共查询到20条相似文献,搜索用时 31 毫秒
1.
E. Ya. Paryev 《Physics of Atomic Nuclei》2006,69(4):721-733
Within the spectator model, we study the reaction γd → K
−Θ+
p → K
−
K
+
np in the threshold energy region. We present the predictions for the exclusive and inclusive K
−-meson angular distributions in the laboratory system for this reaction calculated for two possible parity states of the Θ+ resonance at 1.5-and 1.75-GeV beam energies with and without imposing the relevant kinematical cuts on those parts of the
sampled phase space where the contribution from the main background sources, associated with the ϕ(1020), Λ(1520) production
as well as with the K
−
p rescattering in the final state, is expected to be dominant. We show that, under the chosen kinematics, these distributions
are sensitive to the Θ+ parity and, therefore, can be used as a filter for the determination of its parity.
The text was submitted by the author in English. 相似文献
2.
P. Zh. Aslanyan 《Physics of Particles and Nuclei》2009,40(4):525-557
Exotic strange multibaryon states have been observed in the effective mass spectra of: Λπ±, Λπ+π−, Λp, Λpp, Λπp, ΛΛ and ΛK
s
0, K
s
0
p, K
s
0π± subsystems. The measured Λ/π+ ratio for average multiplicities from the pC reaction is equal to (5.3 ± 0.8) × 10−2, and it is approximately two times larger than the Λ/π+ ratio simulated by the FRITIOF model and than that of experimental pp reactions at the same energy. The observed wellknown resonances Σ*+ (1385) and K*± (892) from PDG are good tests of this method. The mean value of the mass for the Σ*−(1385) resonance is shifted to 1370 MeV/c
2 and the width is two times larger than the same value from PDG. Such kind of behavior for the width and invariant mass of
Σ*− (1385) resonance is interpreted as an extensive contribution from stopped Ξ− → Λπ− and medium effect. There is enhancement of the production contribution for all observed hyperons. A few events were registered
by hypothesis of light H
0 and heavy H
0, + dihyperons. Dihyperons were observed by weak decay channels: (Σ−
p), (Λpπ−), (Λpπ0), and (K
−
pp).
The text was submitted by the author in English. 相似文献
3.
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 final muons 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. 相似文献
4.
The electromagnetic mass splittings of heavier hadrons are estimated in the framework of gauge theory model where ligher quarks
are taken to behave relativistically and the spatial wave functions are described by the spin-spin interaction affected relative
distances between quarks. The predictions for (Ξ−-Ξ0), (Σ*0−Σ*+), (Ξ*−-Ξ*0), (D
c
+−D
c
0) and (D
c
*+
−D
c
*0
) are in fair agreement with the experimental data available whereas those for (D
b
−
−D
b
0
) and (D
b
*−
−D
b
*0
) are in qualitative agreement with other theoretical estimates. 相似文献
5.
V. V. Tarasov P. O. Varlamov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(4):458-463
We report our observations on the resonance signals of masses of 1520, 1670, 1810 (1 820), and 2100 MeV c
−2, produced inclusively in the reaction Σ− + C(Cu) → p + K− + X, and the signals of masses of 1020 and 1525 MeV c
−2, produced inclusively in the reaction Σ− + C(Cu) → K+ + K− + X, with a 600-GeV c
−1- momentum hyperon beam in the SELEX experiment at the Fermilab. The masses, widths, and branching ratios were measured. The
resonance signal of mass of 1520 MeV c
−2 correspond to the known Λ(1520) hyperon. The signals of masses of 1020 and 1525 MeV c
−2 in the K+K− system correspond to the φ0(1020)- and f
2′(1525) mesons, respectively. The branching ratio of the resonance of mass of 1670 MeV c
−2 relative to Λ(1520) is (24.92 ± 0.45 ± 0.48)%, while that of the resonance of mass of 1810 (or 1 820) MeV c
−2 relative to Λ(1520) is (16.13 ± 0.38 ± 0.45)%. The branching ratio of the f
2′(1525) resonance relative to φ0(1020) is (10.75 ± 0.25 ± 0.45)%. Data analysis was performed over 6 × 107 trigger events registered by the SELEX setup on the FNAL Tevatron. 相似文献
6.
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
7.
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
8.
B. P. Barkov V. V. Vladimirskii V. K. Grigor’ev O. N. Erofeeva Yu. V. Katinov I. Ya. Korol’kov V. I. Lisin V. N. Luzin V. N. Nozdrachev V. V. Sokolovskii G. D. Tikhomirov S. A. Uzunyan Yu. P. Shkurenko I. A. Gridnev 《JETP Letters》1999,70(4):248-253
Data are presented which indicate the existence of a previously unknown narrow resonance near mass 1520 MeV, discovered while
analyzing the system K
S
K
S
. The data were obtained at ITEP using the 6-m magnetic spectrometer in a beam of 40-GeV negative particles. The resonance
is observed in π−
p and K
−
p interactions with a total statistical confidence of not less than 5 standard deviations. The width of this state is comparable
to the mass resolution of the spectrometer (∼5 MeV). The mass is 1521.5±2.5 MeV. Estimates of the product σ·BR (K
S
K
S
) give ∼5.0 nb in π−
p interactions and ∼250 nb in K
−
p interactions. From the fact that the production cross section of this resonance in the K
− beam is approximately 50 times greater than the production cross section in the π− beam, it can be concluded that this new state belongs to a system of mesons with hidden strangeness.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 242–246 (25 August 1999) 相似文献
9.
N. Hashimoto T.R. Saitoh G. Sletten R.A. Bark M. Bergström K. Furuno T. Komatsubara T. Shizuma S. Törmänen P.G. Varmette 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):327-330
Abstact: High-spin states in 183Re have been studied using the 176Yb(11B,4n) reaction at 52 and 57 MeV. Two high-K bands have been observed directly by a time-correlated γ-γ coincidence measurement. One of the bands is built on an isomeric
K
π=(25/2)+ state at E
x= 1908 keV with a half-life of 0.82(2) ms. The other band, assigned as K
π=(29/2)− at E
x= 2739 keV, decays to the (25/2)+ band. These bands are interpreted as three-quasiparticle structures, π(5/2)+[402] &⊗ν(9/2)+[624] ⊗ν(11/2)+[615] for the (25/2)+ band and π(9/2)−[514] ⊗ν(9/2)+[624] ⊗ν(11/2)+[615] for the (29/2)− band. The K
π= (29/2)− band becomes strongly Coriolis mixed with increasing spin and is gradually changing into a low-K s-band structure.
Received: 20 April 1998 相似文献
10.
The LHCb collaboration measured CPV at the level of one percent in the difference of asymmetries in $
D^0 (\mathop {D^0 }\limits^ \leftharpoondown )
$
D^0 (\mathop {D^0 }\limits^ \leftharpoondown )
→ π+π−, K + K − decays. If confirmed on a larger statistics and final systematics this would mean New Physics manifestation. The fourth quark-lepton generation can be responsible for the observed effect. 相似文献
11.
The φπ+π− production in pˉp annihilation at rest is strongly enhanced by a two step mechanism with intermediate KˉKππ states. The relative yield of the φ production due to the resonant final state interaction decreases with increasing total
energy of the pˉp system.
Received: 4 August 1997 相似文献
12.
E. P. Shabalin 《Physics of Atomic Nuclei》2010,73(11):1908-1915
The unitarization of the amplitude for the decay process K
10 → π+π− and allowance for the rescattering of final-state pions in the decay process K
+ → π+π+π− make it possible to evaluate, by using the parameters extracted from data on K → 2π decays, the K
+ → π+π+π− decay width. The result agrees with the experimental width value at a level of a few percent. Allowance for corrections for
higher order terms of the momentum expansion of the amplitude for the decay process K
+ → π+π+π− leads to the slope-parameter value of g
++−th = 0.2182, which agrees with its experimental counterpart, g
++−exp = 0.2154 ± 0.0035. 相似文献
13.
M. I. Nagy 《Physics of Particles and Nuclei Letters》2011,8(9):1033-1036
A novel type of quantum mechanical correlations, hypothesized in the 1990’s, the (squeezed) back-to-back correlations, was
predicted to appear in heavy ion collisions among particle-antiparticle (eg. π+π−, K
+
K
−, p[`(p)]p\bar p) pairs, if their in-medium masses are different from the vacuum values. Observation of this correlation would provide new
insight in the freeze-out dynamics of the created matter. The latest status of the PHENIX measurement, comprising the first
measurement of this new effect, is presented. 相似文献
14.
High-statistics data on the γγ → π0η reaction will make it possible to conclude whether the K
+
K
−-loop rescattering mechanism, γγ → K
+
K
− → a
0(980) → π0η, is the main mechanism of the production of a
0(980) isovector resonance. This mechanism provides a reasonable value of 20–30 nb at the maximum for the manifestation of
a
0(980) in the γγ → π0η cross section. It also gives rise to a noticeable narrowing of the a
0(980) peak to its effective (observed) width ≈20–30 MeV in the γγ → π0η channel. The decay width averaged over the resonance mass distribution is 〈Γα
0 → K
+
K
− → γγ〉πη ≈ 0.13 keV. The experimental confirmation of this scenario would be important evidence in favor of the q
2
$
\bar q
$
\bar q
2 nature of light scalar mesons. 相似文献
15.
Inequality of the rates for K
0 → π+
e
− υ− and K
0 → π−
e
+
ν transitions, reported by CPLEAR, and an asymmetry in the distribution of the dihedral angle between the π+π− and e
+
e
− planes in K
L → π+π−
e
+
e
− decays, found by KTeV, have been announced as demonstrations of T-noninvariance. These results are critically interpreted and compared as proofs of the failure of reciprocity. 相似文献
16.
A. Z. Dubničková S. Dubnička E. Goudzovski V. N. Pervushin M. Sečanský 《Physics of Particles and Nuclei Letters》2008,5(2):76-84
We analyze the possibility of experimental investigation of new low-energy relations between the values of resonance masses
in the meson form factors and the differential rate of radiative kaon decay K
+ → π+
e
+
e
−(μ+μ−) at the current level of the experimental precision. A set of arguments is listed in favor that these relations can be a
consequence of weak static interactions in the Standard Model.
The results were presented at the 5th NA48 Mini-Workshop on Kaon Physics, CERN, Dec. 12, 2006.
The text was submitted by the authors in English. 相似文献
17.
E. P. Shabalin 《Physics of Atomic Nuclei》2005,68(1):88-93
The amplitudes of the K
± → 3π and K→ 2π decays are expressed in terms of different combinations of one and the same set of CP-conserving and CP-odd parameters. Extracting the magnitudes of these parameters from the data on K → 2π decays, we estimate an expected CP-odd difference between the values of the slope parameters g
+ and g
− of the energy distributions of “odd” pions in K
+ → π+π+π− and K
− → π−π−π+ decays.
From Yadernaya Fizika, Vol. 68, No. 1, 2005, pp. 89–94.
Original English Text Copyright ? 2005 by Shabalin.
This article was submitted by the author in English. 相似文献
18.
The energy spectra of the even-parity (K
π
= 2+, 3+) and odd-parity (K
π
= 3−, 4−) side-bands in the doubly even nucleus170Yb are studied in the framework of the microscopic method of variation after angular momentum projection with nucleon number
conservation in each projected state. The calculated energy spectra of the ground band and the four side bands in170Yb are in good agreement with the corresponding experimental results. 相似文献
19.
We report on a study of the proton induced hyperon production reactions. We discuss the theoretical efforts made towards understanding
the existing data and the uncertainties involved in the calculations. Our recent calculations of the missing mass spectra
for the pp → K
+ Λp reaction which involve a proper coupled channel treatment of the final state Λp interaction are presented. Significant differences in the results using different models of the hyperon-nucleon interaction
are found. 相似文献
20.
Esraa El-Khateeb 《Indian Journal of Physics》2009,83(11):1525-1548
Existence of the exotic proton-kaon four particle system p
+
k
−
p
−
k
+ is investigated. The Rayleigh-Riyz variational technique is used in calculations. The system tested is found to exist as
bound state and its binding energy is calculated. 相似文献