The differential cross section for final state radiation from primary quarks is obtained from a study of isolated energetic photons produced in the reaction e + e - ? Z 0 ?hadrons+?, as measured in the DELPHI detector at the CERN LEP collider. When combined with the measurement of the total hadronic width of the Z 0 , the observed rate determines the electroweak coupling constants of up and down type quarks, i.e., $$v_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}}^2 + a_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}}^2 = 1.13 \pm 0.29 and v_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-\nulldelimiterspace} 3}}^2 + a_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-\nulldelimiterspace} 3}}^2 = 1.65 \pm 043.$$ No evidence is seen for additional photon production from anomalous decays of the Z 0 or from decays of new particles. This measurement leads to upper limits on the production cross section times branching fraction of (a) the Higgs boson in the reaction e + e - ? Z 0 ? H +?, H ?hadrons, (b) an excited quark, q * ? q +?, and (c) the contribution of an anomalous decay of the Z 0 into a photon and hadrons. These limits, all at the 95% confidence level, vary from 3 to 10pb as the mass of the intermediate state ( H , q * or Z * ) varies from 10 GeV/c 2 to 80 GeV/c 2 .
Study of final state photons in hadronic decay and limits on new phenomena
CIRIO, Roberto;MENICHETTI, Ezio;
1992-01-01
Abstract
The differential cross section for final state radiation from primary quarks is obtained from a study of isolated energetic photons produced in the reaction e + e - ? Z 0 ?hadrons+?, as measured in the DELPHI detector at the CERN LEP collider. When combined with the measurement of the total hadronic width of the Z 0 , the observed rate determines the electroweak coupling constants of up and down type quarks, i.e., $$v_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}}^2 + a_{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}}^2 = 1.13 \pm 0.29 and v_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-\nulldelimiterspace} 3}}^2 + a_{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-\nulldelimiterspace} 3}}^2 = 1.65 \pm 043.$$ No evidence is seen for additional photon production from anomalous decays of the Z 0 or from decays of new particles. This measurement leads to upper limits on the production cross section times branching fraction of (a) the Higgs boson in the reaction e + e - ? Z 0 ? H +?, H ?hadrons, (b) an excited quark, q * ? q +?, and (c) the contribution of an anomalous decay of the Z 0 into a photon and hadrons. These limits, all at the 95% confidence level, vary from 3 to 10pb as the mass of the intermediate state ( H , q * or Z * ) varies from 10 GeV/c 2 to 80 GeV/c 2 .
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
