We have studied 419 τ pair events produced in the reactione+e−→τ+ τ− at a c.m. energy of 34.6 GeV. We measure the cross section and angular distribution, as well as the decay branching ratios. The production characteristics are consistent with the Standard Electroweak Model predictions of γ andZ0 interference. The branching ratios are generally consistent with the τ decaying according to standard weak interaction principles, but we observe somewhat more decays resulting in single charged hadrons plus neutrals than are predicted by present theory.
Corrected for radiative effects.
Measured cross section relative to Standard Model Prediction.
Asymmetry based on fits to angular distribution.
We have measured the deuteron magnetic form factor B(q2) for values of the momentum transfer squared between 7 and 28 fm−2. The data are compared with relativistic and nonrelativistic predictions including meson-exchange-current contributions. Significant disagreement is found for large momentum transfers.
No description provided.
No description provided.
The cross section for the reaction p¯N→μ+μ−X with muon pairs in the mass range 4
No description provided.
We report the observation of 21 dimuon events at the CERN p p Collider with the UA1 detector. The events range in invariant dimuon mass from 2 to 22 GeV / c 2 . The properties of these events are given. The bulk of the events are consistent with heavy-flavour production (mainly b b ) with a few candidates for Drell-Yan production. There remain a few events which are difficult to interpret in terms of these processes, in particular two events with isolated, like-sign muons.
No description provided.
No description provided.
We have measured the process e+e−→μ+μ− at √s =29 GeV using the High Resolution Spectrometer at SLAC PEP. The forward-backward charge asymmetry is Aμμ=-(4.9±1.5±0.5)% based on 5057 events. A subsample of 3488 μ+μ− events in the angular range ‖cosθ‖<0.55 gives a cross-section ratio of Rμμ=0.990±0.017±0.030. The resulting couplings of the weak neutral current are gaegaμ=0.208±0.064± 0.021 and gvegvμ=0.027 ±0.051±0.089. The QED cutoff parameters are Λ+>170 GeV and Λ−>146 GeV at 95% C.L.
Corrected for acceptance and O(alpha**3) QED radiation. Numerical values taken from SUGANO-ANL-HEP-CP-84-90.
Forward-backward asymmetry based on fit to angular distribution. Result is given combined with earlier data from BENDER et al.
No description provided.
Results are presented on the charge exchange reaction\(\bar pp \to \bar nn\) and\(\bar np\) annihilations from bubble chamber exposures to antiproton beam of momenta 700 and 760 MeV/c. The differential cross section of\(\bar pp \to \bar nn\) shows a forward spike followed by a clear dip bump structure. Total annihilation cross section of\(\bar np\) for average\(\bar n\) momentum of 700 MeV/c has been evaluated to be 55.4±2.2 mb. The multiplicity, Feynmanx andpT2 distributions for inclusive charged pions in\(\bar pp\) and\(\bar np\) annihilations are found to be similar. The emission of charged pions from\(\bar np\) annihilations are found to be consistent with thermodynamic models with temperature ∼110 MeV.
No description provided.
No description provided.
No description provided.
Differential cross sections of proton Compton scattering have been measured in the energy range between 400 MeV and 1050 MeV at C.M.S. angles of 150° and 160°.
No description provided.
No description provided.
No description provided.
Differential cross sections of proton Compton scattering have been measured in the angular range between 50° and 130° at incident photon energies from 900 MeV to 1150 MeV. A sharp dip in the angular distribution found by a Bonn group at 110° in the photon energy region around 900 MeV is not observed in the present measurement. A new dip-bump structure is found at photon energies above 1050 MeV, which is similar to that for pion-nucleon scattering.
No description provided.
No description provided.
No description provided.
The antineutron angular distribution in the reaction p¯C→n¯X was measured at 590 MeV/c. The shape of the distribution is found to be similar to that of the elementary process p¯p→n¯n, which indicates that the quasi-free process is the dominant mechanism for p¯C→n¯X. The antineutron production cross section per bound proton in the carbon nucleus is 0.14 times that for a free proton.
No description provided.
No description provided.
Secondary beams of 3 He, 4 He, 6 He, and 8 He were produced through the projectile fragmentation of an 800 MeV/nucleon 11 B primary beam. Interaction cross sections ( σ I ) of all He isotopes of 790 MeV/nucleon on Be, C, and Al targets were measured by a transmission-type experiment. The interaction nuclear radii of He isotopes R I ( He ) = ( σ I π ) 1 2 − R I ( T ) where R I ( T ) is the radius of the target nucleus, have been deduced to be R I ( 3 He ) = 1.59 ± 0.06 fm , R I ( 4 He ) = 1.40 ± 0.05 fm , R I ( 6 He ) = 2.21 ± 0.06 fm , and R I ( 8 He ) = 2.52 ± 0.06 fm .
No description provided.