Measurement of pp annihilation cross sections into charged particles in the momentum range 374–680 MeV/c

$\text{p}\text{p}$ annihilation cross sections into 2-, 4- and 6-prong topologies, and the exclusive annihilation cross sections for the π⁺π^?, K⁺K^?, π⁺π^?π⁰, π⁺π⁺π^?π^?, π⁺π⁺π^?π^?π⁰, π⁺π⁺π⁺π^?π^?π^?, and π⁺π⁺π⁺π^?π^?π^?π⁰ channels in the momentum range 374–680 MeV/c were measured. No prominent structure was observed in the momentum dependence of any of the above cross sections, but a small enhancement in the cross section was observed at 490 MeV/c corresponding to the S meson mass in the topological, and π⁺π^?π⁰ and π⁺π⁺π^?π^?π⁰ cross sections. If the extensive of the S meson with a mass and width of 1935.5 and 2.8 MeV/c² is assumed, our measurement gives a total resonant annihilation cross section into charged particles of 10.0±3.0 mb.     

Study of the process e+e-→π+π-π0π0 at energies √s< 1 GeV

In an experiment with the Spherical Neutral Detector at VEPP-2M collider the cross section of the process e+e-→π+π-π0π0 was measured. At energies √s < 920 MeV this cross section was measured for the first time. The energy dependence of the cross section is well discribed by the vector dominance model with contributions from ρ, ρ' ρ", mesons. The decay probability ρ→π+π-π0π0was found to be Bρ = (1.60±0.74±0.18)×10-5. The upper limit for the decay ω→π+π-π0π0 was improved by two orders of magnitude compared to the previous measurements and is Bω < 2 × 10-4 at 90% confidence level.     

ILC上Z玻色子与荷电top-pion对联合产生过程的研究

在国际直线对撞机(ILC)上顶色辅助的人工色(TC2)模型下对Z玻色子与荷电top-pion对联合产生过程e⁺e^- → Zπ_t⁺π_t^-进行了研究. 计算了过程e⁺e^- → Zπ_t⁺π_t^-的产生截面, 发现在TC2模型所允许的参数空间范围之内该过程的截面最大可达到1 fb. 考虑到荷电top-pion的主要的衰变模式π_t⁺ → tb, 发现该截面在ILC能产生很可观的事例数.     

First observation of the decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-)

First observations of the Cabibbo-suppressed decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-) are reported using 35 pb(-1) of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo-favored decays, from which we obtain B(B(0) → D(+)K(-)π(+)π(-))/B(B(0) → D(+)π(-)π(+)π(-))=(5.9±1.1±0.5)×10(-2) and B(B(-) → D(0)K(-)π(+)π(-))/B(B(-) → D(0)π(-)π(+)π(-))=(9.4±1.3±0.9)×10(-2), where the uncertainties are statistical and systematic, respectively. The B(-) → D(0)K(-)π(+)π(-) decay is particularly interesting, as it can be used in a similar way to B(-) → D(0)K(-) to measure the Cabibbo-Kobayashi-Maskawa phase γ.     

Phenomenological studies on B~0 → [K~-π~+]_(S/V)[π~+π~-]_(V/S) → K~-π~+π~+π~- decay

Within the quasi-two-body decay model,we study the localized CP violation and branching fraction of the four-body decay B~0→[K~-π~+]_(s/V)[π~+π~-]_(V/)S→K-π~+π~-π~+ when the K~-π~+and π~-π~+ pair invariant masses are0.35 m(K~-π~+)2.04 GeV and 0 mπ~-π~+1.06 GeV,with the pairs being dominated by the K_0~*(700)~0,K~*(892)~0,K~*(1410)~0,K_0~*(1430) and K~*(1680)~0,and fo(500),ρ~0(770),ω(782) and fo(980) resonances,respectively.When dealing with the dynamical functions of these resonances,fo(500),ρ~0(770),fo(980) and K_0~*(1430) are modeled with the Bugg model,Gounaris-Sakurai function,Flatte formalism and LASS lineshape,respectively,while the others are described by the relativistic Breit-Wigner function.Adopting the end point divergence parameters ρA ∈[0,0.5] andΦ_A∈[0,2π],our predicted results are F_(CP)(B~0→K~-π~+π~+π~-)∈[-0.365,0.447] and B(B~0→K-π~+π~+π~-)∈[6.11,185.32] x 10~(-8),based on the hypothetical qq structures for the scalar mesons in the QCD factorization approach.Meanwhile,we calculate the CP violating asymmetries and branching fractions of the two-body decays B~0→SV(VS) and all the individual four-body decays B~0→SV(VS)→K~-π~+π~-π~+,respectively.Our theoretical results for the two-body decays B~0→K~*(892)~0 fo(980),B~0→K_0~*(1430)~0ω(782),B~0→K~*(892)~0 f~0(980),B~0→K_0~*(1430)~0ρ,and B~0→(1430)~0ω are consistent with the available experimental data,with the remaining predictions await testing in future high precision experiments.     

Multipion production in photon-photon collisions

The magnitudes of the matrix elements for γγ→2π⁺2π^?, γγ→π⁺π^?2π⁰, γγ→2π⁺2π^?π⁰, γγ→2π⁺2π^?2π⁰, γγ→3π⁺3π^?3π⁺ and γγ→3π⁺3π^?π⁰are deduced from experimental data as a function of the invariant massW of the system (from 1.0 to 3.0 GeV). It is shown that the data are consistent with a universal energy dependence of the reduced channel amplitudes. A statistical model is shown to describe the peaks in the energy dependence of multipion production in γγ collisions quite well without introducing explicit intermediate resonances.     

Excited state charge-transfer effect on the phosphorescence emissions of 4-aminopyridine at 77 K

Absorption and phosphorescence spectral characteristics of 4-aminopyridine (AMP) have been studied in polar and non-polar solvents at 77 K. Absorption data provide evidence that the excited singlet π,π¹ states of the molecule possess substantial charge-transfer (CT) character. The 4-AMP molecule is nonfluorescent in all the solvents used in the investigation but phosphoresces strongly in ethanol glass at 77 K. The phosphorescence emissions have a lifetime and negative polarization characteristic of π,π¹ origin. From the observations that in acidic ethanol glassy medium the phosphorescence quantum yield somewhat decreases and the lifetime moderately increases as compared to that in neutral ethanol glass but the negative polarization persists, it has been concluded that all the coupling schemes ¹π,π¹(CT)^$\text{SO3}$π,π¹, ¹π,π^{1$\text{SO3}$}n,π^{1$\text{vib3}$}π,π¹ and ¹π,π^{1$\text{vib1}$}n,π^{1$\text{SO3}$}π,π¹ are responsible for the phosporescence characteristics of 4-AMP molecule. The substatial reductionsin the values of the phosphorescence quantum yield and lifetime of 4-AMP in non-polar rigid matrix at 77 K have been attributed to enhanced nonradiative process arising from increased vibronic interactions between the closely spaced ³n,π¹ and ³π,π¹ states of the molecule in such environment.     

Effect of self-synchronization of DC motors on the amplitude of vibration of a rectangular plate

The present paper shows the condition for which three motors working on the same plate can enter into synchronization with the phase difference equal to 0, π/5, 2π/5, 4π/5, π 8π/5, or 2π depending on the physical characteristics of the motors and the plate. The motors are considered as non-ideal oscillators and act as external excitation on a specific area of the plate. The analysis of the vibration of the plate indicates through numerical simulation that one can obtain a reduction of vibration when the motors are different and rotates in opposite directions.     

Observation of the cabibbo-suppressed decay xi(+)(c) --> pK(-)pi(+)

We report the first observation of the Cabibbo-suppressed charm baryon decay Ξ_{c}^{+}→pK^{-}π^{+}. We observe 150±22±5 events for the signal. The data were accumulated using the SELEX spectrometer during the 1996-1997 fixed target run at Fermilab, chiefly from a 600 GeV/c Σ^{-} beam. The branching fractions of the decay relative to the Cabibbo-favored Ξ_{c}^{+}→Σ^{+}K^{-}π^{+} and Ξ_{c}^{+}→Ξ^{-}π^{+}π^{+} are measured to be B(Ξ_{c}^{+}→pK^{-}π^{+})/B(Ξ_{c}^{+}→Σ^{+}K^{-}π^{+})=0.22±0.06±0.03 and B(Ξ_{c}^{+}→pK^{-}π^{+})/B(Ξ_{c}^{+}→Ξ^{-}π^{+}π^{+})=0.20±0.04±0.02, respectively.     

Character of frustration on magnetic correlation in doped Hubbard model

The magnetic correlation in the Hubbard model on a two-dimensional anisotropic triangular lattice is studied by using the determinant quantum Monte Carlo method. Around half filling, it is found that the increasing frustration t^′/t could change the wave vector of maximum spin correlation along(π,π) → (π, 5π/6) → (5π/6, 5π/6) → (2π/3, 2π/3),indicating the frustration’s remarkable effect on the magnetism. In the studied filling region ?n? = 1.0 ? 1.3, the doping behaves like some kinds of frustration, which destroys the (π,π) AFM correlation quickly and push the magnetic order to a wide range of the (2π/3, 2π/3)120^° order when the t^′/t is large enough. Our non-perturbative calculations reveal a rich magnetic phase diagram over both the frustration and electron doping.     

Applications of Mueller theory of two-particle inclusive processes

Assuming factorization, and extracting inclusive Reggeon vertices from one-particle inclusive data, we predict Regge corrections to scaling for several two-particle inclusive processes. The data on p + P → π^? + π^? + X, K⁺ + p → π^? + π^? + X, K^? + p → π⁺ + π^? + X, and π⁺ + p → π^? + π^? + X agree with our predictions.     

Search for the rare decays K(L)→π0π0μ+μ- and K(L)→π0π0X0→π0π0μ+μ-

The KTeV E799 experiment has conducted a search for the rare decays, K(L)→π(0)π(0)μ(+)μ(-) and K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-), where the X(0) is a possible new neutral boson that was reported by the HyperCP experiment with a mass of (214.3 ± 0.5) MeV/c(2). We find no evidence for either decay. We obtain upper limits of Br(K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-)) < 1.0 × 10(-10) and Br(K(L)→π(0)π(0)μ(+)μ(-)) < 9.2 × 10(-11) at the 90% confidence level. This result rules out the pseudoscalar X(0) as an explanation of the HyperCP result under the scenario that the dsX(0) coupling is completely real.     

A test of CPT symmetry in K0 vs (K-)0→π+π-π0 decays

I show that the CP-violating asymmetry in K0 vs K-0→π+π-π0 decays differs from that in KL→π+π-,KL→π0π0 or the semileptonic KL transitions,if there exists CPT violation in K0-K-0 mixing.A delicate measurement of this difference at a super flavor factory(e.g.,the φ factory)will provide us with a robust test of CPT symmetry in the neutral kaon system.     

Study of Charged Pion Photoproduction on Deuteron with Tagged Photons

The reactions γd→π~- pp and γd→npπ~+π~- have been studied in an energy range from 0.8 to 1.1 GeV at the tagged photon facility of Laboratory of Nuclear Science,T ohoku University.Charged pions and protons in the final state were measured by using the Neutral Kaon Spectrometer (NKS2).The analysis of the γd→π~- pp was mainly used to check the acceptance of the NKS2 and to calibrate the tagged photon energy.The photoproduction of the Δ~(++)Δ~- was identified in the γd→npπ~+π~- reaction.Since the data analyses are still in progress,we issue an interim report and preliminary results.     

Results from a π−p slow proton trigger experiment at 12 GeV/c

A study of the reaction π^?p → X^?p based on 1.27 × 10⁶ events, corresponding to a mean sensitivity of 200 events/μb, is presented. Properties of the exclusive channels π^?p → π^?π⁰p, π⁺π^?π^?p, π⁺π^?π^?π⁰p, π⁺π⁺π^?π^?π^?p and π⁺π⁺π^?π^?π^?π⁰p are discussed.     

Correlations in the final states ppπ+π−π+π− and ppπ+π−π+π−π+π− from 28.5 GeV/c pp collisions

We compare various invariant mass and angular distributions from the final states ppπ⁺π^?π⁺π^? and ppπ⁺π^?π⁺π^?π⁺π^? with the predictions of two models. The essential input to these models is the correct single-particle distributions with energy and momentum conservation constraints taken into account. The data is from 28.5 GeV/c pp interactions in the BNL 80-inch bubble chamber. Substantial agreement between the data and the models is obtained inferring that the kinematic constraints of energy and momentum conservation play a strong role in determining correlations between particles in these high multiplicity final states.     

D meson production and decay in e+e− annihilation at 4.03 and 4 GeV c.m. energy

Decay modes of the charmed mesons, D⁰ and D⁺, are studied in e⁺e^? annihilation data at 4.03 and 4.41 GeV c.m. energy. The products of cross section times branching ratio are measured for the K^?π⁺, K^?π⁺π⁺π^?, K_Sπ⁺π^? and K^?π⁺π⁺ final states. Upper limits are established for the Cabibbo forbidden decays via π⁺π^?, K⁺K^?, K⁺K^? π⁺, K⁺π⁺π^? and π⁺π^?π⁺. The K^?π⁺π⁺π^? final state is shown to be dominated by K^?π⁺ρ⁰.     

Analysis of e + e −→π+π−π+π− and e + e −→π+π−π0π0 processes in the energy range of \sqrt 2 = 0.98 - 1.38 GeV in experiments with a spherical neutral detector

The cross sections of the e ⁺ e ^?→π⁺π^?π ⁺π^?, e ⁺ e ^?→π⁺π^?π⁰π ⁰, and e ⁺ e ^?→ωπ→ π⁺π^?π ⁰π⁰ processes, as well as the e ⁺ e ^?→π⁺π^?π⁰π⁰ process with subtracted contribution of the ωπ intermediate state, are measured in experiments with a spherical neutral detector on the VEPP-2M collider in the energy range 0.98–1.38 GeV. About 41 000 events of the e ⁺ e ^?→π⁺π^?π⁺π ^? process and more than 54 000 events of the e ⁺ e ^?→π⁺π ^?π⁰π⁰ process have been selected in experiment. The statistical error in determining the cross section is 2–20%, while the systematic error is 7 and 8%.     

A comparative study of the NNπ system: (I). The πd → πd, πd → NN channels

Numerical results are presented for πd → πd, πd NN observables for 290 ? T_π (MeV) ? 50. We discuss sensitivity of predictions for various input elements like the deuteron form factor, the range of the NNπ vertex and the parametrization of the background part of the P₁₁πN scattering matrix and remark on possible parallels for A(π, π) and A(π, 2N) amplitudes. A comparison is made with previously obtained results of similar scope.     

Investigation of rare non-strange decay modes of the f meson in Π+p interactions at 5GeVc

Rare decay modes of the f meson are studied in the final states Δ⁺⁺π⁺π^?π⁺π^?, Δ⁺⁺π⁺π^?MM and Δ⁺⁺π⁺π^?π⁺π^?MM. The ratio $\text{Γ (f → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^0\text{π}{}^0\text{)}\text{Γ(f → π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$ is 0.23 ± 0.09 and Γ(f → 4 π) saturates the f inelasticity. A 2 s.d. upper limit of 0.09 is found for the branching ratio $\text{(f → ηη)}\text{(f → 2π)}$.