115632262
Search for the top quark in the electron-electron and electron-muon channels at D0
We discuss preliminary results of a search for top quarks using their decays in two di-lepton, with the D0 detector at Fermilab. The present analysis has been optimized to search for a top with mass near 100{sub c{sup 2}}/{sup GeV}, consistent with published limits. In the event sample corresponding to an integrated luminosity of 15pb{sup {minus}1} we observe two events passing all selection cuts. The number of events observed is consistent with the expected number of background events. Consequently, we do not claim the observation of a top decay in the present event sample. We note however, that the kinematic properties of one of the events appear to be far removed from known backgrounds. We discuss the event and show results of the mass likelihood analysis when applied to this event.
30659802
Linear momentum transfer and light particle emission in the E/A=25 MeV 6Li+238U reaction.
Inclusive measurements of the linear momentum transfer distribution and exclusive studies of light-charged particles as a function of linear momentum transfer have been performed for the reaction of 150-MeV /sup 6/Li ions with /sup 238/U. Linear momentum transfer properties and an upper limit for the complete fusion cross section for this system were deduced from the folding angle between binary fission events and found to be consistent with data for heavier complex projectiles. The exclusive light-charged-particle data demonstrate the existence of fission following the transfer of all possible subdivisions of the /sup 6/Li projectile, as well as inelastic scattering. Absorptive breakup involving /sup 4/He-/sup 2/H cluster structure is found to be the dominant reaction mechanism. In addition, substantial yields of energetic protons associated with full linear momentum transfer are observed in the backward hemisphere. However, the temperature inferred from these spectra is nearly three times as large as that for a fully equilibrated compound nucleus, suggesting a nonequilibrium source for these particles.
6017780
Proton radiative capture by deuterium between 100 and 200 MeV.
Differential cross sections, (dsigma/d..cap omega..)(theta), and analyzing powers, A/sub y/(theta), have been measured for the reaction /sup 2/H(p-arrow-right,..gamma..) /sup 3/He at laboratory energies of 99.1, 150.3, and 200.7 MeV. The cross sections obtained are found to be in very good agreement with those of other authors. Both the size and shape of the angular distributions for the cross sections are found to be well accounted for by a simple ''quasideuteron'' model. Further support for this model is provided by the measured analyzing powers. Both the shape and size of the angular distributions for A/sub y/ are found to be very similar to those predicted for n(p-arrow-right,..gamma..)d at the same E/sub ..gamma..//sup c.m./.
123498142
Measurement of high momentum transfer reactions by recoil detection
A method is described for studying reactions at medium energies by measuring the magnetic rigidity, time of flight, and energy loss of the resulting recoil products. The method works best for reactions with two-body final states where one of the outgoing particles is relatively light. A magnetic spectrometer with a special focal plane detector has been used. The detector consists of two position sensitive parallel plate avalanche counters and two proportional counters. Differential cross sections for the 12C(p, π+13C reaction at recoil angles which correspond to the pion being emitted at a backward angle in the center of mass have been measured at bombarding energies of 166 and 186 MeV. Data were also obtained for previously unobserved 12C(p, π0)13N reaction. Several advantages of the method are discussed.
118745087
Dijet angular distributions at D0
Measurements of the dijet angular distributions are relatively insensitive to parton distribution functions and thus offer an excellent method of testing the LO and NLO predictions of perturbative QCD. The authors present measurements of the dijet angular distributions for {vert_bar}{eta}{vert_bar} < 3.0 in p{anti p} collisions at {radical}s = 1.8 TeV.