Recent results from the MAC and MARK II detectors at PEP
Data from PEP are presented for the MAC and MARK II detectors. All data are at a center-of-mass energy of 29 GeV and correspond to a data set varying from 15 to 30 pb/sup -1/. R = sigma/sub hadronic//sigma/sub ..mu mu../ is presented by both groups, and inclusive momentum distributions (S(d sigma/dx)) for SPEAR and PEP energies are presented by the MARK II. The S(d sigma/dx) distributions exhibit sizeable scaling violations. Both groups have measured energy-energy correlations. The measurements yield ..cap alpha../sub s/ = 0.20 +- 0.01 +- 0.02 (MAC) and ..cap alpha../sub s/ = 0.19 +- 0.01 +- 0.03 (MARK II) where ..cap alpha../sub s/ is the strong coupling constant to first order. It is stressed however that this measurement of ..cap alpha../sub s/ is a very sensitive to nonperturbative (fragmentation) effects. The MARK II group has observed a clean D/sup *+-/ signal from which they obtain sigma(D/sup *+-/) = 0.25 +- 0.10 as the cross section for producing a charged D* at 29 GeV. The charm fragmentation function is measured and it appears to be fairly hard with an average fractional energy for the D*/sup + -/ of approx. 0.6. The MAC group has measured the tau lifetime and finds a value t/sub tau/ = (4.9 +- 2.0) x 10/sup -13/ secs. The MARK II group has measured the tau branching fractions into one (B/sub 1/) and three B/sub 3/ = 1 - B/sub 1/) charged prongs. They find B/sub 1/ = (86 +- 3 +- 1)%. They also find B/sub 5/ < 0.5% at the 90% confidence level. Also presented from the MARK II group are limits on the production of charged scalar particles (Higgs or technipions; H +-) which couple to tau's. For 2 < H +- mass < 10 GeV/c/sup 2/, the branching fraction for H +- to decay to tau nu/sub tau/ is found to be less than 5% at the 90% confidence level. 32 references.
- Research Organization:
- Stanford Linear Accelerator Center, CA (USA)
- DOE Contract Number:
- AC03-76SF00515; AC02-76ER02114; AC02-76ER00881
- OSTI ID:
- 6535295
- Report Number(s):
- SLAC-PUB-2963; CONF-8206136-2; ON: DE83004155
- Resource Relation:
- Conference: Conference on physics in collision, Stockholm, Sweden, 2 Jun 1982
- Country of Publication:
- United States
- Language:
- English
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
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FRAGMENTATION
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430303* - Particle Accelerators- Experimental Facilities & Equipment
645101 - High Energy Physics- Particle Interactions & Properties-Experimental- Electromagnetic Interactions & Properties