Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · hep-ex/9708024

Tests of the Standard Model and Constraints on New Physics from Measurements of Fermion-pair Production at 130-172 GeV at LEP

The OPAL Collaboration·K. Ackerstaff et al
View original source ↗Read source document ↗Export metadata ↓

Abstract

Production of events with hadronic and leptonic final states has been measured in e^+e^- collisions at centre-of-mass energies of 130-172 GeV, using the OPAL detector at LEP. Cross-sections and leptonic forward-backward asymmetries are presented, both including and excluding the dominant production of radiative Z γevents, and compared to Standard Model expectations. The ratio R_b of the cross-section for bb(bar) production to the hadronic cross-section has been measured. In a model-independent fit to the Z lineshape, the data have been used to obtain an improved precision on the measurement of γ-Z interference. The energy dependence of α_em has been investigated. The measurements have also been used to obtain limits on extensions of the Standard Model described by effective four-fermion contact interactions, to search for t-channel contributions from new massive particles and to place limits on chargino pair production with subsequent decay of the chargino into a light gluino and a quark pair.

Explore related subjects

hep-ex

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

The OPAL Collaboration, K. Ackerstaff et al. 1997-08-17. Tests of the Standard Model and Constraints on New Physics from Measurements of Fermion-pair Production at 130-172 GeV at LEP. https://doi.org/10.1007/s100520050152

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Search for dark matter in a signature with a four-prong large-radius jet in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search for a pair of nonprompt dark matter (DM) candidates produced in association with an initial-state radiation jet, in a signature containing a four-prong large-radius jet, is presented. The signal model contains a heavy vector or axial-vector mediator, which produces long-lived dark-sector particles that decay to a stable DM particle and a light boson, which decays to quarks. The analysis is based on data collected in the years 2016$-$2018 with the CMS detector at the LHC in proton-proton collisions at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. Signal candidates feature large-radius jets, which are identified using a jet substructure tagger based on a graph neural network. The large-radius jet aims to reconstruct the decay of light DM mediators into four quarks, which are produced in association with two stable DM particles. The standard model background contributions are estimated from data using dedicated control regions. The missing transverse momentum spectrum is probed for a potential signal over the expected background. No significant excess over the standard model expectation is observed. Upper limits at 95% confidence level are set on the signal strength as functions of either the mediator mass or the relevant coupling. This is the first search for a pair of nonprompt DM candidates in the Lorentz-boosted topology, characterized by a large-radius jet and large missing transverse momentum.

hep-ex↗
arXiv2026

Charge-dependent atmospheric muon flux at 17 GV geomagnetic cutoff with the mini-ICAL detector

The Iron CALorimeter (ICAL) detector at the India-Based Neutrino Observatory (INO) was conceived as an underground experiment designed to measure atmospheric neutrino oscillation parameters. As part of the R\&D programme, a scaled prototype (mini-ICAL), 85\,ton, approximately 1/600$^{\mathrm{th}}$ the mass of the full detector, was constructed at the IICHEP Transit Campus, Madurai (altitude 150\,m; latitude 9.9372$^\circ$\,N; longitude 78.013$^\circ$\,E; geomagnetic latitude 1.44$^\circ$\,N; vertical cutoff rigidity 17\,GV) and operated between 2018 and 2022. The prototype enabled measurements of charge-dependent cosmic muon spectra in the vicinity of the geomagnetic equator and provided an important validation of detector performance, reconstruction algorithms, and simulation frameworks for the ICAL experiment. Differential fluxes of $μ^{-}$ and $μ^{+}$ were measured over the momentum range $\sim$\,1--5\,GeV/c. The obtained momentum spectra are systematically lower than those reported at sites with smaller geomagnetic cutoff rigidities, consistent with the suppression of low- and intermediate-rigidity primary cosmic rays at the 17\,GV cutoff. The measurements are compared with predictions from different hadronic interaction models available in CORSIKA simulations.

hep-ex↗
arXiv2026

Laboratory constraints on peV-scale mass splitting between ordinary and sterile neutron states

Sterile states of matter, represented by a parallel ``mirror'' sector, may contribute to the observed dark matter in the Universe. We investigated the parameter space of neutron $(n)$ to mirror-neutron $(n')$ oscillations, in the case where the two states are not necessarily mass-degenerate, taking into account interactions in the mirror sector. By tuning the magnitude of an applied magnetic-field in the range $5~μ\mathrm{T} < B < 360~μ\mathrm{T}$ to corresponding resonance conditions for finite mass splitting, we derive exclusion limits for the $n-n'$ oscillation time constant reaching about $20~\text{s}$ over the mass-difference range $0.3 - 22~\text{peV}$. In parts of this parameter range, our limits exceed the model-dependent neutron-star-cooling bound, providing the first experimental constraints in this scenario that are more stringent than this astrophysical estimate.

hep-ex↗