Bottom mesons

Bottom mesons
Name	Bottom mesons
Composition	quark–antiquark (one bottom quark)
Type	meson
Statistics	Boson
Interactions	Weak interaction, Electromagnetic interaction, Strong interaction
Discovered	1977

Bottom mesons Bottom mesons are hadronic states containing a bottom (beautmarked b) quark paired with a lighter antiquark or a charm antiquark, observed in high-energy experiments at facilities such as Fermilab, CERN, and KEK. They play central roles in tests of the Standard Model, studies of CP violation, and measurements of flavor-changing processes at collaborations including LHCb, ATLAS, CMS, Belle II, and historical experiments like CLEO and BaBar. Precision measurements of bottom-meson lifetimes, oscillations, and decay branching fractions constrain parameters of the Cabibbo–Kobayashi–Maskawa matrix, inputs used by global fits from groups like the Heavy Flavor Averaging Group.

Introduction

Bottom mesons were first identified after the discovery of the bottom quark in the late 1970s at facilities such as Fermilab by experiments including E288 (Fermilab experiment). Subsequent precision studies took place at LEP experiments like ALEPH, DELPHI, OPAL, and at dedicated B-factories (Belle at KEK and BaBar at SLAC National Accelerator Laboratory). Modern work is dominated by LHCb at CERN and the upgraded Belle II detector at KEK. These mesons provide windows onto electroweak symmetry breaking tests performed alongside measurements from ATLAS and CMS.

Classification and Properties

Bottom mesons are classified by flavor content into families such as B^0 (b d-bar), B^+ (b u-bar), B_s^0 (b s-bar), and B_c^+ (b c-bar), and by quantum numbers (JP) and isospin handled routinely by groups like the Particle Data Group. Their masses and properties are tabulated from measurements at Fermilab collaborations like CDF and D0, and collider experiments such as Belle, BaBar, LHCb, ATLAS, and CMS. Flavor quantum numbers link analyses to theoretical constructs developed at institutions such as the Institute for Advanced Study and calculations from lattice collaborations like HPQCD and MILC. Bottom-meson lifetimes and decay constants are inputs for global CKM fits coordinated by the CKMfitter Group and the UTfit collaboration.

Production and Decay Modes

Production takes place in high-energy collisions at accelerators run by organizations such as CERN, Fermilab, and KEK, and in fixed-target experiments like NA62 and COMPASS. Hadron colliders produce bottom mesons via gluon-gluon fusion processes modeled using event generators like PYTHIA and HERWIG, and parton distribution functions from groups such as CTEQ and NNPDF. Decay channels probe weak interactions mediated by W bosons studied at CERN and radiative processes constrained by measurements of rare decays like B -> K* gamma by experiments including LHCb and Belle II. Semileptonic decays B -> D(*) l nu connect to determinations of |V_cb| and |V_ub| relevant to the CKM matrix and tensions reported by collaborations such as Belle, BaBar, and LHCb.

Spectroscopy and Excited States

Spectroscopy catalogs ground states and excited resonances: B, B^*, B_s, B_s^*, and orbitally or radially excited states discovered by experiments including LHCb, CDF, D0, Belle, and BaBar. Observations of states such as B_c(2S) and narrow B_s** resonances involved collaborations like ATLAS and theoretical input from groups at CERN Theory and institutes such as Perimeter Institute and Institute for Nuclear Theory. Potential models by researchers affiliated with Princeton University, University of Oxford, and MIT compete with lattice QCD results from FNAL/MILC and HPQCD to predict mass splittings and hyperfine structure.

Experimental Detection and Measurement Techniques

Detectors at LHCb, ATLAS, CMS, Belle II, and earlier at CLEO and BaBar use vertex detectors (e.g., VELO), tracking systems, ring-imaging Cherenkov detectors (RICH), electromagnetic calorimeters, and muon systems to reconstruct bottom-meson decays. Trigger strategies developed at CERN and SLAC select displaced vertices characteristic of b-hadron decays, while flavor tagging methods utilize algorithms developed by collaborations including CDF and D0. Statistical analyses employ tools from groups like ROOT and methodologies refined by experimental teams at IHEP and Brookhaven National Laboratory; systematic uncertainties are constrained using control samples from processes measured at LEP and Tevatron.

Theoretical Frameworks and Models

Theoretical descriptions rely on the Standard Model with effective field theories such as Heavy Quark Effective Theory (HQET) developed by theorists at CERN Theory and universities like Harvard, Cambridge, and Oxford, and Soft-Collinear Effective Theory (SCET) with contributions from researchers at Stanford and Caltech. Lattice QCD computations from collaborations like HPQCD, FNAL/MILC, and RBC/UKQCD provide nonperturbative inputs; perturbative calculations incorporate work by groups at SLAC, DESY, and Purdue University. Global fits and phenomenology are advanced by the CKMfitter Group, UTfit collaboration, and theorists at institutes such as IPPP.

Applications and Significance in Particle Physics

Studies of bottom-meson mixing and CP violation inform constraints on new physics scenarios explored at CERN and Fermilab and influence model-building at centers such as Perimeter Institute and IHEP. Precision measurements of branching fractions and angular observables in decays like B -> K* mu+ mu- by LHCb and Belle II impact searches for lepton-flavor-universality violation discussed by theorists at Princeton and IAS. Results feed into global fits used by communities at SLAC, Brookhaven National Laboratory, and KEK to test extensions such as supersymmetry advocated in studies originating at CERN Theory and University of Chicago.

Category:Mesons