Charm and Beauty Physics at Fermilab

The status of charm and beauty physics studies at Fermilab is reviewed. Data from fixed target experiments on charm production, semi-leptonic decay, and Cabibbo suppressed decays as well as charmonium studies in antiproton annihilation are described. In addition beauty results from CDF and E653 are reviewed and prospects for studies of B physics at collider detectors are discussed. Hadronic production of heavy quarks has long held the promise of very high statistics samples of charm and beauty. With the current generation of charm experiments this promise is now being fulfilled. Experiments have also taken the first steps toward studies of beaUty in fixed target and collider experiments. In this report we present an overview of the current state of charm and beauty studies at Fermilab and comment on expectations for the 1990’s.’ I. Fixed Target Charm Charm experiments at Fermilab began soon after the discovery of the J/V at SLAC. Charm production and decay have been studied using hadron, photon as well as neutrino beams. The program has evolved substantially, continuing to incorporate developments in experimental technology. Crucial developments include1 Secondary vertex detection using silicon strip detectors. These devices can improve the signal/noise by factors of more than IfJo. They also make possible measurements of lifetimes. High rate data acquisition systems. The data acquisition system in E79l can write -10,000 events per second to tape. These systems are complemented by off line computing fames which have the ability to analyze the billions of events collected. @ R. Lipton 1992 -373Sophisticated trigger processors. Some experiments (E690,E789) have chosen to use very high throughput track reconstructing trigger processors to select charm and beauty events. These capabilities give the experiments involved in the current fixed target run the ability to collect samples of charm decays with an order of magnitude more reconstructed decays than previous generations. la. Current Experiments Fixed target experiments are in progress using photon and hadron beams. The experimental framework for the two environments differ. In photoproduction the topology is semi-diffractive. Typically photoproduced charm events have low primary multiplicity and charm pairs which carry a large fraction of the beam momentum The charm pair production cross section is about 1% of the hadroproduction rate (1 pb / I20 pb) . The low primary multiplicity and lack of a beam track mean that primary vertex reconstruction is more difficult in photon beams than in hadronic production experiments. On the other hand the relatively large signal/background ratio means that most photon beam experiments can run with a loose trigger and data reduction can proceed more quickly. In hadroproduction the signal/background, o(np -+ C c X)/o(np 4 X), is about 0. I R ( 30pb /40 mb), a factor of IO smaller than in photoproduction. In addition much of the yield is at low XF, with production parameterized as (I-X)? (I -X)7 depending on beam momentum and composition (K or proton). Typical hadroproduction studies are high rate, triggered experiments. An exception is E791, which substitutes a very high rate data acquisition system for a resuictive trigger. Table 1 summarizes the experiments with new results. E687 has results from a brief run in 1987-88. E769 has studied charm production as a function of beam and target, E69l continues its impressive yield of physics results, and E6.53 has results on charm production and semi-leptonic decay physics. ruble I: Fermilab Charm Experiments 5687 Photoproduction (wide Band) Wide band photon beam < Ey > 220 GeV Open Trigger Silicon p-strip system (8,400 channels) Results from 1987-88 run (60xl06Trig) Currently running (Already > 270x 106 Trig) ~691(y).E769(~,K,p),E791(~) ET Trigger E691 Photon Beam (1985) E769 250 GeV hadron beam (1987) Production, A dependence E791500 GeV hadron beam Very high rate data acquisition (10,ooO events/set) <653(p,rr) Hybrid Emulsion experiment 800 GeV p 1985 600 GeV A 1987 Beauty and Charm results, electronic and emulsion analysis Short Spectrometer, p trigger <690(p) On line event reconstruction Study of diffractive charm production in target fragmentation Currently E791, E690 and E687 are taking data. E79 I and E687 expect more than 100,000 reconstructed charm events from this run (ten times current samples from experiments like E691). E690 will study diffractive charm prqduction using an on line trigger processor. In the future E781, a completely new experiment, will study high X baryon production from hyperon beams. It is worth noting that few of the most impressive results from E69l and E6.53 were anticipated in the proposals. Data makes us more creative.