Search

A search has been performed for the muon-number--violating decay ..mu -->..e/sup +/e/sup +/e/sup -/. No candidate event has been found, the result yielding an upper limit for the branching ratio of B/sub mu3e/ ..e/sup +/e/sup +/e/sup -/..nu../sub e/nu-bar/sub ..mu../ events, eleven such events were observed. They agree in number and spectra with expectations based on standard electroweak theory.

An examination of 3.6\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ${\ensuremath{\mu}}^{+}$ decays yields an improved upper limit for the branching ratio $\frac{\ensuremath{\Gamma}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\gamma})}{\ensuremath{\Gamma}({\ensuremath{\mu}}^{+}\ensuremath{\rightarrow}{e}^{+}{\ensuremath{\nu}}_{e}{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}})}l1.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ with 90% confidence.

We report a measurement of parity nonconservation in the transmission of 800-MeV longitudinally polarized protons through an unpolarized, 1-m liquid-hydrogen target. The dependence of transmission on beam properties was studied to measure and to correct for systematic errors. The measured longitudinal asymmetry in the total cross section is ${A}_{L}=[+2.4\ifmmode\pm\else\textpm\fi{}1.1(\mathrm{statistical})\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{systematic})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$.

A search has been made for parity nonconservation in the scattering of 1.5-GeV/c (800-MeV) polarized protons from an unpolarized water target. The result for the longitudinal asymmetry is A/sub L/ = (1.7 +- 3.3 +- 1.4) x 10/sup -7/, where the second uncertainty is an estimate of systematic effects. This result is significantly smaller than the value of A/sub L/ for H/sub 2/O reported at 6 GeV/c.

The angular distribution of pions scattered by liquid hydrogen has been studied using the collimated pion beams from the Chicago synchrocyclotron. Differential cross sections have been measured for the laboratory angles 45\ifmmode^\circ\else\textdegree\fi{}, 90\ifmmode^\circ\else\textdegree\fi{}, and 135\ifmmode^\circ\else\textdegree\fi{} for positive pions of energies 78 Mev, 110 Mev, and 135 Mev, and for negative pions of 120 Mev and 144 Mev. For negative pions, separate results were obtained for the elastic scattering and for the charge exchange scattering. The scattering of positive pions and charge exchange scattering of negative pions show a larger intensity in the backward direction. The elastic scattering of negative pions is mostly forward.The results have been interpreted in terms of phase shift analysis on the assumption that the scattering is mainly due to states of isotopic spins $\frac{3}{2}$ and \textonehalf{} and angular momenta ${s}_{\frac{1}{2}}$, ${p}_{\frac{1}{2}}$ and ${p}_{\frac{3}{2}}$.The experimental results are represented quite accurately by the following phase shifts expressed in degrees for the angular momentum states in the order indicated above: at 120 Mev, phase shifts \ifmmode\pm\else\textpm\fi{}15, \ifmmode\pm\else\textpm\fi{}4, \ifmmode\pm\else\textpm\fi{}30 for isotopic spin $\frac{3}{2}$ and \ifmmode\pm\else\textpm\fi{}9, \ifmmode\pm\else\textpm\fi{}3, \ifmmode\pm\else\textpm\fi{}2 for isotopic spin \textonehalf{}; at 135 Mev, \ifmmode\pm\else\textpm\fi{}14, \ifmmode\pm\else\textpm\fi{}5, \ifmmode\pm\else\textpm\fi{}38 for isotopic spin $\frac{3}{2}$ and \ifmmode\pm\else\textpm\fi{}10, \ifmmode\pm\else\textpm\fi{}5, \ifmmode\pm\else\textpm\fi{}2 for isotopic spin \textonehalf{}.

A missing-mass spectrometer, employing optical spark chambers with automatic vidicon readout, was used to measure the forward differential cross section ($cos{\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\approx}0.995$) for the reaction $p+p\ensuremath{\rightarrow}d+{\ensuremath{\pi}}^{+}$ at closely spaced settings of the incident proton momentum in the range ${p}_{0}=3.4\ensuremath{-}12.3 \frac{\mathrm{GeV}}{c}$. The deuterons from the reaction were identified by time of flight, and their momentum and angle of emission measured by a reconstruction of the spark-chamber tracks. Since the incoming proton momentum was accurately known, the missing mass associated with deuteron production could be deduced. The reaction $p+p\ensuremath{\rightarrow}d+{\ensuremath{\pi}}^{+}$ was identified by the appearance of a distinct peak corresponding to the pion mass in a missing-mass plot. The data confirm the existence of a prominent peak in the forward cross section at ${E}_{\mathrm{c}.\mathrm{m}.}=3.0$ GeV and show a hitherto unreported shoulder at ${E}_{\mathrm{c}.\mathrm{m}.}=3.7$ GeV. This structure, along with the well-known sharp maximum at ${E}_{\mathrm{c}.\mathrm{m}.}=2.2$ GeV, may be understood on the basis of a one-pion-exchange model as reflecting the behavior of the $T=\frac{3}{2}$ isobars in pion-nucleon scattering. Above ${E}_{\mathrm{c}.\mathrm{m}.}=3.9$ GeV, the forward differential cross section decreases monotonically as the -2.5 power of $s$, the square of the total c.m. energy. This feature also reflects the behavior of the $\ensuremath{\pi}p$ scattering cross section. The structureless upper-energy region can also be accommodated within the framework of Regge theory. The cross section $\frac{d\ensuremath{\sigma}}{\mathrm{du}}$ extrapolated to $u=0$ varies as the -3.2 power of $s$, midway between that expected for the ${N}_{\ensuremath{\alpha}}$ and ${N}_{\ensuremath{\gamma}}$ trajectories.

In general, the pion factories have lived up to the expectations for them with respect to their performance as accelerators and their output of interesting results on the physics of particles and of the nucleus. Interest in kaon factories, seen as an extension of the pion factories, is presently very high, both as to accelerator design and as to facility and experimental program planning.

We measure a limit on a parity-nonconserving asymmetry in the $p$-Be cross section at 6 GeV/c. The result is $\frac{({\ensuremath{\sigma}}_{+}\ensuremath{-}{\ensuremath{\sigma}}_{\ensuremath{-}})}{({\ensuremath{\sigma}}_{+}+{\ensuremath{\sigma}}_{\ensuremath{-}})}=(5\ifmmode\pm\else\textpm\fi{}9)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ where ${\ensuremath{\sigma}}_{+}({\ensuremath{\sigma}}_{\ensuremath{-}})$ is approximately the $p$-Be total cross section for positive (negative) beam helicity. Systematic errors are determined to be 5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$.

New experimental upper limits for the branching ratios of the lepton‐family‐number nonconserving decays μ+ → e+γ and μ+ → e+γγ are presented. A new determination of γ, the ratio of pion axial‐vector to vector form factors, from radiative pion decay is also reported. These results are from data taken with the Crystal Box detector at LAMPF.

Upper limits for the time-averaged flux of air showers from the direction of Cygnus X-3 during the calendar period 2 April 1986 to 3 May 1987 are found to be 1.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ for all events, and 7.6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}14}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ for events with no observed muons in a 44-${\mathrm{m}}^{2}$ muon detector. These are integral fluxes above 50 TeV on the assumption of an ${E}^{\mathrm{\ensuremath{-}}1}$ primary spectrum. A possible observation of a short-term signal from Cygnus X-3, with an anomalous muon content, phase correlated with the 4.8-h orbital period, with an integral flux above 50 TeV of (8.2\ifmmode\pm\else\textpm\fi{}2.0)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ ${\mathrm{sec}}^{\mathrm{\ensuremath{-}}1}$ is also reported.

We measure a helicity dependence in the p‐H20 cross section at 6 GeV/c. The result is (σ+−σ−)/(σ++σ−) =−(15.0±2.8) ×10−6 where σ+ (σ−) is approximately the p‐H2O total cross section for positive (negative) beam helicity. The helicity dependence may be due to background from weakly decaying hyperons produced in the H2O target.

Development of the Crystal Box Spectrometer at the Clinton P. Anderson Meson Physics Facility in Los Alamos has been completed. And a search for the rare muon decays mu to e−gamma, to e−2gamma, and to 3e is ready to start taking data. (AIP)

We have measured the parity‐violating longitudinal asymmetry A=(σ+−σ)/(σ++σ−) in the total cross section for 6 GeV/c protons on a water target. Our present data yield a value of (1.94±71)×10−6 from our scintillation detectors, (3.57±85)×10−6 from our ionization chambers, and (2.61±.55)×10−6 from a combined fit to both. Quoted errors include statistical and systematic contributions.

Branching-ratio limits obtained with the Crystal Box detector are presented for the rare muon decays μ → eee, μ → eγ, and μ → eγγ. These decays, which violate the conservation of separate lepton-family numbers, are expected to occur in many extensions to the standard model. We found no candidates for the decay μ → eee, yielding an upper limit for the branching ratio of Bμ3e < 3.1 × 10-11 (90% C.L.). A maximum-likelihood analysis of the μ → eγ candidates yields an upper limit of Bμeγ < 4.9 × 10-11 and an analogous analysis of μ → eγγ candidates gives an upper limit of Bμeγγ < 7.2 × 10-11. These results strengthen the constraints on models that allow transitions between lepton families.

We report a result of (1\ifmmode\pm\else\textpm\fi{}4)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}7}$ for the parity-nonconserving component in the $p\ensuremath{-}p$ nuclear cross section at 15 MeV. Our experiment uses rapid spin reversal of a longitudinally polarized proton beam and an unpolarized ${\mathrm{H}}_{2}$ target. Sources of systematic error are discussed and found to be ${10}^{\ensuremath{-}7}$.