Limits on $\nu_\mu (\overline{\nu}_\mu) \to \nu_e (\overline{\nu}_e)$ oscillations based on a statistical separation of $\nu_e N$ charged current interactions in the CCFR detector at Fermilab are presented. $\nu_e$ interactions are identified by the difference in the longitudinal shower energy deposition pattern of $\nu_e N \rightarrow eX$ versus $\nu_\mu N \to \nu_\mu X$ interactions. Neutrino energies range from 30 to 600 GeV with a mean of 140 GeV, and $\nu_\mu$ flight lengths vary from 0.9 km to 1.4 km. The lowest 90% confidence upper limit in $sin^2 2\alpha$ of $1.1 \times 10^{-3}$ is obtained at $\Delta m^2 \sim 300 eV^2$. For $sin^2 2\alpha = 1$, $\Delta m^2 > 1.6 eV^2$ is excluded, and for $\Delta m^2 \gg 1000 eV^2$, $sin^2 2\alpha > 1.8 \times 10^{-3}$ is excluded. This result is the most stringent limit to date for $\Delta m^2 > 25 eV^2$ and it excludes the high $\Delta m^2$ oscillation region favoured by the LSND experiment. The $\nu_\mu$-to-$\nu_e$ cross-section ratio was measured as a test of $\nu_\mu (\bar\nu_\mu) \leftrightarrow \nu_e (\bar\nu_e)$ universality to be $1.026 \pm 0.055$.
ALPHA is the neutrino mixing angle. The result for SIN(ALPHA)**2 from the fit at each Delta(M)**2 for NUMU -->NUE oscillations. The 90% CL upper limit is equal to the best fit SIN(ALPHA)**2 + 1.2*SIGMA.
No description provided.
This paper describes an update of the double tagging measurement of the fraction, Rb, of Z0 → bb̅ events in hadronic Z0 decays, with statistics improved by including the data collected in 1994. The presence of electrons or muons from semileptonic decays of bottom hadrons and the detection of bottom hadron decay vertices were used together to obtain an event sample enriched in Z0 → bb̅ decays. The efficiency of the bb̅ event tagging was obtained from the data by comparing the numbers of events having a bottom signature in either one or both thrust hemispheres. Efficiency correlations between opposite event hemispheres are small (< 0.5%) and well understood through comparisons between the real and simulated data samples. A value of Rb= 0.2175 ± 0.0014 ± 0.0017 was obtained, where the first error is statistical and the second systematic. The uncertainty on the decay width Γ(Z0 → cc̅) is not included in these errors. The result depends on Rc as follows: $${⩼ Delta R_{⤪ b}⩈er R_{⤪ b}}=-0.084{⩼ Delta R_{⤪ c}⩈er R_{⤪ c}},$$ where ΔRc is the deviation of Rc from the value 0.172 predicted by the Standard Model.
No description provided.
We report on a measurement of the branching fraction of the Cabibbo-suppressed decay Bu+→J/ψπ+, where J/ψ→μ+μ−. The data were collected by the Collider Detector at Fermilab during 1992–1995 and correspond to an integrated luminosity of 110pb−1 in p¯p collisions at s=1.8TeV. A signal of 28−9+10 events is observed and we determine the ratio of branching fractions B(Bu+→J/ψπ+)/B(Bu+→J/ψK+) to be [5.0−1.7+1.9(stat)±0.1(syst)]%. Using the world average value for B(Bu+→J/ψK+), we calculate the branching fraction B(Bu+→J/ψπ+) to be (5.0−1.9+2.1)×10−5. We also search for the decay Bc+→J/ψπ+ and report a 95% confidence level limit on σ(Bc+)B(Bc+→J/ψπ+)/σ(Bu+)B(Bu+→J/ψK+) as a function of the Bc+ lifetime.
The ratio of the cross sections times the branching fraction.
The production rates of the $J_{P}={1⩈er 2}^{+}$ octet Σ baryons in hadronic Z0 decays have been measured using the OPAL detector at LEP. The inclusive production rates per hadronic Z0 decay of the three isospin states (including the respective antiparticle) have been separately measured for the first time: $άtrix {n_{Sigma^{+}}=0.099pm 0.008pm 0.013ŗ n_{Sigma^{0}}=0.071pm 0.012pm 0.013ŗ n_{Sigma^{-}}=0.083pm 0.006pm 0.009ŗ}$ where the first error is statistical and the second is systematic. Differential cross-sections are also presented for the Σ+ and Σ− and compared with JETSET and HERWIG predictions. Assuming full isospin symmetry, the average inclusive rate is: ${1⩈er 3}[n_{Sigma^{+}+Sigma^{0}+Sigma^{-}}]=0.084pm 0.005 ({⤪ stat.}) pm 0.008 ({⤪ syst.})$.
Differential cross section for SIGMA+ production.
Differential cross section for SIGMA- production.
No description provided.
The total cross sections for the elastic electroproduction of $\rh0$ and $J/\Psi$ mesons for $Q~2$ $>$ 8 GeV$~2$ and $\langle W \rangle \simeq 90$ GeV/c$~2$ are measured at HERA with the H1 detector. The measurements are for an integrated electron$-$proton luminosity of $\simeq$3pb$~{-1}$. The dependences of the total virtual photon$-$proton ($\gamma~* p$) cross sections on $Q~2$, $W$ and the momentum transfer squared to the proton ($t$), and, for the $\rho$, the dependence on the polar decay angle ($\cos \theta~*$), are presented. The $J/\Psi$ : $\rh0$ cross section ratio is determined. The results are discussed in the light of theoretical models and of the interplay of hard and soft physics processes.
Overall EP cross section for M(PI+PI-) < 1.5 GEV.
Overall EP cross section, taking into account the J/PSI --> LEPTON+ LEPTON - branching fraction 0.12.
Integrated EP cross section.
A fresh analysis is reported of high statistics Crystal Barrel data on p p → 3π 0 , ηηπ 0 , ηπ 0 π 0 and ηη ′ π 0 at rest. This analysis is made fully consistent with CERN-Munich data on π + π − → π + π − up to a mass of 1900 MeV, with GAMS data on π + π − → π 0 π 0 , and with BNL and ANL data on π + π − → K K , which are fitted simultaneously. There is evidence for an I = 0, J PC = 2 ++ resonance with weak (≤ 7%) coupling to ππ, strong coupling to both ϱϱ and ωω and pole position 1534 - i90 MeV. This resonance agrees qualitatively with GAMS and VES data on ππ → ωω, previously interpreted in terms of a resonance at 1590–1640 MeV. New masses and widths for (A) ƒ 0 (1370) and (B) ƒ 0 (1500) , fitted to all eight data sets, are M A = 1300 ± 15 Mev, Γ A = 230 ± 15 MeV, M B = 1500 ± 8 MeV, Γ B = 132 ± 15 MeV. Branching ratios to ππ and ηη are given, and differ significantly from earlier determinations because of a new procedure.
A fraction of the initial P-state annihilation into F2(1270) cannot be ruled out. Therefore, the ratio magnitudes include the contribution due to this channel. MESON0 denotes A2(1630) state, not present in RPP.
Preliminary results from WA97 measurements on Λ, Ξ and Ω production in lead-lead and proton-lead collisions are presented, along with a comparison of WA97 proton-lead data with previous WA85 proton-tungsten results. The ratio Ω gX seems to be enhanced in lead initiated reactions compared to proton initiated reactions.
No description provided.
No description provided.
PRELIMINARI DATA.
A study of the reactions p Xe → K + K + X , p Xe → K + H(H → Σ − p)X and p Xe → K + K + H(H → Σ − p)X was performed using the 700-litre xenon bubble chamber DIANA, exposed to the 1 GeV/ c antiproton beam of ITEP (Moscow). From a sample of 7.8 · 10 5 antiproton annihilations at low energy in xenon nuclei 4 events were observed for the reaction p Xe | → K + K + X at rest ( P p ≤ 400 MeV /c ) and 8 for the same reaction in flight ( 400 ≤ P p ≤ 900 MeV /c ). The corresponding probabilities turned out to be 3.1 · 10 −5 and 3.4 · 10 −5 , respectively. No H -event was found in the two semi-inclusive reactions p Xe → K + HX and p Xe → K + K + HX . This lead to the upper limits 6 · 10 −6 and 8 · 10 −6 (90% C.L.), respectively. The corresponding upper limit for the fully inclusive reaction p Xe → HX turned out to be 1.2 · 10 −5 (90% C.L.), which is about one order of magnitude lower than the actual value reported in the literature.
No description provided.
We report measurements of charm particle production asymmetries from the Fermilab photoproduction experiment E687. An asymmetry in the rate of production of charm versus anticharm particles is expected to arise primarily from fragmentation effects. We observe statistically significant asymmetries in the photoproduction of D + , D ∗+ and D 0 mesons and find small (but statistically weak) asymmetries in the production of the D s + meson and the Λ c + baryon. Our inclusive photoproduction asymmetries are compared to predictions from nonperturbative models of charm quark fragmentation.
Production asymmetry. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table. SIG(C=ANTI-CHARM) denotes the reaction with anti-charm production.
Antiparticle/particle production ratio. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table. SIG(C=ANTI-CHARM) denotes the reaction with anti-charm production.
Production asymmetry for particles produced in association with a D*(2010)+-. E-gamma = 200 GeV is mean energy. Only reactions for charm particle production are present in the table.
From a sample of 2.36 million minimum bias events produced in p p collisions at s =630 GeV in the UA1 experiment and from other published data at the CERN S p p S collider we have estimated the relative production of π ± , π 0 , K ± , K S 0 , Λ, Λ , p and p . We obtain a meson over baryon ratio M B = 6.4 ± 1.1 . From the K S 0 π ± ratio we measure the strangeness suppression factor λ = 0.29 ± 0.02 ± 0.01 which, combining with other available data provides a new world average of 0.29 ± 0.015. Both the K S 0 π ± ratio and the strangeness suppression factor λ as a function of s are investigated, and an extrapolation to the LHC energy is performed.
Extrapolation to pt=0.
CONST is strangeness suppression factor, extracted from KS/PI+- ratio (see text).
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