Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Search for beta-delayed charged particles from the halo nucleus sup 1 sup 4 Be

In a search for beta-delayed charged particles from sup 1 sup 4 Be we have obtained an upper limit on beta-delayed alpha particles, B(beta alpha)<1.2x10 sup - sup 4 , and found evidence for beta-delayed tritons at intensity of 6x10 sup - sup 5 <B(beta t)<4x10 sup - sup 4 (both at 95% confidence level). By adding information on the beta-delayed neutron branches from direct measurements at low neutron energy and indirect detection via recoiling nuclei at high energy, and by including also information from earlier experiments, we deduce the beta strength distribution from sup 1 sup 4 Be. This differs significantly from shell-model calculations at high excitation energy

Search for beta-delayed charged particles from the halo nucleus Be-14

In a search for beta-delayed charged particles from Be-14 we have obtained an upper limit on beta-delayed a particles, B(betaalpha