共查询到20条相似文献,搜索用时 515 毫秒
1.
C. Bini 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):446-450
The KLOE experiment at the Frascati e
+
e
- collider DAFNE has completed this year its data taking. An integrated luminosity of 2.7fb^-1 has been collected mostly at
the φ-resonance peak. A wide experimental program is in progress. The detection of φ radiative decays allows to study the properties of the lowest-mass scalar and pseudoscalar mesons and to obtain information
on their structure. The main results are reviewed together with the prospects for low-energy e
+
e
- physics at Frascati. 相似文献
2.
We review high-energy scattering processes that are sensitive to the hadronic structure of the photon, describing theoretical
predictions as well as recent experimental results. These processes include deep-inelastic electron-photon scattering ate
+
e
− colliders; and the production of jets, heavy quarks and isolated photons in the collision of real photons ate
+
e
− colliders, as well as in photon-photon collisions atep colliders. We also comment on minijet based calculations of totalγp andγγ cross-sections, and discuss the possibility that future lineare
+
e
− colliders might produce very large photon fluxes due to the beamstrahlung phenomenon; in the most extreme cases, we predict
more than one hadronicγγ event to occur at every bunch crossing. 相似文献
3.
M. K. Srivastava 《Pramana》2004,63(5):1053-1062
An approximate simple scaling law is obtained for asymmetric (e, 3e) process on helium-like ions for double ionization by fast electrons. It is based on the equation (Z
′3π) exp[-Z(r1 + r2)],Z′ = Z – (5/16) for ground state wave function of helium-like ions and Z′2 scaling of energies. The scaling law is found to work very well if the lower energy electron is ejected along the momentum
transfer direction and the other one is ejected in the opposite direction. It also works quite well if this electron is ejected
within about 90° of the momentum transfer direction with the other electron going in the opposite direction. The scaling law
becomes increasingly accurate as the target nuclear charge and the energy increase. 相似文献
4.
Sayipjamal Dulat Bing-Song Zou 《The European Physical Journal A - Hadrons and Nuclei》2005,26(1):125-134
With accumulation of high statistics data at BES and CLEO-c, many new interesting channels can get enough statistics for partial-wave
analysis (PWA). Among them, ψ↦γpˉ,γΛˉ,γΣˉ,γΞˉ channels provide a good place for studying baryon-antibaryon interactions; the double radiative decays ψ↦γγV with V ≡ ρ,ω,φ have a potential to provide information on the flavor content of any meson resonances (R) with positive charge parity
(C = +) and mass above 1 GeV through ψ↦γR↦γγV; ψ(2s)↦γχc0,1,2 with χc0,1,2↦Kˉπ+π- and 2π+2π- decays are good processes to study χcJ charmonium decays. Using the covariant tensor formalism, here we provide theoretical PWA formulae for these channels. 相似文献
5.
The recently discovered narrow peaks (theψ-particles) in e+e− system at 3.105 and 3.695 GeV are interpreted as hadrons in a broken SU4 symmetry scheme. A new additional additive quantum number, parachargeZ, is combined with the usual SU3 quantum numbers in the group SU4. Theψ (3.1) is assigned to a near ideally mixed15⊕1 multiplet of vector mesons (containing theρ) as theI=Y=0, charge conjugationC=−combination ofZ=±1.members. Theψ (3.7) is assigned correspondingly to another mixed15⊕1 multiplet containing theρ′ (1600). The hadronic electromagnetic interactions are modified by the addition of (non-minimal) anomalous pieces that can
changeZ. The decays of theψ-particles are discussed. New enlarged SU4 multiplets of other hadrons are proposed. Tests of our scheme are put forward. The most crucial test will be the observation
of two rather broad resonances in e+ e− collisions with masses around 4.2 GeV and 5.1 GeV. Another prediction is the presence of energetic photons in the decays
of theψ-particles. Important results concerning the recently observed phenomena in the process e+e−→hadrons follow in this scheme. 相似文献
6.
V. Dorofeev R. Dzhelyadin A. Ekimov Yu. Gavrilov Yu. Gouz A. Ivashin V. Kabachenko I. Kachaev A. Karyukhin Yu. Khokhlov V. Konstantinov M. Makouski V. Matveev A. Myagkov V. Nikolaenko A. Ostankov B. Polyakov D. Ryabchikov N. Shalanda M. Soldatov A. A. Solodkov A. V. Solodkov O. Solovianov E. Starchenko A. Zaitsev 《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):149-154
The isospin-violating decay f
1(1285) → π+π-π0 has been studied at the VES facility. This study is based on the statistics acquired in π-
Be interactions at 27, 36.6 and 41 GeV/c in the diffractive reaction π-
N → (f
1π-)N . The f
1(1285) → π+π-π0 decay is observed. The preliminary ratio of decay probabilities BR(f
1(1285) → π+π-π0) to BR(f
1(1285) → ηπ+π-).
BR(η → γγ) is ∼ 2% .
Original article based on material presented at HADRON 2007. 相似文献
7.
Two kinds of general consequences of the ΔS=0 weak hadron neutral current independent of a gauge model are presented. Firstly are results which depend on the quark parton
model. These involve bounds among neutrino inclusive cross-section and a bound onQ(Z, N) in terms of these inclusive cross-sections. Secondly are results which are independent of the quark-parton model and depend
only on the SU(3) structure of the most general ΔS=0 neutral current. These tests of isopin and speciallyU-spin properties of the current are given forv+N→v+hadron+anything,v+N→v+baryon+meson ande
+
e
−→baryon+anti-baryon. In addition some conjectures are made with regard to the semi-inclusive neutrino-reactions using the
quark parton model. 相似文献
8.
Antiproton proton annihilation reactions allow unique access to the moduli and phases of nucleon electromagnetic form factors
in the time-like region. We present the helicity amplitudes for the unequal-mass single-photon reaction pˉ → l
+
l
- in the s channel including the lepton mass. The relative signs of these amplitudes are determined using simple invariance properties.
Helicity amplitudes for one-photon exchange annihilation reaction pˉ → Bˉ are also given, where B is any spin-one-half particle with structure. Crossing relations between the ep → ep scattering and the pˉ → l
+
l
- annihilation channels are discussed and the crossing matrix for the helicity amplitudes is given. This matrix may be used
to verify known expressions for the space-like helicity amplitudes due to one-photon exchange. 相似文献
9.
The decays η,
→ π+π-
l
+
l
- (with l = e,μ are investigated within a chiral unitary approach which combines the chiral effective Lagrangian with a coupled-channels
Bethe-Salpeter equation. Predictions for the decay widths and spectra are given. 相似文献
10.
J. Ahrens S. Altieri J. R. M. Annand H. -J. Arends R. Beck M. A. Blackston C. Bradtke A. Braghieri N. d'Hose H. Dutz A. Fix S. Goertz P. Grabmayr S. Hasegawa E. Heid H. Holvoet N. Horikawa T. Iwata O. Jahn P. Jennewein F. Klein R. Kondratiev M. Lang B. Lannoy V. Lisin M. Martinez-Fabregate J. C. McGeorge W. Meyer A. Panzeri P. Pedroni T. Pinelli I. Preobrajenski G. Reicherz Ch. Rohlof G. Rosner M. Rost T. Rostomyan D. Ryckbosch M. Schumacher B. Seitz G. Tamas A. Thomas R. Van de Vyver H. R. Weller F. Zapadtka 《The European Physical Journal A - Hadrons and Nuclei》2007,34(1):11-21
The helicity dependence of the total cross-section and the invariant-mass distributions in the (pπ±) and (π+π-) final states for the γp → pπ+π- reaction have been measured for the first time at incident photon energies from 400 to 800MeV. The measurement was performed
with the large-acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. Although this
channel is found to be predominantly excited by the intermediate production of a Δπ state, both the measured unpolarized and
the helicity-dependent observables are generally not well described by the existing theoretical models. 相似文献
11.
《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):831-835
e
+
e
- production was studied using the High Acceptance DiElectron Spectrometer (HADES). In pp collisions at 2.2GeV kinetic beam energy, the exclusive η production and the Dalitz decay η→γe
+
e
- have been reconstructed. The electromagnetic form factor of the latter decay was found to be in good agreement with the existing
theoretical predictions. In addition, an inclusive e
+
e
- invariant-mass spectrum from the 12C + 12C reaction at 2AGeV is presented and compared with a simplified thermal model. 相似文献
12.
The isoscalar-isovector (ρ-ω) interferences in the exclusive reactions π-
p↦ne
+
e
- and π+
n↦pe
+
e
- near the ω threshold leads to a distinct difference of the dielectron invariant-mass distributions depending on beam energy.
The strength of this effect is determined by the coupling of resonances to the nucleon vector-meson channels and other resonance
properties. Therefore, a combined analysis of these reactions can be used as a tool for determining the baryon resonance dynamics.
Received: 14 August 2001 / Accepted: 3 October 2001 相似文献
13.
Ji Xiaobin 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):672-675
The report includes the new observation of X(1835) in J/ψ→γη
′
π
+
π
-, the ωφ threshold enhancement in J/ψ→γωφ, the ωω structure in J/ψ→γωω and the broad 1- structure at the low K
+
K
- invariant-mass spectrum in J/ψ→K
+
K
-
π
0. 相似文献
14.
G. Pancheri O. Shekhovtsova G. Venanzoni 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):458-460
Effects due to the non-pointlike behaviour of pions in the process e
+
e
-→π
+
π
-
γ can arise for hard photons in the final state. By means of a Monte Carlo event generator, which also includes the contribution
of the direct decay φ→π
+
π
-
γ, we estimate these effects in the framework of the resonance perturbation theory. We consider angular cuts used in the KLOE
analysis of the pion form factor at threshold. A method to reveal the effects of the non-pointlike behaviour of pions in a
model-independent way is proposed. 相似文献
15.
S. Tosi 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):695-697
The high integrated luminosity collected by the BABAR detector at the SLAC PEP-II e
+
e
-
B-Factory offers an excellent opportunity for the study of heavy-quark spectroscopy. A selection of the most recent results
reported by BABAR will be presented, focussing on recently observed states with both open- and hidden-charm content. 相似文献
16.
Christoph?Ditsche Bastian?Kubis Ulf-G.?Mei?ner 《The European Physical Journal C - Particles and Fields》2009,60(1):83-105
We re-evaluate the electromagnetic corrections to η→3π decays at next-to-leading order in the chiral expansion, arguing that effects of order e
2(m
u
−m
d
) disregarded so far are not negligible compared to other contributions of order e
2 times a light-quark mass. Despite the appearance of the Coulomb pole in η→π
+
π
−
π
0 and cusps in η→3π
0, the overall corrections remain small. 相似文献
17.
We review the cross-sections for low-energy π-γ reactions in the framework of chiral perturbation theory. Charged-pion Compton scattering, π-γ → π-γ , is considered up to one-loop order where the pion's internal structure enters through the difference of the electric and
magnetic pion polarizability, απ - βπ . The ongoing COMPASS experiment aims at measuring this important structure constant with high statistics using the Primakoff
effect. In the same way, the reaction π-γ → π-π0 serves as a test of the QCD chiral anomaly (via the γ3π -coupling constant F
γ3π . Furthermore, we calculate the total cross-sections for neutral and charged pion-pair production, π-γ → π-π0π0 and π-γ → π-π+π- , which are governed by the chiral ππ -interaction. Finally, we investigate the radiative (correction) process π-γ → π-γγ and calculate the corresponding two-photon mass spectrum. This information will be useful for analyzing the π- Primakoff scattering events with photons in the final state. 相似文献
18.
We discuss the condition for the presence of isoscalar parity violating neutral currents and notice that it is present in
most gauge-theoretic models of weak interactions. We investigate the possibility of testing its presence in e+e− colliding beams and find that parity violation in the reaction e+e−→Λ°Λ° would provide an unambiguous test for such a current. 相似文献
19.
A. C. dos Reis 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):474-478
The issue of Kπ and ππ
S-wave amplitude is addressed using decays of D-mesons. Model-independent measurements of the phases of the π
+
π
+ and K
-
π
+
S-wave amplitude from D
+→π
-
π
+
π
+ and D
+→K
-
π
+
π
+ decays are discussed. The result indicates a deviation from the phase of the K
-
π
+
S-wave amplitude obtained by scattering experiments. This could be interpreted as an indication of the presence of 3-body final-state
interaction, or in other words, that the phases from production and scattering process cannot be directly compared. 相似文献
20.
Configuration assignments are derived for the observed energy levels in the odd-odd deformed nucleus170Lu99 based on the calculations of the two-particle band head energies for a zero range residual interaction, the beta-feeding
characteristics, and the observed features for similar bands in the neighbouring nuclei. In particular, specific assignments
are given for theJ
π
=1+ levels at 198.4 keV, 349.0 keV and 785.5 keV. The ambiguities with respect to the assignments for theK
π=3− bands are discussed. A new isomer withJ
π
=7+ and half-life of several seconds is predicted around (225±25) keV and experiments are suggested to identify it. 相似文献