The glueball mass spectrum in QCD: First results of a lattice Monte Carlo calculation

We perform a variational calculation of the masses of glueballs of various spins and parities in SU(2) gauge theory. The quantum vacuum we use is generated by the lattice Monte Carlo technique. Our first results, obtained on medium sized lattices give m(0⁺) = (3.6 ± 0.35) Λ_mom, m(0^? = (6.0 ± 1.0)Λ_mom, m(2⁺) = (6.5^+1.8_?1.1)Λ_mom, various mass upper bounds and information on glueball wave functions.     

First observation of the production and decay of the Σc+

An event with the decay chain Σ_c⁺ → Λ_c⁺ + π⁰, Λ_c⁺ → K^? + p + π⁺, has been observed in an exposure of BEBC, equipped with a track sensitive target, to the wide band neutrino beam from the SPS at CERN. The event has a unique three constraint kinematic fit to the ΔS = ?ΔQ reaction v + p → μ^? + p + K^? + π⁺ + π⁺ + π⁰ with both gammas from the π⁰ decay detected. The proton and other final state particles are identified. The masses are M(Λ_c⁺) = 2290 ± 3 MeV/c², M(Σ_c⁺) = 2457 ± 4 MeV/c² and M(Σ_c⁺) ? M(Λ_c⁺) = 168 ± 3 MeV/c². Including other data one obtains M (Σ_c⁺⁺) ? M(Σ_c⁺) = 0 ± 4 MeV/c².     

Observation of a doubly charged charmed baryon in the reaction υp→μ−Σ++c

Evidence for the quasi-elastic production of the doubly charged charmed barron Σ⁺⁺_c has been observed in a vp interaction in BEBC. The mass of the Σ⁺⁺_c and of its decay product, the Λ⁺_c, are 2454±5 MeV and 2288±5 MeV, respectively. The mass difference M(Σ⁺⁺_c)? M(Λ⁺_c) is 166±1 MeV. Combining the Λ⁺_c mass value obtained here with the values obtained in the two Λ⁺_c events previously observed in this experiment, thevalue M(Λ⁺_c)=2283±3 MeV is deduced.     

Diffraction dissociation in the reaction p+p→Λ°+K++p at the CERN ISR

The exclusive reaction pp→Λ°K⁺p has been studied at 0.1<?t_pp<0.6 GeV² and energies √s=45 GeV and 53 GeV at the CERN ISR. Diffractive excitation p→Λ°K⁺ occurs predominantly in the mass range M(Λ°K⁺)≈2.1 GeV and peaks at 1.7 GeV. The cross section for pp→Λ°K⁺p is 10±3μb for M(Λ°K⁺)<2.5 GeV, and the t_pp dependence is exp (bt) with b=7.0±0.5 GeV^?2.     

Investigation of the electromagnetic structure of the η meson in the decay η → μ+μ−γ

600 events of the rare electromagnetic decay η → μ⁺μ^?γ have been detected. The branching ratio has been measured as BR(η → μ⁺μ^?γ) = (3.1 ± 0.4) × 10^?4. The electromagnetic form factor of the η meson, F(m_μμ²;0) = (1 ? m_μμ²/Λ²)^?1, has been determined. Λ = (0.72 ± 0.09) GeV/c² is in good agreement with the vector meson dominance model.     

E1-M2-E3 mixing of the 1241.7 keV transition in147Yb

The half-life of theI,K ^π=2, 2^? state at 1318 keV in¹⁷⁴Yb has been measured in the¹⁷³Yb(n, γ) reaction to be 0.486±0.015 ns. This half-life determines the absolute transition probabilities of the gamma-ray transitions to the ground state rotational band yielding the following hindrance factors relative to the Weisskopf estimate:F _W(M 2; 2, 2^?→0, 0⁺)=350;F _W(M2; 2, 2^?→2, 0⁺)≧77F _W(M 2;2, 2^?→4, 0⁺)>740;F _W(E 1; 2, 2^?→2, 0⁺)=4.5×10⁶;F _W(E 3; 2, 2^?→2, 0⁺)≈0.1;F _W(E 3; 2, 2^?→4, 0⁺)≈0.4. These data are compared to analogous transitions in neighboring nuclei.     

Observation and analysis ofE mesons in\bar p p annihilation at rest in H2 gas

Antiproton-proton annihilation at rest in a gaseous H₂ target at NTP into the final state π⁺ π^? K ^± π^? (K ⁰) with an undetectedK ⁰ or \(\bar K^0 \) has been investigated. We observe theE(1420) resonance in the invariant mass spectrum (K ⁰)_miss K ^± π^? with massM _E =1413±8 MeV/c² and widthГ ^E =62 ± 16MeV/c² and find evidence for the production of thef ₁(1285). The absolute branching ratio of \(\bar p\) p → π⁺ π^? E ⁰,E ⁰ →K ₀ ^L K ^± π ^? at (61±6)%P wave annihilation is (3.0±0.9)·10^?4 of all annihilations. The observed suppression of theE production fromP wave with respect to theS wave together with some simple selection rules suggest that the quantum numbers of theE(1420) areJ ^pc=0^?+ and not I⁺⁺.     

A measurement of the lifetime of the Λ3 H hypernucleus

The mean lifetime of the hypernucleus _Λ³H has been measured in a helium bubble chamber with the result, τ(_Λ³H)=(2.46_?0.41^+0.62)×10^?10 sec, based on 16 examples of the decay mode _Λ³H→π^?+³He and 24 examples of the decay mode _Λ³H→π^?+p+d. The decay branching ratio R₃ = Γ(_Λ³H → π^?+^{3He)/Γ(_Λ3H → all π? modes}) has been estimated to be 0.30 ± 0.07.     

Study of the electromagnetic transition form-factor in ω→π0μ+μ− decay

Sixty events of the rare eletromagnetic decay ω→π⁰μ⁺μ^? have been detected. The branching ratio for this decay been obtained to be BR(ω→π⁰μ⁺μ^?) = (9.6 ± 2.3) × 10^?5. The effective mass spectrum for muon pairs has been measured and the electromagnetic transition form-factor for the vertex ωπ⁰, F_ω(m_μμ²;m_π²0) = (1 ? m_μμ²/Λ²)^?1, has been determined, Λ = (0.65 ± 0.03) GeV/c². The results are compared with the vector-meson dominance model.     

Messungen zu den Vibrations- und Zweiquasiteilchenzuständen in172Yb

The Coster-Kronig and Auger spectrum of theL ₁ shell of gaseous argon has been investigated with an electrostatical spectrometer. The ionization in theL ₁ shell of argon was caused by electron impact. Absolute energies and relative intensities of all the Coster-Kronig and Auger transitions have been determined. The relative intensities of transitions within the groupsL ₁ L _{2, 3} M ₁,L ₁ L _{2, 3} M _{2, 3} andL ₁ MM agree fairly well with the theoretical values, calculated byRubenstein for extreme Russel-Saunders coupling, if intermediate coupling theory is used properly. Via the widthγ(L ₁) of theL ₁ level of argon, found in this experiment to be (1.84±0.2) eV, the following absolute group transition probabilities were determined (in units of 10¹⁴ sec^?1):W(L₁ L _{2, 3} M ₁)=(5.5±1.0),W(L₁ L _{2, 3} M _{2, 3})=(20.8±2.8),W(L₁ MM)=(1.44±0.16). The theoretical values are 21.0, 20.4 and 1.27. The possible reason for the large discrepancy between the experimental and theoretical value ofW(L₁ L _{2, 3} M ₁) is the use of the incorrect value of 287 eV for the binding energyE(L₁) byRubenstein. From the energies of theL ₁ MM transitions this value has been determined to beE(L₁)=(326.5±0.5) eV. This is the first direct measurement ofE(L₁) of argon.     

Intensities and half-widths at different temperatures for the 201III←000 band of CO2 at 4854 cm−1

Measurements made at temperatures of 197, 233, and 294°K of the absolute intensities and self-broadening coefficients for the vibration-rotation lines of the 201_III←000 band of the ¹²C¹⁶O₂ molecule, are reported. From these measurements, values have been derived for the vibration-rotation interaction factor (F_VR), the purely vibrational transition moment (|R(O)|), and the intensity (S_Band). The results are: E_VR(m) = 1+(2.2±0.7)×10^?3m+(5.6±1.6)×10^×5m², |R(0)| = (2.064±0.017)×10^?3 debye, S_Band = 21,329±69 cm^?1km^?1atm^?1_STP. The results for the self-broadening coefficients are presented in the text.     

The hadronic cross section of electron-positron annihilation at 9.5 GeV and the ϒ and ϒ′ resonance parameters

The reaction e⁺e^?→ hadrons has been measured in the ? and ?′ region using the DASP detector at the DESY storage ring DORIS. The following final results are obtained: R_had(9.5 GeV)=3.73±0.16±0.28, Γ_ee(?)=(1.23 ± 0.08 ± 0.12) keV, B_μμ(?)=(3.2±1.3±0.3)%, $\text{Γ}{}_{\mathrm{<mtext>ee</mtext>}}\text{Γ}{}_{\mathrm{<mtext>had</mtext>}}\text{Γ}{}_{\mathrm{<mtext>tot</mtext>}}\text{(?′)=(0.55±0.11 ±0.06)}\text{keV}$, and M(?′)?M(?)=(556 ±10) MeV.     

Hyperfeinstrukturuntersuchung des 6p 2 P 3/2-Terms im Au I-Spektrum durch Resonanzstreuung von Licht

From about 6×10⁶ stoppingK ^?-meson reactions in the Saclay 80 cm hydrogen bubble chamber 70Σ ^?→Λe^?¯ν and 11Σ⁺→Λe⁺ν decays have been identified. The ratio of the vector to axial vector coupling constant has been determined,f ₁/g ₁=?0.22±0.28, consistent with the predictionf ₁=0 of the CVC-theory. The branching ratios for the two decay modes are,Γ(Σ ^?→Λe^?ν)/Γ(Σ^?→ all modes)=(0.69±0.12). 10^?4,Γ(Σ⁺→Λe⁺ν)/Γ(Σ⁺→ all modes)=(0.29±0.10). 10^?4. The ratio, Γ(Σ⁺→Λe⁺)/Γ(Σ^?→Λe^?v)=0.69±0.18, agrees with the phase space ratio, 0.61, therefore a theory that includes no second class currents is consistent with the data.     

An interpretation of the energy-momentum tensor of the dirac field with anomalous magnetic moment

The ground state radiative widths of the 1.56 MeV (3/2⁺) and the 1.35 MeV (5/2^?) levels in¹⁹F were determined by inelastic electron scattering. The measured cross sections have been analysed using DWBA calculations. The resultsΓ _y ⁰ (5/2^?→1/2^?,E3)=(8.1±1.7)·10^?10eV andΓ _y ⁰ (3/2⁺→1/2⁺,E2=(1.76±0.15)·10^?4eV are in agreement with, but more accurate than, former measurements.     

Astrophysical S factor for dd interaction at ultralow energies

Experimental results are presented that were obtained by measuring the astrophysical S factor for dd interaction at very low deuteron collision energies by using the liner-plasma technique. The experiment was performed at the high-current generator of the High-Current Electronics Institute (Tomsk, Russia). The values found for the S factor at the deuteron collision energies of 1.80, 2.06, and 2.27 keV are S _dd=114±68, 64±30, and 53±16 keV b, respectively. The corresponding dd cross sections obtained as the product of the barrier factor and the measured astrophysical S factor are σ _dd ⁿ (E _col=1.80 keV)=(4.3±2.6)×10^?33cm², σ _dd ⁿ (E _col=2.06 keV)=(9.8±4.6)×10^?33cm², and σ _dd ⁿ (E _col=2.27 keV)=(2.1±0.6)×10^?32cm².     

Electroexcitation of isovector magnetic dipole and quadrupole transitions in 18O and their relation to radiative pion capture

In a high-resolution ¹⁸O(e, e′) experiment sharp states at E_X=16.38±0.01 MeV (J^π=2^?, ground state analogue of and at E_X=18.86±0.01 MeV (J^π=1⁺) and clustering of strength (possibly with J^π=1^?, 2^?) at E_X≈23.7 MeV have been observed and compared to theoretical predictions. The transition strengths for the narrow states are B(M2) ↑ = 58± 8 μ_K² fm² and B(M1) ↑ = 0.28± 0.04 μ_K², respectively. These results agree qualitatively with the resu lts from the analogous ¹⁸O(π^?, γ)¹⁸N reaction.     

Exotic states X ±(1600, I G (J PC)=2+ (2++)) in photoproduction reactions

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.     

The πd scattering length from Kα X-rays

X-rays from the K_α transition (2P → 1S) of the π^?d mesic atom have been observed. Their energy, 2592.8 _?2.0^+1.6, has been measured by the critical absorber technique, using the M_V absorption edge in bismuth. The strong interaction shift in the 1S state is ?4.8 eV, corresponding to a scattering length a(πd) = ?(0.052_?0.017^+0.022)m_π^?1, in agreement with recent calculations. The intensity ratio K_α/K_total = 0.548 ± 0.015.     

Evidence for a newK * \bar K state at a mass of 1,530 MeV withIJ PC=01++ observed inK − p interactions at 4.2 GeV/c

Evidence is presented for a newK ^* \(\bar K\) +c.c. resonance with a mass of (1,526±6) MeV, a width of (107±15) MeV and quantum numbersIJ ^PC=01⁺⁺. We call itD′ meson. Initially it is observed as aK ^* \(\bar K\) +c.c. enhancement in the reactionsK ^? p→(K _s ⁰ K ^±π^?)Λ at 4.2 GeV/c. The isospin assignmentI=0 comes from its further observation in the reactionsK ^? p→(K _s ⁰ K ^±π^?)Σ ⁰ andK ^? p→(K _s ⁰ K ^±π^?)Σ(1,385)⁰ but not inK ^? p→(K ⁺ K ^?π^?)Σ⁺ orK ^? p→(K _s ⁰ K ^±π^?)Σ(1,385)⁺. A maximum likelihood analysis of the (K \(\bar K\) π) decay Dalitz plots in the reactionsK ^? p→(K _s ⁰ K ^±π^?) determines theJ ^PC of theD′ meson to be 1⁺⁺. A satisfactorySU(3) fit is obtained to a 1⁺⁺ nonet composed of theI-1A ₁, theI=1/2Q _A with theD(1,285) and theD′(1,526) as theI=0 members having a mixing angle close to the magic one.