Charged current neutrino interactions below 30 GeV

Charged current data of a spark chamber neutrino experiment at the 70 GeV Serpukhov accelerator (10 200 events in the v beam and 3600 events in the $\text{v}$ beam with energies up to 30 GeV) have been analyzed. Total neutrino and antineutrino cross sections and v-distributions are obtained.     

Further evidence for formation of a narrow baryon resonance with positive strangeness in K + collisions with Xe nuclei

We have continued our investigation of the charge-exchange reaction K ⁺Xe → K ⁰ pXe’ in the bubble chamber DIANA. In agreement with our previous results based on part of the present statistics, formation of a narrow pK ⁰ resonance with mass of 1537 ± 2 MeV/c ² is observed in the elementary transition K ⁺ n → K ⁰ p on a neutron bound in the xenon nucleus. The visible width of the peak is consistent with being entirely due to instrumental resolution and allows one to place an upper limit on its intrinsic width: Γ < 9 MeV/c ². A more precise estimate of the resonance intrinsic width, Γ = 0.36 ± 0.11 MeV/c ², is obtained from the ratio between the numbers of resonant and nonresonant charge-exchange events. The signal is observed in a restricted interval of incident K ⁺ momentum that is consistent with smearing of a narrow pK ⁰ resonance by Fermi motion of the target neutron. The statistical significance of the signal is some 7.3, 5.3, and 4.3 standard deviations for the estimators and , respectively. This observation confirms and reinforces our earlier results, and offers strong evidence for formation of a pentaquark baryon with positive strangeness in the charge-exchange reaction K ⁺ n → K ⁰ p on a bound neutron. (The DIANA Collaboration) The text was submitted by the authors in English.     

Observation of muon pairs in neutrino interactions at Serpukhov 70 GeV accelarator

A search for dimuons produced in a spark chamber experiment in neutrino and antineutrino beams of the Serpukhov accelerator is reported. The clear dimuon signal has been observed in vN interactions. R_v = N(2ω)/N(1ω)? (6.2 ± 1.7) × 10^?3 in the energy interval 7.5 ÷ 30 GeV. From antineutrino data we conclude that in the same energy range $\text{R}{}_{\mathrm{<mtext>v</mtext>}}\text{? 1.1. × 10}{}^{\mathrm{?2}}\text{(90\% C.L.)}$.     

Evidence for formation of a narrow <Emphasis Type="Italic">K</Emphasis><Stack><Subscript>S</Subscript><Superscript>0</Superscript></Stack><Emphasis Type="Italic">p</Emphasis> resonance with mass near 1533 MeV in neutrino interactions

A narrow baryon resonance is observed in the invariant mass of the K _S ⁰ p system formed in neutrino and antineutrino collisions with nuclei. The mass of the resonance is estimated at 1533±5 MeV. The observed width is less than 20 MeV and is compatible with being entirely due to experimental resolution. The statistical significance of the signal is near 6.7 standard deviations. Since the position of the observed resonance does not match the mass of any known Σ*⁺ states, we believe that it arises from the neutrino production of the Θ⁺ pentaquark baryon. The analysis is based on the data obtained in past neutrino experiments with big bubble chambers: WA21, WA25, WA59, E180, and E632.     

Observation of a narrow charm-strange meson D(+)(sJ)(2632)-->D(+)(s)eta and D(0)K(+)

We report the first observation of a charm-strange meson D(+)(sJ)(2632) at a mass of 2632.5+/-1.7 MeV/c(2) in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D(+)(s)eta and D0K+. In the D(+)(s)eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c(2). There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c(2) in the decay mode D0K+. The decay width of this state is <17 MeV/c(2) at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(D(+)(s)eta) is 0.14+/-0.06. The mechanism that keeps this state narrow is unclear. Its decay pattern is also unusual, being dominated by the D(+)(s)eta decay mode.     

A new limit on the orthomuon mass

Results of the CDHS group NC/CC measurements are used to obtain the 10.3 GeV lower limit on the orthomuon mass.