共查询到20条相似文献,搜索用时 31 毫秒
1.
R. Baldini L. Benussi M. Bertani S. Bianco F. L. Fabbri S. Pacetti A. Zallo 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):645-648
A new study of the dip observed at 1.9GeV by the Fermilab experiment E687 in diffractive photoproduction of 3π
+3π
- is presented. The E687 and the BABAR data on the annihilation cross-section σ(e
+
e
-→3π
+3π
-), obtained with initial-state radiation, are fitted all together. The fit function is based on a simple mixing mechanism
that explains the manifestation of a resonance as a dip. Possible interpretations in terms of hybrids and tetraquark states
are considered. 相似文献
2.
The two-neutrino double beta decay of96Zr isotope for 0+ → 2+ transition has been studied in the PHFB model. In our earlier work, the reliability of the intrinsic wave functions of96Zr and96Mo isotopes has been established by obtaining an overall agreement between a number of theoretically calculated spectroscopic
properties as well as half-lives of 2vββ decay for 0+ → 0+ transition and the available experimental data. In the present work, the half-life of 2vββ decay for 0+ ar 2+ transition T
1
2/2v
(0+ →2+) has been calculated using the same set of intrinsic wave functions. 相似文献
3.
Within the quark parton model the two-component duality idea is generalized to single hadron inclusive distributions in deep-inelastic scattering. The discussion is limited to the current fragmentation region. The number of independent distribution functions is reduced. Relations as well as inequalities among the structure functions are obtained. In particular, the excess of π+ over π? in the electroproduction off a proton comes out as a consequence and the differential cross section for e+e? → π+ anything is fully determined by the electroproduction of pions on nucleons. 相似文献
4.
Vladimir G. Neudatchin Igor T. Obukhovsky Ludmila L. Sviridova Nikolai P. Yudin 《Central European Journal of Physics》2004,2(3):511-522
The pion momentum distributions (MDs) in four channels of virtual decay p→B+π, B = N, Δ, N
1/2-(1535), N
1/2+(1440) are calculated in two models, the microscopic model of 3
P
0 scalar q−q fluctuation with the pion as a composite q−q-system and the chiral semi-microscopic model of πq interaction with the pion as a structureless Goldstone boson. The results of the above models are similar for the baryon
states B = N, Δ, N
1/2-(1535) but are rather different for the Roper resonance N
1/2+(1440) which corresponds to excitation of two oscillator quanta in the nucleon. The experimental investigation of pion MDs
by means of the reaction of quasi-elastic knockout of pion by an electron of a few GeV energy p(e, e′ π)B may be very suitable for Jefferson Laboratory, Virginia (JLab). 相似文献
5.
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
6.
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
7.
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
8.
《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
9.
J. Zuo 《Indian Journal of Physics》2011,85(7):1131-1135
Di-hadron correlations will help understand the parton densities near jets traversing the medium, the process of hadron formation
and the di-hadron correlation away-side shape. We report on the di-hadron correlations between unidentified charged hadron
triggers with identified associated strange particles Λ and K
S
0) in Au+Au collisions at 200 GeV in STAR. Particle yields and ratios are extracted on the near-side and awayside of the trigger
particle. The baryon to meson ratios for associated particles as a function of Δϕ are also extracted. The shape of these ratios on the away-side is studied to understand the away-side’s pattern. The particle-type
composition in the hump regions in away-side is compared to that in the near-side peak. These ratios may help to elucidate
the particle composition in the away-side and near-side of the correlation pattern arising due to a fast parton traversing
the medium. 相似文献
10.
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
11.
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
12.
13.
R. Ramachandran 《Pramana》2005,65(3):381-391
The exotic baryon Θ+(1540 MeV) is visualized as an expected (iso) rotational excitation in the chiral soliton model. It is also argued as a pentaquark
baryon state in a constituent quark model with strong diquark correlations. I contrast these two points of view; observe the
similarities and differences between the two pictures. Collective excitation, the characteristic of chiral soliton model,
points toward small mixing of representations in the wake ofSU (3) breaking. In contrast, constituent quark models prefer near ‘ideal’ mixing, similar to ω-φ mixing. 相似文献
14.
Contact-like nonstandard interactions can be revealed only through deviations of observables from the standard model (SM)
predictions. We consider a number of such nonstandard scenarios, and discuss their identification as sources of deviations
in fermion-pair production processes at the international linear collider (ILC), if they were observed. We emphasize the role
of e
− and e
+ polarization in enhancing the identification reaches.
相似文献
15.
CP-violating rate asymmetry can be generated in a process only if its amplitude possesses an absorptive part. It is pointed
out that such an absorptive part can be provided ine
+
e
− annihilation by the presence of aZ(Z′) resonance of non-zero width. The CP asymmetry in the process
, wherel
i
are charged leptons, is discussed in several models. In a specific two-Z model, large and observable CP asymmetry ine
+
e
− →τ
+
e
− (τ
−
e
+) is shown to be possible at LEP/SLC energies. 相似文献
16.
T. Skorodko M. Bashkanov D. Bogoslawsky H. Calen F. Cappellaro H. Clement L. Demiroers E. Doroshkevich D. Duniec C. Ekström K. Franssen L. Gustafsson B. Höistad G. Ivanov M. Jacewicz E. Jiganov T. Johansson O. Khakimova M. Kaskulov S. Keleta I. Koch F. Kren S. Kullander A. Kupść A. Kuznetsov P. Marciniewski R. Meier B. Morosov C. Pauly H. Petterson Y. Petukhov A. Povtorejko K. Schönning W. Scobel B. Shwartz V. Sopov J. Stepeniak P. Thörngren-Engblom V. Tikhomirov G. J. Wagner M. Wolke A. Yamamoto J. Zabierowski J. Złomanczuk 《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):317-319
In most investigations the Roper resonance is sensed only very indirectly via complex partial-wave analyses. We find indications
for its excitation in the invariant nπ+ mass spectrum of the pp → npπ+ reaction at M ≈ 1360 MeV with a width of ≈ 150 MeV . The values fit very favorably to the most recent phase shift results as well as to
the observations at BES. In the near-threshold two-pion production pp → ppπ0π0 , where the Roper excitation and its subsequent decays via the routes N
* → Δπ → Nππ and N
* → Nσ are the only dominant processes, we find its direct decay into the Nσ channel to be the by far dominating decay process --in favor of a monopole excitation of the Roper resonance. 相似文献
17.
Catherine Silvestre 《The European Physical Journal C - Particles and Fields》2009,61(4):841-845
In this paper, we calculate the decay rates of the D
+→D
0
e
+
ν, D
S
+→D
0
e
+
ν,
, D
S
+→D
+
e
−
e
+ and B
S
0→B
0
e
−
e
+ semileptonic decay processes, in which only the light quarks decay, while the heavy flavors remain unchanged. The branching
ratios of these decay processes are calculated with the flavor SU(3) symmetry. The uncertainties are estimated by considering
the SU(3) breaking effect. We find that the decay rates are very tiny in the framework of the standard model. We also estimate
the sensitivities of the measurements of these rare decays at future experiments, such as BES-III, super-B and LHC-b. 相似文献
18.
19.
Z. Rudy W. Cassing L. Jarczyk B. Kamys P. Kulessa 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):303-314
The production of K+-mesons in proton-nucleus collisions from 1.0 to 2.5GeV is analyzed with respect to one-step nucleon-nucleon ( NN → NYK
+) and two-step Δ-nucleon ( ΔN → K
+
YN) or pion-nucleon ( πN → K
+
Y) production channels on the basis of a coupled-channel transport approach (CBUU) including the kaon final-state interactions.
The influence of momentum-dependent potentials for the nucleon, hyperon and kaon in the final state are studied as well as
the importance of K+ elastic rescattering in the target nucleus. The transport calculations are compared to the experimental K+ spectra taken at LBL Berkeley, SATURNE, CELSIUS, GSI and COSY-Jülich. It is found that the momentum-dependent baryon potentials
affect the excitation function of the K+ cross-section; at low bombarding energies of ∼ 1.0GeV the attractive baryon potentials in the final state lead to a relative
enhancement of the kaon yield, whereas the net repulsive potential at bombarding energies ∼ 2GeV causes a decrease of the
K+ cross-section. Furthermore, it is pointed out that especially the K+ spectra at low momenta (or kinetic energy T
K) allow to determine the in-medium K+ potential almost model independently due to a relative shift of the K+ spectra in kinetic energy that arises from the acceleration of the kaons when propagating out of the nuclear medium to free
space, i.e. converting the potential energy to the kinetic energy of the free kaon.
Received: 28 January 2002 / Accepted: 3 June 2002 / Published online: 19 November 2002
RID="a"
ID="a"e-mail: Wolfgang.Cassing@theo.physik.uni-giessen.de
Communicated by P. Schuck 相似文献
20.
I. Horn A. V. Anisovich G. Anton R. Bantes O. Bartholomy R. Beck Y. Beloglazov R. Bogendörfer R. Castelijns V. Credé A. Ehmanns J. Ernst I. Fabry H. Flemming A. Fösel M. Fuchs Ch. Funke R. Gothe A. Gridnev E. Gutz S. Höffgen J. Hößl J. Junkersfeld H. Kalinowsky F. Klein E. Klempt H. Koch M. Konrad B. Kopf B. Krusche J. Langheinrich H. Löhner I. Lopatin J. Lotz H. Matthäy D. Menze J. Messchendorp V. Metag V. A. Nikonov D. Novinski M. Ostrick H. van Pee A. V. Sarantsev C. Schmidt H. Schmieden B. Schoch G. Suft V. Sumachev T. Szczepanek U. Thoma D. Walther Ch. Weinheimer 《The European Physical Journal A - Hadrons and Nuclei》2008,38(2):173-186
The reaction γp → pπ0η has been studied with the CBELSA detector at the tagged photon beam of the Bonn electron stretcher facility. The reaction
shows contributions from Δ+(1232)η , N(1535)+π0 and pa
0(980) as intermediate states. A partial-wave analysis suggests that the reaction proceeds via formation of six Δ -resonances,
Δ(1600)P
33 , Δ(1920)P
33 , Δ(1700)D
33 , Δ(1940)D
33 , Δ(1905)F
35 , Δ(2360)D
33 , and two nucleon resonances N(1880)P
11 and N(2200)P
13 , for which pole positions and decay branching ratios are given. 相似文献