Search for a Fourth-Generation Quark More Massive than the Z⁰ Boson in pp̅ Collisions at √s = 1.8 TeV

Authors

• T. Affolder, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California
• Kenneth A. Bloom, University of Nebraska-LincolnFollow
• Collider Detector at Fermilab Collaboration

Document Type

Article

Date of this Version

1-31-2000

Comments

Published by American Physical Society. Phys. Rev. Lett. 84, 835 (2000). http://prl.aps.org. Copyright © 2000 American Physical Society. Permission to use.

Abstract

We present the results of a search for pair production of a fourth-generation charge -⅓ quark (b′) in √s =1.8 TeV pp collisions using 88 pb^-1 of data obtained with the Collider Detector at Fermilab. We assume that both quarks decay via the flavor-changing neutral current process b′ → bZ⁰ and that the b′ mass is greater than m_z+ m_b. We studied the decay mode b′b̅′→ Z⁰Z⁰ bb̅ where one Z⁰ decays into e⁺e^- or μ⁺μ^-and the other decays hadronically, giving a signature of two leptons plus jets. An upper limit on the σ _{pp̅→b′b̅′}x [B(b′→ bZ⁰)]² is established as a function of the b0 mass. We exclude at 95% confidence level a b′ quark with mass between 100 and 199 GeV/c² for B(b′→ bZ⁰)=100%.