We present an improved determination of the proton structure functions $F_{2}$ and $xF_{3}$ from the CCFR $\nu $-Fe deep inelastic scattering (DIS) experiment. Comparisons to high-statistics charged-lepton scattering results for $F_{2}$ from the NMC, E665, SLAC, and BCDMS experiments, after correcting for quark-charge and heavy-target effects, indicate good agreement for $x>0.1$ but some discrepancy at lower x. The $Q^{2}$ evolution of the structure functions yields the quantum chromodynamics (QCD) scale parameter $\Lambda_{\bar{MS}}^{NLO,(4)}=337 \pm 28$(exp.) MeV. This corresponds to a value of the strong coupling constant at the scale of mass of the Z-boson of $\alpha _{S}(M_{Z}^{2})=0.119 \pm 0.002 (exp.) \pm 0.004 (theory)$ and is one of the most precise measurements of this quantity.
No description provided.
No description provided.
No description provided.
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.
Deep inelastic charged--current reactions have been studied in $e~+p$ and $e~-p$ collisions at a center of mass energy of about $300\,\gev$ in the kinematic region $Q~2\greater200\,\gev~2$ and $x\greater0.006$ using the ZEUS detector at HERA. The integrated cross sections for $Q~2\greater200\,\gev~2$ are found to be $\sigep=30.3\,{}~{+5.5}_{\mns4.2}\,{}~{+1.6}_{\mns2.6}\,{\rm pb}$ and $\sigem=54.7\,{}~{+15.9}_{\mns\chax 9.8}\,{}~{+2.8}_{\mns3.4}\,{\rm pb}$. Differential cross sections have been measured as functions of the variables $x$, $y$ and $Q~2$. From the measured differential cross sections $d\sigma/dQ~2$, the $W$ boson mass is determined to be $M_W=79\,{}~{+8} _{-7}{}~{+4}_{-4}\,\gev$. Measured jet rates and transverse energy profiles agree with model predictions. A search for charged--current interactions with a large rapidity gap yielded one candidate event, corresponding to a cross section of $\sigep(Q~2\greater200\,\gev~2;\eta_{\rm max}<2.5)=0.8\,{}_{-0.7}~ {+1.8}\,\pm0.1\,{\rm pb}$.
No description provided.
No description provided.
No description provided.
The $Q~{2}$ dependence and the total cross sections for charged and neutral current processes are measured in $e~{\pm}p$ reactions for transverse momenta of the outgoing lepton larger than 25 GeV. Comparable size of cross sections for the neutral current process and for the weak charged current process are observed above $Q~2\approx5000$GeV$~2$. Using the shape and magnitude of the charged current cross section we determine a propagator mass of $m_{W} = 84\ ~{+10}_{-7}$ GeV.
No description provided.
No description provided.
Total cross-section for E-P events.
The Krakow-Louisiana-Minnesota-Moscow Collaboration (KLMM) has exposed a set of emulsion chambers with lead targets to a 158 GeV/c per nucleon beam of Pb208 nuclei, and we report the initial analysis of 40 high-multiplicity Pb-Pb collisions. To test the validity of the superposition model of nucleus-nucleus interactions in this new regime, we compare the shapes of the pseudorapidity distributions with FRITIOF Monte Carlo model calculations, and find close agreement for even the most central events. We characterize head-on collisions as having a mean multiplicity of 1550±120 and a peak pseudorapidity density of 390±30. These estimates are significantly lower than our FRITIOF calculations. © 1996 The American Physical Society.
No description provided.
No description provided.
Cross sections for J ψ,ψ′ and Drell-Yan production in Pb+Pb collisions at 158×A GeV/c are presented and compared with results obtained by the NA38 and NA51 collaborations. The Pb+Pb data have been collected by the NA50 collaboration using the NA38 dimuon spectrometer. The Drell-Yan mechanism is found to scale as (A projectile · B target ) in p+B target and A projectile + B target collisions including Pb+Pb collisions. Regarding J ψ , an anomalous suppression is observed in Pb+Pb collisions with respect to the suppression observed in p+B target , O+B target and S+U collisions. The cross section ratios ψ′ ( J ψ ) are similar in Pb+Pb and S+U collisions.
No description provided.
No description provided.
Minimum Bias production cross sections of $\eta$ mesons have been measured in 200AGeV S+Au and S+S collisions at the CERN SPS by reconstructing the $\eta\rightarrow\gamma\gamma$ decay. The measurements have been made over the rapidity range $2.1 \leq y \leq 2.9$ using the leadglass spectrometer of WA80. Within the statistical and systematical uncertainties the spectral shapes of $\pi~0$ and $\eta$ mesons yields are identical when their invariant differential cross section is plotted as a function of the transverse mass. The relative normalization of the $\eta$ to $\pi~0$ transverse mass spectra is found to be $0.53 \pm 0.07$ for S+Au and $0.43 \pm 0.15$ for S+S reactions. Extrapolation to full phase space leads to an integrated cross section ratio of $\eta$ to $\pi~0$ mesons of $0.15 \pm 0.02 {\rm (stat.)} \pm 0.02 {\rm (syst.)}$, and $0.12 \pm 0.03 {\rm (stat.)} \pm 0.02 {\rm (syst.)}$ for S+Au and S+S collisions, respectively.
No description provided.
No description provided.
No description provided.
The cross sections for the charged current processes ${e~{-}p}\rightarrow{\nu_e+hadrons}$ and, for the first time, ${e~{+}p}\rightarrow{\overline{\nu}_e+hadrons}$ are measured at HERA for transverse momenta larger than 25 GeV.
No description provided.
No description provided.
Data from BEBC experiments are combined to provide large statistics for neutrino interactions. ChargedD* mesons are produced in (1.22±0.25)% of neutrino and (1.01±0.31)% of antineutrino charged current interactions. The mean fraction of the hadronic laboratory energy taken by theD*+ in these events is 0.59±0.03±0.08. Less than 18% of all chargedD* mesons from (anti)neutrino interactions are found to be daughters ofD**0 (at the 90% confidence level).
Mean fractional hadronic energy carried by the D*+- in the laboratory system.
Mean value of the Bjorken scaling variable X.
Rate of charged D* meson production per charged current neutrino interaction.
We report on measurements of low-mass electron pairs in 450 GeV p-Be, p-Au, and 200 GeV/nucleon S-Au collisions at central rapidities. For the proton induced interactions, the low-mass spectra are, within the systematic errors, satisfactorily explained by electron pairs from hadron decays, whereas in the S-Au system an enhancement over the hadronic contributions by a factor of 5.0±0.7(stat)±2.0(syst) in the invariant mass range 0.2
CENTRAL EVENTS.
No description provided.
Forum