation one,contribute the most in the decays of χb0 and χb1. However,the J/ψ production in the χb2 decay is dominated by the color-singlet process. Furthermore,the gluon fragmentation process gives a δ function in the energy fraction distribution of J/ψ,which can be considered to be another characteristic for its identification. From our estimation the branching ratio for these processes is about 10-4-10-5,which indicates that J/ψ inclusive production is detectable at B-factories. Studying these processes would help us to gain a deeper understanding of the color-octet mechanism. 相似文献
2.
平荣刚 《中国物理C(英文版)》2014,(8):1-6
An exclusive event generator is designed for e+e- scan experiments, including initial state radiation effects up to the second order correction. The generator is coded within the framework of BesEvtGen. There are seventy hadronic decay modes available, with effective center-of-mass energy coverage from the two pion mass threshold up to about 6 GeV. The accuracy achieved for the initial state radiation correction reaches the level achieved by the KKMC generator. The uncertainty associated with the calculation of the correction factor to the initial state radiation is dominated by the measurements of the energy-dependent Born cross section. 相似文献
3.
Applying an effective Lagrangian method and an on-shell scheme, we analyze the electroweak corrections to the rare decay b→, s+γ from some special two loop diagrams in which a closed heavy fermion loop is attached to the virtual charged gauge bosons or Higgs. At the decoupling limit where the virtual fermions in the inner loop are much heavier than the electroweak scale, we verify the final results satisfying the decoupling theorem explicitly when the interactions among Higgs and heavy fermions do not contain the nondecoupling couplings. Adopting the universal assumptions on the relevant couplings and mass spectrum of new physics, we find that the relative corrections from those two loop diagrams to the SM theoretical prediction on the branching ratio of B → Xsγ can reach 5% as the energy scale of new physics ANp=200 GeV. 相似文献
4.
Andreas Thomas 《中国物理 C》2009,33(12):1120-1126
The upgraded MAMI C accelerator is delivering electrons with an energy of 1558 MeV routinely. The A2 collaboration is doing experiments with energy marked polarised real photons produced via "Bremsstrahlung". Recent results from the GDH-experiment using a longitudinal polarised frozen spin target in combination with the DAPHNE detector and from the Crystal Ball experiment at MAMI are presented. 相似文献
5.
We discuss model-independent constraints on spin observables in exclusive and inclusive reactions, with special attention to the case of photoproduction. 相似文献
6.
We present the results of a study of the exclusive reactions π+ 4He → π− 4p (double charge exchange, DCE) and π+ 4He → π+ π− 3pn (one-pion production). The experiment was performed with the Oxford/RHEL helium bubble chamber irradiated with a 1.7 GeV/c π+ beam. A general review of DCE models is presented and experimental results at other energies are discussed in the light of these models. None of the existing theoretical models is compatible with out data at 1.7 GeV/c. We propose a new mechanism for DCE, involving three nucleons, which reproduces the integrated as well as the differential cross sections. Some consequences for other models are also discussed. 相似文献
7.
T Madhusoodhanan Samit Mandal MP Sathyavathiamma Ramani NG Puttaswamy TS Mudhole A Mandal DK Avasthi R Shyam SK Datta 《Pramana》1999,53(3):541-544
The inclusive and exclusive measurements were carried out for 7Li projectile breakup on 27Al target at 48 MeV. In the inclusive data we have observed a broad peak around the beam velocity for alphas and tritons.
The exclusive data for alpha-triton coincidences show good agreement with the post-form DWBA theory of breakup reactions. 相似文献
8.
W.J. Briscoe Jason Brudvik K.G. Fissum K. Hansen L. Isaksson M. Lundin B. Nilsson B. Schroder 《中国物理 C》2009,33(12):1159-1166
The upgrade of the MAX-lab injector and the construction of MAX Ⅲ, provided the opportunity for upgrading the tagged-photon facility and thus lead to the possibility of more extensive program in nuclear physics research. This upgrade increased the injected electron energy to an eventual maximum of 250 MeV and allows for the extraction of electrons from the MAX Ⅰ ring operated in the stretcher mode. The first stretched beam was delivered in September 2005. The tagged-photon facility was commissioned in parallel with the commissioning of new experimental equipment. The PAC approved experimental program is current in progress, including measurements of pion photoproduction below the △(1232). The efforts at the tagged photon-facility are pursued within an international collaboration with around fifty members. 相似文献
9.
The symmetric and asymmetric fusion reaction systems forming the same compound nuclei ^26Al, ^30Si, ^38Ar and ^170Hf are investigated with the frame of improved isospin dependent quantum molecular dynamics model. The entrance channel mass asymmetry dependence of compound nucleus formation is found by analyzing the shell correction energies, the Coulomb barriers and the fusion cross sections. The calculated fusion cross sections agree quantitatively with the experimental data. The results indicate that compound nucleus formation is favorable for the systems with larger mass asymmetry because of the smaller Coulomb contribution to the fusion barrier. 相似文献
10.
Rosner JL Adam NE Alexander JP Berkelman K Cassel DG Crede V Duboscq JE Ecklund KM Ehrlich R Fields L Galik RS Gibbons L Gittelman B Gray R Gray SW Hartill DL Heltsley BK Hertz D Jones CD Kandaswamy J Kreinick DL Kuznetsov VE Mahlke-Krüger H Meyer TO Onyisi PU Patterson JR Peterson D Phillips EA Pivarski J Riley D Ryd A Sadoff AJ Schwarthoff H Shi X Shepherd MR Stroiney S Sun WM Urner D Wilksen T Weaver KM Weinberger M Athar SB Avery P Breva-Newell L Patel R Potlia V Stoeck H Yelton J Rubin P 《Physical review letters》2005,95(10):102003
The h(c)((1)P(1)) state of charmonium has been observed in the reaction psi(2S) --> pi(0)h(c) --> (gammagamma)(gammaeta(c)) using 3.08 x10(6) psi(2S) decays recorded in the CLEO detector. Data have been analyzed both for the inclusive reaction, where the decay products of the eta(c) are not identified, and for exclusive reactions, in which eta(c) decays are reconstructed in seven hadronic decay channels. We find M(h(c)) = 3524.4 +/- 0.6 +/- 0.4 MeV which corresponds to a hyperfine splitting DeltaM(hf)(1P) triple-bond pi(0)h(c)) x B(h(c) --> gammaeta(c)) = (4.0 +/- 0.8 +/- 0.7) x 10(-4). 相似文献
11.
12.
The paper gives a brief introduction into the COSY-facility, the currently used detector systems (ANKE, TOF and WASA) and the targets (cluster jet, pellet and ABS), and it presents some recent results, which were obtained in the field of baryon excited states. 相似文献
13.
Hiroyuki Kamano 《中国物理 C》2009,33(12):1077-1084
We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center (EBAC) at Jefferson Lab. Current status of our analysis of the meson production reactions based on the unitary dynamical coupled-channels model is summarized, and the N* pole positions extracted from the constructed scattering amplitudes are presented. Our plans for future developments are also discussed. 相似文献
14.
R. F. Frosch R. E. Rand Hall Crannell J. S. McCarthy L. R. Suelzle M. R. Yearian 《Nuclear Physics A》1968,110(3):657-673
The spectra of electrons scattered inelastically from 4He have been measured at incident energies from 150 MeV to 400 MeV for scattering angles from 38° to 90°. Through the use of a liquid 4He target, a high momentum resolution (≈0.25%) was obtained, and the 20 MeV 0+ state of the -particle was observed for the first time in electron scattering. The excitation energy and the total width of this state were determined and are in good agreement with the results from other experimental methods. It was found that the total disintegration cross section appears be smaller than 2(σp+σn) by more than an order of magnitude at the lowest q2(≈ 0.33 fm−2). In earlier work the assumption of a total cross section of 2(σp+σn) was found to be quite accurate for higher q2. As a new result, the partial radiative width for the 0+ state is determined to be Γrad = 1.1±0.3 meV. 相似文献
15.
D. K. Olsen A. R. Barnett S. F. Biagi N. H. Merrill W. R. Phillips 《Nuclear Physics A》1974,220(3):541-568
The static quadrupole moments of the first excited Jπ = 2+ states in 20Ne and 22Ne and the reduced electric quadrupole transition probabilities of these states to the ground states were measured via projectile Coulomb excitation. The quadrupole moments were deduced from the shapes of γ-ray angular distributions. The results are: Q(20Ne, 2+) = −0.20±0.05 b and Q(22Ne, 2+) = −0.11±0.05 b. The transition strengths were deduced from yield measurements and by comparison with the yields of target γ-rays. The results are: B(E2; 0+ → 2+, 20Ne) = 0.037±0.003 e2 · b2 and B(E2; 0+ → 2+, 22Ne) = 0.025±0.002 e2· b2. The results for the transition strengths are consistent with the results of accurate timing methods and resolve discrepancies between previous experiments. The results for the quadrupole moments are consistent with earlier measurements, although the mean values we obtain are slightly lower. The experimental measurements are compared with theoretical predictions and a detailed discussion is given of corrections to this type of reorientation experiment. 相似文献
16.
We study theΛ formation cross sections andΛ polarizations based on the Regge pole amplitudes in theπ ?+12C→Λ+X(inclusive) reactions and the exclusive kaon channel reactions atp π =4 GeV/c. We found that the experimental data of inclusive cross sections can be reproduced qualitatively well by our calculation. As for the polarization, we have the experimental data that were reported by two different groups, although they have opposite sign and different magnitudes. Our calculated results do not agree with either set of data. We show that the sign of polarization is sensitive to the outgoingΛ kinetic energy in the inclusive reactions and to the outgoing kaon angle in the exclusive kaon channel reactions. 相似文献
17.
Angular distribution measurements have been performed on the 21Ne(p, d)20Ne and 21Ne(d, p)22Ne reactions at Ep = 20 MeV and Ed = 10.2 MeV, respectively. In the 21Ne(p, d) 20Ne reaction, the prolific formation of the Jπ = 2+, 1.63 MeV state was characterized by ln = 2 pickup, and the distribution associated with the 44, 4.25 MeV state was suggestive of a weak ln = 2 pickup. All of the observed ln = 1 pickup strength is associated with formation of the 2−, 4.97 MeV 20Ne level. The 21Ne(d, p)22Ne results indicate that ln = 2 transfer is involved in the formation of the 1.28, 3.36, 5.52, 5.63 and 6.65 MeV 22Ne states. The angular distribution observed for the 2+, 4.46 MeV state and also the unresolved 5.33, 5.36 MeV composite of states required both ln = 0 and ln = 2 components in the associated distorted-wave Born approximation fits. The spectroscopic factors extracted from the present results are compared with those predicted by the Nilsson model without mixing: Applications of the angular momentum projection rule to the 21Ne(d, p)22Ne reaction are considered. 相似文献
18.
R. A. Bark H. Carlsson S. J. Freeman G. B. Hagemann F. Ingebretsen H. J. Jensen T. L nnroth M. J. Piiparinen I. Ragnarsson H. Ryde H. Schnack-Petersen P. B. Semmes P. O. Tj m 《Nuclear Physics A》1998,630(3-4):603-630
Six rotational bands in the odd-odd nucleus 174Ta have been populated with the 160Gd(19F,5n) reaction. High-spin states were identified using the NORDBALL array. Both signatures of the doubly decoupled π1/2− [541] ν1/2− [521] band and semi-decoupled π1/2− [541] ν7/2− [633] band are observed, in addition to the high-K couplings of the π9/2− [514] ν7/2+ [633], π9/2− [514] ν5/2− [512], π7/2+ [404] ν7/2+ [633], and π5/2+ [402] ν5/2− [512] configurations. The signature splitting of the π1/2− [541] ν7/2+ [633] band is inverted from the expected splitting, and this is interpreted as being due to a residual proton-neutron interaction. It is shown empirically that this interaction, together with deformation changes, can account for the increased crossing frequency associated with the alignment of i13/2 neutrons in the π1/2− [541] bands of odd-Z nuclei. 相似文献
19.
Kamal K. Seth
J. Picard
G. R. Satchler
《Nuclear Physics A》1970,140(3):577-597The reaction 40Ca(d, p)41Ca has been studied with a resolution 30 keV. Excitation functions for the first three strong states have been measured in the energy interval 9.80 to 12.12 MeV. Cross section fluctuations are found to be entirely within statistics, i.e. < 5 %, and it is concluded that σCN(θ)/(2Jf+1) < 5 μb/sr. Differential cross sections have been measured for elastic scattering, and the (d, p) transitions to the ground state and the strong single-particle states at E* = 1.949, 2.471, 3.623 and 3.954 MeV at Ed = 12.00 MeV and, over a limited angular range, at Ed = 11.00 MeV. The angular distributions have been analysed by the DWBA method and spectroscopic factors have been determined. It is suggested that the 3.623 MeV state may be the third
state predicted by Gerace and Green rather than
as assigned by earlier studies. 相似文献
20.
We calculate the cross section for the exclusive production of J(PC)=0(++) glueballs G0 in association with the J/psi in e(+)e(-) annihilation using the perturbative QCD factorization formalism. The required long-distance matrix element for the glueball is bounded by CUSB data from a search for resonances in radiative Upsilon decay. The cross section for e(+)e(-)-->J/psi+G0 at sqrt[s]=10.6 GeV is similar to exclusive charmonium-pair production e(+)e(-)-->J/psi+h for h=eta(c) and chi(c0), and is larger by a factor of 2 than that for h=eta(c)(2S). As the subprocesses gamma(*)-->(cc)(cc) and gamma(*)-->(cc)(gg) are of the same nominal order in perturbative QCD, it is possible that some portion of the anomalously large signal observed by Belle in e(+)e(-)-->J/psiX may actually be due to the production of charmonium-glueball J/psiG(J) pairs. 相似文献