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1.
It is shown that the list of unusual mesons that are planned to be studied in photoproduction reactions can be supplemented
with I
G (J
PC)=2+ (2++) exotic states X
±(1600), which are natural to seek as manifestations of the ρ±ρ0 decay channels in the reactions γN → ρ±ρ0
N and γN → ρ±ρ0Δ. A classification of the ρ±ρ0 states according to their quantum numbers is presented. A model for the spin structure of the amplitudes for the reactions
γp → f
2(1270)p, γp → a
2
0
(1320)p, and γN → X
±(N, Δ) is proposed, and estimates are obtained for the corresponding cross sections. At E
γ≈6 GeV, it is found that σ(γP → f
2(1270)p)≈0.12 μb, σ(γp → a
2
0
(1320)p)≈0.25 μb, σ(γN → X
±
N → ρ±ρ0
N) ≈ 0.018 μb, and σ(γp → X
−Δ++ → ρ−ρ0Δ++≈0.031 μb. The problem of isolating signals from X
± states against the natural background that is associated with other channels of π±π0π+π− production is discussed. It is deduced that searches for exotic states X
±(2+ (2++)) in experiments at JLAB will be quite efficient—for example, the yield of about 2.8×106 events per month is expected to correspond to the estimated cross sections for the reactions γN → X
±
N → ρ±ρ0
N.
__________
Translated from Yadernaya Fizika, Vol. 63, No. 10, 2000, pp. 1904–1912.
Original Russian Text Copyright ? 2000 by Achasov, Shestakov. 相似文献
2.
On the basis of the experimental data on diffractive processes in πp, pp and pˉp collisions at intermediate, moderately high and high energies, we restore the scattering amplitude related to the t-channel exchange by vacuum quantum numbers by taking account of the diffractive s-channel rescatterings. At intermediate and moderately high energies, the t-channel exchange amplitude turns, with a good accuracy, into an effective pomeron which renders the results of the additive
quark model. At superhigh energies the scattering amplitude provides a Froissart-type behaviour, with an asymptotic universality
of cross sections such as σtot
πp/σtot
pp→ 1 at s→∞. The quark structure of hadrons being taken into account at the level of constituent quarks, the cross sections of pion
and proton (antiproton) in the impact parameter space of quarks, σπ(r
1⊥, r
2⊥; s) and σp(r
1⊥, r
2⊥, r
3⊥; s), are found as functions of s. These cross sections implicate the phenomenon of colour screening: they tend to zero at |r
i⊥−r
k⊥|→ 0. The effective colour screening radius for pion (proton) is found for different s. The predictions for the diffractive cross sections at superhigh energies are presented.
Received: 15 December 1998 相似文献
3.
A ππ, ˉKK, and ρρ(ωω) fully coupled channel model is used to predict the lowest isospin S, P, D, F-wave phase shifts and inelasticities
for elastic ππ scattering from threshold to 2.0 GeV. As input the S-matrix is required to exhibit poles corresponding to the
meson resonance table of the Particle Data Group. As expected, the ππ inelasticity is very strongly related to the opening
of the ˉK channel near 1 GeV, and the opening of ρρ(4π) and ωω(6π) channels in the 1.5 GeV region. The predictions of this model are
compared to the various elastic ππ→ππ amplitudes, that were obtained from analyses of π− p →π−π+n data. The role of the various resonances, in particular the glueball candidate f
0(1500) and the f
J(1710) is investigated.
Received: 19 November 1997 相似文献
4.
P. V. Fedorets M. Büscher V. P. Chernyshev S. N. Dymov V. Yu. Grishina C. Hanhart M. Hartmann V. Hejny V. Kleber H. R. Koch L. A. Kondratyuk V. P. Koptev A. E. Kudryavtsev P. Kulessa S. I. Merzliakov S. M. Mikirtychiants M. E. Nekipelov H. Ohm R. Schleichert H. Ströher V. E. Tarasov K. -H. Watzlawik I. Zychor 《Physics of Atomic Nuclei》2006,69(2):306-313
The reaction pp → dπ
+
η has been measured at a beam energy of T
p
= 2.65 GeV (p
p
= 3.46 GeV/c) using the ANKE spectrometer at COSY-Julich. The missing-mass distribution of the detected dπ
+ pairs exhibits a peak around the η mass on top of a strong background of multipion pp → dπ
+(nπ) events. The differential cross section d
4
σ/dΩd
dΩ
π
+
dp
d
dp
π
+ for the reaction pp → dπ
+
η has been determined model independently for two regions of phase space. Employing a dynamical model for the a
0
+
production allows one then to deduce a total cross section of σ(pp → da
0
+
→ dπ
+
η) = 1.1 ± 0.3stat ± 0.7syst μb for the production of π
+
η via the scalar a
0
+
(980) resonance and σ(pp → dπ
+
η) = 3.5 ± 0.3stat ± 1.0syst μb for the nonresonant production. Using the same model as for the interpretation of recent results from ANKE for the reaction
, the ratio of the total cross sections is
, which is in agreement with branching ratios in the literature.
The text was submitted by the authors in English. 相似文献
5.
O. G. Tchikilev S. A. Akimenko G. I. Britvich K. V. Datsko A. P. Filin A. V. Inyakin V. A. Khmelnikov A. S. Konstantinov I. Ya. Korolkov V. M. Leontiev V. P. Novikov V. F. Obraztsov V. A. Polyakov V. I. Romanovsky V. I. Shelikhov V. A. Uvarov O. P. Yushchenko V. N. Bolotov S. V. Laptev V. A. Duk A. Yu. Polyarush 《Physics of Atomic Nuclei》2007,70(1):29-34
Using data collected with the ISTRA+ spectrometer during the 2001 run of the U-70 proton synchrotron in Protvino, the first
observation of the radiative kaon decay K
− → μ−π0γν is reported. The ratio Br(K
μ3γ, 5 < E*γ < 30 MeV)/Br(K
μ3) is found to be [0.270 ± 0.029(stat.) ± 0.026(syst.)]% and the ratio Br(K
μ3γ, 30 < E*γ < 60 MeV)/Br(K
μ3) = [0.0448 ± 0.0068(stat.) ± 0.0099(syst.)]%. These ratios are consistent with the theoretical predictions 0.21 and 0.047%,
respectively. The measured angular distribution asymmetry for the region 5 < E*γ < 30 MeV, A(cos ϑ*μγ) = 0.093 ± 0.141, is two standard deviations away from the theoretical prediction of 0.354. The measured asymmetry in the
T-odd variable ξ = pγ · (pμ × pπ)/m
K
3
is −0.03 ± 0.13.
The text was submitted by the authors in English. 相似文献
6.
We calculate target fragmentation in pp→nX and γp→nX reactions in the meson cloud picture of the nucleon. The pp→nX reaction is used to fix the pnπ+ form factor for three different models. We take into account the possible destruction of the residual neutron by the projectile.
Using the form factor from the hadronic reaction we calculate photoproduction and small x
Bj electroproduction of forward neutrons at HERA. Here the qˉq dipoles in the photon can rescatter on the residual neutron. In photoproduction we observe slightly less absorption than
in the hadronic reaction. For deep inelastic events (Q
2 > 10 GeV2) screening is weaker but still present at large Q
2. The signature for this absorptive rescattering is a shift of the dσ/dEn distribution to higher neutron energies for photofragmentation.
Received: 12 June 1999 / Revised version: 12 October 1999 相似文献
7.
R. Escribano 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):454-457
The scalar contributions to the radiative decay φ→K
0ˉ0
γ are studied within the framework of the Linear Sigma Model (LσM). Theoretical predictions for the associated subprocesses φ→f
0
γ and φ→a
0
γ as well as the ratio φ→f
0
γ/a
0
γ are also given. 相似文献
8.
A.V. Anisovich V.V. Anisovich V.A. Nikonov L. Montanet 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):247-249
We discuss γγ partial widths of pseudoscalar/isoscalar mesons η:(M) in the mass region M∼ 1000–1500 MeV. The transition amplitudes η:(1295) →γγ and η:(1440) →γγ are studied within an assumption that the decaying
mesons are the members of the first radial excitation nonet 21
S
0qˉq. The calculations show that partial widths being of the order of 0.1 keV are dominantly due to the nˉn meson component
while the contribution of the sˉs component is small.
Received: 24 September 1999 相似文献
9.
W. Cassing Ye.S. Golubeva L.A. Kondratyuk 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):279-285
We study the possibility to measure the elastic ΦN (Φ≡J/ψ,ψ(2S), ψ(3770), χ2c) scattering cross section in the reaction ˉp+d→Φ+n
sp and the elastic D(ˉD)N scattering cross section in the reaction ˉp+d→D
−
D
0
p
sp. Our studies indicate that the elastic scattering cross sections can be determined for Φ momenta about 4–6 GeV/c and D/ˉD momenta 2–5 GeV/c by selecting events with p
t≥ 0.4 GeV/c for Φ's and p
t(p
sp) ≥ 0.5 GeV/c for D/ˉD-meson production.
Received: 8 November 1999 相似文献
10.
Gui-Jun Ding Rong-Gang Ping Mu-Lin Yan 《The European Physical Journal A - Hadrons and Nuclei》2006,28(3):351-360
X(1835) has been treated as a baryonium with sizable gluon content, and to be almost flavor singlet. This picture allows us
to rationally understand X(1835) production in J/ψ radiative decays, and its large couplings with pˉ, η′ππ. The processes ϒ(1S) → γX(1835) and J/ψ → ωX(1835) have been examined. It has been found that Br(ϒ(1S) → γX(1835))Br(X(1835) → pˉ) < 6.45×10-7, which is compatible with CLEO's recent experimental result (Phys. Rev. D 73, 032001 (2006) hep-ex/0510015). The branching fractions Br(J/ψ → ωX(1835)), Br(J/ψ → ρX(1835)) with X(1835) → pˉ and X(1835) → η′π+π- have been estimated by the quark-pair creation model. We show that they are heavily suppressed, so the signal of X(1835) is very difficult, if not impossible, to be observed in these processes. The experimental checks for these estimations
are expected. The existence of the baryonium nonet is conjectured, and a model-independent derivation of their production
branching fractions is presented. 相似文献
11.
S. Pacetti 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):665-671
We define a general procedure, based on analyticity and dispersion relations, to estimate low-energy amplitudes for processes
like: φ→e
+
e
-
M and φ→γM, starting from cross-section data on e
+
e
-→φM, where M is a generic light scalar or pseudoscalar meson. In particular this procedure is constructed to obtain predictions on the
radiative decay rate which are crucially linked on the assumed quark structure for the meson M under consideration. Three cases are analyzed: M = η, M = f
0(qˉ) and M = f
0(qqˉ). While in the η case the estimate of the branching fraction for the radiative decay φ→ηγ is in agreement with the data, in the case of f
0, such agreement is obtained only under the hypothesis of a tetraquark scalar meson. 相似文献
12.
W. Deconinck 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):653-655
An experimental search for the Θ(1540)- and Λ(1520)-resonance was performed in quasi-real photoproduction on deuterium at the HERMES experiment. While evidence for Θ(1540) was found in the decay channel pK
0
S→pπ
+
π
-, no evidence for the corresponding anti-particle was found. In some models it is expected that the Θ(1540) and the Λ(1520) have similar production mechanisms. The photoproduction cross-sections for the Λ(1520) in the decay channel Λ(1520)→pK
- and the corresponding anti-particle are determined. The partial photoproduction cross-sections for Λ(1520) and ˉ(1520) are obtained as σ
Λ(1520) = 65.3±8.8(stat)±6.9(syst)nb and σ
ˉ(1520) = 9.8±2.6(stat)±0.9(syst)nb, corresponding to a ratio R
Λ(1520) = σ
ˉ(1520)/σ
Λ(1520) = 0.15±0.05(stat)±0.02(syst). 相似文献
13.
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
14.
Using intensity autocorrelation of multiply scattered light, we show that the increase in interparticle interaction in dense,
binary colloidal fluid mixtures of particle diameters 0.115μm and 0.089μm results in freezing into a crystalline phase at volume fractionφ of 0.1 and into a glassy state atφ=0.2. The functional form of the field autocorrelation functiong
(1)(t) for the binary fluid phase is fitted to exp[−γ(6k
0
2
D
eff
t)1/2] wherek
0 is the magnitude of the incident light wavevector andγ is a parameter inversely proportional to the photon transport mean free pathl*. TheD
eff is thel* weighted average of the individual diffusion coefficients of the pure species. Thel* used in calculatingD
eff was computed using the Mie theory. In the solid (crystal or glass) phase, theg
(1)(t) is fitted (only with a moderate success) to exp[−γ(6k
0
2
W(t))1/2] where the mean-squared displacementW(t) is evaluated for a harmonically bound overdamped Brownian oscillator. It is found that the fitted parameterγ for both the binary and monodisperse suspensions decreases significantly with the increase of interparticle interactions.
This has been justified by showing that the calculated values ofl* in a monodisperse suspension using Mie theory increase very significantly with the interactions incorporated inl* via the static structure factor. 相似文献
15.
Yu.S. Surovtsev D. Krupa M. Nagy 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):409-416
In a combined analysis of the experimental data on the coupled processes ππ↦ππ, KˉK in the channel with I
G
J
PC = 0+0+ +, the various scenarios of these reactions (with different numbers of resonances) are considered. In a model-independent approach,
based only on analyticity and unitarity, a resonance is represented by a pole cluster (poles on the Riemann surface) of the
definite type that is defined by the state nature. The best scenario contains the resonances f
0(665) (with properties of the σ-meson), f
0(980) (with a dominant sˉs component), f
0(1500) (with a dominant flavour-singlet, e.g., glueball component) and the f
0(1710) (with a considerable sˉs component). If the f
0(1370) exists, it has a dominant sˉs component. The coupling constants of the observed states with the considered channels and the ππ and KˉK scattering lengths are obtained. The conclusion on the linear realization of chiral symmetry is drawn.
Received: 25 April 2002 / Accepted: 4 June 2002 / Published online: 26 November 2002
RID="a"
ID="a"e-mail: surovcev@thsun1.jinr.ru
RID="b"
ID="b"e-mail: krupa@savba.sk
RID="c"
ID="c"e-mail: fyzinami@nic.savba.sk
Communicated by V.V. Anisovich 相似文献
16.
S. Heinemeyer 《Pramana》2007,69(5):947-951
Electroweak precision measurements can provide indirect information about the possible scale of supersymmetry already at the
present level of accuracy. We review present day sensitivities of precision data in mSUGRA-type models with the gravitino
as the lightest supersymmetric particle (LSP). The χ
2 fit is based on M
W
, sin2
θ
eff, (g−2)
μ
, BR(b → sγ) and the lightest MSSM Higgs boson mass, M
h
. We find indications for relatively light soft supersymmetry-breaking masses, offering good prospects for the LHC and the
ILC, and in some cases also for the Tevatron.
相似文献
17.
The phase structure of the two-dimensional Gross-Neveu model in a spacetime of the form R
1×S
1 and in the presence of a chemical potential μ is investigated. The phase portrait of the model is constructed in the parameter
plane (μ, γ), where γ=1/L and L is the length of the circle S
1. In the portrait there exist two massive phases, with spontaneously broken chiral invariance, as well as infinitely many
massless symmetric phases. Such a vacuum structure leads to oscillations of the critical curve μ
c
(γ) of chiral phase transitions. In addition, the particle number density in the vacuum state of the model oscillates if μ<μ
c
(γl).
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 5, 431–436 (10 September 1998) 相似文献
18.
L. Roca C. Hanhart E. Oset U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2006,27(3):373-380
The Λ(1520)-resonance has been recently studied in a unitarized coupled-channel formalism with πΣ(1385), KΞ(1530), ˉN and πΣ as constituents blocks. We provide a theoretical study of the predictions of this model in physical observables of
the pp → pK+K-p and pp → pK+π0π0Λ reactions. In particular, we show that the ratio between the π0π0Λ and K-p mass distributions can provide valuable information on the ratio of the couplings of the Λ(1520)-resonance to πΣ(1385) and
ˉN than the theory predicts. Calculations are done for energies which are accessible in an experimental facility like COSY at
Jülich or the developing CSR facility at Lanzhou. 相似文献
19.
Uhlmann's transition probability P(ψ, φ) of two normal states of a von Neumann algebra M, which is the supremum of |(Ψ, Φ)|2 for all possible choices of representative vectors Ψ and Φ of ψ and φ, is shown to be the infimum of (∫d(μψ, e)1/2)2 for the induced measures μω, e(B)=ω(e(B)) (B: Borel set in ℝ, ω=ψ, φ) for all possible projection-valued measures e belonging to M. 相似文献
20.
The photoinduced optical absorption α of doped yttrium iron garnets (YIG) is investigated. It is found that the optical absorption
α at a wavelength of 1.1 μm depends on the wavelength of irradiating light in the range 0.6–1.9 μm. It is demonstrated that,
in the Y3Fe5O12 crystal with an acceptor Ba impurity, the photoinduced increase in α is due to the formation of Fe4+ ions in octahedral sites. The charge transfer occurs through photoexcitation of the 6
A
1g
(6
S) → 4
T
1g
(4
G) and 6
A
1g
(6
S) → 4
T
2g
(4
G) transitions of octahedral Fe3+ ions. In the crystal with a donor Si impurity, the increase in α is caused by the formation of Fe2+ ions upon photoionization of silicon.
__________
Translated from Fizika Tverdogo Tela, Vol. 43, No. 7, 2001, pp. 1233–1235.
Original Russian Text Copyright ? 2001 by Doroshenko, Nadezhdin. 相似文献