共查询到20条相似文献,搜索用时 171 毫秒
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H. -J. Behrend L. Criegee J. H. Field G. Franke H. Jung J. Meyer O. Podobrin V. Schr?der G. G. Winter P. J. Bussey et al. 《Zeitschrift fur Physik C Particles and Fields》1991,49(1):43-48
We have studied the 0 production rate in the reaction 3+3– in the energy range 1.6W
7.5 GeV with the CELLO detector at PETRA. Our analysis points to a substantial yield of 00+– events in particular atW
>4.0 GeV. We give cross sections for the 02+2– and 00+– final states and calculate upper limits for the reaction 00 (1700) 00+–.Now at CERN 相似文献
3.
Using the isospin- and momentum-dependent hadronic transport model IBUU04, the effects of symmetry energy on the π^-/π^+ ratio are studied. Our investigations are based on the calculations of the ^132 Sn+^124Sn semi-central collisions at beam energies of 400/AMeV, 600/A MeV and 800/A MeV. It is found that both the transverse momentum and kinetic energy distributions of the π^-/π^+ ratio are rather sensitive to the symmetry energy, especially around the Coulomb peaks. The position of the Coulomb peak is shown to be nearly independent of beam energy. The sensitivity of the π^-/π^+ ratio to the symmetry energy decreases as the beam energy increases from 600/A MeV to 800/A MeV. 相似文献
4.
The e
+
e
− → π
+
π
−
π
+
π
− cross section is calculated for energies of 0.65 ≤ √s ≤ 1 GeV in the framework of the generalized hidden local symmetry model. The calculations are compared with the data of CMD-2
and BaBaR. It is shown that the inclusion of heavy isovector resonances ρ(1450) and ρ(1700) is necessary for reconciling calculations
with the data. It is found that, at √s ≈ 1 GeV, the contributions of the above resonances are much larger, by a factor of 30, than the ρ(770) one, and amount to
a considerable fraction ∼0.3–0.6 of the latter at √s ∼ m
ρ.
The text was submitted by the authors in English. 相似文献
5.
用BESⅠ的7.8×106J/ψ数据更为精确地测定了J/ψ→π03(π+π-)和J/ψ→ω2(π+π-)的分支比(Br(J/ψ→π03(π+π-))=(2.52±0.06±0.43)%,Br(J/ψ→π03(π+π-))=(1.31±0.09±0.21)%.同时对4π不变质量谱和ωππ不变质量谱进行研究分析,试图观察是否存在有兴趣的信号. 相似文献
6.
We have analyzed the D^0→π^+π^- decay with α_s corrections in quantum chromodynamic (QCD) factorization and with the soft-gluon corrections in the light cone QCD sum rules. The soft-gluon effects are firstly calculated in the decay channel. The results show that once the factorization contributions, the α_s corrections, and the soft-gluon effects are all considered, we can satisfactorily explain the experimental data in the decay channel. 相似文献
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S. Rai Choudhury A. S. Cornell Naveen Gaur 《The European Physical Journal C - Particles and Fields》2008,58(2):251-259
Flavor changing neutral current (FCNC) decays of the B-meson are a very useful tool for studying possible physics scenarios beyond the standard model (SM), where of the many FCNC
modes radiative, purely leptonic and semi-leptonic decays of the B-meson are relatively clean tests. Within this context, the BELLE collaboration has measured the process B→K
*
γ and also searched for the B→K
1(1270)γ process. Theoretical analyses of these processes are yielding similar values of the relevant form factors. In this work we
have used this upper bound in studying the angular correlations for the related semi-leptonic decay mode B
−→K
1−(1270)(→ρ
0
K
−)ℓ
+
ℓ
−, where we have used the form factors that have already been estimated for the B→K
1(1270)γ mode. Note that the additional form factors that are required were calculated using large energy effective theory (LEET). 相似文献
10.
Using the technique of helicity amplitudes, the electromagnetic process e
+
e
− → μ+μ− is theoretically investigated in the one-photon approximation. The structure of the triplet states of the final (μ+μ−) system is analyzed. It is shown that in the case of unpolarized electron and positron the finalmuons are also unpolarized,
but their spins are strongly correlated. Explicit expressions for the components of the correlation tensor of the final (μ+μ−) system are derived. The formula for the angular correlation at the decays of final muons μ+ and μ−, produced in the process e
+
e
− → μ+μ−, is obtained. It is demonstrated that spin correlations of muons in the process of electron-positron pair annihilation have
the purely quantum character, since one of the incoherence inequalities for the correlation-tensor components is always violated.
The additional contribution of the weak interaction of lepton neutral currents through the virtual Z
0 boson is considered; it is established that, taking into account the weak interaction, the qualitative character of the muon
spin correlations does not change.
The text was submitted by the authors in English. 相似文献
11.
A. Berglund T. Buran P.J. Carlson C.J.S. Damerell I. Endo A.R. Gillman V. Gracco R.J. Homer M.J. Hotchkiss A. Lundby M. Macri B.N. Ratcliff A. Santroni T. Tso F. Wickens J.A. Wilson 《Physics letters. [Part B]》1975,57(1):100-104
For the first time, the reactions π+p→K+∑+ and K?p→π?∑+ have been studied in the same apparatus. This has been done at an adequately high momentum (10.1 GeV/c) to allow a check of the prediction of exchange degeneracy, that the differential cross sections should be converging at high energy. We have measured the cross section for momentum transfers t between tmin and t = ?0.3 (GeV/c)2. We find that for both reactions the differential cross section shows an exponential fall, with no deviations right in to t =tmin (where some other experiments have shown a dip in the cross section). Furthermore, we find the magnitude of the differential cross sections to be closely similar at t = 0, with a ratio However, the slope for the positive reaction is about 19% steeper than that for the negative reaction. 相似文献
12.
A. Ehresmann W. Kielich L. Werner Ph. V. Demekhin D. V. Omel''yanenko V. L. Sukhorukov K.-H. Schartner H. Schmoranzer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):235-246
Dispersed fluorescence from fragments formed after the de-excitation of the
1s-1π* resonances of N*O and NO* has been
measured in the spectral range of 118–142 nm. This range is dominated by
lines of atomic nitrogen and oxygen fragments and by the
bands in the NO+ ion which result from the participator Auger decay of the 1s-1π* resonances.
Ab-initio calculations of the transition probabilities between vibrational
levels during the reaction NO
N*O
⇒ NO
were used to explain the observed intensity dependence for the
fluorescence bands on the exciting-photon energy across
the resonances and on both v′ and v′′
vibrational quantum numbers. The multiplet structure of the 1s-1π* resonance and lifetime vibrational interference explain the observed exciting-photon energy dependence of the
fluorescence
intensity. A strong spin-orbit coupling between singlet and triplet states
of NO+ is proposed to reduce additional cascade population of the
state via radiative transitions from the
and
states and to explain
remaining differences between measured and calculated integral fluorescence
intensities. 相似文献
13.
L. Cappiello O. Catà G. D’Ambrosio Dao-Neng Gao 《The European Physical Journal C - Particles and Fields》2012,72(1):1872
We study the decay K
+→π
+
π
0
e
+
e
−, currently under analysis by the NA62 Collaboration at CERN. In particular, we provide a detailed analysis of the Dalitz
plot for the long-distance, γ
∗-mediated, contributions (Bremsstrahlung, direct emission and its interference). We also examine a set of asymmetries to isolate
genuine short-distance effects. While we show that charge asymmetries are not required to test short distances, they provide
the best environment for its detection. This constitutes by itself a strong motivation for NA62 to study K
− decays in the future. We therefore provide a detailed study of different charge asymmetries and the corresponding estimated
signals. Whenever possible, we make contact with the related processes K
+→π
+
π
0
γ and K
L
→π
+
π
−
e
+
e
− and discuss the advantages of K
+→π
+
π
0
e
+
e
− over them. 相似文献
14.
S. Senyukov 《The European Physical Journal C - Particles and Fields》2009,62(1):229-235
Heavy quarks, such as charm, are produced in hard scatterings in the early stages of high energy nucleus-nucleus collisions
and are expected to be a powerful tool to investigate the properties of the quark gluon plasma (QGP). The tracking detectors
of the ALICE apparatus will allow to track and identify particles in central rapidity range down to low P
t
. Among D mesons it would be particularly interesting to measure D
s
yield via an exclusive hadronic decay channel because it could help to disentangle different hadronization mechanisms. The
possibility of reconstructing the D
s
meson through its D
s
+→K
+
K
−
π
+ decay channel in the central barrel was studied. The problem considered is characterized by the comparatively low yield of
the D
s
mesons against the huge amount of combinatorial background. Different kinematic and topological cuts have been studied in
order to increase the signal-to-background ratio and the statistical significance. In addition, D
s
mesons preferentially decay through intermediate resonant states and this fact can improve the separation of signal from
background. Results of cut parameters tuning and values of significance for an analysis performed on simulated data are presented. 相似文献
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R. Akers G. Alexander J. Allison K. Ametewee K. J. Anderson S. Arcelli S. Asai D. Axen G. Azuelos A. H. Ball et al. 《Zeitschrift fur Physik C Particles and Fields》1995,67(1):45-55
The properties of hadronic Z0 decays with final state photons, measured with OPAL at LEP, have been compared with predictions from two different matrix element calculations ofO(
s
). Two calculations, GNJETS and EEPRAD, have been investigated which use different schemes to restrict the phase space around the poles of the cross section. Assuming the E0-JADE jet definition, both calculations describe the data well in large regions of phase space fory
cut
values around 0.06. For very large and very small jet-photon masses some deviations from the predictions have been found, indicating the importance of higher order corrections. Significant differences between the calculations are only apparent in the predicted rate of 1-jet plus photon events. The rate is higher in GNJETS which reproduces the data better than EEPRAD. 相似文献
18.
对a2(1320)→π+π+π-过程的衰变振幅进行张量分析,展示了如何得到三体衰变振幅. 相似文献
19.
基于北京谱仪收集的4.03GeV质心系能量下e+e-对撞数据,分析τ±τ±→e±+π±+nπ0+ν's(n=0,1,2)事例,给出分支比值Br(τ±→π±ντ)=(11.64±0.49+0.76-0.73%,Br(τ±→π±π0ντ)=(24.00±1.34+1.36-1.30%,Br(τ±→π±2π0ντ)=(9.39±1.68+1.69-1.66%. 相似文献
20.
Murugesh Duraisamy Alexander L. Kagan 《The European Physical Journal C - Particles and Fields》2010,70(4):921-925
CLEO-c measurements of the timelike form factors F
π
, F
K
at ?s=3.671\sqrt{s}=3.671 GeV provide a direct probe of power corrections (PC’s) at energies near m
B
. PC’s in F
π,K
and B→Kπ,ππ are separated into perturbative and soft parts. In F
π,K
the latter are ≥O(10) larger. A PC fit to the B→Kπ,ππ data also yields a ≥O(10) soft-to-perturbative hierarchy for the QCD penguin PC’s. Hence, both can be attributed to dominance of the soft-overlap
between energetic (approximately) back-to-back collinear partons, and consistency of the B→Kπ,ππ fit with the Standard Model appears to be naturally realized. The CP asymmetries SKs p0S_{K_{s} \pi^{0}}, CKs p0C_{K_{s} \pi^{0}} are well determined, providing a clean test for new physics. 相似文献